International Conference on Signal, Image and Video Processing (ICSIVO) At Indian Institute of Technology, Patna
The Indian Institute of Technology, Patna epitomizes and reveres this limitless power in every way of its life and functioning. Established as an institute of national importance through an act of parliament in 2008, IIT Patna strives to provide world class education and an intellectually stimulating environment in an endeavor to develop well rounded individuals with technical and professional competence of the highest degree.
Scope
Indian Institute of Technology Patna is going to organize International Conference on Signal, Image and Video Processing (ICSIVP) during December 12 to 14, 2011. This conference will provide academia and industry a platform to discuss and present the latest technological advances and research results in the fields of theoretical, experimental, and application of signal, image and video processing. The conference programme will include workshops, special sessions and tutorials, along with prominent keynote speakers, panel discussion, and regular paper presentations.
The scope of the conference includes, but not limited to:
Track 1: Signal Processing
Adaptive Signal Processing, Array Signal Processing, Audio/Speech/Music Processing and Coding, Spoken language processing, Signal processing for communications and networking, Digital and Multirate Signal Processing, Signal Processing for Smart Sensor and Systems, Geophysical/Radar/Sonar Signal Processing, Statistical Signal Processing, FIR and IIR filter design and structures, Optical Signal Processing
Track 2: Image Processing
Image acquisition, Image Compression, Image Segmentation, Image Enhancement, Image Registration, Mosaicing, Content based Image Indexing and Retrieval, Industrial Applications, Super-resolution imaging
Track 3: Video Processing
Video Content Analysis, Video Indexing, Search and Retrieval, Video Processing Techniques, Video Surveillance, Video Summarization, Video Compression and Coding Standards, Stereo Vision, Object Detection, Motion Detection.
Track 4: Biometrics
Face recognition, Fingerprint, IRIS, Signature, Gait, Multimodal and Emerging Biometrics, Biometric Retrieval
Track 5: Information Coding
Information Forensics & Security, Digital Watermarking & Data Hiding, DCT Coding, Cryptography, Steganography, Teleradiology, Index Coding, Signal Encoding, Indexing Documents
Track 6: Pattern Recognition
Object Recognition, Distance Measures, Feature Extraction, Shape Analysis. Document Analysis and Recognition, Handwriting Analysis, Character Recognition, Language Recognition, Multimedia Documents, Text Classification.
Track 7: Theory and Applications of Transforms
Discrete Cosine Transform, Fast Fourier Transform, Discrete Hilbert Transform, Wavelet Transform, Time-Frequency Analysis, Spectral Analysis
Track 8: Medical Image Processing
Biomedical Image and Signal Processing, Breast Cancer Imaging, Segmentation of 3D CT images, Optical Imaging, Embedded VLSI System for medical images, Tele Medicine, Tongue Imaging, Medical Image Registration, 3D imaging/Fusion Imaging, Classification of Liver US Images
Paper Submission
The length of the paper must not exceed FIVE A-4 size pages with 11-point text in standard IEEE Conference Format. The papers should be in pdf or doc formats. At least one author of each accepted paper must register and send the draft along with the final camera ready copy, within the due date, for the paper to be published in the proceedings.
Important Dates
* Last Date for Paper Submission: August 15, 2011
* Acceptance Notification: October 01, 2011
* Last Date for Submitting Camera-Ready
Copy along with Registration Fee: November 01, 2011
Reaching IITP
IIT Patna is on the Navin Government Polytechnic Campus in Patna. This location is approximately 6 (six) kilometers away from Patna Junction and approximately 8 (eight) kilometers away from Lok Nayak Jayapraksh International Airport.
Patna, also known as Patliputra, is one of ancient cities of India. It is situated on the banks of holy Ganga. It has confluence of the Son and the Gandak as well. It has many historical places in its periphery such as Vaishali (the birthplace of democracy), Nalanda (one of the ancient centers of learning), Bodhgaya (center of Lord Buddha's enlightenment), Rajgir (Work place of Lord Mahabir), and Taregana (workplace of a famous mathematician Aryabhatta) among many.
By Rail
Patna junction is served by direct trains from all parts of the country such as Delhi, Mumbai, Kolkata, Chennai, Hyderabad, Bangalore, Lucknow, Kanpur, Guwahati, Puri, and Vasco-de-Gamma among many others.
By Air
Its airport has direct flights to Delhi, Mumbai, Kolkata, and Bangalore with good connectivity to other cities of India.
Contact Us
Dr. Maheshkumar H. Kolekar
Convenor ICSIVP-2011
Assistant Professor,
Department of Electrical Engineering,
Indian Institute of Technology, Patna-800013
Phone: +91-612-2552043,
Mobile: +91-8986184240,
Email: mahesh@iitp.ac.in
website: http://www.iitp.ac.in/ICSIVP2011/index.php
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Saturday, April 30, 2011
National Symposium on Rotor Dynamics At Indian Institute of Technology, Madras
National Symposium on Rotor Dynamics At Indian Institute of Technology, Madras
ABOUT THE SYMPOSIUM
Most machines have one or more rotating parts. Rotating machine elements thus form the backbone of industrial infrastructure and therefore play a pivotal role in the growth and development of the country. Rotor Dynamics is the key in design and maintenance of all such rotating machinery. This area has made tremendous strides in recent years. There is a need to disseminate the knowledge acquired and the progress made in this multi-faceted and multi-disciplinary area.
It is important that we discuss this subject at a national level to bring the desired awareness on the advances in this field among the different researchers working in academia, R&D organizations and industry. With this objective the first National Symposium of Rotor Dynamics (NSRD 2003) was held at IIT Guwahati in 2003.
The Second NSRD is being organized by IIT Madras in association with The Vibration Institute of India during December 19-21, 2011. The main theme of the symposium is on the recent advancements in rotor dynamics. The highlight of NSRD-2011 is to have talks by a galaxy of invited experts from the academia, research establishments and industries along with the presentation of peer-reviewed articles and posters on several important topics in the area of rotor dynamics. The symposium will provide a forum for exchange of ideas and give directions for future research on Rotor Dynamics. It is planned to have about 25 invited presentations of half an hour duration each and about 40 contributed papers including interactive poster sessions on various themes within the broad area of rotor dynamics.
EXHIBITION
Apart from presentations, there is a plan for a modest exhibition from industries dealing with experimental setup / instrumentation/ software in the related area for display of their latest products.
CALL FOR PAPERS
Prospective authors are requested to submit abstracts (not exceeding 500 words clearly stating the objectives, results etc.) by May 15, 2011. Abstract should also include the title of the paper, name of all the authors along with their affiliation-address , telephone number and e-mail. The number of papers is limited and more importantly, NSRD-2011 symposium aims towards setting directions for future research in Rotor Dynamics. Authors of each accepted abstract would be invited to submit full versions of their manuscripts for peer review. Based on the reviews, some papers would be accepted for oral presentation or for poster presentation.
PROCEEDINGS
The symposium proceedings will consist of invited and contributed articles. The Vibration Institute of India will bring out a special issue of the Journal “Advances in Vibration Engineering” in its volume 12 containing the acceptable papers from this symposium according to the peer review practices of this Journal.
Topics
A list of important topics related to rotor dynamics is given below, which provides a broad outline of the scope (but not limited to the topics given) of the Symposium.
* Analytical, computational and experimental methods in rotor dynamics
* Instability in rotor bearing systems
* Misalignment, bow, crack, rub/impact, shrink fit and foundation effects
* Nonlinear, parametric, asymmetry and other effects in rotors
* System identification, model updating and SDM techniques
* Active/semi active rotor vibration control
* Smart material applications for rotor vibration control
* Developments in bearings, dampers and seals
* Non-metallic and composite rotors
* Diagnostics, prognostics and condition monitoring of rotors
* Analysis of bladed disc systems
* Geared systems, transmissions and electrical machinery
* High speed turbopumps and multi-spool gas turbines
* Smart and micro rotor systems
Registration Fee
Student Delegates : Rs 1500
Delegates from academia : Rs 6000
Delegates from Industrial & R&D organizations : Rs 10000
Overseas Delegates : US $ 300
Payment
The payments can be made in the following ways:
* Demand draft drawn in favour of NSRD-2011, payable at Chennai.
* Wire transfer: credited to State Bank of India, IIT Madras (Branch no. 1055)
Account No. NSRD-2011: 31654972926
Important Dates
Receipt of Abstract 15th May 2011
Intimation of acceptance of Abstract 31st May 2011
Submission of full Manuscripts 31st July 2011
Notification of Review comments 1st October 2011
Final submission in camera ready format 15th October 2011
Registration deadline 1st November 2011
Symposium Venue
Industrial Consultancy And Sponsored Research (ICDR)
Indian Institute of Technology,
Madras,
Chennai-600 036.
Contact Us
Prof. A. S. Sekhar
Organizing Secretary, NSRD-2011
Department of Mechanical Engineering
IIT Madras, Chennai 600036, India
Tel.: +91-44-2257-4709(O) : +91-44-2257-5689(O)
Fax: +91-44-2257-4652
E-mail: nsrd2011@gmail.com : as_sekhar@iitm.ac.in
website: http://www.nsrd-2011.iitm.ac.in/contact.php
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ABOUT THE SYMPOSIUM
Most machines have one or more rotating parts. Rotating machine elements thus form the backbone of industrial infrastructure and therefore play a pivotal role in the growth and development of the country. Rotor Dynamics is the key in design and maintenance of all such rotating machinery. This area has made tremendous strides in recent years. There is a need to disseminate the knowledge acquired and the progress made in this multi-faceted and multi-disciplinary area.
It is important that we discuss this subject at a national level to bring the desired awareness on the advances in this field among the different researchers working in academia, R&D organizations and industry. With this objective the first National Symposium of Rotor Dynamics (NSRD 2003) was held at IIT Guwahati in 2003.
The Second NSRD is being organized by IIT Madras in association with The Vibration Institute of India during December 19-21, 2011. The main theme of the symposium is on the recent advancements in rotor dynamics. The highlight of NSRD-2011 is to have talks by a galaxy of invited experts from the academia, research establishments and industries along with the presentation of peer-reviewed articles and posters on several important topics in the area of rotor dynamics. The symposium will provide a forum for exchange of ideas and give directions for future research on Rotor Dynamics. It is planned to have about 25 invited presentations of half an hour duration each and about 40 contributed papers including interactive poster sessions on various themes within the broad area of rotor dynamics.
EXHIBITION
Apart from presentations, there is a plan for a modest exhibition from industries dealing with experimental setup / instrumentation/ software in the related area for display of their latest products.
CALL FOR PAPERS
Prospective authors are requested to submit abstracts (not exceeding 500 words clearly stating the objectives, results etc.) by May 15, 2011. Abstract should also include the title of the paper, name of all the authors along with their affiliation-address , telephone number and e-mail. The number of papers is limited and more importantly, NSRD-2011 symposium aims towards setting directions for future research in Rotor Dynamics. Authors of each accepted abstract would be invited to submit full versions of their manuscripts for peer review. Based on the reviews, some papers would be accepted for oral presentation or for poster presentation.
PROCEEDINGS
The symposium proceedings will consist of invited and contributed articles. The Vibration Institute of India will bring out a special issue of the Journal “Advances in Vibration Engineering” in its volume 12 containing the acceptable papers from this symposium according to the peer review practices of this Journal.
Topics
A list of important topics related to rotor dynamics is given below, which provides a broad outline of the scope (but not limited to the topics given) of the Symposium.
* Analytical, computational and experimental methods in rotor dynamics
* Instability in rotor bearing systems
* Misalignment, bow, crack, rub/impact, shrink fit and foundation effects
* Nonlinear, parametric, asymmetry and other effects in rotors
* System identification, model updating and SDM techniques
* Active/semi active rotor vibration control
* Smart material applications for rotor vibration control
* Developments in bearings, dampers and seals
* Non-metallic and composite rotors
* Diagnostics, prognostics and condition monitoring of rotors
* Analysis of bladed disc systems
* Geared systems, transmissions and electrical machinery
* High speed turbopumps and multi-spool gas turbines
* Smart and micro rotor systems
Registration Fee
Student Delegates : Rs 1500
Delegates from academia : Rs 6000
Delegates from Industrial & R&D organizations : Rs 10000
Overseas Delegates : US $ 300
Payment
The payments can be made in the following ways:
* Demand draft drawn in favour of NSRD-2011, payable at Chennai.
* Wire transfer: credited to State Bank of India, IIT Madras (Branch no. 1055)
Account No. NSRD-2011: 31654972926
Important Dates
Receipt of Abstract 15th May 2011
Intimation of acceptance of Abstract 31st May 2011
Submission of full Manuscripts 31st July 2011
Notification of Review comments 1st October 2011
Final submission in camera ready format 15th October 2011
Registration deadline 1st November 2011
Symposium Venue
Industrial Consultancy And Sponsored Research (ICDR)
Indian Institute of Technology,
Madras,
Chennai-600 036.
Contact Us
Prof. A. S. Sekhar
Organizing Secretary, NSRD-2011
Department of Mechanical Engineering
IIT Madras, Chennai 600036, India
Tel.: +91-44-2257-4709(O) : +91-44-2257-5689(O)
Fax: +91-44-2257-4652
E-mail: nsrd2011@gmail.com : as_sekhar@iitm.ac.in
website: http://www.nsrd-2011.iitm.ac.in/contact.php
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http://www.enjineer.com/forum
Zero Emission Power Plants Using Solid Oxide Fuel Cells and Oxygen Transport Membranes
Zero Emission Power Plants Using Solid Oxide Fuel Cells and Oxygen Transport Membranes
Abstract
Siemens Westinghouse Power Corp. (SWPC) is engaged in the development of Solid Oxide Fuel Cell stationary power systems. SWPC has combined DOE Developmental funds with commercial customer funding to establish a record of successful SOFC field demonstration power systems of increasing size. SWPC will soon deploy the first unit of a newly developed 250 kWe Combined Heat Power System. It will generate electrical power at greater than 45% electrical efficiency.
The SWPC SOFC power systems are equipped to operate on lower number hydrocarbon fuels such as pipeline natural gas, which is desulfurized within the SOFC power system. Because the system operates with a relatively high electrical efficiency, the CO2 emissions, ~1.0 lb CO2/ kW-hr, are low. Within the SOFC module the desulfurized fuel is utilized electrochemically and oxidized below the temperature for NOx generation. Therefore the NOx and SOx emissions for the SOFC power generation system are near negligible. The byproducts of the power generation from hydrocarbon fuels that are released into the environment are CO2 and water vapor. This forward looking DOE sponsored Vision 21 program is supporting the development of methods to capture and sequester the CO2, resulting in a Zero Emission power generation system.
To accomplish this, SWPC is developing a SOFC module design, to be demonstrated in operating hardware, that will maintain separation of the fuel cell anode gas, consisting of H2, CO, H2O and CO2, from the vitiated air. That anode gas, the depleted fuel stream, containing less than 18% (H2 + CO), will be directed to an Oxygen Transport Membrane (OTM) Afterburner that is being developed by Praxair, Inc.. The OTM is supplied air and the depleted fuel. The OTM will selectively transport oxygen across the membrane to oxidize the remaining H2 and CO. The water vapor is then condensed from the totally1.5.DOC
oxidised fuel stream exiting the afterburner, leaving only the CO2 in gaseous form. That CO2 can then be compressed and sequestered, resulting in a Zero Emission power generation system operating on hydrocarbon fuel that adds only water vapor to the environment.
Praxair has been developing oxygen separation systems based on dense walled, mixed electronic, oxygen ion conducting ceramics for a number of years. The oxygen separation membranes find applications in syngas production, high purity oxygenproduction and gas purification. In the SOFC afterburner application the chemical potential difference between the high temperature SOFC depleted fuel gas and the supplied air provides the driving force for oxygen transport. This permeated oxygen subsequently combusts the residual fuel in the SOFC exhaust.
A number of experiments have been carried out in which simulated SOFC depleted fuel gas compositions and air have been supplied to either side of single OTM tubes in laboratory-scale reactors. The ceramic tubes are sealed into high temperature metallic housings which precludes mixing of the simulated SOFC depleted fuel and air streams. In early tests, although complete oxidation of the residual CO and H2 in the simulated SOFC depleted fuel was achieved, membrane performance degraded over time. The source of degradation was found to be contaminants in the simulated SOFC depleted fuel stream. Following removal of the contaminants, stable membrane performance has subsequently been demonstrated. In an ongoing test, the dried afterburner exhaust composition has been found to be stable at 99.2% CO2, 0.4% N2 and 0.6%O2 after 350 hours online. Discussion of these results is presented.
A test of a longer, commercial demonstration size tube was performed in the SWPC test facility. A similar contamination of the simulated SOFC depleted fuel stream occurred and the performance degraded over time. A second test is being prepared.
Siemens Westinghouse and Praxair are collaborating on the preliminary design of an OTM equipped Afterburner demonstration unit. The intent is to test the afterburner in conjunction with a reduced size SOFC test module that has the anode gas separation features incorporated into the hardware.
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Abstract
Siemens Westinghouse Power Corp. (SWPC) is engaged in the development of Solid Oxide Fuel Cell stationary power systems. SWPC has combined DOE Developmental funds with commercial customer funding to establish a record of successful SOFC field demonstration power systems of increasing size. SWPC will soon deploy the first unit of a newly developed 250 kWe Combined Heat Power System. It will generate electrical power at greater than 45% electrical efficiency.
The SWPC SOFC power systems are equipped to operate on lower number hydrocarbon fuels such as pipeline natural gas, which is desulfurized within the SOFC power system. Because the system operates with a relatively high electrical efficiency, the CO2 emissions, ~1.0 lb CO2/ kW-hr, are low. Within the SOFC module the desulfurized fuel is utilized electrochemically and oxidized below the temperature for NOx generation. Therefore the NOx and SOx emissions for the SOFC power generation system are near negligible. The byproducts of the power generation from hydrocarbon fuels that are released into the environment are CO2 and water vapor. This forward looking DOE sponsored Vision 21 program is supporting the development of methods to capture and sequester the CO2, resulting in a Zero Emission power generation system.
To accomplish this, SWPC is developing a SOFC module design, to be demonstrated in operating hardware, that will maintain separation of the fuel cell anode gas, consisting of H2, CO, H2O and CO2, from the vitiated air. That anode gas, the depleted fuel stream, containing less than 18% (H2 + CO), will be directed to an Oxygen Transport Membrane (OTM) Afterburner that is being developed by Praxair, Inc.. The OTM is supplied air and the depleted fuel. The OTM will selectively transport oxygen across the membrane to oxidize the remaining H2 and CO. The water vapor is then condensed from the totally1.5.DOC
oxidised fuel stream exiting the afterburner, leaving only the CO2 in gaseous form. That CO2 can then be compressed and sequestered, resulting in a Zero Emission power generation system operating on hydrocarbon fuel that adds only water vapor to the environment.
Praxair has been developing oxygen separation systems based on dense walled, mixed electronic, oxygen ion conducting ceramics for a number of years. The oxygen separation membranes find applications in syngas production, high purity oxygenproduction and gas purification. In the SOFC afterburner application the chemical potential difference between the high temperature SOFC depleted fuel gas and the supplied air provides the driving force for oxygen transport. This permeated oxygen subsequently combusts the residual fuel in the SOFC exhaust.
A number of experiments have been carried out in which simulated SOFC depleted fuel gas compositions and air have been supplied to either side of single OTM tubes in laboratory-scale reactors. The ceramic tubes are sealed into high temperature metallic housings which precludes mixing of the simulated SOFC depleted fuel and air streams. In early tests, although complete oxidation of the residual CO and H2 in the simulated SOFC depleted fuel was achieved, membrane performance degraded over time. The source of degradation was found to be contaminants in the simulated SOFC depleted fuel stream. Following removal of the contaminants, stable membrane performance has subsequently been demonstrated. In an ongoing test, the dried afterburner exhaust composition has been found to be stable at 99.2% CO2, 0.4% N2 and 0.6%O2 after 350 hours online. Discussion of these results is presented.
A test of a longer, commercial demonstration size tube was performed in the SWPC test facility. A similar contamination of the simulated SOFC depleted fuel stream occurred and the performance degraded over time. A second test is being prepared.
Siemens Westinghouse and Praxair are collaborating on the preliminary design of an OTM equipped Afterburner demonstration unit. The intent is to test the afterburner in conjunction with a reduced size SOFC test module that has the anode gas separation features incorporated into the hardware.
Download full seminar papers At
http://www.enjineer.com/forum
Preliminary Approach Designing an Electromagnetic Bearing for Flywheel Energy Systems
Preliminary Approach Designing an Electromagnetic Bearing for Flywheel Energy Systems
Abstract
Magnetic bearings are nowadays, an important technology that has been used in several high dynamic applications, as for instance, flywheels. Flywheels can be used as an energy storage system, in high range of applications such as low earth orbit satellites, pulse power transfer for hybrid electric vehicles, and many stationary applications. The main goal of this work is to design a magnetic bearing useful for a flywheel energy storage system.
The flywheel’s rotor, the component that storages the energy by means of its kinetic motion was designed in this study by calculating its dimensions, weight and material’s cost. A hybrid bearing was chosen to be used on the flywheel. The design and general characteristics of a hybrid bearing are presented in this thesis.
A hybrid bearing is composed of a passive and an active bearing. The passive bearing was designed to compensate gravitational and centrifugal forces. The active bearing was designed to compensate instabilities that the passive bearing could not compensate.
In addition of the design to the magnetic bearing components (passive bearing and active bearing), the proposed solution was developed taking into account the economic aspects, power and mechanical losses and cost.
Introduction
This chapter gives an overview of the work, establishing the work targets and goals. Also the scope and motivations are brought up. The current State-of-the-Art related to the scope of the work is also presented. At the end of the chapter, the structure of this work is referred and described.
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Abstract
Magnetic bearings are nowadays, an important technology that has been used in several high dynamic applications, as for instance, flywheels. Flywheels can be used as an energy storage system, in high range of applications such as low earth orbit satellites, pulse power transfer for hybrid electric vehicles, and many stationary applications. The main goal of this work is to design a magnetic bearing useful for a flywheel energy storage system.
The flywheel’s rotor, the component that storages the energy by means of its kinetic motion was designed in this study by calculating its dimensions, weight and material’s cost. A hybrid bearing was chosen to be used on the flywheel. The design and general characteristics of a hybrid bearing are presented in this thesis.
A hybrid bearing is composed of a passive and an active bearing. The passive bearing was designed to compensate gravitational and centrifugal forces. The active bearing was designed to compensate instabilities that the passive bearing could not compensate.
In addition of the design to the magnetic bearing components (passive bearing and active bearing), the proposed solution was developed taking into account the economic aspects, power and mechanical losses and cost.
Introduction
This chapter gives an overview of the work, establishing the work targets and goals. Also the scope and motivations are brought up. The current State-of-the-Art related to the scope of the work is also presented. At the end of the chapter, the structure of this work is referred and described.
Download full seminar papers At
http://www.enjineer.com/forum
Control of Magnetic Bearings in Wind Turbines
Control of Magnetic Bearings in Wind Turbines
Abstract
Direct drive generators applied to large wind turbines present some problems, such as very heavy and expensive price. The use of magnetic bearings has a possibility to reduce the weight of the direct drive generator. The control system for such magnetic bearings is considered.
In the beginning, the thesis discusses the problems of direct drive generators in large wind turbines, introduces a hybrid concept of active magnetic bearings, gives a demonstrator of magnetic bearings used in this project, and presents a basic control system of active magnetic bearings.
For the purpose of support such magnetic bearings in wind turbines, this thesis gives a complete control system. This control system includes electrical circuits and decentralized control method. The implementation of the electrical circuits is distributed into two PCBs. The decentralized control method is designed with six PID controllers.
Finally, in order to improve the stability of the system, the H-infinity control method is suggested to magnetic bearing system in wind turbine applications.
Introduction
Wind Energy
Wind energy is a kind of renewable energy, and we have used it for hundreds of years. The kinetic energy of wind can be converted into other useful forms of energy, such as electricity, using wind turbines. Nowadays, two kinds of wind turbines are used to transfer wind energy to electricity. Onshore wind energy is commonly used worldwide, but it takes a large land use. However, the offshore wind energy performs better than onshore energy. The higher wind speed on the sea makes the wind turbines produce more electricity. So there is an increased interest in offshore wind turbines.
Recently, wind energy has been growing faster than before in the world. Both onshore and offshore wind farms are being planed and built in the past few years. Until now the biggest offshore wind farm is Horns Rev 2 in Denmark with 209 megawatt (MW) of installated power [1].
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Abstract
Direct drive generators applied to large wind turbines present some problems, such as very heavy and expensive price. The use of magnetic bearings has a possibility to reduce the weight of the direct drive generator. The control system for such magnetic bearings is considered.
In the beginning, the thesis discusses the problems of direct drive generators in large wind turbines, introduces a hybrid concept of active magnetic bearings, gives a demonstrator of magnetic bearings used in this project, and presents a basic control system of active magnetic bearings.
For the purpose of support such magnetic bearings in wind turbines, this thesis gives a complete control system. This control system includes electrical circuits and decentralized control method. The implementation of the electrical circuits is distributed into two PCBs. The decentralized control method is designed with six PID controllers.
Finally, in order to improve the stability of the system, the H-infinity control method is suggested to magnetic bearing system in wind turbine applications.
Introduction
Wind Energy
Wind energy is a kind of renewable energy, and we have used it for hundreds of years. The kinetic energy of wind can be converted into other useful forms of energy, such as electricity, using wind turbines. Nowadays, two kinds of wind turbines are used to transfer wind energy to electricity. Onshore wind energy is commonly used worldwide, but it takes a large land use. However, the offshore wind energy performs better than onshore energy. The higher wind speed on the sea makes the wind turbines produce more electricity. So there is an increased interest in offshore wind turbines.
Recently, wind energy has been growing faster than before in the world. Both onshore and offshore wind farms are being planed and built in the past few years. Until now the biggest offshore wind farm is Horns Rev 2 in Denmark with 209 megawatt (MW) of installated power [1].
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Dynamics
Dynamics
Introduction
Each of the four labs is taught for two weeks. You will be scheduled to attend lab during one of the two weeks. The dates for your laboratory section will be posted outside room 101 Thurston. In general, you will have a lab once every three weeks, but be aware that this may vary due to exam and break schedules. (Summer session lab schedules will differ.)
See the Secretary in Kimball 212 if you have any problems with your lab schedule. You'll need to get her approval for any changes, so that the lab sections do not become overly full. Turning in a course change form to the registrar is not enough.
TURNING IN YOUR LAB REPORT
Lab reports are due one week from the day you performed the lab, at 8:00 in the morning, unless your TA specifies another time.
Turn in reports in the boxes in Don Conway room on the first floor of Thurston Hall. Be sure to put your report in the correct box corresponding to the TA in charge of your lab section.
MISSED LAB AND LATE REPORT POLICY
All make-up labs must be arranged with your TA and the Secretary, in 212 Kimball Hall. If you know in advance that you'll be gone, you should sign up with her at least one week prior to the scheduled lab. This gives you a better chance to sign up for a convenient time, and there's no point penalty. If you miss your lab without arranging a make-up lab in advance, you should still try to arrange a new time. However, a one-point lab report penalty will be imposed, unless you were ill, etc. You should arrange to make up a missed lab as soon as possible, since the lab setups are changed after a lab is finished. In special circumstances,
labs may be made up at the end of the semester; sign up with your TA and the Secretary in 212 Kimball Hall.
If you show up for lab after it is under way, your lab instructor may ask you to leave, and to perform the lab another time. The ENGRD 203 lab equipment should not be used without proper training. Note also that answers to pre-lab questions are due at the beginning of lab, and will not be accepted for credit later.
Reports turned in late will be marked down 2 points, and 4 points if they are more than a week late. Maximum late penalty is 4 points. Late reports may be handed in until one week after the last regularly scheduled lab of the semester.
Exceptions to the above policies may be made in the case of documented illness or other emergency. Talk to your lab TA about late reports; see your TA and the Secretary in 212 Kimball Hall about making up a lab.
PRE-LAB QUESTIONS
Each lab has pre-lab questions which should be answered before you come to lab. These questions encourage you to read through the laboratory procedure prior to attending the lab, and gain an understanding of what will be done during the laboratory period.
For this reason, your answers are due at the start of the lab.
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http://www.enjineer.com/forum
Introduction
Each of the four labs is taught for two weeks. You will be scheduled to attend lab during one of the two weeks. The dates for your laboratory section will be posted outside room 101 Thurston. In general, you will have a lab once every three weeks, but be aware that this may vary due to exam and break schedules. (Summer session lab schedules will differ.)
See the Secretary in Kimball 212 if you have any problems with your lab schedule. You'll need to get her approval for any changes, so that the lab sections do not become overly full. Turning in a course change form to the registrar is not enough.
TURNING IN YOUR LAB REPORT
Lab reports are due one week from the day you performed the lab, at 8:00 in the morning, unless your TA specifies another time.
Turn in reports in the boxes in Don Conway room on the first floor of Thurston Hall. Be sure to put your report in the correct box corresponding to the TA in charge of your lab section.
MISSED LAB AND LATE REPORT POLICY
All make-up labs must be arranged with your TA and the Secretary, in 212 Kimball Hall. If you know in advance that you'll be gone, you should sign up with her at least one week prior to the scheduled lab. This gives you a better chance to sign up for a convenient time, and there's no point penalty. If you miss your lab without arranging a make-up lab in advance, you should still try to arrange a new time. However, a one-point lab report penalty will be imposed, unless you were ill, etc. You should arrange to make up a missed lab as soon as possible, since the lab setups are changed after a lab is finished. In special circumstances,
labs may be made up at the end of the semester; sign up with your TA and the Secretary in 212 Kimball Hall.
If you show up for lab after it is under way, your lab instructor may ask you to leave, and to perform the lab another time. The ENGRD 203 lab equipment should not be used without proper training. Note also that answers to pre-lab questions are due at the beginning of lab, and will not be accepted for credit later.
Reports turned in late will be marked down 2 points, and 4 points if they are more than a week late. Maximum late penalty is 4 points. Late reports may be handed in until one week after the last regularly scheduled lab of the semester.
Exceptions to the above policies may be made in the case of documented illness or other emergency. Talk to your lab TA about late reports; see your TA and the Secretary in 212 Kimball Hall about making up a lab.
PRE-LAB QUESTIONS
Each lab has pre-lab questions which should be answered before you come to lab. These questions encourage you to read through the laboratory procedure prior to attending the lab, and gain an understanding of what will be done during the laboratory period.
For this reason, your answers are due at the start of the lab.
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Promoting Environmentally Sustainable Transport in the People’s Republic of China
Promoting Environmentally Sustainable Transport in the People’s Republic of China
Executive Summary
The Government of the People’s Republic of China (PRC) has recognized the extreme importance transportation plays in economic development and has promoted the rapid growth of all modes. The challenge is to decouple social progress and economic growth from unsustainable resource depletion and adverse environmental impacts.
The transport system is a major source of greenhouse gas emissions especially in the road and aviation sectors, which are also very energy intensive. Currently, 35% of the PRC’s crude oil consumption is for transport. The highway system has increased nearly 300% in 26 years, and the proportion of private passenger vehicles to total vehicles increased from 6.8% in 1980 to 78.2% in 2006. In terms of kilometers (km) traveled, air passenger traffic tripled from 68 billion passenger-km in 1995 to 237 billion in 2006. Air cargo almost quadrupled in the same period. In the past 2 years, the PRC alone accounted for more than 30% of the world’s incremental consumption of liquid fuels, and its strong growth in consumption has helped support high oil prices. Consumption is projected to grow 3.5 times over the next 30 years.
Numerous initiatives have been undertaken or proposed to reduce the negative environmental and health impacts of the current transport system. There have been significant gains with respect to specific pollutants, notably carbon monoxide and lead, thanks to regulations controlling vehicle emissions and fuel quality; nevertheless, genuine energy conservation has become an urgent task. The revised Energy Conservation Law includes measures to conserve energy in the transport sector by developing and using clean, alternative fuels and by giving incentives for the development, production, and use of alcohol, hybrid, electrical, and compressed natural gas vehicles. The Eleventh Five-Year Plan also prioritizes the development of public transportation with mass rapid transit as a key mode in megacities.
In addition to these measures, a new, target-oriented approach is needed that places energy efficiency, environment, and health at the top of the policy agenda. Environmentally sustainable transport (EST) focuses on vehicle and fuel technology and on infrastructure on the one hand, and on changes in transport activity and management including land use patterns on the other. The latter involves favoring a higher share and use of environmentally sound, healthy modes; increasing vehicle loading and occupancy; reducing the need for motorized transport; changing mobility patterns and driving behaviors; and providing information and education about the efficient use of transport. EST calls for a much greater emphasis on policies to manage transport demand than was necessary in the past.
To realize EST, six broad policy measures with specific activities are recommended: implement administrative reforms, use economic instruments to promote sustainable transport, integrate planning and optimize transportation structure, promote transport equity, promote public transportation and implement mobility management, and conserve resources and promote environmentally friendly transportation.
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Executive Summary
The Government of the People’s Republic of China (PRC) has recognized the extreme importance transportation plays in economic development and has promoted the rapid growth of all modes. The challenge is to decouple social progress and economic growth from unsustainable resource depletion and adverse environmental impacts.
The transport system is a major source of greenhouse gas emissions especially in the road and aviation sectors, which are also very energy intensive. Currently, 35% of the PRC’s crude oil consumption is for transport. The highway system has increased nearly 300% in 26 years, and the proportion of private passenger vehicles to total vehicles increased from 6.8% in 1980 to 78.2% in 2006. In terms of kilometers (km) traveled, air passenger traffic tripled from 68 billion passenger-km in 1995 to 237 billion in 2006. Air cargo almost quadrupled in the same period. In the past 2 years, the PRC alone accounted for more than 30% of the world’s incremental consumption of liquid fuels, and its strong growth in consumption has helped support high oil prices. Consumption is projected to grow 3.5 times over the next 30 years.
Numerous initiatives have been undertaken or proposed to reduce the negative environmental and health impacts of the current transport system. There have been significant gains with respect to specific pollutants, notably carbon monoxide and lead, thanks to regulations controlling vehicle emissions and fuel quality; nevertheless, genuine energy conservation has become an urgent task. The revised Energy Conservation Law includes measures to conserve energy in the transport sector by developing and using clean, alternative fuels and by giving incentives for the development, production, and use of alcohol, hybrid, electrical, and compressed natural gas vehicles. The Eleventh Five-Year Plan also prioritizes the development of public transportation with mass rapid transit as a key mode in megacities.
In addition to these measures, a new, target-oriented approach is needed that places energy efficiency, environment, and health at the top of the policy agenda. Environmentally sustainable transport (EST) focuses on vehicle and fuel technology and on infrastructure on the one hand, and on changes in transport activity and management including land use patterns on the other. The latter involves favoring a higher share and use of environmentally sound, healthy modes; increasing vehicle loading and occupancy; reducing the need for motorized transport; changing mobility patterns and driving behaviors; and providing information and education about the efficient use of transport. EST calls for a much greater emphasis on policies to manage transport demand than was necessary in the past.
To realize EST, six broad policy measures with specific activities are recommended: implement administrative reforms, use economic instruments to promote sustainable transport, integrate planning and optimize transportation structure, promote transport equity, promote public transportation and implement mobility management, and conserve resources and promote environmentally friendly transportation.
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A Social-Cognitive Framework of Multidisciplinary Team Innovation
A Social-Cognitive Framework of Multidisciplinary Team Innovation
Abstract
The psychology of science typically lacks integration between cognitive and social variables. We present a new framework of team innovation in multidisciplinary science and engineering groups that ties factors from both literatures together. We focus on the effects of a particularly challenging social factor, knowledge diversity, which has a history of mixed effects on creativity, most likely because those effects are mediated and moderated by cognitive and additional social variables. In addition, we highlight the distinction between team innovative processes that are primarily divergent versus convergent; we propose that the social and cognitive implications are different for each, providing a possible explanation for knowledge diversity’s mixed results on team outcomes. Social variables mapped out include formal roles, communication norms, sufficient participation and information sharing, and task conflict; cognitive variables include analogy, information search, and evaluation. This framework provides a roadmap for research that aims to harness the power of multidisciplinary teams.
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Abstract
The psychology of science typically lacks integration between cognitive and social variables. We present a new framework of team innovation in multidisciplinary science and engineering groups that ties factors from both literatures together. We focus on the effects of a particularly challenging social factor, knowledge diversity, which has a history of mixed effects on creativity, most likely because those effects are mediated and moderated by cognitive and additional social variables. In addition, we highlight the distinction between team innovative processes that are primarily divergent versus convergent; we propose that the social and cognitive implications are different for each, providing a possible explanation for knowledge diversity’s mixed results on team outcomes. Social variables mapped out include formal roles, communication norms, sufficient participation and information sharing, and task conflict; cognitive variables include analogy, information search, and evaluation. This framework provides a roadmap for research that aims to harness the power of multidisciplinary teams.
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Thursday, April 28, 2011
Hydraulic and Pneumatic Actuators and their Application Areas
Hydraulic and Pneumatic Actuators and their Application Areas
Abstract
Modern robotic systems are difficult. drives are a mechanical part of this systems. Three types of drives are basically used now: electric, pneumatic and hydraulic. Each type has its own advantages and disadvantages.
In this paper I’m going to tell you about pneumatic and hydraulic actuators, about their advantages and disadvantages, about their types and variants of design.
Introduction
Modern robotic systems are difficult. drives are a mechanical part of this systems. Three types of drives are basically used now: electric, pneumatic and hydraulic. Each type has its own advantages and disadvantages.
In this paper I’m going to tell you about pneumatic and hydraulic actuators, about their advantages and disadvantages, about their types and variants of design. Functional schemes of pneumatic and hydraulic drives are similar. We’ll discuss one of them.
Automatic pneumatic drive, its function scheme is shown in the fig. A, generally represents a complex of devices and consists of a source of gas energy, units of gas networks and mains (UGM), pneumatic amplifiers (PA), pneumatic engines (PE), the mechanism of transfer (MT) and directors, converting and summing device (CSD), amplifiers of capacity of electric signals (ACE), electromechanical converters (EMC), devices of feedbacks (DF), adjusting circuits (AC) and internal feedbacks (IF).
All complex of these devices is intended for amplification and transformation of a low-power input signal into mechanical moving of the target shaft of the executive mechanism.
The initial drive size of a drive is electric signal Uip of low power Nip which is corrected and amplifies with the help of additional feed energy of the capacity amplifier in the con-verting and summing device (CSD). The amplified control signal moves on electromechanical converter (EMC) that accordingly moves the managing body of pneumoamplifier (PA) on the size value z. The angle of the turn of electromechanical converter’s (EMC) axis in direct ratio corresponds to the size value z. Due to rigid mechanical connection of the axis of the torque motor with the axis of pneumatic amplifier (PA) jet tube of or with the motion of the choke, the valve or the rod of PA valve, control of the gas stream proceeding from a source of gas energy (GG), through UGM and PA in pneumatic engine (PE) is occurred. Proportinally to the value of the main signal Uip, the gas stream N0 is moved into the engine that transforms this stream into mechanical displacement of the X enging output link. For connection of the engine with loading capacity Nc stipulates the mechanism of transfer (MT) which rigidly connects the moving of the rod of the engine with the movement of the loading Yop of the working mechanism.
To increase dynamic properties and accuracy of reproduction of the input signal the au- tomated drive has feedbacks EF and DF and adjusting circuits (AC) on speed, acceleration 3and loading.
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Abstract
Modern robotic systems are difficult. drives are a mechanical part of this systems. Three types of drives are basically used now: electric, pneumatic and hydraulic. Each type has its own advantages and disadvantages.
In this paper I’m going to tell you about pneumatic and hydraulic actuators, about their advantages and disadvantages, about their types and variants of design.
Introduction
Modern robotic systems are difficult. drives are a mechanical part of this systems. Three types of drives are basically used now: electric, pneumatic and hydraulic. Each type has its own advantages and disadvantages.
In this paper I’m going to tell you about pneumatic and hydraulic actuators, about their advantages and disadvantages, about their types and variants of design. Functional schemes of pneumatic and hydraulic drives are similar. We’ll discuss one of them.
Automatic pneumatic drive, its function scheme is shown in the fig. A, generally represents a complex of devices and consists of a source of gas energy, units of gas networks and mains (UGM), pneumatic amplifiers (PA), pneumatic engines (PE), the mechanism of transfer (MT) and directors, converting and summing device (CSD), amplifiers of capacity of electric signals (ACE), electromechanical converters (EMC), devices of feedbacks (DF), adjusting circuits (AC) and internal feedbacks (IF).
All complex of these devices is intended for amplification and transformation of a low-power input signal into mechanical moving of the target shaft of the executive mechanism.
The initial drive size of a drive is electric signal Uip of low power Nip which is corrected and amplifies with the help of additional feed energy of the capacity amplifier in the con-verting and summing device (CSD). The amplified control signal moves on electromechanical converter (EMC) that accordingly moves the managing body of pneumoamplifier (PA) on the size value z. The angle of the turn of electromechanical converter’s (EMC) axis in direct ratio corresponds to the size value z. Due to rigid mechanical connection of the axis of the torque motor with the axis of pneumatic amplifier (PA) jet tube of or with the motion of the choke, the valve or the rod of PA valve, control of the gas stream proceeding from a source of gas energy (GG), through UGM and PA in pneumatic engine (PE) is occurred. Proportinally to the value of the main signal Uip, the gas stream N0 is moved into the engine that transforms this stream into mechanical displacement of the X enging output link. For connection of the engine with loading capacity Nc stipulates the mechanism of transfer (MT) which rigidly connects the moving of the rod of the engine with the movement of the loading Yop of the working mechanism.
To increase dynamic properties and accuracy of reproduction of the input signal the au- tomated drive has feedbacks EF and DF and adjusting circuits (AC) on speed, acceleration 3and loading.
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Pocket guide to tightening technique
Pocket guide to tightening technique
This booklet provides an introduction to the technique of using threaded fasteners for assembling components, the application of power tools for the assembly and the influence of tool selec- tion on the quality of the joint.
Why threaded fasteners?
There are several ways of securing parts and components to each other, e.g. gluing, riveting, welding and soldering. However, by far the most common method of joining com-ponents is to use a screw to clamp the joint members with a nut or directly to a threaded hole in one of the components. The advantages of this method are the simplicity of design and assembly, easy disassembly, productivity and in the end – cost.
The screw joint
A screw is exposed to tensile load, to torsion and sometimes also to a shear load.
The stress in the screw when the screw has been tightened to the design extent is known as the pre-stress.
The tensile load corresponds to the force that clamps the joint members together. External loads which are less than the clamping force will not change the tensile load in the screw. On the other hand, if the joint is exposed to higher external loads than the pre-stress in the bolt the joint will come apart and the tensile load in the screw will naturally increase until the screw breaks.
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This booklet provides an introduction to the technique of using threaded fasteners for assembling components, the application of power tools for the assembly and the influence of tool selec- tion on the quality of the joint.
Why threaded fasteners?
There are several ways of securing parts and components to each other, e.g. gluing, riveting, welding and soldering. However, by far the most common method of joining com-ponents is to use a screw to clamp the joint members with a nut or directly to a threaded hole in one of the components. The advantages of this method are the simplicity of design and assembly, easy disassembly, productivity and in the end – cost.
The screw joint
A screw is exposed to tensile load, to torsion and sometimes also to a shear load.
The stress in the screw when the screw has been tightened to the design extent is known as the pre-stress.
The tensile load corresponds to the force that clamps the joint members together. External loads which are less than the clamping force will not change the tensile load in the screw. On the other hand, if the joint is exposed to higher external loads than the pre-stress in the bolt the joint will come apart and the tensile load in the screw will naturally increase until the screw breaks.
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Particle swarm optimizer, ant colony strategy and harmony search scheme hybridized for optimization of truss structures
Particle swarm optimizer, ant colony strategy and harmony search scheme hybridized for optimization of truss structures
Abstract
A heuristic particle swarm ant colony optimization (HPSACO) is presented for optimum design of trusses. The algorithm is based on the particle swarm optimizer with passive congregation (PSOPC), ant colony optimization and harmony search scheme. HPSACO applies PSOPC for global optimization and the ant colony approach is used to update positions of particles to attain the feasible solution space. HPSACO handles the problem-specific constraints using a fly-back mechanism, and harmony search scheme deals with variable constraints. Results demonstrate the efficiency and robustness of HPSACO, which performs better than the other PSO-based algorithms having higher converges rate than PSO and PSOPC.
Introduction
In the last decade, many new natural evolutionary algorithms have been developed for optimization of pin-connected tructures, such as genetic algorithms (GAs) [1–5], particle swarm optimizer (PSO) [6,7], ant colony optimization (ACO) [8–10] and harmony
search (HS) [11–13]. These methods have attracted a great deal of attention, because of their high potential for modeling engineer- ing problems in environments which have been resistant to solu- tion by classic techniques. They do not require gradient information and possess better global search abilities than the con- ventional optimization algorithms [14]. Having in common pro- cesses of natural evolution, these algorithms share many similarities: each maintains a population of solutions which are evolved through random alterations and selection. The differences between these procedures lie in the representation technique uti- lized to encode the candidates, the type of alterations used to cre- ate new solutions, and the mechanism employed for selecting new patterns.
Compared to other evolutionary algorithms based on heuristics including evolutionary algorithms (EAs), evolutionary program-ming (EP) and evolution strategies (ES) [15], the advantages of PSO consist of easy implementation and smaller number of parameters to be adjusted. However, it is known that the original PSO (or SPSO) had difficulties in controlling the balance between exploration (global investigation of the search place) and exploita-tion (the fine search around a local optimum) [16]. In order to im-prove this character of PSO, it is hybridized with other approaches such as ACO or HS. PSACO (a hybrid particle swarm optimizer and ant colony approach) which was initially introduced by Shelokar et al. [17] for the solution of the continuous unconstrained prob-lems and recently utilized for truss structures [18], is applied to PSO as a global search technique and the idea of ant colony ap- proach is incorporated as a local search for updating the positions of the particles by applied pheromone-guided mechanism. HPSO (a hybrid particle swarm optimizer and harmony search scheme) was proposed by Li et al. [7] for truss design employed the har- mony memory (HM) operator for controlling the variable constraints.
The present paper hybridizes PSO, ACO and HS, and it is based on the principles of those two methods with some differences. We have applied PSOPC (a hybrid PSO with passive congregation [19]) instead of PSO to improve the performance of the new meth-od. The relation of standard deviation in ACO stage is different with that of Ref. [17], and the inertia weight is changed in PSOPC stage. New terminating criterion is employed to increase the probability of obtaining an optimum solution in a smaller number of itera- tions. In the proposed method, similar to HPSO, HS is utilized for controlling the variable constraint. The resulted method has a good control on the exploration and exploitation compared to PSO and PSOPC. It increases the exploitation, and guides the exploration, and as a result, the convergence rate of the proposed algorithm is higher than other heuristic approaches.
There are some problem-specific constraints in truss optimiza-tion problems that must be handled. The penalty function method has been the most popular constraint-handling technique due to its simple principle and ease of implementation. The main diffi-culty of the penalty function method lies in that the appropriate values of penalty factors are problem-dependent and a large amount of effort is needed for fine-tuning of the penalty factors. Therefore, several techniques have been incorporated to handle the constraints. Compared to other constraint-handling tech-niques, fly-back mechanism is relatively simple and easy to
implement into the PSO [7]. Therefore, this paper handles the problem-specific constraints by using this mechanism.
The present paper is organized as follows: In Section 2, we de-scribe the PSO, ACO and HS. Statement of the optimization design problemis formulated in Section 3. In Section 4, the fly-backmech-anism is described. In Section 5, the new method is presented. Var-ious examples are studied in Section 6. The efficiency of HPSACO is investigated in Section 7. Conclusions are derived in Section 8.
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Abstract
A heuristic particle swarm ant colony optimization (HPSACO) is presented for optimum design of trusses. The algorithm is based on the particle swarm optimizer with passive congregation (PSOPC), ant colony optimization and harmony search scheme. HPSACO applies PSOPC for global optimization and the ant colony approach is used to update positions of particles to attain the feasible solution space. HPSACO handles the problem-specific constraints using a fly-back mechanism, and harmony search scheme deals with variable constraints. Results demonstrate the efficiency and robustness of HPSACO, which performs better than the other PSO-based algorithms having higher converges rate than PSO and PSOPC.
Introduction
In the last decade, many new natural evolutionary algorithms have been developed for optimization of pin-connected tructures, such as genetic algorithms (GAs) [1–5], particle swarm optimizer (PSO) [6,7], ant colony optimization (ACO) [8–10] and harmony
search (HS) [11–13]. These methods have attracted a great deal of attention, because of their high potential for modeling engineer- ing problems in environments which have been resistant to solu- tion by classic techniques. They do not require gradient information and possess better global search abilities than the con- ventional optimization algorithms [14]. Having in common pro- cesses of natural evolution, these algorithms share many similarities: each maintains a population of solutions which are evolved through random alterations and selection. The differences between these procedures lie in the representation technique uti- lized to encode the candidates, the type of alterations used to cre- ate new solutions, and the mechanism employed for selecting new patterns.
Compared to other evolutionary algorithms based on heuristics including evolutionary algorithms (EAs), evolutionary program-ming (EP) and evolution strategies (ES) [15], the advantages of PSO consist of easy implementation and smaller number of parameters to be adjusted. However, it is known that the original PSO (or SPSO) had difficulties in controlling the balance between exploration (global investigation of the search place) and exploita-tion (the fine search around a local optimum) [16]. In order to im-prove this character of PSO, it is hybridized with other approaches such as ACO or HS. PSACO (a hybrid particle swarm optimizer and ant colony approach) which was initially introduced by Shelokar et al. [17] for the solution of the continuous unconstrained prob-lems and recently utilized for truss structures [18], is applied to PSO as a global search technique and the idea of ant colony ap- proach is incorporated as a local search for updating the positions of the particles by applied pheromone-guided mechanism. HPSO (a hybrid particle swarm optimizer and harmony search scheme) was proposed by Li et al. [7] for truss design employed the har- mony memory (HM) operator for controlling the variable constraints.
The present paper hybridizes PSO, ACO and HS, and it is based on the principles of those two methods with some differences. We have applied PSOPC (a hybrid PSO with passive congregation [19]) instead of PSO to improve the performance of the new meth-od. The relation of standard deviation in ACO stage is different with that of Ref. [17], and the inertia weight is changed in PSOPC stage. New terminating criterion is employed to increase the probability of obtaining an optimum solution in a smaller number of itera- tions. In the proposed method, similar to HPSO, HS is utilized for controlling the variable constraint. The resulted method has a good control on the exploration and exploitation compared to PSO and PSOPC. It increases the exploitation, and guides the exploration, and as a result, the convergence rate of the proposed algorithm is higher than other heuristic approaches.
There are some problem-specific constraints in truss optimiza-tion problems that must be handled. The penalty function method has been the most popular constraint-handling technique due to its simple principle and ease of implementation. The main diffi-culty of the penalty function method lies in that the appropriate values of penalty factors are problem-dependent and a large amount of effort is needed for fine-tuning of the penalty factors. Therefore, several techniques have been incorporated to handle the constraints. Compared to other constraint-handling tech-niques, fly-back mechanism is relatively simple and easy to
implement into the PSO [7]. Therefore, this paper handles the problem-specific constraints by using this mechanism.
The present paper is organized as follows: In Section 2, we de-scribe the PSO, ACO and HS. Statement of the optimization design problemis formulated in Section 3. In Section 4, the fly-backmech-anism is described. In Section 5, the new method is presented. Var-ious examples are studied in Section 6. The efficiency of HPSACO is investigated in Section 7. Conclusions are derived in Section 8.
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Optimization of multi-pass face-milling via harmony search algorithm
Optimization of multi-pass face-milling via harmony search algorithm
Abstract
This study presents a harmony search (HS) algorithm to determine the optimum cut-ting parameters for multi-pass face-milling. The optimum value of machining parameters including number of passes, depth of cut in each pass, speed and feed is obtained to min-imize total production cost while considering technological constraints such as allowable speed, feed, surface finish, tool life andmachine tool capabilities. An illustrative example is used to demonstrate the ability of the HS algorithm and for validation purpose, the genetic algorithm (GA) is used to solve the same problem. Comparison of the results reveals that the HS algorithm converges to optimum solution with higher accuracy in comparison with GA.
Introduction
The cost, time and quality of production are highly depen-dent on the cutting parameters such as the number of passes, depth of cut for each pass, speed, and feed. So, determinationof optimal cutting parameters with regard to technological equirements, capability of machine tool, cutting tool and the partmaterial is a crucial task in the process planning of parts. Several methods have been used for the optimization of cutting parameters. Feasible direction method has been used by Tolouei-Rad and Bidhendi (1997) to determine opti- mum machining parameters for milling operations. Sonmez et al. (1999) used the dynamic programming (DP) optimiza- tion method to determine the optimum cutting parameters for multi-pass milling operations like plain-milling and face- milling. The geometric programming (GP) method has been used for optimization by Sonmez et al. (1999), Jha (1990),
Petropoulos (1973) and Wang (1993). Jha (1990) has concluded that the GP-based program is very slow to produce good results. Genetic algorithm has been used by Shunmugam et al. (2000) to optimize the cutting parameters for multi-pass milling operation like plain-milling and face-milling. Wang et al. (2005) presented an approach to select the optimal machining parameters for multi-pass milling based on GA and simulated annealing (SA) to avoid the premature con-vergence of GA by exploiting the local selection strategy of SA. Baskar et al. (2006) used the memetic algorithm that is the hybrid of genetic algorithm and a hill climbing algorithm to determine the optimum cutting parameters for multi-tool milling operations like face-milling, corner milling, pocket milling and slot milling. More recently, similar hybrid appli-cation was adopted by Oktem et al. (2005), for minimization of surface roughness in milling of mold surfaces. Further-more, Bouzid (2005) employed empirical models to optimize
production rates considering tool life, roughness and cutting force whose coefficients were determined experimentally. In another investigation Manna and Salodkar (2008) employed dynamic programming in optimization of production costs of turning operations.
The main objective of this study is to optimize the total production cost inmulti-pass face-milling operation. The opti-mum number of passes and optimal values of the cutting parameters are found by harmony search algorithm which is a recently developedmeta-heuristic algorithm. An illustrative example is used to demonstrate the capability of the HS algo-rithm. For validation purpose GA is used to solve the same problem and the HS results will be compared with those of GA.
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Abstract
This study presents a harmony search (HS) algorithm to determine the optimum cut-ting parameters for multi-pass face-milling. The optimum value of machining parameters including number of passes, depth of cut in each pass, speed and feed is obtained to min-imize total production cost while considering technological constraints such as allowable speed, feed, surface finish, tool life andmachine tool capabilities. An illustrative example is used to demonstrate the ability of the HS algorithm and for validation purpose, the genetic algorithm (GA) is used to solve the same problem. Comparison of the results reveals that the HS algorithm converges to optimum solution with higher accuracy in comparison with GA.
Introduction
The cost, time and quality of production are highly depen-dent on the cutting parameters such as the number of passes, depth of cut for each pass, speed, and feed. So, determinationof optimal cutting parameters with regard to technological equirements, capability of machine tool, cutting tool and the partmaterial is a crucial task in the process planning of parts. Several methods have been used for the optimization of cutting parameters. Feasible direction method has been used by Tolouei-Rad and Bidhendi (1997) to determine opti- mum machining parameters for milling operations. Sonmez et al. (1999) used the dynamic programming (DP) optimiza- tion method to determine the optimum cutting parameters for multi-pass milling operations like plain-milling and face- milling. The geometric programming (GP) method has been used for optimization by Sonmez et al. (1999), Jha (1990),
Petropoulos (1973) and Wang (1993). Jha (1990) has concluded that the GP-based program is very slow to produce good results. Genetic algorithm has been used by Shunmugam et al. (2000) to optimize the cutting parameters for multi-pass milling operation like plain-milling and face-milling. Wang et al. (2005) presented an approach to select the optimal machining parameters for multi-pass milling based on GA and simulated annealing (SA) to avoid the premature con-vergence of GA by exploiting the local selection strategy of SA. Baskar et al. (2006) used the memetic algorithm that is the hybrid of genetic algorithm and a hill climbing algorithm to determine the optimum cutting parameters for multi-tool milling operations like face-milling, corner milling, pocket milling and slot milling. More recently, similar hybrid appli-cation was adopted by Oktem et al. (2005), for minimization of surface roughness in milling of mold surfaces. Further-more, Bouzid (2005) employed empirical models to optimize
production rates considering tool life, roughness and cutting force whose coefficients were determined experimentally. In another investigation Manna and Salodkar (2008) employed dynamic programming in optimization of production costs of turning operations.
The main objective of this study is to optimize the total production cost inmulti-pass face-milling operation. The opti-mum number of passes and optimal values of the cutting parameters are found by harmony search algorithm which is a recently developedmeta-heuristic algorithm. An illustrative example is used to demonstrate the capability of the HS algo-rithm. For validation purpose GA is used to solve the same problem and the HS results will be compared with those of GA.
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Hybridizing harmony search algorithm with sequential quadratic programming for engineering optimization problems
Hybridizing harmony search algorithm with sequential quadratic programming for engineering optimization problems
Abstract
This study presents a hybrid harmony search algorithm (HHSA) to solve engineering optimization problems with continuous design variables. Although the harmony search algorithm (HSA) has proven its ability of finding near global regions within a reasonable time, it is comparatively inefficient in performing local search. In this study sequential quadratic programming (SQP) is employed to speed up local search and improve precision of the HSA solutions. Moreover, an empirical study is performed in order to determine the impact of various parameters of the HSA on convergence behavior. Various benchmark engineering optimization problems are used to illustrate the effectiveness and robustness of the proposed algorithm. Numerical results reveal that the proposed hybrid algorithm, in most cases is more effective than the HSA and other meta-heuristic or deterministic methods.
Introduction
Evolutionary algorithms (EAs) are efficient at exploring entire search space; however, they are relatively poor at finding the precise optimum solution in the region to which the algorithm converges. Many researchers [1–3] have shown that EAs perform well for global searching due to their capability of quickly exploring and finding promising regions in the search space, but they take a relatively long time to converge to a local optimum.
On the other hand, gradient based algorithms are very effective deterministic methods in finding a stationary point near the initial starting point [1]. There exist many efficient gradient descent methods for finding local minima of a function, e.g. the steepest descent method, the Newtonmethod and the quasi Newton methods. In general, gradi-ent based algorithms converge faster and they can obtain solutions with higher accuracy compared to stochastic approaches in fulfilling the local search task. They have been used widely in a large class of problems, especially as a vial component of sophisticated algorithms. However,
these approaches often rely heavily on the initial starting point, the topology of the feasible region and the surface associated with the objective functions. A good starting point is vital for these methods to be executed successfully.
To obtain a more robust optimization technique, it is common to combine different search strategies trying to compensate deficiencies of the individual algorithms. Dur- ing the last few years, new techniques have been developed in order to improve the lack of accuracy of the EAs, using local optimization algorithms. These techniques are based on combination of local optimization procedures, which are good at finding local optima (local exploiter), and glo- bal search methods (global explorer). These are commonly known as hybrid algorithms and have been successfully used to solve a wide variety of problems [1,4] and experi-mental studies. The results show that hybrid methods search more efficiently and often find better solutions [5– 8]. A more detailed and comparative study of these hybrid methods is given at references [9,10].
To improve the efficiency of the HSA, in our previous study [11], we used dynamic parameter adjusting in impro-visation step (defined in Section 2.1.3) and discussed its impacts. The results of our work showed great improve-ment in convergence rate and quality of the HSA solutions. In this study we improve the efficiency of the HSA by incorporation of local search methods. This can be consid-ered as an innovative type of hybridization of the HSA that has not yet been explored in the literature. In particular, we investigate the possibility of the use of SQP as a local opti- mizer. Moreover, different combination strategies in hybridization which are important in computational effi- ciency of the algorithm are discussed.
In this study, first, we present a brief overview of the HSA. Since there are not any precise recommendations for tuning the HSA parameters in the literature, an empir-ical study to determine the impact of different parameters of the algorithm on the solution quality and convergence behavior is performed. Finally the proposed hybrid method is described for engineering optimization problems with continuous design variables. Various standard bench- mark engineering optimization examples including func-tion minimization problems and structural optimization problems from the literature are also presented to show the effectiveness of the HHSA.
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Abstract
This study presents a hybrid harmony search algorithm (HHSA) to solve engineering optimization problems with continuous design variables. Although the harmony search algorithm (HSA) has proven its ability of finding near global regions within a reasonable time, it is comparatively inefficient in performing local search. In this study sequential quadratic programming (SQP) is employed to speed up local search and improve precision of the HSA solutions. Moreover, an empirical study is performed in order to determine the impact of various parameters of the HSA on convergence behavior. Various benchmark engineering optimization problems are used to illustrate the effectiveness and robustness of the proposed algorithm. Numerical results reveal that the proposed hybrid algorithm, in most cases is more effective than the HSA and other meta-heuristic or deterministic methods.
Introduction
Evolutionary algorithms (EAs) are efficient at exploring entire search space; however, they are relatively poor at finding the precise optimum solution in the region to which the algorithm converges. Many researchers [1–3] have shown that EAs perform well for global searching due to their capability of quickly exploring and finding promising regions in the search space, but they take a relatively long time to converge to a local optimum.
On the other hand, gradient based algorithms are very effective deterministic methods in finding a stationary point near the initial starting point [1]. There exist many efficient gradient descent methods for finding local minima of a function, e.g. the steepest descent method, the Newtonmethod and the quasi Newton methods. In general, gradi-ent based algorithms converge faster and they can obtain solutions with higher accuracy compared to stochastic approaches in fulfilling the local search task. They have been used widely in a large class of problems, especially as a vial component of sophisticated algorithms. However,
these approaches often rely heavily on the initial starting point, the topology of the feasible region and the surface associated with the objective functions. A good starting point is vital for these methods to be executed successfully.
To obtain a more robust optimization technique, it is common to combine different search strategies trying to compensate deficiencies of the individual algorithms. Dur- ing the last few years, new techniques have been developed in order to improve the lack of accuracy of the EAs, using local optimization algorithms. These techniques are based on combination of local optimization procedures, which are good at finding local optima (local exploiter), and glo- bal search methods (global explorer). These are commonly known as hybrid algorithms and have been successfully used to solve a wide variety of problems [1,4] and experi-mental studies. The results show that hybrid methods search more efficiently and often find better solutions [5– 8]. A more detailed and comparative study of these hybrid methods is given at references [9,10].
To improve the efficiency of the HSA, in our previous study [11], we used dynamic parameter adjusting in impro-visation step (defined in Section 2.1.3) and discussed its impacts. The results of our work showed great improve-ment in convergence rate and quality of the HSA solutions. In this study we improve the efficiency of the HSA by incorporation of local search methods. This can be consid-ered as an innovative type of hybridization of the HSA that has not yet been explored in the literature. In particular, we investigate the possibility of the use of SQP as a local opti- mizer. Moreover, different combination strategies in hybridization which are important in computational effi- ciency of the algorithm are discussed.
In this study, first, we present a brief overview of the HSA. Since there are not any precise recommendations for tuning the HSA parameters in the literature, an empir-ical study to determine the impact of different parameters of the algorithm on the solution quality and convergence behavior is performed. Finally the proposed hybrid method is described for engineering optimization problems with continuous design variables. Various standard bench- mark engineering optimization examples including func-tion minimization problems and structural optimization problems from the literature are also presented to show the effectiveness of the HHSA.
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A new meta-heuristic algorithm for continuous engineering optimization: harmony search theory and practice
A new meta-heuristic algorithm for continuous engineering optimization: harmony search theory and practice
Abstract
Most engineering optimization algorithms are based on numerical linear and nonlinear programming methods that require substantial gradient information and usually seek to improve the solution in the neighborhood of a starting point. These algorithms, however, reveal a limited approach to complicated real-world optimization problems. If there is more than one local optimum in the problem, the result may depend on the selection of an initial point, and the obtained optimal solution may not necessarily be the global optimum. This paper describes a new harmony search (HS) meta-heuristic algorithm-based approach for engineering optimization problems with continuous design variables. This recently developed HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary. Various engineering optimization problems, including mathematical function minimization and structural engineering optimization problems, are presented to demonstrate the effectiveness and robustness of the HS algorithm. The results indicate that the proposed approach is a powerful search and optimization technique that may yield better solutions to engineering problems than those obtained using current algorithms. 2004 Elsevier B.V. All rights reserved.
Introduction
Over the last four decades, a large number of algorithms have been developed to solve various engineer-ing optimization problems. Most of these algorithms are based on numerical linear and nonlinear program-ming methods that require substantial gradient information and usually seek to improve the solution in the neighborhood of a starting point. These numerical ptimization algorithms provide a useful strategy to ob-tain the global optimum in simple and ideal models. Many real-world engineering optimization problems,however, are very complex in nature and quite difficult to solve using these algorithms. If there is more than one local optimum in the problem, the result may depend on the selection of an initial point, and the ob-tained optimal solution may not necessarily be the global optimum. Furthermore, the gradient search may become difficult and unstable when the objective function and constraints have multiple or sharp peaks.
The computational drawbacks of existing numerical methods have forced researchers to rely on meta-heuristic algorithms based on simulations to solve engineering optimization problems. The common factor in meta-heuristic algorithms is that they combine rules and randomness to imitate natural phenomena. These phenomena include the biological evolutionary process (e.g., the evolutionary algorithm proposed by Fogel et al. [1],DeJong [2], and Koza [3] and the genetic algorithm (GA) proposed by Holland [4] and Goldberg [5]), animal behavior (e.g., tabu search proposed by Glover [6]), and the physical annealing process (e.g., simulated annealing proposed by Kirkpatrick et al. [7]). In the last decade, these meta-heuris-tic algorithms, especially GA-based methods have been studied by many researchers to solve various engi-neering optimization problems. The GA was originally proposed by Holland [4] and further developed by Goldberg [5] and by others. It is a global search algorithm that is based on concepts from natural genetics and the Darwinian survival-of-the-fittest code. Meta-heuristic algorithm-based engineering optimization methods, including GA-based methods, have occasionally overcome several deficiencies of conventional numerical methods. To solve difficult and complicated real-world optimization problems, however, new heuristic and more powerful algorithms based on analogies with natural or artificial phenomena must be explored.
Recently, Geem et al. [8] developed a new harmony search (HS) meta-heuristic algorithm that was con-ceptualized using the musical process of searching for a perfect state of harmony. The harmony in music is analogous to the optimization solution vector, and the musician s improvisations are analogous to local and global search schemes in optimization techniques. The HS algorithm does not require initial values for the decision variables. Furthermore, instead of a gradient search, the HS algorithm uses a stochastic random search that is based on the harmony memory considering rate and the pitch adjusting rate (defined
in harmony search meta-heuristic algorithm section) so that derivative information is unnecessary. Com-pared to earlier meta-heuristic optimization algorithms, the HS algorithm imposes fewer mathematical requirements and can be easily adopted for various types of engineering optimization problems.
In this study, we describe a brief overview of existing meta-heuristic algorithms and a new HS meta-heu-ristic algorithm-based approach for engineering optimization problems with continuous design variables. Various standard benchmark engineering optimization examples including function minimization problems and structural optimization problems from the literature are also presented to demonstrate the effectiveness and robustness of the HS meta-heuristic algorithm method.
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Abstract
Most engineering optimization algorithms are based on numerical linear and nonlinear programming methods that require substantial gradient information and usually seek to improve the solution in the neighborhood of a starting point. These algorithms, however, reveal a limited approach to complicated real-world optimization problems. If there is more than one local optimum in the problem, the result may depend on the selection of an initial point, and the obtained optimal solution may not necessarily be the global optimum. This paper describes a new harmony search (HS) meta-heuristic algorithm-based approach for engineering optimization problems with continuous design variables. This recently developed HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary. Various engineering optimization problems, including mathematical function minimization and structural engineering optimization problems, are presented to demonstrate the effectiveness and robustness of the HS algorithm. The results indicate that the proposed approach is a powerful search and optimization technique that may yield better solutions to engineering problems than those obtained using current algorithms. 2004 Elsevier B.V. All rights reserved.
Introduction
Over the last four decades, a large number of algorithms have been developed to solve various engineer-ing optimization problems. Most of these algorithms are based on numerical linear and nonlinear program-ming methods that require substantial gradient information and usually seek to improve the solution in the neighborhood of a starting point. These numerical ptimization algorithms provide a useful strategy to ob-tain the global optimum in simple and ideal models. Many real-world engineering optimization problems,however, are very complex in nature and quite difficult to solve using these algorithms. If there is more than one local optimum in the problem, the result may depend on the selection of an initial point, and the ob-tained optimal solution may not necessarily be the global optimum. Furthermore, the gradient search may become difficult and unstable when the objective function and constraints have multiple or sharp peaks.
The computational drawbacks of existing numerical methods have forced researchers to rely on meta-heuristic algorithms based on simulations to solve engineering optimization problems. The common factor in meta-heuristic algorithms is that they combine rules and randomness to imitate natural phenomena. These phenomena include the biological evolutionary process (e.g., the evolutionary algorithm proposed by Fogel et al. [1],DeJong [2], and Koza [3] and the genetic algorithm (GA) proposed by Holland [4] and Goldberg [5]), animal behavior (e.g., tabu search proposed by Glover [6]), and the physical annealing process (e.g., simulated annealing proposed by Kirkpatrick et al. [7]). In the last decade, these meta-heuris-tic algorithms, especially GA-based methods have been studied by many researchers to solve various engi-neering optimization problems. The GA was originally proposed by Holland [4] and further developed by Goldberg [5] and by others. It is a global search algorithm that is based on concepts from natural genetics and the Darwinian survival-of-the-fittest code. Meta-heuristic algorithm-based engineering optimization methods, including GA-based methods, have occasionally overcome several deficiencies of conventional numerical methods. To solve difficult and complicated real-world optimization problems, however, new heuristic and more powerful algorithms based on analogies with natural or artificial phenomena must be explored.
Recently, Geem et al. [8] developed a new harmony search (HS) meta-heuristic algorithm that was con-ceptualized using the musical process of searching for a perfect state of harmony. The harmony in music is analogous to the optimization solution vector, and the musician s improvisations are analogous to local and global search schemes in optimization techniques. The HS algorithm does not require initial values for the decision variables. Furthermore, instead of a gradient search, the HS algorithm uses a stochastic random search that is based on the harmony memory considering rate and the pitch adjusting rate (defined
in harmony search meta-heuristic algorithm section) so that derivative information is unnecessary. Com-pared to earlier meta-heuristic optimization algorithms, the HS algorithm imposes fewer mathematical requirements and can be easily adopted for various types of engineering optimization problems.
In this study, we describe a brief overview of existing meta-heuristic algorithms and a new HS meta-heu-ristic algorithm-based approach for engineering optimization problems with continuous design variables. Various standard benchmark engineering optimization examples including function minimization problems and structural optimization problems from the literature are also presented to demonstrate the effectiveness and robustness of the HS meta-heuristic algorithm method.
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Optical properties of plastics and their role for the modelling of the laser transmission welding process
Optical properties of plastics and their role for the modelling of the laser transmission welding process
Abstract
Laser transmission welding of plastics is a joining technique which permits the welding of plastic parts with low process inherent thermal and mechanical stresses. In order to compute the temperature fields during the welding process a simulation model of the process is established. Especially the optical and thermal properties of the welded materials are necessary as input parameters in order to model the process properly. While the thermal properties of polymers are well-investigated, there is little knowledge about the optical properties of plastics. The optical properties of different amorphous and semi-crys-talline thermoplastics are therefore investigated in dependence on material temperature and additive concen-tration. Based on these data it is possible to analytically describe the absorption of laser energy in plastics. The computation of temperature fields during welding is carried out for polypropylene and the results are then compared with experimentally accomplished welding tests. The calculated results show good accordance with the experi-mentally determined melt pool geometries of welded specimens and prove the compatibility of the computation model with the experimental analysis.
Introduction
There are a number of established welding processes for joining plastics, such as vibration welding, ultrasonic welding or hot plate welding [1–3]. Another process has increasingly been gaining in importance over the last years: laser transmission welding. One apparent advantage of this process is that the transmission of energy can be achieved without contact by means of laser radiation. It is advisable to use this process, when there must not be any welding debris, the optical requirements towards the weld seam are very high or if three-dimensional weld seams cannot be avoided. The spectrum for application of laser plastic welding ranges from thin-walled and filigree components, like foils or membranes, for instance, to large thick-walled components from thermoplastics or thermoplastic elasto-mers. One major application area is joining of housings in all sizes for temperature or vibration sensitive parts, such as electronic components. The mechanical and thermal load on the components inside the housing is very low during laser welding. At the same time, the quality of the weld seam is very good and it resists high temperatures and aggressive ambient media. Laser plastic welding is there-fore a frequently applied process in this area [4].
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Abstract
Laser transmission welding of plastics is a joining technique which permits the welding of plastic parts with low process inherent thermal and mechanical stresses. In order to compute the temperature fields during the welding process a simulation model of the process is established. Especially the optical and thermal properties of the welded materials are necessary as input parameters in order to model the process properly. While the thermal properties of polymers are well-investigated, there is little knowledge about the optical properties of plastics. The optical properties of different amorphous and semi-crys-talline thermoplastics are therefore investigated in dependence on material temperature and additive concen-tration. Based on these data it is possible to analytically describe the absorption of laser energy in plastics. The computation of temperature fields during welding is carried out for polypropylene and the results are then compared with experimentally accomplished welding tests. The calculated results show good accordance with the experi-mentally determined melt pool geometries of welded specimens and prove the compatibility of the computation model with the experimental analysis.
Introduction
There are a number of established welding processes for joining plastics, such as vibration welding, ultrasonic welding or hot plate welding [1–3]. Another process has increasingly been gaining in importance over the last years: laser transmission welding. One apparent advantage of this process is that the transmission of energy can be achieved without contact by means of laser radiation. It is advisable to use this process, when there must not be any welding debris, the optical requirements towards the weld seam are very high or if three-dimensional weld seams cannot be avoided. The spectrum for application of laser plastic welding ranges from thin-walled and filigree components, like foils or membranes, for instance, to large thick-walled components from thermoplastics or thermoplastic elasto-mers. One major application area is joining of housings in all sizes for temperature or vibration sensitive parts, such as electronic components. The mechanical and thermal load on the components inside the housing is very low during laser welding. At the same time, the quality of the weld seam is very good and it resists high temperatures and aggressive ambient media. Laser plastic welding is there-fore a frequently applied process in this area [4].
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New Approach to Turbocharger Optimization Using 1-D Simulation Tools
New Approach to Turbocharger Optimization Using 1-D Simulation Tools
ABSTRACT
The paper deals with the investigation of turbocharger op-timization procedures using amended 1-D simulation tools. The proposed method uses scaled flow rate/effficiency maps for different sizes of a radial turbine together with a fictitious compressor map. The compressor pressure ra-tio/efficiency map depends on compressor circumference velocity only and predicts the both compressor specific power and achievable efficiency. At the first stage of opti- mization, it avoids the problems of reaching choking/surge limits. It enables the designer to find a suitable turbine type under realistic unsteady conditions (pressure pulses in exhaust manifold) concerning turbine flow area. Once the optimization of turbine/compressor impeller diameters is finished, the specific compressor map is selected.
The proposed method provides the fast way to the best solution even for the case of a VGT turbine. Additional fea-tures have been developed for the representation of scaled turbine and compressor maps. They are based on appli-cation of versatile regression functions. No recalculation of normalized curves is needed.
The method is presented for the model of a one-loop hot gas stand (steady performance compressor/turbine opti- mization) and for a modelled engine with different com- pressors. The potential of optimized turbocharger is evalu- ated at simulated typical operation points for a passenger car equipped with a 4-cylinder 2 dm3 engine.
INTRODUCTION
The current development of downsized, turbocharged en-gines calls for mastering more effective approach in find-ing an optimal turbocharger or two-stage system of tur-bocharging. The widely used trial-and-error method using a collection of turbocharger maps is not an ideal one be- cause of non-transparent results. It does not provide hints for turbocharger amendment.
The presented procedure of finding optimal turbocharger for an engine is based on authors’ experience with turbo-matching (e.g., 0-D code [4]). An application of the pro-cedure is relatively fast and allows for finding suitable tur-bocharger without a need to calculate all feasible combi-nations of turbine and compressor maps provided by tur-bocharger manufacturers. The paper deals with one of the possible ways, using a 1-D model of turbine [6], amended by a compressor map extrapolation and combined with a 1-D engine simulation package [1]. The main problems are listed in the following section, the newly developed tools are described and finally some results of turbocharger op-timization are commented on.
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ABSTRACT
The paper deals with the investigation of turbocharger op-timization procedures using amended 1-D simulation tools. The proposed method uses scaled flow rate/effficiency maps for different sizes of a radial turbine together with a fictitious compressor map. The compressor pressure ra-tio/efficiency map depends on compressor circumference velocity only and predicts the both compressor specific power and achievable efficiency. At the first stage of opti- mization, it avoids the problems of reaching choking/surge limits. It enables the designer to find a suitable turbine type under realistic unsteady conditions (pressure pulses in exhaust manifold) concerning turbine flow area. Once the optimization of turbine/compressor impeller diameters is finished, the specific compressor map is selected.
The proposed method provides the fast way to the best solution even for the case of a VGT turbine. Additional fea-tures have been developed for the representation of scaled turbine and compressor maps. They are based on appli-cation of versatile regression functions. No recalculation of normalized curves is needed.
The method is presented for the model of a one-loop hot gas stand (steady performance compressor/turbine opti- mization) and for a modelled engine with different com- pressors. The potential of optimized turbocharger is evalu- ated at simulated typical operation points for a passenger car equipped with a 4-cylinder 2 dm3 engine.
INTRODUCTION
The current development of downsized, turbocharged en-gines calls for mastering more effective approach in find-ing an optimal turbocharger or two-stage system of tur-bocharging. The widely used trial-and-error method using a collection of turbocharger maps is not an ideal one be- cause of non-transparent results. It does not provide hints for turbocharger amendment.
The presented procedure of finding optimal turbocharger for an engine is based on authors’ experience with turbo-matching (e.g., 0-D code [4]). An application of the pro-cedure is relatively fast and allows for finding suitable tur-bocharger without a need to calculate all feasible combi-nations of turbine and compressor maps provided by tur-bocharger manufacturers. The paper deals with one of the possible ways, using a 1-D model of turbine [6], amended by a compressor map extrapolation and combined with a 1-D engine simulation package [1]. The main problems are listed in the following section, the newly developed tools are described and finally some results of turbocharger op-timization are commented on.
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Maximum Power Point Tracking Control Scheme for Grid Connected Variable Speed Wind Driven Self-Excited Induction Generator
Maximum Power Point Tracking Control Scheme for Grid Connected Variable Speed Wind Driven Self-Excited Induction Generator
ABSTRACT
This paper proposes a wind energy conversion system connected to a grid using a self-excited induction generator (SEIG) based on the maximum power point tracking (MPPT) control scheme. The induction generator (IG) is controlled by the MPPT below the base speed and the maximum energy can be captured from the wind turbine. Therefore, the stator currents of the IG are optimally controlled using the indirect field orientation control (IFOC) according to the generator speed in order to maximize the generated power from the wind turbine. The SEIG feeds a (CRPWM) converter which regulates the DC-link voltage at a constant value where the speed of the IG is varied. Based on the IG d-q axes dynamic model in the synchronous reference frame at field orientation, high-performance synchronous current controllers with satisfactory performance are designed and analyzed. Utilizing these current controllers and IFOC, a fast dynamic response and low current harmonic distortion are attained. The regulated DC-link voltage feeds a grid connected CRPWM inverter. By using the virtual flux orientation control and the synchronous frame current regulators for the grid connected CRPWM inverter, a fast current response, low harmonic distortion and unity power factor are achieved. The complete system has been simulated with different wind velocities. The simulation results are presented to illustrate the effectiveness of the proposed MPPT control scheme for a wind energy system. In the simulation results, the d-q axes current controllers and DC-link voltage controller give prominent dynamic response in command tracking and load regulation characteristics.
Introduction
Recently, the wind generation system is attracting attention as a clean and safe renewable power source. Induction machines have many advantageous characteristics such as high robustness, reliability and low cost. Therefore, induction machines are used in high-performance applications, which require independent torque and flux control. The induction machines may be used as a motor or a generator. Self-excited induction generators (SEIG) are good candidates for wind-power electricity generation especially in remote areas, because they do not need an external power supplies to produce the excitation magnetic fields [1-3] The excitation can be provided by a capacitor bank connected to the stator windings of the induction generator. Magnetizing inductance is the main factor for voltage build-up of the IG. The minimum and maximum values of capacitance required for self-excitation have been analyzed previously [4-7].
The three phase current regulated pulse-width modulation (CRPWM) AC/DC/AC converters have been increasingly used for wind energy system applications. Their attractive features include: regulated DC-link voltage, low harmonic distortion of the induction generator currents and controllable power factor and efficiency [8-9]. The current regulation of a SEIG in the synchronous frame has the advantages of fast dynamic current response, good accuracy, constant switching frequency and less sensitivity to parameter variations.
In wind generation systems, a variable speed generation system is more attractive than a fixed speed one because of the improvement in the wind energy production. In a variable speed system, wind turbine can be operated to produce its maximum power at every wind speed by adjusting the shaft speed optimally. In order to achieve the maximum power point tracking (MPPT) control, some control schemes have been studied. For example, a search-based or perturbation-based strategy [10,11] , a fuzzy- logic based control [12,13], a wind speed-estimation-based algorithm [14] has been applied.
In this paper, a variable speed high performance generation system using a SIEG is studied. The requirements of high dynamic performance is gained utilizing filed-oriented control (FOC) in which the dynamic model of the induction generator is simplified and decoupled. The FOC strategy studied in this context was developed by Hass and Blashke in Germany some thirty years ago. This technique improves the performance of the induction generator to a level comparable to that of a separately excited DC generator. Therefore, the FOC of an induction generator system permits a high performance dynamic response using decoupled torque and flux control. The FOC strategy can be classified into two types, the direct filed orientation control (DFOC) and indirect filed orientation control (IFOC). The IFOC strategy is simpler than the DFOC strategy. The orientation technique may be done for rotor or stator and/or air-gap flux. The rotor flux orientation is the best one because there is a linear relationbetween the electromagnetic torque and the stator torque current of the induction generator. Some control schemes have been studied using DFOC [15,16] and IFOC with stator flux orientation [17].
The IFOC of the SEIG for the WECS is composed of a dynamic model of the wind turbine, a dynamic model of the IG in the arbitrary and synchronously rotating reference frames, a dynamic model of the IFOC technique (decoupling controller), d-q axes current controllers, a voltage controller, coordinate transformations, a space- vector PWM (SVPWM) and AC/DC/AC CRPWM converters as shown in Fig. 1.
In the proposed wind generation system, the control scheme is based on the MPPT technique. The IFOC technique with the rotor flux of a SEIG is used for controlling the CRPWM converter while the grid connected CRPWM inverter is controlled utilizing the vector control technique. The current vector of the SEIG is suitably controlled according to the IG speed in order to optimize the wind turbine operation for various wind speeds. The IFOC of the SEIG allows for control of the d-q stator currents. So, the output voltage of the CRPWM converter can be regulated and we can maximize the efficiency. In the proposed control scheme with the IFOC of the SEIG, a dynamic model of the induction generator in d-q axes arbitrary reference frame is carried out. At field orientation control (FOC), λqr=0, dλqr/dt=0, dλdr/dt=0, and ωm=ωe, the IFOC is derived in the synchronous reference frame. Based on the transfer function of the IG at FOC, the proportional plus integral (PI) current controllers in the d-q axes are designed and analyzed to meet the time domain specifications: minimum overshot, minimum settling time and minimum steady-state error. After that, a PI voltage controller is designed to accomplish the specifications of the voltage control loop based on the dynamic of the DC-link and the SEIG. Also, this paper studies the design and control of the grid connected CRPWM inverter with the MPPT algorithm and unity power factor. Similarly, by applying the vector control technique to the grid connected CRPWM inverter, we can deduce the transfer function of the inverter with the grid at virtual-flux orientation control (VFOC) and the design of the d-q axes current controllers are accomplished. To verify the design of the controllers and system performance, the WECS is simulated starting with the wind turbine, the SEIG and then the AC/DC/AC CRPWM converter. The dynamic performance of the WECS has been studied under different wind velocities and MPPT. The simulation results are provided to demonstrate the effectiveness of the proposed control scheme.
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ABSTRACT
This paper proposes a wind energy conversion system connected to a grid using a self-excited induction generator (SEIG) based on the maximum power point tracking (MPPT) control scheme. The induction generator (IG) is controlled by the MPPT below the base speed and the maximum energy can be captured from the wind turbine. Therefore, the stator currents of the IG are optimally controlled using the indirect field orientation control (IFOC) according to the generator speed in order to maximize the generated power from the wind turbine. The SEIG feeds a (CRPWM) converter which regulates the DC-link voltage at a constant value where the speed of the IG is varied. Based on the IG d-q axes dynamic model in the synchronous reference frame at field orientation, high-performance synchronous current controllers with satisfactory performance are designed and analyzed. Utilizing these current controllers and IFOC, a fast dynamic response and low current harmonic distortion are attained. The regulated DC-link voltage feeds a grid connected CRPWM inverter. By using the virtual flux orientation control and the synchronous frame current regulators for the grid connected CRPWM inverter, a fast current response, low harmonic distortion and unity power factor are achieved. The complete system has been simulated with different wind velocities. The simulation results are presented to illustrate the effectiveness of the proposed MPPT control scheme for a wind energy system. In the simulation results, the d-q axes current controllers and DC-link voltage controller give prominent dynamic response in command tracking and load regulation characteristics.
Introduction
Recently, the wind generation system is attracting attention as a clean and safe renewable power source. Induction machines have many advantageous characteristics such as high robustness, reliability and low cost. Therefore, induction machines are used in high-performance applications, which require independent torque and flux control. The induction machines may be used as a motor or a generator. Self-excited induction generators (SEIG) are good candidates for wind-power electricity generation especially in remote areas, because they do not need an external power supplies to produce the excitation magnetic fields [1-3] The excitation can be provided by a capacitor bank connected to the stator windings of the induction generator. Magnetizing inductance is the main factor for voltage build-up of the IG. The minimum and maximum values of capacitance required for self-excitation have been analyzed previously [4-7].
The three phase current regulated pulse-width modulation (CRPWM) AC/DC/AC converters have been increasingly used for wind energy system applications. Their attractive features include: regulated DC-link voltage, low harmonic distortion of the induction generator currents and controllable power factor and efficiency [8-9]. The current regulation of a SEIG in the synchronous frame has the advantages of fast dynamic current response, good accuracy, constant switching frequency and less sensitivity to parameter variations.
In wind generation systems, a variable speed generation system is more attractive than a fixed speed one because of the improvement in the wind energy production. In a variable speed system, wind turbine can be operated to produce its maximum power at every wind speed by adjusting the shaft speed optimally. In order to achieve the maximum power point tracking (MPPT) control, some control schemes have been studied. For example, a search-based or perturbation-based strategy [10,11] , a fuzzy- logic based control [12,13], a wind speed-estimation-based algorithm [14] has been applied.
In this paper, a variable speed high performance generation system using a SIEG is studied. The requirements of high dynamic performance is gained utilizing filed-oriented control (FOC) in which the dynamic model of the induction generator is simplified and decoupled. The FOC strategy studied in this context was developed by Hass and Blashke in Germany some thirty years ago. This technique improves the performance of the induction generator to a level comparable to that of a separately excited DC generator. Therefore, the FOC of an induction generator system permits a high performance dynamic response using decoupled torque and flux control. The FOC strategy can be classified into two types, the direct filed orientation control (DFOC) and indirect filed orientation control (IFOC). The IFOC strategy is simpler than the DFOC strategy. The orientation technique may be done for rotor or stator and/or air-gap flux. The rotor flux orientation is the best one because there is a linear relationbetween the electromagnetic torque and the stator torque current of the induction generator. Some control schemes have been studied using DFOC [15,16] and IFOC with stator flux orientation [17].
The IFOC of the SEIG for the WECS is composed of a dynamic model of the wind turbine, a dynamic model of the IG in the arbitrary and synchronously rotating reference frames, a dynamic model of the IFOC technique (decoupling controller), d-q axes current controllers, a voltage controller, coordinate transformations, a space- vector PWM (SVPWM) and AC/DC/AC CRPWM converters as shown in Fig. 1.
In the proposed wind generation system, the control scheme is based on the MPPT technique. The IFOC technique with the rotor flux of a SEIG is used for controlling the CRPWM converter while the grid connected CRPWM inverter is controlled utilizing the vector control technique. The current vector of the SEIG is suitably controlled according to the IG speed in order to optimize the wind turbine operation for various wind speeds. The IFOC of the SEIG allows for control of the d-q stator currents. So, the output voltage of the CRPWM converter can be regulated and we can maximize the efficiency. In the proposed control scheme with the IFOC of the SEIG, a dynamic model of the induction generator in d-q axes arbitrary reference frame is carried out. At field orientation control (FOC), λqr=0, dλqr/dt=0, dλdr/dt=0, and ωm=ωe, the IFOC is derived in the synchronous reference frame. Based on the transfer function of the IG at FOC, the proportional plus integral (PI) current controllers in the d-q axes are designed and analyzed to meet the time domain specifications: minimum overshot, minimum settling time and minimum steady-state error. After that, a PI voltage controller is designed to accomplish the specifications of the voltage control loop based on the dynamic of the DC-link and the SEIG. Also, this paper studies the design and control of the grid connected CRPWM inverter with the MPPT algorithm and unity power factor. Similarly, by applying the vector control technique to the grid connected CRPWM inverter, we can deduce the transfer function of the inverter with the grid at virtual-flux orientation control (VFOC) and the design of the d-q axes current controllers are accomplished. To verify the design of the controllers and system performance, the WECS is simulated starting with the wind turbine, the SEIG and then the AC/DC/AC CRPWM converter. The dynamic performance of the WECS has been studied under different wind velocities and MPPT. The simulation results are provided to demonstrate the effectiveness of the proposed control scheme.
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Micro Machining of Injection Mold Inserts for Fluidic Channel of Polymeric Biochips
Micro Machining of Injection Mold Inserts for Fluidic Channel of Polymeric Biochips
Abstract
Recently, the polymeric micro-fluidic biochip, often called LOC (lab-on-a-chip), has been focused as a cheap, rapid and simplified method to replace the existing biochemical laboratory works. It becomes possible to form miniaturized lab functionalities on a chip with the development of MEMS technologies. The micro-fluidic chips contain many micro-channels for the flow of sample and reagents, mixing, and detection tasks. Typical substrate materials for the chip are glass and polymers. Typical techniques for micro-fluidic chip fabrication are utilizing various micro pattern forming methods, such as wet-etching, micro-contact printing, and hot-embossing, micro injection molding, LIGA, and micro powder blasting processes, etc. In this study, to establish the basis of the micro pattern fabrication and mass production of polymeric micro-fluidic chips using injection molding process, micro machining method was applied to form micro-channels on the LOC molds. In the research, a series of machining experiments using micro end-mills were performed to determine optimum machining conditions to improve surface roughness and shape accuracy of designed simplified micro-channels. Obtained conditions were used to machine required mold inserts for micro-channels using micro end-mills. Test injection processes using machined molds and COC polymer were performed, and then the results were investigated.
Introduction
Recently, with the development of MEMS (micro electro-mechanical system) technologies, conventional biotechnological analytical processes can be rapidly performed using miniaturized biochips. Typical biochips can be categorized into two groups; micro-array and micro-fluidic chips. The micro-array has an array of miniaturized test sites on a chip. The number of micro-arrays varies from a hundred to a few thousand; and the typical size of the test sites ranges from 10 to 500µm. Because the micro-fluidic chip can perform multiple tasks in a typical biochemical analysis laboratory, such as mixing, reaction, separation, and detection, etc., it is often called as LOC (lab-on-a-chip) or µTAS (micro total analysis system).[1,2] Advantages of the LOC are; (1) required time for analysis is much shorter, (2) very small amount of specimen and reagent are required, (3) low cost, high analysis accuracy, low contamination, and easy to use, etc. Thus, the micro-fluidic chips have been focused as a leading technology in related fields.[3-6] Unlike the micro-array, the micro-fluidic chip contains many micro-channels to connect the unit tasks for consecutive processing steps.[1] The continuous flow of input test samples and reagents through the micro-channels can make the analytical process to be performed on a chip by minimizing sample contamination and processing time. Typical substrate materials for micro-fluidic chip fabrication are glasses (such as fused silica glass, etc.) or polymers (such as PDMS (polydimethyl siloxane), PMMA (polymethyl metacrylate), COC (cyclic olefin copolymer) etc.). The substrates for micro-fluidic chips should be biocompatible since most of they are used for biological analysis. Besides, various material properties such as mechanical strength, porosity, and hydrophobicity, etc., are required for real application. Fabrication procedures of such substrate depend on the used material and complexity of the chip. Typical technique for micro-fluidic chip fabrication is based on the soft lithography, such as wet-etching, micro-contact printing, and hot-embossing, micro injection molding, etc.[2-5] Also, LIGA and micro powder blasting processes are applied to form required micro-channels on the biochips.[7] Several studies were performed to replicate microchips using metal mold masters which were prepared by CNC micro-milling processes. [8-11] In the studies, brass [7] and aluminum masters [9-11] with micro-channels were machined to replicate PMMA and thermosetting resin by hot embossing.
In this study, to establish the basis of the micro pattern fabrication and mass production of polymeric micro-fluidic chips using injection molding process, micro machining method was applied to form micro-channels on the LOC molds. As a first step, simplified micro-channels were designed based on existing research results. Then, a series of machining experiments using micro end-mills were performed to determine optimum machining conditions to improve better surface roughness and shape accuracy. Obtained conditions were used to machine required mold inserts for micro-channels using micro end-mills of 400µm diameter. Finally, test injection processes using machined molds and COC polymer were performed, and the results were investigated. As the results, it can be observed that the required micro-fluidic chips can be obtained using injection molding process.
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Abstract
Recently, the polymeric micro-fluidic biochip, often called LOC (lab-on-a-chip), has been focused as a cheap, rapid and simplified method to replace the existing biochemical laboratory works. It becomes possible to form miniaturized lab functionalities on a chip with the development of MEMS technologies. The micro-fluidic chips contain many micro-channels for the flow of sample and reagents, mixing, and detection tasks. Typical substrate materials for the chip are glass and polymers. Typical techniques for micro-fluidic chip fabrication are utilizing various micro pattern forming methods, such as wet-etching, micro-contact printing, and hot-embossing, micro injection molding, LIGA, and micro powder blasting processes, etc. In this study, to establish the basis of the micro pattern fabrication and mass production of polymeric micro-fluidic chips using injection molding process, micro machining method was applied to form micro-channels on the LOC molds. In the research, a series of machining experiments using micro end-mills were performed to determine optimum machining conditions to improve surface roughness and shape accuracy of designed simplified micro-channels. Obtained conditions were used to machine required mold inserts for micro-channels using micro end-mills. Test injection processes using machined molds and COC polymer were performed, and then the results were investigated.
Introduction
Recently, with the development of MEMS (micro electro-mechanical system) technologies, conventional biotechnological analytical processes can be rapidly performed using miniaturized biochips. Typical biochips can be categorized into two groups; micro-array and micro-fluidic chips. The micro-array has an array of miniaturized test sites on a chip. The number of micro-arrays varies from a hundred to a few thousand; and the typical size of the test sites ranges from 10 to 500µm. Because the micro-fluidic chip can perform multiple tasks in a typical biochemical analysis laboratory, such as mixing, reaction, separation, and detection, etc., it is often called as LOC (lab-on-a-chip) or µTAS (micro total analysis system).[1,2] Advantages of the LOC are; (1) required time for analysis is much shorter, (2) very small amount of specimen and reagent are required, (3) low cost, high analysis accuracy, low contamination, and easy to use, etc. Thus, the micro-fluidic chips have been focused as a leading technology in related fields.[3-6] Unlike the micro-array, the micro-fluidic chip contains many micro-channels to connect the unit tasks for consecutive processing steps.[1] The continuous flow of input test samples and reagents through the micro-channels can make the analytical process to be performed on a chip by minimizing sample contamination and processing time. Typical substrate materials for micro-fluidic chip fabrication are glasses (such as fused silica glass, etc.) or polymers (such as PDMS (polydimethyl siloxane), PMMA (polymethyl metacrylate), COC (cyclic olefin copolymer) etc.). The substrates for micro-fluidic chips should be biocompatible since most of they are used for biological analysis. Besides, various material properties such as mechanical strength, porosity, and hydrophobicity, etc., are required for real application. Fabrication procedures of such substrate depend on the used material and complexity of the chip. Typical technique for micro-fluidic chip fabrication is based on the soft lithography, such as wet-etching, micro-contact printing, and hot-embossing, micro injection molding, etc.[2-5] Also, LIGA and micro powder blasting processes are applied to form required micro-channels on the biochips.[7] Several studies were performed to replicate microchips using metal mold masters which were prepared by CNC micro-milling processes. [8-11] In the studies, brass [7] and aluminum masters [9-11] with micro-channels were machined to replicate PMMA and thermosetting resin by hot embossing.
In this study, to establish the basis of the micro pattern fabrication and mass production of polymeric micro-fluidic chips using injection molding process, micro machining method was applied to form micro-channels on the LOC molds. As a first step, simplified micro-channels were designed based on existing research results. Then, a series of machining experiments using micro end-mills were performed to determine optimum machining conditions to improve better surface roughness and shape accuracy. Obtained conditions were used to machine required mold inserts for micro-channels using micro end-mills of 400µm diameter. Finally, test injection processes using machined molds and COC polymer were performed, and the results were investigated. As the results, it can be observed that the required micro-fluidic chips can be obtained using injection molding process.
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Wednesday, April 27, 2011
Hydraulic Power Steering System Design and Optimization Simulation
Hydraulic Power Steering System Design and Optimization Simulation
ABSTRACT
Hydraulic rack and pinion power steering system is a high bandwidth servo with stringent performance requirements on accuracy, reliability, and cost. Design of such a system can be best achieved by using a validated and user friendly computer simulation program. Hydraulic integrated power steering ( HIPS ) program has been developed using basic concepts from science and engineering. HIPS provides a design and test environment for the integrated steering and suspension system subjected to disturbance forces, which may be induced by pump flow oscillations and tire loads. Two real-world automotive hydraulic steering systems are simulated with HIPS. The simulation results agree closely with the dynamometer test results. The application of HIPS for design optimization is also demonstrated.
INTRODUCTION
Figure 1 shows a hydraulic rack and pinion power steering system, which is a high bandwidth nonlinear servo capable of generating a rack force of 4,000 N for cars and 6,000 N for small trucks. About 80% of the rack force comes from hydraulic power assist and the remaining 20% comes from driver’s effort. At on-center position of the steering wheel, a vane pump, which is driven by the engine, circulates the fluid in a closed -loop hydraulic circuit which includes a reservoir, vane pump with flow control and pressure relief, supply and return lines, and the rotary spool valve ( RSV ). The flow control valve which connects the discharge and inlet manifolds of the vane pump, regulates the pump flow rate into the supply line at 2.1 gpm for cars and 3.5 gpm for small trucks, for engine speeds above 900 rpm. When the steering wheel is turned by the driver, RSV diverts the supply line fluid flow to either side of the power piston for a right or left turn of the vehicle. At the same time, RSV passes an equal amount of fluid flow from the other side of the power piston through the return line to the reservoir.
This increases the differential pressure acting on the power piston and yields the desirable hydraulic power assist force. An optional speed sensitive steering controller modulates the fluid flow rate drawn by the RSV from the supply line, using signals from wheel speed sensors and wheel torque sensor. The driver’s steering effort is increased by lowering the hydraulic power assist during highway driving, hence improving driver’s feel of the road during city and highway driving. The steering torque is obtained when the rack force is applied to an off-center joint on the knuckle, which turns about the kingpin at the suspension strut, including a coil spring and damper assembly.
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ABSTRACT
Hydraulic rack and pinion power steering system is a high bandwidth servo with stringent performance requirements on accuracy, reliability, and cost. Design of such a system can be best achieved by using a validated and user friendly computer simulation program. Hydraulic integrated power steering ( HIPS ) program has been developed using basic concepts from science and engineering. HIPS provides a design and test environment for the integrated steering and suspension system subjected to disturbance forces, which may be induced by pump flow oscillations and tire loads. Two real-world automotive hydraulic steering systems are simulated with HIPS. The simulation results agree closely with the dynamometer test results. The application of HIPS for design optimization is also demonstrated.
INTRODUCTION
Figure 1 shows a hydraulic rack and pinion power steering system, which is a high bandwidth nonlinear servo capable of generating a rack force of 4,000 N for cars and 6,000 N for small trucks. About 80% of the rack force comes from hydraulic power assist and the remaining 20% comes from driver’s effort. At on-center position of the steering wheel, a vane pump, which is driven by the engine, circulates the fluid in a closed -loop hydraulic circuit which includes a reservoir, vane pump with flow control and pressure relief, supply and return lines, and the rotary spool valve ( RSV ). The flow control valve which connects the discharge and inlet manifolds of the vane pump, regulates the pump flow rate into the supply line at 2.1 gpm for cars and 3.5 gpm for small trucks, for engine speeds above 900 rpm. When the steering wheel is turned by the driver, RSV diverts the supply line fluid flow to either side of the power piston for a right or left turn of the vehicle. At the same time, RSV passes an equal amount of fluid flow from the other side of the power piston through the return line to the reservoir.
This increases the differential pressure acting on the power piston and yields the desirable hydraulic power assist force. An optional speed sensitive steering controller modulates the fluid flow rate drawn by the RSV from the supply line, using signals from wheel speed sensors and wheel torque sensor. The driver’s steering effort is increased by lowering the hydraulic power assist during highway driving, hence improving driver’s feel of the road during city and highway driving. The steering torque is obtained when the rack force is applied to an off-center joint on the knuckle, which turns about the kingpin at the suspension strut, including a coil spring and damper assembly.
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Modeling of Cutting Forces Under Hard Turning Conditions Considering Tool Wear Effect
Modeling of Cutting Forces Under Hard Turning Conditions Considering Tool Wear Effect
Introduction
Generally, the hard turning process is recognized as the single point turning of materials with hardness from 50 to 70 HRc 1#.It differs from conventional turning in tool/workpiece material prop-erties, cutting tool geometry, chip formation mechanism, and cut-ting conditions applied. As a potential alternative to form grind-ing, the hard turning process can offer attractive benefits in terms of lower equipment costs, shorter setup time, fewer process steps, higher material removal rate, better surface integrity, and the elimination of cutting fluid @1–3#. But for hard turning to be a viable technology, there are still several issues—including tool life, part integrity, and machine stiffness requirements—that need to be addressed. A quantitative understanding of cutting forces under hard turning conditions is a critical element in addressing these issues because of its implications on thermal analysis, tool life analysis, chatter analysis, etc.
In general, significant prior research is available in the area of force modeling in turning operation. However, a comprehensive analysis of hard turning forces has not been well established in view of the unique process conditions involved. In addition to the workpiece and cutting tool material property aspects, hard turning process conditions are defined based on several key characteris- tics: negative tool rake angle, low feed rate, small depth of cut, relatively large tool nose radius, and rapid tool wear rate. These characteristics provide a set of cutting configuration, chip forma- tion mechanism, and force generation process distinctive to the commonly encountered turning conditions. Therefore, the effect of three-dimensional ~3D! engagement and the implication of tool wear must be incorporated in the modeling of hard turning forces. When the effect of flank wear is not considered, the primary scope of cutting force modeling is related to chip formation. A complication with the chip formation in hard turning is the seg- mentation of chips as a result of either catastrophic thermoplastic adiabatic shear @4# or crack/fracture generation @5#. The force variation due to chip segmentation is estimated to be on the order of 63% based on the measurement of Vyas and Shaw @6#. The variation component of cutting force is typically insignificant compared to the average forces component, and the variation frequency—on the order of 10–100 KHz—is beyond the sam- pling rate of typical dynamometers @4,6#. Therefore, the interest of cutting force modeling often focuses on the average force level, but not on the variation due to chip segmentation. One widely used method to model the average cutting force components is the mechanistic modeling approach @7#. This method has a proven prediction accuracy over a range of cutting conditions while re- quiring a minimum number of calibration test data. Suited for the orthogonal cutting configuration, the mechanistic modeling ap-proach is not readily applicable to hard turning due to the 3D cutting geometry and large tool nose radius that make the hard turning process highly three dimensional. When the effect of flank wear on cutting forces is considered, it has been observed in conventional turning that as the tool wears neither the shear angle @8# nor the chip thickness changes notice- ably @9,10#. Similar phenomena were observed in hard turning of HV760 steel @11#. Shintani et al. @12# further found that the effec- tive tool geometry did not change throughout the cubic boron nitride ~CBN! tool life when hard turning carburized steel under practical cutting conditions ~low feed rate, small depth of cut, and gentle cutting speed!. Although the underlying physical mecha- nism is not clear in this phase, these observations suggest that the chip formation process in conventional and hard turning is not significantly affected by the tool wear and also support the hy- pothesis that the total cutting forces can be treated as consisting of two uncoupled parts: forces due to chip formation regardless of the tool sharpness, and forces due to flank wear alone. But some researchers still doubt the efficacy of this decoupling property. Recently, Wang and Liu @13# argued that forces due to chip for- mation and forces due to flank wear should be coupled with each other. Based on the depth of the phase transformed white layer in hard turning, Wang and Liu @13# deduced the temperature profile.
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Introduction
Generally, the hard turning process is recognized as the single point turning of materials with hardness from 50 to 70 HRc 1#.It differs from conventional turning in tool/workpiece material prop-erties, cutting tool geometry, chip formation mechanism, and cut-ting conditions applied. As a potential alternative to form grind-ing, the hard turning process can offer attractive benefits in terms of lower equipment costs, shorter setup time, fewer process steps, higher material removal rate, better surface integrity, and the elimination of cutting fluid @1–3#. But for hard turning to be a viable technology, there are still several issues—including tool life, part integrity, and machine stiffness requirements—that need to be addressed. A quantitative understanding of cutting forces under hard turning conditions is a critical element in addressing these issues because of its implications on thermal analysis, tool life analysis, chatter analysis, etc.
In general, significant prior research is available in the area of force modeling in turning operation. However, a comprehensive analysis of hard turning forces has not been well established in view of the unique process conditions involved. In addition to the workpiece and cutting tool material property aspects, hard turning process conditions are defined based on several key characteris- tics: negative tool rake angle, low feed rate, small depth of cut, relatively large tool nose radius, and rapid tool wear rate. These characteristics provide a set of cutting configuration, chip forma- tion mechanism, and force generation process distinctive to the commonly encountered turning conditions. Therefore, the effect of three-dimensional ~3D! engagement and the implication of tool wear must be incorporated in the modeling of hard turning forces. When the effect of flank wear is not considered, the primary scope of cutting force modeling is related to chip formation. A complication with the chip formation in hard turning is the seg- mentation of chips as a result of either catastrophic thermoplastic adiabatic shear @4# or crack/fracture generation @5#. The force variation due to chip segmentation is estimated to be on the order of 63% based on the measurement of Vyas and Shaw @6#. The variation component of cutting force is typically insignificant compared to the average forces component, and the variation frequency—on the order of 10–100 KHz—is beyond the sam- pling rate of typical dynamometers @4,6#. Therefore, the interest of cutting force modeling often focuses on the average force level, but not on the variation due to chip segmentation. One widely used method to model the average cutting force components is the mechanistic modeling approach @7#. This method has a proven prediction accuracy over a range of cutting conditions while re- quiring a minimum number of calibration test data. Suited for the orthogonal cutting configuration, the mechanistic modeling ap-proach is not readily applicable to hard turning due to the 3D cutting geometry and large tool nose radius that make the hard turning process highly three dimensional. When the effect of flank wear on cutting forces is considered, it has been observed in conventional turning that as the tool wears neither the shear angle @8# nor the chip thickness changes notice- ably @9,10#. Similar phenomena were observed in hard turning of HV760 steel @11#. Shintani et al. @12# further found that the effec- tive tool geometry did not change throughout the cubic boron nitride ~CBN! tool life when hard turning carburized steel under practical cutting conditions ~low feed rate, small depth of cut, and gentle cutting speed!. Although the underlying physical mecha- nism is not clear in this phase, these observations suggest that the chip formation process in conventional and hard turning is not significantly affected by the tool wear and also support the hy- pothesis that the total cutting forces can be treated as consisting of two uncoupled parts: forces due to chip formation regardless of the tool sharpness, and forces due to flank wear alone. But some researchers still doubt the efficacy of this decoupling property. Recently, Wang and Liu @13# argued that forces due to chip for- mation and forces due to flank wear should be coupled with each other. Based on the depth of the phase transformed white layer in hard turning, Wang and Liu @13# deduced the temperature profile.
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HEAT EXCHANGERS
HEAT EXCHANGERS
INTRODUCTION
Most geothermal fluids, because of their elevated temperature, contain a variety of dissolved chemicals. These chemicals are frequently corrosive toward standard materials of construction. As a result, it is advisable in most cases to isolate the geothermal fluid from the process to which heat is being transferred.
The task of heat transfer from the geothermal fluid to a closed process loop is most often handled by a plate heat exchanger. The two most common types used in geother- mal applications are: bolted and brazed.
For smaller systems, in geothermal resource areas of a specific character, downhole heat exchangers (DHEs) pro- vide a unique means of heat extraction. These devices eliminate the requirement for physical removal of fluid from the well. For this reason, DHE-based systems avoid entirely the environmental and practical problems associated with fluid disposal.
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INTRODUCTION
Most geothermal fluids, because of their elevated temperature, contain a variety of dissolved chemicals. These chemicals are frequently corrosive toward standard materials of construction. As a result, it is advisable in most cases to isolate the geothermal fluid from the process to which heat is being transferred.
The task of heat transfer from the geothermal fluid to a closed process loop is most often handled by a plate heat exchanger. The two most common types used in geother- mal applications are: bolted and brazed.
For smaller systems, in geothermal resource areas of a specific character, downhole heat exchangers (DHEs) pro- vide a unique means of heat extraction. These devices eliminate the requirement for physical removal of fluid from the well. For this reason, DHE-based systems avoid entirely the environmental and practical problems associated with fluid disposal.
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Dimensional accuracy and surface roughness of rapid freeze prototyping ice patterns and investment casting metal parts
Dimensional accuracy and surface roughness of rapid freeze prototyping ice patterns and investment casting metal parts
Abstract
The dimensional accuracy and surface finish of ice patterns generated by rapid freeze prototyping were first investi-gated. The dimensional accuracy and surface finish of metal parts made by investment casting with ice patterns were then investi-gated and compared with those made by conventional investment casting with wax patterns. The selection of binder, ceramic pow-der, and catalyst material for ceramic slurries in the process of investment casting with ice patterns and the need for an interface agent to separate the ice pattern from the ceramic slurry in the mold making process are discussed. The parts used in the inves-tigation included circular cylinders with vertical and slant walls and a turbine impeller.
Introduction
Wax is the most commonly used material to make patterns in investment casting [1]. Natural or synthetic waxes and various additives have been used to achieve minimum shrinkage and close reproducibility of pattern dimensions as well as strength for stability in parts handling and storage. However, there still exist some problems in using wax patterns such as expansion of the wax pattern in the process of melting that might cause ceramic shell cracking. New approaches to improve the performance of investment casting processes are constantly being sought.
Freeze cast process (FCP), a novel investment casting pro-cess, was patented by Yodice in 1991 [2]. In this process, ice patterns instead of traditional wax patterns are used to make metal parts. Through ten years of research, Yodice and others have demonstrated the feasibility and advantages of investment casting with ice patterns [3–6]. The advantages of FCP over the competing casting processes include low cost, high quality and fine surface finish. These strengths make FCP a significant alternative to the traditional investment casting for production of quality near-net shape castings at reasonable costs. The FCP
process starts with fabrication of a solid master pattern and the associated silicone mold making. The solid master pattern can be made either by conventional machining methods or by modern rapid prototyping techniques. Then ice patterns are made from the silicone mold by injecting water in the mold and freezing it. There is an advantage of ice pattern in preventing shell cracking during pattern removal. As shown by Richards and Ginger [7], most production wax patterns exhibit an abrupt expansion as the crystalline portion of the microstructure melts during dewaxing. In contrast, the ice pattern will shrink, thus relieving the stress on the shell during pattern removal. Because the ice patterns in the FCP process are made from silicone molds, some problems exist, such as multidirectional water expansion during freezing and air-bubble generation. These problems can be eliminated by making ice patterns with the rapid freeze prototyping (RFP) process, an environmentally conscious rapid prototyping (RP) technique that we recently developed [8, 9].
Similar to other solid freeform fabrication (SFF) tech- niques [10, 11], the RFP process can directly build a three- dimensional ice part based on a computer-aided design (CAD) model, by selectively depositing and rapidly freezing water in a layer-by-layer manner. Figure 1 demonstrates the principle of rapid freeze prototyping. The water in the feeding pipe is ejected drop by drop in a drop-on-demand mode. The build environment is kept at a temperature below water’s freezing point. Pure wa- ter or colorized water is ejected from the nozzle and deposited onto the substrate or the previously solidified ice surface. Wa- ter droplets do not solidify immediately. Instead, they spread and unite together to become part of a continuous water line. Then the newly deposited water is cooled by the low temperature environment through convection and by the previously formed ice layer through conduction. As a result, the deposited material freezes rapidly and binds to the previous layer firmly through the hydrogen bond. After a layer is finished, the nozzle is elevated upwards the height of one layer thickness, waiting a predeter- mined period of time for complete solidification of the deposited water and then depositing water droplets again to build the next layer. This procedure continues until the designed ice part has been fabricated. The most important advantages of the RFP pro- cess include a cheaper and cleaner process, the potential to build accurate ice parts with excellent surface finish, and no residue after part removal in the molding process. Another advantage is decreased likelihood of investment shell cracking as compared with using wax patterns. Some description and explanation about these can be found in [7, 12]. With RFP, it is possible to make ice patterns directly from CAD models in a short time, without the high cost and other issues of mold making. There is a strong synergy between the FCP and RFP. FCP is suitable for quantity production of metal parts by investment casting with ice patterns, while RFP provides a good way to make small to medium quan- tity ice patterns for prototyping and manufacturing purposes. Figure 2 shows the comparison of the operation steps between RFP and FCP.
Unlike other RP processes, the RFP process and its appli- cation in investment casting have unique characteristics. It is apparent that the accuracy and surface finish of ice patterns from the RFP process are two dominant factors that influence the qual- ity of metal castings. It is essential to study the part accuracy and surface finish of ice patterns made by RFP. The effects of different process parameters on the layer thickness and layer width have been studied and reported in a previous paper [9]. The study described in the present paper was aimed at investi- gating the accuracy and surface finish of metal parts made by
investment casting with ice patterns. Though FCP has demon- strated the success of using ice patterns to make metal parts by investment casting, there are few technical details available in the literature. Investment casting with ice patterns was studied as described in this paper in order to understand the fundamentals of the technology of making metal parts from ice patterns and make the knowledge available in the public domain. The selec- tion of the binder material for ceramic slurries and the need for an interface agent to separate the ice pattern from the ceramic shell in the mold-making process are discussed. The process of investment casting with ice patterns is described and the con- trast with the conventional investment casting with wax patterns is made. The accuracy and surface finish of the metal parts from ice patterns are also presented. The parts used in this investiga- tion include circular cylinders with vertical and slant walls and a turbine impeller.
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Abstract
The dimensional accuracy and surface finish of ice patterns generated by rapid freeze prototyping were first investi-gated. The dimensional accuracy and surface finish of metal parts made by investment casting with ice patterns were then investi-gated and compared with those made by conventional investment casting with wax patterns. The selection of binder, ceramic pow-der, and catalyst material for ceramic slurries in the process of investment casting with ice patterns and the need for an interface agent to separate the ice pattern from the ceramic slurry in the mold making process are discussed. The parts used in the inves-tigation included circular cylinders with vertical and slant walls and a turbine impeller.
Introduction
Wax is the most commonly used material to make patterns in investment casting [1]. Natural or synthetic waxes and various additives have been used to achieve minimum shrinkage and close reproducibility of pattern dimensions as well as strength for stability in parts handling and storage. However, there still exist some problems in using wax patterns such as expansion of the wax pattern in the process of melting that might cause ceramic shell cracking. New approaches to improve the performance of investment casting processes are constantly being sought.
Freeze cast process (FCP), a novel investment casting pro-cess, was patented by Yodice in 1991 [2]. In this process, ice patterns instead of traditional wax patterns are used to make metal parts. Through ten years of research, Yodice and others have demonstrated the feasibility and advantages of investment casting with ice patterns [3–6]. The advantages of FCP over the competing casting processes include low cost, high quality and fine surface finish. These strengths make FCP a significant alternative to the traditional investment casting for production of quality near-net shape castings at reasonable costs. The FCP
process starts with fabrication of a solid master pattern and the associated silicone mold making. The solid master pattern can be made either by conventional machining methods or by modern rapid prototyping techniques. Then ice patterns are made from the silicone mold by injecting water in the mold and freezing it. There is an advantage of ice pattern in preventing shell cracking during pattern removal. As shown by Richards and Ginger [7], most production wax patterns exhibit an abrupt expansion as the crystalline portion of the microstructure melts during dewaxing. In contrast, the ice pattern will shrink, thus relieving the stress on the shell during pattern removal. Because the ice patterns in the FCP process are made from silicone molds, some problems exist, such as multidirectional water expansion during freezing and air-bubble generation. These problems can be eliminated by making ice patterns with the rapid freeze prototyping (RFP) process, an environmentally conscious rapid prototyping (RP) technique that we recently developed [8, 9].
Similar to other solid freeform fabrication (SFF) tech- niques [10, 11], the RFP process can directly build a three- dimensional ice part based on a computer-aided design (CAD) model, by selectively depositing and rapidly freezing water in a layer-by-layer manner. Figure 1 demonstrates the principle of rapid freeze prototyping. The water in the feeding pipe is ejected drop by drop in a drop-on-demand mode. The build environment is kept at a temperature below water’s freezing point. Pure wa- ter or colorized water is ejected from the nozzle and deposited onto the substrate or the previously solidified ice surface. Wa- ter droplets do not solidify immediately. Instead, they spread and unite together to become part of a continuous water line. Then the newly deposited water is cooled by the low temperature environment through convection and by the previously formed ice layer through conduction. As a result, the deposited material freezes rapidly and binds to the previous layer firmly through the hydrogen bond. After a layer is finished, the nozzle is elevated upwards the height of one layer thickness, waiting a predeter- mined period of time for complete solidification of the deposited water and then depositing water droplets again to build the next layer. This procedure continues until the designed ice part has been fabricated. The most important advantages of the RFP pro- cess include a cheaper and cleaner process, the potential to build accurate ice parts with excellent surface finish, and no residue after part removal in the molding process. Another advantage is decreased likelihood of investment shell cracking as compared with using wax patterns. Some description and explanation about these can be found in [7, 12]. With RFP, it is possible to make ice patterns directly from CAD models in a short time, without the high cost and other issues of mold making. There is a strong synergy between the FCP and RFP. FCP is suitable for quantity production of metal parts by investment casting with ice patterns, while RFP provides a good way to make small to medium quan- tity ice patterns for prototyping and manufacturing purposes. Figure 2 shows the comparison of the operation steps between RFP and FCP.
Unlike other RP processes, the RFP process and its appli- cation in investment casting have unique characteristics. It is apparent that the accuracy and surface finish of ice patterns from the RFP process are two dominant factors that influence the qual- ity of metal castings. It is essential to study the part accuracy and surface finish of ice patterns made by RFP. The effects of different process parameters on the layer thickness and layer width have been studied and reported in a previous paper [9]. The study described in the present paper was aimed at investi- gating the accuracy and surface finish of metal parts made by
investment casting with ice patterns. Though FCP has demon- strated the success of using ice patterns to make metal parts by investment casting, there are few technical details available in the literature. Investment casting with ice patterns was studied as described in this paper in order to understand the fundamentals of the technology of making metal parts from ice patterns and make the knowledge available in the public domain. The selec- tion of the binder material for ceramic slurries and the need for an interface agent to separate the ice pattern from the ceramic shell in the mold-making process are discussed. The process of investment casting with ice patterns is described and the con- trast with the conventional investment casting with wax patterns is made. The accuracy and surface finish of the metal parts from ice patterns are also presented. The parts used in this investiga- tion include circular cylinders with vertical and slant walls and a turbine impeller.
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Automotive Lighting - State of the Art
Automotive Lighting - State of the Art
Introduction
The history of automotive lighting reaches back for over a hundred years. First of all candles and then gas lights were used for horse-drawn coaches, and gas lights were used for the first cars. In the 1920s electric lights began to be used in cars. Dynamos were installed at this stage solely for electrical lighting. In the thirties and forties optical systems for lighting were devel-oped to include the first projection systems. In the 1950s legal regulations began to cover vehicle lights. In the sixties halogen light sources became available and the voltage was raised to 12 volts. The resulting jump in lu-minous flux initially caused a public outcry, but was quickly accepted. In the eighties the aerodynamic headlamp began to replace the reflector bulb, also known as 'sealed beam’, which had become almost a standard for headlamps in the United States and Scandinavia. In the 1990s the gas dis-charge light source, referred to also as ' xenon ' was introduced. It offered considerably more light and almost vehicle life longevity. Headlamp level-ling became mandatory in Europe. In the first decade of the 21st century night-time design of vehicles became attractive. Also dynamic headlamps that followed the bends of the road were developed and built into cars. The first night visions systems and the first LED headlamps are being intro-duced.
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Introduction
The history of automotive lighting reaches back for over a hundred years. First of all candles and then gas lights were used for horse-drawn coaches, and gas lights were used for the first cars. In the 1920s electric lights began to be used in cars. Dynamos were installed at this stage solely for electrical lighting. In the thirties and forties optical systems for lighting were devel-oped to include the first projection systems. In the 1950s legal regulations began to cover vehicle lights. In the sixties halogen light sources became available and the voltage was raised to 12 volts. The resulting jump in lu-minous flux initially caused a public outcry, but was quickly accepted. In the eighties the aerodynamic headlamp began to replace the reflector bulb, also known as 'sealed beam’, which had become almost a standard for headlamps in the United States and Scandinavia. In the 1990s the gas dis-charge light source, referred to also as ' xenon ' was introduced. It offered considerably more light and almost vehicle life longevity. Headlamp level-ling became mandatory in Europe. In the first decade of the 21st century night-time design of vehicles became attractive. Also dynamic headlamps that followed the bends of the road were developed and built into cars. The first night visions systems and the first LED headlamps are being intro-duced.
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Using High-Temperature Superconductors for Levitation Applications
Using High-Temperature Superconductors for Levitation Applications
INTRODUCTION
The image of a permanent magnet (PM) stably levitated over a bulk high-temperature superconductor has becomea major symbol of high-temperature superconducting (HTS) technology that often evokes visions of applications such as high-speed maglev vehicles and en- ergy-efficient flywheel energy storage. The advantages of noncontacting sur- faces without an active feedback system, the ability to operate in a vacuum, and the potential for extremely low rotational drag should, in many applications, out- weigh the inconvenience of refrigerat- ing the superconductor.
The phenomena associated with the strongly stable passive levitation of the PM/high-temperature superconductor system is not attainable with any other method, and its exploration can provide a tactile and visual indication of many of the basic phenomena associated with high-temperature superconductors, in- cluding persistent superconducting cur- rents and flux pinning. If the PM is pushed up, down, or sideways, or tilted, there is a restoring force that returns the PM to its initial position. The forces can also be highly hysteretic. It is possible to change the equilibrium position of the PM into almost any orientation or to move the center of mass of the PM to a new equilibrium position if pushed hard enough. If the PM is a cylinder with a relatively symmetric magnetic field, it readily rotates about its axis of symme- try. Such behavior suggests that the high-temperature uperconductor could be used in the construction of a super- conducting bearing.
The first stable levitation involving a superconductor was reported in 1945. 1,2 This was followed by investigations of gyroscopes and motors employing bear- ings that incorporated low-temperaturesuperconductors cooled with liquid he-lium. 3 Major interest in superconduct- ing levitation then focused on the use of low-temperature superconducting (LTS) magnets to provide levitational and guid- ance forces for vehicles moving at high speed at low heights above ground-sup- ported guideways. 3–5 Interest in super- conducting levitation increased dramati- cally after the discovery of the first high- temperature superconductor, 6 when ba-sic levitation demonstrations could be done in simple styrofoam cups contain-ing liquid nitrogen. Several reviews of the early experiments on HTS levitation are available 3,7–10.
Although some investigations have been made of the use of wires and thin films in HTS levitation, most of the present efforts involve the use of bulk high-temperature superconductors. Un- like superconducting wire applications, in which the supercurrent must pass from grain to grain along a length that encompasses many grains, a distinction of levitation applications is that the su-percurrent need only circulate within individual grains.
The present material of choice for su-perconducting levitation is Y-Ba-Cu-O (YBCO) and its RE-Ba-Cu-O (where RE denotes rare-earth elements Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, and La) analogs, because they exhibit a high magnetic-irreversibility field Hirr at liq-uid-nitrogen temperatures and many have the ability to grow large grains. Hirr marks a phase transition between the region where magnetic flux is solidly pinned in the superconductor and the region where flux may move. Sometimes the curve is said to denote the boundary between the region where flux is frozen and the region where flux is melted. Compared to some of the members of the bismuth, thallium, or mercury HTS families, YBCO has a relatively low criti-cal temperature of 92 K, but its irrevers-ibility curve is one of the highest at 77 K and lower temperatures. For stable levi-tation, it is important that the flux be frozen in the superconductor; otherwise, the PM slowly loses levitation height.
The levitational force is proportional to the mean magnetization of the high-temperature superconductor. The mag-netization of a bulk high-temperature superconductor is proportional to the product of the critical-current density and the grain diameter. Large grain di- ameters are important to achieve suffi- ciently large magnetizations for useful levitation forces. In bulk YBCO materi- als, the grains grow to diameters of sev- eral centimeters when made by a melt- texturing process11 (Figure 1). In the present state of the art, the upper limit of the grain diameter produced by this pro- cess is ≈10 cm. The ability to produce
good-quality YBCO thin films is also limited to this size. If techniques to grow large grains for other HTS materials with high irreversibility curves were devel- oped, these materials would also be of interest for levitation applications.
Many excellent reviews12–15 and col- lected papers16,17 cover the detailed fab- rication issues of melt-textured high-tem- perature superconductors. In addition to the levitation applications described here, melt-textured high-temperature superconductors can be used in other applications, such as new forms of elec- tric motors 18.
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INTRODUCTION
The image of a permanent magnet (PM) stably levitated over a bulk high-temperature superconductor has becomea major symbol of high-temperature superconducting (HTS) technology that often evokes visions of applications such as high-speed maglev vehicles and en- ergy-efficient flywheel energy storage. The advantages of noncontacting sur- faces without an active feedback system, the ability to operate in a vacuum, and the potential for extremely low rotational drag should, in many applications, out- weigh the inconvenience of refrigerat- ing the superconductor.
The phenomena associated with the strongly stable passive levitation of the PM/high-temperature superconductor system is not attainable with any other method, and its exploration can provide a tactile and visual indication of many of the basic phenomena associated with high-temperature superconductors, in- cluding persistent superconducting cur- rents and flux pinning. If the PM is pushed up, down, or sideways, or tilted, there is a restoring force that returns the PM to its initial position. The forces can also be highly hysteretic. It is possible to change the equilibrium position of the PM into almost any orientation or to move the center of mass of the PM to a new equilibrium position if pushed hard enough. If the PM is a cylinder with a relatively symmetric magnetic field, it readily rotates about its axis of symme- try. Such behavior suggests that the high-temperature uperconductor could be used in the construction of a super- conducting bearing.
The first stable levitation involving a superconductor was reported in 1945. 1,2 This was followed by investigations of gyroscopes and motors employing bear- ings that incorporated low-temperaturesuperconductors cooled with liquid he-lium. 3 Major interest in superconduct- ing levitation then focused on the use of low-temperature superconducting (LTS) magnets to provide levitational and guid- ance forces for vehicles moving at high speed at low heights above ground-sup- ported guideways. 3–5 Interest in super- conducting levitation increased dramati- cally after the discovery of the first high- temperature superconductor, 6 when ba-sic levitation demonstrations could be done in simple styrofoam cups contain-ing liquid nitrogen. Several reviews of the early experiments on HTS levitation are available 3,7–10.
Although some investigations have been made of the use of wires and thin films in HTS levitation, most of the present efforts involve the use of bulk high-temperature superconductors. Un- like superconducting wire applications, in which the supercurrent must pass from grain to grain along a length that encompasses many grains, a distinction of levitation applications is that the su-percurrent need only circulate within individual grains.
The present material of choice for su-perconducting levitation is Y-Ba-Cu-O (YBCO) and its RE-Ba-Cu-O (where RE denotes rare-earth elements Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, and La) analogs, because they exhibit a high magnetic-irreversibility field Hirr at liq-uid-nitrogen temperatures and many have the ability to grow large grains. Hirr marks a phase transition between the region where magnetic flux is solidly pinned in the superconductor and the region where flux may move. Sometimes the curve is said to denote the boundary between the region where flux is frozen and the region where flux is melted. Compared to some of the members of the bismuth, thallium, or mercury HTS families, YBCO has a relatively low criti-cal temperature of 92 K, but its irrevers-ibility curve is one of the highest at 77 K and lower temperatures. For stable levi-tation, it is important that the flux be frozen in the superconductor; otherwise, the PM slowly loses levitation height.
The levitational force is proportional to the mean magnetization of the high-temperature superconductor. The mag-netization of a bulk high-temperature superconductor is proportional to the product of the critical-current density and the grain diameter. Large grain di- ameters are important to achieve suffi- ciently large magnetizations for useful levitation forces. In bulk YBCO materi- als, the grains grow to diameters of sev- eral centimeters when made by a melt- texturing process11 (Figure 1). In the present state of the art, the upper limit of the grain diameter produced by this pro- cess is ≈10 cm. The ability to produce
good-quality YBCO thin films is also limited to this size. If techniques to grow large grains for other HTS materials with high irreversibility curves were devel- oped, these materials would also be of interest for levitation applications.
Many excellent reviews12–15 and col- lected papers16,17 cover the detailed fab- rication issues of melt-textured high-tem- perature superconductors. In addition to the levitation applications described here, melt-textured high-temperature superconductors can be used in other applications, such as new forms of elec- tric motors 18.
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Computer Aided Modeling and Deign of a New Magnetic Sealing Mechanism in Engineering Applications
Computer Aided Modeling and Deign of a New Magnetic Sealing Mechanism in Engineering Applications
Abstract
This article introduces a new type of magnetic sealing mechanism that reduces the lubrication oil pollution and media gaseous leakage in general reciprocating machinery including air compressors and refrigerators. The feasible function and reliable performance of this new sealing mechanism are introduced and analyzed in this paper. The computer aided design, modeling and analysis are being used to study this new sealing mechanism, and the prototype of this sealing mechanism is being tested. The study indicated the proper function of this sealing mechanism. The major advantages of this sealing mechanism include: improved sealing capacity to prevent the gaseous leakage and oil leakage, simple and compact in structure, lower pre-cision requirement on surfaces of reciprocating pistons and shafts in production and manufacturing, and longer services in sealing life span. Also there is almost no frictional loss during the reciprocating motion of piston or shaft.
Introduction
The gaseous leakage and oil pollution in reciprocating machines including compressors and refrigerators are common problems that have not been well resolved and it directly affects the machinery performance [1–4]. The design and development of new sealing mechanism are continued in these years [5–8].
In this research, a new magnetic sealing mechanism using rare-earth magnet as permanent magnet is devel-oped to solve these problems based on theoretic analysis, computational modeling simulation, and prototype tests. The permanent magnet is made from the materials that stay magnetized. Materials that can be magnetized are called ferromagnetic including rare earth magnets. The current research and development of rare earth perma-nent magnets have brought the renovation in the field of magnetic separation and provided the magnetic products that are an order of magnitude stronger than that of con-ventional ferrite magnets. This leads to the development of high-intensity magnetic circuits that operated energy free and surpasses the electromagnets in strength and effectiveness. Common applications of rare-earth mag-nets include: computer hard drives, audio speakers, bicy-cle dynamos, fishing reel brakes, mag-lev wind turbines, and LED throwies.
The prototype testing of this new magnetic sealing mechanism indicated that this sealing mechanism can significantly reduce the leakage problem in reciprocating machines including compressors and oil pollution in cryogenic regenerator. It also shows that this sealing mechanism can replace the oil separation system in re-frigerating compressors. Through the prototype tests, the sealing function of this new mechanism is better than regular rubber seal, diaphragm seal, corrugated pipe seal and magnetic fluid seal.
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Abstract
This article introduces a new type of magnetic sealing mechanism that reduces the lubrication oil pollution and media gaseous leakage in general reciprocating machinery including air compressors and refrigerators. The feasible function and reliable performance of this new sealing mechanism are introduced and analyzed in this paper. The computer aided design, modeling and analysis are being used to study this new sealing mechanism, and the prototype of this sealing mechanism is being tested. The study indicated the proper function of this sealing mechanism. The major advantages of this sealing mechanism include: improved sealing capacity to prevent the gaseous leakage and oil leakage, simple and compact in structure, lower pre-cision requirement on surfaces of reciprocating pistons and shafts in production and manufacturing, and longer services in sealing life span. Also there is almost no frictional loss during the reciprocating motion of piston or shaft.
Introduction
The gaseous leakage and oil pollution in reciprocating machines including compressors and refrigerators are common problems that have not been well resolved and it directly affects the machinery performance [1–4]. The design and development of new sealing mechanism are continued in these years [5–8].
In this research, a new magnetic sealing mechanism using rare-earth magnet as permanent magnet is devel-oped to solve these problems based on theoretic analysis, computational modeling simulation, and prototype tests. The permanent magnet is made from the materials that stay magnetized. Materials that can be magnetized are called ferromagnetic including rare earth magnets. The current research and development of rare earth perma-nent magnets have brought the renovation in the field of magnetic separation and provided the magnetic products that are an order of magnitude stronger than that of con-ventional ferrite magnets. This leads to the development of high-intensity magnetic circuits that operated energy free and surpasses the electromagnets in strength and effectiveness. Common applications of rare-earth mag-nets include: computer hard drives, audio speakers, bicy-cle dynamos, fishing reel brakes, mag-lev wind turbines, and LED throwies.
The prototype testing of this new magnetic sealing mechanism indicated that this sealing mechanism can significantly reduce the leakage problem in reciprocating machines including compressors and oil pollution in cryogenic regenerator. It also shows that this sealing mechanism can replace the oil separation system in re-frigerating compressors. Through the prototype tests, the sealing function of this new mechanism is better than regular rubber seal, diaphragm seal, corrugated pipe seal and magnetic fluid seal.
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Belt-Driven Starter-Generator for Future 42-Volt Systems
Belt-Driven Starter-Generator for Future 42-Volt Systems
ABSTRACT
This paper explores issues related with the design and implementation of belt-driven starter-generators for future 42-V systems. Belt-driven starter-generators can offer many advantages including smooth restarts, high efficiency, and convenient packaging. Future vehicle systems require these characteristics to enable fuel economy functions like “engine off at idle” and “x-by- wire.” Belt-driven starter-generators are often easier to package in contrast with flywheel-mounted systems, which require powertrain modifications and in many cases a longer package. A prototype system based on a belt-driven induction machine mounted on a small, European engine is described in the paper. Test results for both cranking and generation are shown and analyzed. Efficient, high-power generation was confirmed and high-speed (beyond 400 engine rpm) cranking was demonstrated down to the targeted -20°C.The paper also provides comparisons with various engine-starting, machine thermal, and electrical model results.
INTRODUCTION
This study is part of on-going, industry-wide studies of 42-V power systems and components [1-7]. The proposed higher-voltage architectures constitute an opportunity to revisit the idea of combining the starter and generator functions into a single drive. The single unit could be designed to generate at higher power levels than the current Lundell alternators can, and
would be capable of providing smooth starts thus making it possible to turn the engine off at idle. A few years ago, perhaps because of the influence of hybrid vehicle research, much of the focus of starter-generator studies was on so-called flywheel systems, where the starter- generator is placed directly on the crankshaft in the general location of the present flywheel [8-12]. Such systems could provide engine torque smoothing capabilities and could also be scaled up in output power level to provide some hybrid propulsion capabilities.
A possible alternative to the flywheel design consists of driving the starter-generator through mechanical means, belt, chain or gear, an option often referred to as “side- mounted” design. Such a system would allow for a more traditional underhood layout, thus being more evolutionary, yet provide most of the expected benefits from starter-generators in terms of efficient, high power generation and smooth starting. It would, however, be more limited probably in terms of torque-smoothing ability and certainly in terms of propulsion capability.
A prototype belt-driven, induction-machine based starter- generator system was therefore studied, built and tested, see Fig. 1. The general design target was the ability to start a European-style small engine down to -20°C, to generate 3 to 4 kW at most speeds, and at least 1 kW at 6,000 engine r/min. In addition, cranking up to speeds of at least 400 r/min was required at room temperature for smooth restart. The system had to be packageable in the corresponding compact vehicle. The scope of the study was the mechanical drive, the machine and the inverter that interfaces with a single, 42 V bus. A design description, mathematical models and test results are included.
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ABSTRACT
This paper explores issues related with the design and implementation of belt-driven starter-generators for future 42-V systems. Belt-driven starter-generators can offer many advantages including smooth restarts, high efficiency, and convenient packaging. Future vehicle systems require these characteristics to enable fuel economy functions like “engine off at idle” and “x-by- wire.” Belt-driven starter-generators are often easier to package in contrast with flywheel-mounted systems, which require powertrain modifications and in many cases a longer package. A prototype system based on a belt-driven induction machine mounted on a small, European engine is described in the paper. Test results for both cranking and generation are shown and analyzed. Efficient, high-power generation was confirmed and high-speed (beyond 400 engine rpm) cranking was demonstrated down to the targeted -20°C.The paper also provides comparisons with various engine-starting, machine thermal, and electrical model results.
INTRODUCTION
This study is part of on-going, industry-wide studies of 42-V power systems and components [1-7]. The proposed higher-voltage architectures constitute an opportunity to revisit the idea of combining the starter and generator functions into a single drive. The single unit could be designed to generate at higher power levels than the current Lundell alternators can, and
would be capable of providing smooth starts thus making it possible to turn the engine off at idle. A few years ago, perhaps because of the influence of hybrid vehicle research, much of the focus of starter-generator studies was on so-called flywheel systems, where the starter- generator is placed directly on the crankshaft in the general location of the present flywheel [8-12]. Such systems could provide engine torque smoothing capabilities and could also be scaled up in output power level to provide some hybrid propulsion capabilities.
A possible alternative to the flywheel design consists of driving the starter-generator through mechanical means, belt, chain or gear, an option often referred to as “side- mounted” design. Such a system would allow for a more traditional underhood layout, thus being more evolutionary, yet provide most of the expected benefits from starter-generators in terms of efficient, high power generation and smooth starting. It would, however, be more limited probably in terms of torque-smoothing ability and certainly in terms of propulsion capability.
A prototype belt-driven, induction-machine based starter- generator system was therefore studied, built and tested, see Fig. 1. The general design target was the ability to start a European-style small engine down to -20°C, to generate 3 to 4 kW at most speeds, and at least 1 kW at 6,000 engine r/min. In addition, cranking up to speeds of at least 400 r/min was required at room temperature for smooth restart. The system had to be packageable in the corresponding compact vehicle. The scope of the study was the mechanical drive, the machine and the inverter that interfaces with a single, 42 V bus. A design description, mathematical models and test results are included.
Download full seminar papers At
http://www.enjineer.com/forum
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