Vehicle Dynamics & Stability Systems

Vehicle Dynamics & Stability Systems

ABSTRACT

Vehicle Dynamic Instability may be defined as an unexpected and undesired response from a maneuver induced disturbance. Under present circumstances the driver has only a limited number of actuators to resort to under these critical conditions, which often seem to be slow in response and might prove to be fatal depending upon the conditions the driver finds himself into. But active safety systems contain highly precise and advanced mechatronic systems, which provide real-time monitoring in split-second, sense and compute the necessary action to be undertaken and control the vehicle stability while it is in motion. Such active safety technologies have been demonstrated to have the potential to reduce or prevent the occurrence of rollover, skidding and severe, similar types of accidents. These modern stability systems utilize differential braking to improve vehicle response and have been shown to be quite effective in controlling vehicle yaw response. Various stability systems like Anti-Lock Braking System, Traction Control System, etc. have been studied and analysed. The Electronic Stability Program (ESP) is a versatile and effective tool, which combines these systems, following the basic principles of physics and incorporating the power of higher order micro-electronic components in accordance with hydraulic units, improves yaw rate, lateral, and roll stabilities. The objectives of this stability system design are to prevent or reduce the likelihood of rollover, skidding and to stabilize the vehicle or at least bring it in a controllable condition. ESP is shown to stabilize the vehicle in split seconds by differential braking, controlling the torque and if necessary the transmission as well, thereby preventing rollover, and achieving vehicle stability and safety, which obviously and rightly so, is of prime concern when it comes down to human life.

INTRODUCTION

Active safety and stability systems are rightly, an integral part of today’s vehicles. The modern Electronic Stability Systems (ESP) are designed with the prime objective of passenger safety, which obviously is the most important criteria above all. These systems reduce the risk of skids and slide during cornering and keep a car on track even in extreme conditions. Specific braking of individual wheels, by reducing the engine torque and making steering corrections, can stabilize a skidding vehicle. Techniques to influence the brake system automatically or to automatically reduce torque have been in use for some time, but systems with automatic steering intervention are still in the development phase. ESP offers the conscientious driver safety technology, which controls the vehicle in almost every driving situation.

ESP is comprised of a hydraulic modulator and a control unit with sensors, which determine and evaluate the driving situation. ESP hydraulics, quickly builds brake pressure on a single wheel in critical situations in order to counteract the undesired skidding motion. This pressure increase occurs automatically on the wheel, without driver involvement. The brake impulse can thereby stabilize the vehicle at all times and return it to the proper course. The system may also reduce the engine torque, which provides an added stabilization effect.

These systems determine the driver's commands via sensors, process the information electronically and pass on derived steering commands to the actuators.

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