SAFETY RELATED FAULT-TOLERANT SYSTEMS IN VEHICLES

SAFETY RELATED FAULT-TOLERANT SYSTEMS IN VEHICLES

Introduction:

There is a trend in the automobile industry towards an increasing number of safety-related electronic systems in vehicles that are directly responsible for active and passive vehicle safety. These applications will increase overall vehicle safety by liberating the driver from routine tasks and assisting the driver to find solutions in critical situations.

The realisation of such intelligent driver assistance systems requires direct electronic control of the steering, braking, suspension and powertrain actuators, dependent on the current driving conditions and environmental influences. It is expected that the biggest potential lies in the replacement of (hydro-) mechanical backup systems by distributed fault-tolerant mechatronic systems. As a consequence there is a need for a standardised dependable, and cost-effective electronic realisation for mass production.

The general objective of the X-By-Wire project was to achieve a framework for the introduction of such safety-related fault-tolerant electronic systems in vehicles, so-called “x-by-wire systems”. The “x” represents the basis of any safety-related application such as steering, braking, powertrain or suspension control, etc.
More specifically, x-by-wire systems require driver requests to be sensed and interpreted appropriately so as to take proper account of the current driving conditions and environmental influences. These requests have to be translated into optimum steer, brake, and acceleration manoeuvres.

However, with present implementation strategies active safety systems, or even just a subset thereof, cannot be realised within the typical constraints of mass production: low costs, reliability, system modularity, maintainability in the field, whilst meeting the requirements for safety certification. It cannot be expected that cost-effective manufacturable x-by-wire solutions will rely on expensive mechanical backup. Today’s fail-safe systems have in general a reduced limp-home and a driver dependent functionality in case of one significant failure. A fault-tolerant system, on the other hand, guarantees the
whole functionality even after a major failure has occurred.

Because of big expenditure and outlay in advance, no single vehicle manufacturer has up to now introduced really fault-tolerant safety related x-by-wire systems without mechanical backup. The X-By-Wire project was set up to share research effort and to offer European wide accepted solutions, and to prepare the introduction of standards for x-by-wire systems. Additionally, a common approach towards safety certification and clear legal requirements is necessary to avoid European fragmentation and uncoordinated and parallel research.

A common European x-by-wire development, which has the potential to become a European or even a world-wide standard, accompanied by broad and fast dissemination of the results, translates into a significant strategic advantage for the European automotive, supplier and semiconductor industry.

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