Holistic Development and Validation of SbW Systems

Autoren

Dipl.-Ing. Tobias Sandmann, Dipl.-Ing. Daniel Wegener, fka GmbH, Aachen;
Univ.-Prof. Dr.-Ing. Lutz Eckstein, Institut für Kraftfahrzeuge (ika), RWTH Aachen University

Zusammenfassung

Today's automotive industry is challenged by the trade-off between energy efficiency, driving experience and safety. With regard to automated driving facilitating innovative vehicle dynamics and interior concepts, this trade-off may at least partly solved by introducing innovative concepts for steering systems. Conventional steering systems with electric or hydraulic power assistance comprise a mechanical link between the steerable wheels and the driver input control unit. A Steer-by-Wire (SbW) system decouples the mechanical link between the steerable wheels and the driver input control unit. Thinking even further, a wheel-individual Steer-by-Wire system, in which the steerable wheels are no longer mechanically connected to each other, offers an increased function potential.

Steer-by-Wire has been discussed and - from a functional point of view - developed in the past to a satisfying level. However it is not yet established in broad automotive market application for several reasons, such as system costs, complexity as well as limited customer awareness. Technological challenges such as the need for fault tolerant power supply and sufficient availability of electric power are now being overcome by the introduction of 48 V-technology. Automated driving level 4 and 5 requires fault tolerant steering, which is a prerequisite for SbW. Steer-by-Wire facilitates the replacement of the steering wheel by innovative controls and avoids a sudden take over by the driver during automated driving the customer acceptance. This offers new prospects for an increasing market penetration.

Following the V-process according to VDI guideline 2206 facilitates a target-oriented proceeding. The system design and specification phase is to be motivated by a user centered approach providing ultimate customer value and user satisfaction. This may lead to a disruptive redesign of the vehicle interior and HMI with new controls like sidesticks, which are common in modern aircraft.

As the steering system is an utmost safety critical system, special emphasis is to be put on the safety concept and its verification along the development process. Functional safety including the controllability of effects of system failures by the driver needs to be proven in accordance with ISO 26262. A too complex system design not only causes unnecessary costs but may also compromise reliability, a too simplistic approach may induce product safety issues.

Following this design path, a high level of customer acceptance is to be expected, as new functions are associated with low additional costs while offering a convincing and attractive driving experience.

Mitglieder-Login