A Study on the Controllability of the Vehicle Steer-by-Wire Systems

This paper describes the controllability investigation of the vehicle Steer-by-Wire (SbW) system for safety architecture development. In currently used electric steering systems, the safe state will be the intended loss of assist (LOA) for preventing unintended self-steer or inappropriate vehicle lateral control, and the related studies give guidelines for fault-tolerant systems. Regulations regarding steering systems strictly demand the human driver can steer in the LOA condition. e.g., ECE R79. However, in a steer by wire system, there can be no mechanical coupling between the steering wheel and the steering mechanism, the motor-off can be the safe state no longer. Consisting SbW system, Steering Feedback Actuator (SFA), and Road Wheel Actuator (RWA) shall be addressed in different safe states separately. Even though the loss of assist occurs on SFA, RWA can be in the vehicle lateral control state by using the steering angle signal. The paper focuses on the controllability of the SFA failure. The methodological approach is composed of questionnaire jury ratings, driving behaviors, and physiological measures. The results show the possible options for the single fault-tolerant safety architecture of SbW systems.