A Solution for a Fail-Operational Control of Steer-by-Wire System without Mechanical Backup Connection 2021-01-0931

The past five years have seen significant research into autonomous vehicles that employ a by-wire steering rack actuator and no steering wheel. There is a clear synergy between these advancements and the parallel development of complete Steer-by-Wire systems for human-operated passenger vehicle applications. Steer-by-Wire architectures presented thus far in the literature require multiple layers of electrical and/or mechanical redundancy to achieve the safety goals. Unfortunately, this level of redundancy makes it difficult to simultaneously achieve three key manufacturer imperatives: safety, reliability, and cost. Hindered by these challenges, as of 2020 only one production car platform employs a Steer-by-Wire system.

This paper presents a Steer-by-Wire architectural solution featuring fail-operational steering control architected with the objective of achieving all system safety, reliability, and cost goals. This architecture does not require a mechanical backup connection or a fail-operational steering column emulator design. The proposed Steer-by-Wire system is comprised of a fail-safe steering column emulator, fail-operational steering rack actuator, steering column angle sensor module and a fail-operational steering angle control signal. This solution provides a cost effective implementation that maintains safe and controllable operation in the presence of a single electrical fault of the steering column emulator or the steering rack actuator.