Steer-by-wire systems (SBW) offer the potential to enhance steering functionality by enabling features such as automatic lane keeping, park assist, variable steer ratio, and advanced vehicle dynamics control. The lack of a steering intermediate shaft significantly enhances vehicle architectural flexibility. These potential benefits led GM to include steer-by-wire technology in its next generation fuel cell demonstration vehicle, called “Sequel.”
The Sequel's steer-by-wire system consists of front and rear electromechanical actuators, a torque feedback emulator for the steering wheel, and a distributed electronic control system. Redundancy of sensors, actuators, controllers, and power allows the system to be fault-tolerant. Control is provided by multiple ECU's that are linked by a fault-tolerant communication system called FlexRay.
In this paper, we describe the objectives for fault tolerance and performance that were established for the Sequel. An overview of the system design and development process is presented. The resulting component layout and control system architecture is discussed. We conclude that it may be possible for a steer-by-wire system to meet certain objectives for fault tolerance and performance. It can also provide design flexibility that enables new vehicle architectures such as the Sequel fuel cell vehicle.