Steer-by-Wire for Vehicle State Estimation and Control

In order to implement electronically variable dynamics for vehicle handling, the control system requires an accurate knowledge of the vehicle states as well as a means of actuation to precisely influence the vehicle’s motion. Steer-by-wire capability conveniently addresses both of these requirements. This paper first presents an approach to estimating vehicle sideslip angle using steering torque information. This method is especially suited to vehicles equipped with steer-by-wire since the steering torque can easily be determined from the current applied to the steering motor. By combining a linear vehicle model with the steering system model, a simple observer may be devised to estimate sideslip when yaw rate and steering angle are measured. Based on this estimate of sideslip angle, a type of state feedback control has been developed to effectively alter the handling characteristics of a vehicle through active steering intervention. Both the observer and its application to vehicle handling modification are demonstrated on an experimental vehicle equipped with steer-by-wire capability.