Discrete-time iterative learning control for vehicle Steer-by-Wire systems

This paper presents an iterative learning control (ILC) design for a vehicle Steer-by-Wire (SbW) system. First, the SbW system is modeled as a second-order system from the steering motor input voltage to the front wheel angle. For simplicity, the self-aligning torque and the friction between the tires and various road surfaces are treated as unknown external disturbance imposed at the SbW system input. Next, a discretetime ILC is designed for the SbW system under the scenario that the steering reference command is periodic. The ILC is essentially a feedforward control approach which utilizes past information of the control loop to further reduce the tracking error in each iteration. Finally, simulation is carried out to validate the performance of the ILC design. It is shown that the steering tracking error achieved by the ILC is much smaller than a conventional PD controller.