Robust H-infinity Position Control for Vehicle Steering

Preprint, 2021

This paper presents a robust position controller for an electric power assisted steering and a steer-by-wire force-feedback system. A typical position controller is required for the driving automation and the vehicle motion control functions. The same controller could also be used to realize the haptic functions for steering feedback.

The driver’s physical impedance causes a parametric uncertainty during the steering wheel coupling. As a consequence, a classical (single variable) position controller becomes less robust and suffers a tracking performance loss. Therefore, a multi-variable robust position controller is proposed to mitigate the effect of uncertainty.

An investigation is performed by including the sensed torque signal in a classical position controller. Finally, a robust solution is synthesized using the LMI-H-infinity optimization. With this, a desired loop gain shape is achieved: (a) a large loop gain at low frequencies for performance; and (b) a small loop gain at high frequencies for robustness.

Frequency response comparison of different controllers on real hardware is presented. Experiments and simulation results clearly illustrate the improvements in reference tracking and robustness with an optimal torque feedback in the proposed H-infinity position controller.