The control strategy of the electric power steering system for steering feel control

Abstract

The steering feel is mostly indirectly adjusted by directly modifying the assist’s magnitude of the electric power steering system. The adjustment is complex, and workload is large, and the steering feel is highly dependent on the performance of the hardware. It has poor robustness to vehicle performance degradation and external disturbance, so providing a consistent and controllable steering feel is not easy. This paper proposes an EPS control strategy for steering feel control based on closed-loop control of steering motion to solve the above problems. Firstly, take the driver’s desired steering motion intensity and pinion angle position as intermediate variables to decompose the EPS control strategy into three parts: steering style, the desired pinion angle calculation, and the desired steering resistance moment calculation. This decomposition method makes the steering feel control independent of the vehicle dynamics characteristics and reduces the difficulty of vehicle characteristic calibration and correction. In addition, a steering style model based on Stevens’ law and considering hysteresis characteristics is proposed. The steering feel can be directly controlled based on calibrating the vehicle's dynamic characteristics and the designed steering style. The test results driven by ACSL driving simulators of Jilin University show that adopting the control strategy proposed in this paper can improve the vehicle’s return-to-center performance, realize the designed driving style, and provide consistent and controllable steering feel with the design hysteresis characteristic. In addition, it has good robustness against the deterioration of vehicle hardware performance and external disturbance.