Model-based analysis of the hysteresis curve of an electric power steering system

Steering feel delivers torque feedback from the steering wheel of a vehicle to the driver and plays a critical role in communicating useful information related to road and vehicle dynamics. The steering feel of a conventional vehicle is generally evaluated using on-center handling, which is the steering behavior at high speed and a low lateral acceleration boundary. The hysteresis curve is the most widely used method used to observe the characteristic of on-center handling steering feel. The majority of previous research related to hysteresis curves focused on developing an efficient method to test and determine a meaningful index from the hysteresis curve when there is already a well-designed system controller. However, the mathematical relationship between the hysteresis curve and steering system has not been adequately studied. This paper analyzes the hysteresis curve based on the electric power steering model. The shape of the hysteresis curve is characterized by a transfer function consisting of the system and a controller parameter in the frequency domain. The theoretical analysis is verified by simulation results.