Model Reference Control-Based Steering Feel Improvement for Electric Power-Assisted Steering System

Drivers are sensitive to steering feel of a vehicle and significant tuning efforts are placed to set the desired steering feel. This paper discusses a closed-loop torque overlay control system to improve the steering feel of an electric power-assisted steering (EPAS) system. This system has reference model, rack force estimator, and tracking controller. A target steering feel is generated from a reference model in which it uses an estimate of rack force determined from a Kalman filter-based rack force estimator to reflect the actual vehicle operating conditions. A sliding mode controller is designed for tracking the target steering feel. The performance of the proposed control system is evaluated through simulation and a hardware-in-the-loop test. The simulation and experimental results show that the EPAS system with the proposed control method can successfully improve the steering feel under various operation conditions.