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In this paper, we suggest a new steering wheel returnability control strategy for EPS(Electric Power Steering) system to improve on-center handling performance. To improve steering wheel returnability for on-center handling performance, we developed a new control strategy based on estimation of alignment torque generated by tire and road surface. The returnability control algorithm only uses estimated values of the slip angle and the lateral acceleration that can be easily computed from sensor signals commonly available in passenger vehicles. The proposed algorithm was coded with Simulink, and it was cosimulated with the CarSim vehicle model. The performance of the proposed algorithm was compared with that of the conventional algorithm and it demonstrated improvement in both returnability and on-center handling performance.

In this paper, the hardware-in-the loop simulator which is used for evaluating performance of the EPS (Electric Power Steering) system has been developed. The HILS system consists of the steering system of the light commercial vehicle - the steering wheel, the EPS module, the universal joint, and the rack bar. These components were placed in proper spaces based on location of their hard points in an actual vehicle. An electric servo motor has been used for generating the road reaction force which is generated by vehicle's kingpin moment. A real-time simulation environment has been developed using CarSim to evaluate performance of EPS through various handling tests. For verifying reliability of the HILS system, various handling tests were performed and compared with the results of actual vehicle tests in the proving ground. Through the developed EPS HILS system, various handling tests were successfully performed in the laboratory.