Control logic for an electric power steering system using assist motor

Electric power steering (EPS) systems have many advantages over traditional hydraulic power steering systems in engine efficiency, space efficiency, and environmental compatibility. This research aims at developing EPS control logic for reduction of steering torque exerted by a driver, realization of various steering feels, and improvement of return-to-center performance. In addition, the torque sensor capable of measuring the steering torque and steering wheel angle is devised, and the hardware-in-the-loop simulation (HILS) system that can implement an actual load torque delivered to the steering column is also developed. With the proposed EPS logic, the driver can turn the steering wheel with the steering torque whose magnitude is determined from a torque map independent of load torques that tend to vary depending on the driving conditions. Experimental studies show that the proposed EPS control logic can improve return-to-center performance of the steering wheel by control of the assist motor.