On a robust control system design for an electric power assist steering system

This paper presents the application of an active disturbance rejection controller (ADRC) to an electrical power assist steering system (EPAS) in automobiles. The control objective is to reduce the steering torque exerted by a driver so as to achieve good steering feel in the presences of external disturbances and system uncertainties. With the proposed ADRC, the driver can turn the steering wheel with the desired steering torque which is independent of load torques that tend to vary depending on driving conditions. The ADRC is constructed on a column-type EPAS model. The computer simulation and frequency-domain analyses verified the robustness and stability of the ADRC controlled system.