A Control Method Utilizing EPS to Reduce Steering Pull When Driving on Rutted Roads 2009-01-0044

Electric power steering (EPS) systems utilize an electric motor to assist the driver’s steering efforts. Recently, EPS is drawing attention as a mechanism for improving vehicle stability and maneuverability. This paper proposes a control method using EPS to improve steering maneuverability when driving on rutted roads. The disturbance torque generated by the grooves in rutted roads affects maneuverability. Conventional EPS cannot discriminate between torque originating from driver input and aligning torque generated by the road surface. Thus, it is difficult for conventional EPS to reduce the unstable effect caused by ruts without affecting the driver’s steering feel. The method proposed here detects the amount of disturbance torque caused by the ruts in the road, and only when disturbance torque is detected, the EPS system compensates accordingly. As a result, steering pull is reduced without interfering with the driver’s steering feel. We experimented with the proposed control method using a test vehicle and proved that it reduces steering pull. Consequently, steering maneuverability is improved on rutted roads.