Modeling and Nonlinear Control of an Electrohydraulic Closed-Center Power-Steering System

This paper deals with the mathematical modeling and the nonlinear control of an electrohydraulic closed-center power-steering system. The system under consideration is characterized by its high energetic efficiency at a full electric power-steering functionality. Based on a nonlinear mathematical model of the system, a flatness-based controller for the servo actuator is designed. Afterwards, an interpretation of the overall steering control system as a mechanical impedance matching problem yields a controller with good performance and robust behavior. Finally, measurement results on a test stand and in a test car show the usefulness of the proposed control approach.