Optimal control and gain scheduling of electrical power steering systems

In this paper, an optimal control method is employed to design controllers for improved performance and robustness of electrical steering systems. Electric Steering systems are nonlinear MIMO systems with multiple objectives, including fast response to the driver torque command, good driver feel, and attenuation of load disturbance and sensor noises. Since the Electric steering system has nonlinear frictions, component deviations and load disturbances, its linearized model is subject to significant modeling errors and external disturbances. Consequently, electric steering controllers must provide substantial robustness. In this paper, a control design method is introduced which employs the boost curve to form a feedforward control and an MISO H^infin optimal feedback to ensure refined performance, robustness, and disturbance attenuation. The controller is evaluated via simulation on both linearized systems and original nonlinear systems, and verified on vehicle testing data.