Current-Control Approach for Hysteresis Compensation and Linearization of Nonlinear Reluctance Actuator in Motion System Applications

Reluctance actuators (RAs) present a promising alternative to Lorentz actuators for next-generation positioning and scanning systems, such as wafer scanners and deformable mirrors. However, RAs face challenges such as nonlinear output force characteristics, negative stiffness due to gap dependency, and nonlinear magnetic hysteresis. This paper proposes a current control strategy based on an extended high-gain observer to linearize the dynamic behavior of an RA driving a motion system. The controller integrates a PI controller for tracking the desired current and utilizes the extended high-gain observer to estimate unknown uncertainties and nonlinearities in the actuator dynamics, thereby enhancing system robustness and linearizing the actuator’s behavior. The effectiveness of the proposed controller is demonstrated through simulation and experimental testing. Both simulation and experimental results confirm the controller’s ability to linearize the RA and mitigate the negative stiffness effects caused by position dependency. The experimental results demonstrate the system’s linear behavior under the proposed controller, and the controller also increases the system’s frequency bandwidth to fBW =35 Hz compared to fBW =9.5 Hz for the system without a controller.