Feedforward and Sliding Mode Control of a Novel Precision 2-DoF Reluctance Motion System

This paper presents the design and implementation of a hybrid sliding mode control (SMC) strategy for a novel two-degree-of-freedom (2-DoF) motion system. The system, driven by a reluctance actuator (RA) for translational motion and two moving magnet actuators (MMAs) for rotational motion, is intended for high-precision applications such as fast-scan mirrors in extreme ultraviolet (EUV) lithography. The nonlinearities of the RA, along with system uncertainties, challenge the controller. To address the dynamics of each axis, a feedforward controller is implemented for the rotational axis, while a robust SMC is developed for the nonlinear translational axis. The SMC is specifically designed to compensate for the RA's strong force-current-position nonlinearity and parametric uncertainties. A smooth hyperbolic tangent function is used to mitigate chattering. The proposed controller is experimentally validated, demonstrating significant improvements in both transient and dynamic tracking performance and validating its suitability for advanced manufacturing and optical applications.