Model-free control for an industrial long-stroke motion system with a nonlinear micropositioning actuator

Fine positioning stages based on piezoceramic materials have found widespread success in various applications due to their attractive features. However, the inherent hard nonlinear behavior of piezoelectric actuators complicates modeling, control, and synchronization processes. In this study, adopting an input–output perspective, we propose and experimentally verify a model-free control and synchronization technique for these stages. Specifically, our approach introduces a model-free trajectory generator that adjusts the desired trajectory using position measurement data to minimize tracking errors. We validate this technique using a representative precision motion system, consisting of a planner stage and a uni-axial fine stage, under step-and-scan trajectories commonly employed in wafer scanners. Remarkably, despite its simplicity, the proposed design procedure can be seamlessly extended to other robotics and automation applications.