Model-Free Control of a Class of High-Precision Scanning Motion Systems with Piezoceramic Actuators

To enhance the precision of coarse long-stroke motion axes, complementary short-stroke fine positioning stages are usually introduced. Being mechanically attached, the motion of the combined positioning stages needs to be controlled and synchronized. Therefore, typically suitable model-based controllers of fine stages are designed according to the so- phisticated models and identification techniques used. Due to their appealing features, Piezocermamic-based fine positioning stages were successfully utilized in many applications, which recently sparked their use in high-acceleration motion found in wafer scanners, for example, where high-precision motion is required despite the resulting high inertial forces involved. Unfortunately, hard nonlinear behavior is associated with piezo- electric actuators, which adds to the complexity of modeling, control, and synchronization processes. To overcome such a burden, in this study, the design procedure of a model-free control and synchronization technique of piezocermamic-based fine positioning stages is introduced and verified experimentally using a representative precision motion system comprising a planner stage and a uni-axial fine stage under step-and-scan trajectories commonly used in wafer scanners. Despite its sim- plicity, the herein proposed design procedure can be seamlessly extended to other robotics and automation applications.