Robust composite repetitive control with disturbance observer for high-precision tracking of piezo-actuated nano-stages with measurement delays.

In this paper, a robust composite control strategy in the framework of unified infinite-dimensional H∞ optimal control is developed to support nano-scale periodic tracking with improved non-harmonic disturbance attenuation of piezo-actuated nano-stages with sensor-induced measurement delays. In particular, we analyze the electromechanical coupled dynamics and derive a multi-perturbation model, where an extended Youla-Kucera parameterization-based repetitive controller with a disturbance observer is constructed to optimize control performances on high-precision tracking and perturbation rejection. The controller parameters are solved by using a unified infinite-dimensional H∞ optimization method. Comprehensive experiments on a piezo-actuated stage are conducted, where comparative results with representative methods, such as the conventional repetitive control and proportional-integral-derivative control, demonstrate significant performance improvements in hysteresis compensation, trajectory tracking, and disturbance suppression of the proposed method.