Robust Time-Optimal Command Shaping for Piezoelectric Actuators: STM Application

Abstract

A scanning tunneling microscope (STM) uses a piezoelectric actuator to perform constant-velocity scanning motion. Many feedback strategies have been proposed, but their achievable scan rate is substantially limited by the turnaround transients in the scan path. Therefore, a robust time-optimal command shaping technique with an iterative search procedure is introduced in this paper to improve the scan speed of piezoactuators, and is applicable to a general class of systems without rigid-body mode. Furthermore, a time-energy-optimal formulation is presented to reduce the in-maneuver oscillation. The hysteresis nonlinearity of piezoactuators is compensated using the proposed continuous numerical inversion algorithm. Finally, the closed-loop simulation shows the performance robustness in the presence of hysteresis cancellation error and natural frequency perturbation.