Robust motion tracking control of piezo-driven flexure-based four-bar mechanism for micro/nano manipulation

This paper presents a robust motion tracking control methodology for a flexure-based four-bar micro/nano manipulator driven by a piezoelectric actuator. This control methodology is proposed for tracking desired motion trajectories in view of the problems of unknown or uncertain system parameters, non-linearities including the hysteresis effect, and external disturbances in the system. In this paper, equations of the angular stiffness, 'static' linear stiffness, and structural resonance of a flexure-hinged mechanism are presented. In addition, a lumped parameter dynamic model is established for the formulation of the proposed control methodology. The convergence of the position tracking error to zero is assured by the approach in the presence of the aforementioned conditions. The stability of the closed-loop system is proven theoretically, and a precise tracking performance in following a desired motion trajectory is demonstrated in the experimental study. One of the most important advantages of this control methodology is that the approach requires only a knowledge of the estimated lumped parameters in the physical realisation. With the capability of motion tracking, the robust motion control methodology is very attractive in realising high-performance flexure-based control applications in the field of micro/nano manipulation. (c) 2007 Elsevier Ltd. All rights reserved.