Experimental Validation of Ultra-Precision Nanopositioning System

Abstract

In this paper, the development of an ultra-precision XY nanopositioning stage is presented. For system structure, the actuator decoupled parallel compliant mechanism is designed to have the same dynamics in both x- and y-direction so that the coupling crosstalk between two axes can be minimized. Throughout the simulation validation of the deformed XY stage, the motion in the x-axis is not transferred to the motion in the y-axis. For the control structure, the simplified feedforward compensator provides the piezoelectric actuator to reduce the control effort of the system. A proportional double integral (PII) feedback controller is used to minimize the ramp-like disturbances so that the compensation of hysteretic nonlinearity and other disturbances can be effectively reduced. Moreover, the jerk-based optimal reference trajectory is designed so that 10 $\mu \text{m}$ displacement at the constant speed with the smooth accel/deceleration period can be achieved. Having an experimental setup with several scenarios such as the constant speed of 10 $\mu \text{m}$ /s, 20 $\mu \text{m}$ /s, and 40 $\mu \text{m}$ /s, the tracking error can minimize within ± 2.5 nanometers, ± 3 nanometers, and ± 5 nanometers in the x-axis for each case. Moreover, the hysteresis variable is well compensated that the relationship between the reference trajectory and output displacement is almost linear. The proposed control strategies and implementation methods can operate the piezoelectric actuated XY stage system with the nanoscale precision motion for convenience.