A fractional-order active damping control approach for piezo-actuated nanopositioning stages

In this paper, a fractional-order control (FOC) based approach is proposed for piezo-actuated nanopositioning stage. The developed controller is not only to suppress the vibration of the low-damped resonant mode, but also to minimize the tracking error for nanopositioning applications. Firstly, an inverse hysteresis compensator is utilized to compensate for the inherent hysteresis nonlinearity of the piezoelectric actuator. Then, the fractional-order control technique is developed to suppress the unwanted vibration. For implementation, an Oustaloup method is presented to realize the approximation of the fractional differential operator. Meanwhile, the closed-loop poles placement method is employed to optimize the controller parameters. In this sense, a high-gain feedback controller can be designed to minimize the tracking errors of the nanopositioning stage. Finally, the effectiveness of the proposed control approach is demonstrated by comparative experiments on a custom-built nanopositioning stage. The results show that the fractional-order based control approach damps the resonant mode of the nanopositioning stage and improves the bandwidth from 108 Hz to 733 Hz.