Achieving high-bandwidth nanopositioning in presence of plant uncertainties

In the absence of plant parameter uncertainties, inversion-based feedforward techniques have been known to deliver accurate tracking performance. Due to changes in operating conditions like ambient temperature, humidity and loading, piezoelectric-stack actuated nanopositioning platforms can undergo significant changes in their system parameters. Nonlinear effects of hysteresis, an inherent property of a piezoelectric actuator, are also present; charge actuation is applied to reduce the effects of hysteresis. In this work, a suitable feedback controller that reduces the effects of parameter uncertainties is integrated with the inversion-based feedforward technique to deliver accurate nanopositioning over a large bandwidth. It is shown experimentally that by integrating closed-loop damping, inversion-based feedforward and charge actuation, the tracking bandwidth of the platform from can be increased significantly from 310 Hz to 1320 Hz.