A new robust damping and tracking controller for high speed nanopositioning

This paper presents the design and implementation of a novel control architecture with a resonant controller, an integral controller, and a velocity feedback controller to improve the high speed imaging performance of a nanopositioning stage, piezoelectric tube scanner (PTS) used in most of the commercial atomic force microscopes (AFMs). The design of the controller is done by considering the lateral and longitudinal axes of the PTS as an independent single-input single-output (SISO) system. The controller proposed in this paper is able to achieve a bandwidth close to the first resonance frequency of the PTS and the controller is robust against the changes in resonance frequency of the scanner due to the load change on the scanner. The performance of the proposed controller is illustrated by comparing with an integral controller and it is shown that the bandwidth increased by the proposed controller is five times greater than the bandwidth that can be achieved by using the integral controller in a commercial scanner. Experimental images with the open-loop, closed-loop and built-in AFM proportional integral controller are presented at scanning rates of 15.62 Hz, 31.25 Hz, 62.5 Hz, and 125 Hz to demonstrate the advantage of the proposed controller.