A MIMO controller design for damping, tracking, and cross coupling reduction of nanopositioners

This paper presents the design and implementation of a multi-input multi-output (MIMO) controller using a resonant controller, an integral controller, and a velocity feedback controller for damping, tracking and cross coupling reduction of a nanopositioner used in most of the scanning probe microscopes (SPMs). The MIMO dynamics identification of the system are done by using measured data and the design of the controller is based on to achieve large bandwidth and small cross coupling effects between the axes of the nanopositioner. The controller design presented in this paper is able to achieve a bandwidth close to the first resonance frequency of a nanopositioner which is five times greater than the bandwidth that can achieved by using a standard integral controller. Experimental images at scanning rates of 62.5 Hz and 125 Hz obtained by using the proposed controller and the built-in proportional- integral (PI) controller in a SPM are given to illustrate the effectiveness of the proposed controller.