A double velocity feedback controller design for high speed atomic force microscopy

This paper presents a design of a controller using two velocity feedback controllers (VFCs) and an integral controller for a piezoelectric tube scanner (PTS) of an atomic force microscope (AFM) to improve the high speed imaging performance of the AFM by damping the first resonant mode of the PTS and increasing the bandwidth of the closed-loop system. The design of VFC to damp the first resonant mode of the PTS is based on a mixed negative-imaginary and small-gain approach. The X- and Y-axis dynamics of the PTS are treated as two independent single-input singleoutput systems and the systems are identified from measured open-loop data. The performance improvement achieved by the proposed controller is presented by comparing the scanned images obtained by implementing the proposed controller and the built-in proportional-integral (PI) controller of the AFM.