Fast scanning using piezoelectric tube nanopositioners: A negative imaginary approach

Most commercially available atomic force microscopes (AFMs) use piezoelectric tube nano-positioners for scanning. Current scanning frequencies are less than 0.01
f

_r
, where
f

_r
is the frequency of the first resonant mode of the piezoelectric tube used. An improvement in the scanning rates without losing the nano-scale precision is desired. Here, a prototype of the scanning unit of an AFM is considered. The dynamics of the piezo tube, used in the prototype, is approximated by a model that satisfies the negative imaginary property. The resonant mode that hampers the fast scanning is identified from the model and damped using a feedback control technique known as the Integral Resonant Control (IRC). The piezoelectric tube is then actuated to have fast and accurate scans.