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 0.01f(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.