The manipulation of samples in atomic force microscopes (AFMs) is often performed using piezoelectric actuators. In this paper, a metrological AFM with a 3 degree-of-freedom (DOF) stage driven by piezo-stack actuators is considered. The piezo actuators exhibit hysteresis, which can change the system dynamics and/or acts as a non-linear disturbance on the system. This deteriorates the performance of the AFM. The 3 DOF stage exhibits asymmetric hysteresis, which is modeled by extending the Coleman-Hodgdon model. The asymmetry includes a scan range dependent offset and an asymmetry between the trace and retrace directions. Non-linear multi-variable optimization is employed to derive the optimal generic model for all scan ranges. The proposed extended Coleman-Hodgdon model describes the asymmetric hysteresis over all scan ranges with an accuracy of 97%. Based on the model, a feedforward compensation method is developed. Experiments on the metrological AFM show that the application of the hysteresis feedforward largely improves the scanning accuracy.
|Title of host publication||Proceedings of the 28th American Control Conference, (ACC '09) 10 - 12 June 2009, St. Louis, MO, USA|
|Place of Publication||Piscataway, NJ|
|Publisher||Institute of Electrical and Electronics Engineers|
|Publication status||Published - 2009|