Robust 2DOF-control of a piezoelectric tube scanner for high speed atomic force microscopy

Abstract

Utilizing modern model-based control methods improves the performance of an atomic force microscope (AFM) substantially when compared to the state of the art commercial realizations. The design and implementation of a two~degree-of-freedom (2DOF) controller on a commercial AFM system is presented enabling topography measurements on the nano-scale at higher scan rates with reduced measurement error. The closed-loop operation of the AFM system is performed by an H,,,-controller, while the scanner is simultaneously tracked to the last scan line by a model-based feedforward controller. Experimental results obtained at 15 Hz line-scan rate exhibit a maximum control error reduced by a factor of about 6 in comparison with the commercial system.