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G. Schitter, A. Scarpas, F. Allgöwer:
"Robust two-degree-of-freedom control of an atomic force microscope";
Asian Journal of Control, 6 (2004), 2; 156 - 163.

The performance of an atomic force microscope (AFM) is improved
substantially by utilizing modern model-based control methods in comparison
to a standard proportional-integral (PI) controlled AFM system. We present
the design and implementation of a two-degree-of-freedom (2DOF)-
controller to accomplish topography measurements at high scan-rates with
reduced measurement error. An H∞-controller operates the AFM system in a
closed loop while a model-based feedforward controller tracks the scanner to
the last recorded scan-line. Experimental results compare the actual performance
of the standard PI-controlled AFM and the 2DOF controlled system.
The new controller reduces the control error considerably and enables imaging
at higher speeds and at weaker tip-sample interaction forces.

Nanotechnology, fast scanning, AFM, robust control, scanning probe.