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D. Kohl, T. Riel, R. Saathof, J. Steininger, G. Schitter:
"Auto-Tuning PI Controller for Surface Tracking in Atomic Force Microscopy - A Practical Approach";
Vortrag: 2016 American Control Conference, Boston (USA); 06.07.2016 - 08.07.2016; in: "Proceedings of the 2016 American Control Conference", (2016), 6 S.

Correct tuning of feedback gains is important
for AFMs to cope with uncertainties of the system dynamics
coming from a large range of different samples, cantilevers and
scan parameters. For state of the art AFMs gains have to be
adjusted manually by the operator. The typical operator such
as biologist, physicist or material scientist may not have detailed
knowledge about control engineering. In order to increase
usability and acceptance an easy and intuitive approach is
needed. The method presented in this paper is based on the
commonly applied manual tuning strategy for AFM-imaging
and copies the behavior of an experienced user. By spectral
analysis ringing of the feedback loop is detected when feedback
gains are increased beyond the stability margins. Increasing
gains is stopped when an 1/f stop criteria is reached. The
algorithm is successfully tested in simulation and practical AFM
topography measurements with different cantilever - sample
combinations, demonstrating that auto-tuning can be applied
to achieve imaging performance close to ideal settings.