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S. Kuiper, G. Schitter:
"Active damping of a piezoelectric tube scanner using self-sening piezo actuation";
Mechatronics, 20 (2010), S. 656 - 665.

In most Atomic Force Microscopes (AFM), a piezoelectric tube scanner is used to position the sample
underneath the measurement probe. Oscillations stemming from the weakly damped resonances of
the tube scanner are a major source of image distortion, putting a limitation on the achievable imaging
speed. This paper demonstrates active damping of these oscillations in multiple scanning axes without
the need for additional position sensors. By connecting the tube scanner in a capacitive bridge circuit
the scanner oscillations can be measured in both scanning axes, using the same piezo material as an actuator
and sensor simultaneously. In order to compensate for circuit imbalance caused by hysteresis in the
piezo element, an adaptive balancing circuit is used. The obtained measurement signal is used for feedback
control, reducing the resonance peaks in both scanning axes by 18 dB and the cross-coupling at
those frequencies by 30 dB.
Experimental results demonstrate a significant reduction in scanner oscillations when applying the
typical triangular scanning signals, as well as a strong reduction in coupling induced oscillations.
Recorded AFM images show a considerable reduction in image distortion due to the proposed control
method, enabling artifact free AFM-imaging at a speed of 122 lines per second with a standard piezoelectric
tube scanner.

Atomic Force Microscopy Piezoelectric actuators Self-sensing actuation