Self-sensing actuation and damping of a piezoelectric tube scanner for atomic force microscopy

Piezoelectric tube scanners are typically used in atomic force microscopy (AFM) to provide the scanning motion of the sample. Excitation of the weakly damped fundamental resonance of the tube scanner leads to oscillations that can cause severe image distortion. This paper presents self-sensing actuation of a piezoelectric tube scanner in order to actively damp the fundamental resonance. By electrically connecting the tube scanner in a capacitive bridge-circuit, the scanner oscillations can be measured without the need for expensive position sensors. In order to compensate for circuit imbalance caused by hysteresis an adaptation circuit is used. The obtained measurement signal is used for feedback control, adding 18dB of damping to the scanners fundamental resonant mode. AFM images are obtained showing a significant reduction in image distortion compared to the uncontrolled case.