|Reduction of Phase Error between Sinusoidal Motions and Vibration of a Tube Scanner During Spiral Scanning Using an AFM
Habibullah, Hemanshu Pota, and I. R. Petersen
International Journal of Control, Automation, and Systems, vol. 14, no. 2, pp.505-513, 2016
Abstract : The design of a phase-locked loop (PLL)-based proportional integral (PI) controller for compensating
the phase error between motions from the lateral axes of a piezoelectric tube scanner (PTS) during spiral scanning
for an atomic force microscope (AFM) is proposed in this paper. Spiral motion of the PTS for scanning of material
surfaces or biological samples using an AFM is achieved by applying two sinusoidal signals with a 90 degree
phase-shift and of varying amplitudes to the X and Y-axes of the scanner. The phase error between the X and
Y-axes positions and scanner’s vibration due to its mechanical properties increase with increasing scanning speeds
which reduce the imaging performance of the AFM at high frequencies. In the proposed control scheme, a vibration
compensator is used with the X and Y-PTS to damp the vibration of the PTS at its resonant frequency and the phase
error between the displacements of the two lateral axes of the scanner is measured by a phase detector and a PI
controller is used to reduce the error. Comparisons of experimental results for reference tracking and imaging
performance with the AFM PI controller demonstrate the efficiency of the proposed control method.
Atomic force microscope, phase-locked loop control, piezoelectric tube scanner, vibration control.
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