Sensorless Damping Control of a High Speed Flexure Guided Nanopositioner

Abstract

The scan speed of the Atomic Force Microscope (AFM) is limited by the highly resonant nature of the nanopositioner which scans the sample relative to the probe tip. Feedback control may be used to dampen the resonance; however this requires external displacement sensors which may introduce high frequency noise into the feedback loop. In this work an active piezoelectric shunt control system, which requires no external feedback sensors, is designed to damp the resonance of a high speed flexure guided nanopositioner. The shunt impedance is designed in such a way that the closed loop transfer function from applied voltage to actuator displacement is equivalent to that of a displacement feedback system using a Positive Position Feedback (PPF) controller. This impedance design is an improvement over a passive impedance in that higher damping of the resonance is achievable. AFM images of a test sample were obtained to demonstrate the reduction of image artifacts when this control technique is applied.