FPAA-based control of a high-speed flexure-guided AFM nanopositioner

Abstract

This paper presents the design, characterization, and control of a novel flexure-guided piezoelectrically actuated atomic force microscope (AFM) nanopositioner. The planar scanner achieves a scan range of $5.8,\mu m$ in both X- and Y-directions with a first resonance frequency above $15\mathrm{kHz}$. Lateral displacements are measured using an interferometer sensor. A signal-transformation-based control technique and a signal pre-shaping method are explored to enhance raster scanning. An integral resonant controller (IRC) increases closed-loop bandwidth by damping the scanner’s fast axis dominant mode. Since the high-bandwidth system requires a high sampling rate, the IRC scheme is implemented using a field-programmable analog array (FPAA). The tracking performance is improved by a double integrator. The effectiveness of the signal transformation approach (STA) with the pre-shaping method in the closed-loop system is investigated. Tracking errors at frequencies from $10\mathrm{Hz}$ to $300\mathrm{Hz}$ maintained RMS values below $50\mathrm{nm}$. Results demonstrate the technique’s success, achieving rapid time-lapse AFM imaging at 10 frames per second over a $2\mu m\times 2\mu m$ scan area.