Nanopositioning of a multi-axis microactuator using visual servoing

This paper reports on a visual servoing system capable of 2DOF nanopositioning using a novel multi-axis electrostatic MEMS (MicroElectroMechanical System) device. The high-aspect ratio microactuator is bulk microfabricated, producing larger electrostatic forces and requiring lower actuation voltages compared to most existing electrostatic microactuators. A real-time sub-pixel feature tracking algorithm of nanometer resolution is incorporated into the visual servoing loop. A feedforward controller is designed to increase system response. Minimal system calibration is required. The resulting system is capable of visually servoing to a positioning precision of ±16 nm in two axes using the multi-axis microactuator and standard microscope optics with a CCD camera, despite a control rate of 30 Hz which reduces disturbance rejection capability. Potential applications of the system are for nanopositioning in nanomanipulation, such as in the manipulation of subcellular structures within biological cells.