Rattlesnake nanoactuator - a precision high speed closed loop linear actuator with capacitive sensor

Abstract

This thesis describes the development of a novel linear actuator based on a closed loop tightly integrated magnetic motor and capacitive sensor. Mechanical, electrical and software work has resulted in a device achieving a mechanical range of travel of ±1mm with a steady state RMS error of 62nm at a closed loop bandwidth of 3.5kHz, a typical tracking error of hundreds of nanometers (dependent on the waveform shape) and a maximum error in the range of 1 − 10μm. The stiffness of the system at 10Hz is 4N/μm and the actuator has a useful range of motion up to 300 − 500Hz with reduced travel at these speeds due to force limitations. This is possibly an area of continued work; minor modifications could lead to an RMS error of ≈ 20nm, making it possible to outperform piezoelectric actuators in some applications such as adaptive optics or interferometry.