Hybrid reluctance actuator for high-speed scanner with nanometer resolution

Abstract

In high-precision positioning systems, piezoelectric and Lorentz actuators have been the most commonly used actuation technologies. However, these actuators require strict design trade-offs between bandwidth, stroke and force, which limits the achievable system performance. These limitations represent a challenge for the development of a high-speed, long-range scanner for high-precision instruments, such as atomic force microscopes. In order to improve the performance of scanners, this thesis proposes to use a hybrid reluctance actuator for high-speed, long-stroke scanning motion with nanometer resolution. The hybrid reluctance actuator is designed and implemented using finite element analysis. Additionally, for the demonstration of the scanning, the required electronics and sensors are selected, and motion control is applied. The experimental results successfully demonstrate the actuator¿s high positioning resolution of 0.8nm (RMS) and high closed-loop control bandwidth of 3.6 kHz. The measured motor constant is two times higher than the simulated value of a Lorentz actuator, using the same amount of electrical energy. The achieved stroke is 800 ¿m, which is larger than the range of typical piezoelectric actuators for high-speed applications. In order to demonstrate the high-speed scanning capability, the hybrid reluctance actuator is operated with feedforward control. The used motion trajectory is a band-limited triangular wave with a frequency of 400 Hz and an amplitude of ±1 ¿m. The achieved peak-to-peak and RMS tracking errors are 25nm and 3.7nm respectively.