High-speed Scanner with Nanometer Resolution Using a Hybrid Reluctance Force Actuator

This paper proposes a high-precision, high-speed scanner using a hybrid reluctance actuator, which can be stronger than conventionally used comparable Lorentz force actuators. For compactness, its mover is guided by flexures and laterally moved by a hybrid reluctance actuator with a voltage amplifier. To reject disturbances such as thermal drift and hysteresis, the scanner is regulated by cascade control, for which parasitic resonances are damped partially mechanically. As a result, the closed-loop system realizes a high control bandwidth of 3.5 kHz and a high positioning resolution of 0.8 nm at a static point. For high-speed scanning motion, modeling-free inversion-based iterative control (IIC) is proposed to be combined with the cascade control as the scanner's feedforward controller. Experiments demonstrate that the scanner with the cascade control realizes a 2 mu m triangular motion at 400 Hz with a tracking error of 101 nm, and the modeling-free IIC successfully decreases this relatively large error by a factor of 26 to 3.8 nm. Consequently, this paper clearly demonstrates that the proposed scanner with the hybrid reluctance actuator can realize high-precision, high-speed scanning motion.