Design parameters of a reluctance actuation system for stable operation conditions with applications of high‐precision motions in lithography machines

Abstract

Recently, the reluctance actuator has attracted great attention to replace the Lorentz actuator in the next generation of wafer scanners in semi‐conductor lithography machines. The reluctance actuator has a non‐linear position‐force characteristic, which may cause high oscillations and unstable operation. This study presents a linearisation technique by optimising the main parameters of the reluctance actuator to operate away from the saturation point. Also, in this study, the critical current is formulated for the stable dynamic behaviour of the reluctance actuator. Optimisation based on the Grey Wolf Optimiser is performed considering the high‐precision motion requirements and physical constraints. The high‐precision motion requirements include the desired work‐space displacement, natural frequency, and maximum force. The electromechanical dynamic model of the reluctance actuator motion system is formulated to characterise the interaction among electrical, magnetic, and mechanical parts. The simulation results show that the optimal design of the reluctance actuator works in the linear region, and for stable dynamic behaviour, the input current is limited by the critical current. Finally, a feedforward controller is designed based on the approximation of the force–current relationship to improve the tracking performances of the reluctance actuator motion system. The simulation results in time and frequency domains show an improvement in tracking performances using the feedforward controller.

High-Performance Flux Tracking Controller for Reluctance Actuator

“…Voice coil motors (VCM), however, are near their physical limit and cannot provide large enough thrust for the required high acceleration in the photolithography. Thus, a novel reluctance actuator is proposed in [7][8][9]. Compared with VCM, the reluctance motor has the advantages of high output density and low energy consumption, but the strong hysteresis nonlinearity restricts the control accuracy of the reluctance actuator and limits its application in the high-precision positioning system [10][11][12][13], especially when hysteresis is coupled with the displacement effect and eddy current effect, which lead to displacement-dependent and rate-dependent hysteresis in the reluctance actuator.…”

Precision Flux Control of Linear Reluctance Actuator Using the Integral Sliding Mode Method

“…Different from the Lorentz motor, the force of the reluctance motor is not linearly proportional but a square of the excitation current. So it could bring about larger force to current ratio and achieve significantly higher power densities and lower dissipations (Cigarini et al, 2020;Ito et al, 2020;Moya-Lasheras et al, 2020;Burgstaller et al, 2021;Moya-Lasheras et al, 2021;Al Saaideh et al, 2022). As a promising new candidate, the reluctance motor also brings various intractable issues.…”