Abstract
With the development of optoelectronic information technology, high-performance optical systems require an increasingly higher surface accuracy of optical mirrors. The fast tool servo (FTS) based on the piezoelectric actuator is widely used in the compensation machining of high-precision optical mirrors. However, with the low natural frequency of mechanical structures, hysteresis of the piezoelectric actuators, and phase delay of the control systems, conventional FTS systems face problems such as a low working frequency and a large tracking error. This study presents a method for the design of a high-performance FTS system. First, a flexure hinge servo turret with a high natural frequency was designed through multi-objective optimization and finite element simulations. Subsequently, a composite control algorithm was proposed, targeting the problems of hysteresis and phase delay. The modified Prandtl–Ishlinskii inverse hysteresis model was used to overcome the hysteresis effect and a zero-phase error tracker was designed to reduce the phase error. The experimental results reveal that the tracking error of the designed FTS system was <10% in the full frequency range (0–1000 Hz).
Highlights
Ultra-precision optical elements have been widely used in modern optical systems, such as imaging systems, early warning and detection systems, and high-power lasers, and their accuracy typically needs to be >0.1 μm
With the design of the zero-phase error controller, The experimental setup is shown in Figure 11; it consisted of a piezoelectric actuator the high-frequency phase delay of the fast tool servo (FTS) system could be theoretically eliminated
The experimental setup is shown in Figure 11; it consisted of a piezoelectric actuator (PI225.40), a power amplifier (E482.00), a Power PMAC motion controller, a capacitive sensor (D-510.051), and a flexure hinge tool holder
Summary
Ultra-precision optical elements have been widely used in modern optical systems, such as imaging systems, early warning and detection systems, and high-power lasers, and their accuracy typically needs to be >0.1 μm. Because imaging optical systems develop from infrared to visible light and to short wavelengths, a higher machining accuracy is required in optical mirrors. With factors such as clamping and cutting errors in the machining process of ultra-precision lathes [1], achieving the accuracy requirements for optical mirrors through one-time machining is difficult [2]. The real-time compensation of machining errors was shown to improve the machining accuracy of optical mirrors [3,4]. Due to the effects of various machining factors, the machining error surface shape is complex and distributed at various frequencies [5]
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