Large Distance Nano-Positioning Actuation Control Method And System Research

Large distance nano-positioning technology is the key technology to the 3-D measurement system. At present, the micro-distance nano-positioning actuation technology is well developed, while the large distance actuation with nano-positioning accuracy is still in the development stage and needs further study. The large distance nano-positioning actuation system established by a single-level direct actuation mode and grating sensor is the research focus of this paper, involved in which the large distance nano-positioning actuation and control technology for linear motor and nano-grating measurement technology are the difficult problems of the study.This research subject is originated from the National Natural Science Foundation of major international cooperation project "the key technology and system research of 3-D measurement system" and the National Natural Science Foundation project "the key technology research of Nano-CMM". The main research and innovation of this paper are as follows:In view of the existing grating measurement devices, applied in the large distance nano-positioning actuation control system, can not simultaneously meet the requirements of fast response measurement and nano-resolution measurement, this paper proposes the fast grating subdivision algorithm based on complementary function and grating nano-measurement method. The fast grating subdivision algorithm achieves rapid and reliable displacement measurement only by sampling 10 points with same interval in a cycle of grating signals, and the grating nano-measurement method realizes the fast response measurement and nano-resolution measurement. The grating measurement device developed by the author possesses 1 nm measurement resolution and higher than 100mm/s measurement speed, therefore meets the needs for the large distance nano-positioning actuation measurement and feedback control.Considering the existing problem of bimodal ultrasonic motor actuated by presented actuation mode in low speed, this paper proposes a novel wavelet differential actuation mode, which eliminates the limit of minimum actuation speed with the alternative actuation mode, realizes the whole period actuation that is impossible under the pulse actuation mode, overcomes the positioning creep problems existed in DC actuation mode. The novel actuation mode has greatly improved the bimodal ultrasonic motor actuation characteristics in the low actuation speed and realizes the direct large distance nano-positioning actuation and control only with a single actuation mode. The calibration of actuation characteristics has been conducted with the wavelet differential actuation mode using the self-made calibration device for bimodal ultrasonic motor, The result of calibration proves that the minimum actuation resolution can reach 1 nm.Seeing the situation of nano-positioning accuracy influenced by the electromagnetic disturbances and thrust fluctuations existed in tubular permanent magnet linear synchronous motor, this paper puts forward a kind of "eccentric actuation mode", namely the actuation mode combined with the electromagnetic damping produced by the eccentric installation of motor stator and rotor and the guide friction damping. The experimental result indicates that such actuation mode can effectively restrain and absorb the electromagnetic disturbances and therefore decreases the stable positioning error of linear motor from 100nm to 10nm. Besides, the paper studies the algorithm of no overshoot actuation and points out that adopting varied parameter PI control algorithm can inhibit the overshoot and realizes no overshoot large distance actuation and nano-positioning control.The research results of the paper have solved the difficult problem of adopting a single-level direct actuation mode and grating sensor to realize the large distance actuation and nano-accuracy positioning control, and provide the technical support for establishment of minimization of large distance nano-positioning actuation and control system.