| The precise positioning technology is an essential and important technology of miniature machine, precision process, semiconductor manufacturing, electronic product line, bioengineering and nanometer techniques research area etc. Meanwhile, It is also a comprehensive technology involving laser theory, electronics, optics, signal processing, servo drive, intelligent control and some other supporting techniques. Precise positioning technology has some advantages involving high positioning accuracy, good stability, compact system structure etc, which has a broad prospect of application.This paper presents a technology which detects the position and alignment with moire signal of laser. By applying theories of physics optics and Fourier optics, the correlation between displacement of double reflective gratings and the intensity of Moire signal was studied. Besides, a mathematical model of precise displacement detection based on the Moire signal was established and computer-simulated pattern changes were obtained.To improve the accuracy and sensitivity of position signal detection, a reflective precise positioning system which is composed of double reflective gratings measurement equipment and driving system with PT and AC servo motor has been designed. The working principle of the macro positioning system and the control of servo motor have been completed. Based on the reflective grating measurement, a macro drive arithmetic has been designed. The experiment proves that the arithmetic has the characteristics of high speed, high stability and high accuracy. Based on the experimental tests and mechanical analysis, the driving method has been determined. The effective driving of PT has been realied. Finally, according to the characteristics of two stage driving processes, the combination of macro and micro positioning has been realied to complete the precise positioning. By using the method of macro and micro positioning, the high accuracy and quick speed are obtained in the big signal acquisition range, which has effectively solved the contradiction among the position control accuracy, speed and signal capture range.In view of the existing non-linearity and the difficulty in establishing reflective precise positioning model, fuy control method is used in the precise positioning system. The application of neural network PID control realizes the relationship of input and output in fuzzy control and sets up the Fuy neural network controller model. The improved fuy control system which can obtain knowledge automatically has better adapt to the working environment. The Experiment Result shows that Fuzzy neural network PID control can perform excellent control effect, such as better stability, faster response and strong robustness. It could effectively improve position speed with high accuracy. |
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