Research On Ultra - Precision Angle Displacement Measurement And Intelligent Control Technology

Precision angular positioning technology is a compound control system integrated with mechanical, electronic, optical, and intelligent control, which is widely used in precision angular displacement measurement and control such as the detection of the flatness of silicon wafer in the integrated circuit and the straightness measurement of precision guide. This dissertation focuses on the key technology of precision angular displacement measurement and control by utilizing laser Moire signals. The details are as following:The characteristics of angular displacement of Moire signals diffracted by double gratings were analyzed. A mathematic model on intensity deviation of Moire signal corresponding angular displacement was established. The pattern of changes in the angular displacement was simulated with the help of computer. The simulation results indicated that the intensity of Moire signals varied periodically with relative displacement and space of the gratings. Maximum intensity was obtained at the condition of G=nP2|λ, where n is an integer. At the same time, the simulation of angular displacement change rule of Moire signals indicated that the intensity of Moire signals varied periodically within the Fresnel zone with relative angular displacement of the gratings.The macro displacement mechanism of step motor as the core, with a precision lead screw transmission mechanism, according to the pulse command sent by IPC and displacement signal detected by gratings, the alignment range can be narrowed down to within ±5μrad; micro displacement mechanism with piezoelectric ceramics as the core, with flexible hinges as drive mechanism, according to the detection signal of angular displacement, issued the corresponding driving voltage, driving the piezoelectric actuator deformation, so as to drive the transmission mechanism of the micro angle adjustment. The fine displacement accuracy could be ±100nrad. This strategy could achieve precision angular displacement measurement and control in the wide work range and high precision.Due to the existence of non-linearity in the piezoelectric ceramic in the process of precision angular alignment, the input and output characteristics of piezoelectric ceramics were studied by experimental analysis to improve the precision of angular displacement positioning accuracy and stability. And the application of neural network technique to simulate the input and output of the piezoelectric ceramics, reducing the effect of PZT nonlinear of precision angular displacement measurement and control, effectively improve the angular displacement measuring speed with high accuracy.