The Measurement Method Of Three Degreee Freedom Motion Error Based On The No-return Laser Interferometer System

In order to meet various requirements for precision machining and measurement, all countries in the world are developing a variety of precision platforms, and the relevant research and development has progressed rapidly. Two-dimension displacement platform with measurement function, wide range and high precision has a broad application prospect and is of great significance in precision measurement, product manufacture, navigation, etc. On the basis of Michelson’s interference principle, this paper proposes a 3-DOF measurement method with 3-reflector combination as the objective vector, which is also known as the 3-plane-mirror combination method relying on application of the theoretical correlation between interference fringe shape and light intersection angle, so as to achieve micro-angle and micro-displacement measurement. This method realizes the measurements of straightness, deflection, etc. For this system, the corresponding theoretical model is established by using MATLAB to analyze the corresponding data collected by the STM32 microcontroller, designed hardware circuit and software algorithm, and demonstrations were carried out through corresponding experiments.The main research contents are as follows.Firstly, in order to overcome the laser feedback effect caused by laser’s return via the original optical path, this article designed the laser interference measurement system with a 3-reflector combination as the objective vector, according to Michelson’s interference principle. Laser alignment characteristics and optical path design were analyzed. Through light beam direction, and the space vector model of optical path, the feasibility and validity of this system in avoiding laser feedback effect was discussed.Secondly, the relation model between stripe shape and light beam intersection angle was established, and the theoretical relationship between platform angle change and stripe shape was obtained. As signal processing often determines measurement accuracy, we studied the light intensity signal receiving and processing methods of the laser interference system, analyzed the advantages and disadvantages of photoelectric detectors combined with the common CCD identification method, mainly introduced the different calculation methods of phase position for crossed and round four-quadrant photoelectric detectors, and finally conducted the corresponding simulation analysis by using the MATLAB software.Thirdly, the overall implementation plan of the interference measurement system was proposed to realize the process of drive, signal reception and treatment, as well as interface display. The PZT(piezoelectric ceramic) hardware driving circuit and four-quadrant photoelectric conversion circuit was designed to achieve dynamic stripe modulation and signal extraction. In the recognition processing of four-quadrant phase difference, the ellipse fitting algorithm was applied, and the platform displacement and deflection may be obtained through the available parameters, thus realizing the measurement purposes.Finally, through experimental sampling and the synchronous contrast experiment of the advanced angle measurement instrument ELCOMAT3000 dual-axis electronic autocollimator, an error analysis and error compensation were carried out on the measured data to verified the accuracy and feasibility of the corresponding designs proposed in this article. This interference measurement system could well realize the measurements of platform angle deflection and displacement.