Study On The Ultra-precision Laser 3-dimensional Measurement And Control Technology

Coordinate Measuring Machines (CMMs) are playing more and more important role in modern production, advanced manufacture technology, aviation, space flight, and national defense industries since they possess high measuring accuracy and flexibility. With the rapid development of science and technology, more attention paid by the government to the national defense, and the development of new airplanes, bombs and satellites, high measurement accuracy and capability of measuring parts with complicated forms are essential for CMMs. This thesis focuses on the enhancement of CMM measurement accuracy.The enhancement of measurement accuracy includes reduction of structure and probing errors of the CMM, reduction of the uncertainties caused by the environmental factors during measurement. In this thesis, a CMM with three interferometers used for X, Y, and Z direction displacement measurements and a 3-dimensional inductive analog probe is designed. Based on the study of laser interferometric system, 3-dimensional inductive analog probe, real-time position control system, error compensation technology and small-volume environmental control technology, high measurement accuracy has been achieved.The main contents of the thesis include: (1) study on the mechanical structure of the super-accurate CMM, (2) study on the position measurement and control technologies using ultra-accurate laser interferometers, (3) study on high accurate 3-dimensional inductive analog probe, (4) data processing technology in the measurement process and that of the measurement results. (5) study on the coordinate measurement error separation and compensation technologies, (6) study on the small volume environmental control technology.The main creative ideas and innovations of the thesis include the follows.1. A new mechanical structure is proposed and designed. This structure complies with the principle of kinematical design, Abbe , meets the dynamics requirements in assembly and possesses good rigidi ty. The core of the structure is the use of precision air-floating guides with small-hole throttle technology, which offers a motion straightness accuracy of 0.05μm /500mm, and a rigidity of 250N/μm。2. He-Ne laser interferometers are used in the displacement measurement to replace the traditional grating scales. By using this technique high stable and nanometer precision displacement measurement and closed-loop control have been achieved. The displacement measurement resolution reaches 0.01μm, and the response time is less than 5ms.3. A high precision 3-dimensional inductive analog probe is developed to realize the point to point position measurement in the normal direction and continuous scanning measurement. A method for compensating the probe error based on geometric element correction by using repeated iteration is designed. The volumetric measurement uncertainty of the probe has been reduced to 0.2μm.4. A multi-CPU distributed real time position control algorithm with deceleration broken-line approximation, and on-line correction and smoothing is developed to achieve dynamic position control and real time measurement with high accuracy, and to improve the space tracking property of the CMM.