Research On The Precision Theory Of Large-Scale Coordinate Measuring Systems

Large-Scale coordinate measuring systems(LSCMS) are demanded more and more widely in modem industry. Taking advantage of large measuring zone, high accuracy, non-contact, flexibility and dynamic measurement, LSCMS have become substitution of traditional CMMs in the field mentioned above. They play a key role in assuring manufacturing quality. With the development of production and technology there is a increasing need of measuring facility with higher accuracy and more powerful dynamic performance. It is noticed that there is a growing worldwide effort to develop new-type LSCMS. This paper brings into focus the precision theory of LSCMS especially their dynamic measurement accuracy. The project has got support both from National Science Foundation of China with project number 59735120 and from national defence research with project number KBB91 101. The motivation is the desire to promote LSCMS and to improve application level of existing facility. The emphasis is put on the theodolite measuring system, laser tracking system(LTS) with both spherical coordinate frame and trilateration technique. The dissertation covers the following aspects concering the main work and creative research in the project. 1. The bundle adjustment and adjustment of 3D control network for measurement stations are emphatically studied in the orientation of theodolite measuring system. The sequencial adjustment is specially applied to the 3D coordinates estimation. The sequencial adjustment is proven to be identical to the integral adjustment, therefore it is an effective method to improve estimation accuracy of 3D coordinates. The relation between the position error and geometrical configuration in the theodolite measuring system is investigated by which the point with the best measurement accuracy can be located. This lays a foundation for the optimization of arrangement of theodolites with respect to the point to be located. 2. The mathematical models to calibrate inicial distance for two distinct sorts of laser tracking systems(LTS) are established. The length measuring uncertainty of LTS with spherical coordinate frame is analysed and expressed. 3. The direct solution of 3D coordinate in the trilateration system is deduced. This method needs neither the inicial value of coordinate to be calculated nor the identification of vague solution. The algorithm of weighted adjustment to estimate 3D coordinates in trilateration system is firstly presented. Compared to the existing algorithm the new algorithm can supply higher calculation accuracy owing to consideration of random variation of tracker's position. The concept of co-linearity in 4. self-calibration of trilateration system is introduced and the criteria expressing the phenemena is proposed. The co-linearity concept and weighted adjustment algorithm can be applied to all systems similar to trilateration system. 5. The relation between the coordinate error and geometrical configuration in the trilateration system are emphatically investigated. This is critical to obtain optimal configuration and therefore obtain the best measurement accuracy .The fomulas expressing point error with respect to the configuration are deduced for trilateration system. The relationship between calculation precision and normal equation is also dealed with. The factor describing the calculation sensitivity to the normal equation especially to the original measuring equation is introduced and the formula to calculate this factor is provided. The factor can...