Research On Key Technologies In Evaluation And Planning Of Laser-tracking Measurement For Large Scale Manufacturing

With the development of manufacturing technology and measurement technology, coordinate measurement has been the dominant method in manufacturing industry instead of the traditional analog measurement. In the field of large scale manufacturing, such as industry of aerospace, shipbuilding, automobile, heavy equipment, the widespread application of coordinate measuring technology has greatly improved the manufacturing quality and efficiency. Measurement-assisted assembly technology has been fully implemented in some advanced manufacturers, and will soon be extended to the whole of the large scale manufacturing industry. The key factor of successful application is the construction of suitable measuring network for large scale manufacturing measurement needs. Laser tracker has become the most widespread equipment due to its flexibility, high accuracy and wide measurement range in large-scale metrology. However, unlike fixed coordinate measuring machine(CMM), the error model is hard to build, the corresponding traceability system of instruments and the application method is not perfect enough. In addition, the measurement tasks of large scale manufacturing are numerous, the theory and method for traceability of measurement results of specific tasks also need to development.This paper belongs to the research category of coordinate metrology. Take laser tracker as a study object, methods of evaluating the performance of its field application in the large scale manufacturing process has been studied. Based on the above-mentioned research, the method of evaluation task-specific measurement uncertainty in laser-tracking measurement has also been researched. To deal with the problem of low efficiency of measurement process planning, the method of large scale laser tracking measurement planning has been discussed. The research work and the main achievements of this thesis are as follows:1、Several methos for representation of the spatial error are discussed and the merits and faults are addressed. Finally, a discrete point cloud method is presented.2、The measuring network method for performance evaluation of laser tracker in manufacturing field is proposed and a data fusion approach for multi-station laser tracker is presented simultaneously. Moreever, the methods for uncertainty evaluation of data fusion and accuracy improvement of points has been put forward. Intensive experimental studies have been made to check the validity of the proposed methods.3、To the weak rigidity workpiece, the influence of gravity-induced deformation on coordinate measurement is analyzed and the error compensation method based on finite element analysis is presented. Expreiment has been carried out to verify the feasibility. Other error factors in the laser tracking measurement are also analyzed, and corre-sponding control methods and suggestion are given.4、The contributions in the task-specifc laser tracking measurement are analyzed in detail. Based on the study of the existing evaluation method of measurement uncertainty, Monte Carlo method combined with measurement process simulation are put forward to measurement uncertainty evaluation in large scale metrology. In addition, the grey theory and neural network technology are used to evaluate the measurement uncertainty too, and test has been made to validate the availability of the methods.5、To the problem that many surveyors has no understanding and do not pay attention to the coordinate metrology, combined with some relevant cases, this paper states the application situations and methods of measurement uncertainty. The significance of the measurement uncertainty is explained.6、Based on the new generation of GPS theory and STEP standard, a feature based information model is established for coordinate measurement, which provides the specification measuring information and process for the large-scale coordinate measurement, reduces the specificaiton uncertainty, and can aid for the laser tracking measurement planning in the next phase.7、The measurement planning method utilized the PUMA and measurement process simulation is presented on the basis of the study on the measurement uncertainty. In order to verify the combined influence on the measurement results, measurement planning method based on the experimental design is presented. Due to the lots of measurement items in 3D model based coordinat measurement, referenced the CBR technology, the measurement planning method based on library of meta measuring scheme is proposed.8、For the application of laser tracker in aircraft flexible assembly and space missile geometry measurement, on the basis of the above technology, the software for computer aided evaluation and planning based on the three-dimensional model in laser tracking measurement is developed, which inculdes some functions of coordinate measuring specification definition, task-specific measurement uncertainty evaluation and measurement planning based on based on library of meta measuring scheme.