Study On The Key Technique Of Articulated Arm Flexible CMMs

To advance the Photoelectric Digital Guideless On-Line Coordinate MeasuringMachines (CMMs) is one of the development tendencies and proposed key projects ofmetrology equipments of national middle-long-term plan for science and technology.The articulated arm flexible CMM studied in this thesis is one kind of knuckle-typeCMMs. In articulated arm flexible CMM, high-accuracy angle measuring sensors areutilized to measure the rotation angles of knuckles, and the center coordinates of gaugehead are calculated through coordinate transformation. Articulated arm flexible CMMhas many advantages such as simplicity in structure, wide measuring range, smallvolume and low cost. It is convenient to setup on site in production line, easy tooperate and portable, and have very wide prospective application. There is noarticulated arm CMM produced in China, whereas the imported machines also sufferthe problem of low accuracy.This project is financially supported by National Natural Science Foundation ofChina, the number is 50475116. In the beginning of the thesis, number of knuckles andconstitution of articulated arm flexible CMM is studied. All possible errors areanalyzed and classified carefully and in detailed. Then, the mathematical models forthe ideal CMMs and those with errors are established. The error mathematical modelhas important significance in improving the measuring accuracy of articulated armCMM. Furthermore, the investigations in this thesis involve the measurement andcompensation of arm deformations, thermal distortions, verticality errors and the errormotions. And also, the high-accuracy angle measurement with limited sizes ofencoders, high-accurate methods for calibrating the effective parameters of the arms,the development of data processing and error compensation software are presented.Finally, some error analyses were summarized from abundant computer simulatingexperiments of error mathematical model.The tasks accomplished in this thesis will provide a solid base for developingarticulated arm CMMs with our own intellectual properties and accuracy higher than,cost lower than existing imported CMMs.