Research On The Key Techniques Of Portable Articulated CMMs

With the developments of the science & technology, the requirements of the qualityand shape of the products have raised a lot, the application of complex modeling products including free surface has been widely used. To shorten the R&D period of the products and to raise the design efficiency, reverse engineering is the common way to design complex models and a sufficient procedure to realize reverse engineering is processing the collection of the three dimensional data of the parts' surface. In reverse design, measuring machines and scanning machines are widely used to process the digital measurements of curves and planes; however, owing to the current situation that almost all the three dimensional measuring machines and scanning machines have some kinds of restrictions, the flexible coordinate measuring machines expands their application scopes. In order to improve the flexible CMM's measuring accuracy, speed up the measuring process, provide the measuring strategy, argument the function of the system and for technical training and teaching, thus the thesis proposes the R&D system of virtual flexible coordinate measuring machine.The thesis mainly focuses on the functions and key technologies of the virtual flexible CMM. After analyzing the structure of the actual flexible CMM, the geometrical models, the movement models and the error models of it have been detailed described. Based on that, the measuring methods of geometric elements are deeply researched and the software system of the flexible CMM has been well designed.The main contents of this thesis are as follows:The first chapter introduces the developments of the modern manufacturing technology, which raises new requirements for the measurement technologies. Recalls the coordinate measuring technology development home and abroad, analyze the existed problems and then raises the purpose and importance of the research. Finally the main context of this thesis has been released.The second chapter mainly introduces the whole schema of the virtual flexible coordinate measuring machine. At the beginning, the author introduces the conceptual designing idea of the virtual flexible coordinate measuring machine, and analyzes the system modules and main functions based on that concept. The system developing environment is introduced at the end.Chapterâ…¢investigates the real flexible coordinate measuring machine's mechanical structure and movement laws, and then expounds the relevant mathematical model. Right behind that the methods of how to create the corresponding geometrical model, kinematical model and error model are brought forward.Chapterâ…£is about the fitting techniques according to the measurement results in order to retrieve the relevant geometrical information. According to the specifications in GD&T, mentions the construction methods which establish the corresponding error.evaluation method in different mathematical models by means of different kinds of geometries. At last the corresponding experimental results are exhibited.Chapterâ…¤has focused on the subject that implements the virtual measurement in the virtual flexible coordinate measuring machine system. First the collision detection algorithms are introduced, and then considering the actual flexible CMM's structure, a novel hierarchy bounding box tree is brought out. The relevant experiments are followed behind.A comprehensive conclusion will be presented in Chapterâ…¥.