Parallel Machine Tool Structure And Error Analysis Study

The research on PKM involves mechanical engineering, electronics, automation, computer, sensors and so on. It is a new kind of numeral control machining equipments that came into being in 1990's. Although PKM has outstanding advantages when compared with traditional machine tools, it also has a lot of problems which include the principle of the mechanism design and accuracy and so on to be solved nowadays. This problem is the bottleneck for industrialization of this kind of machine tools. Type syntheses of parallel kinematics machine is the main problems of the research on PKM, and nowadays there is not a general way to solve the mechanism design problem of 5-DOF and even more less degree of freedom mechanism, which is to be seen as a hard problem in the word. PKM has more accuracy in theory, although, Because of the complex relationship that errors affect on the machine tool' s accuracy, PKMs do not achieve the kinematic accuracy level of traditional machine tools in practical applications. So the research on the above problems is presented in this thesis.At first, in order to solve the type synthesis, A special coordinates to describe the motion features of the linkages based on the generalized coordinates are proposed in this paper. And the linkages which has specific motion are analyzed. And a structural method on the type synthesis of PKMs is introduced with the analysis on the linkages and the special coordinates. By using this method, a new 6-DOF and a new serial-parallel kinematics machine tool are obtained, which is just the one studied in this paper. As for the kinematics, the methods to get the direct kinematic solutions are discussed by using proper coordinates and matrix methods.As for the error analysis, taking the XNZ63 made by Kunming machine tool stock company as the structural mode, by using differential principle and matrix methods, a error analysis model of the machine is derived. Using the D-H convention and the conclusion from the derivation of kinematic equations, the mapping between the joint clearances and the terminal's error is determined, and the distributing rules of terminal's error in the workspace are obtained.