Study On Dynamics Analysis Method Of Parallel Mechanism In Serial-Parallel Machine Tools

Serial-parallel machine tool is a new kind of machining equipment, which is a kind of robot in machine tools and a combination between traditional machine tools and modern robot. When robot technology is uesed in machine tools, robot technology is being updated itself consequently. Some of current study on robot is based on rigid body dynamics theory. In the others, elastic deformation of components is considered but the deformation of joint is not considered. The robots as machine tools become more and more of high speed, light weight, high load and high stiffness, which make elastic deformation of component increase. The elastic deformation lows robot movement stability and accuracy. Therefore, elastic deformation of joint of serial-parallel machine tools cannot ingored. Traditional study method on rigid robot evidently cannot be used in parallel machine tools.Study on serial-parallel machine tool just begins. Main contents involve rigid body dynamics, elastic body dynamics, stability in machining process and machining precision, et al. In the contents, dynamic characteristic of machine tools is most emergent and practical, which is a key technology in engineering application. 6PM2 is a new serial-parallel machine tool, which is developed by the Institute of Mechanism andAutomation of Xi'an University of Technology. 3 - RPS parallel machanism is its key component. Based on the machine tool, the research efforts have finished in this thesis as follow:1. Based on beam theory, a model for a nonlinear parallel machanism is established. Nonlinear joint stiffnesses and load are computed by measurement data of workbench and finite elment result of machine tool.2. A method is presented, in which solid joint with nonliear elasticity is modeled, and stiffness matrix of contact element is established. This kind of element can make use of joint experiment data to build solid joint model and can include normal nonlinear stiffness and coupling between shear stiffness and normal pressure.3. A method modeling solid joint with column contact surfaces is presented. Shear-expanded effect is studied, owning to numerical dispersion and a solution is presented.4. A global finite element model for serial-parallel machine tool is established, which involve in joint contact and nonlinear elasticity. Static and dynamic characteristic of global models with three kinds of joint analyzed and compared, which are concretion model not involving in joint contact, rigid contact model involving in joint contact and elastic contact model involving in joint contact with nonliear elasticity. Global stiffness of machine tool is studied in experiment and experimental results and computing result sare compared.