Study On Some Key Techniques Of Parallel Machine Tool Based On Virtual Prototype

The parallel machine tool (PMT) has some advantages such as good stiffness, high precision and various layouts in theory due to its closed loop mechanism chain, so it has expensive applied prospect in manufacturing domain. At present, the study and development of PMT in every country of the world are still at a stage of research and trial production. Compared with foreign countries our country still has a long way to go to study the key techniques of PMT like theory, design and application. Therefore, how to effectively analyze the key techniques and rationally evaluate the working capacity of PMT became an urgently problem. Because the layout of PMT possesses variety and the dynamic characteristic, size and shape of workspace and motion parameters are all different, modeling, simulation and virtual reality techniques are indispensable. They refer to the key techniques like mechanism, kinematics, parts modeling, three dimensional realization and motion control and so on. So it is a comprehensive study subject with innovation and use value.This dissertation applies the virtual prototype technique on key techniques of PKM based on former research outcome and takes a 3-TPT PMT as an example, analyzes and simulates its key techniques such as virtual prototype model, kinemics, workspace, flexible multibody dynamics, dynamic characteristic, co-simulation of electronic system and error. It is a significative attempt for realizing high efficient modern design and research. The specific content as follows:(1) The background of the study and the developing history and current situation of PMT are discussed. Both the progress and trend of the key techniques of PMT are summarized. Then the development general situation of virtual prototype technique is surveyed. At last the forward position of applying the virtual prototype on design and development of PMT is demonstrated.(2) The mechanism of 3-TPT PMT is analyzed, the reciprocal screw system of the mechanism for judging the constraints and three freedoms of degree are derived by screw theory, and then the rational input choices and main screw of mechanism of 3-TPT PMT is educed, at last the screw motions which may be realized or restrained are solved. These studies can be used for instructing building the virtual prototype model of PMT. (3) The virtual prototype model of 3-TPT is built by the interface between ADAMS and other 3-D software, and its kinematics is analyzed and simulated. Then the thought for resolving workspace with virtual prototype technique is put forward. The results of workspace graphics are got in ADAMS. This method is simple and feasible compared with analytical method.(4) The flexible multibody dynamics of 3-TPT PMT is studied and its dynamic equations are educed. Then the co-simulation by ADAMS and ANSYS is proposed, and the the simulation loads are loaded on the flexible links to carry out the stress analysis for finding out the weakness link of flexible links, after that the optimization plan is given.(5) The dynamic characteristic of 3-TPT PMT is studied by using virtual prototype simulation and modal experiment. The experiment results are used for testing the simulation results.(6) The control system and dynamics coupling characteristic of 3-TPT PMT are analyzed, then its flowchart of control system is built in MATLAB to drive the mechanism system in ADAMS, so the the co-simulation platform is built. It can be used for judging the control system is good or bad.(7) The error of PMT is analyzed in detail, and the error models of 3-TPT PMT are separately built by uniting matrix and vector methods and error independence principle, the effect factors are also analyzed. The errors caused by flexible links when machine tool moving are simulated by virtual prototype technique, and its effect laws are summarized. At last the error compensation methods are given.The physics prototype needn't to be made after design when using the virtual prototype technique. The evaluation and analysis of performance of products can be carried out by the tree dimensional model and mechanics model of mechanical system built by computer, it can provide the reference for design and manufacturing of products. This dissertation effectively realizes modeling and simulation by virtual prototype technique, the method not only suits the study, design and development of PMT but also other complex mechanism system, so the study method and conclusions have important practical value.