| A parallel mechanism is widely used in various industry applications such as semiconductor packaging equipment including wire bonder, die bonder and point gum machine etc. Traditional approach of analysis for mechanism is incompetent to satisfy rigorous system performance requirements that are characterized by high speed and precision. Therefore, the optimal approach which collects the mechanical parameters variables to optimize objective performance index is very necessary, even essential for high performance desired. In this thesis, the five bar mechanism is chosen as experimental tested, and then a comprehensive analysis procedure is followed.Firstly, kinematics characteristics of the mechanism including forward kinematics and inverse kinematics, open-loop velocity analysis, singular value analysis and workspace are investigated. Secondly, dynamic modeling for the rigid mechanism in purpose of exploring the dynamic properties of whole system is done. Since the rigid body analysis is not enough to meet the requirements so it is followed by formulation of mathematic model of five bar manipulator with flexible links. With that, the displacement of any point can be turned out by interpolation function and node coordinates, especially, we can get the deformations of end points of links which almost the worst place of deformation. Meanwhile, the proposed model is sufficiently validated by numerous simulation results which showed us this modeling of flexible manipulator is not only efficient to describe entire mechanism, but also it is more accurate than rigid ones to describe dynamic process of real system, furthermore, it is necessary for obtaining a high precision position. Next, the natural frequency characteristics of the mechanism is studied, especially for first three order frequencies, and then their plots changing with rigid motion are given. Finally, by introducing the previous formulated flexible model and choosing first natural frequency as objective function, setting mechanical variables as design parameter, defining the limitation from motor, mechanism and so on as constraints, we formulated the integrated design problem for entire system. Then optimal algorithm called Differential Evolution (DE) is used to get results, at last we got the optimal mechanical parameters. At the maximum point of objective function. A lot of simulation results of system with optimal variables confirmed the efficiency of flexible modeling and optimal design method. |
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