| Multi-body system includes the multi-rigid-body system and flexible multi-body system. The flexible multi-body system which contains flexible components is the current popular topic. The traditional research on multi-body system dynamics is mainly implemented in the field of multi-rigid-body, but because the assumption that the components are rigid body, it is difficult to obtain accurate results in special circumstances that the deformation of component is considered. The parallel manipulator attracted wide attention and was highly valued by every country in the world since it was found. With the development that parallel mechanism becomes light, the flexibility of components have been enlarged. The flexible deformation of the components of parallel mechanism causes not only the decline in the system movement accuracy but also the elastic vibration of the system; it will have giant effect on kinematic performance and dynamic performance of parallel mechanism. So it is necessary to consider the impact of elastic distortionof the components on dynamic performance and kinematic accuracy. Flexible multi-body system of parallel mechanism is a multi-closed-loop and rigid-flexible coupling nonlinear dynamic system. Only with the using of rigid body dynamics or elastic mechanics, it is impossible to accurately describe the mechanical behavior of components. Flexible multi-body dynamics must be utilized to describe its mechanical properties.In this paper, parallel mechanism and flexible multi-body system are combined organically. 3-DOF spatial parallel mechanism with flexible members is main research object, and basing on flexible multi-body dynamics, the dynamic characteristics of the 3-TPT parallel mechanism is studied. The main work is as follows:First, the mechanism characteristics and kinematics problem are analyzed, including the calculation of mechanism composition and degree of freedom, the analysis and simulation of forward solution and position inverse solution, the calculation of kinematics influence coefficients(Jacobin matrix), the analysis of speed and acceleration and the study of singularity and stationarity of the mechanism.Next, analyze the dynamics performance of 3-TPT spatial flexible parallel mechanism. Aiming at the complexity of the simulation of flexible parallel mechanism, considering the flexible follower rod’s rigid-flexible coupling characteristic, and using assumed modes method and Lagrange principle, dynamic elastic vibration differential equation of the flexible parallel mechanism as this is established. Basing on the theory of Euler-Bernoulli beam and using assumed modes method, analyze the flexible deformation of each branch chain’s follower rod. Then, by using the Lagrange method, dynamics equation of 3-TPT spatial flexible parallel mechanism is derived. The dynamic model is finished.After that, under the circumstance of MATLAB software, the dynamic model of 3-TPT spatial flexible parallel mechanism are simulated and analyzed. The flexible deformation of each branch chain’s follower rod, including axial deformation, transverse deformation and axial shortening causing by transverse deformation, are calculated. Work out the elastic potential energy produced elastic deformation. The dynamic simulation is finished.In the end, analysis the error of final position of the moving platform caused by drive shaft length error and hinge clearance error which due to the elastic deformation. The error models are established separately based on matrix method and error individual contributions theory. And then, by using the Monte Carlo method, the error model established through matrix method is simulated.In this paper, dynamics modeling and simulation analysis of 3-TPT parallel manipulator is done based on multi-body dynamics, analysis the error of final position of the moving platform caused by drive shaft length error and hinge clearance error which due to the elastic deformation, laid a foundation for further research of dynamic characteristic and the error analysis of parallel mechanism which contains flexible components. |
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