| Parallel mechanism (PM) has many advantages, such as smaller error, higher stiffness, better bearing capacity and so on compared with series mechanism. Meanwhile its shortcoming is also apparent such as complex structure, small workspace and shortage of movement flexibility, which restrict the application and popularization of PM. A kind of five-DOF PM with composite driving legs is presented in this paper,which is relatively simpler in structure, larger in work space and better exercise flexibility, to some extent, compensates for the deficiencies of the traditional PM, following systematic study of its workspace, exercise flexibility, kinematics and dynamics performance.A symmetrical configuration called 2UPS + UPU PM with large workspace and excllent exercise flexibility is selected from a series of five-DOF PMs which are synthesized using CAD variable geometry. Following the secondary development of Solidworks software based on Visual Basic language, we can transform the steps of constructing workspace into programs using the method of CAD variable geometry. Compared with the four-DOF composite driving PM called RRPU+2UPU, the reachable workspace and exercise flexibility advantages of 2UPS+UPU PM can be reflected obviously.Based on geometry constrains existing in this PM, the inverse analytic positional model of PM can be deduced using the vector method. Following the constrained force analysis, the (6×6) Jacobion matrix and (6×6×6) Hessian matrix can be available without the partial differentiation, and then the analytical models of velocity and acceleration of this PM are gained. With the help of CAD variable geometry approach, the simulation frame model can be builded, which is used to verify the inverse analytic positional model. The analytical model of velocity and acceleration can be checked up through the derivation of simulation solutions based on MATLAB programming.According to the velocity and force duality, the statics model with constrained force can be established. Combined with the virtual work principle and d'Alembert principle, a Newton - Euler dynamics model can be established. A SimMechanics integrated simulation system with Force and Kinematic actuators is established, and the quality and inertia moment parameters of each component can be abtained from a solid model in Solidworks. |
