Design And Research On Performance Of A New Hybrid Mechanism

The hybrid mechanism combines the advantages of series mechanism and parallel mechanism to accommodate the higher requirements for production activities.In this paper,a series-parallel hybrid mechanism with large workspace and high flexibility is designed.The paper studies the configuration,kinematics,workspace and kinematics and dynamics simulation of the hybrid mechanism.Firstly,the configuration of the new hybrid mechanism is put forword.The hybrid mechanism is composed of a 3-UPT parallel mechanism and a 2-DOF steering mechanism.A2-DOF steering mechanism is added between the base of 3-UPT parallel mechanism and the frame to constitute the hybrid mechanism with large workspace and high flexibility.The degrees of freedom of the mechanism are analyzed using Kutzbach-Grübler formula and screw theory,respectively.Secondly,the epression of the position solution of the hybrid mechanism is derived.The positive and inverse solutions of 3-UPT parallel mechanism are analyzed using the closed-loop vector method.The positive and inverse solutions of 2-DOF steering mechanism are analyzed using D-H method.The rotation matrices of the two mechanisms are obtained,respectively.Finally,the positive and inverse solutions of the two mechanisms are integrated.The global position solution and the homogeneous rotation transformation matrix of the hybrid mechanism are obtained.Then,the workspace of the hybrid mechanism is studied.The parameters of 3-UPT parallel mechanism are optimized using the motion/force transmission performance index.The ideal parameters of 3-UPT parallel mechanism of the moving platform and the base are obtained.The workspaces of 3-UPT parallel mechanism and 2-DOF steering mechanism areobtained using the numerical search method and the simulation,respectively.Finally,the workspace of the hybrid mechanism is obtained by integrating the two workspaces.The workspace of the hybrid mechanism is divided based on the driving modes.Finally,the Adams simulation software is used to simulate the mechanism.Under the specific driving and loads,the displacement,velocity,acceleration curves of the driving links.The forces and the power changes of the driving links are obtained.