Research Of Workspace And Static Stiffness Of New Parallel Mechanism With Suitable Constraint Branch

In recent years, parallel mechanism becomes a hot topic with its high precision, small error, rigidity, etc. especially in the less DOF parallel mechanism filed. It has been widely used in aerospace, docking areas with further research. Based on a major National Space project, workspace and static stiffness of the suitable constraint branched new parallel mechanism are studied. It lays a theoretical foundation for research of this type in the future.The suitable constraint branched new parallel mechanism is mainly consisted of moving platforms, static platform, the three non-binding initiative UPS and suitable constraint branch PU. Firstly, the parallel mechanism has two rotational and one move degrees and a determined movement after the degrees of freedom calculated by the modified G-K formula. Secondly, a closed vector equation is established to obtain the inverse position model. The screw theory is adopted to get the sub-drived Jacobian matrix and sub-constrained Jacobian matrix and ultimately the full Jacobian matrix. Thirdly, the full rank of Jacobian matrix is solved by algebraic method and the singular institution is not existed through reducing the singularity possibilities by the suitable constraint branch. Then the workspace of the mechanism is analyzed by using Matlab and the reachable workspace of a single degree of freedom and multi degree of freedom movement is obtained.What's more, traditional static stiffness model is established by virtual work principle and the spatial distribution is obtained by using the stiffness matrix method in Matlab simulation. Then the correctness of the model is verified by ANSYS Workbench software and a method is proposed to improve the static stiffness of lock force. The sensitivity of each branched-sectional parameter is analysed by selecting the appropriate local and global static stiffness evaluation. And the overall stiffness is impacted by the suitable costraint branch PU significantly and the branch chain-sectional dimension is selected by optimizing design.