Structure Design And Analysis Of Parallel Mechanism With Large Workspace

A novel method for the design of six degrees of freedom parallel mechanisms (6-DOF PM) with large workspace is proposed to improve the workspace of traditional6-DOF PM in this paper. Structure design of the PM, configuration relationship of joint axes and dimensional design of components are analyzed. We can get the configuration and dimension of PM according to the desired workspace. The main contents are as follows:Firstly, the influence of the joints in parallel limb on the degrees of freedom of the end of the limb and the geometrical relationship between the joint axes are analyzed. Following these, limb structures and joint axes conditions are determined when three translational and three rotational DOFs are required, respectively.Secondly, a novel method for the design of6-DOF parallel mechanisms with three limbs is presented considering the limb structure with three rotational and translational DOFs. To achieve large workspace, simple kinematics and reducing kinematic couple, topological optimization of the PM is conducted. Joint axes conditions between and within all the limbs are analyzed. The preliminary optimization of workspace is carried out.Thirdly, the dimensional design of the6-DOF PM is presented based on the relationship between the reachable workspace of the end of the limb and workspace of the moving platform. The relationships between the dimension of PM and workspace are built, including the dimension of moving platform, components and fixed base. Further optimization of workspace is established.Finally,6-DOF PM is designed with required orientation workspace satisfied. Dimension of moving platform, position and orientation workspace of the PM are chosen as the design objective, the design steps are as follows:choose limb structure, configurate the joint axes position within a limb as well as between limbs, design the dimension of the limb, moving platform and fixed base. The kinematics and workspace are analyzed to verify the feasibility of the proposed design method.