Static analysis on a 2(3PUS+S) parallel manipulator with two moving platforms

The stiffness of a novel 2(3PUS+S) parallel manipulator with two moving platforms was investigated in this study. In the stiffness evaluation, the two moving platforms of the manipulator were driven through three linear modules and the load force on the drive joint was large. The corresponding parts of the two moving platforms were divided into independent subsystems and were integrated through a stiffness modeling method of a serial system to establish the overall stiffness model of the 2(3PUS+S) parallel manipulator. During modeling, elastic deformations on the joint lever and lead screw were involved, the joint lever was simplified as a supported beam, and the axial and torsional stiffness of the lead screw were considered. Numerical analysis on the established stiffness model was validated, and virtual experiments were conducted. Results indicate that the stiffness performance of the 2(3PUS+S) parallel manipulator changes with the variation of structural parameters and moving platform positions. To ensure the minimum stiffness under the required trajectory, the length of the joint lever and the ratio of the moving platform radius to the base platform should be appropriately reduced. Comparisons between the results from the numerical analysis and virtual experiments verified the accuracy of the established stiffness model.