TOPOLOGICAL STRUCTURE OPTIMIZATION AND KINEMATIC PERFORMANCE IMPROVEMENT OF 3-RRR PLANAR PARALLEL MANIPULATOR

The typical 3-RRR planar parallel manipulator with two translations and one rotation has extensive applications such as plane location and motion transfer. But it suffers two disadvantages. One is its analytical direct kinematics is difficult to be got and another is not input-output motion decoupled. This paper focuses on its topological structure optimization and resulting kinematic performance improvementt. First, the coupling degree of this manipulator is calculated being k=1. Second, based on structure coupling-reducing principle, its coupling-reduced manipulator with zero coupling degree is designed, which not only leads to be easy to get its analytic direct kinematic solutions, but also makes input-output motion partially decoupled. Moreover, based on workspace and singularity of this coupling-reduced manipulator, comprehensive comparison of two manipulators before and after coupling-reducing showed that the main performances of structure coupling-reduced manipulator are superior than that of the typical mechanism. The work shows that structure coupling-reducing is effective method for optimization of topology structure.