Performance comparison of three planar 3-DOF parallel manipulators with 4-RRR, 3-RRR and 2-RRR structures

This paper presents a comparison study on the conditioning, velocity, payload and stiffness performance of three planar 3-DOF parallel manipulators with 4-RRR, 3-RRR and 2-RRR structures, respectively. The conditioning, velocity, payload and stiffness indices are developed to compare the performance of the three parallel manipulators. An optimum region is investigated. A comparison of the results indicates that the conditioning performance, payload performance and stiffness performance of the 4-RRR manipulator is the best, and those performances of the 2-RRR one is the worst. The three manipulators have different output velocity performance. The 4-RRR and 2-RRR manipulators have the largest and smallest optimum region, respectively.