Design and experimental evaluation of a dynamically balanced redundant planar 4-RRR parallel manipulator

Shaking forces and shaking moments in high-speed parallel manipulators are a significant cause of base vibrations. These vibrations can be eliminated by designing the manipulator to be shaking-force balanced and shaking-moment balanced. In this article an approach for the design and evaluation of high-speed dynamically balanced parallel manipulators is presented and applied to a comparative experimental investigation of a balanced and unbalanced DUAL-V planar 4-RRR parallel manipulator. For precise simulation of the manipulator motion, the inverse dynamic model of the manipulator is derived and validated. Experiments show that the balanced manipulator has up to 97% lower shaking forces and up to a 96% lower shaking moment. For small inaccuracies of the counter-masses or for a small unbalanced payload on the platform, base vibrations may be considerable for high-speed manipulation, however their values remain significantly low as compared to the unbalanced manipulator. For the balanced manipulator the actuator torques are about 1.6 times higher and the bearing forces are about 71% lower as compared to the unbalanced manipulator.