Nonlinear Synchronous Control For Redundant Drive Parallel Manipulation

Mechanism with redundant actuation presents complicated structure and drive mode which makes it difficult to achieve high accuracy control. Thus, the study of control of redundantly actuated mechanism has significant theoretical and practical value.In this paper, a nonlinear proportional-derivative plus feedforward information control(NP-D+) for a 2-degree-of-feedom redundantly actuated planar parallel manipulator is proposed. The proposed NP-D+ is formulated with a new class of nonlinear saturated function. Furthermore, considering strong coupling among joints of the above planar parallel manipulator, we propose a simple nonlinear synchronization control strategy. The global asymptotic stability of the resulting closed-loop systems is proved by the Lyapunov's direct method and LaSalle invariance principle. Simulation results illustrate the effectiveness of the two proposed approaches.Experiments on the 2-degree-of-feedom redundantly actuated planar parallel manipulator by linear PD control and nonlinear PD control as well as linear synchronization control and nonlinear synchronization control are carried out. The results show that controllers with the nonlinear saturated function and synchronization errors have improved performance.