Adaptive synchronization control of a planar parallel manipulator

A new control algorithm for a planar parallel robotic manipulator with three degrees-of-freedom (DOF) and parametric uncertainties has been developed. From its mechanical structure, the studied planar parallel manipulator is categorized as a P-R-R type and can be treated as comprised of three constrained submanipulators. Key to the successful trajectory tracking control of the P-R-R manipulator is the motion of the submanipulators: each sub-manipulator should be controlled to follow its pre-determined trajectory while coordinating motions with the other sub-manipulators. The control algorithm developed employs the above idea and incorporates synchronization technology with the adaptive control architecture by feeding back position, velocity errors of the actuated joints and a newly defined synchronization error. Employment of the synchronization error, verified by simulations, substantially reduces the pose error of the end-effector of the P-R-R manipulator during trajectory tracking. From theoretical analysis, the proposed control algorithm is shown to guarantee the convergence of tracking errors and the synchronization error at the same time. Finally, simulation results demonstrate that the proposed controller can achieve excellent trajectory tracking performance.