Controller design applied to planar parallel manipulators for trajectory tracking control

In this paper, we develop a new control method for a P-R-R type planar parallel manipulator, termed adaptive synchronized (A-S) control. The novelty of the proposed A-S control, a combination of synchronized control and adaptive control, is in the application of synchronized control to a planar parallel manipulator. To improve trajectory control, based on the kinematics of the planar parallel manipulator, we design a synchronization feedback control signal, termed the synchronization error, which represents the degree of coordination amongst the actuated joints. Employment of the synchronization error is shown to substantially reduce the pose error of the moving platform of the planar parallel manipulator during trajectory tracking. An adaptive controller is also used to estimate uncertain dynamic parameters of the manipulator. Under the assumption of persistent excitation, the proposed A-S control algorithm is theoretically proved to simultaneously guarantee the convergence of tracking errors and the synchronization error. Moreover, the estimated unknown parameters are guaranteed to converge to their true values as well. Finally, experiments are conducted to verify these claims and evaluate the performance of the proposed controller. Experimental results show that A-S control yields good trajectory tracking performance. © 2005 IEEE.