Convex synchronized control for a 3-DOF planar parallel manipulator

In this paper, in order to improve tracking accuracy and satisfy multiple closed-loop performance specifications simultaneously during high-speed, high-acceleration trajectory tracking for a 3 degree-of-freedom (DOF) planar parallel manipulator, we propose a new control approach, termed convex synchronized (C-S) control. The C-S control is base on the so-called convex combination method and synchronized control. To implement the synchronized control scheme, a feedback signal, termed the synchronization error, is employed, which represents the degree of coordination of the active joints in the parallel manipulator based on the kinematics of the parallel manipulator, and thus tracking accuracy is improved. On the other hand, the convex combination method utilizes the convex property of the required closed-loop performance specifications. Through combining multiple linear controllers, so-called sample controllers, each of which satisfies at least one closed-loop performance specification, a C-S controller is algebraically calculated, which satisfies all closed-loop performance specifications simultaneously. Compared with traditional trial-and-error method, the convex combination method is more straightforward and efficient. Hence, possessing advantages of the synchronized control and the convex combination method, the proposed C-S control method can both improve tracking accuracy and satisfy multiple closed-loop performance specifications simultaneously (MSS). Experiments conducted on a 3-DOF P-R-R type planar parallel manipulator demonstrate the above claims