| In this thesis, in order to solve the trajectory tracking control problem of parallel robotic manipulators, we propose a new control approach, termed synchronized control. In this control scheme, considering the closed-loop kinematic chain mechanism of parallel robotic manipulators, an additional feedback signal, termed the synchronization error, is employed. Different from the traditional tracking errors, i.e., position errors and velocity errors, the synchronization error represents the coordination degree of the active joints in a parallel robotic manipulator. Therefore, compared with traditional control approaches, e.g., PD control and PID control, the employment of the synchronization error in a synchronized controller improves the tracking performance of a parallel robotic manipulator. Experimental results also demonstrate this claim.; With respect to different operation conditions and tracking performance requirements, based on the synchronized control, we propose two new control approaches, termed adaptive synchronized (A-S) control and convex synchronized (C-S) control. The former is proposed to address unknown parameters in the dynamic model of a parallel robotic manipulator during practical operations. Through estimating unknown parameters during tracking control process by an estimator, the influence of the unknown parameters is eliminated. The latter is proposed to address the multiple simultaneous specification (MSS) problem during trajectory tracking. By using the convex combination method, the C-S controller is designed through combining multiple synchronized controllers. This control approach substantially lessens the burden of tuning control gains.; In principle, the proposed synchronized control, A-S control and C-S control are all suitable for parallel robotic manipulators with various structures. Experiments conducted on a 3-DOF P-R-R planar parallel robotic manipulator demonstrate the validity and effectiveness of these three control approaches. |
