Comparison of Control Approaches For Tracking Control of a 3 DOF Parallel Robot: Experimental Results

In this paper, to study the effect of different control approaches on improving trajectory tracking accuracy for a 3 degree-of-freedom (DOF) planar parallel robot, we tested two synchronized-type controllers: PI-type synchronized control and adaptive synchronized (A-S) control; and conventional PID control and adaptive control. Here PID control and PI-type synchronized control are dynamic model-free while the adaptive control and A-S control are dynamic model-based. Because of the closed-loop kinematic chain mechanism of the experimental planar parallel robot used in this study, trajectory tracking control of this robot may be treated as a synchronization problem, and consequently, use of the synchronized control approaches can substantially improve the trajectory tracking performance of the robot end-effector compared with approaches without synchronization. Through conducting experiments on an experimental 3-DOF P-R-R type planar parallel robot by using the four control approaches, the above claims are demonstrated.