Experimental Comparison of Control Approaches on Trajectory Tracking Control of a 3-DOF Parallel Robot

In this paper, the effect of control approaches on improvement of trajectory tracking accuracy of a 3-degree-of-freedom (DOF) planar parallel robot is studied through the experimental evaluation of four controllers: proportional-integral (PI)-type synchronized control, adaptive synchronized (A-S) control, conventional proportional-integral-differential (PID) control and adaptive control. The adaptive control and A-S control are dynamic model-based while the PID and PI-type synchronized control are not. Given the closed-loop kinematic chain mechanism structure, tracking control of the planar parallel robot may be treated as a synchronization control problem; hence, use of the synchronized-type control approaches can substantially improve tracking accuracy of the robot end-effector compared with use of the nonsynchronized-type control approaches. Further, with uncertain dynamic parameters, use of the A-S control, a model-based synchronized control approach, can, thus, improve the tracking performance. Through experiments conducted on an experimental 3-DOF planar parallel robot, the previous claims are demonstrated.