Synchronous PID controller for a 4-DOF parallel manipulator in practice

In this paper, a synchronous controller is proposed for a 4-DOF parallel robot in practice. The robot test bench is built with four arms driven by four AC servo motors that perform torque control mode. Four motors work together to control the trajectory tracking moving platform and create a closed kinematic chain structure. Therefore, the problem of synchronous control between the arms is a challenge. To solve this problem, the synchronous Proportional-Integral-Derivative (SPID) controller is proposed based on the Proportional-Integral-Derivative (PID) controller to improve the quality of the system. The cross-coupling error of the synchronization algorithm provides the motion information of itself and adjacent joints. The synchronous controller drives both of the synchronous error and the tracking error of the system simultaneously to zero. The results of the experiment on the 4-DOF parallel robot model are compared with conventional PID controllers to demonstrate the efficiency.