Multi-input Multi-output Sliding Mode Control with High Precision and Robustness for a 6-PSU Parallel Robot

In high precision tasks, the parallel robot is a good choice due to their advantages of no cumulative errors and high stiffness. The six-degree-of-freedom (six-DOF) 6-PSU parallel robot has a much lower inertia, but is a multi-input multi-output (MIMO) system with complex non-linear dynamics. Currently, there are rare studies on high-precision robust control methods for 6-PSU parallel robots. In this paper, a simplified dynamics model of the robot is presented first. We distribute the mass of the connecting rod on the two end joints, and then establish a general second-order system model to characterize the dynamic characteristics of the system at a minimum cost. By introducing the sliding mode, a six-DOF sliding mode controller (6PSU-SMC) is developed, which can effectively suppress the internal model error disturbance and external disturbance. The results show that the developed controller perfectly solves the dynamics control problem and achieve a high precision and robustness tracking task.