The Application Of A Fast Terminal Sliding Mode Control To A Parallel Robot

Parallel robot is a new kind of robot, which becomes the focal point for its features of big toughness, high bearing capacity, small error, high precision and so on. It has the complementarity with serial robot which being applied widely and expands the applied field of robot. The robot control system is the kernel of robot. Thus, the function of robot has direct mutuality with the performance of the control system.As parallel robot has complex structure and is a multi-variable, multi-parameter coupled nonlinear system, the control results of conventional control methods can’t be satisfied with it. However, sliding mode control can effectively solve the nonlinear problem, also has strong robustness to uncertain parameters and external disturbances. Thus, it fits for the control of parallel robot.In this paper, a new type of sliding mode control method which is called fast terminal sliding mode control is proposed. It combines the advantages of traditional sliding mode control and the terminal sliding mode control. It ensures that the system state can quickly converge to equilibrium in the limited time. Meanwhile, the control law of fast terminal sliding mode control is continuous, and has no switching item, so that it can effectively eliminate the system buffeting caused by switching function.In this paper,2-DOF parallel robot control system is constructed. The mathematical model of AC servo motor is established at the base of kinematic analysis of parallel mechanism, and the fast terminal sliding mode controller is designed. The simulation results show that the control system tracks well and has small system error, which satisfies the requirements of the control of parallel robot. Compared with conventional sliding mode control, the control system has quick state response and the system state can converge to zero in the limited time.Finally, an efficient control software is designed by the use of VC++based on MFC multi-threading technology. The test results of parallel robot drived by AC servo are given. The results confirm the correctness and effectiveness of control strategy.