Abstract:  Aiming at the problem that the existing PID control methods were difficult to apply to the control of manipulator under variable payload, an adaptive PID control strategy was proposed in the present work. The dynamic model of manipulator under variable payload was firstly constructed, and the defects of classical PID control under variable payload were discussed. Based on the equivalence between time delay control (TDC) and PID control in discrete domain, the proposed adaptive PID control law was designed, the gain coefficients of the proposed adaptive PID control strategy were determined, the advantages of the proposed method were discussed, and the gain coefficient tuning method was given. Combined with Lyapunov theory, the stability of the proposed control strategy was proved, and the robustness of the method to the payload change of the manipulator was illustrated. The effectiveness and robustness of the proposed control strategy under variable payload were verified by simulation analysis and physical experiments. The results show that compared with the classical PID and existing adaptive PID control methods, the proposed control method has better control robustness for the manipulator under the condition of large payload change (resulting in the maximum increase of joint inertia by 124.4%), and can provide a reference for more complex and accurate adaptive control methods.

Key words:  robotic manipulator;variable payload;adaptive PID control;time-delay control(TDC);Lyapunov theory