Double-loop adaptive sliding mode control of flexible manipulator based on disturbance observer

In order to further improve the disturbance resistance and tracking speed of the underdriven two-link flexible manipulator, this paper proposes a double-loop adaptive sliding mode control (ASMC) method based on an adaptive sliding mode disturbance observer (ASMDO). Firstly, a nested adaptive law is designed by defining the observation error, and the ASMDO is further constructed using this law and the observation error to accurately estimate the system’s matched and unmatched disturbances. Then, the joint angle and joint velocity errors are used to design the sliding mode surface and the adaptive law of power convergence, and the unmatched disturbance estimates are used to design the outer-loop controllers. Next, the outer-loop controller output is used as a desired command for the inner-loop rotor angle, and the sliding mode surface and adaptive law of power convergence are used to design the inner-loop controller using the matched disturbance estimates. Finally, the stability of the control algorithm is rigorously demonstrated using Lyapunov stability theory, and the effectiveness of the proposed control method is verified through simulation experiments.