Abstract: Aiming at the problem of decreased trajectory tracking accuracy caused by actuator failure and offset faults in industrial robot arms,a terminal sliding mode adaptive fault-tolerant control method based on high-order sliding mode observer was proposed. Firstly,the dynamic equation of the industrial robot arm with actuator faults was established by analyzing the motion state of the industrial robot arm. Then,a high-order sliding mode observer was designed to accurately estimate the fault terms within the system,and an adaptive fault-tolerant control law was designed based on the terminal sliding mode surface to compensate for the impact of actuator faults. Finally,the stability analysis was conducted using Lyapunov function,demonstrating that the proposed control method can accurately track the command signal of the motion trajectory of industrial robot arms.The simulation results of a 6-degree-of-freedom industrial robot arm show that the designed high-order sliding mode observer can accurately estimate the faults within the system,with a maximum estimation error of only 0.011 (°)/s². The proposed terminal sliding mode adaptive fault-tolerant control law can effectively overcome the impact of actuator faults on the motion trajectory of industrial robot arms,and the maximum and average errors on the entire motion trajectory are 0.64 and 0.24 mm,respectively,demonstrating strong robustness. The positioning test results of fixed coordinate points in three-dimensional space show that the proposed terminal sliding mode adaptive fault-tolerant control law has high control accuracy,with maximum and average positioning errors of 0.89 and 0.31 mm,respectively,verifying the strong engineering practicality of the proposed control method.

Key words: industrial robot arm, actuator malfunction, high-order sliding mode observer, terminal sliding mode, adaptive fault-tolerant control