Dual sliding mode control of a robotic arm based on a novel extended state observer compensation

Abstract Considering the modeling errors and external time-varying disturbances of robotic arm systems in practical applications, this paper proposes a nonsingular fast terminal sliding mode controller (NFTSMC) based on a sliding mode nonlinear extended state observer (SMNESO). Firstly, a SMNESO is designed to solve the problems of slow tracking speed and low tracking accuracy of traditional observers on the system state. Then, a novel variable-exponential power convergence law is introduced, which is adaptively regulated according to different stages in the system convergence process. Combining the terminal sliding mode with an observer, using the observer to estimate the total disturbance of the system in real time and feeding the estimate back into the system for feed-forward compensation, improves the steady-state accuracy of the system and the speed of error convergence. The stability of the closed-loop system is analyzed according to the Lyapunov theory, which ensures that the state of the system converges to the origin in finite time. Finally, it is verified by simulation that the proposed control method has quicker convergence speed and better robustness and effectively suppresses the jitter phenomenon.