An Extended State Observer-based on the Terminal Sliding Mode Control for 6-DOF Manipulator Against Lumped Uncertainties

This paper presents an extended state observer (ESO) based on the terminal sliding mode control (TSMC) for a 6-degree-of-freedom (DOF) manipulator under the presence of dynamics error, unknown friction force, external disturbance, and loss-of-effectiveness on actuators. The proposed control strategy is constructed by the TSMC and ESO to eliminate the lumped uncertainties and enhance the tracking error performance. Initially, the tracking trajectory control is handled by the TSMC, which inherits the advantages of the conventional sliding mode control (SMC) and gives the system state errors approach the zero point in finite-time convergence and robustness against nonlinearity. Next, a linear ESO is investigated to estimate the lumped uncertainties to improve the effectiveness and descend the high oscillatory on the TSMC. In addition, the stability analysis of the control system is proven by the Lyapunov stability theorem. Finally, numerical simulations are established on MATLAB Simulink. To demonstrate its effectiveness and precision, the proposed control results are compared with alternative controllers via performance indices.