A Nonsingular Terminal Sliding Mode Control for a 6DOF Manipulator with Unknown Payloads

This paper presents a nonsingular terminal sliding mode control (NTSMC) for a 6-DOF manipulator with the prior unknown payloads. Firstly, the sliding mode control (SMC) is a robust nonlinear controller used to eliminate the nonlinear components and deal with uncertainties. However, the SMC gives a slow convergence time when the state variables reach the equilibrium points; therefore, a terminal sliding mode (TSM) surface is established to deal with the convergence time in finite time. On the other hand, the singularity point is the issue that existed on the TSM manifold. Hence, a nonsingular terminal sliding mode (NTSM) surface is proposed to solve the singularity phenomenon, enhance the tracking precision, and allow the system to converge in a finite time. Furthermore, the Lyapunov theory is applied to analyse and prove the stability of the proposed control. Finally, the simulation results verify the effectiveness and robustness of the proposed control algorithm against the Proportional Derivate (PD) and conventional SMC via MATLAB Simulink.