An Adaptive Terminal Sliding Mode Control for Robot Manipulators With Non-Singular Terminal Sliding Surface Variables

This paper presents an adaptive terminal sliding mode control (TSMC) algorithm for robot manipulators. The contribution of our control method is that the suggested controller can enable the advantages of non-singular TSMC such as non-singularity, high robustness, small transient error, and finite time convergence. To develop the suggested system, a non-singular terminal sliding variable is selected and does not have any complex-value or constraints of the exponent in conventional TSMC. Therefore, it prevents the singularity that occurs in the conventional TSMC and eliminates the reaching phase glitch. Accordingly, the suggested system can ensure that the controlled variables reach the desired values within a randomly known finite time using an efficiently smooth and chattering-free definite control input. In addition, sliding motion in finite time can be achieved by employing the adaptive self-tuning rules with no prior information regarding the upper bounds of undefined parameters (e.g., friction, disturbances, and uncertainties). Furthermore, the finite-time convergence and global stability of the proposed algorithm are proved by the Lyapunov stability theory. Finally, the proposed control algorithm is applied to the joint position tracking control simulation for a 3-DOF PUMA560 robot. The trajectory tracking performance of the proposed method is compared with those of the conventional terminal sliding mode control and the conventional continuous sliding mode control. This comparison shows the efficiency and superiority of the proposed algorithm.