We propose a backstepping global fast terminal sliding mode control for trajectory tracking control of industrial robotic manipulators in this article. An integral of the global fast terminal sliding mode surface is firstly suggested to improve the dynamic performance and fast convergence of Sliding Mode Control (SMC) and Terminal SMC (TSMC), which also obtains a finite-time convergence. A controller is then developed from the proposed sliding surface using the backstepping control method and High-Order SMC (HOSMC) to ensure the global stability of the control system. Thanks to this proposed method, the controller provides small position and velocity control errors with less oscillation, smooth control torque, and convergence of the control errors in the short time. The stability and convergence also are guaranteed with Lyapunov theory. Finally, computer simulation verifies the effectiveness of the designed controller.

This study aims to build a novel tracking control algorithm using a finite-time disturbance observer which obtains fast convergence within a predetermined amount of time and strong stability for a class of second-order nonlinear systems. Firstly, a nonlinear sliding mode manifold with fast finite-time convergence is introduced. Then, according to the designed manifold for the guarantee of finite-time convergence and robustness stabilization, a nonlinear control algorithm based on theory of finite-time control is developed. Specifically, the information of the lumped uncertainty was achieved by a new finite-time Disturbance Observer (DO). Thanks to the synthetic advantages of the above techniques, the designed controller marked with powerful features including a practical design, fast convergence rate, high precision, a convergence of the control errors in finite-time, along with impressive small chattering in the control actions. Furthermore, the control proposal also eliminates the necessity of the upper boundary of the uncertainties affecting the system and its finite settling time can be estimated in advance by designating the appropriate design parameters. The finite-time stability of the proposed DO, sliding surface, and control algorithm has been fully confirmed by Lyapunov principle. Trajectory tracking simulation for a 3-DOF manipulator and trajectory tracking experiment for a Maglev System (MLS) has been performed under different operating conditions using MATLAB/SIMULINK to testify the effectiveness and feasibility of the suggested strategy.

In this research, a new robust control method is developed, which achieves a fixed-time convergence, robust stabilization, and high accuracy for trajectory tracking control of uncertain magnetic levitation systems. A hybrid controller is a combination of an adaptive fixed-time disturbance observer and a fixed-time control algorithm. First, to estimate precisely the total uncertain component in fixed-time, an adaptive disturbance observer is constructed. Then, a new robust control method is designed from a proposed fixed-time sliding manifold, disturbance observer's information, and a continuous fixed-time reaching law. A global fixed-time stability and convergence time boundary of the control system is obtained by Lyapunov criteria in which the settling time can be arbitrarily set using design parameters regardless of the system's initial state. Finally, the designed control strategy is implemented for a magnetic levitation system and its control performance is compared with other existing finite-time control methods to evaluate outstanding features of the proposed system. Trajectory tracking experiments in MATLAB/SIMULINK environment have been performed to exhibit the effectiveness and practicability of the designed approach.