Observer-based free-will arbitrary time sliding mode control for uncertain robotic manipulators

This paper studies a free-will arbitrary time sliding mode control (FATSMC) based on the predefined-time sliding mode observer (PTSMO) for tracking control of robotic manipulators. First, a PTSMO is constructed to estimate the coupled uncertainty of the robotic manipulator system in a preset time. Then, a FATSMC scheme is proposed to realize the free-will arbitrary time tracking control for uncertain robotic manipulators and preset the upper bound on the settling time in the reaching phase. The proposed control strategy has high tracking accuracy and smooth control torque, while the convergence time of the system is nonconservative. The stability of the FATSMC and the PTSMO are rigorously demonstrated using the Lyapunov stability theory. Finally, a three-degree-of-freedom uncertain manipulator is utilized for numerical simulation. The effectiveness and superiority of the proposed control strategy are demonstrated by comparing it with several control strategies.