Disturbance observer based adaptive predefined-time sliding mode control for robot manipulators with uncertainties and disturbances

This article develops a predefined-time sliding mode control approach for systems with external disturbances and uncertainties through a nonlinear disturbance observer (DO). For addressing predefined-time stabilization problem of robotic manipulator system, a predefined-time sliding mode surface is proposed, ensuring system states converge to origin within a predefined-time once sliding mode surface is attained. Compared to conventional fixed-time and finite-time control strategies, a distinctive advantage of this scheme is that system settling time can be explicitly chosen in advance and independent of system states. To achieve predefined-time performance, a disturbance observer is introduced to generate the disturbance estimate, which can be incorporated into controller to counteract disturbance. To address the systems uncertainty, an adaptive law is employed to estimate the unknown upper boundary of system uncertainties. Finally, the effectiveness and performance of the proposed scheme are illustrated by simulation and experiment.