Unknown Disturbance Estimator Based Adaptive Nonsingular Fast Terminal Sliding-Mode Control for n-DOF Nonlinear Robotic Systems

This paper develops an improved second-order filter unknown disturbance estimator (UDE) with adaptive nonsingular fast terminal sliding mode control (ANFTSMC) to solve the trajectory tracking problem of uncertainties and external disturbances in robotic system. The developed UDE -ANFTSMC controller not only uses the advantages of NFTSM theory to ensure fast convergence speed, avoid singularity and robustness to uncertainties and external disturbances, but also uses UDE to estimate and suppress unknown disturbances in the system. Firstly, UDE is introduced, and then the ANFTSM control scheme is designed with a NTFSM surface. Lyapunov stability theory was used for stability analysis, and the manipulator mathematic model and SolidWorks’ prototype were used to demonstrate the effectiveness of the proposed control scheme.