Robust Finite Time Tracking Control for Robotic Manipulators Based on Nonsingular Fast Terminal Sliding Mode

In this paper, a novel disturbance observer-based robust nonsingular fast terminal sliding mode control (RNFTSMC) technique is proposed for tracking control of robotic manipulators with time-varying disturbances. First, an improved form of nonsingular fast terminal sliding manifold is developed to achieve the strong robustness and finite time convergence of the system, and to avoid the singularity problem. Second, a continuous robust reaching law is designed not only to attenuate chattering phenomena without deteriorating the system tracking precision, but also to guarantee the finite time stability of the system. Furthermore, a nonlinear disturbance observer (NDOB) is employed to estimate the system uncertainties and decrease the switching gain, so that the prior information about the perturbations is not required, and the control signal can be reduced with fewer chattering effect. The system stability is analyzed according to the Lyapunov stability theory. Finally, the superiority of the proposed control scheme is validated by comparative simulation studies.