Non-Singular Fast Terminal Sliding Mode Control With Disturbance Observer for Underactuated Robotic Manipulators

This paper proposes a novel non-singular fast terminal sliding control technique for underactuated robotic manipulators. The proposed approach combines the robustness properties of sliding mode-based control approaches with the approximation accuracy of disturbance observers to suppress both matched and mismatched uncertainties. It also solves the singularity and complex-value number problems associated with fast terminal sliding mode control (FTSMC), while guaranteeing fast convergence rate, robustness and tracking accuracy. The performance of the proposed approach is assessed using a three-link underactuated robotic manipulator with and without holding brakes. The obtained results confirmed the fast convergence rate of the disturbance approximation and position tracking errors along with the excellent robustness and dynamic performance of the proposed control approach. Additionally, due to the estimation properties of the disturbance observer, fast and excellent tracking performance was achieved without the use of large feedback gains.