A Novel Proposed Second Order Terminal Sliding Mode Controller for a Knee Joint Orthosis Robot Subjected to Disturbances and Uncertainties

In this article, a robust finite time tracking problem is investigated for the knee joint orthosis (exoskeleton) robot subjected to external disturbances and model uncertainties. By developing the second order nonsingular terminal sliding mode control (NTSMC) approach, a new input torque (control law) is suggested to steer the handicapped person’s shank to the desired path within a tunable finite time. Moreover, the Lyapunov theorem is employed to demonstrate the global finite time stability of the closed-loop orthosis system. Also, a new formula (in the form of inequality) is derived to estimate the upper bound of the needed finite time. Eventually, a numerical simulation is given to illustrate the applicability and the effectiveness of the suggested control law.