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 isinvestigated for the knee joint orthosis (exoskeleton) robotsubjected to external disturbances and model uncertainties.By developing the second order nonsingular terminalsliding mode control (NTSMC) approach, a new inputtorque (control law) is suggested to steer the handicappedperson’s shank to the desired path within a tunable finitetime. Moreover, the Lyapunov theorem is employed todemonstrate the global finite time stability of the closedlooporthosis system. Also, a new formula (in the form ofinequality) is derived to estimate the upper bound of theneeded finite time. Eventually, a numerical simulation isgiven to illustrate the applicability and the effectiveness ofthe suggested control law.