Robust Finite Time Tracking Control for the Knee Joint Exoskeleton Robot

In this paper, finite time tracking problem for the knee jointexoskeleton (orthosis) robot is addressed in the presence ofmodel uncertainties and external disturbances. Based on thesecond order non-singular terminal sliding mode control(NTSMC) method, a novel actuator’s torque (control input)is designed to exactly reach the subject’s shank to thedesired trajectory within the adjustable total finite time. Theglobal finite time stability of the closed-loop exoskeletonrobot system is mathematically proven by using Lyapunovtheorem. Moreover, a new relation is derived fordetermining the required finite time. Finally, a numericalsimulation is given to illustrate the good performance of thesuggested actuator’s torque.