Adaptive integral terminal sliding mode control of an upper limb exoskeleton

This paper presents an adaptive integral terminal sliding mode control strategy applied to an upper limb exoskeleton. The controller is designed to address the problem of non knowledge of the dynamic parameters of the human limb since they differ from a person to another and the compensation for external disturbances. The proposed control scheme which supposes known only the upper bound of the inertia matrix of the system, guarantees high tracking performance when assisting wearers with shoulder, elbow and wrist joint movements. The reaching of the sliding mode as well as the tracking errors and the uncertainty bounds estimation convergence in finite time is proven. Simulations were performed to evaluate the performance and the efficiency of the proposed controller in tracking trajectories that correspond to passive arm movements.