Homogeneous Finite Time Higher Order Sliding Mode Control Applied to an Upper Limb Exoskeleton Robot

Abstract

A homogeneous continuous sliding mode control scheme based on finite time stability is developed in this paper for an upper limb exoskeleton robot dedicated for rehabilitation. Indeed this type of robot interacts directly with human limbs whose dynamics are unknown and different for users. Therefore, the main idea is to provide a robust motion control of the exoskeleton robot using a continuous higher order sliding mode controller despite parameters variations, uncertainties and external disturbances. The proposed controller combines the homogeneity concept and the super-twisting algorithm. Finite time stabilization is achieved using the first part of the controller while disturbance rejection is granted by the second part of the controller. Performance of the controller and its robustness are illustrated through simulations of trajectory tracking tests corresponding to passive rehabilitation exercises.