Non-singular terminal sliding mode controller: Application to an actuated exoskeleton

This paper presents a robust controller of an active orthosis used for rehabilitation purposes. The system is composed of the orthosis worn by the shank and has a complex dynamical model. No prior knowledge is considered on the dynamical model and the flexion/extension movements considered are of sinusoidal form and are generally defined by the doctor. The used non-singular terminal sliding mode technique permits to have a finite time convergence. The experimental results have been conducted online on an appropriate dummy and then on three healthy subjects. A comparison of performances obtained by the proposed approach with those obtained by a conventional controller has also been realized. Several situations have been considered to test the robustness and it has been concluded with the effectiveness of the developed controller.