Flatness Based Control of a Novel Smart Exoskeleton Robot

Abstract

This article presents the design, implementation, and validation of a novel robust control strategy based on variables transformation, i.e., transforming variables to obtain the triangular flat canonical normal form for nonlinear dynamic systems satisfying the flatness geometric property. A differential flatness, integrated with a geometrical transformation-based method, was developed to control an exoskeleton robot named smart robotic exoskeleton (SREx). The SREx was designed to provide upper limb rehabilitation therapy to the stroke survivors. The proposed flatness control technique ensures continuous enhanced trajectory tracking and the system’s high robustness during following a trajectory representing rehabilitation exercises. Furthermore, utilizing the Lyapunov theory, all signals were shown to be bounded in the closed-loop form. Experiments and comparative studies were carried out to validate the effectiveness of the proposed control scheme. Controlled experiments were further conducted using healthy subjects, maneuvering the SERx to provide rehabilitation exercise and to validate the control scheme in real-time.