Structural Design and Sliding Mode Control Approach of a 4-DoF Upper-Limb Exoskeleton for Post-stroke Rehabilitation

In this research, a 4-DoF upper limb exoskeleton was designed to assist patients while performing cross-pattern movements in a Proprioceptive Neuromuscular Facilitation (PNF) rehabilitation task. The mechanical design included 3 DoF for the shoulder and one for the elbow. The exoskeleton was designed and validated by structural simulation based on finite element analysis. The rehabilitation trajectory was obtained from a healthy person by image processing and a Sliding Mode Control (SMC) strategy was applied for tracking. Results from the structural simulation show that the factor of safety is over 1.3 on average for the proposed exoskeleton design. In addition, results show that the controller is robust to variations in the arm weight, with a tracking error of less than 0.0025 rad.