Control Strategy Based on Kinetic Motor Primitives for Lower Limbs Exoskeletons

Abstract

In order to assist after-stroke individuals with hemiparetic gait pattern to rehabilitate their movements, many research centers have developed exoskeletons for lower limbs and control strategies for them. The present work aims to develop a robotic control strategy based on kinetic motor primitives capable of assisting the recovery of patients with compromised movements. The joint positions of a healthy subject walking on a treadmill, wearing and not wearing a six degree- of-freedom exoskeleton, were obtained through IMUs (Inertial Measurements Units) and used to calculate the joint torques using the OpenSim software. Motor primitives of the kinetic data (torques), and their respective weights, were then computed using Principal Component Analysis (PCA). Based on the ratio of the weights, a control strategy was designed to generate the necessary robot torque in order to assist the individual during the walking wearing the exoskeleton. The proposed strategy was evaluated with the subject wearing a torque-controlled orthosis for 120 seconds at 1.5 km/h on a treadmill. The torques and angles of the individual were obtained for posterior analysis.