Evaluation of motor primitive-based adaptive control algorithms for lower limb exoskeletons

• Autor(a) principal: Nunes, Polyana Ferreira
• Data de Publicação: 2021
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/18/18149/tde-02072021-124003/
• topic: Biomecatrônica; Biomechatronics; Exoesqueleto; Exoskeleton; Lower limbs; Membros inferiores; Motor primitives; Primitivas motoras; Reabilitação robótica; Rehabilitation robotics

In order to assist in the rehabilitation of individuals with motor disabilities, especially stroke victims, to rehabilitate their movements, research centers have developed lower limbs exoskeletons and control strategies for these robotic devices. Robot-assisted therapy can help not only by providing support, accuracy, and precision while performing exercises, but also by being able to adapt to different patient needs, according to their impairments. The proposed approach was evaluated on a lower limbs exoskeleton, in which the knee joint was driven by a series elastic actuator. First, to extract the motor primitives, the user torques are estimated by means of a generalized momentum-based disturbance observer combined with an extended Kalman filter. These data were provided to the control algorithm, which, at every swing phase, assisted the subject to perform the desired movement, based on the analysis of his previous step. Tests were performed in order to evaluate the controller performance for a subject walking actively, passively, and at a combination of these two conditions. Results suggest that the robot assistance is capable of compensating the motor primitive weight deficiency when the subject exerts less torque than expected. Furthermore, though only the knee joint was actuated, the motor primitive weights with respect to the hip joint were influenced by the robot torque applied at the knee. The robot also generated torque to compensate for eventual asynchronous movements of the subject, and adapted to a change in the gait characteristics within three to four steps.