Background: To improve design of robotic lower limb exoskeletons for gait rehabilitation, it is critical to identify neural mecha-nisms that govern locomotor adaptation to robotic assistance. Previously, we demonstrated soleus muscle recruitment decreased by ~35% when walking with a pneumatically-powered ankle exoskeleton providing plantar flexor torque under soleus proportional myoelec-tric control. Since a substantial portion of soleus activation during walking results from the stretch reflex, increased reflex in-hibition is one potential mechanism for reducing soleus recruitment when walking with exoskeleton assistance. This is clinically re-levant because many neurologically impaired populations have hyperactive stretch reflexes and training to reduce the reflexes could lead to substantial improvements in their motor ability. The purpose of this study was to quantify soleus Hoffmann (H-) reflex res-ponses during powered versus unpowered walking. Methods: We tested soleus H-reflex responses in neurologically intact subjects (n=8) that had trained walking with the soleus controlled robotic ankle exoskeleton. Soleus H-reflex was tested at the mid and late stance while subjects walked with the exoskeleton on the treadmill at 1.25 m/s, first without power (first unpowered), then with power (powered), and finally without power again (second unpowered). We also collected joint kinematics and electromyography. Re-sults: When the robotic plantar flexor torque was provided, subjects walked with lower soleus electromyographic (EMG) activation (27-48%) and had concomitant reductions in H-reflex amplitude (12-24%) compared to the first unpowered condition. The H-reflex am-plitude in proportion to the background soleus EMG during powered walking was not significantly different from the two unpowered conditions. Conclusion: These findings suggest that the nervous system does not inhibit the soleus H-reflex in response to short-term adaption to exoskeleton assistance. Future studies should determine if the findings also apply to longterm adaption to the exo-skeleton.

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Background: Stair climbing up and down is an essential part of everyday’s mobility. To enable wheelchair-dependent patients the repetitive practice of this task, a novel gait robot, G-EO-Systems (EO, Lat: I walk), based on the end-effector principle, has been designed. The trajectories of the foot plates are freely programmable enabling not only the practice of simulated floor wal-king but also stair climbing up and down. The article intended to compare lower limb muscle activation patterns of hemiparetic sub-jects during real floor walking and stairs climbing up, and during the corresponding simulated conditions on the machine, and se-condly to demonstrate gait improvement on single case after training on the machine. Methods: The muscle activation pattern of se-ven lower limb muscles of six hemiparetic patients during free and simulated walking on the floor and stair climbing was measured via dynamic electromyography. A non-ambulatory, sub-acute stroke patient additionally trained on the G-EO-Systems every workday for five weeks. Results: The muscle activation patterns were comparable during the real and simulated conditions, both on the floor and during stair climbing up. Minor differences, concerning the real and simulated floor walking conditions, were a delayed (prolonged) onset (duration) of the thigh muscle activation on the machine across all subjects. Concerning stair climbing conditions, the shank muscle activation was more phasic and timely correct in selected patients on the device. The severely affected subject regained wal-king and stair climbing ability. Conclusions: The G-EO-Systems is an interesting new option in gait rehabilitation after stroke. The lower limb muscle activation patterns were comparable, a training thus feasible, and the positive case report warrants further clinical studies.

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Ce projet s’inscrit dans l’effort développé par l’Agence Spatiale Européenne (ESA) pour robotiser les activités extravéhiculaires à bord de la Station Spatiale Internationale et lors des futures missions d’exploration planétaire. Un aspect important de ces projets concerne le retour de force et la capacité, pour la personne qui commande les mouvements du robot, à ressentir les efforts qui lui sont appliqués. Le but est d’améliorer la qualité et l’immersion de la téléopération. L’objectif de cette thèse est la conception d’une interface haptique de type exosquelette pour le bras, pour ces missions de téléopération à retour de force. Ce système doit permettre une commande intuitive du robot téléopéré tout en reproduisant le plus fidèlement possible les efforts. Les chapitres 2 et 3 présentent les études réalisées sur un banc de test à 1 degré de liberté, destinées à comprendre le contrôle haptique ainsi qu’à évaluer différentes technologies d’actionnements et de capteurs. Les principales méthodes de contrôle sont décrites théoriquement et comparées en pratique sur le banc de test. Les chapitres 4 et 5 décrivent le développement de l’exosquelette SAM destiné aux futures applications de téléopération spatiale. La conception cinématique, le choix des actionneurs et des capteurs sont décrits. Différentes méthodes de contrôle sont également comparées avec des expériences de réalité virtuelle (sans robot esclave) et de téléopération. Pour finir, le chapitre 6 présente le projet EXOSTATION, un démonstrateur de téléopération haptique spatiale, dans lequel SAM est utilisé comme interface maître.

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This paper introduces a newly developed Hand Exoskeleton Rehabilitation Robot (HEXORR). This device has been designed to provide full range of motion (ROM) for all of the hand’s digits. The thumb actuator allows for variable thumb plane of motion to incorporate different degrees of extension/flexion and abduction/adduction. Compensation algorithms have been developed to improve the exoskeleton’s backdrivability by counteracting gravity, stiction and kinetic friction. We have also designed a force assistance mode that provides extension assistance based on each individual’s needs. A pilot study was conducted on 9 unimpaired and 5 chronic stroke subjects to investigate the device’s ability to allow physiologically accurate hand movements throughout the full ROM. The study also tested the efficacy of the force assistance mode with the goal of increasing stroke subjects’ active ROM while still requiring active extension torque on the part of the subject.

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Background: Hemiparesis after stroke often leads to impaired ankle motor control that impacts gait function. In recent studies, robotic devices have been developed to address this impairment. While capable of imparting forces to assist during training and gait, these devices add mass to the paretic leg which might encumber patients’ gait pattern. The purpose of this study was to assess the effects of the added mass of one of these robots, the MIT’s Anklebot, while unpowered, on gait of chronic stroke sur-vivors during overground and treadmill walking. Methods: Nine chronic stroke survivors walked overground and on a treadmill with and without the anklebot mounted on the paretic leg. Gait parameters, interlimb symmetry, and joint kinematics were collected for the four conditions. Repeated-measures analysis of variance (ANOVA) tests were conducted to examine for possible differences across four conditions for the paretic and nonparetic leg. Results: The added inertia and friction of the unpowered anklebot had no statis-tically significant effect on spatiotemporal parameters of gait, including paretic and nonparetic step time and stance percen-tage, in both overground and treadmill conditions. Noteworthy, interlimb symmetry as characterized by relative stance duration was grea-ter on the treadmill than overground regardless of loading conditions. The presence of the unpowered robot loading reduced the non-paretic knee peak flexion on the treadmill and paretic peak dorsiflexion overground (p < 0.05). Conclusions: Our results suggest that for these subjects the added inertia and friction of this backdriveable robot did not significantly alter their gait pattern. (далее…)

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