In the domain of space exploration, as in other dangerous environments, strength, endurance, and dexterity are key issues to insure the health of the involved people. Hands are by their very nature one of our primary interfaces to influence and interact with the external world. For these reasons, at the center for Space Humanoid Robotics (SHR) we are studying ways to help cosmonauts overcome the stiffness of the gloves used for extra vehicular activity (EVA) by mean of a lightweight active hand exoskeleton. In this paper we position our work on electromyography (EMG) of the upper limbs as a tool to control a device like the hand exoskeleton. In fact, we are studying EMG signals to extrapolate information about the muscular status of the hands and concurrently we are using the information to support cosmonauts movement.

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Robotic lower limb exoskeletons have been built for augmenting human perfor-mance, assisting with disabilities, studying human physiology, and re-training motor deficiencies. At the University of Michigan Human Neuromechanics Laboratory, we have built pneumatically-powered lower limb exoskeletons for the last two purposes. Most of our prior research has focused on ankle joint exoskeletons because of the large contribution from plantar flexors to the mechanical work performed during gait. One way we control the exoskeletons is with proportional myoelectric control, effectively increasing the strength of the wearer with a physiological mode of control. Healthy human subjects quickly adapt to walking with the robotic ankle exoskeletons, reducing their overall energy expenditure. Individuals with incomplete spinal cord injury have demonstrated rapid modification of muscle recruitment patterns with practice walking with the ankle exoskeletons. Evidence suggests that proportional myoelectric control may have distinct advantages over other types of control for robotic exoskeletons in basic science and rehabilitation.

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Robotic exoskeletons are currently developed to augment human motor performance or assist in the gait rehabilitation of individuals with neurological injuries. While the robo-tic technology is rapidly advancing, there is a large gap in our understanding of how humans respond to exoskeleton assistance during locomotion. To build successful robotic devices, it is critical to under-stand the principles governing mechanical human-machine interaction. In this dissertation, I used lightweight ankle exoskeletons powered by artificial pneumatic muscles to provide mechanical assistance to neurologically intact human subjects. The exoskeletons allowed me to investigate some general principles of motor adaptation in human walking. In the first experiment, an exoskeleton provided subjects with increased dorsiflexor torque. The results demonstrated that there are different adaptation responses for the type bursts of tibialis anterior recruitment during walking. In the second experiment, an exoskeleton provided plantar flexor torque with two artificial pneumatic muscles, increasing the exoskeleton mechani-cal output compared to past studies. With this assistance, subjects rapidly decreased soleus recruitment to walk with a total ankle moment pattern similar to unassisted gait. However, subjects adapted at a slower rate for the stronger exoskeleton. In the third experiment, I quantified soleus monosynaptic reflex responses to determine if reflex inhibition is one of the mechanisms for reducing soleus recruitment during robotic-assisted walking. Subjects demonstrated similar soleus H-reflex amplitudes corresponding to background muscle activation during powered versus unpowered walking. This indicates the reflex gain is not modified during short-term adaptation to the robotic exoskeleton. In the final experiment, I used the exoskeleton as a tool to quantify the mechanical output of plantar flexor reflex responses during perturbed gait. I introduced a perturbation by turning off the robotic assistance unexpectedly in midstance. During the perturbed steps, subjects greatly increased muscle activation to maintain total ankle moment patterns similar to unperturbed steps. Overall these studies demonstrated that the nervous system prioritizes a given ankle joint moment pattern during human walking, both with robotic assistance and when encountering gait perturbations. The combined results of these experiments will help guide the design of future robotic devices and could lead to better strategies for robotic-assisted gait rehabili-tation.

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ANTHROPOMORPHISM has served as a useful guiding principle for design and control of robotic systems in man’s pursuit of “making a machine in his own image.” The renewed interest in recent years arises from the need to develop human-like robotic and mechatronic systems (and subsystems) to operate in, interact with, and cohabit human-built environments. From a morphological perspective, numerous novel designs have been proposed ranging from prosthetic/robotic hands, for performing dexterous grasping and manipulatory tasks, to lower limb exoskeletons and walking robots, for enabling ambulation in our homes and the outdoors. The new generations of anthropomorphic mechatronic systems (and subsystems) capitalize on advances in miniaturization of sensing/actuation and the ongoing revolutions in embedded computation and wireless communication.

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Powered exoskeletons gained increasing relevance in the field of rehabilitation robotics during the last years. These robots can be exploited to control the movements of patients having neuro-muscular impairment, following, e.g., stroke, spinal cord injuries (SCI), or cerebral palsy, to restore their lost functionalities. Compared to end-point external machines, exoskele-tons present the advantage of independently controlling each degree of mobility of the user’s limb, thanks to the specific interaction between the robot links and the user’s body segments. This theoretical advantage is however hardly achieved by the real system performances, due to several issues, mainly related to design of the physical human-robot interface (pHRI). In fact, the pHRI design has to merge human-oriented requirements, such as inherent safety, adaptability to anthropometry variability, and wearing easiness, with an effective bi-directional transfer of torque. In recent years, several applications for hand or fingers rehabilitation have been presented. In this work, we present HandExos, a novel wearable active device, which mechanical and kinematic pHRI design tries to satisfy the requirements presented above.

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