This study proposes a lower-limb exoskeleton system that is controlled by a wearer’s muscle activity. This system is designed by following procedure. First, analyze the muscle activation patterns of human leg while walking. Second, select the adequate actuator to support the human walking based on calculation of required force of knee joint for step walking. Third, unit type knee and ankle orthotics are integrated with selected actuator. Finally, using this knee-assistive system (KAS) and developed muscle stiffness sensors (MSS), the muscle activity pattern of the subject is analyzed while he is walking on the stair. This study proposes an operating algorithm of KAS based on command signal of MSS which is generated by motion intent of human. A healthy and normal subject walked while wearing the developed powered-knee exoskeleton on his/her knees, and measured effectively assisted plantar flexor strength of the subject’s knees and those neighboring muscles. Finally, capabilities and feasibility of the KAS are evaluated by testing the adapted motor pattern and the EMG signal variance while walking with exoskeleton. These results shows that developed exoskeleton which controlled by muscle activity could help human’s walking acceptably.

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In this internship report the development of an impedance control method for an anthropomorphic lower extremity exoskeleton is described. This exoskeleton can be used to restore the gait of paralyzed people. Webots simulations are used to test the control method. Therefore a realis-tic model of both the human as the exoskeleton has to be made. The lower extremities of the human model have 6 DOF all in the sagital plane. The human model has only passive elements simulating that the human is fully paralyzed. The actuation is done by the exoskeleton. The human model is compared to a Matlab model of the TU Delft. The joint angle trajectories of both models are approximately the same. The exoske-leton model is anthropomorphic and is assumed to be rigidly at-tached to the user. The actuation is done directly at the joints, so that all sup-plied power is converted into joint rotation. The parameters of the impedance control, stiness, damping and reference trajectory, are phase dependent. They are determined using particle swarm optimization. The optimizations are able to find a gait pattern of the human model wearing the exoskeleton. This gait pattern is compared to the gait of a healthy subject, tracked by the University of Twente. The joint angles of the simulated gait have large similarities with the tracked angles. The developed model can be used to develop and test more complex control methods. By using a monotone fitness function and an adjusted fitness function the result can further improve.

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Previous studies have demonstrated that humans are sometimes capable of initiating arm movements towards visual stimuli at extremely short latencies, implying the presence of a short-latency neural pathway linking visual input to limb motor output. However, little is known about the neural mechanisms that underlie such hastened arm responses. One clue may come from recent demonstrations that the appearance of a visual target can elicit a rapid response in neck muscles that is time-locked to target appearance and functionally relevant for orienting gaze (head and eye) towards the target. Because oculomotor structures thought to contribute to ‘visual responses’ on neck muscles also target some arm muscles via a tecto-reticulo-spinal pathway, we hypothesized that a similar visual response would be present in arm muscles. Our results were consistent with this hypothesis as we observed the presence of rapid arm muscle activity (< 100 ms latency) that was time-locked to target appearance and not movement onset. We further found that the visual response in arm muscles: was present only when an immediate reach towards the target was required; had a magnitude that was predictive of reaction time; was tuned to target location in a manner appropriate for moving the arm towards the target; and was more prevalent in shoulder muscles than elbow muscles. These results provide evidence for a rapid neural pathway linking visual input to arm motor output and suggest the presence of a common neural mechanism for hastening eye, head and arm movements. (далее…)

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A hybrid neuroprosthesis (HNP) was developed with the goal of providing improved gait to individuals with paraplegia relative to existing assistive gait systems. The HNP is an approach to restoring gait by combining a lower extremity exoskeleton with functional neuromuscular stimu-lation (FNS). Individually, exoskeletons apply constraints for support, but provide limited step length and depend on upper extremity actions on a walker for forward propulsion. Conversely, FNS mobilizes the limbs through electrical pulses to paralyzed muscles. However, muscles targeted for stimulation quickly fatigue and provide inadequate postural support. The HNP was designed to functionally combine the sup-portive features of the exoskeleton and joint mobility of FNS. Controllable knee and hip joint mechanisms were developed to support the user while allowing for functional motion from FNS for forward progression. These mechanisms were optimized for maximal torque when supporting a joint and minimal resistance when driven by FNS. A closed-loop controller based on sensor measurements of joint dynamics was developed to synchronize exoskeletal operation with muscle stimulus activity. The objectives were to modulate joint constraints to provide continual support to the user while minimizing the deleterious effects of the constraints on joint mobility, deactivate stimulus to target muscles when certain exoskeletal constraints are engaged to allow the target muscles to rest, and modulate FNS from baseline levels to achieve functi-onal joint positions. The operational response of the controller and mechanisms were characterized through simulation, bench, and able-bodied testing. Implementation of the HNP with an individual with paraplegia respectively showed a 40 % and 16 % reduction in maximum exerted upper extremity forces relative to exoskeleton-only and FNS-only gait. Step lengths were shown to be comparable between HNP and FNS-only gait. When comparing the HNP with and without the FNS modulation, the average gait speed was increased by 16 % with FNS modulation due to a 10 % increase in the hip range of motion. Reductions in muscle activity were feasible when the exoskeletal constraints were enabled. Future work to optimize joint coordination or apply an active mechanism to the exoskeleton to assist hip extension may improve postural control and forward progression.

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This monograph is presented to further a discussion that has persisted for decades, namely: Is it possible to reduce the weight of the combat load on the in-fantry soldier that will allow for nearly unimpeded speed and tempo in foot mobile operations? Since the mid-1990’s the Marine Corps has advanced future operating concepts that seek to achieve the promise of maneuver warfare, that is, the capability to maneuver against the weaknesses of an adversary so rapidly that they are unable to respond to the multiple threats presented across the battlefield, thus shattering their cohesion and decision making ability. An impediment to achieving this endstate has been the fact that foot mobile infantry forces are so overloaded with equipment that they have been unable to maneuver at the desired speed and with the desired distribution on the battlefield to achieve this maneuver effect. Through the ages three solutions have been attempted to reduce the load on the average infantryman: reduce the weight of equipment, transfer the load to some vehicle or beast of burden, and improve individual fitness and endurance. Even as the weight of individual components is decreasing, more pieces of equipment are being added to the combat load for communications, target acquisition, navigation, self protection, and night operating capability. Organizational loads are also increasing as infantry companies are now being given command and control responsibilities that were once reserved for a battalion or higher. There-fore, it is time to explore another alternative to weight mitigation that has never been tried before: wearable exoskeleton technology. The Marine Corps has acknowledged that not enough aviation or vehicles assets exist to move the force in the initial stages of a forcible entry operation, thus, the Marine Corps needs to provide every Marine with the capability to carry the load in the form of some wearable mechani-cal augmentation, which is what an exoskeleton provides.

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