Today, commercially available ankle-foot prostheses are completely passive, and consequently, their mechanical properties remain fixed with walking speed and terrain. Conversely, normal human ankle stiffness varies within each gait cycle and also with walking speed. Furthermore, some studies have indicated that one of the main functions of the human ankle is to provide adequate energy for forward progression of the body. Thus, an ideal ankle-foot prosthesis should be able to actively control joint impedance, motive power, and joint position. Understanding the dynamic inter-action between an amputee and an active prosthesis is critical to developing truly functional leg pros-theses. For this reason, we have developed a novel robotic ankle-foot emulator. The emulator is capable of changing mechanical impedance and providing sufficient mechanical energy for forward propulsion. In this paper, we present pilot data on the actual interaction between an amputee and the ankle emulator during walking. These data support the hypothesis that actively controlling ankle joint impedance may provide a more natural gait than a conventional passive prosthesis. Furthermore, adding additional mechanical energy beyond that a passive spring ankle can provide during powered plantar flexion can dramatically increase the self-selected walking speed of an amputee.

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In this study, we developed a fuzzy-logic-controlled PGO (Power Gait Othosis) that controls the flexion and extension of each PGO joint using bio-signals and an FSR sensor. The PGO driving system works to couple the right and left sides of the orthosis by spe-cially-designed hip joints and pelvic section. This driving system consists of the orthosis, sensor, and control system. An air supply system for muscle action is composed of an air compressor, 2-way sole-noid valve (MAC, USA), accumulator and pressure sensor. The role of this system is to provide constant “air muscle” with compressed air at the hip joint. With the output signal of the EMG and foot sensors, air muscles assist the flexion of the hip joint during the PGO gait.

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We constructed a powered ankle–foot orthosis for human walking with a novel myoelectric controller. The orthosis included a carbon fiber and polypropylene shell, a metal hinge joint, and two artificial pneumatic muscles. Soleus electromyography (EMG) activated the artificial plantar flexor and inhibited the artificial dorsiflexor. Tibialis anterior EMG activated the artificial dorsi-flexor.We collected kinematic, kinetic, and electromyographic data for a naive healthy subject walking with the orthosis. The current design improves upon a previous prototype by being easier to don and doff and simpler to use. The novel controller allows naive wearers to quickly adapt to the orthosis without artificial muscle co-contraction. The orthosis may be helpful in studying human walking biomechanics and assisting patients during gait rehabilitation after neurological injury.

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Actualmente algunas de las aplicaciones de los exoesqueletos de partes superiores son la rehabilitación y la amplificación de las habilidades del brazo humano. Nuestro estudio se enfoca en las aplicaciones de rehabilitación, en las cuales se busca restaurar las funciones de los miembros atrofiados. Como etapa esencial en el entendimiento de la movilidad del brazo, está el análisis cinemático, análisis hecho a partir de las mismas teorías que envuelven el estudio de actuadores robóticos industriales. Este estudio es la base para el objetivo final de una primera etapa: determinar del espacio de trabajo del brazo humano teniendo en cuenta los rangos de movilidad en las articulaciones a los cuales un exoesqueleto estaría sometido. Para este análisis se consideró un modelo de 7 GDL que describe los movimientos y las restricciones de cada una de las articulaciones del brazo (hombro, codo y muñeca) y con él se define el alcance real que tiene la muñeca a través del espacio de trabajo del sistema. Gráficas y conclusiones acompañan este documento.

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This chapter discusses the advantages and feasibility of using compliant actuators in exoskeletons. We designed compliant actuation for use in a gait rehabilitation robot. In such a gait rehabilitation robot large forces are required to support the patient. In case of poststroke patients only the affected leg has to be supported while the movement of the unaffected leg should not be hindered. Not hindering the motions of one of the legs means that mechanical impedance of the robot should be minimal. The combination of large support forces and minimal impedances can be realised by impedance or admittance control. We chose for impedance control. The consequence of this choice is that the mass of the exoskeleton including its actuation should be minimized and sufficient high force bandwidth of the actuation is required. Compliant actuation has advantages compared to non compliant actuation in case both high forces and a high force tracking bandwidth are required. Series elastic actuation and pneumatics are well known examples of compliant actuators. Both types of compliant actuators are described with a general model of compliant actuation. They are compared in terms of this general model and also experimentally. Series elastic actuation appears to perform slightly better than pneumatic actuation and is much simpler to control. In an alternative design the motors were removed from the exoskeleton to further minimize the mass of the exoskeleton. These motors drove an elastic joint using flexible Bowden cables. The force bandwidth and the minimal impedance of this distributed series elastic joint actuation were within the requirements for a gait rehabilitation robot.

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