The availability of accurate and comprehensive models of human limbs, combining high reliability and real-time operation, is required to develop seamless and intuitive human-machine interfaces. Biomechanist have developed complex models of the human lower limb, combining kinematics and kinetics data with neural signals for the purpose of studying human motor control strate-gies. The complexity prevent their application to situations with stringent real-time requirements. We are currently working on the enhancement of an EMG-driven model of the human lower extremity to achieve compre-hensiveness, accuracy, and fast runtime execution. Starting from the very complex model developed by Lloyd et al. we have evaluated how this model can be enhanced to achieve higher performances in terms of compu-tation time with no loss of prediction accuracy. The enhanced model will be applied to the control of powered orthosis and to the development of advanced biomimetic control systems for humanoids robots. We started our investigation with the analysis of the impact of modeling the tendon as an infinitely stiff body and quantitatively evaluated the changes in the behavior of the modified model w.r.t. the original one. We also integrated a runtime anatomical model that allowed to execute the whole EMG-driven model at runtime. This is a significant improvement as the previous available model could not entirely be executed at runtime due to the complexity of the original anatomical model.

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A major goal of powered lower-limb exoskeletons is to act in parallel with the user’s leg muscles and reduce metabolic energy con-sumption during locomotion. Recent designs have focused on portable devices that can mimic the normal torque output of the lower-limb joints over the full gait cycle using large, powerful motors under high gain force control. Powerful motors are heavy, require bulky gears and mounting frames, and rely on even larger power sources. Furthermore, we are unaware of any study to date that de-monstrates a metabolic savings during walking with a portable lower-limb exoskeleton. On the other hand, a recent study indicates that when humans don tethered (i.e. nonportable), bilateral, lightweight, pneumatically powered ankle exoskeletons that replace only ~63% of the ankle muscletendon mechanical work during push-off, they reduce their metabolic energy consumption by 10-12% du-ring treadmill walking . Thus, supplying mechanical energy at a single joint (i.e. the ankle) during a key propulsive phase of wal-king (i.e. pushoff) can have appreciable metabolic benefits. Our goal in this study was to develop a portable device capable of providing ankle joint mechanical assistance during walking without using external power from onboard actuators (i.e. an ‘energy-neutral’ solution). Human walkers exploit a key passive dynamic principle of locomotion: elastic energy storage and return. Early in stance, strain energy is stored in the Achilles’ tendon and then it is recovered later, providing up to 60% of the ankle joint mechanical work during push-off . We hypothesize that a passive wearable device using parallel elastic elements during the walking cycle is capable of recycling a significant portion of the ankle joint mechanical work and could reduce the metabolic cost of walking by up to 18% .

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Many countries of the world including Japan will become a full-fledged aged society. According to report in Japan, the elderly population aged 65 years or over in Japan will number 33 million and will account for more than 25 percent of the population. We have to support the elderly for independence in old age so that a variety of lifestyles is possible. With the development of the robot technologies, robotics researchers have developed various kinds of human assist robot such as walking aid system and manipulation aid system for supporting the elderly.

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This paper presents an approach to the development of bipedal robotic control techniques for multiple locomotion behaviors. Insight into the fundamental behaviors of human loco-motion is obtained through the examination of experimental human data for walking on flat ground, upstairs and downstairs. Specifically, it is shown that certain outputs of the human, independent of locomotion ter-rain, can be characterized by a single function, termed the extended canonical human function. Optimized functions of this form are tracked via feedback linearization in simulations of a planar robotic biped walking on flat ground, upstairs and downstairs — these three modes of locomotion are termed “motion primi-tives.” A second optimization is presented, which yields controllers that evolve the robot from one motion primitive to another — these modes of locomotion are termed “motion transitions.” A final simulation is given, which shows the controlled evolution of a robotic biped as it transitions through each mode of loco-motion over a pyramidal staircase.

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WHEN HUMANS AND OTHER ANIMALS run and hop, they operate with muscle efficiencies nearly twice those observed during cycling. This “free energy” is due to the storage and return of elastic energy in muscles and tendons during the stretch-shorten cycles of landing and takeoff. If spring-like tendons and muscles can save substantial energy, could artificial springs added to the legs further reduce the metabolic costof locomotion?

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