While powered prosthetic feet with monoarticular actuation allow for the restoration of human ankle biomechanics, gait asymmetries and increased walking effort have been found for transtibial amputees. We hypothesize ...
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While powered prosthetic feet with monoarticular actuation allow for the restoration of human ankle biomechanics, gait asymmetries and increased walking effort have been found for transtibial amputees. We hypothesize that this is because of the missing mechanical coupling between the foot and the thigh, which is realized in human legs by the biarticular gastr.cnemius (GAS) muscle. This work investigated the effects of a powered prosthetic foot that includes a monoarticular powered prosthetic foot and a biarticular GAS actuator on nine non-impaired subjects while walking on a treadmill. While maintaining total ankle torque, we modulated the torque contribution ratio κ of the GAS actuator to the total ankle torque and recorded kinematics, kinetics and metabolic cost. We found a maximum reduction in metabolic cost by up to 8.8%±4.4% on average for a κ of 0.36±0.09. We attribute this reduction to (a) reduced biological hip work due to energy transfer from the GAS actuator to assist hip flexion, (b) increased inter-leg symmetry of center of mass collision and propulsive work, knee push-off work and step length and (c) increased efficiency of the center of mass movement caused by a reduction in contralateral leg collision work. Our study demonstr.tes that the biarticular actuator provides an additional degree of freedom that allows for the modulation of human gait biomechanics.
The problem of autonomous rendezvous and docking with a non-cooperative target spacecraft is studied in this paper. A new guidance control method, potential function guidance combined with fuzzy logic, is proposed. Th...
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This paper investigates the dynamics model for analysis of the space station during the module redocking. The deformation mainly concerns three bodies: the core station, the redocking unit and the manipulator arm. Wit...
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This paper discusses the robust tracking problem of dynamic WMRs subject to nonholonomic constr.ints and actuator saturations. A moving horizon H ∞ tracking scheme is proposed, where a constr.ined H ∞ control proble...
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This paper discusses the robust tracking problem of dynamic WMRs subject to nonholonomic constr.ints and actuator saturations. A moving horizon H ∞ tracking scheme is proposed, where a constr.ined H ∞ control problem is solved at each sampling time with the update of not only the initial condition but also the prediction model. Hence, the suggested scheme is potentially less conservative than those on fixed prediction models. Closed-loop properties are discussed in the framework of dissipation theory.
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