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Session: Prostheses
Session starts: Thursday 24 January, 13:30
Presentation starts: 13:30
Room: Lecture room 558

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Ramazan Unal (University of Twente)
Sebastiaan Behrens (University of Twente)
Raffaella Carloni (University of Twente)
Edsko Hekman (University of Twente)
Stefano Stramigioli (University of Twente)
Bart Koopman (University of Twente)

Abstract:
In this study, we present the principle design of a fully-passive transfemoral prosthesis for normal walking, inspired by the power flow in human natural gait. The working principle of the mechanism is based on three parts, which are responsible of the energetic coupling between the knee and ankle joints. The design parameters of the prosthesis have been determined according to the energy absorption intervals of the natural human gait. Test results show that significant amount of energy can be stored to deliver for ankle push-off generation. The research interest on transfemoral prostheses is clearly motivated by their crucial impact to human life. In particular, a still open challenge is the design of a prosthesis that can both adapt to various walking conditions and can be energy efficient with respect to the metabolic energy consumption and external actuation. Therefore, we proposed a fully-passive transfemoral prosthesis design that is inspired by the power flow in human gait as in [1]. According to power flow through the joints, functions of the joints can be explained by dividing gait into three phases: Stance; the knee absorbs a certain amount of energy during flexion and generates as much as the same energy for its extension. In the meantime, the ankle joint absorbs energy, due to the weight bearing. Push-off; the knee starts absorbing energy, while the ankle generates the main part of the energy for the push-off, which is about the 80% of the overall energy generation. Swing; the knee joint absorbs energy due to kinetic energy of shank during late swing phase, while the energy flow in the ankle joint is negligible. In this study, we present a mechanism that can cover the energy absorption phases and deliver the total energy at the ankle joint for push-off. This mechanism has three distinct parts: Linkage mechanism, CL that couples the knee and ankle joints kinematically and is responsible for the exchange of the energy between the two joints during push-off. Coupling elastic element, C2 that couples the upper and lower leg and is responsible for the absorption and transfer of the energy during swing phase and for a part of absorption during stance phase. Ankle elastic element, C3 that connects the foot and lower leg and is responsible for the main part of the absorption during stance phase. According to the power analysis and biological leg dimensions, we set the design parameters for the prosthesis and realize the prototype for normal walking in order to examine the power absorption capacity on healthy and amputee subjects. Primary functional tests have shown promising results towards to fully passive energy efficient transfemoral prosthesis.