Powered Knee Prosthesis Incorporating Battery-Capacitor Hybrid

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DESCRIPTION (provided by applicant): Approximately 623,000 people currently live in the United States with a lower limb amputation, with 30,000 new transfemoral amputations conducted each year. The latest commercial product is a prosthetic knee powered by an electric motor designed to function as an integrated extension of its user. Such a knee allows users to more naturally perform tasks such as climbing stairs or rising from a seated position and thereby reduce joint damage caused by compensatory movements. Current devices require replacing the rechargeable battery once a year. The battery pack costs several hundred dollars and represents a considerable cost for owners of powered-knee prosthetics. The proposed project will reduce the need for battery replacement, thereby making powered-knee prosthetics more affordable to the general public. The prosthetic knee requires fluctuating power requirements to fully emulate the mechanical behavior of the human knee joint. Currently, the power requirements are met primarily using a battery. Batteries are designed for continuous energy supply and are best operated at constant operating conditions; they perform poorly in the presence of power fluctuations and cannot efficiently handle spike high power demands. Giner, Inc. proposes to optimize power supplies for prostheses by designing and demonstrating an integrated battery/capacitor hybrid power source. Capacitors, while having very low energy densities, have very high power densities. In a battery/capacitor hybrid (BCH), the capacitor handles most of the power spikes, allowing the battery to function under more constant conditions. Giner Inc.'s approach will be to incorporate its advanced all-solid capacitor with rechargeable lithium-polymer batteries to provide high energy and power densities. The combination of rechargeable batteries and capacitors is anticipated to offer specific high power under certain frequency during gait cycles. The battery continues to meet ongoing low-power requirements while the capacitor will provide peak power needs for 100-250ms during each gait cycle. This design will allow the battery pack to work under much lower and steadier current level, thereby increasing its lifetime. High- concentration sulfuric acid is not required as in the case of typical electrolytic capacitors, thereby eliminating the need for hermetic packaging. Phase I will include: (1) battery testing; (2) computer modeling of potential BCH power supplies; (3) design, fabrication, and testing of capacitor units; (4) electronic investigation of BCH power supplies; and (5) comparisons with commercial battery packs. PUBLIC HEALTH RELEVANCE: The rechargeable batteries in electric motor-powered prosthetic limbs need replacement on a yearly basis. The proposed project will reduce the need for expensive battery replacement by using a battery/capacitor hybrid (BCH) which will allow the battery pack to work under much lower and steadier current level, thereby increasing its lifetime, and making powered-knee prosthetics more affordable to the general public.