Abstract
With the advancement trend of lower limb prosthetics headed towards bionics (active ankle and knee) and smart prosthetics (gait and condition monitoring), there is an increasing integration of various sensors (micro-electromechanical system (MEMS) accelerometers, gyroscopes, magnetometers, strain gauges, pressure sensors, etc.), microcontrollers and wireless systems, and power drives including motors and actuators. All of these active elements require electrical power. However, inclusion of a heavy and bulky battery risks to undo the lightweight advancements achieved by the strong and flexible composite materials in the past decades. Kinetic energy harvesting holds the promise to recharge a small on-board battery in order to sustain the active systems without sacrificing weight and size. However, careful design is required in order not to over-burden the user from parasitic effects. This paper presents a feasibility study using measured gait data and numerical simulation in order to predict the available recoverable power. The numerical simulations suggest that, depending on the axis, up to 10s mW average electrical power is recoverable for a walking gait and up to 100s mW average electrical power is achievable during a running gait. This takes into account parasitic losses and only capturing a fraction of the gait cycle to not adversely burden the user. The predicted recoverable power levels are ample to self-sustain wireless communication and smart sensing functionalities to support smart prosthetics, as well as extend the battery life for active actuators in bionic systems. The results here serve as a theoretical foundation to design and develop towards regenerative smart bionic prosthetics.
Highlights
Lower limb prosthetics are crucial to the quality of life of amputees, by making it possible to lead both an independent and physically active lifestyle [1]
This paper focuses on a typical modern energy storage and return (ESR) lower limb prosthetic design illustrated in Figure 3 [36], with a pneumatic air spring below the knee and a carbon fibre mechanical spring as the foot
It is predicted that nearly 0.4 W of average electrical power can be recovered for a running gait (9 km/h) and 45 mW for walking gait (3 km/h)
Summary
Lower limb prosthetics are crucial to the quality of life of amputees, by making it possible to lead both an independent and physically active lifestyle [1]. One of the earliest documented examples of lower limb prosthetics date back to the Romans, circa 300 B.C. Development of prosthetics since the 1980s involved the increasing use of composite materials such as carbon fibre [5], as a lightweight, flexible and strong material compared with plastic, wood and metal. There is a growing research interest to include active elements, such as active ankle and knee driven by actuators and controlled by feedback information from sensors, to develop towards lower limb bionics in order to further reduce the human energy cost and improve gait pattern of transtibial amputees [7]. An ideal prosthetics is thought to possess a high 3C-level
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