A footwear harvester needs to fulfill both technical and practical functionalities, including but not limited to energy extracting and storage, easy implantation and durability. The very limited space in a shoe is the key challenge to the design of a footwear harvester. This paper presents the design, optimization, modeling and testing of an embedded piezoelectric footwear harvester for energy scavenging from human walking. A force amplification frame is designed and optimized to transmit and amplify the vertical heel-strike force to the inner piezoelectric stack deployed in the horizontal direction. Two heel-shaped aluminum plates are employed to gather and transfer the dynamic force over the heel to the sandwiched force amplification frames. The dynamic force at the heel is measured to design, optimize and simulate the piezoelectric footwear harvester. A numerical model is developed and validated to be capable of precisely predicting the electrical outputs of the harvester. Two prototypes, respectively including eight and six stacks, are fabricated and tested on a treadmill at different walking speeds and external resistances. The numerical simulations agree well with experiments. The harvester with fewer piezoelectric stacks could produce more power at the same walking speed and matched resistance. Experimental results manifest that the footwear harvesters with eight and six stacks, respectively, have 7 mW/shoe and 9 mW/shoe average power outputs at the walking speeds of 3.0 mph (4.8 km/h). Simulation results from the validated numerical model show that the harvester with four piezoelectric stacks could harvest 14 mW/shoe and 20 mW/shoe average power at 3.0 mph (4.8 km/h) and 3.5 mph (5.6 km/h), respectively.
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机译：鞋类收割机需要同时满足技术和实用功能，包括但不限于能量提取和存储，易于植入和耐用性。鞋中非常有限的空间是鞋类收割机设计的关键挑战。本文介绍了一种嵌入式压电鞋类采集器的设计，优化，建模和测试，该采集器可以消除人的步行能量。设计并优化了一个力放大框架，以将垂直的后跟打击力传递和放大到在水平方向上展开的内部压电叠层中。使用两个鞋跟形铝板将脚跟上的动态力收集并传递到夹心力放大框架。测量脚后跟处的动力，以设计，优化和模拟压电式鞋类收割机。开发并验证了一个数值模型，该模型能够精确预测收割机的电输出。在跑步机上以不同的步行速度和外部阻力在两个跑步机上分别制造了两个原型，分别包括八个和六个堆栈。数值模拟与实验吻合良好。具有较少压电堆的收割机可以在相同的步行速度和匹配的电阻下产生更多的功率。实验结果表明，在速度为3.0 mph（4.8 km / h）的行走速度下，具有八叠和六叠的鞋类收割机分别具有7 mW /鞋和9 mW /鞋的平均功率输出。经过验证的数值模型的仿真结果表明，带有四个压电堆的收割机在3.0 mph（4.8 km / h）和3.5 mph（5.6 km / h）的速度下分别可以收获14 mW /瓦和20 mW /瓦的平均功率。
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