Human motion energy harvester for biometric data monitoring

Abstract

In this paper we present an energy autonomous sensor system fully integrated into the heel of a shoe for biometric data monitoring. For powering the wireless sensor system a pulse-driven energy harvester was developed, which uses the acceleration-impulses from heel-strike during walking. In preparation of the device development acceleration measurements were carried out. The pulse-driven energy harvester is based on the electromagnetic conversion principle and incorporates a 4×4 coil matrix. A beam fixed at both ends is used for suspending the magnetic circuit. The geometric parameters of coil and magnetic circuit were optimized for maximum power output. For an idealized acceleration pulse with a width of 5 ms and a height of 200 m/s2 an average power output of 0.7 mW was generated using a step frequency of 1 Hz. The functionality of the self-sustained sensor system is demonstrated by measuring the temperature and step-frequency of a walking person and transmitting the data to a base station. We also found that the implementation of the suspension can have a significant impact on the harvester performance reducing the power output. © Published under licence by IOP Publishing Ltd.