MP-HAR: A Novel Motion-powered Real-time Human Activity Recognition System (IoTJ, IF=10.6)

Abstract

With the rapid advance of the Internet of Things (IoT), more and more wearable devices are being developed for real-time monitoring. Most of these existing monitors are powered by chemical batteries. Replacing and disposing of batteries for an exponentially increasing number of IoT nodes will result in prohibitively labor-intensive and environmental-unfriendly. Energy harvesting (EH), reclaiming the wasted ambient energy, is a promising technology for battery-free IoT. In this paper, we have presented a novel motion-powered real-time human activity recognition (HAR) system, called MP-HAR, where the harvester works as both an energy source and sensor. MP-HAR emphasizes low-power as well as low-cost characteristics, encompassing four necessary units, energy transduction unit (ETU), energy management unit (EMU), energy user unit (EUU), and edge computing unit (ECU). In particular, the unique intermittent operation based on the re-configurable on/off threshold voltages given by the well-rounded energy-aware circuit has been discussed in detail. The balance between energy supply and information demand in MP-HAR has been achieved by a handy design. Utilizing the unique correspondence between human arm swing frequency and harvested energy, the information flows along with energy inside the system. By knowing the interval between transmitted packets, MP-HAR has realized HAR in real-time. Moreover, an all-in-one prototype has been fabricated to better validate the performance of the proposed system. Lab tests and field tests have demonstrated that MP-HAR is capable of reliably recognizing different human activities, such as standing, walking, jogging, and running. As a cyber-electro-mechanical co-design, MP-HAR has brought a promising solution for pervasive HAR and ubiquitous IoT.