InfiniTime: Multi-sensor wearable bracelet with human body harvesting

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• 作者：Michele Magno^a ; ^c ; ^{michele.magno@iis.ee.ethz.ch" class="auth_mail" title="E-mail the corresponding author} ; Davide Brunelli^b ; Lukas Sigrist^c ; Renzo Andri^c ; Lukas Cavigelli^c ; Andres Gomez^c ; Luca Benini^a ; ^c
• 关键词：Wearable devices ; Autonomous systems ; Zero-power ; Indoor energy harvesting ; Human harvesting ; Power management
• 刊名：Sustainable Computing: Informatics and Systems
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：11
• 期：Complete
• 页码：38-49
• 全文大小：2766 K

文摘

Wearable technology is gaining popularity, with people wearing everything “smart” from clothing to glasses and watches. Present-day wearables are typically battery-powered, and their limited lifetime has become the critical issue. Most devices need recharging every few days or even hours, falling short of the expectations for a truly satisfactory user experience. This paper presents the design, implementation and in-field evaluation of InfiniTime, a novel sensor-rich smart bracelet powered by energy harvesting. It is designed to achieve self-sustainability using solar cells with only modest indoor light levels and thermoelectric generators (TEG’s) with small temperature gradients from the body heat. The wearable device is equipped with an ultra-low power camera and a microphone, in addition to accelerometer and temperature sensors commonly used in commercial devices. Experimental characterization of the fully operational prototype demonstrates a wide range of energy optimization techniques used to achieve self-sustainability with harvested energy only. Our experiments in real-world scenarios show an average of up to 550 μW for photovoltaic in indoor and 98 μW for TEG with only 3 ° temperature gradient and up to 250 μW for 5° gradient. Simulations using energy intake measurements from solar and TEG modules confirm that InfiniTime achieves self-sustainability with indoor lighting levels and body heat for several realistic applications featuring data acquisition from the on-board camera and multiple sensors, as well as visualization and wireless connectivity. The highly optimized low-power architecture of the presented prototype features image acquisitions at 1.15 frames per second, powered only from the energy harvesters.