A multiple energy-harvester combination for pattern-recognizable power-free wireless sensing to vibration event

Abstract By using combination of multiple energy-harvesters, a novel self-powered wireless-sensing-node is proposed and developed for event-driven autonomous alarming, where the vibration pattern can be recognized. The energy-harvester based wireless-sensing-node has three unique advantages of (1) vibration pattern distinguishable sensing, (2) event-driven autonomous wireless monitoring and alarming, and (3) no electric-power supply needed. In the sensing microsystem, two threshold-triggered harvesters are designed and fabricated to monitor vibration in a vibration pattern distinguishable way. Each of the two threshold-triggered harvesters can independently switch into electric-generating state only when the monitored acceleration exceeds the preset-threshold. In the dual-harvester array, one threshold-triggered harvester is more sensitive to low-frequency shake and the other is triggered more easily by high-frequency knock, thereby, both vibration amplitude and frequency can be distinguished that allows vibration pattern identification. For quick wireless-transmission, another electromagnetic energy-harvester is involved to rapidly generate electric-power. The wireless-sensing-node is installed onto a protection-fence for engineering protection. In this experiment, the device can clearly distinguish the vibration patterns between hand-shake and hammer-knock. The vibration-event induced alarm messages together with the vibration pattern information is wirelessly sent to a phone. The developed technique is really promising for smart wireless-monitoring where no on-site power can be supplied.