Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless Sensors

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Direct load monitoring of helicopter rotating structural components could provide enhanced condition based maintenance and improved flight regime recognition for future health and usage monitoring systems (HUMS). Our objective was to design, develop, bench and flight test a system capable of harvesting the energy of operation to power a wireless pitch link loads monitor. Piezoelectric materials converted the cyclic strains of pitch link operation into power for the microelectronics, which included strain gauge signal conditioning, analog-to-digital converter, microprocessor, non-volatile memory, precision time-keeper, and 802.15.4 transceiver. Loads were measured with a full bridge of bonded strain gauges, which amplified tensile and compressive loads and cancelled bending moments and thermal influences. The processor's embedded software included energy aware operating modes, which enabled the wireless system to self adjust its energy consumption according to the amount of energy available. The system was successfully flight tested on a Bell model 412 helicopter in February 2007.