Tracking Pitch Link Dynamic Loads with Energy Harvesting Wireless Sensors

Direct load monitoring of helicopter rotating structural components could provide enhanced condition based maintenance & improved flight regime recognition for future health & usage monitoring systems (HUMS). Our objective was to design, develop, bench & 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 & 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.