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Energy Harvesting, Wireless Structural Health Monitoring System for Helicopter Rotors


OBJECTIVE: Provide a novel low weight, high-speed structural health monitoring (SHM) system, capable of transferring health and usage sensor data (e.g. pressure, strain, vibrations, temperature) from the rotating frame to a base station unit in the non-rotating frame via wireless transmission. DESCRIPTION: Health and Usage Monitoring Systems (HUMS) have been developed and implemented for both commercial and military helicopters, the latter group including platforms such as the H-60, H-1, H-53, and V-22. Onboard HUMS enable the realization of Condition Based Maintenance (CBM), a set of maintenance processes and capabilities that are derived from real time or near real time assessment of system condition from onboard embedded sensors. Current HUMS technologies require direct connection for data acquisition from sensors. To transmit data from the rotating system down to the non-rotating system, a device known as a slip ring is used. The slip ring assembly allows the wiring from the rotating system to rotate without tangling or interfering with one another by ensuring a continuous electrical connection between a series of sliding brushes and the conductive housing. As the number of rotor mounted sensors increases, the weight of the slip ring assembly can range from 6.5 lbs to 15 lbs, making this approach undesirable. Also, fiber optic sensors currently require significant amounts of power to acquire data at acceptable sampling rates; therefore the SHM unit must be able to harvest sufficient energy to support a distributed fiber optic network. Significant challenges for data acquisition include a periodically obstructed transmission path, multi-path reflections, Doppler shifts of signal, and electromagnetic radiation interference from other electronic equipment on the aircraft and ship. Despite the advances in local sensor technology such as miniaturization, energy harvesting, and local data processing, methods for transferring the sensor data from the rotor system down to the fuselage are stagnant. The low-weight, high-speed SHM system should be capable of transferring health and usage sensor data from the rotor blades to a base station unit in the non-rotating frame via wireless transmission. This data would provide engineers with cycle-by-cycle loading histories in the blades, allowing for more accurate fatigue life assessment. The sample data rates shall be programmable depending on the data source, ranging from 10-5000 Hz, for customizable use. Sampling rates should be a minimum of 5x the maximum input signal frequency of interest. The system must optimize use of materials and electronics to achieve a low weight, not to exceed 2 pounds. Also, these blade sensors would be able to detect the onset of significant structural damage, and the growth of such damage under continued operation. The robustness of fiber optic sensors has been tested in harsh environmental conditions such as wind and engine turbines, which makes it a suitable technology for use in helicopter rotor blades. PHASE I: Develop a novel approach for a reliable, low-weight, SHM system described above with wireless communication between rotating and stationary frames of reference. Demonstrate the feasibility of this approach by bench testing in a lab environment. PHASE II: Build a prototype based upon the Phase l approach. Evaluate data quality and accuracy of the prototype by transferring sensor data in parallel through a conventional slip ring during a helicopter flight test. Develop a plan for full system airworthiness qualification onboard a Navy/Marine helicopter, including environmental, vibration, and shock per MIL-STD-810, electromagnetic environmental effects (E3) per MIL-STD-464, and electromagnetic interference (EMI) per MIL-STD-461. PHASE III: Perform full system airworthiness qualification onboard a Navy/Marine helicopter, including environmental, vibration, and shock per MIL-STD-810, electromagnetic environmental effects (E3) per MIL-STD-464, and electromagnetic interference (EMI) per MIL-STD-461. Evaluate qualification test results and provide procurement specification for transition to an actual production platform. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The results of this SBIR effort can be commercialized through the major helicopter OEMs for the private sector market. This type of data system could lead to an automated track and balance system that could drastically improve the vibration environment in both military and commercial helicopters. Additional applications include automotive tire condition monitoring, wind turbines, and leak/damage detection along oil/gas pipelines where the transmission path of mechanical health data is not constant. This technology could also benefit industrial applications which use conventional slip rings such as: measurement and testing, robotics and turntables for packaging, bottling, and tooling/inspection machines. REFERENCES: 1. Lieven, N.A.J., du Bois, J.L., & Todd, M. (2009). Towards a wireless powering and interrogation strategy for rotorcraft health monitoring. Proceedings of the IMAC-XXVII. Society for Experimental Mechanics Inc. Orlando, FL. 2. Burrow, S.G., Lieven, N.A.J., Escamilla-Ambrosio, J.P., Clare, L.; Lester, G., Heggie, W., Stark, J., Hazelden, R., Cooper, P., & Stinchcombie, M. (2008). WISD: Wireless sensors and energy harvesting for rotary wing aircraft Health and Usage Monitoring Systems. In Proc. Nanopower Forum, Costa Mesa, CA. 3. Lester, G.A.; Heggie, W., Burrow, S.G., Clare, L.R., Bunniss, P.; Liu, X., Escamilla-Ambrosio, P.J., Lieven, N.A.J., Hazelden, R., Benson, C., & Cooper, P. (2009). WISD Wireless Intelligent Sensing Devices. Proceedings from Sixth DSTO International Conference on Health and Usage Monitoring. AIAC-13 Australian International Aerospace Congress. 4. Rademakers, L.W.M.M., Vebruggen, T.W., van der Werff, P.A., Korterink, H., Richon, D., Rey, P., Lancon, F. Fiber Optic Blade Monitoring. Proceedings from the European Wind Energy Conference, London, 22-25 November 2004. 5. Verbruggen, T.W.; Load monitoring for wind turbines, Fibre optic sensing and data processing. Report from We@Sea program, Measurement system Load Monitoring and O & M Optimization. Energy Research Center of the Netherlands. 6. Pulliam, W., Russler, P. High-Temperature, High Bandwidth, Fiber-Optic, MEMS Pressure Sensor Technology for Turbine Engine Component Testing. Proceedings from Fiber Optic Sensor Technology and Applications 2001. Published 14 February 2002. 7. MIL-STD-810. Environmental Engineering Considerations and Laboratory Tests. Revision G, 31 October 2008. 8. MIL-STD-464. Electromagnetic Environmental Effects Requirements for Systems. Revision C, 1 December, 2010. 9. MIL-STD-461. Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment. Revision F, 10 December 2007.
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