SBIR-STTR Award

When rotating machinery deteriorates, vibration patterns change. The key is knowing where and how deeply to look. Gear mesh frequencies change in amplitude and the slimness or "All of their peaks change, indicating wear. Weakened teeth, due to root cracking or other gear damage,cause detectable changes. There have been problems -- until now -- using these phenomena for detailed assessment of machinery like high-performance aircraft gearboxes. An artificial "noise floor" and the sensor limitations of accelerometer technologies have caused this. Epoch Engineering, Inc. (EEI) has developed and has demonstrated a unique acoustic detection ability. Our Robust Laser Interferometer is able to detect and display frequencies from below 1 Hz to 100 KHz at amplitude differences up to 11 orders of magnitude (110 dB). The unique capability, when compared to customary accelerometer field implementations, allows measurements not previously practical (effectively dropping the noise floor in spite of the presence of high amplitude vibrations). This process allows us to interrogate the outside of such a machine as a gearbox and detect signals originating inside. It can "baseline" a gearbox on the test stand and then monitor its performance on wing and serve as the fundamental sensing technology for automated systems of machinery monitoring.

Keywords:
Laser Fiberoptic Vibration Measurement Machinery Monitoring

Epoch Engineering, Inc. (EEI) has developed a Robust Laser Interferometer with the demonstrated ability to measure vibrations in a line-of-sight fashion with a dynamic range and bandwidth that exceeds any accelerometer instrumentation system. In Phase I, the RLI demonstrated a bandwidth from fractional Hertz to 64 KHz and a dynamic range in excess of 150 dB (acceleration) in a continous fashion. In Phse I, EEI conducted measurements on two helicopter main gearboxes under full power test on instrumented test stands. The RLI demonstrated the ability to record high amplitude gear mesh vibrations of over 100 g's while simultaneously recording gearbox rotational signals less than .001 g. The RLI revealed signals of known mechanical origin within the helicopter gearboxes that are unavailable from accelerometer systems. In the proposed Phase II, EEI will team with Sikorsky Aircraft, and demonstrate the ability to detect faults on "returned from service" gearboxes prior to overhaul at Sikorsky. The laser signal will be transmitted and returned fiberoptically. In addition, EEI will demonstrate that the RLI measurements are compatible with fault detection algorithms developed by Sikorsky. Several other potential advantages of the RLI, including the fiberoptic transmission of the laser signal, will be demonstrated.

Keywords:
Laser Interferometry Helocopter Gearbox Bearing Fault Vibration Measurement