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Sensors designed to predict helicopter transmission failures are now used to detect problems in train tracks.

Spinoff is NASA's annual publication featuring successfully commercialized NASA technology. This commercialization has contributed to the development of products and services in the fields of health and medicine, consumer goods, transportation, public safety, computer technology, and environmental resources.

RotoSense microelectromechanical systems-based accelerometers, originally developed to monitor components of helicopter transmissions, were reconfigured for use in detecting potentially dangerous anomalies in train tracks.

When Ridgetop Group (Tucson, AZ) created its RotoSense rotational vibration sensor under Small Business Innovation Research (SBIR) contracts with NASA's Glenn Research Center, the company envisioned applications not just in helicopters, but also in automobile transmissions, industrial equipment, and oil and gas drilling. But train axles also rotate at a high rate of speed, and can indicate anomalies by vibrating irregularly.

The technology began with NASA's Subsonic Rotary Wing Project that is working to ensure the competitiveness of the U.S. helicopter industry and meet Department of Defense requirements, with goals like higher efficiency, less noise, and means to assess and predict the health of components. It was with that last objective in mind that Glenn granted SBIR work to Ridgetop.

“The goal was to develop a wireless accelerometer that could be installed on a rotating gear in a helicopter transmission to monitor its health and condition,” said Dave Lewicki, who ran Glenn's Helicopter Transmission Test Stand when the work was being carried out, and oversaw both SBIR contracts. Normally, sensors would be placed on the outside of the transmission housing, whereas the microelectromechanical systems (MEMS)-based accelerometers Ridgetop came up with were to be attached directly to components inside the transmission, which is not a friendly environment.

Ridgetop delivered two prototype sensors for testing in the transmission of a Bell OH-58 Kiowa helicopter. The first test showed that Ridgetop's MEMS sensor, mounted on a gear inside the transmission, performed at least as well as traditional sensors attached to the outside housing. Ridgetop began partnering with companies to develop its NASA-validated sensing system into a commercial product.

The company marketed its sensors under the name RotoSense, with the hub that communicates with the sensors dubbed Sentinel Gateway. The Roto-Sense Data Conditioner prepares data from the sensors for processing with the company's patented Adaptive Remaining Useful Life Estimator (ARULE) software, and the whole product line is known as Sentinel Motion.

A rolling train axle is not mechanically very different from the axles in any other vehicle, but an automobile can go more or less wherever its driver likes, while a train is bound to the same track on every pass. And while a pothole in the road is an annoyance, an anomaly in a train track can mean disaster. So the company hit on the idea of monitoring vibrations in train axles to detect and locate problems with the rails.

The RailSafe sensor fits on the ends of a train's axles, where it monitors for vibrations caused when the wheels roll over anomalies in the rails.

The sensors had to be repackaged to sit on each end of a train axle, right above the meeting of the wheel and rail for maximum sensitivity. The basic algorithms for noise elimination remain unchanged, but programming to identify the significance of any anomalies had to be rewritten specifically for rails. Calling the retooled system RailSafe, Ridgetop took it to the Federal Railway Administration's Transportation Technology Center in Pueblo, CO for testing.

Ridgetop launched RailSafe in mid-2015 as a kit containing the necessary sensors, data collection hub, and software packages to outfit and monitor trains; the analytical tools can also be used with sensors other than its own. Just the ability to detect a problem in a rail can avert catastrophe, but prognostic capability for wheels and rail would not only go further toward preventing accidents, but also save the cost of unnecessary preventive maintenance. The sensors can also perform the simpler task of ensuring that certain standards are met, such as limits on G-forces resulting from cars being coupled.

The technology is planned to ultimately perform prognostic reasoning for both wheels and rail by predicting their lifetime and warning of possible failures before they occur through monitoring of long-term changes in vibration. Meanwhile, the company is exploring applications in wind and water turbines, as well as factory floor machinery.

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