Rail passengers in Europe get a more comfortable ride, thanks to a computer-powered track-monitoring system.
Schmid Engineering AG in Switzerland designed its RailSurf sled to monitor track rails as an operator pulls it along with a small rail vehicle. It carries several sensors that note such problems as holes on the rails, wavy irregularities in the rail surface called corrugations, and variations in rail gauge and inclination that can make passing trains shudder, shake, and vibrate.
Schmid used a Blackfin processor from Analog Devices Inc. to run the six asynchronous tasks that manage and filter the sensor signals. Engineers created the necessary programs through use of a LabView Embedded Module from National Instruments Corp., Austin, Tex.
The RailSurf sled carries two eddy-current sensors for measuring variations in rail height, a wire sensor for noting changes in the separation between the two rails, a precision inclinometer, and a GPS transceiver. A linear-magnetic encoder used with a magnetic ring serves as an odometer while the sled is pulled along the tracks. Signals from the GPS and odometer pinpoint problems as the system detects them.
In typical operation, the system reads its sensors every time the odometer generates a pulse. The signals feed to an FIR (finite-impulse response) filter prior to storage in removable memory. Filtering operations sift through sensor data to find symptoms of interest. Corrugations, for example, get detected through a Fast-Fourier-transform analysis, which watches for their characteristic 20 to 100-mm wavelength. The system looks for holes on the tracks by comparing eddy-current signals to memorized reference patterns. Designers can tweak filter parameters for track conditions to minimize false alarms.