Jan 31 2006
Train brakes and wheel bearings of trains must work without fail. Because this is so important, the temperature and other operating parameters are monitored from the track. A covering of snow causes problems that can be prevented by flexibly controlling data acquisition.
A damaged or poorly lubricated roller bearing will overheat during operation. Its inner workings expand, the friction and temperature rise higher and higher, and boiling grease leaks out or evaporates. The bearing seizes up, it becomes red-hot, its parts fuse together and finally the forward traction destroys it completely. To prevent such disasters from occurring in the first place, sensors measure the infrared radiation emitted by train bearings and brakes, and this in turn indicates their temperature. However, freight trains do not have an end-to-end onboard electrical system. This is one reason why stationary hot box / hot wheel detectors (german abbreviation FUES) have been and are still being installed. Some 250 of these special ties are deployed in the German railway network, and about 700 in the whole of Europe. About the size of a conventional cross-tie, they are also fitted with induction sensors that enable them to register passing wheels through fluctuations in the strength of the magnetic field. An electronic evaluation system beside the railroad track uses these values to compute the length, speed, acceleration and even the make of each train. If it detects critical operating conditions, it alerts the movements inspector.
The FUES ties are built and maintained by GE Transportation Systems, a subsidiary of General Electric. The company has collaborated for many years with scientists at the Fraunhofer Institute for Industrial Mathematics ITWM in the field of data collection and processing. “All national railroad operators have their own specific requirements,” reports project manager Thomas Redenbach from experience. “Most of our work consists of constantly adapting the existing software to new environments and improving the evaluation quality. As for the precision of the mathematical models employed, we definitely head the field.”
Here are two examples of control signals in use: When it snows, the infrared sensor goes blind. To prevent this from happening, winter heating systems have been integrated in the FUES ties of the Matterhorn Gotthard Railway in Switzerland. The on-off control devised by the ITWM computer scientists causes the heating elements to switch themselves on and off correctly, depending on the temperature conditions along the track. They are not intended to superheat, but simply to thaw the snow. A lot of snow falls in Sweden, too, but there it is cleared off the tracks by snow plows. To prevent snow from falling into the measuring orifices of the FUES ties, the engineer presses a button to close them just before driving the plow across. Afterwards he re-activates them from the other side.
http://www.itwm.fraunhofer.de/