DB Systemtechnik in Minden consistently works on optimizing and further developing the method to eliminate the above-described drawbacks of the measuring wheelsets. One approach that is currently being followed is to use optical strain gages like K-OL from HBM (Fig. 3).
Reduced installation effort
A major benefit when using optical strain gages is the significantly reduced installation effort. "Using optical strain gages would enable us to shorten installation times from four to five weeks at present to few days," explains Andreas Brodtka, head of production of measuring wheelsets at DB Systemtechnik. The reduced installation effort and less maintenance during the test runs would, of course, result in reduced costs. As the complex compensation for interference would not be needed anymore, 20 strain gages per wheel would be sufficient. "The fact that up to 20 optical strain gages are installed in a single fiber is of special importance", states the test engineer.
Installation of the signal lines without drilling
In addition, the thin glass fiber could be led to the exterior without any hole having to be drilled in the axle. A solution enabling laying of the optical fiber without any hole is currently being developed. In the area of transition from the rotating to the stationary part on the wheelset that will still be necessary, the signals transmitted by the optical fiber could be sent via a so-called optical slip-ring assembly. The interrogator evaluating the signals of the optical strain gages could then be located well-protected inside the vehicle and receive signals via optical fibers. The interference-prone electronics in the axle would no longer be needed.
At present, optical strain gages are being used at DB Systemtechnik in Minden only within the scope of a research project, but the test results show the potential of the optical strain gages.