SEMINARIESCHEMA FÖR MATEMATISK STATISTIK 

Torsdag   28/3  13.15     Jesper Ryden,
          1996            Mat stat i Lund, presenterar sitt examensarbete:

                          Detection of wheel flats using stochastic
                          wave analysis


Abstract:


In railway dynamics, irregularities and defects of wheels and track
cause an increase in dynamic forces. One type of imperfection is a
wheel flat --- a flat zone on the wheel tread. In this study, the aim
has been to develop methods for detection of wheel flats, given a
time~series.

Field measurements from a train where one wagon had an artificial
wheel flat have been analysed. A filtering of the process was
performed by using concepts and theory from image analysis and
stochastic wave analysis.

In an approach where each wheel was treated
separately, the process was first convolved with a Gaussian kernel and
rainflow cycles in the resulting signal were analysed. 
Two parameters were found necessary: one bandwidth
parameter to determine the degree of smoothing and one threshold
parameter. In the filtered signal, the
number of local extrema will determine whether there is wheel flat or not.
An alternative way is to treat the passage of the whole train and
afterwards visualize the result in a diagram. 


  
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