2. A curve profile control method using locally unbalanced centrifugal acceleration
  • Development of a method to control curve profile irregularities that cause low-frequency lateral movement
  • Confirmation that this method is highly correlated with the lateral movement of actual cars
  •       To control track displacements, the amplitude of the waveform measured by a track inspection car is used as an index to evaluate the track displacement and determine the amount of the adjustment of track alignment. In this process, curve profile components are removed from the measured waveform using the moving average method. The curve profile components thus removed contain alignment and cross-level irregularities of long wavelengths, and will cause lateral movement of tilting trains that run on curves at high speed. The RTRI therefore developed a method of controlling curve profile irregularities using track inspection data.
          This method substitutes the local radius values of curve and cant at different points (obtained from track inspection data) into the formula to calculate the unbalanced centrifugal acceleration (used to design curve profiles or discuss curve negotiating speeds), and uses the this value of locally unbalanced centrifugal acceleration (Fig. 1) as an evaluation index.
          This method :
      1) Uses the force working at the car body center of gravity as the index, and the method has an explicit relation with the lateral movement of car body.
      2) Has a high correlation with low-frequency lateral movement not only on curves but also in straight sections. This enables extraction of the following factors on the track side that cause low-frequency lateral movement (Fig. 2) (around 0.3Hz), which is highly-correlated with motion sickness:
    a) Plane curve/cant irregularities and alignment/cross-level displacements of long wavelengths
    b) Plane curve/cant displacements
          Some railway companies have already adopted this method in their curve improvement work.

    Fig. 1 Locally unbalanced centrifugal acceleration

    Fig. 2 Relation between locally unbalanced centrifugal acceleration and measured lateral movement (0.3Hz)

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