Technical Reports

Track Profile Approximation Using Railcar Body Acceleration Data

  • 31
  • Dec
  • 2014
AUTHOR: Federal Railroad Administration
OFFICE: RPD
SUBOFFICE: RPD-31
REPORT NUMBER: DOT/FRA/ORD-14/42
KEYWORDS: Track geometry; vehicle-track interaction; ride quality; Track Profile Approximation Using Railcar Body Acceleration Data
ABSTRACT: Accelerations are frequently measured from the car body of a rail vehicle, which is mounted above one or more suspension systems. Measuring accelerations in the car body is largely done for convenience, as mounting an accelerometer to a truck or axle of a railcar is more cumbersome than simply placing an accelerometer inside the railcar body. For those involved with track research, maintenance, and safety, there is a desire to correlate these car body accelerations with track conditions. However, a railcar suspension system acts as a filter that can interfere with taking precise acceleration measurements. To complicate matters further, the railcar body, in combination with the suspension system, has several natural modes of vibrations. As a result, some accelerations that exceed a predefined threshold measured from the railcar body do not correlate with track conditions. Thus, the use of acceleration data in this manner to accurately and reliably identify track defects or exceptions may be hampered-- potentially triggering further inspection by railroad personnel when unnecessary--or masking such indicators. This report puts forth a simplified model of a railcar and a corresponding deconvolution filter (also known as an inverse filter) which theoretically eliminates the amplification and attenuation effects of the railcar suspension system.

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