Reducing uncertainties in structure gauging

Abstract This project investigated uncertainties in the gauging process to permit the development of improved methods. Preliminary studies investigated the potential sources of error in the areas of measurement, track and structure position, and vehicle position (including the effects of wind). A Mo...

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Bibliographic Details
Published in:Proceedings of the Institution of Mechanical Engineers. Part F, Journal of rail and rapid transit Journal of rail and rapid transit, 2008-09, Vol.222 (3), p.287-295
Main Authors: Bradbury, W M S, Westwood, T
Format: Article
Language:English
Subjects:
Alignment
Allowances
Bias
Error analysis
Fault tolerance
Gaging
Gauges
Mathematical analysis
Monte Carlo simulation
Permissible error
Position measurement
Probabilistic methods
Probability theory
Safety
Steering
Structure gauging
Superposition (mathematics)
Systems analysis
Tolerances
Tracking
Uncertainty
Vehicles
Wind effects
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Summary:Abstract This project investigated uncertainties in the gauging process to permit the development of improved methods. Preliminary studies investigated the potential sources of error in the areas of measurement, track and structure position, and vehicle position (including the effects of wind). A Monte-Carlo and an approximate analytic, method quantified individual and total propagated biases and uncertainties in the clearance. The dominant sources of bias were found to be the track tolerances, measurement error allowances, steering allowances, and conservatism in the swept envelope. The dominant sources of uncertainty were found to be specific measurement uncertainties, surface position variations for irregular or poorly aligned structures, approximations in the swept envelope calculation, and the effects of cant variation or wind on the swept envelope. The present method of applying tolerances (by linear super-position) can be challenged as individual tolerances do not bear a consistent relationship with the potential errors and variations they represent and because the superposition results in a level of safety that will vary according to the relative importance of factors at different locations. An improved method for determining and applying tolerances is recommended. This is based on the probabilistic approach used for the uncertainty analysis.
ISSN:0954-4097
2041-3017
DOI:10.1243/09544097JRRT134