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Accuracy problems in weighing vehicles during motion

Popov, P. A. (1992). Accuracy problems in weighing vehicles during motion. (Unpublished Doctoral thesis, City, University of London)

Abstract

The objective of this study is to help solving some of the measurement accuracy and reliability problems of present WIM systems. The theoretical part of the study is focused on vehicle dynamic effects since they have long been identified as one of the major causes of error in high speed dynamic vehicle weighing.

A detailed system analysis describes the functionality of the basic elements of the WIM process - vehicle suspension dynamics, sensor system, and signal processing. In the metrological analysis the standard measurement categories accuracy, repeatability, reproducibility etc., are defined for the technique, and the main sources of measurement errors are identified. Mathematical models are presented of the vehicle suspension/tyres, and a rigid sensor platform with its ground foundation, which are later used in a series of vehicle - roadsurface dynamic interaction computer simulations. A locally developed interactive modelling package is used to run the simulations. Two major sets of simulations are performed - 1) vehicle interaction with road profiles of deterministic shapes, 2) vehicle interaction with road surfaces of stochastic description. The effects of different factors influencing the outcome of the measurement, e.g. vehicle speed, platform protrusion level, vehicle physical parameters, etc., are investigated.

As part of the experimental work a concept for a capacitive sensor is proposed in line with the trend of developing low-cost, easy to install WIM systems. Finite element modelling is used to derive the optimal sensor strip profile. Finally a frequency modulated capacitance measurement circuit incorporating frequency drift compensation is developed and tested with good results.

Most of the study results are presented in both tabular and graphical form. The corresponding conclusions are drawn on the basis of the obtained data, regarding the design, installation and usage of WIM equipment.

Publication Type: Thesis (Doctoral)
Subjects: T Technology > TJ Mechanical engineering and machinery
Departments: School of Science & Technology > Engineering > Electrical & Electronic Engineering
School of Science & Technology > School of Science & Technology Doctoral Theses
Doctoral Theses
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