machine vision recognition of three-dimensional specular surface for gas tungsten arc weld pool

199 Pages·2016·6.67 MB·English

by  Hongsheng Song

UUnniivveerrssiittyy ooff KKeennttuucckkyy
UUKKnnoowwlleeddggee
University of Kentucky Doctoral Dissertations Graduate School
2007
MMAACCHHIINNEE VVIISSIIOONN RREECCOOGGNNIITTIIOONN OOFF TTHHRREEEE--DDIIMMEENNSSIIOONNAALL
SSPPEECCUULLAARR SSUURRFFAACCEE FFOORR GGAASS TTUUNNGGSSTTEENN AARRCC WWEELLDD PPOOOOLL
Hongsheng Song
University of Kentucky, [email protected]
RRiigghhtt cclliicckk ttoo ooppeenn aa ffeeeeddbbaacckk ffoorrmm iinn aa nneeww ttaabb ttoo lleett uuss kknnooww hhooww tthhiiss ddooccuummeenntt bbeenneefifittss yyoouu..
RReeccoommmmeennddeedd CCiittaattiioonn
Song, Hongsheng, "MACHINE VISION RECOGNITION OF THREE-DIMENSIONAL SPECULAR SURFACE FOR
GAS TUNGSTEN ARC WELD POOL" (2007). University of Kentucky Doctoral Dissertations. 531.
https://uknowledge.uky.edu/gradschool_diss/531
This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been
accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of
UKnowledge. For more information, please contact [email protected].
ABSTRACT OF DISSERTATION

Hongsheng Song

The Graduate School
University of Kentucky
2007
MACHINE VISION RECOGNITION OF THREE-DIMENSIONAL
SPECULAR SURFACE FOR GAS TUNGSTEN ARC WELD POOL

ABSTRACT OF DISSERTATION

A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy in the
College of Engineering
at the University of Kentucky

By
Hongsheng Song
Lexington, Kentucky
Director: Dr. YuMing Zhang, Professor of Electrical Engineering
Lexington, Kentucky
2007
Copyright © Hongsheng Song 2007
ABSTRACT OF DISSERTATION

MACHINE VISION RECOGNITION OF THREE-DIMENSIONAL
SPECULAR SURFACE FOR GAS TUNGSTEN ARC WELD POOL

Observing the weld pool surface and measuring its geometrical parameters is
a key to developing the next-generation intelligent welding machines that can
mimic a skilled human welder who observes the weld pool to adjust welding
parameters. It also provides us an effective way to improve and validate welding
process modeling. Although different techniques have been applied in the past
few years, the dynamic specular weld pool surface and the strong weld arc
complicate these approaches and make the observation /measurement difficult.
In this dissertation, a novel machine vision system to measure three-
dimensional gas tungsten arc weld pool surface is proposed, which takes
advantage of the specular reflection. In the designed system, a structured laser
pattern is projected onto the weld pool surface and its reflection from the
specular weld pool surface is imaged on an imaging plane and recorded by a
high-speed camera with a narrow band-pass filter. The deformation of the molten
weld pool surface distorts the reflected pattern. To derive the deformed surface
of the weld pool, an image processing algorithm is firstly developed to detect the
reflection points in the reflected laser pattern. The reflection points are then
matched with their respective incident rays according to the findings of
correspondence simulations. As a result, a set of matched incident ray and
reflection point is obtained and an iterative surface reconstruction scheme is
proposed to derive the three-dimensional pool surface from this set of data based
on the reflection law. The reconstructed results proved the effectiveness of the
system.
Using the proposed surface measurement (machine vision) system, the
fluctuation of weld pool surface parameters has been studied. In addition,
analysis has been done to study the measurement error and identify error
sources in order to improve the measurement system for better accuracy. The
achievements in this dissertation provide a useful guidance for the further studies
in on-line pool measurement and welding quality control.

KEYWORDS: Machine Vision, Welding Sensor, Specular Surface, Image
Processing, Reconstruction

______Hongsheng Song______________

_________07/24/2007_________________
MACHINE VISION RECOGNITION OF THREE-DIMENSIONAL
SPECULAR SURFACE FOR GAS TUNGSTEN ARC WELD POOL

By
Hongsheng Song

_______ YuMing Zhang___________
Director of Dissertation

_______ YuMing Zhang___________
Director of Graduate Studies

________07/24/2007_____________
Date
RULES FOR THE USE OF DISSERTATIONS

Unpublished dissertations submitted for the Doctor’s degree and deposited
in the University of Kentucky Library are as a rule open for inspection, but
are to be used only with due regard to the rights of the authors.
Bibliographical references may be noted, but quotations or summaries of
parts may be published only with the permission of the author, and with the
usual scholarly acknowledgements.

Extensive copying or publication of the dissertation in whole or in part also
requires the consent of the Dean of the Graduate School of the University
of Kentucky.

A library that borrows this dissertation for use by its patrons is expected to
secure the signature of each user.

Name Date
DISSERTATION

Hongsheng Song

The Graduate School
University of Kentucky
2007
MACHINE VISION RECOGNITION OF THREE-DIMENSIONAL
SPECULAR SURFACE FOR GAS TUNGSTEN ARC WELD POOL

DISSERTATION

A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy in the
College of Engineering
at the University of Kentucky

By
Hongsheng Song

Lexington, Kentucky

Director: Dr. YuMing Zhang, Professor of Electrical Engineering

Lexington, Kentucky

2007

Copyright © Hongsheng Song 2007
DEDICATED TO MY FAMILY