model analysis and predictive control of double electrode submerged arc welding process for fillet

144 Pages·2017·3.83 MB·English

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Theses and Dissertations--Electrical and
Electrical and Computer Engineering
Computer Engineering
2014
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Yi Lu
University of Kentucky, [email protected]
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Lu, Yi, "MODEL ANALYSIS AND PREDICTIVE CONTROL OF DOUBLE ELECTRODE SUBMERGED ARC
WELDING PROCESS FOR FILLET JOINTS WITH ROOT OPENING" (2014). Theses and Dissertations--
Electrical and Computer Engineering. 44.
https://uknowledge.uky.edu/ece_etds/44
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Yi Lu, Student
Dr. YuMing Zhang, Major Professor
Dr. Cai-Cheng Lu, Director of Graduate Studies
MODEL ANALYSIS AND PREDICTIVE CONTROL OF
DOUBLE ELECTRODE SUBMERGED ARC WELDING
PROCESS FOR FILLET JOINTS WITH ROOT OPENING

_________________________________________________________________________
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

Yi Lu

Lexington, Kentucky

Co-Directors: Dr. YuMing Zhang, Professor of Electrical and Computer Engineering
and Dr. Lawrence E. Holloway, Professor of Electrical and Computer Engineering

Lexington, Kentucky

Copyright © Yi Lu 2014
ABSTRACT OF DISSERTATION

MODEL ANALYSIS AND PREDICTIVE CONTROL OF
DOUBLE ELECTRODE SUBMERGED ARC WELDING
PROCESS FOR FILLET JOINTS WITH ROOT OPENING

Submerged Arc Welding (SAW) for fillet joints is one of the major applications in the
shipbuilding industry. Due to the requirement for the weld size, a sufficient amount of
metal must be deposited. In conventional SAW process, the heat input is proportional to
the amount of metal melted and is thus determined by the required weld size. To meet
this requirement, an excessive amount of heat is applied causing large distortions on the
welded structures whose follow-up straightening is highly costly. In order to reduce the
needed heat input, Double-Electrode (DE) technology has been practiced creating the
Double-Electrode SAW (DE-SAW) method for fillet joints. The reduction in the heat input,
however, also reduces the penetration capability of the process, and the ability to
produce required weld beads has to be compromised. To eliminate the unwanted side
effect after using DE-SAW, a root opening between the panel and the tee has been
proposed in this dissertation to form a modified fillet joint design. Experimental results
verified that the use of root opening improves the ability of DE-SAW to produce the
required weld beads at reduced heat input and penetration capability. Unfortunately,
the use of root opening decreases the stability of the process significantly. To control
the heat input at a minimally necessary level that guarantees the weld size and
meanwhile the process stability, a feedback is needed to control the currents at their
desired levels. To this end, the fillet DE-SAW process is modeled and a multivariable
predictive control algorithm is developed based on the process model. Major
parameters including the root opening size, travel speed and heat input level have been
selected/optimized/minimized to produce required fillet weld beads with a minimized
heat input based on qualitative and quantitative analyses. At the end of this dissertation,
a series of experiments validated the feasibility and repeatability of the predictive
control based DE-SAW process for fillet joints with root opening.

KEYWORDS: Submerged Arc Welding (SAW), Fillet Joint, Double-Electrode (DE),
Predictive Control, Root Opening

Yi Lu
Feb 18, 2014
MODEL ANALYSIS AND PREDICTIVE CONTROL OF
DOUBLE ELECTRODE SUBMERGED ARC WELDING
PROCESS FOR FILLET JOINTS WITH ROOT OPENING

By
Yi Lu

Dr. YuMing Zhang
___________________________
Director of Dissertation

Dr. Cai-Cheng Lu
___________________________
Director of Graduate Studies

Feb 18, 2014
___________________________
Date
ACKNOWLEDGEMENTS

This research is funded by the Navy under contracts N65538-08-M-0049 and N00024-
09-C-4140 and Kentucky Cabinet for Economic Development (CED) Office of
Commercialization and Innovation through Kentucky Science and Engineering Corp.
under agreements KSTC-184-512-08-038 and KSTC-184-512-09-067. I would like to
gratefully and sincerely thank my advisor, Dr. YuMing Zhang, for his guidance, patience,
support, and most importantly, his encouragement during my graduate studies at
University of Kentucky. Also thanks to my dissertation committee members Drs. Alan T.
Male, Larry Holloway and Yuan Liao for their help both in my graduate courses and my
dissertation research. Moreover, my appreciation is also given to my colleagues from
Adaptive Intelligent Systems LLC and Welding Research Lab: Xiangrong Li, Jinsong
Chen, Kun Qian, Zeng Shao, Chenglin Yi, Yi Huang, Xiaoji Ma, Weijie Zhang, Yan
Shao, Yukang Liu and Kehai Li. Last but most important, I want to express my deep
gratitude to my parents and girlfriend for their love, faith in me, and long-term solid
support for my work.

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Table of Contents

ACKNOWLEDGEMENTS ............................................................................................................ iii
Table of Contents ............................................................................................................................ iv
List of Tables ................................................................................................................................. vii
List of Figures ............................................................................................................................... viii
Chapter 1 Introduction .................................................................................................................... 1
1.1 Background ............................................................................................................................ 1
1.2 Objectives .............................................................................................................................. 2
1.3 Organization ........................................................................................................................... 4
Chapter 2 Review of Double-Electrode Technology ........................................................................ 6
2.1 Background ............................................................................................................................ 6
2.2 Principle of Double-Electrode GMAW ................................................................................. 7
2.3 Non-Consumable DE-GMAW Using Constrained Bypass Arc .......................................... 11
2.4 Non-Consumable DE-GMAW Using Unconstrained Bypass Arc ...................................... 13
2.5 Metal Transfer in Non-Consumable DE-GMAW Using Unconstrained Bypass Arc ......... 17
2.6 Consumable DE-GMAW and Analysis ............................................................................... 20
2.7 Control of Consumable DE-GMAW ................................................................................... 23
2.8 Variants of DE-GMAW and Double-electrode Arc Welding .............................................. 25
2.8.1 Dual-Bypass GMAW .................................................................................................... 26
2.8.2 Arc Assisted Hot-Wire GTAW ..................................................................................... 28
2.8.3 Arcing-Wire GTAW and Double-Electrode Arc Welding ........................................... 30
Chapter 3 DE-SAW and Use of Root Opening ................................................................................ 34
3.1 Submerged Arc Welding (SAW) ......................................................................................... 34
3.2 Double-Electrode SAW (DE-SAW) .................................................................................... 36
3.3 Fillet DE-SAW and Use of Root Opening ........................................................................... 40
3.4 Necessity of Effective Control in DE-SAW for Fillet Joints ............................................... 42
Chapter 4 Parameters Selection .................................................................................................... 47
4.1 Experimental Conditions ..................................................................................................... 48
4.2 Root Opening Effect and Selection ...................................................................................... 48
iv
4.2.1 “No Root Opening” Experiment ................................................................................... 49
4.2.2 “Small Root Opening” Experiment ............................................................................... 51
4.2.3 “Large Root opening” Experiment ............................................................................... 54
4.2.4 Remarks on Root Opening Effect ................................................................................. 55
4.3 Travel Speed Optimization .................................................................................................. 56
4.3.1 Analysis Method ........................................................................................................... 57
4.3.2 Experiment Design and Study Approaches................................................................... 60
4.3.3 Experimental Results and Analysis ............................................................................... 61
4.3.4 Standard Deviation and Extreme Difference Analysis ................................................. 66
4.3.5 Average and Minimum Leg Sizes Analysis .................................................................. 67
4.3.6 Remarks on Travel Speed Optimization ....................................................................... 68
4.4 Heat Input (Initial Main Wire Feed Speed) Selection .......................................................... 69
4.4.1 Experiment Design ........................................................................................................ 70
4.4.2 Experimental Results and Analysis ............................................................................... 71
4.4.3 Standard Deviation and Extreme Difference Analysis ................................................. 74
4.4.4 Average and Minimum Leg Sizes Analysis .................................................................. 76
4.4.5 Heat Input Comparison ................................................................................................. 77
4.4.6 Remarks on Heat Input Optimization ........................................................................... 78
4.5 Chapter Summary ................................................................................................................ 79
Chapter 5 Process Modeling .......................................................................................................... 81
5.1 Physical Process ................................................................................................................... 81
5.2 Basic Equations .................................................................................................................... 82
5.3 Linearization and Static Incremental Model ........................................................................ 84
5.4 Filter Design and Dynamic Incremental Model ................................................................... 87
Chapter 6 Predictive Control Algorithm Design ............................................................................. 90
6.1 Review of Predictive Control ............................................................................................... 90
6.2 Output Prediction ................................................................................................................. 91
6.3 Trajectory ............................................................................................................................. 96
6.4 Cost Function and Control Law ........................................................................................... 97
Chapter 7 Experiments and Analysis ........................................................................................... 100
7.1 Experimental Conditions ................................................................................................... 100
7.2 Bead-On-Plate Experiment ................................................................................................ 101
v
7.3 Fillet Welding Experiments ............................................................................................... 103
7.4 Weld Bead and Heat Input Comparison ............................................................................ 108
7.5 Experiments and Analysis on Large Panels ....................................................................... 110
Chapter 8 Simplified Version of Predictive Control ..................................................................... 113
8.1 Background ........................................................................................................................ 113
8.2 Algorithm Simplification ................................................................................................... 113
8.3 Experiment and Analysis on Small Panels ........................................................................ 116
8.4 Experiment and Analysis on Large Panels ........................................................................ 120
Chapter 9 Conclusion and Future Work ....................................................................................... 123
9.1 Conclusion ......................................................................................................................... 123
9.2 Future Work ....................................................................................................................... 124
References .................................................................................................................................... 126
VITA ............................................................................................................................................ 130

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