The arc weld pool is always deformed by plasma jet. In a previous study, a novel sensing mechanism was proposed to sense the free weld pool surface. The specular reflection of pulsed laser stripes from the mirror-like pool surface was captured by a CCD camera. The distorted laser stripes clearly depicted the 3D shape of the free pool surface. To monitor and control the welding process, the on-line acquisition of the reflection pattern is required. In this work, the captured image is analyzed to identify the torch and electrode. The weld pool edges are then detected. Because of the interference of the torch and electrode, the acquired pool boundary may be incomplete. To acquire the complete pool boundary, models have been fitted using the edge points. Finally, the stripes reflected from the weld pool are detected. Currently, the reflection pattern and pool boundary are being related to the weld penetration and used to control the weld penetration.

Issue Section:
Research Papers
Topics:
Electrodes, Image processing, Lasers, Mirrors, Plasma jets, Reflection, Shapes, Welding
1.
Rokhlin
S. I.
, and
Guu
A. C.
,
1993
, “
A Study of Arc Force, Pool Depression, and Weld Penetration during Gas Tungsten Arc Welding
,”
Welding Journal
, Vol.
72
, No.
8
, pp.
381s–390s
381s–390s
.
2.
Lin, M. L., and Eagar, T. W., 1983, “Influence of Surface Depression and Convection on Arc Weld Pool Geometry,” Transport Phenomena in Material Processing, ASME PED 10, Edited by M. M. Chen, J. Mazumder, and C. L. Tucker III, November 13–18, pp. 63–69.
3.
Lin
M. L.
, and
Eagar
T. W.
,
1985
, “
Influence of Arc Pressure on Weld Pool Geometry
.”
Welding Journal
, Vol.
64
, No.
6
, pp.
163s–169s
163s–169s
.
4.
Renwick
R. J.
, and
Richardson
R. W.
,
1983
, “
Experimental Investigation of GTA Weld Pool Oscillations
,”
Welding Journal
, Vol.
62
, No.
2
, pp.
29s–35s
29s–35s
.
5.
Zacksenhouse
M.
, and
Hardt
D. E.
,
1983
, “
Weld Pool Impedance Identification for Size Measurement and Control
,”
ASME Journal of Dynamic Systems, Measurement and Control
, Vol.
105
, No.
3
, pp.
179
–
184
.
6.
Xiao
Y. H.
, and
Ouden
G. den
,
1993
, “
Weld Pool Oscillation During GTA Welding of Mild Steel
,”
Welding Journal
, Vol.
72
, No.
8
, pp.
428s–434s
428s–434s
.
7.
Nagarajan
S.
,
Banerjee
P.
,
Chen
W.
, and
Chin
B. A.
,
1992
, “
Control of the Welding Process Using Infrared Sensors
.”
IEEE Transactions on Robotics and Automation
, Vol.
8
, No.
1
, pp.
86
–
93
.
8.
Beardsley
H. E.
,
Zhang
Y. M.
, and
Kovacevic
R.
,
1994
, “
Infrared Sensing of Full Penetration State in Gas Tungsten Arc Welding
,”
International Journal of Machine Tool and Manufacturing
, Vol.
34
, No.
8
, pp.
1079
–
1090
.
9.
Carlson
N. M.
, and
Johnson
J. A.
,
1988
, “
Ultrasonic Sensing of Weld Pool Penetration
,”
Welding Journal
, Vol.
67
, No.
11
, pp.
239s–246s
239s–246s
.
10.
Cannon, I., Maram, J., and Smith, M., 1987, “Weld Penetration Sensor for an Experimental Welder.” Transactions of NAMRC/SME, Vol. XV.
11.
Zhang
Y. M.
, et al.,
1993
, “
Determining Joint Penetration in GTAW With Vision Sensing of Weld Face Geometry
.”
Welding Journal
, Vol.
72
, No.
10
, pp.
463s–469s
463s–469s
.
12.
Zhang
Y. M.
,
Kovacevic
R.
, and
Wu
L.
,
1996
, “
Dynamic Analysis and Identification of Gas Tungsten Arc Welding for Weld Penetration Control
,”
ASME JOURNAL OF ENGINEERING FOR INDUSTRY
, Vol.
118
, No.
1
, pp.
123
–
136
.
13.
Kovacevic, R., Zhang, Y. M., and Ruan, S., 1993, “Three-Dimensional Measurement of Weld Pool Surface,” Proceedings of the International Conference on Modeling and Control of Joining Processes, pp. 600–607, Orlando, FL, Dec. 8–10.
14.
Kovacevic
R.
,
Zhang
Y. M.
, and
Ruan
S.
,
1995
, “
Sensing and Control of Weld Pool Geometry for Automated GTA Welding
,”
ASME JOURNAL OF ENGINEERING FOR INDUSTRY
, Vol.
117
, No.
2
, pp.
210
–
222
.
15.
Zhang
Y. M.
,
Beardsley
H.
, and
Kovacevic
R.
,
1994
, “
Real-Time Image Processing for 3D Measurement of Weld Pool Surface
,”
Manufacturing Science and Engineering
, PED-Vol.
68–1
, pp.
255
–
262
, ASME.
16.
Kashyap, R. L., and Chellappa, R., 1985, “Stochastic Models for Closed Boundary Analysis: Representation and Reconstruction,” Digital Image Processing and Analysis, Vol. 2, pp. 109–119, R. Chellappa, and A. A. Sawchuk, eds., IEEE Computer Society.
17.
Pandit, S. M., and Wu, S. M., 1983, “Time Series and System Analysis with Applications,” Chapter 2, John Wiley and Sons, New York.
18.
Kovacevic, R., and Zhang, Y. M., “Sensing Free Surface of Arc Weld Pool Using Specular Reflection: Principle and Analysis,” to appear in Proc Instn Mech Engrs, Part B, Journal of Engineering Manufacture.
19.
Kovacevic, R., and Zhang, Y. M., 1996, “Apparatus and Method for Measuring 3-D Weld Pool Shape,” United States Patent, #5,481,085, January. 2.
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