Abstract:
In order to realize the feedback control for variable polarity
plasma arc welding (VPPAW) formation in the welding process, the
geometrical sizes of the keyhole image must be extracted. With
the properties of multiscale edge through the wavelet theory,
the edge points were detected by getting the maximum modules of
the gradient vector in the direction towards which the gradient
vector points in the image plane. At coarse scales, the local
maxima of modules have different positions and only detected the
sharp edge. At fine scale, there are many maxima created by the
image noise, The best scale where the edges are well
discriminated from noises is discussed by the multiscale
transform. At last, a new method of peak analysis for threshold
selection is provided. It is based on the wavelet transform
which provides a multiscale analysis of the information of the
histogram. Many experiments show these ways are effective for
the keyhole image to get the geometry parameters of the keyhole
in the real-time VPPAW image processing.
Key words: PAW Variable polarity Keyhole Image
*
This project
is supported by national Defense Technology Committee and National Key
Laboratory of Advanced Welding Production Technology. Manuscript
received on March 10, 2000; revised manuscript July 10, 2000
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