Study On The Variation Of Illumination Under Different Waveband In The Vicinity Of CO₂ Welding Pool

Nowadays,the demand for automated welding and intelligent welding is becoming more and more urgent in the field of welding manufacturing.In terms of such advantages of CO₂ welding,the application of the CO₂ welding seam tracking technology based on vision in aerospace,automobile and other industries has been developed rapidly.The acquisition method of weld and weld pool image as well as the reliability and efficiency of image processing are also highly valued.However,the spatter of metal,the illumination intensity distribution and its complex changes in the vicinity of the weld pool in short circuit transfer of CO₂ welding process seriously influence on the real-time property and dependability when extracting the weld seam characteristics.And the development of the CO₂ welding seam tracking technology which is based on vision has been severely restricted.In view of the light intensity detection instrument response rate in the second grade,it is difficult to describe the process of arc changes when there are voltage and current change.Therefore,this paper establishes the relationship model between the image gray value and the intensity of the electric arc,and regards it as a bridge.From the perspective of image gray value reflected light intensity,this paper carried out the study on the variation regularity of different band ranges in the vicinity of the CO₂welding pool.Firstly,the orthogonal experiment was used to optimize the exposure,the central wavelength and the welding current;On the basis of the orthogonal test,two factors were fixed,and the influence of the other factors on the gray level of the image near the weld pool was studied;then,the influence of different CCD cameras and different types of weld metal on the gray value of the image in the vicinity of the weld pool is explained by theory,and the optimum results are obtained.The follow-up research is ensured on the high efficiency and reliability.Secondly,the relationship between the gray value of the image and the instantaneous voltage has established and the error test has been given,which reveals the law of the illumination change with time in a complete welding cycle.Again,the camera system was firstly calibrated.Then,the relationship between the gray value of the image and the distance under different wavelengths of the narrowband filter is established,and the distribution of the illumination in the vicinity of the molten pool is revealed.Finally,the two-dimensional model of the gray value of the image with the instantaneous current and distance is established at the center wavelength of 550nm.Based on this,the two-dimensional model of the gray value of the image with the instantaneous current and distance under different band is obtained by multiplying the k-factor.This model comprehensively reveals the essential law of the change of illuminance under different wavelength bands near the CO₂ welding pool,and improves the reliability and high efficiency of the melting as well as weld feature extraction under this condition.This study will lay an important experimental and theoretical basis for the application of CO₂ welding seam automatic tracking technology which is based on vision.