The principle and system structure of the depth measurement of weld pool surface in tungsten insert gas (TIG) welding are first introduced in the paper, then the problem of the common phase lines is studied. We analyze the causes and characteristics of the phase lines, and propose a phase correction method based on line ratio. The paper presents the principle and detail processing steps of this phase correction algorithm, and then the effectiveness and processing characteristics of the algorithm are verified by simulation. Finally, the algorithm is applied to phase processing in the depth measurement of the TIG weld pool surface and obtains satisfying results.
Selecting an appropriate pitch is one of the most important aspects to ensure the system measurement range and
precision in grating projection principle of 3D profile measurement while the Fourier transform frequency spectrum is
separated completely. According to the concept of the equivalent wavelength, the basic requirement for measurement
system and the selection of projection grating pitch are discussed in this paper to avoid shadows and frequency spectrum
alias in a crossed-optical-axes system in Fourier Transform Profilometry (FTP). The influence of CCD sampling to the
FTP is also discussed to obtain CCD sampling condition. When the CCD sampling frequency is unchanged, it is
necessary to reduce the grating frequency which means to increase the grating pitch to satisfy the sampling condition.
Finally, the range of the grating pitch is determined, and the optimal grating pitch is obtained after the experiments.
The method with sensing of MIG welding pool surface is studied in this paper.The distributing of arc action
spectrum, pool reflecting action spectrum and pool radiating action spectrum are analyzed. The radiation is weaker at
interzone 500-700nm. So, the structured light source is confirmed to semiconductor laser at wavelength 650nm. Narrow
band filter and neutral density filter are mounted on CCD, they are good for restrained the influence of arc. The pool
width is studied on small current by experimented, deforming and distributing of structured light are confirmed. The
form and sort of splash are studied, the method of reducing and protecting splash are also studied. Welding current is
selected properly to restrained splash. Incident angle of structured light is 30 degree. The MIG pool image is captured by
CCD. Deformed structured light fringes are reflected the information of the concave or convex of the pool.
An active vision sensing system which established by low power laser and common CCD is used to shoot GTAW
welding pool images. Based on choose the appropriate LASER and filters, projected angle of laser and shoot angle of
CCD, we avoid the disturbance of arc effectively and obtain clear images of the welding pool. The shape parameters of
welding pool can obtain by demarcated and calculated. And then a three-dimentional numerical model of GTAW welding
pool is established based on the theories of fluid dynamics and heat transfer. It considered the convection heat transfer of
liquid metal and heat conduction of solid metal. And FLUENT software is used for simulate the GTAW welding pool.
Extract the weld pool shape parameters and done comparative study with the vision detection of pool. This will be
beneficial to avoid repeat experiments and improve work efficiency.
Laser position detecting to weld seam is based on the principle of structured light measuring. The intense arc, combusting gas and spatters influence the acquisition of weld seam image in the process of welding. Therefore, the problem of anti-light disturbance is studied in four aspects. First, the forming factors of the light disturbance such as the arc and the melting cell radiation and so on is studied from the viewpoint of the distribution of spectrum energy. Matching the narrow-band filter with the wavelength of laser can obstruct the ultraviolet and infrared radiation. Secondly, the influence brought by the reflection on the surface of steel plate is studied and a neutral filter is used to absorb the light disturbance and then the signal-to-noise ratio of an image is improved. Thirdly, there are still some stripes of spatters on image after compound filtering. For calculating the position of weld seam, the technology of digital image processing is also adopted. And finally, obstructing the light disturbance by a mechanical part is also an important measure. A baffle installed between the welding torch and the laser sensor can effectively obstruct some of the spatters. After taking the above four aspects measures, the light disturbance is better eliminated and a clear image is acquired. It can be used to track the weld seam by crawling arc welding robot.