JPS5994585A - Controlling method of torch height - Google Patents

Abstract

PURPOSE:To control torch height with good accuracy without installing any sensor near the torch by detecting the difference in the local luminance distribution in a groove by making use of arc light, and controlling the torch height in accordance with the detected value thereof. CONSTITUTION:A weld zone is photographed, via a filter, by a television camera, from the front of a weld zone and a luminance distribution at AA', a luminance distribution at BB' and a luminance distribution at CC' are respectively measured from the video thereof. The luminance distribution at AA' is in the lateral direction at a right angle to a weld line, and is the line distribution including a torch 2 or chip 3 at the preset normal torch height. The luminance distribution at BB' is in the lateral direction at a right angle to the weld line and is the distribution of the line including a welding wire 4 right under the AA' line. The luminance distribution at CC' is the line distribution in the direction intersecting orthogonally the AA' line and BB' line near the central part in the groove, i.e., in the torch height direction. The torch height is controlled by these three luminance distribution signals.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of detecting a local brightness distribution difference within a groove by utilizing a welding arc phenomenon, that is, arc light, and controlling the torch position height on-line.

Copying the weld line is essential in the welding process, and contact sensors such as copying rollers and probes, as well as non-contact sensors using magnetism, air pressure, etc., have been developed as devices for copying the weld line. Some are in practical use. However, these conventional methods have the following drawbacks.

(1) In both cases, it is necessary to install various sensors near the welding torch, which increases the complexity of the welding equipment.

(11) Due to the high temperature of the weld, various sensors cannot be brought too close to the weld, but the accuracy is poor when detecting from a distance.

(iii) Contact sensors are susceptible to surface irregularities that are not directly related to the weld.

Gv) The sensor is easily damaged by the ivy coming out of the weld.

(V) Particularly in the narrow groove welding, it is difficult to control the height of the torch position in accordance with the unevenness of the groove bottom surface of the welded part or the surface of the front layer weld bead.

The present invention has been made in view of the above circumstances, and its purpose is to accurately control the height of the torch position without installing a sensor near the welding torch, and to be able to precisely control the height of the welding torch without installing a sensor near the welding torch. The objective is to obtain a torch height control method suitable for welding.

That is, the present invention provides a brightness distribution in the torch height direction at the center of the weld groove, a brightness distribution in the direction perpendicular to the welding line including the torch or chin ff, and a brightness distribution in the direction perpendicular to the welding line including the welding wire. The present invention is characterized in that the tip position of the torch or tip is detected by measuring and binarizing these brightness distributions, and the torch height is controlled based on this detected value.

Hereinafter, the present invention will be explained with reference to the drawings.

First, as shown in FIG. 1, the welded area is photographed from in front of the welded area using a television camera 1 through a suitable filter (not shown). Then, the luminance distribution of AA', BB', and CC' are measured from the photographed images. The brightness distribution of A A' is in the left and right direction perpendicular to the welding line, and is the same as torch 2 or chi f3'f! at a preset normal torch height. It is a line distribution including c. B
The brightness distribution of B' is in the left and right direction perpendicular to the welding line, and
This is the distribution of the line including the welding wire 4 directly under A' Terran. The brightness distribution of CC' is A near the center of the groove.
The A' line and the BB' line are line distributions in a direction perpendicular to each other, that is, in the torch height direction. The torch height is then controlled by these three brightness distribution signals.

In other words, the brightness distribution of the A A' line is, for example, as shown in Figure 3 (
The state shown in b) is reached, with the torch 2 at the center of the groove becoming a dark area, and only the surrounding area within the groove becoming a bright area. When this is binarized using a threshold value P, a signal V is obtained. Similarly, the brightness distribution of B B' Terran is as shown in Figure 3 (b), with dark areas outside the welding wire 4 and the left and right side walls, and bright areas inside the other grooves due to reflection from the arc source. becomes. When this is binarized using a threshold value Q, a signal T is obtained. These signals V and T can be used for horizontal tracing of the torch in the groove, but they alone cannot control the torch height.

The brightness distribution of the CC' line in the height direction near the center of the 10,000-groove groove is as shown in Figure 3 (c), with the highest brightness at the arc origin (bottom of the groove) and then moving toward the top. As the brightness increases, the brightness decreases. When this brightness distribution is binarized using a threshold value R, a binarized signal W is obtained, and the position a of the groove bottom can be determined from this signal. If the brightness distribution obtained from this CC' line is located at a position that includes torch 2 (or tip 3), the brightness will decrease rapidly at the tip of the torch (tip). In some cases, the position can also be detected. In this case, the distance from the groove bottom a to the tip of the torch (tip) can be detected only by detecting the brightness distribution of the c c' line and image processing. If the value of L is always kept constant, the torch height can be controlled in accordance with changes in the height of the welded part.

However, there may be cases where the brightness distribution at the tip of the torch (tip) changes relatively little, and there may also be cases where the horizontal position of the torch changes constantly, and there is a risk that the CC' line may deviate from torch 2 (or step 3). There is. In this case, it becomes difficult to detect the position of the tip of the torch (tip).

Therefore, in the present invention, the above-mentioned groove left and right direction detection line A
A', B B, 'f are always set at a constant height from the groove bottom position a detected from the cc' line.

In other words, under normal conditions, AA' is connected to torch 2 (Terra 7).
3), and B B' is set to a line that includes only the welding wire 4. Even if the tip of the torch (Tera f) cannot be detected using only the K and CC' lines, the position of the tip of the torch (tip) can always be controlled using the signals obtained from the AA' and BB' lines. I can do it.

For example, as shown in Figure 5 (a), the bottom of the groove moves from point X to
If the welding arc point decreases to 2 points, the welding arc point decreases accordingly, and the wire elongation from the tip of the tip extends until i, where the torch 2 is in a constant state, and a good welding condition may not be maintained. At this time, it is possible to quickly detect that the position of the groove bottom has changed from a to a'4C by the detected binary signal of the vertical CC' line (see FIG. 4). Therefore, the positions of the horizontal direction detection lines AA' and BB', which were set a certain distance (L t m ) above point a, are t,
Since m is kept constant, it descends downward by the amount that the bottom of the groove has fallen, as shown in FIG. 5(b). That is, A.A.
', BB' both detect the horizontal direction line containing only the welding wire 4, and AA'1BB' detects the same signal.The normal state shown in Fig. 5(a) is will be in a different state.

When a signal indicating such a state is obtained, a preset control program sends a signal for lowering the torch downward to the torch holding drive device, thereby lowering the torch 2 and returning it to the normal state, i.e. By stopping the torch descent at the point when the signals from AA' and BB' have descended to a position where the same state as in Fig. 5 (a) can be obtained (Fig. 5 (c)), the previous normal state can be achieved. The torch can always be maintained and controlled at the same height.

Note that welding arc light contains strong violet and infrared light in addition to visible light, and an appropriate filter is required to photograph the welded area with a television camera. It is also preferable that the television camera uses an infrared camera to remove ultraviolet rays as much as possible.

Alternatively, the detection of the upper, lower, left, and right lines of the welded portion may be performed continuously, but in this case, three systems of image processing devices are required and the equipment becomes expensive. Also, these A A',
Detection of B B', CC' terraces may be carried out, for example, by an intermittent sampling method with a negative time interval. In this case, if a method is adopted in which each detection signal is stored by using a microconbeater and recalled and compared as needed, the equipment will be inexpensive.

As described above, according to the present invention, the height of the torch position can be controlled more precisely by utilizing the welding arc phenomenon,
In particular, it is suitable for performing height control in response to unevenness of the inner bottom of the groove in thick plate multilayer welding in narrow groove welding.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a perspective view showing the position of the television camera, FIG. 2 is an explanatory diagram showing the brightness distribution line to be detected, and FIG. A diagram showing the brightness distribution. Figure (B) is a diagram showing the brightness distribution of B B' Terran. Figure (C) is a diagram showing the brightness distribution of CC' Terran. Figure 4 is a diagram showing the brightness distribution of CC' Terran. FIGS. 5A to 5C are explanatory diagrams sequentially showing the control method of the present invention. 1...TV camera, 2...torch, 3...chip, 4...welding wire. Applicant's sub-agent Patent attorney Takehiko Suzue Figure 1 (A) (B) 1, Figure 2, Figure 4 ′ (zS)

Claims (1)

[Claims] Measure the brightness distribution in the torch height direction at the center of the weld groove, the brightness distribution in the direction perpendicular to the welding line including the torch or the tip f, and the brightness distribution in the direction perpendicular to the welding line including the welding wire. A torch height control method comprising: detecting the tip position of a torch or tip by binarizing the luminance distribution; and controlling the torch height based on this detected value.