JPH0375268B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention directly detects the welding groove width, the wire position within the groove, and the arc generation situation based on a visual function that utilizes welding phenomena, that is, welding arc. Concerning how to control position.

Tracing the weld line is essential for automating the welding process. This copying method involves in-process control in which the welding torch follows the welding line while welding, and a method in which a teaching operation is performed before welding so that the welding robot memorizes the trajectory of the welding line and then reproduces it to copy the welding line. There is.

The method using a welding robot, combined with advances in control software technology, allows for relatively highly accurate tracing. However, since a teaching process is always required before welding, it is unsuitable for large structures with different dimensions and shapes. Therefore, in-process control is advantageous in such cases.

Contact sensors using tracing rollers, probes, etc., and non-contact sensors using magnetic/fluid elements have been developed as devices for in-process control, and some of them have been put into practical use. However, conventionally proposed contact sensors cannot cope with extreme irregularities on the surface of the workpiece. Further, it has drawbacks such as being affected by spatter generated during welding and being difficult to apply to narrow areas inside the groove of a thick plate.

On the other hand, non-contact sensors basically follow the weld line on the surface of the welded part. For this reason, it is difficult to expect accurate tracing accuracy when welding within the thickness of a plate, such as narrow gap welding of a thick plate. Additionally, this type of sensor generally has poor heat resistance, so detection must be performed at a certain distance from the weld. Additionally, all of these sensors must be mounted near the welding head, which increases the complexity of the welding equipment.

The present invention was made in view of the above circumstances, and its purpose is to enable in-process control, without installing a special sensor near the welding head, and without regard to thin plate welding or thick plate multilayer welding. ,
The purpose of this invention is to provide a welding position control method that allows highly accurate tracing and adaptive control of welding conditions.

That is, the present invention detects the brightness distribution including the welding wire in a direction perpendicular to the welding line and the brightness distribution including arc light in the direction perpendicular to the welding line, and performs a binarization process on each brightness distribution. The method is characterized in that the groove width of the material to be welded and the relative position of the welding wire are calculated, and the torch position is controlled based on these calculated values.

The present invention will be explained below based on the drawings.

First, as shown in FIG. 1, a television camera 1 is placed in front or behind the welding area, and
Then, an image is taken through filter 2 at a substantially right angle to the direction of the welding line, and its brightness distribution is detected. In this case, the detected brightness distribution is the brightness distribution on the lateral direction A-A' line including the welding wire 3 and the B-B' line including the arc light section 4, as shown in FIG. Next, the detected brightness distribution is input to the image processing device 5 and binarized, the groove width W of the workpiece 6 and the relative position D of the welding wire 3 are calculated, and calculation control is performed based on these calculated values. The torch position is controlled by the device 7 so that the welding torch 8 is placed at the required position in the groove.

That is, by photographing the welded part from in front of the welded part with the television camera 1, it is possible to photograph an image of a plane perpendicular to the welding line, as shown in FIG. At this time, the left and right materials to be welded 6, 6 are dark, and the inside of the groove appears relatively bright due to the arc light, but the welding wire 3 inside the groove appears dark. When the brightness distribution of a line AA' perpendicular to the welding wire 3 including the wire portion is detected, for example, a brightness distribution as shown by AA' in A in FIG. 3 is obtained. At this time, if the inside of the groove is sufficiently bright due to the arc light, a sufficient brightness distribution can be obtained over the groove widths a and b. However, if you photograph the weld from the front as shown in Figure 4, for example,
Above the arc light, such as the AA′ line, the background is the inside of the groove at the back and the already solidified weld. Therefore, the brightness of that part is low, and it is not possible to obtain a contrast (temperature difference) between the welding wire 3 and the welding wire 3.

Also, as shown in Figure 5, the TV camera 1 is
When photographing the welded part diagonally downward from 30 to 50 degrees above,
An unsolidified molten pool 9 is reflected in the background of the AA′ line.
Therefore, the inside of the groove receives light from the high-temperature molten pool, and the brightness inside the groove is relatively high, and only the wire portion appears dark, and the wire position within the groove can be determined from the difference in brightness. However, even in this case, the areas near the side walls of the left and right welding materials are already at a low temperature or have begun to solidify, so the brightness of those areas is lower than the center, and the brightness of the chevron shape as shown at AA' in Figure 3A. distribution. In other words, the brightness distribution near points a and b on the groove sidewall is extremely weak. For example, if such a brightness distribution is binarized using a threshold value P, a signal as shown in AA' in Figure 3 (b) can be obtained. . As a result, the wire position point c can be detected, but the groove side wall points a and b cannot be clearly detected. For this reason, the exact groove width is not known and the wire position cannot be traced with high precision.

Therefore, in the present invention, the AA' line is detected, and the horizontal line BB' containing the arc light below is simultaneously detected. This part has a strong brightness distribution over the entire width of the groove due to the strong arc light. Therefore, it is possible to obtain a luminance such as BB' in FIG. 3A, for example. This brightness distribution is
It has strong brightness even slightly inside from the groove sidewalls a and b. If this is binarized using a threshold Q, for example, a signal as shown in BB' in the figure (b) can be obtained, and the positions of the side walls a and b can be accurately determined, and as a result, the groove width W can be detected.

Therefore, the distance D from one side wall to the welding wire 3 can be determined from this groove width W and the wire position c based on the signal from the AA' line detected earlier, and the distance D and the groove width W can be determined. The wire position within the groove can be controlled from For example, by operating the motor connected to the torch position control device so that D=1/2W, the welding wire can always follow the center of the groove width.

Furthermore, since the absolute value of the groove width W itself can be detected, it is also possible to know the behavior of the welded object due to thermal deformation during welding, that is, the contraction and expansion of the groove width. Therefore, welding conditions can be controlled according to the value, and defects such as poor fusion can be prevented.

Note that the light emitted from the welding arc contains a lot of ultraviolet rays. Therefore, in the present invention, it is desirable to employ an infrared camera or an infrared filter for the television camera 1 and filter 2 to remove ultraviolet rays as much as possible.

Further, in the image calculation process of the present invention, the torch position can be controlled online by comparing and calculating the detection signal with a value such as the groove width inputted in advance using a microcomputer. As the torch position control motor, either a pulse motor or a servo motor can be applied.

Furthermore, the detection of the signal does not have to be continuous. For example, even if the torch position is controlled by detecting it once every 10, 20, or 30 seconds, there is practically no negative effect on accuracy.

Alternatively, the detection signal for a certain period of time may be integrated and the control may be performed using the average value thereof. In this case, it is not necessary to move the torch position from side to side all the time, which may be practical.

As described above, according to the present invention, the groove width and the relative position of the welding wire are calculated from the lateral brightness distribution including the welding wire and the lateral brightness distribution including the arc light, and based on these calculated values. Since the torch position is controlled by
In-process control allows highly accurate copying. It also has remarkable effects, such as being able to adaptively control welding conditions.

[Brief explanation of drawings]

The drawings show an example of the method of the present invention, FIG. 1 is an explanatory diagram of a welding position control device, FIG. 2 is a diagram showing detection positions of brightness distribution, and FIG. 3A is a diagram showing an example of brightness distribution. Figure B is a diagram showing an example of binary processing of the brightness distribution in Figure 3 A, Figure 4 is an explanatory diagram showing the TV camera installed horizontally, and Figure 5 is a diagram showing the TV camera installed diagonally upward. FIG. 1...TV camera, 2...filter, 3...
... Welding wire, 4 ... Arc light section, 5 ... Image processing device, 6 ... Material to be welded, 7 ... Arithmetic control device,
8... Welding torch, 9... Molten pool.

Claims (1)

[Claims] 1. Detect the brightness distribution including the welding wire in the direction perpendicular to the welding line and the brightness distribution including the arc light in the direction perpendicular to the welding line, and perform binarization processing on each brightness distribution to determine the welding material. A welding position control method comprising: calculating a groove width and a relative position of a welding wire; and controlling a torch position based on these calculated values.