JPH0649231B2 - Butt weld tracking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a covering material (composite wire and copper tape) for a circular core material.
The present invention relates to an associative welding part tracking device for automatically tracking and associating an associative part of a metal material such as a welded pipe.

<Prior Art> In butt welding of a medium-thickness plate or a thin-thickness plate, the plate material is easily deformed due to thermal strain during welding. If it is deformed, the aim of the arc is deviated, the predetermined strength cannot be obtained, and the welding quality is deteriorated. Further, in the butt welding of the covering material of the circular core material, while the shaping material is shaped into a circular shape by the shaping roller and is fed, shaping defects, bending of the core material, etc. occur, and the welding position is displaced, so that the predetermined strength is obtained. Hard to get.

Therefore, when butt-welding medium-thickness plates or thin-thickness plates, etc.
It is necessary to detect the butt section, that is, the arc line, by some kind of sensor, and have the torch track the butt section.

As a conventional tracking device for the matching section, there are a method of bringing the sensor into contact with the matching section and a method of not contacting the sensor with the matching section.

The contact type tracking device calculates the welding position by contacting a disc-shaped probe to the abutting part and measuring the variation of the probe position to track the torch.

According to the non-contact method, there are a tracking device that uses a laser beam and a tracking device that uses a magnetic sensor.

The one that uses a laser beam scans the laser beam and irradiates it to the matching section, detects the light spots from the matching section with a light receiver, and calculates the positions of the light spots one after another by the principle of triangulation. Then, the shape of the butt portion is obtained, and the torch is tracked to the position to be welded.

In the case of using a magnetic sensor, the magnetic sensor is brought close to the butt portion, and the change in the leakage magnetism caused by the current flowing inside the non-welded object during arc welding is detected by the magnetic detection coil to obtain the maximum magnetism. The torch is being tracked to the position.

<Problems to be Solved by the Invention> However, in the contact type, the thin plate is distorted by the arc, the butt portion is deformed, the disc-shaped probe comes off the butt portion, and the center line of the butt welded portion. There was a problem that it was not possible to measure continuously. . In addition, since the probe is used in contact with the butting portion, there is a problem that the probe is worn.

In the case of using a laser beam, there is a problem that the laser beam has a width and the arc light becomes noise, so that the center line of the butt-welded portion cannot be measured with high accuracy and continuously. More specifically, in covering welding of circular core material with covering material, in order to obtain a desired welding strength, in order to keep the torch tip end at a constant distance from the welding position and track the torch, It is necessary to measure the tip position and the alignment center position with accuracy on the order of several tens of μm. However, since the laser beam has a width, it is not possible to measure the center line of the abutting portion on the order of several tens of μm. Further, since the arc light fluctuates greatly, the level of the arc light incident on the light receiver may be higher than the light receiving level of the laser beam. In this case, the center line of the matching portion cannot be detected, which causes a problem of interrupting the measurement.

In the case of using a magnetic sensor, since the leakage magnetic flux has a certain spread, it is impossible to measure the torch tip position and the center position of attachment with high accuracy as described above.

This invention has been made in view of the above problems,
The torch tip position and the center position of the attachment are highly accurate,
An object of the present invention is to provide a butt welding portion tracking device that enables continuous measurement.

<Means for Solving the Problems> To achieve the above object, a tracking device for a butt welding part is a two-dimensional CCD camera that images the periphery of the butt part and the torch tip and a CCD camera. The amount of deviation between the A / D conversion unit for converting the lightness value of the welded image into a digital value of a plurality of gradations and the torch tip position and the center line of the attachment portion is calculated based on the digitally converted lightness data. It has an arithmetic processing unit and a control unit which outputs a tracking control signal for tracking the torch tip position to the center line of the attaching unit in accordance with the shift amount calculated by the arithmetic processing unit.

However, the arithmetic processing unit may be a second-order derivative of the function of the lightness data in the direction orthogonal to the matching direction, and the peak value of the second-order differentiated function may be the center position of the matching. Then, when the function of the lightness data is secondarily differentiated, it is preferable that the lightness data is added in the fitting direction, and further the weighted moving average processing is performed to remove the noise due to the welding light.

Further, the arithmetic processing section may apply the torch peripheral portion to an asymmetric polynomial and measure the peak value of the asymmetric polynomial as the torch tip position.

<Operation> According to the butt welding portion tracking device described above, the shaping roller feeds the metal materials while attaching them, and the sensor for detecting the center line of the butt portion of the metal materials precedes the torch. When the tip position of the torch is tracked to a desired welding position based on the output of
By imaging the center line of the butt-welding portion and the torch tip with a CD camera, the center line of the butt-welding portion that is slightly darker than the arc light can be captured as brightness data. Further, since the center line of the butt-welded portion is shaded by the arc light, a difference in brightness always occurs even if there is an influence of the arc. Then, the lightness value of the welding image picked up by the CCD camera is converted into digital values of a plurality of gradations, and the arithmetic processing unit calculates the amount of deviation between the torch tip position and the center line of the attachment portion based on the lightness data. By doing so, the torch tip position and the center line of the butting portion can be measured with high accuracy and continuously.

In addition, when the arithmetic processing unit is a second-order derivative of the function of the lightness data in the direction orthogonal to the attachment direction, and the peak value of the second-order differentiated function is used as the attachment center position, the attachment is performed. The fitting centerline can be detected with little influence of asymmetric changes in brightness in the peripheral portion.

Then, when the arithmetic processing unit performs the second-order differentiation of the function of the lightness data, the lightness data is added in the fitting direction, and further the weighted moving average processing is performed to remove the noise due to the welding light. It is possible to improve the measurement strength of the center position of the butt welded portion.

Further, when the arithmetic processing unit applies the torch peripheral portion to the asymmetric polynomial and measures the peak value of the asymmetric polynomial as the torch tip position, reduce the measurement error due to the asymmetry of the torch tip image in the vertical direction. You can

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 1 is a diagram showing an embodiment of a butt welding portion tracking device according to the present invention, FIG. 2 is a diagram showing a welding image taken by the butt welding portion tracking device, and FIG. 3 is a calculation process. It is a figure for demonstrating the detection process of the matching center position by a part.

The butt welding part tracking device holds a core material (1) having a circular cross section and a copper tape (2) and feeds the core material (1) in the x direction while attaching the copper tape (2) to the shaping roller (3). And shaping rollers (3)
A torch (4) for welding the copper tape (2) attached by the method based on the TIG welding method, a two-dimensional CCD camera (5) for imaging the periphery of the attachment position and the tip of the torch, and a CC
An A / D converter (6) for converting the lightness value of the welding image picked up by the D camera (5) into digital values of a plurality of gradations, and an image data memory (7) for storing the lightness data digitally converted. , The image data memory (7) is accessed to read the stored lightness data, the torch tip position based on the lightness data, and the deviation amount between the center line of the butting portion is calculated based on a predetermined program, An arithmetic processing unit (8) that outputs a tracking control signal that causes the torch tip position to track the center line of the matching section according to the calculated displacement amount, and a torch according to the tracking control signal from the arithmetic processing unit (8). It has an output interface (9) for moving the tip in the y direction or in the direction opposite to the y direction to position it on the center line of the fitting portion.

More specifically, the two-dimensional CCD camera (5) is
A lens group (51) with dimming and diaphragm functions, a photodiode array, a horizontal switch, a vertical switch, a horizontal shift register, a vertical shift register, etc.
A two-dimensional image sensor (52). The two-dimensional image sensor (52) converts the welding image (torch tip, attachment part, etc.) obtained through the lens group (51) by the photodiode array into electric quantity according to the brightness, temporarily stores it, and horizontally shifts it. A register and a vertical shift register electrically connect the horizontal switch and the vertical switch to successively transfer the welding images stored in the photodiode array.

The welding image taken by the CCD camera (5) is as shown in FIG. That is, the torch (4)
And the center line of the matching part that appears slightly darker than the arc light
(L) and are imaged. However, this welding image is a state in which the change in brightness at the joining center line (L) is very slight, and the distinction between the center line (L) and the joining periphery is unclear,
Since the arc light is powerful and changes greatly, it is not possible to reliably detect the center position of the joint with this condition.
Have difficulty.

The line A-A 'shows a reference line for detecting the center position of the attachment, and FIG. 3A is a plot of the lightness data on the line A-A' in FIG. Also, (L ′) is the torch
(4) Indicates the extension line of the tip.

The A / D conversion unit (6) is a conventionally known one, and the CC
The brightness value (analog data) of the welding image transferred from the D camera (5) is converted into a digital value of a plurality of gradations (specifically, 64 gradations).

The image data memory (7) stores the digital value from the A / D converter (6) at the address corresponding to the pixel position.

FIG. 4 shows a functional block diagram of the arithmetic processing unit (8). The arithmetic processing unit (8) reads the brightness data of 64 gradations (see FIG. 3A) read from the image data memory (7) as x By the filter unit (81) that performs noise addition by the arc light by adding in the direction (see FIG. 3B), moving average processing the added data (see FIG. 3C), and by the filter unit (81). A center line detector (82) that second-order differentiates the noise-removed lightness data function (see FIG. 3D) and detects the peak position of the second-order differentiated function as the center line (L) of the matching part. The torch tip measurement unit (83) that fits the outer circumference of the torch tip image stored in the image data memory (7) to an asymmetric polynomial and measures the position of the torch tip from the peak value of the curve of the polynomial, and the center line Center line (L) of the matching part detected by the detection part (82) and torch tip measurement part (83) Shift amount calculating unit that calculates more shift amount between the extension line (L ') of the measured torch tip (D) and (84), the deviation amount from the shift amount calculating section (84)
It has a control section (85) which receives (D) as an input and outputs a tracking control signal for positioning the tip of the torch at the center line (L) of the butt welding section.

It should be noted that the moving average processing can adopt a processing method of increasing the weight each time the center of the average is approached.

The output interface (9) is a torch moving table (94) that moves the pulse generator (91), the pulse motor (92), and the torch via the connecting rod (93) in the y direction or in the opposite direction.
It is equipped with. That is, the pulse generator (91) includes a control unit (8
A pulse signal for rotating the rotating shaft of the pulse motor (92) by a predetermined angle is generated according to the tracking control signal from 5). The pulse motor (92) rotates a predetermined angle to drive the torch moving table (94). The torch transfer table (94) has a connecting rod (9
Move 3) in the ± y direction by a distance corresponding to the amount of deviation (D).

The operation of the butt welded portion tracking device having the above configuration is as follows.

That is, the shaping roller (3) holds the core material (1) having a circular cross section and the copper tape (2), and feeds the core material (1) in the x direction while attaching the copper tape (2).

The lens group (51) of the two-dimensional CCD camera (5) dims the arc light to the extent that the two-dimensional image sensor (52) can detect the welding image and expands it to 10 μm / pixel, Take a welding image. Then, the two-dimensional image sensor (52) converts the electric quantity (electric charge) corresponding to the brightness of the welding image, and converts the electric charge in the horizontal direction (x direction) and the vertical direction (y).
Direction) and sequentially transfer them to the A / D converter (6).
That is, since the welding image is two-dimensionally captured in the x direction and the y direction by the CCD camera (5), unlike the conventional measuring method using a magnetic sensor or laser beam, the torch tip position is attached. The center line (L) of the mating portion can be measured directly and simultaneously.

The A / D converter (6) converts the brightness value of the welding image picked up by the CCD camera (5) into digital values of a plurality of gradations and outputs it to the image data memory (7).

The image data memory (7) stores the digitally converted lightness data at an address corresponding to a pixel.

The processing unit (8) measures the center line (L) of the torch tip and the butt weld by the following procedure, and in the step, the torch tip is moved to the center position of the butt weld. To control tracking. That is, the image data memory (7) is accessed to read the brightness data on the line AA 'in FIG. 2 stored in the image data memory (7).

In the filter section (81), the read brightness data is sequentially added in the x direction (see FIG. 3B), and the added data is subjected to moving average processing (see FIG. 3C) to remove noise due to arc light. .

In the center line detection unit (82), the function of the lightness data from which noise has been removed is secondarily differentiated (see FIG. 3D), and the peak position of the secondarily differentiated function is detected as the center line (L) of the matching unit. To do. That is, by quadratic differentiating the function of the brightness data, it is possible to detect the fitting center line (L) with almost no influence of the non-symmetrical change in the brightness in the fitting peripheral portion. Further, the accuracy of measurement can be improved by approximating the vicinity of the peak value of the quadratic differential function by the quadratic function by the least square method.

In the torch tip measuring unit (83), in parallel with the detection process of the center line (L) of the associating unit, the outer circumference of the torch tip is fitted to an asymmetric polynomial, and the peak value of the curve of the polynomial is used to determine the torch tip end portion. Measure the position. In this way
By measuring the position of the tip of the torch, it is possible to reduce the measurement error due to the vertical asymmetry of the torch tip image.

In the deviation amount calculation unit (84), the deviation amount (D) between the center line (L) of the detected butting portion and the extension line (L ′) of the torch tip detected by the torch tip measurement unit (83) ) Is calculated. The measurement error due to the above process is ± 20 to ±
It was on the order of 30 μm. This is ± of the image sensor
The accuracy corresponds to a few pixels. The processing described above can be performed in about 1 second by performing high-speed processing with a microcomputer or the like.

The control section (85) outputs a tracking control signal for tracking the torch tip position to the center line (L) of the matching section based on the shift amount (D).

The output interface (9) moves the tip of the torch in the y direction or in the direction opposite to the y direction in accordance with the tracking command signal from the control unit (85) to position it on the center line of the matching unit. That is, the amount of deviation can be set to "0" by matching the tip of the torch with the center line of the butting portion.

FIG. 5 shows the result of continuously measuring the automatic tracking by the butt welding portion tracking device of FIG. 1 for 100 minutes.
FIG. 5A shows the variation of the centering position of attachment, FIG. 5B shows the tracking position of the tip position of the torch, and FIG. 5C shows the amount of deviation between the center position of attachment and the position of the torch tip.

From the results shown in FIG. 5, it can be seen that the torch tip position accurately tracks the variation of the attachment center position, and the deviation amount between the attachment center position and the torch tip position is within ± 0.2 mm. .

The present invention is not limited to the above-mentioned embodiment, and for example, a torch compliant with the MIG welding method can be used in place of the torch compliant with the TIG welding method, and other aspects. It is possible to make various design changes as long as is not changed.

<Effect of the Invention> As described above, according to the butt-welding portion tracking device of the present invention, the center line of the butt-welding portion and the tip of the torch are imaged by the two-dimensional CCD camera, so that it is possible to compare with the arc light. The center line of the butt weld, which becomes slightly darker, can be captured as brightness data. Then, the lightness value of the welding image picked up by the CCD camera is converted into digital values of a plurality of gradations, and the arithmetic processing unit calculates the amount of deviation between the torch tip position and the center line of the attachment portion based on the lightness data. By doing so, the tip position of the torch and the center line of the butting portion can be continuously measured with high accuracy.

Therefore, the torch tip portion can be made to accurately follow the center line of the butt-welded portion, and there is a unique effect that desired welding strength can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a butt welding portion tracking device according to the present invention, FIG. 2 is a welding image taken by the butt welding portion tracking device of FIG. 1, and FIG. FIG. 4 is a diagram for explaining the detection process, FIG. 4 is a functional block diagram of the arithmetic processing unit (8), and FIG. 5 is a diagram showing the results of measurement and automatic tracking by the butt welding unit tracking device of FIG. (5) ... Two-dimensional CCD camera, (6) ... A / D converter, (7) ...
Image data memory, (8) ... arithmetic processing unit, (85) ... control unit, (9) ... output interface

Claims (4)

[Claims] 1. A shaping roller is used to feed metal materials together while attaching them, and a sensor for detecting the center line of the joint portion of the metal materials precedes the torch, and the tip position of the torch is determined based on the output from the sensor. A two-dimensional CC that images the periphery of the butt joint and the torch tip in a butt weld tracking device that tracks the center line of the butt joint.
A D camera, an A / D conversion unit for converting the lightness value of the welding image picked up by the CCD camera into digital values of a plurality of gradations, a torch tip position based on the digitally converted lightness data, and an associating unit. It has a calculation processing unit that calculates the amount of deviation from the center line, and a control unit that outputs a tracking control signal that causes the torch tip position to track the center line of the attaching unit in accordance with the amount of deviation calculated by the calculation processing unit. A butt welding part tracking device characterized in that 2. The arithmetic processing unit is characterized in that a function of lightness data in a direction orthogonal to the fitting direction is quadratic differentiated, and a peak value of the quadratic differentiated function is used as a fitting center position. The butt-welding part tracking device according to claim 1. 3. The arithmetic processing unit adds the brightness data in the matching direction when the function of the brightness data is secondarily differentiated, and further performs weighted moving average processing to remove noise due to welding light. The butt welding part tracking device according to claim 2, wherein the device is a butt welding part tracking device. 4. An arithmetic processing unit applies a peripheral portion of a torch to an asymmetric polynomial, and measures a peak value of the asymmetric polynomial as a torch tip position. Matching weld tracking device.