JPH08193811A - Apparatus and method for detecting welding part - Google Patents

Abstract

PURPOSE: To simplify a processing circuit of an apparatus in comparison with an apparatus using a CCD camera device and make the apparatus resistive to mechanical vibrations and inexpensive in comparison with an apparatus using a rotary mirror by obtaining the displacement amount an direction of a groove part, based on the photodetecting quantity of a photodiode. CONSTITUTION: A laser light is cast to a welding groove part 3 through a projecting lens 5 to spread with a predetermined degree. The reflected laser light is detected by a photodiode 14 through a bundle of optical fibers 13 formed by arranging a plurality of optical fibers 12 in a predetermined arrangement. The position of the photodetecting center of gravity in a lateral cross section of the groove part 3 is detected on the basis of direct current signals from the photodiodes 14. A displacement index is calculated based on the position, and compared with a reference index indicating the normal position of the groove part. The amount and direction of a displacement obtained by the comparison are judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding portion detecting device and a welding portion detecting method for detecting an installation error of a workpiece to be welded and a displacement of a welding portion due to thermal strain during welding in welding by an automatic welding device. It is about.

[0002]

2. Description of the Related Art Conventionally, when performing automatic welding by an automatic welding device (including a welding robot device), a deviation of a welded portion (welding line) due to an installation error of a workpiece to be welded or a thermal strain during welding is detected. As an apparatus, for example, a laser cut image when a laser beam is spread in a fan shape and irradiated on a measurement object is a CCD.
What is imaged by a camera device is proposed (for example,
Kobe Steel Technical Report: VOL 37, NO.2 1987).

Further, as a method of spreading the laser light in a fan shape, there is a method of scanning a mirror as disclosed in Japanese Patent Publication No. 30524/1992.

[0004]

According to the configuration in which the laser cutting image is picked up by the CCD camera device as in the former case described above, it is difficult to set the image pickup speed higher than the video rate due to the nature of the CCD camera device. At the same time, since it is necessary to perform position detection processing by image processing, there is a problem that a high-speed arithmetic circuit is required and the device becomes expensive.

When the mirror is rotated as in the latter case, it is difficult to miniaturize the sensor itself due to its rotating mechanism portion, and it is vulnerable to mechanical vibration.

Therefore, an object of the present invention is to provide a welding portion detecting device and a welding portion detecting method which can solve the above problems.

[0007]

In order to solve the above-mentioned problems, a welding portion detecting apparatus of the present invention comprises an irradiator for irradiating a welding portion with a laser beam so as to have a predetermined spread through a light projecting lens. An optical fiber bundle that receives the laser light reflected at the weld, a photodiode that detects the light from each optical fiber of this optical fiber bundle, and a signal processing device that converts the electrical signal from each photodiode into a DC signal And a processing unit that detects the position of the welded portion based on the DC signal obtained by this signal processing device and that calculates the amount of deviation with respect to the reference welding portion. A center of gravity detection circuit that detects the position of the center of gravity of the received light on the cross section of the weld based on the input DC signal, and a shift index is calculated based on the position of the center of gravity obtained by this center of gravity detection circuit. Index calculation circuit, a comparison calculation circuit that compares the deviation index obtained by this index calculation circuit with a reference index indicating a normal weld position, and the deviation amount and deviation direction obtained by this comparison calculation circuit are determined. And a shift discriminating circuit.

In order to solve the above-mentioned problems, the welding portion detecting method of the present invention irradiates the welding portion with a laser beam so as to have a predetermined spread through a light projecting lens, and reflects this laser beam. Detected by a photodiode through an optical fiber bundle in which a plurality of optical fibers are arranged in a predetermined array, convert the electric signal from each of these photodiodes into a DC signal, and based on this converted DC signal The position of the light receiving center of gravity in the cross section of the weld is detected, a displacement index is calculated based on this position of the center of gravity, and this displacement index is compared with a reference index indicating a normal weld position, and the displacement amount obtained by this comparison And a method of determining the deviation direction.

[0009]

In the above-described detection device and detection method, when the laser light is applied to the welded portion and the reflected laser light is detected, the photodiodes arranged in the predetermined direction are used and the light received by each photodiode is received. Based on quantity
By obtaining the light receiving center of gravity position and comparing the center of gravity position with the reference position of the normal welded portion, the amount of the deviation is obtained and in which direction the deviation is made is determined.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, 1 is, for example, a steel plate 2A,
A welding line detection device for detecting a welding line (for example, a welding groove at the welded portion) 3 when welding 2B to each other. It is driven by a laser driver 4 and a laser beam is applied to the welding line 3 via a light projecting lens 5. An irradiator 6 for irradiating light (for example, a semiconductor laser element is used), a light receiver 8 for receiving reflected light of this laser light via a light receiving lens 7 and outputting an electric signal, and this light receiver 8 A signal processing device 9 for subjecting the obtained electric signal to a predetermined process, a position of the welding line 3 is detected based on the signal processed by the signal processing device 9, a deviation from a reference welding line is obtained, and an automatic welding device is provided. (Of course,
(Including a welding robot apparatus) and an arithmetic processing unit 10 that outputs a control signal to a drive control unit 11 that drives a welding torch.

The optical lens 5 is used to spread the laser light emitted from the irradiator 6 into a fan-shaped slit light. The laser driver 4 causes the laser light emitted from the irradiator 6 to have a duty cycle. Ratio is 50%, 455
Pulse modulation of kHz is applied.

Note that the modulation to 455 kHz is
This is because the arc light generated during welding has a frequency component of about DC to 100 kHz and suppresses the influence of this arc light.

As shown in FIG. 4, the number of the light receivers 8 is 15 in a row (of course, the number is not limited to 15 and may be 15 or more or less. The optical fiber bundle 1 is formed by arranging the optical fibers 12 of which the number is enough to cover the allowable deviation amount.
3 and a photodiode 14 arranged corresponding to each optical fiber 12 of the optical fiber bundle 13. The optical fibers 12 are arranged side by side in a line and, as described above, are provided with a width that can sufficiently detect the cross section of the welding line 3.

The signal processing device 9 includes a tuning circuit 21 for extracting a signal having a 455 kHz component from a signal converted from an optical signal into an electric signal by the photodiode 14, that is, a current, and the tuning circuit 21. A signal conversion circuit 22 for converting the extracted signal into a DC signal capable of responding at 100 kHz, and a light intensity detection circuit 2 for detecting the light intensity of the converted DC signal for each optical fiber 12.
3 and an A / D converter 24 for A / D converting the signal level of the light intensity detected by the light intensity detection circuit 23, that is, the amount of received light.

As shown in FIG. 2, the arithmetic processing unit 10 performs statistical processing on the data inputted from the signal processing unit 9 to remove noise, for example, a statistical processing circuit (for example, spatter at welding or fumes). Error caused by a disturbance such as when the measurement is performed only once, and is provided to prevent this from occurring) 31 and a centroid detection circuit for obtaining the centroid position of the light intensity data processed by the statistical processing circuit 31. Three
2 and an index calculation circuit 33 for calculating an index indicating the overall center position from the position of the center of gravity obtained by the center of gravity detection circuit 32.
And a comparison calculation circuit 34 for calculating the difference between the indexes by inputting the index calculated by the index calculation circuit 33 and a reference index indicating the position of a normal welding line, and the comparison calculation circuit 34.
And a deviation determination circuit 35 that determines how the groove 3 is displaced based on the displacement calculated in step S1 and outputs correction data to the drive control unit 11 of the welding torch of the automatic welding apparatus. Has been done.

Next, based on the above welding line detection device 1,
A method of detecting a V-shaped welding line will be described. Here, the principle of detecting the welding line 3 will be described.

For example, when a laser beam is radiated obliquely from above to a welding groove (welding line), since the irradiation position of the laser beam differs depending on the depth, this reflected light reflects the shape of the groove. It will be what you did. This is generally called a laser cut image, and this is used to detect the groove groove 3.

First, as shown in FIG.
Laser light pulse-modulated at a frequency of 55 kHz is applied to the V-shaped groove 3 as shown in FIGS. 3 (a) and 3 (b), and the reflected light is passed through the optical fiber bundle 13. The light is received by a photodiode 14 provided corresponding to the optical fiber 12.

The relationship between the amount of light received from each photodiode 14 and the position of each optical fiber 12 is shown in the graph of FIG. Since the groove 3 has a V-shape, the signal obtained from the photodiode 14 is a signal obtained by cutting the V-shape in the middle in the horizontal direction, and therefore the amount of light received increases at two locations.

That is, in the graph of FIG. 4, the amount of received light is large at two points A and B, that is, at the positions of the fourth and twelfth optical fibers 12, the groove 3 You can see that

Then, using the points A and B, the deviation amount and the deviation direction of the groove 3 with respect to the reference position (the position in the normal state) are converted into the following equations and equations. Based on this, a horizontal shift index and a vertical shift index are obtained.

[0022] _{(L A + L B) /} 2 = horizontal deviation indicator ···· L _B -L _A = vertical displacement indicator ....... Next, each misalignment indicator determined by the formula and the formula When,
In advance, the comparison calculation circuit 34 compares and calculates the reference index when it is in the correct position.

For example, if the position of the groove 3 is shifted upward, the state shown in FIG. 5B is obtained, and if it is shifted downward, the state shown in FIG. 5C is obtained, and the groove 3 is shifted to the right. Then, the state becomes as shown in FIG. 5D, and when it shifts to the left side, the state becomes as shown in FIG. 5E. Note that FIG.
(A) has shown the state where the groove groove 3 exists in a correct position.

[0024] As can be seen from FIG. 5, deviates upward, the index is small (L _B -L _A), deviates downward, increases the index of (L _B -L _A), displaced to the right Then, the index of [(L _A + L _B ) / 2] becomes smaller, and when it shifts to the left, the index of [(L _A + L _B ) / 2] becomes larger. That is, by comparing these two types of indexes with the reference indexes, it is possible to determine how much the groove groove 3 is and in which direction the groove 3 is displaced.

Therefore, the received light amount of the reflected light of the laser light received by the optical fiber bundle 13 is measured to obtain each of the above-mentioned deviation indices and also to compare with the reference index, and the obtained deviation index and the reference index are The control signal for moving the welding torch so that they coincide with each other is the deviation determination circuit 35.
Is output to the drive control unit 11. That is, the welding torch can be accurately aligned with the groove groove 3.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, as shown in FIGS. 6A and 6B, a case where the welded portion is the overlapping portion 3 will be described.

In this case, the welding line, that is, the overlapping portion 3
Since it is necessary to detect in a two-dimensional manner, that is, as a plane, the optical fiber bundle 13 used in the photodetector 8 has, for example, 6 optical fibers 12 arranged in a row as shown in FIG. 3 (Y direction)
The optical fiber bundle 13 arranged in three rows) is used.
Also in this case, the arrangement of the optical fiber bundles 13 is not limited to the arrangement of 6 pieces × 3 rows, and the arrangement may be such that the welded portions can be covered even when the welded portions are displaced. .

Further, as the arithmetic processing unit 41, one having a structure as shown in FIG. 8 is used. In the first embodiment, the change position of the received light amount only in the X direction is detected, whereas in the second embodiment, in addition to the X direction, the Y position is detected.
It is necessary to detect the change position of the received light amount in the direction as well, and a circuit for this is newly provided.

That is, the arithmetic processing unit 41 includes a statistical processing circuit 51 for removing noise and the statistical processing circuit 5.
Y-direction center-of-gravity detection circuit 52A and X-direction center-of-gravity detection circuit 52B for obtaining the Y-direction and X-direction center-of-gravity positions of the light intensity data processed in 1 and these center-of-gravity detection circuits 52, respectively.
The index calculation circuit 53 that calculates an index indicating the overall center position from the barycentric positions in the Y and X directions obtained by A and 52B, and the index obtained by this index calculation circuit 53 and the position of a normal welding line are displayed. By inputting the reference index shown, the comparison calculation circuit 54 for calculating the difference between the two indexes and how the superposition section 3 is displaced based on the deviation amount calculated by the comparison calculation circuit 54 are determined, and The correction data is output to the drive control unit 11 of the welding torch of the automatic welding device, and the shift determination circuit 55 is provided.

The method of detecting the overlapping portion 3 will be described below. First, the overlapping unit 3 is irradiated with laser light from the irradiator 6, and the reflected light is received by the optical fiber bundle 13.

Then, the statistical processing circuit 51 statistically processes the received light amount data to remove noise. next,
As shown in FIGS. 9A to 9F, the same position (X position)
In the Y direction center of gravity detection circuit 52A, the amount of received light received by the optical fibers 12 in each row (Y direction), that is, the center of gravity position in the Y direction is detected from the light intensity.

Then, similarly to this, FIG.
As shown in (c), the barycentric position (correctly referred to as a boundary position) in the X direction in each column (Y direction) refers to the boundary determination level (threshold value) to detect the barycentric direction in the X direction. It is detected by the circuit 52B.

Next, each of these centroid detection circuits 52A, 52
The center-of-gravity position and the boundary position detected in B are input to the index calculation circuit 53, where the left and right position shift indices and the upper and lower position shift indices are obtained.

For example, the average of the point F in the second column and the point G in the third column is obtained and used as the left and right position shift index. Further, as shown in (a) to (f) of FIG. 9, the received light amount in the Y direction, that is, the light intensity at each X position is obtained, and the average of these is calculated, and this average value is shifted in the vertical direction. Use as an index.

For example, if the position of the overlapping portion 3 is shifted upward, the state shown in FIG. 11B is obtained, and if it is shifted downward, the state shown in FIG. 11C is obtained, and the state is shifted to the right. Then, the state becomes as shown in FIG.
If it shifts to the left side, the state shown in FIG. In addition, FIG. 11A shows a state in which the overlapping portion 3 is in the correct position.

Then, each of these deviation indexes and the reference index indicating the normal state are compared by the comparison operation circuit 54, and the compared index values, that is, the deviation amount and deviation direction are input to the deviation judgment circuit 55, Here, the amount of deviation and the direction in which the deviation is made are determined, and correction data is output from the deviation determination circuit 55 to the drive control unit 11 of the welding torch of the automatic welding apparatus, and the welding torch is
Control is always performed so as to follow the overlapping portion, that is, the welding line 3.

As described above, the laser light reflected from the welded portion is received by the plurality of photodiodes arranged in the predetermined direction, and the position of the weld line, which is the welded portion, is detected based on the received light amount. Therefore, it is possible to detect the shift amount and the shift direction at a much higher speed than the one that uses a CCD camera device and image-processes the captured image, and the laser light is emitted by the light projecting lens. Since it is designed to expand, the structure can be made simpler than that of expanding the laser beam by, for example, a rotating mirror, and the device is very strong against mechanical vibration.

By the way, in each of the above embodiments, the deviation determining circuit outputs the correction data. However, for example, only the deviation amount and the deviation direction data are output to the drive control unit of the welding torch, The drive control unit may create correction data.

As the welded portion, the V-shaped groove and the overlapping portion are shown in the above-mentioned embodiments.
It can also be applied to other welds such as fillet welds.

[0040]

As described above, according to the detecting device and the detecting method of the present invention, the photodiodes arranged in the predetermined direction are used for irradiating the laser beam on the welded portion and detecting the reflected laser beam. At the same time, based on the amount of light received by each photodiode, the position of the light receiving center of gravity is obtained, and the position of the center of gravity is compared with the reference position of the normal welded portion, so that the amount of deviation and the direction of deviation are obtained. For example, as compared with the case of using a CCD camera device, the arithmetic processing circuit becomes very simple, and it is not necessary to shake the laser light like a rotating mirror, and therefore, the structure is strong against mechanical vibration and The device itself becomes inexpensive.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic overall configuration of a welding line detection device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an arithmetic processing unit in the welding line detection apparatus of the first embodiment.

FIG. 3 shows a concrete example of a welded portion in the first embodiment, wherein (a) is a perspective view and (b) is a sectional view thereof.

FIG. 4 is a graph showing how a laser beam is received from a welded portion in the first embodiment.

FIG. 5 is a diagram showing a displaced state of a welded portion in the first embodiment.

FIG. 6 shows a specific example of a welded portion in the second embodiment of the present invention, (a) is a perspective view and (b) is a sectional view thereof.

FIG. 7 is a sectional view showing how a laser beam is received from a welded portion in the second embodiment.

FIG. 8 is a block diagram showing a configuration of an arithmetic processing unit in the welding line detection apparatus according to the second embodiment.

FIG. 9 is a graph showing how a laser beam is received from a welded portion in the second embodiment.

FIG. 10 is a graph showing a light receiving state of laser light from a welded portion in the second embodiment.

FIG. 11 is a diagram showing a displaced state of a welded portion in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding line detection device 3 Welding line 5 Light emitting lens 6 Irradiator 7 Light receiving lens 8 Light receiver 9 Signal processing device 10 Arithmetic processing device 11 Drive control unit 12 Optical fiber 13 Optical fiber bundle 14 Photodiode 31 Statistical processing circuit 32 Centroid detection Circuit 33 Index calculation circuit 34 Comparison calculation circuit 35 Deviation determination circuit 41 Calculation processing device 51 Statistical processing circuit 52A Y direction centroid detection circuit 52B X direction centroid detection circuit 53 Index calculation circuit 54 Comparison calculation circuit 55 Deviation determination circuit

Claims (2)

[Claims] 1. An irradiator for irradiating a welded portion with a laser beam so as to have a predetermined spread through a light projecting lens, an optical fiber bundle for receiving the laser beam reflected by the welded portion, and an optical fiber bundle for the optical fiber bundle. A photodiode that detects the light from each optical fiber, a signal processing device that converts the electrical signal from each of these photodiodes into a DC signal, and the position of the welded portion is detected based on the DC signal obtained by this signal processing device. And a processing unit that calculates the amount of deviation with respect to the reference weld, and this processing unit detects the position of the center of gravity of light reception in the transverse section of the weld based on the DC signal input from the signal processing unit. The center of gravity detection circuit, an index calculation circuit that calculates a displacement index based on the position of the center of gravity obtained by this center of gravity detection circuit, and the displacement index obtained by this index calculation circuit A comparison operation circuit for comparing the reference index indicating the part position, weld detection apparatus characterized by being composed of a determined deviation determination circuit The resulting shift amount and shift direction in this comparison operation circuit. 2. A laser beam irradiating a welded portion through a light projecting lens so as to have a predetermined spread, and the reflected laser beam is a light beam in which a plurality of optical fibers are arranged in a predetermined array. It is detected by the photodiode through the fiber bundle, the electric signal from each of these photodiodes is converted into a DC signal, and the light receiving center of gravity position is detected in the cross section of the welded part based on this converted DC signal. A welding part detecting method, characterized in that a deviation index is calculated based on the above, the deviation index is compared with a reference index indicating a normal weld portion position, and the deviation amount and deviation direction obtained by this comparison are determined.