JPH0660809B2 - Joint detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a joint detection method using a visual sensor in an automatic welding device, an automatic sealing device, or the like, and particularly to irradiating a joint portion with slit light to produce a joint light. The present invention relates to a joint detection method in which a slit light image is picked up by an image pickup device and an image signal from the image pickup device is processed to detect the joint portion.

[Prior Art] In recent years, the automation of welding work and sealing work has been promoted for the purpose of high productivity and cost reduction. However, in order to obtain high quality welded joints and seals, it is necessary to use joints with high precision. We need technology to perform welding or sealing work while copying.

Therefore, conventionally, various joint detection methods have been tried for joint copying, and among them, the optical cutting method is a powerful method that enables non-contact and highly accurate joint copying. FIG. 4 is an overall configuration diagram showing a basic configuration of a joint detection device (method) for performing welding copying using this optical cutting method. The figure shows the welding base material 1b on the plane of the welding base material 1a. It shows a case where horizontal fillet welding with no groove is performed to weld T in a T shape.

In FIG. 4, reference numeral 3 denotes a slit light source such as a laser projector, which irradiates a joint portion (welding line) 2 with slit light 3a in a direction intersecting with the welding line 2 and welding base materials 1a and 1b.
A slit light image (light cutting line image) 3b in the direction of cutting the welding line 2 is formed on the top. Reference numeral 4 denotes an image pickup device, which picks up a slit light image 3b formed by the slit light source 3 and picks up the slit light image 3b (an example is shown by ABC in FIG. The image signal (video signal) including the position (corresponding to the position) is sent to the signal processing unit 5A. In this signal processing unit 5A, the address of the highest luminance level is obtained from the input video signal, the shape of the welding line 2 is obtained based on this address, and based on the difference between this shape and the reference shape data stored in advance. The drive device 6 is configured to perform welding by setting the position of the welding torch 7 so as not to shift from the welding line 2.

Further, FIG. 5 is a block diagram (Japanese Patent Laid-Open No. 59-202006) showing a specific configuration of a conventional signal processing unit 5A used in the above-mentioned optical disconnection type joint detecting device, and is shown in FIG. As described above, the signal processing unit 5A includes the imaging device 4
It is composed of a signal pre-processing unit 11 for extracting a slit light image from a slit image based on a video signal from the above, and an arithmetic processing unit 12 for obtaining its shape from the extracted slit light image. The configuration of the preprocessing unit 11 and the method of extracting the slit light image by the signal preprocessing unit 11 will be described.

The horizontal synchronizing signal generating circuit 13 and the vertical synchronizing signal generating circuit 14 of the signal preprocessing unit 11 are for synchronizing the image pickup device 4 and the signal processing unit 5A, and the video signal passes through the low-pass circuit 15. After passing through it to remove high-frequency noise, it is input to the peak hold circuit 16. The peak hold circuit 16 detects the maximum brightness level from the hold value of the video signal during one horizontal scanning line, and sends a signal indicating this maximum brightness level to the A / D conversion circuit 17 and the x-coordinate detection position counter 18. To do. Further, 19 is a comparison circuit, and the maximum luminance level is preset based on the digital video signal output from the A / D conversion circuit 17.
When the threshold value which is the brightness level in the slit light image is exceeded, a trigger signal is output to the position counter 18 to stop the counting operation of the position counter 18.

The position counter 18 counts the pulses from the pulse generation circuit 20 that generates a predetermined number of pulses between one horizontal scanning line, and the count value at the time of stopping upon receiving the trigger signal from the comparison circuit 19 is the maximum. The x-coordinate value of the brightness level point is output to the arithmetic processing unit 12, and the maximum brightness level signal from the peak hold circuit 16 is converted into a digital signal and output to the arithmetic processing unit 12. y-coordinate detection position counter 21
Counts the number of pulses of the horizontal synchronizing signal, and the counted value is y
The coordinate value is output to the arithmetic processing unit 12.

In this way, the x-coordinate value and the y-coordinate value obtained by the x-coordinate detection position counter 18 and the y-coordinate detection counter 21 are obtained.
The combination with the coordinate value is the brightest point of the slit light image on one horizontal scanning line forming the slit image.

The x-coordinate detection position counter 18 is cleared by the horizontal synchronizing signal, and the y-coordinate detection position counter 21
Is cleared by the vertical sync signal.

On the other hand, the arithmetic processing unit 12 uses the x-coordinate detection position counter 1
8 and a parameter related to the shape of the welding line 2 based on the count value from the y-coordinate detection position counter 21, and as shown in FIG. 6, a storage circuit 12a for storing the x-coordinate value and the x-coordinate value. A difference circuit 12b that calculates a difference value between a coordinate value and an adjacent x coordinate value, and if the difference value exceeds a reference value, the x and y coordinate values at that time are used as the bending point positions.
(Comparison circuit 12c for outputting as point B in FIG. 7).

As described above, the address (bending point) of the highest brightness level, that is, the shape of the welding line 2 is obtained in the signal processing unit 5A,
The drive device 6 drives the welding torch 7 based on this shape, and the welding operation (or sealing operation) is automatically performed while following the welding line 2 (joint portion).

[Problems to be Solved by the Invention] In the conventional joint detection method using such a light cutting method, when the slit light is radiated to the actual welding base materials 1a and 1b and an image thereof is captured, There is a problem of multiple reflected light as shown in the figure, and the slit light image extraction used in the prior art is impossible. That is, as shown in FIG. 8, the light emitted from the slit light source unit 3 and forming the slit light 3a and traveling in the direction of a is the surface texture of the welding base metal 1a at the position of the surface D of the welding base metal 1a. Diffuse reflection according to. Of the irregularly reflected light, the light that travels in the direction of b is observed by the imaging device 4 as one-time reflected light. The collection of the once-reflected light forms a slit light image, which is called in the prior art. However, what has proceeded in the direction of c at the position of the surface D is diffusely reflected again at the position of the surface E of the welding base metal 1b, and of these, what has proceeded in the direction of d is observed by the imaging device 4 as twice reflected light. Will be. Hereinafter, similarly, reflected light is generated three times or more and observed by the imaging device 4. Like this, 2
Due to the influence of multiple times of reflected light, the slit image generally shows a portion 48 due to the once reflected light as shown in FIG.
And a portion 47 due to multiple reflected light appears. Note that FIG. 9 shows a cislit optical image when the horizontal scanning line direction substantially coincides with the welding direction.

Here, due to the diffused reflection characteristics of the welding base materials 1a and 1b, and the positional relationship between the welding base materials 1a and 1b and the optical system including the image pickup device 4 and the slit light source device 3, multiple reflections than once reflected light are obtained. The light intensity (luminance) of the reflected light may be observed stronger. FIG. 10 shows the luminance distribution along the horizontal scanning line (for example, along the line XX in FIG. 9) in this case. In such a case, in the conventional technique, the peak hold circuit 16 is used.
The position of the peak P ₁ , which is the highest brightness level, is detected by the, and the trigger signal is output from the comparison circuit 19 at that position, so the x-coordinate detection position counter 18 forms a true slit light image by one reflection. There is a possibility that the position of the peak P ₁ due to multiple reflection may be erroneously recognized as a slit light image, instead of the peak P ₂ .

In addition, as described above, due to the diffused reflection characteristics of the welding base materials 1a and 1b and the positional relationship between the optical system and the welding base materials 1a and 1b, the light intensity of the multiple reflection light is not necessarily observed to be stronger than that of the single reflection light. Without being limited thereto, it is extremely difficult to predict the reference shape data of the slit light image in advance as in the conventional technique.

The present invention is intended to solve the above-mentioned problems, and prevents the image due to multiple reflection light from being erroneously recognized as a slit light image due to one-time reflection light, thereby enabling accurate detection of the joint portion. An object of the present invention is to provide a joint detection method.

[Means for Solving the Problems] Therefore, in order to achieve the above object, the joint detection method of the present invention determines a predetermined interval between one horizontal scanning line of image data depending on the scanning direction. The time point at which the signal level exceeds the threshold value is extracted, and the x coordinate value of the slit light image in one horizontal scanning line is obtained for each horizontal scanning line from the extraction timing, and the count value of the horizontal scanning line at that time From the above, the y coordinate value of the slit light image in the one horizontal scanning line is obtained for each horizontal scanning line, and then the obtained x coordinate value and the horizontal scanning line immediately before the one horizontal scanning line are obtained. The difference value with the x-coordinate value of the slit light image is obtained, and when the difference value does not exceed a preset difference limit value, the newly obtained x, y coordinate values correspond to the slit light image. To judge On the other hand, when the difference value exceeds the difference limit value, the slit light is determined from the image data while determining that the newly obtained x and y coordinate values do not correspond to the slit light image as abnormal values. The feature is that the shape of the image is obtained and the seam position is detected from the shape.

[Operation] In the joint detection method of the present invention described above, when the slit light is applied to the seam position and the image is picked up by the image pickup device, the multiple reflection light contained in the slit light image is different from the single reflection light. The fact that it always appears in only one direction is used. That is, when the horizontal scanning line direction and the welding direction are substantially the same direction, the time point at which the signal level first exceeds a predetermined threshold value corresponds to the x coordinate of the once reflected light, while the horizontal direction is the horizontal direction. When the scanning line direction and the welding direction are almost opposite to each other, the last time when the signal level exceeds the predetermined threshold value,
This corresponds to the x coordinate of the once-reflected light.

Therefore, by extracting the time point at which the signal level exceeds the predetermined threshold value at the beginning or at the end depending on the scanning direction, the image due to the multiple reflection light is excluded from the slit light image, and the true seam position is obtained. Only the position of the slit light image by the once-reflected light that indicates

In addition, x of the slit light image obtained for each horizontal scanning line
By determining whether the difference value between the coordinate value and the x coordinate value of the slit light image obtained for the previous horizontal scanning line exceeds a preset difference limit value, the seam position is formed and the slit is formed. When the slit light image is cut or discontinuous on the way due to the influence of scratches or surface properties on the work base material surface that reflects light, and multiple reflection light is mistakenly detected as a slit light image, etc. , The detected x coordinate value is excluded as an abnormal value. The seam position can be accurately detected from the shape of the slit light image thus obtained.

Embodiments of the Invention Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a signal processing unit of an apparatus to which a joint detecting method as a first embodiment of the present invention is applied.
The apparatus of this embodiment is basically the same as the conventional apparatus shown in FIG. 4 in its basic structure, but in this embodiment, the conventional signal processing unit 5A (see FIG. 5) is replaced by the arrangement shown in FIG. The signal processing unit 5 as shown is used.

However, in this embodiment, an industrial television camera or the like is used as the image pickup device 4, and the horizontal scanning line direction is arranged so as to substantially coincide with the welding direction as in the case shown in FIG. As a result, as shown in FIG. 9, if the video signal based on the once-reflected light is supplied before the video signal based on the multiple-reflected light and the time point at which the signal level first exceeds the threshold value is extracted, the true A slit light image will be obtained.

Based on such a principle, the signal processing unit 5 of the present embodiment
As shown in FIG. 1, a slit light image extraction unit 3 that removes multiple reflected light and extracts a true slit light image by one-time reflected light.
0 and a feature extraction unit 31 that detects a joint seam position by extracting a feature such as a bent portion from the slit light image obtained by the slit light image extraction unit 30.

Next, the configuration of the slit light image extraction unit 30 will be described in detail. In FIG. 1, 32 is an A / D converter for digitally converting the video signal from the image pickup device 4, 33 and 34 are horizontal synchronization signals and The horizontal synchronization signal generation circuit and the vertical synchronization signal generation circuit output the vertical synchronization signal to each circuit in the image pickup apparatus 4 and the signal processing unit 5 to synchronize the image pickup apparatus 4 and the signal processing unit 5.

Reference numeral 35 is a comparison circuit, which compares the predetermined threshold value set in advance in the threshold value register 42 by the feature output unit 31 with the video signal from the A / D converter 32 to determine if the video signal is threshold. If it is larger than the value, the position counter 36, which will be described later,
A count stop signal is output to 38. An x-coordinate detection circuit 36 counts the pulses of the pulse generation circuit 37 until it is cleared by the horizontal synchronization signal from the horizontal synchronization signal generation circuit 33 and receives a count stop signal from the comparison circuit 35, and outputs the count value as the current x-coordinate value. The position counter 38 is a y-coordinate detection position counter which counts the horizontal synchronizing signal of the horizontal synchronizing signal generating circuit 33 which is cleared by the vertical synchronizing signal from the vertical synchronizing signal generating circuit 34, and receives a count stop signal from the comparing circuit 35. The count value at that time is output to the feature extraction unit 31 as the current y coordinate value.

Further, 39 indicates the count value from the position counter 36 as x.
A difference circuit which is supplied as a coordinate value and obtains a difference value of the x coordinate value from the previous x coordinate value, 40 is a predetermined difference limit value preset in the difference limit value register 41 by the feature extraction unit 31 and a difference circuit 39 from the difference circuit 39. In the comparison circuit for comparing with the difference value, if the difference value is smaller than the difference limit value, the current x
While the coordinate value is bypassed to the feature extraction unit 31, when the difference value is larger than the difference limit value, the current x coordinate value is regarded as an abnormal value and both the current x and y coordinate values are excluded.

The slit light image extraction unit 30 is composed of the components indicated by the reference numerals 32 to 42.

The joint detecting method according to the first embodiment of the present invention is executed as follows by the apparatus having the above-mentioned configuration.

First, for each horizontal scanning line of image data obtained by the image pickup device 4 and digitally converted, the time point at which the video signal becomes a signal level exceeding a predetermined threshold value set in the threshold value register 42 is compared. Extracted by the circuit 35. At the extraction timing, the comparison circuit 35 moves the position counter 3
A count stop signal is output to 6 and 38, and the count values of the position counters 36 and 38 at that time are obtained as x and y coordinate values of the slit light image in the horizontal scanning line this time.

Then, the difference value between the current x-coordinate value obtained by the position counter 36 and the previous x-coordinate value is obtained in the difference circuit 39, and the difference value and the difference limit value register 41 in advance.
In the comparison circuit 40, the difference limit value set to (1) is compared.

When the difference value is smaller than the difference limit value as a result of the comparison by the comparison circuit 40, it is determined that the x-coordinate value of this time corresponds to the true slit light image (light image of the once reflected light). Then, the y-coordinate value from the position counter 38 is output to the feature extracting unit. On the other hand, when the difference value is larger than the difference limit value, the x-coordinate value of this time does not correspond to the true slit light image (light image of the light reflected once) and is determined as an abnormal value, and the x-value of this time is determined. , Y coordinate values are excluded.

At this time, an arithmetic unit such as the feature extraction unit 31 is used to interpolate the excluded x, y coordinate value portion by linear extrapolation or the like.

Based on the x and y coordinates of the slit light image thus extracted, the feature extraction unit 31 detects the features such as the bent portion and the cut portion of the slit light image, and the feature data given for each joint in advance. A feature that is a seam position is selected, and this is the seam position in the slit light image to be obtained. Based on the seam position detected by the feature extraction unit 31, the drive device 6 sets the position of the close torch (see reference numeral 7 in FIG. 4) so as not to deviate from the welding line, as in the conventional case, and performs welding.

As described above, according to the first embodiment of the present invention, the influence of flaws or surface properties on the surface of the work base material (reference numerals 1a and 1b in FIG. 4) that reflects slit light and the influence of multiple reflected light are provided. It is possible to obtain a slit light image based on only one reflected light without receiving the light and to accurately detect the seam position.

In addition, in the first embodiment, the case where the horizontal scanning line direction of the image pickup device 4 substantially coincides with the welding direction has been described. On the contrary, the image pickup device 4 is welded in the horizontal scanning line direction thereof. You may arrange | position so that it may correspond to the reverse direction of a direction substantially. However, in this case, a true slit light image can be obtained by extracting the time point at which the video signal of the once-reflected light is supplied after the video signal of the multiple-reflected light and the signal level finally exceeds the threshold value. Therefore, it is necessary to slightly change the configuration circuit.

That is, a buffer is provided in the position counter 36, and each time the comparison circuit 35 detects that the video signal exceeds a predetermined threshold value, the count value of the position counter 36 held in the buffer is updated. Then, when the next horizontal synchronizing signal is received, the count value held in the buffer is supplied to the difference circuit 39.

As a result, the time point at which the signal level finally exceeds the threshold value is extracted, and the slit light image by the once reflected light is obtained, and the same effect as that of the above-described embodiment is obtained.

Next, a joint detecting method as a second embodiment of the present invention will be described with reference to FIGS. 2 and 3, FIG. 2 is a block diagram showing a signal processing unit of an apparatus to which the joint detecting method is applied, and FIG. 4 is a flowchart for explaining the operation in FIG. In the second embodiment, a signal processing unit 50 as shown in FIG. 2 is used instead of the signal processing unit 5 according to the first embodiment.

The signal processing unit 50 includes the imaging device interface circuit 4
3, the image memory 44 and the image processing unit 45. The image pickup interface circuit 43 supplies a vertical synchronizing signal and a horizontal synchronizing signal to the image pickup device 4 to control the image pickup device 4, and also takes in a video signal from the image pickup device 4 in response to a command from the image processing unit 45 to obtain an image memory 44. This is written in sequence. Further, the image processing unit 45 detects the seam position from the slit image captured in the image memory 44 based on the flowchart shown in FIG.

Next, referring to FIG. 3, an operation (execution procedure of the joint detection method) by the apparatus having the above-described configuration will be described.

In FIG. 3, L is a predetermined threshold value, D is a difference limit value, Di, j is image data, and subscripts i and j are the x coordinate value and y coordinate value of the image data, and H is the subscript i. , V is the maximum value of the subscript j, and Sj is the x-coordinate value of the y-coordinate value j of the image data forming the slit light image.
Further, in the present embodiment, the direction in which the subscript i increases (horizontal scanning line direction) is in the same direction as the welding direction (that is, when the video signal by the once reflected light is supplied before the video signal by the multiple reflected light). ), The image data in the image memory 44 is referred to in this direction.

In the image processing unit 45, first, the threshold value L and the difference limit value D are set (step S1), and then the image data is loaded into the image memory 44 by the imaging device 4 (step S2). And the origin (i = 0, J = 0; upper left part of the screen)
After setting (step S3), the image data Di, j is read from the image memory 44 (step S4).

Then, it is determined whether the read image data Di, j is larger than the threshold value L (step S5). When the image data Di, j is smaller than the threshold value L, it is determined that the position of the slit light image has not yet been reached, and it is determined whether or not the i, which is the x coordinate, is the maximum value H. Perform (step S6). If i ≠ H is determined in step S6, the process returns to step S4 and the next x coordinate is i + 1.
On the other hand, if it is determined that i = H while performing the process of (step S7), the x coordinate of the slit light image is not detected for the j coordinate which is the y coordinate at this time, and the process proceeds to step S10 described later.

On the other hand, when it is determined in step S5 that the image data Di, j is larger than the threshold value L, i at that time is determined.
Is the x coordinate value Sj of the y coordinate value of j (step S8), the y coordinate value is j-1 in step S9.
The difference value | Sj-Sj-1 | with the x-coordinate value Sj-1 of the object is obtained and compared with the difference limit value D. Where the difference value |
When it is determined that Sj-Sj-1 | is smaller than the difference limit value D, the process proceeds to step S11 described later, while it is determined that the difference value | Sj-Sj-1 | is larger than the difference limit value D. If the y coordinate value is j, the present x coordinate value Sj is judged to be an abnormal value, and step S
10, the x coordinate values Sj-1 and Sj of the previous time and the time before the last time
Using -2, the interpolated value 2Sj-1-Sj-2 by the first-order extrapolation is obtained as the current x coordinate value Sj.

Then, in step S11, it is determined whether or not j, which is the y coordinate, has the maximum value V. Where j
If it is determined that V is not equal to V, the process returns to step S4 and the same process is performed from i = 0 for j + 1 which is the next y coordinate (step S12). If it is determined that j = V, one screen is scanned. When it is determined that the process is completed, joint detection is performed by feature extraction (step S13).

Thus, according to the second embodiment of the present invention, the first
It is possible to obtain the same effect as that of the embodiment.

In the second embodiment, the case where the direction in which the subscript i increases is the same as the welding direction is explained, but the coordinates of the slit light image can also be determined by referring to the image data in the opposite direction. It is possible to extract.

Further, although the joint detection method according to the present invention is applied to the entire slit image in both the first and second embodiments, the joint detection method can be applied only to a specific area.

For example, an area of a predetermined size is set such that the seam position obtained for the previous screen is the center of the area, and several horizontal scan lines before and after the horizontal scan line that starts the slit light image extraction operation are set. The signal level of the image data having the same x coordinate value of the line may be averaged to obtain the image data forming the first slit light image. Further, the processing according to the present invention may not be applied to all the horizontal scanning lines of the image data, but the processing may be applied every several lines.

[Effects of the Invention] As described in detail above, according to the joint detection method of the present invention,
When the slit light is radiated to the seam position and the image is picked up by the image pickup device, the multiple reflection light included in the slit light image always appears in only one direction with respect to the once reflection light. By extracting the time point at which the signal level exceeds the predetermined threshold at the beginning or at the end, the image due to the multiple reflection light is eliminated from the slit light image, and the single reflection indicating the true seam position is performed. Since only the position of the slit light image by light is extracted, and the abnormality of the x-coordinate value can be determined from the difference value between the current x-coordinate value and the previous x-coordinate value, the work mother that reflects the slit light can be determined. The slit light image can be obtained by only the single reflected light without being affected by the flaws and surface properties on the material surface and the influence of the multiple reflected light, and the joint position can be accurately detected.

[Brief description of drawings]

1 and 2 show the first and second aspects of the present invention, respectively.
FIG. 4 is a block diagram showing a signal processing unit of an apparatus to which the joint detection method as an embodiment is applied, FIG. 3 is a flow chart for explaining the operation of the apparatus according to the second embodiment, and FIG.
FIG. 5 is an overall configuration diagram showing a basic configuration of a conventional joint detection device (method) for performing welding copying using an optical cutting method. FIG. 5 is a block diagram showing a signal processing unit of the conventional device. 6 is a block diagram showing an arithmetic processing unit in the signal processing unit, FIG. 7 is a diagram showing one frame of a picked-up image in the above-mentioned conventional example, FIG. 8 is a diagram for explaining multiple reflected light, and FIG. Is a diagram showing a slit light image including multiple reflected light,
FIG. 10 is a graph showing the luminance distribution along the line XX in FIG. In the figure, 4 ... Imaging device, 5 ... Signal processing unit, 6 ...
... Drive device, 30 ... Slit light image extraction unit, 31 ... Feature extraction unit, 32 ... A / D converter, 33 ... Horizontal synchronization signal generation circuit, 34 ... Vertical synchronization signal generation circuit, 35 ...
Comparator circuit, 36 ... Position counter for detecting x coordinate, 37 ...
... pulse generation circuit, 38 ... y-coordinate detection position counter, 39 ... difference circuit, 40 ... comparison circuit, 41 ... difference limit value register, 42 ... threshold value register, 43 ...
... image pickup device interface circuit, 44 ... image memory,
45 ... Image processing unit, 50 ... Signal processing unit.

Claims (1)

[Claims] 1. A joint for forming required position information by imaging a slit light image formed by irradiating a joint seam position with slit light by an imaging device and performing signal processing on image data obtained from the imaging device. In the detection method, between the horizontal scanning lines of the image data, the time point at which the signal level exceeds a predetermined threshold value is first or last extracted according to the scanning direction, and the horizontal scanning line is extracted from the extraction timing. The x-coordinate value of the slit light image in each horizontal scanning line is obtained for each horizontal scanning line, and the y-coordinate value of the slit light image in the one horizontal scanning line is calculated for each horizontal scanning line from the count value of the horizontal scanning lines at that time. Then, the difference value between the obtained x-coordinate value and the x-coordinate value of the slit light image obtained for the horizontal scanning line immediately before the one horizontal scanning line is obtained. When the difference limit value set for the slit light image is not exceeded, it is determined that the newly obtained x and y coordinate values correspond to the slit light image, while when the difference value exceeds the difference limit value, Obtaining the shape of the slit light image from the image data and determining the seam position from the shape while judging that the newly obtained x and y coordinate values are abnormal values and does not correspond to the slit light image. A joint detection method characterized by the above.