JP5744933B2 - Welding sensor - Google Patents

Description

  The present invention relates to a welding sensor that measures a groove shape of a welding workpiece and a position of a welding line based on an image obtained by imaging a slit light irradiated to a welding workpiece from a light projecting unit. The present invention relates to a welding sensor capable of detecting an abnormality occurring in the sensor itself using an image of light.

  Conventionally, a welding torch is attached to an industrial robot or the like, and automatic welding is performed while a shielding gas such as an inert gas is emitted from the periphery of the welding torch. When performing automatic welding, a welding sensor is used to measure the position of the welding workpiece, the groove shape, the position of the weld line, and the like. This welding sensor is often attached to the arm of an industrial robot together with a welding torch.

As a welding sensor, an image sensor that obtains the shape data of a welded part by irradiating the welding work with slit light emitted from a projector and capturing the reflection (light cutting line) of the slit light with an imaging unit (camera) Is used.
Such an image sensor stores the above-described projector and imaging unit inside a casing, and a translucent window plate (protective body) is provided on the front surface of the casing (the side facing the welding workpiece). ing. This window plate has a role of protecting the projector and the imaging unit from spatter, fume, dust and the like generated by welding.

  Now, when welding is performed while detecting the shape of the welding workpiece using such an image sensor, the surface of the window plate becomes dirty due to spatter and fume deposition and deposition as welding progresses. Due to this dirt, the slit light emitted from the projector is blocked and does not reach the welding workpiece, and the slit light reflected by the welding workpiece is blocked and does not reach the imaging unit, so accurate shape data of the welding site is obtained. I can't do that. In order to avoid this inconvenience, a shielding plate for shielding spatter and fume is provided between the welding torch and the welding sensor, but the shielding effect is not perfect.

Therefore, in the welding sensor, it is necessary to develop a technology for judging the replacement timing of the window plate against the contamination of the window plate that protects the projector and the imaging unit from spatter, fume, dust, and arc light generated by welding. Yes.
Patent Document 1 discloses a technique for determining the replacement time of an arc sensor protection window (window plate).

  The arc sensor protection window replacement method disclosed in Patent Document 1 is provided with a standard reflecting surface at a predetermined distance from the front surface of the arc sensor protection window attached to the arc sensor, and when the arc sensor protection window is not used, A laser beam is scanned on the standard reflecting surface to detect a first received light amount of the reflected light. After the arc sensor protective window is used for arc welding, the laser beam is scanned on the standard reflecting surface and reflected. A second received light amount of light is detected, and a replacement time of the arc sensor protection window is determined based on the first received light amount and the second received light amount.

JP-A-4-307339

  The technique disclosed in Patent Document 1 irradiates a standard reflection surface as a reference surface prepared in advance with a laser beam (point laser), detects the luminance at the standard reflection surface with a light receiving element, and further welds. After the operation, the brightness of the irradiated point laser is detected by a light receiving element, and the brightness before and after welding is compared to detect the degree of contamination of the arc sensor protection window (window plate).

However, in the technique of Patent Document 1, since a point laser is used and a PD (photodiode) is used as a light receiving element, only a change in luminance in a narrow region of the window plate is detected, and the entire imaging screen is detected. Brightness change, that is, contamination in a wide area of the window plate cannot be detected.
In addition, the technique of Patent Document 1 has a problem that it is impossible to check the thickness (light width) of laser light, which is an important element of detection accuracy, and to detect other problems such as distortion of a shielding plate.

  That is, when the brightness of the laser beam decreases or the thickness or width of the laser beam widens due to the deterioration of the projector itself, the quality of the laser beam itself decreases. This makes it difficult to distinguish between them and causes a problem that the detection rate of the light cutting line is lowered. However, the technique of Patent Document 1 cannot detect such a deterioration in the quality of the laser beam itself. In the first place, until now, there has been no technique for detecting a failure of the sensor itself represented by a deterioration in the quality of the laser beam itself in the welding sensor.

  The present invention has been made in view of the above-described problems, and is a welding sensor using a technique of a light cutting method, and an abnormality that has occurred in the welding sensor itself using an image of slit light captured by the welding sensor. It is an object of the present invention to provide a welding sensor capable of detecting the above.

In order to achieve the above object, the present invention employs the following technical means.
A welding sensor according to the present invention includes a light projecting unit that irradiates a welding work with slit light, and an imaging unit that images the welding work irradiated with the slit light. In the meantime, a transparent window plate is provided so that the welded workpiece irradiated with the slit light can be imaged, and the shape measurement of the welded workpiece is performed based on the image including the slit light imaged by the imaging unit. A composite image creating unit that is a possible welding sensor and creates an integrated image obtained by integrating the slit light imaged by the imaging unit and a reference integrated image obtained by integrating the reference slit light And a difference image generation unit that generates a difference image by taking a difference between the integrated image generated by the composite image generation unit and the reference integrated image, and luminance information of the difference image generated by the difference image generation unit Based on An abnormality determination unit that determines an abnormality of the plate, provided with a, an image storage section for storing a plurality of images existing slit light at any position across the other side from the one side of the field of view of the imaging unit, respectively And the synthesized image creating unit accumulates a plurality of images accumulated in the image accumulating unit to create an accumulated image and / or a reference accumulated image .

Here, the reference accumulated image, the window plate in the normal state, the imaging unit but it may also be an image obtained by integrating the detection light captured.

The welding sensor according to the present invention includes a light projecting unit that irradiates a welding work with slit light and an imaging unit that images the welding work irradiated with the slit light, and the light projecting unit, the imaging unit, and the weld Between the workpieces, a window plate having transparency is provided so that the welded workpiece irradiated with the slit light can be imaged, and the shape of the welded workpiece is based on the image including the slit light imaged by the imaging unit. A welding sensor capable of measurement, an image accumulating unit for accumulating a plurality of images each having slit light at any position from one side to the other side of the field of view of the imaging unit, and the image accumulating unit A luminance distribution acquisition unit that acquires a luminance distribution in a direction along the line width of the slit light on the image based on the image accumulated in the unit, and the image based on the luminance distribution acquired by the luminance distribution acquisition unit Upper slit light linearity A linear degree detecting unit for detecting, based on the straightness of the straight line detecting unit detects the abnormality determination unit that determines an abnormality of the window pane and / or the light projecting unit, characterized in that is provided.

  Here, based on the luminance distribution acquired by the luminance distribution acquisition unit, there is a line width detection unit that detects the line width of the slit light on the image, and the abnormality determination unit is detected by the line width detection unit The abnormality of the window plate and / or the light projecting unit may be determined based on the line width.

  According to the welding sensor of the present invention, in the welding sensor using the technique of the optical cutting method, it is possible to detect an abnormality occurring in the welding sensor itself using an image of slit light imaged by the welding sensor.

It is a figure which shows schematic structure of the welding sensor and welding torch by this invention. It is a block diagram which shows the structure of the signal processing part provided in the welding sensor. It is a figure explaining the production | generation order of a difference image. It is explanatory drawing which shows the procedure which images the image before use and the image after use. It is a figure which shows the graph showing the relationship between a laser output and a luminance value. It is a figure which shows the processing flow of the abnormality determination using a difference image. It is a figure explaining the derivation order of a luminance distribution curve. It is a figure which shows the processing flow of abnormality determination using a luminance distribution curve.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
In addition, embodiment described below is an example which actualized this invention, Comprising: The structure of this invention is not limited with the specific example. Therefore, the technical scope of the present invention is not limited to the contents disclosed in the present embodiment.
Before describing the welding sensor 1 according to the present embodiment, first, a welding manipulator (welding robot) to which the welding sensor 1 is attached will be described. Note that the welding sensor 1 according to the present embodiment may be attached to a welding-dedicated machine or the like instead of the welding robot.

  The welding manipulator to which the welding sensor 1 is attached is a vertical 6-axis multi-joint robot having a welding torch T for welding the welding workpiece W at the tip, and a weld line of a groove formed by two welding workpieces W ( Arc welding is performed along the welding direction. In the vicinity of the welding torch T of the welding manipulator, a welding sensor 1 for measuring the shape of the groove formed by the two welding workpieces W is arranged. The shape of the groove of the welding workpiece W is measured by the welding sensor 1, and two welding workpieces W are joined to each other by arc welding based on the measured shape data of the groove.

As shown in FIG. 1, during arc welding by the welding torch T, scattered matter such as spatter and fume scatters from the arc point X (tip) by the welding torch T.
Therefore, since the welding sensor 1 arranged in the vicinity of the welding torch T is exposed to an atmosphere in which spatter and fume exist, the welding sensor 1 has a casing (sensor housing) in which the projector 11 and the imaging unit 12 are built. ) 10 and on the front surface of the sensor housing 10 (between the projector 11 and the imaging unit (camera) 12 and the welding workpiece W), a protective window plate 13 that shields scattered objects from the welding torch T during arc welding. Similarly, a protective shielding plate 14 that protects the protective window plate 13 by blocking scattered matter from the welding torch T is provided as a protective body.

Below, the detail of the welding sensor 1 is demonstrated, referring FIG.1 and FIG.2.
FIG. 1 shows a welding torch T and a welding sensor 1, and the welding sensor 1 is attached to the hand of the welding manipulator and in the vicinity of the welding torch T.
The welding sensor 1 has a projector (laser light source) 11 that irradiates the welding work W with sheet light and an imaging unit (camera) 12 that captures line light that is reflection of the sheet light irradiated onto the welding work W. Thus, the groove shape of the welding workpiece W and the position of the welding line can be measured three-dimensionally.

  Furthermore, the welding sensor 1 includes a sensor housing 10 incorporating the projector 11 and the camera 12, and a protection attached to the welding workpiece W side so as to close the sensor housing 10 incorporating the projector 11 and the camera 12 so as to be isolated from the outside. A window plate 13 (hereinafter simply referred to as a window plate 13) and a protective shielding plate that is provided outside the sensor housing 10 in the vicinity of the window plate 13 on the welding torch T side and shields scattered objects from the arc point X of the welding torch T. 14 (hereinafter simply referred to as a shielding plate 14).

The projector 11 built in the sensor housing 10 outputs sheet-like detection light (slit light) having a laser semiconductor element as a light source toward the window plate 13 at a predetermined angle. The emitted slit light is emitted to the outside of the sensor housing 10 through the window plate 13 and irradiated to the groove portion of the welding workpiece W.
The camera 12 is an area camera such as a CCD (charge coupled device) camera, and images the surface of the welding workpiece W including slit light irradiated so as to intersect the groove of the welding workpiece W. That is, the detection light reflected by the welding workpiece W (slit light obtained by optically cutting the groove portion) enters the sensor housing 10 through the window plate 13 and is imaged by the camera 12. Thus, the detection light incident on the camera 12 is captured as image data.

  The projector 11 and the camera 12 are provided such that the slit light output from the projector 11 is reflected on the welding workpiece W and is incident on the camera 12 as detection light. The irradiation axis of the projector 11 and the camera 12 The optical axis is at a predetermined angle. Therefore, if the optical cutting method is used for the detection light imaged by the camera 12, the groove shape of the welding workpiece W is three-dimensionally detected by detecting the displacement of the coordinates along the longitudinal direction of the detection light in the image data. Can be measured.

The sensor housing 10 containing the projector 11 and the camera 12 is a substantially rectangular parallelepiped housing, and the front side (welding workpiece W side) of the projector 11 and the camera 12 incorporated therein is an opening.
As shown in FIG. 1, a protective window plate (window plate) 13 is provided on the sensor housing 10 so as to cover the opening of the sensor housing 10 immediately before the projector 11 and the camera 12, and the protective shielding plate 14 ( A shielding plate 14) is provided at a position closest to the welding torch T on the welding workpiece W side of the sensor housing 10.

The window plate 13 is, for example, an optical filter that transmits the slit light emitted from the projector 11 toward the outside of the sensor housing 10 and transmits the detection light reflected by the welding workpiece W toward the inside of the sensor housing 10. It is a member.
The shielding plate 14 is a plate-like member made of a transparent resin or the like, and has a shape and a size that can block scattered matter and the like flying directly from the arc point X of the welding torch T to the window plate 13. For example, the shielding plate 14 is a plate that is bent in a substantially “<” shape in a direction away from the welding torch T in a side view.

As a result, when the window plate 13 is viewed from the arc point X, the window plate 13 is hidden behind the shielding plate 14, so that scattered objects from the arc point X can be prevented from reaching the window plate 13.
As shown in FIG. 1, the welding sensor 1 having the above-described configuration is based on the reflected image of the slit light captured by the camera 12, such as abnormalities (that is, the window plate 13, the shielding plate 14, and the projector 11). And a signal processing unit 2 for detecting an abnormality occurring in the welding sensor 1 itself.

As described above, since the welding sensor 1 measures the groove shape of the welding workpiece W in three dimensions, the signal processing unit 2 includes a three-dimensional measurement unit (not shown).
The three-dimensional measuring unit measures the three-dimensional shape of the groove of the welding workpiece W in a non-contact manner based on the principle of the optical cutting method. The light cutting method uses the fact that when the surface shape of the welding workpiece W changes, the position of the detection light in the imaging area of the camera 12 changes according to the vertical displacement of the surface. The amount of displacement of the surface is obtained by triangulation using the amount of change in the position of the projector 11, the angle formed by the irradiation axis of the projector 11 and the optical axis of the camera 12, and the distance from the welding workpiece W to the camera 12. This is a method for measuring the three-dimensional shape.

FIG. 2 is a block diagram showing a configuration for detecting an abnormality occurring in the welding sensor 1 itself among the configurations of the signal processing unit 2.
Referring to FIG. 2, the signal processing unit 2 accumulates an image before use of the welding sensor 1 (image before use) captured by the camera 12 and an image after use of the welding sensor 1 (image after use). 20, a pre-use image stored by the image storage unit 20, and a composite image creation unit 21 that composites the post-use image, and a composite that stores the pre-use image and the post-use image synthesized by the composite image creation unit 21. An image storage unit 22, a difference image generation unit 23 that generates a difference image that is a difference between the pre-use image and the post-use image, and the window plate 13, the shielding plate 14, and the sensor based on the difference image generated by the difference image generation unit 23 An abnormality determination unit 24 for determining abnormality of the arc point X is provided.

Such a processing path from the image storage unit 20 to the abnormality determination unit 24 through the difference image generation unit 23 is referred to as a difference image determination path. The difference image discrimination path will be described in detail later.
Further, the signal processing unit 2 is a slit extraction unit 25 that extracts detection light that is slit light from the pre-use image and the post-use image stored by the image storage unit 20, and the detection light extracted by the slit extraction unit 25 is the slit extraction image. For each pixel recorded by the slit position pixel recording unit 27, the slit position pixel recording unit 27 for recording the luminance of the pixel at the slit position in the slit extraction image stored by the slit extraction image storage unit 26, A luminance distribution curve deriving unit 28 for deriving a luminance distribution curve in a direction crossing the slit extracted image based on the luminance of the slit, and a line width of the slit extracted image based on the luminance distribution curve derived by the luminance distribution curve deriving unit 28 A laser line width deriving unit 29 for deriving the line width is provided.

The abnormality determination unit 24 determines the abnormality of the lens of the window plate 13 and the projector 11 by evaluating the linearity of the slit extracted image based on the luminance distribution curve derived by the luminance distribution curve deriving unit 28, and derives the laser line width. An abnormality in the laser line width is determined by evaluating the laser line width derived by the unit 29.
Such a processing path from the image storage unit 20 through the luminance distribution curve deriving unit 28 to the abnormality determination unit 24 is referred to as a luminance distribution determination path. The luminance distribution determination path will be described in detail later.

With reference to FIGS. 2 to 6, the difference image determination path that is a processing path from the image storage unit 20 to the abnormality determination unit 24 through the difference image generation unit 23 will be described.
As shown in FIG. 2, the image accumulating unit 20 images the reference plane on the welding workpiece W before using the welding sensor 1 and without any abnormality in the window plate 13, the shielding plate 14, and the projector 11. A first accumulator that accumulates an image as a pre-use image (reference image) and a first sensor that accumulates an image obtained by imaging the same reference surface on the welding workpiece W as a post-use image (determination image) after using the welding sensor 1. 2 It has a storage part.

The pre-use image stored in the first storage unit is captured as follows.
A reference plane is provided on the surface of the welding workpiece W, and the reference plane is captured in the field of view (frame) of the camera 12. FIG. 3 shows an image G (0), an image G (m), and an image G (M) captured by camera pixels arranged in N rows and M columns. In each of the images G (0) to G (M), detection light extending from the 0th row to the Nth row is captured. For example, in the image G (m), the detection light is in the m-th column. Since the image is captured by the camera pixel, it is shown as an image K (m).

Such an image K is imaged by operating the welding sensor 1 as follows.
As shown in FIG. 4, the image K is obtained by imaging the reference plane while moving the welding sensor 1 capturing the reference plane in the field of view (frame) of the camera 12 in a direction perpendicular to the reference plane. That is, if the irradiation axis of the projector 11 is at a predetermined angle with respect to the optical axis of the camera 12 and the distance between the camera 12 and the reference plane changes, the position of the detection light in the field of view of the camera 12 changes. . Accordingly, if the reference surface is continuously imaged while moving the welding sensor 1 in the direction perpendicular to the reference surface, each of the images G (0) to G (M) can be imaged.

  Specifically, first, as shown in FIG. 4 (a), the slit which the welding sensor 1 is irradiated with the slit light from the projector 11 to one end of the visual field of the camera 12 on the reference plane and reflected by the reference plane. The light is moved to a position where it is captured as detection light in the 0th row of camera pixels. Thereafter, the welding sensor 1 is lowered from the position shown in FIG. 4A, and as shown in FIG. 4B, the detection light passes through a position where the detection light is captured in the m-th column of the camera pixels, and then FIG. ), The slit light from the projector 11 is applied to the other end of the field of view of the camera 12, and the slit light reflected by the reference plane is lowered to a position where it can be captured as detection light in the Mth column of the camera pixels.

In this process, the camera 12 of the welding sensor 1 images the reference plane at a timing (frequency) at which each of the 0th to Mth columns of camera pixels captures the detection light, and the detection light is in the 0th column of the camera pixels. Each of the image K (0) to the image K (M) in each column of the Mth column is stored in the first storage unit as a pre-use image.
The after-use image stored in the second storage unit is captured as follows.

  That is, after performing a welding operation for a predetermined time, a similar method (an image in which slit light is reflected while the welding sensor 1 is moved in the vertical direction is continuously applied to a reference surface obtained by imaging a pre-use image. The reference plane is imaged at a timing (frequency) at which each of the 0th to Mth columns of the camera pixels captures the detection light, and each of the 0th to Mth columns of the camera pixels is detected by the detection light. The images K ′ (0) to K ′ (M) are stored in the second storage unit as post-use images.

  Referring to FIG. 3, the composite image creation unit 21 integrates the images K (0) to K (M) that are the pre-use images accumulated by the first accumulation unit of the image accumulation unit 20 to obtain an image K ( A reference plane image (reference integrated image) G (b) in which the detection lights of 0) to K (M) are arranged from the 0th column to the Mth column is generated. In addition, the composite image creation unit 21 integrates the images K ′ (0) to K ′ (M), which are the used images accumulated by the second accumulation unit of the image accumulation unit 20, and obtains the image K ′ (0). A luminance image (integrated image) G (a) in which the detection lights of the images K ′ (M) are arranged from the 0th column to the Mth column is generated. The term “integration” used herein refers to creating an image in which brighter pixels are enabled by performing an OR operation between the images.

As shown in FIG. 3, the reference plane image G (b) is one image as pre-use luminance information, and the luminance image G (a) is one image as post-use luminance information.
In the reference plane image G (b), on the right side of the plane of FIG. 3, there is luminance unevenness that is a region where the luminance is partially low or high. On the other hand, in the luminance image G (a), an island-shaped luminance unevenness is present on the left side of the luminance unevenness also existing in the reference plane image G (b). This island-shaped brightness unevenness is an example of brightness unevenness generated due to dirt or deformation of the protective window plate 13 after the welding sensor 1 is used.

The composite image storage unit 22 stores the reference plane image G (b) and the luminance image G (a) generated by the composite image creation unit 21 through the above-described procedure.
The difference image generation unit 23 takes the difference between the reference plane image G (b) and the luminance image G (a) accumulated by the composite image accumulation unit 22 and generates a difference luminance image D (a). As shown in FIG. 3, the difference luminance image D (a) is obtained as one image showing a luminance difference that is a difference between luminance values (luminance information) between the reference plane image G (b) and the luminance image G (a). It is done.

  Since the luminance value of each column of the difference luminance image D (a) is the difference between the luminance values of the reference image G (b) and the luminance image G (a), the luminance value indicated by the difference luminance image D (a) is large. It can be determined that the luminance value of the luminance image G (a) is smaller than the luminance value of the reference image G (b). This can be considered that the luminance value of the luminance image G (a) is smaller than that of the reference image G (b) due to contamination of the window plate 13.

  The abnormality determination unit 24 determines whether or not the peak luminance value of the difference luminance image D (a) generated by the difference image generation unit 23 is 137 gradations or more with respect to 255 gradations. In addition, if the luminance value is less than 137 gradations, the abnormality determination unit 24 has no abnormality in the window plate 13 because the difference between the luminance values of the reference image G (b) and the luminance image G (a) is small. If the luminance value is 137 gradations or more, the difference between the luminance values of the reference image G (b) and the luminance image G (a) is large, and it is determined that the window plate 13 is abnormal. The reason why the gradation of the luminance value is used in order to determine the abnormality of the window plate 13 and 137 is selected as the gradation value as the reference for the determination will be described below.

FIG. 5 is a graph showing the relationship between the laser output of the projector 11 and the luminance value of 255 gradations obtained by experiment. The graph of FIG. 5 shows the image of the machined surface while changing the output of the slit light applied to the machined surface, detects the peak of the luminance value of each captured image in which the detection light is imaged, and then captures each imaged image. The peak of the luminance value with respect to the laser output of the image is shown.
According to the experimental result shown in FIG. 5, it is shown that the detection light image in the captured image can be discriminated if the peak of the luminance value is 91 gradations or more in all 255 gradations. Based on this experimental result, if the peak of the luminance value in the difference luminance image D (a) that is the difference between the reference surface image G (b) and the luminance image G (a) is 91 gradations or more, the reference surface image It can be considered that there is a significant difference in luminance value between G (b) and the luminance image G (a).

That is, by determining the luminance value of the difference luminance image D (a), if the luminance value peak is 91 gradations or more, the images K ′ (0) to K ′ (M) that are the used images are integrated. It can be determined that the luminance image G (a) thus obtained has changed significantly from the reference plane image G (b), and that there is a possibility that some change has occurred in the window plate 13 of the welding sensor 1.
Therefore, the abnormality determination unit 24 secures a margin of 50% with respect to the 91 gradations, and the luminance value peaks of the difference luminance image D (a) are 137 gradations (91 gradations) in all 255 gradations. Less than 150%), it is determined that there is no abnormality in the window plate 13.

  Further, if the luminance value is 137 gradations or more, the abnormality determination unit 24 detects a variation in the luminance value from the 0th column to the Mth column of the difference luminance image D (a), and the luminance value of each column is Whether the luminance values are evenly reduced (whether a substantially constant luminance value is detected in the differential luminance image D (a)), or is the luminance value reduction biased only in some columns (differential luminance image D ( Whether or not a large luminance value change is partially detected in a) is determined, and if there is no deviation, an abnormality in the welding arc point X, purge air, or shielding plate 14 is notified.

Further, the abnormality determination unit 24 determines the elapsed time from the previous replacement of the window pane when there is a bias in the decrease in the luminance value of each column in the difference luminance image D (a). If only a few minutes have passed since the previous replacement of the plate window, the window plate 13 cannot be contaminated by normal welding, so it is determined that the purge air flow rate or the output of the projector 11 is abnormal.
Hereinafter, the operation of the difference image determination path in the signal processing unit 2 will be described with reference to the flowchart of FIG.

The signal processing unit 2 moves the welding sensor 1 to a position on the reference plane shown in FIG. 4A and captures the detection light in the m-th column (m-th column of pixels) of the frame of the camera 12. (M) is imaged, and the image K (m) is stored in the first accumulation unit of the image accumulation unit 20 as a pre-use image (step S10, hereinafter referred to as S10).
The signal processing unit 2 moves the welding sensor 1 from the position shown in FIG. 4A to the position shown in FIG. 4C through the position shown in FIG. (M + 1) is imaged and stored in the first storage unit of the image storage unit 20 (S11).

The signal processing unit 2 determines whether or not the imaging of the image K (M) in which the detection light is captured in the Mth column (Mth column of pixels) of the frame of the camera 12 is finished (S12).
If the imaging of the image K (M) is not completed in step S12, the signal processing unit 2 returns to step S10 and captures the next image K. If the imaging of the image K (M) has been completed, the acquisition of the pre-use image is terminated, and the process proceeds to step S13, which is the next process.

The composite image creation unit 21 integrates the images K (0) to K (M) stored by the first storage unit of the image storage unit 20 to synthesize the reference image G (b), and the composite image storage unit 22. (S13).
After the welding operation is completed, the signal processing unit 2 moves the welding sensor 1 to the position on the reference plane shown in FIG. 4A again, and the m-th column (m-th column of pixels) of the frame of the camera 12. The image K ′ (m) capturing the detection light is captured, and the image K ′ (m) is stored in the second storage unit of the image storage unit 20 as a post-use image (S14).

The signal processing unit 2 moves the welding sensor 1 from the position shown in FIG. 4A to the position shown in FIG. 4C through the position shown in FIG. '(M + 1) is imaged and stored in the first storage unit of the image storage unit 20 (S15).
The signal processing unit 2 determines whether or not the imaging of the image K ′ (M) in which the detection light is captured in the M-th column (M-th column of pixels) of the frame of the camera 12 is finished (S16).

If the imaging of the image K ′ (M) has not been completed in step S16, the signal processing unit 2 returns to step S14 and images the next image K ′. If the imaging of the image K ′ (M) has been completed, the acquisition of the used image is terminated, and the process proceeds to step S17 which is the next process.
The composite image creation unit 21 integrates the images K ′ (0) to K ′ (M) stored by the second storage unit of the image storage unit 20 to synthesize the luminance image G (a), and stores the composite image. The data is stored in the unit 22 (S17).

When the acquisition of the after-use image in step S17 is completed, the abnormality determination unit starts an abnormality determination process for determining an abnormality of the welding sensor 1 (S18).
When the abnormality determination unit starts the abnormality determination process, the difference image generation unit 23 generates a difference luminance image D (a) that is a difference image between the reference image G (b) and the luminance image G (a) (S180).
The abnormality determination unit detects the peak of the luminance value in the difference luminance image D (a), and determines whether or not there are 137 gradations or more (S181).

If it is not determined in step S181 that the gradation is 137 or more, the abnormality determination unit determines that there is no abnormality in the window plate 13, and ends the series of processes from step S180 (S182).
If it is determined in step S181 that there are 137 gradations or more, the abnormality determination unit refers to the luminance value of each column of the difference luminance image D (a) and determines whether or not the dirt on the window plate 13 is biased. Judgment is made (S183). If the luminance value of each column of the difference luminance image D (a) indicates a substantially equal value, the abnormality determining unit decreases the luminance value of the luminance image G (a), which is a post-use image, almost uniformly over the entire image. Therefore, it is determined that the dirt on the window plate 13 is not biased. In addition, the abnormality determination unit determines that the dirt on the window plate 13 is biased if the decrease in the brightness value is biased only in a part of the columns of the difference luminance image D (a).

  In step S183, when it is determined that the dirt on the window plate 13 is biased, the abnormality determination unit determines that the positional relationship between the welding sensor 1 and the arc point X is abnormal or the shielding plate 14 is abnormal (S184). ). When judging the unevenness of the dirt on the window plate 13, if attention is paid to the change in the luminance value on the shielding plate 14 side of the differential luminance image D (a), the abnormality of the shielding plate 14 can be determined more accurately.

  That is, when the shielding plate 14 is not captured in the field of view of the camera 12 in a normal state, if the luminance value on the shielding plate 14 side of the difference luminance image D (a) is large, contact with the workpiece W or the like. There is a possibility that the shielding plate 14 is deformed and the deformed shielding plate 14 is reflected in the luminance image G (a). At this time, the abnormality determination unit can determine that the shielding plate 14 is abnormal. Further, when the shielding plate 14 is captured in the field of view of the camera 12 in a normal state, if there is a region where the luminance value increases on the shielding plate 14 side of the difference luminance image D (a), the luminance image G (a) is captured. There is a possibility that the position of the shielding plate 14 is different from the position of the shielding plate 14 shown in the reference image G (b). This is considered to be caused by the fact that the shielding plate 14 is deformed by contact with the workpiece W and is present at a position different from the normal position. Can be determined.

If the abnormality determination unit determines that there is an abnormality in step S184, the abnormality determination unit transmits (outputs) abnormality information including the occurrence of the abnormality and the content of the abnormality to the operator (S188).
If it is determined in step S183 that the dirt on the window plate 13 is not biased, the abnormality determination unit determines whether or not the elapsed time since the previous replacement of the window plate 13 is within a predetermined time (for example, about 5 minutes). Determination is made (S185).

  If it is determined in step S185 that a predetermined time or more has elapsed since the previous replacement of the window plate 13, the dirt on the window plate 13 is not biased, and the elapsed time since the previous replacement of the window plate 13 It is not extremely short. Therefore, the abnormality determination unit determines that the decrease in the luminance value of the luminance image G (a) is caused by the contamination of the normal window plate 13 due to the use of the welding robot, and requests replacement of the window plate 13 (S186).

If it is determined in step S186 that the replacement of the window plate 13 is requested, the abnormality determination unit outputs abnormality information requesting the replacement of the window plate 13 to the operator (S188).
If it is determined in step S185 that the predetermined time or more has not passed since the previous replacement of the window plate 13, the dirt on the window plate 13 is not biased. The elapsed time is extremely short. Therefore, the abnormality determination unit determines that the decrease in the luminance value of the luminance image G (a) reflecting the dirt on the window plate 13 is caused by the abnormality of the welding robot, that is, the abnormality of the purge air flow rate or the abnormality of the laser output. (S187).

If it is determined in step S186 that the dirt on the window plate 13 is caused by an abnormality in the flow rate of the purge air or an abnormality in the laser output, the abnormality determination unit outputs abnormality information indicating an abnormality in the flow rate of the purge air or an abnormality in the laser output. (S188).
According to the above-described difference image determination path, the welding sensor 1 performs the evaluation of the luminance value peak indicated by the difference luminance image D (a), the nonuniformity of the luminance value indicated by the difference luminance image D (a), and the previous time. By taking into account the elapsed time since the replacement of the window plate 13, it is possible to detect an abnormality that has occurred in the welding sensor 1 itself and that is mainly related to the window plate 13.

Next, the processing route from the image storage unit 20 through the luminance distribution curve deriving unit 28 to the abnormality determination unit 24 will be described with reference to FIGS. 2, 7, and 8.
The slit extraction unit 25 includes the images K (0) to K (M) accumulated by the first accumulation unit of the image accumulation unit 20 and the images K ′ (0) to K ′ (M) accumulated by the second accumulation unit. ), Detection lights each having a width in the row direction are extracted.

The slit extracted image accumulating unit 26 uses each detection light extracted by the slit extracting unit 25 as a slit extracted image of the image K (0) to the image K (M) and the image K ′ (0) to the image K ′ (M). accumulate.
The slit position pixel recording unit 27, for each of the slit extracted images of the images K (0) to K (M) and the images K ′ (0) to K ′ (M) accumulated by the slit extracted image accumulation unit 26. The luminance centroid in the width direction in each row from the 0th row to the Nth row is derived, and the center position of the slit extraction image is extracted by connecting the derived luminance centroids of each row. The slit position pixel recording unit 27 records the center position of the extracted slit extraction image and the luminance values of all the pixels of the slit extraction image.

As shown in FIG. 7, the slit position pixel recording unit 27 obtains and records the center position along the column direction of the slit extracted image having a line width in the row direction.
The luminance distribution curve deriving unit 28 crosses the slit extraction image in each row from the 0th row to the Nth row based on the luminance values of all pixels of the slit extraction image recorded by the slit position pixel recording unit 27 (row direction). ) To derive the luminance distribution curve.

As shown in FIG. 7, from one slit extracted image having a line width in the row direction, a luminance distribution curve that is a distribution of luminance values having a peak at substantially the center position of the slit extracted image is represented by the 0th to Nth rows. Is obtained for each line up to.
The laser line width deriving unit 29 totals N lines of the center positions extracted by the slit position pixel recording unit 27 for each of the slit extracted images of the images K (0) to K (M), and the variation in the center position is detected. (Linearity tolerance) Lpt is derived, and similarly, for each of the slit extracted images of the images K ′ (0) to K ′ (M), the center position extracted by the slit position pixel recording unit 27 is set to N rows. The total is calculated to derive the center position variation (linearity) Lp.

Further, the laser line width deriving unit 29 uses, for example, the peak luminance value of the luminance distribution curve in the luminance distribution curve regarding each slit extracted image of the images K (0) to K (M) derived by the luminance distribution curve deriving unit 28. width at the position of 1 / e ² of the (typically about 100 [mu] m) is derived as the laser linewidth tolerance Lwt slit light, for each slit extracted image of the image K '(0) ~ image K' (M) In the luminance distribution curve, the width at the position of 1 / e ² of the peak luminance value of the luminance distribution curve is derived as the laser line width Lw of the slit light.

The abnormality determination unit 24 compares the linearity tolerance Lpt derived by the laser line width deriving unit 29 with the linearity Lp, and when linearity Lp> linearity Lpt is satisfied, the image K ′ (0) to the image K '(M) Since the variation in the center position of the slit extracted image is large, it is determined that there is an abnormality in the accuracy of the surface of the window plate 13 and the laser lens.
Further, the abnormality determining unit 24 compares the laser line width allowable value Lwt derived by the laser line width deriving unit 29 with the laser line width Lw, and when the laser line width Lw> the laser line width allowable value Lwt, Since the line width of the slit extracted images of K ′ (0) to K ′ (M) exceeds the allowable value, it is determined that the laser line width of the projector 11 is abnormal.

  The correlation between the increase in the linearity Lp (center position variation) and the accuracy of the surface of the window plate 13 and the occurrence of an abnormality in the laser lens has been found by the inventors of the present application through experiments and experience. That is the fact. The correlation between the increase in the laser line width Lw and the occurrence of an abnormality in the laser line width of the projector 11 is also a fact that the inventors of the present application have found through experiments and experiences.

Hereinafter, the operation of the luminance distribution determination path in the signal processing unit 2 will be described with reference to the flowchart of FIG.
The slit extraction unit 25 of the signal processing unit 2 performs the image K (0) to image K (M) and the image K ′ (0) to image stored in the image storage unit 20 by the processing from step S10 to step S16 in FIG. Detection light that is a slit extraction image is extracted from K ′ (M), and the slit position pixel recording unit 27 extracts the center position of the extracted slit extraction image (S20).

The slit position pixel recording unit 27 records the center position of the extracted slit extraction image and the luminance values of all the pixels of the slit extraction image (S21).
The luminance distribution curve deriving unit 28, based on the luminance values of all pixels of the slit extracted image recorded by the slit position pixel recording unit 27 in step S21, the image K (0) to the image K (M) and the image K ′ ( 0) to luminance distribution curves of the slit extracted images of the image K ′ (M) are derived (S22).

The laser line width deriving unit 29 aggregates the center positions extracted by the slit position pixel recording unit 27, and the variation in the center positions of the slit extracted images of the images K (0) to K (M) (linearity tolerance). Similarly, Lpt is derived, and similarly, for each of the slit extracted images of the images K ′ (0) to K ′ (M), the center position variation (linearity) Lp is derived (S23).
The laser line width deriving unit 29 derives the laser line width allowable value Lwt based on the slit extracted images of the images K (0) to K (M) based on the luminance distribution curve derived by the luminance distribution curve deriving unit 28, Similarly, the laser line width Lw is derived from the slit extracted images of the images K ′ (0) to K ′ (M) (S24).

When the allowable linearity value Lpt and the linearity Lp are derived in step S23, and the allowable laser line width value Lwt and the laser line width Lw are derived in step S24, the abnormality determination unit determines whether the welding sensor 1 is abnormal. Judgment processing is started (S25).
When the abnormality determination process is started, the abnormality determination unit compares the linearity allowable value Lpt with the linearity Lp and determines whether or not the linearity Lp is larger than the linearity allowable value Lpt (S250).

If it is determined in step S250 that the linearity Lp is equal to or less than the linearity allowable value Lpt, the abnormality determination unit determines that no abnormality has occurred in the welding sensor 1 (S251).
If it is determined in step S250 that the linearity Lp is greater than the linearity tolerance Lpt, the abnormality determination unit is the variation in the center position of the slit extracted images of the images K ′ (0) to K ′ (M). It is determined that the cause of the increase in the linearity Lp is a decrease in the surface accuracy of the window plate 13 or an abnormality in the laser lens of the projector 11, indicating a decrease in the surface accuracy of the window plate 13 or an abnormality in the laser lens of the projector 11. Abnormal information is output (S252).

Following step S251 or step S252, the abnormality determination unit compares the laser line width allowable value Lwt with the laser line width Lw, and determines whether the laser line width Lw is larger than the laser line width allowable value Lwt (S253). ).
If it is determined in step S253 that the laser line width Lw is equal to or smaller than the laser line width allowable value Lwt, the abnormality determination unit determines that there is no abnormality in the laser line width (S254).

If it is determined in step S253 that the laser line width Lw is greater than the laser line width allowable value Lwt, the abnormality determination unit determines that an abnormality has occurred in the line width of the laser light emitted from the projector 11, and the laser Abnormal information indicating an abnormal line width of light is output (S254).
According to the above-described luminance distribution determination path, the welding sensor 1 uses the linearity and laser beam of the slit extracted images of the image K (0) to the image K (M) and the image K ′ (0) to the image K ′ (M). By considering the width and the like, it is possible to detect an abnormality that has occurred in the welding sensor 1 itself and that is related to the projector 11 that mainly emits slit light (laser light).

  In step S22, the luminance distribution curve deriving unit 28 derives luminance distribution curves of all slit extracted images of the image K (0) to the image K (M) and the image K ′ (0) to the image K ′ (M). However, several to tens of slit extracted images are selected from the images K (0) to K (M) and the images K ′ (0) to K ′ (M), and the luminance distribution curve is set. It may be derived. In this case, the processing after step S22 is performed on the derived luminance distribution curves of several to several tens of slit extracted images.

In summary, the welding sensor 1 according to the embodiment of the present invention not only detects the three-dimensional shape of the welded part by using the technique of the optical cutting method, but also uses the image of the slit light imaged by the welding sensor 1. Thus, an abnormality occurring in the welding sensor 1 itself can be reliably detected.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Welding sensor 2 Signal processing part 10 Sensor housing 11 Floodlight 12 Imaging part 13 Protection window board 14 Protection shielding board 20 Image storage part 21 Composite image creation part 22 Composite image storage part 23 Difference image generation part 24 Abnormality determination part 25 Slit extraction part 26 Slit Extracted Image Storage Unit 27 Slit Position Pixel Recording Unit 28 Luminance Distribution Curve Deriving Unit 29 Laser Line Width Deriving Unit W Welding Work T Welding Torch

Claims (4)

A light projecting unit that irradiates the welding work with slit light, and an image capturing unit that images the welding work irradiated with the slit light, and the slit light between the light projecting part and the imaging unit and the welding work. A welding sensor capable of measuring the shape of the welding workpiece based on an image including slit light imaged by the imaging unit, in order to be able to image the welding workpiece irradiated with
A composite image creation unit for creating an integrated image obtained by integrating the slit light imaged by the imaging unit and a reference integrated image obtained by integrating the slit light serving as a reference;
A difference image generation unit that generates a difference image by taking a difference between the accumulated image created by the composite image creating unit and the reference accumulated image;
Based on the luminance information of the difference image generated by the difference image generation unit, an abnormality determination unit that determines abnormality of the window plate,
Equipped with a,
An image accumulating unit for accumulating a plurality of images each having slit light in any position from one side to the other side of the field of view of the imaging unit;
The welding sensor, wherein the composite image creation unit creates a cumulative image and / or a reference cumulative image by integrating a plurality of images stored in the image storage unit .   2. The welding sensor according to claim 1, wherein the reference integrated image is an image obtained by integrating detection light captured by the imaging unit in a window plate in a normal state. A light projecting unit that irradiates the welding work with slit light, and an image capturing unit that images the welding work irradiated with the slit light, and the slit light between the light projecting part and the imaging unit and the welding work. The welding sensor is provided with a transparent window plate so as to be able to image the welded workpiece irradiated with the image, and is capable of measuring the shape of the welded workpiece based on the image including the slit light imaged by the imaging unit. And
An image accumulating unit for accumulating a plurality of images each having slit light at any position from one side to the other side of the field of view of the imaging unit;
A luminance distribution acquisition unit that acquires a luminance distribution in a direction along the line width of the slit light on the image based on the image stored in the image storage unit ;
Based on the luminance distribution acquired by the luminance distribution acquisition unit, a linearity detection unit that detects the linearity of slit light on the image;
Based on the linearity detected by the linearity detection unit, an abnormality determination unit that determines abnormality of the window plate and / or the light projecting unit,
A welding sensor. Based on the luminance distribution acquired by the luminance distribution acquisition unit, having a line width detection unit that detects the line width of the slit light on the image,
The welding sensor according to claim 3 , wherein the abnormality determining unit determines an abnormality of the window plate and / or the light projecting unit based on the line width detected by the line width detecting unit.