JP2000351072A - Measuring unit for position to be welded - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more correctly estimate the three dimensional position of a portion to be welded during arc welding, to control the arc welding while copying properly a groove line, and to estimate its tip position in particular even if a twist and a bend exist on a welding wire. SOLUTION: A measuring unit is equipped with an image pickup device 2 fixed to a welding torch 1 and an arithmetic unit, and the image pickup device 2 is equipped with an image pickup mechanism having an image pickup surface 21 and a filter function and a picture processing mechanism, and performs the image pickup of a welding wire 12 projecting from the welding torch 1. According to relation between the equation of eyes to be obtained from the two dimensional coordinates values of the tip of the welding wire in the image pickup surface of the image pickup device 2 and a surface including the axis of the welding torch, the three dimensional position of the tip of the welding wire is calculated and a position to be welded is estimated by the arithmetic unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding position measuring device for estimating a welding position during welding and a welding control device using the same, and more particularly, to a two-dimensional image obtained by imaging a tip portion of a welding wire in arc welding. Correct based on 3
The present invention relates to a welding position measuring device for estimating a three-dimensional position and a welding control device using the same.

[0002]

2. Description of the Related Art Conventionally, in a remote control type welding machine or an automatic welding machine, welding has been performed by following a groove line with a welding torch while checking a groove position of a member to be welded from now on with a camera. JP-A-5-138354 discloses that
There is disclosed a welding automatic copying apparatus in which an image of a light cutting surface of a groove and a welding torch obtained by projecting a laser slit light is captured by an ITV camera and is copied on a welding line based on an image obtained.

Since this method controls the position of the welding torch with respect to the groove, the projection length of the welding wire changes or the welding wire bends due to the curl and the like, and the relationship between the welding torch and the welding position changes. In this case, the arc position deviates from the target position of the groove, and a defect or a defective bead shape occurs, so that proper welding cannot be performed. For this reason, there has been a request to control the welding by obtaining an accurate welding position from the image acquired by the imaging device, but halation occurs in a normal camera because the brightness is large at the welding portion during welding, Welding position could not be measured accurately.

Japanese Patent Laid-Open No. Hei 10-94872 discloses a groove copying method in which a groove is copied based on an image of a welding wire or an arc. This method is based on image data of a welding site during welding, which is taken in advance, and obtains a correlation coefficient with image data obtained by imaging during profile welding, and determines a location having a high correlation with a welding wire, a weld pool, or the like. This is a method that recognizes the position of the target object such as a groove. According to this groove copying method, since the influence of the fluctuation of the welding arc light is small, the reliability of the automatic copying control using the TV camera is improved, and it is said that the method can contribute to automation and unmanned welding process.

However, according to this method, the actual position of the welding wire can be estimated, but the deviation in the depth direction of the welding wire cannot be known, and the tip position of the welding wire cannot be accurately grasped. Can not. Therefore, even though this method is based not on the welding torch but on the position of the welding wire, the welding wire is eventually projected straight from the welding torch and the welding line is controlled under the assumption that the projection length is constant. I could only do it. In addition, since the present method is to cut out the captured image data while shifting it little by little, calculate a two-dimensional correlation coefficient with the reference screen, and search for a place having the highest correlation, the processing is performed online to perform control. In order to use it, an extremely high speed and high arithmetic processing capacity is required.

Further, the present applicant has already filed Japanese Patent Application No.
No. 98528 discloses a method of visualizing the state of a groove, a welding wire, a molten pool, a welding arc, and the like from an imaging screen of a welding portion. In this method, a plurality of imaging devices having different sensitivities are used to image a welded portion from almost the same direction, and these images are combined so that a welding state can be monitored. According to the disclosed method, the tip position of the welding wire can also be visualized and grasped. However, it has been difficult to measure a three-dimensional position from one two-dimensional image acquired by the imaging apparatus. Particularly when the wire is bent, it is difficult to accurately estimate the tip position.

[0007]

The problem to be solved by the present invention is to more accurately estimate the three-dimensional position of a welding site such as the position of the tip of a welding wire during arc welding, and in particular, torsion and bending. The purpose is to estimate the tip position of a welding wire having a shape and control the arc welding appropriately following the groove line.

[0008]

In order to solve the above-mentioned problems, a welding position measuring device according to the present invention includes an image pickup device and an arithmetic device fixed to a welding torch, and the image pickup device includes an image pickup mechanism and an image processing mechanism. Image of the welding wire protruding from the welding torch in preparation for
Calculating the three-dimensional position of the tip of the welding wire based on the relationship between the two-dimensional coordinate value of the tip of the welding wire and the plane including the axis of the welding torch, and estimating the welding position. Features.

The image formed on the imaging surface of the imaging device has a similar relationship to a projected image of the subject viewed from the optical center (principal point) of the imaging device. Accordingly, the position of the tip of the welding wire is determined by specifying the tip position of the welding wire protruding from the welding torch in the imaging screen where the welding wire is being captured and determining the coordinate value in the two-dimensional coordinate system fixed on the imaging surface. , Ie, a line of sight connecting the optical center with the optical center. Further, in order to know the three-dimensional position of the tip of the welding wire, the position where the above-mentioned line of sight intersects with the surface on which the welding wire exists may be obtained. In the present invention, since the welding wire is protruded along the axis of the welding torch and the welding torch has a relatively constant relationship with the imaging device, the welding wire is determined based on the plane including the axis of the welding torch. Is estimated.

For example, assuming that the welding wire is projected straight along the axis of the welding torch as a first approximation, the position of the tip of the welding wire is at the intersection of the line of sight and the plane containing the axis of the welding torch. That is, it can be estimated by the apparatus of the present invention. If the plane including the axis of the welding torch used for the above calculation is a plane including a horizontal line perpendicular to the optical axis of the imaging device, not only when the tip of the welding wire is shifted left and right from the welding torch axis, but also in the front-rear direction. The correction calculation can be performed relatively easily even when the position is deviated.

Further, the image pickup apparatus used in the present invention includes a plurality of image pickup mechanisms having different sensitivities, each having a filter having a different spectral sensitivity and arranged so as to photograph the welded portion from substantially the same direction. Is preferred. The image processing mechanism generates a composite image that combines the image information obtained by each imaging mechanism, so that the surrounding objects and portions such as the high-intensity welding arc are each expressed with appropriate brightness, so that the welding state can be determined. It can be grasped accurately and the tip of the welding wire can be clearly recognized.

The arithmetic unit stores the camera parameters obtained based on the imaging results of six or more known points, and determines the two-dimensional position of the tip of the welding wire on the imaging screen and the three-dimensional position in space. You may make it associate by this camera parameter. These relationships can be expressed, for example, by the following equation (1) relating to the line of sight that sees the target point from the imaging device.

(Equation 2)

When the welding wire is bent, the position of the tip of the welding wire is determined by taking into account the distance from the plane including the axis of the welding torch, which is estimated based on the diameter of the welding wire in the image screen. Can be calculated. Since the diameter of the welding wire does not change from top to bottom, by comparing the diameter in the imaging screen expected when the welding torch axis is included with the diameter of the actually captured welding wire, This is because the deviation in the direction can be evaluated. At this time, since the relative position of the welding torch and the imaging device does not change during the welding process, the welding wire diameter in the imaging screen is evaluated based on the diameter of the welding wire at the welding torch tip position actually reflected. Is also good. When the tip position of the welding wire can be accurately estimated in this way, the displacement of the groove copying that has been conventionally seen due to the twisting of the welding wire tip can be prevented, and accurate welding line copying control can be performed.

Further, the welding control device of the present invention is provided with a control device in addition to the welding position measuring device, and controls welding conditions based on the protrusion length of the welding wire calculated by the welding position measuring device. And As the welding wire progresses and the distance to the welding object fluctuates while the welding progresses, the payout length changes.However, when the protrusion length of the welding wire changes, the distance from the feeding point inside the welding torch to the welding wire tip is changed. Therefore, it is necessary to make an adjustment to maintain an appropriate welding current. The welding control device, which knows the welding wire protrusion length by measuring the welding position represented by the welding wire tip, etc., can perform high-quality welding by controlling welding conditions based on the estimated value. it can.

The welding control device of the present invention further includes a groove position measuring device, and the groove tracing control based on the groove position measured by the groove position measuring device and the welding position estimated by the welding position measuring device. May be performed. The groove position for the welding machine is actually measured by a groove position measuring device,
By combining the groove position information with the three-dimensional position information of the welding part, more precise groove scanning control becomes possible. The groove position information and the welding position information can be easily combined by performing coordinate conversion into one coordinate system such as a coordinate system used by a welding device.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments with reference to the drawings.

[0017]

FIG. 1 is a block diagram illustrating the arrangement of components in the present embodiment, FIG. 2 is a perspective view illustrating the principle of measurement, FIG. 3 is a block diagram illustrating the configuration of the present embodiment, and FIG. FIG. 5 is a conceptual diagram illustrating a conversion method, and FIG. 5 is a conceptual diagram illustrating a control operation at the time of welding. This embodiment is a welding position measuring device including an imaging device fixed to a welding torch. As the imaging device, a device such as a CCD camera or an ITV camera that can express a position of an image in a two-dimensional coordinate system fixed on an imaging surface is used. Further, in the present embodiment, a groove position measuring device such as a laser distance measuring device for grasping the state of the groove is provided to enable the groove line to be traced.

Referring to the drawings, an imaging device 2 is fixed to a mounting bracket 11 fixed to a welding torch 1. The groove position measuring device 3 is also mounted on the mounting bracket 11. The welding wire 12 extends from the tip of the welding torch 1 along the central axis, and is welded between the tip of the welding wire and the surface of the workpiece 4 by a welding current supplied from a welding power supply of the welding torch control device 13. An arc 14 is formed. It is assumed that the welding proceeds in the right direction in the drawing in FIG. 1 and in the left direction in the drawing in FIG. 2, as indicated by thick arrows in the drawing.

An image pickup device 2 includes an image pickup section 22 having an image pickup surface 21 such as a CCD device for converting a video projected through an optical system into two-dimensional position information and an image for clearly displaying each part of a subject. The processing unit 23 is provided. Imaging unit 22
Generates a two-dimensional image by photographing an area including a welding portion. The image processing unit 23 uses an appropriate threshold value regarding brightness, color information, and the like having different values depending on the target, so that the target used for welding management, such as the tip of a welding wire or a welding arc, can be clearly classified.

Based on the method disclosed in Japanese Patent Application No. 10-98528, a plurality of CCD cameras having filters having different spectral sensitivity characteristics and having different sensitivities are arranged so as to capture images in substantially the same field of view. An image signal is output by converting portions having different luminances into appropriate brightnesses, and the image processing section 23 superimposes these image signals and synthesizes them on one screen. All elements such as a molten pool, a welding torch, a welding wire, and a welding arc can be separately displayed or image data.

A feature point such as a tip of a welding wire is extracted from the image data obtained in this manner by using a well-known image processing method, and the two-dimensional feature point on the imaging coordinate system set on the imaging surface is extracted. Find coordinates. Next, the imaging coordinates are converted into a three-dimensional object coordinate system set for the target object. The object coordinate system can be arbitrarily determined. However, when an automatic welding device or the like is used, the Z-axis is set along the track of the bogie on which the welding machine is mounted, and the XY plane is determined perpendicular to the Z-axis. It is preferable to set the coordinate system with reference to the axis. The object coordinates of the feature points are determined based on the camera's line of sight obtained in the object coordinate system obtained from the imaging coordinates and a plane set in the object coordinate system space with the object as a reference.

The method of obtaining the camera line of sight from the imaging coordinates is as follows.
This is a coordinate conversion method performed using camera parameters derived based on a linearization method using a homogeneous coordinate system. If the optical relationship of the imaging device is idealized, it can be represented by a perspective transformation model in which a pinhole is provided at the principal point F of the optical system as shown in FIG. In this perspective transformation model, the camera line of sight is defined as one straight line passing through a pinhole.
In an actual image pickup apparatus, the object, the lens system, and the image pickup surface are arranged in this order. However, for simplicity, it is assumed that the image pickup surface is virtually on the front surface of the lens, that is, on a virtual imaging plane V arranged on the side where the object exists. . The distance between the virtual imaging plane V and the lens principal point F is a focal length f, which is the same as the distance between the actual imaging plane I and the lens principal point F.

Considering the imaging coordinate system fixed to the camera, taking the virtual imaging plane V as a reference of this imaging coordinate system, the origin O is set at the center of the virtual imaging plane, and the virtual imaging plane V is defined as the 2nd of the imaging coordinate system. The plane includes the axis (X, Y). It is also assumed that the remaining one axis (Z) is taken in the direction of the optical axis. A point P ′ (x) obtained by projecting a point P (x, y, z) in the space onto the virtual imaging plane V
_{c, y} c, _{z c)} is the intersection of the virtual image plane and the line of sight directed toward the measuring point P, is given by the following equation (2).

(Equation 3) Here, z _c = 0. Further, α = f / (f + z).

The above perspective transformation is a non-linear transformation,
Linearization can be achieved by using a homogeneous coordinate system that is one-dimensionally enhanced by adding a parameter. Using W _h as a parameter, a three-dimensional point (x, y, z) is converted to a four-dimensional point (x _h , y _h ,
z _h , w _h ), the perspective transformation can be described by the matrix operation of the following equation (3). Here, x = x _h / w _h ,
y = y _h / w _h and z = z _h / w _h . Also, (x,
(y, z, 1) are the coordinates of the object point P in the homogeneous coordinate system representation, and (x _ch , y _ch , z _ch , w _ch ) are the coordinates of the projection point P ′ on the imaging surface.

(Equation 4)

Actually, it is more convenient to express the measurement object in an object coordinate system based on an object, rather than in an imaging coordinate system based on an imaging device. In particular, in a case where the profile welding is automatically performed by a robot or an automatic welding machine, it is preferable to employ a coordinate system associated with a movement trajectory of a robot or an actuator. The coordinate transformation T relating the object coordinate system and the imaging coordinate system is expressed by the following expression (4) including rotation and translation in a homogeneous coordinate system.

(Equation 5)

Therefore, the conversion from the point P in the object coordinate system to the point P 'in the imaging coordinate system can be represented by the following equation (5).

(Equation 6)

In the imaging plane in the imaging coordinate system, z _ch is always used.
= 0, the two-dimensional position M (m ₁ , m ₂ ) of the image on the imaging surface and the three-dimensional position R in the space are obtained from the above equation (5).
The following equation (6) representing the conversion of (r ₁ , r ₂ , r ₃ ) is obtained. Note that α corresponds to a parameter.

(Equation 7)

The coefficient matrix of three rows and four columns includes all data relating to the camera, such as the position, posture, and angle of view, and is generally called a camera parameter, and expresses the line of sight of the camera. Since the arrangement of the camera and the focal length of the lens to be used are different depending on the size and form of the object, the measurement environment, and the like, the camera parameters must be calibrated each time the conditions change. Each coefficient of the camera parameter can be obtained from the measured value of the focal length of the lens or the position or orientation of the camera, but it is inaccurate and takes time. Therefore, it is practical to use an object whose shape or position is a known reference and to calibrate using an object measured by an imaging device.

Reference points (r ₁ , r ₂ ,
If two sets of r ₃ ) and corresponding positions (m ₁ , m ₂ ) on the imaging surface are given, two equations are established. Camera parameters are 12
Since there are six elements, calibration can be performed using six mutually independent reference points. In order to improve the accuracy of calibration, it is preferable to use a method of estimating an unknown by the least squares method using a large number of reference points exceeding six. Based on the camera parameters obtained in this manner, a line-of-sight equation that looks through the tip of the welding wire is obtained based on the position of the image on the imaging surface.

Normally, the tip of the welding wire projects straight along the axis of the welding torch, so it is highly likely that the point where the above-mentioned line of sight hits the plane including the axis of the welding torch is the welding wire tip position. If the plane including the welding torch axis is represented as a shape equation on the object coordinate system, the intersection with the line of sight can be easily obtained.

According to the welding position measuring apparatus of the present embodiment, the three-dimensional position of an element, such as a welding torch or a welding wire, which is imaged in the imaging plane 21 can be obtained by the following procedure and used for welding control. .

That is, a three-dimensional object coordinate system to be used when a welding cart carrying a welding robot or the like travels is determined. A shape equation that expresses welding equipment such as a welding torch and a welding wire on the object coordinate system is determined. A conversion parameter between a two-dimensional imaging coordinate system and a three-dimensional fixed coordinate system of a camera for photographing a welding site is calculated.

After making such preparations, an image of the welded part being welded is taken, and a feature point such as a welding torch or a welding wire is extracted from the image acquired by the imaging camera. Find the coordinates above. A transformation parameter is applied to the imaging coordinate value of the feature point to determine a line-of-sight equation that sees through the point. A coordinate value on the three-dimensional fixed coordinates of the target point is calculated as an intersection of the shape equation of the welding equipment and the line-of-sight equation.

According to the welding position measuring device of the present embodiment, the three-dimensional position of the tip of the welding wire during welding can be accurately estimated and output as three-dimensional coordinate values. By doing this, instead of using the position of the welding torch as a substitute for profiling control, it is possible to control based on the welding position, such as the position of the tip of the welding wire. Profile welding control can be performed. The shape equation determined by the above procedure may be, for example, an equation representing a plane including the axis of the welding torch when targeting a welding wire. Further, as the conversion parameter calculated in the procedure, the 3 × 4 coefficient matrix known as the camera parameter described above can be used.

As shown by the point B in FIG. 2, the welding wire may be bent due to the influence of the winding habit attached before feeding, and the actual welding wire may deviate from the shape equation. In such a case, the displacement of the welding wire can be estimated based on the difference between the diameters of the welding wire and the actual welding wire when they are located on the shape equation. Therefore, when the welding wire is located on the shape equation obtained by the procedure, the width of the welding wire to be displayed on the imaging surface 21, the width of the actually measured wire on the imaging surface, and the actual position B The correction formula obtained by quantifying the relationship between the displacement L and the position B ′ on the shape equation is calculated in advance by the arithmetic unit 51.
To memorize it.

When the width of the imaged welding wire is different from the width of the welding wire expected when the welding wire is on the shape equation, first, the tip B of the welding wire is positioned on the shape equation. Three-dimensional position B '
Then, the distance L is calculated based on a correction expression quantified in advance, and the position is corrected by that distance along the line of sight to obtain a correct three-dimensional position. By using the above method, even when the welding wire is twisted or bent, a correct three-dimensional position of the tip of the welding wire can be obtained and used for welding line profiling control.

The protrusion length from the welding torch can be known from the result of measuring the three-dimensional coordinates of the tip of the welding wire by the method of the above embodiment. If the protrusion length of the welding wire changes, the welding current fluctuates and a good welding result cannot be obtained.However, the protrusion length of the welding wire can be measured even during welding. Control becomes possible, and precise welding condition control can be performed by finer control of welding heat input than before.

For example, as shown in the left diagram of FIG. 5, a welding arc 14 formed between the tip of the welding wire 12 protruding from the welding torch 1 and the work 4 causes a welding current of 300 A under certain welding conditions. During welding at a voltage of 33 V and a wire protrusion length of 15 mm, as shown in the right diagram of FIG.
mm, the electric resistance of the welding wire portion 12 increases, and the welding current supplied from the welding power source 15 grounded to the workpiece 4 via the contact electrode 16 changes to 280A.

As a result, the amount of heat input to the welding object decreases,
The quality of the joint is reduced due to the reduced penetration of the weld. In such a case, adjust the welding power supply to compensate for the decrease in welding current due to resistance heating, or secure the necessary heat input, or secure the welding current by bringing the welding torch closer to the welding target and returning the wire protrusion length to its original length. There is a need to. In the above example, when the wire protrusion length is 20 mm, the current 330
A. When the voltage was adjusted to 34 V, the welding quality was maintained and the joint quality was secured.

In the welding position measuring apparatus of the present embodiment, the wire protrusion length can be accurately evaluated, so that precise welding current control based on the wire protrusion length is possible, and the welding condition control for managing the welding heat input more finely than before is possible. It becomes possible. In addition, by storing in the welding control device a comparison table that gives the optimum relationship between the wire protrusion length and the welding power source, automatic welding in which the wire protrusion length is taken into the control variables becomes possible. Since the method of calculating the wire protrusion length and performing feedback control to the position of the welding torch is more direct, the control logic is simple.

Further, by automatically attaching the groove position measuring device 3 and taking in the information, the automatic copy welding along the groove line can be easily performed. The groove position measuring device 3 is a laser distance meter, and is used by being fixed to the welding torch 1. The laser range finder 3 irradiates the portion to be welded with a laser beam 31 while scanning it, measures the groove position and shape from the reflected light, and uses the groove position coordinate conversion unit 32 to convert the result into the object coordinate system. Expressed by coordinate values. The control device 5 can control the position of the welding torch based on the welding wire tip position coordinate information and the groove position coordinate information expressed on one object coordinate system to perform groove tracing control.

In the above embodiment, a CCD device is used for the image pickup section 22 of the image pickup apparatus 2. However, as long as a target image can be expressed in two-dimensional coordinates, various vacuum tube type image pickup tubes can be used. Good. Further, it is needless to say that a linearly arranged CCD element may be used. In addition, although the tip of the welding wire is used as a representative of the welding position, a welding arc or another material closely related to the welding position may be used. Further, a laser distance meter was used as a groove position measuring device, but a method using a result obtained by photographing a light cutting line formed by irradiating a laser or the like as slit light with an image pickup device. Is also good. Further, the straight line equation representing the line of sight can also be calculated by calculation using the fact that the target line of sight is a line connecting the coordinates on the imaging surface and the principal point of the optical system.

[0043]

As described above, if the welding position measuring device and the welding control device of the present invention are used, the position of the tip of the welding wire during welding can be obtained in real time. In addition, accurate welding line scanning control based on the welding wire tip position can be performed, and high quality welding can be performed with few defects and bead shape defects.
Further, welding condition control for managing welding heat input based on the protrusion length of the welding wire can be performed, and appropriate automatic welding can be performed by incorporating a wire protrusion length management algorithm into the welding control device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a welding position measuring device of the present invention.

FIG. 2 is a perspective view illustrating a measurement principle in the present embodiment.

FIG. 3 is a block diagram illustrating the configuration of the present embodiment.

FIG. 4 is a conceptual diagram illustrating a coordinate conversion method according to the present embodiment.

FIG. 5 is a view for explaining the concept of adjusting welding conditions in the present embodiment.

[Explanation of symbols]

 Reference Signs List 1 welding torch 11 mounting bracket 12 welding wire 13 welding torch control device 14 welding arc 15 welding power source 16 contact electrode 2 imaging device 21 imaging surface 22 imaging unit 23 image processing unit 3 groove position measuring device 31 measuring beam 32 groove position Coordinate conversion unit 4 Member to be welded 5 Controller 51 Calculation unit

[Procedure amendment]

[Submission date] July 5, 2000 (2007.5.5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Satoru Sakayama, 118 Futatsuka, Noda-shi, Chiba Kawasaki Heavy Industries Noda Plant (72) Inventor Takahisa Iizuka 118, Futatsuka, Noda-shi, Chiba Kawasaki Heavy Industries Noda Plant

Claims (6)

[Claims] 1. An arc welding device comprising: an imaging device fixed to a welding torch; and an arithmetic device, wherein the imaging device includes an imaging mechanism and an image processing mechanism, and the imaging mechanism protrudes from the welding torch during arc welding. The image processing mechanism obtains a two-dimensional coordinate value of the tip of the welding wire in the imaging screen based on the captured image acquired by the imaging mechanism, and the arithmetic unit calculates the two-dimensional coordinate value of the tip of the welding wire. A welding position measuring device for estimating a welding position by calculating a three-dimensional position of a tip of a welding wire based on a relationship between the welding torch axis and a plane including the axis of the welding torch. 2. The image processing apparatus according to claim 1, wherein said image pickup device includes filters having different spectral sensitivity characteristics, and a plurality of image pickup mechanisms having different sensitivities are arranged so as to respectively photograph the welding portion from substantially the same direction. 2. The welding position measuring device according to claim 1, wherein the generating unit generates a composite image in which the image information acquired by each imaging mechanism is combined. 3. The arithmetic unit determines that the two-dimensional position M (m ₁ , m ₂ ) of the tip of the welding wire in the imaging screen and the three-dimensional position R (r ₁ , r ₂ , r ₃ ) in space are α. Camera parameters C (c _ij (where i = 1 to 3, j =
The welding position measuring device according to claim 1, wherein a straight line connecting the tip of the welding wire and the principal point of the image pickup device is calculated by using the relations of the following formulas according to 1) to 4)). . (Equation 1) 4. A three-dimensional position of a tip of the welding wire by estimating a distance from a plane including an axis of the welding torch based on a diameter of the welding wire in the imaging screen. The welding position measuring device according to any one of 1 to 3. 5. A welding position measuring device and a control device according to claim 1, wherein a projection length of the welding wire is calculated from a three-dimensional position of the welding wire calculated by the welding position measuring device. A welding control device for controlling welding conditions based on the protrusion length. 6. A groove tracing control based on a groove position measured by the groove position measuring device and a welding position estimated by the welding position measuring device. The welding control device according to claim 5, wherein: