JPH0394979A - Welding position detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wire contact type position detection device that detects the welding position of a welded material by bringing the tip of a welding wire into contact with the welded material; The present invention relates to a welding position detecting device which is suitable as a welding line copying device for a fully automatic welding robot, and includes an optical position detecting device which irradiates a slit-shaped light beam and detects the welding position from the optically sectioned image.

[Conventional technology]

Conventionally, this type of welding position detection device is disclosed in, for example, Japanese Unexamined Patent Publication No. 1986-
As described in Japanese Patent No. 50984, a laser beam sharply focused into a slit shape is irradiated from a light projecting means to a groove portion of the workpiece preceding the arc point, and the reflected light from the groove portion is reflected from the groove portion. The position to be welded is determined by detecting with a light receiving means such as an ITV camera and analyzing the obtained light section image. When such a device is applied to a welding robot to control a welding torch, it is attached to the tip of the robot arm as a torch with a detection device that integrates the welding torch, light emitting means, and light receiving means.

In addition, as a conventional wire contact type device, the robot Nα
25 (1979)↓pages 6-20, the welding process is performed by moving the welding torch close to the part to be welded according to the actions taught in advance before welding, and protruding from the welding torch with a certain protrusion length. There was a wire contact type welding position detection device that detects the welding position by detecting contact with the tip of the wire.

[Problem to be solved by the invention]

An optical welding position detection device consisting of a light emitting means and a light receiving means can obtain three-dimensional position information in the robot coordinate system about the welding position of the welded part preceding the arc generation point. It is not possible to detect bends in the welding wire that is fed out from the welding wire. Therefore, even if the welding position can be detected accurately, if the welding wire is bent, the target position of the wire will be shifted, resulting in a problem that a satisfactory weld bead cannot be obtained. In addition, this type of optical device has a narrow field of view and the range in which it can detect the m-contact position is limited, so the cenotening position of the next actual workpiece may deviate greatly from the position of the blind workpiece that has been taught in advance. There was a problem that detection could not be performed if

On the other hand, a wire contact type weld line detection device can detect three-dimensional positional information of a welded part at a welding start point and a welding end point, but cannot detect the weld line path in the middle of welding progress. For this reason, it has been difficult to ensure the quality of welding when errors in the shape of the weld line, assembly errors, or thermal deformation of the workpiece during welding occur.

An object of the present invention is to provide a welding position detection device that can accurately detect the welding position even if a welding wire protruding from the tip of a welding torch is bent.

[Means to solve the problem]

In order to achieve the above object, the welding position detection device of the present invention irradiates a linear beam of light onto the groove of the welded material that is a certain distance ahead of the arc point generated on the welded material by the welding torch. , an optical position detection device that detects a welding position by image processing a reflected image of the linear light beam reflected from the groove surface;
A wire that detects the welding position by bringing the welding torch close to the material to be welded according to the motion taught in advance before welding, and detecting the contact of the tip of the welding wire that protrudes from the welding torch at a certain length. A welding position detection device combined with a contact type position detection device,
The amount of bending of the welding wire is determined based on the difference between the coordinates of the welding position detected by the wire contact type position detection device at the welding start point and the coordinates of the welding position detected by the optical position detection device after moving the welding torch. It is characterized by detecting.

This welding position detection device includes a welding robot and a robot control device for controlling the welding robot, and is suitable for use by being mounted on the wrist of the welding robot.

In addition, when the welding position detection device is installed on a welding robot, the wire contact type position detection device is activated and the tip of the welding wire is brought into contact with the welding wire to detect the coordinates of the welding end point in the welding progress direction, and During the welding process, it is preferable to operate the optical position detection device to detect the welding position. Alternatively, when a welding position detection device is installed on a welding robot, the coordinates of the welding end point in the welding direction are taught in advance, and the coordinates of the welding point detected in the welding direction in the welding direction detected at the welding start point are taught in advance. The difference is calculated by comparing the coordinates in the welding direction, and the coordinates of the welding end point in the welding direction are shifted and corrected by the difference, and during welding, the optical position detection device is activated to determine the welding position. may be detected.

[Effect]

The operation of the welding position detecting device when the welding position detecting device composed of a wire contact type position detecting device and an optical position detecting device is mounted on a welding robot will be explained.

First, at the welding starting point, the welding wire is brought into contact with the material to be welded using a wire contact type positioning device to detect the coordinates of the welding position, and then the welding torch is controlled by a welding robot for a certain distance in the direction of welding progress. Move in the opposite direction to set the optical position detection device at the welding start point. The optical position detection device obtains three-dimensional information about the groove position in a robot coordinate system whose origin is a point at a certain distance (the protruding length of the welding wire) from the tip of the welding torch. Both coordinate systems are arranged so that when the welding wire comes out straight in the axial direction of the welding torch, the coordinates of the welding position detected by the wire contact type position detection device and the coordinates of the welding position detected by the optical position detection device match. is set, so if the difference between the detection results of both coordinates is measured, the amount of bending of the wire can be determined from that difference. During welding work, a wire contact type position detection device operates at the welding start point to position the welding wire at a predetermined welding position, and an optical position detection device operates while the arc is ignited and moves from the welding start point to the welding end point. The device operates so that the arc comes to a predetermined welding position while correcting the detected welding position by the amount of bending of the welding wire.

Additionally, a wire contact type position detection device is used to set the welding end point. In other words, one setting method is to directly detect the coordinates in the welding direction by bringing the tip of the welding wire into contact with the welding end point, and another setting method is to directly detect the welding position detected at the welding start point. The difference between the coordinates in the welding direction and the previously taught coordinates of the welding start point in the welding direction is calculated, and the previously taught welding end point is corrected by the difference.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic structural diagram showing an example of a fully automatic arc welding robot to which a welding position detection device according to an embodiment of the present invention is applied. In FIG. 1, 1 is a welding torch, 2 is a light projecting means, 3 is a light receiving means, 4 is an image processing device, 5 is a wire contact type position detection device to be described later, 6 is a welding robot, and 7 is a welding wire feeding device. , 8 is a welding power source, and 9 is a robot control device.6 FIG. 2 schematically shows an embodiment for explaining the detection principle of an optical position detecting section of the welding position detecting device according to the present invention. FIG. 2 is a perspective view showing a state in which a groove portion 12 of a plate material to be welded 10.11 is arc-welded using a welding torch. The welding torch 1 has an electrode part 13 at the tip,
The electrode part 3 is placed opposite the groove formed at the intersection of the workpiece 10 and the workpiece 11 placed on the plate surface, and the welding wire 14 fed out from the electrode part 13 and An electric arc is generated between the grooves 12'. The support body 15 is rotatably attached to the axis of the welding torch ↓. The light projecting means 2 and the light receiving means 3 are integrally fixed to the support body 15. Light 16 (hereinafter referred to as linear condensed light ray l6) is sharply condensed into a slit shape from the light projecting means 2.
is applied to a position in the vicinity of the arc point preceding the arc point 12' of the groove portion of the workpiece 10.11 to be welded. Line segment QEQ in the diagram
．． ,Q. Q. represent the light cutting lines generated on the welding material 11 and 12 by the linear condensed light beam, respectively. Light receiving means 3
is, for example, an ITV camera, which observes the optical cutting line and detects the welding tracing position from the intersection Q2 of the line segment.

FIG. 3 shows the positional relationship between the optical position detection section and the robot. The welding robot 6 has an absolute coordinate system XYZ at the fixed position of the welding robot 6, and further has a movement mechanism of the XWYWZW wrist coordinate system at the wrist to which the welding torch 1 is attached. Here, the wrist coordinate system XwYwZw has a Zw axis in the direction of the rotational axis of the wrist, and a YW axis and a Zw axis in two directions orthogonal to this, so that the origin of the wrist coordinate system coincides with the wire tip position of the welding torch ↓. Set. In addition, the welding torch 1 has a torch center axis on the plane formed by the YW axis and the Zw axis, and the Z
It is fixed to the wrist of the welding robot 6 using a mounting bracket 17 so that the angle with respect to the W axis is 45 degrees. The welding torch 1 has a ZS axis in the direction of the torch center axis, an XS axis on the Xw, and a Ys axis in a direction perpendicular to the XsZs plane.
The sensor orthogonal coordinate system is set so that the origin of the XsYsZs coordinate system coincides with the position of the wire tip of the welding torch 1. Furthermore, a camera coordinate system XcYcZc having its origin on the XSYS plane and a certain distance away from the Zs axis is integrally formed on the support 15. As described above, the support body 15 has a structure that can rotate around the Zs axis of the welding torch 1, and as the support body 5 rotates, the camera coordinate system XcYcZc also rotates around the axis of the welding torch 1. The angle formed by XS and Xc during rotation is called sensor rotation angle OS.

FIG. 4 shows the camera coordinate system XcYcZc and the positional relationship between the light projecting means 2 and the light receiving means 3. As shown in the figure, the central axis 8 of the linear condensed light beam 16 formed by the light projecting means 2 and the imaging central axis 19 of the light receiving means 3 are on the xczc plane, intersect at the origin of the camera coordinate system, and the Zc axis and α respectively
, β, and further linear condensed ray 16 and XcYc
The angle between the line of intersection with the plane and the XC axis is γ, and the coordinate axes u and v of the plane coordinate system held by the imaging section 3' of the light receiving means 3 are X. c,Yc
Each is parallel to the axis.

FIG. 5 shows an example of detection of a groove image obtained by the welding position detection device shown in FIG. 2. In the figure, line segment Q.
Q. is the reflected image generated on the surface of the lower plate 10, and the line segment Q
2Q, is a reflected image produced on the surface of the upper plate 11, and the line Q. Q. and Q. The intersection point Q2 of Q3 is the groove position. The image processing device 4 described above performs predetermined processing on the obtained groove image to obtain the detected position coordinates (cutv) of the welding line Q2.

The detected position coordinates (u, 2) thus obtained are calculated by using the distance P from the origin of the camera coordinate system to the light receiving means 3, the imaging magnification m of the light receiving means 3, and the calibration data of α, β, and γ mentioned above. Detection data of camera coordinate system (Xc, yC,
Zc). The processed results are then added to the rotation axis OS of the sensor. Using the mounting angle (45°) of welding torch 1, the wrist coordinate system (X w H Y w + Z w
). The robot control device 9 converts the detection result converted into the wrist coordinate system into robot coordinates (X, Y, Z) using the angle information of each rotation axis at the time of detection, and stores it in the memory as the target position for welding. Remember.

By the above procedure, it is possible to detect the groove position of the welded part at a position preceding the tip position of the welding torch.

FIG. 6 shows the principle of detecting the groove position of a welded member by bringing the ends of the wire into contact using a wire contact type welding position detection device. In the figure, W is the workpiece position at the time of teaching, and Ws is the actual workpiece to be welded, which is installed offset from the position at the time of teaching. In fact, when dealing with mass-produced products, the setting positions of the workpiece used for teaching and the workpieces that follow are often misaligned. The welding torch and welding wire indicated by broken lines in the figure are for the case where the welding wire has a bend, and the operation in this case will be described later. This detection method, for example,
In order to detect the positional deviation of the actual workpiece in the Y direction, the positions and distances of a point P1 away from the workpiece and a point P2 on the workpiece are stored in advance by teaching. Next, the welding torch is moved in the direction from P1 to P2 during the play pack, and when it comes into contact with the workpiece WS, the contact type detection device 5 (Fig. 1) detects the current flowing between the welding wire and the workpiece, and this point is detected. The distance between P and -Pv is detected as Pv, and compared with the previously stored distance between p and -p, and the difference is detected as the shift amount ΔY of the workpiece position in the Y direction. Similarly, the welding torch 1 moves in the direction from P, to P.
The point where it touches the workpiece is Pz, and P3-P
The distance between P and -P4, which stores the distance between z, is compared, and the difference is detected as the shift amount ΔZ of the workpiece in the Z direction. In the figure, PT is the teaching point of the groove position. The groove position Ps when the work is actually installed can be found by correcting the position of Pt using the detection results of ΔY and Δ2 described above.

The case where a bend in the welding wire has occurred is also shown by the broken line in Fig. 6, but in this case as well, the position is detected by contacting the end of the welding wire with the bend, so the position of the actual workpiece is detected in the same way as described above. It is possible to correctly correct the position of the wire tip and aim at the groove position PS.

The above describes the principle of detecting the groove position by bringing the ends of the welding wire into contact. On the other hand, the optical welding position detection device described using Figs. 2 to 5 can detect the groove position at the position preceding the arc point, but has the disadvantage that it cannot obtain information on the bending of the welding wire. There is. Therefore, even if the groove position is detected correctly and the position of the welding wire tip is controlled in a tracing manner, the target welding position will shift if the wire itself is bent.

Fig. 7 shows a system for detecting bends in the tip of a wire by combining the optical position detection device shown in Figs. This figure shows an embodiment of the present invention in which the groove position is copied. In the figure, Q2 indicates the welding start position. The workpiece position at this point is measured by touching the end of the welding wire. P.Y.
, PZ indicates the detection portion of the workpiece position in the Y and Z directions. As a result, when the welding wire has a bend, a detection result of the workpiece position including the bend in the welding wire can be obtained as shown by the broken line in FIG. next,
Based on the welding start position Q2, the welding torch is moved in the opposite direction to the welding direction (X-axis) by a distance of ΔS corresponding to the position detected earlier in the X direction of the welding torch 1 by the optical welding position detection device described above. Move (evacuate) only the position of the workpiece without changing its posture relative to the workpiece. At this point, the optical welding position detection device is activated to determine the groove position Qx (P v * P
z') is detected. When there is no bend in the welding wire in the Y and Z directions, PY and Py' and Pz and Pg' respectively match. When bending occurs, there will be a difference in each value, so by finding the difference, it is possible to determine the Y direction or Z direction.
A bend in direction can be detected.

In this way, after detecting the amount of bending of the welding wire,
The torch is moved to the welding start point Q2, a target welding position is determined taking into consideration the amount of bending of the wire, and welding is started. After the start of welding, while detecting the groove position at a position preceding the arc point, tracing control including the amount of bending of the wire is sequentially performed in the same way as at the welding start point.

FIG. 8 is a flowchart showing a schematic procedure for performing copy welding using the welding position detection device according to the embodiment of the present invention. In the figure, step SL is an operation for setting the protruding length of the welding wire to be constant. In step S7, a desired welding operation is performed from the welding start position to the welding end point.

When applying the device of the present invention to a robot to perform welding work up to the final welding work point, after detecting the groove position at the welding start point and the bending of the wire, the following two steps must be taken.
Choose one method and do it.

In the first method, as shown in FIG. 7, the wire end is brought into contact with the final work point to detect the coordinate position PX' in the X-axis direction. In this way, Y on the way from the welding start point to the final work point
, Z directions are detected by operating the welding position detection device using optical means as described above, and copy welding is performed.

In the second method, the coordinate position in the X direction of the final welding point is taught in advance, and the detection result of the X coordinate of the groove at the welding start point and the X coordinate position of the previously taught starting point are used.
The difference between the two coordinates is detected, and the teaching coordinate position of the final welding point in the X direction is shifted and corrected by the difference between the two, and the intermediate groove position is determined by optical means in the same way as in the method of step 1. Activate the welding position detection device and perform copy welding.

Welding wire bends because the direction and degree of bending usually changes slightly depending on changes in the orientation of the welding torch.
In actual welding work, welding may be performed by correcting the bending of the welding wire in accordance with the procedure shown in FIG. 8 for each welding part.

〔Effect of the invention〕

According to the present invention, the welding position detection device is composed of a wire contact type position detection device and an optical position detection device, and the bending of the welding wire is determined from the difference in the coordinates of the welding position determined by both types of devices at the welding start point. Since the amount can be detected, even if there is a bend in the wire, it has the effect of allowing highly accurate welding tracing without being affected by the bend. In addition, even if the bend of the welding wire changes over time, that is, while processing a large number of workpieces, or if the setting value for the wire tip changes when replacing the torch, there is no need to modify the teaching data for the wire's target position. Since welding work can be carried out at any time, it is also effective in reducing work time. In addition, since it also uses a method with a wide detection range that detects the welding position by bringing the ends of the wire into contact, it can be applied to workpieces with large positional deviations.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an example of a fully automatic arc welding robot to which a welding position detection device according to the present invention is applied;
The figure is a perspective view showing the detection principle of the optical position detection unit.
The figure is a perspective view showing the positional relationship between the optical position detection unit and the robot, Figure 4 is a diagram showing the positional relationship between the camera coordinate system and the light projecting means and the light receiving means, and Figure 5 is a diagram showing the positional relationship between the optical position detection unit and the robot. Detection example: Fig. 6 is a principle diagram of detecting the groove position of a welded member by bringing the ends of the wire into contact, and Fig. 7 is an embodiment of the present invention in which the bending of the tip of the welding wire is detected and the groove position is traced. , FIG. 8 is a flowchart showing a schematic procedure for performing copy welding using the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Welding torch, 2... Light emitting means, 3... Light receiving means, 4... Image processing device, 5... Wire contact type position detection device, 6... Welding robot, 12...・Group part,
↓4...Welding wire, Q2...Welding start point.

Claims (1)

[Claims] 1. A linear beam of light is irradiated from a welding torch onto the groove of the welded material that is a certain distance ahead of the arc point generated on the welded material, and the ray is reflected from the groove surface. an optical position detection device that detects a welding position by image processing a reflected image of the shaped light beam;
A wire that detects the welding position by bringing the welding torch close to the material to be welded according to the motion taught in advance before welding, and detecting the contact of the tip of the welding wire that protrudes from the welding torch at a certain length. A welding position detection device combined with a contact type position detection device,
The amount of bending of the welding wire is determined based on the difference between the coordinates of the welding position detected by the wire contact type position detection device at the welding start point and the coordinates of the welding position detected by the optical position detection device after moving the welding torch. A welding position detection device characterized by detecting. 2. The welding position detection device according to claim 1, comprising a welding robot and a robot control device for controlling the welding robot, and is mounted on the wrist of the welding robot. 3. By activating the wire contact type position detection device and bringing the tip of the welding wire into contact, the coordinates of the welding end point in the welding progress direction are detected, and during welding, the optical position detection device is activated to perform welding. The welding position detection device according to claim 2, wherein the welding position detection device detects a position. 4. The coordinates of the welding end point in the welding direction are taught in advance, and the coordinates in the welding direction of the welding position detected at the welding start point are compared with the coordinates in the welding direction of the welding starting point taught in advance to determine the difference. Claim 2, wherein the coordinates of the welding end point in the welding progress direction are shifted and corrected by the difference, and during welding, the optical position detection device is operated to detect the welding position. The described welding position detection device.