JP2613739B2 - Position detecting method and device by wire touch sensing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to welding performed using an arc welding robot, and a welding wire (hereinafter, also simply referred to as a wire) protruding from a welding torch by a predetermined length.
In the case of detecting the position of the welding target using the above (hereinafter, also referred to as wire touch sensing), it is necessary to correct the deviation of the detected position caused by the bending habit of the protruding wire and obtain the true position. The present invention relates to a wire touch sensing method and device that can be used.

[0002]

2. Description of the Related Art When welding a welded structure using an arc welding robot, there is a method of detecting a welding position by wire touch sensing. In this method, a certain voltage is applied to a wire cut to a predetermined length, and a signal is transmitted to the robot when the tip of the wire comes into contact with an object to be welded. If the wire is straight at this time, there is no problem. However, since the wire is usually wound on a reel or pulled out while using a hoop in a pail while straightening it, it is generally the same value as the wire diameter when the wire protrusion length is 20 mm. Causes bending.

Accordingly, it is necessary to correct the welding position obtained by the wire touch sensing described above by the amount of bending of the wire to know the correct position of the welding target. One of the means is disclosed in, for example, JP-A-3-94979. The publication discloses a method of detecting and correcting the bending of a wire by combining an optical position detecting device and a wire contact type position detecting device. FIG. 5 is a perspective view showing the detection principle of the optical position detection unit of the welding position detection device described in the above publication.

In FIG. 1, a welding torch 51 has an electrode portion 58 at a distal end thereof opposed to a groove formed at a portion where a member 54 to be welded and a material 55 to be welded standing on a plate surface thereof intersect. , The welding wire 5 fed from the electrode portion 58
An electric arc is generated between the groove 9 and the groove 57. Support 6
Numeral 0 designates a rotatable attachment with respect to the axis of the welding torch 51, and a linear condensed light beam 61 from the light projecting means 52.
Irradiation is performed at a position near the arc point preceding the arc point 57 at the groove portion of 4, 55.

[0005] In the above configuration, at the welding start point, the welding wire is brought into contact with the material to be welded by a wire contact type position device to detect the coordinates of the welding position, and then the welding torch is controlled by a welding robot for a fixed distance. Then, the optical position detecting device is moved in the direction opposite to the welding traveling direction to set the optical position detecting device at the welding start point.

The optical position detecting device obtains three-dimensional information of a groove position in a robot coordinate system having a point at a fixed distance from the tip of the welding torch (the protrusion length of the welding wire) as an origin. When the welding wire comes straight out in the welding torch axis direction, the two coordinate systems are set so that the coordinates of the welding position detected by the wire contact type position detecting device and the coordinates of the welding position detected by the optical position detecting device coincide. So, if it is measured that there is a difference between the two coordinate detection results,
It is assumed that the difference is the amount of bending of the wire.

[0007]

However, the above-mentioned prior art has the following problems. When continuously welding a plurality of members, the wire fluctuates in various directions each time, and when position detection is performed by touch sensing as it is, a position including an error due to bending is detected, so that the position accuracy of the detected workpiece is poor. Adversely affect welding quality.

[0008] The welding start position can be automatically measured in two of the three dimensions, but the remaining one dimension (the traveling direction of the torch)
It is necessary to set a torch, it takes time to set and there is a possibility that sufficient accuracy cannot be obtained. To measure the amount of wire bending and welding position,
Since the values measured by the optical position detecting device using the laser slit light and the values measured by the contact position detecting device using a wire are used together, there are always errors and deviations due to the difference between the measuring method and the measuring position. thing.

It can be applied only to straight fillet welding. Since the amount of bending of the wire is measured using an object to be actually welded and the position of the torch is corrected based on the measured amount, it takes time from the installation of the object to the start of welding. Since it is necessary to provide a sensor such as a light emitter / receiver in the welding torch near the area where the temperature becomes high due to the arc, the welding torch is complicated, and there is a possibility that the reliability is reduced. In addition to being unsuitable for sensing when there is an obstacle in a narrow position or around it, it is difficult to detect and correct this one by one because the wire bending direction after welding starts changes in various directions. Had the problem of.

The present invention has been made in order to solve such a problem, and when detecting the welding position of an object to be welded by wire touch sensing, a simple configuration increases the wire bending habit during wire touch sensing. It is an object of the present invention to provide an apparatus and a method for detecting a welding object by detecting with high accuracy.

[0011]

The above object is attained by a method and an apparatus for detecting a position by wire touch sensing described in the claims. That is, (1) a dummy tip formed linearly having the same length as a wire tip on which a welding wire having a protrusion length at the time of welding is mounted, on a reference gauge mounted on a fixed base of an arc welding robot. Means for detecting the reference position of the reference gauge at the tip of the welding wire, and means for detecting the reference position of the reference gauge at the tip of the welding wire by projecting the welding wire from the welding torch with a constant protrusion length. Means for estimating and correcting the amount of bending of the welding wire from the detected detection position data, and performing position correction in the robot coordinate system based on the amount of bending of the welding wire. . (2) The reference gauge mounted on the fixed base of the arc welding robot is sensed by the tip of the dummy chip mounted on the welding torch, and the position is detected by X, in the robot coordinate system.
The reference gauge is sensed at the tip of a welding wire protruding from the welding torch at a constant protruding length, and its position is determined as X, Y in the robot coordinate system.
The difference between the position data obtained by the above two sensings is converted into a tool as a correction value of the amount of bending habit of the wire into six components of the robot coordinate system. Position detection method using wire touch sensing to correct the position. It is. Hereinafter, the operation and the like of the present invention will be described based on examples.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment according to the present invention, a case where a branch pipe is welded to a main pipe using an arc welding robot will be described. 1 to 4 are diagrams for explaining the present embodiment. FIG. 1 is a diagram for explaining the positional relationship between each chip when sensing with a wire chip to which a bent wire is attached and a dummy chip. FIG. 2 uses a dummy chip. For explaining the procedure for sensing the reference position of the reference gauge by using FIG.
Is a schematic perspective view of a reference gauge, and FIG. 4 is a perspective view of a welded portion between a main pipe and a branch pipe.

First, a dummy chip 1 is formed by attaching a conductive straight rod having the same length as the protruding length of the wire to a chip for feeding power to the wire. The reference gauge reference position 13 is detected.

FIG. 3 shows an example of the reference gauge 6. In the figure, a reference gauge 6 is formed of steel or the like and is mounted on a table 14. After mounting the reference gauge 6 on the fixed base of the arc welding robot, first, the dummy chip 1 was pushed out toward the reference gauge 6 from a position 7 perpendicular to the axis of the reference gauge 6, and the tip contacted the reference gauge 6. The coordinates of the point A10 are obtained.

Next, the reference gauge 6 is pulled in, moved horizontally to a position sufficiently distant on the opposite side of the axis of the reference gauge 6, and pushed out the dummy chip 1 by the same stroke as when it came into contact with the point A10 (FIG. 2). 8).

The dummy chip 1 is moved in the direction of the reference gauge 6 while maintaining the extruded stroke, and the coordinates of the point B11 at which the tip of the dummy chip 1 contacts the reference gauge 6 are obtained. The points A10 and B11 are the dummy chip 1
Of the reference gauge 6 is equal to the point A
This is a position on the bisector of 10 and the point B11.

Further, on the bisector, the reference gauge 6
The point at which the dummy chip is moved toward the surface of the jig and the point on the surface of the reference gauge 6 on the center line is determined. The point at which the tip of the chip 1 contacts the table 14 is determined. This point is referred to as a reference position 13 shown in FIG.
The CALP22 value in FIG. 1 is used.

Next, the dummy chip 1 is removed and replaced with a normal wire chip 2, the wires are protruded and cut so that the wire length becomes the same as the dummy chip 1. By running the same program as in the position measurement, the coordinates of the reference position 13 of the reference gauge 6 are obtained, and that point is set as CALG0 in FIG.

If there is no bending tendency of the wire, CALP22
And CALG0 should be the same value, but if they are different, the difference will be the amount of bending habit of the wire. The bending habit amount of the wire is obtained by the X, Y, and Z components of the robot coordinate system. That is, in FIG. 1, the bending habit amount of the wire is obtained as the HOSEI value, and the tool is converted into a welding torch to move the reference position measured by the wire. That is, the tool conversion value obtained by adding the wire bending habit to the tool conversion value (X _T , Y _T , Z _T , O _T , A _T , T _T ) is (X _T + ΔX, Y _T + ΔY, Z _{T + ΔZ, O T, A} T,
T _T ).

A case will be described in which welding is actually performed by a robot using the amount of bending of the wire thus obtained. When the branch pipe 16 is joined to the mother pipe 15 as shown in FIG. 4 by welding, first, the branch pipe 16 is temporarily attached to the mother pipe 15 and then the wire tip protruding from the welding torch by a specified length is used to detect the above-described detection procedure. Reference position 17 based on
Sensing. Since the tool conversion value has been corrected in advance at the time of the sensing, the reference position 17 of the welded portion of the branch pipe 16 is determined.
Is detected correctly. Thereafter, the tool conversion value is returned to the state before correction, and then the branch pipe 16 is automatically welded to the mother pipe 15 by a robot according to a welding program.

When the above welding is completed, the traveling device equipped with the robot and the nozzle cleaner with the wire cutter is moved to the position of the branch pipe 16 where the welding is to be performed next, based on a preset program. Next, stick out the wire,
The tip of the wire is cut so that the length of the wire is the same as that of the dummy chip 1 and the oxide film portion at the tip is removed, and the reference position detected and registered in advance by the dummy chip 1 is registered. By sensing the reference position 13 of the reference gauge 6, the amount of bending habit of the wire is obtained.

Next, the tool conversion value is corrected by the amount of the bending habit, based on which the reference position of the branch pipe 16 is sensed to determine the true position of the branch pipe 16, and the tool conversion value is returned to the state before correction. The branch pipe 16 is automatically welded to the mother pipe 15 by a robot based on the true position of the pipe 16. Or later,
The above procedure is repeated to complete the welding of all the branch pipes 16 to the mother pipe 15.

Since the bending of the welding wire is not always constant and changes variously during welding, it is difficult to predict and detect the value and to prevent the occurrence of the bending. In the case where the position of the object to be welded is determined based on the wire touch sensing and the welding is performed, the welding accuracy is rather reduced.

In ordinary welding, if the object to be welded is at a true position, the effect of the bending of the wire after the start of welding on the quality of welding is negligible and can be neglected. The purpose is to detect the true position of the.

According to the present invention, in addition to the above, by correcting the bending habit of the wire which is considered to be hardly changed during welding due to the bent portion of the torch neck or the like, the uniform and high quality can be continuously obtained. Products can be obtained.

On the other hand, with respect to the change in the bending tendency of the wire caused by the wear of the power supply portion on the inner surface of the welding tip, the sensing of the reference gauge is performed each time the welding target changes, and the wire of the wire at that time is sensed. By taking in the bending data and performing tool conversion, intermediate follow-up and correction can be performed accurately and welding can be performed accurately.

Further, when the traveling device is moved to the position of the object to be welded and the welding wire is cut with reference to the position of the reference gauge previously detected and registered by the dummy chip, the welding wire is fixed by the welding wire. Since the tool gauge is detected based on the obtained reference gauge and the tool conversion is performed based on the obtained bending tendency of the wire, the time required for tool conversion can be significantly reduced as compared with the conventional method.

The present inventors have experimentally confirmed the function of correcting the amount of wire bending habit during wire touch sensing based on the above-described configuration and method. Table 1 shows the test equipment, and Table 2 shows the outline of the test method.

[0029]

[Table 1]

[0030]

[Table 2]

Tables 3 to 5 show the test results.
Is the calibration of the reference position of the nozzle to be sensed, Table 4 shows an example of the amount of wire bending habit, and Table 5 shows the traceability of the wire bending habit amount correction function, for three components of X, Y, and Z, respectively.
The average and variance were obtained.

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

From the results of the above test, the following points were confirmed. (1) From the calibration result of the reference position of the sensing target nozzle,
Judging from the generally referred to X ± 3S, an error of about 1.5 times the robot position repeatability (± 0.2 mm) is expected. (2) Based on the average value of the calibration values at the reference position of the nozzle to be sensed, when the traceability of the correction function for the bending habit of the forcibly attached wire is evaluated, it is 1/4 to 1 of the bending habit.
It should be considered that the tracking performance is good because of the difference of about / 5 times.

[0036]

As described above, according to the present invention, the following effects can be obtained as described in the above embodiment. The sensing function using a wire and the simple jig such as a dummy chip and a reference gauge make it possible to accurately detect the position even when the wire is bent. First, the reference position of the reference gauge is detected and registered by the dummy chip, and thereafter, the reference position of the reference gauge is detected by the welding wire protruding from the welding torch, and the wire is compared with the reference position of the registered reference gauge. Since the true position of the welding object can be detected by wire touch sensing based on the measurement of the amount of bending of the welding object, the time required for detecting the position of a series of welding objects and, consequently, the time required for welding can be significantly reduced. obtain. By converting the amount of bending of the wire obtained by the measurement according to the present invention into the six components of the robot, the bending of the wire measured and obtained in advance regardless of the direction in which the torch is sensed is determined. It is possible to make the correction by reflecting the amount without fail. Since both the sensing by the dummy chip and the sensing by the wire are based on touch sensing, a highly reliable and accurate measurement result can be obtained without causing an error due to a difference in measurement method. The bending habit amount of the wire, which changes every time the wire is cut, can be corrected. The position can be corrected by sensing in the same posture as the posture for welding the member to be welded. There is no need to provide a special device for sensing near the torch, which is heated by the arc.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a positional relationship between chips when sensing is performed by a dummy chip and a wire.

FIG. 2 is a diagram illustrating a procedure for sensing a reference position of a reference gauge using a dummy chip.

FIG. 3 is a schematic perspective view of a reference gauge.

FIG. 4 is a perspective view of a welded portion between a mother pipe and a branch pipe.

FIG. 5 is an example of the prior art.

[Explanation of symbols]

Reference Signs List 1 dummy chip 2 wire chip 3 bent wire 5 dummy chip registered in tool conversion value 6 reference gauge 7, 8, 9 position of dummy chip 10 point A 11 point B 12 center position of reference gauge 13 reference gauge reference position 14 units 15 mother pipe 16 branch pipe 17 reference position CALP22 reference gauge reference position CALG0 reference gauge reference position measured by wire HOSEI wire bending habit 51 welding torch 52 light emitting means 53 light receiving means 54, 55 welded material 57 groove Part 58 electrode part 59 welding wire 60 support body 61 linear condensed light beam

Continued on the front page (72) Inventor Shoji Takeichi 1 Shinhama-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Heavy Industries, Ltd. Chiba Plant (72) Inventor Chiaki Ito 1 Shinhama-cho, Chuo-ku, Chiba, Chiba Kawasaki Heavy Industries, Ltd. Chiba Factory (72) Inventor Shingo Yonemoto 1 Shinhama-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Heavy Industries, Ltd.Chiba Factory (72) Inventor Mitsuo Sato 1, Shinhama-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Heavy Industries, Ltd. Inside the factory (72) Inventor Mitsuo Suzaki 1st place, Shinhama-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Heavy Industries, Ltd. Chiba factory (56) References JP-A-3-94979 (JP, A) JP-A-54-163750 ( JP, A) JP-A-60-261676 (JP, A) JP-A 62-25066 (JP, U) JP 4-61750 (JP, B2) JP-B 3-21044 (JP, B2) Hei 3-20048 (JP, Y2) Jikken Sho 51-50815 (JP, Y2)

Claims (2)

(57) [Claims] 1. A welding using an arc welding robot, the same length as a reference gauge mounted on a fixed base of the arc welding robot, and a wire tip having a welding wire with a projection length at the time of welding. Means for detecting a reference position of the reference gauge at the tip of a linearly formed dummy tip having: a welding wire protruding from the welding torch with a constant protrusion length, and the reference at the tip of the welding wire. Means for detecting the reference position of the gauge, and means for estimating and correcting the amount of bending of the welding wire from the detected position data obtained, and correcting the position of the robot coordinate system by the amount of bending of the welding wire. A position detection device based on wire touch sensing. 2. A reference gauge mounted on a fixed base of an arc welding robot is sensed at a tip of a dummy chip mounted on a welding torch, and its position is obtained as X, Y, Z components of a robot coordinate system. The reference gauge is sensed at the tip of a welding wire protruding from the torch with a constant protrusion length, and its position is obtained as the X, Y, Z components of the robot coordinate system. The difference between the position data obtained by the above two sensings A tool conversion into six components of a robot coordinate system as a correction value of the amount of bending of the wire, thereby correcting the detection position of a detection target by wire touch sensing.