JPH11216565A - Torch position detecting device and detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deterioration of the torch position detecting accuracy to be caused by a variation of a wire protrusion length when a wire touch sensing is carried out, wherein a wire protrusion length adjusting time can be curtailed at a torch position detecting time. SOLUTION: By the use of a torch position detecting device being composed of two independent detecting units 3 which activate a given position of a welding torch 2 mounted to the fingers' end of an arc welding robot, and a judging unit 4 which utilizes an output of the detecting unit 3 as an input, a high precision torch position detecting device which does not need a wire protrusion length adjusting time can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torch position detecting device for detecting the amount of displacement of the tip of a torch when the torch interferes with an object, a jig or the like in a work performed using a robot. .

[0002]

2. Description of the Related Art Conventionally, as a method of detecting a position of a tip end of a welding wire protruding from a welding torch attached to a robot hand, there has been a method by wire touch sensing. In this method, a voltage is applied between the welding wire and the welding object protruding from the tip of the welding torch by a certain length to detect the position of the wire tip when the wire tip and the welding object make electrical contact. Is what you do. As a technique for detecting a position shift of the tip of the torch using the wire touch sensing, there is a method disclosed in Japanese Patent Application Laid-Open No. 1-257593. FIG. 8 is a diagram illustrating a detection operation according to the related art.

[0003] In the figure, a jig 13 composed of three conductive plates is disposed within the operating range of a robot, and a welding wire 7 protrudes from a welding torch 2 attached to a robot hand. In the above configuration, a voltage is applied between the welding wire 7 and the jig 13 and the robot is operated in the direction previously stored in the storage unit of the robot control device to determine the electrical contact position between the welding wire 7 and the jig 13. The position of the welding wire tip is calculated by the arithmetic unit of the robot controller from the difference between the contact position detected before the torch deformation and the contact position detected after the torch deformation, and is stored in the storage unit. Then, in the subsequent operation, the correction operation is performed by shifting the tip of the welding wire in a direction in which the displacement amount is breathed.

[0004]

However, in order to perform high-accuracy position detection in the above-described prior art, the welding wire protruding from the torch must have a predetermined length, and the wire length must be reduced during the detection operation. It is necessary that it does not change. There is an automatic wire cutting machine as a means to automatically adjust the length of the wire to an appropriate length.However, since the automatic wire cutting machine is usually separated from the torch and installed at another place within the robot operation range, The wire must be cut after positioning the tip of the torch at a predetermined position of the automatic cutting machine. Therefore, when the torch is greatly deformed, it is not possible to cut the wire at the correct position, so the operator must adjust the length of the wire. there were.

Further, there has been a problem that the posture of the torch changes during the detection operation, and the protruding length of the wire changes due to the pressure when the wire and the jig come into contact during wire touch sensing.

[0006] The present invention is to solve the above problems,
Provided is a torch position detecting device that can correct a positional deviation of a welding wire tip with high accuracy without being limited to a type of a torch when correcting a positional deviation of a welding wire tip due to deformation of a welding torch. The purpose is.

[0007]

In order to achieve the above object, the present invention provides a detector for detecting the position of a torch attached to the hand of a robot, and a torch in which the detector is arranged within the operating range of the robot. A step of operating the robot in the direction of the detector, comprising the steps of: rotating the torch around the tip position of the torch after the step; and operating the robot in the direction of the detector after the rotation. .

The present invention further comprises a detector for detecting the position of the torch attached to the hand of the robot, and a torch position detecting device in which the detector is arranged in parallel with a two-axis plane in the robot's orthogonal coordinate system. Operating the robot in a detector direction from a direction perpendicular to the axis plane;
After the step, there is a step of rotating the robot by 90 degrees around one axis constituting a two-axis plane around the torch tip position, and a step of operating the robot in the direction of the detector after the rotation.

In addition, two independent detectors for detecting the position of the welding torch attached to the hand of the arc welding robot and a determiner to which the output of the detector is input are provided.

Further, the tip portion of the welding tip is set to a specific position. Further, two detectors are arranged at positions facing each other with the electrodes of the welding torch interposed therebetween.

Further, as the detector, an elastic body having one end fixed and a limit switch disposed at the other end of the elastic body are used.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, since the position of a torch, not a welding wire, can be detected by contacting two detectors, the torch can be detected irrespective of the projecting length of the welding wire. The position can be detected.

An embodiment of the present invention will be described below.
1 to 7 are diagrams for explaining the present embodiment. FIG. 1 is a schematic diagram showing the overall configuration of a robot and a torch position detecting device,
FIG. 2 is a schematic diagram showing a detection operation on the side of the welding torch, and FIG.
FIG. 4 is a schematic diagram illustrating a detection operation at the tip of the welding tip, and FIG. 4 is a detailed diagram illustrating a detection operation at the tip of the welding tip. As shown in FIG. 1, the robot main body 1 is controlled by a robot control device 5. The torch position detector 3 is installed within the robot operating range, and the output signal line of the torch position detector 3 is
Is connected to the robot control device 5 via the.

Next, the position detecting operation on the side surface of the welding torch will be described with reference to FIG. The torch position detector 3 is composed of two independent position detectors. The two independent position detectors are formed by a combination of the torch contact portion 8 and the limit switch 10 and a combination of the torch contact portion 9 and the limit switch 11. That is, the torch contact portions 8 and 9 are commonly supported by the support portion 12. When an external force is applied from above, the torch contact portion 8 rotates around the support portion 12 as a fulcrum, pushes down the limit switch 10, and activates the limit switch 10. Similarly, when an external force is applied from above, the torch contact portion 9 rotates around the support portion 12 and pushes down the limit switch 11 to operate the limit switch 11. When the external force disappears, the limit switches 10 and 11 return to the positions before the external force was applied due to the reaction of the internal spring. The torch contact portions 8, 9 are arranged at regular intervals, and the interval is larger than the diameter of the welding wire 7 and smaller than the diameter of the welding tip 6.

In the following description, an example in which the torch position detector 3 is installed in parallel with the XY plane of the robot coordinate system and the sensing direction is performed in the Z-axis direction will be described. In addition, it is also possible to detect the torch position based on the installation position and the sensing direction of the torch position detector 3 other than those described in the example.

Referring to FIG. 6, a description will be given of a position detecting operation stored in the robot controller in advance.

Steps 1 and 2 store a position detecting operation for obtaining the inclination of the torch with respect to the Z axis. In step 1, as shown in FIG. 2B, the welding torch 2 is set in a posture such that the torch length direction is parallel to the X-axis direction of the robot coordinate system, and along the Z-axis while maintaining the posture of the welding torch. When sensing is performed, a sensing operation in which the welding torch 2 strikes the torch contact portions 8 and 9 of the torch position detector 3 is stored. In step 2, the operation of sensing along the Z-axis from the position where the position of the torch is moved in parallel by a fixed amount H along the X-axis in the same torch posture as in step 1 is stored.

In steps 3 and 4, a position detecting operation for obtaining the inclination of the torch with respect to the Y axis is stored. In step 3, the torch is rotated by -90 degrees around the X axis while the torch tip position is fixed with respect to the torch attitude in step 1, and the operation of sensing along the Z axis is stored. By rotating by −90 degrees about the X axis, sensing in the Z axis direction can be regarded as sensing in the Y axis direction. In step 4, the operation of sensing along the Z-axis from the position where the position of the torch is translated by a fixed amount H along the X-axis with the same torch posture as in step 3 is stored.

In step 5, a position detecting operation for obtaining a vertical displacement of the torch is stored. Step 1
When sensing along the Z-axis while maintaining the posture of the welding torch in the same posture as above, the sensing operation such that the welding torch 2 hits the torch contact portions 8 and 9 of the torch position detector 3 is stored.

Step 6 is perpendicular to the torch and step 5
A position detection operation for obtaining a position shift in a direction perpendicular to the direction of the position shift detected in step (1) is stored. When sensing along the Z-axis while maintaining the posture of the welding torch in the same posture as in step 3, the sensing operation is stored such that the welding torch 2 hits the torch contact portions 8 and 9 of the torch position detector 3.

In step 7, a position detection operation for obtaining a position shift in the direction along the torch is stored. As shown in FIG. 3, the welding torch 2 is set so that the torch length direction is perpendicular to the torch position detector 3. When sensing along the Z axis while maintaining this posture, FIG.
As shown in (a), the welding tip 6 is connected to the torch contacts 8 and 9.
Is stored in the middle of the sensing operation.

When performing the detection operations of steps 1 to 6 in FIG. 6, the decision unit 4 in FIG.
When either one of the detection signals 0 and 11 is input,
A detection signal is transmitted to the robot controller 5, and the robot controller 5 stores the torch tip position and posture with respect to the robot coordinate system at the time when the signal is input.

When performing the detection operation in step 7 in FIG.
When both of the detection signals of the limit switches 10 and 11 are input, the determination unit 4 of FIG. 1 transmits a detection signal to the robot control device 5, and the robot control device 5 transmits the detection signal to the robot coordinate system at the time when the signal is input. The torch tip position and attitude are stored. As shown in FIG. 4B, when the torch position is not located between the torch contact portions 8 and 9 and only one of the limit switch detection signals is input, an error signal is transmitted to the robot controller 5 to control the robot. The device 5 performs error processing such as stopping the robot.

Next, before the welding torch is deformed, the position detecting operations of steps 1 to 7 in FIG.
Respectively corresponding to the detection positions P1, P2, P3, P4
P5, P6, and P7 are stored.

From the position data P1 to P4, the unit vector i in the torch direction in Step 1 before the torch deformation is obtained.
Is calculated. As shown in FIG. 5, an arbitrary one of the torch tip positions stored at the time of performing the detection operation in step 1 is defined as a position T1, and a YZ plane passing a point separated by a fixed amount H from the position T1 along the X-axis direction. Assuming that the position of the intersection of the torch and the center line of the torch before deformation is T2, the position T2 is T2 = f
As shown in (T1, ΔP12z, ΔP34z), it is expressed by a relational expression of the difference ΔP12z between the Z direction components of P1 and P2, the difference ΔP34z between the Z direction components of P3 and P4, and the position T1.

The center line of the torch is located at the positions T1, T
2, the unit vector i in the torch direction at this time
Is the position T1 and the position T2 as i = f (T1, T2).
Is represented by the following relational expression.

An orthogonal three-axis unit vector (i, j, k) of a tool coordinate system having the unit vector i in the torch direction obtained by i = f (T1, T2) as the X axis is appropriately determined and stored.

Next, the position detection operation after the welding torch is deformed and the method of calculating the torch correction amount will be described with reference to FIG.

In step a, the position detection operations of steps 1 to 4 in FIG. 6 are performed, and the respective detection positions P1 ', P2
', P3' and P4 'are stored.

In step b, the torch posture correction value ΔM is calculated from the position data P1 ′ to P4 ′ and stored. An arbitrary one of the torch tip positions stored at the time of performing the detection operation in Step 1 is defined as a position T1, and a torch deformation passing through a point separated from the position T1 by a fixed amount H along the X axis and a position T1. Assuming that the position of the intersection where the line parallel to the center line of the later torch intersects is T2 ', the position T2' is T2 '.
2 ′ = f (T1, ΔP12′z, ΔP34′z) The difference ΔP12 ′ between the Z-direction components of P1 ′ and P2 ′
z, the difference ΔP34′z between the Z-direction components of P3 ′ and P4 ′,
It is expressed by the relational expression of the position T1.

The center line of the torch is defined by the positions T1 and T
Since it is parallel to the line passing through 2 ', the unit vector i' in the torch direction at this time is represented by a relational expression of the position T1 and the position T2 'as i' = f (T1, T2 ').

The orthogonal three-axis unit vector (i ', j', k ') of the tool coordinate system having the torch direction unit vector i' determined by i '= f (T1, T2') as the X axis is determined. Remember.

A rotation matrix ΔM for converting and correcting the unit vector (i ′, j ′, k ′) of the tool coordinate system after the torch deformation into the unit vector (i, j, k) of the tool coordinate system before the torch deformation. Is ΔM = f ((i, j, k), (i ′, j)
', K')).

This ΔM is stored as a torch attitude correction value. In step c, the position detection operations of steps 5 to 6 in FIG. 6 are performed with the ΔM corrected, and the detected positions P5 ′ and P6 ′ are stored.

At step d, the Z-direction component of the position P5 'and the detection position P5 before the torch deformation stored in advance are stored.
Is converted to a value ΔP5t for the tool coordinate system in step 5 of FIG. 6 and stored. Similarly, the difference ΔP between the Z-direction component of the position P6 ′ and the previously stored Z-direction component of the detection position P6 before the torch deformation is detected.
6 with the value ΔP for the tool coordinate system in step 6 of FIG.
Converted to 6t and stored.

In step e, ΔM, ΔP5t + ΔP6
The position detection operation of step 7 in FIG. 6 is performed with t corrected, and the detected position P7 'is stored.

In step f, the Z-direction component of the position P7 'and the detection position P7 before the torch deformation stored in advance are stored.
Is converted to a value ΔP7t for the tool coordinate system in step 7 of FIG. 6 and stored.

By the above-described position detection operation, the correction amount of the torch position with respect to the tool coordinate system (ΔP5t + ΔP6t + Δ
P7t) and the torch posture correction amount ΔM are stored. Then, the operation can be performed by correcting the position and the posture with respect to the operation taught and stored before the torch deformation.

[0039]

As is apparent from the above description, according to the present invention, two independent position detectors for detecting a specific position of the welding torch attached to the hand of the welding robot, and the output of the detector. By using the torch position detection device consisting of a judgment device with the input of the torch, it is possible to reduce the time required for adjusting the wire protrusion length when detecting the torch position by touch sensing of the welding wire, and the wire touch sensing In this case, it is possible to provide a high-accuracy torch position detection device that can solve the problem that the detection accuracy is deteriorated due to a change in the wire protrusion length.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an overall configuration of a robot and a torch position detecting device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a detection operation on a side surface of the welding torch in the embodiment.

FIG. 3 is a schematic diagram showing a detection operation at the tip of the welding tip in the embodiment.

FIG. 4 is a detailed view showing a detection operation at the tip of the welding tip in the embodiment.

FIG. 5 is a view for explaining a position of a torch in the embodiment.

FIG. 6 is a flowchart showing a position detection operation stored in advance in the embodiment.

FIG. 7 is a flowchart showing a position detection operation after torch deformation in the embodiment.

FIG. 8 is a diagram illustrating a detection operation according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Robot main body 2 Welding torch 3 Torch position detector 4 Judgment device 5 Robot controller 6 Welding tip 7 Welding wire 8, 9 Torch contact part 10, 11 Limit switch 12 Support part 13 Conductive jig

Claims (6)

[Claims] 1. A detector for detecting a position of a torch attached to a hand of a robot, and a torch position detecting device having the detector arranged within an operation range of the robot, and operating the robot in the direction of the detector. A torch position detecting method comprising: rotating the torch around the torch tip position after the step; and operating the robot in the direction of the detector after the rotation. 2. A torch position detecting device comprising: a detector for detecting a position of a torch attached to a hand of a robot; and a torch position detecting device having the detector arranged in parallel with a two-axis plane in a rectangular coordinate system of the robot. Operating the robot in a detector direction from a direction perpendicular to the axis plane, rotating the torch by 90 degrees around one axis constituting a two-axis plane around the torch tip position after the step, A method for detecting a torch position, comprising the step of operating a robot in the direction of a detector. 3. A torch position detecting device provided with two independent detectors for detecting the position of a torch attached to a hand of a robot, and a determiner which receives an output of the detector as an input. 4. The torch position detecting device according to claim 3, wherein the tip of the torch is used as a detection position. 5. The two torch at opposite positions with the electrode of the torch interposed therebetween.
4. The torch position detecting device according to claim 3, wherein two detectors are arranged. 6. The torch position detecting device according to claim 3, wherein an elastic body having one end fixed and a limit switch disposed at the other end of the elastic body are used as the detector.