JP2003181645A - Robot control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot control system in which distance between tool base materials is managed per set value, favorable metal working result is obtained free from defective deviation from an aiming point of a metal working line and a robot locus can be taught in a short period of time. <P>SOLUTION: The robot control system for a work robot holding a metal work tool is equipped with a work base material distance setting means for setting the distance being an interval in the height direction of the work tool to a work to be worked, a work tool height direction vector computing means for computing the height direction vector of the work tool and a tool base material distance adding means for adding the work tool height direction vector computed by the work tool height direction vector computing means to the robot locus. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot controller for a work robot that holds a metal working tool, and more particularly to simplification of teaching work.

[0002]

2. Description of the Related Art Teaching work is a very important control item in a work robot holding a metal working tool. The quality of the work result is affected by the quality of the teaching work. The conventional teaching work will be described below by taking a welding robot holding a welding torch as an example. FIG. 13 is a configuration diagram of a non-consumable electrode type arc welding robot system. The robot controller 1 uses the robot command cable 8 to move the robot 2
To the welding power source 3 through the operation command and the welding command cable 9 to perform various controls. A welding torch 4 having a non-consumable electrode 5 is attached to the arm tip of the robot 2. Welding work consisting of base metal 6 and base metal 7 and non-consumable electrode
A voltage is applied between the 5 through the power cable 10 by the welding power source 3 to join the base material 6 and the base material 7. Robot 2
The work program in which the operation locus and the welding conditions are set and stored can be displayed and confirmed on the work program display means 30.
FIG. 14 is a diagram simply showing an internal functional configuration of the robot controller 1. The robot controller 1 operates on the robot position registration means 15 for registering the robot position, the welding condition setting means 14 for setting the welding conditions and the welding section, the work program storage means 11 for storing the program created in the teaching work, and the robot 2. It has robot operation command output means 13 for outputting a command and welding command output means 12 for outputting a welding command to the welding power source 3. Further, the work program storage means 11
Consists of welding condition storage means 16 and robot trajectory storage means 17.

At the time of teaching, the robot position is registered by the robot position registration means 15 and stored in the robot trajectory storage means 17 in the work program storage means 11. Further, the welding condition and the welding section are set by the welding condition setting means 14, and the set contents are stored in the welding condition storage means 16 in the work program storage means 11. During automatic operation, the robot operation command output means 13 outputs an operation command to the robot 2 according to the contents stored in the robot trajectory storage means 17, and the robot 2 operates. Further, in the welding section, according to the setting contents stored in the welding condition storage means 16, the welding command output means 12 outputs a welding command to the welding power source 3 to perform welding.

Next, the procedure of teaching work will be described with reference to FIG. Figure 11 shows the base metal 7 in a direction perpendicular to the welding progress direction.
The state of the welding work seen from the side is shown. First, the robot 2 is manually operated to move the tip of the non-consumable electrode 5 of the welding torch 4 to the point A and register the position of the point A. Next, the tip of the non-consumable electrode 5 of the welding torch 4 is moved to a point B above the point B ′ existing on the welding line between the base metal 6 and the base metal 7. As shown in FIG. 12, the robot 2 is manually operated so that the welding line of the welding work and the tip of the non-consumable electrode 5 of the welding torch 4 are on the axis in the work tool height direction. At this time, the distance between the tip of the non-consumable electrode 5 of the welding torch 4 and the tool base material of the welding work (the distance between the points B and B '), that is, the arc length, is visually controlled so that the desired value is obtained. Register the position by manually operating the tip of the non-consumable electrode 5 of 4 to point B. This tool base material distance is usually set to about 2 to 3 mm. Similarly, the tip of the non-consumable electrode 5 of the welding torch 4 is manually operated to the point C above the point C ′ existing on the welding line, and the distance between the tool base materials is controlled by visual measurement so that the distance between the tool base materials becomes a desired value. Register point C. Point B corresponds to the welding start point and point C corresponds to the welding end point. Finally, the tip of the non-consumable electrode 5 of the welding torch 4 is manually operated at the point D to register the point D.

A program created by teaching in this way is shown in FIG. Non-consumable electrode 5 on welding torch 4 in step 1
The tip moves to point A and moves to point B which is the welding start point in step 2. Next, in step 3, a welding start command is output to the welding power source 3 to start welding work. In step 4, welding work is executed while moving to point C. In step 5, the welding end command is output to the welding power source 3 and the welding work is completed. Move to point D in step 6. The welding section is from step 3 to step 5. As described above, in the prior art, the teaching work is performed by managing the distance between the tool base materials by visual measurement.

[0006]

However, in the teaching method by the conventional robot control device, the distance between the tool base materials is controlled by visual observation, so that the distance between the tool base materials does not reach a desired set value, or Since the teaching is performed in a space away from the welding line, the target position of the welding line may be displaced.
FIG. 16 shows teaching positions when the distance between tool base materials is visually controlled and taught. When the distance between the tool base materials is not as set and the target position of the welding line is deviated as described above, there is a problem that a good welding result cannot be obtained and a breakage or a penetration failure occurs. Further, since the teaching is performed in the space away from the welding line, there is a problem that it takes time to move to a desired teaching point. In particular, when the height direction of the welding torch is not parallel to the one axis direction of the manual operation of the robot, it is necessary to operate the robot in multiple axes, which makes teaching work difficult and troublesome.

According to the present invention, the distance between tool base materials is managed according to the set value, a good welding result can be obtained without causing the target position deviation of the welding line, and the robot trajectory can be easily taught in a short time. The present invention provides a robot control device that can be used.

[0008]

In order to solve the above-mentioned problems, a robot controller according to a first aspect of the present invention is a work robot holding a metal working tool, and the robot trajectory, work conditions and work sections are stored in advance. In a robot controller having a work program display means for controlling the robot and a metalworking power source by the created work program and displaying the contents of the work program, the height of the work tool with respect to the work to be processed is limited to the work section. Work base-to-base material distance setting means for setting a distance which is an interval between directions, work tool height direction vector calculation means for calculating a height direction vector of a work tool, and the work tool height direction vector calculation for the robot trajectory. Tool base material distance adding hand for adding the work tool height direction vector calculated by means It is characterized by comprising and.

According to a second aspect of the present invention, the work program display means displays the tool base material distance for each step in the work section of the work program.

A robot controller according to a third aspect of the present invention is a work robot which holds a metal working tool, and controls the robot and the metal working power source by a work program in which a robot trajectory, work conditions and work sections are stored in advance. A robot controller having work program display means for displaying the contents of the work program; and a tool base material distance setting means for setting a distance in the height direction of the work tool with respect to a workpiece, and a height direction of the work tool. Work tool height direction vector calculation means for calculating a vector; tool base material distance addition means for adding the work tool height direction vector calculated by the work tool height direction vector calculation means to the robot position; The robot position is set at the position where the work tool height direction vector is added to the robot position. A robot position correction request means for outputting a command for moving the door, and the robot current position reading means for acquiring data of the robot position, characterized in that a robot position storage means for storing the robot position.

According to a fourth aspect of the present invention, there is provided a robot position return request means for outputting a command for returning the robot to the robot position stored in the robot position storage means when teaching the work program. It is characterized by that.

A robot controller according to a fifth aspect of the present invention is a work robot in which a metal processing tool is a welding torch with a non-consumable electrode, and stores a relationship between an optimum distance between tool base materials with respect to a set welding current. It is characterized in that an inter-distance optimum condition storage means is provided.

According to a sixth aspect of the present invention, there is provided a robot control device comprising force detection means for detecting contact between the work and the work tool.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 shows the first embodiment of the present invention.
It is a block diagram in the Example of. An example of arc welding using a welding torch with a non-consumable electrode for a metal working tool will be described. In the first embodiment of the present invention, a tool base material distance setting means 21, a work tool height direction vector calculation means 22, and a tool base material distance addition means 23 are added to the configuration of the prior art shown in FIG. Is a feature. The work tool height direction vector will be described with reference to FIG. As shown in FIG. 17, the work tool height direction vector is a vector having a direction opposite to the direction in which an arc is generated from the non-consumable electrode 5 to the base materials 6 and 7. The work tool height direction vector calculation means 22 of FIG. 1 calculates a vector in the work tool height direction using the tool base material distance (arc length) set by the tool base material distance setting means 21 as a vector length. . The tool base material distance adding means 23 adds the vector in the work tool height direction calculated by the work tool height direction vector calculation means 22 to the robot trajectory to correct the trajectory.

Next, the procedure of the teaching work of the present invention will be described.
It will be explained using 7. FIG. 7 shows the state of the welded work seen from the base metal 7 side in a direction perpendicular to the welding proceeding direction. First, the robot 2 is manually operated to move the tip of the non-consumable electrode 5 of the welding torch 4 to the point A and register the position of the point A. Next, the position is registered as a teaching point at point B'on the welding line. Welding torch
Since the tip of the non-consumable electrode 5 of 4 is in contact with the welding line of the welding work as shown in FIG. 8, there is no possibility that the target displacement as seen in FIG. 16 of the prior art occurs. Similarly, the tip of the non-consumable electrode 5 of the welding torch 4 is manually operated and the position is registered as a teaching point at point C ′ on the welding line. Point B'corresponds to the welding start point and point C'corresponds to the welding end point. Finally, the tip of the non-consumable electrode 5 of the welding torch 4 is manually operated at the point D to register the point D.
Further, the tool base material distance setting means 21 sets an amount for correcting the locus of the welding section B ′ point C ′ in the work tool height direction, that is, the tool base material distance setting means 21. As described above, it is sufficient to register the teaching point position by bringing the welding line of the welding work into contact with the tip of the non-consumable electrode 5 of the welding torch 4 in the welding section at the time of teaching, and set the tool base material distance.

Next, the operation of the robot 2 in automatic driving will be described with reference to FIG. FIG. 11 shows the state of the welding work viewed from the base metal 7 side in a direction perpendicular to the welding proceeding direction. During automatic operation, first, the tip of the non-consumable electrode 5 of the welding torch 4 moves to point A. Next, the tip of the non-consumable electrode 5 of the welding torch 4 is moved by the amount set by the tool base metal distance setting means 21 from the taught point B ′ to the tool base material distance adding means 23.
Corrects the locus by and moves to point B. Similarly, taught
The tip of the non-consumable electrode 5 of the welding torch 4 is corrected from the point C ′ by the amount set by the tool base material distance setting means 21 by the tool base material distance adding means 23 to operate at point C. Finally move to point D. In this way, in the welding section, the robot trajectory is a robot operation in which the trajectory is corrected by the distance between the tool base materials set in the work tool height direction. As described above, in the first embodiment of the present invention, FIG.
As shown in Fig. 8, the welding work is taught so that the non-consumable electrode 5 of the welding torch 4 contacts in the welding section, and during automatic operation, the trajectory is corrected in the welding section by the set distance between the tool base metal at the teaching point. The feature is that it operates as shown in FIG. According to such a teaching method, since the trajectory is taught in which the target position deviation of the welding line does not occur and an accurate tool base material distance is secured, the welding quality is improved and stable welding can be realized. Further, the teaching work is facilitated and the teaching time is shortened.

(Embodiment 2) A second embodiment of the present invention is shown in FIG. FIG. 2 is a work program created by the teaching method shown in the first embodiment of the present invention. It shows a state in which the set value of the distance between tool base materials for correcting the trajectory in the welding section is additionally displayed on the work program display means. "+2" is additionally displayed in the instruction of the section from Step 2 to Step 5 in Fig. 2, that is, the welding section, and this indicates the value of the set distance between tool base materials (unit: mm). As described above, the second embodiment of the present invention is characterized in that it is possible to easily grasp the step of trajectory correction and the amount of trajectory correction in the welding section in the automatic operation.

(Embodiment 3) FIG. 3 shows a block diagram of a third embodiment of the present invention. In the configuration of the conventional technology shown in FIG. 14,
Tool base material distance setting means 21, work tool height direction vector calculation means 22, tool base material distance adding means 23, robot position correction requesting means 24, robot position storing means 25, robot current position reading means 29 are added. The feature is the point. The work tool height direction vector calculation means 22 calculates a vector in the work tool height direction using the tool base material distance (arc length) set by the tool base material distance setting means 21 as a vector length. The tool base material distance adding means 23 adds the vector in the work tool height direction calculated by the work tool height direction vector calculating means 22 to the robot position to correct the trajectory. The robot position correction requesting means 24 gives a robot movement request command to the work tool height vector direction calculated by the work tool height direction vector calculating means 22, and the robot current position reading means 29 gives the robot position correction requesting means 24. The current position of the robot immediately before is executed is read, and the robot position storage means 25 stores the robot position. To the stored robot position, the tool base material distance adding means 23 adds the vector in the work tool height direction calculated by the work tool height direction vector calculation means 22 to correct the locus, and the robot operation command output means 13 The robot works.

Next, the procedure of the teaching work of the present invention will be described.
It will be explained using 9. FIG. 9 shows a state of the welding work viewed from the base metal 7 side in a direction perpendicular to the welding progress direction. First, the amount by which the locus of point B'and C'is corrected in the work tool height direction, that is, the distance between tool base materials is the tool base material distance setting means 21.
To set the desired value. The robot 2 is manually operated to move the tip of the non-consumable electrode 5 of the welding torch 4 to the point A and register the point A. Next, the tip of the non-consumable electrode 5 of the welding torch 4 is manually operated at the point B'on the welding line. Welding torch
Since the tip of the non-consumable electrode 5 of 4 is in contact with the welding line of the welding work as shown in FIG. 8, there is no possibility that the target displacement as seen in FIG. 16 of the prior art occurs. When the robot position correction requesting means 24 is executed when the tip of the non-consumable electrode 5 of the welding torch 4 is located at the point B ', the robot current position reading means 29 stores the current position of the robot in the robot position storing means 25 and stores it. The robot position is corrected by adding the tool base material distance set by the tool base material distance setting means 21 to the robot position to correct the set tool base material distance in the work tool height direction. It operates and robot 2 stops. Since this stop point corresponds to point B, the position is registered as a teaching point. Similarly, the tip of the non-consumable electrode 5 of the welding torch 4 is manually operated at the point C'on the welding line. When the robot position correction requesting means 24 is executed when the tip of the non-consumable electrode 5 of the welding torch 4 is located at the point C ', the robot current position reading means 29
The current position of the robot is stored in the robot position storage means 25, and the robot position is corrected and set by adding the tool base material distance set by the tool base material distance setting means 21 to the stored robot position. The robot operates in the height direction of the work tool so as to secure the distance between the tool base materials.
Will stop. Since this stop point corresponds to point C, the position is registered as a teaching point. Finally, the tip of the non-consumable electrode 5 of the welding torch 4 is manually operated at the point D to register the point D.

As described above, at the time of teaching, in the welding section, the welding line of the welding work and the tip of the non-consumable electrode 5 of the welding torch 4 are brought into contact with each other to be the reference point, and the work tool height direction vector is calculated to calculate the desired tool mother. Since the robot operates and stops at the distance between the materials, the stop point may be registered as a teaching point. According to such a teaching method, since the trajectory is taught in which the target position deviation of the welding line does not occur and an accurate tool base material distance is secured, the welding quality is improved and stable welding can be realized. Also, teaching work becomes easier,
Teaching time is shortened. The work program created by such a teaching method is exactly the same as the work program created by being taught accurately with the conventional technique shown in FIG. The operation during automatic operation is the same as in the prior art, and will not be described.

(Embodiment 4) FIG. 4 shows a block diagram of a fourth embodiment of the present invention. A feature is that a robot position return requesting means 26 is added to the configuration of the third embodiment shown in FIG. For example, the present invention operates the tip of the non-consumable electrode 5 of the welding torch 4 at point B in FIG.
Again, it is effective in confirming that the B'point, which is the reference point of B point, exists on the welding line and there is no misalignment of the target position. The teaching procedure at point B will be described below as an example. First, the tip of the non-consumable electrode 5 of the welding torch 4 is moved to point B'on the welding line by manual operation. At the same time that the robot position correction requesting means 24 commands the movement to point B, the robot current position reading means 29
The robot position of the point is read and stored in the robot position storage device 25. The tool base material distance adding means 23 adds the work tool height direction vector to the robot position of B'point to correct the trajectory, and the tip of the non-consumable electrode 5 of the welding torch 4 moves to B point and teaches B point. Register the position as a point. Here, there is a case where it is desired to check again whether the position of point B'exists on the welding line. In such a case, robot position return requesting means
When step 26 is executed, the input portion of the work tool height direction vector of the tool base material distance adding means 23 is disconnected, and only the robot position stored in the robot position storage means 25 is stored in the tool base material distance adding means 23. Is entered. That is, the movement command to the reference point B'is the robot operation command output means.
The robot 2 is returned to the point B ', which is given to the reference point 13 as a reference point. With such a method, the position of the point B ′, which is the reference point of the point B, can be easily confirmed, and the target position of the welding line can be managed.

(Fifth Embodiment) FIG. 5 shows a fifth embodiment of the present invention. In the fifth embodiment, the embodiment described so far,
For example, a tool base material distance optimum condition storage means 27 is added to the first embodiment. First, the tool base material distance optimum condition storage means 27 will be described. FIG. 10 shows the relationship between the welding current and the welding voltage and the distance between the tool base materials (arc length) with respect to the welding current. Since non-consumable electrode type arc welding uses a welding power source having a constant current characteristic, the operator only needs to set the welding current, and the welding voltage is determined by the arc length. Therefore, the welding conditions may be set by the welding current used and the distance between the tool base materials (arc length). In FIG. 10, the area surrounded by an ellipse is the optimum welding condition area. The optimum conditions are the arc length L1 for the welding current I1 used, the arc length L2 for the welding current I2 used, and the arc length L3 for the welding current I3 used. The relationship between the tool-base metal distance with respect to the welding current used is stored in the tool-base metal distance optimum condition storage means 27. Therefore,
In the fifth embodiment of the present invention, if the welding current used is set,
The optimum tool base material distance is automatically determined and set in the tool base material distance setting means 21. As described above, the feature is that even if the operator does not set the distance between the tool base materials, the optimum distance between the tool base materials is derived and set.

(Sixth Embodiment) FIG. 6 shows a sixth embodiment of the present invention. In the sixth embodiment, the embodiment described so far,
For example, the force detecting means 28 is added to the first embodiment. The force detecting means 28 is the non-consumable electrode 5 of the welding torch 4.
And a change in force generated when the welding work comes into contact with each other to detect the contact between the non-consumable electrode 5 and the welding work. The force detection means 28 detects the contact between the non-consumable electrode 5 of the welding torch 4 and the welding work, and the robot operation command output means 13 and the robot 2
The robot is stopped instantly by separating the spaces. As a result, it is possible to prevent a mistake in teaching that the operator accidentally strongly collides the non-consumable electrode with the welding work, and protect the non-consumable electrode.

(Other Application Examples) Similar effects can be achieved even when a tool used for laser cutting, laser welding, plasma cutting, or plasma welding is used as the metal working tool.

[0025]

As described above, according to the robot control device of the first aspect, the reference point is provided on the welding line, and only the distance between the tool base materials set in the work tool height direction is calculated from the reference point. By correcting the trajectory in the height direction of the tool and operating the robot, the distance between the tool base materials can be maintained as set, and the welding trajectory can be taught without the target position deviation of the welding line. Is improved. Further, by calculating the work tool height direction vector having the set distance between the tool base materials, there is no need to visually check the distance between the tool base materials to teach, so the teaching work becomes easy and the teaching time becomes longer. Shortened. According to the robot control device of the second aspect, it is possible to easily grasp the steps of trajectory correction and the amount of trajectory correction of the welding section in the automatic operation by the work program display means. According to the robot control device of claim 3, a reference point is provided on the welding line, and the trajectory is corrected in the work tool height direction by calculating only the distance between the tool base materials set in the work tool height direction from the reference point, By operating the robot,
The tool base metal distance as set can be maintained, and the welding locus can be taught without the target position deviation of the welding line occurring, thus improving the welding quality. Further, by calculating the work tool height direction vector having the set distance between the tool base materials, there is no need to visually check the distance between the tool base materials to teach, so the teaching work becomes easy and the teaching time becomes longer. Shortened. According to the robot control device of claim 4, it is possible to move the robot to the reference point by the robot position return request means, easily reconfirm the position of the reference point, and manage the target position of the welding line. it can. According to the robot control device of the fifth aspect, by including the tool base material distance optimum condition storage means, it is possible to automatically select the optimum tool base material distance for the set welding current.
According to the robot control device of claim 6, the force detection means is provided to detect the contact between the metal working tool and the work and stop the robot operation, so that the metal working tool is not accidentally struck. The tool can be protected.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a teaching operation according to the first embodiment of the present invention.

FIG. 8 is a diagram showing teaching points according to the first embodiment of the present invention.

FIG. 9 is a diagram showing teaching work according to a third embodiment of the present invention.

[Fig. 10] Diagram showing the relationship among welding current, welding voltage, and distance between tool base materials

FIG. 11 is a diagram showing teaching contents and robot operation of automatic driving.

[Fig. 12] Diagram showing correct teaching contents

[Fig. 13] Configuration diagram of a non-consumable electrode type arc welding robot system

FIG. 14 is a block diagram of a conventional robot controller

[Fig.15] Work program taught

FIG. 16 is a diagram showing incorrect teaching contents.

FIG. 17 is a diagram showing a work tool height direction vector.

[Explanation of symbols]

1: Robot controller 2: Robot 3: welding power source 4: welding torch 5: Non-consumable electrode 6: Base material 7: Base material 8: Robot command cable 9: Welding command cable 10: Power cable 11: Work program storage means 12: Welding command output means 13: Robot operation command output means 14: Welding condition setting means 15: Robot position registration means 16: Welding condition storage means 17: Robot trajectory storage means 21: Tool base material distance setting means 22: Work tool height direction vector calculation means 23: Tool base material distance adding means 24: Robot position correction requesting means 25: Robot position storage means 26: Robot position return request means 27: Tool base material distance optimal condition storage means 28: Force detection means 29: Robot current position reading means 30: Work program display means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinji Okumura             2-1, Kurosaki Shiroishi, Hachiman Nishi-ku, Kitakyushu City, Fukuoka Prefecture               Yasukawa Electric Co., Ltd. F-term (reference) 3C007 AS11 JU03 KS17 KS31 LS01                       LS16 MT04                 5H269 AB12 AB33 CC09 QE18

Claims (6)

[Claims] 1. A work robot holding a metal working tool, wherein the robot and the metal working power source are controlled by a work program in which a robot trajectory, work conditions and work sections are stored in advance, and the work program contents are displayed. In a robot controller having a work program display means, a work base material distance setting means for setting a distance, which is an interval in a height direction of the work tool with respect to a work to be processed, only for the work section, and a work tool height. Working tool height direction vector calculating means for calculating a height direction vector, and tool base material distance adding means for adding the work tool height direction vector calculated by the work tool height direction vector calculating means to the robot trajectory. And a robot controller. 2. The robot controller according to claim 1, wherein the work program display means displays the distance between the tool base materials for each step in the work section of the work program. 3. A work robot holding a metal working tool, wherein the robot and the metal working power supply are controlled by a work program in which a robot trajectory, work conditions, and work sections are stored in advance, and the work program contents are displayed. In a robot controller having a work program display means, a tool base material distance setting means for setting a distance in the height direction of the work tool with respect to a work, and a work tool height for calculating a height direction vector of the work tool Direction vector calculation means, tool tool inter-material distance adding means for adding the work tool height direction vector calculated by the work tool height direction vector calculation means to the robot position, and the work tool height at the robot position A robot that outputs a command to move the robot to the position where the direction vector is added A robot control apparatus comprising: a position correction requesting means, a robot current position reading means for acquiring data of the robot position, and a robot position storing means for storing the robot position. 4. The robot position return request means for outputting a command for returning the robot to the robot position stored in the robot position storage means when teaching the work program. The robot controller described in 3. 5. A work robot using a metal processing tool as a welding torch with a non-consumable electrode, comprising a tool base metal distance optimum condition storage means for storing a relationship between an optimum tool base metal distance with respect to a set welding current. Claim 1 characterized in that
5. The robot controller according to claim 4. 6. The robot controller according to claim 1, further comprising a force detection unit that detects contact between the work and the work tool.