Robot welding system

Abstract

To provide a robot welding system which enables improvement of operation controllability of a robot in friction stir welding.SOLUTION: A robot welding system 1 performs friction stir welding to a workpiece 2 and includes: a multi-joint robot 5; a spindle 6 provided at an arm tip of the robot 5; and a sensor part S whose position is fixed relative to the spindle 6 and which measures distances in directions in a first mode and a second mode. The sensor part measures the distances in an x axis direction, a y axis direction, and a z axis direction in the first mode and measures distances from a first position, a second position, and a third position to the z axis direction in the second mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a robotic welding system for friction stir welding workpieces. [Background technology]

[0002] Friction stir welding (friction stir joining) is sometimes used in metal welding. Friction stir welding is disclosed, for example, in Patent Document 1. In addition, friction stir welding is suitable for welding aluminum parts in the electric vehicle field, for example, and is therefore expected to be applied in a wider range of applications. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-340975 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in friction stir welding, welding is performed while pressing a spindle attached to the tip of a robot's arm against a workpiece, so there is a possibility that bending may occur in, for example, a joint of the robot where the spindle is attached. When bending occurs, it becomes difficult to accurately estimate the state of the spindle's position, etc., based on the robot's joint angle, etc., and the controllability of the robot decreases.

[0005] In view of the above problems, an object of the present invention is to provide a robot welding system capable of improving the controllability of the operation of a robot in friction stir welding. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the robot welding system of the present invention is a robot welding system that friction stir welds workpieces, and includes a multi-joint robot, a rotating member provided at the end of an arm of the multi-joint robot, and a sensor unit whose position is fixed relative to the rotating member and that measures distances in each direction in a first mode and a second mode, wherein in the first mode, the sensor unit measures distances in each of two directions that are perpendicular to the rotation axis of the rotating member and perpendicular to each other, and a direction that is parallel to the rotation axis of the rotating member and perpendicular to the two directions, and in the second mode, measures distances in a direction parallel to the rotation axis of the rotating member from each of a first position located in a first radial direction relative to the rotation axis of the rotating member, a second position located in a second radial direction perpendicular to the first radial direction, and a third position located in a third radial direction perpendicular to the second radial direction.

[0007] In addition, the robot welding system further includes a control device that controls the articulated robot, and the control device includes a position estimation unit that estimates a position of the rotating member based on a measurement result of the sensor unit corresponding to the first mode.

[0008] In addition, in the robot welding system, the control device further includes an inclination estimation unit that estimates an inclination of the rotating member based on measurement results corresponding to each of the first position, the second position, and the third position corresponding to the second mode of the sensor unit.

[0009] In addition, in the robot welding system, the control device further includes a generation unit that generates correspondence data between the articulated robot and each of a plurality of reference positions on a reference surface based on information about moving the articulated robot so that the rotation axis of the rotating member is perpendicular to the reference surface at the reference position. Effect of the Invention

[0010] According to the robot welding system of the present invention, it is possible to provide a robot welding system that can improve the controllability of the robot's operation in friction stir welding. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of an overall configuration of a robot welding system according to an embodiment of the present invention. [Diagram 2] 2A to 2C are diagrams illustrating an example of a position estimation mode and an inclination estimation mode of a sensor unit in the robot welding system of FIG. 1. [Diagram 3] 2 is a block diagram showing an example of various functions of a control device provided in the robot welding system of FIG. 1. [Figure 4] FIG. 2 is a diagram showing an example of a reference plane of the pedestal of FIG. 1. [Diagram 5] 2 is a flowchart showing an example of a flow of a friction stir welding process in the robot welding system of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same reference numerals are used to designate the same components in each drawing, and duplicated description will be omitted as appropriate.

[0013] === Implementation form === <Overall composition> 1 is a diagram illustrating an example of the overall configuration of a robot welding system 1 according to an embodiment of the present invention (hereinafter, referred to as "the present embodiment"). The robot welding system 1 welds a workpiece 2, which is an object to be welded, using a robot. In particular, the robot welding system 1 welds the workpiece 2 by friction stir welding (FSW). The workpiece 2 is a member to be welded, and is a member made of metal, such as aluminum. The workpiece 2 is placed on a stand 3, for example.

[0014] Here, friction stir welding is a type of solid-phase welding method, and has advantages such as being less subject to restrictions on metal materials and less thermal distortion. In friction stir welding, the spindle 6 described below is rotated in a set direction and pressed into the workpiece 2. As a result, the workpiece 2 is softened and stirred and mixed by frictional heat generated between the spindle 6 and the workpiece 2. Then, by moving the spindle 6 relative to the workpiece 2, the softened and stirred and mixed part loses frictional heat and is cooled and solidified, and the part where the spindle 6 has moved is softened and stirred and mixed. By repeating the above action with the movement of the spindle 6, welding can be performed on the part where the spindle 6 has moved. As a result, for example, the butt part of the workpiece 2 is joined and integrated.

[0015] As shown in FIG. 1, the robot welding system 1 includes a robot 5, a spindle 6, a control device 7, and a sensor unit S as main components.

[0016] The robot 5 is an articulated robot, and has a plurality of arms 8 and a plurality of joints 9. Each joint 9 is provided with a drive motor (not shown). The robot 5 is moved by controlling the drive motor provided in each joint 9 of the robot 5. Note that the configuration of the robot 5 in FIG. 1 is an example.

[0017] The spindle 6 is a rotating member provided at the tip of the arm 8 of the robot 5. The spindle 6 is also called a joining tool. Specifically, the spindle 6 is detachably attached to the robot 5 at the tip of the arm 8 of the robot 5.

[0018] The spindle 6 has an appropriate tool shape selected according to the material of the workpiece 2. For example, the material of the spindle 6 is a Ni-based alloy, a cobalt alloy, or tungsten carbide. In addition, a probe (protrusion) is provided at the tip of the spindle 6.

[0019] The spindle 6 is connected to a bidirectional motor (rotation motor) (not shown) and is configured to be bidirectionally rotatable. That is, the spindle 6 is configured to be controllable for both forward and reverse rotation. The direction of rotation is set by the control device 7, which will be described later.

[0020] The control device 7 is a robot welding control device, and is an information processing device that controls the operation of the robot 5 and the spindle 6. That is, the control device 7 controls the operation of each part of the robot welding system 1 to control the welding of the workpiece 2. In friction stir welding, the spindle 6 is pushed into the workpiece 2 to perform welding. Since the spindle 6 is pressed against the workpiece 2, the robot 5 may bend. In particular, the joints 9 between the arms 8 of the robot 5 may bend. When bending occurs, a force in the opposite direction to the control direction of each joint 9 controlled to push the spindle 6 for welding acts on each joint 9, and the joint 9 moves slightly in the opposite direction to the control direction. That is, when bending occurs, the state of each joint 9 becomes different from the control amount, and due to this, the position of the spindle 6 provided at the tip of the arm 8 of the robot 5 may be shifted from the target position. For this reason, the control device 7 performs welding based on the measurement result of the sensor unit S described later.

[0021] The sensor unit S is a sensor that measures distance. The sensor unit S is configured using, for example, a laser displacement meter. In this embodiment, the sensor unit S is configured with three sensors, a sensor S1, a sensor S2, and a sensor S3. The positions of the sensors S1, S2, and S3 are fixed with respect to the spindle 6. Therefore, the positional relationship between the spindle 6 and the sensor unit S does not change due to the movement of the robot 5 or the rotation of the spindle 6. Therefore, the measurement result by the sensor unit S corresponds to the position of the spindle 6.

[0022] The sensor unit S can switch between two modes: a position estimation mode (first mode) and an inclination estimation mode (second mode). In each mode, the measurement directions of the sensors S1, S2, and S3 are different. Therefore, the position estimation mode and the inclination estimation mode can be changed by switching the measurement direction of the sensor unit S. For example, the switching is performed by rotating the measurement directions of the sensors S1 and S2 by 90 degrees.

[0023] FIG. 2 is a diagram showing an example of the sensor unit S corresponding to the position estimation mode and the tilt estimation mode. In FIG. 2, the measurement direction of the sensors S1, S2, and S3 of the sensor unit S corresponding to the position estimation mode is shown as M1, and the measurement direction of the sensors S1, S2, and S3 of the sensor unit S corresponding to the tilt estimation mode is shown as M2. In the position estimation mode, the sensor unit S measures distances in a plurality of directions different from each other. The sensor unit S is perpendicular to the rotation axis of the spindle 6 and measures distances in two directions perpendicular to each other. The two directions are the x-axis direction and the y-axis direction. The sensor unit S is parallel to the rotation axis of the spindle 6 and measures distances in a direction perpendicular to the two directions. The direction is the z-axis direction. In this way, the sensor unit S measures distances in three directions, the x-axis direction, the y-axis direction, and the z-axis direction, which are perpendicular to each other. That is, the sensor S1 measures the distance in the x-axis direction, the sensor S2 measures the distance in the y-axis direction, and the sensor S3 measures the distance in the z-axis direction. In this manner, by measuring the distances in three directions, the x-axis direction, the y-axis direction, and the z-axis direction, with the sensor unit S, it is possible to measure the position of the spindle 6.

[0024] It should be noted that the installation positions of the sensors for measuring the three directions are not limited to those shown in FIG. 2, so long as the positions are fixed relative to the spindle 6.

[0025] In the tilt estimation mode, the sensor unit S measures the distance in the z-axis direction, which is a direction parallel to the rotation axis of the spindle 6, from different positions.

[0026] In the tilt estimation mode, the sensor S1 measures the distance in the z-axis direction from a first position located in a first radial direction with respect to the rotation axis of the spindle 6. The sensor S2 measures the distance in the z-axis direction from a second position located in a second radial direction perpendicular to the first radial direction. The sensor S3 measures the distance in the z-axis direction from a third position located in a third radial direction perpendicular to the second radial direction. Note that the first position, the second position, and the third position are each assumed to be at the same position with respect to the axial direction of the spindle 6. In this way, by measuring the distance in the z-axis direction from each of the first position, the second position, and the third position, it is possible to measure the tilt of the spindle 6 with respect to a surface arranged in the z-axis direction.

[0027] For example, if the measurement results for a surface arranged in the z-axis direction by sensors S1, S2, and S3 are equal, it indicates that the rotation axis of the spindle 6 is perpendicular to the surface. On the other hand, if the measurement results for the surface are different, it indicates that the rotation axis of the spindle 6 is not perpendicular to the surface.

[0028] ≪Functional configuration≫ 3 is a block diagram showing an example of various functions of the control device 7. The friction stir welding process is carried out by the functions of each block.

[0029] As shown in FIG. 3, the control device 7 mainly includes a position estimation unit 21, a tilt estimation unit 22, a generation unit 23, and a welding execution unit 24.

[0030] The position estimation unit 21 estimates the position of the spindle 6 based on the measurement result of the sensor unit S. Specifically, the position estimation unit 21 acquires the distance measurement result in the x-axis direction from the sensor S1 in the sensor unit S in the position estimation mode. The position estimation unit 21 also acquires the distance measurement result in the y-axis direction from the sensor S2. The position estimation unit 21 also acquires the distance measurement result in the z-axis direction from the sensor S3. Since the positions of the sensors S1, S2, and S3 are fixed with respect to the spindle 6, the positions of the sensors S1, S2, and S3 and the position of the spindle 6 can be converted to each other. For this reason, the position estimation unit 21 converts the distance in the x-axis direction, the distance in the y-axis direction, and the distance in the z-axis direction acquired from the sensors S1, S2, and S3, respectively, into the positions of the spindle 6 in the x-axis direction, the y-axis direction, and the z-axis direction. Then, the position estimation unit 21 estimates the position of the spindle 6. For example, the estimated position of the spindle 6 is the position of the rotation axis on the surface of the spindle 6 that contacts the workpiece 2, and is the position of the probe. For example, the relationship between the measurement results of the sensors S1, S2, and S3 and the position of the spindle 6 is established in advance using a function, a table, etc. Then, the position estimation unit 21 refers to this correspondence and estimates the position of the spindle 6 from the measurement results.

[0031] When estimating the position of the spindle 6, it is preferable to provide a reference plane in each of the x-axis direction, y-axis direction, and z-axis direction measured by each of the sensors S1, S2, and S3, and estimate the position of the spindle 6 based on the reference plane. For example, the x-axis direction and the y-axis direction are measured by providing a reference plane on the stand 3, and the z-axis direction is measured based on the surface of the workpiece 2. The accuracy of estimating the position is improved by measuring the distance in each of the x-axis direction, y-axis direction, and z-axis direction using the reference plane.

[0032] In the position estimation unit 21, the position of the spindle 6 is estimated by the sensor unit S provided on the spindle 6, so that even if bending occurs and a positional deviation occurs in the spindle 6, the position of the spindle 6 can be accurately grasped. The estimated position of the spindle 6 is used by the welding execution unit 24, which will be described later.

[0033] The inclination estimation unit 22 estimates the inclination of the spindle 6 based on the measurement results of the sensor unit S. Specifically, in the sensor unit S in the inclination estimation mode, the inclination estimation unit 22 acquires the distance measurement result in the z-axis direction from the sensor S1, acquires the distance measurement result in the z-axis direction from the sensor S2, and acquires the distance measurement result in the z-axis direction from the sensor S3. That is, the inclination estimation unit 22 acquires the measurement results in the z-axis direction from the sensor unit S at a first position, a second position, and a third position that are shifted at 90° intervals in the circumferential direction around the rotation axis of the spindle 6.

[0034] Then, the inclination estimation unit 22 estimates the inclination of the spindle 6 based on the measurement results. Specifically, the inclination estimation unit 22 compares the distances in the z-axis direction to estimate the inclination of the spindle 6 with respect to a surface arranged in the z-axis direction. For example, the relationship between the measurement results of the sensors S1, S2, and S3 and the inclination (perpendicularity) of the rotation axis of the spindle 6 is associated with each other using a function, a table, or the like, and the inclination estimation unit 22 estimates the inclination from the measurement results by referring to this correspondence.

[0035] The generating unit 23 generates correspondence data between the robot 5 and a reference position. When the robot 5 welds the workpiece 2, the robot 5 and the stand 3 to which the workpiece 2 is fixed are disposed at different positions. The surface of the stand 3 to which the workpiece 2 is fixed is set as a reference surface (work plane). A plurality of reference positions are set on the reference surface.

[0036] 4 is a diagram showing an example of a reference plane of the gantry 3. For example, three reference positions, that is, reference position P1, reference position P2, and reference position P3, are provided on the reference plane. It is preferable that a line passing through the reference position P1 and the reference position P2 and a line passing through the reference position P1 and the reference position P2 are mutually perpendicular.

[0037] The generating unit 23 generates correspondence data between the robot 5 and each reference position based on information obtained by moving the robot 5 so that the rotation axis of the spindle 6 is perpendicular to the reference plane at each reference position. The information is obtained by controlling the robot 5 to move the spindle 6 to the reference position so that it is perpendicular to the reference plane. Note that the information may be obtained by having an operator move each joint of the robot 5 to move the spindle 6 to the reference position so that it is perpendicular to the reference plane. The estimation result of the tilt estimating unit 22 is used to determine whether the rotation axis of the spindle 6 is perpendicular to the reference plane.

[0038] As a result, state information of the robot 5 when the spindle 6 is moved to the reference position and state information of the robot 5 when the spindle 6 is perpendicular to the reference plane at the reference position are acquired at each of the reference positions. Based on this, the generating unit 23 generates correspondence data between the robot 5 and each reference position. The correspondence data is data including a relative positional relationship between the robot 5 and each reference position. Specifically, the correspondence data is work plane data. The work plane data is data of a plane including each reference position and includes a positional relationship with respect to the robot 5. For example, the work plane data is based on the reference position P1, a vector to the reference position P2 is a first vector B1, and a vector to the reference position P3 is a second vector B2, and the first vector B1 and the second vector B2 indicate positions on a plane including each reference position. For example, the work plane data includes position information of the reference position P1 with respect to the robot 5, and each position on a plane including each reference position with respect to the robot 5 can be specified. Furthermore, the posture of the robot 5 in which the spindle 6 is perpendicular to each position on a plane including each reference position can also be specified.

[0039] As described above, by creating the work plane data, the position of the base 3, which is the reference plane, can be accurately grasped by the robot 5. This allows the robot 5 to accurately grasp the position of the workpiece 2 fixed to the base 3. Furthermore, since the posture of the robot 5 with the spindle 6 perpendicular to the base 3, which is the reference plane, is also confirmed, it becomes possible to press the spindle 6 perpendicularly against the workpiece 2.

[0040] The welding execution unit 24 performs welding using the spindle 6. Specifically, the welding execution unit 24 starts rotating the spindle 6 in a preset rotation direction and rotation speed. The rotation speed is preset based on, for example, the material and welding quality of the workpiece 2. Then, while the spindle 6 is rotating, the welding execution unit 24 presses the spindle 6 against a predetermined position, which is a welding start position on the workpiece 2, and moves the spindle 6 in a predetermined welding direction while pressing the spindle 6. The welding direction is set along, for example, a predetermined welding position on the workpiece 2. As a result, welding of the workpiece 2 proceeds in the welding direction from the welding start position, and the workpiece 2 is joined. When welding proceeds in the welding direction and welding is completed up to the welding end position, the spindle 6 is separated from the workpiece 2. In this way, the welding execution unit 24 performs welding of the workpiece 2.

[0041] In this way, the welding execution unit 24 performs welding, and the welding execution unit 24 performs feedback control based on the position of the spindle 6 estimated by the position estimation unit 21. That is, when moving the spindle 6, the robot 5 is controlled to move the position of the spindle 6 while referring to the estimated position of the spindle 6 so that the estimated position of the spindle 6 follows the target position. As a result, even if the spindle 6 is deflected when pressed against the workpiece 2, the error due to the deflection can be corrected and the spindle 6 can be accurately controlled to the target position. Therefore, it is possible to suppress the positional deviation of the spindle 6 from the welding start position to the welding direction to the welding end position.

[0042] Furthermore, the welding execution unit 24 controls the robot 5 based on the work plane data. By referring to the work plane data as described above, the robot 5 can accurately grasp the position of the base 3 and the position of the workpiece 2, thereby improving the accuracy of the position control of the spindle 6.

[0043] <Processing flow> 5 is a flowchart showing an example of the flow of the friction stir welding process according to the present embodiment. Each process of the following steps is started, for example, when an execution instruction is given by an operator. Note that the order and contents of each step can be changed as appropriate.

[0044] (Step SP10) The welding execution unit 24 moves the spindle 6 to a welding start position of the workpiece 2 based on the position of the spindle 6 estimated by the position estimation unit 21. Note that in step SP10, the spindle 6 is separated from the workpiece 2 and is not in contact with the workpiece 2.

[0045] (Step SP11) The welding execution unit 24 rotates the spindle 6 in a predetermined direction and at a predetermined number of rotations.

[0046] (Step SP12) The welding execution unit 24 presses the spindle 6 against a welding start position of the workpiece 2 while rotating the spindle 6 .

[0047] (Step SP13) Based on the position of the spindle 6 estimated by the position estimation unit 21, the welding execution unit 24 moves the spindle 6 in the welding direction while rotating it.

[0048] (Step SP14) Welding execution unit 24 determines whether or not the spindle 6 has reached the welding end position based on the position of the spindle 6 estimated by position estimation unit 21. If the spindle 6 has reached the welding end position, the process proceeds to step SP15, and if the spindle 6 has not reached the welding end position, step SP13 is executed again.

[0049] (Step SP15) The welding execution unit 24 moves the spindle 6 away from the workpiece 2 .

[0050] In the above flowchart, an example is shown of control being performed by constantly feeding back the position of the spindle 6 estimated by the position estimation unit 21. However, control may also be performed to correct the position deviation when the position of the spindle 6 estimated by the position estimation unit 21 deviates from the target position by a predetermined value or more.

[0051] <Action and effect> As described above, in this embodiment, the sensor unit S is provided, whose position is fixed with respect to the spindle 6, and which measures distances in different directions. Then, in the first mode (position estimation mode), distances are measured in three directions: two directions that are perpendicular to the rotation axis of the spindle 6 and perpendicular to each other, and a direction that is parallel to the rotation axis of the spindle 6 and perpendicular to the two directions, that is, the x-axis direction, the y-axis direction, and the z-axis direction. As a result, even if the position of the spindle 6 cannot be accurately estimated from information on each joint of the robot 5 due to bending, for example, the three-dimensional position of the spindle 6 can be accurately grasped from information on the sensor unit S. In the second mode (tilt estimation mode), the distances in the z-axis direction are measured from each of the first position, the second position, and the third position, thereby making it possible to estimate the tilt of the spindle 6. In this way, the controllability of the spindle 6 is improved, and therefore it is possible to improve the welding quality.

[0052] Furthermore, by estimating the position of the rotating member based on the measurement results of the sensor unit S corresponding to the first mode (position estimation mode) by the position estimation unit 21, it is possible to improve the controllability of the position of the spindle 6. For example, even if bending occurs during welding, it is possible to estimate the position of the spindle 6 including the bending, so that it is possible to correct the position deviation due to the bending.

[0053] Furthermore, in the tilt estimation unit 22, it is possible to estimate the tilt of the spindle 6 based on the measurement results corresponding to the first position, the second position, and the third position corresponding to the second mode (tilt estimation mode). For example, it is possible to confirm the posture of the robot 5 in which the spindle 6 is perpendicular to the workpiece 2.

[0054] In addition, correspondence data between the robot 5 and each reference position is generated based on information obtained by moving the robot 5 so that the rotation axis of the spindle 6 is perpendicular to the reference plane at multiple reference positions. By performing control based on the correspondence data, the relative positional relationship between the robot 5 and each reference position and the posture of the robot 5 with the spindle 6 perpendicular to the reference plane at each reference position can be known, thereby improving control accuracy.

[0055] <<Variations>> The present invention is not limited to the above-described embodiment. In other words, the above-described specific example may be modified by a person skilled in the art as appropriate, and the modifications may be included in the scope of the present invention as long as they include the features of the present invention. In addition, the elements of the above-described embodiment and the following modifications may be combined to the extent technically possible, and the combinations of these may be included in the scope of the present invention as long as they include the features of the present invention.

[0056] For example, in the above embodiment, the sensor unit S is configured with the sensor S1, the sensor S2, and the sensor S3. However, a single sensor may be used as long as it is capable of measuring distances in each direction.

[0057] For example, in the above embodiment, the case where the sensor S1 measures the distance in the x-axis direction, the sensor S2 measures the distance in the y-axis direction, and the sensor S3 measures the distance in the z-axis direction in the position estimation mode has been described, but it is also possible to configure the sensor unit S with three or more sensors. In other words, the configuration of the sensor unit S is not limited as long as it can measure distances in a plurality of mutually different directions.

[0058] For example, in the above embodiment, a case has been described in which the position estimation mode and tilt estimation mode of the sensor unit S are switched by rotating the measurement direction of the sensor by 90 degrees, but the sensor used in the position estimation mode and the sensor used in the tilt estimation mode may be installed separately.

[0059] For example, in the above embodiment, the case where the estimation result of the inclination of the spindle 6 by the inclination estimation unit 22 is used to create the work plane data has been described, but the estimation result of the inclination may be used for purposes other than creating the work plane data. For example, when performing welding, it may be used to check whether the spindle 6 is perpendicular to the workpiece 2. [Explanation of symbols]

[0060] 1: Robot welding system 2: Work 5: Robot (articulated robot) 6: Spindle (rotating member) 7: Control device 8: Arm 21:Position estimation part 22: Tilt estimation unit 23: Generation part 24: Welding Execution Department P1~P3: Reference position S: Sensor section S1~S3: Sensors

Claims

1. 1. A robotic welding system for friction stir welding a workpiece, comprising: Articulated robots and A rotating member provided at the tip of an arm of the articulated robot; a sensor unit whose position is fixed with respect to the rotating member and which measures distances in each of the first and second directions in the first and second modes; Equipped with The sensor unit includes: In the first mode, distances are measured in two directions, each of which is perpendicular to a rotation axis of the rotating member and perpendicular to each other, and in a direction parallel to the rotation axis of the rotating member and perpendicular to the two directions; The robot welding system is characterized in that, in the second mode, distances in a direction parallel to the rotation axis of the rotating member are measured from each of a first position located in a first radial direction with respect to the rotation axis of the rotating member, a second position located in a second radial direction perpendicular to the first radial direction, and a third position located in a third radial direction perpendicular to the second radial direction.

2. A control device for controlling the articulated robot is further provided. The control device includes:

2. The robot welding system according to claim 1, further comprising a position estimating unit that estimates a position of the rotating member based on a measurement result corresponding to the first mode of the sensor unit.

3. 3. The robot welding system according to claim 2, wherein the control device further includes an inclination estimation unit that estimates an inclination of the rotating member based on measurement results corresponding to each of the first position, the second position, and the third position corresponding to the second mode of the sensor unit.

4. The robot welding system according to claim 3, characterized in that the control device further comprises a generation unit that generates correspondence data between the articulated robot and each of a plurality of reference positions on a reference surface based on information on moving the articulated robot so that the rotation axis of the rotating member is perpendicular to the reference surface at the reference position.

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