Robot welding system and robot welding control device

Abstract

To provide a robot welding system which enables improvement of welding quality in friction stir welding, and to provide a robot welding control device.SOLUTION: A robot welding system 1 performs friction stir welding to a workpiece 2 and includes: a robot 5; a spindle 6 provided at an arm tip of the robot 5; and a control device 7 which controls operations of the robot 5 and the spindle 6. The control device 7 has: an estimate part which estimates a deflection direction of the robot 5 when the spindle 6 is pressed against the workpiece 2 by using an arm 8 of the robot 5; and a setting part which sets a rotation direction of the spindle 6 based on the deflection direction so that a friction force generated by the spindle 6 contacting with the workpiece 2 is generated in a direction opposite to the deflection direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a robot welding system for friction stir welding workpieces and a robot welding control device. [Background technology]

[0002] Friction stir welding (friction stir welding) 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, when welding is performed while pressing a spindle provided at the end of a robot's arm against a workpiece, bending may occur in, for example, a joint of the robot to which the spindle is provided. If bending occurs, the position of the spindle may shift, which may affect the welding quality.

[0005] In view of the above problems, an object of the present invention is to provide a robot welding system and a robot welding control device that can improve welding quality in friction stir welding. [Means for solving the problem]

[0006] In order to solve the above 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 control device that controls the operation of the multi-joint robot and the rotating member, and the control device has an estimation unit that estimates the bending direction of the multi-joint robot when the rotating member is pressed against the workpiece using the arm of the multi-joint robot, and a setting unit that sets the rotation direction of the rotating member based on the bending direction so that the frictional force generated when the rotating member comes into contact with the workpiece is generated in the direction opposite to the bending direction.

[0007] Also, in the robot welding system, the estimation unit estimates the deflection direction based on the posture of the articulated robot that welds the workpiece with the rotating member.

[0008] In the robot welding system, the estimation unit estimates the deflection direction based on an angle of each joint of the articulated robot. Effect of the Invention

[0009] According to the robot welding system and robot welding control device of the present invention, it is possible to improve welding quality. [Brief description of the drawings]

[0010] [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] 2 is a block diagram showing an example of various functions of a control device provided in the robot welding system of FIG. 1. [Diagram 3] FIG. 13 is a diagram showing an example of friction stir welding in a reference example. [Figure 4] 2 is a diagram showing an example of friction stir welding in the robot welding system 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

[0011] 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.

[0012] === 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.

[0013] 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.

[0014] As shown in FIG. 1, the robot welding system 1 includes a robot 5, a spindle 6, and a control device 7 as main components.

[0015] 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.

[0016] The spindle 6 is a rotating member provided at the tip of the arm 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 of the robot 5.

[0017] 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.

[0018] 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 in both forward and reverse directions (right and left rotation). The direction of rotation is set by the control device 7, which will be described later.

[0019] 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 of the robot 5 may be shifted from the target position. For this reason, the control device 7 performs operation control so as to suppress the position shift of the spindle 6 due to bending.

[0020] ≪Functional configuration≫ Fig. 2 is a block diagram showing an example of various functions of the control device 7 in Fig. 1. The friction stir welding process is carried out by the functions of each block.

[0021] As shown in FIG. 2, the control device 7 mainly includes an estimation unit 21, a setting unit 22, and a welding execution unit .

[0022] The estimation unit 21 estimates the deflection of the robot 5. Specifically, the estimation unit 21 estimates the deflection direction based on the posture of the robot 5 welding the workpiece 2. The deflection direction is estimated as a deflection in a direction perpendicular to the rotation axis of the spindle 6, for example.

[0023] Since the posture of the robot 5 is related to the angle of each joint 9 of the robot 5, for example, the estimation unit 21 estimates the bending direction based on the angle of each joint 9 of the robot 5. The angle of the joint 9 is estimated based on, for example, the control amount of the drive motor of the joint 9. Note that it is also possible to use information other than the angle of the joint 9 as long as it is related to the posture of the robot 5.

[0024] The estimation unit 21 estimates the deflection direction before welding of the workpiece 2 by the spindle 6 is started. Therefore, the estimation unit 21 estimates the deflection direction based on the posture of the robot 5 before welding is started. For example, the estimation unit 21 obtains in advance target values ​​of the control amounts of the joints 9 of the robot 5 for performing welding, and estimates the deflection direction. Note that as long as the deflection direction can be estimated before welding is started, the estimation is not limited to the above, and for example, the posture of the robot 5 may be confirmed by moving the robot 5 to a welding start position.

[0025] The setting unit 22 sets the rotation direction of the spindle 6 based on the deflection direction. Specifically, the setting unit 22 sets the rotation direction of the spindle 6 so that a frictional force generated when the spindle 6 comes into contact with the workpiece 2 occurs in a direction opposite to the deflection direction. In the following description, the direction of friction generated when the rotating spindle 6 comes into contact with the workpiece 2 is referred to as the "rotational friction direction."

[0026] The spindle 6 rotates in contact with the surface of the workpiece 2 with its rotation axis approximately perpendicular to the surface of the workpiece 2 and moves in the welding direction, but friction occurs on the surface of the spindle 6 that contacts the surface of the workpiece 2 toward the welding direction. That is, on the contact surface between the workpiece 2 and the spindle 6, friction occurs greater forward in the welding direction where the surface of the workpiece 2 is not sufficiently softened and stirred than backward in the welding direction where the surface of the workpiece 2 is sufficiently softened and stirred. For this reason, the rotation direction of the spindle 6 is set so that the frictional force generated on the forward side of the welding direction on the contact surface between the workpiece 2 and the spindle 6 is generated in the opposite direction to the deflection direction.

[0027] The setting unit 22 sets the rotation direction of the spindle 6 before starting welding of the workpiece 2 by the spindle 6. Specifically, the setting unit 22 sets the rotation direction of the spindle 6 before starting a welding process by a welding execution unit 23, which will be described later.

[0028] The welding execution unit 23 performs welding by the spindle 6. Specifically, the welding execution unit 23 starts rotating the spindle 6 in the rotation direction set by the setting unit 22. The spindle 6 is rotated so that the number of rotations of the spindle 6 becomes a preset target number of rotations. The target number of rotations is preset, for example, based on the material and welding quality of the workpiece 2. Then, the welding execution unit 23 presses the spindle 6 against a predetermined position, which is a welding start position on the workpiece 2, while the spindle 6 is rotating, and moves the spindle 6 in a predetermined welding direction while pressing the spindle 6. The welding direction is set, for example, along a predetermined welding position on the workpiece 2. As a result, the welding of the workpiece 2 proceeds in the welding direction from the welding start position, and the workpiece 2 is joined. When the welding proceeds in the welding direction and welding is completed to the welding end position, the spindle 6 is separated from the workpiece 2. In this way, the welding execution unit 23 performs welding of the workpiece 2.

[0029] <Welding example> 3 and 4 show an example of friction stir welding. FIG. 3 shows an example of friction stir welding in a reference example, and FIG. 4 shows an example of friction stir welding in the robot welding system 1 of FIG. 1. In FIG. 3 and FIG. 4, the welding direction and the bending direction are the same. In FIG. 3 and FIG. 4, the welding direction in the example is shown as A1, and the bending direction is shown as A2. In the example of FIG. 3, the rotation direction of the spindle 6 is shown as R1, and the rotational friction direction is shown as A3. In the example of FIG. 4, the rotation direction of the spindle 6 is shown as R2, and the rotational friction direction is shown as A4.

[0030] Figure 3 shows a case where the deflection direction and the rotational friction direction are the same. When the spindle 6 is rotated in the rotation direction of R1, a frictional force is generated in the direction of A3. Since the deflection direction and the rotational friction direction are the same, a large force is generated in that direction. This may cause the spindle 6 to become misaligned.

[0031] Figure 4 shows a case where the deflection direction and the rotational friction direction are opposite to each other. When the spindle 6 is rotated in the rotation direction of R2, a frictional force is generated in the direction of A4. Because the deflection direction and the rotational friction direction are opposite to each other, the forces act in directions that cancel each other out. Therefore, compared to the case of Figure 3, the positional deviation of the spindle 6 is suppressed.

[0032] FIG. 4 shows a case where the force generated in the bending direction is greater than the friction force generated in the rotational friction direction. However, even if the force generated in the bending direction is equal to or less than the friction force generated in the rotational friction direction, misalignment can be suppressed in the same manner.

[0033] The control device 7 sets the rotation direction of the spindle 6 so that the direction of rotational friction occurs in the opposite direction to the bending direction as shown in the example of FIG.

[0034] <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.

[0035] (Step SP10) The estimation unit 21 estimates the bending direction based on the posture of the robot 5. For example, the estimation unit 21 estimates the bending direction based on the angle of each joint 9 of the robot 5 performing welding.

[0036] (Step SP11) The setting unit 22 determines the rotation direction of the reversible spindle 6 based on the bending direction. Specifically, it determines whether or not a frictional force opposite to the bending direction occurs when the spindle 6 rotates clockwise. If a frictional force opposite to the bending direction occurs when the spindle 6 rotates clockwise, the process proceeds to step SP12, and if a frictional force opposite to the bending direction does not occur when the spindle 6 rotates clockwise, the process proceeds to step SP13.

[0037] (Step SP12) The setting unit 22 sets the rotation direction of the spindle 6 as clockwise rotation.

[0038] (Step SP13) The setting unit 22 sets the rotation direction of the spindle 6 as counterclockwise rotation.

[0039] The above steps SP10 to SP13 are pre-processing steps carried out before welding is performed.

[0040] (Step SP14) The welding execution unit 23 causes the robot 5 to move the spindle 6 to a welding start position for the workpiece 2. In step SP14, the spindle 6 is separated from the workpiece 2 and is not in contact with the workpiece 2.

[0041] (Step SP15) The welding execution unit 23 rotates the spindle 6 in a set rotation direction.

[0042] (Step SP16) The welding execution unit 23 presses the spindle 6 against the welding start position of the workpiece 2 while rotating the spindle 6, and moves it in the welding direction.

[0043] (Step SP17) After moving the spindle 6 to the welding end position, the welding execution unit 23 moves the spindle 6 away from the workpiece 2.

[0044] Friction stir welding is performed by the above process. In particular, since the direction of frictional rotation caused by the rotation of the spindle 6 is controlled to occur in the opposite direction to the bending direction of the robot 5, positional deviation of the spindle 6 due to bending is suppressed.

[0045] <Action and effect> As described above, in this embodiment, the bending direction of the robot 5 when the spindle 6 is pressed against the workpiece 2 is estimated, and the rotation direction of the spindle 6 is set so that the frictional force generated by the contact of the spindle 6 with the workpiece 2 occurs in the opposite direction to the bending direction. This makes it possible to suppress the positional deviation of the spindle 6 in the bending direction due to the frictional force caused by the rotation of the spindle 6. This makes it possible to improve the welding quality.

[0046] The deflection direction can be estimated based on the posture of the robot 5 that welds the workpiece 2 with the spindle 6, and the rotation direction of the spindle 6 can be set appropriately.

[0047] Based on the angles of the joints 9 of the robot 5, the posture of the robot 5 can be grasped, and the bending direction can be estimated.

[0048] <<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.

[0049] For example, in the above embodiment, the rotation speed of the spindle 6 is controlled to a preset target rotation speed, but the present invention is not limited to the above. For example, it is also possible to control the rotation speed of the spindle 6. In this case, it is preferable to set the rotation speed of the spindle 6 so as to cancel out the forces caused by the bending. That is, the rotation speed is set so as to estimate not only the bending direction but also the force in the bending direction and to cancel out the force with the rotational friction force.

[0050] For example, in the above embodiment, the case where welding is started after the rotation direction is set, the welding direction is moved from the welding start position to the welding end position, and welding is performed to the welding end position is described. That is, in the above embodiment, the bending direction is approximately the same direction from the welding start position to the welding end position, and the position shift can be suppressed by the friction force of the set rotation direction. However, if the bending direction and the rotation friction direction in the set rotation direction are no longer opposite directions between the welding start position and the welding end position, an intermediate position may be provided between the welding start position and the welding end position, and the rotation direction may be changed at the intermediate position. In this case, it is preferable that the spindle 6 is once separated from the workpiece 2 at the intermediate position, and after the rotation direction is changed, the spindle 6 is pressed against the workpiece 2 again to resume welding.

[0051] For example, in the above embodiment, a case has been described in which the bending direction is opposite to the direction of rotational friction (i.e., 180 degrees), but the same is applicable if the frictional force caused by the rotation of the spindle 6 has a component in the opposite direction to the bending direction. For example, when the frictional force caused by the rotation of the spindle 6 is 120 degrees with respect to the bending direction, half of the frictional force (=cos60 degrees) becomes a component in the opposite direction to the bending direction. In this case, too, it can be said that the frictional force generated by the contact of the spindle 6 with the workpiece 2 occurs in the opposite direction to the bending direction.

[0052] For example, in the above embodiment, the rotation direction is set before the start of welding, but if there is no problem with the welding quality of the friction stir welding, the rotation direction may be set after the start of welding. After the start of welding means, for example, after the spindle 6 is pressed against the workpiece 2. [Explanation of symbols]

[0053] 1: Robot welding system 2: Work 5: Robot (articulated robot) 6: Spindle (rotating member) 7: Control device (robot welding control device) 8: Arm 9: Joints 21: Estimation part 22: Setting section 23: Welding Execution Department

Claims

1. 1. A robotic welding system for friction stir welding a workpiece, comprising: Articulated robots and A rotating member provided at the arm tip of the articulated robot; A control device for controlling the operation of the articulated robot and the rotating member; Equipped with The control device includes: an estimation unit that estimates a deflection direction of the articulated robot when the arm of the articulated robot is used to press the rotating member against the workpiece; a setting unit that sets a rotation direction of the rotating member based on the bending direction so that a frictional force generated when the rotating member comes into contact with the workpiece is generated in a direction opposite to the bending direction; A robot welding system comprising:

2. The robot welding system according to claim 1 , wherein the estimating unit estimates the deflection direction based on a posture of the articulated robot that welds the workpiece with the rotating member.

3. The robot welding system according to claim 2 , wherein the estimating unit estimates the deflection direction based on an angle of each joint of the articulated robot.

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