Robot control device and welding wire feeding control method

Abstract

The present invention provides a robot control device and a welding wire feeding control method that can appropriately identify arc generation defects. [Solution] The robot control device 100 is a robot control device that controls the operation of a collaborative robot 200, and includes a feed control unit 110 that controls the feeding of the welding wire 211 to generate an arc, and an external force detection unit 120 that detects external forces acting on the collaborative robot 200, and the feed control unit 110 stops feeding the welding wire 211 when the external force detected by the external force detection unit 120 is greater than or equal to a second threshold which is smaller than a first threshold which detects a collision with the collaborative robot 200.

Description

Technical Field

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[0001] The present invention relates to a robot control device and a welding wire feeding control method.

Background Art

[0002] In recent years, many robots have become widespread in the industrial world. Such robots are used, for example, in the assembly, welding, and conveyance of electronic components and mechanical parts, and the efficiency and automation of factory production lines are being achieved.

[0003] In addition, conventionally, the development of collaborative robots that work adjacent to workers, replacing or working together with workers for some of the work that was previously done by workers, has also progressed. Since collaborative robots work adjacent to workers rather than in a safely enclosed area, it is important to ensure the safety of the workers.

[0004] For example, in Patent Document 1, it is disclosed that a physical quantity that changes according to the contact force received by a robot is detected, and according to the magnitude of the physical quantity, the robot is stopped according to a predetermined stopping method or stopped in a shorter time than the predetermined stopping method.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the robot system disclosed in Patent Document 1, although a collision with a collaborative robot can be detected, in other cases, for example, it may not be possible to appropriately detect a defective generation of an arc.

[0007] From the operator's perspective, there is a problem in that if a collision with the collaborative robot is not detected and the collaborative robot is operating, and the arc is not being generated properly, they cannot determine the cause.

[0008] Therefore, the present invention aims to provide a robot control device and a welding wire feeding control method that can appropriately identify arc generation defects. [Means for solving the problem]

[0009] A robot control device according to one aspect of the present invention is a robot control device for controlling the operation of a collaborative robot, comprising: a feeding control unit that controls the feeding of welding wire to generate an arc; and an external force detection unit that detects an external force acting on the collaborative robot, wherein the feeding control unit stops feeding the welding wire if the external force detected by the external force detection unit is greater than or equal to a second threshold that is smaller than a first threshold that detects a collision with the collaborative robot.

[0010] In this embodiment, the external force detection unit monitors the external force acting on the collaborative robot, and the wire feeding control unit stops feeding the welding wire when the external force detected by the external force detection unit exceeds a second threshold. This allows the operator to properly identify arc generation failures, including situations where the welding wire pushes the workpiece and the tip of the welding torch (welding wire) is subjected to the reaction force.

[0011] In the above embodiment, the wire feeding control unit may stop feeding the welding wire if the external force detected by the external force detection unit is less than the second threshold and no arc occurs for a predetermined period of time.

[0012] According to this embodiment, if an arc does not occur for a predetermined period of time, it is possible to avoid abnormal stopping based on collision detection with the collaborative robot and to appropriately identify the arc generation failure.

[0013] In the above embodiment, the wire feeding control unit may, after stopping the feeding of the welding wire, pull the welding wire back in the reverse direction.

[0014] In this embodiment, the wire feeding control unit reverses the feeding of the welding wire and then resumes feeding the welding wire, which allows for the removal of slag that was causing arc generation failure, for example. As a result, abnormal stops based on collision detection with the collaborative robot can be avoided, and arc starting performance can be maintained.

[0015] In the above embodiment, a notification unit may be further provided to notify the system if the feeding control unit stops feeding the welding wire.

[0016] According to this embodiment, the notification unit notifies the operator when the feeding control unit stops feeding the welding wire, allowing the operator to more appropriately identify arc generation problems.

[0017] A welding wire feeding control method according to one aspect of the present invention is a welding wire feeding control method executed by a robot control device that controls the operation of a collaborative robot, and includes a feeding control step that controls the feeding of the welding wire to generate an arc, and an external force detection step that detects an external force acting on the collaborative robot, wherein in the feeding control step, if the external force detected in the external force detection step is greater than or equal to a second threshold that is smaller than a first threshold that detects a collision with the collaborative robot, the feeding of the welding wire is stopped.

[0018] In this embodiment, the external force detection step monitors the external force acting on the collaborative robot, and in the feed control step, if the external force detected in the external force detection step exceeds a second threshold, the feeding of the welding wire is stopped. This allows the operator to properly identify arc generation failures, including situations where the welding wire pushes the workpiece and the tip of the welding torch (welding wire) is subjected to the reaction force, in which case the arc is not generated properly. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a robot control device and a welding wire feeding control method that can appropriately grasp the occurrence of arc defects.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic diagram showing the configuration of a robot system 10 according to an embodiment of the present invention. [Figure 2] It is a functional block diagram for explaining each function in a robot control device 100 according to an embodiment of the present invention. [Figure 3] It is a diagram showing a state where a work W is fillet welded by a collaborative robot 200. [Figure 4] It is an enlarged view showing a portion A1 around the tip of the welding torch 210 in FIG. 3. [Figure 5] It is a flowchart showing the flow of processing of a welding wire feeding control method M100 executed by a robot control device 100 according to an embodiment of the present invention. [Figure 6] It is a flowchart showing the flow of processing of a welding wire feeding control method M101 executed by a robot control device 100 according to an embodiment of the present invention when the welding wire 211 is fed backward. [Figure 7] It is a diagram showing the relationship between the external force applied to the collaborative robot 200 and the feeding control of the welding wire.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. Note that the embodiments described below are merely specific examples for carrying out the present invention and do not limit the interpretation of the present invention. Also, for ease of understanding of the description, the same reference numerals are attached to the same components in each drawing as much as possible, and duplicate descriptions may be omitted.

[0022] <One Embodiment> [Robot System Configuration] Figure 1 is a schematic diagram showing the configuration of a robot system 10 according to one embodiment of the present invention. As shown in Figure 1, the robot system 10 comprises a robot control device 100, a collaborative robot (manipulator) 200, and a power supply device 300.

[0023] The robot system 10 does not require the collaborative robot 200 to be enclosed by a safety fence and works in cooperation with the worker. In this embodiment, the robot system 10 may be an industrial robot used for welding, for example, and the collaborative robot 200 will be described using a 6-axis vertical articulated manipulator with a welding torch 210 attached as an end effector to the tip of its arm as an example.

[0024] The robot control device 100 controls the operation of the collaborative robot 200 based on a work program. For example, the work program may be generated in advance based on the operation of the collaborative robot 200 taught by the operator using a teaching terminal (teach pendant) and / or by direct teaching, where the operator directly operates the collaborative robot 200. Based on this work program, the robot control device 100 controls the operation of the collaborative robot 200 so that welding can be performed appropriately.

[0025] Specifically, the robot control device 100 controls the motors on each axis of the collaborative robot 200, thereby rotating each axis and moving and rotating the arm and wrist. The robot control device 100 also controls the welding voltage (welding current) supplied to the welding torch 210 (welding wire) and base material (workpiece) by the power supply device 300, and further controls a wire feeding device (not shown) that feeds the welding wire.

[0026] Thus, the welding system is configured to generate an arc between the tip of the welding torch 210 and the base material at the appropriate welding position, thereby ensuring proper welding.

[0027] As described above, the collaborative robot 200 moves and rotates its arms and wrists, etc., by rotating each axis with motors based on the operation instructions from the robot control device 100, thereby moving the welding torch 210 to the appropriate position and angle.

[0028] Furthermore, the collaborative robot 200 detects the torque applied to each axis using a torque sensor and notifies the robot control device 100 of the detected torque.

[0029] The power supply unit 300 supplies a welding voltage (welding current) to generate an arc between the tip of the welding torch 210 and the base material. The welding voltage (welding current) supplied by the power supply unit 300 is controlled by the robot control device 100.

[0030] [Functions of the robot control system] Figure 2 is a functional block diagram illustrating the functions of a robot control device 100 according to one embodiment of the present invention. As shown in Figure 2, the robot control device 100 comprises a feed control unit 110, an external force detection unit 120, a robot control unit 130, and a power supply control unit 140, and controls the operation of the collaborative robot 200, the welding current supplied to the welding torch 210 (welding wire) via the power supply unit 300, and the welding wire fed from the tip of the welding torch 210 via the wire feed device 220.

[0031] In this example, the robot control device 100 is configured to include the wire feeding control unit 110 and the power supply control unit 140 within the same housing. However, the wire feeding control unit 110 and the power supply control unit 140 may be functions configured in separate housings. For example, at least a portion of the wire feeding control unit 110 may be included in the wire feeding device 220, and at least a portion of the power supply control unit 140 may be included in the power supply device 300.

[0032] First, the robot control unit 130 controls the operation of the collaborative robot 200 based on the work program, the wire feeding control unit 110 feeds the welding wire to the tip of the welding torch 210 by controlling the wire feeding device 220, and the power supply control unit 140 supplies a welding voltage (welding current) to generate an arc between the tip of the welding torch 210 (welding wire) and the base material (workpiece) by controlling the power supply unit 300.

[0033] (Collision with collaborative robot) In this case, if, for example, a collision occurs with the collaborative robot 200 while welding is being performed by the robot system 10, the collaborative robot 200 is typically stopped for safety reasons.

[0034] Specifically, if the collaborative robot 200 collides with an object (for example, a worker), the collision may be detected based on the torque applied to each axis of the collaborative robot 200. The external force detection unit 120 in the robot control device 100 detects the external force acting on the collaborative robot 200.

[0035] For example, the external force detection unit 120 monitors the torque applied to each axis of the collaborative robot 200 and determines a collision with the collaborative robot 200 based on that torque. If the external force detection unit 120 determines, based on that torque, that the external force applied to the collaborative robot 200 is equal to or greater than a threshold (first threshold), it may determine that a collision with the collaborative robot 200 has occurred.

[0036] Furthermore, a collision with the collaborative robot 200 includes not only collisions with the collaborative robot 200 itself, but also collisions with peripheral equipment such as the welding torch 210 attached to the collaborative robot 200. In other words, collisions with peripheral equipment such as the welding torch 210 affect the torque applied to each axis of the collaborative robot 200, and a collision with the collaborative robot 200 may be determined based on that torque.

[0037] (Failure to generate arc) Figure 3 shows the workpiece W being fillet welded by the collaborative robot 200. As shown in Figure 3, the tip of the welding torch 210 mounted on the collaborative robot 200 is positioned at the joint portion of the workpiece W and fillet welds it.

[0038] Furthermore, insulators such as slag may adhere to the joint portion of such workpiece W, and this adhered slag may accumulate. Here, a square joint is given as an example, but it is not limited to this; other welds such as T-joints, which have a structure where slag adheres or accumulates, may also be used.

[0039] Figure 4 is an enlarged view showing area A1, which is the area around the tip of the welding torch 210 in Figure 3. As shown in Figure 4, slag S is adhering between the welding wire 211 and the workpiece W at the tip of the welding torch 210.

[0040] In this case, the welding wire 211 is fed from the tip of the welding torch 210 by the wire feeding device 220 (forward feeding towards the workpiece W), and the welding voltage (welding current) is supplied to the tip of the welding torch 210 (welding wire 211) and the workpiece W by the power supply device 300. However, because slag S is adhering between the tip of the welding torch 210 (welding wire 211) and the workpiece W, the arc does not generate properly.

[0041] Furthermore, as the welding wire 211 is continuously fed from the tip of the welding torch 210, the welding wire 211 pushes the workpiece W, and the tip of the welding torch 210 (welding wire 211) receives a reaction force F.

[0042] The external force detection unit 120 in the robot control device 100 detects the reaction force F by acquiring the torque applied to each axis of the collaborative robot 200 from the collaborative robot 200.

[0043] In other words, the external force detection unit 120 monitors the external force acting on the collaborative robot 200, and if the external force acting on the collaborative robot 200 exceeds a threshold (second threshold), it determines that the welding wire 211 is pushing the workpiece W and the tip of the welding torch 210 (welding wire 211) is receiving a reaction force F in a situation where the arc is not being generated properly. Here, the second threshold is smaller than the first threshold, which determines that there is a collision with the collaborative robot 200.

[0044] Then, if the external force detected by the external force detection unit 120 is greater than or equal to the second threshold, the wire feeding control unit 110 stops feeding the welding wire 211. Specifically, the wire feeding control unit 110 controls the wire feeding device 220 to stop feeding the welding wire 211 from the tip of the welding torch 210 (forward feeding towards the workpiece W).

[0045] Furthermore, the wire feeding control unit 110 may also determine that an abnormal condition exists if an arc does not occur for a predetermined period of time, in addition to when the external force detected by the external force detection unit 120 is equal to or greater than the second threshold, and may control the wire feeding device 220 to stop feeding the welding wire 211 (forward feeding towards the workpiece W).

[0046] The robot control device 100 may also stop feeding the welding wire 211 (forward feeding as it approaches the workpiece W) and notify the operator that the feeding of the welding wire 211 has been stopped, for example, by displaying it on a teach pendant (notification unit). Alternatively, the notification unit may notify the operator using sound, such as a warning sound.

[0047] [Welding wire feeding control method] Figure 5 is a flowchart showing the processing flow of a welding wire feeding control method M100 performed by a robot control device 100 according to one embodiment of the present invention. As shown in Figure 5, the welding wire feeding control method M100 includes steps S110 to S140, each step being performed by a processor or the like included in the robot control device 100.

[0048] In step S110, the feed control unit 110 starts and controls the feeding of the welding wire to generate an arc (feed control step). Specifically, in order to weld a workpiece W by a collaborative robot 200 (including a welding torch 210), the feed control unit 110 controls the wire feeding device 220 to feed the welding wire 211 from the tip of the welding torch 210 at the welding position (forward feeding towards the workpiece W).

[0049] In step S120, the external force detection unit 120 detects the external force acting on the collaborative robot 200 and determines whether the external force is equal to or greater than a threshold (second threshold) (external force detection step). Specifically, the external force detection unit 120 continuously monitors the torque applied to each axis of the collaborative robot 200 and calculates the external force acting on the collaborative robot 200 based on the torque. If the external force detection unit 120 determines that the external force is equal to or greater than the threshold (second threshold) ("Yes" in step S120), it proceeds to the process in step S140. If it determines that the external force is less than the threshold (second threshold) ("No" in step S120), it proceeds to the process in step S130.

[0050] Here, the second threshold is set to a value corresponding to the state in which the welding wire 211 pushes the workpiece W and the tip of the welding torch 210 (welding wire 211) receives the reaction force F, and is smaller than the first threshold which determines that it is a collision with the collaborative robot 200.

[0051] In step S130, the robot control device 100 determines whether a predetermined time has elapsed without arc generation (arc generation determination step). Specifically, if the robot control device 100 determines that a predetermined time has elapsed without arc generation, even though the power supply control unit 140 is supplying welding voltage (welding current) to the tip of the welding torch 210 (welding wire 211) and the workpiece W via the power supply unit 300, it proceeds to step S140 if it determines that the predetermined time has not elapsed (step S130 "No"). If it determines that the predetermined time has not elapsed, it returns to step S120.

[0052] In step S140, the wire feed control unit 110 stops feeding the welding wire (welding wire feed stop step). Specifically, the wire feed control unit 110 controls the wire feed device 220 to stop feeding the welding wire 211 from the tip of the welding torch 210 (forward feeding towards the workpiece W).

[0053] As described above, according to the robot system 10, robot control device 100, and welding wire feeding control method M100 of one embodiment of the present invention, the external force detection unit 120 monitors the external force applied to the collaborative robot 200, and the feeding control unit 110 stops feeding (forward feeding) the welding wire 211 when the external force applied to the collaborative robot 200 detected by the external force detection unit 120 exceeds a threshold (second threshold). As a result, the operator can appropriately identify arc generation defects, including situations where the welding wire 211 pushes the workpiece W and the tip of the welding torch 210 (welding wire 211) receives a reaction force F.

[0054] As a result, by continuing to feed the welding wire 211 in the direction approaching the workpiece W (forward feeding), the reaction force acting on the welding torch 210 (external force acting on the collaborative robot 200) increases, which can prevent the collaborative robot 200 from stopping abnormally (collision detection).

[0055] In this embodiment, the feeding control unit 110 stopped feeding the welding wire 211 (forward feeding) when the external force applied to the collaborative robot 200 detected by the external force detection unit 120 exceeded a threshold (second threshold). However, the welding wire 211 may also be fed in a direction away from the workpiece W (reverse feeding).

[0056] Figure 6 is a flowchart showing the processing flow of the welding wire feeding control method M101 executed by the robot control device 100 according to one embodiment of the present invention when feeding the welding wire 211 in reverse. As shown in Figure 6, the welding wire feeding control method M101 includes steps S110 to S150, with step S150 added compared to the welding wire feeding control method M100 shown in Figure 5.

[0057] In step S150, the wire feed control unit 110 pulls back the welding wire that was stopped being fed in step S140 (welding wire pull-back step). Specifically, the wire feed control unit 110 controls the wire feed device 220 so that the welding wire 211 at the tip of the welding torch 210 is pulled back away from the workpiece W (reverse feeding). Here, the distance pulled back is, for example, a few millimeters.

[0058] Then, returning to the process of step S110, the feed control unit 110 resumes feeding (forward feeding) of the welding wire 211 to generate an arc.

[0059] For example, if an insulator such as slag S attached to the joint portion of the workpiece W peels off, an arc will be generated appropriately, causing the "No" process in step S120 and the "No" process in step S130 to be repeated.

[0060] On the other hand, as shown in Figure 4, if insulating material such as slag S remains attached to the joint portion of the workpiece W, the process of "Yes" in steps S110, S120 or S130, S140 and S150 will be repeated. As this process (forward and reverse feeding of the welding wire 211) is repeated, insulating material such as slag S attached to the joint portion of the workpiece W will be removed, and an arc will be generated properly.

[0061] Furthermore, if an arc is not properly generated even after repeating this process (forward and reverse feeding of the welding wire 211) a predetermined number of times (for example, 3 to 10 times), the robot control device 100 may stop feeding the welding wire 211, stop supplying welding voltage (welding current) from the power supply device 300, stop the collaborative robot 200, and notify the robot accordingly.

[0062] Figure 7 shows the relationship between the external force applied to the collaborative robot 200 and the feeding control of the welding wire. As shown in Figure 7, the forward feeding, reverse feeding, and stopping of the welding wire 211 are controlled according to the external force applied to the collaborative robot 200.

[0063] The feed control unit 110 feeds the welding wire 211 in the forward direction, and the power supply control unit 140 supplies a welding voltage (welding current) between the welding wire 211 and the base material (workpiece W), thereby normally generating an arc appropriately.

[0064] For example, if an insulator such as slag S adheres to the joint portion of the workpiece W, the external force applied to the collaborative robot 200 increases. If the external force detection unit 120 determines that the external force is equal to or greater than the second threshold, the feed control unit 110 stops feeding the welding wire 211 and reverses the feeding process to pull the welding wire 211 back.

[0065] Subsequently, the feed control unit 110 resumes feeding the welding wire 211 in the forward direction. However, here, the external force detection unit 120 again determines that the external force is above the second threshold, and the feed control unit 110 stops feeding the welding wire 211 and repeatedly feeds it in the reverse direction to pull it back.

[0066] Then, by repeating the above process three times, the insulating material such as slag S that was attached to the joint portion of the workpiece W is removed, and after that, an arc is generated appropriately.

[0067] Note that while this example shows proper arc generation by repeating the above process three times, it is not limited to this, and proper arc generation may also occur by repeating the above process less than three times or four or more times.

[0068] Thus, even if arc generation failure occurs due to the adhesion of an insulator such as slag S to the joint portion of the workpiece W, according to the robot control device 100 and welding wire feeding control method M101, if the external force applied to the collaborative robot 200 detected by the external force detection unit 120 exceeds a threshold (second threshold), the feeding control unit 110 stops feeding the welding wire 211 (forward feeding) and performs forward feeding and reverse feeding (repeated). As a result, the insulator such as slag S that was adhering to the joint portion of the workpiece W is removed, preventing abnormal stopping of the collaborative robot 200 (collision detection) and maintaining arc starting ability.

[0069] In this embodiment, the collaborative robot 200 is described as a 6-axis vertical articulated robot, but it is not limited to this. For example, it may be a 7-axis vertical articulated robot, or any other robot, as long as it is a welding robot capable of detecting external forces acting on the collaborative robot.

[0070] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The elements, arrangement, materials, conditions, shapes, and sizes of the embodiments are not limited to those exemplified and can be modified as appropriate. Furthermore, it is possible to partially substitute or combine the configurations shown in different embodiments. [Explanation of Symbols]

[0071] 10...Robot system, 100...Robot control device, 110...Feeding control unit, 120...External force detection unit, 130...Robot control unit, 140...Power supply control unit, 200...Collaborative robot (manipulator), 210...Welding torch, 211...Welding wire, 220...Wire feeding device, 300...Power supply device, M100, M101...Welding wire feeding control method, S110~S150...Each step of welding wire feeding control method M100 and M101, W...Workpiece, S...Slag, F...Reaction force

Claims

1. A robot control device for controlling the operation of a collaborative robot, A wire feeding control unit controls the feeding of the welding wire to generate an arc, It includes an external force detection unit that detects external forces acting on the collaborative robot, The feeding control unit stops feeding the welding wire if the external force detected by the external force detection unit is greater than or equal to a second threshold that is less than a first threshold for detecting a collision with the collaborative robot. Robot control device.

2. The feeding control unit stops feeding the welding wire if the external force detected by the external force detection unit is less than the second threshold and the arc does not occur for a predetermined period of time. The robot control device according to claim 1.

3. The feeding control unit, after stopping the feeding of the welding wire, pulls back the feeding of the welding wire in the reverse direction. The robot control device according to claim 1 or 2.

4. The system further includes a notification unit that notifies the user if the feeding control unit stops feeding the welding wire. The robot control device according to claim 1 or 2.

5. A welding wire feeding control method performed by a robot control device that controls the operation of a collaborative robot, A feed control step that controls the feeding of the welding wire to generate an arc, This includes an external force detection step for detecting an external force acting on the collaborative robot, In the feeding control step, if the external force detected in the external force detection step is greater than or equal to a second threshold that is smaller than a first threshold for detecting a collision with the collaborative robot, the feeding of the welding wire is stopped. A method for controlling the feeding of welding wire.

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