robot systems

Abstract

This provides a robot system that can accurately teach the contact position between the tool tip and the workpiece. [Solution] The robot system 1 comprises a robot 2 to which a tool 23 is attached, a control device 3 that controls the movement of the robot 2, and a teaching device 4 used for teaching the robot 2. The robot system 1 further comprises a distance sensor 5 fixed to the robot 2 and measuring the distance in a direction parallel to the central axis of the tool 23, a reference member 6 having a reference plane 61 for calibration work of the distance sensor 5, and a contact sensor 7 that detects contact between the reference plane 6 and the tool 23. With the reference member 6 set in a set position, the control device 3 controls the movement of the robot 3 in accordance with commands from the teaching device 4 to repeatedly move the tip of the tool 23 closer to the reference plane 61 and stop. When the contact sensor 7 detects contact between the reference plane 61 and the tool 23, the distance sensor 5 performs its own calibration process so that the contact detection position becomes the reference point.

Description

Technical Field

[0001] The present invention relates to a robot system that teaches the contact position between the tip of a tool and a workpiece.

Background Art

[0002] Friction stir joining is a joining method in which the tip of a rotated tool is pressed into a workpiece, the workpiece is softened by frictional heat, and the periphery of the joint is plastically flowed and kneaded by stirring with rotation to integrate a plurality of members. Friction stir joining is also called FSW (Friction Stir Welding), and there are a method using a dedicated friction stir device (see Patent Document 1) and a method using a general-purpose articulated robot. When using a general-purpose articulated robot, due to its high degree of freedom, it is possible to join complex shapes such as curved surfaces or continuously join from the upper surface to the side surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In friction stir joining, the accuracy of the contact position between the tip of the tool and the workpiece affects the joining quality. On the other hand, in the case of a dedicated friction stir device as in Patent Document 1, since the workbench on which the workpiece is placed is integrated, it is easy to ensure the accuracy of the contact position between the tip of the tool and the workpiece. On the other hand, in the case of a general-purpose articulated robot, it is not integrated with the workbench, and it is difficult to ensure the accuracy of the contact position between the tip of the tool and the workpiece.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a robot system that can accurately teach the contact position between the tip of a tool and a workpiece.

Means for Solving the Problems

[0006] The present invention, for achieving the aforementioned objectives, is a robot system comprising: a robot to which a tool is attached; a control device for controlling the operation of the robot; and a teaching device for teaching the robot, further comprising: a distance sensor fixed to the robot and measuring the distance in a direction substantially parallel to the central axis of the tool; a reference member having a reference plane for calibration work of the distance sensor; and a contact sensor for detecting contact between the reference plane and the tool, wherein the control device controls the operation of the robot to repeatedly move the tip of the tool closer to the reference plane and stop, in accordance with a command from the teaching device, with the reference member installed in a set position, and the distance sensor performs its own calibration process when the contact sensor detects contact between the reference plane and the tool, so that the contact detection position becomes a reference point.

[0007] The control device controls the robot to repeatedly move the tip of the tool closer to the workpiece and stop, in accordance with commands from the teaching device, with the workpiece placed in a set position. The teaching device outputs the sensor value of the distance sensor. Furthermore, the control device may also accept commands from the teaching device to register teaching points. [Effects of the Invention]

[0008] The present invention provides a robot system that can accurately teach the contact position between the tip of a tool and the workpiece. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of a first arrangement of the robot system according to an embodiment of the present invention. [Figure 2] Enlarged view of area II in Figure 1. [Figure 3] A flowchart showing an example of the processing flow performed in the first configuration shown in Figures 1 and 2. [Figure 4]This figure shows an example of a second arrangement of the robot system according to an embodiment of the present invention. [Figure 5] Enlarged view of region V in Figure 4. [Figure 6] A flowchart showing an example of the processing flow performed in the second configuration shown in Figures 4 and 5. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a diagram showing an example of a first arrangement of a robot system according to an embodiment of the present invention. As shown in Figure 1, the robot system 1 comprises a robot 2, a control device 3 for controlling the operation of the robot 2, and a teaching pendant (hereinafter referred to as "TP") 4 which is a teaching device used for teaching the robot 2, and performs friction stir welding. Note that the teaching device may be something other than a TP.

[0011] Robot 2 has an arm 21 and a base 22 that supports the arm 21. A rotatable tool 23 is attached to the tip of the arm 21. The arm 21 is composed of a linkage mechanism with multiple links and has joints connecting the links. Each joint is provided with a drive motor (not shown). An example of robot 2 is a vertical articulated robot with 6 joints. However, the present invention is also applicable to other robots.

[0012] The tool 23 is connected to the arm 21 via a spindle 24. The spindle 24 has a rotating part (not shown) inside that is connected to a drive motor (not shown), and the rotating part rotates at high speed. The tool 23 is held by a holder 25 connected to the rotating part of the spindle 24 and rotates together with the rotating part of the spindle 24.

[0013] The CPU (Central Processing Unit) 31, memory 32, storage unit 33, and input / output interface (I / F) unit 34 of the control device 3 are connected via a bus 35. The CPU 31 reads a control program, which is pre-stored in the storage unit 33, etc., into the memory 32 and executes multiple instructions sequentially. The storage unit 33 is a hard disk drive or solid-state drive, etc., and stores data used for processing described later. The input / output interface (I / F) unit 34 receives signals from the robot 2, TP4, etc., and outputs signals to them. Note that all or part of the functions of the control device 3 may be configured with logic circuits or analog circuits, and the processing of various programs may be configured with electronic circuits such as FPGAs (Field Programmable Gate Arrays).

[0014] The control device 3 may be built into the base 22 of the robot 2, or it may be installed outside the robot 2. In the latter case, the robot 2 and the control device 3 are connected to communicate via a communication cable. The control device 3 and TP4 are also connected to communicate via a communication cable. The robot 2 and the control device 3, and the control device 3 and TP4, may be connected wirelessly. There may be one control device 3 or multiple control devices. In the case of multiple control devices, the control devices 3 are connected to each other to communicate. The control device 3 may consist of, for example, a numerical control device that controls the movement of the spindle 24 and a robot control device that controls the movement of the arm 21 of the robot 2. In the following description, we will assume that there is one control device 3, and that this one control device 3 controls the movement of the robot 2.

[0015] The CPU (Central Processing Unit) 41, memory 42, storage unit 43, input unit 44, output unit 45, and input / output interface (I / F) unit 46 of TP4 are connected via a bus 47. The CPU 41 reads a control program, which is pre-stored in the storage unit 43, etc., into the memory 42 and executes multiple instructions sequentially. The storage unit 43 is an auxiliary storage device such as a hard disk drive or solid-state drive, and stores data used for processing described later. The input unit 44 is an input device such as a physical button, touch panel, or microphone. The output unit 45 is an output device such as a display or speaker. The input / output interface unit 46 receives signals from the control device 3, etc., and outputs signals to them.

[0016] In friction stir welding, the projection (also called a probe) of the rotating tool 23 is pressed into the butt joint between two workpieces, such as aluminum. If the tool 23 is pressed in too far or too far, the quality of the joint may be affected. Therefore, it is necessary to accurately teach the contact position between the tip of the tool 23 and the workpiece. Since the projection of the tool 23 wears down, it is desirable to teach the tool each time the workpiece is set up or the tool 23 is replaced. However, errors are likely to occur if teaching is done solely by human visual inspection. In particular, it is difficult to teach a tool 23 with a large diameter. Therefore, this embodiment provides a method that can accurately teach the contact position between the tip of the tool 23 and the workpiece.

[0017] Figure 2 is an enlarged view of area II in Figure 1. In the first configuration shown in Figures 1 and 2, the robot system 1 includes a distance sensor 5, a reference member 6 having a reference plane 61 for calibration of the distance sensor 5, and a contact sensor 7 for detecting contact between the reference plane 61 and the tool 23. The distance sensor 5 is fixed to the robot 2 and measures the distance in a direction D that is substantially parallel to the central axis 26 of the tool 23. The central axis 26 of the tool 23 substantially coincides with the rotation axis of the rotating part of the spindle 24.

[0018] The distance sensor 5 is installed on the outer surface 24a of the spindle 24. Since the outer surface 24a of the spindle 24 does not rotate even when the rotating part of the spindle 24 rotates, the distance sensor 5 does not rotate at high speed. The distance sensor 5 is, for example, a laser displacement meter, which irradiates a laser beam onto the surface of an object and measures the displacement amount of the object by detecting the reflected or scattered light.

[0019] The control device 3 and the distance sensor 5 are communicably connected via a communication cable or wirelessly. The distance sensor 5 transmits its own sensor value to the control device 3. The control device 3 transmits the sensor value received from the distance sensor 5 to TP4. T4 outputs the sensor value received from the control device 3 to a display or the like.

[0020] The reference member 6 is placed on the workbench 8 and has a top plate 62 and four legs 63 that support the top plate 62. The top plate 62 is connected to the legs 63 via springs 64. The reference plane 61 is the surface of the top plate 62. Since the top plate 62 is supported by the springs 64, the position of the reference plane 61 changes downward in the vertical direction by the amount by which it is pushed.

[0021] The installation position of the contact sensor 7 is, for example, near the center of the back surface of the top plate 62, but it is not particularly limited as long as the displacement of the reference plane 61 can be detected. The contact sensor 7 is, for example, a contact displacement sensor, and detects the displacement of the top plate 62 due to the contact between the tip 23a of the tool 23 and the reference plane 61. Also, the contact sensor 7 may be a force sensor that can detect a small force such as contact. The distance sensor 5 and the contact sensor 7 are communicably connected via a communication cable or wirelessly.

[0022] Figure 3 is a flowchart showing an example of the flow of processing executed in the first arrangement shown in FIGS. 1 and 2. As shown in FIGS. 1 and 2, the robot system 1 performs the calibration process of the distance sensor 5 in a state where the reference member 6 is installed at the set position. The control device 3 controls the operation of the robot 2 in the teaching mode. In the teaching mode, the user operates TP4, TP4 sends a command to the control device 3, and the control device 3 controls the operation of the robot 2 according to the command of TP4.

[0023] As shown in Figure 3, the control device 3 controls the movement of the robot 2 in accordance with the command from TP4 so that the tip 23a of the tool 23 is brought closer to the reference plane 61 in an inching motion and then stops (step S1). Inching refers to a small movement of the robot 2 in a small amount of time, and is also called inching. The control device 3 controls the movement of the robot 2 so that the tip 23a of the tool 23 is brought closer to the reference plane 61 along a direction perpendicular to the reference plane 61.

[0024] Next, the contact sensor 7 checks whether or not it has detected contact between the tip 23a of the tool 23 and the reference plane 61 (step S2). When the contact sensor 7 detects the displacement of the top plate 62, it determines that there has been contact between the tip 23a of the tool 23 and the reference plane 61. If no contact is detected (No in step S2), the user repeats the process from step S1. If contact is detected (Yes in step S2), the contact sensor 7 notifies the distance sensor 5 that there has been contact between the tip 23a of the tool 23 and the reference plane 61 (step S3).

[0025] When the distance sensor 5 receives a contact notification from the distance sensor 5, it performs its own calibration process so that the contact detection position by the contact sensor 7, i.e., the current position, becomes the reference point (step S4). The reference point is, for example, the origin (zero point). Once the calibration process of the distance sensor 5 is complete, the user terminates the process shown in Figure 3. The reference point calibrated in step S4 becomes the reference for aligning the contact position between the tip 23a of the tool 23 and the workpiece.

[0026] As described above, the control device 3 controls the movement of the robot 2 in accordance with the command from TP4, so as to repeatedly bring the tip of the tool 23 closer to the reference plane 61 and then stop. When the contact sensor 7 detects contact between the reference plane 61 and the tool 23, the distance sensor 5 performs its own calibration process so that the contact detection position becomes the reference point. This allows the registration process of teaching points, which will be described later, to be performed by referring to the sensor value of the distance sensor 5.

[0027] Figure 4 shows an example of a second arrangement of the robot system according to an embodiment of the present invention. Figure 5 is an enlarged view of region V in Figure 4. A description of a configuration similar to the first arrangement is omitted.

[0028] In the second configuration shown in Figures 4 and 5, the distance sensor 5 is installed in the same manner as in the first configuration, and a pair of workpieces 9, 9 are placed on the workbench 8. The pair of workpieces 9, 9 are held in place by a jig 81 fixed to the workbench 8, with the sides 91, 91 of the joint portion abutting against each other. The upper surfaces 92, 92 of the pair of workpieces 9, 9 are almost flush with each other, without any steps.

[0029] Figure 6 is a flowchart showing an example of the processing flow performed in the second arrangement shown in Figures 4 and 5. As shown in Figures 4 and 5, the robot system 1 performs the process of registering the teaching point, which will be the starting position for friction stir welding, with the pair of workpieces 9, 9 placed in the set position. The control device 3 controls the operation of the robot 2 in teaching mode.

[0030] As shown in Figure 6, the control device 3 controls the movement of the robot 2 in accordance with the command from TP4 so that the tip 23a of the tool 23 is brought in an increment and stopped near the pair of workpieces 9, 9 (step S11). The control device 3 controls the movement of the robot 2 so that the tip 23a of the tool 23 is brought near the pair of workpieces 9, 9 along a direction perpendicular to the upper surfaces 92, 92 of the pair of workpieces 9, 9.

[0031] Furthermore, the distance sensor 5 transmits its own sensor value to the control device 3, and TP4 outputs the sensor value of the distance sensor 5 received from the control device 3 via the output unit 45 (step S12). Alternatively, if the distance sensor 5 is equipped with an output unit such as a display or speaker, the distance sensor 5 may output its own sensor value.

[0032] The user checks whether the sensor value of distance sensor 5 output by TP4 or distance sensor 5 is near the reference point (step S13). Alternatively, if TP4 acquires the sensor value of distance sensor 5, TP4 may check whether the sensor value of distance sensor 5 is near the reference point and notify the user.

[0033] If the sensor value is not near the reference point (No in step S13), the user repeats the process from step S11. If the sensor value is near the reference point (Yes in step S13), the user presses the teaching point registration button (not shown) displayed on the TP4's display. The control device 3 registers the current position of the tip 23a of the tool 23 as a teaching point according to the command from TP4 (step S14). For example, if TCP (Tool Center Point) is the center point of the tip 23a of the tool 23, in step S14, the control device 3 registers the current position of TCP as a teaching point. TCP is a reference point for determining the position and orientation of the tool 23.

[0034] Once the registration of the teaching point for the starting position of the friction stir welding shown in step S14 is complete, the user finishes the process shown in Figure 6. After the process shown in Figure 6 is complete, the user registers teaching points related to the movement path of the tool 23 to the end position of the friction stir welding. Once the registration of all teaching points from the starting position to the end position is complete, the user finishes the teaching work.

[0035] As described above, the control device 3 controls the movement of the robot 2 in accordance with the command from TP4, so as to repeatedly bring the tip of the tool 23 closer to the pair of workpieces 9, 9 and then stop. The distance sensor 5 or TP4 outputs the sensor value of the distance sensor 5. The control device 3 then receives a command from TP4 to register teaching points. This allows the teaching point registration process to be performed by referring to the sensor value of the distance sensor 5, without relying solely on human visual observation.

[0036] As described above, the robot system 1 in this embodiment can accurately teach the contact position between the tip of the tool 23 and the workpiece 9, thereby ensuring the bonding quality of friction stir welding. Furthermore, by referring to the sensor value of the distance sensor 5, the time required for positioning can be reduced, thereby reducing the burden of teaching each time the workpiece is set up or the tool 23 is replaced. Moreover, although teaching a tool 23 with a large diameter was difficult, referring to the sensor value of the distance sensor 5 makes teaching a tool 23 with a large diameter easier.

[0037] As shown in Figures 4 and 5, the robot system 1 in this embodiment is effective not only when joining the upper surfaces 92, 92 of a pair of workpieces 9, 9 together, but also when joining the side surfaces 91, 91 together. Furthermore, it is effective regardless of the angle of the joining surfaces of the pair of workpieces 9, 9 (= the surfaces that the tip 23a of the tool 23 contacts).

[0038] In the explanation above, the example given was teaching the starting position of friction stir welding, but the same method can be applied to teaching the contact position between tool 23 and workpiece 9.

[0039] Preferred embodiments of the robot system and the like according to the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications and alterations can be conceived within the scope of the technical idea disclosed herein, and these will naturally also fall within the technical scope of the present invention. [Explanation of Symbols]

[0040] 1…Robot system 2…Robot 3…Control device 4. Teaching device (Teaching pendant) (TP) 5… Distance sensor 6………Standard Member 7... Contact sensor 9...Work 23... Tools 26………Central Axis 61………Reference Plane

Claims

1. A robot system comprising a robot to which a tool is attached, a control device for controlling the movement of the robot, and a teaching device used for teaching the robot, A distance sensor fixed to the robot and measuring the distance in a direction substantially parallel to the central axis of the tool, A reference member having a reference plane for the calibration work of the distance sensor, A contact sensor that detects contact between the reference plane and the tool, Furthermore, The control device controls the robot's movement to repeatedly bring the tip of the tool closer to the reference plane and stop, in accordance with commands from the teaching device, while the reference member is installed in the set position. When the contact sensor detects contact between the reference plane and the tool, the distance sensor performs its own calibration process so that the contact detection position becomes the reference point. A robotic system characterized by the following features.

2. The control device controls the robot to repeatedly move the tip of the tool closer to the workpiece and stop, in accordance with commands from the teaching device, while the workpiece is placed in the set position. The teaching device outputs the sensor value of the distance sensor, Furthermore, the control device receives a command to register teaching points from the teaching device. The robot system according to feature 1.

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