Welding device and control method for welding device

Abstract

To control a position and an angle of a fusion hand to workpiece using a force sensor.SOLUTION: A fusion device includes: a robot arm (20); a fusion hand (30) which is mounted on the robot arm (20) and has a fusion head (32) for melting and joining workpiece (W) in the state of separated from workpiece (W); a support (40) which is provided on the fusion hand (30) and is brought into contact with the workpiece (W); a force sensor (35) for detecting force and a moment received from the workpiece through the support (40); and a control part for controlling operation of the robot arm (20) on the basis of the parameter calculated from an output signal of the force sensor (35).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a welding apparatus provided with a force sensor.

Background Art

[0002] Conventionally, there is a welding apparatus using a robot. For example, Patent Document 1 discloses a welding apparatus including a welding robot and a welding hand attached to the arm of the welding robot. The welding apparatus is provided with a force sensor. The force sensor is disposed between the tip of the arm of the welding robot and the welding hand. A plurality of electrode tips provided on the welding hand grip the work from both sides, and the force sensor detects the deflection of the work with respect to the welding hand. The control unit controls the robot arm so that the input value of the detection signal from the force sensor is within the set range, thereby controlling the position of the welding hand with respect to the work.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, welding methods are classified into fusion welding, pressure welding, and brazing. Here, fusion welding refers to a welding method in which the work is melted and joined. Fusion welding is performed in a state where the welding hand is separated from the work. Therefore, it is impossible to detect the force acting on the welding hand from the work using a force sensor, and as a result, it is impossible to control the position of the welding hand with respect to the work using a force sensor. Therefore, it is impossible to control the position and angle of the welding hand with respect to the work using a force sensor as in Patent Document 1.

[0005] One aspect of the present invention has been made in view of the above problems, and an object thereof is to realize a welding apparatus and a control method for the welding apparatus that control the position and angle of a welding hand with respect to a workpiece using a force sensor. **Means for Solving the Problems**

[0006] In order to solve the above problems, a welding apparatus according to one aspect of the present invention includes a robot arm, a welding hand attached to the robot arm and having a welding head that melts and joins the workpiece in a state of being separated from the workpiece, a support provided on the welding hand and contacting the workpiece, a force sensor for detecting a force and a moment received from the workpiece via the support, and a control unit that controls the operation of the robot arm based on a parameter calculated from an output signal of the force sensor. **Advantages of the Invention**

[0007] According to one aspect of the present invention, it is possible to realize a welding apparatus and a control method for the welding apparatus that accurately control the position of the welding hand with respect to the workpiece. **Brief Description of the Drawings**

[0008]

Figure 1

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Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0009] In the following embodiments, as an example of a welding apparatus that performs welding, the case of performing arc welding will be described. Here, in the present application, welding refers to a welding method in which energy is released toward the joint portion of the workpiece in a state separated from the workpiece, and the workpiece is joined by heating or melting the joint portion of the workpiece. For example, gas welding, arc welding, electro-slag welding, electron beam welding, laser beam welding, etc. are applicable. In the present application, what is emitted from the welding head and transmitted to the workpiece (electricity, light, heat) is collectively expressed as "energy".

[0010] 〔Embodiment 1〕 Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 5. FIG. 1 is a diagram showing the overall structure of the welding apparatus 1 according to Embodiment 1. FIG. 2 is a diagram showing a main part of the welding apparatus 1 according to Embodiment 1. FIG. 3 is a view of the welding hand 30 shown in FIG. 2 as viewed from the X1 direction. FIG. 4 is a diagram showing the force sensor 35 disposed in the welding apparatus 1 shown in FIG. 1. FIG. 5 is a diagram for explaining the force and moment acting on the support 40. In explaining each configuration and positional relationship of the welding apparatus 1, for convenience of explanation, it is defined by three coordinate axes in the X (X1 - X2) direction, Y (Y1 - Y2) direction, and Z (Z1 - Z2) direction as shown in FIG. 1 and the like.

[0011] As shown in FIG. 1, the welding apparatus 1 includes a welding operation unit 5, a welding robot 2, and a control device 50.

[0012] The welding operation unit 5 is connected to the welding hand 30. The welding operation unit 5 is a mechanism for discharging energy from the welding head 32. The welding operation unit 5 is controlled by a control device 50 described later and supplies power to the welding hand 30. The welding operation unit 5 has a welding power supply unit that applies a voltage to the welding head 32 and the workpiece W. The welding operation unit 5 may have a molten material supply unit such as a wire, or may have a gas supply unit that supplies shielding gas or active gas.

[0013] The workpiece W to be welded is made of metal. Also, an example of the joint of the workpiece W is a butting joint in which the workpieces W are butted against each other. However, the joint of the workpiece is not limited to this, and may be a T-joint, a corner joint, etc. Also, the workpiece to be welded may be a workpiece having a so-called groove formed on the joint, that is, a workpiece having a groove formed.

[0014] The control device 50 controls the welding device 1.

[0015] The welding robot 2 includes a base 10, a robot arm 20, a welding hand 30, and a support 40. The base 10 is fixed to the floor surface.

[0016] The robot arm 20 is provided on the base 10. The base end of the robot arm 20 is attached to the base 10. The robot arm 20 is provided rotatably with respect to the base 10. The robot arm 20 has a plurality of links. The links of the robot arm 20 are rotatably attached at the joint portions connecting to adjacent links. A welding hand 30 is attached to the tip of the robot arm 20.

[0017] The welding hand 30 is a hand for welding the workpiece W. An attachment member 33 is provided on the welding hand 30. The welding hand 30 is connected to the robot arm 20 via the attachment member 33.

[0018] The welding hand 30 has a hand body 31 and a welding head 32. The welding head 32 is provided on the tip side of the hand body 31. The welding head 32 is a part that emits energy toward the joint A of the workpiece W in a state of being separated from the workpiece W. In the present embodiment, the welding head 32 is an electrode for generating an arc, which is electrical energy.

[0019] A support 40 is provided on the welding hand 30. The support 40 is a member that abuts against the workpiece W. The support 40 is fixed to the welding hand 30 at a predetermined angle. More specifically, the support 40 is attached to the hand body 31 by a fixture (not shown). Thereby, the support 40 is fixed to the welding hand 30.

[0020] As shown in FIGS. 2 and 3, the support 40 has a first column 42, a second column 43, and a connection part 41.

[0021] The first column 42 and the second column 43 are members that extend from the welding hand 30 side toward the workpiece W side (Z2 direction). The first column 42 has a hand-side first column 421 and a workpiece-side first column 422. A force sensor 35, which will be described later, is disposed between the hand-side first column 421 and the workpiece-side first column 422. The second column 43 has a hand-side second column 431 and a workpiece-side second column 432. A force sensor 35 is disposed between the hand-side second column 431 and the workpiece-side second column 432. Incidentally, the force sensor 35 may be disposed between the connection part 41 and the end of the first column 42 on the welding hand 30 side, and between the connection part 41 and the end of the second column 43 on the welding hand 30 side.

[0022] The first column 42 and the second column 43 are provided with rollers 44 that contact the workpiece W. By providing the rollers 44 on the first column 42 and the second column 43, the support 40 can smoothly travel on the workpiece W. Further, the roller 44 is formed of an insulating member that is electrically insulated. Since the roller 44 is formed of an insulating member, it is possible to prevent a short circuit between the workpiece W and the roller 44. Note that the roller 44 may be provided on either one of the first column 42 and the second column 43.

[0023] The connecting portion 41 connects the ends of the first column 42 and the second column 43 on the side of the welding hand 30. More specifically, the connecting portion 41 connects the end of the hand-side first column 421 on the side of the welding hand 30 and the end of the hand-side second column 431 on the side of the welding hand 30. The connecting portion 41 is a member attached to the hand body 31 by a fixture.

[0024] When the welding hand 30 moves due to the operation of the robot arm 20, the support 40 also travels on the workpiece W together. The support 40 is provided so as not to travel on the welded portion Y. More specifically, the support 40 is provided to travel in front of the welding hand 30 in the traveling direction (X2 direction) of the welding hand 30. Further, the support 40 travels so that the joint portion A of the workpiece W is located between the first column 42 and the second column 43. In other words, the first column 42 travels on one of the butted workpieces W, and the second column 43 travels on the other butted workpiece W. Thereby, the support 40 can move on the workpiece in a stable state. Note that the support 40 may travel on one of the workpieces W. For example, when the workpiece W to be welded is a T-joint or a corner joint, etc., the support 40 may be provided on the welding hand so as to travel on one of the workpieces W at an interval from the joint portion A of the workpiece W and along the joint portion A.

[0025] FIG. 4 is a diagram showing the force sensor 35 disposed in the welding apparatus 1 shown in FIG. 1. As described above, the force sensor 35 is disposed on the support 40. Thereby, since the force sensor 35 can detect the force and moment directly acting on the support 40 from the work W, the operation program of the robot arm 20 can be easily created. As shown in FIG. 4, the force sensor 35 is a six-axis force sensor that can detect loads (Fx, Fy, Fz) in the X-axis direction, Y-axis direction, and Z-axis direction, and can simultaneously detect moments (Mx, My, Mz) in the X-axis direction, Y-axis direction, and Z-axis direction. The force sensor 35 is a strain gauge type sensor having a first member 36 having a first surface 36a, a second member 37 having a second surface 37a, and a strain generating body (not shown) disposed between the first member 36 and the second member 37. Note that the force sensor 35 is not limited to a strain gauge type sensor, and a piezoelectric type, an optical type, or other force sensors may be used.

[0026] The force sensor 35 is a sensor for detecting the force and moment received from the work W via the support 40. More specifically, the force sensor 35 disposed on the first column body detects the force and moment acting on the first column body 42. The force sensor 35 disposed on the second column body detects the force and moment acting on the second column body 43. The force sensor 35 disposed on the first column body 42 is disposed such that the first surface 36a of the first member 36 faces the welding hand 30 side. The force sensor 35 disposed on the second column body 43 is disposed such that the second surface 37a of the second member 37 faces the work W side.

[0027] With reference to FIG. 5, the force and moment acting on the support 40 will be described. The welding hand will be described as moving in the X2 direction. As shown in FIG. 5, the control device 50 controls the operation of the robot arm 20 so that the support 40 abuts against the work W.

[0028] When the support 40 contacts the work W, a force and a moment act on the support 40 from the work W. The force sensor 35 detects the force FZ in the Z direction, which is the vertical resistance force acting on the support 40. Based on the value of FZ detected by the force sensor 35, the control device 50 controls the operation of the robot arm 20 in the direction of approaching the work W or moving away from the work W. Thereby, the position of the welding hand 30 with respect to the work W is maintained at a predetermined position. By maintaining the vertical resistance force Fz acting on the support 40 constant, even if the work W has unevenness or a curved surface, the position of the welding head 32 with respect to the work W can be made constant.

[0029] When the welding hand 30 approaches an inclined surface portion that is inclined in the traveling direction (X2 direction), the first rotational moment MY acts on the support 40. The first rotational moment MY is horizontal with respect to the surface of the work W that contacts the support 40, and is a moment having an axis perpendicular to the traveling direction of the welding hand 30 as the rotation axis. In other words, the first rotational moment MY is a moment having an axis perpendicular to the traveling direction of the support 40 as the rotation axis. The control device 50 controls the inclination of the robot arm 20 with respect to the work so that the first rotational moment MY detected by the force sensor 35 is within a predetermined range. Thereby, the angle of the welding head 32 with respect to the work W is maintained under predetermined conditions.

[0030] Also, although not shown, when the welding hand 30 approaches an inclined surface portion that is inclined in a direction (Y1 - Y2) intersecting the traveling direction (X2 direction), the second rotational moment MX acts on the support 40. The second rotational moment MX is horizontal with respect to the surface of the work W that contacts the support 40, and is a moment having the traveling direction of the welding hand 30 as the rotation axis. In other words, the second rotational moment MX is a moment having the traveling direction of the support 40 as the rotation axis. The control device 50 controls the inclination of the robot arm 20 with respect to the work so that the second rotational moment MX detected by the force sensor 35 is within a predetermined range. Thereby, the angle of the welding head 32 with respect to the work W is maintained under predetermined conditions.

[0031] FIG. 6 is a diagram showing the hardware configuration of the welding apparatus 1. As shown in FIG. 6, the control device 50 includes a processor 51, a memory 52, and an input / output IF 53. The control device 50 is realized by, for example, a personal computer (PC) or a programmable logic controller (PLC). The processor 51, the memory 52, and the input / output IF 53 are electrically connected to each other via a bus.

[0032] The processor 51 performs various controls and various calculations by executing various programs stored in the memory 52. As the processor 51, for example, a central processing unit (CPU), a graphic processing unit (GPU), a digital signal processor (DSP), a micro processing unit (MPU), or a combination thereof can be used. The processor 51 controls, for example, the operation of the robot arm 20.

[0033] The memory 52 stores various programs executed by the processor 51. A program related to welding is stored in the memory 52. The program related to welding is a program that describes the operation and control routine of the entire welding apparatus 1. As the memory 52, for example, a read only memory (ROM), a random access memory (RAM), or the like can be used.

[0034] The input / output IF 53 is an interface that communicates with the robot arm 20, the force sensor 35, and the welding operation unit 5. As the input / output IF 53, for example, a universal serial bus (USB), an advanced technology attachment (ATA), a small computer system interface (SCSI), serial communication, or the like can be used.

[0035] <Control Method of Welding Device> A control method of the welding device 1 will be described with reference to FIG. 6. FIG. 6 is a flowchart showing the control method of the welding device 1 according to Embodiment 1.

[0036] In step S1, when a program related to welding is executed by the processor 51, the control device 50 controls the operation of the robot arm 20. According to the control of the control device 50, the operation of the robot arm 20 is adjusted so that the position and angle of the robot arm 20 with respect to the workpiece W satisfy predetermined conditions. As a result, the position and angle of the welding head 32 with respect to the workpiece W become positions and angles that satisfy predetermined conditions. The position and angle of the welding head 32 with respect to the workpiece W are adjusted so as to maintain predetermined conditions in the maintaining step. This maintaining step will be described in detail later. Further, according to the control of the control device 50, the operation of the robot arm 20 is controlled so that the welding hand 30 moves along the joint portion A of the workpiece W.

[0037] In step S2, the welding operation unit 5 applies a voltage to the electrode of the welding head 32 and the workpiece W according to the control of the control device 50. When the voltage is applied, an arc is generated from the welding head 32, and the joint portion A of the workpiece W is welded.

[0038] In parallel with steps S1 and S2, steps S3 and S4 are repeatedly performed.

[0039] In step S3, the force sensor 35 detects the force and moment received from the workpiece W via the support 40. More specifically, the force sensor 35 detects the force and moment acting on the support 40. The values of the force and moment detected by the force sensor 35 are input to the control device 50 via the input / output IF 53.

[0040] In step S4, the control device 50 corrects and controls the operation of the robot arm 20 based on the force and moment detected in step 3 so that the position and angle of the welding head 32 with respect to the workpiece W meet predetermined conditions. Thereby, the position and angle of the welding head 32 with respect to the workpiece W are maintained to meet the predetermined conditions.

[0041] As shown in FIG. 8, the control device 50 determines whether or not the value of the vertical resistance force FZ acting on the support 40 is within a predetermined range (S5). If the value of the vertical resistance force FZ is within the predetermined range (YES in S5), the process proceeds to step S7. If the value of the vertical resistance force FZ is not within the predetermined range (NO in S5), the control device 50 corrects the operation of the robot arm 20 so that the detected value of the vertical resistance force FZ is within the predetermined range (S6). After correcting the operation of the robot arm 20 in step S6, the process proceeds to step S7.

[0042] Next, the control device 50 determines whether or not the value of the first rotational moment MY acting on the support 40 is within a predetermined range (S7). If the value of the first rotational moment MY is within the predetermined range (YES in S7), the process proceeds to step S9. If the value of the first rotational moment MY is not within the predetermined range (NO in S7), the control device 50 corrects the operation of the robot arm 20 so that the detected value of the first rotational moment MY is within the predetermined range (S8). After correcting the operation of the robot arm 20 in step S8, the process proceeds to step S9.

[0043] Next, the control device 50 determines whether or not the value of the second rotational moment MX acting on the support 40 is within a predetermined range (S9). If the value of the second rotational moment MX is within the predetermined range (YES in S9), the maintenance process S4 ends. If the value of the second rotational moment MX is not within the predetermined range (NO in S9), the control device 50 corrects the operation of the robot arm 20 so that the detected value of the second rotational moment MX is within the predetermined range (S10). After correcting the operation of the robot arm 20 in step S10, the maintenance process S4 ends.

[0044] <First Modification Example> A first modification example of the support 40 in Embodiment 1 will be described with reference to FIG. 9. FIG. 9 is a diagram showing a first modification example of the support 40a according to Embodiment 1. In the first modification example, a force sensor 35 is provided on the attachment portion 45.

[0045] As shown in FIG. 9, the support 40a in this modification example further has an attachment portion 45 in addition to the first column body 42a, the second column body 43a, and the connection portion 41. The attachment portion 45 is provided on the connection portion 41. The attachment portion 45 is a member that is attached to the fixture of the welding hand 30. The attachment portion 45 has a hand-side attachment portion 451 and a work-side attachment portion 452. The force sensor 35 is disposed between the hand-side attachment portion 451 and the work-side attachment portion 452. Note that the force sensor 35 may be provided between the hand main body 31 and the hand-side end portion of the attachment portion 45. The force sensor 35 in this modification example detects the force and moment acting on the connection portion 41.

[0046] In the above-described step S3, the force sensor 35 detects the normal force FZ, the first rotational moment MY, and the second rotational moment MX acting on the connection portion 41. Next, in the above-described step S4, the control device 50 determines whether the normal force FZ, the first rotational moment MY, and the second rotational moment MX are within a predetermined range. If at least one of the values of the normal force FZ, the first rotational moment MY, and the second rotational moment MX is not within the predetermined range, the control device 50 corrects the operation of the robot arm 20 so that the normal force FZ, the first rotational moment MY, and the second rotational moment MX are within the predetermined range.

[0047] Thereby, the first column body 42a and the second column body 43a can always be kept in contact with the work W, and the force and moment received from the work W via the support 40a can be detected more accurately. As a result, the position and angle of the welding head 32 with respect to the work W are maintained to be in predetermined conditions.

[0048] 〔Embodiment 2〕 Other embodiments of the present invention will be described below with reference to FIG. 10. For convenience of explanation, members having the same functions as those described in the above embodiments are denoted by the same reference numerals, and their descriptions will not be repeated.

[0049] FIG. 10 is a diagram showing a main part of the welding apparatus according to Embodiment 2. The welding apparatus according to Embodiment 2 is different from the welding apparatus 1 according to Embodiment 1 in that the force sensor 35 is disposed between the tip of the robot arm 20 and the welding hand 30. Further, the welding apparatus according to Embodiment 2 is different from the welding apparatus 1 according to Embodiment 1 in that the force sensor 35 directly detects the force and moment acting on the welding hand 30.

[0050] As shown in FIG. 10, the force sensor 35 is disposed between the tip of the robot arm 20 and the mounting member 33. The force sensor 35 is disposed such that the first surface 36a is on the tip side of the robot arm 20 and the second surface 37a is on the welding hand 30 side. The force sensor 35 detects the force and moment acting on the welding hand 30 via the support 40.

[0051] The force and moment acting on the welding hand 30 detected by the force sensor 35 are input to the control device 50 via the input / output IF 53. The control device 50 corrects and controls the operation of the robot arm 20 so that the position and angle of the welding head 32 with respect to the workpiece W satisfy predetermined conditions based on the detected force and moment.

[0052] In the above-described embodiments, a welding apparatus that performs arc welding for discharging electric energy from a welding head has been described, but the present invention is not limited thereto. The present application is also applicable to welding that discharges other energy (light, heat) from the welding head, such as laser welding or gas welding. In the case of laser welding, the welding operation unit 5 has a laser oscillation unit, and the welding head is provided with a lens that converges the laser light excited by the laser oscillation unit. In the case of gas welding, the welding operation unit 5 has a gas supply unit, and the welding head is provided with a torch that discharges the gas from the gas supply unit and a point bottom that ignites the discharged gas.

[0053] In the above-described embodiments, the control device has been described as being inside the welding apparatus, but the present invention is not limited thereto. The control device may be provided outside the welding apparatus.

[0054] In the above-described embodiments, the robot arm provided on the base fixed to the floor surface has been described, but the present invention is not limited thereto. The robot arm may have wheels and be attached to a movable base.

[0055] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0056] 1 Welding apparatus 2 Welding robot 5 Welding operation unit 10 Base 20 Robot arm 35 Force sensor 30 Welding hand 31 Hand body 32 Welding head 33 Mounting member 36 First member 37 Second member 40 Support 41 Connection part 42 First cylinder 43 Second cylinder 44 Roller 45 Mounting part 50 Control device 51 Processor 52 Memory 53 Input / output IF

Claims

1. A robot arm, a welding hand attached to the robot arm and having a welding head that melts and joins the workpiece while being separated from the workpiece, a support provided on the welding hand and contacting the workpiece, a force sensor for detecting a force and a moment received from the workpiece via the support, and a control unit that controls the operation of the robot arm based on a parameter calculated from an output signal of the force sensor, wherein the parameter includes a vertical reaction force received from the workpiece via the support, and the control unit controls the operation of the robot arm such that the magnitude of the vertical reaction force becomes constant. A welding apparatus characterized by this.

2. The parameter is a moment received from the workpiece via the support, and includes a first rotational moment having an axis orthogonal to the traveling direction of the welding hand as a rotation axis, and the control unit controls the operation of the robot arm such that the first rotational moment falls within a predetermined range. The welding apparatus according to claim 1, characterized by this.

3. The force sensor is disposed on the support. The welding apparatus according to claim 1 or 2, characterized by this.

4. The support has a first column and a second column that each contact the workpiece and between which a joint portion of the workpiece is located, and the force sensor is disposed on each of the first column and the second column. The welding apparatus according to any one of claims 1 to 3, characterized by this.

5. The support has a roller that contacts the workpiece. The welding apparatus according to any one of claims 1 to 4, characterized by this.

6. The force sensor is disposed between the robot arm and the welding hand. The welding apparatus according to claim 1 or 2, characterized by this.

7. A control method for a welding apparatus including a robot arm, a welding hand attached to the robot arm and having a welding head that melts and joins the workpiece while being separated from the workpiece, a support provided on the welding hand and contacting the workpiece, and a force sensor for detecting a force and a moment received from the workpiece via the support, wherein the operation of the robot arm is controlled based on a parameter calculated from an output signal of the force sensor. The parameter includes a vertical resistance force received from the work via the support, and controls the operation of the robot arm so that the magnitude of the vertical resistance force becomes constant. A control method for a welding apparatus, characterized by the above.

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