Welding system and program

Abstract

To obtain good weld quality even curvature centers of respective curved parts of a steel pipe and a guide rail are different from each other.SOLUTION: A welding system controls a welding robot that welds a first steel pipe straight part, a steel pipe curved part and a second steel pipe straight part of a steel pipe while moving on a rail having a rail straight part and a rail curved part along the steel pipe. A curvature center of the rail straight part is positioned on a center side of the steel pipe with respect to a curvature center of the steel pipe curved part. A control part perform control so that: when a tip of a welding torch welds the first steel pipe straight part to a start position of the steel pipe curved part, a direction of the welding torch is made orthogonal to the steel pipe straight part; when the tip of the welding torch welds the steel pipe curved part, the direction of the welding torch is made coincident with a normal direction of the steep pipe curved part and; when the tip of the welding torch welds the second steel pipe straight part from an end position of the steel pipe curved part, the direction of the welding torch is made orthogonal to the second steel pipe straight part.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a welding system , and Regarding the program. [Background technology]

[0002] Steel pipe columns formed by joining square steel pipes by welding are used in large buildings such as high-rise buildings. As disclosed in Patent Document 1, a welding robot that can move around the steel pipes along guide rails is used to join the square steel pipes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-058078 Summary of the Invention [Problem to be solved by the invention]

[0004] The corners of the steel pipe are curved in an arc shape. The corners of the guide rail are also formed to be curved in an arc shape. Because the guide rail is provided on the outside of the steel pipe, the curved portion of the steel pipe and the curved portion of the guide rail have different circumferential lengths. In Patent Document 1, the speed at which the welding robot travels along the guide rail is calculated in advance so that the moving speed of the tip of the welding torch along the curved portion of the steel pipe is constant, and the welding robot is moved in accordance with this speed. This keeps the welding speed at the curved portion of the steel pipe constant.

[0005] In many cases, the center of curvature of the curved portion of the steel pipe is different from the center of curvature of the curved portion of the guide rail. In this case, the distance between the steel pipe and the guide rail at the curved portion is not constant in the circumferential direction. Therefore, with the method of Patent Document 1, it is difficult to maintain a constant distance between the tip of the welding torch and the welded portion of the steel pipe at the curved portion while maintaining a constant welding speed at the curved portion of the steel pipe. It is also difficult to always point the tip of the welding torch perpendicular to the welded portion of the steel pipe at the curved portion. As a result, the quality of the weld may be reduced.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a welding system, welding method, and program that can obtain good welding quality even when the centers of curvature of the curved sections of the steel pipe and the guide rail are different. [Means for solving the problem]

[0007] A welding system according to a first aspect of the present invention is a welding system that controls a welding robot that moves on a rail having a rail straight section and a rail curved section along a steel pipe and welds a first steel pipe straight section, a steel pipe curved section, and a second steel pipe straight section of the steel pipe, the welding system comprising: a welding torch held by the welding robot; a torch direction change unit that changes the direction of the welding torch; a speed change unit that changes the moving speed of the welding robot; and a control unit that controls the torch direction change unit and the speed change unit, wherein the center of curvature of the rail curved section is located closer to the center of the steel pipe than the center of curvature of the steel pipe curved section, and the control unit controls the welding robot to move the tip of the welding torch from the first steel pipe straight section to a start position of the steel pipe curved section. the control unit controls the direction of the welding torch so that when welding from the end position of the curved section of the steel pipe to the start position of the curved section of the steel pipe, the direction of the welding torch is perpendicular to the first straight section of the steel pipe; when the tip of the welding torch welds the curved section of the steel pipe, the direction of the welding torch is controlled to coincide with the normal direction of the curved section of the steel pipe; when the tip of the welding torch welds the second straight section of the steel pipe from the end position of the curved section of the steel pipe, the direction of the welding torch is controlled to be perpendicular to the second straight section of the steel pipe; and the control unit controls the welding robot to accelerate when the tip of the welding torch approximately reaches the start position of the curved section of the steel pipe, and controls the welding robot to decelerate when the tip of the welding torch approximately reaches the end position of the curved section of the steel pipe.

[0008] A welding system according to a second aspect of the present invention is a welding system that controls a welding robot that moves in a predetermined direction along a steel pipe on a rail having a rail straight section and a rail curved section, while welding a first steel pipe straight section, a steel pipe curved section, and a second steel pipe straight section of the steel pipe, the welding system comprising: a welding torch held by the welding robot; a torch direction changing unit that changes the direction of the welding torch; a speed changing unit that changes the moving speed of the welding robot; and a control unit that controls the torch direction changing unit and the speed changing unit; The center of curvature of the curved portion is located closer to the center of the steel pipe than the center of curvature of the curved portion of the steel pipe, and the curved portion of the steel pipe has a curve start position which is a start position, a curve end position which is an end position, and a curve intermediate position which is an intermediate position between the curve start position and the curve end position of the steel pipe, and the control unit controls the welding torch so that the inclination of the welding torch toward the predetermined direction increases as the tip of the welding torch welds the first straight portion of the steel pipe up to the curve start position of the steel pipe, and and controls the inclination of the welding torch toward the predetermined direction to decrease as the tip of the welding torch welds from the intermediate position of the curved steel pipe to the intermediate position of the curved steel pipe, controls the inclination of the welding torch toward the opposite side to the predetermined direction to increase as the tip of the welding torch welds from the intermediate position of the curved steel pipe to the end position of the curved steel pipe, and controls the inclination of the welding torch toward the opposite side to the predetermined direction to decrease as the tip of the welding torch welds from the end position of the curved steel pipe to the second straight section of the steel pipe, and the control unit controls the welding torch. the welding robot is controlled to accelerate when the tip of the welding torch nearly reaches the start position of the steel pipe curve, the welding robot is controlled to decelerate as the tip of the welding torch welds from the start position of the steel pipe curve to the intermediate position of the steel pipe curve, the welding robot is controlled to accelerate as the tip of the welding torch welds from the intermediate position of the steel pipe curve to the end position of the steel pipe curve, and the welding robot is controlled to decelerate when the tip of the welding torch nearly reaches the end position of the steel pipe curve.

[0009] A welding system according to a third aspect of the present invention is a welding system for controlling a welding robot that moves on a rail having a straight rail section and a curved rail section along a steel pipe while welding the straight steel pipe section and the curved steel pipe section of the steel pipe, and the welding system includes a welding torch held by the welding robot, a torch direction changing unit that changes the direction of the welding torch, a speed changing unit that changes the moving speed of the welding robot, and a control unit that controls the torch direction changing unit and the speed changing unit, and wherein the center of curvature of the curved rail section is closer to the center of the steel pipe than the center of curvature of the curved steel pipe section. the control unit controls the welding robot to orient the welding torch perpendicular to the straight section of the steel pipe when the welding robot welds the straight section of the steel pipe, and controls the welding robot to orient the welding torch in the normal direction to the curved section of the steel pipe when the welding robot welds the curved section of the steel pipe; the control unit controls the welding robot to accelerate when the tip of the welding torch nearly reaches the start position of the curved section of the steel pipe, and controls the welding robot to decelerate when the tip of the welding torch nearly reaches the end position of the curved section of the steel pipe.

[0010] A welding system according to a fourth aspect of the present invention is a welding system that controls a welding robot that moves in a predetermined direction along a steel pipe on a rail having a rail straight section and a rail curved section, while welding a first steel pipe straight section, a steel pipe curved section, and a second steel pipe straight section of the steel pipe, and is equipped with a welding torch held by the welding robot, a torch direction changing unit that changes the direction of the welding torch, a speed changing unit that changes the moving speed of the welding robot, and a control unit that controls the torch direction changing unit and the speed changing unit, and wherein the center of curvature of the rail curved section is located closer to the center of curvature of the steel pipe curved section than the center of curvature of the steel pipe curved section. The control unit controls the welding robot to be positioned on the rail straight section and the welding torch to be oriented perpendicular to the first steel pipe straight section when the welding robot is positioned on the rail straight section and the tip of the welding torch welds the first steel pipe straight section to the steel pipe curve start position, and the control unit controls the welding robot to be positioned on the rail curved section and the welding torch to be oriented perpendicular to the first steel pipe straight section when the welding robot is positioned on the rail curved section and the tip of the welding torch welds the first steel pipe straight section to the steel pipe curve start position. As the tip of the welding torch welds from the steel pipe curve start position to the steel pipe curve intermediate position, the inclination of the welding torch toward the predetermined direction is controlled to become larger as the tip of the welding torch welds from the steel pipe curve start position to the steel pipe curve intermediate position, the inclination of the welding torch toward the opposite side to the predetermined direction is controlled to become larger as the tip of the welding torch welds from the steel pipe curve intermediate position to the steel pipe curve end position, and the inclination of the welding torch toward the opposite side to the predetermined direction is controlled to become smaller as the tip of the welding torch welds from the steel pipe curve end position to the second steel pipe straight section. The control unit controls the welding robot to accelerate when the tip of the welding torch nearly reaches the start position of the steel pipe curve, controls the welding robot to decelerate as the tip of the welding torch welds from the start position of the steel pipe curve to the intermediate position of the steel pipe curve, controls the welding robot to accelerate as the tip of the welding torch welds from the intermediate position of the steel pipe curve to the end position of the steel pipe curve, and controls the welding robot to decelerate when the tip of the welding torch nearly reaches the end position of the steel pipe curve.It is characterized by the following.

[0011] A welding system according to a fifth aspect of the present invention is a welding system that controls a welding robot that moves along a steel pipe on a rail having a rail straight section and a rail curved section, and welds a first steel pipe straight section, a steel pipe curved section, and a second steel pipe straight section of the steel pipe, the welding system comprising: a welding torch owned by the welding robot; a torch direction changing unit that changes the direction of the welding torch; and a control unit that controls the torch direction changing unit, wherein the center of curvature of the steel pipe curved section is located closer to the center of the steel pipe than the center of curvature of the rail curved section, The control unit controls the orientation of the welding torch so that it is perpendicular to the first steel pipe straight section when the tip of the welding torch welds the first steel pipe straight section up to the start position of the steel pipe curved section, controls the orientation of the welding torch so that it is aligned with the normal direction of the steel pipe curved section when the tip of the welding torch welds the steel pipe curved section, and controls the orientation of the welding torch so that it is perpendicular to the second steel pipe straight section when the tip of the welding torch welds the second steel pipe straight section from the end position of the steel pipe curved section.

[0012] A welding system according to a sixth aspect of the present invention is a welding system for controlling a welding robot that moves in a predetermined direction along a rail having a first rail straight section, a rail curved section, and a second rail straight section, while welding a first steel pipe straight section, a steel pipe curved section, and a second steel pipe straight section of the steel pipe, the welding system comprising: a welding torch owned by the welding robot; a torch direction changing unit that changes the direction of the welding torch; and a control unit that controls the torch direction changing unit, wherein the center of curvature of the steel pipe curved section is located closer to the center of the steel pipe than the center of curvature of the rail curved section, the rail curved section has a rail curve start position that is a start position, a rail curve end position that is an end position, and a rail curve intermediate position that is an intermediate position between the rail curve start position and the rail curve end position, the steel pipe curved section has the steel pipe curve start position that is a start position, and the steel pipe curve end position that is an end position, When welding the first steel pipe straight section up to the steel pipe curve start position, the direction of the welding torch is controlled to be perpendicular to the first steel pipe straight section; when the tip of the welding torch welds the steel pipe curved section, the welding robot is controlled to increase the inclination of the welding torch toward the opposite side to the predetermined direction as it moves along the first rail straight section to the rail curve start position; the welding robot is controlled to decrease the inclination of the welding torch toward the opposite side to the predetermined direction as it moves from the rail curve start position to the rail curve intermediate position; the welding robot is controlled to increase the inclination of the welding torch toward the predetermined direction as it moves from the rail curve intermediate position to the rail curve end position; and the welding robot is controlled to decrease the inclination of the welding torch toward the predetermined direction as it moves along the second rail straight section from the rail curve end position.

[0013] A welding system according to a seventh aspect of the present invention is a welding system for controlling a welding robot that moves in a predetermined direction on a rail having a straight rail section and a curved rail section along a steel pipe while welding the straight steel pipe section and the curved steel pipe section of the steel pipe, the welding system comprising: a welding torch held by the welding robot; a torch direction changer that changes the direction of the welding torch; a speed changer that changes the moving speed of the welding robot; and a control unit that controls the torch direction changer and the speed changer, wherein the center of curvature of the curved rail section is located closer to the center of the steel pipe than the center of curvature of the curved steel pipe section, and the curved steel pipe section has a steel pipe curve start position that is a start position, a steel pipe curve end position that is an end position, and a distance between the steel pipe curve start position and the steel pipe curve end position. and a steel pipe curve intermediate position which is an intermediate position between the curved rail position and the curved rail position, and the control unit controls the welding robot to be positioned at the rail curved section, and as the tip of the welding torch welds the steel pipe straight section to the curved rail start position, the control unit controls the welding torch to be tilted more toward the predetermined direction as the tip of the welding torch welds from the curved rail start position to the curved rail intermediate position, the control unit controls the welding robot to be tilted less toward the predetermined direction as the tip of the welding torch welds from the curved rail start position to the curved rail intermediate position, and the control unit controls the welding robot to be tilted more toward the predetermined direction as the tip of the welding torch welds from the curved rail intermediate position to the curved rail end position.

[0014] A welding system according to an eighth aspect of the present invention is the welding system according to the seventh aspect, wherein the control unit controls the welding robot to accelerate when the tip of the welding torch approximately reaches the start position of the steel pipe curve, and controls the welding robot to decelerate when the tip of the welding torch approximately reaches the end position of the steel pipe curve.

[0015] A welding system according to a ninth aspect of the present invention is a welding system for controlling a welding robot that moves in a predetermined direction on a rail having a straight rail section and a curved rail section along a steel pipe while welding a straight steel pipe section and a curved steel pipe section of the steel pipe, the welding system comprising: a welding torch owned by the welding robot; a torch direction changing unit that changes the direction of the welding torch; a torch position changing unit that changes the position of the welding torch; and a control unit that controls the torch direction changing unit and the torch position changing unit, wherein the center of curvature of the curved rail section is located closer to the center of the steel pipe than the center of curvature of the curved steel pipe section, and the curved steel pipe section has a curve start position that is a start position, a curve end position that is an end position, and a curve intermediate position that is an intermediate position between the curve start position and the curve end position, and the control unit controls the welding robot to control the welding torch so that the tip of the welding torch is As the straight section of the steel pipe is welded up to the start position of the curved steel pipe, the inclination of the welding torch towards the predetermined direction increases, and the welding torch is controlled to move away from the steel pipe; as the tip of the welding torch welds from the start position of the curved steel pipe to the intermediate position of the curved steel pipe, the inclination of the welding torch towards the predetermined direction decreases, and the welding torch is controlled to move away from the steel pipe; as the tip of the welding torch welds from the intermediate position of the curved steel pipe to the end position of the curved steel pipe, the inclination of the welding torch towards the opposite side to the predetermined direction increases, and the welding torch is controlled to move closer to the steel pipe; and as the tip of the welding torch welds the straight section of the steel pipe from the end position of the curved steel pipe, the inclination of the welding torch towards the opposite side to the predetermined direction decreases, and the welding torch is controlled to move closer to the steel pipe.

[0016] A welding system according to a tenth aspect of the present invention is a welding system for controlling a welding robot that moves in a predetermined direction along a steel pipe on a rail having a straight rail section and a curved rail section while welding the straight steel pipe section and the curved steel pipe section of the steel pipe, the welding system comprising: a welding torch owned by the welding robot; a torch orientation changing unit that changes the orientation of the welding torch; a torch position changing unit that changes the position of the welding torch; and a control unit that controls the torch orientation changing unit and the torch position changing unit, wherein the center of curvature of the curved steel pipe section is located closer to the center of the steel pipe than the center of curvature of the curved rail section, and the curved rail section has a rail curve start position that is a start position, a rail curve end position that is an end position, and a rail curve intermediate position that is an intermediate position between the rail curve start position and the rail curve end position, and the control unit controls the welding robot to weld the curved steel pipe section. When performing the welding, the welding robot controls the welding torch so that as the welding robot moves along the straight rail section to the rail curve start position, the inclination of the welding torch toward the opposite side to the predetermined direction becomes larger and the welding torch approaches the steel pipe; as the welding robot moves from the rail curve start position to the rail curve intermediate position, the inclination of the welding torch toward the opposite side to the predetermined direction becomes smaller and the welding torch approaches the steel pipe; as the welding robot moves from the rail curve intermediate position to the rail curve end position, the inclination of the welding torch toward the predetermined direction becomes larger and the welding torch moves away from the steel pipe; and as the welding robot moves along the straight rail section from the rail curve end position, the inclination of the welding torch toward the predetermined direction becomes smaller and the welding torch moves away from the steel pipe.

[0017] A welding system according to an eleventh aspect of the present invention is a welding system that controls a welding robot that moves on a rail arranged along a steel pipe, the rail having a curved portion, and welds the curved portion of the steel pipe, and is equipped with an acquisition unit that acquires the center of curvature of the curved portion of the steel pipe as a first center of curvature, and a setting unit that sets welding conditions for the welding robot using the first center of curvature acquired by the acquisition unit, wherein the welding robot is equipped with a welding torch, and the welding conditions include a welding torch orientation that is the orientation of the welding torch with respect to the curved portion of the steel pipe, and when the first center of curvature does not coincide with a second center of curvature that is the center of curvature of the curved portion of the rail, the welding conditions are set using the first center of curvature.

[0018] A welding system according to a twelfth aspect of the present invention is a welding system that controls a welding robot that moves on a rail arranged along a steel pipe, the rail having a curved portion, and welds the curved portion of the steel pipe, and is equipped with an acquisition unit that acquires the center of curvature of the curved portion of the steel pipe as a first center of curvature, and a setting unit that sets welding conditions for the welding robot using the first center of curvature acquired by the acquisition unit, wherein the welding robot is equipped with a welding torch, the welding conditions include an aim position of the welding torch, and when the first center of curvature does not coincide with a second center of curvature, which is the center of curvature of the curved portion of the rail, the welding conditions are set using the first center of curvature.

[0019] A welding system according to a thirteenth aspect of the present invention is the welding system according to the eleventh or twelfth aspect, wherein the welding conditions differ depending on whether the first center of curvature and the second center of curvature coincide with each other.

[0020] A welding system according to a 14th aspect of the present invention is the welding system according to the 11th aspect, further comprising a torch orientation change unit that changes the orientation of the welding torch, wherein the setting unit sets the welding torch orientation using the first center of curvature and the second center of curvature, and the torch orientation change unit changes the orientation of the welding torch so that the orientation of the welding torch with respect to the curved portion of the steel pipe matches the welding torch orientation set by the setting unit.

[0021] A welding system according to a 15th aspect of the present invention is the welding system according to the 11th or 14th aspect, wherein the welding torch orientation includes the orientation of the welding torch when, when viewed from above, the orientation of the tip of the welding torch coincides with the normal direction of the curved portion of the steel pipe, and the setting unit sets the welding torch orientation according to the position of the welding robot.

[0022] A welding system according to a 16th aspect of the present invention is the welding system according to the 14th aspect, wherein the torch orientation changing unit includes a first rotation unit that can rotate the welding torch around a first axis parallel to the direction in which the welding robot moves, and a second rotation unit that can rotate the welding torch around a second axis parallel to the longitudinal direction of the steel pipe, one of the first rotation unit and the second rotation unit rotates the other together with the welding torch, the welding torch orientation includes the orientation of the welding torch when the tip of the welding torch is positioned in the groove of the steel pipe, as viewed along the direction in which the welding robot moves, and the setting unit sets the welding torch orientation in accordance with the rotation by one of the first and second rotation units.

[0023] A welding system according to a seventeenth aspect of the present invention is the welding system according to any one of the eleventh to sixteenth aspects, wherein the welding conditions include a welding movement speed, which is a movement speed of the tip of the welding torch.

[0024] A welding system according to an 18th aspect of the present invention is the welding system according to the 17th aspect, further comprising a speed change unit that changes the movement speed of the welding robot, wherein the setting unit sets the welding movement speed using the first center of curvature and the second center of curvature, and the speed change unit changes the movement speed of the welding robot so that the movement speed of the tip of the welding torch matches the welding movement speed set by the setting unit.

[0025] A welding system according to a 19th aspect of the present invention is the welding system according to the 17th aspect, further comprising a robot position change unit that changes the position of the welding robot, wherein the setting unit sets the welding movement speed using the first center of curvature and the second center of curvature, and the robot position change unit changes the position of the welding robot so that the movement speed of the tip of the welding torch matches the welding movement speed set by the setting unit.

[0026] A welding system according to a 20th aspect of the present invention is the welding system according to the 12th aspect, further comprising a torch position change unit that changes the position of the welding torch, wherein the setting unit sets the target position using the first center of curvature and the second center of curvature, and the torch position change unit changes the position of the welding torch so that the position of the welding torch coincides with the target position set by the setting unit.

[0027] A welding method according to a 21st aspect of the present invention is a welding method performed by a welding system that controls a welding robot that moves on a rail arranged along a steel pipe, the rail having a curved portion, and welds the curved portion of the steel pipe, and includes an acquisition step of acquiring the center of curvature of the curved portion of the steel pipe as a first center of curvature, and a setting step of setting welding conditions for the welding robot using the first center of curvature acquired in the acquisition step, wherein the welding conditions include a welding torch orientation, which is the orientation of the welding torch of the welding robot relative to the curved portion of the steel pipe, and in the setting step, when the first center of curvature does not coincide with a second center of curvature, which is the center of curvature of the curved portion of the rail, the welding conditions are set using the first center of curvature.

[0028] A welding method according to a 22nd aspect of the present invention is a welding method performed by a welding system that controls a welding robot that moves on a rail arranged along a steel pipe, the rail having a curved portion, and welds the curved portion of the steel pipe, and includes an acquisition step of acquiring the center of curvature of the curved portion of the steel pipe as a first center of curvature, and a setting step of setting welding conditions for the welding robot using the first center of curvature acquired in the acquisition step, wherein the welding conditions include an aim position of a welding torch of the welding robot, and in the setting step, when the first center of curvature does not coincide with a second center of curvature, which is the center of curvature of the curved portion of the rail, the welding conditions are set using the first center of curvature.

[0029] A program according to a 23rd aspect of the present invention is a program for causing a computer to function as the welding system according to any one of the first to 20th aspects. [Effects of the Invention]

[0030] According to the present invention, a welding system, welding method, and program can be provided that can obtain good welding quality even when the circumferential length or center of curvature of the curved section of the steel pipe and the guide rail are different. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is an overall view showing a welding system according to a first embodiment. [Figure 2] 1 is a block diagram illustrating an overview of a welding system according to a first embodiment. [Figure 3] 1A and 1B are diagrams showing a welding robot according to a first embodiment, in which (a) is a side view and (b) is a link diagram of (a). [Figure 4] FIG. 2 is a rear view of the welding robot according to the first embodiment. [Figure 5] FIG. 2(a) is a side view showing a first rotation part of the welding robot according to the first embodiment, and FIG. 2(b) is a plan view showing a second rotation part of the welding robot. [Figure 6] FIG. 1 is a side view of a welding robot according to a first embodiment. [Figure 7] 1A and 1B are diagrams showing a steel pipe and a guide rail in the first embodiment, where (a) is a plan view and (b) is a link diagram of (a). [Figure 8] FIG. 4 is a diagram for explaining welding of a curved portion in the first embodiment. [Figure 9] 1 is a system block diagram of a system control device according to a first embodiment. [Figure 10] 2 is a system block diagram of a control unit of the system control device according to the first embodiment. FIG. [Figure 11] 5 is a flowchart showing an example of the flow of welding processing of a curved portion executed by the system control device in the first embodiment. [Figure 12] FIG. 10 is a diagram illustrating welding of a curved portion in the second embodiment. [Figure 13] 10 is a flowchart showing an example of the flow of welding processing of a curved portion executed by a system control device in a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] [First embodiment] A welding system 100 according to a first embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a welding system 100 is used to weld together the ends of steel pipes 8 arranged side by side in the vertical direction. The steel pipe 8 is a square steel pipe having four arc-shaped curved sections 8a arranged at the corners and four straight sections 8b connecting the curved sections 8a (continuing the curved sections 8a without interruption). The axis of the steel pipe 8 extends vertically. In the initial state, the steel pipe 8 is temporarily fixed by an erection jig 9. The erection jig 9 is attached to the straight sections 8b of the steel pipe 8.

[0033] [Welding system overview] First, an overview of a welding system 100 will be described with reference to Figures 1 and 2. The welding system 100 includes a welding robot 1, a guide rail 2, an imaging device 3, a welding power source 4, a wire feeder 5, and a system control device 6.

[0034] The welding robot 1 includes a plurality of motors 32 and a welding torch 13. The welding robot 1 is also communicably connected to a system control device 6. The welding robot 1 includes a relay panel (not shown) that receives control from the system control device 6. Motor 32 is a motor that drives welding robot 1 under the control of system control device 6. Motor 32 includes a servo motor (speed change unit, robot position change unit) that moves welding robot 1 along guide rail 2.

[0035] The welding torch 13 is used to weld together the ends of the steel pipe 8. Welding using the welding torch 13 is performed by, for example, arc welding. A welding wire is disposed inside the welding torch 13.

[0036] The guide rail 2 is arranged along the steel pipe 8. The guide rail 2 is arranged in a ring shape in the circumferential direction of the steel pipe 8 so as to surround the steel pipe 8. The guide rail 2 has four arc-shaped curved sections 2a arranged at the corners and four straight sections 2b connecting the curved sections 2a. The welding robot 1 is movable along the guide rail 2.

[0037] The photographing device 3 is attached to the welding robot 1. The photographing device 3 photographs the welding portion of the steel pipe 8 in the sensing process before welding. The photographing device 3 also photographs the state of welding by the welding robot 1 in the welding process. The photographing device 3 is, for example, a camera. The photographing device 3 is connected to the system control device 6 so as to be able to communicate with the system control device 6, and the images or videos (hereinafter referred to as the photographing results) acquired by the photographing device 3 are transmitted to the system control device 6.

[0038] Welding power source 4 supplies power to wire feeder 5. Wire feeder 5 supplies welding wire to welding torch 13. Welding torch 13 is connected to wire feeder 5 via a welding torch cable. Wire feeder 5 supplies power to welding torch 13.

[0039] System controller 6 controls the operation of welding system 100. Specifically, system controller 6 controls the operations of welding robot 1, welding power source 4, and wire feeder 5. The welding robot 1 is connected to the system control device 6 via a control cable. The control cable transmits to the welding robot 1 a control signal that is sent from the system control device 6 and that controls the welding robot 1.

[0040] [Welding robot configuration] Next, the configuration of the welding robot 1 will be described with reference to FIGS. Fig. 3(a) is a side view of the welding robot 1. Fig. 3(b) is a link diagram of Fig. 3(a). Fig. 4 is a rear view of the welding robot 1. Fig. 5(a) is a side view showing a first rotation unit 35 (described later) of the welding robot 1. Fig. 5(b) is a plan view showing a second rotation unit 36 ​​(described later) of the welding robot 1. In the following, the direction along the vertical direction will be referred to as the up-down direction x of the welding robot 1. The direction in which the welding robot 1 moves along the guide rail 2 will be referred to as the left-right direction y of the welding robot 1. The direction perpendicular to the up-down direction x and the left-right direction y of the welding robot 1 will be referred to as the front-rear direction z of the welding robot 1.

[0041] The welding robot 1 includes a main body 11, a welding torch 13, and a support 14. The main body 11 is a base of the welding robot 1. The main body 11 includes a motor 32. The main body 11 includes a wheel unit 12 attached to the guide rail 2. The welding robot 1 moves along the guide rail 2 as the wheel unit 12 slides on the guide rail 2.

[0042] Support portion 14 is provided between main body portion 11 and welding torch 13, and supports welding torch 13. Support portion 14 has a case 21, a first link member 22, a second link member 23, and a third link member 24.

[0043] The case 21 is provided to cover the outside of the main body 11. The case 21 is movable relative to the main body 11 in the front-to-rear direction z of the welding robot 1. The main body 11 and the case 21 form a front-to-rear moving unit 33 (torch position changing unit). In the link diagram shown in FIG. 3(b), the front-to-rear moving unit 33 is shown as a linear joint.

[0044] The first link member 22 includes a vertical arm 22a extending vertically downward, a horizontal arm 22b extending horizontally from the lower end of the vertical arm 22a, and a connection panel 22c connected to the horizontal arm 22b and extending vertically downward. The vertical arm 22a, the horizontal arm 22b, and the connection panel 22c are connected to each other so as not to be able to move relative to each other. The upper end of vertical arm 22a is connected to case 21 inside case 21. Vertical arm 22a (first link member 22) is movable in the up-down direction x of welding robot 1 relative to case 21. Case 21 and first link member 22 form a vertical movement unit 34 (torch position change unit). In the link diagram shown in FIG. 3(b), vertical movement unit 34 is shown as a linear joint.

[0045] The second link member 23 is in the form of a panel. The upper end of the second link member 23 is connected to the lower end of the connecting panel 22c via a first link pin 351. As shown in FIG. 5(a), the second link member 23 is rotatable about the central axis of the first link pin 351 (hereinafter also referred to as the first axis) relative to the connection panel 22c. The central axis of the first link pin 351 is parallel to the left-right direction y of the welding robot 1. The connection panel 22c and the second link member 23 form a first rotation unit 35 (torch direction changing unit). In the link diagram shown in FIG. 3(b), the first rotation unit 35 is shown as a rotary joint. The first rotation unit 35 rotates the second rotation unit 36 ​​(described later) together with the welding torch 13.

[0046] The third link member 24 is connected to the lower end of the second link member 23 via a second link pin 361. The third link member 24 is a holder on which the welding torch 13 is supported. As shown in FIG. 5(b), the third link member 24 is rotatable relative to the second link member 23 about the central axis of the second link pin 361 (hereinafter also referred to as the second axis). When the second link member 23 is not rotated relative to the connection panel 22c, the central axis of the second link pin 361 is parallel to the vertical direction x of the welding robot 1. The second link member 23 and the third link member 24 form a second rotation unit 36 ​​(torch direction changing unit). In the link diagram shown in FIG. 3(b), the second rotation unit 36 ​​is shown as a rotary joint.

[0047] The forward / backward moving unit 33, the vertical moving unit 34, the first rotating unit 35, and the second rotating unit 36 ​​are all driven by the motor 32.

[0048] [Control Method] A control method for welding system 100 having the above configuration will be described. The control method according to this embodiment is mainly characterized by welding of the periphery of the curved portion 8a (hereinafter simply referred to as welding of the curved portion 8a) of the steel pipe 8. The curved portion 8a of the steel pipe 8 and the curved portion 2a of the guide rail 2 have different circumferential lengths. Furthermore, in many cases, the first center of curvature C1 of the curved portion 8a of the steel pipe 8 and the second center of curvature C2 of the curved portion 2a of the guide rail 2 are different. Therefore, the distance between the steel pipe 8 and the guide rail 2 at the curved portions 8a, 2a is not constant in the circumferential direction. Even in such a case, this embodiment achieves high-quality welding regardless of the position of the steel pipe 8 by adjusting the movement amount of the welding robot 1 according to the welding conditions.

[0049] First, the basic concept of the control method will be explained below with reference to FIG. Fig. 7(a) is a plan view showing the steel pipe 8 and the guide rail 2. Fig. 7(b) is a link diagram of Fig. 7(a).

[0050] The distance between the steel pipe 8 and the guide rail 2 varies depending on the position of each curved section 8a, 2a. Therefore, in this control method, the welding of the curved section 8a is divided into multiple areas, and the method for calculating the movement amount of the welding robot 1 is adjusted for each area. When dividing the welding of the curved portion 8a into a plurality of areas, a steel pipe coordinate system is defined based on the steel pipe 8. This steel pipe coordinate system is defined for each curved portion 8a of the steel pipe 8. Hereinafter, the vertical direction will be referred to as the X direction in the steel pipe coordinate system. The direction perpendicular to the X direction and along one of the two straight line portions 8b that connect to one curved line portion 8a will be referred to as the Y direction in the steel pipe coordinate system. The direction perpendicular to the X and Y directions will be referred to as the Z direction. The Z direction is the direction along the other of the two straight line portions 8b. For example, the origin position of the steel pipe coordinate system is set to a position that coincides with the X direction and the position (target position) of the tip of the welding torch 13 that satisfies the welding conditions described below, and also coincides with the first center of curvature C1 of the curved line portion 8a of the steel pipe 8 when viewed from above (YZ plane). In addition, among the X directions, the upward vertical direction is referred to as the +X direction, and the downward vertical direction is referred to as the -X direction. Among the Y directions, the direction toward the outside of the steel pipe 8 based on the origin position (first curvature center C1) of the steel pipe coordinate system is referred to as the +Y direction, and the direction toward the inside of the steel pipe 8 is referred to as the -Y direction. Among the Z directions, the direction toward the outside of the steel pipe 8 based on the origin position (first curvature center C1) of the steel pipe coordinate system is referred to as the +Z direction, and the direction toward the inside of the steel pipe 8 is referred to as the -Z direction.

[0051] [Curved section of steel pipe and curved section of guide rail] The curved portion 8a of the steel pipe 8 and the curved portion 2a of the guide rail 2 will be described. In top view (YZ plane), curved portion 8a is an arc having a radius of Rc and a center at first center of curvature C1, and curved portion 2a is an arc having a radius of Rg and a center at second center of curvature C2.

[0052] In this embodiment, the position of the first curvature center C1 is different from the position of the second curvature center C2. The second curvature center C2 is located closer to the center of the steel pipe 8 than the first curvature center C1. The distance between the straight portion 8b of the steel pipe 8 and the straight portion 2b of the guide rail 2 is l cg Then, the distance e in the Y direction (or Z direction) between the first center of curvature C1 and the second center of curvature C2 is expressed by the following equation. e=Rc+l cg -Rg That is, the second center of curvature C2 is located at a position shifted by −e in the Y and Z directions from the first center of curvature C1.

[0053] As shown in FIG. 8, the welding of the steel pipe 8 is divided into area 1, area 2, area 3, and area 4 according to the welding form. In the following, the start position of curved portion 2a will be referred to as Pg1, and the end position as Pg2. The start position of curved portion 8a will be referred to as Pc2, and the end position as Pc3. The intersection of the straight line connecting second center of curvature C2 and position Pg1 with straight portion 8b of steel pipe 8 will be referred to as position Pc1. The intersection of the straight line connecting second center of curvature C2 and position Pg2 with straight portion 8b of steel pipe 8 will be referred to as position Pc4.

[0054] Area 1 is an area where the steel pipe 8 is welded from position Pc1 to position Pc2. That is, area 1 is an area where the tip of the welding torch 13 moves from position Pc1 to position Pc2. In area 1, the welding robot 1 welds the straight portion 8b of the steel pipe 8 while moving along the curved portion 2a of the guide rail 2. That is, in area 1, the welding robot 1 is positioned above the curved portion 2a of the guide rail 2, and the portion that the welding robot 1 welds is the straight portion 8b of the steel pipe 8. Area 2 is an area where the steel pipe 8 is welded from position Pc2 to position Pc3. That is, area 2 is an area where the tip of the welding torch 13 moves from position Pc2 to position Pc3. In area 2, the welding robot 1 welds the curved portion 8a of the steel pipe 8 while moving along the curved portion 2a of the guide rail 2. That is, in area 2, the welding robot 1 is positioned above the curved portion 2a of the guide rail 2, and the portion that the welding robot 1 welds is the curved portion 8a of the steel pipe 8. Area 3 is an area where the steel pipe 8 is welded from position Pc3 to position Pc4. That is, area 3 is an area where the tip of the welding torch 13 moves from position Pc3 to position Pc4. In area 3, the welding robot 1 welds the straight portion 8b of the steel pipe 8 while moving along the curved portion 2a of the guide rail 2. That is, in area 3, the welding robot 1 is positioned above the curved portion 2a of the guide rail 2, and the portion that the welding robot 1 welds is the straight portion 8b of the steel pipe 8. Area 4 is an area other than areas 1 to 3 of the steel pipe 8. In area 4, the welding robot 1 welds the straight portion 8b of the steel pipe 8 while moving along the straight portion 2b of the guide rail 2. That is, in area 4, the welding robot 1 is positioned on the straight portion 2b of the guide rail 2, and the portion that the welding robot 1 welds is the straight portion 8b of the steel pipe 8. In this embodiment, welding of the curved portion 8a means welding of areas 1 to 3.

[0055] [Welding conditions] To ensure good welding quality, the following points must be met regardless of the area: <1> ~ <4> It is preferable to satisfy the welding conditions shown below. <1> The speed at which the tip of the welding torch 13 moves along the welding portion of the steel pipe 8 (hereinafter also referred to as the welding movement speed Vw) becomes constant. <2> The direction of the welding torch 13 in top view (hereinafter also referred to as the welding torch direction) coincides with the normal direction of the curved portion 8a of the steel pipe 8 or is perpendicular to the straight portion 8b of the steel pipe 8. <3> The target angle θn of the welding torch 13 is constant. Note that the target angle θn of the welding torch 13 is the orientation of the welding torch 13 when the tip of the welding torch 13 is positioned in the groove of the steel pipe 8, as viewed along the left-right direction y of the welding robot 1, as shown in Fig. 6. The target angle θn is appropriately adjusted depending on the condition of the welding portion of the steel pipe 8 (for example, groove information). <4> The distance between the tip of welding torch 13 and the welding portion of steel pipe 8 (hereinafter also referred to as the target position of welding torch 13) is constant. The position in the X direction of the tip of welding torch 13 that satisfies the above welding conditions is constant and coincides with the origin position of the steel pipe coordinate system in the X direction. As shown in Figure 6, the distance in the X direction (the vertical direction x of welding robot 1) between the X direction position of the tip of welding torch 13 that satisfies the above welding conditions and the lower end 2c of guide rail 2 is defined as H.

[0056] Here, in area 4, the distance between the steel pipe 8 (straight portion 8b) and the guide rail 2 (straight portion 2b) is constant. Therefore, the movement amount of the welding robot 1 that satisfies the above welding conditions is determined uniformly. <2> ~ <4> By moving welding robot 1 at welding movement speed Vw with the welding torch direction, aim angle, and aim position of welding torch 13 set to satisfy the above, welding can be performed that satisfies the above welding conditions.

[0057] On the other hand, in areas 1 to 3, the distance between the steel pipe 8 and the guide rail 2 varies depending on the circumferential position, so the movement amount of the welding robot 1 that satisfies the above welding conditions cannot be determined uniformly. In this embodiment, in welding areas 1 to 3 (welding of the curved portion 8a), inverse kinematics is used to calculate the movement amount of the welding robot 1. Calculating a target position and a target posture of the welding torch 13 that satisfy the above welding conditions (hereinafter also referred to as the target position and posture of the welding torch 13), The amount of movement of the welding robot 1 to achieve this is calculated.

[0058] Specifically, a matrix U (the above) representing the target position and target posture of the welding torch 13 that satisfies the above welding conditions is This matrix U is a matrix that represents the target position and target posture of the welding torch 13 at the welding position at time t. The welding position at time t is determined by the welding conditions <1> The welding position is determined based on Vw·t using the welding movement speed Vw. For example, if the welding position at time 0 is Pc1, it can be determined which of areas 1 to 3 the welding position is located in at time t based on the magnitude of Vw·t. In addition, a matrix T (as described above) representing the position and posture of the welding torch 13 when the welding robot 1 moves a predetermined distance is ) is generated. By determining the amount of movement of welding robot 1 such that matrix U is equal to matrix T and controlling the drive of motor 32 in accordance with this amount of movement, welding that satisfies the above welding conditions can be performed. In other words, by making these matrices U and T equal, the amount of movement required to achieve the target position and posture of welding torch 13 at a predetermined time t (welding position) can be determined. By controlling welding robot 1 to achieve this amount of movement, high-quality welding can be achieved.

[0059] [About matrix U] The generation of the matrix U will be explained in detail with reference to FIG. Matrix U is a matrix for expressing the target position and target posture of welding torch 13 that satisfy the above welding conditions, with the origin position (first center of curvature C1) of the steel pipe coordinate system as a reference. Matrix U is the target position and posture of welding torch 13 at a specific welding position. Matrix U is determined for each welding position of steel pipe 8. Matrix U is determined regardless of the position of welding robot 1. In this embodiment, welding of straight section 8b is performed in areas 1 and 3, and welding of curved section 8a is performed in area 2. Therefore, the target position and target posture of welding torch 13 that satisfy the above welding conditions differ between areas 1 to 3. For this reason, a matrix U is generated for each of areas 1 to 3. As described above, the position in the X direction of the tip of welding torch 13 that satisfies the above welding conditions is constant, and is a position that coincides with the origin position of the steel pipe coordinate system in the X direction.

[0060] In area 1, the tip of welding torch 13 moves from position Pc1 to position Pc2 at a welding movement speed Vw. The movement of the tip of welding torch 13 in area 1 is at a welding movement speed Vw in the Y direction (+Y direction). Therefore, the Y-direction position of the tip of welding torch 13 varies depending on time. The time when the tip of welding torch 13 reaches position Pc1 is set to 0. The Y-direction position of the tip of welding torch 13 at time t is a position moved +Vw·t in the Y direction from position Pc1. Note that the Y-direction position of position Pc1 is a position moved -e in the Y direction from the origin position (first center of curvature C1) of the steel pipe coordinate system. Furthermore, in area 1, the Z-direction position of the tip of welding torch 13 is always a position moved +Rc in the Z direction from the origin position (first center of curvature C1) of the steel pipe coordinate system. Furthermore, at the welding position at time t, the welding torch orientation of welding torch 13 that satisfies the above welding conditions is a direction perpendicular to straight portion 8b. At the welding position at time t, the aim angle of welding torch 13 is always constant (θn). At the welding position at time t, the distance between the tip of welding torch 13 and straight portion 8b is always constant. The matrix U in area 1 is generated as a homogeneous transformation matrix that represents the position and posture of the welding torch 13 as described above.

[0061] In area 2, the tip of welding torch 13 moves from position Pc2 to position Pc3 at a welding movement speed Vw. In area 2, the tip of welding torch 13 moves along curved portion 8a. That is, the movement of the tip of welding torch 13 that satisfies the above welding conditions in area 2 is a rotational movement around first center of curvature C1 on the YZ plane at welding movement speed Vw. In the YZ plane, the time when the tip of welding torch 13 reaches position Pc2 is set to 0, and the position of the tip of welding torch 13 at time t is a position rotated by an amount of rotation θc (radians) from position Pc2 around first center of curvature C1. Note that the amount of rotation θc is expressed by the following equation using radius Rc of curved portion 8a and welding movement speed Vw: θc=(Vw·t÷2πRc)×2π Furthermore, at the welding position at time t, the welding torch orientation of welding torch 13 that satisfies the above welding conditions is a direction that coincides with the normal direction of curved portion 8a. At the welding position at time t, the target angle of welding torch 13 is always constant (θn). At the welding position at time t, the distance between the tip of welding torch 13 and curved portion 8a is always constant. The matrix U in area 2 is generated as a homogeneous transformation matrix that represents the position and posture of the welding torch 13 as described above.

[0062] In area 3, the tip of welding torch 13 moves from position Pc3 to position Pc4 at a welding movement speed Vw. The movement of the tip of welding torch 13 in area 3 is at a welding movement speed Vw in the Z direction (-Z direction). Therefore, the Z direction position of the tip of welding torch 13 varies depending on time. The time when the tip of welding torch 13 reaches position Pc3 is set to 0. The Z direction position of the tip of welding torch 13 at time t is a position moved in the Z direction by -Vw·t from position Pc3. Note that the Z direction position of position Pc3 is the same as the origin position (first curvature center C1) of the steel pipe coordinate system in the Z direction. Furthermore, in area 3, the Y direction position of the tip of welding torch 13 is always a position moved in the Y direction by +Rc from the origin position (first curvature center C1) of the steel pipe coordinate system. Furthermore, at the welding position at time t, the welding torch orientation of welding torch 13 that satisfies the above welding conditions is a direction perpendicular to straight portion 8b. At the welding position at time t, the aim angle of welding torch 13 is always constant (θn). At the welding position at time t, the distance between the tip of welding torch 13 and straight portion 8b is always constant. The matrix U in area 3 is generated as a homogeneous transformation matrix that represents the position and posture of the welding torch 13 as described above.

[0063] [About the movement distance of the welding robot] 3 to 6, the movement amount of welding robot 1 will be described. In this embodiment, welding system 100 controls welding robot 1 to move a distance Mx of welding torch 13 in a vertical direction x, a distance My of welding robot 1 in a horizontal direction y, a distance Mz of welding torch 13 in a front-rear direction z, and a distance M of welding torch 13 about a first axis. B , and the movement amount M of the welding torch 13 around the second axis T That is, the movement amount of the welding robot 1 is a movement amount Mx, a movement amount My, a movement amount Mz, a movement amount M B , and the movement amount M T Includes. In addition, the movement amounts Mx, Mz, and M B , and M T indicates the amount of movement from the reference position of welding torch 13. The reference position of welding torch 13 is the position and posture of welding torch 13 when welding torch 13 is not moving, rotating, or the like. The movement amount My indicates the movement amount of the welding robot 1 based on a predetermined position of the guide rail 2. The predetermined position is set to the start position Pg1 of the curved portion 2a of the guide rail 2, for example.

[0064] 3(a), the movement amount Mx is controlled by the vertical movement unit 34. That is, the vertical movement unit 34 changes the position of the welding torch 13 in the vertical direction x of the welding robot 1 by moving the first link member 22 in the vertical direction x of the welding robot 1 relative to the case 21. The operation of the vertical movement unit 34 is controlled by driving a motor 32 (servo motor).

[0065] As shown in FIG. 4, the movement amount My is controlled by changing the movement speed of the welding robot 1 by the motor 32 (servo motor).

[0066] 3(a), the movement amount Mz is controlled by the front-rear movement unit 33. That is, the front-rear movement unit 33 moves the case 21 in the front-rear direction z of the welding robot 1 relative to the main body 11, thereby changing the position of the welding torch 13 in the front-rear direction z of the welding robot 1. The operation of the front-rear movement unit 33 is controlled by driving a motor 32 (servo motor).

[0067] As shown in FIG. 5(a), the movement amount M B is controlled by first rotating unit 35. That is, first rotating unit 35 rotates second link member 23 about the first axis relative to connection panel 22c, thereby rotating welding torch 13 about the first axis. First rotating unit 35 changes the orientation of welding torch 13 about the first axis. The operation of first rotating unit 35 is controlled by driving motor 32 (servo motor).

[0068] As shown in Fig. 5(b), the movement amount M T is controlled by second rotation unit 36. That is, second rotation unit 36 ​​rotates third link member 24 about the second axis relative to second link member 23, thereby rotating welding torch 13 about the second axis. Second rotation unit 36 ​​changes the orientation of welding torch 13 about the second axis. The operation of second rotation unit 36 ​​is controlled by driving motor 32 (servo motor).

[0069] [About matrix T] The matrix T is a matrix of the movement amount of the welding torch 13 in the vertical direction x of the welding robot 1, the movement amount of the welding torch 13 in the front-rear direction z of the welding robot 1, and the movement amount of the welding torch 13 around the first axis line. B , the movement amount of the welding torch 13 around the second axis is M T and the amount of movement of the welding robot 1 relative to position Pg1 is My, the matrix T is used to represent the position and posture of the welding torch 13 relative to the origin position (first center of curvature C1) of the steel pipe coordinate system. In this embodiment, the matrix T is a common matrix for areas 1 to 3. In areas 1 to 3, the welding robot 1 moves on the curved portion 2a. That is, the movement of the welding robot 1 in areas 1 to 3 is a rotational movement around the second center of curvature C2 on the YZ plane. If the amount of rotation of the welding robot 1 around the second center of curvature C2 from position Pg1 on the YZ plane is θg (radian), the movement amount My can be expressed as the rotation amount θg as shown in the following equation. Rg is the radius of the curved portion 2a. θg=(My÷2πRg)×2π

[0070] The matrix T is made up of a matrix T1 for translating the origin position (first curvature center C1) of the steel pipe coordinate system to the position of the second curvature center C2, a matrix T2 for representing the position obtained by rotating the welding robot 1 from position Pg1 around the second curvature center C2 by the rotation amount θg (i.e., the position obtained by moving the welding robot 1 by the movement amount My from position Pg1), and a matrix T3 for representing the position of the welding robot 1 after rotation by matrix T2 by the movement amounts Mx, Mz, and M B , and M T and matrix T3 which represents the position and attitude of the tip of welding torch 13 when it moves by

[0071] The matrix T1 is generated by moving the origin position (first curvature center C1) of the steel pipe coordinate system by −e in the Y direction and the Z direction.

[0072] Matrix T2 is generated by rotating position Pg1 by a rotation amount θg around second center of curvature C2. Note that position Pg1 is a position moved by +Rg in the Z direction from second center of curvature C2.

[0073] The matrix T3 will be described with reference to FIG. FIG. 3(b) shows the link structure of welding robot 1 and the distances between each link when welding torch 13 is in the reference position. In FIG. 3(b), "a" indicates the distance in the front-to-rear direction z of welding robot 1 between first link pin 351 and second link pin 361 when welding torch 13 is in the reference position (see also FIG. 5(a)). "b" indicates the distance in the up-down direction x of welding robot 1 between first link pin 351 and second link pin 361 when welding torch 13 is in the reference position (see also FIG. 5(a)). "c" indicates the distance in the up-down direction x of welding robot 1 between lower end 2c of guide rail 2 and first link pin 351 when welding torch 13 is in the reference position. "d" indicates the distance in the front-to-rear direction z of welding robot 1 between guide rail 2 and first link pin 351 when welding torch 13 is in the reference position. L indicates the distance from second link pin 361 to the tip of welding torch 13 (see also FIG. 5(b)). Using these parameters a to d and L, the position and posture of welding torch 13 at the reference position are expressed. The matrix T3 expresses the position and posture of the welding torch 13 at the reference position, which are expressed using the parameters a to d and L as described above, as a function of the movement amounts Mx, Mz, M B , M T is a homogeneous transformation matrix generated by translating and rotating the

[0074] [Formula for calculating the movement distance of a welding robot] Regarding the matrices U and T generated as described above, by setting matrix U=matrix T, the movement amounts Mx, My, Mz, and M of the welding robot 1 that satisfy the above welding conditions can be calculated. B , M T This calculation formula is derived from the movement amounts Mx, My, Mz, and M B , M T This calculation formula is derived for each of areas 1 to 3.

[0075] [Welding system control system] Next, the control system of welding system 100 will be described with reference to FIGS. As described above, the control system determines the movement amount of the welding robot 1 so that the matrix U is equal to the matrix T, and controls the drive of the motor 32 according to the movement amount, thereby enabling welding that satisfies the above welding conditions. 9 is a diagram showing an example of the hardware configuration of the system control device 6 in the embodiment. The system control device 6 includes a processor 91 such as a CPU (Central Processing Unit) and a memory 92 connected by a bus, and executes a program. By executing the program, the system control device 6 functions as a device including a control unit 61, a communication unit 62, an input unit 63, a storage unit 64, and an output unit 65.

[0076] More specifically, in the system control device 6, the processor 91 reads a program stored in the storage unit 64 and stores the read program in the memory 92. When the processor 91 executes the program stored in the memory 92, the system control device 6 functions as a device including the control unit 61, the communication unit 62, the input unit 63, the storage unit 64, and the output unit 65.

[0077] The control unit 61 controls the operation of various functional units included in the system control device 6. The control unit 61 controls, for example, the operation of the welding robot 1. The control unit 61 causes, for example, the welding robot 1 to perform welding. The control unit 61 causes, for example, the welding robot 1 to perform welding of the curved section 8a. When controlling the operation of the welding robot 1, for example, the control unit 61 may also control the operation of the welding robot 1 by controlling the operation of the welding power source 4 and the operation of the wire feeder 5. Other functions of the control unit 61 will be described later.

[0078] The communication unit 62 includes a communication interface for connecting the system control device 6 to an external device. The communication unit 62 communicates with the external device via a wired or wireless connection. The external device is, for example, the welding robot 1. The communication unit 62 communicates with the welding robot 1 via, for example, a control cable. The communication unit 62 transmits a control signal to the welding robot 1. The external device is, for example, the imaging device 3. The communication unit 62 acquires imaging results by communicating with the imaging device 3. The external device is, for example, the welding power source 4. The external device is, for example, the wire feeder 5. The communication unit 62 acquires information (hereinafter referred to as welding robot position information) relating to the position of the welding robot 1, for example, via a control cable. The welding robot position information is, for example, a target value (hereinafter also simply referred to as a target value) for controlling a servo motor (motor 32) related to the movement of the welding robot 1.

[0079] The input unit 63 includes input devices such as a mouse, keyboard, and touch panel. The input unit 63 may be configured as an interface that connects these input devices to the system control device 6. The input unit 63 accepts input of various information to the system control device 6. For example, an instruction to start welding is input to the input unit 63.

[0080] The storage unit 64 is configured using a computer-readable storage medium device such as a magnetic hard disk drive or a semiconductor storage device. The storage unit 64 stores various information related to the welding system 100 including the system control device 6 itself. The storage unit 64 stores information input via, for example, the communication unit 62 or the input unit 63. The storage unit 64 stores various information generated by the execution of processing by, for example, the control unit 61. The storage unit 64 stores, for example, the imaging results acquired by the imaging device 3.

[0081] The storage unit 64 stores in advance information about the shape of the steel pipe 8 (hereinafter also referred to as steel pipe shape information) for each type of steel pipe 8. The steel pipe shape information includes the radius Rc of the curved portion 8a, the curvature of the curved portion 8a, the position of the first center of curvature C1 of the curved portion 8a, the length of the straight portion 8b, etc. The storage unit 64 stores in advance information about the shape of the guide rail 2 (hereinafter also referred to as guide rail shape information) for each type of guide rail 2. The guide rail shape information includes the radius Rg of the curved portion 2a, the curvature of the curved portion 2a, the position of the second center of curvature C2 of the curved portion 2a, the length of the straight portion 2b, etc. The storage unit 64 stores the movement amounts Mx, My, Mz, and M of the welding robot 1 when the matrix U and the matrix T are equal, which are derived in advance for each of the areas 1 to 3. B , M T Memorize the formula to calculate this. The storage unit 64 stores the target value (welding robot position information). The storage unit 64 stores the reference position of the welding torch 13. The storage unit 64 stores a predetermined position of the guide rail 2 that serves as the reference for the movement amount My.

[0082] The output unit 65 outputs various types of information. The output unit 65 includes a display device such as a CRT (Cathode Ray Tube) display, a liquid crystal display, or an organic EL (Electro-Luminescence) display. The output unit 65 may be configured as an interface that connects these display devices to the system control device 6. The output unit 65 outputs information input to the input unit 63, for example. The output unit 65 may also display the results of processing executed by the control unit 61, for example.

[0083] 10 is a diagram showing an example of the functional configuration of the control unit 61 in this embodiment. The control unit 61 includes a data acquisition unit 610, a welding robot control unit 620, a memory control unit 630, an input control unit 640, and an output control unit 650.

[0084] The data acquisition unit 610 acquires the welding robot position information stored in the storage unit 64. The data acquisition unit 610 acquires the movement amounts Mx, My, Mz, M of the welding robot 1 stored in advance in the storage unit 64. B , M T The data acquisition unit 610 acquires the photographing results of the photographing device 3 stored in the storage unit 64. The data acquisition unit 610 acquires steel pipe shape information corresponding to the type of steel pipe 8 to be used from the storage unit 64. The data acquisition unit 610 acquires guide rail shape information corresponding to the type of guide rail 2 to be used from the storage unit 64. The type of steel pipe 8 to be used and the type of guide rail 2 are input to the input unit 63 by, for example, the user.

[0085] Welding robot control unit 620 controls the operation of welding robot 1. Welding robot control unit 620 includes a position information acquisition unit 621, a shape information acquisition unit 622 (acquisition unit), a curvature center determination unit 623 (determination unit), a parameter setting unit 624, a welding time counting unit 625, an area determination unit 626, a target torch position calculation unit 627, a movement amount setting unit 628, and a curved portion welding execution control unit 629. Note that the parameter setting unit 624, the target torch position calculation unit 627, and the movement amount setting unit 628 constitute a setting unit in this embodiment.

[0086] The position information acquisition unit 621 acquires welding robot position information via the storage unit 64 and the data acquisition unit 610 .

[0087] The shape information acquisition unit 622 acquires steel pipe shape information and guide rail shape information via the storage unit 64 and the data acquisition unit 610.

[0088] The curvature center determination unit 623 determines whether the position of the first curvature center C1 and the position of the second curvature center C2 coincide with each other, based on the steel pipe shape information and the guide rail shape information acquired by the shape information acquisition unit 622. Furthermore, if the positions of the first curvature center C1 and the second curvature center C2 do not coincide with each other, the curvature center determination unit 623 determines which of the first curvature center C1 and the second curvature center C2 is located closer to the center of the steel pipe 8.

[0089] The parameter setting unit 624 acquires the photographing results of the photographing device 3 via the storage unit 64 and the data acquisition unit 610. The parameter setting unit 624 determines the shape and state of the welded portion (for example, groove information) based on the photographing results of the photographing device 3 and the steel pipe shape information and guide rail shape information acquired by the shape information acquisition unit 622. Parameter setting unit 624 sets specific values ​​of welding movement speed Vw, welding torch direction, target angle θn, and target position of welding torch 13 as welding conditions based on the determined shape and state of the welded portion.

[0090] The welding time counting unit 625 counts the elapsed time t from the start of welding the curved section 8a (that is, from the time when the welding robot 1 reaches the position Pg1 in the area 1).

[0091] Area determination unit 626 acquires welding movement speed Vw set by parameter setting unit 624. Area determination unit 626 acquires elapsed time t from welding time counting unit 625. Area determination unit 626 calculates the target position of the tip of welding torch 13 at the acquired elapsed time t. Specifically, since the tip of welding torch 13 moves along steel pipe 8 at welding movement speed Vw, the position of the tip of welding torch 13 at time t is a position moved by Vw·t along steel pipe 8 from position Pc1. Area determination unit 626 determines in which of areas 1 to 3 the calculated target position of the tip of welding torch 13 is located.

[0092] The target torch position calculation unit 627 calculates the movement amounts Mx, My, Mz, and M of the welding robot 1 via the storage unit 64 and the data acquisition unit 610. B , M T Target torch position calculation unit 627 acquires specific values ​​of welding movement speed Vw, welding torch orientation, target angle θn, and target position of welding torch 13 that are set by parameter setting unit 624. Target torch position calculation unit 627 reflects the specific values ​​of welding movement speed Vw, welding torch orientation, target angle θn, and target position of welding torch 13 that are set by parameter setting unit 624 in the above calculation formula.

[0093] The movement amount setting unit 628 determines the movement amounts Mx, My, Mz, and M of the welding robot 1 at a predetermined time t based on the calculation formula acquired by the target torch position calculation unit 627. B , M T These are set as the movement amounts of the welding robot 1. That is, based on the matrix U and the matrix T, the movement amount setting unit 628 determines the movement amounts Mx, My, Mz, M of the welding robot 1 that satisfy the welding movement speed Vw, welding torch direction, target angle θn, and target position of the welding torch 13 under the above welding conditions. B , M T Set.

[0094] The curved portion welding execution control unit 629 controls the movement amounts Mx, My, Mz, and M set by the movement amount setting unit 628. B , M T In response to the change, the position of welding robot 1 and the position and posture of welding torch 13 are changed, and welding robot 1 is caused to perform welding of curved section 8a. Specifically, curved portion welding execution control unit 629 drives motor 32 to operate up-down movement unit 34, and changes the position of welding torch 13 in the up-down direction x of welding robot 1 according to the movement amount Mx set by movement amount setting unit 628. Curved portion welding execution control unit 629 drives motor 32 to operate front-back movement unit 33, and changes the position of welding torch 13 in the front-back direction z of welding robot 1 according to the movement amount Mz set by movement amount setting unit 628. Curved portion welding execution control unit 629 drives motor 32 to operate first rotation unit 35, and changes the position of welding torch 13 in the front-back direction z of welding robot 1 according to the movement amount Mz set by movement amount setting unit 628. B The curved portion welding execution control unit 629 drives the motor 32 to operate the second rotation unit 36, and changes the direction of the welding torch 13 around the first axis in accordance with the movement amount M set by the movement amount setting unit 628. T The direction of welding torch 13 around the second axis is changed in accordance with the movement amount My set by movement amount setting unit 628. Curved portion welding execution control unit 629 drives motor 32 (servo motor) to change the position of welding robot 1 in accordance with movement amount My set by movement amount setting unit 628.

[0095] The memory control unit 630 records various types of information in the memory unit 64. The memory control unit 630 records various types of information generated by, for example, the operation of the control unit 61 in the memory unit 64. The information generated by the operation of the control unit 61 is, for example, information indicating the content of the control of the welding robot 1 by the welding robot control unit 620.

[0096] The input control unit 640 controls the operation of the input unit 63. The output control unit 650 controls the operation of the output unit 65.

[0097] [Example of control performed by the welding system] An example of control executed by welding system 100 will be described with reference to FIG. FIG. 11 is a flowchart showing an example of the flow of the welding process for the curved section 8a executed by the system control device 6 in this embodiment.

[0098] Before welding the curved portion 8a, the curvature center determination unit 623 determines whether the position of the first curvature center C1 coincides with the position of the second curvature center C2. If the position of the first curvature center C1 does not coincide with the position of the second curvature center C2, the curvature center determination unit 623 determines which of the first curvature center C1 and the second curvature center C2 is located closer to the center of the steel pipe 8. Hereinafter, in this embodiment, the flow of welding the curved portion 8a when the curvature center determination unit 623 determines that the second curvature center C2 is located closer to the center of the steel pipe 8 than the first curvature center C1 will be described.

[0099] The welding process of curved section 8a starts when welding robot 1 reaches position Pg1. At this time, the tip of welding torch 13 is located at position Pc1 in area 1. For example, the start determination of welding process of curved section 8a is performed by estimating the position of welding robot 1 based on the welding robot position information acquired by position information acquisition unit 622, and determining whether the estimated position of welding robot 1 has reached position Pg1.

[0100] When the welding process of the curved portion 8a is started, the welding time counting unit 625 starts counting the elapsed time t from the start of the welding process of the curved portion 8a (step S101). Area determination unit 626 calculates the target position of the tip of welding torch 13 at elapsed time t (step S102). Area determination unit 626 determines in which of areas 1 to 3 the calculated target position of the tip of welding torch 13 is located (step S103).

[0101] When it is determined that the tip of welding torch 13 is located in area 1 (step S103: A1), movement amount setting unit 628 sets the movement amounts Mx, My, Mz, M of welding robot 1 corresponding to area 1. B , M T The movement amount setting unit 628 calculates the rotation amount θg of the welding robot 1 from the position Pg1 on the curved portion 2a of the guide rail 2 at the elapsed time t based on the above calculation formula (step S111). Furthermore, the movement amount setting unit 628 calculates the movement amounts Mx, My, Mz, M of the welding robot 1 at the elapsed time t based on the above calculation formula. B , M T is calculated and set as the movement amount of the welding robot 1 (step S112). After that, the process proceeds to step S105.

[0102] When it is determined that the tip of welding torch 13 is located in area 2 (step S103: A2), movement amount setting unit 628 sets the movement amounts Mx, My, Mz, M of welding robot 1 corresponding to area 2. B , M T Here, in area 2, the movement of the tip of welding torch 13 is a rotational movement around first center of curvature C1, so target torch position calculation unit 627 calculates the target position of the tip of welding torch 13 calculated in step S102 as the amount of rotation θc of the tip of welding torch 13 at curved portion 8a of steel pipe 8 (step S121). Movement amount setting unit 628 calculates the amount of rotation θg from position Pg1 of welding robot 1 at curved portion 2a of guide rail 2 at elapsed time t based on the above calculation formula (step S122). Furthermore, movement amount setting unit 628 calculates the amounts of movement Mx, My, Mz, M of welding robot 1 at elapsed time t based on the above calculation formula. B , M T is calculated and set as the movement amount of the welding robot 1 (step S123). After that, the process proceeds to step S105.

[0103] When it is determined that the tip of welding torch 13 is located in area 3 (step S103: A3), movement amount setting unit 628 sets the movement amounts Mx, My, Mz, M of welding robot 1 corresponding to area 3. B , M T The movement amount setting unit 628 calculates the rotation amount θg of the welding robot 1 from the position Pg1 on the curved portion 2a of the guide rail 2 at the elapsed time t based on the above calculation formula (step S131). Furthermore, the movement amount setting unit 628 calculates the movement amounts Mx, My, Mz, M of the welding robot 1 at the elapsed time t based on the above calculation formula. B , M T is calculated and set as the movement amount of the welding robot 1 (step S132). After that, the process proceeds to step S105.

[0104] The curved portion welding execution control unit 629 drives each motor 32 to perform the movement amounts Mx, My, Mz, and M set by the movement amount setting unit 628. B , M T In response to the change, the position of welding robot 1 and the position and posture of welding torch 13 are changed, and welding robot 1 is made to perform welding of curved section 8a (step S105).

[0105] Thereafter, area determination unit 626 determines whether the position of the tip of welding torch 13 has reached end position Pc4 of area 3 (step S106). If it is determined that the position of the tip of welding torch 13 has reached position Pc4 (step S106: YES), curved portion welding execution control unit 629 ends the welding process for curved portion 8a (step S206). On the other hand, if the position of the tip of welding torch 13 has not reached position Pc4 (step S106: NO), the process returns to step S102, in which case welding of curved portion 8a continues.

[0106] The following describes specific control details of the welding robot 1 in each area when the above control is performed. Note that the control details of the welding robot 1 shown below are just an example, and the present invention is not limited to this.

[0107] First, the control details in area 4 (i.e., the area other than the welding of curved section 8a) will be explained. In area 4, welding robot 1 moves at a constant speed (welding movement speed Vw). Hereinafter, the movement speed of welding robot 1 in area 4 will also be referred to as reference speed. Also, the movement amount Mx of welding torch 13 in the up-down direction x is constant (hereinafter also referred to as up-down direction movement reference value). The movement amount Mz of welding torch 13 in the forward-backward direction z is constant (hereinafter also referred to as forward-backward direction movement reference value). The movement amount M of welding torch 13 around the first axis line B is constant (hereinafter also referred to as the first axis rotation reference value), and welding torch 13 is rotated vertically downward around the first axis. The movement amount M of welding torch 13 around the second axis T is constant and is 0 (zero). That is, when viewed along the up-down direction x, the welding torch 13 is always perpendicular to the left-right direction y (i.e., the straight portion 8b of the steel pipe 8), which is the direction in which the welding robot 1 moves. In the following description, it is assumed that the movement amount Mx increases when the welding torch 13 moves downward and decreases when it moves upward. It is assumed that the movement amount Mz increases when the welding torch 13 moves rearward (i.e., away from the steel pipe 8) and decreases when it moves forward (i.e., closer to the steel pipe 8). The movement amount M B is said to increase when the vertical downward tilt of the welding torch 13 increases. T is set to 0 when welding torch 13 is perpendicular to the traveling direction of welding robot 1 when viewed along the vertical direction x, increases when welding torch 13 is tilted toward the traveling direction of welding robot 1, and decreases when welding torch 13 is tilted opposite to the traveling direction of welding robot 1.

[0108] The control details in area 1 will be explained. In area 1, the movement speed of welding robot 1 becomes slower than the reference speed. That is, welding robot 1 instantaneously decelerates to the movement speed in area 1. "Instantaneous" refers to the moment when welding robot 1 arrives at area 1 from area 4. The movement amount Mx is equal to the vertical movement reference value. The movement amount Mz increases from the reference value of movement in the forward / backward direction as the tip of welding torch 13 moves from position Pc1 to position Pc2. That is, as the tip of welding torch 13 moves from position Pc1 to position Pc2, welding torch 13 moves in a direction away from steel pipe 8. Travel amount M B increases from the first axis rotation reference value as the tip of welding torch 13 moves from position Pc1 to position Pc2. In other words, as the tip of welding torch 13 moves from position Pc1 to position Pc2, the downward tilt of welding torch 13 in the vertical direction increases. Travel amount M T increases from 0 as the tip of welding torch 13 moves from position Pc1 to position Pc2. In other words, as viewed along the vertical direction x, welding torch 13 tilts toward the direction of travel of welding robot 1 as the tip of welding torch 13 moves from position Pc1 to position Pc2.

[0109] The control details in area 2 will be explained. In area 2, the movement speed of welding robot 1 becomes greater than the reference speed. That is, welding robot 1 instantaneously accelerates to the movement speed in area 2. "Instantaneous" refers to the moment when welding robot 1 reaches area 2 from area 1. Also, when the tip of welding torch 13 is in the range from position Pc2 to an intermediate position between positions Pc2 and Pc3, welding robot 1 continues to decelerate at a predetermined negative acceleration from the start position Pc2 of area 2 to the intermediate position. Note that even in this case, the movement speed of welding robot 1 is greater than the reference speed. Thereafter, when the tip of welding torch 13 is in the range from the intermediate position between positions Pc2 and Pc3 to position Pc3, welding robot 1 continues to accelerate at a predetermined positive acceleration from the intermediate position to the end position Pc3 of area 2. The movement amount Mx is equal to the vertical movement reference value. Movement amount Mz increases as the tip of welding torch 13 moves from position Pc2 to the intermediate position between positions Pc2 and Pc3, and decreases as the tip of welding torch 13 moves from the intermediate position between positions Pc2 and Pc3 to position Pc3. In other words, welding torch 13 moves away from steel pipe 8 in the range from position Pc2 to the intermediate position between positions Pc2 and Pc3, and moves toward steel pipe 8 in the range from the intermediate position between positions Pc2 and Pc3 to position Pc3. Travel amount M B decreases as the tip of welding torch 13 moves from position Pc2 to the intermediate position between positions Pc2 and Pc3, and increases as the tip of welding torch 13 moves from the intermediate position between positions Pc2 and Pc3 to position Pc3. B is never smaller than the first axis rotation reference value. In other words, as the tip of welding torch 13 moves from position Pc2 to an intermediate position between positions Pc2 and Pc3, the downward vertical tilt of welding torch 13 decreases, and as the tip of welding torch 13 moves from an intermediate position between positions Pc2 and Pc3 to position Pc3, the downward vertical tilt of welding torch 13 increases. Travel amount M T decreases as the tip of the welding torch 13 moves from the position Pc2 to the position Pc3. T becomes 0 when the tip of welding torch 13 is located at the midpoint between positions Pc2 and Pc3. That is, when viewed along the vertical direction x, when the tip of welding torch 13 is located at position Pc2, which is the end position of area 1, welding torch 13 is tilted toward the traveling direction of welding robot 1. As the tip of welding torch 13 moves from position Pc2 to the midpoint between positions Pc2 and Pc3, the tilt of welding torch 13 toward the traveling direction of welding robot 1 becomes smaller, and when the tip of welding torch 13 reaches the midpoint between positions Pc2 and Pc3, welding torch 13 becomes perpendicular to the traveling direction of welding robot 1. Thereafter, as the tip of welding torch 13 moves from the midpoint between positions Pc2 and Pc3 to position Pc3, welding torch 13 tilts toward the opposite side to the traveling direction of welding robot 1.

[0110] The control details in area 3 will be explained. In area 3, the movement speed of welding robot 1 becomes slower than the reference speed. That is, welding robot 1 instantaneously decelerates to the movement speed in area 3. "Instantaneous" refers to the moment when welding robot 1 reaches area 3 from area 2. The movement amount Mx is equal to the vertical movement reference value. Movement amount Mz decreases as the tip of welding torch 13 moves from position Pc3 to position Pc4, and becomes equal to the reference value for forward / backward movement when the tip of welding torch 13 reaches position Pc4. In other words, welding torch 13 moves in a direction approaching steel pipe 8 as the tip of welding torch 13 moves from position Pc3 to position Pc4. Travel amount M B decreases as the tip of welding torch 13 moves from position Pc3 to position Pc4, and becomes equal to the first axis rotation reference value when the tip of welding torch 13 reaches position Pc4. In other words, as the tip of welding torch 13 moves from position Pc3 to position Pc4, the downward tilt of welding torch 13 in the vertical direction decreases. Travel amount M T increases as the tip of welding torch 13 moves from position Pc3 to position Pc4, and becomes 0 when the tip of welding torch 13 reaches position Pc4. In other words, when viewed along the vertical direction x, when the tip of welding torch 13 is located at position Pc3, which is the end position of area 2, welding torch 13 is tilted in the opposite direction to the traveling direction of welding robot 1. As the tip of welding torch 13 moves from position Pc3 to position Pc4, the tilt of welding torch 13 in the opposite direction to the traveling direction of welding robot 1 becomes smaller, and when the tip of welding torch 13 reaches position Pc4, welding torch 13 is perpendicular to the traveling direction of welding robot 1.

[0111] The welding system 100 of this embodiment is a welding system 100 that controls a welding robot 1 that welds the curved portion 8a of the steel pipe 8 while moving on a guide rail 2 that is arranged along the steel pipe 8 and has a curved portion 2a, and is equipped with a shape information acquisition unit 622 that acquires a first center of curvature C1 of the curved portion 8a, and a setting unit that sets the welding conditions of the welding robot 1 using the first center of curvature C1 acquired by the shape information acquisition unit 622.

[0112] Even if the centers of curvature of the curved portion 8a of the steel pipe 8 and the curved portion 2a of the guide rail 2 are different, the welding conditions are set using the first center of curvature C1 of the curved portion 8a of the steel pipe 8 to be welded, so that the curved portion 8a can be well welded regardless of variations in the distance between the steel pipe 8 and the guide rail 2. Therefore, good welding quality can be obtained.

[0113] Welding system 100 also includes a curvature center determination unit 623 that determines whether first curvature center C1 and second curvature center C2 coincide with each other. If curvature center determination unit 623 determines that first curvature center C1 and second curvature center C2 do not coincide with each other, the setting unit sets the welding conditions using first curvature center C1. When curvature center determination unit 623 determines that first curvature center C1 and second curvature center C2 do not coincide with each other, welding conditions are set using first curvature center C1, which simplifies the control of welding system 100.

[0114] The welding conditions also include the welding torch direction, which is the direction of the welding torch 13 relative to the curved portion 8 a of the steel pipe 8 . Welding system 100 includes first rotation unit 35 and second rotation unit 36 ​​that change the orientation of welding torch 13. The setting unit sets the orientation of welding torch 13 using first center of curvature C1 and second center of curvature C2. First rotation unit 35 and second rotation unit 36 ​​change the orientation of welding torch 13 so that the orientation of welding torch 13 relative to curved portion 8a of steel pipe 8 matches the welding torch orientation set by the setting unit. The welding torch orientation includes the orientation of the welding torch 13 when, when viewed from above, the orientation of the tip of the welding torch 13 coincides with the normal direction of the curved portion 8a of the steel pipe 8, and the setting unit sets the welding torch orientation according to the position of the welding robot 1. This allows the welding torch 13 to always be directed in a direction perpendicular to the steel pipe 8, thereby improving the welding quality.

[0115] Furthermore, one of first rotating unit 35 and second rotating unit 36 ​​rotates the other together with welding torch 13. The orientation of the welding torch includes the orientation of welding torch 13 when the tip of welding torch 13 is positioned in the groove of steel pipe 8, as viewed along the direction in which welding robot 1 moves, and the setting unit sets the orientation of the welding torch in accordance with the rotation by one of them. This allows the orientation of welding torch 13 when the tip of welding torch 13 is positioned in the groove of steel pipe 8 (i.e., the aim angle θn of welding torch 13) to be constant when viewed along the direction in which welding robot 1 moves, thereby improving welding quality. For example, the aim angle θn can be made constant by setting the angle of first rotation unit 35 according to the angle of second rotation unit 36. More specifically, as the smaller of the two angles formed by the forward / backward direction z and welding torch 13 increases due to the rotation of second rotation unit 36, the smaller of the two angles formed by the upward / downward direction x and welding torch 13 decreases due to the rotation of first rotation unit 35.

[0116] The welding conditions also include a welding movement speed Vw, which is the movement speed of the tip of welding torch 13. Welding system 100 includes motor 32 (servo motor) that changes the position (movement speed) of welding robot 1. A setting unit sets welding movement speed Vw using first center of curvature C1 and second center of curvature C2. Motor 32 (servo motor) changes the position (movement speed) of welding robot 1 so that the movement speed of the tip of welding torch 13 matches welding movement speed Vw set by the setting unit. This allows the position (movement speed) of the welding robot 1 to be controlled so that the tip of the welding torch 13 moves at a predetermined speed (welding movement speed Vw) along the welding portion of the steel pipe 8, thereby improving the welding quality.

[0117] The welding conditions also include the target position of welding torch 13 . Welding system 100 includes a front-rear movement unit 33 and a vertical movement unit 34 that change the position of welding torch 13. The setting unit sets the target position using first center of curvature C1 and second center of curvature C2. Front-rear movement unit 33 and vertical movement unit 34 change the position of welding torch 13 so that the position of welding torch 13 coincides with the target position set by the setting unit. This allows the position of welding torch 13 to be controlled so that the distance between the tip of welding torch 13 and the welded portion of steel pipe 8 is a predetermined length, thereby improving the welding quality.

[0118] Second Embodiment A welding system 100 according to a second embodiment of the present invention will be described below with reference to FIGS. In this embodiment, a control method in the welding system 100 will be described when the first center of curvature C1 is located closer to the center of the steel pipe 8 than the second center of curvature C2. The basic configuration and operation of the welding system 100 used in this embodiment are similar to those of the welding system 100 of the first embodiment.

[0119] [Curved section of steel pipe and curved section of guide rail] Referring to FIG. 12, the curved portion 8a of the steel pipe 8 and the curved portion 2a of the guide rail 2 will be described. 12, in this embodiment, the first center of curvature C1 is located closer to the center of the steel pipe 8 than the second center of curvature C2. The second center of curvature C2 is located at a position shifted by e in the Y direction and the Z direction from the first center of curvature C1.

[0120] In this embodiment, the welding of the steel pipe 8 is divided into areas 5, 6, 7, and 8 according to the welding form. In the following, the start position of curved portion 8a will be referred to as Pc5 and the end position as Pc6. The start position of curved portion 2a will be referred to as Pg6 and the end position as Pg7. The intersection of a straight line connecting first center of curvature C1 and position Pc5 with straight portion 2b of guide rail 2 will be referred to as position Pg5. The intersection of a straight line connecting first center of curvature C1 and position Pc6 with straight portion 2b of guide rail 2 will be referred to as position Pg8.

[0121] Area 5 is an area in which welding robot 1 moves from position Pg5 to position Pg6 on guide rail 2. In area 5, welding robot 1 welds curved portion 8a of steel pipe 8 while moving along straight portion 2b of guide rail 2. That is, in area 5, welding robot 1 is located on straight portion 2b of guide rail 2, and the portion that welding robot 1 welds is curved portion 8a of steel pipe 8. Area 6 is an area where welding robot 1 moves from position Pg6 to position Pg7 on guide rail 2. In area 6, welding robot 1 welds curved portion 8a of steel pipe 8 while moving along curved portion 2a of guide rail 2. That is, in area 6, welding robot 1 is located at curved portion 2a of guide rail 2, and the portion that welding robot 1 welds is curved portion 8a of steel pipe 8. Area 7 is an area where welding robot 1 moves from position Pg7 to position Pg8 on guide rail 2. In area 7, welding robot 1 welds curved portion 8a of steel pipe 8 while moving along straight portion 2b of guide rail 2. That is, in area 7, welding robot 1 is located on straight portion 2b of guide rail 2, and the portion that welding robot 1 welds is curved portion 8a of steel pipe 8. Area 8 is an area other than areas 5 to 7 of the steel pipe 8. In area 8, the welding robot 1 welds the straight portion 8b of the steel pipe 8 while moving along the straight portion 2b of the guide rail 2. That is, in area 8, the welding robot 1 is positioned on the straight portion 2b of the guide rail 2, and the portion that the welding robot 1 welds is the straight portion 8b of the steel pipe 8. In this embodiment, welding of the curved portion 8a means welding of the areas 5 to 7.

[0122] [Welding conditions] As in the first embodiment, in order to improve the quality of the weld, the following conditions must be met regardless of the area: <1> ~ <4> It is preferable to satisfy the welding conditions shown below. <1> The speed at which the tip of the welding torch 13 moves along the welding portion of the steel pipe 8 (hereinafter also referred to as the welding movement speed Vw) becomes constant. <2> The direction of the welding torch 13 in top view (hereinafter also referred to as the welding torch direction) coincides with the normal direction of the curved portion 8a of the steel pipe 8 or is perpendicular to the straight portion 8b of the steel pipe 8. <3> The target angle θn of the welding torch 13 is constant. <4> The distance between the tip of welding torch 13 and the welding portion of steel pipe 8 (hereinafter also referred to as the target position of welding torch 13) is constant.

[0123] In the area 8, the distance between the steel pipe 8 (straight portion 8b) and the guide rail 2 (straight portion 2b) is constant. Therefore, the movement amount of the welding robot 1 that satisfies the above welding conditions is determined uniformly.

[0124] On the other hand, in areas 5 to 7, the distance between the steel pipe 8 and the guide rail 2 varies depending on the circumferential position, so the movement amount of the welding robot 1 that satisfies the above welding conditions cannot be determined uniformly. Therefore, in this embodiment, as in the first embodiment, for welding in areas 5 to 7 (welding of the curved portion 8a), inverse kinematics is used to calculate the welding distance. Calculating a target position and a target posture of the welding torch 13 that satisfy the above welding conditions; The amount of movement of the welding robot 1 to achieve this is calculated. Specifically, a matrix U (the above) representing the target position and target posture of the welding torch 13 that satisfies the above welding conditions is In addition, a matrix T (corresponding to the above) is generated, which represents the position and posture of the welding torch 13 when the welding robot 1 moves by a predetermined amount. By calculating the movement amount of welding robot 1 that makes matrix U equal to matrix T and controlling the driving of motor 32 in accordance with the movement amount, welding that satisfies the above welding conditions can be performed.

[0125] [About matrix U] The matrix U is a matrix for expressing the target position and target attitude of the welding torch 13 that satisfy the above welding conditions, with the origin position (first curvature center C1) of the steel pipe coordinate system as the reference. In this embodiment, welding is performed on the curved portions 8a in all of the areas 5 to 7. Therefore, a matrix U common to the areas 5 to 7 is generated.

[0126] In areas 5 to 7, the tip of welding torch 13 moves along curved portion 8a. That is, the movement of the tip of welding torch 13 that satisfies the above welding conditions in areas 5 to 7 is a rotational movement around first center of curvature C1 on the YZ plane at welding movement speed Vw. In the YZ plane, the time when the tip of welding torch 13 reaches position Pc5 is defined as time 0. The position of the tip of welding torch 13 at time t is a position rotated by an amount of rotation θc (radians) around first center of curvature C1 from position Pc5. Note that the amount of rotation θc is expressed by the following equation using radius Rc of curved portion 8a and welding movement speed Vw: θc=(Vw·t÷2πRc)×2π Furthermore, at the welding position at time t, the welding torch orientation of welding torch 13 that satisfies the above welding conditions is a direction that coincides with the normal direction of curved portion 8a. At the welding position at time t, the target angle of welding torch 13 is always constant (θn). At the welding position at time t, the distance between the tip of welding torch 13 and curved portion 8a is always constant. The matrix U is generated as a homogeneous transformation matrix that represents the position and orientation of the welding torch 13 as described above.

[0127] [About matrix T] The matrix T is a matrix of the movement amount of the welding torch 13 in the vertical direction x of the welding robot 1, the movement amount of the welding torch 13 in the front-rear direction z of the welding robot 1, and the movement amount of the welding torch 13 around the first axis line. B , the movement amount of the welding torch 13 around the second axis is M T and the movement amount of the welding robot 1 relative to the position Pg1 is My, this is a matrix for expressing the position and posture of the welding torch 13 relative to the origin position (first center of curvature C1) of the steel pipe coordinate system. In this embodiment, the welding robot 1 moves along the straight line portion 2b in areas 5 and 7, and moves along the curved line portion 2a in area 6. Therefore, the matrix T is generated for each of areas 5 to 7.

[0128] The generation of matrix T in area 5 will be described. Matrix T in area 5 is composed of matrix T4 for representing the position of welding robot 1 after moving it from position Pg5 by the movement amount My, and matrix T5 for representing the position of welding robot 1 after moving it by matrix T4, where the welding robot 1 moves by the movement amounts Mx, Mz, and M B , and M T and matrix T3 which represents the position and attitude of the tip of welding torch 13 when it moves by In area 5, the welding robot 1 moves in the Y direction (+Y direction) on the straight section 2b. Therefore, the matrix T4 is generated by moving the position Pg5 by +My in the Y direction. The position Pg5 is a position moved by +Rg in the Z direction from the first center of curvature C1. Note that the matrix T3 is the same as the matrix T3 in the first embodiment, and therefore will not be described here.

[0129] The generation of matrix T in area 6 will be explained. Matrix T in area 6 includes matrix T1 for translating the origin position (first curvature center C1) of the steel pipe coordinate system to the position of the second curvature center C2, matrix T5 for representing the position obtained by rotating welding robot 1 from position Pg6 around the second curvature center C2 by the rotation amount θg (i.e., the position obtained by moving welding robot 1 from position Pg6 by the movement amount My), and matrix T6 for representing the position of welding robot 1 after rotation by matrix T5, ​​which represents the movement amounts Mx, Mz, and Mx of welding robot 1. B , and M T and matrix T3 which represents the position and attitude of the tip of welding torch 13 when it moves by In area 6, the welding robot 1 moves on the curved portion 2a. That is, the movement of the welding robot 1 in area 6 is a rotational movement around the second center of curvature C2 on the YZ plane. If the amount of rotation of the welding robot 1 around the second center of curvature C2 from position Pg6 on the YZ plane is θg (radian), the movement amount My can be expressed as the rotation amount θg as shown in the following equation. Note that Rg is the radius of the curved portion 2a. θg=(My÷2πRg)×2π Matrix T2 is generated by rotating position Pg6 by a rotation amount θg around the second center of curvature C2. Note that position Pg6 is a position moved by +Rg in the Z direction from the second center of curvature C2. Note that matrices T1 and T3 are the same as matrices T1 and T3 in the first embodiment, and therefore description thereof will be omitted here.

[0130] The generation of matrix T in area 7 will be described. Matrix T in area 7 is composed of matrix T6 for representing the position of welding robot 1 after moving it from position Pg7 by the movement amount My, and matrix T7 for representing the position of welding robot 1 after moving it by matrix T6, where the movement amounts Mx, Mz, and M B , and M T and matrix T3 which represents the position and attitude of the tip of welding torch 13 when it moves by In area 7, the welding robot 1 moves in the Z direction (-Z direction) on the straight section 2b. Therefore, the matrix T6 is generated by moving the position Pg7 by -My in the Z direction. The position Pg7 is moved by +Rg in the Y direction and +e in the Z direction from the first center of curvature C1. Note that the matrix T3 is the same as the matrix T3 in the first embodiment, and therefore will not be described here.

[0131] [Formula for calculating the movement distance of a welding robot] Regarding the matrices U and T generated as described above, by setting matrix U=matrix T, the movement amounts Mx, My, Mz, and M of the welding robot 1 that satisfy the above welding conditions can be calculated. B , M T This calculation formula is derived from the movement amounts Mx, My, Mz, and M B , M T This formula is derived for each of areas 5 to 7.

[0132] [Welding system control system] The basic structure and operation of the control system of welding system 100 in this embodiment are similar to those of the control system in the first embodiment. On the other hand, in this embodiment, the matrix U is generated as a matrix common to the areas 5 to 7. The matrix T is generated for each of the areas 5 to 7. The storage unit 64 stores the movement amounts Mx, My, Mz, and M of the welding robot 1 when the matrix U and the matrix T are equal, which are derived in advance for each of the areas 5 to 7. B , M T The target torch position calculation unit 627 acquires the above calculation formula via the storage unit 64 and the data acquisition unit 610. The movement amount setting unit 628 determines the movement amounts Mx, My, Mz, M of the welding robot 1 at a predetermined time t based on the above calculation formula. B , M T These are set as the movement amounts of the welding robot 1. The configuration and operation of the control system other than those described above are the same as those of the control system of the first embodiment, and therefore will not be described again.

[0133] [Example of control performed by the welding system] An example of control executed by welding system 100 will be described with reference to FIG. FIG. 13 is a flowchart showing an example of the flow of the welding process for the curved section 8a executed by the system control device 6 in this embodiment.

[0134] Before welding the curved portion 8a, the curvature center determination unit 623 determines whether the position of the first curvature center C1 and the position of the second curvature center C2 coincide with each other. If the positions of the first curvature center C1 and the second curvature center C2 do not coincide with each other, the curvature center determination unit 623 determines which of the first curvature center C1 and the second curvature center C2 is located closer to the center of the steel pipe 8. Hereinafter, in this embodiment, the flow of welding the curved portion 8a when the curvature center determination unit 623 determines that the first curvature center C1 is located closer to the center of the steel pipe 8 than the second curvature center C2 will be described.

[0135] The welding process of curved section 8a starts when welding robot 1 reaches position Pg5. At this time, the tip of welding torch 13 is located at position Pc5 in area 5. For example, the start determination of welding process of curved section 8a is performed by estimating the position of welding robot 1 based on the welding robot position information acquired by position information acquisition unit 622, and determining whether the estimated position of welding robot 1 has reached position Pg5.

[0136] When the welding process of the curved portion 8a is started, the welding time counting unit 625 starts counting the elapsed time t from the start of the welding process of the curved portion 8a (step S201). Area determination unit 626 calculates the target position of the tip of welding torch 13 at elapsed time t (step S202). In this embodiment, since the movement of the tip of welding torch 13 is a rotational movement about first center of curvature C1 in all of areas 5 to 7, target torch position calculation unit 627 calculates the target position of the tip of welding torch 13 calculated in step S202 as the amount of rotation θc of the tip of welding torch 13 at curved portion 8a of steel pipe 8 (step S203).

[0137] Area determination unit 626 determines in which area of ​​areas 5 to 7 the calculated target position of the tip of welding torch 13 is located (step S204).

[0138] When it is determined that the tip of welding torch 13 is located in area 5 (step S204: A5), movement amount setting unit 628 sets the movement amounts Mx, My, Mz, M of welding robot 1 corresponding to area 5. B , M T The movement amount setting unit 628 obtains a formula for calculating the movement amounts Mx, My, Mz, and M of the welding robot 1 at the elapsed time t based on the above formula. B , M T is calculated and set as the movement amount of the welding robot 1 (step S211). After that, the process proceeds to step S205.

[0139] When it is determined that the tip of welding torch 13 is located in area 6 (step S204: A6), movement amount setting unit 628 sets the movement amounts Mx, My, Mz, M of welding robot 1 corresponding to area 6. B , M T In area 6, the movement of welding robot 1 is a rotational movement around second center of curvature C2, so movement amount setting unit 628 first calculates the amount of rotation θg from position Pg6 of welding robot 1 on curved portion 2a of guide rail 2 at elapsed time t based on the above calculation formula (step S221). Furthermore, movement amount setting unit 628 calculates the amounts of movement Mx, My, Mz, M of welding robot 1 at elapsed time t based on the above calculation formula. B , M T is calculated and set as the movement amount of the welding robot 1 (step S222). After that, the process proceeds to step S205.

[0140] When it is determined that the tip of welding torch 13 is located in area 7 (step S204: A7), movement amount setting unit 628 sets the movement amounts Mx, My, Mz, M of welding robot 1 corresponding to area 7. B , M T The movement amount setting unit 628 obtains a formula for calculating the movement amounts Mx, My, Mz, and M of the welding robot 1 at the elapsed time t based on the above formula. B , M T is calculated and set as the movement amount of the welding robot 1 (step S231). After that, the process proceeds to step S205.

[0141] The curved portion welding execution control unit 629 drives each motor 32 to perform the movement amounts Mx, My, Mz, and M set by the movement amount setting unit 628. B , M T In response to the change, the position of welding robot 1 and the position and posture of welding torch 13 are changed, and welding robot 1 is made to perform welding of curved section 8a (step S205).

[0142] Thereafter, area determination unit 626 determines whether the position of the tip of welding torch 13 has reached end position Pc6 of area 7 (step S206). If it is determined that the position of the tip of welding torch 13 has reached position Pc6 (step S206: YES), curved portion welding execution control unit 629 ends the welding process for curved portion 8a. On the other hand, if the position of the tip of welding torch 13 has not reached position Pc6 (step S206: NO), the process returns to step S202, in which case welding of curved portion 8a continues.

[0143] The following describes specific control details of the welding robot 1 in each area when the above control is performed. Note that the control details of the welding robot 1 shown below are just an example, and the present invention is not limited to this.

[0144] First, the control details in area 8 (i.e., the area other than the welding of curved section 8a) will be explained. In area 8, welding robot 1 moves at a constant speed (welding movement speed Vw). Hereinafter, the movement speed of welding robot 1 in area 8 will also be referred to as reference speed. Also, the movement amount Mx of welding torch 13 in the up-down direction x is constant (hereinafter also referred to as up-down direction movement reference value). The movement amount Mz of welding torch 13 in the forward-backward direction z is constant (hereinafter also referred to as forward-backward direction movement reference value). The movement amount M of welding torch 13 around the first axis line B is constant (hereinafter also referred to as the first axis rotation reference value), and welding torch 13 is rotated vertically downward around the first axis. The movement amount M of welding torch 13 around the second axis T is constant and is 0 (zero). That is, when viewed along the up-down direction x, the welding torch 13 is always perpendicular to the left-right direction y (i.e., the straight portion 8b of the steel pipe 8), which is the direction in which the welding robot 1 moves.

[0145] The control details in area 5 will be explained. In area 5, the movement speed of welding robot 1 becomes greater than the reference speed. That is, welding robot 1 instantaneously accelerates to the movement speed in area 5. "Instantaneous" refers to the moment when welding robot 1 reaches area 5 from area 8. After that, welding robot 1 continues to decelerate at a predetermined negative acceleration from start position Pg5 to end position Pg6 of area 5. Note that even in this case, the movement speed of welding robot 1 is greater than the reference speed. The movement amount Mx is equal to the vertical movement reference value. The movement amount Mz decreases from the reference value for movement in the forward / backward direction as the welding robot 1 moves from position Pg5 to position Pg6. That is, the welding torch 13 moves in a direction approaching the steel pipe 8 as the welding robot 1 moves from position Pg5 to position Pg6. Travel amount M B increases from the first axis rotation reference value as welding robot 1 moves from position Pg5 to position Pg6. In other words, as welding robot 1 moves from position Pg5 to position Pg6, the downward tilt of welding torch 13 in the vertical direction increases. Travel amount M T decreases from 0 as the welding robot 1 moves from position Pg5 to position Pg6. In other words, as viewed along the vertical direction x, as the welding robot 1 moves from position Pg5 to position Pg6, the welding torch 13 tilts in the direction opposite to the moving direction of the welding robot 1.

[0146] The control details in Area 6 will be explained. In area 6, the movement speed of welding robot 1 is greater than the reference speed but less than the movement speed in area 5. That is, welding robot 1 instantaneously decelerates to the movement speed in area 6. "Instantaneous" refers to the moment when welding robot 1 reaches area 6 from area 5. Furthermore, in the range from position Pg6 to an intermediate position between positions Pg6 and Pg7, welding robot 1 continues to accelerate at a predetermined positive acceleration from the start position Pg6 of area 6 to the intermediate position. Thereafter, in the range from the intermediate position between positions Pg6 and Pg7 to position Pg7, welding robot 1 continues to decelerate at a predetermined negative acceleration from the intermediate position to the end position Pg7 of area 6. Note that even in this case, the movement speed of welding robot 1 is greater than the reference speed but less than the movement speed in area 5. The movement amount Mx is equal to the vertical movement reference value. The movement amount Mz decreases as the welding robot 1 moves from position Pg6 to the intermediate position between positions Pg6 and Pg7, and increases as the welding robot 1 moves from the intermediate position between positions Pg6 and Pg7 to position Pg7. In other words, the welding torch 13 moves in a direction approaching the steel pipe 8 in the range from position Pg6 to the intermediate position between positions Pg6 and Pg7, and moves in a direction away from the steel pipe 8 in the range from the intermediate position between positions Pg6 and Pg7 to position Pg7. Travel amount M B decreases as the welding robot 1 moves from the position Pg6 to the intermediate position between the positions Pg6 and Pg7, and increases as the welding robot 1 moves from the intermediate position between the positions Pg6 and Pg7 to the position Pg7. B is never smaller than the first axis rotation reference value. That is, as welding robot 1 moves from position Pg6 to the intermediate position between positions Pg6 and Pg7, the downward vertical tilt of welding torch 13 decreases, and as welding robot 1 moves from the intermediate position between positions Pg6 and Pg7 to position Pg7, the downward vertical tilt of welding torch 13 increases. Travel amount M T increases as the welding robot 1 moves from position Pg6 to position Pg7. T becomes 0 when welding robot 1 is located at the midpoint between positions Pg6 and Pg7. That is, when viewed along the vertical direction x, welding robot 1 is located at position Pg6, which is the end position of area 5, welding torch 13 is tilted toward the opposite side to the traveling direction of welding robot 1. As welding robot 1 moves from position Pg6 to the midpoint between positions Pg6 and Pg7, the tilt of welding torch 13 toward the opposite side to the traveling direction of welding robot 1 becomes smaller, and when welding robot 1 reaches the midpoint between positions Pg6 and Pg7, welding torch 13 becomes perpendicular to the traveling direction of welding robot 1. Thereafter, as welding robot 1 moves from the midpoint between positions Pg6 and Pg7 to position Pg7, welding torch 13 tilts toward the traveling direction of welding robot 1.

[0147] The control details in Area 7 will be explained below. In area 7, the movement speed of welding robot 1 is greater than the reference speed and greater than the movement speed in area 6. That is, welding robot 1 instantaneously accelerates to the movement speed in area 7. "Instantaneous" refers to the moment when welding robot 1 reaches area 7 from area 6. After that, welding robot 1 continues to accelerate at a predetermined positive acceleration from start position Pg7 in area 7 to end position Pg8. Note that even in this case, the movement speed of welding robot 1 is greater than the reference speed and the movement speed in area 6. The movement amount Mx is equal to the vertical movement reference value. The movement amount Mz decreases as the welding robot 1 moves from position Pg7 to position Pg8, and becomes equal to the reference value for movement in the forward / backward direction when the welding robot 1 reaches position Pg8. In other words, the welding torch 13 moves in a direction away from the steel pipe 8 as the welding robot 1 moves from position Pg7 to position Pg8. Travel amount M B decreases as welding robot 1 moves from position Pg7 to position Pg8, and becomes equal to the first axis rotation reference value when welding robot 1 reaches position Pg8. In other words, as welding robot 1 moves from position Pg7 to position Pg8, the downward tilt of welding torch 13 in the vertical direction decreases. Travel amount M T decreases as welding robot 1 moves from position Pg7 to position Pg8, and becomes 0 when welding robot 1 reaches position Pg8. In other words, when viewed along the vertical direction x, when welding robot 1 is located at position Pg7, which is the end position of area 6, welding torch 13 is tilted toward the direction of travel of welding robot 1. As welding robot 1 moves from position Pg7 to position Pg8, the tilt of welding torch 13 toward the direction of travel of welding robot 1 becomes smaller, and when welding robot 1 reaches position Pg8, welding torch 13 is perpendicular to the direction of travel of welding robot 1.

[0148] The welding system 100 according to this embodiment can also achieve the same effects as those of the first embodiment. That is, the welding system 100 according to this embodiment includes a shape information acquisition unit 622 that acquires the first center of curvature C1 of the curved section 8a, and a setting unit that sets the welding conditions of the welding robot 1 using the first center of curvature C1 acquired by the shape information acquisition unit 622. Therefore, even if the circumferential length or center of curvature of the curved portion 8a of the steel pipe 8 and the curved portion 2a of the guide rail 2 differ, the welding conditions are set using the first center of curvature C1 of the curved portion 8a of the steel pipe 8 to be welded, so that the curved portion 8a can be well welded regardless of variations in the distance between the steel pipe 8 and the guide rail 2. Therefore, good welding quality can be obtained.

[0149] Although the second embodiment is described separately from the first embodiment, it is possible to perform the welding process for curved portion 8a described in the second embodiment by generating a matrix U common to areas 5 to 7 and a matrix T corresponding to each of areas 5 to 7 in welding system 100 of the first embodiment. That is, the welding control of the first embodiment and the welding control of the second embodiment can be performed using one welding system 100.

[0150] [When the first center of curvature C1 and the second center of curvature C2 coincide] Hereinafter, a control method in welding system 100 when first center of curvature C1 and second center of curvature C2 coincide will be described. In this case, the circumferential distance between the steel pipe 8 (curved portion 8a) and the guide rail 2 (curved portion 2a) is constant. Therefore, the welding torch direction, target angle, and target position of the welding torch 13 are set according to the above welding conditions. <2> ~ <4> In this state, welding that satisfies the above welding conditions can be performed by setting the movement speed of welding robot 1 so that the tip of welding torch 13 moves at welding movement speed Vw. In this case, the movement speed of welding robot 1 is constant.

[0151] The present invention is not limited to the above-described embodiment explained with reference to the drawings, and various modifications are possible within the technical scope of the present invention.

[0152] For example, in the above embodiment, the welding conditions are as follows: <1> ~ <4> However, the welding conditions <1> ~ <4> The movement amount of the welding robot 1 may be controlled so as to satisfy at least one of the above.

[0153] In the above embodiment, the objects to be controlled by welding system 100 are the movement amount Mx of welding torch 13 in the up-down direction x of welding robot 1, the movement amount My of welding robot 1 in the left-right direction y, the movement amount Mz of welding torch 13 in the front-back direction z of welding robot 1, and the movement amount M of welding torch 13 around the first axis. B , and the movement amount M of the welding torch 13 around the second axis T However, the control target of welding system 100 may be at least one of the above movement amounts.

[0154] In the above embodiment, the steel pipes 8 are arranged in a vertical direction, but the steel pipes 8 may also be arranged in a horizontal direction.

[0155] In addition, all or part of the functions of welding system 100 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. The program may be transmitted via a telecommunications line.

[0156] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modified examples may be combined as appropriate. [Explanation of symbols]

[0157] 100 Welding System 1. Welding robot 2 Guide rails (rails) 2a Curve section 6 System Control Unit 8 Steel pipe 8a Curve section 13 Welding torch 33 Front and rear moving part (torch position changing part) 34 Up / down movement unit (torch position change unit) 35 First rotating part (torch direction changing part) 36 Second rotating part (torch direction changing part) 620 Welding robot control unit 621 Location information acquisition unit 622 Shape information acquisition unit (acquisition unit) 623 Center of curvature determination section (determination section) 624 Parameter setting section (setting section) 625 Welding time counter 626 Area Determination Unit 627 Target torch position calculation unit (setting unit) 628 Movement amount setting unit (setting unit)

Claims

1. A welding system for controlling a welding robot that moves in a predetermined direction along a steel pipe on a rail having a straight rail portion and a curved rail portion, and welds a first straight steel pipe portion, a curved steel pipe portion, and a second straight steel pipe portion of the steel pipe, a welding torch provided in the welding robot; a torch direction changing unit that changes the direction of the welding torch; a speed change unit that changes the moving speed of the welding robot; a control unit that controls the torch direction change unit and the speed change unit; Equipped with the center of curvature of the rail curved portion is located closer to the center of the steel pipe than the center of curvature of the steel pipe curved portion, The steel pipe curved portion has a steel pipe curve start position which is a start position, a steel pipe curve end position which is an end position, and a steel pipe curve intermediate position which is an intermediate position between the steel pipe curve start position and the steel pipe curve end position, The control unit Controlling the inclination of the welding torch toward the predetermined direction so that it increases as the tip of the welding torch welds the first steel pipe straight section up to the steel pipe curve start position, Controlling the inclination of the welding torch toward the predetermined direction to decrease as the tip of the welding torch welds from the start position of the curve of the steel pipe to the intermediate position of the curve of the steel pipe, Controlling the inclination of the welding torch in the opposite direction to the predetermined direction so that it increases as the tip of the welding torch welds from the intermediate position of the curved steel pipe to the end position of the curved steel pipe, The inclination of the welding torch in the direction opposite to the predetermined direction is controlled to become smaller as the tip of the welding torch welds the second straight section of the steel pipe from the end position of the curved section of the steel pipe, The control unit Controlling the welding robot so that it accelerates when the tip of the welding torch substantially reaches the curve start position of the steel pipe; Controlling the welding robot to decelerate as the tip of the welding torch welds from the start position of the curve of the steel pipe to the intermediate position of the curve of the steel pipe; Controlling the welding robot so that it accelerates as the tip of the welding torch welds from the intermediate position of the curved steel pipe to the end position of the curved steel pipe; Controlling the welding robot so that it decelerates when the tip of the welding torch substantially reaches the end position of the curve of the steel pipe. A welding system comprising:

2. A welding system for controlling a welding robot that moves in a predetermined direction along a steel pipe on a rail having a straight rail portion and a curved rail portion, and welds a first straight steel pipe portion, a curved steel pipe portion, and a second straight steel pipe portion of the steel pipe, a welding torch provided in the welding robot; a torch direction changing unit that changes the direction of the welding torch; a speed change unit that changes the moving speed of the welding robot; a control unit that controls the torch direction change unit and the speed change unit; Equipped with the center of curvature of the rail curved portion is located closer to the center of the steel pipe than the center of curvature of the steel pipe curved portion, The steel pipe curved portion has a steel pipe curve start position which is a start position, a steel pipe curve end position which is an end position, and a steel pipe curve intermediate position which is an intermediate position between the steel pipe curve start position and the steel pipe curve end position, The control unit When the welding robot is positioned at the straight section of the rail and the tip of the welding torch welds the first straight section of the steel pipe, the direction of the welding torch is controlled so as to be perpendicular to the first straight section of the steel pipe; When the welding robot is positioned at the curved rail section, Controlling the inclination of the welding torch toward the predetermined direction so that it increases as the tip of the welding torch welds the first steel pipe straight section up to the steel pipe curve start position, Controlling the inclination of the welding torch toward the predetermined direction to decrease as the tip of the welding torch welds from the start position of the curve of the steel pipe to the intermediate position of the curve of the steel pipe, Controlling the inclination of the welding torch in the opposite direction to the predetermined direction so that it increases as the tip of the welding torch welds from the intermediate position of the curved steel pipe to the end position of the curved steel pipe, The inclination of the welding torch in the direction opposite to the predetermined direction is controlled to become smaller as the tip of the welding torch welds the second straight section of the steel pipe from the end position of the curved section of the steel pipe, The control unit Controlling the welding robot so that it accelerates when the tip of the welding torch substantially reaches the curve start position of the steel pipe; Controlling the welding robot to decelerate as the tip of the welding torch welds from the start position of the curve of the steel pipe to the intermediate position of the curve of the steel pipe; Controlling the welding robot so that it accelerates as the tip of the welding torch welds from the intermediate position of the curved steel pipe to the end position of the curved steel pipe; Controlling the welding robot so that it decelerates when the tip of the welding torch substantially reaches the end position of the curve of the steel pipe. A welding system comprising:

3. A welding system for controlling a welding robot that moves in a predetermined direction along a steel pipe on a rail having a straight rail portion and a curved rail portion while welding the straight steel pipe portion and the curved steel pipe portion of the steel pipe, a welding torch provided in the welding robot; a torch direction changing unit that changes the direction of the welding torch; a speed change unit that changes the moving speed of the welding robot; a control unit that controls the torch direction change unit and the speed change unit; Equipped with the center of curvature of the rail curved portion is located closer to the center of the steel pipe than the center of curvature of the steel pipe curved portion, The steel pipe curved portion has a steel pipe curve start position which is a start position, a steel pipe curve end position which is an end position, and a steel pipe curve intermediate position which is an intermediate position between the steel pipe curve start position and the steel pipe curve end position, The control unit The welding robot is positioned at the rail curved section, Controlling the inclination of the welding torch toward the predetermined direction so that it increases as the tip of the welding torch welds the straight section of the steel pipe up to the curve start position of the steel pipe, As the tip of the welding torch welds from the start position of the curve of the steel pipe to the intermediate position of the curve of the steel pipe, the inclination of the welding torch toward the predetermined direction is reduced and the welding robot is controlled to decelerate; As the tip of the welding torch welds from the intermediate position of the curved steel pipe to the end position of the curved steel pipe, the inclination of the welding torch in the opposite direction to the predetermined direction becomes large, and the welding robot is controlled to accelerate. A welding system comprising:

4. The control unit Controlling the welding robot so that it accelerates when the tip of the welding torch substantially reaches the curve start position of the steel pipe; Controlling the welding robot so that it decelerates when the tip of the welding torch substantially reaches the end position of the curve of the steel pipe. The welding system of claim 3 .

5. A program for causing a computer to function as the welding system according to any one of claims 1 to 4.

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