JP2006021241A - Device and method for controlling welding robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controlling device of a welding robot with which necessary and adequate preflow time is secured in the controlling device of the welding robot which is controlled by a work program including a plurality of teaching steps. <P>SOLUTION: This controlling device 20 of the welding robot 10 carries out a plurality of teaching steps for moving a welding torch 16 from the operation starting position to the welding starting position and welding is performed by generating an arc after moving the torch to the welding stating position. The jetting timing of shielding gas before the welding torch 16 is moved to the welding starting position is computed on the basis of the time which is required for controlling the operation of the welding torch 16 in accordance with each teaching step of the plurality of the teaching steps and a preset preflow controlling time and the shielding gas is jetted at this jetting timing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a welding robot control apparatus for welding a workpiece and a welding robot control method.

  Conventionally, when welding is performed on a workpiece, gas shield welding is used in which an arc is generated in a gas atmosphere by shielding the periphery of a welding point with a gas. In this gas shield welding, so-called preflow control is performed in which the gas generation timing is advanced by a predetermined time (hereinafter referred to as “preflow time”) from the arc generation timing (see, for example, Patent Document 1). .)

JP-A-11-216567.

  The technique of the above publication relates to a case in which welding is immediately performed when an operator instructs welding start. More specifically, the pre-flow control time can be arbitrarily changed by setting the first welding switch operation as a gas ejection command and the second welding switch operation as a welding command.

  On the other hand, welding robots that automatically perform welding on workpieces are widely used. In this welding robot, gas shield welding is used, and preflow control is employed for the purpose of performing good welding. In the welding robot, the welding operation is started after the welding torch is moved to the welding position, and a series of processes for welding a predetermined range is automatically controlled. For this reason, the setting of the preflow time is also preset in the automatic control program.

  As a specific procedure of the gas shield welding in which the preflow control is adopted, as shown in FIG. 8, the welding torch 51 of the welding robot is made to reach the welding start point B from the operation start point A (FIG. 8 (a )), With the welding torch 51 stopped, the shielding gas is released for a preset preflow time (see FIG. 8B), and an arc is generated after the preflow time has elapsed (FIG. 8C). reference).

  As the preflow time in the preflow control, a predetermined time (for example, 0.1 to 0.5 seconds) is set in advance. This is because a certain amount of time is required until the gas flow rate becomes constant after the shielding gas is released because the shielding gas is a fluid. If the preflow time is not sufficient, the gas shielding effect is insufficient, and welding defects may occur at the welding points. Also, in the so-called pulse-controlled welding method in which the current that flows to generate an arc is changed periodically, if the shielding effect at the start of welding is not sufficient, droplet transfer may become unstable and welding defects may occur. . Therefore, securing the preflow time at the start of welding is one of the important matters in gas shield welding.

  By the way, welding work using recent welding robots is generally automated, improving productivity by minimizing the cycle time (time required to produce one work (including welding work)) as much as possible. Efforts are being made to do this.

  For example, the movement of the welding torch from the operation start point to the welding start point is normally performed at a constant speed, but recently, the movement time of the welding torch has been shortened. In addition, the welding process itself is accelerated to improve the cycle time.

  Therefore, in the welding procedure as shown in FIG. 8, while the preflow control is being performed, the welding torch remains stopped and welding is not performed, and time is lost. Such a method has also been proposed. That is, as shown in FIG. 9, during the movement of the welding torch 51 before reaching the welding start point B, the shield gas is released in advance at a predetermined timing (see FIG. 9 (a)). Then, after the welding torch 51 reaches the welding start point B, an arc is generated immediately (see FIG. 9B). As described above, if the preflow control is performed during the movement of the welding torch 51, the shield gas can be released in advance using the moving time of the welding torch 51, that is, the preflow time can be secured. The cycle time can be improved.

  The welding robot used for the welding operation operates according to a predetermined operation program, and the operation program includes a plurality of teaching steps. The teaching step represents a series of movements and movements of the welding robot divided for each predetermined unit movement.

  As described above, when welding is performed by the welding robot, the welding torch is moved from the operation start point to the welding start point. This movement operation is also included in the teaching step. However, a plurality of teaching steps are determined from the operation start point to the welding start point, and when the operation required time of the teaching step executed immediately before the welding start is relatively short, that is, the preflow time is better. If it is longer than the required operation time of the teaching step, a sufficient preflow time cannot be ensured, causing a welding failure.

  The present invention has been conceived under the circumstances described above, and in a welding robot control device controlled by a work program including a plurality of teaching steps, a necessary and sufficient preflow time can be ensured. It is an object of the present invention to provide a welding robot control device that can be used.

  In order to solve the above problems, the present invention takes the following technical means.

  The welding robot control device provided by the first aspect of the present invention performs a plurality of teaching steps for moving the welding torch from the operation start position to the welding start position, and moves the arc to the welding start position. A welding robot control apparatus for generating and welding based on a time required to control the operation of a welding torch corresponding to each teaching step of the plurality of teaching steps and a preset preflow control time The shield gas is ejected at the ejection timing before the welding torch is moved to the welding start position, and the shield gas is ejected at the ejection timing. Note that the “operation start position” includes a section in which arcs are not generated in a series of welding operations of workpieces, and when there is a section in which arcs are generated again thereafter, when preflow control is performed in a section in which arcs are not generated, It also includes the start position of the section where no occurrence occurs.

  According to this configuration, the welding torch moves to the welding start position based on the time required to control the operation of the welding torch corresponding to each teaching step of the plurality of teaching steps and the preset preflow control time. Since the shielding gas ejection timing before the calculation is calculated and the shielding gas is ejected at this ejection timing, preflow control can be performed over a plurality of teaching steps, and a necessary and sufficient preflow time can be ensured. Therefore, it is possible to provide a method for controlling a welding robot that can perform good welding.

  According to a preferred embodiment, the time required to control the operation of the welding torch corresponding to each teaching step is accumulated, and the accumulated time is compared with the preset preflow control time. Extraction means for extracting a teaching step by which the welding torch should eject a shielding gas; calculation means for calculating a timing of jetting shield gas from the welding torch in the teaching step extracted by the extraction means; and the calculation means. It is good to provide the ejection means which ejects the shielding gas of the said welding torch at the calculated ejection timing.

  According to a second aspect of the present invention, there is provided a welding robot control method comprising: performing a plurality of teaching steps for moving a welding torch from an operation start position to a welding start position; And a welding robot control method for performing welding, based on a time required to control the operation of the welding torch corresponding to each teaching step of the plurality of teaching steps and a preset preflow control time And calculating a shield gas ejection timing before the welding torch moves to the welding start position, and ejecting the shield gas at the ejection timing.

  According to a preferred embodiment, the time required to control the operation of the welding torch corresponding to each teaching step is accumulated, and the accumulated time is compared with the preset preflow control time. A step of extracting a teaching step in which the welding torch should eject a shielding gas; a step of calculating a shielding gas ejection timing of the welding torch in the extracted teaching step; and the welding torch at the calculated ejection timing. And a step of ejecting the shielding gas.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram showing a control system including a control device for a welding robot according to the present invention. In this control system, welding is performed on a workpiece by a welding torch provided in a welding robot. In particular, in this control system, a shield gas is supplied in advance before the welding torch reaches the welding start point from the operation start point. So-called preflow control is performed around the welding torch.

  The control system is roughly constituted by a welding robot 10, a robot control device 20, a welding power supply device 30, and a gas cylinder 40.

  The welding robot 10 automatically performs, for example, arc welding on the workpiece W. The welding robot 10 includes a base member 11 fixed to an appropriate place such as a floor, a plurality of arms 12 connected to the base member 11 via a plurality of shafts, a link member 13, and a plurality of motors 14 (partially not shown). ) And the wire feeding device 15. The welding robot 10 includes a welding torch 16 at the distal end portion of the arm 12 provided on the most distal end side.

  The welding robot 10 is driven and controlled by the robot control device 20, and the motor 14 and the like are driven to rotate, whereby the welding torch 16 is movable left and right and back and forth.

  The welding torch 16 includes a wire 17 having a diameter of, for example, about 1 mm as a filler material, generates an arc between the tip of the wire 17 fed by the wire feeding device 15 and the workpiece W, and heats the wire. By welding 17, the workpiece W is welded.

  Inside the welding torch 16, for example, as shown in FIG. 2, a discharge path 18 is formed for discharging a shielding gas such as an inert gas or a carbon dioxide gas. This shielding gas is supplied from the gas cylinder 40 and is discharged through the discharge path 18 via a gas electromagnetic valve 41 (described later), thereby being used for the above-described preflow control.

  The motor 14 is provided at both ends or one end of the plurality of arms 12, and is driven to rotate by a drive command from the robot control device 20 to move the plurality of arms 12 and the welding torch 16. The motor 14 is provided with an encoder (not shown). The output of the encoder is given to the robot controller 20, and the robot controller 20 recognizes the current position of the welding torch 16 by the output of the encoder.

  The wire feeding device 15 is a device for feeding the wire 17 to the welding torch 16 at a predetermined timing.

  The robot control device 20 is for controlling the operation of the welding robot 10. The robot control device 20 drives and controls the motor 14 of the welding robot 10 based on a work program stored in advance, coordinate information from an encoder (not shown), and the like, so that the welding torch 16 is welded to the workpiece W from the operation start point. The point is moved from the welding point to another welding point or from the welding point to the retracted position.

  The welding power source device 30 includes a welding power source (not shown), and a high voltage is supplied between the welding torch 16 and the workpiece W (base material) by the welding power source. A gas electromagnetic valve 41 is connected to the welding power supply device 30, and the gas electromagnetic valve 41 is controlled to be opened and closed by the welding power supply device 30 to permit or release the shield gas supplied from the gas cylinder 40 to the welding point. Ban.

  FIG. 3 is a block diagram showing an internal configuration of the robot control device 20. The robot control device 20 includes a microcomputer and a memory, and more specifically, a work program analysis unit 21, a memory unit 22, a track planning unit 23, a track stack 24, a servo control unit 25, and a servo drive unit 26. The current position monitoring unit 27 and the welding control unit 28 are configured.

  The memory unit 22 stores a work program that defines the operation of the welding robot 10. This work program is composed of a plurality of teaching steps in which a series of movements and movements of the welding robot are divided for each predetermined unit movement. For example, the teaching step includes a command for moving the welding torch of the welding robot 10 from one position to another position. The teaching step includes a welding start command for starting welding and a preflow start command for starting preflow control in addition to such a movement command.

  The work program analysis unit 21 reads the work program stored in the memory unit 22 for each teaching step and analyzes the contents. For example, the work program analysis unit 21 reads a trajectory command (consisting of data such as coordinates and speed information) included in the work program and notifies the trajectory plan unit 23 of the read out command.

  The trajectory planning unit 23 stores various operation commands sent from the work program analysis unit 21 in the trajectory stack 24. Further, the trajectory planning unit 23 reads out the operation commands stored in the trajectory stack 24, makes a trajectory plan for the welding torch 16 based on the operation command, and provides information such as the rotation angle and rotation speed of the motor 14 to the servo control unit 25. Notify against. Further, the trajectory planning unit 23 obtains a teaching step for starting the preflow control and obtains a timing for starting the preflow control with reference to a required operation time of the teaching step, as will be described later.

  The trajectory planning unit 23 is provided with a temporary area 23a as a storage area, and the value of the preflow time is stored in the temporary area 23a as necessary.

  The trajectory stack 24 is composed of a so-called first-in first-out (FIFO) memory, and stores trajectory commands sent from the trajectory planning unit 23.

  The servo control unit 25 sends a drive signal to the servo drive unit 26 to rotationally drive the motor 14 based on the track plan sent from the track planning unit 23. The servo control unit 25 acquires an output from an encoder (not shown) and sends the information to the current position monitoring unit 27.

  The servo drive unit 26 outputs a drive command to each motor 14 based on a command from the servo control unit 25.

  The current position monitoring unit 27 monitors the current position of the welding torch 16 based on a detection signal from an encoder (not shown) provided in the motor 14.

  The welding control unit 28 causes the welding power source device 30 to perform welding by the welding torch 16 and release of the shielding gas based on various commands from the current position monitoring unit 27. Specifically, the welding control unit 28 outputs a control signal for causing the welding power source device 30 to release the shielding gas based on a preflow start command from the current position monitoring unit 27. The welding power source device 30 performs opening / closing control of the gas electromagnetic valve 41 based on this control signal. Further, the welding control unit 28 outputs a control signal for performing welding by the welding power source device 30 based on a welding start command from the current position monitoring unit 27.

  The servo drive unit 26 sends drive signals to the various motors 14 based on the drive signal from the servo control unit 25.

  Next, the operation of this embodiment will be described with reference to the flowcharts shown in FIGS. 4 and 5 and the diagram showing the temporal relationship between the teaching step and the preflow control shown in FIG.

  First, when the automatic operation is started, the work program analysis unit 21 reads the work program stored in the memory unit 22 and analyzes the work program for each teaching step (S1). Next, the work program analysis unit 21 notifies the trajectory command included in the teaching step to the trajectory planning unit 23 (S2). This trajectory command includes information such as the position coordinates to which the welding torch 16 should move and the moving speed.

  When the trajectory command is sent from the work program analysis unit 21, the trajectory planning unit 23 stores the trajectory command in the trajectory stack 24 for each teaching step (S3). Then, the trajectory planning unit 23 formulates a trajectory plan based on the trajectory command (S4). That is, based on information such as the position coordinates and the moving speed of the welding torch 16 to be moved, the rotation speed, the rotation start timing, the rotation stop timing and the like of each motor 14 in the trajectory along which the welding torch 16 moves are determined. . Then, the trajectory planning unit 23 notifies the planned trajectory plan to the servo control unit 25 (S5).

  The servo control unit 25 controls the rotation of each motor 14 based on the trajectory plan notified by the trajectory plan unit 23. That is, control signals such as the angle and rotation speed of the motor 14 are transmitted to the servo drive unit 26. The servo drive unit 26 rotationally drives each motor 14 by these control signals from the servo control unit 25.

  On the other hand, the work program analysis unit 21 determines whether or not a welding start instruction is included in the read teaching step (S6). When it is determined by the work program analysis unit 21 that a teaching start instruction is not included in the teaching step (S6: NO), the process returns to step S1 to analyze the next teaching step.

  If the work program analysis unit 21 determines in step S6 that a welding start command is included in the teaching step (S6: YES), the track planning unit 23 sends a preflow start time calculation request command and a welding start command. A request command is notified (S7).

  Now, as shown in FIG. 6, the work program includes three teaching steps (first to third teaching steps A1, A2, and A3) from the operation start point to the welding point of the workpiece W. Are included, the trajectory commands in the first to third teaching steps A1, A2, and A3 are stored in the trajectory stack 24, respectively. In the example shown in FIG. 6, a welding start command is included in the third third teaching step A3. Hereinafter, description will be made based on the example shown in FIG.

  When the preflow start time calculation request command is sent from the work program analysis unit 21, the trajectory planning unit 23 performs processing for recognizing a teaching step for starting preflow control and processing for calculating the start time of preflow control (S8). ).

  First, the trajectory planning unit 23 stores the value of the preflow time T in the temporary area 23a (S9). The preflow time T (see FIG. 6) is a necessary and sufficient time for ensuring the shielding effect by the shielding gas, and is determined in advance and stored in the memory unit 22.

  The trajectory planning unit 23 refers to the trajectory command of the teaching step stored immediately before in the trajectory stack 24. According to the example shown in FIG. 6, the trajectory instruction of the third teaching step A3 stored in the trajectory stack 24 most recently is referred to among the first to third teaching steps A1, A2, A3.

  Next, the trajectory planning unit 23 calculates the required travel time T3 in the trajectory command in the third teaching step A3 (S10). The trajectory planning unit 23 compares the calculated required travel time T3 with a predetermined preflow time T, and determines whether the calculated required travel time T3 is smaller than the preflow time T (S11).

  If it is determined in step S11 that the calculated required travel time T3 is smaller than the preflow time T (S11: YES), the trajectory planning unit 23 subtracts the calculated required travel time T3 from the preflow time T (T− T3) is calculated (S12). Then, the trajectory planning unit 23 newly stores it in the temporary area 23a as a preflow time, and refers to the trajectory command of the second teaching step A2 stored in the trajectory stack 24 immediately before the third teaching step A3. (S13).

  Then, returning to step S10, the required travel time T2 in the second teaching step A2 is calculated again, and the required travel time T2 is compared with the newly replaced preflow time (T-T3) (S11).

  If it is determined in step S11 that the calculated required travel time T2 is greater than the new preflow time (T-T3) (S11: NO), the trajectory planning unit 23 calculates the required travel time T2. The current position monitoring unit 27 is notified of the reference number A2 and the preflow time (T-T3) stored in the temporary area 23a as a preflow start time calculation request command (S14). This indicates that the teaching step for starting the preflow control is the second teaching step A2.

  Further, the trajectory planning unit 23 notifies the current position monitoring unit 27 of the reference number of the third teaching step A3 including the welding start command as a welding start request command (S15).

  In the robot controller 20, the process for obtaining the teaching step for starting the preflow control based on the required time of the teaching step and the preflow time as described above, and the operation of the welding torch 16 is actually controlled based on the teaching data. The process is controlled so that a certain time difference occurs. This is because if the operation control based on the teaching data of the welding torch 16 is processed in real time or at a speed close thereto, it is not possible to calculate the processing for obtaining the teaching step for starting the preflow control.

  The current position monitoring unit 27 monitors in which teaching step the current position of the welding torch 16 is located by an encoder (not shown) provided in each motor 14 (S16 in FIG. 5). Then, the current position monitoring unit 27 includes a preflow start trigger request command in the teaching step that is currently in progress, and, as shown in FIG. 6, the welding torch 16 at the current point a enters the next third teaching step A3. It is determined whether or not the arrival time Ta until reaching is smaller than the newly replaced preflow time (T-T3) (S17).

  When the arrival time Ta until reaching the next third teaching step A3 becomes shorter than the newly replaced preflow time (T-T3) (S17: YES), the current position monitoring unit 27 starts the preflow control. To the welding control unit 28 (S18). Thereby, in the welding control part 28, the gas electromagnetic valve 41 is opened, shield gas is discharge | released, and preflow control is started.

  Next, the current position monitoring unit 27 determines whether or not the teaching step currently in progress includes a welding start trigger request command and the welding torch 16 has reached the welding point (S19). If the teaching step currently in progress includes a welding start trigger request command and the welding torch 16 reaches the welding point (S19: YES), the current position monitoring unit 27 notifies the welding control unit 28 of the start of welding. To do. Thereby, the welding control part 28 notifies that to the welding power supply device 30 (S20). The welding power supply device 30 outputs an instruction to send the wire 17 to the wire feeding device 15, and thereby the wire 17 is fed from the wire feeding device 15. Further, when a predetermined voltage is applied between the welding torch 16 and the workpiece W by the welding power supply device 30, an arc is generated and welding is started.

  Thus, by obtaining the teaching step for starting the preflow control from among the plurality of teaching steps, the preflow control can be executed over the plurality of teaching steps. Therefore, even when the operation required time of the teaching step executed immediately before the start of welding is relatively short, the preflow control can be started from another teaching step executed before the teaching step. Therefore, a necessary and sufficient preflow time for achieving the shielding effect can be ensured, and good welding can be performed.

  In the above description, the case where the preflow time T is shorter than the time (T2 + T3) obtained by integrating the required movement time T3 in the third teaching step A3 and the required movement time T2 in the second teaching step A2 has been described. In some cases, the preflow time T is longer than the accumulated time (T2 + T3) described above. In such a case, the pre-flow time is compared with the time (T2 + T3) obtained by integrating the required moving time T3 in the third teaching step A3 and the required moving time T2 in the second teaching step A2, and the welding torch 16 is You may extract the teaching step which should eject a shielding gas.

  More specifically, in step S13 of the flowchart shown in FIG. 4, the trajectory command of the second teaching step A2 stored immediately before the third teaching step A3 is referred to. Next, returning to step S10, the required travel time T2 in the second teaching step A2 is calculated again, and the required travel time T2 is compared with the newly replaced preflow time (T-T3).

  Here, when the preflow time T is longer than the required movement time (T2 + T3) in the second teaching step A2 and the third teaching step A3, the calculated movement time T2 is greater than the new preflow time (T−T3). Since it is determined to be small, in such a case, the required travel time T3 in the third teaching step A3 and the required travel time T2 in the second teaching step A2 are integrated. Then, the accumulated travel time (T2 + T3) is subtracted from the preflow time T, and the remaining time (T− (T2 + T3)) is calculated.

  Thereafter, the remaining time (T− (T2 + T3)) is set as a new preflow time T, and the required movement time T1 in the first teaching step A1 stored immediately before the second teaching step A2 and the new preflow time T And compare. If it is determined in this comparison result that the calculated required travel time T1 is greater than the new preflow time (T− (T2 + T3)), the travel required time T1 is set as shown in step S14 of the flowchart shown in FIG. The current position monitoring unit 27 is notified of the calculated reference number of the second teaching step A1 and the preflow time (T− (T2 + T3)) as a preflow start time calculation request command.

  As described above, when the preflow time T is larger than the integrated value of the required moving times of the plurality of teaching steps, the teaching step in which the welding torch 16 should eject the shield gas should be extracted in consideration of this. Good. In the above description, there are three teaching steps, but the number of teaching steps is not limited to this. Further, the preflow time T may be compared with an integrated value of the required travel time in three or more steps.

It is a block diagram which shows the control system containing the control apparatus of the welding robot which concerns on this invention. It is principal part sectional drawing of a welding torch. It is a block diagram which shows the internal structure of a robot control apparatus. It is a flowchart for demonstrating the effect | action of this invention. It is a flowchart for demonstrating the effect | action of this invention. It is a figure which shows the time relationship between a teaching step and preflow control. It is a figure which shows the other temporal relationship between a teaching step and preflow control. It is a figure for demonstrating the conventional preflow control. It is a figure for demonstrating the other conventional preflow control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Welding robot 16 Welding torch 17 Wire 20 Robot control apparatus 21 Work program analysis part 22 Memory part 23 Trajectory plan part 24 Trajectory stack 25 Servo control part 27 Current position monitoring part 28 Welding control part 30 Welding power supply device 41 Gas electromagnetic valve W Workpiece

Claims (4)

A control device for a welding robot that performs a plurality of teaching steps for moving a welding torch from an operation start position to a welding start position, generates an arc after moving to the welding start position, and performs welding.
The shield before the welding torch moves to the welding start position based on the time required to control the operation of the welding torch corresponding to each teaching step of the plurality of teaching steps and a preset preflow control time A welding robot control device that calculates a gas ejection timing and ejects the shield gas at the ejection timing. By integrating the time required to control the operation of the welding torch corresponding to each teaching step, and comparing the accumulated time with the preset preflow control time, the welding torch releases the shielding gas. Extraction means for extracting teaching steps to be ejected;
A calculating means for calculating the timing of spraying the shielding gas of the welding torch in the teaching step extracted by the extracting means;
The welding robot control device according to claim 1, further comprising: an ejection unit that ejects a shielding gas of the welding torch at an ejection timing calculated by the calculation unit. A control method for a welding robot that performs a plurality of teaching steps for moving a welding torch from an operation start position to a welding start position, generates an arc after moving to the welding start position, and performs welding.
The shield before the welding torch moves to the welding start position based on the time required to control the operation of the welding torch corresponding to each teaching step of the plurality of teaching steps and a preset preflow control time A method for controlling a welding robot, comprising: calculating a gas ejection timing and ejecting the shield gas at the ejection timing. By integrating the time required to control the operation of the welding torch corresponding to each teaching step, and comparing the accumulated time with the preset preflow control time, the welding torch releases the shielding gas. Selecting a teaching step to be ejected;
Calculating the ejection timing of the shielding gas of the welding torch in the selected teaching step;
The method for controlling a welding robot according to claim 3, further comprising a step of ejecting a shielding gas of the welding torch at the calculated ejection timing.

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