JPH08197248A - Tracking control method for multi-layer welding - Google Patents

Abstract

PURPOSE: To make weld line tracking control possible when welding for rotating/traveling work is executed under the state that the torch supported by a robot is fixed. CONSTITUTION: A cylindrical work W is rotated in the arrow direction mark as an additional axis. A welding torch 2, laser beam sensor 3 are supported at an arm tip part A. A scanning laser beam LB of a laser sensor 3 is projected to the front region of a weld point 4, a beam spot locus 5, is formed in the direction perpendicular to a weld line 6. By photographing with a camera C, a weld line position 7 is detected. At welding of a first layer, tracking control based on the data for position correcting prepared from sensor data is executed, along with this action, data for correcting at every fixed quantity traveling of additional axis is written in the prescribed region of buffer memory. At welding of a second layer and after, the written in data for position correcting is read out at every fixed quantity traveling of additional axis and is used for tracking travel control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method during execution of multi-layer welding, and more specifically, a welding torch for arc welding is supported by a robot and a workpiece to be welded is rotated by using an additional axis of the robot. However, the present invention relates to a control method for executing multi-layer welding by welding line tracking with the tool tip point fixed (do not execute a path movement command).

[0002]

2. Description of the Related Art In a welding line follow-up control system using a laser sensor which is currently used, a laser sensor senses a region in front of a tool tip point of a robot to detect the position of the welding line, and the detection result is detected. The position correction data created based on the sensor data indicating the robot position and the data indicating the robot position at the time of detection are sequentially written in a predetermined buffer memory area, while the stored data are sequentially read to determine the robot movement target position. Meanwhile, control is performed to move the tool tip point of the robot along the welding line.

When performing multi-layer welding by this method, the position correction data created during the welding of the first layer is used not only for tracking during the welding of the first layer, but also for the robot position correction for the second and subsequent layers. Therefore, at least a part thereof is stored as it is or after being appropriately processed.

That is, when the welding line of the first layer is followed, data for position correction is written in a certain buffer memory area at regular intervals in some form in preparation for tracking control during welding of the second and subsequent layers. Saved. The writing interval of the data for position correction can be specified by either the moving distance or the time, but it goes without saying that the former (distance) and the latter (time) are the actual values. In the processing, the writing timing is controlled by converting the distance traveled by the robot (tool tip point, the same applies below).

In the welding of the second layer, the robot is moved by tracking while sequentially reading out the position correction data created and stored during the welding of the first layer. The reading interval (cycle) at that time is also written. As in the case of insertion, the read iming is controlled using the movement distance of the robot as an index.

There is no particular problem in applying this method if the robot is controlled under the teaching that the tool tip point is moved. However, in the case where teaching is performed without moving the tool tip point and welding is performed around the workpiece that is rotationally driven by the additional axis of the robot,
Writing data for position correction (usually when executing the first layer)
It was not possible to determine the timing of reading and reading (usually during execution of the second and subsequent layers) based on the movement distance of the robot. Therefore, it is difficult to apply the tracking method by the above method in such a case.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to overcome the above-mentioned problems, and for a work rotated and driven by an additional axis of a robot, perform multi-layer welding around the work in a form that does not move the tool tip point. In the application of the type to be applied, it is to realize the tracking control of the robot using the laser sensor, and to maintain the high welding accuracy in the welding work of the type through it.

[0008]

The present invention has, as a basic configuration for solving the above technical problems, "a robot controller, a robot controlled by the robot controller, and a robot supported by the robot. And a welding robot system including a welding torch, a welding target workpiece rotating means driven by an additional axis controlled by the robot controller, and a laser sensor for detecting the position of a welding line on the welding target workpiece. This is a tracking control method for overlay welding, and when the welding of the first layer is executed, the robot position is corrected using the position correction data created based on the sensor data obtained by the laser sensor. In parallel with this, it corresponds to the position correction data at a timing determined based on a preset movement amount θad of the additional axis. The data to be sequentially written to a predetermined buffer memory area set in the welding robot system including the robot control device for tracking at the time of executing the welding of the second and subsequent layers, and at the time of performing the welding of the second and subsequent layers. , The data sequentially written in the predetermined buffer memory area is sequentially read at a timing determined based on the preset movement amount θad of the additional axis, and the robot position is corrected based on the read data. The tracking control method for the above-mentioned multi-pass welding is proposed.

Further, in order to more rationally perform tracking control during multi-layer welding, the basic configuration described above is added to "additional axis serving as a reference for determining the timing for creating correction data used in the first layer". It is also proposed to impose the requirement that "the amount of movement should match the reference θad that determines the generation timing of the correction data used in the second layer".

Further, as another aspect of the present invention, "a timing for creating the position correction data created based on the sensor data at the time of executing the first layer welding is set in advance for the data creation. Additional axis movement θa
proposed based on d '(≠ θad) ”.

[0011]

According to the method of the present invention, the tracking control based on the position correction data created from the sensor data is performed at the time of welding the first layer of the workpiece which is rotationally driven by the additional axis. And the additional axis is a certain amount θad
The position correction data is written in a predetermined buffer memory area each time the movement is performed. At the time of welding of the second and subsequent layers, the written position correction data is read every fixed amount θad movement of the additional axis and used for tracking movement control.

With respect to the position correction data created from the sensor data during the welding of the first layer, the creation timing can be determined for each movement of the fixed amount θad ′ of the additional axis. This movement amount θad ′ is the constant movement amount θad of the additional axis which is the standard for determining the write timing and the read timing of the position correction data stored in the buffer memory area for welding the second and subsequent layers. It is preferable that they are set equally.

According to the invention of the present application, a robot using a laser sensor is used in an application of a type in which multi-layer welding is performed around a work in such a manner that a tool tip point is not moved, with respect to a work driven to rotate by an additional axis of the robot. Tracking control becomes feasible. Further, through that, it is possible to improve the welding accuracy in the welding work of the mold.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sketch showing the outline of the arrangement when the present invention is applied to welding along the circumferential direction of a work having an overall cylindrical shape. In the figure, W is a workpiece to be welded having a cylindrical outer shape, and is placed on a roller RL driven by a motor M. The motor M is connected to the robot controller 10 and is controlled as an additional axis of the robot controller 10.

Reference numeral 6 represents a welding line. In this case, the ring-shaped member W ′ fitted in the work W is the work W.
It is exemplified as a line welded and fixed to the outer peripheral surface of the. A robot (main body mechanism section) 1 is installed at a position where the welding line 6 can be easily accessed. The robot 1 is connected to a robot controller 10 that controls its operation. As will be described later, a welding torch and a laser sensor are attached to the arm tip portion A of the robot 1 (not shown in FIG. 1).

A welding voltage and current are supplied to the welding torch from the power source section 30. Further, the welding gas is supplied from the cylinder 40, and the welding wire is supplied from the welding wire container 50. The robot controller 10 includes a power supply unit 30.
It also controls the supply of voltage and current from the power supply unit 30 to the welding torch.

Next, FIG. 2 is an enlarged schematic view of the arm tip portion A of the robot 1 in FIG. 1 together with the periphery of the welding line of the work W in order to show how the robot 1 is performing a welding operation. is there. In the figure, reference numeral AX
The arrow AR indicates the rotation axis and the rotation direction of the work W. A welding torch 2 and a laser sensor 3 are attached to the tip end portion of the robot arm designated by reference numeral A while omitting most of the robot main body through an appropriate attachment mechanism.
Reference numeral 4 represents a welding torch tip position (hereinafter also referred to as a welding point) set as a tool tip point of the welding robot.

A scanning beam LB is projected from the laser sensor 3 toward a region slightly ahead of the welding point (a portion to be welded immediately after), and a light spot locus 5 is formed along a direction orthogonal to the welding line 6. To be done. As described above, the welding line 6 is provided as a line for welding and fixing the edge portion of the ring-shaped member W ′ to the work W. Reference numeral 8 represents a weld bead that has already been formed.

The laser sensor 3 is equipped with a CCD camera C for photographing the light spot locus 5 obliquely to the scanning plane (fan-shaped plane) of the laser beam LB. Camera C
The light spot locus 5 photographed in (1) is analyzed by a well-known method in an image processing device described later, and the position of the bending point 7 of the light spot locus 5 is detected as the position of the welding line 6.

The robot 1 has a world coordinate system Σ
0 is set here, where the tangential direction of the welding line 6 at the taught welding point 4 is the X axis, the radial direction of the workpiece W at the similarly taught welding point 4 is the Y axis, and the Z axis is the direction of the rotation axis AX. It is assumed that the axis is set. Laser beam L
The scanning direction of B is parallel to the Z axis. The angle of the welding torch 2 during the welding operation is appropriately tilted with respect to the XYZ axes according to the robot posture specified by the operation program.

Next, FIG. 3 is a block diagram showing an outline of a system configuration corresponding to the arrangements shown in FIGS. 1 and 2. To explain this, reference numeral 10 is a robot controller having both a welding robot control function and an image processing apparatus function, which is a central processing unit (hereinafter referred to as CPU) 1.
1 and the CPU 11 has a memory 1 including a ROM.
2, a memory 13 including a RAM, a non-volatile memory 14,
A general-purpose interface 1 connected to a laser sensor 3 having a CCD camera C and a power supply unit 30 for a welding torch.
5, a frame memory 16, an image processor 17, a teaching operation panel 19 having a liquid crystal display device (LCD) 18, and a motor M (see FIG. 1) controlled as an additional axis through the robot body 1 and a servo circuit 22. The connected robot axis control units 21 are connected to each other via a bus 23. The laser sensor 3 includes a laser beam projection unit and a CCD camera C, and scans the laser beam LB and takes an image of a light spot locus according to a command from the CPU 11. CC
The image signal captured by the D camera is stored in the frame memory 16 via the general-purpose interface 15. The image information read from the frame memory 16 is processed by the image processor 17, and the position of the point 7 (see FIG. 2) where the laser beam LB crosses the welding line 6 is obtained.

The power supply section 30 has a function of controlling the welding voltage and welding current supplied to the welding torch in accordance with a command from the CPU 11. In the ROM 12, the CPU 11
Stores various programs for controlling the robot body 1, the laser sensor 3, the power supply unit 30, and the robot controller 10 itself. This includes a program for causing the CPU 11 to execute various processes (contents will be described later) for carrying out the present invention.

The RAM 13 is a memory that can be used for temporary storage of data and calculation. In addition, the nonvolatile memory 14
Stores various programs and parameter setting values that define the operation content of the robot system. This parameter setting value includes additional axis movement amounts Δθad and Δθad ′ that specify the data writing interval in the process described later.

Further, two buffer memory areas A and B in which the position correction data created based on the data of the position of the detection point 7 that is sequentially obtained are written are set in the non-volatile memory 14.

Given the system configuration and functions described above, an outline of the processing when the method of the present invention is carried out for the cases shown in FIGS. 1 and 2 will be described below with reference to FIGS. 4 and 5. .

FIG. 4 is a flow chart outlining the processing contents related to writing to the buffer memory area A.
First, the laser sensor 3 is activated, and the capturing of an image from the camera C is started (step S1). The image data is analyzed at an appropriate cycle corresponding to the image capturing cycle, and sensor data which is a source for calculating the welding line position 7 is created and stored (step S2).

Then, it is confirmed that the welding of the first layer is not completed (step S3), and the moving amount of the additional axis is further checked (step S4). Unless the amount of movement of the additional axis exceeds the set value θad, the process returns to step S2 and the generation / storage of sensor data is repeated.

If it is determined in step S4 that the amount of movement of the additional axis exceeds the set value θad, the amount of positional deviation of the welding line (by the program, based on the data of the robot position corresponding to the sensor data created during that time). Position correction data representing the amount of deviation from the designated point) is created and written in the buffer memory area A in the nonvolatile memory 14 (step S5).

Since the data written in the buffer memory area A here represents the positional deviation of the welding line at the sensing position preceding the robot position at the time of fetching the data, this data is actually used. The amount of movement of the additional axis at the time of is different from θad. If the amount of movement of the additional axis while the robot moves between the tool tip point position and the sensing position of the robot is Δθad,
The additional axis movement amount at the time of using the data is θad + Δθad.

The steps S2 to S5 are as follows.
It is repeated until the welding of the first layer is completed. Since the laser sensor 3 does not perform the welding during the welding of the second and subsequent layers, if the welding of the first layer is completed, step S
From 3 to step S6, the laser sensor 3 is deenergized and the process ends.

Next, the flow chart of FIG. 5 is the same as that of FIG.
7 is an outline of a process executed in parallel with the process described in the flowchart of FIG. First, in step T1, one point of program data is read, and it is judged whether or not it is related to the movement of the multi-layer welding execution section (step T2). Further, if it is related to the movement of the multi-layer welding execution section, it is determined whether or not it is related to the welding of the first layer (step T3).

If YES is determined in steps T3 and T4, the moving amount of the additional axis at that time (the first time is measured from an appropriate reference position, for example, the additional axis position when the laser sensor is activated). Check) (step T4). If the amount of movement of the additional axis exceeds the set value θad measured from the previous reading time, the position correction data written in the buffer memory area A in step S5 in the flowchart of FIG. 4 is read (step T5).

If the amount of movement of the additional axis is measured from the time of writing in the buffer memory area A, the movement distance used as the judgment reference in step T4 is not θad, but θad + Δθad obtained by adding Δθad to the above. Become.

At the subsequent step T6, the movement target position of the robot is corrected using the read position correction data (step T6). If the movement amount of the additional axis measured at the time of the previous reading does not exceed the set value θad at step T4, the process directly proceeds to step T6, and the robot movement is performed based on the data previously read from the buffer memory area A. The target position is corrected.

As a result, the preparation for the tracking movement at the time of welding the first layer is completed. Next, the position correction data used for position correction is written in the buffer memory area B this time (step T7).

Then, from the correction amount corrected in step T6, the moving amount of each axis is obtained by the calculation of the inverse conversion to calculate the distribution pulse, and this is sent to the servo control section of each axis (step T11). In the following step T12, it is judged whether or not the program execution for one point can be ended. If the determination in step T12 is YES, the end of the program itself is further confirmed (step T13). If not completed, the process returns to step T1 and the above processing cycle is executed again.

When the welding of the first layer is completed, step T3
Then, a negative determination is made, and the control shifts to tracking movement control using the position correction data. First, at step T8, if the amount of movement of the buffer additional axis measured from the previous reading time of the buffer memory area B exceeds the set value θad, the position correction data created in the first layer is read from the buffer memory area B. (Step T9).

Then, the movement target position of the robot is corrected using the read position correction data (step T10). If the additional axis movement amount does not exceed the set value θad measured at the time of the previous reading from the buffer memory area B in step T8, the direct step T1 is performed.
The process proceeds to 0, and the movement target position of the robot is corrected based on the data previously read from the buffer memory area B.

As a result, the preparation for the tracking movement at the time of welding the second layer is completed. Then, from the correction amount corrected in step T10, the moving amount of each axis is obtained by the calculation of the inverse conversion, the distribution pulse is calculated, and the pulse is sent to the servo control section of each axis (step T11).

Thereafter, the same processing is repeated, and when it is determined that all the instructions of the program to be executed are completed (step T13), all the processing is ended. In addition,
Program commands other than movement of the multi-layer execution section (for example,
When each axis movement for approaching the work from the air cut point) is read, the process goes directly from step T2 to step T11 to calculate the distribution pulse and send it to the servo control section of each axis. Be done). Therefore, in this case, tracking control is not performed. Then, when the program data of the multi-pass welding section is read again, a yes determination is made in step T2, the tracking control is restarted, and the welding of the first layer or the second and subsequent layers is performed based on the processing described above. Is executed.

In the process described above (see FIGS. 4 and 5)
Of the buffer memory area A, a read cycle from the buffer memory area A, a write cycle to the buffer memory area B, and a read from the buffer memory area B in order to simplify the processing. Although all the cycles have a common value (θad), these do not necessarily have to match.

For example, the creation cycle of the position correction data created on the basis of the sensor data at the time of executing the welding of the first layer is a value θad ′ (≠ θad) preset in addition to θad for the data creation. Can be

The read data from the buffer memory area A used for position correction is transferred to the buffer memory area B.
In the case of writing in, it is not deviated from the technical idea of the present invention to perform some processing (for example, sampling processing).

In the embodiment described here, the case where welding is carried out over the entire circumference of the cylindrical work W has been described, but the work W does not necessarily have to be cylindrical, and the work W does not have to have the entire circumference. The present invention can also be applied to the case where the multi-layer welding is performed on a part of the surface. The laser sensor to be used is not limited to the CCD camera type, but a type using a one-dimensional optical sensor (one-dimensional PSD, line sensor, etc.) may be used, but the above embodiment is slightly modified. The present invention can be applied only by this.

[0045]

The welding torch supported by the robot is fixed to the robot when performing the multi-layer welding along the outer periphery of the workpiece to be welded by rotating the additional axis of the robot in a fixed form. It has become possible to perform line following operation. Therefore, by applying the invention of the present application to the welding work of the above-described mold, it becomes possible to perform welding of higher quality than the conventional one.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of arrangement when the present invention is applied to welding along a circumferential direction of a work having an overall cylindrical shape.

FIG. 2 is an enlarged schematic view of an arm tip portion A of the robot 1 in FIG. 1 together with a peripheral portion of a welding line of a work W.

FIG. 3 is a block diagram showing an outline of a system configuration corresponding to the arrangements shown in FIGS. 1 and 2.

FIG. 4 is a flowchart outlining a process related to writing to a buffer memory area A in this embodiment.

5 is a flowchart showing an outline of processing executed in parallel with the processing shown in the flowchart of FIG. 4 in the present embodiment.

[Explanation of symbols]

 1 Robot main body 2 Welding torch 3 Laser sensor 4 Welding point (welding torch tip point, tool tip point) 5 Light spot locus 6 Welding line 7 Detection point (light spot locus bending point) 8 Weld bead 10 Robot controller 11 Central processing unit (CPU) 12 Memory (ROM) 13 Memory (RAM) 14 Nonvolatile memory 15 General-purpose interface 16 Frame memory 17 Image processor 18 LCD 19 Teaching operation panel 21 Robot axis control unit 22 Servo circuit 23 Bus 30 Power supply unit 40 Gas cylinder 50 Welding wire container A Robot arm tip part AR Direction of rotation of workpiece W to be welded AX Rotation axis of workpiece W to be welded LB Scanning laser beam M Motor controlled as an additional axis RL Roller W to mount workpiece to be welded Target work W'ring member

Claims (3)

[Claims] 1. A robot control device, a robot controlled by the robot control device, a welding torch supported by the robot, and a welding target work rotating means driven by an additional axis controlled by the robot control device. And a tracking control method for multi-layer welding using a welding robot system including a laser sensor that detects the position of a welding line on the workpiece to be welded, wherein the laser sensor While correcting the robot position using the position correction data created based on the sensor data obtained by the above, in parallel with this, at the timing determined based on the preset movement amount θad of the additional axis. The robot controller for tracking the data corresponding to the position correction data when performing the welding of the second and subsequent layers. Including the sequential writing in a predetermined buffer memory area set in the welding robot system, and at the time of executing the second and subsequent layers of welding, the data sequentially written in the predetermined buffer memory area is added to the preset additional axis. Of the tracking control method for the multi-layer welding, wherein the robot position is sequentially read based on the read data and the robot position is corrected based on the read data. 2. The timing for creating the position correction data created on the basis of the sensor data at the time of executing the welding of the first layer is based on the preset movement amount θ of the additional axis.
The tracking control method for multilayer welding according to claim 1, wherein the tracking control method is defined based on ad. 3. The position of the position correction data created based on the sensor data at the time of executing the welding of the first layer is based on a preset movement amount θad ′ (≠ The tracking control method for multi-layer welding according to claim 1, wherein the tracking control method is defined based on θad).