JP3579237B2 - Data sampling method for welding machine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data sampling method in a welding machine, and particularly to a welding method in which a welding torch is weaved to the left and right with respect to the direction of welding by using a pulse command type servo control. The present invention relates to a method of sampling welding data in synchronization with a position.
[0002]
[Prior art]
FIG. 2 shows an example of a configuration of a welding machine that automatically welds a circumferential seam of a pipe. In FIG. 2, a personal computer 21 is for creating CAD data for automatic welding, and the created data is recorded on a flexible disk 21a. The control device 22 is for performing substantial control of the automatic welding (control of the power supply and the position of the torch, etc.), and reads CAD data from the flexible disk 21a. Then, the control device 22 sets actual welding conditions using the read data, and sets various welding parameters in accordance with the set conditions by using data previously recorded in the logic table.
[0003]
Further, the control device 22 converts the set welding parameters into an NC language used for actual welding control, and records the converted language as control data in an internal memory in the form of a control table. The power supply device 23 and the welding head 24 are driven and controlled using the control data recorded in the memory, and the arc scanning related correction is performed using the measured and analyzed values of the pulse voltage waveform and the pulse current waveform. ing. The main control items of the control device 22 include the welding voltage and current of the welding head 24, the weaving of the welding torch 27 mounted on the welding head 24 with respect to the pipe groove 30, the moving speed of the welding head 24, and the like. is there.
[0004]
The welding head 24 is connected to the power supply device 23 by a power transmission cable 28, and is mounted on a guide rail 29 wound around the pipe so as to be movable in the circumferential direction. On the welding head 24, a wire supply unit 26 for supplying a welding wire to a welding torch 27 is mounted.
[0005]
FIG. 3 shows an electrical connection relationship between the control device 22, the power supply device 23, the welding head 24, and the pipe 25. As can be seen from the figure, a pulse welding voltage is applied between the wire 31 of the welding head 24 and the pipe 25 via the power transmission cable 28 from the power supply device 23. Thereby, an arc is generated between the wire 31 and the surface of the pipe 25. The wire 31 is fed at a constant speed, melted by an arc to become a deposited metal, and solidified in the pipe groove 30 to form a base material.
[0006]
FIG. 4 shows a detailed view of the welding head 24. The welding head 24 has a position (in hours and minutes) X-axis on the outer periphery of the pipe, a Y-axis in the width direction of the groove of the weaving of the welding torch 27 (axial direction of the pipe), and a Z-axis in the welding height direction (radial direction of the pipe) , And a servo mechanism for each of the welding torch rotation axes, and these four axes are controlled by the control device 22. Weaving is two-dimensional weaving. That is, the welding torch 27 is moved along the groove in the Y axis direction and the Z axis direction orthogonal to the welding progress direction (X axis).
[0007]
In order to perform welding automatically, various automatic controls are performed. Representative examples are shown below.
[0008]
<Welding speed control>
Control is performed so that the traveling speed of the welding head 24 in the pipe circumferential direction (X-axis direction) becomes a preset value. Specifically, the speed of the X-axis direction drive motor is controlled to a preset value.
[0009]
<Vertical arc copying>
The vertical arc copying corrects the vertical position of the welding torch 27 so that the command current value and the measured current value match. When the current value becomes higher than the command current value, it is determined that the welding torch 27 is too low and the wire protrusion length is short, and the welding torch 27 is raised. Conversely, when the current value is lower than the command current value, it is determined that the welding torch 27 is too high and the wire protrusion length is long, and the welding torch 27 is lowered.
[0010]
<Arc voltage adjustment (arc length correction)>
The arc voltage adjustment is for automatically adjusting the arc voltage in order to absorb fluctuations in the arc voltage due to environmental conditions during the welding operation. Specifically, the voltage command is adjusted so that the arc short time ratio becomes a set value. The arc short is a state in which the distance between the welding wire and the base material or the molten metal is too short, and a short circuit occurs between the two (a short circuit occurs).
[0011]
<Left and right arc copying>
The left and right arc copying is to control the weaving center of the welding torch 27 to accurately pass through the center of the pipe groove 30 and to shift the center position of the welding torch 27 so that the left and right current values are equal. . If the center of the weaving is displaced from the center of the pipe groove 30, the gap between the groove wall at the left and right ends is different, so that the current value at the left and right ends is different. Therefore, by detecting the difference between the current values, it is possible to detect the deviation of the center of the weaving. Therefore, the center position of weaving is adjusted so as to eliminate the difference between the current values at the left and right ends.
[0012]
Sampling of these controls, particularly welding machine data (welding current, welding voltage, arc short time, arc short rate, etc.) for performing right and left arc copying control is performed in synchronization with the position of the welding torch. An example is shown in FIG.
[0013]
In FIG. 5, the horizontal axis represents time, and the vertical axis represents the Y axis, that is, the position in the groove width direction. A solid line is a command locus which is a locus of the command value of the welding torch position, and a broken line is a servo locus which is a locus of the actual welding torch position. In the example of FIG. 5, the weaving width (moving range in the Y-axis direction) is divided into five sections of a right end, a right, a center, a left, and a left end, and various data are sampled for each section.
[0014]
As shown in FIG. 5, due to the delay of the response of the servo mechanism to the movement command of the welding torch, the servo trajectory follows the command trajectory with a delay, and the amplitude is smaller than the command trajectory. Therefore, in a servo system in which the actual position of the welding torch can be measured, the actual position of the welding torch is measured, the position of the welding torch in the section is determined based on the measured position, and data is sampled. I have.
[0015]
[Problems to be solved by the invention]
However, the pulse command type servo control mechanism does not measure the actual position of the welding torch. FIG. 6 shows an example of a control block diagram of a pulse command type servo control mechanism. A command pulse corresponding to a change in the command trajectory is given from the controller 41 to the servo amplifier 42. The servo amplifier 42 has a counter 43 and counts this pulse. The value of the counter 43 is converted into an analog value by the D / A converter 44 and supplied to the servomotor 45.
[0016]
The movement of the servomotor 45 is detected by a pulse transmitter 46, and the pulse is input to the counter 43 as a feedback pulse. Since the count directions of the command pulse and the feedback pulse are reversed, the value of the counter 43 becomes zero when the number of command pulses and the number of feedback pulses match, that is, when the servomotor 45 rotates by the number of command pulses. And the servo motor 45 stops.
[0017]
In such a servo control system, the absolute value of the rotation amount of the servomotor, that is, the actual value of the weaving amount of the welding torch cannot be detected. Therefore, as described above, there is a problem that data sampling cannot be performed in synchronization with the actual position of the welding torch. Since the command trajectory can be grasped by the controller 41, data sampling may be performed in synchronization with the command trajectory. However, as shown in FIG. 6, since the command trajectory does not coincide with the servo trajectory, Inevitably, sampling errors occur.
[0018]
The present invention has been made to solve such a problem, and even when using a pulse command type servo control in which the actual position of the welding torch cannot be measured, sampling of data synchronized with the actual position of the welding torch is possible. It is an object to enable a data sampling method in a welding machine.
[0019]
[Means for Solving the Problems]
A first means for solving the above-mentioned problem is that, in a welding method in which a pulse torch type servo control is used and a welding torch is weaved to the right and left with respect to a welding progress direction, the welding torch is synchronized with a weaving position. Data sampling in a welding machine, wherein when welding data is sampled, a welding torch actual position is predicted from a welding torch position command value, and data sampling timing is determined based on the predicted welding torch actual position. A method (claim 1).
[0020]
In this means, the actual position of the welding torch is predicted from the position command value of the welding torch. That is, the followability of the actual position of the welding torch to a change in the position command value is obtained analytically or experimentally, and the two are related in the form of, for example, a transfer function. Then, a time-dependent change (servo trajectory) of the actual position of the welding torch is calculated and predicted by, for example, performing a transfer function calculation on the actual position command value (command trajectory). Since the data sampling timing is determined based on the predicted actual position of the welding torch, even if the actual position of the welding torch cannot be detected, data sampling synchronized with the actual position of the welding torch can be performed.
[0021]
A second means for solving the above-mentioned problem is the first means, wherein the response delay of the welding torch actual position to the welding torch position command is a first-order delay, and the welding torch actual position is predicted. (Claim 2).
[0022]
Generally, the delay of the servo trajectory from the command trajectory can be approximated by a first-order lag. Therefore, when the actual position of the welding torch is predicted assuming that the response delay of the actual position of the welding torch to the position command of the welding torch is a first-order delay, the calculation can be simplified and the actual position of the welding torch can be accurately predicted.
[0023]
A third means for solving the above-mentioned problem is the first means, wherein a response delay of the welding torch actual position to the welding torch position command is a primary delay and a dead time, and the welding torch actual position is determined. The present invention is characterized in that it is predicted (claim 2).
[0024]
Assuming that the response delay of the servo trajectory with respect to the command trajectory is a combination of the primary delay and the dead time, and predicting the actual position of the welding torch based on the result, the calculation is not so complicated, and compared to the second means, The actual position of the welding torch can be more accurately predicted.
[0025]
A fourth means for solving the above problem is the first means, wherein a response delay of the welding torch actual position to the welding torch position command is a secondary delay, and the welding torch actual position is predicted. (Claim 4).
[0026]
Assuming the response delay of the servo trajectory to the command trajectory as a secondary delay and predicting the actual position of the welding torch based on the secondary delay, the actual position of the welding torch can be more easily compared to the second means without significantly complicating the calculation. Can be accurately predicted.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention. In FIG. 1, 1 is a controller, 2 is a servo amplifier, 3 is a counter, 4 is a D / A converter, 5 is a servomotor, 6 is a pulse transmitter, 7 is a command value counter, 8 is actual position calculation means, 9 Is a data sampling means.
[0028]
A command pulse corresponding to a change in the command trajectory is given from the controller 1 to the servo amplifier 2. The servo amplifier 2 has a counter 3, and the value of the counter 3 is converted into an analog value by a D / A converter 4 and supplied to a servomotor 5 (actually, a speed control device is provided after the D / A converter). , Power amplifiers, but illustration and description thereof are omitted).
[0029]
The movement of the servo motor 5 is detected by a pulse transmitter 6, and the pulse is input to the counter 3 as a feedback pulse. Since the counting directions of the command pulse and the feedback pulse are reversed, the value of the counter 3 becomes zero when the number of command pulses and the number of feedback pulses match, that is, when the servomotor 5 rotates by the number of command pulses. And the servo motor 5 stops.
[0030]
On the other hand, the command pulse is also given to the command value counter 7, and the command value is calculated. The contents of the command value counter 7 correspond to the command locus. The actual position calculating means 8 calculates the actual position of the welding torch based on the contents of the command value counter 7. In this embodiment, the actual position calculating means 8 comprises a primary delay element, and predicts the current position of the welding torch assuming that the welding torch follows the position command with a primary delay.
[0031]
The predicted position of the welding torch is provided to the data sampling means 9. The data sampling means 9 samples the welding current, welding voltage, and the like in synchronization with the given welding torch position by the same method as in the related art.
By adopting such a method, even if there is no means for detecting the current position of the welding torch, the position can be predicted and data sampling synchronized with the position can be performed.
[0032]
Another embodiment of the present invention is the same as the above embodiment, except that the actual position calculating means 8 is composed of an element in which the primary delay and the dead time are combined. This calculation can be easily realized by delaying the input in the storage means in the actual position calculation means 8 for a fixed time and inputting it to the primary delay element. According to this method, the current position of the welding torch can be predicted with higher accuracy than when the actual position calculation means is simply a first-order delay.
[0033]
Another embodiment of the present invention is the same as the above embodiment, except that the actual position calculating means 8 comprises a second-order lag element. The second-order lag element can be easily realized by using a microcomputer. According to this method as well, the current position of the welding torch can be predicted with higher accuracy than when the actual position calculation means is simply a first-order delay.
[0034]
【The invention's effect】
As described above, in the present invention, the welding torch actual position is predicted from the welding torch position command value, and the data sampling timing is determined based on the predicted welding torch actual position. Even when using the pulse command type servo control whose position cannot be measured, data sampling synchronized with the actual welding torch position can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a configuration of an automatic welding machine.
FIG. 3 is a diagram showing an electrical connection relationship of the automatic welding machine.
FIG. 4 is a diagram showing details of a welding head.
FIG. 5 is a diagram showing a section in which welding machine data is sampled.
FIG. 6 is a diagram illustrating an example of a control block of a servo control mechanism of a pulse command system.
[Explanation of symbols]
Reference Signs List 1 Controller 2 Servo amplifier 3 Counter 4 D / A converter 5 Servo motor 6 Pulse transmitter 7 Command value counter 8 Actual position calculating means 9 Data sampling means

Claims (4)

In the welding method using the pulse command type servo control and weaving the welding torch to the left and right with respect to the welding progress direction, the position command of the welding torch is used when sampling welding data in synchronization with the weaving position of the welding torch. A data sampling method in a welding machine, wherein a welding torch actual position is predicted from a value, and data sampling timing is determined based on the predicted welding torch actual position. 2. The data sampling method for a welding machine according to claim 1, wherein the actual position of the welding torch is predicted on the assumption that the response delay of the actual position of the welding torch to the position command of the welding torch is a first-order delay. 2. The data sampling method for a welding machine according to claim 1, wherein a response delay of the welding torch actual position to the welding torch position command is a primary delay and a dead time, and the welding torch actual position is predicted. 2. The data sampling method according to claim 1, wherein the actual position of the welding torch is predicted on the assumption that the response delay of the actual position of the welding torch to the position command of the welding torch is a secondary delay.

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