JPH0435266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for extracting the weaving-dependent component of an arc welding current, which can be advantageously implemented in various weld joints, such as, for example, downward fillet weld joints.

Prior Art FIG. 6 shows the technology to which the present invention relates, and also explains the prior art. A welding torch 3 is attached to a workpiece 2 having a V-shaped joint 1.
Arc welding is performed using a welding rod 4 attached to the welding rod 4 . A straight line 5 passing through the center of the joint 1 of the welded member 2 is in the vertical direction and is indicated by reference numeral 5. The welding torch 3 is weaved (ie, oscillated or rocked) between the right end position shown at the right end in FIG. 61 and the left end position shown by reference numeral 3a. Axis line 3R of welding torch 3, 3a,
When the line 5 passing through the center line 6 of the 3L weaving and the center position of the joint 1 is shifted to the left as shown in FIG. 6, the arc welding current flowing through the welding torch 3 is 7 When the welding torch 3 is at the right end position with the axis 3R as shown in FIG. 1, a small value Ir flows, and the welding torch 3 is at the left end position 3a as shown by the axis 3L. At some times, a large arc welding current Il flows. In this way, a difference ΔI1 occurs between the currents Il and Ir, and the current Ic shows a value when the axis of the welding rod 4 is on the axis 5.

A driving means, such as an industrial robot, which grips and weaves the welding torch 3 and displaces the joint 1 in the longitudinal direction (perpendicular to the plane of the paper in FIG. In other words, so that the difference ΔI becomes zero, the welding torch 3 is displaced to the right in the case of FIG. match. With this, the 6th
As shown in FIG. 2, the welding state is established where the currents Il and Ir are equal, and high-quality welding is performed at the joint 1.

As shown in FIG. 6, when the center line 6 of the weaving of the welding torch 3 deviates to the right of the straight line 5 passing through the center position of the joint 1, the axis 6
Compared to the current value Ir when R is at the right end position, the arc welding current value Il at the axis 3L at the left end position 3a is smaller, resulting in a difference ΔI2. The welding torch 3 is moved in a horizontal plane so that this difference ΔI2 becomes zero, and the welding torch 3 is displaced so that the center line 6 of the weaving coincides with the straight line 5 passing through the center position of the joint 1.

In this way, the welding torch 3 is inserted into the sixth position along the joint 1.
A downward fillet weld joint can be formed by moving perpendicular to the plane of the figure. Such a basic configuration is disclosed, for example, in Japanese Patent Publication No. 57-2428.

Other prior art techniques include, for example, as shown in FIG.
Therefore, the welding torch 3 is moved in a horizontal plane so that the centerline 6 of the weaving of the welding torch 3 coincides with the centerline 5 of the joint 1.

Problem to be solved by the invention In each of these prior art, welding torch 3
The welding rods 4 attached to the
When the tip of the welding rod 4 comes into contact with the workpiece 2, the tip of the welding rod 4 is instantaneously fused, and therefore the tip of the welding rod 4 contacts and separates from the workpiece 2. repeat. As a result, the arc welding current does not actually have a smooth waveform as shown in FIG. 7, but contains many whisker-like noise components. Therefore, it is necessary to accurately extract the weaving-dependent components shown in FIGS. 7 1 to 7 3 from the arc welding current containing such noise components, otherwise the welding torch 3 The center line 6 of the weaving cannot be accurately displaced and aligned with the straight line 5 passing through the center position of the joint 1.

In order to remove the whisker-like noise components contained in the arc welding current, it is simply conceivable to use a low-pass filter with a sufficiently large time constant. When such a low-pass filter is used, the weaving-dependent components are also smoothed out, making it impossible to accurately control the welding torch 3. Furthermore, a low-pass filter having such a large time constant has a large phase difference between its input and output, and this phase difference also makes it impossible to accurately control the welding torch 3.

An object of the present invention is to provide a method that can accurately extract only the weaving-dependent components of arc welding current and remove whisker-like noise components.

Means for Solving the Problems The present invention provides automatic weaving of the welding torch at the joint of the joint to be welded, and constant control of the welding torch along the joint by changes in the arc welding current in response to changes in the position of the welding torch. Using a welding machine, input the detection output I1 of the arc welding current to the low-pass filter, and then input the arc welding current I1 and the output I2 of the low-pass filter.
Welding is performed by calculating the difference between A method for extracting components that depend on weaving of arc welding current, which is characterized in that after obtaining a signal sliced at a constant width around the DC component of current I1, the signal is smoothed using another low-pass filter. be.

Effect According to the present invention, the detected value of the arc welding current including the weaving-dependent component and the noise component is input to the low-pass filter, and the output I2 of the low-pass filter is subtracted from this arc welding current I1.
The subtracted value I3 is sliced. This subtracted current value I3 does not include a DC component and includes a weaving-dependent component and a noise component in the same phase as the detected value I1 of the arc welding current. By slicing the value I3 obtained by this subtraction, the amplitude of the noise component is suppressed. Therefore, the output I2 of the low-pass filter and the sliced output I4 are added to obtain the signal I5. As a result, the signal I5 is in the same phase as the detected value I1 of the arc welding current, contains a weaving-dependent component, and contains only a very small noise component whose amplitude has been suppressed by slicing. , by smoothing this using a low-pass filter, a smooth current value can be detected using a filter with a small time constant.

Embodiment FIG. 1 is an electrical circuit diagram of an embodiment of the present invention. The industrial robot 11 is equipped with a welding torch 12, and performs arc welding on a joint 14, which is a groove of a member to be welded 13, to form a downward fillet weld joint. Arc welding current is supplied to this welding torch 12 from a welding power source 16 via a line 15. The arc welding current flowing through this line 15 is
It is detected by the current detector 17.

FIG. 2 is a cross-sectional view showing the welded state of the welded member 13. The welding torch 12 includes a welding rod 20
is attached, and this welding torch 12 is designated by reference numeral 12
As shown by a and 12b, the width direction (second
The welding operation is performed while weaving in the horizontal plane (left-right direction in FIG. 1). The axis of the welding torch 12 when the welding torch 12 is at the right end in FIG. is indicated by reference numeral 12L.
The industrial robot 11 moves the welding torch 12 between the right end position 12R and the left end position axis 12L.
Weaving drive is performed over a distance ΔL. A straight line passing through the center of the joint 14 is in the vertical direction, as indicated by reference numeral 14a.

The welding rod 13 is continuously fed in the longitudinal direction at a predetermined feeding speed V1.
V1 is a value larger than the weaving speed V2 that moves the welding torch 12 over the distance ΔL (V1>
V2). This welding torch 12 performs a weaving motion by moving in the horizontal direction as described above without being displaced in the vertical direction, for example, in order to form an upward fillet weld joint of the horizontal joint 14. .

As shown in FIG. 2, when the workpiece 13 to be welded is arranged at an angle compared to the state shown in FIG.
The weaving drive is performed in the vertical direction with respect to the axis 14a.

A detection value I1 of the arc welding current detected by the current detector 17 is provided to a first low-pass filter 18. The time constant of the first low-pass filter 18 depends on the weaving of the arc welding current, is set to a time constant that accurately obtains the weaving-dependent component, and is not an excessively large value. The waveform of the detection value I1 of the arc welding current detected by this current detector 17 is as shown in FIG.
A noise component with a whisker-like large amplitude that occurs when I1a and the welding rod 20 contact the workpiece 13 to be welded
I1b. An output I2 of the detected value I1 of the arc welding current passed through the first low-pass filter 18 is given to a subtraction circuit 19, whereby the detected value I1
The value I2 is subtracted from . If the output of the subtraction circuit 19 is I3, then I3=I1-I2 (1).

It is assumed that the detected value I1 of the arc welding current is expressed by the second equation to simplify the explanation.

I1=Asin(ωt)+Bsin(nωt)+I0...(2) Here, A, B, n, ω are constants, t represents time, and Asin(ωt) represents the component I1a that depends on weaving. In addition, Bsin(nωt) indicates the noise component I1b, and I0 corresponds to the DC component of the arc welding current.

The output I2 of the first low-pass filter 18 is A1,
If B1 is a constant, it is expressed by the third equation.

I2=A1sin(ωt-θ)+B1sin(nωt-θ)+I0
(3) Here, θ represents the phase difference caused by the first low-pass filter 18. The constant B1 is a value close to zero, and the component B1sin(nωt−θ) corresponding to this noise
can be ignored.

Therefore, the output I3 of the subtraction circuit 19 is as shown in the fourth equation.

I3=I1−I2 = Asin(ωt)−A1sin(ωt−θ)+Bsin(nωt)
...(4) The output I3 of the subtraction circuit 19 is given to the slice circuit 21. As shown in FIG. 4, this slice circuit 21 outputs the output I3 at the slice level Vs set in the slice level setting circuit 22.
Slice by insulation value |Vs|.

The output I4 of the slice circuit 21 is as shown by the fifth equation.

I4=Asin(ωt) −A1sin(ωt−θ)+B2sin(nωt)……(5) In the fifth equation, reference mark B2 is a constant, and this constant B2 is
is the suppressed value.

B2Vs ……(6) Slice level Vs for slice circuit 21
is set to a value exceeding the amplitude A of the component Asin(ωt) that depends on weaving.

Vs>A (7) The output I4 of the slice circuit 21 and the output I2 of the first low-pass filter 18 are added in the adder circuit 23. The output I5 of this adder circuit 23 is the 8th
As shown in Eq.

I5=Asin(ωt)+B2sin(nωt)+I0...(8) In this way, the output I5 of the adder circuit 23 includes a weaving-dependent component Asin(ωt) with no phase lag, a DC component I0, and a subtle noise component. B2sin
(nωt) included.

The output I5 of the adder circuit 23 is given to the second low-pass filter 24. This second low-pass filter 24 has a similar configuration to the first low-pass filter 18 described above, and has a small time constant. The output I6 of the second low-pass filter 24 is the peak detection circuit 2
5 and the peaks are detected.

FIG. 5 1 shows a current detector 17 for arc welding current.
The value I1 detected by is as shown in FIG. 3 above. The output I2 of the first low-pass filter 18 is as shown in FIG. 5, and has a waveform in which the noise component I1b is almost removed.

The output I3 of the subtraction circuit 19 is as shown in FIG. 5, and the output I3 of the subtraction circuit 19 does not include the DC component I0. In this way, the output I3 of the subtraction circuit 19, which does not contain the DC component I0, is applied to the slicing circuit 21 to perform slicing as shown in FIG. 4. The waveform in FIG. 5 shows the output I4 of the slice circuit 21.

The output I5 of the adder circuit 23 is as shown in FIG.
It has a waveform that is the sum of By applying the output I5 of the adder circuit 23 to the second low-pass filter 24, the output I6 of the second low-pass filter 24 has the waveform shown in FIG. 5.

In this way, the peak detection circuit 25 detects the welding torch 1
For example, the peak value Ir1 of the arc welding current is detected when the welding torch 12 is at the right end position as shown by the right end axis 12R as shown in FIG. The peak value Il1 in the state indicated by 12L is detected.

The signal processing circuit 26 in FIG. 1 adjusts the welding torch 12 so that these peak values Ir1 and Il1 are equal.
A control signal is created so that the center position of the weaving distance ΔL coincides with the center position 14a of the welding position 14, and is given to the robot controller 28 via the line 27. Robot controller 2
8 displaces the welding torch 12 in a horizontal plane in response to the control signal via this line 27, thereby driving the welding torch 12 so that the center position of the weaving coincides with the center position 14a of the joint 14.

As another embodiment of the present invention, the processing circuit 26 derives a control signal for making the integral values S1 and S2 of the arc welding current equal, as described in connection with FIG. 7, and controls the robot controller. 28, or the welding torch 12 may be controlled in other control manners.

According to the invention, the second low-pass filter 24 may be omitted.

Effects of the Invention As described above, according to the present invention, noise components contained in the arc welding current can be removed, and weaving-dependent components can be accurately obtained.

[Brief explanation of drawings]

Fig. 1 is an electrical circuit diagram of an embodiment of the present invention;
The figure is a sectional view showing the welding state of the welded member 13, FIG. 3 is an actual waveform diagram of the detected value I1 of the arc welding current, FIG. 4 is a diagram for explaining the operation of the slice circuit 21, and FIG. is a waveform diagram for explaining the operation of the electrical configuration shown in FIG. 1, FIG. 6 is a sectional view for explaining the principle underlying the present invention and the prior art, and FIG. FIG. 3 is a waveform chart showing arc welding current in each shown welding state. 11...Industrial robot, 12...Welding torch, 13...Member to be welded, 14...Joint part, 16
... Welding power source, 17 ... Welding current detector, 18
...First low-pass filter, 19...Subtraction circuit,
20...Welding rod, 21...Slice circuit, 22...
...slice level setting circuit, 23...addition circuit,
24...Second low-pass filter, 25...Peak detection circuit, 26...Processing circuit, 28...Robot controller.

Claims (1)

[Claims] 1. Using an automatic welding machine that weaves the welding torch at the joint of the joint to be welded and constantly controls the welding torch along the joint by changing the arc welding current in response to changes in the position of the welding torch. , the arc welding current detection output I1 is input to the low-pass filter, and the arc welding current I1 and low-pass filter output I2 are
Welding is performed by calculating the difference between A method for extracting a component dependent on weaving of an arc welding current, which is characterized by obtaining a signal sliced at a constant width around the DC component of the current I1, and then smoothing it using another low-pass filter.