JPH02104475A - Method for extracting component depending on weaving of arc welding current - Google Patents

Abstract

PURPOSE:To accurately extract and grasp a component depending on weaving in a welding current by detecting and eliminating a noise component in the detected output of the arc welding current through low-pass filters at the time of weaving a welding torch in a weld zone groove to perform welding. CONSTITUTION:While weaving the welding torch 12 from a position 12 to positions 12a and 12b in the groove part 14 to be welded of materials 13 to be welded, arc welding is performed by an welding rod 20. The welding current flowing in a line 15 to connect between a welding power source 16 and the welding torch 12 is detected by a detector 17 and its detected value 11 is inputted to a first low pass-filter 18 to obtain the difference 13 of the output 12 between the arc welding current 11 and the low-pass filter 18. This is sliced and a signal 15 added with the sliced output 14 to the output 12 of the low-pass filter 18 is obtained and a signal sliced at a prescribed width with a DC part of the welding current 11 as a center is obtained and then, smoothed by a second low-pass filter 24, by which only the current 11a which depends on weaving in the arc welding current 11 and is utilized directly for welding is extracted.

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 Section 6 shows the technology to which the present invention is related, and also explains the prior art. Arc welding is performed on a member to be welded 2 having a ``■''-shaped joint 1 using a welding rod 4 attached to a welding torch 3. 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 (i.e. oscillated or oscillated) between the right end position shown at the right end of FIG. When the centerline 6 of weaving 3R, 3L and the straight line 5 passing through the center position of the joint 1 are deviated to the left as shown in FIG. 6(1), the arc flowing in the welding torch 3 The welding current becomes as shown in Fig. 7 (1), and the welding torch 3
When the welding torch 3 is at the right end position with the axis 3R, a small value 1r flows, and when the welding torch 3 is at the left end position 3a as shown by the axis 3, a large arc welding current Il flows. Thus, the current 11, the difference Δ in lr
11 occurs. The current Ic is calculated when the axis of the welding rod l is the axis 5.
Indicates the value when it is above.

A driving means, such as an industrial robot, which grips and weaves the welding torch 3 and displaces the welding torch 3 in the longitudinal direction of the welding part 1 (in the direction perpendicular to the plane of the paper in FIG. 6) in a horizontal plane,
The welding torch 3 is adjusted as shown in Fig. 6 (1) so that the currents 1ffi and Ir are equal, that is, the difference ΔI is zero.
, the weaving center line 6 is displaced to the right.
is made to coincide with the straight line 5 passing through the center position of the first joint. As a result, as shown in No. 6111(2), the current 1
The welding state is equal to 1°Nr, and high-quality welding is performed at the joint 1.

As shown in FIG. 6 (3), when the weaving center line 6 of the welding torch 3 passes through the center position of the joint 1 and deviates to the right of the straight line 115, when the axis 3R is at the right end position. The arc welding current value 11 at the axis 3L at the left end position 3a is smaller than the current value 1r, and the difference ΔI
2. The welding torch 3 is moved in a horizontal plane so that the 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 can be moved along the joint 1 in a direction perpendicular to the plane of the paper of FIG. 6 to form a downward welded joint. Such a basic configuration is disclosed, for example, in Japanese Patent Publication No. 57-2428.

In another prior art, for example, as shown in FIG. 7(1), the weaving of the welding torch 3 is performed so that a hatched area S1 is equal to another hatched area S2. The welding torch 3 is moved in a horizontal plane so that the center line 6 of the joint 1 coincides with the center line 5 of the joint 1.

Problems to be Solved by the Invention In each of these prior art, the welding rods 4 attached to the welding torch 3 are sequentially supplied, and when the tip of the welding rods 4 comes into contact with the workpiece 2, the welding is completed. The tip of the welding rod 4 melts instantaneously, and therefore this welding rod 4
The tip of the welding member 2 repeatedly comes into contact with and separates from the workpiece 2. As a result, the arc welding current does not actually have a smooth waveform as shown in Fig. 7, but has many irregular noise components. Contains. 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
It is no longer possible to accurately displace the weaving center line 6 to match the straight line 5 passing through the center position of the joint 1.

In order to remove the vertical noise component contained in the arc welding current, it is simply possible to use a low-pass filter with a sufficiently large time constant.When such a low-pass filter is used, weaving The result is that the components that depend on
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.

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

Means for Solving the Problems The present invention provides an automatic welding machine that weaves a welding torch at a joint of a joint to be welded and constantly controls the welding torch along the joint by changes in arc welding current in response to changes in the position of the welding torch. , input the arc welding current detection output ■1 to the low-pass filter, find the difference between the arc welding current 11 and the low-pass filter output ■2, and slice the difference l3 (=11-I2), By obtaining a signal 15 (=I2+14) that is the sum of the output ■2 of the low-pass filter and the sliced output I4, a signal sliced at a constant width around the DC component of the welding current ■1 is obtained, and then This is a method for extracting a weaving-dependent component of an arc welding current, which is characterized by smoothing using yet another low-pass filter.

According to the present invention, the detected value of the arc welding current including a weaving-dependent component and a noise component is input to a low-pass filter, and the output I2 of the low-pass filter is subtracted from this arc welding current 11. Slice the value I3. This subtracted electricity? ifa I 3 does not contain a DC component, and the weaving-dependent component and noise component are the detected value 11 of the arc welding current.
The amplitude of the noise component is suppressed by slicing the value I3 obtained by this subtraction, which is included in the same phase as . Therefore, the signal generator 5 is obtained by adding the output I2 of the low-pass filter and the sliced output I4.

As a result, the signal 15 is in the same phase as the detected value of the arc welding current (■1), contains a component dependent on weaving, and contains only a very small noise component whose amplitude has been suppressed by the slicing (♂). If this is smoothed with a low-pass filter, a smooth current value can be detected using a filter with a small time constant.

Embodiment No. 1121 shows an electric circuit diagram T'4 of an embodiment of the present invention. The industrial robot 11 is equipped with a welding torch 12 and arc welds the joint 14, which is the groove of the workpiece 13, to form a downward welded joint. 6. 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 detected by a current detector 17.

FIG. 2(1) is a sectional view showing the welded state of the member 13 to be welded. A welding rod 20 is attached to the welding torch 12, and the welding torch 12 is attached to the welding torch 12 in the width direction (Fig. The welding torch 12 performs welding motion while weaving in the horizontal plane in the horizontal direction (left and right direction in (1)) when the welding torch 12 is at the right end in FIG. 2 (1)
The axis of the welding torch 1 is designated by reference numeral 12R.
The axis of the welding torch 12 in the state where 2 is at the left end and is indicated by reference R12b is indicated by reference numeral 12L. The industrial robot 11 moves this welding torch 12 to the rightmost position 11f.
Weaving drive is performed over a distance ΔL between l 2R and the axis 12L at the left end position. 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 ■1, and the feeding speed ■1 is a value larger than the weaving speed ■2 at which the welding torch 12 moves the distance ΔL. (Vl>V2), this welding torch 1
2 performs a weaving movement by moving horizontally as described above without being displaced in the vertical direction, for example to form an upward fillet weld joint of the horizontal joint 14.

As shown in FIG. 2 (2), the workpiece 13 is
When the welding torch 12 is arranged at an angle compared to the state shown in FIG.
Weaving is driven in the vertical direction with respect to.

A detected value 11 of the arc welding current detected by the current detector 17 is provided to a tenth-pass filter 18 .

The time constant of the tenth pass filter 18 is determined to be a time constant that accurately obtains the weaving-dependent component of the arc welding current, and is not an excessively large value for the arc welding current detected by the current detector 17. The waveform of the detected value 11 is as shown in FIG.
It has a noise component 11b having a large amplitude and a slanting shape that is generated when it comes into contact with the noise component 11b. Arc welding current detection value 11
The output (2) passed through the 10th pass filter 18 is given to a subtraction circuit 19, whereby the value (2) is subtracted from the detected value 11 (-). The output of the subtraction circuit 19 is
Then, 13=11-12
...(1).

The detected value 11 of the arc welding current is assumed to be expressed by the second equation to simplify the explanation.

I 1=A sin (ωt) )B*in (nωt
) +I O- (2) where A, B, n, ω are constants, t represents time, As1n(ωt) represents the component 11a that depends on weaving, and B 5in(r
+ (L) t ) indicates the noise component 11b, and IO
corresponds to the DC component of the arc welding current.

The output I2 of the tenth-pass filter 18 is At.

If B1 is a constant, it is expressed by the third equation.

I2=A1sin (ωt-θ) +-B1si
n (nωt-θ)+-IO・(3) Here, θ is the first
It represents the phase difference caused by the 0-pass filter 18. The constant 81 is a value close to zero, and the component B corresponding to this noise
15 inches (r+ωt-θ) can be ignored.

Therefore, the output I3 of the subtraction circuit 19 is given by the fourth formula %.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, with the absolute value I V s l
Slice.

The output (4) of the slice circuit 21 is as shown by the fifth equation.

l4=Asin(ωt)-A1+in(ωt-θ)MoB
25in (r+ωt)・= (5) In the fifth equation,
Reference numeral B2 is a constant, and this constant B2 is a value obtained by suppressing the value B by the slice circuit 21.

B2ΣVs...(
6) The slice level ■S for the slice circuit 21 is:
Amplitude A of component As1n(ωt) depending on weaving
Set to a value exceeding .

■s: Nino A...-(7) The output I4 of the slice circuit 21 and the output I2 of the 10th pass filter 18 are added in the adder circuit 23. The output I5 of this adder circuit 23 is as shown in the eighth equation.

I 5=A sin (ωt) +82 sin (nωt
) +I O- (8) Thus, the output I5 of the adder circuit 23
is the component As1 that depends on weaving without phase delay.
n(ωt) and a DC component IO, and further includes a minute noise component B25in(nωt).

The output I5 of the adder circuit 23 is sent to the 20th pass filter 24.
given to. This 20th-pass filter 24 has a similar configuration to the aforementioned 10th-pass filter 18, and has a small time constant. 20th - Output I of bus filter 24
6 is applied to the peak detection circuit 25 to detect the peak.

FIG. 5(1) shows the value 11 of the arc welding current detected by the current detector 17, as shown in FIG. 3 above. The output I2 of the tenth bus filter 18 is as shown in FIG. 5(2), and has a waveform in which the noise component tb is almost removed.

The output I3 of the subtraction circuit 19 is as shown in FIG. 5 (3), and the output I3 of the subtraction circuit 19 is a DC component.
Does not include 0. In this way, the output I3 of the subtraction circuit 19, which does not contain the DC component 10, is applied to the slicing circuit 21 and sliced as shown in FIG. 5(4).The waveform of FIG. 5(4) is , the output of the slice circuit 21 ■4
shows.

The output 5 of the adder circuit 23 is as shown in FIG. have The output 5 of this adder circuit 23 is added to the 20th
- the 20th
- The output (6) of the pass filter 24 has the waveform shown in FIG. 5 (6).

In this way, the peak detection circuit 25 detects the peak value 1rl of the arc welding current when the welding torch 12 is at the right end position as shown by the right end axis 12R as shown in FIG. welding torch 12
Detects the peak value IZI when the axis of is in the state indicated by the reference mark 12L at the right end position.

The signal processing circuit 26 in FIG.
, IZI are made equal, a control signal is created so that the center position of the weaving distance ΔL of the welding torch 12 coincides with the center position 14a of the welding position 14, and is given to the robot controller 28 via the line 27. . In response to the control signal via this line 27, the robot controller 28 displaces the welding torch 12 in a horizontal plane, 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 St and S2 of the arc welding current equal, as described in relation to FIG. 7(1) above. It may be given to the robot controller 28, or the welding torch 12 may be controlled by other control methods.

According to the invention, the 20th-pass filter 24 may be omitted.

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

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of an embodiment of the present invention, FIG. 2 is a sectional view showing the welding state of a member to be welded 13, FIG. 3 is an actual waveform diagram of detected value 11 of arc welding current, and FIG. The figure is a diagram for explaining the operation of the slice circuit 21, FIG. 5 is a waveform diagram for explaining the dynamic fY of the electrical configuration shown in FIG. 1, and FIG. 6 is the principle underlying the present invention. FIG. 7 is a waveform chart showing the arc welding current in each welding shape shown in FIG. 6. 11... Industrial robot, 12... Welding torch, 1
3... Member to be welded, 14... Joint portion, 16... Welding power source, 17... Welding current detector, 18... First
0 - Bus filter, 1... Subtraction circuit, 20... Welding rod, 21... Slice circuit, 22... Slice level setting circuit, 23... - Addition circuit, 24... 20th
-Pass filter, 25...Peak detection circuit, 26...
・Processing circuit, 28...Robot controller agent Patent attorney Number of strokes Keiichi 12WA Figure 3 Figure 4 Figure 6 Kai - o.

Claims (1)

[Claims] Using an automatic welding machine that weaves a welding torch at a joint of a joint to be welded and constantly controls the welding torch along the joint by changes in arc welding current in response to changes in the position of the welding torch, Input the detection output I1 of the arc welding current to a low-pass filter, find the difference between the arc welding current I1 and the output I2 of the low-pass filter, slice the difference I3 (=I1-I2), and obtain the output I2 of the low-pass filter. and the sliced output I4 to obtain a signal I5 (=I2+I4) to obtain a signal sliced at a constant width around the DC component of the welding current I1, and then another low-pass signal. A method for extracting a weaving-dependent component of an arc welding current, characterized by smoothing it using a filter.