JPH0438511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling a welding torch.

When controlling the position of a welding robot's torch based on so-called teaching data, a deviation often occurs between the torch movement trajectory and the actual welding line. Therefore, a method has been implemented in which the above-mentioned deviation is detected as a difference in welding current at both ends of the weaving, and teaching data is corrected based on the detection result to cause the welding torch to follow the welding line.

According to this method, for example, if the workpiece 2 deviates to the right with respect to the center line of the torch 1 as shown in FIG. 1a, or to the left as shown in FIG. As shown, the position of the torch 1 is corrected in such a manner that the center line of the torch 1 is located on the center line of the workpiece 2, that is, on the welding line. In other words, the torch 1 for the welding line of the workpiece 2
Following control is performed.

By the way, when the above-described tracing control of the torch 1 is performed, the following problems may occur depending on the welding mode. i.e. for example torch angle
When performing horizontal fillet welding at 45°, if the above-mentioned tracing control is performed, welding point 3 will move as shown in Figure 2.
The bead toes 3a overlap, resulting in a decrease in the fatigue strength of the welded portion 3.

Furthermore, if the torch angle cannot be arbitrarily set due to interference with a workpiece during teaching, the angle of the torch 1 may be set to 60° or 30° as shown in FIG. 3 or 4 out of necessity. In such a case, at a torch angle of 60°, the target position of torch 1 with respect to workpiece 2' is a distance l ₁ (=2 to 3 mm) from the welding line.
Also, at a torch angle of 30°, the target position will be a distance l ₂ (=2 to 3 mm) behind the welding line, which may make it impossible to obtain a proper bead toe shape or cause the welded area to This may result in quality deterioration, such as poor penetration.

In view of this situation, the present invention changes the aiming position of the torch with respect to the workpiece according to the welding mode,
The aim is to obtain welded products of the highest quality.

Therefore, in the present invention, the welding torch is weaved, the welding current at both ends of the weaving is detected, the difference between the respective currents is determined, and the welding torch is biased relative to the welding line based on the difference in the current. a step of detecting a positional amount, a step of determining a positional correction amount of the welding torch based on an offset amount of the welding torch with respect to the welding line preset from the deviation amount, and a step of calculating the teaching data by the positional correction amount. and positioning the welding torch based on the corrected teaching data.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 5 shows a control device for a welding robot that is applied when carrying out the method of the present invention.

In the figure, an actuator 15 is a drive source disposed in a welding robot, and moves the welding torch 1 shown in FIG. 6a in the left-right direction. and,
When the welding torch 1 is moved, the actuator 1
The encoder 16 linked to the welding torch 1 outputs a number of pulse signals corresponding to the amount of left-right movement of the welding torch 1, and the tachogenerator 20 linked to the actuator 15 outputs a signal indicating the left-right movement speed of the welding torch 1. .

Now, when the positioning control signal S ₁ consisting of a pulse train is output from the arithmetic unit 13 composed of a CPU etc., the deviation between the control signal S ₁ and the output signal of the encoder 16 is calculated from the subtracter 17 consisting of an up-down counter etc. It is output as a command signal, and this signal is applied to a subtracter 19 via a D/A converter 18.

The subtracter 19 outputs a signal indicating the deviation between the speed command signal and the speed feedback signal output from the tachogenerator 20, and the actuator 15 is driven by this signal.

As a result, actuator 15 moves welding torch 1 to the position commanded by positioning control signal _S1 .

By the way, as shown by the dotted line in FIG. 6a, the welding torch 1 welds the welding line of the workpiece 2 while weaving from side to side. At this time, the arc sensor 10 shown in FIG. The welding current that changes with the current is detected.

Based on the output of the arc sensor 10, the computing device 13 detects each welding current at both ends of the weaving, for example, the welding currents I _R and I _L shown in FIG. Calculate the difference in welding current ΔI = I _R - I _L.

The current difference ΔI corresponds to the horizontal deviation amount Δl of the torch 1 with respect to the welding line of the workpiece 2. Therefore, the calculation device 13 calculates, based on the current difference ΔI,
Teaching data so that the above deviation is corrected
_DT is corrected, and a positioning control signal _S1 based on the corrected teaching data is output.

According to this control signal _S1 , the torch 1 is
As shown in Figure 2, the welding current is positioned directly above the welding line, and the welding current I _R at both ends of the weaving is
I _L becomes equal as shown in Figure b.

In the above, general tracing control that corrects the deviation between the position of the torch 1 based on the teaching data D _T and the actual position of the welding line of the workpiece 2 has been explained. Control for quantitative offset will be explained.

Now, as shown by the dotted line in Figure 10, the torch 1
Consider the case where the welding line of workpiece 2 is always offset to the left by L _i from the welding line of workpiece 2. In addition, in the figure, the left direction with respect to the weld line as the center is negative, and the right direction is positive.

Now, for example, as shown by the solid line in Fig. 10, the torch 1 is deviated to the left by Δl with respect to the welding line,
Assuming that the torch 1 is weaved left and right across the welding line as shown by the broken line in FIG. 6, each welding current at both ends of the weaving
The difference ΔI (<0) between I _{R and} I _L corresponds to the above deviation amount Δl.

Therefore, in order to realize the above offset, the deviation amount Δl (<
The position correction amount of the torch 1 may be obtained by subtracting the offset amount L _i (<0) from 0), and the teaching data _DT may be corrected using this position correction amount.

That is, when the teaching data D _T is corrected with the position correction amount based on the deviation amount Δl,
As mentioned above, the position of the torch 1 is corrected so that it is located directly above the welding line, but teaching is performed using the position correction amount obtained by subtracting the offset amount L _i from the deviation amount Δl. Data D _T
When correcting, the position of the torch 1 is corrected so that it is located to the left of the welding line by L _i .

That is, in the example of FIG. 10, the torch 1 is set at a distance Δl
- Just move L _i to the right. Therefore, if the position correction amount Δl−L _i is added to the teaching data D _T to correct the data D _T and the positioning control signal S ₁ based on this corrected data is output from the arithmetic unit 13, the torch 1 is L _i to the left from the weld line
It will be located offset by the same amount.

When the teaching data _DT is corrected as described above, the offset amount is set based on the actual weld line position of the workpiece 2, rather than the weld line position based on the teaching data. Then, the torch 1 follows the welding line while maintaining the distance L _i from the welding line.

The memory 14 shown in FIG.
L _i (L ₁ , L ₂ , L ₃ ...) is stored in advance,
The arithmetic unit 13 reads out the specified offset amount L _i from the memory 14 based on external input information for specifying the desired offset amount L _i . and,
Based on the read offset amount L _i and the deviation amount Δl known from the current difference ΔI, the above-mentioned correction process of the teaching data D _T is executed, and a positioning control signal S ₁ based on this corrected data is created and output. do.

FIG. 8 shows an example in which the method of the present invention is applied to horizontal fillet welding. If the contents of the memory 14 are selected so that the torch 1 aims at a point l ₃ = 2 to 3 mm from the welding line as shown in the figure, the shape of the bead toe 3a will be smooth as shown in Figure 9. A welding result is obtained and the overlapping phenomenon as shown in FIG. 2 is prevented.

Furthermore, even when the torch angle is limited as shown in FIGS. 3 and 4 due to constraints during teaching, good welding results can be obtained by appropriately deflecting the torch 1 according to the method of the present invention. I can do it.

According to the present invention, there is no need to adjust the target welding position during teaching, so the teaching work can be facilitated and speeded up. Further, it is possible to conveniently set the target welding position without being affected by missetting of the workpiece or the like.

[Brief explanation of drawings]

Figures 1a, b, and c are conceptual diagrams illustrating aspects of tracing control using arc sensors, respectively; Figure 2 is a conceptual diagram illustrating welding results when the torch is directed toward the weld line in horizontal fillet welding; 3 and 4 are conceptual diagrams illustrating how to set the torch angle in horizontal fillet welding, respectively. FIG. 5 is a block diagram illustrating an example of the configuration of an apparatus for carrying out the method of the present invention. Figures a and 7a are conceptual diagrams illustrating a torch control mode according to the method of the present invention, respectively;
Figures 6b and 7b are diagrams showing changes in welding current under the torch control modes shown in Figures a, respectively, and Figure 8 is a diagram showing the horizontal fillet welding mode according to the method of the present invention. FIG. 9 is a conceptual diagram showing the welding process result shown in FIG. 8, and FIG. 10 is a conceptual diagram illustrating an embodiment in which the torch is offset. 1...Torch, 2,2'...Work, 10...
Arc sensor, 13... Arithmetic device, 14... Memory, 17, 19... Subtractor, 15... Actuator, 16... Pulse encoder.

Claims (1)

[Scope of Claims] 1 Applied to a welding robot that teaches the position of a welding line in advance and positions a welding torch based on the teaching data obtained thereby, weaving the welding torch in a manner that crosses the welding line. and detecting the welding currents at both ends of the weaving, determining the difference between the respective currents, and detecting the amount of deviation of the welding torch with respect to the welding line based on the difference in the currents, Based on the deviation amount and the offset amount of the welding torch with respect to the preset welding line,
A method for controlling a welding robot, comprising: determining a position correction amount for the welding torch; and correcting the teaching data by the position correction amount, and positioning the welding torch based on the corrected teaching data.