JPS6033871A - Method and device for profiling detection for welding - Google Patents

Abstract

PURPOSE:To perform profiling detection which decreases disturbance by noise and can surely with a slight change with high accuracy by using the impedance of a welding arc as an input signal for controlling the position of a welding torch. CONSTITUTION:The impedance Za of the arc obtd. by dividing an arc voltage by welding current is used as an input signal for automatic control of the distance between a welding torch 2 and materials 1 to be welded and automatic follow-up control of the weld line in the stage of said control. An arithmetic circuit 4 for the impedance is constituted of variable resistors VR-1, VR-2, arithmetic amplifiers OP-1, OP-2 and a divider D. A voltage input signal E and current input signal I are respectively inputted to input terminals tiE, tiI and the impedance Za is operated. If the impedance signal 5 obtd. in such a way is used as the input signal for controlling the position of the torch, the operation of the control circuit is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a consumable electrode constant rate feed type automatic arc welding device or a consumable electrode constant rate feed type arc welding port d? The present invention relates to a welding trace detection method and device for automatically controlling the distance between a welding torch and a workpiece in a welding process and automatically following a welding line.

Automatic arc welding equipment or teaching/regeneration type arc welding port d (
When performing arc welding using a welding kit, even if installation errors, dimensional errors, or deformation of the welded material occur, these fluctuations are detected and automatically corrected to ensure that the welding material is always properly maintained. It is necessary to be able to weld. Conventionally, there have been various proposals and methods for detecting the above fluctuation amount associated with arc welding.
Among them, the so-called 1-arc sensor, which detects the change in the atmospheric characteristic value of the welding arc and uses this as an input signal for the above-mentioned correction, is also often used. There is.

Here, the operating principle of arc sensors that are currently mainly used will be explained with reference to FIGS. 1 and 2.

FIG. 1 shows the current/voltage characteristics in shielded arc welding using a general consumable electrode constant-rate feed, and an example of the external characteristics of a general welding power source. As shown in the figure, the distance between the workpiece 1 and the welding torch 2 is ±Δh around ha.
As a result, the characteristic curves move up and down while remaining substantially similar. On the other hand, when the arc is loaded by a welding power source with external characteristics (close to constant voltage characteristics) as shown in the figure, when h=ho, PNS h=h6+Δ
At h, PLsh=ho-Δh, p, stable energization is performed at each intersection, and a steady welding state is obtained.

That is, the distance M1h between the material to be welded 1 and the welding torch 2
Correspondingly, the operating point of the welding power source is PN+pL+P
B, etc., and this fluctuation causes the stain current and voltage to fluctuate.

As is clear from the figure (, h = ho to h ”” h 6+
If ΔhK changes, the current l changes from IO to IO−ΔΔ, the voltage E changes from EO to Eo+ΔE, and h=
If it changes from llo to h=h, -Δh, I-4, +ΔI
, E=B, and -ΔE, respectively.

In this way, both ■ and E change due to a change in h, but as you can see from the figure, the change in I is much larger than the change in E, so in reality, the change in I is not used. te, 1
Therefore, the so-called arc sensor utilizes this phenomenon.

FIG. 2 is an explanatory diagram of an example of a method for controlling the position of a welding torch using the phenomenon shown in FIG. 1. FIG. 2 fat shows an example of automatic target value control of the distance h (ie, two axes) between the workpiece 1 and the welding torch 2 during welding on a flat plate.

The same figure (bl shows an example of automatic target value control for h during butt welding, and (cl shows an example of automatic target value control for h during fillet welding.) In the Hz diagram (a3 to (c)),
ti is an input terminal to which the current I or arc current IEE is applied, LPFiJ is a low/main filter, COM is a comparison discriminator that compares and discriminates the output of the threshold setter SR and the output of the low/4' filter LPI. SA is a surf amplifier, SM is a motor, and DM is a drive mechanism for the welding torch 2. This drive mechanism DM drives the welding torch 2 in the Z-axis and Y-axis directions shown when the Y-axis is perpendicular to the plane of the paper. In the case of fal in Figure 2, only the Z axis is driven (in the case of bl and +cl, h changes not only in response to changes in the Z axis but also in the Y axis, so both axes are driven). In other words, it can be used for automatic control related to
bl, fc), if the Y axis is fixed, (a)
Similarly, only the Z-axis is controlled. Next, if the Z-axis is fixed, h will change due to changes in the Y-axis direction, so welding 1 and -2 should be oscillated (oscillating or weaving) in the YI141+ direction in advance while proceeding (in the X-axis direction). The change in h due to the change in the Y-axis direction is detected, and the detected value is compared and discriminated with the corresponding electric threshold value by the comparison discriminator COM, and the weaving folding is performed. By determining the light point and advancing it repeatedly, the automatic tracking function of the welding line is activated (++if). Next, in the M 21ffl fb) When both are to be controlled, Z-axis control is performed on h near the center of the Y-axis, and Y-axis control is performed on h at the end of the weaving in the Y-axis direction, as described above, to achieve both.

Thus, by skillfully utilizing the phenomenon shown in Figure 1, it is possible to control the position of the welding torch while detecting changes in the current as shown in Figure 2. It has its drawbacks.

+II The change in I due to the change in h is much larger than the change in E, but when performing subtle control in the Z-axis direction or Y-axis direction, the input signal due to the change in Therefore, stable comparative discrimination may be difficult.

(2) In order to make the droplet transfer a stable sougret transfer,
There are cases where a sharp waveform current is superimposed on the welding current, and in such a case, the control input signal is also superimposed with a sharp waveform waveform, resulting in malfunction of the control circuit. May be stable.

It is an object of the present invention to alleviate such drawbacks, and to provide a highly accurate and low-cost method and device for detecting welding traces, which causes less noise interference and can reliably respond to minute changes.

In order to achieve the above object, the present invention uses the arc impedance Za obtained by dividing the arc electric current /EE by the welding current I as a control input signal for controlling the position of the welding torch.
When using , the following characteristics can be mentioned.

■ Welding torch/workpiece #llJ] The magnitude of the change rate of the arc characteristic value due to the change in distance #ch is E(I(Za and υ, if Za is used as the control input signal, the conventional I
When using this method, a large rate of change can be obtained, which is effective in improving the accuracy of comparison and discrimination and preventing erroneous operation due to busy conditions.

■ When a somewhat luscious current flows due to the /4' lusus generator built into the welding power source, the voltage changes with the same sign as the current change along the arc load characteristic curve, which has no relation to the external characteristics of the power source. Since the impedance changes, the impedance does not change much. Therefore, the noise disturbance due to the sharp N flow is reduced accordingly, and the control accuracy can be improved.

(2) Since the impedance Za is obtained by dividing the voltage E by the current I, the circuit configuration is easy and can be realized at low cost.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a block configuration example for explaining the welding trace detection method according to the present invention, and FIG. 4 shows a specific circuit configuration example for arc impedance detection. FIG. 3 is an example of a block configuration for arc impedance detection in shielded arc welding using general consumable electrode constant-speed feeding and positioning of a welding torch based on this detection. Figure 3 (a) shows an example of a configuration for welding on a flat plate and the automatic target value control of the distance between the welding torch and the workpiece in flat plate welding, when two-axis control is performed using the arc impedance as an input signal. This shows an example of a block configuration.

In the figure, 1 is the material to be welded, 2 is the welding torch, and h is the material to be welded 1
and the welding torch 2, ■ indicates the arc voltage, ■ indicates the welding current, ■e indicates the polarity of the welding power source, and Z and Y indicate the drive shafts to be controlled in the welding torch position, respectively. Also, 3B
is a current input signal, 3b is an arc voltage input signal, 4 is an impedance calculation circuit, 5 is an impedance signal, 6 is a low-pass filter, 7 is a comparison/discrimination circuit, srd:, a threshold setting circuit for comparison/discrimination, 9 is a sir yW Amplifier, 10-2
Is it a 2-axis sir? Motors 11-2 each indicate a two-axis drive mechanism. Next, Figure 3 (bl) shows a configuration example during butt welding and target value control of the distance between the welding torch and 17 welding materials in butt welding by two-axis control using the arc impedance as an input signal. This figure shows an example of the block configuration in the case of carrying out the operation, and each of its constituent elements has the same function as those in Figure 3 (a).

Next, Fig. 3 re) shows an example of the configuration for fillet welding and target value control of the distance between the welding torch and the workpiece in butt welding using Y-axis control using the arc impedance as an input signal. 1.2 is an example of creating a push-pull when performing
．． h, @, ■.

The components $e, z, y and 3a, 3b, -9 are components having the same functions as those in (a) and rb) of the same figure, and 10'-'l is Y Axis chi d? The motor, 11-Y is a Y-axis drive mechanism, and 12 is a Y-axis Leibitz mechanism of a welding torch.

FIG. 4 shows a specific example of the arc impedance detection section and the arithmetic circuit 4, which are the basis of the present invention, among the functional components shown in FIG. 3. FIG. 4(a) shows an example of a circuit configuration when calculating impedance from an arc voltage using a divider and an operational amplifier. In the figure, 1 is the material to be welded, 2 is the welding torch, and 3a is the Current input signal, 3b is arc voltage input signal, 4 is impedance calculation circuit, 5
is an impedance signal, SH is a current divider, and voltage input signal [F] is an input terminal t111. The current input signals are respectively input to the long sword terminals tH. and common terminal t. A common line COM is connected to. Figure 4 rbl shows an example of the circuit configuration when calculating impedance from arc voltage and current using a multiplier and an operational amplifier, where VR-1 and VR-2 are variable resistors, 0P-1 to 0P-3 is an operational amplifier, and M is a multiplier. FIG. 4(c) shows an example of a circuit configuration in which impedance is calculated from arc voltage and current using an operational amplifier and transistors, and TR-1 to TR-3 are transistors.

Next, the operation of the welding tracing detection device d configured as described above will be described. First, the operation related to arc impedance detection will be explained.

Figure 3 (a), (b), (1 and 2 in cl.
, 3*, 3b+4.5 and Fig. 4(a), fbl
, [The arc impedance is detected by each functional element in cl as follows. The impedance Za of the arc can be defined as shown in the following formula.

Za=-... (1) ■ Therefore, in the arithmetic circuit shown in f44 figure (a), the basic arithmetic function of the divider is 2' V, '=10... ......Using (2), one circuit is configured so that 2/ is input with the ■ component, X is with the E component, and vo' is calculated to calculate G.
P-J, 0P-2 are linear amplification or sign inversion effects, 'V
R-1. VR-2 acts as a level adjuster for the ■ component and the E component.

Furthermore, in the arithmetic circuit shown in FIG. 4 fb), the multiplier M
As a basic calculation function, insert it into the negative feedback circuit of the operational amplifier,
The circuit is configured to calculate Z a = '■ by comprehensively configuring the divider, and in the figure, 0P-1
~0P-J is linear amplification or sign inversion, VR-J, V
R-J acts as a level adjuster for the ■ component and the E component. Furthermore, the arithmetic circuit shown in FIG. 4(c) is constructed to calculate za-■ by utilizing the logarithmic conversion and anti-logarithmic conversion effects of an operational amplifier and a transistor.

[e: base of natural logarithm]

In the figure, OP-1, 0P-2, 0P-4 to op-y are linear amplification, sign and transformation are logarithmic/antilogarithmic conversion functions together with transistors TR-1 to TR-J, and VR-1 and VR-2 are ■
Acts as a level adjuster for the E component and the E component. Next, a description will be given of the operation when the impedance Za, which is a characteristic value of the arc determined by the arithmetic circuit, is used as an input signal for controlling the distance between the welding torch and the workpiece.

FIG. 5 shows current/voltage characteristics in general consumable electrode constant-rate feed shielded arc welding and an example of external characteristics of a general welding power source. As shown in the figure, as the distance between the welding torch and the welded material changes up and down by Δh around hO, the A-A voltage characteristic curve moves up and down while remaining substantially similar.

On the other hand, when applying the above arc to a welding power source with external characteristics (close to constant voltage characteristics) as shown in the figure, h
=ho, PNxh=h, +Δh, pL, h=h, -
At Δh, stable energization is performed at each intersection of P8, and a steady welding state is obtained. In other words, the operating point changes to PM*PL+Ps, etc. in response to a change in the distance between the workpiece 1 and the welding torch 2, and this change causes the current and 'α pressure to change. As is clear from the figure, h=
If h changes from ha to h=h (1+Δh, the current ■ becomes ■o
to ■o-Δ■, the voltage E changes from Eo to Eo+ΔE, and if h=h'o changes to ho-Δh, I
■. It can be seen that E changes to +ΔI and go to −ΔE, respectively. In this way, both I and E change due to a change in h, but as you can see from the figure, the change in I is much greater than the change in E, so the change in ■ can be used to determine the target for h. Value control has conventionally been carried out, and so-called arc sensors are based on this principle.

On the other hand, in the present invention, the arc impedance Za
The target value of h is controlled using the change in h.

That is, in FIG. 5, the curve shown by the broken line is the current/impedance characteristic curve corresponding to the current/voltage characteristic curve shown by the solid line, h=h, (1=1., E=Eo).
The operating point at PN2, the corresponding impedance 2& are Za=Za・o, and h=b, +Δh(r-t
, -ΔI.

The operating point at E=go+ΔE) is PL', and Za is za-O+ΔZa.

Furthermore, h=ho−Δh(r=Io+ΔI, E=E,
-ΔE) is expressed as PB' and Za=Za·0−ΔZa, respectively. Such impedance Z
Table 1 describes the characteristics when a is used as the h control input signal.

Table 1 shows the results of comparing the changes in I, E, and Za as h changes. As can be seen from the table, when h changes from ha to ho + Δh or hO - Δh, The impedance change rate Za/Za・0 is larger than either the current change rate T/Io or the voltage change rate g/Eo, which means that as an input signal for h control, it is better than E and than ■. It can be seen that 2& has a higher degree of discrimination, that is, by using Za as an input signal, it is possible to stabilize the control and improve accuracy.

Next, in order to stabilize droplet transfer (spraying), an A-wave current may be superimposed on the welding current. In such a case, regardless of whether current I, voltage E, or impedance Za is used as a control signal, the
Mother wave ratios are different. The situation is shown in Figure 6. FIG. 6 shows a case where the welding current ■ is composed of a base current ■0 and a /4′ current IP superimposed (r=rO+rp). Further, Table 2 shows the changes in the arc voltage E and impedance Za at this time and their rate of change.

As can be seen from Table 2, the current I is from 10 to I O + I P
, the operating value Po moves to Pp and the voltage E becomes E
. It changes from Eo+EP. Current change rate 1 in this case
/7roS Comparing the voltage change rate FAo and the impedance change rate Z a/Z a-o, Z a/2 a
- It turns out that 0 is closest to 1. In other words, if za is used as a control input signal, even if a sharp/less current is superimposed on the temporary current, the 0/20's ratio in the input signal will be smaller than when using other characteristic values. , it is possible to improve and stabilize control accuracy.

As is clear from the embodiments described above, the present invention provides input for two-axis control and Y-axis control regarding the distance hK between the welding torch and the workpiece in welding rope pit or automatic arc welding. Arc impedance Za as a signal
, welding current ■ or arc voltage E
(bigger signal discrimination ability and higher control than control)
If the welding current is superimposed with a 1000-degree current and stability is obtained, by adopting za as the control input signal, the A? The pulse wave ratio can be minimized, improving control stability. Also, existing automatic arc welding equipment or welding donkey? It can be installed on a kit with almost no modification or modification, and since the main parts are constructed using simple analog circuits, it can be implemented at low cost. Furthermore, it not only provides a powerful means of realizing labor savings through the automation and rosette of welding-related equipment, but also strengthens market competitiveness by improving the functionality of welding robots or automatic welding equipment and reducing costs. .

As described above, according to the present invention, by using the arc impedance obtained by dividing the arc voltage voltage by the welding current as a control input signal to control the position of the welding torch, noise interference is reduced and minute changes are avoided. It is possible to provide a high-accuracy, low-cost method and device for detecting welding traces that can reliably respond.

[Brief explanation of drawings]

Figure 1 shows an example of the current/voltage characteristics and the external characteristics of the welding power source in general consumable electrode constant-speed gas shielded arc welding, and Figure 2 shows the position of the welding torch using the characteristics in Figure 1. FIG. 3 is a circuit diagram showing a specific configuration example of an implementation for explaining the welding tracing detection method and device according to the present invention, and FIG. FIG. 3 is a diagram for explaining the effect when a pulsed current is superimposed on a current. DESCRIPTION OF SYMBOLS 1... Material to be welded, 2... Welding torch, 3m... Current number, 6... Low pass filter, 7... Comparison/discrimination circuit, 8... Threshold value setting circuit, 9...・Sir is an amplifier, 10-Z, 1O-Y-f-I MoJ, 11-Z, 1
1-Y=drive mechanism. Procedural Amendment July 25, 1939 Manabu Shiga, Director General of the Patent Office], Indication of Case, Patent Application No. 141313/1988 2, Title of Invention Method and Apparatus for Welding Trace Detection 3, Supplementary If Yo Case Relationship with Patent Applicant (620) Mitsubishi Heavy Industries, Ltd. 4, Successor Attorney 5, Voluntary Amendment 7. Contents of the Amendment (11 Correct "tcJ" in line 1 of page 11 of the specification to "c". (2) Figures 3(C) and 5 of the drawings will be corrected as shown in the attached sheet.

Claims (2)

[Claims] (1) In the welding trace detection method for automatic control of the distance between the welding torch and the workpiece in an automatic arc welding device or arc welding port 4C cut, and for automatic tracking control of the weld line, the impedance of the welding arc is detected. , which is used as an input signal for controlling the m-joint torch position for automatic control of the distance between the welding torch and the welded material and automatic tracking control of the welding line. (2) Welding tracing detection device d for automatic control of the distance between the welding torch and workpiece in automatic arc welding equipment or arc welding spout, and automatic follow-up control of the weld line.
A welding tracing detection device according to the invention, characterized in that it is equipped with an arithmetic circuit that outputs a welding current signal and an in≠≠guns signal as a manual signal for controlling the position of a welding torch.