JPS6234470B2 - - Google Patents

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 robot, which automatically controls the welding width of the welding torch using a control input signal obtained by an arc sensor method. The present invention relates to a welding profile detection device for automatic tracking control of welding groove width. When performing arc welding using an automatic arc welding device or a teaching/regeneration type arc welding robot, even if installation errors, dimensional errors, or deformation of the welded material occur during welding, the amount of variation can be detected. However, it is necessary to automatically correct it so that proper welding can be performed at all times. Conventionally, various methods have been proposed and put into practical use as methods for detecting the above-mentioned fluctuations associated with arc welding, but in particular, there is a method that detects changes in the electrical characteristic values of the welding arc and corrects them using the above-mentioned correction method. Also often used is a so-called "arc sensor" that is used as an input signal for 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 general consumable electrode constant-speed gas-shielded arc welding and an example of the external characteristics of a general welding power source. As shown in the figure, as the distance h between the workpiece 1 and the welding torch 2 changes up and down by ±Δh around h ₀ , the characteristic curves move up and down while remaining substantially similar. On the other hand, when the arc is loaded with a welding power source having external characteristics (close to constant voltage characteristics) as shown in the figure, when h=h ₀ , P _N ,
Stable current is applied at each intersection of P _L at h=h ₀ +Δh and P _S at h=h ₀ −Δh, and a steady welding state is obtained. That is, in response to changes in the distance h between the workpiece 1 and the welding torch 2, the operating point of the welding power source changes to P _N , P _L , P _S, etc., and the current and voltage change due to this change. . As is clear from the figure, when changing from h=h ₀ to h=h ₀ +Δh, the current I changes from I ₀ to I ₀ −ΔI, and the voltage E changes from E ₀ to E ₀ +ΔE
and from h=h ₀ to h=h ₀ −Δh
It can be seen that if it changes to I=I ₀ +ΔI and E=E ₀ −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 larger than the change in E, so in reality, the change in I is not used. Therefore, it becomes possible to control the target value of h, and a 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 by utilizing the phenomenon shown in FIG. FIG. 2a shows an example of automatic target value control of the distance h (ie, Z axis) between the workpiece 1 and the welding torch 2 during welding on a flat plate. In the same figure, b shows an example of automatic control of the target value of h during butt welding, and c shows an example of automatic control of the target value of h during fillet welding.
In Figures 2 a to c, ti is an input terminal to which current I or voltage E is applied, LPF is a low-pass filter,
COM is a comparison discriminator that compares and discriminates the output of the threshold setter SR and the output of the low-pass filter LPF;
SA is a servo amplifier, SM is a servo motor, and DM is a drive mechanism for the welding torch 2. This drive mechanism DM is located at the Z axis shown in the figure when the direction perpendicular to the plane of the paper is the X axis.
The welding torch 2 is driven in the axial and Y-axis directions. In the case of Figure 2a, only the Z axis is driven, but
In the case of b and c, not only the Z axis but also the Y axis changes h, so that it can be used for automatic control regarding both axes. That is, Fig. 2b,
In c, if the Y-axis is fixed, only the Z-axis can be controlled as in a. Next, if the Z axis is fixed, the Y
Since h changes due to changes in the axial direction, by operating the welding torch 2 in advance so as to vibrate (oscillate or weave) in the Y-axis direction and move it forward (in the X-axis direction), the change in the Y-axis direction can be adjusted. Detecting the accompanying change in h, comparing and discriminating the detected value with the corresponding electrical threshold value using the comparison discriminator COM, determining the weaving turning point, and repeating this process to proceed. This provides an automatic weld line tracking function. Next, in Figure 2 b and c, if both the Z-axis and Y-axis are to be controlled,
Perform Z-axis control on h near the center of the Y-axis, and
Axis control is similar to the above, with h at the end of the weaving in the Y-axis direction.
Both can be achieved by doing so. In this way, 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 I as shown in Figure 2. It has the disadvantages mentioned above. (1) 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 due to the change in I Stable comparative discrimination may be difficult for signals. (2) In order to make the droplet transfer into a stable spray transfer, a sharp pulse-like current may be superimposed on the welding current, and in such a case, the control input signal based on I also has a sharp pulse-like current. Since the waveforms are superimposed, the operation of the control circuit may become unstable. (3) When changing or modifying the welding current, it is necessary to reset the threshold value of the discrimination threshold setting device. The reasons for this are as follows. That is, by fixing the position of the welding torch in the Z-axis direction and moving it forward (in the X-axis direction) while weaving it in the Y-axis direction, changes in h due to changes in the position in the Y-axis direction can be detected. The detected value is compared with the corresponding electrical threshold value to determine the weaving turning point, and by repeating this process, the weaving width automatic control function and the welding groove width automatic Equipped with tracking function and automatic welding line tracking function.
Here, the case where these functions are provided will be described in detail with reference to FIGS. 3 and 4. Figure 3 shows an example of how the operating point changes when the reference current level _I0 in Figure 1 is changed to three levels, _I1 , _I2 , and _I3 . be. In other words, with h = h ₀ constant, the current I is
When changing I ₁ , I ₂ , I ₃ , in order to keep the arc length constant, the operating point of the welding power source must be set to P _1N , P _2N ,
In that case, by changing the external characteristics of the power source, for example, W ₁ , W ₂ , W _{3 ,} stable arc current flow can be achieved at each operating point. In this way, even if there is a change in the current I and a corresponding fluctuation in the operating point, h=
When changing from h ₀ to h = h ₀ + Δh or h = h ₀ - Δh, it operates on exactly the same principle as in Fig. 1, and for example, as shown in Fig. 3, W = W ₁ , h = h ₀ , I=I ₁ ,
When the operating point P = P _1N changes to h = h ₀ + Δh, P shifts to P _1L , I is smaller than I ₁ , and E becomes
E Slightly larger than ₁ . On the contrary, h=h ₀ −Δh
When it changes to , P becomes P _1S and I is larger than I ₁ ,
E becomes slightly smaller than _E1 . Similarly, W=
W ₂ , h=h ₀ , I=I ₂ , P=P _2N to h=h ₀ ±Δh
, W=W ₃ , h=h ₀ , I=I ₃ ,
It can be seen that when changing from P=P _3N to h=h ₀ ±Δh, the operating point P, current I, and voltage E all change. Figure 4 shows a case where the operating principle of Figure 3 is applied to provide automatic weaving width control, automatic welding groove width tracking function, and automatic welding line tracking function when performing butt welding and fillet welding. This is an example of the configuration of the equipment and an example of its operation. That is, Fig. 4 a shows an example of the equipment configuration during butt welding, b shows an example of the equipment configuration during fillet welding, and c shows the welding groove by automatic control of the weaving width in the Y-axis direction in a or b. An example of a functional configuration of an automatic width tracking device is shown. Here, the difference in Fig. 4c from Fig. 2c is that a left/right progression hold circuit HLD is provided between the comparison discriminator COM and the servo amplifier SA, and a servo motor speed setting device SR- is provided in the servo amplifier SA. This means that the setting value of 2 is added. Further, FIG. d shows an example of a change in current value during weaving of a welding torch, and an example of setting an electrical threshold value for determining a weaving turning point (current peak point). Therefore, in FIGS. 4a to 4d, by keeping the position of the welding torch 2 constant in the Z-axis direction and moving it while weaving in the Y-axis direction, the change in h as the position in the Y-axis direction changes. The change is detected by the change in current, the detected value is compared and discriminated against the corresponding electrical threshold value, the weaving turning point is determined, and this is repeated to proceed, thereby providing the control and functions described above. be able to. However, in the case of such a configuration, if the current I is changed to I ₁ , I ₂ , I _{3 ,} etc., as shown in FIG. 4d, the current peak point discrimination for determining the weaving turning point can be performed. The threshold value for use must also be changed to S ₁ , S ₂ , S ₃ , etc. Therefore, since the magnitude of the welding current is the factor that has the greatest influence on the welding result, consideration must be given to its adjustment to obtain as high precision as possible, and the magnitude of the welding current must be adjusted to be as accurate as possible. It must have a function that can be adjusted arbitrarily without distinction. However, in conjunction with this, it was necessary to reset the threshold value of the discrimination threshold setter with high accuracy, which was a drawback when applying this method. The present invention alleviates the above-mentioned drawbacks, provides a high-precision, low-cost arc sensor system that has little noise interference, can reliably respond to minute changes, and is always stable for any given welding current. It is an object of the present invention to provide a high-precision, low-cost welding trace detection device that can automatically obtain a comparative discrimination effect. Therefore, in order to achieve this purpose, the present invention
(1) "Arc conductance G" as a control signal
(2) Develop and introduce an "equalization amplifier circuit" for control signals.
The characteristics are as follows. (1) Detect and use the "arc conductance G" as a control signal. The arc conductance G changes the current I to the voltage E.
Since it is a characteristic value obtained by dividing by , the following characteristics can be mentioned when using this as a control input signal. The magnitude of the change rate of the arc characteristic value due to the change in the distance h between the welding torch and the welded material is E>I
>G, and if G is used as a control input signal, a larger rate of change can be obtained than in the conventional case of using I, which is effective in improving accuracy in comparison and discrimination and preventing malfunctions. When a pulsed current from the pulse generator built into the welding power source flows, the voltage changes along the arc load characteristic curve with the same sign as the current change, regardless of the external characteristics of the power source, so the conductance is Therefore, the noise interference caused by the sharp pulsed current is reduced accordingly, and the control accuracy can be improved. Since the conductance G is obtained by dividing the current I by the voltage E, the circuit configuration is easy and can be realized at low cost. (2) Develop and introduce an "equalization amplifier circuit" for control signals. In automatic welding width control, automatic welding groove width tracking, and automatic welding line tracking control based on the arc sensor method, the arc conductance level changes as the welding current value changes to an arbitrary level at any time. The EQUALIZER AMP circuit also uses an EQUALIZER AMP.
) was developed. By applying this circuit, it is no longer necessary to change the threshold value for peak value comparison discrimination every time the welding current level changes, and it is always stable and the same even if the welding current changes. The feature is that the weaving width of the pattern can be controlled. An embodiment of the present invention will be described below with reference to the drawings. An example of the block configuration of the welding tracing detection device according to the present invention is shown in FIG. 5, and a specific example of the circuit configuration for detecting arc conductance, which is the core of the present invention, is shown in FIG. An example of the configuration of the amplifier circuit is shown in FIG. Figure 5 shows the automatic welding width control and welding groove width automatic follow-up control mechanism using a welding current signal in butt welding or fillet welding using a general consumable electrode constant-rate feed gas shield welding method. This is an example of a block configuration in which an arc conductance detection circuit and a conductance signal equalization amplifier circuit according to the present invention are applied. Figure 5a shows an example of equipment configuration for butt welding, in which 1 is the material to be welded, 2 is the welding torch,
is the arc voltage, is the welding current, is the polarity of the welding power source, and Z and Y are the names of the drive shafts that can be set based on the welding torch. In this case, the Z-axis direction is fixed, and Y
In the axial direction, weaving is performed.
FIG. 5b shows an example of a configuration for fillet welding, and since each component thereof has the same function as those shown in FIG. 5a, a description thereof will be omitted. Next, FIG. 5c shows an arc conductance signal detection circuit and a conductance signal detection circuit based on the present invention for automatic welding width control and automatic welding groove width tracking control in the butt welding shown in FIG. 5a. This figure shows an example of a configuration using the equalizing amplifier circuit of FIG. In the figure, 1 and 2 are the same functional elements as the same reference numerals in a or b in the figure, 3a is a current input signal,
3b is an arc voltage input signal, 4 is a conductance calculation circuit, 5 is a conductance signal, 6 is a low-pass filter, 7 is a conductance signal, and 8 is an equalization amplifier circuit. Further, 9 is an equalization conductance output signal EQ/G of the equalization amplifier circuit 8, 10 is a comparison and discrimination circuit, 11 is a comparison and discrimination threshold setting circuit, 1
2 is a set threshold output signal S, 13 is a left/right progression discrimination and hold circuit, 14 is a servo amplifier, 15 is a servo amplifier input level setting (servo motor speed setting) circuit, 16 is a Y-axis drive servo motor, Reference numeral 17 indicates a Y-axis drive device. The structure related to fillet welding shown in FIG. 5b is also exactly the same as the structure related to butt welding described above. Next, FIG. 6 shows a specific example of the arc conductance detection section and the arithmetic circuit 4, which are the basis of the present invention, among the functional components shown in FIG. Figure 6a shows an example of a circuit configuration when calculating conductance from arc voltage and current using a divider and a division amplifier.
is a welding torch, 3a is a current input signal, 3b is an arc voltage input signal, 4 is a conductance calculation circuit,
5 is a conductance signal, and SH is a current shunt. The above conductance calculation circuit 4 is a variable resistor
VR-1, VR-2, operational amplifier OP-1, OP-
2. It is composed of a divider D, and the voltage input signal is inputted to the input terminal _tiE , and the current input signal is inputted to the input terminal _tiI . A common line COM is connected to the common terminal tic. Figure 6b shows an example of a circuit configuration when calculating conductance from arc voltage and current using a multiplier and an operational amplifier, where VR-1 and VR-2 are variable resistors, and OP-1 to OP-3. is an operational amplifier, and M is a multiplier. Figure 6c shows an example of a circuit configuration when calculating conductance from arc voltage and current using an operational amplifier and a transistor.
VR-1, VR-2 are variable resistors, OP-1, OP-
2, OP-4 to OP-7 are operational amplifiers, TR-1 to
TR-3 is a transistor. Next, FIG. 7 shows a specific example of an arc conductance signal equalization amplifier circuit, which is another basic part of the present invention among the functional components shown in FIG. 5.
FIG. 7a shows an example of a circuit configuration in which the conductance input signal G is calculated by a multiplier, a divider, and an operational amplifier and is output as an equalized conductance signal EQ.G. 8 and 9 have the same meanings as the same reference numerals in FIG. Furthermore, as detailed components of the equalization amplifier circuit 8, 8A is a linear amplifier, 8B is a divider D used as an element, 8C is a peak hold related to the output of the divider 8B, 8D is a multiplier M, and VR1 is an input level. The adjustment variable resistor, VR2, is a reference amplification setting variable resistor, and COM is a common base line. In FIG. 7b, the conductance input signal G is calculated by a multiplier M and an operational amplifier,
This shows an example of the circuit configuration when outputting as an equalized conductance signal EQ.G. In element 8B shown in the same figure, M1 is a multiplier, OP2 is an operational amplifier, and other elements are as shown in a in the same figure. Those with the same symbol as , mean the same element.
FIG. 7c is an example of a circuit configuration in which the conductance input signal G is operated by a multiplier M, an operational amplifier, and a transistor and is output as an equalized conductance signal EQ.G, and the elements shown in the figure are 8B, OP2 to OP4 are operational amplifiers, TR1 and TR2 are transistors, and other elements having the same symbols as a or b in the figure mean the same elements. Next, the operation of the welding trace detection device configured as described above will be described. First, the operation related to arc conductance detection will be explained. 1, 2, 3a, 3 in Figure 5 a, b, c
The conductance of the arc is detected as follows using the functional elements having the same symbols in FIGS. The conductance G of the arc can be defined as in equation (1). G=I/E...(1) [G: arc conductance (), I: current (A), E: arc voltage (V)] Therefore, in the arithmetic circuit shown in Figure 6a, division is The basic arithmetic function of device D is V ₀ ′=10・Z′/X′ ……(2) [V ₀ ′: Divider output (quotient), Z′: Divider input (dividend), X′ : Divider input (divisor)] The circuit is configured so that the I component is input to Z' and the E component is input to X', and G can be calculated as V ₀ '. -1, OP-2 are linear amplification or sign inversion, VR-1, VR-2 are I component and E
Acts as a component level regulator. Therefore, in Fig. 6a, when arc voltage E and arc current I in welding are applied to the respective input terminals, the levels of arc voltage E and arc current I are adjusted by variable resistors VR-1 and VR-2. and is input to operational amplifiers OP-1 and OP-2. The operational amplifiers OP-1 and OP-2 linearly amplify or invert the sign of the arc voltage E and arc current I and apply them to the divider D, where the calculation of V ₀ ′=10・Z′/X′ is performed. The conductance G is output as V ₀ '. In addition, in the arithmetic circuit shown in Fig. 6b, the basic arithmetic function of the multiplier M is V ₀ =1/10X・Y...(3) [V ₀ : Multiplier output (product), ), Y: multiplier input (multiplier)], insert this into the negative feedback circuit of the operational amplifier, compose the divider as a whole, and configure the circuit to calculate G=I/E. In the figure, OP-
1 to OP-3 are linear amplification or sign inversion, VR-
1. VR-2 acts as a level adjuster for I and E components. Therefore, when level-adjusted arc voltage E and arc current I are input to operational amplifiers OP-1 and OP-2 through signal paths similar to those shown in Figure 6a, these signals are linearly amplified or sign-inverted. The output of the operational amplifier OP-1 is applied to the input terminal X of the multiplier M, and the output of the operational amplifier OP-2 is applied to the input terminal Y of the multiplier M through the operational amplifier OP-3, where V ₀ = X・Y/10
The following calculations are performed. Then, the calculation result V ₀
By inserting G into the negative feedback circuit of operational amplifier OP-3, division is performed comprehensively, and the result is output as conductance G. Further, the arithmetic circuit shown in FIG. 6c is configured to calculate G=I/E using logarithmic conversion and anti-logarithmic conversion functions using operational amplifiers and transistors. G=I/E=e ^{(logeI-logeE)} ...(4) [e: base of natural logarithm] In the figure, OP-1, OP-2, OP-4 to OP-7 are linear amplification, sign inversion or is transistor TR-1~
Along with TR-3, logarithm/anti-logarithm conversion effect, VR-
1. VR-2 acts as a level adjuster for I and E components. Therefore, as in FIG. 6a, the arc voltage E and arc current I, linearly amplified or sign-inverted by the operational amplifiers OP-1 and OP-2, are applied to the operational amplifiers OP-4 and OP-5 and the transistors.
They are logarithmically converted and added by TR-1 and TR-2, and then only the negative signal is passed through to the operational amplifiers OP-6 and OP-7 and the transistor TR.
Dividing is performed comprehensively by performing anti-logarithmic transformation at -3, and the result is output as conductance G. Next, the operation when the conductance G as the characteristic value of the arc obtained by the arithmetic circuit in this manner is used as an input signal for controlling the distance h between the welding torch and the workpiece to be welded will be explained. FIG. 8 shows the current/voltage characteristics in general consumable electrode constant-speed gas-shielded arc welding and an example of the external characteristics of a general welding power source. As shown in the figure, as the distance h between the welding torch and the welded material changes up and down by Δh around h ₀ , the arc voltage characteristic curve moves up and down while remaining substantially similar.
On the other hand, when the arc is loaded by a welding power source having external characteristics (close to constant voltage characteristics) as shown in the figure, P _N is applied at h=h ₀ , P _L is applied at h=h ₀ +Δh, and h=h ₀ − At Δh, stable energization is performed at each intersection of P _S and a steady welding state is obtained. In other words, the operating points change as P _N , P _L , P
_S , etc., and this fluctuation causes current and voltage to fluctuate. As is clear from the figure, h=h ₀ to h=
If it changes to h ₀ +Δh, the current I changes from I ₀ to I ₀ −ΔI
If the voltage E changes from E ₀ to E ₀ +ΔE, and from h=h ₀ to h ₀ −Δh, then I becomes I ₀ +Δ
It can be seen that E changes to E ₀ -ΔE. 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 larger than the change in E, so the change in I can be used to set the target for h. Value control has conventionally been carried out, and so-called arc sensors are based on this principle. In contrast, in the present invention, the target value of h is controlled using changes in the conductance G of the arc. That is, in FIG. 8, the curve shown by the broken line is the current/conductance characteristic curve corresponding to the current/voltage characteristic curve shown by the solid line, and h
The operating point at =h ₀ (I=I ₀ , E=E ₀ ) is P _N ',
The corresponding conductance G is G=G ₀ and h=h ₀ +Δh (I=I ₀ −ΔI, E=E ₀ +ΔE)
_{The operating point at _ _ _} It represents. The characteristics when such conductance G is used as an h control input signal will be explained with reference to Table 1.

_[ Table] Table 1 shows the results of comparing the changes in I, _E , and G as h changes _. When it changes to Δh, the current change rate I/I ₀ or the voltage change rate E/E ₀
The rate of change in conductance G/G ₀ is larger than either of the two, and this means that G has a higher degree of discrimination as an input signal for h control than E and than I, that is, G is used as an input signal. By doing so,
It can be seen that it is possible to stabilize control and improve accuracy. Next, in order to stabilize droplet transfer (spraying), a pulsed current may be superimposed on the welding current. In such a case, the pulse wave ratio included in the input signal differs depending on which of the current I, voltage E, and conductance G is used as the control signal.
The situation is shown in Figure 9. Figure 9 shows welding current I
shows a case where the reference current I ₀ and the pulse current I _P are superimposed (I=I ₀ +I _P ). Further, Table 2 shows the changes in the arc voltage E and conductance G at this time and their rate of change.

[Table] As can be seen from Table 2, the current I varies from I ₀ to I ₀ + I _P
, the operating point P ₀ moves to P _P and the voltage E becomes
Changes from E ₀ to E ₀ +E _P. Comparing the current change rate I/I ₀ , voltage change rate E/E ₀ and conductance change rate G/G ₀ in this case, it is found that G/G ₀ is closest to 1. In other words, if G is used as a control input signal, even if a sharp pulse current is superimposed on the temporary current, the pulse ratio in the input signal will be smaller than when using other characteristic values, and the control accuracy will be improved. It is possible to improve and stabilize the Next, the equalization amplification effect of the arc conductance G will be described. First, the principle of equalization amplification will be explained with reference to FIG. Figure 10a shows an example of a conventional automatic gain control (AGC) circuit configuration, in which variable gain element VG, DC conversion
Its feature is that the functional elements of DC, comparator COM, and peak hold PH form a closed loop feedback circuit between the output and input, and it has a constant output leveling function and linearity maintenance for a wide range of input signal levels. There is a problem with this. On the other hand, FIG.
The functional elements of DC conversion DC, peak hold PH, and multiplier M form an open-loop arithmetic circuit, allowing highly accurate constant output levels for all levels within the allowable input/output range of divider D and multiplier M. It has the feature of being able to obtain functions and linearity. As described above, the equalizing amplifier circuit according to the present invention has a major feature in that the configuration, operating principle, and operation are fundamentally different from conventional automatic gain control circuits. FIG. 11 is a diagram for specifically explaining the operation of the equalization amplifier circuit according to the configuration of FIG. 7. 11th
Figure a is a conceptual diagram when the welding torch is advanced while weaving in the Y-axis direction during butt welding, and the configuration is exactly the same for fillet welding. 7b shows the input signal 7 shown in FIG. 7 (common to a, b, and c), that is, the arc conductance signal G. As shown in the figure, as the welding torch 2 moves in the Y-axis, It can be seen that the conductance increases compared to the vicinity. In the figure, G ₁ , G ₂ , and G ₃ represent conductance changes that occur when the welding current level is changed. FIG. 11c shows the output of VR2 in the equalization amplifier circuit 8 shown in FIG. 7, that is, the basic amplification signal, which is a constant a. d in the figure shows the output signal of element 8B (divider) shown in FIG. 7, that is, the inverse conductance signal a/G obtained by dividing the constant a shown _in c by the conductance signal _; It is changing in response to the change in G ₃ . Figure 11e is the seventh
The output signal of the peak hold 8C shown in the figure, ie, the peak hold (a/G) _PEAK of the inverse conductance signal a/G shown in d, changes in response to changes in G ₁ , G ₂ , and G ₃ . _The figure f shows _the output of the multiplier 8D shown in Fig. ₇ , that is, the equalized conductance signal EQ _.
The output level remains constant regardless of changes in . Although the basic operation has been explained above, the conductance calculation circuit 4 to the low pass filter 6
As shown in FIG. 7a, the conductance signal 7 obtained through It is input to the divider 8B, and here the basic calculation is performed as V ₀ =Z'/X' based on the setting value of the variable resistor VR-2 for setting the reference amplification level to obtain the reverse conductance signal. . This inverse conductance signal and the signal from the peak hold 8C that holds the peak value of the conductance signal from the linear amplifier 8A are added to the multiplier 8D, where the basic calculation is performed as V ₀ =X・Y, etc. It is output as a conductance signal 9 and sent to a comparison/discrimination circuit 10.
The threshold signal 12 from the threshold setting circuit 11 is
It is compared and discriminated. The above explanation of the action is about Fig. 7a, but
The cases in Fig. 7b and c are basically the same, and the only difference is the specific circuit configuration for performing the division function of the divider 8B, and the same point is obtained in that the inverse conductance signal is obtained. The explanation will be omitted. As can be seen from the above explanation, due to the effect of the equalization amplifier circuit according to the present invention, even if the conductance level of the arc changes due to changes in the welding current level,
This is extremely effective in equalizing this to a constant output level and simplifying and increasing the accuracy of the subsequent comparison and discrimination circuit configuration and its functions. In addition, FIG. 7 a, b, and c are element 8B in the figure.
The detailed effects differ depending on the configuration of the divider. That is, in Figure a, a divider D is applied as element 8B, and an inverse conductance signal a/G is obtained by its basic arithmetic function V ₀ =Z'/X'. b is element 8B and multiplier M1 (basic arithmetic function V ₀
=X.Y) is inserted into the negative feedback circuit of the operational amplifier OP2, thereby obtaining a comprehensive inverse conductance signal a/G. c is element 8B, which performs logarithmic conversion using an operational amplifier and a transistor.
The inverse conductance signal a/G is obtained comprehensively by using the inverse logarithmic transformation function. As is clear from the above-mentioned embodiments, in the present invention, Z regarding the distance h between the welding torch and the workpiece in welding robot or automatic arc welding is
Since the arc conductance G is used as the input signal for axis control and Y-axis control,
Compared to control using welding current I or arc voltage E, signal discrimination ability is large, and high control accuracy and stability can be obtained. By employing it as an input signal, the pulse wave ratio in the signal can be minimized, improving control stability. In addition, by applying a conductance equalization amplifier circuit, welding current can be controlled in automatic welding width control, automatic welding groove width tracking, and automatic welding line tracking control based on the arc sensor method in welding robots or automatic arc welding equipment. Even if the arc conductance level changes by changing to an arbitrary level at any time, it is possible to convert it to a constant output level with high accuracy, simplifying the configuration and function of the subsequent comparison/discrimination circuit. It is extremely effective for increasing precision. Furthermore, not only can it be easily added to existing welding robots or automatic arc welding equipment, but the main parts are composed of simple analog circuits, so it can be realized at low cost, and labor savings can be achieved through automation and robotization of welding-related equipment. Moreover, it has the advantage of strengthening the market competitiveness by improving the functionality and reducing costs of welding robots or automatic welding equipment. As described above, according to the present invention, the conductance of the welding arc is detected and used as a control input signal for controlling the position of the welding torch, and even if the level of the conductance signal changes to an arbitrary level at any time, the output remains unchanged. Since a conductance signal equalization amplifier circuit that can always maintain a constant level is provided, it is possible to create a high-precision, low-cost arc sensor system that generates little noise interference and can reliably respond to minute changes, while also being able to adapt to any welding current. It is possible to provide a highly accurate, low-cost welding trace detection device that can always automatically obtain a stable comparative discrimination effect.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the current/voltage characteristics and external characteristics of the welding power source in general consumable electrode constant-rate gas shielded arc welding, and Figure 2 is a diagram showing the position control of the welding torch using the characteristics in Figure 1. Figure 3 is a diagram for explaining an example of how the operating point changes when the current level is changed in three stages instead of the reference current level in Figure 1. Configuration example and operation of equipment when equipped with automatic weaving width control, welding groove width automatic tracking function, and welding line automatic tracking function when performing butt welding and fillet welding by applying the operating principle shown in Figure 3 FIG. 5 is a configuration explanatory diagram showing an embodiment of the welding tracing detection device according to the present invention, and FIG. 6 is a circuit diagram showing a specific configuration example for detecting arc conductance in the same embodiment. 7 is a diagram showing a specific configuration example of the arc conductance signal equalization amplifier circuit in the same embodiment, and FIG. 8 is a diagram showing the current corresponding to the current/voltage characteristic curve for explaining the operation of the same embodiment.・Conductance characteristic curve diagram, Figure 9 is a diagram to explain the effect when a pulsed current is superimposed on the welding current, Figure 10 is a diagram to explain the operating principle of the arc conductance signal equalization amplifier circuit, Figure 11 7 is a diagram for explaining a specific operation of the conductance signal equalization amplifier circuit shown in FIG. 7. FIG. 1... Material to be welded, 2... Welding torch, 3a...
Current input signal, 3b... Voltage input signal, 4... Conductance calculation circuit, 5, 7... Conductance signal, 6... Low pass filter, 8... Equalization amplifier circuit, 9... Equalization conductance output signal, 1
0...Comparison discrimination circuit, 11...Threshold value setting circuit, 12...Threshold output signal, 13...Left and right progression discrimination and hold circuit, 14...Servo amplifier, 15...Level setting device for servo amplifier , 16
...Y-axis drive servo motor, 17...Y-axis drive device.

Claims (1)

[Claims] 1. A comparison discriminator to which a welding current signal or a welding voltage signal is input and compares and discriminates it with a threshold value set in a threshold value setting device, a left/right progression hold circuit that holds the output that has been compared and discriminated by this comparison discriminator, and this The arc is equipped with a servo motor that responds to the deviation between the output of the left and right advancement hold circuit and the speed setting value set in the servo motor speed setting device, and a shaft drive mechanism that is driven by this servo motor and operates the welding torch while weaving. In a welding profile detection device for automatic welding width control and automatic welding groove width tracking control using control input signals obtained by a sensor method, welding current signals and arc a conductance calculation circuit that calculates the conductance of the welding arc by inputting a voltage signal; and an input level adjustment variable resistor that adjusts the input level of the conductance signal output from the conductance calculation circuit;
A linear amplifier that linearly amplifies the output of this variable resistor, a divider that calculates inverse conductance based on the output of this linear amplifier and the setting value of the variable resistor for setting the reference amplification level, and a peak of the output of the linear amplifier. It consists of a peak hold that holds a value and a multiplier that calculates an equalized conductance based on the output of this peak hold and the output of the divider, and the equalized conductance signal obtained from the conductance signal is transmitted to the welding torch. and an equalizing amplifier circuit that outputs as an input signal to the comparison discriminator necessary for determining a welding torch weaving end turning point for automatic weaving width control and automatic follow-up control of welding groove width. Welding tracing detection device.