JPS6234468B2 - - Google Patents

Description

Detailed Description of the Invention The present invention uses a consumable electrode constant-rate feed type automatic arc welding device or a consumable electrode constant-rate feed type arc welding robot to automatically control welding weaving width by an arc sensor method based on a welding current signal. The present invention relates to a welding trace detection device for automatic welding groove width tracking control.

When performing arc welding using an automatic arc welding device or a teaching/regeneration type arc welding robot, even if there is an installation error in the workpiece or deformation during welding, these fluctuations are detected and automatic It is necessary to make corrections to ensure proper welding at all times. In the past, various methods have been proposed and put into practical use as methods for detecting the above-mentioned fluctuations associated with arc welding, but among them, there is a method that detects changes in the electrical characteristic values of the welding arc and uses them for the above-mentioned correction. A so-called "arc sensor" that is used as an input signal is also often used.

Here, the operating principle of arc sensors mainly used at present 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 by a welding power source with 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, the operating point of the welding power source changes to P _N , P _L , P _S , etc. in response to a change in the distance h between the workpiece 1 and the welding torch 2, and this change causes the current and voltage to fluctuate. . As is clear from the figure, if we change from h=h ₀ to h=h ₀ +Δh,
The current I is from I ₀ to I ₀ −ΔI, and the voltage E is from E ₀ to E ₀ +
ΔE, and h=h ₀ to h=h ₀ −
It can be seen that if it changes to Δh, it changes to I=I ₀ +ΔI and E=E ₀ −ΔE, respectively. In this way, both I and E change as h changes, but
As you can see from the figure, the change in I is much more significant than the change in E, so in reality, using the change in I,
This makes it possible to control the target value of h, and so-called arc sensors utilize 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 arc voltage E is applied, LPF is a low-pass filter, and COM is a comparison judgment for comparing and judging 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,
DM is the drive mechanism of welding torch 2, and this drive mechanism
The DM drives the welding torch 2 in the Z-axis and Y-axis directions shown when the X-axis is perpendicular to the paper surface. In the case of Figure 2 a, only the Z axis is driven, but in the cases of b and c, h changes not only in response to changes in the Z axis but also in the Y axis, so it is used for automatic control related to both axes. I have made it possible. That is, in FIGS. 2b and 2c, if the Y-axis is fixed, only the Z-axis can be controlled as in a. Next, if the Z-axis is fixed, h will change depending on the change in the Y-axis direction, so operate the welding torch 2 in advance by vibrating (oscillating or weaving) in the Y-axis direction and moving it forward (in the X-axis direction). By doing so, Y
Detect the change in h due to the change in the axial direction, compare and discriminate the detected value with the corresponding electrical threshold value using the comparison discriminator COM, determine the weaving turning point, and repeat this process. By automatically following the welding line, the welding line can be automatically followed. Next, in Fig. 2b and c, if both the Z-axis and Y-axis are to be controlled, the Z-axis control is performed on h near the center of the Y-axis, and the Y-axis control is performed on the Y axis as described above.
Both can be achieved by performing the process on the axial weaving end h.

In this way, by skillfully utilizing the phenomenon shown in Fig. 1, it is possible to control the position of the welding torch while detecting changes in the current I as shown in Fig. 2. Among the control methods, by fixing the position in the Z-axis direction and operating the welding torch so as to move it forward (in the X-axis direction) while weaving in the Y-axis direction, h changes as the position in the Y-axis direction changes. is detected, the detected value is compared and discriminated by the corresponding electric threshold value by the comparison discriminator COM, the weaving turning point is determined, and by repeating this process, automatic weaving width control is performed. A case in which the function, welding groove width automatic tracing function, and welding line automatic tracing function are provided will be described in detail.

FIG. 3 explains an example of how the operating point changes when the reference current level I ₀ in FIG. 1 is changed to three levels of current levels I ₁ , I ₂ , and I ₃ . It is something. In other words, when h = h ₀ is constant and the current I is varied as I ₁ , I ₂ , I ₃ , the operating point must be moved to P _1N , P _2N , P _3N in order to keep the arc length constant. In such a case, by changing the external characteristics of the power source, for example, w ₁ , w ₂ , w ₃ , stable arc energization 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=h ₀
When changing from h=h ₀ +Δh or h=h ₀ −Δh, W=W ₁ , h=h ₀ , I= When the state of I ₁ and the operating point P=P _1N changes to h=h ₀ +Δh, P shifts to P _1L , I becomes smaller than I ₁ , and E becomes slightly larger than E ₁ . On the other hand, when h = h ₀ - Δh, P becomes P _1S , I is greater than I ₁ , and E becomes
E Slightly smaller than ₁ . Similarly, W=W ₂ , h
When changing from = h ₀ , I = I ₂ , P = P _2N to h = h ₀ ±Δh, also W = W ₃ , h = h ₀ , I = I ₃ , P =
It can be seen that when changing from P _3N to h=h ₀ ±Δh, the operating point P, current I, and voltage E all change.

Fig. 4 shows an operation in which the welding torch 1 is kept at a constant position in the Z-axis direction during butt welding and fillet welding, and moved while weaving in the Y-axis direction, applying the operating principle shown in Fig. 3. By doing this, the change in h due to the change in position in the Y-axis direction is detected by the change in current, and the detected value and the corresponding electrical threshold are discriminated by the comparison discriminator COM and the weaving is turned back. This is an example of the configuration and operation of equipment in the case where automatic weaving width control, automatic welding groove width tracking function, and automatic welding line tracking function are provided by determining a point and repeating this process. . In other words, Fig. 4a shows an example of the equipment configuration for butt welding, b shows an example of the equipment configuration for fillet welding, and c shows an automatic welding groove width tracking device by automatic control of the weaving width in the Y-axis direction in a or b. Functional configuration example, d
1 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).

In Fig. 4c, ti is an input terminal into which a current signal is input, LPF is a low-pass filter, and COM is a peak value discrimination device that compares and discriminates the output of the peak value discrimination threshold setter SR and the output of the low-pass filter LPF. HD is left/right progression discrimination/hold circuit, SA
DM is a servo amplifier that compares and amplifies this left/right progression discrimination/hold circuit and the output of the servo motor speed setter SMR, and DM is a drive mechanism that drives the welding torch 2 along the Y axis using the output.

As can be seen from FIG. 4, if the current I is changed to I ₁ , I ₂ , I _{3 ,} etc., the current peak point discrimination threshold for determining the weaving turning point also changes to S ₁ , S ₂ , S ₃ , etc. Since the magnitude of the welding current is the factor that has the greatest influence on the welding result, consideration has been given to adjusting it to obtain as high precision as possible, and a function that allows arbitrary adjustment without distinction after welding has started is also provided. However, in conjunction with this, it is necessary to reset the discrimination threshold with high accuracy, which is a drawback when applying this method.

The present invention alleviates these drawbacks and provides a high-precision, low-cost welding trace detection device that can automatically obtain a stable comparison and discrimination effect even with any change in welding current level. It is an object.

In order to achieve the above object, the present invention provides a welding tracing detection device for automatic welding width control, automatic welding groove width tracking, and automatic welding line tracking control based on an arc sensor method based on a welding current signal. Even if the welding current value changes to an arbitrary level at any time, an equalization amplifier circuit is provided that can always obtain a constant level current pattern, and a current peak value comparison discriminator is used to determine the turning point at the weaving end. By using the input signal as the input signal, it is possible to always stably control the weaving width in the same pattern even if the welding current changes.

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

FIG. 5 shows an example of the block configuration of the welding tracing detection device according to the present invention, and FIG. 6 shows a specific example of the configuration of the current signal equalization amplifier circuit.

Figure 5 shows the functions of automatic welding width control and automatic follow-up control of welding groove width 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 when a current signal equalization amplifier circuit according to the present invention is applied. Figure 5a shows an example of equipment configuration for butt welding, and in the figure,
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, Z,
Y indicates the name of the drive shaft that can be set with the welding torch as a reference, and in this case represents a situation in which the Z-axis direction is fixed and the Y-axis direction is woven. Figure 5b
1 shows an example of a configuration for fillet welding, and each component thereof has the same function as those in FIG. Next, Fig. 5c shows the automatic welding width control and the automatic welding groove width tracking control using the welding current signal in the butt welding shown in Fig. 5a, and the current signal equalization amplifier circuit based on the present invention. An example of a configuration is shown in which 1 and 2 are applied.
are the same functional elements as the same reference numerals in a or b in the figure, 3 is an input terminal to which the current input signal I is applied, 4 is a low-pass filter, 5 is the current signal I, 6 is an equalization amplifier circuit, and 7 is an equalization current Output signal EQ.I, 8 is a comparison and discrimination circuit, 9 is a comparison and discrimination threshold setting circuit, 10 is a set threshold output signal, 11 is a right/left progression discrimination and hold circuit, 12 is a servo amplifier, 1
3 is a servo amplifier input level setting (servo motor speed setting) circuit, 14 is a Y-axis drive servo motor, and 15 is a Y-axis drive device. In addition,
The structure related to fillet welding in FIG. 5b is completely the same as the structure related to the above-mentioned butt welding.

Next, FIG. 6 shows a specific example of a current signal equalization amplifier circuit which is the basis of the present invention among the functional components shown in FIG. Figure 6a shows the current input signal I
is calculated by a multiplier, a divider, and an operational amplifier, and is output as an equalized current signal EQ.I. In the figure, 5, 6, and 7 are the fifth
These are the same as those with the same reference numerals in the figure. The current signal equalization amplifier circuit 6 includes a linear amplifier 6A as its detailed constituent elements, a divider D as an arithmetic element 6B,
A peak hold 6C related to the output of the divider 6B, a multiplier M as an arithmetic element 6D, a variable resistor VR1 for adjusting the input level, and a variable resistor VR for setting the reference amplification level.
2. Consists of a common baseline COM. FIG. 6b is an example of a circuit configuration in which the current input signal I is operated by a multiplier M and an operational amplifier and outputted as an equalized current signal EQ.I.
B is composed of a multiplier M1 and an operational amplifier OP2, and other elements having the same reference numerals as a in the figure are the same elements. FIG. 6c is an example of a circuit configuration in which the current input signal I is operated by a multiplier M, an operational amplifier, and a transistor and outputted as an equalized current signal EQ.I. It is composed of amplifiers OP2 to OP4 and transistors TR1 and TR2, and other elements having the same reference numerals as a or b in the figure are the same elements.

Next, the operation of the welding trace detection device configured as described above will be described.

Since the general operation related to the functional configuration shown in FIG. 5 is recognized to be publicly known, the equalization amplification operation related to the configuration shown in FIG. 6, which is the center of the present invention, will be explained here.

First, the principle of equalization amplification will be explained with reference to FIG. FIG. 7a shows an example of a conventional automatic gain control (AGC) circuit configuration, in which a variable gain element VG, a DC converter RE,
Its feature is that the functional elements of the comparator COM and peak hold PH form a closed loop feedback circuit between the output and input, but it is difficult to maintain constant output leveling and linearity over a wide range of input signal levels. There is. On the other hand, Figure b shows the principle of equalization amplification according to the present invention, in which the functional elements of divider D, DC converter RE, peak hold PH, and multiplier M constitute an open-loop arithmetic circuit. By doing so, it is possible to obtain a highly accurate constant output leveling function and linearity for all levels within the allowable input/output range of the divider D and multiplier M. As described above, it should be noted that the equalization amplifier circuit according to the present invention is fundamentally different in configuration, operating principle, and operation from conventional automatic gain control circuits.

FIG. 8 is a concrete explanatory diagram of the equalization amplification effect according to the configuration of FIG. 6. FIG. 8a is a conceptual diagram when the welding torch progresses while weaving in the Y-axis direction during butt welding, and fillet welding also has exactly the same relative configuration. 6b shows the input signal, that is, the current signal I5 in FIG. 6 (common to a, b, and c), and as shown in the figure, the Y
As the shaft weaves, the current increases at the weaving ends compared to near the center. In the figure, I ₁ , I ₂ , and I ₃ represent the situation when the welding current level is changed. FIG. 8c shows the VR2 output of FIG. 6, that is, the basic amplification signal, which is a constant a. d in the same figure is the 6th
The reverse current signal a/I obtained by dividing the output signal of the figure (calculation element 6B), that is, the constant a shown in c, by the current signal is shown, and changes in response to changes in I ₁ , I ₂ , and I ₃ . Figure 8e is the peak hold 6c in Figure 6.
output signal, i.e., the reverse current signal a/I shown in d
peak, and changes in response to changes in I ₁ , I ₂ , and I ₃ . In the same figure, f is the calculation element 6D (multiplier) in Figure 6.
output, that is, the equalized current signal EQ.I=I・(a/
I) peak, and the output level remains constant regardless of changes in I ₁ , I ₂ , and I ₃ . Although the basic operation has been explained above, the current signal 5 that has passed through the low-pass filter 4 is level-adjusted by the input level adjustment variable resistor VR-1 that constitutes the equalization amplifier circuit 6, and then linearly amplified by the linear amplifier 6A. Alternatively, the sign is inverted and input to the divider 6B, where it is combined with the signal from the reference amplification setting resistor VR-2 and as a basic calculation, V ₃ '=
A reverse current signal is obtained by calculating Z'/X'. The peak value of this reverse current signal is obtained by a peak hold 6C, and this peak value and the current signal from the linear amplifier 6A are added to a multiplier 6D, where the basic calculation is V ₀ =X・Y. is outputted as an equalized current signal 7, which is compared and discriminated with a threshold signal 10 from a threshold setting circuit 9 in a comparison/discrimination circuit 8.

The above explanation of the action is regarding Fig. 6a, but
The cases in Fig. 6b and c are basically the same, and the only difference is the specific circuit configuration for performing the division function of the divider 6B, but the point of obtaining the reverse current signal is the same, so we will not discuss them here. The explanation will be omitted. As can be seen from the above explanation, even if the welding current level fluctuates, the equalizing amplifier circuit according to the present invention equalizes it to a constant output level, simplifying the subsequent comparison/discrimination circuit configuration and its function. This is extremely effective for increasing precision.

Note that the detailed operations in FIGS. 6a, b, and c differ due to the difference in the configuration of the arithmetic element 6B. That is, in Figure a, a divider D is applied as 6B, and a reverse current signal a/I is obtained by its basic arithmetic function V ₀ =Z'/X'. b is 6B, and the circuit configuration is such that a 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 reverse current signal a/I. c is 6B, and a reverse current signal a/I is obtained comprehensively by using logarithmic conversion and anti-logarithmic conversion functions by an operational amplifier and a transistor.

As is clear from the above embodiments, the present invention uses a welding robot or an automatic arc welding device to automatically control welding width, automatically track welding groove width, and weld line based on an arc sensor method based on a welding current signal. In a welding tracing detection device for performing automatic follow-up control, an equalizing amplifier circuit is used that always outputs an equalized current signal at a constant level even if the welding current is input and its level changes to an arbitrary level at any time. By providing the equalized current signal as an input signal to the comparator and discriminator necessary for determining the weaving end turning point, it is extremely effective in simplifying and increasing the accuracy of the subsequent comparator and discriminator circuit configuration and its function. In addition, it can be easily added to existing welding robots or automatic arc welding equipment, and since the main parts are composed of simple analog circuits, it can be realized at low cost. Furthermore, it not only provides useful clues for realizing labor savings through automation and robotization of welding-related equipment, but also strengthens market competitiveness by improving the functionality and reducing costs of welding robots or automatic welding equipment.

As described above, according to the present invention, a current signal pattern of a constant level is always obtained even with any change in the level of welding current, and this is used as the current peak for determining the turning point of the weaving end. Since the input signal is used as an input signal to the value comparison discriminator, a stable comparison and discrimination effect can be automatically obtained at all times, and a high-precision, low-cost welding profile detection device can be provided.

[Brief explanation of the drawing]

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. 3 is an explanatory diagram showing an example of a change in the operating point when the reference current vector in FIG. 1 is changed to three levels of current. Figure 4 is an explanatory diagram of an example of the configuration and operation of the equipment when performing butt welding and fillet welding by applying the operating principle of Figure 3, and Figure 5 is an implementation of the welding tracing detection device according to the present invention. A configuration diagram showing an example, FIG. 6 is a specific configuration diagram of the current signal equalization amplification circuit in the same example, FIG. 7 is a diagram explaining the principle of equalization amplification action, and FIG. FIG. 3 is a diagram for specifically explaining such an equalization amplification effect. DESCRIPTION OF SYMBOLS 1... Material to be welded, 2... Welding torch, 3... Input terminal, 4... Low pass filter, 5... Current signal, 6... Equalization amplifier circuit, 7... Equalized current output signal, 8... ...Comparison discrimination circuit, 9...Threshold setting circuit for comparison and discrimination, 10...Threshold output signal, 11
. . . Left/right progression discrimination/hold circuit, 12 . . . Servo amplifier, 13 . . . Input level setting circuit for servo amplifier, 14 .

Claims (1)

[Claims] 1. A comparison discriminator to which a welding current signal is input and compares and discriminates it with the threshold value set in the threshold setting device, a left/right progression discrimination/hold circuit that holds the output that has been compared and discriminated by this comparison/discriminator, and this left/right progression discrimination/hold circuit. The arc is equipped with a servo motor that responds to the deviation between the output of the discrimination/hold circuit and the speed setting value set on the servo motor speed setting device, and a shaft drive mechanism that is driven by this servo motor and moves the welding torch while weaving. In a welding tracing detection device that performs welding weaving width automatic control and welding groove width automatic follow-up control using a sensor method, an input level adjustment variable resistor for adjusting the input level of the welding current signal is provided on the input side of the comparison discriminator. , a linear amplifier that linearly amplifies the output of this variable resistor, a divider that calculates a reverse current signal based on the output of this linear amplifier and the setting value of the variable resistor for setting the reference amplification level, and the output of the linear amplifier. and a multiplier that calculates an equalized current signal based on the output of the peak hold and the output of the divider, and calculates the equalized current signal obtained from the reverse current signal. A current signal equalization amplifier circuit is provided to output as an input signal to the comparison discriminator necessary for determining a welding torch weaving end turning point for the welding torch weaving width automatic control and the welding groove width automatic follow-up control. 1. A tracing detection device for welding, characterized in that an equalized current signal at a constant output level can always be obtained even when the welding current level changes.