JPH0687077A - Weld line profile controller - Google Patents

Abstract

PURPOSE:To provide the weld line profile controller having satisfactory followability even under conditions of a low arc stability. CONSTITUTION:When arc running out is generated, the quantity of electricity corresponding to an arc of a welding torch is changed greatly as compared with that at the time of steady welding. This invention is characterized by paying attention to this point and constitutes a characteristic feature that the quantity of electricity corresponding to the arc of the welding torch is obtained by a Y-axis integrator 26, the deviation (output of an amplifier 33) with the output of a reference value setting device 25 is monitored and the deviation exceeds a predetermined value DELTAI. by which the relative corrective movement of a weld line and the welding torch is restricted by a limiter circuit 35. Even if arc running out is generated, the deviation by this is invalidated, hence the weld line profile controller having satisfactory followability can be provided even under the conditions of low arc stability.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for butt welding with a groove, fillet welding, etc., and in particular, the arc current or voltage flowing in the welding torch, that is, The present invention relates to a welding line tracing control device that detects the amount of electricity corresponding to an arc and controls the position of the welding torch. 2. Description of the Related Art It is already known to detect an arc current flowing in a welding torch and follow the position of the welding torch so as not to deviate from a predetermined welding line. One specific method is to compare the detected value of the arc current with a predetermined fixed amount of reference value and control the position of the welding torch based on the result. If the welding torch weaves, for example, the detected value of the arc current at the center of the weaving pattern is compared with a certain reference value corresponding thereto, and the position of the welding torch is controlled based on the result. It's a way. Another concrete method focuses on the weaving of the welding torch, and compares the detected values of the arc current at both ends of the weaving pattern with one another as a reference amount, and controls based on this result. It is a method. For example, if the course of the welding torch deviates to the right side (left side) of the welding line along the groove, the right side (left end) in the weaving pattern.
This phenomenon utilizes a phenomenon that the arc current of the above becomes larger than that of the other end. FIG. 1 and FIG. 2 are characteristic diagrams of a conventional control system that corrects the positional deviation of the welding torch based on the detection of the amount of electricity with respect to the movement path of the welding torch preset to follow the welding line. is there. This figure shows the case where the arc current of the welding torch is used as the quantity of electricity corresponding to the arc of the welding torch. In these figures, the horizontal axis ΔI is the deviation, for example, the difference between the detected value of the arc current and a predetermined fixed amount of reference value, or the detected value of the arc current at the center of the weaving pattern and its reference value. Or the mutual difference with the arc current detection values at both ends of the weaving pattern. These differences may be differences in values or ratios. The vertical axis X is the correction amount of the welding torch. In the case shown in FIG. 1, the deviation ΔI is ΔI 0
Alternatively, the welding torch is modified only when -ΔI0 is exceeded. In this case, the correction amount X is always a constant amount a. In something like this,
The band between the deviation ΔI0 and the deviation −ΔI0 in which the correction amount X is zero is generally called a dead zone. The one shown in FIG.
A predetermined correction is made in proportion to the deviation ΔI. In this figure, the slope G0 of the characteristic line can be arbitrarily determined depending on the nature of the control system. By the way, the use of carbon dioxide gas as the shield gas is inexpensive and is in great demand. However, there is a drawback that arc breakage easily occurs. This is especially because the welding current is 2
This is remarkable under conditions where the arc stability is low, such as 00 [A] or less, or 300 [A] or more. Therefore, let us consider a case where the welding torch is controlled by the control system shown in FIG. 1 or 2 under such a condition that arc breakage easily occurs. First, consider the control system shown in FIG. FIGS. 3, 4, and 5 are explanatory diagrams for this purpose. FIG. 3 shows a weaving waveform, FIG. 4 shows a welding current, and FIG. 5 shows a locus of the weaving center position of the welding torch. The time axis t is the same in each figure. In FIG. 5, the time axis t can be regarded as the welding line WL. Figure 4
In the figure, it is shown that arc breakage occurs at times t1, t2, t3, t4 and t5. Further, in this case, the welding line WL of the workpiece and the weaving center position without correction were set in advance. However, as shown in FIG. 5, the control system judges that the deviation ΔI has occurred each time an arc break occurs, and a1, a2, a3
A correction amount such as is added to the welding torch. It will be apparent from the above description and FIGS. 3, 4 and 5 that this modification is unnecessary. This phenomenon is shown in Figure 1.
Even when a control system having the characteristics shown in is used, the correction amount a
The same applies except that 1, a2 and a3 are constant amounts a. Under welding conditions with low arc stability, arc breakage occurs at unsteady times. When this phenomenon occurs,
The conventional control system corrects the relative position between the welding torch and the welding line due to the change in the amount of electricity due to this, although the welding torch is not displaced from the welding line. Therefore, under the condition that such arc breakage occurs frequently, especially when this condition continues for a long time, the welding torch largely deviates from the welding line WL, and in the worst case, it completely deviates, and the welding line WL follows. May become difficult. As is clear from FIG. 4, when the arc breaks, the electric quantity with respect to the arc length of the welding torch changes greatly compared to that during steady state. Therefore, particularly when a control system that outputs a predetermined correction amount X proportional to the deviation ΔI as shown in FIG. 2 is used, the welding torch and the welding line WL are largely corrected, and therefore the welding line WL is welded. The percentage that the torch comes off is considerably higher. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to copy a welding line having good followability even under conditions where the arc stability is low. To get the controller. As described above, when an arc break occurs, the amount of electricity corresponding to the arc of the welding torch greatly changes compared to that during steady welding. The present invention has been made by paying attention to this point, and is characterized by a movement control means for relatively moving and controlling a welding torch and a workpiece along a welding line, and welding power to the welding torch. For detecting the arc current supplied to the welding torch from the power supply means and supplying a predetermined correction amount corresponding to a deviation between the detected current and a predetermined reference amount to the movement control. In a welding line tracing control device having a correction control means for correcting the position of the welding torch applied to the means, a control means for limiting the correction amount when the deviation exceeds a predetermined value is provided. is there. The correction control means detects the arc current of the welding torch and applies the deviation from the predetermined reference amount to the movement control means as a correction amount. The movement control means controls the movement of the welding torch and the work relative to each other along the welding line while correcting the position of the welding torch based on the correction amount from the correction control means. When the correction amount exceeds the predetermined value, the relative correction movement between the welding line and the welding torch is restricted. An embodiment of the present invention will be described below with reference to the drawings. FIG. 7 is an overall view of an automatic welding apparatus embodying the present invention. Reference numeral 1 denotes a control device, which realizes control of each servo motor of the movable portion 2 and control according to the present invention. The movable part 2 includes an up-down slide part 5, a left-right moving part 6, a front-back moving part 3, and a front-back moving rail 4, and each moving part is driven by a servo motor. The welding system includes a power supply device 12 as a power supply means, a wire feeding device 8, and a welding torch 7. Reference numeral 9 is a work, and 10 is a work fixing base for positioning the work 9. The front-rear moving part 3 is a rail 4
Along the direction of the arrow Z, the left and right moving portions 6 can move in the up and down direction indicated by the arrow y with respect to the vertical slide portion 5, and can move in the left and right direction indicated by the arrow X. The movable part 2 drives the left and right moving parts 6 by driving an appropriate servomotor which constitutes a drive source for these parts.
The welding torch 7 attached to the tip of the is given the movement required for its operation or weaving. The control device 1 and the power supply device 12 are connected by a signal line 11 so that the arc current value during the welding operation can be input to the control device 1. The work 9 is arranged on the work fixing base 10 so that the welding line WL thereof is substantially parallel to the rail 4. According to the above configuration, the welding speed of the work 9 is determined by the moving speed of the front-rear moving unit 3. In this embodiment, the vertical slide portion 5 and the horizontal movement portion 6 are controlled to perform welding with high accuracy. Hereinafter, for convenience of description, the vertical direction y is referred to as the Y axis, the horizontal direction x is referred to as the X axis, and the front-back direction z is referred to as the Z axis. FIG. 8 is a control circuit diagram showing the main part of the present invention, and shows the one having the characteristics shown in FIG. 2 in the steady state. Hereinafter, this figure will be described. Reference numeral 20 is a correction means, which is configured as follows. Reference numeral 21 denotes a shunt resistor, which is incorporated inside the welding power source 12 in FIG. 7, converts the arc current during welding into a small voltage suitable for the control device 1, and sends this to the control device 1. A low-pass filter 22 removes high-frequency components peculiar to the arc as noise from the arc current detection value detected by the shunt resistor 21. Reference numeral 23 is a weaving signal generator, and a low frequency oscillator of 10 [Hz] or less is generally used. This weaving signal generator 23
Has two outputs. One of them is to send the output waveform as it is to the X-axis servomotor XS to cause the welding torch 7 to perform a weaving operation. The other one is sent to the switching logic 24 and used for the purpose of synchronizing the input and output of each integrator described later. The switching logic 24 outputs the weaving signal W from the weaving signal generator 23.
S is input and, based on this, predetermined timing signals T1, T2, T3, T4 shown in FIG. 9 are generated. Reference numeral 25 is a reference value setting device, which includes setting means (not shown) and a storage device for storing the setting value, and outputs a value corresponding to an appropriate welding current value and the like. The integrators 26, 27, 28 are synchronized by the switching logic 24. The Y-axis integrator 26 receives the timing signal T1 while the timing signal T1 is being input, that is, over the entire period of the weaving waveform WS.
The detected arc current value is integrated. The right integrator 27 inputs the timing signal T2 and performs integration for a fixed time TS near the right end of the weaving waveform WS. Left integrator 2
A timing signal T3 is input to 8 and near the left end of the weaving, similarly, integration is performed for a constant time TS. Comparator 29
Reference numerals 30 and 30 subtract the output values of the reference value setting device 25 and the Y-axis integrator 26, and the output values of the right integrator 27 and the left integrator 28, and output the subtraction as a deviation ΔI. Reference numerals 31 and 32 denote gate circuits, each of which inputs the timing signal T4 from the switching logic 24, and while this signal T4 is being input, its gate is opened to allow the output signals from the comparators 29 and 30 to pass therethrough. Reference numerals 33 and 34 denote amplifiers, each of which is composed of a multiplier having magnifications GY and GX. 35,
Reference numeral 36 is a limiter circuit which constitutes a control means which is a main part of the present invention. Each of the limiter circuits 35 and 36 is shown in FIG.
It is configured as shown in. Hereinafter, this figure will be described. Reference numeral 40 denotes a reference value setting device, which has the same configuration as the reference value setting device 25 shown in FIG. 8, but the setting values set by the setting means are different. That is, the setting value in this case is
It is assumed that the arc current value in the steady state and the arc current value in the case of arc breakage can be distinguished from each other.
This can be determined in advance by experiments or the like. 41, 4
Reference numeral 2 is a comparator, and 43 and 44 are diodes. As can be understood from the above description, the amplifiers 33, 3
The output signal from 4 swings in the positive and negative directions. Therefore, the diodes 43 and 44 are connected in antiparallel to the amplifiers 41 and 42, respectively, and the diode 41 extracts the positive direction component and the diode 44 extracts the negative direction component. Further, the direction of the negative direction component is inverted by the inverter 45. The positive direction component is output via the gate circuit 46, and the negative direction component is output via the gate circuit 47 and the inverter 48. Comparator 41 is diode 43
Of the arc current value, that is, whether or not the positive direction component of the arc current value exceeds the preset value set in the reference value setting device 40, and if it exceeds, a signal corresponding thereto is output and the gate circuit 4
Close 6 Further, the comparator 42 determines whether or not the value obtained by inverting the output of the diode 44 by the inverter 45 exceeds the predetermined value, and when it exceeds the predetermined value, outputs a signal corresponding to the predetermined value and closes the gate circuit 47. The output from the gate circuit 46 is sent as it is, and the output from the gate circuit 47 is sent as the output from the limiter circuits 35 and 36 via the inverter 48. The correction amount x output from the amplifiers 33 and 34 via the limiter circuits 35 and 36 is the Y-axis servo motor YS,
Input to each X-axis servo motor XS. The Y-axis servomotor YS is incorporated in the vertical slide unit 5 shown in FIG. 7, and drives the welding torch 7 to move to a height according to a command signal or the like. The X-axis servomotor XS drives the left and right moving unit 6 shown in FIG. 7, and drives the welding torch 7 to perform a weaving operation and move in the X-axis direction. Although not shown, a Z-axis servo motor that drives the moving unit 3 in the Z-axis direction based on a command signal from the control device 1 is provided as another servo motor. These X-, Y-, and Z-axis servomotors form the main drive source that controls the movement of the welding torch 7 along the welding line WL. Although only the servomotors YS, XS and the weaving signal generator 23 are shown as the movement control means in FIG. 8, the movement control means has a setting unit for presetting the movement path of the welding torch 7 as in the conventional case. For example, a storage unit, a control unit that drives and controls each servomotor based on the stored contents of the storage unit, and the like are included. Further, in FIG. 8, the limiter circuits 35, 3
Although the output of 6 is directly applied to the servo motors YS and XS, this is originally added to each servo motor YS and XS via the control circuit, and is omitted for simplification of description. Please understand that it is shown by. Figure 1
As is clear from the description of 0, the limiter circuits 35 and 36
Outputs the input signal via the gate circuits 46 and 47. The gate circuits 46 and 47 are open / close controlled by the outputs of the comparators 41 and 42. Therefore, when the value of the input signal is within the value set in the setter 40, the gate circuits 46 and 47 are opened and the input signal is output as it is. However, if the value of the input signal is
When the value set to 0 is exceeded, the gate circuits 46 and 47 are closed, the input and output signals are blocked, and the limiter circuits 46 and 4 concerned are shut off.
The output of 7 becomes zero. FIG. 11 shows the limiter circuit 35,
FIG. 9 is a control characteristic diagram of the control circuit shown in FIG. 8 in which 36 is incorporated, and shows the case where the setting value I1 is set in the setter 40. As described above, the set value I1 is a planned value that can distinguish the arc current value in the steady state from the arc current value when the arc breaks, and this is a value that can be determined in advance by experiments or the like. That is, in the control system according to the present embodiment, the correction amount x increases in proportion to the deviation ΔI within the range of the deviation ΔI from ΔI1 to −ΔI1 as in the case of FIG. However, when this range is exceeded, that is, when an arc break occurs, the correction amount x is forcibly set to zero. In addition, the setting device 40 of the limiter circuit 35
Although the set value of 1 and the set value of the setter 40 of the limiter circuit 36 are specifically different, this will be described below as the same for simplification of description. The operation of the embodiment will be described below with reference to FIGS. 3, 4, and 6. As described above, FIG. 3 shows the weaving signal waveform, which corresponds to the output of the weaving signal generator 23 of FIG. FIG. 4 shows a welding current, that is, an arc current waveform, which corresponds to the output of the low pass filter 22 in FIG. The sixth shows the locus of the weaving center position of the welding torch 7 in the present embodiment. First, in a steady state, the welding torch 7 is based on the movement path information preset in the control device 1,
It is driven to move by the movable part 2 whose movement is controlled by the control device 1. Here, when the timing signal T1 is output from the switching logic 24 at the time ta in FIG. 9, the Y-axis integrator 26 receives the signal t1 from the timing signal T1.
During the period from the time point a to the time point tf, the low-pass filter 22
Integrate the arc current from. The right integrator 27 outputs the timing signal T2 from the switching logic 24 at time tb, so that the period Ts up to time tc is reached.
During this period, the arc current from the low pass filter 22 is integrated. Similarly, the left integrator 28 integrates the arc current from the low-pal filter 22 during the period Ts up to te by the timing signal T3 being output from the switching logic 24 at time tb. The integrated value of the Y-axis integrator 26 integrated as described above and the reference value setter 25
Set value, and the integrated value of the right integrator 27 and the left integrator 28
The integrated value of is constantly compared by the comparators 29 and 30,
The deviation is always output. However, this deviation is blocked by the gate circuits 31, 32, and the amplifiers 33, 3
Not entered in 4. Y-axis integrator 26, right integrator 27,
When the timing signal T4 is output from the switching logic 24 at time tg after the left integrator 28 finishes integrating the arc current in the predetermined period, respectively, the gate circuits 31 and 32 are opened and the comparators 29 and 30 are opened. The output from is input to the amplifiers 33 and 34. Then, the amplified deviation is Y through the limiters 35 and 36, respectively.
It is input to the axis servo motor YS and the X axis servo motor XS, and the welding torch 7 is corrected and driven by the correction amount corresponding to the deviation. Here, when the welding torch 7 approaches or separates from the welding line WL in the Y-axis direction more than a desired distance, a difference occurs between the set value of the setter 25 and the integrated value of the Y-axis integrator 26, The comparator 29 detects the deviation between the two. Then, based on this deviation, the Y-axis servomotor YS adjusts the distance of the welding torch 7 in the Y-axis direction, and this adjustment works so that the deviation becomes zero. If the center position of the weaving pattern deviates to either the right side or the left side with respect to the welding line WL, a difference occurs in the integrated value between the right integrator 27 and the left integrator 28. Then, the comparator 30 detects the difference between the two and the X-axis servomotor XS is drive-controlled by the detected value. Then, this control is continued until the welding line WL and the center position of the weaving pattern match. In this way, the welding torch 7 is controlled along the welding line WL. Although omitted in the description, each of the integrators 26, 27, and 28 has a timing signal T4.
Needless to say, it is cleared in the period from the disappearance of the timing signal to the rise of the timing signal T1. The above is a general case where arc breakage does not occur, that is, the deviation ΔI is within the range of ΔI1 to −ΔI1 in FIG. In this case, since the outputs of the amplifiers 33 and 34 do not exceed the set value I1 of the setter 40, the gate circuits 46 and 47 are both opened, and the outputs of the amplifiers 33 and 34 are the limiter circuit 35 and
After passing through 36, the servo motors YS and XS are directly added. Here, it is assumed that an arc break occurs as shown at time points t1, t2, t3, t4, and t5 in FIG. Then, first, the influence of the arc break at the time t1 appears after the time T41 when the timing signal T4 is generated as shown in FIG. The set value of the setter 25, the integrated value of the Y-axis integrator 26, and the right integrator 27 are generated due to the arc break at the t1 signal.
There is a difference between the integrated value of and the integrated value of the left integrator 28. Normally, according to this difference, the servomotors YS, X
S is controlled. However, this difference is caused by arc breakage, and this difference is quite large. That is, the set value I1 in FIG. 10 is exceeded. The comparators 41 and 42 detect this, and the gate circuit 4
Close 6, 47. Therefore, the signal based on this deviation is not output from the limiter circuit, and the servo motor YS,
The XS has no movement control and maintains the past state. Similarly, the limiter circuits 35 and 36 work to limit the output even when the arc is cut off at the time points t2, t3, t4, and t5, and the deviation due to this is ignored. That is, as shown in FIG. 6, the locus of the center position of the weaving pattern is not affected by the arc break and travels along the welding line WL. As described above, in the embodiment, the case where the workpiece having the welding line WL is fixed and the movement of the welding torch 7 is controlled with respect to the welding line WL has been described. However, conversely, the welding torch 7 is fixed and the welding line WL is fixed. May be controlled to move. Further, the deviation ΔI is shown in the embodiment.
The case where the correction amount x is made zero by exceeding the predetermined amount ΔI1 has been explained, but this is not zero, and the effect of the present invention can be sufficiently achieved if it is a value smaller than the correction amount corresponding to the deviation. Is. FIG. 12 shows an example thereof, in which the correction amount x is set as the correction amount a1 when the deviation ΔI exceeds the predetermined amount ΔI1. Further, the limited correction amount x is not always a constant value, but may be gradually decreased as shown in FIG. Further, in FIG. 14, the control characteristic of the correction control means has a dead zone, and the present invention can be applied regardless of the characteristics of the correction control means. What kind of value or characteristic is to be selected for this limited correction amount is determined by the characteristics of the automatic welding apparatus or work to which the present invention is applied,
Generally, it is desirable that it is zero. In the embodiment, the correction amount x increases almost in proportion to the deviation ΔI when the absolute value of the deviation ΔI is equal to or smaller than the predetermined value I1. However, this is the magnitude of the deviation ΔI. The same can be applied to that of FIG. 1 that outputs a constant correction amount x by. FIG. 15 shows a characteristic diagram in this case. Even in this case, the correction amount x may be selected from the above-mentioned value instead of zero because the deviation ΔI exceeds the predetermined value I1. For example, FIG. 16 shows the case where the correction amount is limited to a1. Further, FIG. 17 shows a case where the correction amount x is gradually reduced. Further, in the embodiment, the deviation between the detected amount of electricity and the predetermined reference amount is
The case where it is determined whether or not the predetermined value is exceeded by the deviation at the output position of the correction control means 20 has been described, but this is at another position, for example, the gate circuits 31 and 3.
Deviations in the two output portions may be used and the invention is not limited to those positions. Further, the detection of the amount of electricity corresponding to the arc of the welding torch has been described using the arc current as an example, but this may be the one that detects the voltage of the welding torch as described above. As is apparent from the above description, according to the present invention, even if an arc break occurs, the deviation caused by the arc break is nullified.
It is possible to obtain a welding line copying control device having good followability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a control characteristic diagram of a conventional device. FIG. 2 is a control characteristic diagram of a conventional device. FIG. 3 is a weaving signal waveform diagram. FIG. 4 is an arc current waveform diagram. FIG. 5 is a diagram showing a locus of a weaving center position in the conventional apparatus. FIG. 6 is a diagram showing a locus of a weaving center position in the example. FIG. 7 is a schematic view of an entire automatic welding apparatus to which the present invention is applied. FIG. 8 is a block diagram showing an embodiment of the present invention. FIG. 9 is a time chart showing signals of respective parts for explaining FIG. FIG. 10 is a block diagram showing an example of limiting means. FIG. 11 is a control characteristic diagram (first example) of the embodiment of the present invention. FIG. 12 is a control characteristic diagram (second embodiment) showing another embodiment of the present invention.
Example). FIG. 13 is a control characteristic diagram (third embodiment) showing another embodiment of the present invention.
Example). FIG. 14 is a control characteristic diagram (fourth embodiment) showing another embodiment of the present invention.
Example). FIG. 15 is a control characteristic diagram (fifth embodiment) showing another embodiment of the present invention.
Example). FIG. 16 is a control characteristic diagram (sixth embodiment) showing another embodiment of the present invention.
Example). FIG. 17 is a control characteristic diagram (seventh embodiment) showing another embodiment of the present invention.
Example). [Explanation of Codes] 7 ... Welding torch, 12 ... Power supply means, 20 ... Correction control means, 21 ... Shunt resistance, 23 ... Weaving signal generator, 25 ... Reference value setting device, 24 Switching logic, 26 ... Y-axis integration Vessel, 27 ... right integrator, 28 ... left integrator, 29 ... comparator, 30 ... comparator, 35 ... limiting means, 36 ... limiting means, WL ... welding line, YS ... Y axis servo motor, XS ... axis servo motor,

Claims (1)

[Claims] 1. A movement control means for relatively moving and controlling the welding torch and the work along the welding line, a power supply means for supplying welding power to the welding torch, and an arc current supplied from the power supply means to the welding torch. Detecting, in the welding line copying control device provided with the correction control means for applying the predetermined correction amount corresponding to the deviation between the detected current and the predetermined reference amount to the movement control means and correcting the position of the welding torch, A welding line copying control device comprising a control means for limiting the correction amount when the deviation exceeds a predetermined value. 2. The welding line copying control device according to claim 1, wherein the control means limits the correction amount to zero when the deviation exceeds the predetermined value. 3. The welding line copying control device according to claim 1, wherein the control means shuts off the correction amount when the deviation exceeds the predetermined value.