JPH0378188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field The present invention relates to an automatic control device for a welding machine.

(b) Prior art When welding is performed by automatically moving a welding torch along the shape of the welding part, there are methods that use mechanical contact or visual devices such as television cameras to detect the welding part. Methods that utilize changes in physical phenomena such as voltage, current, sound, and magnetism during welding are used. Among methods that utilize changes in physical phenomena, methods that utilize changes in voltage or current during welding have the advantage that there is no need to install special equipment around the welding torch. FIG. 1 shows a welding torch and a welded part when detecting a welded part using changes in welding current. Objects to be welded 10 and 1
The end of the contact surface of No. 2 is the welding portion 14 to be arc welded. The welding torch 16 is arranged above the welding part 14 and moves in a direction perpendicular to the plane of the paper to weld the welding part 1.
Perform welding in step 4. At this time, the welding torch 16 is swung in a plane perpendicular to the direction of movement of the welding torch 16 (a plane parallel to the plane of the paper). The welding current during welding is measured, and the welding torch 16 is moved in the X direction or Y direction so that the current values at swing end points A and B are always equal. By doing this, the swing center position C of the welding torch 16 is located at the welding part 1.
It is held in the position directly above 4. This method is advantageous because the parts 10 and 12 to be welded are geometrically symmetrical with respect to a vertical plane passing through the welding part 14, so that the welding torch 16
This is based on the idea that if the swing center position C is within the vertical plane, the welding currents at swing end points A and B should be equal.

However, with the conventional methods as described above, it is difficult to reliably detect a welded part under all welding conditions and automatically perform welding with high precision in accordance with the detected welded part. This is because arc welding utilizes an unstable discharge phenomenon, and various conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, and the presence of tack joints change during welding. In reality, the welding current changes in a very complex manner, as shown in FIG. 2, for example, and the relationship between the difference in welding current at the end point of the swing and the deviation of the welding torch 16 from the welding part 14 is always clear. That's because it's not. Therefore, under welding conditions where the relationship between the change in welding current and the deviation of the welding torch 16 is relatively clear, such as the so-called downward welding method in which the welding torch 16 is directed directly downward as shown in FIG. Automatic welding can also be performed by conventional methods such as the above, but it is difficult to reliably move the welding torch 16 along the welding part 14 under the above-mentioned specific welding conditions. .

(c) Purpose of the Invention The present invention is capable of reliably detecting a welded part without being affected by changes in conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, and the presence or absence of tacked parts. The object of the present invention is to obtain an automatic control device for a welding machine that can automatically perform welding.

(D) Structure of the Invention The present invention oscillates the welding torch at a constant period in a plane perpendicular to the direction of movement of the welding torch, multiplies the welding current by the amount of oscillation of the welding torch, and calculates the multiplication value for each oscillation. Integrate for each cycle, determine the correction direction of the welding torch from the sign of the integral value obtained by the above integration, and change the welding torch oscillation center position in this correction direction by an amount corresponding to the absolute value of the above integral value. The above objective is achieved by moving. That is, the automatic control device for a welding machine according to the present invention includes a welding torch 20, a swinging device 22 that swings the welding torch 20, and a lateral movement that allows the swinging device 22 to move in the swinging direction of the welding torch 20. device 28 and a vertical movement device 38 capable of moving the swing device 22 in a direction perpendicular to the swing plane of the welding torch 20.
, a wire feeding device 24 that feeds the wire to the welding torch 20, and a welding power source 50 that supplies welding current to the wire, and a current detector that detects the current of the welding power source 50. 52
and a swing position detector 6 that outputs a signal when the welding torch 20 passes through the swing center position from one direction.
0, and a controller 56 that outputs a command signal to the lateral movement device 28 based on signals from the current detector 52 and the swing position detector 60. Immediately after the position detector 60 issues a signal for passing the swing center position of the welding torch 20, the current detector 5
Current data storage means (steps 104, 106, 108) reads and stores signals from the welding torch 20 corresponding to the amount of oscillation from the oscillation center position of the welding torch 20 at each minute time elapsed based on a preset function. Oscillation amount data determination means (step 109) that determines the data, each value of the current data stored in the current data storage means, and each value of the welding torch oscillation amount data obtained by the oscillation amount data determination means. A calculation means (step
110), and drive signal output means (steps 112, 114) for outputting a signal for operating the lateral movement device 28 in a direction that reduces the absolute value of the calculated value based on the calculated value obtained by the calculation means. ,have. Note that the reference numerals in parentheses indicate corresponding members in the embodiments.

The reason why the positional deviation of the welding torch can be detected with the above configuration is based on the following principle. In other words, regarding the magnitude and direction of the positional deviation of the welding torch, the magnitude of this is the same component as the oscillation frequency component of the welding torch among the frequency components of the welding current, that is, the welding torch is oscillated in a sinusoidal manner. In this case, it can be made to correspond to the magnitude of the frequency component that is the same as the oscillation period of the welding torch, and the direction of this can be determined by the positive/inverse relationship of the phase of the above frequency component with respect to the oscillation of the welding torch. . This is clear from the following explanation. The welding current corresponds to the distance between the wire tip and the mating member. In other words, the smaller the distance, the more the current increases. For example, when the welding torch is greatly displaced from the welding part as shown in Figure 10a, the slope M on the left side has almost no effect on the welding current;
The welding current is determined in relation to only the slope N on the right side. Therefore, during one oscillation period, the welding torch approaches the slope N once, and moves farthest away once.
Accordingly, the maximum current is obtained only once, and once
The minimum current is obtained only once. Therefore, the welding current changes as shown in FIG. 10b. The period of this welding current matches the oscillation period. Therefore, the magnitude (amplitude) of the frequency component of the welding current that is the same as the oscillation frequency of the welding torch is increasing. On the other hand, as shown in FIG. 11a, if the positional deviation of the welding torch is relatively small, it will be affected even when it swings toward the slope M side. However, the degree of influence of slope M is smaller than the degree of influence of slope N. Therefore, as shown in FIG. 11b, the welding current produces two large and small peaks during one oscillation cycle. That is, a current waveform is obtained in which a frequency component having the same frequency as the oscillation period of the welding torch and other components are combined. Therefore, the degree of frequency components that are the same as the oscillation period of the welding torch becomes relatively small. Furthermore, as shown in Figure 12a, when there is no deviation of the welding torch, the slope M and the slope N have the same influence for each swing, and the frequency is the same as the swing period. There will be no identical frequency components. In this way, as the state changes from Fig. 10 to Fig. 12, the frequency component that is the same as the oscillation period decreases (in other words, the current change per oscillation is 1).
(the number of occurrences decreases). Therefore,
As mentioned above, the magnitude (amplitude) of the frequency component of the welding current that is the same as the oscillation frequency of the welding torch is:
This increases in accordance with the magnitude of the positional deviation of the welding torch from the welding part. On the other hand, the influence of changes in conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, and the presence or absence of temporary attachment parts is due to the effects of changes in conditions such as falling droplets, bending of the wire, and the presence or absence of temporary attachment parts. It has almost no effect on the magnitude of the frequency component that is the same as the oscillation frequency. On the other hand, the positive and reverse phase relationships differ depending on the direction of the welding torch shift, as shown in Figures 13a and b and Figure 14a.
This becomes clear when comparing and b. That is,
The degree of influence between the M plane and the N plane becomes completely opposite depending on the direction of the welding torch shift. Therefore, for the same welding torch oscillation, the phase relationship of the current waveform is a positive/reverse relationship (in-phase or anti-phase relationship, i.e.
(a relationship with a phase difference of 180 degrees), and for this reason,
Among the frequency components of the current, the phase relationship of the frequency components that are the same as the welding torch oscillation period also becomes a positive and negative relationship.
Based on the principle explained above, the degree and direction of positional deviation of the welding torch can be determined only from the magnitude and phase of the frequency component of the welding current that is the same as the oscillation period of the welding torch. By moving the welding torch position in the opposite direction by an amount corresponding to (proportional to) the degree of , the welding torch can be positioned directly above the weld. By repeating this operation, it becomes possible to move the welding torch directly above the welding area and hold it in this position.

(E) Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 3 to 8 of the accompanying drawings.

FIG. 3 shows an automatic welding device according to the present invention. This is an example in which the present invention is applied to downward fillet welding. The welding torch 20 is pivoted by a swing device 22 . The swinging device 22 can swing the welding torch 20 at regular intervals.
A wire 26 can be fed to the welding torch 20 from a wire feeding device 24 . The swinging device 22 is connected to a lateral movement device 28 via a support member 30. The lateral movement device 28 has a motor 28a, and by operating the motor 28a, the support member 30 can be moved in the horizontal direction in FIG. That is, by driving the motor 28a, the swinging device 22 and the welding torch 20 supported by the swinging device 22 can be moved in the horizontal direction. The motor 28a is a pulse motor,
It rotates forward or reverse depending on the input pulse for forward or reverse rotation. The lateral movement device 28 is provided on a carriage 38 supported on a frame 32 via bearings 34 and 36 so as to be movable in the horizontal direction (direction perpendicular to the plane of the paper). Note that a drive device for driving the carriage 38 is not shown. This carriage 38 and the drive device constitute a longitudinal movement device. By moving the carriage 38, the welding torch 20 can be moved in a direction perpendicular to the plane of the paper. The objects to be welded 40 and 42 are placed on a table 44 . The contact surface ends of the objects 40 and 42 to be welded are the welding portions 46 to be welded. Wire feeding device 2
4 and stand 44 are connected to a welding power source 50 by power supply lines 47 and 48, respectively. Welding power source 5
0 is provided with a current detector 52, and a signal 54 from the current detector 52 is input to a controller 56. The current detector 52 may be a magnetic current detector or shunt resistor using a Hall element,
A signal 54 proportional to the welding current is generated. A signal 64 from a swing position detector 60 provided in the swing device 22 is also input to the controller 56 . The swing position detector 60 generates a pulse-like signal 64 when the welding torch 20 passes the swing center position from one direction (that is, once per swing cycle). 20, and a slit mechanism and a photoelectric switch. The controller 56 can output a signal 66 that commands the amount and direction of rotation to the motor 28a. The configuration of the controller 56 is shown in a block diagram in FIG. A signal 54 from the current detector 52 and a signal 64 from the swing position detector 60 are input to the controller 56 . The controller 56 is the AD converter 7
0, a microprocessor 72, a memory 74, and a drive signal output means 76. The AD converter 70 receives an analog signal 54 from the current detector 52.
is converted into a digital signal 80. The microprocessor (central processing unit CPU) 72 has a storage device 74.
Based on the program stored in the computer, signal reading, calculation, signal output, etc. are controlled to achieve the functions described below. The memory 74 stores programs for operating the microprocessor 72 and data necessary for calculations, and also temporarily stores numerical data during calculations. The drive signal output means 76 outputs a pulse signal 66 for driving the motor 28a by a predetermined amount in a predetermined direction in response to a signal 82 from the microprocessor 72.

Next, the operation of this embodiment will be explained. Third
Welding is performed in the following manner using the apparatus shown in FIG. The welding torch 20 is oscillated by the oscillating device 22 in a plane parallel to the plane of the paper while moving on the traveling base 38.
The welding section 46 shown in FIG. 5 is arc welded by moving in a direction perpendicular to the plane of the drawing. welding torch 2
The motor 28a is rotated by a signal 66 from the controller 56, and the welding torch 20 is moved in the horizontal direction so that the welding torch 20 passes directly above the welding part 46. The controller 56 outputs a signal 66 to the motor 28a based on the pulse-like signal 64 from the swing position detector 60 and the signal 54 from the current detector 52 in accordance with the procedure of the flowchart shown in FIG. Determine. First, by detecting that the signal 64 from the swing position detector 60 is turned on, it is detected that the welding torch 20 first passes the swing center position from one direction (step 102), and this is detected. At the same time as the detection, the signal 80 from the AD converter 70 is read and stored in the memory 74 (step 104). Next, after a minute idle time ΔT (for example, 1/100 of the oscillation period), (step 106),
It is determined whether the welding torch 20 is at the swing center position (step 108), and if it has not returned to the swing center position, the process returns to step 104 and the signal 80 after a minute time ΔT is read and stored in the memory. 74. This reading and storing of the signal 80 is repeated until the welding torch 20 returns to the swing center position (that is, until the signal 64 from the swing position detector 60 is turned on). That is, during one swing period, signal 80 is measured 100 times every ΔT time,
The data is stored as data A ₁ , A _{2 .} . . A ₁₀₀ . When one oscillation cycle is completed and the welding torch 20 returns to the oscillation center position, the process proceeds to step 109, where the oscillation center of the welding torch 20 is adjusted every time △T based on a preset function (for example, a sine wave function). Data (Ri) corresponding to the amount of swing from the position is determined (step 109). If the welding torch 20 is oscillated in a sinusoidal manner, that is, the amount of oscillation R is expressed as R=sin(2πt/T) (where t is the elapsed time and T is the period), then Ri=sin (2πi/N) (However, N is the total number of current data; in the above example, N=100) Ri, which is expressed by the formula, can be regarded as indicating the amount of fluctuation after △T × i time has passed. . Then,
Proceeding to step 110, the calculation shown in the following equation is performed.

S= _N 〓 ⁱ⁼¹ (Ai・Ri) Ai...measurement data of signal 80 Ri...oscillation amount data corresponding to Ai In other words, the above calculation result S is the welding current (Ai)
is multiplied by the amount of oscillation (Ri) of the welding torch 20,
It is the integral of the multiplied value (however, since the number of data is finite, the calculation formula is written as a series). Note that when the welding torch 20 swings in a sinusoidal manner, the above calculation is performed on the welding torch 20.
The fact that the frequency component is extracted as the same frequency component as the oscillation frequency of is explained based on the Fourier series. That is, if the function f(t) is periodic in the domain -π≦t≦π, then f(t)=(1/2)・a ₀ + _∞ 〓 ⁿ⁼¹ (a _o・cosnt+b _o・sinnt). Here, a _o = (1/π)∫〓 _- 〓f(t)・cosntdt b _o = (1/π)∫〓 _- 〓f(t)・sinntdt. Therefore, the frequency component that is the same as the oscillation period is a ₁ = (1/π)∫〓 _- 〓(t)・cosntdt b ₁ = (1/π)∫〓 _- 〓(t)・sinntdt However, by oscillating the welding torch 20 in a sinusoidal manner, there is no need to consider a ₁ and only b ₁ needs to be considered.

Therefore, the frequency component (fundamental wave component) S that is the same as the oscillation period is S= _b1 . This relationship is shown in drawings 5 to 7.
The result will be as shown in the figure. That is, as shown in FIG. 5, let x be the horizontal positional deviation of the welding torch 20 from the welding part 46, and let x be the frequency component of the welding current that is the same as the oscillation frequency of the welding torch 20. If the size is z, the relationship between x and z is as shown in FIG. That is, as the absolute value of x increases, the value of z also increases. Also,
As shown in FIG. 7, the phase is reversed depending on the direction of displacement of the welding torch 20 (that is, whether the value of x is positive or negative). This allows the direction of displacement of the welding torch 20 to be detected. Based on the value of S as described above, an operation command signal D proportional to the value of S is calculated (step 112). Here, the proportionality coefficient is
Although it differs depending on the rotational characteristics of the motor 28a used, it is determined as appropriate considering the tendency that increasing the value improves the responsiveness of torch position correction, and conversely, decreasing the value increases stability. This operation command signal D is input as a signal 82 to the drive signal output means 76.
The drive signal output means 76 outputs a predetermined number of forward rotation or reverse rotation pulses as a signal 66 to the motor 28a depending on the magnitude and sign of the input signal 82 (step 114). Then, the program returns and the same routine as above is executed repeatedly. Therefore, the horizontal position of the welding torch 20 is adjusted every swing period of the welding torch 20. Note that the float chart (Fig. 8) of this example is based on the step
109→114 is the signal 80 at step 104→108
This assumes that steps 104→108 are executed fast enough so as not to affect the periodic loading of
The above premise is not necessary if so-called parallel processing is performed in which steps 109 and 114 are executed simultaneously in parallel.

By the action of the controller 56 as described above, the welding torch 20 is controlled so as to always be located directly above the welding part 46. For example, if the position of the welding torch 20 is shifted from the position directly above the welding part 46, the welding torch 20 out of the frequency components included in the welding current
The frequency component that is the same as the oscillation period of 0 becomes large (see FIG. 6), but the signal 66 from the drive signal output means 76 is transmitted to the motor 28a in the direction of decreasing this frequency component.
Rotate. The rotation direction of the motor 28a is determined by signal 8.
2, and the welding torch 20 is moved to a position directly above the welding part 46. welding torch 2
0 is located directly above the welding part 46,
Among the frequency components included in the welding current, the frequency component that is the same as the oscillation period of the welding torch 20 is extremely small, so the motor 28a hardly rotates and the welding torch 20 does not move. As described above, the position of the welding torch 20 is controlled to be directly above the welding part 46 for each period of oscillation, and the welding torch 20 is always held directly above the welding part 46 during welding, and is Welding is performed by moving the table 38.
During welding, fluctuations occur in conditions such as falling droplets, bending of the wire, fluctuations in wire feeding speed, uneven melting of the wire, and the presence or absence of temporary attachment parts.The frequency components of these fluctuations are This is different from the frequency component of the oscillation frequency of the welding torch 20, and has almost no effect on the frequency component that is the same as the oscillation frequency of the welding torch. Therefore, the welding torch 20 is reliably held directly above the welding part 46 despite the above-mentioned fluctuations in welding conditions.

Further, in the above embodiment, the position of the rocking device 22 is controlled by a pulse motor, but the amount of movement of the rocking device 22 is detected using, for example, a potentiometer, and this feedback signal and a microprogram are used. The signal 82 from the setter 72 may be input to a drive signal output section (for example, a servo amplifier), thereby driving a motor (servo motor).

(F) Effects of the Invention As explained above, the automatic welding device according to the present invention detects the current at every minute time interval based on the signal of the welding torch passing through the swing center position emitted from the swing position detector. The controller reads and stores the signals from the welding torch, internally generates data corresponding to the amount of oscillation from the oscillation center position of the welding torch at each minute elapsed time based on a preset function, and then calculates the value of these current data. and the value of data equivalent to the amount of welding torch oscillation are multiplied and summed for each oscillation cycle, and the lateral movement device is operated based on this calculated value, so there is no need to provide an external oscillation amount detector. In addition, it is possible to correct misalignment of the welding torch without necessarily changing the oscillation form to a sinusoidal waveform, thereby preventing droplets from falling during welding, bending of the wire, fluctuations in wire feeding speed, and uneven melting of the wire. , the welding torch can be moved along the welding part without being affected by the presence or absence of tack-welding parts, and arc welding can be performed reliably as desired, not only with downward fillet welding but also with other welding methods. It can be performed.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a welding torch and a welding part in a conventional welding machine, Fig. 2 is a diagram showing changes in welding current with respect to the swing position, and Fig. 3 is a diagram showing a welding machine to which the present invention is applied. FIG. 4 is a block diagram showing the automatic control device according to the present invention, FIG. 5 is a diagram showing a welding torch in a misaligned state, and FIG. 6 is a line showing the relationship between the amount of misalignment and the frequency component current value. 7 is a diagram showing the relationship between positional deviation and phase, FIG. 8 is a flowchart of the control device, and FIG. 9 is a diagram showing the relationship between each component of the present invention. Fig. 10 shows the current waveform when the positional deviation is large, Fig. 11 shows the current waveform when the positional deviation is small, Fig. 12 shows the current waveform when there is no positional deviation, and Fig. 13 shows the current waveform when the positional deviation is small. The figure shows the current waveform when the position shifts to the right, and FIG. 14 shows the current waveform when the position shifts to the left. 20... Welding torch, 22... Rocking device, 24
... wire feeding device, 26 ... wire, 28 ...
Lateral movement device, 28a... Motor, 30... Supporting member, 32... Frame, 34, 36... Bearing, 38... Travel platform, 40, 42... Member to be welded, 44... Stand, 46... ...Welded part, 47, 48...
...Feeding line, 50... Welding power source, 52... Current detector, 54, 64, 66... Signal, 56... Controller, 60... Rocking position detector, 70... AD converter, 72... ...Microprocessor, 74...Memory device, 76...Drive signal output means, 80, 82...
signal.

Claims (1)

[Scope of Claims] 1. A welding torch, a swinging device for swinging the welding torch, a lateral movement device capable of moving the swinging device in the swinging direction of the welding torch, and a swinging device for swinging the welding torch. In an automatic control device for a welding machine, the device includes a vertical movement device movable in a direction perpendicular to a moving surface, a wire feeding device that feeds a wire to a welding torch, and a welding power source that supplies welding current to the wire. , a current detector that detects the current of the welding power source, a swing position detector that outputs a signal when the welding torch passes the swing center position from one direction, and a current detector that outputs a signal when the welding torch passes the swing center position from one direction. a controller that outputs a command signal to the lateral movement device based on the signal, and the controller is configured such that the welding torch swing center position passage signal is emitted by the swing position detector. a current data storage means that reads and stores the signal from the current detector every minute time period from immediately afterward; and a current data storage means that reads and stores the signal from the current detector at every minute time elapsed, and corresponds to the amount of oscillation of the welding torch from the center position of the welding torch at every minute time elapsed based on a preset function. Oscillation amount data determining means for determining data;
Each value of the current data stored in the current data storage means is multiplied by each value of the welding torch swing amount equivalent data obtained by the swing amount data determining means, respectively, and the sum of the multiplied values is calculated. The present invention includes a calculating means for calculating, and a drive signal outputting means for outputting a signal for operating the lateral movement device in a direction that reduces the absolute value of the calculated value based on the calculated value obtained by the calculating means. Features: Automatic control device for welding machines.