JP2518733B2 - Back bead control method in single-sided welding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a back bead control method in single-sided welding by fuzzy control.

[Prior Art] A conventional back bead control method in single-sided welding is to control the voltage and current between a welded member and a conductive tape adhered in a groove of an insulating backing material as control parameters. Generally, a deviation between a parameter and a preset reference value is obtained, and welding conditions such as welding current, voltage, and welding speed are generally controlled so that the deviation is always within a certain range. There is also a method of converting the amount of light detected by an optical sensor attached to a backing material into a voltage or a current for use (Japanese Patent Publication No. 62-36787).

In any case, it is necessary to find the correlation between the detected voltage and current and the width of the back bead by experiments etc. (JP-A-61-137676 and JP-A-61-180677). .

[Problems to be Solved by the Invention] However, the above-mentioned correlation is generally obtained on the assumption that the groove shape is a standard groove shape in which the groove shape does not fluctuate. Not only can it be applied to various things, but it is necessary to perform a huge amount of experiments in consideration of various conditions in order to determine the width of the threshold value with respect to the reference value. It was complicated.

Fluctuations in the groove shape can often occur in actual single-sided welding.In such a case, usually temporary tack welding is performed to match the standard groove shape before main welding. Weld defects in the welded joint become a problem.

Further, the conventional control method is rough because the control value is 0 or 1 and there is no intermediate value. Therefore, if the groove shape changes even a little, the control followability deteriorates and the back bead shape becomes defective. Met. Further, since the increasing / decreasing tendency of the control amount is unknown, the control response is poor, and accurate control according to the change of the groove shape is impossible.

Therefore, it is desired to develop a control method that can perform one-sided welding (main welding) immediately without temporary welding even if there is a change in the groove shape, and that can obtain a good back bead shape.

The present invention has been made to meet this demand,
It is an object of the present invention to solve the problems included in the above-mentioned conventional methods and to provide an efficient back bead control method capable of obtaining a very stable back bead shape.

[Means for Solving the Problems] In order to achieve the above object, in the back bead control method in single-sided welding according to the present invention, the initial welding speed in single-sided welding is set in advance, and the welding speed after that is set. Detects the voltage or current between the member to be welded and the backing material every predetermined time, and performs a fuzzy operation using the deviation e between the detected value and the reference value and the time derivative de / dt of the deviation. The increase / decrease amount Δv of the welding speed is calculated, and the increase / decrease amount Δv
Is added to the welding speed at that time, the welding speed is sequentially corrected, and the welding torch is caused to travel at the corrected welding speed.

[Operation] Since the present invention is configured as described above, when the root gap becomes wider or narrower, the voltage or current between the welded member and the backing material changes, so From the deviation e with respect to the reference value and the time derivative de / dt of the deviation, the magnitude of the amount of change and the increasing / decreasing direction can be known, and if a fuzzy calculation is performed according to a certain rule as described later, the increasing / decreasing amount of welding speed Δv The welding speed after the initially set welding speed can be obtained by adding the welding speed increase / decrease amount Δv obtained every predetermined time to the welding speed at that time. As a result, an appropriate penetration amount is maintained according to the change in groove shape, so a stable back bead shape can be obtained, and control with excellent responsiveness is possible without setting a threshold value for the reference value. Become.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a control system applied to the back bead control method of the present invention.

The bottom portion of the groove 3 formed on the members to be welded 1 and 2 is covered with a backing tape 4 such as glass fiber, and an insulating backing material 5 such as ceramics is further interposed between the members to be welded 1 and 2 through the backing tape 4. It is pressed and fixed on the back side. A conductive tape 11 is attached in the groove of the backing material 5.

The welding torch 6 is installed on a member 1 to be welded and is mounted on a carriage 7 that can travel in the groove line direction. A feed mechanism (not shown) in the groove width direction (X axis) and a torch height direction (Y axis). It is supported by the feeding mechanism. In addition, a rotating mechanism (not shown) may be provided on the welding torch 6 in order to give a circular motion to the tip of the welding wire 8 to rotate the arc 9.

In this embodiment, the case of detecting voltage is shown.
Therefore, the voltmeter 10 is connected between the conductive tape 11 stuck in the groove of the ceramic backing material 5 and the member 2 to be welded.

The conductive tape 11 melts as the welding progresses, and normally does not make electrical contact with the member to be welded or the weld metal.

In this embodiment, the insulating ceramic backing material is used and the voltage between the member to be welded and the conductive tape 11 stuck in the groove of the backing material 5 is detected. In the case of a construction method in which the metal does not make electrical contact with the backing material, a conductive material such as a copper plate can be used as the backing material 5 and the voltage between the welded member and the backing material can be directly detected. .

The voltage Vd detected by the voltmeter 10 is passed through a filter circuit 12 to remove noise, and then compared with a preset reference value VR to deviate from the reference value VR.
(= VR-Vd) is required. This deviation e is also time-differentiated in the differentiating circuit 13, and its de / dt and the above-mentioned deviation e are input to the fuzzy operation circuit 14, where fuzzy operation is performed according to the following rules to obtain the welding speed increase / decrease amount Δv. .

1. If e = N and de / dt = N, then Δv = NL.

2. If e = Z0 and de / dt = N, then Δv = NS.

3. If e = P and de / dt = N, then Δv = Z0.

4. If e = N and de / dt = Z0, then Δv = NS.

5. If e = Z0 and de / dt = Z0, then Δv = Z0.

6. If e = P and de / dt = Z0, then Δv = PS.

7. If e = N and de / dt = P, then Δv = Z0.

8. If e = Z0 and de / dt = P, then Δv = PS.

9. If e = P and de / dt = P, then Δv = PL.

Where N: negative value NS: small negative value NL: large negative value P: positive value PS: small positive value PL: large positive value Z0: zero

The table above shows the above rules.

The above-mentioned fuzzy calculation is periodically performed at predetermined time intervals, and the obtained increase / decrease amount Δv of the welding speed is added to the calculated value adding circuit 15
And the cumulative value ΣΔv is sent as the welding speed v to the welding torch traveling speed control device 16 so that the carriage 7 travels at the speed v.

The reason why the cumulative value ΣΔv is used as the welding speed from the obtained increase / decrease amount Δv of the welding speed in the calculated value adding circuit 15 will be described below.

For example, if the welding speed before the i-th time is vi−1 and the fuzzy calculation result is Δvi, the i-th welding speed vi after the fuzzy calculation is as follows.

vi = vi-1 + Δvi (1) Here, assuming that the initial speed is vo, the welding speed vi-1 at the time of fuzzy calculation is expressed by the following expression from the expression (1).

Here, assuming that the initial speed is vo = 0, the equation (2) becomes the following equation.

Substituting the equation (3) into the equation (1) gives the following equation.

The equation (4) can also be expressed as the following equation (5).

vi = {Δv1 + Δv2 ......... Δvi-1} + Δvi (5) Here, when the welding speed vi of the i-th time is obtained from the equation (5), the following equation (6) is obtained. When the equation (6) is simplified, the output of the calculation value adding circuit is represented by the following equation (7).

vi = ΣΔv (7) That is, in the embodiment of the present invention, when the initial welding speed vo is set to vo = 0, the initially obtained increase / decrease amount Δv1 becomes the first welding speed. Next, the result of the fuzzy calculation using the deviation e between the present voltage and the reference value obtained after a predetermined time and the time derivative de / dt of the deviation is the welding speed increase / decrease amount Δv2, and the calculated value adding circuit 15 first The increase / decrease amount Δv2 is added to the welding speed of, and the added value becomes the cumulative value ΣΔv (Δv1 + Δv2), which is the corrected welding speed. Then, based on the corrected welding speed and the current voltage obtained after a predetermined time, the amount of increase / decrease Δ
The calculated value adding circuit 15 adds v3 to the corrected welding speed to calculate the cumulative value ΣΔv (Δv1 + Δv2 +
Δv3) is set as the next corrected welding speed, and the current welding speed is thus corrected by the increase / decrease amount Δv obtained every predetermined time.

When the initial welding speed vo is vo = 0, the welding voltage Vd decreases as the root gap is filled with the weld metal and becomes narrower, and the fuzzy calculation is e = P and de / dt =
P, Δv = PL, the welding speed rapidly increases, and welding progresses accordingly.

In the above embodiment, when the initial welding speed vo is vo = 0,
Although the amount of increase / decrease Δv obtained first is the initial welding speed, it goes without saying that the present invention can be applied to the case where the initial welding speed vo is not vo = 0.

For example, when the root gap of the groove 3 becomes wider, the arc voltage Vd becomes larger, so that the deviation e from the reference value VR gradually becomes smaller, and in some cases becomes a negative value from zero. Such a tendency can be known by obtaining the time derivative de / dt of the deviation e, and if the sign is negative, it is in the decreasing direction,
If it is positive, it is increasing. If de / dt is zero, of course, there is no change. The fuzzy arithmetic circuit 14 weights the deviation e and the time derivative de / dt in each case to determine the welding speed increase / decrease amount Δv at regular intervals. When the root gap is wide, Δv tends to decrease, so
The welding speed v will also decrease. Conversely, the welding speed v increases as the root gap becomes narrower. In this way, the welding speed v can be rapidly and finely controlled in accordance with the change in the groove shape, so that the weld metal penetration amount is accurately maintained and a stable back bead shape can be obtained. Further, it is not necessary to provide a threshold value for the reference value VR, and the control response is good.

It should be noted that even if the welding current I is detected instead of the arc voltage Vd, the same operational effect is obtained.

[Effects of the Invention] As described above, according to the present invention, the initial welding speed in single-sided welding is set in advance, and the subsequent welding speed is between the welded member and the backing material at predetermined intervals. Of the welding speed is detected, the fuzzy operation is performed using the deviation e between the detected value and the reference value and the time derivative de / dt of the deviation, and the increase / decrease amount Δv of the welding speed is obtained. The welding speed is calculated by adding it to the welding speed at that time, and the welding speed is corrected sequentially.Therefore, even if there is a change in the groove shape, the amount of penetration is maintained accordingly. can get. Moreover, it is not necessary to set a threshold value for the reference value, control is simple and responsiveness is good.
It is possible to control the shape of the back bead efficiently.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a control system of the back bead control method of the present invention. 1,2 ...... Welded member 3 ...... Bevel arc 4 …… Backing tape Welded member 5 …… Backing material 6 …… Welding torch 7 …… Truck 8 …… Welding wire 9 …… Arc 10 …… Voltmeter 11 …… Conductive tape 12 …… Filter circuit 13 …… Differentiation circuit 14 …… Fuzzy calculation circuit 15 …… Calculation value addition circuit 16 …… Welding torch traveling speed controller

Claims (1)

(57) [Claims] 1. In a back bead control method in one-sided welding, in which a welding torch is run at a controlled welding speed to perform one-sided welding, an initial welding speed is preset, and a subsequent welding speed is set to a predetermined value. The voltage or current between the member to be welded and the backing material is detected every time, and the fuzzy calculation is performed using the deviation e between the detected value and the reference value and the time derivative de / dt of the deviation to determine the welding speed. A back bead control method for single-sided welding, wherein an increase / decrease amount Δv is obtained, the increase / decrease amount Δv is added to the welding speed at that time, and the welding speed is sequentially corrected.