JPS6372480A - Application control method for gap of welding groove - Google Patents

Abstract

PURPOSE:To enlarge the application range for a robot welding by detecting a groove gap with the analysis of the image picked-up peculiar place in an arc light shape, changing the welding conditions, etc., and performing a weaving by selecting the amplitude as well. CONSTITUTION:A gap (g) is set between an upper plate 2 and lower plate 1, an arc welding is performed with the wire 5 of a welding torch 4 and the image pickup of an arc light is performed by setting up a TV camera 3 at the upper part. The groove gap can be detected by analyzing the peculiar place in a recessed shape of the arc light picked up. The distance of the peculiar shaped place up to the weld line is then found at the weaving both end parts by fetching the arc light image during the robot weaving. The welding conditions and wire aiming position are changed based on the results thereof and the weaving is performed as well by selecting the amplitude. Due to the allowance degrees of the jig accuracy, etc., being made larger the robot welding application range is enlarged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to directly viewing welding arc light and recognizing its pattern in arc welding, particularly lap joint welding, fillet joint welding, and butt joint welding. The present invention relates to a method for detecting a welding groove gap and performing adaptive control for the groove gap.

[Conventional technology]

In arc welding, the welding part, including the molten pool, current-carrying tip, wire, welding groove, etc., is imaged with an industrial television camera (ITV), and the resulting images are analyzed.
Methods of controlling welding positions, welding conditions, etc. have been known for a long time.

However, arc light is more intense than the brightness of the surrounding area (for example, the molten pool) and contains large amounts of infrared and ultraviolet rays, making it difficult to detect welded parts.

Conventionally, the following solutions have been taken.

That is, one method is to add some innovation to the imaging device or the optical filter. For example, JP-A-51-7293
In Publication No. 8, in addition to providing filters to limit infrared rays, heat rays, color, and light intensity, a silicon vidicon picture tube is used in the television camera to limit the radiation from the welded part only in the visible light region and near-infrared region. I'm trying to let it pass.

Furthermore, in Japanese Patent Application Laid-Open No. 59-212172, an infrared television camera captures an image through a filter that allows only infrared rays to pass through. In Japanese Unexamined Patent Publication No. 58-159980, a CCD (solid-state image sensor) is used as an imaging device, thereby eliminating the need for a filter.

Another way to overcome the effects of arc light is to equip industrial television cameras with high-speed shutters9, e.g.
In Japanese Unexamined Patent Publication No. 58-7776, the opportunity for the arc to disappear when the arc is short-circuited is taken advantage of, and the shutter is opened only when the short-circuit occurs. Also, JP-A-59-202178
In this publication, in pulse welding, the shutter is opened only when the arc light during the base current period is attenuated.

Furthermore, as a method of imaging the weld zone while distinguishing it from the arc light, there is a method of providing a light source for imaging. A light source is provided, and a wavelength band in which the amount of disturbance light is smaller than the amount of light from the light source is defined as a detection wavelength. Further, in Japanese Patent Application Laid-Open No. 59-191574, a light source is provided for projecting light forward in the traveling direction of the welding torch to represent an image of the welding groove as a contour divided by shading.

What is common in the various conventional examples mentioned above is that
The object to be imaged is a welded part such as a molten pool, and the arc light is a disturbance light that disturbs it. Therefore, it can be said that the object to be imaged is to separate and remove the arc light from the image to be imaged.

However, since the intensity of arc light is intense and its wavelength covers almost the entire range, it is difficult to completely remove it, and the equipment must be complicated and expensive.

On the other hand, in the case of narrow gap welding, there are cases in which the arc light itself is monitored. I'm looking for the center of rotation. Also, JP-A-58-187268
In the publication, a photodetector is provided at the tip of the torch, and the movement of the torch is controlled by comparing the detector outputs.

[Problem that the invention seeks to solve]

In contrast to the conventional method of detecting the welding position described above, the method of detecting the weld groove gap uses laser light.
Although there are methods for detecting changes in the step height of a workpiece, there is no method that detects changes in the height direction of the step difference in the workpiece from images taken by an ITV during welding. Furthermore, the method of detecting a gap by directly imaging the gap has many problems because the arc light is too intense compared to the surrounding brightness.

Next, there is a method to fill the detected gap, but simply changing the welding conditions (current, voltage, speed) may cause the workpiece to melt, making it difficult to set the welding conditions. If only the conditions were changed, the allowable gap would be too small. Another method is to perform weaving using an automatic welding device capable of weaving to fill the gap, but since the weaving amplitude is constant, it cannot respond to real-time changes in the gap amount due to thermal distortion etc. during welding.

The present invention solves the above problems, detects the welding groove gap by directly looking at the arc itself and recognizing its pattern, and performs adaptive control for the groove gap without adding any special equipment. With the goal.

[Means for solving problems]

In order to achieve this object, the present invention is a method for detecting a welding groove gap in arc welding and performing adaptive control welding for the gap. By analyzing the locations where the light has a unique shape, the groove gap can be detected, and in order to fill the groove gap, changes can be made to welding conditions such as welding current, welding voltage, and welding speed, as well as to the target position of the wire. Weaving is performed by selecting an amplitude according to the detected groove gap.

[Effect]

In the present invention, in an automatic welding device capable of weaving welding, when a television camera is installed almost above the weld joint to take an image of the welding situation, the intense arc light is present, and the television image only shows the outline of the arc light. Although it cannot be identified, it has been confirmed through experiments that the outline of the arc light strongly reflects the state of the welding groove. In particular, if there is a gap in the welding groove, the contour of the arc light imaging shape will be negative.
In the present invention, this phenomenon is utilized to detect the weld groove gap.

It has been confirmed through experiments that welding groove gap detection can also be performed by weaving welding, and by selecting the amplitude of weaving welding according to the gap, appropriate welding can be performed for the welding groove gap.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments of lap joint welding shown in the drawings.

The present invention has two major features: gap detection by pattern analysis of arc light, and gap adaptive welding by weaving with the weaving amplitude controlled by pattern analysis of arc light.

The first part shows the overall flow of the present invention. First, a teaching operation is started and a gap is detected.

When a gap is detected in step 120, weaving is started. The initial value of the amplitude at this time varies depending on the variation in the gap due to warping, but in the case of a lap joint, it is set to about 2 to 3 times the plate thickness. If the weaving amplitude is not appropriate, change the amplitude, and if it is appropriate, perform gap detection during weaving welding operation (step 150).
Weaving is continued while the gap is being detected, and this operation is repeated until the teaching operation is completed.

Next, the principle of the gap detection method according to the present invention will be explained.

If there is no gap between the lower plate 1 and the upper plate 2 as shown in Figure 2 (ta+), the arc light will exit above the upper plate 2 by about half its width, as shown in Figure 2 (bl). In contrast, Fig. 3 (a
If there is a gap g between the lower plate 1 and the upper plate 2 as shown in ), the arc light will not be able to exit much to the upper plate 2 as shown in Fig. 2). Therefore, by observing the arc light with the TV camera 3 on the top of the workpiece, the gap between the workpieces can be detected based on the size of the arc light on the upper plate side.In the figure, 4 is the welding torch, 5 is the wire, and A is the arc. be.

Moreover, as a result of experimental observation, it has been confirmed that when a gap exists in the workpiece, the arc light on the upper plate side not only becomes smaller, but also exhibits a concave shape as shown in FIG. This makes it possible to detect gaps based on the arc shape. An example of the flowchart of these detections is shown in Figure 5.First, as an initial setting, a window containing arc light with the welding line as the y-coordinate is set.Next, when the robot's teaching operation starts, Correct the discrepancy. Correct the horizontal deviation and enter the gap detection routine. An example of a gap detection routine will now be described.

1) Method A Scan in parallel to the Y axis from the upper left, detect level changes of 0-1-0-1, and detect gaps. This takes advantage of the fact that the arc light on the upper plate side has a concave shape due to the presence of a gap.

2) Method B Scan in parallel to the X-axis from the upper left, detect the inflection point C by the wire, and measure the distance H1+, 1t to the welding line. l,
and i, and if aXl<i'l (a is a constant determined by experiment), a gap is detected. This takes advantage of the fact that, as shown in FIG. 3, when a gap exists, the arc light on the upper plate side becomes smaller.

3) Method C (see FIG. 6) Similar to method B, this method utilizes the fact that the arc light on the upper plate side becomes smaller when a gap exists. By determining the area S of the arc light on the upper plate side, it is detected that the arc light becomes smaller. Note that St is a constant determined by experiment; if the area S of the arc light is smaller than the constant S, it is determined that this is a gap; otherwise, the process returns to step 230 in FIG.

Next, a method of changing the weaving amplitude with respect to the gap will be explained.

If the size of the gap does not change, a constant weaving amplitude is sufficient. However, when the size of the gap changes, it is necessary to perform control such that if the gap is large, the weaving amplitude is increased, and if the gap is small, the weaving amplitude is decreased.

The present invention determines whether the weaving amplitude is appropriate for the gap based on the arc light pattern, and determines whether the weaving amplitude is appropriate for the gap.
If the amplitude is too large or too small), the amplitude is changed. FIG. 7 shows a flow for detecting whether the weaving amplitude for the gap is appropriate.

In the flowchart of FIG. 7, during the robot weaving operation, synchronization is first achieved at the time of Left wax, and an image is captured. And the distance to the welding line 1. ,l.

Measure 11 and 2. Make a comparison. 1. If ×a>1°, the amplitude in the Left direction is large, 1. Xal<I
If g, then 1. It is determined that the amplitude in the ef direction is small. Here, aI+at is a constant determined by experiment. This is to detect whether or not the arc light on the upper plate side is of an appropriate size to fill the gap when left max, that is, when weaving is performed toward the upper plate side. If the arc light on the upper plate side is small, the gap cannot be filled, and if it is large, the bead appearance will be poor.

Next, synchronization is performed when Right is max, and an image is captured. and the distance e to the welding line, 1. Measure 1
Compare 3 and 14, A, if Xa3<14, Ri
If the amplitude in the ght direction is large, /3Xa4>1. In this case, it is determined that the amplitude in the R4ght direction is small. here,
a3+84 is a constant determined by experiment.

This is to detect whether the arc light on the lower plate side has an appropriate size to fill the gap when performing right waxing, that is, when weaving to the lowest plate side.

If the arc light on the lower plate side is small, the gap cannot be filled, and if it is large, the bead appearance will be poor.

Gap detection during weaving is synchronized when the welding torch comes to the center of weaving, and if an image is captured, it is possible to detect gaps using the same detection method as in straight welding.

Further, if the weaving amplitude becomes less than a certain value by amplitude control, it is assumed that there is no gap, and it is possible to have the same function as gap detection by returning to straight welding.

This example is a method of detecting whether the amplitude is appropriate for each cycle of weaving and controlling the next cycle.

〔Effect of the invention〕

As explained above, in the present invention, by directly observing the arc light and analyzing the locations where the arc light has a unique shape, the groove gap is detected and the welding process is performed to fill the groove gap. I try to do it.

This allows adaptive control even for real-time fluctuations due to thermal strain during welding of the gap.

Therefore, the tolerances for workpiece precision and jig precision are dramatically increased, and the scope of application of robot welding can be expanded.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the overall flow of control according to the present invention, Figs. 2 and 3 are explanatory diagrams showing the principle of gap detection according to the present invention, and Fig. 4 shows the arc light of the workpiece when there is a gap. 5 is a flowchart of the gap detection method of the present invention, FIG. 6 is a flowchart of method C, and FIG. 7 is a flowchart of detecting whether the amplitude of weaving is appropriate for the gap. 1: Lower board 2: Upper board 3: TV camera 4:? Contact torch 5: Wire A: Arc g: Gap

Claims (1)

[Claims] 1. In the method of detecting the welding groove gap in arc welding and performing adaptive control welding for the gap, the shape of the arc light is imaged from above the welding part, and the area where the arc light has a peculiar shape due to the groove gap By analyzing this, the groove gap is detected, and in order to fill the groove gap, the welding conditions such as welding current, welding voltage, welding speed, and the target position of the wire are changed. An adaptive control method for a welding groove gap, characterized by performing weaving by selecting a corresponding amplitude.