JPH0275492A - Method and device for profiling weld line - Google Patents

Abstract

PURPOSE:To enhance the follow-up property of a welding torch against a bending state of a weld line by detecting a change with the lapse of time of a position of the weld line on a photographing screen of a camera and predicting the subsequent bending state of the weld line, and correcting a position of the camera, based on a result of its prediction. CONSTITUTION:By detecting a change with the lapse of time of a position of a weld line 15 on a photographic screen of a camera 12, the subsequent bending state of the weld line 15 is predicted, and based on a result of its prediction, a position of the camera 12 is corrected. Therefore, even if the bending state of the weld line 15 is large, the weld line 15 can be held surely in a visual field of the camera 12, and also, it is unnecessary to enlarge the visual field of the camera 12, the detection accuracy of the camera 12 is not lowered, and irrespective of whether the bending state of the weld line 15 is large or small, the position of the weld line 15 can be detected with high accuracy. Moreover, since a position of a welding torch 19 is corrected, based on a high accuracy position detection of the weld line 15, the follow-up property against the bending state of the weld line 15 can be enhanced remarkably, and welding can be homogenized.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention provides a welding line tracing method for tracing a welding torch on a welding line while monitoring the degree of curvature of the welding line with a camera. Regarding the device.

(Prior Art) In recent years, a welding line copying device as shown in FIG. 9, for example, has been developed to automate welding work. This welding line copying device fixes a camera 2 with a slit light source (not shown) on the lower right side of a main body 1, and irradiates a welding line 5 of a workpiece 4 with semiconductor laser light 3 from the slit light source. The reflected light is received by the light receiving surface of the camera 2 and visualized. A welding torch 6 is provided on the left side of the main body 1 so as to be movable in the direction of arrow B (Y-axis direction in the X-Y coordinates) by a drive means 7.

In this case, during welding work, the main body 1 is linearly moved in the direction of arrow A (X-axis direction). At this time, the photographic screen 2a of the camera 2 (see FIG. 10) shows the workpiece 4a (hatched area) illuminated by the slit light source and the groove width W of the weld line 5, and the image signal is It is input to the control device 8 (see FIG. 9).

Then, the control device 8 controls the groove center C of the weld line 5.
(see FIG. 10) to find the deviation fid of the groove center C with respect to the camera reference K (the center line of the photographic screen 2a). From the time when the deviation amount d is obtained in this way, td
The position is corrected by moving the welding torch 6 in the direction of arrow B (Y-axis direction) by the amount of deviation d described above after a delay of seconds (see equation (1) described later), and by repeating the above-mentioned operation. The welding torch 6 is made to trace the welding line 5. The delay time td is td - D/υ (1) where D is the distance between the detection point (position of camera 2) and the welding point (position of welding torch 6), and υ is This is the welding speed (moving speed of the main body 1), and means that the welding point is delayed by td seconds with respect to the detection point.

(Problems to be Solved by the Invention) In the conventional configuration described above, the camera 2 is fixed to the main body 1, and the camera 2 only moves linearly in the X-axis direction. , the weld line 5 protrudes from the field of view of the camera 2, making it impossible to follow it. Therefore, as a method for improving the ability to follow the bending of the welding line 5, a method has been adopted in the past in which the field of view of the camera 2 is widened and the movement stroke of the welding torch 6 is also increased accordingly.

However, when the field of view of the camera 2 is widened, the detection accuracy decreases. This is because the resolution R of the video signal (the size of the object per horizontal scanning line) is proportional to the field of view V [mm] in the X-axis direction, as shown in the following equation (2).

Here, m is the magnification of the light receiving surface with respect to the field of view V in the X-axis direction. The resolution R in equation (2) is calculated using a 1/2-inch CCD camera (with a light-receiving surface size of 4, 8 ++n
6,4 +u, the effective number of horizontal scanning lines is approximately 242 per field), and the magnification is m-4,8
/V.

In this way, by widening the field of view of camera 2, the detection accuracy (
Since the resolution R) deteriorates, even if the movement stroke of the welding torch 6 is increased (even if the movement stroke of the welding torch 6 is increased), the accuracy of the tracing operation of the welding torch 6 decreases, resulting in non-uniform welding quality.

Therefore, in order to ensure welding quality, there is a limit to the expansion of the field of view of the camera 2, and therefore, there has been a strong desire to develop a new technique that improves the ability to follow the bending of the welding line 5.

The present invention was made in consideration of such circumstances, and
Therefore, the purpose is to provide a welding line tracing method and device that can improve the followability of the welding line to the degree of bending and can achieve uniform welding even when the degree of bending is relatively large. be.

[Structure of the Invention] (Means for Solving the Problems) The welding line tracing method of the present invention moves a camera along the welding line to trace the welding line with a welding torch, and detects the curve of the welding line. This method corrects the position of the welding torch according to the degree of curvature of the welding line while monitoring the condition, and detects changes over time in the position of the welding line on the camera's photographic screen to determine the degree of subsequent curvature of the welding line. After predicting, based on the prediction result, the camera position is corrected so that the welding line is placed in the center of the field of view, and the correction amount of the camera position and the position of the welding line on the camera's shooting screen are adjusted. Based on this, the position of the welding torch is corrected.

In order to carry out this weld line tracing method,
The welding line copying device of the present invention includes a welding torch, a camera that is moved along the welding line together with the welding torch to monitor the degree of curvature of the welding line, and a camera that monitors the position of the welding line over time on a photographic screen of the camera. a detection means for detecting the change; a prediction means for predicting the degree of bending of the weld line thereafter based on the detection result of the detection means; and a prediction means for predicting the degree of bending of the weld line thereafter based on the detection result of the prediction means; A camera position correction means for correcting the welding line so as to fit the welding line; and a welding torch position for correcting the position of the welding torch based on the amount of correction of the camera position by the camera position correction means and the position of the welding line on the photographic screen of the camera. The correction means is also provided.

(Function) According to the welding line tracing method of the present invention, in order to detect the temporal change in the position of the welding line on the photographic screen of the camera and predict the degree of bending of the welding line thereafter, based on the result of its child AP1, By correcting the position of the camera, the weld line can be reliably placed within the field of view of the camera even if the weld line is highly curved. By correcting the position of the welding torch based on the correction amount of the camera position and the position of the welding line on the camera's shooting screen, the welding torch can be adjusted with high precision even if the welding line is highly curved. It can be followed.

Further, according to the welding line copying device of the present invention, the detection means detects a change over time in the position of the welding line on the photographic screen of the camera, and based on the detection result, the degree of bending of the welding line thereafter can be predicted. -1 means to predict, and based on the prediction result, correct the camera position by camera position correction means;
The position of the welding torch is corrected by the welding torch position correction means based on the correction amount of the camera position and the position of the welding line on the photographic screen of the camera.

(Example) Hereinafter, a first example of the present invention will be described based on FIGS. 1 to 4. 11 is the main body of the welding line copying device, which is moved in the direction of arrow A (X-axis direction) by a drive device (not shown) during welding.
It is designed to be moved in a straight line. On the lower right side of the main body 11, there is provided a slit light source (not shown) movable in the direction of arrow B (Y-axis direction). The welding line 15 of the object 14 is irradiated, and the reflected light is received by the light receiving surface of the camera 12 and visualized. A camera position correction means 16 corrects the position of the camera 12 in the direction of arrow B, and its operation is automatically controlled by a control device 17. As shown in FIG. 2, this control device 17 includes an image processing circuit 17a that binarizes the image signal from the camera 12, an arithmetic processing circuit 17b that functions as a detection means and a prediction means to be described later,
It is composed of a RAM 17c that stores various data, and images are displayed on the screen of the monitor 18 based on the output of the image processing circuit 17a. On the other hand, in FIG. 1, 19 is a welding torch that uses CO2 laser light as a heat source, and the main body 1
The welding torch position is corrected by the welding torch position correction means 20. The operation of this welding torch position correction means 2o is automatically controlled by a control device 17.

In this case, the control device 17 controls the operation as follows according to the control program shown in the flowchart of FIG. First, move the main body 11 in the X-axis direction (direction along the welding line 15).
(step PI). As a result, each time the main body 11 (camera 12) moves a distance, the camera 12
As shown in FIG. 3, by processing the image signal of 3
The figure shows that each time the camera 1.2 moves a distance, the shooting screen 1
2a, the image 14a of the workpiece 14 projected at the center, the groove center C, and the deviation ff1d.

(The smaller the subscript attached to d indicates the earlier data), the deviation Jnd is stored as data in the RAM 17c (step P2). By repeatedly detecting the deviation End at regular intervals in this manner, the control device 17 functions as a detection means for detecting changes over time in the position of the welding line 15 on the photographic screen 12a of the camera 12. Then, when the amount of deviation d has been detected three times, the direction of movement E of the weld line 15, that is, the degree of bending, is predicted based on the data d1°d2+d3 of the previous three times (step P3). For example, the following two methods can be considered for this prediction method.

■ Obtain as an arrow connecting d1 (first data) and d3 (second data) with a straight line. In this case, d2
(second data) is ignored in principle, and d2 is used when d3 is out of the field of view of the camera 12 and cannot be detected, and dl and d2 are connected with a straight line.

(2) Obtain a straight arrow starting from d1 and passing through the middle of d2 and d3 (average the data).

As described above, the control device 17 functions as a preliminary 11-1 means for predicting the degree of bending of the weld line 15 (progressing direction E). After the prediction, drive the camera position correction means 16,
Move the camera 12 to the extension line of the welding line 15 in the direction of travel E.
The camera 12 is moved in the axial direction, thereby correcting the position of the camera 12 so that the welding line 15 is placed in the center of its field of view (photographing screen 12a) as shown by the dotted line in FIG. The position F is stored in absolute coordinates (step P4). Next, the welding torch position correction means 20 is driven to move the welding torch 19 in the Y-axis direction to the groove center C at the position F of the camera 12 td seconds ago, thereby changing the position of the welding torch 19 onto the welding line 15. Correct to (
Step P5). Note that td is the delay time defined by the above-mentioned equation (1). By repeating the above-mentioned operations until the welding work is completed (step P6), welding is performed while the welding torch 19 accurately follows the welding line 15.

According to the first embodiment, the change over time of the position of the weld line 15 on the photographic screen 12a of the camera 12 is detected, the degree of bending of the weld line 15 (progressing direction E) thereafter is predicted, and the Since the position of the camera 12 is corrected based on the prediction result, even if the weld line 15 is highly curved, the weld line 15 can be reliably placed within the field of view of the camera 12, and the field of view of the camera 12 can be There is no need to increase
There is no need to reduce the detection accuracy (resolution R,) of the camera 12, and regardless of the degree of bending of the weld line 15, the weld line 1
5 position can be detected with high accuracy. Since the position of the welding torch 19 is corrected based on such highly accurate position detection of the welding line 15, the welding torch 19 can be made to follow the welding line 15 with high precision even if the welding line 15 is highly curved. As a result, it is possible to greatly improve the ability to follow the bending of the welding line 15, and it is possible to achieve uniform welding even when the bending of the weld line 15 is relatively large.

Incidentally, in the first embodiment, the moving direction of the camera 12 is one-dimensional (Y-axis direction only), but the present invention is not limited to this. For example, the present invention shown in FIGS. 5 to 8 As in the second embodiment, the welding line 15 may be captured by moving the camera 12 two-dimensionally. That is, the camera 12 in this second embodiment is capable of horizontal rotation in the direction of arrow G in addition to movement in the Y-axis direction (direction of arrow B), and the rotational movement moves the camera to a newly established camera position. Correction means 21
executed by The purpose of adding the rotational motion in this way is that, as shown in FIG. 7, when the angle α of the advancing direction E (curvature) of the weld line 15 becomes large, the groove width W of the weld line 15 becomes too large. This is because image processing and control of the welding torch 19 become difficult.

In the second embodiment, the control device 17 controls the operation as follows according to the control program shown in the flowchart of FIG. First, the main body 11 is linearly moved in the X-axis direction (direction along the welding line 15) (step Pi).

As a result, each time the main body 11 moves a distance, the groove center C of the welding line 15 is adjusted based on the camera reference, similarly to the first embodiment.
The amount of deviation d between the two is calculated and the amount of deviation d is stored as data (step P2). Then, when the deviation md has been detected three times, the welding line 1
5, that is, the degree of bending is predicted (step P3). Next, the angle α between the traveling direction E of the welding line 15 and the camera reference is calculated (step P4). Then, the camera 12 is moved in the Y-axis direction to the extension line of the traveling direction E of the welding line 15 to correct the position of the camera 12 in the Y-axis direction, and the camera position correction means 21 for rotational operation is driven. The camera 12 is rotated by the above angle α, and the corrected position F of the camera 12 is stored in absolute coordinates (step P5). In this case, as the camera 12 rotates, the camera reference is also rotated by the angle α, and 1 becomes the new camera reference, and the welding line 1
5 become parallel and the groove width W1 becomes smaller, making image processing and control of the welding torch 19 easier. Incidentally, the relationship expressed by the following equation (3) holds between the groove width W before rotation and the groove width Wl after rotation.

W−W, /CO8α ・・・・・・(3)(−2/π
(α + 2/π) However, in order for this formula (3) to hold true, the optical system must be adjusted so that the image 14a of the workpiece 14 is located on the rotation center O of the camera 12; Two conditions are required: the vertical/horizontal magnification of the field of view must be the same.

Then, in step P6, the welding torch 19 is
The position of the welding torch 19 is corrected by moving in the Y-axis direction to the groove center C at the position F of the camera 12 seconds ago. At this time, by converting the data of the groove center C1 on the camera reference Kl after rotation into the data on the original camera base *K (corresponding to the X axis of absolute coordinates) using the above equation (3), the camera Welding torch 19 controlled using coordinates above the reference (absolute coordinates)
A positional correction can be made to I'EIif.

After correcting the position of the welding torch 19, it is determined whether or not the welding work is completed (step P7). If the welding work is not completed, the main body 11 is moved in the traveling direction E (X, axial direction) of the welding line 15.
(step P8), and thereafter repeating the operations from step P2 described above until the welding work is completed, so that the welding torch 19 accurately follows the welding line 15 and welds. In FIG. 7, the X-Y coordinates are absolute coordinates, and the Xl-Y1 coordinates are new coordinates after correcting the angle α of the camera 12. After correcting the angle α, the welding direction (
The moving direction of the main body 11) is the Xl axis direction, and the camera 12
The direction of movement is Y, which is the axial direction.

In the second embodiment, since the camera 12 is moved two-dimensionally, the ability to follow the curve of the welding line 15 can be further improved.

In each of the above embodiments, the degree of bending of the welding line 15 (
Although the traveling direction E) is predicted n1 in advance, the degree of bending may be predicted every time the amount of deviation is detected twice or four times or more.

[Effects of the Invention] As is clear from the above description, according to the welding line tracing method and its device of the present invention, changes over time in the position of the welding line on the photographic screen of the camera are detected and subsequent welding lines are Since the degree of curvature of the weld line is predicted and the position of the camera is corrected based on the predicted result, it is possible to reliably keep the weld line within the field of view of the camera even if the degree of curvature of the weld line is large. There is no need to increase the field of view of the camera at the cost of reducing detection accuracy (resolution), and the position of the weld line can be detected with high precision regardless of the degree of curvature of the weld line.

Since the position of the welding torch is corrected based on such highly accurate position detection of the welding line, the welding torch can be made to follow the welding line with high precision even if the welding line is highly curved. , it is possible to achieve uniform welding even when the degree of bending is relatively large.

[Brief explanation of the drawing]

1 to 4 show a first embodiment of the present invention, in which FIG. 1 is an overall perspective view, FIG. 2 is a block diagram showing the electrical configuration, and FIG. 3 is a concept of image processing. FIG. 4 is a flowchart of the control program. 5 to 8 show a second embodiment of the present invention. FIG. 5 is a diagram equivalent to FIG. 1, FIG. 6 is a diagram equivalent to FIG. 2, and FIG. 7 is a diagram equivalent to FIG. 3. Equivalent diagram, FIG. 8 is a diagram equivalent to FIG. 4. 9 and 10 show conventional examples, with FIG. 9 being a diagram corresponding to FIG. 1, and FIG. 10 being a diagram corresponding to FIG. 3. In the drawing, 11 is the main body, 12 is the camera, 14 is the object to be welded,
15 is a welding line, 16 is a camera position correction means, 17 is a control device (detection means, prediction means), 19 is a welding torch, 20
21 is a welding torch position correction means, and 21 is a camera position correction means. Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. In order to trace the welding line with the welding torch, the camera is moved along the welding line and the position of the welding torch is adjusted according to the curvature of the welding line while monitoring the degree of curvature of the welding line. This is a method of correcting according to the situation, which detects changes over time in the position of the weld line on the photographic screen of the camera, predicts the degree of curvature of the weld line after that, and then performs the correction according to the prediction result. The position of the camera is corrected so that the welding line is placed in the center of its field of view, and the position of the welding torch is corrected based on the amount of correction of the camera position and the position of the welding line on the photographic screen of the camera. A welding line copying method characterized by: 2. A welding torch, a camera that moves along the welding line with the welding torch and monitors the degree of curvature of the welding line, and a detection means that detects changes over time in the position of the welding line on the camera's photographic screen. a prediction means for predicting the degree of subsequent bending of the weld line based on the detection result of the detection means; and a prediction means for predicting the degree of bending of the weld line thereafter based on the detection result of the detection means, and a position of the camera so as to fit the weld line in the center of the field of view based on the prediction result of the prediction means. A camera position correction means for correcting the welding torch, and a welding torch position correction means for correcting the position of the welding torch based on the amount of camera position correction by the camera position correction means and the position of the welding line on the photographic screen of the camera. A welding line copying device.