JPS6242004A - Seam position detecting device for electric welded pipe - Google Patents

Abstract

PURPOSE:To correctly detect the position of the seam part after the welding bead is cut by providing the projector to scan the incident light located in the plane including the pipe central axis by the incident optical axis in the pipe circumferential direction of the pipe surface including the seam part. CONSTITUTION:A seam position detecting device reciprocates a mirror 3b in the right-angled direction to a central axis 6 of an electric welded pipe 5 by a beam scanner 4, and thereby, the device scans the laser beam reflected by the mirror 3b parallelly within the scope of + or -25mm. The laser beam having the optical axis parallel to the central axis 6 of the electric welded pipe 5 is made incident on by the constant angle theta (70 deg.<=theta<=90 deg.) to the surface of the electric welded pipe 5 by mirrors 3c and 3d. By operating the laser beam parallelly in the right-angled direction to the central axis 6 of the electric welded pipe 5, the equal effect is obtained approximate to scan the incident light in the plane including the central axis 6 of the electric welded pipe 5 by the incident optical axis in the pipe circumferential direction of the electric welded pipe 5. By the scanning method, the action of a beam scanner 4 is monitored by a potentiometer 7, and thereby, the beam irradiating position in the surface of the electric welded pipe 5 can be known easily and correctly.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a seam position detection device for an electric resistance welded pipe.

[Prior Art] Ultrasonic flaw detection is performed on a seam portion of a welded portion of an electric THI tube after cutting a weld bead.

In this ultrasonic work, when attempting to automate the work of following the seam with a flaw detector, automatic detection technology for the seam is essential.

On the other hand, it has been widely known that when a laser beam is projected onto an abnormal point such as a scratch or cutting mark on the surface of an object, a characteristic reflection pattern corresponding to the shape and direction of the abnormal point is generated. A proposal has been made to apply this principle unconditionally to automatic detection of the seam portion.

[Problems to be Solved by the Invention] However, in the method using the above-mentioned laser light reflection pattern, there are scales or traces of scale falling off on the seam after annealing, and the directionality of cutting scratches is affected. Because it is extremely indistinct, the difference in anisotropy of the laser beam reflection pattern is unclear. ■ Scale or traces of scale falling off are present on the seam after annealing, and the laser beam reflectance is due to the reflection of the tube surface. Since it changes significantly depending on the position, if you do not use reflection pattern judgment logic according to the reflection intensity, it will be difficult to detect the correct reflection pattern, and there is a high possibility of erroneously detecting the position of the seam, making it unsuitable for practical use. There is.

An object of the present invention is to enable accurate detection of the position of a seam after cutting a weld bead.

[Means for Solving the Problems] The present invention provides a seam position detection device for an ERW pipe that detects the position of a seam after cutting a weld bead. (B) An image receiving device that images a reflection pattern representing a light reflection intensity distribution from the tube surface.

(C) a scanning line selection circuit that selects a qualified scanning line suitable for recognizing the anisotropy of the reflection pattern from a plurality of scanning lines in each image captured by the image receiving device during one scanning by the projector; D) a scan line signal width detection circuit that detects the effective reflected signal width V of each eligible scan line selected by the scan line selection circuit in each image; A reflection pattern width detection circuit detects the maximum value W of each effective reflection signal width J, and (F) a seam is calculated from the maximum effective reflection signal width Wn of each image detected by the reflection pattern width detection circuit during one scan. and a seam position detection circuit that identifies the seam portion and the base material portion and detects the position of the seam portion.

[Operation] According to the present invention, a qualified scanning line suitable for recognizing the anisotropy of a reflection pattern is selected in each image, an effective reflection signal width J of each qualified scanning line is detected, and each effective Reflected signal width V
Since the maximum value W of is detected, it is possible to correctly detect the anisotropy of the reflection pattern without being affected by changes in the reflection intensity, which varies significantly depending on the reflection position on the tube surface. Therefore, it is possible to identify with high precision the base material portion that produces a vaguely masculine reflection pattern and the seam portion that exhibits an anisotropic reflection pattern, and to accurately detect the position of the seam portion.

[Embodiment] FIG. 1 is a schematic diagram showing a sensor head l of a seam detection device according to an embodiment of the present invention. Laser light 2 with a wavelength of 833 nm emitted from Hs-Ne laser IA is irradiated onto mirror 3b of beam scanner 4 via mirror 3a. 5 is an electric resistance welded pipe, and 5A is a seam portion after cutting with a weld bead. The laser beam 2 has an optical axis parallel to the central axis 6 of the electric resistance welded tube 5 due to the mirror 3b. By reciprocating the mirror 3b by the beam scanner 4 in a direction perpendicular to the central axis 6 of the electric resistance welded tube 5, the laser beam reflected by the mirror 3b is scanned in parallel within a range of ±25 mm. The laser beam, which has an optical axis parallel to the central axis 6 of the ERW tube 5, is incident on the surface of the ERW tube 5 at a constant angle θ (70 degrees≦θ≦90 degrees) by mirrors 3c and 3d. do.

In the above light projecting device, by operating the laser beam parallel to the central axis 6 of the ERW tube 5, the incident light whose incident optical axis is within a plane including the center axis 6 of the ERW tube 5 is illuminated. Approximately the same effect as scanning in the circumferential direction of the tube 5 can be obtained.

Further, according to this scanning method, by monitoring the movement of the beam scanner 4 with the potentiometer 7, the beam irradiation position on the surface of the electric resistance welded tube 5 can be easily and accurately determined. The laser beam 2 irradiated by the above-mentioned light projecting device is reflected on the surface of the electric tube 5, and a reflection pattern 9 of the reflected laser beam 8 is projected onto the screen 10. The reflection pattern projected onto the screen 10 is reflected by a solid-state camera 11 that includes the screen 10 in its field of view.
is perceived by. The reflection pattern image received by the solid-state camera 11 is transmitted to the signal processing circuit together with the output of the potentiometer 7 representing the position of the laser beam at that time.

The video output transmitted from the solid-state camera 11, whose block diagram of the signal processing circuit is shown in FIG. The scanning lines located at After that, in the reflection pattern width detection circuit, the maximum value W of the values of each effective reflection signal width U is detected. Maximum effective reflection signal width Wn of the reflection pattern for each image obtained in this way during one scan
(r+=1 to 50...when 50 frames of images are input per one scan of the laser beam) is input to the seam position detection circuit and used to calculate the center position of the seam portion.

The control signal output unit calculates the amount of deviation between the calculated center position of the seam part and the center position of the flaw detector, and further averages each center position calculated in the longitudinal direction of the ERW tube 5 and eliminates abnormal values. will be carried out. The control signal obtained by the above processing is input to the sensor head drive motor 12 as a flaw detector drive unit, and a seam tracing operation is performed via the fan-shaped gear 13. 14 is a potentiometer for detecting the position of the sensor head.

FIG. 3 is a block diagram showing all the detection circuits of the above embodiment, and FIG. 4 is a flowchart showing the processing contents of the seam position detection circuit and the control signal output section.

The scanning line selection circuit calculates Th1 = Ip 1=1~10
0), select only those that satisfy Pi>Thl.

On the other hand, the scanning line signal width detection circuit detects the peak (+a P 1 ) of each scanning line and calculates Th2=PiXβ+
C2...(2) (β and C2 are set constants) are calculated, and the effective reflected signal width Ll/l of each scanning line signal is detected using Th2 as a slice level.

Next, in the reflection pattern width detection circuit, these effective reflection signal widths 1. Select only the scanning lines where Pi>Thl from L/i, and then select the maximum value Wn(
n=1 to 50). In this way, the width of the reflection pattern (extension in the circumferential direction) of each image can be determined without being affected by the peak intensity of the video signal, distortion of the reflection pattern, etc.

The maximum effective reflection signal width Wn of each image obtained by the reflection pattern width detection circuit is determined from the maximum value Wa + ax after being input to the seam position 1 detection circuit Th3 = Wma
x X y+C3-- (3) (γ and C3 are set constants) each maximum effective reflected signal width Wn is converted into a floating z value. (Hn=0 or 1). From this result, the seam center position for each laser beam scan is calculated according to the flowchart shown in FIG. Furthermore, the results are averaged and abnormal values removed by the control signal output section shown in FIG.

FIG. 5 is a Vj diagram showing the seam center detection results by this apparatus. The broken line indicates the actually measured position of the seam center, and the solid line indicates the detection position according to the present invention. According to the present invention, it was confirmed that the seam portion could be detected with an accuracy of ±3 m.

FIG. 6 is a state diagram showing the results of automatic tracing of a seam section when this device is actually installed in a flaw detection field. The horizontal axis shows the pipe position during running, and the vertical axis shows the amount of deviation between the center of the seam and the center of the deeply damaged blade.As a result, according to the present invention, ±5 feet
It was confirmed that it is possible to perform automatic copying with an accuracy of .

[Effects of the Invention] As described above, the present invention provides a seam position detection device for an ERW pipe that detects the position of a seam after cutting a weld bead. (B) an image receiving device that captures an image of a reflection pattern representing the light reflection intensity distribution from the tube surface; (C) (D) a scanning line selection circuit that selects a qualified scanning line suitable for recognizing the anisotropy of the reflection pattern from a plurality of scanning lines in each image captured by the image receiving device during one scanning by the light projecting device; (E) a scan line signal width detection circuit that detects the effective reflected signal width J of each eligible scan line selected by the scan line selection circuit in each image; A reflection pattern width detection circuit detects the maximum value W of the effective reflection signal width V, and (F) the maximum effective reflection signal width Wn of each image detected by the reflection pattern width detection circuit during one scan is used to calculate the seam portion and the width. The seam position detection circuit identifies the material part and detects the position of the seam part.

Therefore, a base material part that produces an isodirectional reflection pattern,
It becomes possible to identify the seam portion exhibiting an anisotropic reflection pattern with high accuracy and accurately detect the position of the seam portion after cutting the weld bead.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a sensor head of a seam position detection device according to the present invention, FIG. 2 is a block diagram showing a signal processing circuit used in the present invention, and FIG. 3 is a signal processing circuit used in the present invention. A block diagram showing the hardware configuration of the circuit, Fig. 4 is a flowchart showing the processing contents of the seam position detection circuit and control signal output section, Fig. 5 is a line diagram showing the detection results of the seam center position, and Fig. 6 is an automatic copying FIG. 3 is a state diagram showing the results. 1...Sensor head, lA...Laser, 2.8
... Laser light, 4... Beam scanner, 5...
ERW pipe, 5A... Seam part, 6... Center axis, 9...
-Reflection pattern, 11...camera. Agent Patent Attorney Osamu Shiokawa Figure 5 Figure 6 Robive a1 (TrL)

Claims (1)

[Claims] (1) In a seam position detection device for an ERW pipe that detects the position of a seam after cutting a weld bead, (A) an incident light whose incident optical axis is located within a plane that includes the pipe center axis, including the seam; (B) an image receiver that captures an image of a reflection pattern representing the distribution of light reflection intensity from the tube surface; (C) a light projector that scans the tube surface in the circumferential direction; (D) a scanning line selection circuit that selects a qualified scanning line suitable for recognizing the anisotropy of the reflection pattern from a plurality of scanning lines in each captured image; (E) A scanning line signal width detection circuit that detects the effective reflected signal width ω of each eligible scanning line; and (E) Detecting the maximum value W of each effective reflected signal width ω detected by the scanning line signal width detection circuit in each image. (F) Identify the seam part and the base material part from the maximum effective reflection signal width Wn of each image detected by the reflection pattern width detection circuit during one scan, and determine the position of the seam part. 1. A seam position detection device for an electric resistance welded pipe, comprising a seam position detection circuit for detecting the seam position.