JP4374845B2 - Method and apparatus for detecting bead shape of ERW pipe - Google Patents

Description

により、ｘ_c＝−0.0781と算出した値を用い、ビード範囲の設定は予め設定した概略のビード幅Ｗ₀＝4mmを用いて、
ｘ_L＝ｘ_c−Ｗ₀／２＝−2.0781mm
ｘ_R＝ｘ_c＋Ｗ₀／２＝1.9029mm
とした。ここで、ｉ_L，ｉ_Rはそれぞれビード範囲の左端、右端に相当する形状データのアドレスである。また、以下で用いるｉ_cは、前記のように求められたｘ_cに相当する形状データ列のアドレスである。
【００３９】
ビード形状近似回路１２０は、前記のようにして設定したビードの左半分（左側の境界ｘ＝ｘ_iLから頂点ｘ＝ｘ_icまで）、右半分（頂点ｘ＝ｘ_icから右側の境界ｘ＝ｘ_iRまで）について、下記のＥ_L、Ｅ_Rをそれぞれ最小化する関数ｆ_L（ｘ）を算出する。
【００４０】
【数２】

【００４１】
ここで、左半分と右半分で以下に説明する処理は同じになるため、以降、代表して、和記号等はビードの左側半分についてだけ説明する。また、ビード部の左右それぞれの形状データの近似関数としては、円弧、多項式等を用いても良いが、本実施例では好適例として、次のように定義される線分の集合体を用いた。
【００４２】
【数３】

【００４３】
ただし、ｎは線分の本数であり、ｉ_P1，…，ｉ_Pnはｉ_L＜ｉ_P1＜…＜ｉ_Pj＜…＜ｉ_Pn-1＜ｉ_Cを満たす連結点（線分が切り替わる位置）のアドレスである。連結点の個数、すなわち線分の本数は任意に設定してよいが、演算時間を考慮して本実施例ではｎ＝２とした。従って、本実施例では連結点が１つであるので、以降ではｐ１はｐと添字を省略して表記することがある。
【００４４】
さて、この場合、ｆ_L（ｘ）を算出するには、ａ_L1、ｂ_L1、ａ_L2、ｂ_L2、ｘ_p1の５つのパラメータに関するＥ_Ｌの最小値問題を解くことになるが、これは下記のようなステップに分けることにより算出できる。
【００４５】
（１）まずｘ_ｐを固定して、その場合についてのａ_L1、ｂ_L1、ａ_L2、ｂ_L2を算出する。その場合、データの集合（ｘ，ｚ）に対する直線の最小二乗回帰であるから代数的に求めることができ、
【数４】

である。
【００４６】
（２）上記で算出したａ_L1、ｂ_L1、ａ_L2、ｂ_L2を用いて、ｘ＝ｘ_pの場合の近似誤差Ｅ（ｘ_p）を算出する。
【００４７】
【数５】

【００４８】
（３）上記の（１）、（２）の演算をすべての
【数６】

に対して実行し、Ｅ（ｘ_ip）が最小となるｘ_ipが求める連結点である。
【００４９】
（４）上記で算出したｘ_ipに対応したｆ_L（ｘ）を、当該ビード部を含む管表面の形状の近似関数とする。
【００５０】
（５）頂点位置よりも右側のビード形状の近似関数についても同様に、上記の（１）〜（４）において、ｉ_Ｌをｉ_ｃに、ｉ_ｃをｉ_Ｒにおきかえて同様の演算を実行すればよい。
【００５１】
そして、図５は、図４のビード部を含む管表面の形状データのうちの頂点位置よりも左側の形状データに関して、各ｘ_pと上記近似誤差Ｅ（ｘ_p）の関係をプロットした例であるが、図のようにｘ_p＝−0.7031において最小値をとっており、これにより、当該左側のビード形状の近似関数を、
【数７】

と決定できる。
【００５２】
素管形状近似回路１３０は、ビード部を含む管表面の形状データのうち、ビード部を除く範囲に対して、近似関数ｆ_P（ｘ）を算出する。この近似関数ｆ_P（ｘ）としては、円、楕円を用いてもよいが、冪関数、中でも２次以上の偶数次多項式を近似曲線として用いるのが好ましい。
【００５３】
図６は、この根拠を説明するために、円の上半分の曲線を２次、４次、６次、８次の多項式で回帰した場合の多項式の次数と近似誤差のＲＭＳ（二乗平均の平方根）の関係を表したグラフであり、図より、２次以上の偶数次多項式、好適には４次以上の偶数次多項式により、楕円の形状を十分な精度で回帰できることが示されている。したがって本実施例では４次関数で近似を行うこととした。具体的には、図４のビード部を含む管表面の形状データの座標範囲
【数８】

に関して、次のように定義される誤差の二乗和
【数９】

が最小となる４次関数
【数１０】

の係数を算出する。これは代数的に解くことができて、
【数１１】

により算出する（ただし、ｉｎｖ（Ａ）は行列Ａの逆行列を表す）。本実施例においては、上式により、
ｆ_p（ｘ）＝1.60921＋0.055776ｘ−0.02129ｘ²−0.00015ｘ³＋0.000057ｘ⁴
と算出できた。
【００５４】
ビード範囲再設定回路１４０は、上記のようにして算出した左右それぞれのビード形状の近似関数ｆ_L（ｘ）、ｆ_R（ｘ）、および素管形状の近似関数ｆ_p（ｘ）の交点を算出し、算出された左右両交点の中間に相当する領域を新たなビード範囲（ｘ_L’，ｘ_R’）として出力する。
【００５５】
本実施例において算出されたｆ_L（ｘ）、ｆ_R（ｘ）、ｆ_p（ｘ）は図７のようになり、ビード範囲再設定回路は、
ｘ_{L ’}＝−2.2266、ｘ_{R ’}＝3.5938
を出力した。なお、図７において破線でプロットされているのは、図４と同じビード部を含む管表面の形状データである。
【００５６】
特徴量検出回路１５０は、上記のように算出したビード範囲、頂点位置、左右それぞれのビード形状の近似関数、素管形状の近似関数、ビード部を含む管表面形状データより、ビードの高さＨ、幅Ｗ、左右のビード部の立上がり角度θ_L、θ_R、左右のビード部の境界の段差Δを算出する。
【００５７】
それぞれの特徴量の好適な決定方法として、本実施例では、
・ビードの幅Ｗ：ビード範囲再設定回路が出力する左右のビード境界の管周方向位置の間隔
・ビードの高さＨ：ビード頂点位置におけるビード部を含む管表面の形状データと素管形状の近似関数の値の差
・ビードの立上がり角θ_L、θ_R：左右それぞれのビード形状の近似関数と素管形状の近似関数の境界における微分係数により定義されるそれぞれの傾きの逆正接・ビード部と素管部の左右境界の段差Δ：ビード範囲再設定回路１４０が出力する左右のビード境界位置における左右それぞれのビード形状の近似関数と素管形状の近似関数の値の差
なる定義に従って算出した。
【００５８】
ビードの立上がり角の算出方法について更に詳細に説明する。一例として、左側のビードの立上がり角の算出手順を説明すると、上記素管形状の近似関数ｆ_p（ｘ）および左側のビード形状の近似関数ｆ_L（ｘ）のｘ＝ｘ_iLにおける傾きベクトルν_P，ν_Lは
【数１２】

であるから、両者のなす角θ_Lに関して、
【数１３】

により、θ_Lを算出する。
【００５９】
θ_Rについても、上記と同様にして算出する。
【００６０】
本実施例においては、上記のような定義により、
ビードの幅(mm) Ｗ＝ｘ_{R ’}−ｘ_{L ’}＝5.8204
ビードの高さ(mm) Ｈ＝Ｚ（ｘ_c）−ｆ_p（ｘ_c）＝2.9150
左側ビードの立上がり角度(deg) θ_L＝38.335
右側ビードの立上がり角度(deg) θ_R＝21.392
左右ビード境界の段差(mm) Δ＝｜ｆ_p（ｘ_Ｌ）−ｆ_p（ｘ_R）｜＝0.1576
と算出できた。
【００６１】
【発明の効果】
本発明によれば、光学的手法によって検出するビード部を含む管表面の形状データに基いて電縫溶接管のビード形状の特徴量を算出するようにしたので、溶接部の透磁率変化の影響等を受けずにビード形状を検出することができる。
【００６２】
また、ビードの立上がり角が急峻であるとか、ビードの形状が台形であるといった仮定を行わずに、ビード形状の特徴量を算出するようにしたので、ビードの立ち上がりが非常に滑らかな場合やビードの高さが低い場合、ビードの高さが長手方向でばらついている場合、あるいはビード形状が三角形や台形から外れた場合や切り立っているような場合でも、正確にビード形状を検出することができる。
【００６３】
さらに、本発明によれば、ビード形状データの微分演算を行うことなくビード形状の特徴量を算出するようにしたので、形状データにぎざぎざ状のノイズが乗っているような場合でも、その影響を受けず、また、ビード位置の誤検出や立上がり角算出の誤差が大きくなることなく正確にビード形状を検出することができる等、電縫管の溶接ビード形状の特徴量定量化において優れた効果を発揮する。
【図面の簡単な説明】
【図１】本発明にかかる電縫溶接管のビード形状検出装置の要部の構成を示す概略図
【図２】ビード形状算出手段を構成する回路群の構成を示すブロック図
【図３】ビード部を含む電縫管表面の光切断画像の例を示す図
【図４】本発明にかかる光切断画像を細線化処理したビード部を含む電縫管表面の形状データを示す図
【図５】図４のビード部を含む管表面の形状データのうちの頂点位置よりも左側の形状データに関して、各ｘ_pと上記近似誤差Ｅ（ｘ_p）の関係をプロットした図
【図６】円の上半分の曲線を２次、４次、６次、８次の多項式で回帰した場合の多項式の次数と近似誤差のＲＭＳ（二乗平均の平方根）の関係を表した図
【図７】本発明にかかるビード形状検出方法の実施例において、ビード形状近似回路が算出した左右のビード形状の近似関数ｆ_L（ｘ）、ｆ_R（ｘ）、および素管形状近似回路が算出した素管形状の近似関数ｆ_p（ｘ）を、ビード部を含む管表面の形状データとともにプロットした図
【符号の説明】
１０…投光手段（光源）
２０…撮像手段（カメラ）
３０…ビード形状算出手段
４０…データ処理装置
５０…表示装置
１００…頂点位置設定回路
１１０…ビード範囲設定回路
１２０…ビード形状近似回路、
１３０…素管形状近似回路
１４０…ビード範囲再設定回路
１５０…特徴量算出回路
２００…電縫管
２１０…溶接ビード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for detecting a bead shape of an electric resistance welded pipe.
[0002]
[Prior art]
In general, ERW welded pipe (hereinafter referred to as “ERW pipe” for short in the text), for example, ERW steel pipe is formed by forming a metal band (including a metal plate) such as a steel band into a tubular shape. While being conveyed in the longitudinal direction, both width ends of the metal strip such as the steel strip are continuously butt welded in the longitudinal direction by means such as high frequency induction heating pressure welding or resistance heating pressure welding.
[0003]
In the welded portion of the electric resistance welded pipe, a bulge by pressure welding, that is, a weld bead (hereinafter, also referred to as “bead” for short) occurs on the inner and outer surfaces of the pipe. Although this bead is cut in the course of pipe manufacture, it is conventionally known that the raised shape (width, height, etc.) of this bead before cutting is related to the weld strength at the final product stage. For this reason, conventionally, in the welding process, the worker adjusts the welding current and the like while visually observing the bead after welding. Since it is left to the subjectivity, there is a problem that differences between workers and temporal variations occur, and universality and reproducibility deteriorate. For this reason, attempts have been made to automatically measure the bead shape by various methods. As for the invention relating to a conventional method or apparatus for detecting a welded bead of steel pipe, a mechanical method, an optical method and the like have been proposed.
[0004]
As a mechanical method, for example, Patent Document 1 proposes a method of detecting runout of an outer surface welded portion of a traveling pipe with a contact roller.
[0005]
[Patent Document 1]
Japanese Examined Patent Publication No. 59-2593 [0006]
As an optical method, as disclosed in Patent Document 2, a light cutting profile obtained by irradiating slit light to a moving raw tube before bead cutting is optically received and obtained. An electric resistance welded tube that detects the width and height of the weld bead from the received optical cutting profile image signal and calculates the metal flow angle of the weld based on the detected width and height of the bead thus obtained. A metal flow angle measurement method has been proposed.
[0007]
[Patent Document 2]
Japanese Patent Publication No. 60-7586 [0008]
Moreover, in patent document 3, the optical cutting profile obtained by irradiating slit light to the welding part of the moving raw pipe before bead cutting is optically received, respectively, and the obtained optical cutting profile image receiving signal is received. The surface position of the bead corresponding to a predetermined height within a range of 3/4 to 1/3 of the maximum height of the bead relative to the rising position of the weld bead is detected, and thus obtained A weld metal flow angle measurement of an ERW weld pipe that calculates a metal flow angle of the weld based on a horizontal distance from the rising position at the surface position of the bead corresponding to a predetermined height and the predetermined height. A method has been proposed.
[0009]
[Patent Document 3]
Japanese Patent Publication No. 60-25234 [0010]
[Problems to be solved by the invention]
However, when a contact-type roller as disclosed in Patent Document 1 and a speedometer are used in combination, the height of the bead needs to be substantially constant in the longitudinal direction and the unevenness thereof is relatively steep. There is a problem that accurate detection cannot be performed when the surface is very smooth, the bead height is low, or the bead height is not constant in the longitudinal direction.
[0011]
Further, in Patent Document 2, it is assumed that the shape of the weld bead is a trapezoid, and the relationship between the width / height ratio and the metal flow angle is calculated by a shape index calculation circuit based on an empirical formula. However, due to recent advances in welding technology, the bead rise angle has become smaller, and the optimum rise angle varies depending on the plate thickness and application, so a calibration curve is experimentally obtained in each case. There is a problem that it is very complicated to switch and operate.
[0012]
In addition, in Patent Document 3, in addition to the above-mentioned problems, information on the bead width at 3/4 and 1/3 of the height of the bead is used. In the case of a deviated shape, for example, when 1/3 to 3/4 of the height is vertical, the denominator of the metal flow calculation becomes zero and the calculation result becomes abnormal. there were.
[0013]
In addition, a method of detecting the transverse direction (perpendicular to the axis) shape of the tube including the weld bead and calculating the bead position and rising angle based on the differential value is also conceivable, but in such a method, the detected shape When noise is added to the data, there is a problem that it is emphasized by the differential operation, and the error in detecting the bead shape and calculating the rising angle becomes large.
[0014]
The present invention has been made to solve the problems of the prior art as described above, and it is an object to accurately detect the bead shape from the shape data of the ERW weld pipe detected by the optical cutting method. To do.
[0015]
[Means for Solving the Problems]
According to the first aspect of the present invention, an image or scanning of the slit light irradiated on the surface of the tube including the bead portion by irradiating the surface of the tube including the bead portion by the welding of the ERW welded tube or scanning the spot light. An electric-welded welded pipe that detects the bead shape of the electric-welded welded pipe by performing predetermined image processing on an image obtained by capturing an image of the locus of the spotted light from an angle different from the irradiation direction of the slit light In the bead shape detection method, the shape data of the tube surface including the bead portion calculated as a result of the image processing is set in the bead portion based on the predetermined boundary between the left and right ends of the bead portion and the vertex position of the bead portion calculated separately. obtains the shape data of the corresponding portion of the tube surface, divided shape data of the tube surface of a portion corresponding to the bead portion into two left and right regions, the left and right about the shape data, arcs, polynomials, the line segment Obtains an approximate function of each bead shape lateral approximated by a function of either polymer, further, base tube except for the shape data of the pipe surface of the portion corresponding to the bead portion from the shape data of the pipe surface including bead portion The shape data is approximated by a function to obtain an approximate function of the tube shape, and the left and right bead shape approximate functions f _L (x) and f _R (x) and the tube shape approximate function f _p (x) Calculate the crosswise position x _L ', x _R ' of the cross-section of the ERW welded pipe , and at least one of the width, height, rising angle of the bead and the step between the left and right boundaries between the bead and the base pipe The problem is solved by calculating according to the following definition .
・ Bead width: the distance between the above x _L 'and x _R '
・ Bead height: difference between the shape data of the pipe surface including the bead and the approximate function f _p (x) of the pipe shape at the position in the cross direction of the ERW weld pipe at the apex of the bead
• Rise angle of the bead: the approximate functions f _L (x) and f _R (x) of the left and right bead shapes in the x _L ′ and x _R ′ and the approximate function f _p (x) of the tube shape The arc tangent of the slope defined by the derivative of
Step difference at the left and right boundary between the bead part and the raw pipe part: the approximate functions f _L (x) and f _R (x) of the bead shape and the approximate function f _p (x of the raw pipe shape in each of the above x _L ′ and x _R ′ ) Difference in value [0016]
According to a second aspect of the present invention, in the first aspect of the invention, the left and right bead-shaped approximate functions defined by the assembly of the line segments , the position at which the line segments are switched , the slope and intercept of each line segment are parameters. As described above, calculation is performed so as to minimize an error between the approximate function of the left and right bead shapes and the shape data of the tube surface including the bead portion.
[0020]
According to a third aspect of the present invention, there is provided light projecting means for irradiating the surface of a tube including a welded portion of an ERW welded tube with slit light or scanning spot light, and the surface of the tube including the welded portion is irradiated from the light projecting means. An image pickup means for picking up the captured image from an angle different from that of the light projecting means, and a bead shape calculation means for calculating a bead shape of the electric resistance welded pipe by applying predetermined image processing to an image obtained by the image pickup means; An apex position setting circuit and a bead range setting circuit for calculating the bead apex position and the boundary position between the bead part and the bare pipe part excluding the bead part based on the bead shape data calculated by the bead shape calculating unit; , based on the output left and right boundary position sandwiching the vertex position and the vertex position of the vertex position setting circuit and a bead range setting circuit, arc, polynomials, one of a collection of line segments using Approximation function f _L of left and right bead shape (x), f _R and (x) bead shape approximation circuit for calculating a, based on the outside of the base pipe shape data from the left and right boundary position output by the said bead range setting circuit A tube shape approximating circuit for calculating the tube shape approximating function f _p (x) , and bead shape approximating functions f _L (x) and f _R (x) output by the bead shape approximating circuit. The bead range for resetting the crosswise position x _L ′, x _R ′ of the ERW weld pipe at the intersection with the approximate function f _p (x) of the pipe shape output from the pipe shape approximating circuit as the left and right boundary positions Based on the outputs of the reset circuit, the bead range setting circuit, the bead shape approximating circuit, and the tube shape approximating circuit, at least the width, height, rising angle of the bead, and the left and right boundaries between the bead portion and the tube portion Calculate one of the steps according to the following definition: The present invention provides a bead shape detection device for an electric resistance welded pipe, characterized by comprising a feature amount calculation circuit to be output.
・ Bead width: the distance between the above x _L 'and x _R '
・ Bead height: difference between the shape data of the pipe surface including the bead and the approximate function f _p (x) of the pipe shape at the position in the cross direction of the ERW weld pipe at the apex of the bead
• Rise angle of the bead: the approximate functions f _L (x) and f _R (x) of the left and right bead shapes in the x _L ′ and x _R ′ and the approximate function f _p (x) of the tube shape The arc tangent of the slope defined by the derivative of
Step difference at the left and right boundary between the bead part and the raw pipe part: the approximate functions f _L (x) and f _R (x) of the bead shape and the approximate function f _p (x of the raw pipe shape in each of the above x _L ′ and x _R ′ ) Value difference [0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a schematic view showing a configuration example of a bead shape detection device for an electric resistance welded pipe according to the present invention. In FIG. 1, 200 is an electric sewing tube, 10 is a light projecting means, 20 is an imaging means, 30 is a bead shape calculating means, 40 is a data processing device, and 50 is a display device.
[0023]
The light projecting means 10 is a slit light source in which light emitted from a light emitting element such as a laser or a lamp is converged in a planar shape by a cylindrical lens or the like, or a light that converges in a point shape at an irradiation position by a mirror or the like. A scanning point light source that scans in the direction may be used, but it is preferable to use a small slit light source in which a semiconductor light emitting element (LED) and a lens system are integrated. It is desirable that the slit width is also sufficiently small compared to the height of the weld bead, preferably 50 μm or less, but ultimately the shape of the part to be measured is calculated as a single line by image processing described later. This is not essential.
[0024]
As the imaging means 20, an ITV camera or PSD (optical position detection element) can be used, but it is preferable to use a CCD camera in consideration of data conversion to a subsequent image processing apparatus. Although not shown in the figure, a lens system for imaging the irradiated light, an aperture and a shutter mechanism for adjusting the amount of received light to an appropriate range, etc. are generally selected and mounted. Good. Here, when the point light source is scanned as the light projecting means 10, it is necessary to expose the light while irradiating the entire range in the width direction at least once. If this condition is met and the tube and bead shape are almost stationary while scanning is completed, the collected images will be the same for both slit light and point light source scanning. I will explain only.
[0025]
The incident angle α of the light from the light projecting means 10 and the arrangement angle β of the imaging means 20 are preferably (α + β) being approximately 90 °, and the number of pixels and the field of view of the camera are the width of the bead portion and What is necessary is just to determine based on required resolution. In the present invention, the slit light irradiation angle α from the light projecting means 10 = 60 °, the imaging angle β = 30 °, the field of view width × height = (25 mm × 20 mm), and the number of pixels is horizontal × vertical = 640 ×. 480 pixels were used as the preferred value. As a result, the resolution in the height direction is
20/480 * cos (60 °) / sin (60 ° + 30 °) = 0.0209 (mm)
The resolution in the width direction is
25/640 = 0.0391 (mm)
Thus, in this embodiment, the bead shape can be detected with a resolution of 40 μm in the width direction (cross-tube direction) and 20 μm in the height direction (tube axis direction).
[0026]
The bead shape calculating means 30 converts the slit light image into one line by an appropriate image processing means, and then calculates a bead shape (profile) by geometric calculation determined from the arrangement of the light projecting means 10 and the imaging means 20. Is. Here, the profile is the contour shape of the inner surface or the outer surface of the ERW welded tube, and the shape data of the tube surface including the bead portion is a part of the profile data. As the image processing means, those generally known as those capable of performing thinning processing may be used. However, it is preferable to use the thinning means proposed by the inventors in Japanese Patent Application No. 2002-128497.
[0027]
As shown in FIG. 2, the data processor 40 includes a vertex position setting circuit 100, a bead range setting circuit 110, a bead shape approximating circuit 120, a tube shape approximating circuit 130, and a bead range re-setting circuit. A setting circuit 140 and a feature amount calculation circuit 150 are provided.
[0028]
Hereinafter, each part in the data processing device 40 will be described.
[0029]
The apex position setting circuit 100 sets the apex position of the bead from the shape data of the tube surface including the bead portion calculated as described above. This may be manually input by the operator judging from the shape data of the tube surface including the bead portion, but more preferably the maximum value of the height is indicated in the shape data of the tube surface including the bead portion. Find the position. Furthermore, the calculation may be performed by appropriately adding processing by calculation such as a weighted average.
[0030]
The bead range setting circuit 110 sets the bead range from the shape data of the tube surface including the bead portion calculated in the same manner as described above. Alternatively, the operator may manually input the boundary between the left and right ends of the bead portion based on the shape data of the pipe surface including the bead portion, and set an area corresponding to the middle between the left and right boundaries as the bead range. As disclosed in Patent Document 3, the rising position may be detected based on the difference between adjacent shape data. More preferably, the vertex position of the bead output by the vertex position setting circuit 100 is centered. The bead width set in advance may be divided by half, or may be set in accordance with the method disclosed in the method for detecting the weld bead shape of an electric resistance welded pipe proposed by the inventors in Japanese Patent Application No. 2002-277802.
[0031]
The bead shape approximating circuit 120 divides the bead range set as described above into two of the left side x _l <x <x _c and the right side x _c <x <x _r of the apex, and the shape of the bead portion in each range Is approximated by a predetermined function, and the function is determined for each of the left and right shapes of the bead portion. The preferred method will be described in the operation section below.
[0032]
The raw tube shape approximating circuit 130 is obtained by removing the shape data of the bead range set as described above from the shape data of the tube surface including the bead portion, and a predetermined shape such as a power function. It approximates with a function and calculates specific parameters such as each coefficient of the function. The preferred method will be described in the operation section below.
[0033]
The bead range reset circuit 140 recognizes the position at which the values of the approximate function of the left and right bead shapes determined as described above and the approximate function of the tube shape intersect as the boundary position between the bead portion and the tube portion. It can be constructed again from a function value arithmetic circuit and a comparator.
[0034]
The feature amount detection circuit 150 calculates the bead width from the bead range, apex position, right and left bead shape approximation functions, the tube shape approximation function, and the tube surface shape data including the bead portion calculated as described above. , Height, left and right rising angles, and steps at the boundaries between the left and right bead portions and the raw tube portion.
[0035]
The display device 50 displays bead-shaped feature values detected by the feature value detection circuit 150. This may be displayed by updating each value with a numerical value or a bar graph from time to time, but it is preferable to display the shape data of the tube surface including the bead portion and each feature amount as a time chart.
[0036]
Further, the output of the feature amount detection circuit 150 may be output to a recorder or business computer (not shown) at a suitable time interval by a communication port or external output circuit (not shown), and data may be accumulated.
[0037]
Next, the operation of this embodiment will be described.
[0038]
FIG. 3 is a light cut image of the slit light source 10 that is the light projecting means that covers the range of the tube surface including the bead portion, which is picked up by the image pickup means 20, and this is thinned by the bead shape calculation means 30. The result of conversion into coordinates on the display device 50 is the shape data of the tube surface including the bead portion as shown in FIG. The arrows written in FIG. 4 indicate the x-coordinates of the bead range and the vertex position calculated by the vertex position setting circuit 100 and the bead range setting circuit 110, respectively. In this embodiment, the vertex position calculation is performed with a bead having a predetermined bead range as a defined area for the shape data string (x _i , z _i ) (i = 0,..., N−1) of the tube surface including the bead portion. Weighted average of tube surface shape data (x _i , z _i ) (i = i _L ,..., I _R ) including the part

Accordingly, the value calculated as x _c = −0.0781 is used, and the bead range is set using a preset bead width W ₀ = 4 mm.
x _L = x _c −W ₀ /2=−2.0781 mm
_{x R = x c + W 0} /2=1.9029mm
It was. Here, i _L and i _R are the addresses of the shape data corresponding to the left end and the right end of the bead range, respectively. Further, the i _c used in the following, the address of shape data string corresponding to the determined as x _c.
[0039]
The bead shape approximating circuit 120 includes the left half of the bead set as described above (from the left boundary x = _xiL to the vertex x = x _ic ) and the right half (from the vertex x = x _ic to the right boundary x = x). _{For up to iR} ), a function f _L (x) that minimizes the following E _L and E _R is calculated.
[0040]
[Expression 2]

[0041]
Here, since the processing described below is the same for the left half and the right half, only the left half of the bead will be described below as a representative example. In addition, as an approximation function of the shape data on the left and right sides of the bead portion, an arc, a polynomial, or the like may be used. However, in this embodiment, a set of line segments defined as follows is used as a preferred example. .
[0042]
[Equation 3]

[0043]
Here, n is the number of line segments, and i _P1 ,..., I _Pn is a connection point satisfying i _L <i _P1 <... <i _Pj <... <i _Pn-1 <i _C (position where the line segment switches). Address. The number of connection points, that is, the number of line segments may be set arbitrarily, but n = 2 in this embodiment in consideration of the calculation time. Therefore, in this embodiment, since there is one connecting point, hereinafter, p1 may be expressed by omitting p and the subscript.
[0044]
In this case, in order to calculate f _L (x), an E _L minimum value problem for five parameters a _L1 , b _L1 , a _L2 , b _L2 , and x _p1 is solved. It can be calculated by dividing into the following steps.
[0045]
(1) First, _xp is fixed, and a _L1 , b _L1 , a _L2 , and b _L2 for that case are calculated. In that case, since it is a least-squares regression of a straight line over the data set (x, z), it can be obtained algebraically,
[Expression 4]

It is.
[0046]
(2) Using the a _L1 , b _L1 , a _L2 , and b _L2 calculated above, an approximate error E (x _p ) when x = x _p is calculated.
[0047]
[Equation 5]

[0048]
(3) Perform the above calculations (1) and (2) for all

This is the connection point obtained by x _ip that minimizes E (x _ip ).
[0049]
(4) Let f _L (x) corresponding to x _ip calculated above be an approximate function of the shape of the tube surface including the bead portion.
[0050]
(5) Similarly, for the bead-shaped approximation function on the right side of the vertex position, the same calculation is performed by replacing i _L with i _c and i _c with i _R in (1) to (4) above. do it.
[0051]
FIG. 5 is an example in which the relationship between each x _p and the approximation error E (x _p ) is plotted with respect to the shape data on the left side of the apex position among the shape data of the tube surface including the bead portion of FIG. There is a minimum value at x _p = −0.7031 as shown in FIG.
[Expression 7]

Can be determined.
[0052]
The raw tube shape approximating circuit 130 calculates an approximate function f _P (x) for a range excluding the bead portion in the shape data of the tube surface including the bead portion. As this approximate function f _P (x), a circle or an ellipse may be used. However, it is preferable to use a power function, especially a second-order or higher order polynomial as an approximate curve.
[0053]
In order to explain this reason, FIG. 6 shows the order of the polynomial when the upper half curve of the circle is regressed with a second-order, fourth-order, sixth-order, and eighth-order polynomial, and the RMS (square root mean square) of the approximation error. ), And the figure shows that the shape of the ellipse can be regressed with sufficient accuracy by an even-order polynomial of the second or higher order, preferably an even-order polynomial of the fourth or higher order. Therefore, in this embodiment, approximation is performed using a quartic function. Specifically, the coordinate range of the shape data of the tube surface including the bead portion of FIG.

With respect to the sum of squared errors defined as

A quartic function that minimizes

The coefficient of is calculated. This can be solved algebraically,
[Expression 11]

(Where inv (A) represents the inverse of matrix A). In this embodiment, the above formula
f _p (x) = 1.60921 + 0.055776x−0.02129x ² −0.00015x ³ + 0.000057x ⁴
It was possible to calculate.
[0054]
The bead range reset circuit 140 calculates the intersection of the left and right bead-shaped approximation functions f _L (x) and f _R (x) and the tube-shaped approximation function f _p (x) calculated as described above. An area corresponding to the middle of the calculated left and right intersections is output as a new bead range (x _L ', x _R ').
[0055]
The f _L (x), f _R (x), and f _p (x) calculated in this embodiment are as shown in FIG. 7, and the bead range reset circuit is
x _{L '} = -2.2266, x _{R '} = 3.5938
Was output. In addition, what is plotted with a broken line in FIG. 7 is the shape data of the tube surface including the same bead portion as in FIG.
[0056]
The feature amount detection circuit 150 calculates the bead height H from the bead range, apex position, right and left bead shape approximation functions, the tube shape approximation function, and the tube surface shape data including the bead portion calculated as described above. , The width W, the rising angles θ _L and θ _{R of} the left and right bead portions, and the step difference Δ at the boundary between the left and right bead portions.
[0057]
As a preferred method for determining each feature amount, in this embodiment,
The width W of the bead: the interval between the positions in the pipe circumferential direction of the left and right bead boundaries output by the bead range reset circuit. The height H of the bead H: the shape data of the pipe surface including the bead portion at the bead apex position and the shape of the raw pipe shape. Approximate function value difference / bead rise angle θ _L , θ _R : Inverse tangent / bead part of each slope defined by the differential coefficient at the boundary between the right and left bead shape approximate functions and the tube shape approximate function And the step difference Δ between the left and right boundary of the pipe part: calculated according to the definition of the difference between the values of the approximate function of the right and left bead shapes and the approximate function of the pipe shape at the right and left bead boundary positions output by the bead range reset circuit 140 .
[0058]
The method for calculating the bead rising angle will be described in more detail. As an example, the procedure for calculating the rising angle of the left bead will be described. The slope vector ν of the approximate function f _p (x) of the tube shape and the approximate function f _L (x) of the left bead shape at x = x _iL . _P and ν _L are given by

Therefore, regarding the angle θ _L formed by both,
[Formula 13]

To calculate θ _L.
[0059]
θ _R is also calculated in the same manner as described above.
[0060]
In this embodiment, the definition as described above,
Bead width (mm) W = x _{R '} -x _{L '} = 5.8204
Bead height (mm) H = Z (x _c ) −f _p (x _c ) = 2.9150
Left bead rise angle (deg) θ _L = 38.335
Rising angle of right bead (deg) θ _R = 21.392
Step difference between left and right bead boundaries (mm) Δ = | f _p (x _L ) −f _p (x _R ) | = 0.1576
It was possible to calculate.
[0061]
【The invention's effect】
According to the present invention, the feature amount of the bead shape of the ERW welded pipe is calculated based on the shape data of the surface of the pipe including the bead portion detected by an optical technique. It is possible to detect the bead shape without receiving the above.
[0062]
In addition, since the bead shape feature value is calculated without assuming that the rise angle of the bead is steep or the shape of the bead is trapezoidal, the bead rise is very smooth or The bead shape can be detected accurately even when the bead height is low, when the bead height varies in the longitudinal direction, or when the bead shape deviates from the triangle or trapezoid, .
[0063]
Furthermore, according to the present invention, since the feature value of the bead shape is calculated without performing the differential operation of the bead shape data, the influence is exerted even when jagged noise is on the shape data. In addition, it is possible to accurately detect the bead shape without misdetecting the bead position and increasing the rise angle calculation error. Demonstrate.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a main part of a bead shape detecting device for an electric resistance welded pipe according to the present invention. FIG. 2 is a block diagram showing a configuration of a circuit group constituting a bead shape calculating unit. FIG. 4 is a diagram showing an example of a light cut image on the surface of an electric resistance tube including a portion. FIG. 6 is a graph plotting the relationship between each x _p and the above approximate error E (x _p ) with respect to the shape data on the left side of the apex position among the shape data of the tube surface including the bead portion in FIG. FIG. 7 is a graph showing the relationship between the degree of a polynomial and the RMS (root mean square) of approximation error when a half curve is regressed with a second-order, fourth-order, sixth-order, and eighth-order polynomial. In the embodiment of the bead shape detection method, the left and right bead values calculated by the bead shape approximation circuit are used. Approximation of de shape function _{f L (x), f R} (x), and approximation function f _p of mother tube shaped blank tube shape approximation circuit is calculated (x), plotted along with the shape data of the pipe surface including bead portion Figure 【Explanation of symbols】
10 ... Projection means (light source)
20 ... Imaging means (camera)
30 ... Bead shape calculation means 40 ... Data processing device 50 ... Display device 100 ... Vertex position setting circuit 110 ... Bead range setting circuit 120 ... Bead shape approximation circuit,
130 ... Element shape approximation circuit 140 ... Bead range resetting circuit 150 ... Feature amount calculation circuit 200 ... ERW pipe 210 ... Weld bead

Claims (3)

Irradiating the surface of the tube including the bead portion by welding an electro-welded pipe with slit light or scanning with spot light, the image of the slit light irradiated on the surface of the tube including the bead portion or the locus of the scanned spot light In the bead shape detection method for an ERW weld pipe, the bead shape of the ERW weld pipe is detected by performing predetermined image processing on an image obtained by capturing the image of the image from an angle different from the irradiation direction of the slit light.
With respect to the shape data of the tube surface including the bead portion calculated as a result of the image processing, the tube surface of the portion corresponding to the bead portion is determined based on the predetermined boundary between the left and right ends of the bead portion and the vertex position of the bead portion calculated separately Find shape data,
Divide the shape data of the tube surface of the part corresponding to the bead part into two left and right regions,
For each of the left and right shape data, approximate by a function of an arc, a polynomial, or an assembly of line segments to obtain an approximate function of the left and right bead shapes,
Furthermore, for the tube shape data obtained by removing the shape data of the tube surface corresponding to the bead portion from the shape data of the tube surface including the bead portion, an approximate function of the tube shape is obtained by approximating with a function,
The position X _L ′, x _R ′ in the transverse direction of the ERW weld pipe at the intersection of the approximate functions f _L (x), f _R (x) of the left and right bead shapes and the approximate function f _p (x) of the tube shape Calculate
A method for detecting the bead shape of an electric resistance welded pipe, wherein at least one of the width, height, rising angle of the bead, and the step between the left and right boundaries between the bead part and the base pipe part is calculated according to the following definition : .
・ Bead width: the distance between the above x _L 'and x _R '
・ Bead height: difference between the shape data of the pipe surface including the bead and the approximate function f _p (x) of the pipe shape at the position in the cross direction of the ERW weld pipe at the apex of the bead
• Rise angle of the bead: the approximate functions f _L (x) and f _R (x) of the left and right bead shapes in the x _L ′ and x _R ′ and the approximate function f _p (x) of the tube shape The arc tangent of the slope defined by the derivative of
Step difference at the left and right boundary between the bead part and the raw pipe part: the approximate functions f _L (x) and f _R (x) of the bead shape and the approximate function f _p (x of the raw pipe shape in each of the above x _L ′ and x _R ′ ) Value difference In Claim 1, the right and left bead shape approximation functions defined by the assembly of the line segments are used as parameters for the position at which the line segments are switched and the slope and intercept of each line segment , respectively. A method for detecting a bead shape of an electric resistance welded pipe, wherein calculation is performed so as to minimize an error between the approximate function and the shape data of the pipe surface including the bead portion. A light projecting means for irradiating the surface of the tube including the welded portion of the ERW welded tube or scanning the spot light;
An image pickup means for picking up an image irradiated from the light projecting means to the tube surface including the welded portion from an angle different from that of the light projecting means;
Bead shape calculating means for calculating a bead shape of the electric resistance welded pipe by performing predetermined image processing on an image obtained by the imaging means;
Based on the bead shape data calculated by the bead shape calculating means, a vertex position setting circuit and a bead range setting circuit for calculating the bead apex position and the boundary position between the bead part and the bare pipe part excluding the bead part, respectively; ,
Based on the vertex position output by the vertex position setting circuit and the bead range setting circuit and the left and right boundary positions sandwiching the vertex position, each of the left and right bead shapes using an arc, a polynomial, or an assembly of line segments A bead shape approximating circuit for calculating approximate functions f _L (x) and f _R (x) of
A tube shape approximating circuit for calculating an approximate function f _p (x) of the tube shape based on tube shape data outside the left and right boundary positions output by the bead range setting circuit;
The right and left bead shape approximation functions f _L (x) and f _R (x) output from the bead shape approximation circuit and the tube shape approximation function f _p (x) output from the tube shape approximation circuit. A bead range reset circuit for resetting the crosswise position x _L ′, x _R ′ at the intersection of the electric resistance welded pipe as the left and right boundary positions;
Based on the outputs of the bead range setting circuit, the bead shape approximating circuit, and the tube shape approximating circuit, at least one of the width, the height, the rising angle of the bead, and the step between the left and right boundaries between the bead portion and the tube portion. A feature quantity calculation circuit for calculating one according to the following definition ;
An apparatus for detecting a bead shape of an electric resistance welded pipe, comprising:
・ Bead width: the distance between the above x _L 'and x _R '
・ Bead height: difference between the shape data of the pipe surface including the bead and the approximate function f _p (x) of the pipe shape at the position in the cross direction of the ERW weld pipe at the apex of the bead
• Rise angle of the bead: the approximate functions f _L (x) and f _R (x) of the left and right bead shapes in the x _L ′ and x _R ′ and the approximate function f _p (x) of the tube shape The arc tangent of the slope defined by the derivative of
Step difference at the left and right boundary between the bead part and the raw pipe part: the approximate functions f _L (x) and f _R (x) of the bead shape and the approximate function f _p (x of the raw pipe shape in each of the above x _L ′ and x _R ′ ) Value difference

Images