CN104084669B - A kind of circumferential weld visible detection method detected based on decoupling zero - Google Patents

A kind of circumferential weld visible detection method detected based on decoupling zero Download PDF

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CN104084669B
CN104084669B CN201410279698.5A CN201410279698A CN104084669B CN 104084669 B CN104084669 B CN 104084669B CN 201410279698 A CN201410279698 A CN 201410279698A CN 104084669 B CN104084669 B CN 104084669B
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weld
point
weld seam
image
welding gun
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CN201410279698.5A
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CN104084669A (en
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陈海永
王萌
马子涵
孙鹤旭
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河北工业大学
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00Arc welding or cutting
    • B23K9/12Automatic feeding or moving of electrodes or work for spot or seam welding or cutting
    • B23K9/127Means for tracking lines during arc welding or cutting
    • B23K9/1272Geometry oriented, e.g. beam optical trading
    • B23K9/1274Using non-contact, optical means, e.g. laser means
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00Arc welding or cutting
    • B23K9/02Seam welding; Backing means; Inserts
    • B23K9/028Seam welding; Backing means; Inserts for curved planar seams

Abstract

The present invention relates to a kind of based on decoupling zero detect circumferential weld visible detection method, for V-butt annular weldment weld seam detection, identify and weld, it is characterized in that the concrete steps of the method are: the first step, image procossing and feature extraction; Second step, image information decoupling zero.The three-dimensional characteristics of weld seam information that the present invention is extracted by decoupling zero single-frame images, the departure of welding gun relative Weld pipe mill in two dimensional surface can be calculated, and then the accurate location that can realize at three dimensions solder joint, monocular vision is adopted to carry out decoupling algorithm when obtaining weld seam two-dimensional signal, avoid the matrixing loaded down with trivial details when demarcating weld information, greatly save and demarcated and computing time, significantly improve the real-time of system, avoid on the one hand and set up complicated camera imaging model, enhance the precision of camera calibration on the other hand, robustness and adaptability.

Description

A kind of circumferential weld visible detection method detected based on decoupling zero

Technical field

The present invention relates to the detection method and location of determining circumferential weld bond pad locations, specifically a kind of circumferential weld visible detection method based on decoupling zero detection and device.

Background technology

Along with the requirement of modernization welding production to product quality and production efficiency is more and more higher, how to ensure welding quality, improve Automation of Welding level and become the key subjects of pendulum in face of people.The working environment of welding process is very severe for welding robot human visual system, inevitably there is the interference such as a large amount of arc lights, splashing, flue dust as welding job; Through the workpiece that polishing rear surface is smooth, under LASER Light Source irradiates, the multiple reflections due to surface presents irregular reflective interference; Surface of the work is irregularity sometimes, often has the vestiges such as iron filings, greasy dirt, chalk mark; The weld shape of workpiece is different, and the material of weldment is also incomplete same.All of these factors taken together constitutes the challenge to vision system image procossing and acquisition of information.When strong jamming is severe, the acquisition of visual information and image processing problem research become the current welding robot vision-based detection application of restriction, realize a technical bottleneck of Weld Seam Tracking Control.In general camera calibration process, often first determine the inside and outside parameter of camera, camera internal parameter only need be demarcated once, but external parameter need along with the rotation of weldment constantly change, not easily demarcate, and operand is very large.Binocular vision needs the information to two video cameras obtain to merge when obtaining weld seam three-dimensional information, amount of calculation is large, influential system real-time.

Chinese patent CN101954557 discloses the two-dimensional position information extracting method that a kind of structure light welding seam image is followed the tracks of, the method obtains weld image by a structured light formula image weld seam tracking sensor, sensor processes this image, thus obtain the center of weld seam, for weld joint tracking directly provides the left-right deviation information of weld seam; Simultaneously, utilize the geometry site of sensor and welding work pieces, the previous frame image of Real-time Obtaining and a rear frame are compared, draw the variable quantity of welding gun short transverse, thus provide welding gun height tolerance information, its weak point is: the center of the current frame image that video camera can be caused to obtain due to the impact of the factors such as light, arc light, reflective, splashing in welding process is inaccurate, if front and back two two field picture compares, deviation will be made more and more inaccurate.

Summary of the invention

For the deficiencies in the prior art, the technical problem that quasi-solution of the present invention is determined is, provides a kind of circumferential weld visible detection method based on decoupling zero detection and device.This detection method carries out decoupling zero according to the three-dimensional characteristics of weld seam information extracted single-frame images, calculate the departure of welding gun relative Weld pipe mill in two dimensional surface, do not relate to extensive matrixing, amount of calculation is less, make to there is not coupled relation between the change of characteristics of image and welding gun motion, the accurate location at three dimensions solder joint can be realized.This checkout gear vision detection system comprises monocular-camera, laser instrument and the support both connection, and its structure is simple, can identify bond pad locations accurately and rapidly.

The present invention solves the technical scheme that described method and technology problem adopts, and designs a kind of circumferential weld visible detection method detected based on decoupling zero, for the weld seam of V-butt annular weldment detection, identify and weld, it is characterized in that the concrete steps of the method are:

The first step, image procossing and feature extraction

1-1 Image Acquisition: obtained the welded seam area image comprising laser stripe by smart camera sensor;

The laser stripe scope in the picture of the image that 1-2 region of interesting extraction: determining step 1-1 obtains;

1-3 image threshold adaptivenon-uniform sampling: on the basis of step 1-2, determines the available point of laser stripe;

1-4 laser structure light center line drawing: adopt the mode extracted by column to extract V-butt circular weld center line array method;

The filtering of 1-5 center line and interpolation: the missing point in the laser structure light center line that interpolation completion is extracted, adopt the further stress release treatment interference of gauss low frequency filter afterwards;

1-6Hough straight line converts: on the basis of step 1-5, carry out hough fitting a straight line to the laser stripe after differential filtering;

1-7 feature point extraction: the ordinate value of the line correspondences obtained after converting according to the ordinate value of center line group of the laser stripe extracted and hough compares the flex point obtaining laser stripe, and the mid point of two flex points is exactly weld bead feature points.

Second step, image information decoupling zero

2-1 horizontal direction deviation identification: utilize the linear relationship of weld width and weld seam developed width on the plane of delineation to obtain the departure in welding-torch horizontal direction;

2-1 vertical direction deviation identification: obtain the departure of welding gun vertical direction in the space geometry relation that vertical direction is formed according to the weld seam on the plane of delineation and the welding gun in space.

The technical scheme that the present invention solves the employing of described device technique problem is, design a kind of circumferential weld vision inspection apparatus detected based on decoupling zero adopting above-mentioned detection method, it is characterized in that this device comprises vision detection system, the first support, cross adjusting bracket, welding gun and fixture, described vision detection system comprises video camera, the second support and laser instrument, described video camera is connected with cross adjusting bracket by the first support, is fixedly linked by the second support and laser instrument; Cross adjusting bracket bottom is connected with welding gun top, and cross adjusting bracket can drive welding gun to move together, laser instrument distance welding gun front 5-10cm; Below welding gun, be provided with fixture, V-butt annular weldment can be fixed by the scroll chuck on fixture.

Compared with prior art, the three-dimensional characteristics of weld seam information that the inventive method is extracted by decoupling zero single-frame images, can calculate the departure of welding gun relative Weld pipe mill in two dimensional surface, and then can realize the accurate location at three dimensions solder joint.Apparatus of the present invention adopt monocular vision to carry out decoupling algorithm when obtaining weld seam two-dimensional signal, avoid the matrixing loaded down with trivial details when demarcating weld information, greatly save and demarcated and computing time, significantly improve the real-time of system, avoid on the one hand and set up complicated camera imaging model, enhance the precision of camera calibration, robustness and adaptability on the other hand.In the process that image detects, achieve decoupling zero, simplify control algolithm, reduce the requirement to controller.

Accompanying drawing explanation

Fig. 1 the present invention is based on the circumferential weld visible detection method of decoupling zero detection and the hardware configuration schematic diagram of a kind of embodiment assembling test of device platform;

Fig. 2 be the present invention is based on decoupling zero detect circumferential weld visible detection method and a kind of embodiment Uncoupled procedure of device in vision detection system elements relative position relationship schematic diagram;

Fig. 3--6 for the present invention is based on the position relationship of video camera 1 and weld seam 9 in circumferential weld visible detection method and a kind of embodiment Uncoupled procedure of device that decoupling zero detects and the laser stripe schematic diagram at the position relationship of the plane of delineation;

Fig. 7 the present invention is based on the geometric graph asked for of weld seam Y-direction deviation in circumferential weld visible detection method and a kind of embodiment Uncoupled procedure of device that decoupling zero detects;

Fig. 8 is the geometric graph of partial enlarged drawing that the present invention is based on Fig. 7 in circumferential weld visible detection method and a kind of embodiment Uncoupled procedure of device that decoupling zero detects;

Fig. 9 the present invention is based on the analogous diagram that circumferential weld visible detection method that decoupling zero detects and device do not add the abscissa of characteristic point when decoupling algorithm does not have a starting the arc;

Figure 10 the present invention is based on the analogous diagram that circumferential weld visible detection method that decoupling zero detects and device do not add the ordinate of characteristic point when decoupling algorithm does not have a starting the arc;

Figure 11 the present invention is based on the analogous diagram that circumferential weld visible detection method that decoupling zero detects and device add the abscissa of characteristic point when decoupling algorithm does not have a starting the arc;

Figure 12 the present invention is based on the analogous diagram that circumferential weld visible detection method that decoupling zero detects and device add the ordinate of characteristic point when decoupling algorithm does not have a starting the arc;

Figure 13 is the analogous diagram of the lateral deviation that the present invention is based on welding gun when circumferential weld visible detection method that decoupling zero detects and device add the decoupling algorithm starting the arc;

Figure 14 is the analogous diagram of the longitudinal bias that the present invention is based on welding gun when circumferential weld visible detection method that decoupling zero detects and device add the decoupling algorithm starting the arc;

In the drawings, video camera 1, the second support 2, laser instrument 3, cross adjusting bracket 4, welding gun 5, V-butt annular weldment 6, fixture 7, the first support 8, weld seam 9, the plane of delineation 10, straight plate weldment 11, laser stripe 12.

Detailed description of the invention

Below in conjunction with embodiment and accompanying drawing, the invention will be further described.

Circumferential weld visible detection method (the abbreviation method detected based on decoupling zero of the present invention's design, see Fig. 1-14) be mainly used in industry spot, the detection of V-butt circular weld, identify and to carry out with welding simultaneously, detection algorithm fully adapts to field condition, two-dimentional weld image is utilized to obtain the positional information of three-dimensional weld seam, make to there is not coupled relation between the change of characteristics of image and welding gun motion, the concrete steps of the method are:

The first step, image procossing and feature extraction

1-8 Image Acquisition: obtained the welded seam area image comprising laser stripe by smart camera sensor;

The laser stripe scope in the picture of the image that 1-9 region of interesting extraction: determining step 1-1 obtains;

1-10 image threshold adaptivenon-uniform sampling: on the basis of step 1-2, determines the available point of laser stripe;

1-11 laser structure light center line drawing: adopt the mode extracted by column to extract V-butt circular weld center line array method;

The filtering of 1-12 center line and interpolation: the missing point in the laser structure light center line that interpolation completion is extracted, adopt the further stress release treatment interference of gauss low frequency filter afterwards;

1-13Hough straight line converts: on the basis of step 1-5, carry out hough fitting a straight line to the laser stripe after differential filtering;

1-14 feature point extraction: the ordinate value of the line correspondences obtained after converting according to the ordinate value of center line group of the laser stripe extracted and hough compares the flex point obtaining laser stripe, and the mid point of two flex points is exactly weld bead feature points.

Second step, image information decoupling zero

2-1 horizontal direction deviation identification: utilize the linear relationship of weld width and weld seam developed width W on the plane of delineation to obtain the departure in welding-torch horizontal direction;

2-1 vertical direction deviation identification: obtain the departure of welding gun vertical direction in the space geometry relation that vertical direction is formed according to the weld seam on the plane of delineation and the welding gun in space.

The inventive method is further characterized in that the overall diameter of described V-butt annular weldment 6 is greater than 180mm, and groove width is 10-20mm, and groove depth is greater than 4mm.

The inventive method is further characterized in that described weld bead feature points is the mid point of two flex point lines of weld image V-butt.

The inventive method is further characterized in that described weld seam initial characteristics point is the mid point of two flex point lines of weld image V-butt; In the not starting the arc and weldment does not rotate, N (5<N<10) two field picture limited in vision system acquisition time sequence, records the image coordinate at every two field picture plane V-butt center i=1,2 ... N, and the arithmetic mean of instantaneous value calculating N frame center point value obtains weld seam initial characteristics point (x int, y int), computing formula is (1) formula

x I n t = 1 N &Sigma; i = 1 N x m i d i y I n t = 1 N &Sigma; i = 1 N y m i d i - - - ( 1 ) .

The inventive method is further characterized in that described horizontal departure is known method for distinguishing and is: adopt the method for real-time calibration to constantly update the ratio of weld width on weld seam developed width and the plane of delineation, namely often gather a two field picture and recalculate horizontal direction proportionality coefficient k xdvalue, if the position (x of weld seam initial characteristics point int, y int) and the position coordinates of weld seam n-th frame characteristic point wherein the n-th two field picture horizontal departure is the characteristic point coordinate that this frame calculates with the welding gun initial characteristics point coordinates (x calculated int, y int) compare, obtain plane of delineation weld seam deviation amount, converted by line style, welding gun is in the horizontal direction relative to the departure of actual welds, and computing formula is (4) formula

ΔX=k xd (n)×δx(4)。

The welding gun that the further feature of the inventive method is also the identification of described vertical direction deviation is (8) formula relative to the computing formula of the departure of actual welds in the vertical direction

AD=AA 1/cosθ=AB/(cos(90°-α)×cosθ)(8)。

The present invention adopts circumferential weld vision inspection apparatus (the abbreviation device detected based on decoupling zero of above-mentioned detection method, see Fig. 1-2) comprise vision detection system, the first support 8, cross adjusting bracket 4, welding gun 5 and fixture 7, described vision detection system comprises video camera 1, second support 2 and laser instrument 3, video camera 1 is connected with cross adjusting bracket 4 by the first support 8, is fixedly linked with laser instrument 3 by the second support 2; Cross adjusting bracket 4 bottom is connected with welding gun 5 top, and cross adjusting bracket 4 can drive welding gun 5 to move together, and laser instrument 3 is apart from welding gun 5 front 5-10cm; Below welding gun 5, be provided with fixture 7, V-butt annular weldment 6 can be fixed by the scroll chuck on fixture 7.

Apparatus of the present invention are further characterized in that described laser instrument 3 and video camera 1 optical axis included angle α=45 °, laser instrument 3 and vertical direction install angle theta ≈ 20 °, video camera 1 is to the distance L on V-butt annular weldment 6 between 180mm ~ 200mm, and the horizontal range distance of laser stripe on pad and V-butt annular weldment 6 is between 45mm ~ 50mm.

The further feature of apparatus of the present invention is also that described laser instrument 3 is laser line generator.

The present invention should reflect weld seam horizontal departure when choosing weld bead feature points, reflects weld seam vertical missing again, considers and selects the mid point of two flex point lines of weld image V-butt the most suitable as weld bead feature points.

Vision detection system and welding gun 5 are rigidly connected, and before welding starts, welding gun are adjusted to suitable welding initial position, namely on V-butt center line; In the not starting the arc and weldment does not rotate, N (5<N<10) two field picture (in this example N selected value 6) limited in vision system acquisition time sequence, records the image coordinate at every two field picture plane V-butt center i=1,2 ... N, and the arithmetic mean of instantaneous value calculating N frame center point value obtains weld seam initial characteristics point (x int, y int), computing formula is (1) formula, so, and acquiescence weld seam initial characteristics point (x int, y int) for welding gun is in the position of the plane of delineation 10;

x I n t = 1 N &Sigma; i = 1 N x m i d i y I n t = 1 N &Sigma; i = 1 N y m i d i - - - ( 1 ) .

Vision detection system, welding gun, V-ring seam weldment are separated (see Fig. 2) by apparatus of the present invention from test platform, embodiment illustrated in fig. 2ly to show, laser instrument 3 and video camera 1 optical axis included angle α=45 °, laser instrument 3 and vertical direction install angle theta ≈ 20 °, video camera 1 is to the distance L on V-butt annular weldment 6 between 180mm ~ 200mm, and the horizontal range of laser stripe 12 on pad and V-butt annular weldment 6 is between 45mm ~ 50mm.

The change in location of video camera 1 of the present invention and the variation relation of laser stripe 12 on the plane of delineation 10 (see Fig. 3-6), adopt this device, straight plate weldment 11 with weld seam 9 is placed on fixture 7, open laser instrument 3, a laser stripe 12 appears in the vertical direction of weld seam 9, and video camera 1 is above laser stripe 12.

1) when video camera 1 is when the left side of weld seam 9, on the plane of delineation 10, the groove of laser stripe 12 is positioned at the right side (see Fig. 3) of the plane of delineation 10, when video camera 1 level moves to right a segment distance and video camera 1 when the right side of weld seam 9, the groove of the laser stripe 12 on the plane of delineation 10 can horizontal left (see Fig. 4);

2) when video camera 1 is above weld seam 9, on the plane of delineation 10, laser stripe 12 is in the position (see Fig. 5) of the partial below of the plane of delineation 10, when video camera 1 moves a certain distance straight down, laser stripe 12 meeting vertically on image 10 moves (see Fig. 6).

From the analysis of weld image (see 3-6), can reflect that the point of weld width information is the intersection point that deformation part and undeformed part occur laser stripe 12, i.e. two intersection points of both sides straight line portion and intermediate curve part.Extraction for this point can adopt method center line array being asked to first derivative from image on one side within the scope of certain length, but this method is inapplicable to situation irregular in welding bead.

So, the feature of combining image, and the straight line of matching after hough conversion above, determine flex point, and then determine weld bead feature points, concrete steps are:

A. according to system accuracy, setting threshold value T c;

B. search for from image side, according to y seam(t)-y it formula judges whether viewpoint to () > T (i=1,2), if difference is greater than threshold value, recording this point is x 1acontinue search, when difference is less than threshold value, recording this point is x 1b, these two points are one group, record x successively 1a, x 1b, x 2a, x 2b;

Wherein, y seamt () is the ordinate of the centerline points on t row, y 1t () is that t arranges and carries out to the left-half of laser stripe the ordinate that hough converts the Points on Straight Line obtained, y 2t () is that t arranges and carries out to the right half part of laser stripe the ordinate that hough converts the Points on Straight Line obtained, if t is in the left-half of laser stripe, then with y 1t the value of () compares, if at the right half part of laser stripe, should with y 2t the value of () compares.

C. detect the position of the trisection point often organizing the line segment that array becomes, determine whether groove (groove as the laser stripe 12 on the plane of delineation 10), no, and one group of point is rejected;

The deformation quantity that can cause than weld seam under situation is removed in the deformation one of the structured light center line d. caused due to interfere information is little, therefore finds two numbers can be judged as striped flex point apart from maximum one group, and image coordinate corresponding to V-butt two flex points is

E. the mid point of flex point is exactly weld bead feature points.

Change can be there occurs according to the horizontal level of the groove of laser stripe 12 on the plane of delineation 10 accordingly and show that welding gun 5 exists deviation in the horizontal direction for weld seam 9, show that welding gun 5 exists deviation on weld seam 9 vertical direction when the vertical position of the groove of the laser stripe 12 on the plane of delineation 10 there occurs change.

(1) horizontal direction deviation identification

In the horizontal direction, can regard the demarcation on two dimensional surface as, on the plane of delineation, weld width wpixel and weld seam developed width W (known) is linear, and wherein weld seam developed width W is measured value, and be fixed value, can be considered invariant in welding process.Adopt the method for real-time calibration to constantly update the ratio of weld width wpixel on weld seam developed width W and the plane of delineation, namely often gather a two field picture and recalculate horizontal direction proportionality coefficient k xdvalue.If the position (x of weld seam initial characteristics point int, y int) and weld seam before the position coordinates of frame characteristic point wherein the n-th two field picture horizontal departure is the characteristic point coordinate that this frame calculates with the welding gun initial characteristics point coordinates (x calculated int, y int) compare, obtain plane of delineation weld seam deviation amount, converted by line style, obtain welding gun in the horizontal direction relative to the departure of actual welds, computing formula is (2), (3), (4) formula, and concrete steps are:

A. proportionality coefficient is calculated

k x d ( n ) = W / | x 2 ( n ) - x 1 ( n ) | - - - ( 2 )

B. plane of delineation weld seam deviation amount is obtained

&delta; x = x m i d ( n ) - x I n t - - - ( 3 )

C. calculate and export controlled quentity controlled variable, namely welding gun is in the horizontal direction relative to the departure of actual welds

ΔX=k xd (n)×δx(4)

(2) vertical direction deviation identification

In actual welding, due to the position deviation of V-butt annular weldment holder, or due to the cause of backing welding dislocation, there will be rotation angled with the annular weldment geometrical axis of V-butt, in rotary course, weld seam phase Butt welding gun there will be larger departure.Adopt a kind of algorithm of effective practicality to obtain the regulated quantity of welding gun vertical direction to this, reach the welding effect of expection.

The algorithm (see Fig. 7-8) of vertical direction deviation of the present invention identification, the position of weld seam 9 when curve S 1 is initial acquisition, curve S 2 is the image of weld seam 9 spatial position change that the n-th frame collects.Former laser structure light and V-butt annular weldment meet at A point, and rear because V-butt annular weldment 6 is when rotating, the position of weld seam 9 can change, and intersects at A with curve S 2 1point.The light that straight line L1 reflexes to the light of camera image plane when being shooting the n-th two field picture, straight line L2 reflexes to camera image plane 10 when being shooting the (n+1)th two field picture, because video camera 1 and the distance of V-butt annular weldment 6 are about 180mm, deviation is maximum within 10mm, and therefore two light straight line L1 and straight line L2 can be similar to and regard parallel lines as.Straight line L3 is the straight line at LASER Light Source place.α is the angle between laser instrument 3 and video camera 1 optical axis, and during actual Design of Vision System, in order to ensure imaging effect, α can not be zero, θ is that laser instrument 3 vertical direction installs angle, and being measurable magnitude, after vision system fixed installation, is given value.

If PQ is the plane vertical with video camera 1 optical axis, is recorded on the known two dimensional surface vertical at camera optical axis by experiment and follow linear transformation, and k xd≈ k yd.AB line segment is embodied by the offset deviation of laser stripe straight line longitudinal direction in the value of the plane of delineation, and namely the physical length of line segment AB is AA 1length, can try to achieve according to formula (5), (6), (7) formula, namely

A. AB line chart is obtained as plane welded seam deviate

&delta; y = y m i d ( n ) - y I n t - - - ( 5 )

B. AB is calculated

AB=k xd (n)×δy(6)

C. by geometric operation, AA 1tried to achieve by formula (7)

AA 1=AB/cos(90°-α)(7)

D.A 1d is the straight line with laser light source projects plane orthogonal, hands over AC in D point (see Fig. 8), calculates AD length, be welding gun in the vertical direction relative to the departure of actual welds:

AD=AA 1/cosθ=AB/(cos(90°-α)×cosθ)(8)

In the height direction, offset distance should be AC, therefore needs to analyze the value of CD.When other welding surroundings are constant, the caliber of weldment is less, and CD value is larger; In weldment caliber one timing, weldment side-play amount on the vertical direction of x-y plane is larger, and the value of CD is also larger.Therefore can obtain, the caliber of weldment is the factor of major effect CD value with weldment side-play amount on the direction that x-y plane is vertical, and wherein weldment pipe radius is the leading factor affecting CD.

If A 1d and A 1the angle of C direction tangent line is β, due to arc A 1c is very short, can be approximated to be straight line, therefore has following relational expression:

&angle; ADA 1 = &pi; 2 - &theta; - - - ( 9 )

&angle; ACA 1 = &pi; 2 - &theta; - &beta; - - - ( 10 )

A 1D=ADsinθ(11)

Obtain according to sine:

sin &angle; ACA 1 A 1 D = s i n &beta; C D - - - ( 12 )

Formula (10), (11) are brought into formula (12) and are obtained:

C D = A D &times; s i n &theta; &times; s i n &beta; s i n ( &pi; 2 - &theta; - &beta; ) - - - ( 13 )

To arrange further:

C D = s i n &theta; s i n &beta; c o s ( &theta; + &beta; ) A D - - - ( 14 )

Because θ value is known, CD → 0, β → 0.During β ≠ 0, formula (14) can arrange further again and be:

C D = 1 cot &theta; cot &beta; - 1 A D - - - ( 15 )

Now, CD increases along with the angle increase of β, and β value affects by weldment pipe radius and eccentric distance, the minimum pipe that native system is measured is 180mm, welding system requires that the maximum deviation that rotates a circle is no more than 10mm, now β maximum is 33 °, now CD ≈ 0.3AD, known by experiment, within the scope of the maximum deviation that welding system allows, the AD value that every frame draws is at below 1mm, and therefore CD length is less than 0.3mm, and this value does not add up, when next frame calculates, obtain new less value.Therefore, the impact of CD on system fading margin can not be considered.

Embodiment 1

The present embodiment connects device on request, and the overall diameter selecting V-butt annular weldment is 195mm, and groove width is 14mm, and groove depth is 7mm.

First camera power supply is opened, mobile welding gun is to initial weld position, and simultaneous camera 1 gathers image and processes, and obtains weld image coordinate and welding seam position information, the reference picture coordinate of record weld seam initial characteristics point, can start soldering joint automatic tracking function after completing.In soldering joint automatic tracking process, each sampling period extracts a weld image coordinate as the value of feedback of current position while welding, by the decoupling zero detection algorithm based on the plane of delineation, directly calculates the actual deviation amount in welding gun 5 both direction.

Vision detection system and welding gun 5 are rigidly connected, and before welding starts, welding gun are adjusted to suitable welding position, namely on V-butt center line.In the not starting the arc and weldment does not rotate, 6 two field pictures limited in vision detection system acquisition time sequence, the image coordinate at every two field picture plane V-butt center is respectively (296,455), (295,455), (296,455), (296,455), (296,455), (296,455).And by formula (1), the arithmetic mean of instantaneous value calculating 6 frame center's point values obtains (296,455).So, this point is defaulted as the position of welding gun 5 at the plane of delineation 10, i.e. the reference picture coordinate of weld seam initial characteristics point.

x I n t = 1 N &Sigma; i = 1 N x m i d i y I n t = 1 N &Sigma; i = 1 N y m i d i - - - ( 1 )

Wherein, for the coordinate of every two field picture, i=1,2 ... N, (x int, y int) weld seam initial characteristics dot image coordinate.

(1) horizontal departure identification

In the horizontal direction, can regard the demarcation on two dimensional surface as, on the plane of delineation, weld width wpixel and weld seam developed width W (known) is linear, wherein W is measured value, and be fixed value, can be considered invariant in welding process, in the present embodiment W=14.Adopt the method for real-time calibration to constantly update the ratio of weld seam developed width and plane of delineation weld width, namely often gather a two field picture and recalculate horizontal direction proportionality coefficient k xdvalue.The position (296 of weld seam initial characteristics point, 455), V-butt annular weldment 6 is video camera 1 constantly capturing pictures in the process rotated, and choose 5 frames wherein in this example, its coordinate is respectively (295,424), (291,426), (294,425), (295,426), (293,425), the coordinate of this 5 two field picture is made comparisons with weld seam initial characteristics point coordinates (296,455) respectively, obtains plane of delineation departure, converted by line style, obtain welding gun 5 in the horizontal direction relative to the departure of actual welds.Try to achieve by formula (2), (3) and (4), wherein the coordinate of present frame weld seam two flex points, position coordinates for weld seam present frame characteristic point:

A. proportionality coefficient is calculated

k x d ( n ) = W / | x 2 ( n ) - x 1 ( n ) | - - - ( 2 )

B. pixel planes weld seam deviation value is obtained.

&delta; x = x m i d ( n ) - x I n t - - - ( 3 )

C. calculate and export controlled quentity controlled variable, namely welding gun 5 is in the horizontal direction relative to the departure of actual welds

ΔX (n)=k xd (n)×δx(4)

Δ X is obtained by above step (1)=-6, Δ X (2)=-2, Δ X (3)=-1, Δ X (4)=-4, Δ X (5)=-4.

(2) vertical direction deviation identification (see Fig. 7-8)

In actual welding, due to the position deviation of V-butt annular weldment 6 holder, or due to the cause of backing welding dislocation, there will be rotation angled with annular weldment 6 geometrical axis of V-butt, in rotary course, weld seam phase Butt welding gun there will be larger departure.Adopt a kind of algorithm of effective practicality to obtain the regulated quantity of welding gun 5 vertical direction to this, reach the welding effect of expection.

If PQ is the plane vertical with video camera 1 optical axis, owing to following linear transformation on the vertical two dimensional surface of video camera 1 optical axis, and k xd≈ k yd.AB line segment is embodied by the offset deviation of laser stripe straight line longitudinal direction in the value of the plane of delineation, i.e. AD length.Therefore the physical length of line segment AB can be tried to achieve according to (5)-(7), namely

A. AB line chart is obtained as plane welded seam deviate

&delta; y = y m i d ( n ) - y I n t - - - ( 5 )

B. AB is calculated

A B = k x d ( n ) &times; &delta; y - - - ( 6 )

C. by geometric operation, AA 1tried to achieve by formula (7)

AA 1=AB/cos(90°-α)(7)

D.A 1d is the straight line with laser light source projects plane orthogonal, hands over AC in D point, calculates AD length, be welding gun in the vertical direction relative to the departure of actual welds:

AD=AA 1/cosθ=AB/(cos(90°-α)×cosθ)(8)

By checking above, CD can ignore on the impact of system, and like this, the vertical regulated quantity of welding gun being obtained 5 two field pictures by above step is respectively-2,2,0,2,0.

So far, the welding gun 5 obtaining 5 two field pictures is in the side-play amount of level and vertical direction, again the validity of departure is judged, if coordinate does not exceed limit value, can be considered virtual value, PLC (programmable logic controller (PLC)) exports pulsed quantity according to both mathematic interpolation, drives welding gun 5 to do correction adjustment by cross adjusting bracket 4.

In order to obtain stable control effects, need to introduce PID controller, this experiment need use incremental timestamp, output signal due to controller is the pulse signal of stepper motor, therefore need to increase a pulse equivalency before PID controller, the image error namely eliminating a unit needs the stepper motor umber of pulse exported.The incremental timestamp device of tape pulse equivalent is as shown in formula (16):

p(k)=S{K p[e(k)-e(k-1)]+K ie(k)+K d[e(k)-2e(k-1)+e(k-2)]}(16)

Wherein, p (k) is that the pulse in k moment exports, and S is pulse equivalency, K p, K i, and K dthe ratio of PID controller, integration, the differential gain respectively.In test, pid parameter is respectively: K p=0.5, K i=0.07 and K d=0.005.

In above-described embodiment, laser instrument used is laser line generator.

In order to the reliability of verification algorithm, when using rotation, serious eccentric test block is tested, and when not playing arc welding, when not adding decoupling algorithm, 100ms gathers a two field picture, and record weld bead feature points is at the coordinate value of the plane of delineation 10.Obtain the abscissa value (see Fig. 9) of weld bead feature points and the curve map of ordinate value (see Figure 10), Figure 10 can find out that the ordinate of weld bead feature points reaches the position of high 480 pixels of image, cause owing to not carrying out adjustment, the position of structured light beyond the visual field of video camera 1, illustrate the axle center of test block and axis of rotation angle larger.Namely the weld bead feature points calculated by front 6 two field pictures is considered as welding gun 5 position, when so rotating, can find out that welding gun 5 has obviously departed from weld seam 9 center.

Use test block (the same), when not playing arc welding, add decoupling algorithm, 100ms gathers a two field picture, and record weld bead feature points transverse and longitudinal coordinate value, represents with Figure 11, Figure 12 respectively; When playing arc welding, add decoupling algorithm, 100ms gathers a two field picture, and record welding gun needs transversal displacement and the vertical misalignment amount of movement, represents respectively with Figure 13 and Figure 14.

After adding decoupling algorithm, continuous Butt welding gun 5 carries out horizontal and vertical adjustment, welding gun reaches 6 pixels (see Figure 11), current Proportional coefficient K 1=0.075 the deviation in plane of delineation x direction is maximum, then welding gun maximum deviation is 0.45mm (see Figure 13).In y-direction, maximum deviation is 11 pixels (see Figure 12), and short transverse maximum deviation is 0.75mm (see Figure 14).And known by Figure 13 and Figure 14, the calculating of Butt welding gun side-play amount, meets rule, illustrates that decoupling zero detection algorithm achieves the accurate positioning control of welding gun to three-dimensional weld seam.

Equipment involved in above-described embodiment all can by commercially available.

The inventive method is mainly used in industry spot, the detection of V-butt circular weld, identify and to carry out with welding simultaneously, detection algorithm fully adapts to field condition, utilize two-dimentional weld image to obtain the positional information of three-dimensional weld seam, make to there is not coupled relation between the change of characteristics of image and welding gun motion.Each two field picture of obtaining according to video camera after the starting the arc 1 for the acquisition of the horizontal and vertical deviation of directivity of weld seam with the non-starting the arc before the center of V-butt circular weld that obtains compare, the deviate obtained.Because welding surroundings is very complicated, the center of the current frame image that video camera 1 may be caused to obtain due to the impact of the factors such as light, arc light, reflective, splashing in welding process may be inaccurate, if front and back two two field picture compares, deviation may be made more and more inaccurate, if but with the non-starting the arc before the center that obtains make comparisons, even if the incorrect deviation that also can not have influence on next frame image weld seam of deviation that present frame obtains.Improve the accuracy rate that weld seam deviation is corrected.Apparatus of the present invention can provide corresponding warning message according to the anomaly occurred in welding process, also can be observed the relevant information in welding process by display, only need video camera 1 (comprising camera lens, optical filter etc.) and laser instrument 3 just can complete extraction and the location of weld information.

The present invention does not address part and is all applicable to prior art.

Claims (4)

1. based on decoupling zero detect a circumferential weld visible detection method, for V-butt annular weldment weld seam detection, identify and weld, it is characterized in that the concrete steps of the method are:
The first step, image procossing and feature extraction
1-1 Image Acquisition: obtained the welded seam area image comprising laser stripe by smart camera sensor;
The laser stripe scope in the picture of the image that 1-2 region of interesting extraction: determining step 1-1 obtains;
1-3 image threshold adaptivenon-uniform sampling: on the basis of step 1-2, determines the available point of laser stripe;
1-4 laser structure light center line drawing: adopt the mode extracted by column to extract V-butt circular weld center line array method;
The filtering of 1-5 center line and interpolation: the missing point in the laser structure light center line that interpolation completion is extracted, adopt the further stress release treatment interference of gauss low frequency filter afterwards;
1-6Hough straight line converts: on the basis of step 1-5, carry out hough fitting a straight line to the laser stripe after differential filtering;
1-7 feature point extraction: the ordinate value of the line correspondences obtained after converting according to the ordinate value of center line group of the laser stripe extracted and hough compares the flex point obtaining laser stripe, and the mid point of two flex points is exactly weld bead feature points;
Second step, image information decoupling zero
2-1 horizontal direction deviation identification: utilize the linear relationship of weld width and weld seam developed width on the plane of delineation to obtain the departure in welding-torch horizontal direction; Horizontal departure knows method for distinguishing: adopt the method for real-time calibration to constantly update the ratio of weld width on weld seam developed width and the plane of delineation, namely often gather a two field picture and recalculate horizontal direction proportionality coefficient k xdvalue, if the position (x of weld seam initial characteristics point int, y int) and the position coordinates of weld seam n-th frame characteristic point wherein the n-th two field picture horizontal departure is the characteristic point coordinate that this frame calculates with the welding gun initial characteristics point coordinates (x calculated int, y int) compare, obtain plane of delineation weld seam deviation amount by linear transformation, obtain welding gun in the horizontal direction relative to the departure of actual welds, computing formula is (4) formula:
ΔX=k xd (n)×δx(4);
2-1 vertical direction deviation identification: obtain the departure of welding gun vertical direction in the space geometry relation that vertical direction is formed according to the weld seam on the plane of delineation and the welding gun in space; The welding gun of vertical direction deviation identification is (8) formula relative to the computing formula of the departure of actual welds in the vertical direction:
AD=AA 1/cosθ=AB/(cos(90°-α)×cosθ)(8),
In formula, the position of weld seam when curve S 1 is initial acquisition, curve S 2 is the image of the weld seam spatial position change that the n-th frame collects, and A point is the intersection point of former laser structure light and V-butt annular weldment, A 1when point is for the weldment rotation of V-butt annular, with the intersection point of curve S 2, AA 1line segment is A point and A 1the line of point; AB line segment is the offset deviation of laser stripe straight line longitudinal direction; α is the angle of laser instrument and camera light between centers, and θ is that laser instrument vertical direction installs angle, and AD line segment is that welding gun is in the vertical direction relative to the departure of actual welds.
2. the circumferential weld visible detection method detected based on decoupling zero according to claim 1, it is characterized in that the overall diameter of described V-butt annular weldment is greater than 180mm, groove width is 10-20mm, and groove depth is greater than 4mm.
3. the circumferential weld visible detection method detected based on decoupling zero according to claim 1, is characterized in that described weld bead feature points is the mid point of two flex point lines of weld image V-butt.
4. the circumferential weld visible detection method detected based on decoupling zero according to claim 3, it is characterized in that in the not starting the arc and weldment does not rotate, N two field picture limited in vision system acquisition time sequence, the span of N is 5<N<10, records the image coordinate at every two field picture plane V-butt center i=1,2 ... N, and the arithmetic mean of instantaneous value calculating N frame center point value obtains weld seam initial characteristics point (x int, y int), computing formula is (1) formula:
x I n t = 1 N &Sigma; i = 1 N x m i d i y I n t = 1 N &Sigma; i = 1 N y m i d i - - - ( 1 ) .
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