CN103954216B - Strong specular reflection workpiece thin and narrow groove detection device and method based on spherical surface light sources - Google Patents
Strong specular reflection workpiece thin and narrow groove detection device and method based on spherical surface light sources Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
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Abstract
The invention provides a strong specular reflection workpiece thin and narrow groove detection device and method based on spherical surface light sources, and belongs to the field of welding automation. According to the device and the method, the spherical surface light sources irradiate the surface of a workpiece so that a workpiece surface image with the uniform gray level can be obtained, and the automatic detection on a strong specular reflection workpiece thin and narrow groove is achieved by determining the relative position and posture between a welding gun and the workpiece through a laser array. According to the device and the method, the spherical surface light sources irradiate the surface of the strong specular reflection workpiece so that the uniform-illumination workpiece surface image can be obtained, the characteristics of the groove in the image are obvious, the center position of the groove is conveniently and accurately extracted, and the detection accuracy can reach 0.03 mm; the relative position and posture between the workpiece and the welding gun can be rapidly and accurately obtained through the laser array; the system structure is simple, the detection accuracy is high, instantaneity is high, cost is low, and the strong specular reflection workpiece thin and narrow groove detection device and method can be applied to automatic detection of the groove of the strong specular reflection workpiece surface and are particularly suitable for the occasion of high-energy beam welding automatic tracking of the thin and narrow groove workpiece with the groove gap smaller than 0.1 mm.
Description
Technical Field
The invention belongs to the field of welding automation, and particularly relates to a device and a method for detecting a narrow groove of a strong specular reflection workpiece based on a spherical light source.
Background
The lightweight development and increased reliability requirements of aerospace components present significant challenges to weld visual inspection and tracking. Firstly, the groove form of a workpiece to be welded is generally an I-shaped butt joint groove, the gap of the groove is extremely small (generally not more than 0.1mm), the relative pose of a welding gun and the groove is slightly shifted, so that serious welding defects can be caused, and the requirements on detection and tracking precision are extremely high; secondly, the aerospace members are mostly made of aluminum-magnesium alloy, the reflectivity can reach more than 95%, and the strong specular reflection light on the surface of the aerospace members causes the brightness of images to be extremely uneven, and even possibly covers the main characteristic information of grooves. The traditional welding seam tracking method identifies the area to be welded by detecting the distortion characteristics of the structural light strip, and the method too depends on the macroscopic geometric structural characteristics of the groove and cannot be applied to the detection occasion of the narrow groove with unobvious distortion of the structural light strip.
Chinese patent document (publication No. CN101927395B) discloses a weld joint tracking detection apparatus and method, which projects a laser spot having a specific profile feature on a workpiece surface, uses a CCD camera to collect an image of the workpiece surface, detects a lateral deviation of a bevel by detecting a shadow of the bevel in the spot, and calculates a relative pose between the workpiece surface and a welding gun by detecting changes in the shape, position, and size of the spot. The gray scale of the image acquired by the method is very uneven, which brings difficulty to the accurate extraction of the light spot edge, on one hand, the image is locally saturated because the metal surface generates strong mirror reflection to the laser; on the other hand, the laser forms speckles on the metal surface, which aggravates the gray scale nonuniformity. The influence of specular reflection light can be reduced to a certain extent by methods of reducing exposure time, reducing aperture, using a polaroid for extinction and the like, but the laser speckle phenomenon is more obvious, and the uniformity of image gray scale cannot be improved.
In summary, there is no device and method suitable for detecting the narrow and thin groove of the workpiece with the strong specular reflection surface, which has high detection precision, strong real-time performance and good image gray level uniformity.
Disclosure of Invention
The invention aims to provide a device and a method for detecting a narrow and thin groove of a strong specular reflection workpiece based on a spherical light source, aiming at solving the problems of limited detection precision, uneven image gray scale caused by strong specular reflection of the surface of the workpiece, difficult accurate determination of the relative pose of a welding gun and the workpiece and the like in the prior art so as to realize automatic identification of the groove, and particularly aiming at the occasion of automatically detecting the narrow and thin groove with the groove gap smaller than 0.1 mm.
The technical scheme of the invention is as follows:
fine and narrow groove detection device of strong specular reflection work piece based on spherical light source, its characterized in that: the device comprises a control unit, a sensor shell, a spherical light source, a laser array, an imaging element and a filter element, wherein the spherical light source, the laser array, the imaging element and the filter element are arranged in the sensor shell; the control unit is respectively connected with the spherical light source, the laser array and the imaging element through leads; the sensor shell is fixedly connected with the welding gun; the spherical light source comprises a light emitting diode array, a spherical diffuse reflection shell and a light hole; the light emitting diode array is distributed at the bottom of the spherical diffuse reflection shell, and light rays emitted by the light emitting diode array are projected on the surface of a workpiece after being reflected by the spherical diffuse reflection shell; or the light emitting diode array is distributed on the surface of the spherical diffuse reflection shell, one part of light emitted by the light emitting diode array is directly projected on the surface of a workpiece, and the other part of light is projected on the surface of the workpiece after being reflected by the spherical diffuse reflection shell; the laser array comprises at least three lasers; laser spots emitted by the laser array are projected on the surface of the workpiece; reflected light on the surface of the workpiece is shot into the imaging element for imaging after passing through the light hole and the filtering element;
fine and narrow groove detection device of strong specular reflection work piece based on spherical light source, its characterized in that: the imaging element is a charge coupled device, a complementary metal oxide semiconductor imaging device, a position sensitive device or a charge injection device; the light-emitting wavelength of the spherical light source and the light-emitting wavelength of the laser array are consistent with the central wavelength of the filter element; the central wavelength of the filter element is in the sensitive wavelength range of the imaging element;
the method for detecting the narrow and thin groove of the strong specular reflection workpiece based on the spherical light source is characterized by comprising the following steps of:
1) establishing an imaging element coordinate system { C }, wherein the origin of the imaging element coordinate system { C } is the optical center of an imaging element, and the vertical axis direction is the same as the optical axis direction of the imaging element; establishing a pixel coordinate system { P } on an image acquired by an imaging element; the laser array is provided with N lasers, wherein N is a positive integer greater than or equal to 3;
2) calibrating the imaging element to obtain any point (u, v) in a pixel coordinate system { P }TWith the midpoint (x, y, z) of the imaging element coordinate system { C })TThe conversion relationship between:
and in the imaging element coordinate system { C }, the laser propagation path equation emitted by the ith laser is as follows:
Xi＝Xi,0+tiSi
wherein f is1，f2Is a transfer function between the pixel coordinate system { P } and the imaging element coordinate system { C }; i is a positive integer greater than or equal to 1 and less than or equal to N; xiAnd Xi,0Is a point on the laser propagation path emitted by the ith laser; siIs a unit direction vector of a laser propagation path emitted by the ith laser; t is tiIs a point XiAnd Xi,0A directed distance therebetween;
3) the control unit sends a trigger signal to enable the laser array and the spherical light source to be alternately lightened, and enables the imaging element to synchronously shoot images when different light sources are lightened; when the laser array is lightened, the control unit processes the image collected by the imaging element to obtain the coordinate (u) of the ith laser spot in the pixel coordinate system { P }i,vi)T(ii) a According to the coordinate (u) of the ith laser spot in the pixel coordinate system { P }i,vi)TCalculating the coordinate A of the ith laser spot in the imaging element coordinate system { C }i：
Ai＝[Xi,0+ti,1(ui,vi)·Si+ti,2(ui,vi)·Vi(ui,vi)]/2
Wherein,
assuming that the surface of the workpiece projected by the laser spot is approximate to a plane, and recording the plane as W; let the equation of plane W be XTα＝1，
Wherein α is the normal vector of the plane W, and X is any point on the plane W, according to the point AiAll on the plane W, there are:
namely:
obtaining a normal vector alpha of the plane W by using a linear least square method;
when the spherical surface light source is lightened, the control unit processes the image collected by the imaging element to obtain the coordinate (u) of the groove center point in the pixel coordinate system { P }w,vw)T(ii) a Obtaining the coordinate system of the groove center point on the imaging element according to the position of the groove center point on the plane WCoordinate B in { C }:
B＝Vw(uw,vw)/[αTVw(uw,vw)]
wherein,
Vw(uw,vw)＝[f1(uw,vw),f2(uw,vw),1]T。
the invention adopts a spherical light source to irradiate the surface of a workpiece to obtain the position deviation of the groove, and adopts a laser array to determine the pose information of the surface of the workpiece, thereby realizing the detection of the narrow groove of the workpiece with strong specular reflection. The device and the method of the invention can meet a plurality of target requirements during groove detection: the image gray scale is uniform, the groove characteristic is obvious, and the real-time and accurate detection of the groove position is facilitated; the pose information of the welding gun relative to the surface of the workpiece can be quickly and accurately determined, wherein the pose information comprises transverse offset, height direction offset, transverse deflection angle, longitudinal deflection angle and the like of the welding gun; the detection precision is high and can reach 0.03 mm; the system has simple structure, low cost and high real-time property, is suitable for automatic detection of the groove of a strong specular reflection workpiece (such as an aluminum alloy workpiece) and is particularly suitable for the detection occasion of a narrow groove with the groove gap smaller than 0.1 mm.
Drawings
Fig. 1 is a schematic structural diagram of a strong specular reflection workpiece narrow groove detection device based on a spherical light source according to a first embodiment.
Fig. 2 is a schematic structural diagram of a second embodiment of a strong specular reflection workpiece narrow groove detection device based on a spherical light source.
Fig. 3 is a groove image acquired by the imaging element when the spherical light source is turned on in the first and second embodiments of the present invention.
Fig. 4 is a schematic diagram of the determination of the pose of a workpiece using a laser array according to the first and second embodiments of the present invention.
Fig. 5 is a flowchart of groove detection in the first and second embodiments of the present invention.
In fig. 1 to 5:
1-a control unit; 2-a sensor housing; 3-spherical light source; 31-an array of light emitting diodes; 32-spherical diffuse reflection shell; 33-light hole; 4-laser array; 41 — a first laser; 42-a second laser; 43 — a third laser; 5-an imaging element; 6-a filter element; 7, a workpiece; 71-base material; 72-groove; 8, welding gun.
Detailed Description
The structure, principle and operation of the present invention will be further described with reference to the accompanying drawings.
Fig. 1 is a schematic structural principle diagram of a strong specular reflection workpiece narrow and thin groove detection device and method based on a spherical light source according to a first embodiment of the present invention, and the device and method includes a control unit 1, a sensor housing 2, a spherical light source 3, a laser array 4, an imaging element 5, and a filter element 6. The control unit 1 is connected with the spherical light source 3, the laser array 4 and the imaging element 5 through leads; the control unit 1 sends a trigger signal to enable the spherical light source 3 and the laser array 4 to alternately strobe, and enable the imaging element 5 to synchronously acquire surface images of the workpiece 7 irradiated by different light sources; the sensor shell 2 is fixedly connected with a welding gun 8; the spherical light source 3 comprises a light emitting diode array 31, a spherical diffuse reflection shell 32 and a light hole 33; the light emitting diode array 31 is distributed at the bottom of the spherical diffuse reflection shell 32, and light emitted by the light emitting diode array is reflected by the spherical diffuse reflection shell 32 and then projected on the surface of the workpiece 7; the laser array 4 comprises at least three lasers; laser spots emitted by the laser array are projected on the surface of the workpiece 7; the reflected light on the surface of the workpiece 7 is shot into the imaging element 5 for imaging after passing through the light-transmitting hole 33 and the filter element 6. In this embodiment, the number of the lasers is three, which are the first laser 41, the second laser 42 and the third laser 43, respectively, and the wavelength is 635 nm; the imaging element 5 is a 1024 × 1024 CCD camera, the field range is 30mm × 30mm, and the detection precision is 0.03 mm; the wavelength range of emergent light of the light emitting diode array 31 is 635-645 nm; the filter element 6 is a narrow-band filter, the central wavelength is 635nm, and the full width at half maximum is 10 nm; the light intensity of arc light at 635-645 nm is relatively weak, so the selected filter element 6 can effectively filter arc light interference.
The spatial distribution of the light intensity emitted from the led array 31 has large non-uniformity, which is derived from the sparse arrangement of the leds on the one hand and the directional non-uniformity of the light intensity of each led on the other hand. The inner surface of the spherical diffuse reflection shell 32 is equivalent to an ubtilissian sphere, and the light intensity integral effect of the ubtilissian sphere can eliminate the nonuniformity of the emergent light intensity of the light emitting diode array 31 to a certain extent, so that the light intensity projected on the surface of the workpiece 7 is uniform; the emergent light of the light emitting diode array 31 is incoherent light, the speckle problem of a laser light source does not exist, and the uniformity of light intensity is good.
Fig. 2 is a schematic structural principle diagram of a strong specular reflection workpiece narrow groove detection device and method based on a spherical light source according to a second embodiment of the present invention. Unlike the first embodiment, the led array 31 is distributed on the inner surface of the spherical diffuse reflection housing 32 in this embodiment. Due to the light intensity integration effect of the spherical diffuse reflection shell 32, the light intensity projected on the surface of the workpiece 7 is very uniform.
Fig. 3 is an original image of the bevel acquired by the imaging element 5 when the spherical light source 3 is turned on in the first and second embodiments of the present invention. The base material 71 and the groove 72 have a great difference in optical reflection characteristics: the gray scale approaches saturation due to strong specular reflection on the surface of the base material 71; the light projected on the groove 72 is reflected by the side wall of the groove 72, fails to be incident on the imaging element 5, and appears as a curve with a gray scale close to zero in the image. The strong difference between the gray scales of the parent metal 71 and the groove 72 provides guarantee for the rapid and accurate extraction of the position of the groove 72.
Fig. 4 is a schematic diagram of the determination of the pose of a workpiece using a laser array according to the first and second embodiments of the present invention. Since the light spot projected on the surface of the workpiece by the spherical light source 3 has no obvious edge profile feature, it is difficult to determine the pose of the welding gun 8 relative to the workpiece 7. The present invention uses the laser array 4 to determine the pose of the welding gun 8 relative to the workpiece 7. It is assumed that the laser array 4 is composed of N lasers, N being a positive integer. Establishing a pixel coordinate system { P } on the image acquired by the imaging element 5, wherein any point on the pixel coordinate system { P } represents the pixel coordinate value of the image of the imaging element 5; an imaging element coordinate system { C } is established, the origin of the imaging element coordinate system { C } is the optical center of the imaging element 5, and the vertical axis direction is the same as the optical axis direction of the imaging element 5.
Fig. 5 is a flowchart of groove detection in the first and second embodiments of the present invention. When the laser array 4 is lightened and the spherical light source 3 is extinguished, the pose of the welding gun 8 relative to the surface of the workpiece 7 can be obtained through calculation; when the spherical light source 3 is turned on and the laser array 4 is turned off, the three-dimensional space coordinate of the groove center point can be obtained through calculation by combining the pixel coordinate of the groove center point in the image of the imaging element 5 and the pose relation of the welding gun 8 relative to the surface of the workpiece 7. The control unit 1 is responsible for triggering the spherical light source 3, the laser array 4 and the imaging element 5, processing the image collected by the imaging element 5, and automatically adjusting the relative pose of the welding gun 8 and the workpiece 7 according to the calculation result to realize automatic tracking.
When the laser array 4 is turned on and the spherical light source 3 is turned off, the equation of the laser propagation path emitted by the ith laser in the imaging element coordinate system { C } is set as follows:
Xi＝Xi,0+tiSi(1)
wherein, XiAnd Xi,0For points on the path of propagation of the laser light from the ith laser, SiIs a unit direction vector, t, of a laser propagation path emitted by the ith laseriIs a point XiAnd point Xi,0Is measured.
After calibration by Zhangzhen et al, X in formula (1) can be obtainedi,0And SiAnd an arbitrary point (u, v) on the pixel coordinate system { P }TAnd corresponds to a point (x, y, z) on the imaging element coordinate system { C }TThe relationship between, namely:
wherein the function f1And f2Can be obtained by calibration.
Suppose that the pixel coordinate of the spot projected on the workpiece 7 by the ith laser in the image of the imaging element 5 is (u)i,vi)TCorresponding to a point on the imaging element coordinate system { C } being Ai＝(xi,yi,zi)TI is more than or equal to 1 and less than or equal to N, and i is a positive integer, and can be obtained according to the formula (2):
Ai＝ti,2(ui,vi)Vi(ui,vi) (3)
wherein, Vi(ui,vi)＝[f1(ui,vi),f2(ui,vi),1]T，ti,2(ui,vi) Is dependent on uiAnd viTo be determined parameters. Formula (3) shows that point AiOn a straight line represented by the formula (3) passing through the origin of the imaging element coordinate system { C } and having a direction vector of Vi(ui,vi)。
Due to point AiOn a straight line represented by formula (1), therefore:
Ai＝Xi,0+ti,1(ui,vi)Si(4)
wherein, ti,1(ui,vi) Is dependent on uiAnd viTo be determined parameters.
Point AiIs the intersection of two straight lines expressed by the formulas (3) and (4), and the vector SiAnd Vi(ui,vi) Not parallel, otherwise point AiWill not be present. However, the straight lines expressed by the expressions (3) and (4) are generally non-coplanar straight lines due to measurement errors, interference noise, and the like, and the point a is taken at this timeiIs the midpoint of the common vertical line of the two straight lines. Because the length of the common perpendicular line segment of the two different-surface straight lines is the shortest one of the line segments respectively connecting two points on the two different-surface straight lines, an objective function is established:
and the minimum value of the objective function g is solved, thus t can be determinedi,1(ui,vi) And ti,2(ui,vi) Thereby determining point AiThe coordinate values of (2).
Order to
Namely:
the determinant of coefficients of equation set of equation (7):
wherein,<Si,Vi(ui,vi)>represents a vector SiAnd Vi(ui,vi) The included angle of (a). Due to the vector SiAnd Vi(ui,vi) Non-parallel, so the determinant of equation (8) is greater than zero, there is a unique solution to equation set (7), and its solution is:
due to point AiIs the midpoint of the common perpendicular to the straight lines represented by equations (3) and (4), and therefore:
Ai＝[Xi,0+ti,1(ui,vi)·Si+ti,2(ui,vi)·Vi(ui,vi)]/2 (11)
it can be confirmed that when the straight lines expressed by the expressions (3) and (4) are not the non-coplanar straight lines, the intersection coordinates thereof still satisfy the expression (11).
To this end, the coordinates of the spot projected on the surface of the workpiece 7 by the ith laser with respect to the imaging element coordinate system { C } are given by equation (11). During actual detection, all laser spots are ensured to be projected near the groove 72, the workpiece surface projected by the laser spots is assumed to be approximately a plane, the plane is assumed to be W, and the equation is XTα is 1, where α is the normal vector to plane W due to point aiAre all on the plane W, so:
namely:
only when N is more than or equal to 3, the formula (13) has a unique least square solution, and the equation of the plane W can be determined, so that the laser array 4 is required to comprise at least three lasers in the invention.
When the spherical light source 3 is turned on and the laser array 4 is turned off, the imaging element 5 acquires a gray image of the surface of the workpiece. The image acquired by the imaging element 5 is subjected to threshold segmentation to obtain a binary image I, wherein the gray value of the parent metal 71 in the image I is one, and the gray value of the groove 72 is zero. For the j-th row of the image of the imaging element 5, the coordinates of the groove center point in the pixel coordinate system { P } are:
uw＝j (14)
wherein, I (j, v) represents the gray scale values of the jth row and the vth column of the image I, # { v: I (j, v) ═ 0} represents the total number of pixels satisfying I (j, v) ═ 0, and sum { v: I (j, v) ═ 0} represents the sum of the column numbers of pixels satisfying I (j, v) ═ 0.
The local area of the workpiece surface can be approximated as a plane W and a point (u)w,vw) The point B in the corresponding imaging element coordinate system C is on the plane W. Equation X according to equation (2) and plane WTWhen α is 1, point B satisfies:
B＝tw(uw,vw)Vw(uw,vw) (16)
BTα＝1 (17)
wherein, tw(uw,vw) Is dependent on uwAnd vwAnd:
Vw(uw,vw)＝[f1(uw,vw),f2(uw,vw),1]T(18)
the coordinates of the groove center point B in the imaging element coordinate system { C } can be calculated from equations (16) and (17):
B＝Vw(uw,vw)/[αTVw(uw,vw)](19)
and automatically adjusting the relative pose of the welding gun and the workpiece according to the coordinate of the central point of the groove and the normal vector of the surface of the workpiece so as to realize the automatic identification and tracking of the narrow groove.
It should be noted that the above embodiments are only used for illustrating the invention and do not limit the scheme described in the invention; therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art will appreciate that modifications and equivalents may be made to the present invention, for example, in order to make the number of lasers included in the laser array 4 greater than 3 to improve the detection accuracy of the relative pose of the welding gun and the surface of the workpiece, to use a higher resolution imaging element to improve the groove detection accuracy, to use a monochromator or other spectroscopic element as the filter element 6, and so on; all such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.
The invention adopts a spherical light source, a laser array, an imaging element and the like to realize the detection of the narrow and thin grooves of the strong specular reflection workpiece; the detection method does not depend on the macroscopic geometric structural characteristics of the groove, and the detection precision can reach 0.03 mm; the spherical light source is adopted to irradiate the surface of the workpiece, so that the brightness of the surface of the workpiece is uniform, the gray level of a parent metal part is close to saturation, and the gray level of a groove area is close to zero, so that on one hand, the groove position in an image can be accurately extracted, and on the other hand, the difficulty of image processing and the complexity of an algorithm are reduced; the laser array is adopted to determine the pose information of the surface of the workpiece, the detection method is simple, and the pose offset of the welding gun relative to the surface of the workpiece can be quickly and accurately calculated; the interference of ambient light, arc light and the like on the imaging element is eliminated by using the light filtering element, and the adaptability of the system to the actual welding operation environment is improved; the system has simple structure, high detection precision, good real-time property and lower cost, is suitable for detecting the bevel of a strong specular reflection workpiece, and is particularly suitable for the automatic tracking occasions of high-energy beam welding (laser welding, electron beam welding, plasma arc welding and the like) of thin and narrow bevel workpieces with the bevel clearance smaller than 0.1 mm.
Claims (3)
1. Fine and narrow groove detection device of strong specular reflection work piece based on spherical light source, its characterized in that: the device comprises a control unit (1), a sensor shell (2), and a spherical light source (3), a laser array (4), an imaging element (5) and a filter element (6) which are arranged in the sensor shell; the control unit (1) is respectively connected with the spherical light source (3), the laser array (4) and the imaging element (5) through leads; the sensor shell (2) is fixedly connected with a welding gun (8); the spherical light source (3) comprises a light emitting diode array (31), a spherical diffuse reflection shell (32) and a light hole (33); the light emitting diode arrays (31) are distributed at the bottom of the spherical diffuse reflection shell (32), and light rays emitted by the light emitting diode arrays are projected on the surface of the workpiece (7) after being reflected by the spherical diffuse reflection shell (32); or the light emitting diode array (31) is distributed on the surface of the spherical diffuse reflection shell (32), one part of light emitted by the light emitting diode array is directly projected on the surface of the workpiece (7), and the other part of light is projected on the surface of the workpiece (7) after being reflected by the spherical diffuse reflection shell (32); the laser array (4) comprises at least three lasers; laser spots emitted by the laser array (4) are projected on the surface of the workpiece (7); reflected light on the surface of the workpiece (7) is shot into the imaging element (5) for imaging after passing through the light hole (33) and the filter element (6).
2. The spherical light source-based fine and narrow groove detection device for the strong specular reflection workpiece, according to claim 1, wherein: the imaging element is a charge coupled device, a complementary metal oxide semiconductor imaging device, a position sensitive device or a charge injection device; the light-emitting wavelength of the spherical light source and the light-emitting wavelength of the laser array are consistent with the central wavelength of the filter element; the central wavelength of the filter element is in the sensitive wavelength range of the imaging element.
3. The method for detecting the narrow groove of the strong specular reflection workpiece based on the spherical light source by adopting the device as claimed in claim 1, which is characterized by comprising the following steps:
1) establishing an imaging element coordinate system { C }, wherein the origin of the imaging element coordinate system { C } is the optical center of an imaging element, and the vertical axis direction is the same as the optical axis direction of the imaging element; establishing a pixel coordinate system { P } on an image acquired by an imaging element; the laser array is provided with N lasers, wherein N is a positive integer greater than or equal to 3;
2) calibrating the imaging element to obtain any point (u, v) in a pixel coordinate system { P }TWith the midpoint (x, y, z) of the imaging element coordinate system { C })TThe conversion relationship between:
and in the imaging element coordinate system { C }, the laser propagation path equation emitted by the ith laser is as follows:
Xi＝Xi,0+tiSi
wherein f is1，f2Is a transfer function between the pixel coordinate system { P } and the imaging element coordinate system { C }; i is a positive integer greater than or equal to 1 and less than or equal to N; xiAnd Xi,0Is a point on the laser propagation path emitted by the ith laser; siIs a unit direction vector of a laser propagation path emitted by the ith laser; t is tiIs a point XiAnd Xi,0A directed distance therebetween;
3) the control unit sends a trigger signal to enable the laser array and the spherical light source to be alternately lightened, and enables the imaging element to synchronously shoot images when different light sources are lightened; when the laser array is lightened, the control unit processes the image collected by the imaging element to obtain the coordinate (u) of the ith laser spot in the pixel coordinate system { P }i,vi)T(ii) a According to the coordinate (u) of the ith laser spot in the pixel coordinate system { P }i,vi)TCalculating the coordinate A of the ith laser spot in the imaging element coordinate system { C }i：
Ai＝[Xi,0+ti,1(ui,vi)·Si+ti,2(ui,vi)·Vi(ui,vi)]/2
Wherein,
Vi(ui,vi)＝[f1(ui,vi),f2(ui,vi),1]T
assuming that the surface of the workpiece projected by the laser spot is approximate to a plane, and recording the plane as W; let the equation of plane W be XTα is 1, where α is the normal vector of plane W and X is any point on plane W, according to point AiAll on the plane W, there are:
namely:
obtaining a normal vector alpha of the plane W by using a linear least square method;
when the spherical surface light source is lightened, the control unit processes the image collected by the imaging element to obtain the coordinate (u) of the groove center point in the pixel coordinate system { P }w,vw)T(ii) a Obtaining the coordinate B of the groove center point in the imaging element coordinate system { C } according to the fact that the groove center point is located on the plane W:
B＝Vw(uw,vw)/[αTVw(uw,vw)]
wherein,
Vw(uw,vw)＝[f1(uw,vw),f2(uw,vw),1]T。
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| JP2015563076A JP6101370B2 (en) | 2014-05-13 | 2014-09-18 | Apparatus and method for detecting narrow groove of workpiece reflecting specularly |
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| CN106425015A (en) * | 2016-11-15 | 2017-02-22 | 合肥通用机械研究院 | All-position self-adaptive welding process for large low-alloy high-strength steel ball tank |
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| CN108788550B (en) * | 2018-06-27 | 2019-07-12 | 清华大学 | Detection device, the control method and device that areola welding bead is detected using detection device |
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