CN115464263A - Automatic tracking method, detection method and device for laser welding seam - Google Patents
Automatic tracking method, detection method and device for laser welding seam Download PDFInfo
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- CN115464263A CN115464263A CN202211155049.5A CN202211155049A CN115464263A CN 115464263 A CN115464263 A CN 115464263A CN 202211155049 A CN202211155049 A CN 202211155049A CN 115464263 A CN115464263 A CN 115464263A
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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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
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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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/70—Auxiliary operations or equipment
- B23K26/702—Auxiliary equipment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1656—Programme controls characterised by programming, planning systems for manipulators
- B25J9/1664—Programme controls characterised by programming, planning systems for manipulators characterised by motion, path, trajectory planning
Abstract
The invention relates to an automatic tracking method for a laser welding seam, which comprises the following steps: installing a focus tool and a tool point fixing tool, determining a reference point of the focus tool and a fixed point of the tool point tool, and establishing a focus coordinate system of the laser welding gun by adopting a four-point method; establishing a robot base coordinate system by taking an installation base of the robot as a reference, and determining a coordinate relation between the robot base coordinate system and a focal point coordinate system of the laser welding gun according to a pose matrix of the robot base coordinate system; scanning the edge of a rib plate to obtain a surface profile image of a test piece to be welded, extracting weld characteristic points of two side edges of a laser band from the obtained surface profile image of the test piece to be welded, and respectively making a first line segment and a second line segment for the weld characteristic points of the two side edges; and fitting the line segment I and the line segment II of the welding seam characteristics, solving the intersection point of the line segments I and the line segment II, namely the coordinate of the welding seam center track, and aiming at replacing manual teaching, automatically completing welding seam welding and postwelding detection and greatly improving the welding efficiency and quality stability.
Description
Technical Field
The invention belongs to the technical field of laser welding automatic processing of complex space curved surface thin-wall structural parts, and particularly relates to an automatic tracking method, a detection method and a device for a laser welding seam.
Background
The rib wall plates of aviation, automobiles and the like are generally in a T-shaped welding seam structure, the T-shaped welding seam welding generally adopts a double-beam laser welding mode to weld from the left side and the right side, the laser welding quality and efficiency of the T-shaped welding seam structure directly influence the development speed and laser welding application and popularization of the industries, the robot double-beam laser welding is one of main production and processing modes of titanium alloy assemblies, riveting and spot welding cannot be used in order to meet the requirements of stealth and light weight, the consistency of welding seams to be welded is poor due to workpiece thermal forming deformation, rib plate processing errors and clamping errors, an offline programming track cannot be directly used for welding, each welding seam needs to be manually taught and calibrated, the manually taught welding quality is poor in consistency and low in efficiency, the robot double-beam laser welding seam welding is not suitable for rapid development of new generation airplanes in China, and the production quality and efficiency of titanium alloy assemblies of airplanes in China are seriously influenced.
The laser welding difficulty of the aviation titanium alloy complex space curved surface thin-wall structural part is high, firstly, the welding measurement space is narrow, rib plates are criss-cross, the shape of the space curved surface is complex, a measuring device needs to measure remotely without interfering with a tool and a workpiece, the precision of the measuring device is reduced along with the increase of the measuring range of the measuring device, the laser welding requirement precision is very high, the quality of a welding seam reaches I level, and the deviation of the center of the welding seam is not more than +/-0.1 mm, so that the system requires the measuring device to be small and compact in size and structure, and meanwhile, higher measuring precision is ensured; secondly, the titanium alloy wall plate is cleaned by laser before being welded, the reinforcing ribs are vertically assembled on the bottom plate, the effect similar to the vertical arrangement of two mirror surfaces is formed, multiple reflections are easily generated during the measurement of the sensor, and the measurement precision is seriously influenced.
The general structured light sensor has large attenuation of measurement precision along with the increase of measurement visual field and measurement distance, and cannot meet the process requirement, while the structured laser sensor with small visual field cannot meet the welding accessibility of the T-shaped joint of the titanium alloy laser welding and the measurement visual field requirement. In addition, the laser welding speed reaches 6-12 m/min, the dynamic tracking speed of the robot welding seam measuring system is slow, and the quality of a welding forming track is poor due to the fact that the welding track is dynamically adjusted, so that the process requirement cannot be met.
In the aspect of post-welding weld joint detection, the requirement of the double-beam welding weld joint reaches the I-grade weld joint standard of a navigation mark, and the requirement mainly comprises the requirements of the internal quality, the mechanical property and the appearance of the weld joint, the main detection means of the internal defects of the weld joint is X-ray flaw detection, and the common defects are cracks, incomplete penetration, incomplete fusion, air holes, slag inclusion and the like; the mechanical property mainly adopts a tensile experiment method, and the tensile strength and the shear strength meet the technical requirements; the appearance and appearance quality is required, the welding seam is in uniform transition, no defects such as pits, welding beading, undercut and the like exist at the arc striking and arc ending part, and the height difference of the welding leg is less than or equal to 0.3mm. Appearance quality is an important evaluation standard of quality of a double-beam welding process, surface defects are mainly checked by manual visual inspection at present, and the height difference of a welding leg is measured by adopting a metallographic method. The metallographic method for measuring the height of the weld leg needs to cut the T-shaped weld joint to manufacture a metallographic specimen, and the method has low efficiency and cannot detect an actual welded workpiece.
Disclosure of Invention
The invention mainly aims at the problems and provides an automatic tracking method, a detection method and a device for a laser welding seam, which replace manual teaching, automatically complete welding seam welding and postweld detection, and greatly improve welding efficiency and quality stability.
In order to achieve the aim, the invention provides an automatic tracking method for a laser welding seam, which comprises the following steps:
step 1: installing a focus tool at the tail end of a laser welding gun, determining a reference point of the focus tool, fixing a tool nose tool on a workbench, determining a fixed point of the tool nose tool, adopting a four-point method to enable the reference point to be just contacted with the fixed point, and establishing a focus coordinate system of the laser welding gun through data of four position points;
and 2, step: establishing a robot base coordinate system by taking a mounting base of a linear laser sensor mounted on a robot as a reference, and determining a coordinate relation between the robot base coordinate system and a laser welding gun focus coordinate system according to a pose matrix of the robot base coordinate system;
and 3, step 3: the robot drives the line laser sensor to move along the position to be welded of the test piece to be welded, the edge of the rib plate is scanned to obtain the surface profile image of the test piece to be welded,
and 4, step 4: extracting weld characteristic points of two side edges of a laser band from the obtained surface profile image of the test piece to be welded, respectively drawing a first line segment and a second line segment on the weld characteristic points of the two side edges, and taking the first line segment and the second line segment as weld characteristics;
and 5: and fitting the first line segment and the second line segment of the weld joint characteristics, and solving the intersection point of the first line segment and the second line segment to obtain the coordinate of the weld joint center track.
Further, in step 1, the calibration process for establishing the focal point coordinate system of the laser welding gun comprises:
calibrating the position of the center point of the tool: the hand-operated robot moves the laser welding gun from four different directions to the fixed point, and records four points P 1 、P 2 、P 3 、P 4 Pose data of robot end flange (X, Y, Z, theta) 1 、θ 2 、θ 3 ) The coordinates of the central point of the fourth tool in a world coordinate system are equal, and calculation is completed on an operation demonstrator to obtain a tool coordinate system TCP (X, Y, Z);
tool coordinate system attitude calibration: and moving the tool coordinate system TCP to any fixed point for measurement, moving a point in the negative direction of the Y axis to the fixed point for measurement, then moving any point with a negative value X in the XY plane to the fixed point for measurement, recording data, and completing calculation and calibration on an operation demonstrator.
Further, in step 2, the step of determining the coordinate relationship between the robot base coordinate system and the laser welding gun focus coordinate system includes:
when the robot is in a certain pose, the pose matrix of the welding seam welding end executor relative to the base coordinate of the robot is T 1 The position and pose matrix from the coordinate system of the line sensor to the end flange is X 1 The position and pose of the world coordinate system under the robot base coordinate system are P 1 ＝T 1 X 1 M 1 When the robot moves to another pose, the parameter is changed into T 2 、X 2 、P 2 Since the line sensor is fixed to the tip, X 1 ＝X 2 And since the world coordinate system and the end coordinate system are stationary, P 1 ＝P 2 Let us order
There is an AX = XB,
assuming that a is an m × n matrix, B is an n × n matrix, and X is an m × n matrix, the matrix direct product definition indicates:
when A or B is an identity matrix, there are
Assuming that a and b are constants, then there is,
vec(aA+bB)＝a×vec(A)+b×vec(B)
suppose that
AX = XB can be expressed as:
to determine the unique solution of the above equation, two sets of motions with non-parallel axes of rotation are required, and the two sets of motions yield simultaneous equations:
solving the eigenvector v = [ v ] corresponding to the minimum singular value by using a least square method 1 v 2 …v 13 ]Then the relationship matrix is:
further, the step 3 comprises forming an included angle of 45 degrees between a YZ plane of the laser welding gun and the vertical surface of the rib plate, and setting a plurality of points S on the test piece to be welded 0 、S 1 ……、S n 、S n+1 So that the robot drives the line laser sensor along S 0 、S 1 ……、S n 、S n+1 Are scanned sequentially, at S 0 And a pulse instruction is sent by a PLC (programmable logic controller) line-feeding laser sensor at the point to trigger data acquisition, a three-dimensional line-structured laser vision system sends line-structured laser, and the edge of the rib plate is scanned to obtain a surface profile image of the test piece to be welded.
Further, in step 4, before the first line segment and the second line segment are respectively performed on the weld characteristic points on the two side edges, filtering processing is further performed on the weld characteristic points.
Further, in step 5, fitting the first line segment and the second line segment of the weld joint characteristics, and solving an intersection point of the first line segment and the second line segment as a weld joint center track coordinate comprises the following steps:
according to the known fitting function of the weld characteristic points, the square of the distances from all the weld characteristic points to the straight line is minimized, and the sum of the squares of the errors from the weld characteristic points to the straight line is calculated, namely:
wherein k and b are equation coefficients to be solved, z i 、x i For the collected coordinate data, k and b are respectively derived to obtain:
order to
Obtaining:
in the formula, A and B are weld characteristic points in a first line segment, C and D are weld characteristic points in a second line segment, and the first line segment can be determined: z is a radical of 1 ＝k 1 x+b 1 And a line segment two: z is a radical of formula 2 ＝k 2 x+b 2 The intersection X can be obtained from two line segments A ，Z A (ii) a And performing linear interpolation on all sampling points to obtain the actual welding seam center track coordinate.
Further, after the step 5, the method further comprises the step of correcting the welding track on the basis of the coordinate of the welding seam center track.
In order to achieve the above object, the present invention provides a laser welding seam detection method, comprising: collecting a laser welding seam stripe image after the surface of a test piece to be welded is welded; preprocessing the laser welding seam stripe image; the pretreatment process comprises the following steps: extracting key points of the preprocessed laser welding line stripe image, wherein the step of extracting the key points of the laser welding line stripe image comprises the following steps:
extracting a welding seam contour curve, dividing an interested area of the original data, and setting a welding seam detection starting point A and a welding seam detection end point D;
traversing all weld contour characteristic data points in the divided regions of interest, finding a corresponding abscissa of a highest point E of an arc line in laser two-dimensional coordinates, respectively searching in the direction of a longitudinal coordinate or an abscissa by taking the point as a reference until a weld key characteristic inflection point B and a weld key characteristic inflection point C are found when the distance between the point and a bottom plate and a vertical plate is zero, and marking coordinates of the point;
and fitting the line segments AB and CD by adopting a least square method, taking the intersection point O of the two line segments as the center of the weld joint, calculating the height difference | OB-OC | of the weld leg, judging whether the height difference | OB-OC | of the weld leg is less than or equal to a preset value, and judging that the weld joint is unqualified when the height difference | OB-OC | exceeds a threshold value.
Further, the pretreatment process further comprises: carrying out gray processing, noise reduction, binarization, image enhancement and key region extraction on the graph.
In order to achieve the above object, the present invention provides an apparatus for an automatic tracking method of a laser welding bead, the apparatus comprising: the welding line welding robot comprises a robot moving device, a robot, a welding line welding end executor, a working platform and a laser; robot moving devices are arranged on two sides of the working platform, and the robots are installed on sliding tables of the robot moving devices; the welding seam welding measuring end executor is mounted on an end flange of the robot; the welding seam welding end effector at least comprises a linear laser sensor, a wire feeding device, a laser welding gun and a CCD module which are integrated into a whole.
The technical scheme of the invention has the following advantages:
the system automatically calculates and analyzes the center coordinate of a welding seam of a workpiece to be welded, the robot drives a sensor to scan a welding path, the system automatically calculates the actual welding seam track coordinate, and the robot end effector tool coordinate pose and the robot motion track are automatically corrected through matrix transformation. And after welding, scanning the welding line by using a sensor, automatically identifying the welding line, calculating the height of a welding leg, analyzing the quality of common appearance and providing a basis for workpiece detection.
Drawings
Fig. 1 is a general structural diagram of an apparatus for an automatic tracking method of a laser welding seam according to the present disclosure.
FIG. 2 is a three-dimensional view of a weld seam welding end effector as disclosed herein.
FIG. 3 is an elevation view of a weld seam welding end effector as disclosed herein.
FIG. 4 is a side view of a weld seam welding end effector of the present disclosure.
FIG. 5 is a schematic view of a welding direction according to the disclosure of the present invention.
Fig. 6 is a schematic diagram of the sensor measurement disclosed in the present invention.
FIG. 7 is a flowchart of a method for detecting a weld trace and a post-weld profile according to the present invention.
FIG. 8 is a diagram of a torch focus TCP setup disclosed herein.
FIG. 9 is a schematic view of a welding gun TCP calibration disclosed in the present invention.
FIG. 10 is a schematic diagram of TCF calibration according to the present disclosure.
FIG. 11 shows sample points for scanning a test piece according to the present disclosure.
FIG. 12 is a cross-sectional view of a T-shaped weld according to the present disclosure.
FIG. 13 is a schematic view of a post-weld profile according to the present disclosure.
In the figure: 001. a robot motion device; 002. a robot control cabinet; 003. a dust removal cabinet; 004. a robot; 005. a wire feeder; 006. a working platform; 007. a water cooling machine; 008. a laser; 009. ribbed wallboard workpieces; 010. a console; 100. welding seam measuring and welding end executor; 101. a line laser sensor; 102. a sensor holder; 103. a wire feeder; 104. a connecting flange; 105. a transfer flange; 106. a coaxial shielding gas kit; 107. a filament feeding head; 108. a wire feeding pipe; 109. a laser welding gun; 110. a base; 111. a CCD module; 112. a wire feeding fixing plate; 200. a base plate; 201. a vertical plate; 202. a first tool pressing plate; 203. and a second tool pressing plate.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus are not to be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Fig. 1 is a schematic assembly diagram of an apparatus for automatically tracking a laser welding seam according to a preferred embodiment of the present invention.
Referring to fig. 1, fig. 1 is an assembly structure schematic diagram of an apparatus for an automatic tracking method for a laser welding seam according to an embodiment of the present invention.
In the embodiment shown in fig. 1, the assembly structure mainly includes two sets of weld seam welding end effectors 100, two sets of robots 004 (six-degree-of-freedom robots), two sets of robot motion devices 001, a robot control cabinet 002, a dust removal cabinet 003, a working platform 006, a laser 008, a water cooler 007, a console 010, measurement and control analysis software, and the like (see fig. 1). The working platform 007 is arranged in the middle of the system, the working platform 006 is fixed with a ground foundation through expansion bolts and used for installing welding tools and workpieces, two sets of robot motion devices 001 are symmetrically arranged on two sides of the working platform 007, two sets of robots 004 are respectively installed on sliding tables of the two sets of robot motion devices 001, the robot motion devices 001 serve as external shafts of the robots 004, the motion processing range of the robots 004 is expanded, two sets of welding seam welding end effectors 100 are respectively installed on end flanges of the robots 004 and are symmetrical in the left and right sides, see, 2 and fig. 3, two sets of laser welding guns 109 are respectively and integrally installed on the two sets of welding seam welding end effectors 100, two sets of lasers 008 are connected with laser welding guns 109 through optical fibers to provide welding laser energy for the lasers 008, each set of lasers 008 is provided with one water cooling machine 007, the water cooling machines 007 are placed beside the lasers 008, the lasers 008 and the water cooling machines 007 are arranged on the inner side of the system, and moving parts and static parts are placed separately. The console 010 is arranged outside the system, so that an operator can conveniently control the console.
As shown in fig. 1-4, the welding seam welding end effector 100 is composed of a line laser sensor 101, a sensor holder 102, a wire feeder 103, a connecting flange 104, an adapter flange 105, a coaxial shielding gas kit 106, a wire feeder head 107, a wire feeding tube 108, a laser welding gun 109, a base 110, a CCD module 111, a wire feeding fixing plate 112, and the like.
The connection of the components of the weld seam welding end effector 100 will be described in detail below.
The connecting flange 104 is connected with the sensor fixing seat 102 through screws, the adapter flange 105 is installed at the top of the connecting flange 104 and is in butt joint with a terminal flange of the robot 004, the adapter flange 105 can be designed according to different robot interfaces, the installation is convenient, the base 110 is fixedly connected with the connecting flange 104 through screws, the laser welding gun 109 is installed on the base 110, the coaxial protection gas suite 106 is installed at the lower end of the laser welding gun 109, the side face of the coaxial protection gas suite 106 is provided with an air inlet, protection gas is communicated, gas protection is provided for welding, and the surface forming quality of parts is improved.
The CCD module 111 is installed on the top of the laser welding gun 109, the CCD module 11 is a high-definition camera, the welding line can be clearly seen through the internal lens group, and the filter lens is configured, so that the laser welding process can be monitored.
The axis of the measuring laser is parallel to the center of the welding gun, an included angle of 45 degrees is formed between the center of the welding gun and the reinforcing rib (vertical plate) during measurement, and the welding gun properly returns along the Z axis to avoid interference with a tool; during welding, the welding gun extends out along the Z axis, so that the welding gun head is positioned at a welding position of a welding wire, and the welding gun and the reinforcing rib form an included angle of 60 degrees.
A weld seam tracing system based on a linear laser sensor mainly comprises a PLC, an industrial personal computer, a data acquisition card, a motion controller, a robot system, a communication module and the like, wherein the PLC is connected and communicated with the robot system and the industrial personal computer through a Modbus-TCP, the robot and a laser are respectively subjected to I/O control with the PLC, and a main control console is connected with a left side measuring and welding system and a right side measuring and welding system through EtherCat interfaces, so that the cooperative control of the double robot systems is realized.
The line structured laser vision system is composed of a laser driver, a line structured laser, an image sensor, an image filter, an image processor, a control logic board and the like (as shown in fig. 6). The method comprises the steps of sending line structure laser through a three-dimensional line structure laser vision system, scanning the surface of a workpiece to be detected (namely a to-be-welded sample) to obtain a surface profile image of the workpiece to be detected, processing the surface profile image through an image filter and a data acquisition card to obtain a three-dimensional point cloud coordinate of the surface of the workpiece to be detected, automatically calculating and analyzing the center coordinate of a welding seam of the workpiece to be welded by the system, scanning a welding path by a robot driving sensor, automatically resolving an actual welding seam track coordinate by the system, obtaining a tool coordinate pose of a robot end effector through matrix transformation, and automatically correcting a motion track of the robot. And after welding, scanning the welding line by using a sensor, automatically identifying the welding line, calculating the height of a welding leg, analyzing the quality of common appearance and providing a basis for workpiece detection.
It will be understood by those skilled in the art that the assembly structure of the apparatus for an automatic tracking method of a laser welding seam shown in fig. 1 to 6 does not constitute a limitation of the apparatus, the apparatus may include more or less components than those shown, some components do not belong to the essential constitution of the apparatus, and some components may be omitted or combined as necessary within a scope not changing the essence of the invention.
According to the embodiment, the customized high-precision linear structured light sensor with the large field of view and the long field depth develops an automatic laser welding T-shaped structured welding seam track recognition system, achieves automatic planning of a welding seam path program of a double-beam laser welding process, replaces manual teaching, develops a welded welding seam appearance analysis system, forms a complete system unit with software and hardware, meets the product quality requirement, and achieves automatic laser welding engineering application of the T-shaped welding seam of the titanium alloy wallboard.
As shown in fig. 7-9, an embodiment of the present invention provides an automatic tracking method for a laser welding seam, including the following steps:
step 1: establishing a laser welding gun tool coordinate system, and calibrating a TCP (top center po i nt, namely a tool center point);
installing a focus tool at the tail end of a laser welding gun, determining a reference point of the focus tool, fixing a tool nose tool on a workbench, determining a fixed point of the tool nose tool, adopting a four-point method to enable the reference point to be just contacted with the fixed point, and establishing a focus coordinate system of the laser welding gun through data of four position points.
It can be understood that, firstly, the focal length position of the laser welding gun is determined, and then the tool coordinate system TCP is established according to the focal length position, the focal point tool is installed on the tail end of the laser welding gun, and the position from the tip of the focal point to the center of the focusing lens of the laser welding gun is the focal length of the welding gun (as shown in fig. 8).
Fixing a tool tip calibrating tool on a workbench, using the tip of the tool tip calibrating tool as a reference point, and calibrating a laser welding gun focus coordinate system TCP (too l center po i nt, namely a tool center point) by adopting a four-point method.
The pose relationships between the base coordinate system { B }, the end flange coordinate system { F }, the tool coordinate system { T }, and the end flange coordinate system { F } to the base coordinate system { B } may be defined in a matrix
It is shown that the process of the present invention,
wherein the content of the first and second substances,
a rotation matrix of the end flange coordinate system { F } relative to the base coordinate system { B } containing three position vectors
The direction cosines of the 3 unit principal vectors of F with respect to B respectively,
is the position vector of the origin of F relative to B,
can be derived from a positive solution of robot kinematics.
A transformation matrix representing T relative to base coordinates B,
a transformation matrix representing the tool coordinates { T } relative to the end flange coordinates { F } since the tool is mounted on the robot flange
Is a fixed value, the tool TCP calibration is the determination
Is determined by the parameters of (a) and (b),
and F P tcp 。
a calibration process: calibrating a tool center point position (TCP); and (b) calibrating the tool coordinate system attitude (TCF).
As in fig. 9, tool center point position (TCP) is calibrated: the hand-operated robot moves the laser welding gun from four different directions to the fixed point, and records four points P 1 、P 2 、P 3 、P 4 Pose data (X, Y, Z, theta) of robot end flange 1 、θ 2 、θ 3 ) And the coordinates of the four tool center points are equal in the world coordinate system, and the calculation is completed on the operation demonstrator to obtain a tool coordinate system TCP (X, Y, Z).
As in fig. 10, tool coordinate system pose (TCF) calibration: and moving the tool coordinate system TCP to any fixed point for measurement, moving a point in the negative direction of the Y axis to the fixed point for measurement, then moving any point with the X value in the XY plane to the fixed point for measurement, recording data, and completing calculation and calibration on an operation demonstrator.
Step 2: calibrating coordinates of the line laser sensor;
and establishing a robot base coordinate system by taking an installation base of the linear laser sensor on the robot as a reference, and determining a coordinate relation between the robot base coordinate system and the laser welding gun focus coordinate system according to the pose matrix of the robot base coordinate system.
Specifically, the calibration of the coordinates of the line laser sensor mainly comprises the determination of the coordinate relationship between the coordinate system of the line laser sensor and the focal point of the laser welding gun. When the robot is in a certain pose, the pose matrix of the welding seam welding end executor relative to the base coordinate of the robot is T 1 The position and pose matrix from the coordinate system of the line sensor to the end flange is X 1 The position and pose of the world coordinate system under the robot base coordinate system are P 1 ＝T 1 X 1 M 1 When the robot moves to another pose, the parameter is changed into T 2 、X 2 、P 2 Since the line sensor is fixed to the tip, X 1 ＝X 2 And since the world coordinate system and the end coordinate system are stationary, P 1 ＝P 2 Let us order
There is an AX = XB,
assuming that a is an m × n matrix, B is an n × n matrix, and X is an m × n matrix, the matrix direct product defines:
when A or B is an identity matrix, there are
Assuming that a and b are constants, then,
vec(aA+bB)＝a×vec(A)+b×vec(B)
suppose that
AX = XB can be expressed as:
to determine a unique solution to the above equation, two sets of motions with non-parallel axes of rotation are required, which result in simultaneous equations:
solving the eigenvector v = [ v ] corresponding to the minimum singular value by using a least square method 1 v 2 … v 13 ]Then the relationship matrix is:
and 3, step 3: planning a scanning program;
and driving the line laser sensor to move along the position to be welded of the test piece to be welded by the robot, and scanning the edge of the rib plate to obtain a surface profile image of the test piece to be welded.
In this step, firstly, a robot measurement program is written in the off-line programming software, so that an included angle of 45 degrees is formed between a YZ plane of a laser welding gun and a vertical surface of a rib plate (shown in FIG. 11), and a plurality of points S are set on a test piece to be welded 0 、S 1 ……、S n 、S n+1 To make the robot drive the linear laser sensor along S 0 、S 1 ……、S n 、S n+1 Are scanned sequentially, at S 0 And (3) sending a pulse instruction to the linear laser sensor by the PLC at the point, triggering data acquisition, sending linear structure laser by the three-dimensional linear structure laser vision system, scanning the edge of the rib plate to obtain a surface profile image of the test piece to be welded, and further obtaining a three-dimensional point cloud coordinate of the surface of the test piece to be welded. The line laser sensor moves to the position S 1 Stopping the measurement instruction, returning the line laser sensor to the edge position information of the rib plate, and moving the line laser sensor to S 2 ～S n+1 Position, PLC sends out pulse measurement instruction to obtain each sampling point S i Three-dimensional point cloud coordinate information, each sampling point pauses for 1-3 seconds, measurement precision loss caused by robot motion is reduced, and the line laser sensor moves to S n Position, PLC trigger pulse measurement command, line laser sensor movement S n+1 And (5) stopping collecting the instruction, and returning the edge information of the stud plate by the line laser sensor.
And 4, step 4: identifying weld joint features;
and extracting weld characteristic points of two side edges of the laser band from the obtained surface profile image of the test piece to be welded, respectively drawing a first line segment and a second line segment on the weld characteristic points of the two side edges, and taking the first line segment and the second line segment as weld characteristics.
As shown in fig. 12, taking a T-shaped weld seam as an example, a vertical plate 201 is vertically placed on a bottom plate 200 under the action of a first tool pressing plate 202 and a second tool pressing plate 203, so as to eliminate tool features, and take line segments AB and CD as weld seam features.
And 5: calculating the central coordinate of the T-shaped welding seam track;
and fitting the line segment I and the line segment II of the weld joint characteristics, and solving the intersection point of the line segments I and the line segments II to obtain the weld joint center track coordinate.
Continuing with fig. 12, the line segments AB, CD are fitted separately using the least squares method, i.e. the square of the distances from all points to the straight line is minimized according to the point-fitted function, and the sum of the squares of the errors from points to the straight line is calculated, i.e.:
where k and b are the coefficients of the equation, z is to be solved i 、x i For the collected coordinate data, k and b are respectively derived to obtain:
order to
Obtaining:
in the formula, A and B are weld characteristic points in a first line segment, C and D are weld characteristic points in a second line segment, and the first line segment can be determined: z is a radical of 1 ＝k 1 x+b 1 And a line segment two: z is a radical of formula 2 ＝k 2 x+b 2 The intersection X can be obtained from two line segments A ，Z A (ii) a And performing linear interpolation on all sampling points to obtain the actual welding seam center track coordinate.
And 6: correcting the track of the robot;
on the basis of calibrating the welding track, the robot applies track correction data obtained by measurement and calculation on a tool coordinate system TCP and calls a track deviation instruction to realize the correction of the welding track.
The Modbus-TCP communication function is mainly used for communication between welding seam locating software and the robot, and data sent by the welding seam locating software mainly comprises track correction XYZ coordinate offset, a measuring and calculating completion flag bit and the like; the data sent by the robot comprises the in-place state of the robot, the current point number and the like; by adopting a distributed transmission method, the correction data is sent and stored to a specific register of the robot system after each point is measured, and is uniformly called when a welding program is executed, so that the communication transmission bandwidth and the communication transmission rate are ensured not to influence the welding process.
And 7: automatic welding by a robot;
according to the process requirements, signal instructions such as light emitting, attenuation and wire discharging are added, a double-beam synchronous welding signal is added, a welding program is tried to run, a laser and a wire feeder are disconnected for enabling, the light spot track of a laser welding gun is verified and guided, the welding program is run, and the welding of parts is completed.
After the steps 1 to 7 are completed, the double-beam welding seam requirements reach the navigation mark I-grade welding seam standard and mainly comprise the requirements on the internal quality, the mechanical property and the appearance of the welding seam, so that the positions of the welded parts need to be detected, the main detection means of the internal defects of the welding seam at present is X-ray flaw detection, and the common defects comprise cracks, incomplete penetration, incomplete fusion, air holes, slag inclusion and the like; the mechanical property mainly adopts a tensile experiment method, and the tensile strength and the shear strength meet the technical requirements; the appearance and appearance quality is required, the welding seam is in uniform transition, no defects such as pits, welding beading, undercut and the like exist at the arc striking and arc ending part, and the height difference of the welding leg is less than or equal to 0.3mm. Appearance quality is an important evaluation standard of quality of a double-beam welding process, surface defects are mainly checked by manual visual inspection at present, and the height of a welding leg is measured by adopting a metallographic method. The metallographic method for measuring the height of the weld leg requires cutting of a T-shaped weld joint to manufacture a metallographic test piece, and the method has low efficiency and cannot detect a welded workpiece.
Therefore, the embodiment also provides a laser welding seam detection method, which is used for detecting the height difference of the T-shaped welding seam welding foot based on a laser vision method and carrying out online detection on common morphological defects. The method is quick, accurate and effective, improves the quality evaluation level of the welding line, and comprises the following steps 8-9, and the specific steps are as follows:
and step 8: scanning a welded seam after welding;
before detection, the three-dimensional data of the surface of the test piece to be welded is collected by the line laser sensor, and the three-dimensional data of the surface of the test piece to be welded is transmitted to the industrial personal computer through the Ethernet.
And step 9: weld quality analysis
After the online quality detection system software acquires the data of the line laser sensor, image preprocessing is carried out on the data, then the filtered data are converted into a gray image and a three-dimensional point cloud image, the 2D/3D image is displayed on a software interface, and output and welding seam appearance data can be displayed.
The preprocessing of the laser seam stripe image includes, but is not limited to: carrying out gray processing, noise reduction, binaryzation, image enhancement and key region extraction, wherein:
and (4) graying, namely performing graying processing on the original image by adopting a weighted average method so as to keep the original image form and improve the measurement accuracy.
The filtering and noise reduction are realized, and the line laser sensor can be influenced by environmental disturbance, light and the like in the data image acquisition process, so that the image processing and analysis are not facilitated, and therefore, the filtering and noise reduction processing is realized by adopting a proper filtering algorithm. And performing Gaussian filtering by using a convolution template according to a weld locating filtering method so as to eliminate the influence of noise.
And image binarization is performed to reduce the image data amount and improve the operation efficiency. Binarization processing by maximum space method, D 1 Gray scale range [0, g ]]In the image scale of m 0 Mean gray value p 0 ，D 2 Gray scale range [ g +1, H]In the image ratio m 1 Mean gray value p 1 The total average gray value of the image is p, s is D 1 And D 2 The number of pixels with the gray value less than g is K 0 The number of pixels with gray value larger than g is K 1 Then, there are:
s＝m 0 m 1 (p 0 -p 1 ) 2
the maximum inter-class variance method is to perform binarization processing on the weld image subjected to noise reduction processing based on a threshold value g corresponding to the maximum value s in the image gray distribution, so that the threshold value is automatically obtained, the edge information of the original image is retained, and fewer broken parts are arranged.
And image enhancement, namely, when the original image is subjected to corrosion operation, the target image-text is gradually contracted, and a part of the image area is blurred, so that the image is possibly distorted, the image enhancement processing is performed, the image is subjected to closed operation, the effective part of the image is enhanced, and the extraction of a key area is facilitated.
And extracting key areas of the image, selecting effective line segments AB and CD of the image, reducing the operation times and improving the efficiency.
Extracting key points of the weld image, wherein after the weld laser image is obtained, the detection and judgment of the appearance quality of the weld can be carried out only by further extracting the key points in the image, and the extraction of the key points is shown in figure 13, and the method comprises the following steps:
extracting a welding seam contour curve, dividing an interested area of the original data, and setting a welding seam detection starting point A and a welding seam detection end point D;
traversing all weld contour characteristic data points in the divided regions of interest, finding out a corresponding abscissa of the highest point E of the arc line in the laser two-dimensional coordinates, respectively searching in the direction of a longitudinal coordinate or an abscissa by taking the point as a reference until a weld key characteristic inflection point B and a weld key characteristic inflection point C are found when the distance between the point and the bottom plate and the vertical plate is zero, and marking the coordinates of the point;
and fitting the line segments AB and CD by adopting a least square method, taking the intersection point O of the two line segments as the center of the weld joint, calculating the height difference | OB-OC | of the weld leg, judging whether the height difference | OB-OC | of the weld leg is less than or equal to a preset value of 0.3mm, judging that the weld joint is unqualified when the height difference | OB-OC | exceeds a threshold value, and performing rework treatment. And performing the next process after the product is qualified.
And similarly, high points and concave points on the curve BEC can be judged, a threshold value is set, and disqualification is judged when the threshold value is exceeded.
Throughout the description and claims of this application, the words "comprise/comprises" and the words "have/includes" and variations of these are used to specify the presence of stated features, values, steps or components but do not preclude the presence or addition of one or more other features, values, steps, components or groups thereof.
Some features of the invention which are, for clarity, described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, certain features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination in different embodiments.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. An automatic tracking method for a laser welding seam is characterized by comprising the following steps:
step 1: installing a focus tool at the tail end of a laser welding gun, determining a reference point of the focus tool, fixing a tool tip tool on a workbench, determining a fixed point of the tool tip tool, enabling the reference point to be just contacted with the fixed point by adopting a four-point method, and establishing a laser welding gun focus coordinate system through data of four position points;
step 2: establishing a robot base coordinate system by taking a mounting base of a linear laser sensor mounted on a robot as a reference, and determining a coordinate relation between the robot base coordinate system and a laser welding gun focus coordinate system according to a pose matrix of the robot base coordinate system;
and 3, step 3: the robot drives the line laser sensor to move along the position to be welded of the test piece to be welded, the edge of the rib plate is scanned to obtain the surface profile image of the test piece to be welded,
and 4, step 4: extracting weld joint feature points of two side edges of a laser band from the obtained surface profile image of the test piece to be welded, respectively drawing a first line segment and a second line segment on the weld joint feature points of the two side edges, and taking the first line segment and the second line segment as weld joint features;
and 5: and fitting the first line segment and the second line segment of the weld joint characteristics, and solving the intersection point of the first line segment and the second line segment to obtain the coordinate of the weld joint center track.
2. The method for automatically tracking the laser welding seam according to claim 1, wherein in the step 1, the calibration process for establishing the focal coordinate system of the laser welding gun comprises the following steps:
calibrating the position of the center point of the tool: the hand-operated robot moves the laser welding gun from four different directions to the fixed point, and records four points P 1 、P 2 、P 3 、P 4 Pose data (X, Y, Z, theta) of robot end flange 1 、θ 2 、θ 3 ) The coordinates of the four tool center points are equal in a world coordinate system, and calculation is completed on an operation demonstrator to obtain a tool coordinate system TCP (X, Y, Z);
calibrating the posture of a tool coordinate system: and moving the tool coordinate system TCP to any fixed point for measurement, moving a point in the negative direction of the Y axis to the fixed point for measurement, then moving any point with a negative value X in the XY plane to the fixed point for measurement, recording data, and completing calculation and calibration on an operation demonstrator.
3. The automatic tracking method for the laser welding seam as claimed in claim 1, wherein in step 2, the step of determining the coordinate relationship between the robot base coordinate system and the focal point coordinate system of the laser welding gun comprises the following steps:
when the robot is in a certain pose, the pose matrix of the welding seam welding end effector relative to the base coordinate of the robot is T 1 The position matrix from the coordinate system of the line sensor to the end flange is X 1 The position and pose of the world coordinate system under the robot base coordinate system are P 1 ＝T 1 X 1 M 1 When the robot moves to another pose, the parameter is changed into T 2 、X 2 、P 2 Since the line sensor is fixed to the tip, X 1 ＝X 2 Due to the world coordinate systemAnd the end coordinate system is stationary, so P 1 ＝P 2 Let us order
There is an AX = XB,
assuming that a is an m × n matrix, B is an n × n matrix, and X is an m × n matrix, the matrix direct product definition indicates:
when A or B is an identity matrix, there are
Assuming that a and b are constants, then there is,
vec(aA+bB)＝a×vec(A)+b×vec(B)
suppose that
AX = XB can be expressed as:
to determine a unique solution to the above equation, two sets of motions with non-parallel axes of rotation are required, which result in simultaneous equations:
solving the eigenvector v = [ v ] corresponding to the minimum singular value by using a least square method 1 v 2 … v 13 ]Then the relationship matrix is:
4. the automatic tracking method for the laser welding seam according to claim 1, characterized in that the step 3 comprises forming an included angle of about 45 degrees between a YZ plane of the laser welding gun and a vertical surface of the rib plate, and setting a plurality of points S on a test piece to be welded 0 、S 1 ……、S n 、S n+1 So that the robot drives the line laser sensor along S 0 、S 1 ……、S n 、S n+1 Are scanned sequentially, at S 0 And (3) sending a pulse instruction to the linear laser sensor by the PLC at the point to trigger data acquisition, sending linear structure laser by the three-dimensional linear structure laser vision system, and scanning the edge of the rib plate to obtain a surface profile image of the test piece to be welded.
5. The method as claimed in claim 1, wherein in step 4, before performing the first line segment and the second line segment on the weld characteristic points on the two side edges, the method further comprises filtering the weld characteristic points.
6. The automatic tracking method for the laser welding seam as claimed in claim 1, wherein in step 5, fitting the first segment and the second segment of the seam feature, and solving the intersection point as the coordinate of the seam center track comprises the following steps:
according to the known weld characteristic point fitting function, the square of the distances from all the weld characteristic points to a straight line is minimized, and the sum of the squares of errors from the weld characteristic points to the straight line is calculated, namely:
wherein k and b are equation coefficients to be solved, z i 、x i For the collected coordinate data, k and b are respectively derived to obtain:
order to
Obtaining:
in the formula, A and B are weld characteristic points in a first line segment, C and D are weld characteristic points in a second line segment, and the first line segment can be determined: z is a radical of 1 ＝k 1 x+b 1 And a line segment two: z is a radical of 2 ＝k 2 x+b 2 The intersection X can be obtained from two line segments A ，Z A (ii) a And performing linear interpolation on all sampling points to obtain the actual welding seam center track coordinate.
7. The method as claimed in claim 1, further comprising, after step 5, correcting the welding trajectory based on the coordinates of the center trajectory of the welding seam.
8. A laser welding seam detection method comprises the following steps: collecting a laser welding seam stripe image after the surface of a test piece to be welded is welded; preprocessing the laser welding seam stripe image; characterized in that the pretreatment process comprises: extracting key points of the preprocessed laser welding line stripe image, wherein the step of extracting the key points of the laser welding line stripe image comprises the following steps:
extracting a welding seam contour curve, dividing an interested area of the original data, and setting a welding seam detection starting point A and a welding seam detection end point D;
traversing all weld contour characteristic data points in the divided regions of interest, finding a corresponding abscissa of a highest point E of an arc line in laser two-dimensional coordinates, respectively searching in the direction of a longitudinal coordinate or an abscissa by taking the point as a reference until a weld key characteristic inflection point B and a weld key characteristic inflection point C are found when the distance between the point and a bottom plate and a vertical plate is zero, and marking coordinates of the point;
and fitting the line segments AB and CD by adopting a least square method, taking the intersection point O of the two line segments as the center of the weld joint, calculating the height difference | OB-OC | of the weld leg, judging whether the height difference | OB-OC | of the weld leg is less than or equal to a preset value, and judging that the weld joint is unqualified when the height difference | OB-OC | exceeds a threshold value.
9. The laser weld detection method of claim 8, wherein the preprocessing step further comprises: and carrying out gray processing, noise reduction, binarization, image enhancement and key region extraction on the graph.
10. An apparatus for the automatic tracking method of the laser welding seam according to any one of claims 1 to 7, wherein the apparatus comprises: the welding line measuring and welding system comprises a robot moving device, a robot, a welding line measuring and welding end effector, a working platform and a laser; robot moving devices are arranged on two sides of the working platform, and the robots are installed on sliding tables of the robot moving devices; the welding seam welding measuring end executor is mounted on an end flange of the robot; the welding seam welding end effector at least comprises a line laser sensor, a wire feeding device, a laser welding gun and a CCD module which are integrated into a whole.
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| CN116329824A (en) * | 2023-04-24 | 2023-06-27 | 仝人智能科技(江苏)有限公司 | Hoisting type intelligent welding robot and welding method thereof |
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