CN116571845B - Weld joint tracking detection robot and weld joint tracking method thereof - Google Patents
Weld joint tracking detection robot and weld joint tracking method thereof Download PDFInfo
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- CN116571845B CN116571845B CN202310857397.5A CN202310857397A CN116571845B CN 116571845 B CN116571845 B CN 116571845B CN 202310857397 A CN202310857397 A CN 202310857397A CN 116571845 B CN116571845 B CN 116571845B
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- 238000001514 detection method Methods 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000003466 welding Methods 0.000 claims abstract description 58
- 230000035772 mutation Effects 0.000 claims description 10
- 230000008859 change Effects 0.000 claims description 7
- 239000000523 sample Substances 0.000 description 21
- 230000007246 mechanism Effects 0.000 description 18
- 230000005540 biological transmission Effects 0.000 description 8
- 230000006872 improvement Effects 0.000 description 8
- 238000007689 inspection Methods 0.000 description 8
- 230000007547 defect Effects 0.000 description 5
- 230000008569 process Effects 0.000 description 4
- 238000003384 imaging method Methods 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
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- 239000011324 bead Substances 0.000 description 2
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- 238000010586 diagram Methods 0.000 description 2
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- 230000003028 elevating effect Effects 0.000 description 1
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- 230000003287 optical effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
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Classifications
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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
- B23K9/12—Automatic feeding or moving of electrodes or work for spot or seam welding or cutting
- B23K9/127—Means for tracking lines during arc welding or cutting
- B23K9/1272—Geometry oriented, e.g. beam optical trading
- B23K9/1274—Using non-contact, optical means, e.g. laser means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J5/00—Manipulators mounted on wheels or on carriages
- B25J5/007—Manipulators mounted on wheels or on carriages mounted on wheels
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
Abstract
The application relates to the field of weld joint detection robots, in particular to a weld joint tracking detection robot and a weld joint tracking method thereof. The application discloses a welding seam tracking and detecting robot, which comprises the following components: a left driving part provided with a left wheel; a right driving part hinged to the left driving part, the right driving part being provided with a right wheel; the laser profile sensor is used for acquiring a welding line track; and the control system is used for carrying out differential control on the left wheel and the right wheel so as to enable the laser profile sensor to move along the weld track. According to the weld joint tracking detection robot, the left driving part can adjust the angle relative to the right driving part according to the shape of the outer wall or the inner wall of the large container, so that the left wheel and the right wheel are more attached to the side wall of the large container, and slipping is reduced. The application also discloses a weld joint tracking method. The weld tracking method controls the weld tracking detection robot to walk along a straight line or deflect towards the middle point of the laser contour image.
Description
Technical Field
The application relates to the field of weld joint detection robots, in particular to a weld joint tracking detection robot and a weld joint tracking method thereof.
Background
The welding seam detection robot is used for detecting welding seams of large containers. The existing welding seam detection robot is added with a welding seam detection function, so that the welding seam detection robot automatically walks along a welding seam and detects the welding seam, however, in the walking process of the robot, if the outer wall or the inner wall of a large container is an arc surface, the contact area between the magnetic wheel of the robot and the large container is reduced, the magnetic wheel of the robot is easy to slip, the walking direction of the robot is deviated, and the welding seam tracking precision of the robot is further affected.
Disclosure of Invention
The application aims to provide a weld joint tracking detection robot and a weld joint tracking method thereof, which are used for solving one or more technical problems in the prior art and at least providing a beneficial selection or creation condition.
The technical scheme adopted for solving the technical problems is as follows:
a weld tracking inspection robot, comprising:
a left driving part provided with a left wheel;
a right driving part hinged to the left driving part, the left driving part rotating relative to the right driving part about an axis extending in the front-rear direction, the right driving part being provided with a right wheel;
the laser profile sensor is connected to the left driving part or the right driving part, and is arranged right in front of the midpoint of the connecting line between the left wheel and the right wheel and used for acquiring a welding line track;
and the control system is used for performing differential control on the left wheel and the right wheel so as to enable the welding seam tracking and detecting robot to move along the welding seam track.
The beneficial effects of the application are as follows: when the left wheel and the right wheel are magnetically attracted to the outer wall or the inner wall of the large container, the left driving part and the right driving part are hinged, so that the left driving part can adjust the angle relative to the right driving part according to the shape of the outer wall or the inner wall of the large container, and the left wheel and the right wheel are attached to the side wall of the large container more, so that slipping of the left wheel and the right wheel is reduced; and the welding seam track of the large container is obtained through the laser contour sensor, so that the control system carries out differential control on the left wheel and the right wheel, the welding seam tracking and detecting robot can move along the welding seam track, the tracking of the welding seam is realized, and the walking precision of the welding seam tracking and detecting robot along the welding seam is improved.
As a further improvement of the above technical solution, the weld tracking inspection robot further includes a locking member, where the locking member is connected to the left driving portion and the right driving portion, and locks the locking member to lock the relative positions of the left driving portion and the right driving portion.
The angle of the side walls at two sides of the welding line of the large container is changed slightly along the extending direction of the welding line, so that after the left driving part adjusts the angle relative to the right driving part according to the shape of the side wall of the large container, the locking piece locks the relative positions of the left driving part and the right driving part, abnormal shaking caused by changing the angle between the left driving part and the right driving part after the left wheel or the right wheel presses sundries adhered on the side wall of the large container is avoided, and the interference of the abnormal shaking to the laser profile sensor is avoided.
As a further improvement of the technical scheme, the left wheel and the right wheel are symmetrically distributed on the left side and the right side of the laser profile sensor.
The laser profile sensor is positioned at the center position between the left wheel and the right wheel, so that the welding seam tracking and detecting robot can walk right above the welding seam track, and the laser profile sensor can continuously acquire the welding seam track in the moving process.
As a further improvement of the above technical solution, the weld tracking inspection robot further includes:
a lifting mechanism provided in the left driving unit or the right driving unit;
the detection probe is connected to the lifting mechanism, and the lifting mechanism drives the detection probe to move up and down.
The detection probe is arranged on the lifting mechanism, and if a higher obstacle is encountered, the lifting mechanism lifts the detection probe to avoid damage of the detection probe after the detection probe collides with the obstacle.
As a further improvement of the technical scheme, the control system is externally connected with a manual controller for controlling the lifting mechanism to lift.
Setting the walking speed and control parameters of the welding seam tracking detection robot to a control system through a manual controller, and manually inserting and controlling the welding seam tracking detection robot when necessary through manually operating the walking of the welding seam tracking detection robot; and when the welding seam tracking detection robot encounters an obstacle in the walking process, the manual controller is manually operated to control the lifting mechanism to lift the detection probe so as to avoid the obstacle.
The weld tracking method comprises the weld tracking detection robot, and further comprises the following steps:
s1, the laser profile sensor sends laser to the weld joint track, and a laser profile image is shot and sent to the control system;
s2, calculating the midpoint position of the laser profile image by using the control system, and making a central line extending forwards by using the center of the welding seam tracking detection robot, wherein the distance from the midpoint to the central line is calculated as X0 by the control system;
s3, setting a deflection threshold value to be XP for the control system, if X0 is less than or equal to XP, enabling the welding seam tracking detection robot to walk along a straight line, and if X0 is more than XP, enabling the welding seam tracking detection robot to deflect towards the direction of the middle point.
Before the weld tracking detection robot performs weld tracking, after the angle between the left driving part and the right driving part is adjusted, the laser contour sensor is required to be opposite to the weld track so as to ensure that the laser contour sensor can acquire the laser contour image of the weld track, the control system calculates the distance X0 between the middle point of the laser contour image and the central line of the weld tracking detection robot, sets a deflection threshold XP, and controls the weld tracking detection robot to walk along a straight line or deflect towards the middle point of the laser contour image after comparing the X0 with the XP.
As a further improvement of the above-described technical solution, in the step S1, a distance from the center to the front-rear direction of the laser profile sensor is L0;
in the step S3, if X0 > XP, an included angle θ=arctan (X0/L0) between the moving direction of the weld tracking detection robot and the extending direction of the weld track, and the weld tracking detection robot deflects toward a direction in which the included angle θ is reduced.
The laser contour sensor emits laser along the vertical downward direction to form a laser contour image on the weld track, the distance from the center of the weld tracking detection robot to the front and rear directions of the laser contour sensor is measured to be L0, and then the actual size of the offset angle theta between the moving direction of the weld tracking detection robot and the weld track can be calculated, so that the angle of deflection of the weld tracking detection robot to the middle point of the laser contour image can be quantified, and the deflection of the robot is more accurate.
As a further improvement of the above technical solution, in the step S3, the running speed of the seam tracking detection robot is set to V, assuming that the time required for the seam tracking detection robot to rotate by an angle θ is t, the width between the left wheel and the right wheel is D, the control system controls the rotation speed of the left wheel to vl=v+d×θ/2t, and the control system controls the rotation speed of the right wheel to vr=v-d×θ/2t.
According to the displacement angle theta of the movement direction of the weld tracking detection robot and the weld track and the current walking speed V of the robot, if the control system needs to control the deflection angle of the robot, the respective speeds of the left wheel and the right wheel are calculated, so that differential control of the left wheel and the right wheel is realized, and the robot can deflect accurately.
As a further improvement of the technical scheme, the control system carries out differential control on the left wheel and the right wheel through a PID control method.
The displacement direction of the welding seam tracking detection robot and the deflection angle theta of the welding seam track or the distance X0 between the middle point of the laser contour image and the central line of the welding seam tracking detection robot are used as error values, the error values are introduced into PID control to form a control quantity guiding control system to control the walking of the welding seam tracking detection robot, and the walking stability of the robot is improved.
As a further improvement of the above-mentioned technical solution, the method for calculating the midpoint position in the step S2 includes the steps of:
s21, dividing the laser contour image into a plurality of line segments and replacing straight lines by a least square fitting method to form a plurality of fitting line segments;
s22, comparing the slopes of every two adjacent fitting line segments and finding out slope mutation points;
s23, the slope abrupt change point is an edge point of the laser contour image;
s24, finding out two edge points of the laser profile image, and then calculating the midpoint.
The method comprises the steps of comparing the slopes of all fitting line segments through a least square fitting method, finding out the position with larger slope difference as a mutation point, determining the mutation point as an edge point of the laser contour image, and calculating the midpoint position of the laser contour image through two edge points, so that the midpoint position of the laser contour image is more accurate.
Drawings
The application is further described below with reference to the drawings and examples;
FIG. 1 is a schematic view of an embodiment of a seam tracking inspection robot according to the present application;
FIG. 2 is a schematic diagram of a weld profile image obtained by a laser profile sensor according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a seam tracking detection robot in an embodiment of the seam tracking method according to the present application;
FIG. 4 is a flowchart of a method for tracking a weld according to an embodiment of the present application.
10. Weld path, 20, laser profile image, 21, midpoint, 22, edge point, 30, center, 31, center line, 100, left drive section, 110, left wheel, 200, right drive section, 210, right wheel, 300, laser profile sensor, 400, locking piece, 500, elevating mechanism.
Detailed Description
Reference will now be made in detail to the present embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein the accompanying drawings are used to supplement the description of the written description so that one can intuitively and intuitively understand each technical feature and overall technical scheme of the present application, but not to limit the scope of the present application.
In the description of the present application, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present application and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.
In the description of the present application, if there is a word description such as "a plurality" or the like, the meaning of a plurality is one or more, and the meaning of a plurality is two or more, and greater than, less than, exceeding, etc. are understood to not include the present number, and above, below, within, etc. are understood to include the present number.
In the description of the present application, unless explicitly defined otherwise, terms such as arrangement, installation, connection, etc. should be construed broadly and the specific meaning of the terms in the present application can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical scheme.
Referring to fig. 1, the weld tracking inspection robot of the present application makes the following embodiments:
the welding seam tracking and detecting robot comprises a left driving part 100, a right driving part 200, a laser profile sensor 300, a locking piece 400, a lifting mechanism 500 and a detecting probe.
The left driving part 100 and the right driving part 200 are arranged in mirror symmetry. Taking the left driving part 100 as an example, two left wheels 110 are arranged at the left side of the left driving part 100, and the two left wheels 110 are distributed at intervals in the front-back direction.
The inside of left drive portion 100 is equipped with motor, reducing gear box, gear drive, and the output of motor is connected with the input of reducing gear box, and the output of reducing gear box is connected with gear drive's driving gear, and gear drive is equipped with two driven gears, and two driven gears and driving gear meshing transmission, two driven gears one-to-one cover are located in the pivot of two left wheels 110, and the power is transmitted to gear drive's driving gear through the reducing gear box after the motor starts, and driving gear drives driven gear rotation and makes left wheel 110 rotate.
Because the reduction gearbox and the gear transmission mechanism all adopt gear transmission, the relative sliding among all transmission parts can be effectively reduced, the rotation speed conversion among all transmission parts is more accurate, the rotation speed output by the motor is more accurately converted into the rotation speed of the left wheel 110, and the accuracy of the rotation speed of the left wheel 110 is improved.
The front side of the left driving part 100 is provided with a lifting mechanism 500, the lifting mechanism 500 is an electric screw rod transmission mechanism, a transmission nut of the lifting mechanism 500 is connected to the detection probe, and the transmission screw rod of the lifting mechanism 500 drives the nut to move up and down along the up and down direction so as to enable the detection probe to move up and down.
The right driving part 200 has the same structure, and two right wheels 210 are provided on the right side of the right driving part 200 at intervals.
The front side of the right driving part 200 is also provided with a lifting mechanism 500 and is connected to a detection probe, and the left driving part 100 and the right driving part 200 detect the weld by the detection probes on the front side, respectively. The detection probe is an ultrasonic probe. The detection probe can detect the weld joint by adopting an ultrasonic diffraction time-of-flight diffraction (TOFD) method, and detect defects in the weld joint, such as whether the weld joint has problems of cracks, unfused holes, slag inclusion, incomplete penetration and the like. If the detection probe adopts an ultrasonic diffraction time-of-flight method (TOFD), the detection probe consists of a transmitting head and a receiving head, the transmitting head and the receiving head are symmetrically arranged left and right relative to the central line of the welding seam, the transmitting head generates unfocused longitudinal wave beams to be incident into a detected workpiece at a certain angle, part of the beams propagate along the near surface and are received by the receiving head, part of the beams are reflected by the bottom surface and are received by the receiving head, and the receiving head determines the position and the self height of the defect through receiving diffraction signals of the tip of the defect and the time difference of the diffraction signals. The laser profile sensor 300 is a necessary component for the weld seam tracking and detecting robot to realize the tracking function, the detecting probe is a necessary component for the weld seam tracking and detecting robot to perform the defect detecting function on the weld seam, and the connection between the laser profile sensor 300 and the detecting probe is as follows: the weld seam tracking and detecting robot realizes the tracking of the weld seam by using the laser contour sensor 300, so that the weld seam tracking and detecting robot moves along the weld seam, and the detecting probe detects the internal defects of the weld seam in the process that the weld seam tracking and detecting robot moves along the weld seam.
The left wheel 110 and the right wheel 210 are magnetic wheels so that the left wheel 110 and the right wheel 210 are attracted to the side walls of the large container.
The left driving part 100 and the right driving part 200 are distributed in a left-right mirror symmetry, and a space is left between the left driving part 100 and the right driving part 200.
The right side of left drive portion 100 is equipped with left hinge, and the left side of right drive portion 200 is equipped with right hinge, and left hinge is equipped with the hinge hole that link up along the fore-and-aft direction, and right hinge is equipped with the screw hole that link up along the fore-and-aft direction, and locking piece 400 is the screw, and locking piece 400 passes in the screw hole after the hinge hole for left drive portion 100 can rotate around locking piece 400, screw up locking piece 400 and make right hinge compress tightly with left hinge, prevent left hinge rotation for right hinge through the frictional force between left hinge and the right hinge, thereby make left drive portion 100 fixed for the position of right drive portion 200.
The laser profile sensor 300 is connected to the right side of the left driving part 100, and the laser profile sensor 300 is located in the space between the left driving part 100 and the right driving part 200.
Assuming that the width between the left wheel 110 and the right wheel 210 is D, the center 30 of the seam tracking inspection robot is located at an intermediate position between the left wheel 110 and the right wheel 210, and the laser profile sensor 300 is located right in front of the center 30 of the seam tracking inspection robot.
An extension line is made from the center 30 of the weld tracking inspection robot to the front, the extension line being the center line 31. The laser profile sensor 300 emits a line laser vertically downward, perpendicular to the centerline 31.
The laser profile sensor 300 includes a laser emitter, a CCD linear camera, and a digital signal processor, the laser emitter and the CCD linear camera are mounted to the right side of the left driving part 100, and the digital signal processor is disposed in the robot, the digital signal processor is connected to the CCD linear camera through a cable, the laser emitter emits a linear laser along a direction perpendicular to a horizontal plane, a distance between the laser emitter and the horizontal plane is known, the CCD linear camera is inclined to the horizontal plane, an angle between a lens of the CCD linear camera and the horizontal plane is known, the laser emitter emits a visible linear laser to a surface of an object to be measured, the linear laser reflected by the object is received through the lens of the CCD linear camera, and the CCD linear camera can capture the light spot at different angles according to different distances.
According to the angle between the CCD linear camera and the horizontal plane and the known distance between the linear line laser and the laser transmitter, the digital signal processor can calculate the distance between the laser transmitter and the measured object. The distance from the laser profile sensor 300 to the surface of the measured object and the position information of the laser along the linear line are calculated by the digital signal processor because the positions of the light reflected by the different points on the surface of the measured object in the CCD linear camera imaging are different. In a two-dimensional coordinate system with the laser profile sensor 300 as an origin, the laser profile sensor 300 can output a set of two-dimensional coordinate values.
The laser profile image 20 is a line formed by a line of light irradiated on an object by a line of laser light. Reflected on the image is a discrete set of pixels. In order to facilitate the shooting of the image favorable for contour extraction, a filter is generally added in front of the lens of the camera, and only the light of the laser wave band enters the camera, so that the image acquired by the camera is a picture representing the contour by a group of relatively bright pixels, and the part of other objects not illuminated by the laser is very dark because no reflected light exists on the image. Thus we can easily extract from this map a set of pixel coordinates (c 0, r 0), (c 1, r 1) … on the profile, and then calculate a set of coordinates (x 0, z 0), (x 1, z 1) … for this tangent plane profile based on "triangulation".
The laser profile sensor 300 employs the principle of laser triangle reflection. The laser beam is amplified to form a static laser line which is projected onto the surface of the object to be measured through a special lens group. The laser line forms diffuse reflection on the surface of the measured object, and the reflected light is projected onto the sensitive photosensitive imaging matrix through the high-quality optical system. The distance from the laser profile sensor 300 to the surface of the measured object and the position information along the laser line are obtained through calculation because the positions of the light reflected by the different points on the surface of the measured object in the imaging matrix are different. In a two-dimensional coordinate system with the laser profile sensor 300 as an origin, the laser profile sensor 300 can output a set of two-dimensional coordinate values.
From the above, the laser profile sensor 300 can obtain depth data of the weld, i.e. Z-axis coordinates of the weld spot relative to the laser profile sensor 300, and obtain left and right data of the weld, and X-axis coordinates of the weld spot relative to the laser profile sensor 300. The obtained (X, Z) coordinate position is a time sequence, in which when the Z-axis height is from normal to the seam allowance, a first mutation point exists, and the Z-axis height returns to normal from the seam allowance, and a second mutation point exists, so that the mutation point of the picked-up data sequence is the key for identifying the welding seam.
The control system is arranged in the welding seam tracking and detecting robot and is connected with the digital signal processor of the left driving part 100, the right driving part 200 and the laser contour sensor 300 of the welding seam tracking and detecting robot through cables.
The control system individually controls the motor speed of the left driving unit 100 and the motor speed of the right driving unit 200, and performs differential control of the left wheel 110 and the right wheel 210.
The control system is also provided with an external manual controller, the manual controller is electrically connected to the lifting mechanism 500, and the lifting mechanism 500 is controlled by the manual controller to drive the detection probe to ascend or descend. And the manual controller is also provided with a functional module for speed adjustment and direction control of the welding seam tracking and detecting robot, so that a user can control the welding seam tracking and detecting robot through the manual controller.
In some embodiments, the left driving part 100 and the right driving part 200 can be freely rotated after being hinged, so that the left wheel 110 or the right wheel 210 can adjust the angle between the left driving part 100 and the right driving part 200 when passing through the convex or concave position of the side wall of the large container, thereby properly avoiding the rugged position and avoiding the occurrence of larger vibration of the welding seam tracking detection robot.
Referring to fig. 2 to 4, the seam tracking method of the present application makes the following examples:
the weld tracking method comprises the following steps:
s1, before the robot is placed on the side wall of the large container, the locking member 400 is released to enable the left driving part 100 to rotate relative to the right driving part 200, the position of the left driving part 100 relative to the right driving part 200 is adjusted according to the shape of the side wall of the large container, and then the locking member 400 is locked.
Placing the adjusted robot on the side wall of the large container, enabling the left wheel 110 and the right wheel 210 to be adsorbed on the side wall of the large container, enabling the laser profile sensor 300 to be located right above the welding seam track 10, opening the laser profile sensor 300, emitting a linear laser beam to irradiate the welding seam track 10 on the side wall of the large container, enabling an included angle between the linear laser beam and the welding seam track 10 to be smaller than 90 degrees, enabling a lens of the laser profile sensor 300 to receive the linear laser beam on the welding seam track 10 and form a laser profile image 20, and sending the laser profile image 20 to a control system.
At this time, the distance between the center 30 of the robot and the laser profile sensor 300 in the front-rear direction is L0, and the L0 data is recorded in the control system.
S21, the control system divides the laser contour image 20 into a plurality of line segments, and the line segments are replaced by straight lines through a least square fitting method to form a plurality of fitting line segments.
S22, comparing the slopes of every two adjacent fitting line segments, wherein the position with the largest slope change is a slope mutation point, and then performing the next calculation on the two fitting line segments positioned at the two sides of the slope mutation point.
S22 further comprises the steps of:
s221, dividing two fitting line segments on two sides of the slope abrupt change point into a plurality of line segments, and performing straight line substitution by a least square fitting method to form a plurality of fitting line segments with the length Ln;
s222, comparing the slopes of every two adjacent fitting line segments and finding out slope mutation points;
s223, setting the stop length as Ls, if Ln > Ls, repeating the steps S221 and S222, and if Ln is less than or equal to Ls, executing the step S23.
Dividing the fitting line segment where the slope abrupt change point is located into a plurality of smaller line segments, replacing a straight line by a least square fitting method to form a plurality of fitting line segments with the length Ln, comparing the slopes of every two adjacent fitting line segments, and finding out the slope abrupt change point.
S23, slope abrupt points are edge points 22 of the laser profile image, and x coordinates of the two edge points 22 are Xr1 and Xr2 respectively.
S24, two edge points 22 of the laser profile image 20 are found through Xr1 and Xr2, then a middle point 21 is calculated, and the x coordinate of the middle point 21 is xr= (xr1+xr2)/2, so that a center line 31 extending forwards is formed by the center 30 of the robot.
Since the centerline 31 passes directly below the laser profile sensor 300, the control system can calculate the distance X0 from the midpoint 21 to the centerline 31 based on the position of the midpoint 21.
S3, referring to fig. 3, it is known that the angle between the traveling direction of the robot and the extending direction of the weld path 10 is θ, and that θ=arctan (X0/L0).
The angle of the robot travel direction from the weld path 10 can be determined.
And the deflection threshold value is XP, if X0 is less than or equal to XP, the robot walks along a straight line, and if X0 is more than XP, the robot deflects towards the direction of reducing the included angle theta.
In step S3, the travel speed of the robot is set to V, and the time required for the robot to rotate the angle θ is set to t, and the width between the left wheel 110 and the right wheel 210 is set to D.
When the robot turns right, the angle θ between the traveling direction of the robot and the extending direction of the bead track 10 is a positive number. The angular velocity of the robot is w, the turning radius of the robot is r, the rotational speed of the left wheel 110 is VL, the rotational speed of the right wheel 210 is VR, w=v/r=vl/(r+d/2) =vr/(r-D/2), w=vl/(r+d/2), θ=w×t, w=v/r can calculate that the rotational speed of the control system controlling the left wheel 110 is vl=v+d×θ/2t, and w=vr/(r-D/2), θ=w×t, w=v/r can calculate that the rotational speed of the control system controlling the right wheel 210 is vr=v-d×θ/2t. When the robot turns to the left, the angle θ between the traveling direction of the robot and the extending direction of the bead track 10 is negative.
The control system performs differential control on the left wheel 110 and the right wheel 210 by a PID control method.
The left wheel 110 and the right wheel 210 are differentially controlled by a PID control method, and an included angle between the walking direction of the robot and the extending direction of the weld track 10 is θ, or a distance X0 from a midpoint 21 of the laser profile image 20 to a central line 31 is used as a deviation to introduce a proportional link, an integral link and a differential link, from the aspect of time, the proportional action is to control the current error of the system, the integral action is to the history of the system error, and the differential action reflects the change trend of the system error, and the combination of the three is perfect combination of the past, the present and the future, so that the robot can stably move along the weld track 10.
In order to accurately track the trend of the welding line, the robot adopts a position type PID algorithm, and parameters such as walking speed, PID and the like are input on a control system of the robot.
After the start of the robot tracking, first, the laser profile sensor 300 recognizes the laser profile image 20 of the weld path 10, and then, two edge points 22 on the left and right sides of the laser profile image 20 are found, and the distance difference X0 between the center point 21 of the laser profile image 20 and the center line 31 is calculated.
If X0 is in a reasonable range, namely X0 is less than or equal to XP, the robot keeps linear motion; if X0 is out of a reasonable range, that is, X0 > XP, calculating the specific deviation, integral deviation and differential deviation of X0, converting the specific deviation, integral deviation and differential deviation into linear speeds of the left wheel 110 and the right wheel 210, and deflecting the robot towards the direction of the weld track 10, thereby reducing X0 or theta.
And under the circulation, the seam tracking and seeking of the seam tracking and detecting robot are completed.
While the preferred embodiment of the present application has been described in detail, the application is not limited to the embodiments, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the application, and these modifications and substitutions are intended to be included in the scope of the present application as defined in the appended claims.
Claims (4)
1. A weld joint tracking method is characterized in that: including welding seam tracking detection robot, welding seam tracking detection robot includes:
a left driving part provided with a left wheel;
a right driving part hinged to the left driving part, the left driving part rotating relative to the right driving part about an axis extending in the front-rear direction, the right driving part being provided with a right wheel;
the laser profile sensor is connected to the left driving part or the right driving part, and is arranged right in front of the midpoint of the connecting line between the left wheel and the right wheel and used for acquiring a welding line track;
the control system is used for performing differential control on the left wheel and the right wheel to enable the welding seam tracking and detecting robot to move along the welding seam track;
the weld tracking method further comprises the following steps:
s1, the laser profile sensor emits laser to the weld joint track, a laser profile image is shot and sent to the control system, and the distance from the center to the front and back directions of the laser profile sensor is L0;
s2, calculating the midpoint position of the laser profile image by using the control system, and making a central line extending forwards by using the center of the welding seam tracking detection robot, wherein the distance from the midpoint to the central line is calculated as X0 by the control system;
s3, setting a deflection threshold value XP to the control system, if X0 is less than or equal to XP, enabling the welding seam tracking detection robot to walk along a straight line, and if X0 is more than XP, enabling an included angle theta=arctan (X0/L0) between the moving direction of the welding seam tracking detection robot and the extending direction of the welding seam track, and enabling the welding seam tracking detection robot to deflect towards the direction for reducing the included angle theta.
2. The weld tracking method according to claim 1, characterized in that: in the step S3, the running speed of the seam tracking detection robot is set to V, assuming that the time required for the seam tracking detection robot to rotate by an angle θ is t, the width between the left wheel and the right wheel is D, the control system controls the rotation speed of the left wheel to vl=v+d×θ/2t, and the control system controls the rotation speed of the right wheel to vr=v-d×θ/2t.
3. The weld tracking method according to claim 2, characterized in that: and the control system performs differential control on the left wheel and the right wheel through a PID control method.
4. The weld tracking method according to claim 1, characterized in that: the method of calculating the midpoint location in the step S2 includes the steps of:
s21, dividing the laser contour image into a plurality of line segments and replacing straight lines by a least square fitting method to form a plurality of fitting line segments;
s22, comparing the slopes of every two adjacent fitting line segments and finding out slope mutation points;
s23, the slope abrupt change point is an edge point of the laser contour image;
s24, finding out two edge points of the laser profile image, and then calculating the midpoint.
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