CN112265000B - Device and method for rapidly acquiring magnetic particle grinding track on inner surface of bent pipe - Google Patents
Device and method for rapidly acquiring magnetic particle grinding track on inner surface of bent pipe Download PDFInfo
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- 238000000227 grinding Methods 0.000 title claims abstract description 88
- 238000000034 method Methods 0.000 title claims abstract description 46
- 239000006249 magnetic particle Substances 0.000 title claims abstract description 26
- 238000012545 processing Methods 0.000 claims abstract description 40
- 238000003384 imaging method Methods 0.000 claims abstract description 33
- 230000000007 visual effect Effects 0.000 claims abstract description 22
- 230000033001 locomotion Effects 0.000 claims abstract description 18
- 238000004891 communication Methods 0.000 claims abstract description 13
- 230000005540 biological transmission Effects 0.000 claims abstract description 4
- 210000000078 claw Anatomy 0.000 claims abstract description 4
- 239000011159 matrix material Substances 0.000 claims description 22
- 230000001502 supplementing effect Effects 0.000 claims description 11
- 238000004364 calculation method Methods 0.000 claims description 10
- 238000000605 extraction Methods 0.000 claims description 7
- 239000006185 dispersion Substances 0.000 claims description 3
- 238000013519 translation Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 238000011161 development Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000017105 transposition Effects 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/70—Determining position or orientation of objects or cameras
- G06T7/73—Determining position or orientation of objects or cameras using feature-based methods
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J11/00—Manipulators not otherwise provided for
- B25J11/005—Manipulators for mechanical processing tasks
- B25J11/0065—Polishing or grinding
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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
- B25J9/1602—Programme controls characterised by the control system, structure, architecture
- B25J9/161—Hardware, e.g. neural networks, fuzzy logic, interfaces, processor
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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
-
- 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
- B25J9/1679—Programme controls characterised by the tasks executed
-
- 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
- B25J9/1694—Programme controls characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion
- B25J9/1697—Vision controlled systems
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- G06T5/70—
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/10—Segmentation; Edge detection
- G06T7/136—Segmentation; Edge detection involving thresholding
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/10—Image acquisition modality
- G06T2207/10024—Color image
Abstract
The invention relates to the technical field of processing of the inner surface of an elbow, in particular to a device and a method for rapidly acquiring the grinding track of magnetic particles on the inner surface of an elbow. Comprises an industrial robot, a magnetic field generating device, a visual imaging device, an elbow clamping device and a workbench; the magnetic field generating device is fixed at the end part of the industrial robot claw, the visual imaging device and the bent pipe clamping device are fixed on the workbench, and the bent pipe clamping device clamps the bent pipe; the method comprises the steps of acquiring an elbow image in a grinding state by a visual imaging device, performing image processing by an industrial personal computer, extracting and converting data points, fitting a track, calculating and processing grinding pose, obtaining motion pose data of an industrial robot in the grinding process of the elbow, realizing pose data transmission between the industrial personal computer and an industrial robot control system by Socket communication, and further controlling an industrial robot traction magnetic field generating device to finish grinding processing on the inner surface of the elbow. Is suitable for popularization and application in production practice, and has high accuracy, rapidness and high repeatability.
Description
Technical Field
The invention relates to the technical field of processing of the inner surface of an elbow, in particular to a device and a method for rapidly acquiring the grinding track of magnetic particles on the inner surface of an elbow.
Background
In the technical fields of aerospace, automobiles and the like, an engine is compact and complex in structure, and a space bent pipe with small space occupation rate is often adopted to enable a narrow space inside a machine to meet use requirements. The bent pipe is mainly processed by cold bending, folds, pits and extended microcracks are generated on the inner surface of the bent part, and because the surface of the inner cavity is rough, turbulence, vibration and other phenomena are generated when liquid or gas flows through the bent pipe, and the inner wall of the bent pipe is easy to corrode, so that the mechanical property of the bent pipe is reduced, the mechanical work is unstable, the power is reduced, and the inner surface of the bent pipe is required to be ground and polished.
Because the shape of the bent pipe is very complex, the traditional process is difficult to polish, and the magnetic particle grinding method has the advantages of small particle size of grinding particles, high non-contact flexibility and the like, and is better applied to the field of grinding and polishing of the inner surface of the bent pipe at the present stage. The most common processing mode of the magnetic particle grinding method in grinding and polishing the inner surface of the bent pipe is as follows: the special grinding device is fixed at the tool end of the industrial robot and driven by the industrial robot to grind and process the bent pipe fixed on the workbench. Whether the motion trail of the bent pipe grinding can be accurately obtained plays a decisive role in whether the whole process can be successfully applied and the effect is achieved.
The commonly used bent pipe grinding track acquisition method is a manual point acquisition method, and comprises the following specific steps: the robot demonstrator is controlled manually by an operator, the robot is controlled to slowly move in an incremental mode along the curved pipe track under the condition that the grinding device at the tool end of the robot does not interfere with the curved pipe, the gesture of the robot is carefully adjusted, the magnetic particle grinding process requirements are met as much as possible, and after the robot moves to a new position and the gesture is adjusted, the current gesture data of the robot are recorded until all the grinding areas of the curved pipe are collected. And generating a robot motion track for grinding processing by means of data point interpolation, so that the bent pipe can be ground.
The whole process is time-consuming and labor-consuming, the efficiency is extremely low, pose data acquired by different operators are different, random errors are large, consistency of grinding tracks is difficult to guarantee, further grinding effects of the inner surface of the bent pipe are seriously affected, and the process of manually acquiring the pose data is relatively complicated and is not suitable for popularization and application in the production process.
Disclosure of Invention
In order to solve the technical problems, the invention provides the device and the method for acquiring the magnetic particle grinding track on the inner surface of the bent pipe, which are suitable for being popularized and applied in production practice, and are accurate, quick and high in repeatability.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the device comprises an industrial robot, a magnetic field generating device, a visual imaging device, a bent pipe clamping device and a workbench; the magnetic field generating device is fixed at the end part of the industrial robot claw, the visual imaging device and the bent pipe clamping device are fixed on the workbench, and the bent pipe clamping device clamps the bent pipe; the method comprises the steps of acquiring an elbow image in a grinding state by a visual imaging device, performing image processing by an industrial personal computer, extracting and converting data points, fitting a track, and performing grinding pose calculation to obtain motion pose data of the industrial robot in the elbow grinding process, and realizing pose data transmission between the industrial personal computer and an industrial robot control system by Socket communication so as to control an industrial robot traction magnetic field generating device to finish grinding processing on the inner surface of the elbow.
The magnetic field generating device comprises a servo motor, a driving belt wheel and a rotating magnetic field mechanism; the servo motor drives the permanent magnet pole on the rotating magnetic field mechanism to rotate through the driving belt wheel.
The visual imaging device comprises a bracket, an industrial camera and a light supplementing lamp; the height of the support is adjustable, and the industrial camera and the light supplementing lamp are both hinged on the support.
The bent pipe clamping device comprises a chuck bracket and a three-grab chuck, wherein the three-grab chuck is fixedly connected to the chuck bracket, and the chuck bracket is fixedly connected to the workbench.
The method for quickly acquiring the grinding track of the magnetic particles on the inner surface of the bent pipe and grinding the magnetic particles comprises the following steps:
(1) And (5) acquiring an elbow image. Through adjusting the angle of light filling, shoot clearer return bend image to pass through the net twine and transmit it in the industrial computer.
(2) And (5) processing an elbow image. The digital images are stored in a matrix in the computer, so processing the digital images is essentially processing the elements in the matrix. The bent pipe image shot by the industrial camera is a color image, partial noise exists due to an imaging sensor and the like, and the trace extraction is inconvenient to directly carry out, so that image pretreatment is needed, a binary image which is convenient to carry out computer operation is finally obtained, a single-pixel skeleton of the bent pipe is obtained by using a skeleton extraction algorithm, and branches on the single-pixel skeleton are removed by using a branch removal algorithm, so that a smooth bent pipe contour central line is obtained.
(3) And (5) extracting and converting pixel coordinates. The pixel coordinates of all points on the curved line contour center line in the picture are obtained after the image processing, the pixel coordinates are converted into a base coordinate system of a robot in a three-dimensional space through an imaging model of an industrial camera, so that specific information of characteristic points on the curved line center line in the three-dimensional space is obtained, and the next grinding track calculation is facilitated. The camera imaging model is shown as follows:
wherein: u and v are pixel coordinates of points on the image, and the unit is pixel;
X w 、Y w 、Z w the unit is mm for the space coordinates of the pixel points on the image in the three-dimensional space;
f x 、f y the unit is pixel/mm for the focal length of the camera in the x and y directions;
u 0 、v 0 coordinates of principal points on an imaging plane of the camera are given in pixel units;
s is a camera miscut coefficient; matrix arrayCalled an intra-camera parameter matrix, which is determined by the performance of the camera and can be obtained by camera calibration, 0= [ 00 00] T ；
Matrix M 2 The camera external parameter matrix is determined by the pose of the camera in the three-dimensional space, R is a rotation matrix of the camera in the three-dimensional space, and T is a translation vector of the camera in the three-dimensional space; k is the Z-axis coordinate of the space point in the camera coordinate system, the unit is mm, the space point can be obtained through the calibrated external parameter matrix, and the value is regarded as the scale factor of the calibration plane in the camera coordinate system.
(4) Fitting the central line of the bent pipe profile. The spatial coordinates of the points on the central line of the bent pipe profile in the robot base coordinate system are obtained in the step (3), but the smoothness of the central line formed by all the points is insufficient, so that curve fitting is needed to be carried out on all the spatial points, and the central line is changed into a smooth curve. The space point curve fitting method selects 6 times polynomial fitting or three times non-rational B spline curves with higher precision to perform fitting.
Assume a given data point is P i (x i ,y i ) Then the polynomial fit of degree n is:
f(x)＝a 0 +a 1 x+a 2 x 2 +…+a n-1 x n-1 +a n x n
the three non-rational B-spline curve fitting formulas are:
wherein: n is a given data point P i Number N of (2) i,p (u)P i To define a vector at an aperiodic nodeThe definition of the above p-th order B spline basis function is as follows:
wherein: the node vector U is a dimensionless constant, and the normal value of a and b without special description is a=0, and b=1; data point is P i (x i ,y i ) The coordinate value of the pixel point on the central line of the bent pipe under the world coordinate system is expressed in mm.
(5) And (5) calculating the grinding pose of the bent pipe. And (3) taking a first derivative of the curve obtained in the step (4), then performing equal step dispersion on the original curve to obtain the position information of each point on the central track of the bent pipe, calculating the tangential angles at each position through the first derivative, and further obtaining the posture data of each point on the central track of the bent pipe, thereby calculating all the posture data of the robot on the movement track in the grinding process of the bent pipe.
(6) And the industrial personal computer exchanges data with the industrial robot controller and the servo motor driver to finish grinding processing. And the industrial personal computer is used as a server to exchange data with the industrial robot controller in a Socket communication mode for the calculated grinding pose data of the robot, so that the industrial robot is controlled to finish grinding movement. Meanwhile, the industrial personal computer and the servo driver are in RS485 communication through the communication board card, the rotating speed and the direction of the servo motor are controlled, and then the rotating magnetic field device is controlled to generate a magnetic field in a specific form, and the magnetic field device is matched with the magnetic abrasive filled in the bent pipe to finish the grinding processing of the magnetic particles on the inner surface of the bent pipe.
Compared with the prior art, the invention has the beneficial effects that:
the magnetic field generating device is arranged at the tool end of the industrial robot, the industrial robot pulls the magnetic field generating device to move according to a specific track, the bent pipe is horizontally clamped on the bent pipe clamping device, the bent pipe clamping device and the visual imaging device are fixed on the workbench, and the visual imaging transposition is adjusted, so that the bent pipe image in the clamping state can be clearly shot. The shot elbow image is transmitted to an industrial personal computer through a network cable, an image processing algorithm is utilized to calculate and obtain the contour center line of the elbow, namely the grinding track of the elbow, then the pixel points on the obtained center line of the elbow are subjected to discrete fitting to obtain a smooth elbow center line, pose data of a robot in the grinding process along the center line are calculated according to the characteristics of a magnetic particle grinding process, finally the industrial personal computer is communicated with a robot controller, the calculated pose data of the robot are transmitted to the robot controller, and the current pose data of the robot are returned to the industrial personal computer for data processing, so that the robot is controlled to move along the grinding track of the elbow, and the grinding processing of the inner surface of the elbow is completed. The bent pipe grinding track is obtained by only acquiring an image of the bent pipe through an industrial camera and then calculating by utilizing an image processing algorithm, the whole process does not need to manually acquire data, and the calculation result is quick, accurate and good in consistency.
According to the invention, the grinding track of the bent pipe is obtained by utilizing a machine vision technology, and the grinding motion is completed, so that the obtaining efficiency of the grinding track in the grinding process of the magnetic particles on the inner surface of the bent pipe can be greatly improved; calculating the contour center line of the bent pipe through an image processing algorithm, generating grinding pose, and finishing all calculation processes in an industrial personal computer, wherein the calculation speed is high, the precision is high, the random error is small, and the repeatability is high; the grinding process realizes the full-integrated control of the motion state of the robot and the rotation state of the magnetic field generating device in the industrial personal computer, and facilitates the follow-up higher-level algorithm development of the motion state and the rotation state of the magnetic field generating device. The invention improves the acquisition form of the magnetic particle grinding process for the inner surface of the bent pipe in the current stage to a great extent, improves the automation degree of the magnetic particle grinding process for the inner surface of the bent pipe, and lays a foundation for the innovative development of the magnetic particle grinding process acquisition technology for the bent pipe in the magnetic particle grinding process for the inner surface of the bent pipe.
Drawings
FIG. 1 is a schematic perspective view of the present invention;
FIG. 2 is a schematic perspective view of a magnetic field generating device according to the present invention;
FIG. 3 is a schematic perspective view of a visual imaging apparatus according to the present invention;
FIG. 4 is a schematic perspective view of the bent pipe clamping device of the present invention;
FIG. 5 is a flow chart of the present invention;
FIG. 6 is a flowchart of the elbow image processing of the present invention.
In the figure: 1-an industrial robot 2-a magnetic field generating device 3-a visual imaging device 4-an elbow clamping device 5-a workbench 6-an elbow 21-a servo motor 22-a driving belt wheel 23-a rotating magnetic field mechanism 24-a permanent magnet pole 31-an industrial camera 32-a light supplementing lamp 33-a U-shaped base 34-a vertical beam 35-a cross beam 36-an angle code 41-a chuck bracket 42-a three-grabbing chuck
Detailed Description
Examples:
the following is a further description of embodiments of the invention, taken in conjunction with the accompanying drawings:
as shown in FIG. 1, the device for quickly acquiring the grinding track of the magnetic particles on the inner surface of the bent pipe comprises an industrial robot 1, a magnetic field generating device 2, a visual imaging device 3, a bent pipe clamping device 4 and a workbench 5. The industrial robot 1 is an existing product, and the industrial robot is of the type: KUKA KR16.
The magnetic field generating device 2 is fixed at the end part of the industrial robot claw, the visual imaging device 3 and the bent pipe clamping device 4 are fixed on the workbench 5, and the bent pipe clamping device 4 clamps the bent pipe 6. The visual imaging device 3 is used for acquiring an image of the bent pipe in a grinding state, the image processing is carried out through the industrial personal computer, the data point extraction and conversion, the track fitting and the grinding pose calculation are carried out, the motion pose data of the industrial robot 1 in the bent pipe grinding process are obtained, the pose data transmission between the industrial personal computer and the industrial robot 1 control system is realized by utilizing Socket communication, and further the industrial robot 1 human traction magnetic field generating device 2 is controlled to finish the grinding processing of the inner surface of the bent pipe 6.
As shown in fig. 2, the magnetic field generating device 2 includes a servomotor 21, a drive pulley 22, and a rotating magnetic field mechanism 23; the rotating magnetic field mechanism 23 is provided with a permanent magnetic pole 24, and the servo motor 21 drives the rotating magnetic field mechanism 23 to rotate through the driving belt wheel 22, so as to drive the permanent magnetic pole 24 to rotate.
As shown in fig. 3, the visual imaging apparatus 3 includes a stand, an industrial camera 31, and a light supplement lamp 32. The bracket is made of an aluminum profile and comprises a U-shaped base 33, a vertical beam 34 and a cross beam 35, wherein the vertical beam 34 is vertically and fixedly connected to the U-shaped base 33 through an angle bracket 36, and the cross beam 35 is vertically and fixedly connected to the vertical beam 34 through the angle bracket 36. The industrial camera 31 and the light supplementing lamp 32 are existing products, and the industrial camera is of the type: huatengwei vision HT-U300C; light filling lamp model: the industrial camera 31 and the light supplementing lamp 32 are hinged to the end portion of the beam 35, and pitching angles of the industrial camera 31 and the light supplementing lamp 32 are adjustable. The cross beam 35 is detachably and vertically fixedly connected to the vertical beam 34 through an angle bracket 36, and the height of the industrial camera 31 and the light supplementing lamp 32 can be adjusted by adjusting the height of the cross beam 35 mounted on the vertical beam 34. The U-shaped base 33 is fixedly connected to the workbench 5 through bolts.
As shown in fig. 4, the pipe bending clamping device 4 comprises a chuck bracket 41 and a three-grip chuck 42, wherein the three-grip chuck 42 is fixedly connected to the chuck bracket 41, and the chuck bracket 41 is fixedly connected to the workbench 5.
As shown in fig. 5 and 6, a method for quickly acquiring magnetic particle grinding tracks on the inner surface of an elbow and grinding magnetic particles comprises the following steps:
the magnetic field generating device 2 is arranged at the tool end of the industrial robot 1, the industrial robot 1 pulls the tool end to move according to a specific track, the bent pipe 6 is horizontally clamped on the bent pipe clamping device 4, the bent pipe clamping device 4 and the visual imaging device 3 are fixed on the workbench 5, and the position of the visual imaging device 3 is adjusted, so that an image of the bent pipe 4 in a clamping state can be clearly shot.
(1) And (5) acquiring an elbow image.
The industrial camera 31 can shoot a clearer image of the bent pipe 6 by adjusting the angle of the light supplementing lamp 32 and transmits the clearer image to the industrial personal computer through a network cable.
(2) And (5) processing an elbow image.
The digital images are stored in a matrix in the computer, so processing the digital images is essentially processing the elements in the matrix. The image of the bent pipe 6 shot by the industrial camera 31 is a color image, and partial noise exists due to the imaging sensor, so that the trace extraction is inconvenient to directly perform, the image pretreatment is needed, a binary image which is convenient to perform computer operation is finally obtained, a single-pixel skeleton of the bent pipe 4 is obtained by using a skeleton extraction algorithm, and branches on the single-pixel skeleton are removed by using a branch removal algorithm, so that a smooth bent pipe 6 contour central line is obtained. The processing is shown in fig. 6.
3) And (5) extracting and converting pixel coordinates.
The pixel coordinates of all points on the contour center line of the bent pipe 6 in the picture are obtained after the image processing, the pixel coordinates are converted into a basic coordinate system of the industrial robot 1 in the three-dimensional space through an imaging model of the industrial camera 31, so that specific information of the characteristic points on the center line of the bent pipe 6 in the three-dimensional space is obtained, and the next grinding track calculation is facilitated. The imaging model of the industrial camera 31 is shown as follows:
wherein: u and v are pixel coordinates of points on the image, and the unit is pixel;
X w 、Y w 、Z w the unit is mm for the space coordinates of the pixel points on the image in the three-dimensional space;
f x 、f y is the focal length of the industrial camera 31 in the x and y directions, in pixel/mm;
u 0 、v 0 imaging principal point coordinates on a plane for the industrial camera 31 in pixels;
s is a camera miscut coefficient;
matrix arrayThe matrix of parameters in the industrial camera 31, which is determined by the performance of the industrial camera 31 and can be obtained by camera calibration, 0= [ 00 00] T ；
Matrix M 2 The external parameter matrix of the industrial camera 31 is determined by the pose of the industrial camera 31 in the three-dimensional space, R is a rotation matrix of the industrial camera 31 in the three-dimensional space, and T is a translation vector of the industrial camera 31 in the three-dimensional space; k is Z-axis coordinate of the space point under the coordinate system of the industrial camera 31, the unit is mm, and the space point can pass through the calibrated outer partThe parameter matrix is derived and this value is taken as a scaling factor of the calibration plane in the coordinate system of the industrial camera 31.
4) Fitting the central line of the bent pipe profile.
The spatial coordinates of the points on the central line of the contour of the bent pipe 6 in the basic coordinate system of the industrial robot 1 are obtained in the step (3), but the smoothness of the central line formed by all the points is insufficient, so that curve fitting is needed to be carried out on all the spatial points, and the central line is changed into a smooth curve. The space point curve fitting method selects 6 times polynomial fitting or three times non-rational B spline curves with higher precision to perform fitting. Assume a given data point is P i (x i ,y i ) Then the polynomial fit of degree n is:
f(x)＝a 0 +a 1 x+a 2 x 2 +…+a n-1 x n-1 +a n x n
the three non-rational B-spline curve fitting formulas are:
wherein: n is a given data point P i Number N of (2) i,p (u)P i To define a vector at an aperiodic nodeThe definition of the above p-th order B spline basis function is as follows:
wherein: the node vector U is a dimensionless constant, and the normal value of a and b without special description is a=0, and b=1; data point is P i (x i ,y i ) The coordinate value of the pixel point on the central line of the bent pipe under the world coordinate system is expressed in mm.
5) And (5) calculating the grinding pose of the bent pipe.
And (3) taking a first derivative of the curve obtained in the step (4), then performing equal step dispersion on the original curve to obtain the position information of each point on the central track of the bent pipe 6, calculating the tangential angles at each position through the first derivative, and further obtaining the posture data of each point on the central track of the bent pipe 6, thereby calculating all the posture data of the industrial robot 1 on the movement track in the grinding process of the bent pipe 6.
(6) And the industrial personal computer exchanges data with the industrial robot controller and the servo motor driver to finish grinding processing. The industrial personal computer serves as a server to exchange data between the calculated grinding pose data of the industrial robot 1 and the industrial robot 1 controller in a Socket communication mode, so that the industrial robot 1 is controlled to finish grinding movement. Meanwhile, the industrial personal computer and the servo driver are in RS485 communication through the communication board card, the rotating speed and the direction of the servo motor 21 are controlled, the magnetic field device 2 is further controlled to generate a magnetic field in a specific form, and the magnetic field device is matched with the magnetic abrasive filled in the bent pipe to finish the grinding processing of the magnetic particles on the inner surface of the bent pipe 6.
According to the invention, only the visual imaging device 3 is used for shooting an image of the bent pipe 6 in a grinding state and carrying out image processing on the image, so that the grinding track of the bent pipe 6 is obtained and the grinding movement is completed, and the obtaining efficiency of the grinding track in the grinding process of the magnetic particles on the inner surface of the bent pipe can be greatly improved; calculating the contour center line of the bent pipe 6 through an image processing algorithm, generating grinding pose, and finishing all calculation processes in an industrial personal computer, wherein the calculation speed is high, the precision is high, the random error is small, and the repeatability is high; the grinding process realizes the full-integrated control of the motion state of the industrial robot 1 and the rotation state of the magnetic field generating device 2 in the industrial personal computer, and facilitates the follow-up higher-level algorithm development of the motion state and the rotation state of the industrial robot 1 and the rotation state. The invention improves the acquisition form of the grinding track of the bent pipe in the magnetic particle grinding process of the inner surface of the bent pipe at the present stage to a great extent, improves the degree of automation, and lays a foundation for the innovation and development of the acquisition technology of the grinding track of the bent pipe in the magnetic particle grinding process of the inner surface of the bent pipe.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (1)
1. A method for quickly acquiring magnetic particle grinding tracks on the inner surface of an elbow is characterized in that,
the device comprises an industrial robot, a magnetic field generating device, a visual imaging device, an elbow clamping device and a workbench; the magnetic field generating device is fixed at the end part of the industrial robot claw, the visual imaging device and the bent pipe clamping device are fixed on the workbench, and the bent pipe clamping device clamps the bent pipe; acquiring an elbow image in a grinding state by a visual imaging device, performing image processing, data point extraction and conversion, track fitting and grinding pose calculation processing by an industrial personal computer to obtain motion pose data of the industrial robot in the elbow grinding process, and realizing pose data transmission between the industrial personal computer and an industrial robot control system by Socket communication to further control an industrial robot traction magnetic field generating device to finish grinding processing on the inner surface of the elbow;
the magnetic field generating device comprises a servo motor, a driving belt wheel and a rotating magnetic field mechanism; the servo motor drives the permanent magnet pole on the rotating magnetic field mechanism to rotate through the driving belt wheel;
the visual imaging device comprises a bracket, an industrial camera and a light supplementing lamp; the height of the bracket is adjustable, and the industrial camera and the light supplementing lamp are both hinged on the bracket;
the bent pipe clamping device comprises a chuck bracket and a three-grab chuck, wherein the three-grab chuck is fixedly connected to the chuck bracket, and the chuck bracket is fixedly connected to the workbench;
the method specifically comprises the following steps:
1) Acquiring an elbow image;
shooting an elbow image with the resolution ratio of 1080P or more by adjusting the light supplementing angle, and transmitting the elbow image to an industrial personal computer through a network cable;
2) Processing an elbow image;
the method comprises the steps that gray processing is firstly carried out on a color bent pipe image shot by an industrial camera, then filtering processing is carried out, a binary image is obtained, a single-pixel framework of the bent pipe is obtained by utilizing a framework extraction algorithm, and finally branches on the single-pixel framework are removed by utilizing a branch removal algorithm, so that a smooth bent pipe contour central line is obtained;
3) Extracting and converting pixel coordinates;
the pixel coordinates of all points on the curved line contour line in the picture are obtained after image processing, the pixel coordinates are converted into a base coordinate system of a robot in a three-dimensional space through an imaging model of an industrial camera, the specific information of the characteristic points on the curved line center line in the three-dimensional space is obtained, and the imaging model of the camera is shown as the following formula:
；
wherein:u、v pixel coordinates of points on the image are given in pixel units;
Xw、Yw、Zw the unit is mm for the space coordinates of the pixel points on the image in the three-dimensional space;
fx、fy is at the camerax、y Focal length in direction in pixel/mm;
u0、v0 coordinates of principal points on an imaging plane of the camera are given in pixel units;
s is a camera miscut coefficient; matrix arrayCalled in-camera parameter matrix, determined by the performance of the camera, obtainable by camera calibration,/->；
Matrix M 2 The camera external parameter matrix is determined by the pose of the camera in the three-dimensional space, R is a rotation matrix of the camera in the three-dimensional space, and T is a translation vector of the camera in the three-dimensional space;
Kis Z-axis coordinate of space point under camera coordinate system, singleThe position is mm, and can be obtained through a calibrated external parameter matrix, wherein the value is a scale factor of a calibration plane under a camera coordinate system;
4) Fitting the profile center line of the bent pipe;
step 3) selecting 6 times of polynomial fitting or adopting three times of non-rational B spline curves with higher precision for fitting;
assume a given data point isThen the polynomial fit of degree n is:
；
the three non-rational B-spline curve fitting formulas are:
wherein:n for a given data pointPi Is used in the number of (a) and (b),
to define the vector +.>Upper part of the cylinderp sub-B spline basis function
The definition of the basis functions is as follows:；
wherein: the node vector U is a dimensionless constant, the values of a and b are a=0, and b=1; the data points areCoordinate values of pixel points on the central line of the bent pipe under a world coordinate system are given in mm;
5) Calculating the grinding pose of the bent pipe;
taking a first derivative of the curve obtained in the step 4), and then performing equal step dispersion on the original curve to obtain the center of the bent pipe
Position information of each point on the track, and calculating tangential angles at each position through a first derivative to obtain a curve
Gesture data of each point on the pipe center track, so as to calculate all movement tracks of the robot in the bent pipe grinding process
Pose data;
6) The industrial personal computer exchanges data with the industrial robot controller and the servo motor driver to finish grinding;
the industrial personal computer is used as a server to communicate the calculated grinding pose data of the industrial robot with an worker in a Socket communication mode
The industrial robot controller performs data exchange so as to control the industrial robot to finish grinding movement; simultaneously, the industrial personal computer and the servo driver
The actuator carries out RS485 communication through the communication board card, controls the rotating speed and the direction of the servo motor, and further controls the rotating magnetic field device
And generating a magnetic field in a specific form, and matching with the magnetic abrasive filled in the bent pipe to finish the grinding processing of the magnetic particles on the inner surface of the bent pipe.
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