CN111590899A - Vision auxiliary positioning device for mechanical arm 3D printing and positioning method thereof - Google Patents
Vision auxiliary positioning device for mechanical arm 3D printing and positioning method thereof Download PDFInfo
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- 238000010146 3D printing Methods 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000007639 printing Methods 0.000 claims abstract description 62
- 230000000007 visual effect Effects 0.000 claims abstract description 35
- 239000000523 sample Substances 0.000 claims abstract description 22
- 238000006243 chemical reaction Methods 0.000 claims abstract description 7
- 239000011159 matrix material Substances 0.000 claims description 6
- 239000013598 vector Substances 0.000 claims description 6
- 230000011218 segmentation Effects 0.000 claims description 4
- 101100163433 Drosophila melanogaster armi gene Proteins 0.000 claims description 3
- GIYXAJPCNFJEHY-UHFFFAOYSA-N N-methyl-3-phenyl-3-[4-(trifluoromethyl)phenoxy]-1-propanamine hydrochloride (1:1) Chemical compound Cl.C=1C=CC=CC=1C(CCNC)OC1=CC=C(C(F)(F)F)C=C1 GIYXAJPCNFJEHY-UHFFFAOYSA-N 0.000 claims description 2
- 230000001788 irregular Effects 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 abstract description 2
- 238000005516 engineering process Methods 0.000 description 5
- 239000004568 cement Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 206010052428 Wound Diseases 0.000 description 2
- 208000027418 Wounds and injury Diseases 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000013075 data extraction Methods 0.000 description 1
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- 230000010354 integration Effects 0.000 description 1
- 230000000399 orthopedic effect Effects 0.000 description 1
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical compound C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 1
- 239000012255 powdered metal Substances 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
- B29C64/386—Data acquisition or data processing for additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
- B29C64/386—Data acquisition or data processing for additive manufacturing
- B29C64/393—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
- B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
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Abstract
The invention discloses a visual auxiliary positioning device for 3D printing of a mechanical arm and a positioning method thereof, wherein the device comprises the mechanical arm and a positioning device, wherein the mechanical arm is used for 3D printing; the calibration frame is used for determining the pose relationship between the mechanical arm and the visual positioning equipment, and is arranged at the tail end of the mechanical arm; the space point position acquisition probe is held by a human hand and is used for acquiring a printing boundary; the visual positioning equipment is arranged on one side of the mechanical arm and is used for collecting the coordinate positions of a plurality of first positioning target balls on the calibration frame and collecting the coordinate positions of a plurality of second positioning target balls on the space point position collecting probe; and the computer is in signal connection with the visual positioning equipment, performs coordinate system parameter and coordinate conversion operation, and communicates with the mechanical arm to perform motion control of the mechanical arm. The method realizes the planning and resolving of the 3D printing track with any section and any orientation, omits complex site modeling and simplifies the preparation work before printing.
Description
Technical Field
The invention discloses a vision auxiliary positioning device for mechanical arm 3D printing and a positioning method thereof, and belongs to the technical field of machine vision positioning.
Background
3D printing is one of the rapid prototyping technologies, which is a technology for constructing an object by printing layer by layer using an adhesive material such as powdered metal or plastic based on a digital model file. At present, 3D prints and mainly adopts X, Y, Z coordinate system form, and the printer is carried out X by the motor drive shower nozzle when printing, Y, thereby the ascending motion in Z direction is accomplished and is printed, consequently also X, Y, Z formula 3D printer can only print on the bottom surface platform that has already confirmed, just so restricted 3D printing's flexibility to because X, Y, the structural feature of Z printer leads to if when being printed the size of piece great, the size of printer also need correspondingly become very big.
Along with the development of the mechanical arm, the application of the mechanical arm is more and more extensive, and meanwhile, due to the flexibility and changeability of the mechanical arm, the programmable characteristic enables the mechanical arm to gradually take an important role in 3D printing. Combine arm and 3D printing technique can solve present flexibility demand to 3D printing well, but because arm itself possess own coordinate system, and 3D prints and has its coordinate system again, if the two can not unify can make the precision variation that the arm printed on the contrary even can't print.
The application publication number is CN 109514690A, the name is 'a novel movable mechanical arm type 3D printing equipment', and the novel movable mechanical arm type 3D printing equipment comprises a movable base and a main support fixedly installed on the movable base, wherein the main support is connected with an mechanical arm through a turntable; the top end of the mechanical arm, which is far away from the main support, is connected with a printing nozzle; the equipment also comprises a cement conveying mechanism and a control driving mechanism; the cement conveying mechanism is connected with the printing spray head; the control driving mechanism is respectively connected with the movable base, the cement conveying mechanism and the mechanical arm. The mechanical arm comprises a main arm and at least one slave arm; one end of the main arm is connected with the turntable, and the other end of the main arm is connected with the slave arm through a rotating shaft; the mechanical arm further comprises a hydraulic telescopic rod, the fixed end of the hydraulic telescopic rod is connected with the main arm, and the output end of the hydraulic telescopic rod is connected with the slave arm; the top end of the slave arm, which is far away from the connecting point with the master arm, is connected with the printing spray head.
Application publication number is CN 108790162A, and the name is "a medical treatment 3D printing device" discloses a medical treatment printing device, including printing the framework the printing the framework in install mobilizable arm the tip of arm install and beat printer head and the both sides deckle board of printing the framework on still imbed respectively and install the controller the one end of controller link to each other with the printer head of arm lower extreme through the wire. According to the invention, the grooves for accommodating the controllers are arranged on the two sides of the printing frame body, the controllers are arranged and installed in the grooves, the joint grooves are arranged on the outer side of the frame body, the controllers and the external scanning device are communicated through the installed crystal joints, the space occupied by the controllers is greatly reduced, the space occupied by the internal printing heads is greatly increased, the interior of the printing frame body is moved through the mechanical arm, control signals of the controllers are transmitted to the printing heads for printing, the whole structure is compact, the use is convenient, the printing efficiency is good, and the printing effect is good.
The above patent also has the following technical problems:
first, when 3D printing is performed using a robot arm, in order to better exhibit flexibility of the robot arm, a printing plane needs to be recognized, and in many existing robot arm 3D printing technologies, initial state setting for 3D printing is performed by a method of printing a plane by a known target, but flexibility of a 6-degree-of-freedom robot arm cannot be exhibited.
Secondly, the method comprises the following steps. The 3D printing technology usually needs to first model a printing object and then print the printing object, but for some scenes, for example, when the 3D printing technology is used in medical field to perform wound treatment, data of a wound part of a patient cannot be extracted in a short time, and at this time, boundary setting and planning are needed on site to complete a 3D printing task.
Disclosure of Invention
Aiming at the technical problems, the invention provides a visual auxiliary positioning device and a positioning method thereof for mechanical arm 3D printing, the device and the method can realize the purpose of 3D printing aiming at any plane or even curved surface, and simultaneously provide an algorithm based on boundary acquisition and path planning of visual positioning to solve the requirement of field data extraction and printing.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a vision-assisted positioning device for robotic arm 3D printing, comprising:
the calibration frame is arranged at the tail end of the mechanical arm and consists of a first target ball fixing frame and a plurality of first positioning target balls fixed on the first target ball fixing frame, and the first positioning target balls are asymmetrically distributed;
the space point position acquisition probe is held by a human hand and is used for acquiring a printing boundary, and the space point position acquisition probe consists of a second target ball fixing frame, a plurality of second positioning target balls and probes which are fixed on the second target ball fixing frame;
the visual positioning equipment is arranged on one side of the mechanical arm and is used for collecting the coordinate positions of a plurality of first positioning target balls on the first target ball fixing frame and collecting the coordinate positions of a plurality of second positioning target balls on the second target ball fixing frame;
and the computer is in signal connection with the visual positioning equipment, performs coordinate system parameter and coordinate conversion operation, and communicates with the mechanical arm to perform motion control of the mechanical arm.
The number of the positioning target balls comprises 4, and the four positioning target balls are respectively positioned at four end points of the first target ball fixing frame in a cross structure.
The tail end of the mechanical arm is connected with an L-shaped connecting part, a first target ball fixing frame is mounted on the L-shaped connecting part through a bolt fastener, and the first target ball fixing frame is of a cross structure;
the number of the first positioning target balls comprises 4, and the four first positioning target balls are respectively positioned at four end points of the first target ball fixing frame in a cross structure;
the second target ball fixing frame is of a Y-shaped structure;
the number of the second positioning target balls comprises 4, namely three second positioning target balls positioned at three end positions of the second target ball fixing frame in a Y-shaped structure and one second positioning target ball positioned at the middle position of the second target ball fixing frame in a Y-shaped structure. The invention further discloses a positioning method based on the visual auxiliary positioning device for the mechanical arm 3D printing, which comprises the following steps:
s1.1, calibrating by using visual positioning equipment and a mechanical arm to obtain the pose relation of a mechanical arm coordinate system { B } and a visual positioning coordinate system { C }:
s1.2, acquiring the pose relation between a target printing plane coordinate system { G } and a mechanical arm coordinate system { B }, and determining the initial motion pose of the mechanical arm according to the pose relation;
s2 real-time path planning for 3D printing of mechanical arm
S2.1, collecting a printing boundary by using a space point position collection probe and planning a mechanical arm path based on a printing path filling algorithm;
and S2.2, converting the path planning path point position to a target printing plane coordinate system and driving the mechanical arm to finish printing.
S1.1, determining the pose relationship between the mechanical arm and the visual positioning equipment comprises the following steps:
tool coordinate system matrix with mechanical arm
Is [ n ]x，ny，nz，p]，
S1.1.1, acquiring a first positioning target ball coordinate set of a calibration frame at the tail end of a mechanical arm at the initial position of the mechanical arm;
s1.1.2, the mechanical arm moves in the x-axis direction to obtain a second coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.3, the mechanical arm moves in the y-axis direction to obtain a third coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.4, the mechanical arm rotates once around any spatial axis of the center O of the six-axis flange plate to obtain a fourth coordinate set of the first positioning target ball of the end calibration frame;
s1.1.5, the mechanical arm performs one-time rotation on an axis which is different from any axis in space in S1.1.4 and bypasses the center O of the six-axis flange plate to obtain a fifth coordinate set of the first positioning target ball of the end calibration frame;
s1.1.6, determining a third end calibration frame first positioning target ball coordinate system according to the third mechanical arm end calibration frame first positioning target ball coordinate set, determining a fourth end calibration frame first positioning target ball coordinate system according to the fourth mechanical arm end calibration frame first positioning target ball coordinate set, and determining a fifth end calibration frame first positioning target ball coordinate system according to the fifth mechanical arm end calibration frame first positioning target ball coordinate set;
s1.1.7, calculating n in the coordinate system of the robot tool by the first coordinate system, the second coordinate system and the third coordinate systemx，nyNz term;
calculating the coordinate system p item of the mechanical arm tool according to the coordinate system three, the coordinate system four and the coordinate system five to obtain
S1.1.8, determining and calculating the position and posture relation between the mechanical arm and the vision positioning equipment, wherein the formula is
Wherein,
{ O } is a six-axis flange coordinate system of the mechanical arm;
{ B } is the mechanical arm base coordinate system;
{ C } is the camera base coordinate system.
And S1.2, adopting a space point position acquisition probe to carry out point position acquisition and establishing a target printing plane coordinate system.
And S2.1, discretizing and dividing the printing boundary in the irregular shape, and determining the path points of the mechanical arm through a 3D printing path filling Zigzag algorithm to complete path planning.
S2.2, Y is set as the coordinate of the path point in the target printing plane coordinate system, [ x ]i，yi，zi，1](i 1, 2, 3., n is the original printing boundary acquisition coordinate, { C } is the visual positioning device coordinate system, and { G } is the printing target plane coordinate system, according to the following conversion formula
The coordinate representation of the path point in the G coordinate system is obtained.
S1.1.6, the method for determining the target ball coordinate system of the end calibration frame according to the target ball coordinate set of the end calibration frame of the mechanical arm comprises the following steps:
and taking any three target balls which are not in a straight line in the target ball coordinate set, and setting the three target balls as K, N and M. And taking K as an origin, N as a point on an x-axis, taking a normal vector perpendicular to a plane where K, N and M are located as a z-axis, and then obtaining a y-axis by vector cross multiplication of the current x-axis and the z-axis, thereby determining homogeneous matrix representation of the current target sphere coordinate system under the coordinate system of the visual positioning equipment.
The invention has the beneficial effects that:
1. the establishment of any printing plane is realized through the assistance of a vision system, the application range of 3D printing is expanded, and the 3D printing is not limited on a single plane of the frame.
2. The mode of getting the point through space point position acquisition probe has realized on-the-spot 3D and has printed the boundary establishment, has saved the complicated modeling process of 3D printing and has repaired for the part, and medical orthopedics damaged tissue repairs and provides the possibility from the technical level.
Drawings
FIG. 1 is a schematic diagram of the printed boundary fitting of the present invention
Wherein, 1, an actual track; 2. a visual collection point; 3. fitting a track;
FIG. 2 is a graph of discretized segmentation boundaries;
wherein, 4, quadrilateral boundary; l, presetting a printing interval;
FIG. 3 is a space point location acquisition probe;
wherein, 5, a probe; 6. a second set of target balls; 7. a second target ball fixing frame;
FIG. 4 is a calibration rack;
8, a first target ball fixing frame; 9. a first set of target balls;
FIG. 5 is a diagram of the overall hardware configuration of the system;
10, a calibration frame; 11. a mechanical arm; 12. a computer; 13. a visual positioning device; 14. and acquiring probes at spatial point positions.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the drawings and the specific embodiments in the specification.
The invention solves the defects by introducing a visual positioning system, obtains the pose relationship between the mechanical arm { B } and the visual positioning equipment { C } through calibration of visual positioning equipment and the mechanical arm in the acquisition of the target printing plane, then acquires the pose relationship between the target printing plane and the mechanical arm by utilizing a space point position acquisition probe and determines the initial motion pose of the mechanical arm according to the pose relationship.
After calibration of a target printing plane and determination of an initial motion pose of the mechanical arm are completed, a space point position acquisition probe is used for acquiring a target boundary, in the process, the visual positioning equipment can acquire the actual pose of the space point position acquisition probe at a certain time interval, a quadrilateral discretization segmentation mode is used for segmentation after boundary extraction is completed, and a 3D printing path is filled with a Zigzag algorithm to determine path points of the mechanical arm so as to complete path planning and printing.
In the process of calibrating the target printing plane, the required devices are shown in fig. 5, and the device comprises a mechanical arm, a visual positioning device and positioning target balls fixed on the mechanical arm, wherein four target balls are asymmetrically distributed on a target ball fixing piece.
The whole positioning method and the path planning method comprise the following steps:
s1, auxiliary positioning for 3D printing of the mechanical arm:
s1.1, calibrating the visual positioning equipment and the mechanical arm to obtain the pose relation of a mechanical arm coordinate system { B } and a visual positioning coordinate system { C }. Tool coordinate system matrix with mechanical arm
Is [ n ]x，ny，nz，p]The first three columns of the matrix are respectively represented by vectors of x, y and z axes of the transformed coordinate system in the original coordinate system, and p is a vector of the original coordinate system with the origin pointing to the transformed coordinate system.
S1.1.1, acquiring a first positioning target ball coordinate set integration of a mechanical arm tail end calibration frame at the initial position of a mechanical arm:
s1.1.2, moving the mechanical arm in the x-axis direction to obtain a second coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.3, moving the mechanical arm in the y-axis direction to obtain a third coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.4, the mechanical arm rotates once around any spatial axis of the center O of the six-axis flange plate to obtain a fourth coordinate set of the first positioning target ball of the end calibration frame;
s1.1.5, the mechanical arm performs one-time rotation around the axis of any shaft in space in S1.1.4, which is different from the center O of the six-shaft flange plate, to obtain a fifth coordinate set of the first positioning target ball of the end calibration frame;
s1.1.6, determining a third end calibration frame first positioning target ball coordinate system according to the third mechanical arm end calibration frame first positioning target ball coordinate set, determining a fourth end calibration frame first positioning target ball coordinate system according to the fourth mechanical arm end calibration frame first positioning target ball coordinate set, and determining a fifth end calibration frame first positioning target ball coordinate system according to the fifth mechanical arm end calibration frame first positioning target ball coordinate set;
s1.1.7, calculating n in the coordinate system of the robot tool by the first positioning target ball coordinate set of the robot end calibration frame, the second positioning target ball coordinate set of the robot end calibration frame and the third positioning target ball coordinate set of the robot end calibration framex，ny，nzAn item. See FIG. 4 forFour target balls at the tail end of the mechanical arm are respectively K, N, M and Q, and the coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm is integrated as follows:
[xK1，yK1，zK1]，[xN1，yN1，zN1]，[xM1，yM1，zM1]，[xQ1，yQ1，zQ1]the coordinate set of the target ball at the tail end of the mechanical arm is two [ x ]K2，yK2，zK2]，[xN2，yN2，zN2]，[xM2，yM2，zM2]，[xQ2，yQ2，zQ2]The coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm is III
[xK3，yK3，zK3]，[xN3，yN3，zN3]，[xM3，yM3，zM3]，[xQ3，yQ3，zQ3]。nx，ny，nzThe calculation process of (2) is as follows:
nx1＝[xK2，yK2，zK2]-[xK1，yK1，zK1](2)
nx2＝[xN2，yN2，zN2]-[xN1，yN1，zN1](3)
nx3＝[xM2，yM2，zM2]-[xM1，yM1，zM1](4)
nx4＝[xQ2，yQ2，zQ2]-[xQ1，yQ1，zQ1](5)
nx＝(nx1+nx2+nx3+nx4)/4 (6)
n is calculated according to the formulas (2), (3), (4) and (5)x1，nx2，nx3，nx4Then n is calculated according to the formula (6)x。
ny1＝[xK3，yK3，zK3]-[xK2，yK2，zK2](7)
ny2＝[xN3，yN3，zN3]-[xN2，yN2，zN2](8)
ny3＝[xM3，yM3，zM3]-[xM2，yM2，zM2](9)
ny4＝[xQ3，yQ3，zQ3]-[xQ2，yQ2，zQ2](10)
ny＝(ny1+ny2+ny3+ny4)/4 (11)
N is calculated according to the formulas (7), (8), (9) and (10)y1，ny2，ny3，ny4Then n is calculated according to formula (11)y。
By
nz＝nx×ny
To obtain nz
Calculating the coordinate system p items of the mechanical arm tool according to the coordinate system three, the coordinate system four and the coordinate system five, recording the three coordinate systems as t1}，{t2}，{t3Let p be [ x ]0，y0，z0]The converted coordinate form is [ x ]0，y0，z0，1]TWhen X is recorded, the system of equations can be obtained:
p can be obtained by solving equation set (12) to obtain
S1.1.8, determining and calculating the position and posture relation between the mechanical arm and the vision positioning equipment, wherein the formula is
{ O } is a six-axis flange coordinate system of the mechanical arm;
{ B } is the mechanical arm base coordinate system;
{ C } is the camera base coordinate system.
S1.2, in determining
Then, a space point position acquisition probe is used for acquiring four corner points of the target printing plane to obtain the representation of the target printing plane coordinate system under a { C } system
According to
The initial motion pose of the robot arm can be obtained.
S2 real-time path planning for 3D printing of mechanical arm
S2.1 as shown in fig. 1, firstly, using the spatial point location acquisition probe shown in fig. 3 to acquire boundary points, after the acquisition is completed, the algorithm classifies the point locations into a finite number of quadrangles or triangles (a triangle will appear when the point is an odd number) as shown in the above diagram, and for a single quadrangle, the Zigzag algorithm is used to segment the quadrangles:
as shown in FIG. 2, the x-axis and y-axis of the x-axis and y-axis target print plane coordinate system, and the four vertex positions of the quadrangle are determined by the above-described division.
S2.2, after all the mechanical arm motion path points are obtained, the collected path point coordinates need to be converted into a target printing plane coordinate system, and the conversion method comprises the following steps:
let Y be the coordinate of the path point in the target print plane coordinate system, [ x ]i，yi，zi，1](i 1, 2, 3.., n) is the original printing boundary acquisition coordinates, { C } is the visual positioning device coordinate system, and { G } is the printing target plane coordinate system, according to the following conversion formula
Then a coordinate representation of the path point in the G coordinate system can be obtained.
After obtaining the path point coordinates, the mechanical arm is made to reciprocate at a preset printing interval, so that the target printing area is filled with the 3D printing material.
According to the invention, a visual system is adopted to determine the printing plane, and a space point position acquisition probe is adopted to acquire point positions to determine the printing boundary, so that 3D printing track planning and resolving in any section and any direction are realized, complex site modeling is omitted, and preparation work before printing is simplified.
Claims (8)
1. A vision-aided positioning device for 3D printing of a mechanical arm, comprising:
the mechanical arm is used for 3D printing;
the calibration frame is arranged at the tail end of the mechanical arm and consists of a first target ball fixing frame and a plurality of first positioning target balls fixed on the first target ball fixing frame, and the first positioning target balls are asymmetrically distributed;
the space point position acquisition probe is held by a human hand and is used for acquiring a printing boundary, and the space point position acquisition probe consists of a second target ball fixing frame, a plurality of second positioning target balls and probes which are fixed on the second target ball fixing frame;
the visual positioning equipment is arranged on one side of the mechanical arm and is used for collecting the coordinate positions of a plurality of first positioning target balls on the first target ball fixing frame and collecting the coordinate positions of a plurality of second positioning target balls on the second target ball fixing frame;
and the computer is in signal connection with the visual positioning equipment, performs coordinate system parameter and coordinate conversion operation, and communicates with the mechanical arm to perform motion control of the mechanical arm.
2. The visual auxiliary positioning device for 3D printing by the mechanical arm according to claim 1, wherein the tail end of the mechanical arm is connected with an L-shaped connecting part, a first target ball fixing frame is mounted on the L-shaped connecting part through a bolt fastener, and the first target ball fixing frame is of a cross structure;
the number of the first positioning target balls comprises 4, and the four first positioning target balls are respectively positioned at four end points of the first target ball fixing frame in a cross structure;
the second target ball fixing frame is of a Y-shaped structure;
the number of the second positioning target balls comprises 4, namely three second positioning target balls positioned at three end positions of the second target ball fixing frame in a Y-shaped structure and one second positioning target ball positioned at the middle position of the second target ball fixing frame in a Y-shaped structure.
3. A positioning method of a visual auxiliary positioning device for robotic arm 3D printing based on claim 1 or 2, characterized by comprising the following steps:
s1, auxiliary positioning for 3D printing of the mechanical arm:
s1.1, calibrating by using visual positioning equipment and a mechanical arm to obtain the pose relation of a mechanical arm coordinate system { B } and a visual positioning coordinate system { C }:
s1.2, acquiring the pose relation between a target printing plane coordinate system { G } and a mechanical arm coordinate system { B }, and determining the initial motion pose of the mechanical arm according to the pose relation;
s2, 3D printing of the mechanical arm and real-time path planning:
s2.1, collecting a printing boundary by using a space point position collection probe and planning a mechanical arm path based on a printing path filling algorithm;
and S2.2, converting the path planning path point position to a target printing plane coordinate system and driving the mechanical arm to finish printing.
4. The positioning method of the vision-aided positioning device for the 3D printing of the mechanical arm according to the claim 3 is characterized in that in the step S1.1, the determination of the pose relation between the mechanical arm and the vision positioning equipment comprises the following steps:
tool coordinate system matrix with mechanical arm
Is [ n ]x，ny，nz，p]，
S1.1.1, acquiring a first positioning target ball coordinate set of a calibration frame at the tail end of a mechanical arm at the initial position of the mechanical arm;
s1.1.2, the mechanical arm moves in the x-axis direction to obtain a second coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.3, the mechanical arm moves in the y-axis direction to obtain a third coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.4, performing one-time rotation on any spatial axis bypassing the center O of the six-axis flange plate by the mechanical arm to obtain a fourth coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.5, the mechanical arm performs one-time rotation around the axis of any shaft in the space in S1.1.4, which is different from the axis of the six-shaft flange plate center O, to obtain a fifth coordinate set of the first positioning target ball of the calibration frame at the tail end of the mechanical arm;
s1.1.6, determining a third mechanical arm end calibration frame first positioning target ball coordinate system according to the third mechanical arm end calibration frame first positioning target ball coordinate set, determining a fourth mechanical arm end calibration frame first positioning target ball coordinate system according to the fourth mechanical arm end calibration frame first positioning target ball coordinate set, and determining a fifth mechanical arm end calibration frame first positioning target ball coordinate system according to the fifth mechanical arm end calibration frame first positioning target ball coordinate set;
s1.1.7, calculating n in the coordinate system of the robot tool by the first positioning target ball coordinate set of the end calibration frame, the second positioning target ball coordinate set of the end calibration frame and the third positioning target ball coordinate set of the end calibration framex，ny，nzAn item;
calculating the coordinate system p item of the mechanical arm tool according to the coordinate system three, the coordinate system four and the coordinate system five to obtain
S1.1.8, determining and calculating the position and posture relation between the mechanical arm and the vision positioning equipment, wherein the formula is
Wherein,
{ O } is a six-axis flange coordinate system of the mechanical arm;
{ B } is the mechanical arm base coordinate system;
{ C } is the camera base coordinate system.
5. The positioning method of the visual auxiliary positioning device for the 3D printing of the mechanical arm according to the claim 3, wherein a space point position acquisition probe is adopted in S1.2 for point position acquisition and a target printing plane coordinate system is established.
6. A positioning method of a visual auxiliary positioning device for 3D printing of a mechanical arm according to claim 3, characterized in that in S2.1, discretized segmentation is performed on the printing boundary of irregular shape, and then path point determination of the mechanical arm is performed through 3D printing path filling Zigzag algorithm to complete path planning.
7. The method of claim 3, wherein Y is the coordinate of the path point in the target printing plane coordinate system, [ x ] in S2.2i，yi，zi，1](i 1, 2, 3.., n) is the original printing boundary acquisition coordinates, { C } is the visual positioning device coordinate system, and { G } is the printing target plane coordinate system, according to the following conversion formula
The coordinate representation of the path point in the G coordinate system is obtained.
8. A method for positioning a vision-assisted positioning apparatus for 3D printing by a robotic arm as claimed in claim 3, wherein the method for determining the target ball coordinate system of the end calibration jig from the target ball coordinate set of the end calibration jig of the robotic arm in S1.1.6 comprises:
and taking any three target balls which are not in a straight line in the target ball coordinate set, and setting the three target balls as K, N and M. And taking K as an origin, N as a point on an x-axis, taking a normal vector perpendicular to a plane where K, N and M are located as a z-axis, and then obtaining a y-axis by vector cross multiplication of the current x-axis and the z-axis, thereby determining homogeneous matrix representation of the current target sphere coordinate system under the coordinate system of the visual positioning equipment.
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