CN111986268B - 3D line laser scanning camera hand-eye calibration method - Google Patents
3D line laser scanning camera hand-eye calibration method Download PDFInfo
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- CN111986268B CN111986268B CN202010861658.7A CN202010861658A CN111986268B CN 111986268 B CN111986268 B CN 111986268B CN 202010861658 A CN202010861658 A CN 202010861658A CN 111986268 B CN111986268 B CN 111986268B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
- G06T7/85—Stereo camera calibration
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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
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Abstract
The invention provides a 3D line laser scanning camera hand-eye calibration method which has small calculated amount, can obtain more obvious characteristics, reduces calibration time and improves calibration precision. In the technical scheme of the invention, a regular triangular pyramid is arranged as a calibration block, the vertex of the calibration block is used as a reference, and a robot respectively acquires the calibration block in two different coordinate systems through a 3D line scanning camera: and (3) establishing an equation equivalent relation according to the coordinates in the line laser coordinate system and the base coordinate system and the same point to obtain a calibration matrix, thereby realizing hand-eye calibration.
Description
Technical Field
The invention relates to the technical field of robot calibration, in particular to a hand-eye calibration method of a 3D line laser scanning camera.
Background
In recent years, the development of the robot vision technology is extremely rapid, the mechanical arm based on the vision servo is widely applied to industrial automatic production, and the movement path of the mechanical arm is planned in a vision guiding mode, so that the intelligent level of the mechanical arm is improved, and the production efficiency is improved. The 3D line laser scanning camera, as a 3D vision sensor, may be used to measure the outline shape, size, coordinate position, etc. of an object. Typically, a 3D line laser scanning camera will be mounted as an eye of the robot, either at the end of the robot or in a fixed position relative to the robot base on the production line. Pose calibration of the mechanical arm and the vision system is an important condition for ensuring normal operation of the vision servo mechanical arm system.
Camera calibration is typically performed by a calibration module to determine the relationship between the vision sensor coordinate system and the robot arm coordinate system. In the prior art, the 3D line laser calibration generally uses a sphere as a calibration block and uses a round (sphere) center or a sphere surface as a collection point; however, in the calibration process, the calculated amount is relatively large, and the requirement on the equipment performance is relatively high; meanwhile, when the robot changes the pose for scanning, the surface characteristics obtained based on the point cloud processing are not obvious enough, so that the calibration result is not accurate enough, and the robot action is inaccurate.
Disclosure of Invention
In order to solve the problems that in the prior art, the sphere is used as a calibration block, the calculated amount is large, and the obtained surface characteristics are not obvious enough, the invention provides the 3D line laser scanning camera hand-eye calibration method, which has the advantages of small calculated amount, obvious characteristics, reduced calibration time and improved calibration precision.
The technical scheme of the invention is as follows: A3D line laser scanning camera hand-eye calibration method comprises the following steps:
s1: the calibration block is placed in the movement space range of the robot;
The method is characterized in that:
The calibration block is a regular triangular pyramid;
it also comprises the following steps:
s2: driving a robot to move a 3D line scanning camera to a data acquisition position above the regular triangular pyramid vertex of the calibration block;
S3: respectively carrying out data acquisition at the N different data acquisition positions, wherein N is a positive integer;
Respectively recording calibration data acquired at N data set acquisition positions to obtain N groups of calibration data;
The calibration data includes: vertex coordinates of the calibration block acquired under a base coordinate system and vertex pixel coordinates of the calibration block under a line laser coordinate system;
S4: and according to the corresponding relation of the vertex coordinates of the calibration block under the base coordinate system and the line laser coordinate system, based on a quaternion and a least square method, a pose transformation matrix between the base coordinate system and the line laser coordinate system is obtained, so that hand-eye calibration is realized.
It is further characterized by:
in step S4, the calculation formula is:
Wherein S 1,S2...Sn is a pose transformation matrix under a robot base coordinate system, P c1,Pc2...Pcn is a pixel coordinate under a corresponding line laser coordinate system, and X is a transformation matrix of a 3D line laser scanning camera, namely a hand-eye calibration matrix;
The base coordinate system is read in a robot;
the line laser coordinate system is read in the 3D line scanning camera;
the data acquisition location includes: the position in the plane above the vertex plane of the regular triangular pyramid-shaped calibration block;
the N different data acquisition positions and the vertexes of the calibration block do not form a straight line;
N is more than or equal to 3;
the side length of the regular triangular pyramid is 30mm;
Each set of data of vertex coordinates of the calibration block acquired under the base coordinate system comprises: a translation matrix and a rotation matrix;
in step S4, a pose transformation matrix between the base coordinate system and the line laser coordinate system is obtained based on a quaternion and a least square method, and the method includes the steps of:
a1: reading vertex pixel coordinates p= (P c1,Pc2…Pcn) of the calibration block under the line laser coordinate system Q c;
Reading vertex coordinate data s= (S 1,S2…Sn) of the calibration block in the base coordinate system Q b;
a2: the vertex coordinate data of the calibration block comprises: a translation matrix R and a rotation matrix T;
The translation matrix R of the vertex coordinates of the calibration block is expressed based on quaternion and is marked as Q;
a3: s, P, Q is taken to the formula:
after the calibration matrix X is obtained, the minimum solution is obtained based on the least square method, and thus the hand-eye calibration is realized.
According to the 3D line laser scanning camera hand-eye calibration method provided by the invention, the regular triangular pyramid is arranged as the calibration block, the vertexes of the calibration block are used as the reference, the light can be ensured to irradiate on the same tip when being compared under different postures, and meanwhile, the judgment on the vertexes of the calibration block on the point cloud picture is easier, so that the technical scheme of the invention can use smaller calculated amount to obtain more obvious characteristics, the calibration time is shortened, and the calibration precision is improved.
Drawings
FIG. 1 is a schematic diagram of a hand-eye calibration method according to the present invention.
Detailed Description
As shown in fig. 1, the method for calibrating the hand and eye of the 3D line laser scanning camera of the invention comprises the following steps:
S1: the method comprises the steps of placing a regular triangular pyramid-shaped calibration block in a movement space range of a robot;
when the calibration block is selected, the dimension of the calibration block needs to ensure that the robot posture is convenient to change in a movable area of the robot, and meanwhile, the 3D line laser scanning camera can collect the vertex of the calibration block, which is fixed and unchanged; too large would waste material and not be suitable for too small, in this embodiment, the regular triangular pyramid-shaped side is 30mm.
S2: driving a robot to move the 3D line scanning camera to a data acquisition position above the regular triangular pyramid vertex of the calibration block; the data acquisition location includes: the position in the plane above the vertex plane of the regular triangular pyramid-shaped calibration block ensures that the 3D line laser scanning camera can acquire the position of the vertex of the calibration block which is fixed.
S3: respectively carrying out data acquisition at N different data acquisition positions, wherein N is a positive integer;
The N different data acquisition positions and the vertex of the calibration block do not form a straight line;
The more the number of times of collection, the higher the accuracy of the calibration result is, the more stable the calibration result is after 3 times, the higher the accuracy of the number of times improvement is, and on the basis of ensuring enough accuracy and proper calculated amount, in the embodiment, the value of N is 3;
respectively recording calibration data acquired at N data set acquisition positions to obtain N groups of calibration data;
The calibration data includes: vertex coordinates of the calibration blocks collected under the base coordinate system and vertex pixel coordinates of the calibration blocks under the line laser coordinate system;
The base coordinate system is read in a demonstrator of the robot; reading a line laser coordinate system in a 3D line scanning camera;
the data of the vertex coordinates of each set of calibration blocks acquired under the base coordinate system comprises: translation matrix, rotation matrix.
As shown in fig. 1, the calibration block 1 is placed in a motion space range of the robot 3, the robot 3 drives the 3D line laser scanning camera 4 to change positions above a plane of a vertex 2 of the regular triangular pyramid type calibration block 1, and sets a data acquisition position, and in this embodiment, the method includes: data acquisition position 5, data acquisition position 6, data acquisition position 7.
S4: according to the corresponding relation of the vertex coordinates of the calibration block under the base coordinate system and the line laser coordinate system, based on the quaternion and the least square method, a pose transformation matrix between the base coordinate system and the line laser coordinate system is obtained, so that hand-eye calibration is realized;
The method specifically comprises the following steps:
Reading vertex pixel coordinates p= (P c1,Pc2…Pcn) of the calibration block under the line laser coordinate system Q c;
Reading vertex coordinate data s= (S 1,S2…Sn) of the calibration block in the base coordinate system Q b;
The vertex coordinate data of the calibration block comprises: a translation matrix R and a rotation matrix T;
the translation matrix R of the vertex coordinates of the calibration block is expressed based on quaternion and is marked as Q;
Setting a robot tool coordinate system as Q t;
the conversion of the line laser coordinate system Q c to the tool coordinate system Q t is:
Pt＝r×Pc+t；
Wherein r and t are rotation matrix and translation matrix of the line laser coordinate system Q c to the tool coordinate system Q t respectively;
The conversion of the tool coordinate system Q t to the base coordinate system Q b is:
Pb＝R×Pt+T
Wherein R, T is the rotation matrix and translation matrix of the tool coordinate system Q t to the base coordinate system Q b, respectively;
Then: the relationship between the base coordinate system Q b and the line laser coordinate system Q c is obtained as follows:
Pb＝R×(r×Pc+t)+T
Namely:
Since it is known that under the robot base coordinate system Q b, even if the robot pose changes, the vertex coordinates of the calibration block are unchanged, there are:
Wherein S 1,S2...Sn is a pose transformation matrix under a robot base coordinate system, P c1,Pc2...Pcn is a pixel coordinate under a corresponding line laser coordinate system, and X is a transformation matrix of a 3D line laser scanning camera, namely a hand-eye calibration matrix;
in this embodiment, N takes a value of 3, and the rotation matrix R is represented by a quaternion Q:
Q＝(q0q1q2q3)；
s, P, Q is taken to the formula:
calculating based on a least square method, and solving a least solution for obtaining a calibration matrix X, namely realizing hand-eye calibration;
According to the technical scheme, the calibration block is arranged to be triangular pyramid, and under different pose conditions, the triangular pyramid vertex can be easily found according to the depth information, compared with the existing sphere calibration method in the prior art, curved surface reconstruction is not needed, a Qu Miandian cloud processing process is not needed, and the calculation process in the technical scheme is simple, low in calculation amount and higher in execution efficiency; after the robot collects the data of the vertex of the calibration block through the 3D line scanning camera, the robot is respectively arranged in two different coordinate systems according to the data: the line laser coordinate system Q c and the coordinate under the base coordinate system Q b establish an equation equivalent relation according to the same point, and the calibration matrix X is obtained after calculation, so that hand-eye calibration is realized.
Claims (7)
1. A3D line laser scanning camera hand-eye calibration method comprises the following steps:
s1: the calibration block is placed in the movement space range of the robot;
The method is characterized in that:
The calibration block is a regular triangular pyramid;
it also comprises the following steps:
s2: driving a robot to move a 3D line scanning camera to a data acquisition position above the regular triangular pyramid vertex of the calibration block;
the data acquisition location includes: the position in the plane above the vertex plane of the regular triangular pyramid-shaped calibration block;
S3: respectively carrying out data acquisition at the N different data acquisition positions, wherein N is a positive integer;
respectively recording calibration data acquired at N data acquisition positions to obtain N groups of calibration data;
The calibration data includes: vertex coordinates of the calibration block acquired under a base coordinate system and vertex pixel coordinates of the calibration block under a line laser coordinate system;
S4: according to the corresponding relation of the vertex coordinates of the calibration block under the base coordinate system and the line laser coordinate system, based on a quaternion and a least square method, a pose transformation matrix between the base coordinate system and the line laser coordinate system is obtained, so that hand-eye calibration is realized;
in step S4, the calculation formula is:
Wherein S 1,S2...Sn is a pose transformation matrix under a robot base coordinate system, P c1,Pc2...Pcn is a pixel coordinate under a corresponding line laser coordinate system, and X is a transformation matrix of a 3D line laser scanning camera, namely a hand-eye calibration matrix;
in step S4, a pose transformation matrix between the base coordinate system and the line laser coordinate system is obtained based on a quaternion and a least square method, and the method includes the steps of:
a1: reading vertex pixel coordinates p= (P c1,Pc2…Pcn) of the calibration block under the line laser coordinate system Q c;
Reading vertex coordinate data s= (S 1,S2…Sn) of the calibration block in the base coordinate system Q b;
a2: the vertex coordinate data of the calibration block comprises: a translation matrix R and a rotation matrix T;
The translation matrix R of the vertex coordinates of the calibration block is expressed based on quaternion and is marked as Q;
a3: s, P, Q is taken to the formula:
after the calibration matrix X is obtained, the minimum solution is obtained based on the least square method, and thus the hand-eye calibration is realized.
2. The method for calibrating the hand and eye of the 3D line laser scanning camera according to claim 1, wherein the method comprises the following steps: the base coordinate system is read in the robot.
3. The method for calibrating the hand and eye of the 3D line laser scanning camera according to claim 1, wherein the method comprises the following steps: the line laser coordinate system is read in the 3D line scan camera.
4. The method for calibrating the hand and eye of the 3D line laser scanning camera according to claim 1, wherein the method comprises the following steps: the N different data acquisition positions and the vertex of the calibration block do not form a straight line.
5. The method for calibrating the hand and eye of the 3D line laser scanning camera according to claim 1, wherein the method comprises the following steps: n is more than or equal to 3.
6. The method for calibrating the hand and eye of the 3D line laser scanning camera according to claim 1, wherein the method comprises the following steps: the side length of the regular triangular pyramid is 30mm.
7. The method for calibrating the hand and eye of the 3D line laser scanning camera according to claim 1, wherein the method comprises the following steps: each set of data of vertex coordinates of the calibration block acquired under the base coordinate system comprises: translation matrix, rotation matrix.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014018932A (en) * | 2012-07-20 | 2014-02-03 | Kobe Steel Ltd | Calibration method for robot with optical sensor |
| CN109732600A (en) * | 2018-12-29 | 2019-05-10 | 南京工程学院 | A kind of Full-automatic sequential multi-drop measuring system and measurement method |
| CN110487213A (en) * | 2019-08-19 | 2019-11-22 | 杭州电子科技大学 | Full view line laser structured light three-dimensional image forming apparatus and method based on spatial offset |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014018932A (en) * | 2012-07-20 | 2014-02-03 | Kobe Steel Ltd | Calibration method for robot with optical sensor |
| CN109732600A (en) * | 2018-12-29 | 2019-05-10 | 南京工程学院 | A kind of Full-automatic sequential multi-drop measuring system and measurement method |
| CN110487213A (en) * | 2019-08-19 | 2019-11-22 | 杭州电子科技大学 | Full view line laser structured light three-dimensional image forming apparatus and method based on spatial offset |
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