CN111986268A - Hand-eye calibration method for 3D line laser scanning camera - Google Patents
Hand-eye calibration method for 3D line laser scanning camera Download PDFInfo
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- CN111986268A CN111986268A CN202010861658.7A CN202010861658A CN111986268A CN 111986268 A CN111986268 A CN 111986268A CN 202010861658 A CN202010861658 A CN 202010861658A CN 111986268 A CN111986268 A CN 111986268A
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- 239000011159 matrix material Substances 0.000 claims abstract description 38
- 230000009466 transformation Effects 0.000 claims description 11
- 238000004364 calculation method Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 description 3
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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
- G06T2207/10—Image acquisition modality
- G06T2207/10004—Still image; Photographic image
- G06T2207/10012—Stereo images
Abstract
The invention provides a hand-eye calibration method for a 3D line laser scanning camera, 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 the robot respectively collects the three-dimensional coordinates in two different coordinate systems through a 3D line scanning camera: and establishing an equation equivalence relation according to the coordinates under the line laser coordinate system and the base coordinate system according to 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 for a 3D line laser scanning camera.
Background
In recent years, the development of a robot vision technology is extremely rapid, the mechanical arm based on visual servo is widely applied to industrial automatic production, and the motion path of the mechanical arm is planned in a visual guide 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 can be used for measuring the outline shape, the size, the coordinate position and the like of an object. Typically, the 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. The pose calibration of the mechanical arm and the vision system is an important condition for ensuring the normal work of the vision servo mechanical arm system.
Camera calibration is generally performed by a calibration module to determine the relationship between the coordinate system of the vision sensor and the coordinate system of the mechanical arm. In the prior art, 3D line laser calibration usually uses a sphere as a calibration block, and uses a circle (sphere) center or a sphere surface as an acquisition point; however, during calibration, the calculated amount is large, and the requirement on the performance of equipment is high; meanwhile, when the robot changes the pose and scans, the surface characteristics obtained based on point cloud processing are not obvious enough, so that the calibration result is not accurate enough, and the robot action is not accurate.
Disclosure of Invention
In order to solve the problems that in the prior art, the calculated amount is large and the obtained surface features are not obvious enough due to the fact that a sphere is used as a calibration block, the invention provides the hand-eye calibration method for the 3D line laser scanning camera, the calculated amount is small, the more obvious features can be obtained, the calibration time is reduced, and the calibration precision is improved.
The technical scheme of the invention is as follows: a hand-eye calibration method for a 3D line laser scanning camera comprises the following steps:
s1: placing the calibration block in the motion space range of the robot;
the method is characterized in that:
the calibration block is in a regular triangular pyramid shape;
it also includes the following steps:
s2: driving a robot to move a 3D line scanning camera to a data acquisition position above the vertex of the regular triangular pyramid of the calibration block;
s3: respectively acquiring data at 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: the vertex coordinates of the calibration block collected under the base coordinate system and the vertex pixel coordinates of the calibration block under the 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, respectively, solving a pose transformation matrix between the base coordinate system and the line laser coordinate system based on a quaternion and a least square method, thereby realizing the hand-eye calibration.
It is further characterized in that:
in step S4, the calculation formula is:
wherein S1,S2...SnIs a pose transformation matrix P under a robot base coordinate systemc1,Pc2...PcnThe pixel coordinates under the corresponding line laser coordinate system are shown, and X is a transformation matrix of the 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 comprises: a position in a plane above a vertex plane of the regular triangular pyramid-shaped calibration block;
the N different data acquisition positions and the top point of the calibration block do not form a straight line;
the value of N is more than or equal to 3;
the side length of the regular triangular pyramid is 30 mm;
each set of data of the vertex coordinates of the calibration block acquired under the base coordinate system includes: a translation matrix and a rotation matrix;
in step S4, the method of finding the pose transformation matrix between the base coordinate system and the line laser coordinate system based on the quaternion and least squares includes the steps of:
a 1: reading the line laser coordinate system QcThe vertex pixel coordinate P ═ of the calibration block described below (P)c1,Pc2…Pcn)；
Reading the base coordinate system QbIs as followsThe vertex coordinate data S of the calibration block is (S)1,S2…Sn)；
a 2: the vertex coordinate data of the calibration block includes: a translation matrix R and a rotation matrix T;
marking a translation matrix R of the vertex coordinates of the calibration block as Q based on quaternion representation;
a 3: bringing S, P, Q into the formula:
after the calibration matrix X is obtained, the minimum solution is obtained based on the least square method, and then the hand-eye calibration is realized.
According to the hand-eye calibration method for the 3D line laser scanning camera, the regular triangular pyramid is arranged to serve as the calibration block, the vertex of the calibration block serves as a reference, light can be ensured to shine on the same tip when comparison is conducted under different postures, and meanwhile, the vertex of the calibration block on the point cloud picture is easier to judge.
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 invention relates to a hand-eye calibration method for a 3D line laser scanning camera, which comprises the following steps:
s1: placing the regular triangular pyramid type calibration block within the motion space range of the robot;
when the calibration block is selected, the size 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 acquire the fixed and unchangeable vertex of the calibration block; too large will waste material, is not suitable for too small, in this embodiment, the side length of the regular triangular pyramid is 30 mm.
S2: the robot is driven to move the 3D line scanning camera to a data acquisition position above the vertex of the regular triangular pyramid of the calibration block; the data acquisition location includes: the position of the regular triangular pyramid type calibration block in the plane above the vertex plane is ensured, namely the position of the vertex of the calibration block which is fixed and unchanged can be acquired by the 3D line laser scanning camera.
S3: respectively acquiring data at N different data acquisition positions, wherein N is a positive integer;
the N different data acquisition positions and the top point of the calibration block do not form a straight line;
the more the acquisition times, the higher the calibration result precision, the more stable the result after 3 times, the higher the precision of the times improvement, and on the basis of ensuring sufficient precision and proper calculated amount, in the embodiment, the value of N is 3;
respectively recording calibration data acquired at the N data set acquisition positions to obtain N groups of calibration data;
the calibration data includes: the vertex coordinates of the calibration block collected under the base coordinate system and the vertex pixel coordinates of the calibration block under the line laser coordinate system;
wherein the base coordinate system is read in a teach pendant 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 collected under the base coordinate system includes: translation matrix, rotation matrix.
As shown in fig. 1, the calibration block 1 is placed in the motion space range of the robot 3, and the robot 3 drives the 3D line laser scanning camera 4 to change the pose on the plane above the vertex 2 of the calibration block 1 in the regular triangular pyramid shape, and sets the data acquisition position, 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, respectively, solving a pose transformation matrix between the base coordinate system and the line laser coordinate system based on a quaternion and a least square method, thereby realizing the hand-eye calibration;
the method specifically comprises the following steps:
reading line laser coordinate system QcTop of lower fixed blockPoint pixel coordinate P ═ P (P)c1,Pc2…Pcn)；
Reading the base coordinate system QbVertex coordinate data S ═ of the lower calibration block (S)1,S2…Sn)；
The vertex coordinate data of the calibration block includes: a translation matrix R and a rotation matrix T;
marking a translation matrix R of the vertex coordinates of the calibration block as Q based on quaternion representation;
set the robot tool coordinate system as Qt；
Line laser coordinate system QcTo the tool coordinate system QtIs converted into:
Pt＝r×Pc+t；
wherein r and t are respectively a linear laser coordinate system QcTo the tool coordinate system QtA rotation matrix and a translation matrix of (a);
tool coordinate system QtTo base coordinate system QbIs converted into:
Pb＝R×Pt+T
r, T being respectively a tool coordinate system QtTo base coordinate system QbA rotation matrix and a translation matrix of (a);
then: obtaining a base coordinate system QbSum line laser coordinate system QcThe relationship of (a) to (b) is as follows:
Pb＝R×(r×Pc+t)+T
namely:
since the coordinate system Q of the robot is knownbNext, even if the pose of the robot changes, the vertex coordinates of the calibration block do not change, and there are:
wherein S1,S2...SnFor pose transformation under a robot base coordinate systemMatrix, Pc1,Pc2...PcnThe pixel coordinates under the corresponding line laser coordinate system are shown, and X is a transformation matrix of the 3D line laser scanning camera, namely a hand-eye calibration matrix;
in this embodiment, if N is 3, the rotation matrix R is represented by a quaternion Q:
Q＝(q0q1q2q3)；
bringing S, P, Q into the formula:
calculating based on a least square method, and solving to obtain a minimum solution of a calibration matrix X, namely realizing hand-eye calibration;
in the technical scheme of the invention, the calibration block is set to be triangular pyramid, and the vertex of the triangular pyramid can be easily found according to the depth information under the condition of different poses; after the robot collects the data of the top point of the calibration block through the 3D line scanning camera, the data are respectively processed according to the data in two different coordinate systems: line laser coordinate system QcA base coordinate system QbAnd establishing an equation equivalence relation according to the same point, and calculating to obtain a calibration matrix X to realize hand-eye calibration.
Claims (10)
1. A hand-eye calibration method for a 3D line laser scanning camera comprises the following steps:
s1: placing the calibration block in the motion space range of the robot;
the method is characterized in that:
the calibration block is in a regular triangular pyramid shape;
it also includes the following steps:
s2: driving a robot to move a 3D line scanning camera to a data acquisition position above the vertex of the regular triangular pyramid of the calibration block;
s3: respectively acquiring data at 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: the vertex coordinates of the calibration block collected under the base coordinate system and the vertex pixel coordinates of the calibration block under the 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, respectively, solving a pose transformation matrix between the base coordinate system and the line laser coordinate system based on a quaternion and a least square method, thereby realizing the hand-eye calibration.
2. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: in step S4, the calculation formula is:
wherein S1,S2...SnIs a pose transformation matrix P under a robot base coordinate systemc1,Pc2...PcnAnd X is a transformation matrix of the 3D line laser scanning camera, namely a hand-eye calibration matrix.
3. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: the base coordinate system is read in the robot.
4. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: the line laser coordinate system is read in the 3D line scan camera.
5. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: the data acquisition location comprises: a position in a plane above a vertex plane of the regular triangular pyramid-shaped calibration block.
6. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: the N different data acquisition locations do not form a straight line with the apex of the calibration block.
7. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: the value of N is more than or equal to 3.
8. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: the side length of the regular triangular pyramid is 30 mm.
9. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: each set of data of the vertex coordinates of the calibration block acquired under the base coordinate system includes: translation matrix, rotation matrix.
10. The hand-eye calibration method for the 3D line laser scanning camera according to claim 1, characterized in that: in step S4, the method of finding the pose transformation matrix between the base coordinate system and the line laser coordinate system based on the quaternion and least squares includes the steps of:
a 1: reading the line laser coordinate system QcThe vertex pixel coordinate P ═ of the calibration block described below (P)c1,Pc2…Pcn)；
Reading the base coordinate system QbThe vertex coordinate data S of the calibration block (S ═ S)1,S2…Sn)；
a 2: the vertex coordinate data of the calibration block includes: a translation matrix R and a rotation matrix T;
marking a translation matrix R of the vertex coordinates of the calibration block as Q based on quaternion representation;
a 3: bringing S, P, Q into the formula:
after the calibration matrix X is obtained, the minimum solution is obtained based on the least square method, and then the hand-eye calibration is realized.
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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 |
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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