Background technique
Since First has the intelligent robot Shakey birth of visual sensor in the world within 1966, vision is passed
Sensor is widely used in robot autonomous avoidance and navigation, medical operating, the fields such as automobile manufacture.Utilizing robot vision system
It when system carries out AUTONOMOUS TASK, needs for video camera to be fixed on the end effector of robot arm and constitutes hand-eye system, pass through
Visual sensor provides the function of eye to robot movement-control system.Assess the pass of above-mentioned robotic vision system measurement accuracy
Key step first is that accurately calculating the relative bearing relationship between robot coordinate system and visual sensor coordinate system, i.e. trick
Problem of calibrating.
Major part hand and eye calibrating method is all to solve camera by the object of reference (such as gridiron pattern target) of Accurate Calibration at present
Outer parameter, representative method have the unit quaternion method of the linear dichotomy of Zhuang etc., Horaud etc., Shah etc.
Dual quaterion method, the probability statistics based on Lie Group & Lie Algebra of Li et al. of Matrix Direct Product method, Daniilidis and Ulrich etc.
The synchronization scaling method of the both arms such as global optimization method, the Wu of method, Heller etc. cooperation robot and the polyphaser of Amy etc. change
Dai Fa.However, in some special applications, such as mobile robot and operating robot, it is contemplated that load-carrying and aseptic condition
Limitation is difficult to complete hand and eye calibrating process by traditional calibrated reference, in consideration of it, Andreff etc. proposes that one kind does not need
The hand and eye calibrating improved method of calibrated reference directly obtains the phase of missing scale factor using SFM method from natural scene
Unknown scale factor, hand and eye calibrating equation is substituted into together with trick relationship and is solved by the outer parameter of machine.In recent years, it is this not
The hand and eye calibrating improved method of calibrated reference is needed to obtain the most attention of scholars.For example, in the hand and eye calibrating of Andreff
On the basis of model, Schmidt etc. proposes the nonlinear optimization method extended based on dual quaterion, and Heller and Chen Mingwei etc. are mentioned
Out the propositions such as the global optimization method based on Second-order cone programming, Pachtrachai based on CAD (Computer
Aided Design, CAD) import model micro-wound operation robot hand and eye calibrating method.However, these methods can only calculate hand
Eye relationship and scale factor, cannot solve robot coordinate system and world coordinate system position relation, and by characteristic point simultaneously
Influence with error and space scale factor size variation, often precision is lower for the hand and eye calibrating method based on SFM scene rebuilding,
It is not able to satisfy mobile robot and operating robot vision guided navigation and positions growing accuracy requirement.
In view of the above-mentioned problems, set forth herein a kind of Robotic Hand-Eye Calibration method based on natural scene.
Summary of the invention
The Robotic Hand-Eye Calibration method based on natural scene that the purpose of the present invention is to propose to a kind of, this method pass through SFM
Algorithm carries out natural scene reconstruction, under the premise of not needing to calculate scale factor, solves machine simultaneously using Matrix Direct Product method
Manpower eye relationship and robot coordinate system and world coordinate system position relation, to extend the application neck of hand and eye calibrating problem
Domain.
For achieving the above object, the technical scheme is that a kind of Robot Hand-eye mark based on natural scene
Determine method, comprising the following steps:
S1, natural scene reconstruction is carried out by SFM algorithm, sets rotation error threshold value, utilizes adaptive RANSAC algorithm
To nominal data collection CnIn Camera extrinsic number carry out prescreening;
S2, make equivalence transformation to trick calibration equation A (s) X=YB, eliminate calibration equation mesoscale factor s, utilize matrix
Direct product method is the product of matrix and vector the product representation of matrix in trick calibration equation, meets error for what is filtered out in S1
The Camera extrinsic number of threshold requirement substitutes into the hand and eye calibrating equation of parametrization, establishes system of homogeneous linear equations;
S3, the hand and eye calibrating equation parameterized in S2 is solved using singular value decomposition, obtains meeting linear homogeneous
Then orthogonal and unit is added to it and constrains to obtain correct trick relationship X and robot coordinate system by non trivial solution vector value x
With world coordinate system position relation Y.
The present invention is based on exercise recovery structure algorithm (Structure From Motion, SFM) to solve Camera extrinsic number,
Dependence of the traditional robot hand and eye calibrating in the process to ceramic gridiron pattern flat target can be got rid of, is asked by Matrix Direct Product parametric method
Solution eliminates the hand and eye calibrating equation after scale factor, avoids influence of the scale factor to calibration equation solving precision.
The present invention resolves the Camera extrinsic number on the basis of being defined on a scale factor using SFM;Then, eliminate scale because
Son establishes improved hand and eye calibrating equation, the spin matrix being introduced into Matrix Direct Product theoretical parameter calibration equation and is translated towards
Amount;Finally, solving trick relationship and robot coordinate system and world coordinate system position relation simultaneously by least square method.
Specific embodiment
Below in conjunction with attached drawing, technical scheme in the embodiment of the invention is clearly and completely described.
As shown in Figure 1, a kind of Robotic Hand-Eye Calibration method based on natural scene, which is characterized in that including following step
It is rapid:
S1, natural scene reconstruction is carried out by SFM algorithm, as shown in Fig. 2, setting rotation error threshold value, using adaptive
RANSAC algorithm is to nominal data collection CnIn Camera extrinsic number carry out prescreening;
Camera extrinsic number includes transformation matrix A of the camera coordinate system to reference substance world coordinate systemiIn rotating part
Camera extrinsic number RAi, robot tool coordinate system to robot basis coordinates system transformation matrix BiIn rotating part Camera extrinsic
Number RBi, RAi、RBiScreening technique specifically include:
S1.1, video camera is fixed on end effector of robot, acquires nominal data, driven and imaged using robot
Machine chooses N number of different positions and pose every time and takes pictures imaging to ceramic gridiron pattern flat target, is combined available M=N (N- two-by-two
1)/2 group nominal data collection Cn, the rotating part R in hand and eye calibrating matrix is solved using linear methodXAnd RY;
S1.2, nominal data rotation error screening model is established:
Wherein, eRFor error threshold;
S1.3, using adaptive RANSAC algorithm to nominal data collection CnMiddle Camera extrinsic number RAi、RBiCarry out prescreening.Tool
Body includes: the minimum strong point n=2 of setting, and setting meets error threshold eRIt is required that interior ratio initial value wO=0.5, K sampling
In all samples be bad sample probability z=0.02, rotation error threshold value initial value eR=0.01, terminate the item of RANSAC sampling
Part is to meet error threshold eRNominal data collection CX>=9, it is sampled using adaptive algorithm and updates wOAnd eR, until demarcating number
According to collection CX>=9, write down angle threshold e at this timeh, sampling is terminated, the nominal data collection C that screening is obtainedXSubstitute into S2.
S2, make equivalence transformation to trick calibration equation A (s) X=YB, eliminate calibration equation mesoscale factor s, utilize matrix
Direct product method is the product of matrix and vector the product representation of matrix in trick calibration equation, meets error for what is filtered out in S1
The Camera extrinsic number of threshold requirement substitutes into the hand and eye calibrating equation of parametrization, establishes system of homogeneous linear equations;It specifically includes:
As shown in Fig. 2, defining A is transformation matrix of the object of reference world coordinate system to camera coordinate system, B is expressed as machine
Transformation matrix of people's tool coordinates system to robot basis coordinates system, X expression camera coordinate system to robot tool coordinate system
Transformation matrix, Y indicate robot basis coordinates system to the transformation matrix of object of reference world coordinate system, then hand and eye calibrating equation can be with table
It is shown as:
A (s) X=YB
In formula (1), A, B, X and Y are 4 × 4 matrix, expand into the form of spin matrix and translation vector are as follows:
By formula (2) it is found that only having translation vector part to be influenced by scale factor s in calibration equation, by translation vector portion
Divide both members all multiplied by antisymmetric matrixEliminating scale factor s can obtain:
Wherein
Then the hand and eye calibrating equation in formula (2) can convert are as follows:
Matrix product in formula (3) is expressed as to the form of Matrix Direct Product, establishes system of homogeneous linear equations:
In formula (4), W (A, B) is 18 × 24 matrixes;X is system of homogeneous linear equations solution vector value, is 24 × 1 vector;
Vec (R) is vectorization operator, can be indicated are as follows:
Wherein, r11、r12、…、r1n、r21、r22、…、rnmRepresent R3×3Each of matrix element.
S3, the hand and eye calibrating equation parameterized in S2 is solved using singular value decomposition, obtains meeting linear homogeneous
Then orthogonal and unit is added to it and constrains to obtain correct trick relationship X and robot coordinate system by non trivial solution vector value x
With world coordinate system position relation Y;It specifically includes:
If U=vec-1(x1:9), V=vec-1(x10:18), x1:9It is first 9 of system of homogeneous linear equations solution vector value x,
x10:18For the 10-18 item of system of homogeneous linear equations solution vector value x, non trivial solution RXAnd RYThe ratio differed with solution vector value x because
Sub- β meets:
U=β RX, V=β RY
By above formula reverse scale factor β are as follows:
Therefore, it trick relationship X and robot coordinate system and spin matrix in world coordinate system position relation Y and is translated towards
Amount can indicate are as follows:
Due to measuring the influence of noise,WithAnd it is unsatisfactory for stringent orthogonality, it needs to reuse Schmidt orthogonal
Change carries out equivalence transformation to it.
Feasibility of the above method in actual measurement is verified with validity below by way of specific experiment, such as
Shown in Fig. 3, DENSO robot, Japan electric coating company VS-6577GM, company, Daheng MER-500-14GM/GC model are utilized
CMOS industrial camera builds actual measurement experiment porch.As Figure 4-Figure 6, made respectively using ceramic gridiron pattern flat target, books, statue
Hand and eye calibrating equation is solved for object of reference.The repetitive positioning accuracy of DENSO robot all directions is ± 0.020mm, each joint angle
Resolution ratio is 5 ", camera resolution is 2592 × 1944pixels, and pixel dimension is 2.2 μm of 2.2 μ m, and lens focus is
Video camera is first fixed tightly on end effector of robot ring flange by 12mm before experiment.Due to actual measurement experiment in can not be direct
The absolute true value for measuring trick relationship X and robot orientation Y, in order to verify the precision and reliability of the method for the present invention, with tradition
Using ceramic gridiron pattern flat target as the result X of the hand and eye calibrating method of object of referencebarAnd YbarIt is for true value, it is upper with utilization
The carry out trick relationship X that the method for stating is calculatedsceneWith robot orientation YsceneIt is worth comparative analysis.Detailed process are as follows:
1, it defines trick relationship and robot azimuthal error is respectively as follows:
EX=| | Xbar-Xscene||2 EY=| | Ybar-Yscene||2
2, drive industrial camera centered on ceramic gridiron pattern flat target origin using robot, radius is about 600mm
Hemisphere face on 9 different positions take pictures imaging to 11mm × 11mm ceramics gridiron pattern flat target shown in Fig. 4, recorder
People's tool coordinates system is to robot basis coordinates system transformation matrix;
3, with Zhang Zhengyou method calibration for cameras intrinsic parameter, Camera extrinsic number is solved, the tradition based on target object of reference is used
Scaling method calculates trick relationship XbarWith robot orientation Ybar;
4, it is taken pictures imaging with books or statue, previous step camera internal reference numerical value obtained by calibrating and SFM algorithm is utilized to calculate
The Camera extrinsic number for lacking scale factor, obtains space characteristics point by Feature Points Matching, triangulation and beam optimum adjustment
Three-dimensional information, be illustrated in figure 7 in Fig. 5 object of reference 5035 characteristic points rebuild after result.Using based on nature field
The Robotic Hand-Eye Calibration method of scape solves trick relationship XsceneWith robot orientation Yscene, calculate trick relationship and robot
Azimuthal error EXAnd EY。
In order to verify the reliability of the method for the present invention, 10 groups of completely self-contained calibration experiments are repeated, are averaged
It is compared analysis, as shown in table 1:
1 natural scene object of reference hand and eye calibrating experimental result (unit: mm) of table
As known from Table 1: 2 kinds of different types of natural scene objects of reference are directed to, it is proposed by the present invention based on natural scene
The trick relationship X that Robotic Hand-Eye Calibration improved method is calculatedsceneWith robot orientation YsceneValue is close to based on ceramics
The trick relationship X that gridiron pattern flat target is calculatedbarWith robot orientation YbarValue.Show in no calibrated reference as empty
Between constrain under conditions of, method of the invention is it is also ensured that certain stated accuracy and reliability.
Described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.Based on the present invention
In embodiment, every other implementation obtained by those of ordinary skill in the art without making creative efforts
Example, belongs to the scope of the present invention.