CN108645428A - The monoblock type scaling method of six degree of freedom laser target - Google Patents
The monoblock type scaling method of six degree of freedom laser target Download PDFInfo
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Abstract
The present invention designs large scale space six-degree-of-freedom posture fields of measurement, to propose a kind of monoblock type scaling method for large scale 6D laser targets, the advantages that can make full use of the high-precision and PLC technology of accurate three-axle table, artificial participation part is not included in the process, the reliability for improving calibration greatly improves calibration efficiency again.For this purpose, of the invention：The monoblock type scaling method of six degree of freedom laser target, it drives 6D laser targets to be rotated before the emergent light of front total powerstation to construct measurement controlling filed using the outline border and center of the accurate three-axle table of high-precision, projected position of the light vector under camera coordinates system is calculated；And the real projection position of camera is obtained by detection, establish the posture relation equation of inclinator coordinate system and turntable coordinate system, the posture relationship of inclinator coordinate system and camera coordinates system is obtained, so far, 6D laser targets resolve unknown relation parameter in model, and all calibration obtains.Present invention is mainly applied to six-degree-of-freedom posture measurements.
Description
Technical field
The present invention designs large scale space six-degree-of-freedom posture fields of measurement, is related to sensor attitude and measures in resolving model
The problem of calibrating of unknown parameter.
Background technology
Laser target measuring system is now widely used for tunnel guiding as a kind of novel large scale 6D measuring systems
In engineering.Laser target measuring principle is visible：[1] Meng Xiangrui, Yang schoolmate, soar, and wait laser target six degree of freedom measuring techniques
[J] photoelectric projects, 2015,42 (5):27-33. [2] Yang Wenhui, Lin Jiarui, soars, and waits laser target pose measurement systems
Modeling and error analysis [J] nanotechnologies and precision engineering, 2015 (4):293-298..6D laser targets realize spatial attitude
It measures, the form of expression is 3 d space coordinate and three attitude angles (azimuth, roll angle and pitch angle).6D laser targets by
Nicked total reflection prism (201), area array cameras (202) and inclinator (203) composition.Attitude algorithm model needs to be imaged system
It unites intrinsic parameter and the outer parameter of the barycenter of hot spot, inclinator output angle, total powerstation angle measurement and area array cameras.By inclinator
Coordinate system is defined as 6D laser target coordinate systems, then the outer parameter of camera is the posture pass of camera coordinates system and inclinator coordinate system
System.
It is worth noting that the intrinsic parameter of camera and outer parameter not directly measure, need to obtain by scaling method.
In the system of multi sensor combination, the calibration effect of Relation Parameters is very big on measurement accuracy influence.Improve Relation Parameters calibration
Reliability be major issue in field of precision measurement.In addition, the difference of scaling method can lead to the difference for demarcating efficiency, carry
Height calibration efficiency will improve engineering efficiency.
Invention content
In order to overcome the deficiencies of the prior art, the present invention is directed to propose a kind of monoblock type mark for large scale 6D laser targets
The advantages that determining method, can make full use of the high-precision and PLC technology of accurate three-axle table does not include artificial ginseng in the process
With part, the reliability for improving calibration greatly improves calibration efficiency again.For this purpose, the technical solution adopted by the present invention is：Six freely
The monoblock type scaling method for spending laser target drives 6D laser targets to exist using the outline border and center of the accurate three-axle table of high-precision
It is rotated before the emergent light of front total powerstation and constructs measurement controlling filed, established in turntable rotary course, according to laser vector from turning
Light vector is calculated under camera coordinates system using camera imaging principle in the transformation relation of platform coordinate system to camera coordinates system
Projected position；And the real projection position of camera is obtained by detection, is projected by minimizing real projection position and calculating
The difference of position obtains the intrinsic parameter of camera and outer parameter, using gravitational vectors as intermediate variable, establishes inclinator coordinate system and turntable
The posture relation equation of coordinate system drives 6D laser targets using the center and inside casing of turntable, obtains gravity under multiple positions and swears
The coordinate value under turntable coordinate system and inclinator coordinate system is measured, posture relation equation is solved and obtains inclinator coordinate system and turntable
The posture relationship of coordinate system, and because the posture relationship of turntable coordinate system and camera coordinates system has also obtained, thus inclined
The posture relationship of angle instrument coordinate system and camera coordinates system, so far, 6D laser targets resolve unknown relation parameter in model and all mark
Surely it obtains.
Specific steps are refined as：
Step 1：6D laser targets, are fixed on the inside casing outer wall of the three-axle table by the accurate three-axle table rotation of control
On, the position of placement will ensure that total powerstation is unimpeded to 6D laser target light paths in the rotation process of center；
Step 2：After placing 6D laser targets, the phase of the total powerstation and three-axle table setting zero-bit is adjusted
To posture so that under three-axle table zero-bit, the substantially vertical image plane center for being incident on 6D laser targets of the incident light of total powerstation；
Step 3：Open total powerstation locking mode, centered on this position, three-axle table outline border -15 ° to 15 ° it
Between rotate, three-axle table center rotates between -12 ° to 12 °, and step-length is set as 2 °, can at least generate 16 × 13=208 in this way
A calibration position, and all target surfaces of camera are substantially covered, the calibration for camera and inclinator posture relationship, three shaft rotations
Platform center and inside casing all rotate between -10 ° to 10 °, and step-length is set as 5 °, in this way 5 × 5=25 calibration position of generation, and three
The rotation of shaft rotation platform first carries out the rotation of outline border and center by programming Control, then carries out the rotation of center and inside casing, is marked
Fixed number evidence simultaneously finally calculates unknown relation parameter.
It is as follows in one example：
1) calibration configuration is defined with coordinate system
Accurate three-axle table coordinate system is defined before calibration, origin is rotation of rotary table center, the Z of turntable coordinate system
Axis, X-axis and Y-axis are identical as the outline border shaft of turntable, center shaft and inside casing shaft, under this position, define outline border angle of rotation α
=0 °, center angle of rotation β=0 ° and inside casing angle of rotation γ=0 °；
The each framework of three-axle table needs to rotate multiple positions in calibration process, when outline border rotational angle α (i) to i-th
Position, i=0,1,2 ..., l, center rotational angle β (j) to j-th position, j=0,1,2 ..., m, inside casing rotational angle γ
(k) to k-th of position when, k=0,2 ..., n, three-axle table coordinate system opposite base and its initial position are become
Change, since the corner of three frameworks is just corresponding with three Eulerian angles, the transformation matrix of turntable coordinate systemRR(i,j,k)For
Pre-defined α (0)=0 °, β (0)=0 ° and γ (0)=0 °；
2) camera parameter defines
If light vector of a branch of incident light under camera coordinates system isCV=[Cv(x) Cv(y) Cv(z)]T, whereinCv(x)
、Cv(y)、CV (z) is respectively light vectorCComponents of the v in camera coordinates system x, y, z axis direction, according to ideal pin-hole imaging mould
Type has
Wherein (u, v) indicates that the coordinate of ideal image position of the light beam in image plane, (x, y) are ideal normalization
Imager coordinate afterwards, (ax,ay,u0,v0) be imaging model internal reference, (ax,ay) it is scale factor, (u0,v0) indicate imaging plane
On optical centre, i.e. the O of camera coordinates systemCZCThe intersection point of axis and image plane；
Introduce imaging system distortion model：Since radial distortion is usually most conclusive factor in distortion model, if
(x ', y ') is true normalized image coordinate, then has
Wherein k1And k2For coefficient of radial distortion；
In addition to this, the transformation matrix between three-axle table coordinate system and camera coordinates systemUnder turntable coordinate system
Light vectorRν0It is also unknown, therefore the known variables that the inside and outside ginseng of camera calibration model includes in total are
3) camera internal reference is demarcated
Camera internal reference is demarcated using three-axle table, light path is blocked in order to avoid turntable itself constructs, 6D laser marks
The installation of target necessarily deviates the three-axle table centre of gyration, and in ORXRYRAbove plane, such installation cause when turntable outline border and
When center rotates, laser target prismatic reflection center both horizontally and vertically can all generate variation；
Because the total powerstation that laser target is locked under pattern persistently tracks, therefore the angle during Action of Three-axis Motion Turntable
It deviates and is corrected by the variable quantity of the horizontal angle and vertical angle that read total powerstation, the light vector under turntable coordinate systemRν0It is expressed as
Following form：
WhereinThe azimuth for being light beam under turntable coordinate system and pitch angle, andIt is as corresponding inclined
Corner, azimuthValue be unknown, and since turntable and total powerstation are level, if pitch angle ψ=0 °, the angle of deviationValue directly read by total powerstation；
During camera calibration, inside casing need not be rotated around inner axis, and inside casing corner remains 0 °, when three-axle table outline border
When moving angle [alpha] (i) and center around outline border shaft rotation and moving angle beta (j) around center shaft rotation, turntable coordinate system be relatively fixed pedestal and
Its initial position is changed, then coordinate of the laser beam light vector under turntable coordinate system at this timeRν(i,j)Become
Rv(i,j)=RR(i,j,0)·Rv0
WhereinRR(i,j,0)For the transformation matrices of turntable coordinate system；
Then value of the laser beam vector under camera coordinates system at this timeCν(i,j)For
Establishing equation has risen in turntable rotary course, the transformation relation of laser vector to camera coordinates system, camera calibration mould
The unknown quantity that the inside and outside parameter of type includes altogether isAssuming that (u '(i,j),v′(i,j)) it is light vector
AmountCv(i,j)The projected position in image plane being calculated according to national forest park in Xiaokeng, andIt is that camera detects
Actual position, then both ideally answer equal, thus establish and minimize object function：
It is a Nonlinear Optimization Problem to solve the object function, Levenberg-Marquardt algorithms can be used to solve,
To solve spin matrixUnit orthogonality constraint problem, be broken down into three Eulerian angles to resolve；
4) Camera extrinsic is demarcated
Step 3) has calibrated the relationship of camera coordinates system and turntable coordinate system, therefore by demarcating 6D laser targets
The posture relationship of coordinate system and turntable coordinate system, just obtains the attitude matrix of camera coordinates system to be asked and inclinator coordinate systemRealize calibration in multiple positions by changing turntable center (103) and inside casing (102)；
Since three-axle table is leveling, value of the gravitational vectors under turntable coordinate system is under initial positionRg0=[0
0 1]T, turntable outline border (104) in fact rotates in the horizontal plane, therefore has no effect to the measured value of inclinator, calibrated
Cheng Zhong, outline border need not rotate, and outline border corner remains 0 °.When turntable center pivoting to j-th of position β(j)And inside casing
Pivoting is to k-th of position γ(k)When, turntable coordinate system is relatively fixed pedestal and its initial position is changed, then
Coordinate of the gravitational vectors under turntable coordinate system becomes at this time：
The spin matrix of turntable coordinate system to 6D laser target coordinate systems isThen obtained by above formula, under turntable coordinate system
The value of gravitational vectors may be shifted under inclinator coordinate system：
In addition, the gravitational vectors under 6D laser target coordinate systems can directly be acquired by the output quantity of inclinator, then above formula
Become
Wherein (η(j,k),μ(j,k)) indicate that turntable rotates β in center(j), inside casing rotation γ(k)When inclinator original measurement
Value, the m × n such equations that add up out are as follows：
Above formula can be reduced toForm, wherein A and B are 3 × n matrixes, as n >=3,Minimum
Two, which multiply solution, to be acquired by SVD decomposition：
Wherein V and U is matrix A BTRight unusual and left singular matrix, in this way, the turntable coordinate obtained along with step 3)
It is the spin matrix to camera coordinates system, it is as follows obtains matrix to be asked：
That is Camera extrinsic number calibration result.
The features of the present invention and advantageous effect are：
Accurate three-axle table (positioning accuracy is generally 1 ") is reference data to the present invention with high precision, and reference data is more smart
Really, calibration result is relatively reliable, so that measurement accuracy improves.It is realized in addition, calibration process programming is automatic, without artificial dry
In advance, the accidental error for having lacked human factor introducing, substantially increases the reliability of calibration.Finally, laser target in calibration process
Without dismounting, monoblock type integration calibration is realized, calibration efficiency is substantially increased.
Description of the drawings：
Fig. 1 is the schematic device of monoblock type scaling method of the present invention；
Fig. 2 is laser target internal structure schematic diagram；
Fig. 3 camera imaging model schematics；
Fig. 4 is the variation of 6D laser targets and total powerstation laser beam in calibration process.
Reference numeral：101-6D laser targets, 102- turntable inside casings, 103- turntable centers, 104- turntable outline borders, 105- are complete
It stands instrument, the nicked total reflection prisms of 201-, 202- area array cameras, 203- inclinators.
Specific implementation mode
The present invention provides a kind of monoblock type scaling methods for large scale 6D laser targets, take full advantage of precision three
The advantages that high-precision and PLC technology of shaft rotation platform, does not include artificial participation part, improves the reliability of calibration in the process
Calibration efficiency is substantially increased again.The present invention utilizes total powerstation light vector angle measurement information, without considering area array cameras internal reference
Turntable center and 6D laser targets center alignment issues, eliminate the accidental error artificially brought before calibration, and improve calibration effect
Rate.The present invention demarcates when joining outside area array cameras without dismounting 6D laser targets, it can be achieved that monoblock type integration calibration, same to eliminate
The accidental error artificially brought.Finally, accurate three-axle table is controlled by program in calibration process, is not necessarily to manual intervention, effect
Rate and height, method are reliable.
The purpose of the present invention is what is be achieved through the following technical solutions：
One kind being directed to the monoblock type scaling method of large scale 6D laser targets (101), and core is accurate three shaft rotations of high-precision
Platform.Drive 6D laser targets in the emergent light forward of front total powerstation (105) using the outline border (104) and center (103) of turntable
It moves to construct measurement controlling filed, establishes in turntable rotary course, transformation of the laser vector from turntable coordinate system to camera coordinates system
Relationship.Using camera imaging principle, projected position of the light vector under camera coordinates system can be calculated.And camera is true
Projected position can detect, can be obtained in camera by minimizing real projection position and calculating the difference of projected position
Parameter and outer parameter.Using gravitational vectors as intermediate variable, the posture relation equation of inclinator coordinate system and turntable coordinate system is established.
Drive 6D laser targets using the center and inside casing (102) of turntable, obtain under multiple positions gravitational vectors in turntable coordinate system and
Coordinate value under inclinator coordinate system, solution posture relation equation can obtain the posture of inclinator coordinate system and turntable coordinate system
Relationship.And the posture relationship of turntable coordinate system and camera coordinates system has also obtained, and can obtain inclinator coordinate system and phase
The posture relationship of machine coordinate system.So far, 6D laser targets resolve unknown relation parameter whole calibration in model and obtain.
A kind of monoblock type scaling method for large scale 6D laser targets includes the following steps：
Step 1：The accurate three-axle table of control turns to position shown in Fig. 1, and 6D laser targets (101) are fixed on inside casing
(102) on outer wall, notice that the position placed will ensure that total powerstation (105) arrives 6D laser target light paths in the rotation process of center
It is unimpeded.
Step 2：After placing 6D laser targets, the relative attitude of total powerstation and turntable setting zero-bit is adjusted so that turn
Under platform zero-bit, the substantially vertical image plane center for being incident on 6D laser targets of the incident light of total powerstation.
Step 3：Open total powerstation locking mode, centered on this position, turntable outline border (104) -15 ° to 15 ° it
Between rotate, turntable center (103) rotates between -12 ° to 12 °, and step-length generally may be configured as 2 °.It can at least generate 16 in this way ×
13=208 calibration position, and substantially cover all target surfaces of camera (202).For camera and inclinator (203) posture
The calibration of relationship, turntable center and inside casing all rotate between -10 ° to 10 °, and step-length is traditionally arranged to be 5 °, it can generate 5 in this way ×
5=25 calibration position.The rotation of turntable first carries out the rotation of outline border and center by programming Control, then carry out center with it is interior
The rotation of frame obtains nominal data and finally calculates unknown relation parameter.
Compared with prior art, advantageous effect caused by technical scheme of the present invention is：The present invention is accurate with high precision
Three-axle table (positioning accuracy is generally 1 ") it is reference data, reference data is more accurate, and calibration result is relatively reliable, to make
Measurement accuracy is obtained to improve.It is realized in addition, calibration process programming is automatic, is not necessarily to human intervention, lacked the accidental of human factor introducing
Error substantially increases the reliability of calibration.Finally, laser target realizes monoblock type one without dismounting in calibration process
Change calibration, substantially increases calibration efficiency.
The invention will be further described below in conjunction with the accompanying drawings.
A kind of monoblock type scaling method for large scale 6D laser targets is a kind of accurate three-axle table realization pair of utilization
The method that camera (202) inside and outside parameter is demarcated in 6D laser targets (101) attitude algorithm model.Below to monoblock type mark
Determine process point three parts to elaborate, it is described below：
1) calibration configuration is defined with coordinate system
Accurate three-axle table coordinate system is defined before calibration, origin is rotation of rotary table center, the Z of turntable coordinate system
Axis, X-axis and Y-axis are identical as outline border (104) shaft of turntable, center (103) shaft and inside casing (102) shaft.Under this position,
We define outline border angle of rotation α=0 °, center angle of rotation β=0 ° and inside casing angle of rotation γ=0 °.
Each axis of calibration process intermediate station needs to rotate multiple positions.As outline border rotational angle α (i) (i=0,1,2 ..., l)
To i-th of position, center rotational angle β (j) (j=0,1,2 ..., m) to j-th of position, inside casing rotational angle γ (k) (k=
0,2 ..., n) to k-th of position when, turntable coordinate system opposite base and its initial position are changed, due to three
The corner of framework is just corresponding with three Eulerian angles, and therefore, the transformation matrix of turntable coordinate system is
It should be noted that pre-defined α (0)=0 °, β (0)=0 ° and γ (0)=0 °.
3) camera parameter defines
Such as Fig. 3, if light vector of a branch of incident light under camera coordinates system isCV=[Cv(x) Cv(y) Cv(z)]T, according to
Ideal pin-hole imaging model, has
Wherein (u, v) indicates ideal image position of the light beam in image plane, (x, y) be after ideal normalization at
As coordinate, (ax,ay,u0,v0) be imaging model internal reference, (ax,ay) it is scale factor, (u0,v0) indicate imaging plane on light
Center, the i.e. O of camera coordinates systemCZCThe intersection point of axis and image plane.
Introduce imaging system distortion model.Since radial distortion is usually most conclusive factor in distortion model.If
(x ', y ') is true normalized image coordinate, then has
Wherein k1And k2For coefficient of radial distortion.
In addition to this, the transformation matrix between turntable coordinate system and camera coordinates systemTurntable coordinate system
Under light vectorRν0It is also unknown.Therefore the known variables that the inside and outside ginseng of camera calibration model includes altogether are
3) camera internal reference is demarcated
Camera internal reference is demarcated using three-axle table, light path is blocked in order to avoid turntable itself constructs, 6D laser marks
The installation of target (101) necessarily deviates rotation of rotary table center, and in ORXRYRAbove plane.Such installation causes to work as turntable outline border
(104) when and center (103) rotates, laser target prismatic reflection center both horizontally and vertically can all generate variation,
This variation can be illustrated by Fig. 4.
Because laser target is locked the total powerstation (105) under pattern and persistently tracks, therefore the angle in turntable motion process
Degree offset can be corrected by the variable quantity of the horizontal angle and vertical angle that read total powerstation.Exactly because there is modification method,
So that the requirement of installation site is not stringent on turntable to laser target.In this case, the light vector under turntable coordinate system
AmountRν0It can be expressed as following form
Wherein (φ, ψ) is azimuth and pitch angle of the light beam under turntable coordinate system, as shown in Figure 1.And (δ φ, δ ψ) is i.e.
For corresponding deflection angle.The value of azimuth φ is unknown, and since turntable and total powerstation are level, can set pitch angle ψ=
0 °, the value of the angle of deviation (δ φ, δ ψ) can directly be read by total powerstation, as described in Figure 4.
During camera calibration, inside casing (102) need not be rotated around inner axis, and inside casing corner remains 0 °.When outside turntable
When frame moves angle [alpha] (i) and center around outline border shaft rotation and moves angle beta (j) around center shaft rotation, turntable coordinate system be relatively fixed pedestal with
And its initial position is changed.Then coordinate of the laser beam light vector under turntable coordinate system at this timeRν(i,j)Become
Rv(i,j)=RR(i,j,0)·Rv0
WhereinRR(i,j,0)For the transformation matrices of turntable coordinate system.
Then value of the laser beam vector under camera coordinates system at this timeCν(i,j)For
Establishing equation has risen in turntable rotary course, the transformation relation of laser vector to camera coordinates system, camera calibration mould
The unknown quantity that the inside and outside ginseng of type includes altogether isAssuming that (u '(i,j),v′(i,j)) it is light vector
AmountCv(i,j)The projected position in image plane being calculated according to national forest park in Xiaokeng, andIt is that camera detects
Actual position then both is ideally answered equal.Thus it establishes and minimizes object function：
It is a Nonlinear Optimization Problem to solve the object function, Levenberg-Marquardt algorithms can be used to solve.
To solve spin matrixUnit orthogonality constraint problem, three Eulerian angles can be broken down into resolve.
4) Camera extrinsic is demarcated
Second part has calibrated the relationship of camera (202) coordinate system and turntable coordinate system, therefore by demarcating 6D
The posture relationship of laser target coordinate system (101) and turntable coordinate system, so that it may to obtain camera coordinates system to be asked and inclinator
The attitude matrix of coordinate systemMultiple positions by changing turntable center (103) and inside casing (102) may be implemented to demarcate.
Since turntable is leveling, value of the gravitational vectors under turntable coordinate system is under initial positionRg0=[0 0
1]T.Turntable outline border (104) in fact rotates in the horizontal plane, therefore has no effect to the measured value of inclinator (203), mark
During fixed, outline border need not rotate, and outline border corner remains 0 °.When turntable center pivoting angle beta(j)(j-th of position)
And inside casing pivoting angle γ(k)When (k-th of position), turntable coordinate system is relatively fixed pedestal and its initial position
Changed.Then coordinate of the gravitational vectors under turntable coordinate system becomes at this time
Assuming that the spin matrix of turntable coordinate system to 6D laser target coordinate systems isThen obtained by above formula, turntable coordinate system
The value of lower gravitational vectors may be shifted under inclinator coordinate system：
In addition, the gravitational vectors under 6D laser target coordinate systems can directly be acquired by the output quantity of inclinator, then above formula
Become
Wherein (η(j,k),μ(j,k)) indicate turntable in center rotation β (j), the original survey of inclinator when inside casing rotates γ (k)
Magnitude.M × n such the equations that can add up out are as follows：
Above formula can be reduced toForm, wherein A and B are 3 × n matrixes.As n >=3,Minimum
Two, which multiply solution, to be acquired by SVD decomposition：
Wherein V and U is matrix A BTRight unusual and left singular matrix.In this way, the turntable obtained along with second part is sat
It is as follows can to obtain matrix to be asked to the spin matrix of camera coordinates system for mark system：
That is Camera extrinsic number calibration result.
The present invention is not restricted the model of each device, as long as the device of above-mentioned function can be completed.
Claims (3)
1. a kind of monoblock type scaling method of six degree of freedom laser target, characterized in that utilize the accurate three-axle table of high-precision
Outline border and center drive 6D laser targets to be rotated before the emergent light of front total powerstation to construct measurement controlling filed, establish turntable rotation
During turning, calculated using camera imaging principle according to transformation relation of the laser vector from turntable coordinate system to camera coordinates system
Obtain projected position of the light vector under camera coordinates system；And the real projection position of camera is obtained by detection, passes through minimum
The difference for changing real projection position and calculating projected position obtains the intrinsic parameter of camera and outer parameter, is intermediate become with gravitational vectors
Amount, establishes the posture relation equation of inclinator coordinate system and turntable coordinate system, and 6D laser is driven using the center and inside casing of turntable
Target obtains coordinate value of the gravitational vectors under turntable coordinate system and inclinator coordinate system under multiple positions, solves posture relationship
Equation obtains the posture relationship of inclinator coordinate system and turntable coordinate system, and because of the posture of turntable coordinate system and camera coordinates system
Relationship has also obtained, and thus obtains the posture relationship of inclinator coordinate system and camera coordinates system, and so far, 6D laser targets resolve
All calibration obtains unknown relation parameter in model.
2. the monoblock type scaling method of six degree of freedom laser target as described in claim 1, characterized in that specific steps refine
For：
Step 1：The accurate three-axle table rotation of control, 6D laser targets are fixed on the inside casing outer wall of the three-axle table, are pacified
The position put will ensure that total powerstation is unimpeded to 6D laser target light paths in the rotation process of center；
Step 2：After placing 6D laser targets, the opposite appearance of the total powerstation and three-axle table setting zero-bit is adjusted
State so that under three-axle table zero-bit, the substantially vertical image plane center for being incident on 6D laser targets of the incident light of total powerstation；
Step 3：The locking mode for opening total powerstation, centered on this position, three-axle table outline border turns between -15 ° to 15 °
Dynamic, three-axle table center rotates between -12 ° to 12 °, and step-length is set as 2 °, can at least generate 16 × 13=208 mark in this way
Positioning is set, and substantially covers all target surfaces of camera, the calibration for camera and inclinator posture relationship, in three-axle table
Frame and inside casing all rotate between -10 ° to 10 °, and step-length is set as 5 °, generate 5 × 5=25 calibration position, three shaft rotations in this way
The rotation of platform first carries out the rotation of outline border and center by programming Control, then carries out the rotation of center and inside casing, obtains calibration number
According to and finally calculate unknown relation parameter.
3. the monoblock type scaling method of six degree of freedom laser target as described in claim 1, characterized in that in an example
It is as follows：
1) calibration configuration is defined with coordinate system
Accurate three-axle table coordinate system is defined before calibration, origin is rotation of rotary table center, Z axis, the X of turntable coordinate system
Axis and Y-axis are identical as the outline border shaft of turntable, center shaft and inside casing shaft, under this position, definition outline border angle of rotation α=
0 °, center angle of rotation β=0 ° and inside casing angle of rotation γ=0 °；
The each framework of three-axle table needs to rotate multiple positions in calibration process, when outline border rotational angle α (i) to i-th position,
I=0,1,2 ..., l, center rotational angle β (j) to j-th position, j=0,1,2 ..., m, inside casing rotational angle γ (k) to
When k position, k=0,2 ..., n, three-axle table coordinate system opposite base and its initial position are changed, due to three
The corner of a framework is just corresponding with three Eulerian angles, therefore, the transformation matrix of turntable coordinate systemRR(i,j,k)For
Pre-defined α (0)=0 °, β (0)=0 ° and γ (0)=0 °；
2) camera parameter defines
If light vector of a branch of incident light under camera coordinates system isCV=[Cv(x) Cv(y) Cv(z)]T, whereincv(x)、cv
(y)、cV (z) is respectively light vectorcComponents of the v in camera coordinates system x, y, z axis direction, according to ideal pin-hole imaging model,
Have
Wherein (u, v) indicates that the coordinate of ideal image position of the light beam in image plane, (x, y) are after preferably normalizing
Imager coordinate, (ax,ay,u0,v0) be imaging model internal reference, (ax,ay) it is scale factor, (u0,v0) indicate on imaging plane
Optical centre, the i.e. O of camera coordinates systemCZCThe intersection point of axis and image plane；
Introduce imaging system distortion model：Since radial distortion is usually most conclusive factor in distortion model, if (x ',
Y ') be true normalized image coordinate, then have
Wherein k1And k2For coefficient of radial distortion；
In addition to this, the transformation matrix between three-axle table coordinate system and camera coordinates systemUnder turntable coordinate system
Light vectorRν0It is also unknown, therefore the known variables that the inside and outside ginseng of camera calibration model includes in total are
3) camera internal reference is demarcated
Camera internal reference is demarcated using three-axle table, light path is blocked in order to avoid turntable itself constructs, 6D laser targets
Installation necessarily deviates the three-axle table centre of gyration, and in ORXRYRAbove plane, such installation causes to work as turntable outline border and center
When rotation, laser target prismatic reflection center both horizontally and vertically can all generate variation；
Because the total powerstation that laser target is locked under pattern persistently tracks, therefore the angle offset during Action of Three-axis Motion Turntable
It is corrected by the variable quantity of the horizontal angle and vertical angle that read total powerstation, light vector under turntable coordinate systemRν0It is expressed as follows
Form：
WhereinThe azimuth for being light beam under turntable coordinate system and pitch angle, andAs corresponding deflection angle,
AzimuthValue be unknown, and since turntable and total powerstation are level, if pitch angle ψ=0 °, the angle of deviation's
Value is directly read by total powerstation；
During camera calibration, inside casing need not be rotated around inner axis, and inside casing corner remains 0 °, when three-axle table outline border is around outer
When frame shaft rotation moves angle [alpha] (i) and center and moves angle beta (j) around center shaft rotation, turntable coordinate system be relatively fixed pedestal and it
Initial position is changed, then coordinate of the laser beam light vector under turntable coordinate system at this timeRν(i,j)Become
Rv(i,j)=RR(i,j,0)·Rv0
WhereinRR(i,j,0)For the transformation matrices of turntable coordinate system；
Then value of the laser beam vector under camera coordinates system at this timeCν(i,j)For
Establishing equation has risen in turntable rotary course, the transformation relation of laser vector to camera coordinates system, camera calibration model
The unknown quantity that inside and outside parameter includes altogether isAssuming that (u '(i,j),v′(i,j)) it is light vectorCv(i,j)The projected position in image plane being calculated according to national forest park in Xiaokeng, andIt is true to be that camera detects
Real position, then both ideally answer equal, thus establishes and minimizes object function：
It is a Nonlinear Optimization Problem to solve the object function, Levenberg-Marquardt algorithms can be used to solve, for solution
Certainly spin matrixUnit orthogonality constraint problem, be broken down into three Eulerian angles to resolve；
4) Camera extrinsic is demarcated
Step 3) has calibrated the relationship of camera coordinates system and turntable coordinate system, therefore by demarcating 6D laser target coordinates
The posture relationship of system and turntable coordinate system, just obtains the attitude matrix of camera coordinates system to be asked and inclinator coordinate systemIt is logical
Realize calibration in the multiple positions for crossing variation turntable center (103) and inside casing (102)；
Since three-axle table is leveling, value of the gravitational vectors under turntable coordinate system is under initial positionRg0=[0 0
1]T, turntable outline border (104) in fact rotates in the horizontal plane, therefore has no effect to the measured value of inclinator, calibration process
In, outline border need not rotate, and outline border corner remains 0 °.When turntable center pivoting to j-th of position β(j)And inside casing around
Axis turns to k-th of position γ(k)When, turntable coordinate system is relatively fixed pedestal and its initial position is changed, then this
When coordinate of the gravitational vectors under turntable coordinate system become：
The spin matrix of turntable coordinate system to 6D laser target coordinate systems isThen obtained by above formula, gravity under turntable coordinate system
The value of vector may be shifted under inclinator coordinate system：
In addition, the gravitational vectors under 6D laser target coordinate systems can directly be acquired by the output quantity of inclinator, then above formula becomes
Wherein (η(j,k),μ(j,k)) indicate that turntable rotates β in center(j), inside casing rotation γ(k)When inclinator original measurement value, tire out
Add m × n such equations as follows：
Above formula can be reduced toForm, wherein A and B are 3 × n matrixes, as n >=3,Least square
Solution can be decomposed by SVD and be acquired：
Wherein V and U is matrix A BTRight unusual and left singular matrix, in this way, the turntable coordinate system obtained along with step 3) arrives
It is as follows to obtain matrix to be asked for the spin matrix of camera coordinates system：
That is Camera extrinsic number calibration result.
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| CN109341546A (en) * | 2018-11-16 | 2019-02-15 | 厦门大学 | A kind of light beam scaling method of dot laser displacement sensor under any installation position appearance |
| CN109454472A (en) * | 2018-11-01 | 2019-03-12 | 东南大学 | A kind of space multiple degrees of freedom positioning device and its spatial position calculation method |
| CN109682399A (en) * | 2019-01-07 | 2019-04-26 | 华南农业大学 | It is a kind of based on three-axle table to the precision checking method of total station pose measurement result |
| CN109884659A (en) * | 2019-03-04 | 2019-06-14 | 北京工业大学 | Large-scale precision turntable scaling method based on laser traces instrument multistation level measuring system |
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