CN104820217B - A kind of calibration method of the polynary linear array detection imaging laser radar of many Normal planes - Google Patents

Abstract

The present invention relates to the calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes, comprise the following steps: 1) obtain the observation data of the plane target plank of multiple different azimuth, matching target plate plane equation；2) obtain the cloud data of multiple plane target plank in calibration region and carry out pretreatment, setting up multilasered optical radar systematic error calibration model based on many Normal planes；3) according to systematic error calibration model, resolved by repeating adjustmet, obtain rudimentary system error calibration parameter；4) rudimentary system error calibration parameter is carried out elimination of rough difference, it is thus achieved that optimal checking parameter, it may be judged whether containing the observation more than given threshold value, the most then rough error value rejected and return step 3), if it is not, then carry out step 5)；5) evaluate the precision of rudimentary system error calibration parameter, obtain final calibration parameter.Compared with prior art, the present invention has population parameter calibration model, simplifies the advantages such as calibration field experiment is set up, experimental result is accurate.

Description

A kind of calibration method of the polynary linear array detection imaging laser radar of many Normal planes

Technical field

The present invention relates to the calibration method of a kind of radar, especially relate to the calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes.

Background technology

Three-dimensional imaging laser radar has three-D profile and appearance imaging capability, can obtain the multiple image of target, such as Range Profile, intensity image and distance-angle picture etc., there is high distance and angular resolution, characteristics of image is stable, and capacity of resisting disturbance is strong, and anti-target stealth capabilities is strong.Polynary linear array detection imaging laser radar uses linear array detector to receive, distance and the echo strength data of 16 positions of string can be obtained every time, sweep or two dimensional opti mechanism scan realizes the collection of all pixel datas by pushing away, the multiple laser spots of final acquisition and intensity image, its imaging rate is far above single-element detector two-dimensional scan imaging technique, and owing to linear array detector product is abundanter, array element number is many, higher resolution image can be obtained, it it is a kind of imaging detection technology having much advantage and potential, it is suitable for accurate avoidance, navigation, guidance, landing drop point selects, spacecraft space spacecrafts rendezvous, remote sensing of the earth is observed, mapping, unmanned vehicle and the avoidance of robot, navigation etc., it is respectively provided with vast potential for future development and application demand in the big field of the army and the people two.Polynary linear array detection imaging laser radar is affected by multiple error component, including multiple laser ranging errors, angle error and other errors etc. during measuring.In order to ensure the quality of data, it is necessary to the error component affecting polynary linear array detection imaging laser infrared radar imaging quality is modeled, calculate correlated error, improve the quality of polynary linear array detection imaging laser radar.

Summary of the invention

Defect that the purpose of the present invention is contemplated to overcome above-mentioned prior art to exist and provide a kind of population parameter calibration model, simplify calibration field experiment set up, the calibration method of the polynary linear array detection imaging laser radar of the accurate many Normal planes of experimental result.

The purpose of the present invention can be achieved through the following technical solutions:

1. the calibration method of the polynary linear array detection imaging laser radar of Normal plane more than a kind, it is characterised in that comprise the following steps:

1) the High Accuracy Observation data of the plane target plank of multiple different azimuth, matching target plate plane equation are obtained；

2) by the cloud data of multiple plane target plank in polynary linear array detection imaging laser radar acquisition calibration region, including polynary distance and the polar value of angle, cloud data is carried out pretreatment, sets up multilasered optical radar systematic error calibration model based on many Normal planes；

3) according to multilasered optical radar systematic error calibration models based on many Normal planes, systematic error and elements of exterior orientation to polynary linear array detection imaging laser radar are iterated adjustment and resolve, and obtain rudimentary system error calibration parameter；

4) rudimentary system error calibration parameter is carried out elimination of rough difference, carry out statistical analysis according to the residual distribution of adjustment result, it may be judged whether containing the observation more than given threshold value, if, then rough error value rejected and return step 3), if it is not, then carry out step 5)；

5) evaluate the precision of the rudimentary system error calibration parameter after elimination of rough difference according to the distance offsets of the cloud data after correcting with target plate plane equation, obtain final calibration parameter.

Described step 1) specifically include following steps:

11) by high precision total station, target plate plane is observed, obtains the high-precision three-dimensional space coordinates being uniformly distributed discrete point in plane；

12) utilize method of least square that three dimensional space coordinate matching is obtained target plate plane equation.

Described step 2) in pretreatment be by cloud data polar value (x' under laser scanning coordinate system, y', z') rectangular coordinate value (X' based on total powerstation rectangular coordinate system is converted to, Y', Z'), the polar value of described cloud data includes radial distance, horizontal angle and vertical angle, and according to each plane ownership situation of some cloud, cloud data is carried out segmented extraction, sets up identiflication number.

The polar value of described cloud data is converted to the formula of rectangular coordinate value (X', Y', Z'):

$n=\left[\begin{array}{c}-sin2{{\mathrm{\θ}}_x}^{\′}\\ -cos2{{\mathrm{\θ}}_x}^{\′}\·sin2{{\mathrm{\θ}}_y}^{\′}-cos2{{\mathrm{\θ}}_y}^{\′}\·{\mathrm{tan\θ}}_i\\ \cos 2{{\mathrm{\θ}}_x}^{\′}\·\cos 2{{\mathrm{\θ}}_y}^{\′}-\sin 2{{\mathrm{\θ}}_y}^{\′}\·{\mathrm{tan\θ}}_i\end{array}\right]$

Wherein, (X₀,Y₀,Z₀) it is the translation parameters of laser scanning coordinate system and total station instrument coordinate system,It is referred to as elements of exterior orientation, ρ for the anglec of rotation between laser scanning coordinate system and total powerstation rectangular coordinate system, translation parameters and the anglec of rotation_i' it is the distance measure after correcting, θ_x' it is the horizontal angle surveying value after correcting, θ_y' it is the vertical angle measured value after correcting, θ_iFor the vertical angle between each probe unit of polynary linear array detection imaging laser radar, b and e is known instrument design parameter.

Described step 2) in multilasered optical radar systematic error calibration models based on many Normal planes be:

${{\mathrm{\ρ}}_i}^{\′}={\mathrm{\ρ}}_i+v_{{\mathrm{\ρ}}_i}+{\mathrm{\Δ\ρ}}_i$

Δρ_i=A_i

${{\mathrm{\θ}}_x}^{\′}={\mathrm{\θ}}_x+v_{{\mathrm{\θ}}_x}+{\mathrm{\Δ\θ}}_x$

Δθ_x=B₁+B₂sec(θ_y)+B₃tan(θ_y)

${{\mathrm{\θ}}_y}^{\′}={\mathrm{\θ}}_y+v_{{\mathrm{\θ}}_y}+{\mathrm{\Δ\θ}}_y$

Δθ_y=C₁

Wherein, ρ_iFor i-th probe unit observation, ρ_i' it is the distance measure after correcting,For the random error of i-th probe unit distance measurement value, Δ ρ_iFor the systematic error of i-th probe unit range finding, A_iFor the zero point biased error of i-th probe unit, θ_x' for polynary linear array detection imaging laser radar correct after horizontal angle value, θ_xFor the observation of polynary linear array detection imaging laser radar horizontal angle,For the correction of azimuth observation value, Δ θ_xFor the systematic error of horizontal angle measurement, B₁For the motor offset error of horizontal pendulum mirror, B₂For boresight misalignments, B₃For horizontal axis error, C₁For vertical pendulum mirror error, θ_y' for polynary linear array detection imaging laser radar correct after vertical angle value, Δ θ_yFor the systematic error of vertical angle, θ_yFor the observation of polynary linear array detection imaging laser radar vertical angle,Correction for Vertical right angle observation value.

Described step 3) in the Iterative of systematic error calibration model of polynary linear array detection imaging laser radar comprise the following steps:

31) suppose that the unit normal vector of certain plane j is n under total station instrument coordinate system_j=(a_j,b_j,c_j), the vertical dimension of the initial point of total station instrument coordinate system to this plane j is d_j, any point in this plane can be expressed as:

$\[a_j,b_j,c_j\]\left[\begin{array}{c}{X}^{\′}\\ Y^{\′}\\ Z^{\′}\end{array}\right]-d_j=0;$

32) the observation collection L (ρ of polynary linear array detection imaging laser radar is set₁,ρ₂,...,ρ_k,θ_x,θ_y) and undetermined parameter collectionThen step 31) in equation be expressed as:

$f(\hat{L},\hat{T})=0$

Wherein,For the maximal possibility estimation collection of L,Maximal possibility estimation collection for T；

33) to step 32) in formula carry out linearisation, obtaining the formula after linearisation is:

$f(L_0,T_0)+\frac{\∂f}{\∂\hat{L}}{|}_{L_0,T_0}\·V+\frac{\∂f}{\∂\hat{T}}{|}_{L_0,T_0}\·t=0$

Wherein, V is the correction of observed quantity approximation, and t is the correction of error parameter approximation, L₀ForInitial value, T₀ForInitial value,For the correction of three-dimensional laser scanner k probe unit distance observation altogether, Δ A₁、ΔA₂......ΔA_kFor the correction of k range error parameter approximation, Δ B₁、ΔB₂、ΔB₃、ΔC₁It is respectively the correction of motor offset error of horizontal pendulum mirror, the correction of boresight misalignments, the correction of horizontal axis error, the correction of numerical value pendulum mirror error,Δ ω, Δ κ, Δ X, Δ Y, Δ Z are respectively the correction of 6 elements of exterior orientation error parameter approximations, X₀,Y₀,Z₀,ω, κ are respectively 6 elements of exterior orientation error parameter approximations；

34) setting up Iterative equation, Iterative equation is:

$\underset{m\×n}{A}\underset{n\×1}{V}+\underset{m\×n}{B}\underset{n\×1}{t}-\underset{m\×1}{W}=0$

$\left\{\begin{array}{c}A=\frac{\∂f}{\∂\hat{L}}{|}_{L_0,T_0}\\ B=\frac{\∂f}{\∂\hat{L}}{|}_{L_0,T_0}\\ W=-f(L_0,T_0)+A\·(L_0-L)\end{array}\right.$

Wherein, m is the number of the point participating in adjustment, and n is observation number and n=k+2, and u is the number of undetermined parameter, and u=k+10；

35) being iterated Iterative equation resolving, iteration is initial, setsInitial value equal to L,Initial value equal to 0, in adjustment iterative process each time, L₀And T₀It is updated according to the correction after last adjustment, obtains rudimentary system error calibration parameter.

Compared with prior art, the invention have the advantages that

One, population parameter calibration model: propose the calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes, establish the population parameter calibration model of polynary linear array laser radar, the elements of exterior orientation correction overall adjustment of systematic error, random error and two coordinate systems is calculated, consider, to be accurately calculated comprehensively.

Two, simplify calibration field experiment set up: this method use multiple different directions plane target plank as datum plane, set up calibration place, can quickly, colleges and universities complete multilasered optical radar systematic error calibration work.

Three, experimental result is accurate: experiment uses the systematic error calibration method of the present invention, makes precision improvement be up to 90%, is effectively increased image quality and the certainty of measurement of polynary linear array detection imaging laser radar.

Accompanying drawing explanation

Fig. 1 is the method flow diagram of the embodiment of the present invention.

Fig. 2 is the point cloud chart in embodiment before calibration.

Fig. 3 is the point cloud chart in embodiment after calibration.

Detailed description of the invention

The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.

Embodiment:

The present invention relates to the calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes, it specifically comprises the following steps that

1) acquisition of plane target plank benchmark data: utilize high precision total station to be observed target plate plane, obtains the high-precision three-dimensional space coordinates being uniformly distributed discrete point in plane, and utilizes method of least square to go out the Datum Equations of plane according to measurement coordinate fitting；

2) acquisition of plane target plank scanner cloud data: use polynary linear array detection imaging laser radar, obtains the cloud data in calibration region, and by original polar value (radial distance, horizontal angle and vertical angle), it is converted into rectangular coordinate value (X', Y', Z')；According to each plane ownership situation of some cloud, the cloud data of polynary linear array detection imaging laser radar is carried out segmented extraction, and it is set up identiflication number；

3) systematic error calibration based on plane resolves: utilize multilasered optical radar systematic error calibration model based on plane, uses the method that repeating adjustmet resolves；

4) resolve the robust estimation of parameter: utilize the residual distribution of adjustment result to carry out statistical analysis, detect the corresponding raw observation more than given threshold value, rough error value is rejected and re-started previous step and resolves, until calculating optimal calibration parameter；

5) accuracy assessment of parameter is resolved: with reference value comparative analysis after raw observation being corrected resolving system error parameter, count the precision of final argument.

This polynary linear array detection of three dimensional laser radar scanner uses 16 laser acquisition unit, horizontal and vertical angular samples rate is 2mrad, in the range of 50～100m, the interval of adjacent scanning element can reach 10cm～20cm, and i.e. at 100m, the laser spots density of scanning is about 25 points/m2.Calibration field puts 11 surface plates with different angle and orientation altogether, and the size of each plane is 4m × 2m, and volume is 1 to No. 11, for laser radar scanner systematic error calibration the most successively.

Original point cloud is as shown in Figure 2, there is range finding and the angle error of multiple probe unit in the polynary linear array detection imaging laser radar due to non-calibration, and the systematic error of each probe unit differing, therefore original point cloud cannot reflect real plan-position and shape, horizontal sweep motor also exists angular error simultaneously, and plane also exists on different scanning band and is substantially misaligned phenomenon.

Use the calibration method of based on plane the polynary linear array detection imaging laser radar of present invention proposition, polynary linear array detection imaging laser radar is carried out calibration.Point cloud after calibration is as it is shown on figure 3, flat shape can be gone out actual response, and diversity bigger between the different probe units being originally present, also basic correction, the inconsistent phenomenon between each scanning strip is eliminated.

Plane each before and after calibration is fitted, and calculates each point cloud range deviation (i.e. plane fitting error) to respective planes equation, evaluate calibration quality.Respectively can be seen that from table 1, the flatness of each plane, middle error before calibration is substantially at about 30cm, after calibration, error significantly reduces, in addition to No. 1 of edge and No. 11 planes, the flatness of remaining plane is better than 4cm, precision is the highest improves 90%, owing to the Hardware Design affects, the polynary linear array detection imaging laser radar optimum level angle of visual field of experiment is ± 12 °, 1 and No. 11 plane is positioned at horizontal field of view edge, 13 ° are reached with the angle of field of view center line, although not within optimal field range, but after calibration flatness can also reach 7.5cm, prove that the method can be effectively improved certainty of measurement and the image quality of polynary linear array detection imaging laser radar.

Table 1 calibration anterior-posterior plane precision

The calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes that this patent proposes, on the basis of need not use special hardware device, the random error of elements of exterior orientation, polynary errors of the distance measurement system, horizontal angle error, vertical angle error and each observation is carried out unified Modeling, and use method based on plane, systematic error is accurately calculated.Use context of methods that domestic polynary linear array detection imaging laser radar is carried out systematic error calibration, planar smoothness after calibration can be better than 4cm, precision improvement is up to 90%, is effectively increased image quality and the certainty of measurement of polynary linear array detection imaging laser radar.

Claims (5)

1. the calibration method of the polynary linear array detection imaging laser radar of Normal plane more than a kind, it is characterised in that comprise the following steps:

1) the High Accuracy Observation data of the plane target plank of multiple different azimuth, matching target plate plane equation are obtained；

2) by the cloud data of multiple plane target plank in polynary linear array detection imaging laser radar acquisition calibration region, including polynary distance and the polar value of angle, cloud data is carried out pretreatment, set up multilasered optical radar systematic error calibration model based on many Normal planes, described step 2) in multilasered optical radar systematic error calibration models based on many Normal planes be:

${{\mathrm{\ρ}}_i}^{\′}={\mathrm{\ρ}}_i+v_{{\mathrm{\ρ}}_i}+{\mathrm{\Δ\ρ}}_i$

Δρ_i=A_i

${{\mathrm{\θ}}_x}^{\′}={\mathrm{\θ}}_x+v_{{\mathrm{\θ}}_x}+{\mathrm{\Δ\θ}}_x$

Δθ_x=B₁+B₂sec(θ_y)+B₃tan(θ_y)

${{\mathrm{\θ}}_y}^{\′}={\mathrm{\θ}}_y+v_{{\mathrm{\θ}}_y}+{\mathrm{\Δ\θ}}_y$

Δθ_y=C₁

Wherein, ρ_iFor i-th probe unit observation, ρ_i' it is the distance measure after correcting,For the random error of i-th probe unit distance measurement value, Δ ρ_iFor the systematic error of i-th probe unit range finding, A_iFor the zero point biased error of i-th probe unit, θ_x' for polynary linear array detection imaging laser radar correct after horizontal angle value, θ_xFor the observation of polynary linear array detection imaging laser radar horizontal angle,For the correction of azimuth observation value, Δ θ_xFor the systematic error of horizontal angle measurement, B₁For the motor offset error of horizontal pendulum mirror, B₂For boresight misalignments, B₃For horizontal axis error, C₁For vertical pendulum mirror error, θ_y' for polynary linear array detection imaging laser radar correct after vertical angle value, Δ θ_yFor the systematic error of vertical angle, θ_yFor the observation of polynary linear array detection imaging laser radar vertical angle,Correction for Vertical right angle observation value；

3) according to multilasered optical radar systematic error calibration models based on many Normal planes, systematic error and elements of exterior orientation to polynary linear array detection imaging laser radar are iterated adjustment and resolve, and obtain rudimentary system error calibration parameter；

4) rudimentary system error calibration parameter is carried out elimination of rough difference, carry out statistical analysis according to the residual distribution of adjustment result, it may be judged whether containing the observation more than given threshold value, if, then rough error value rejected and return step 3), if it is not, then carry out step 5)；

5) evaluate the precision of the rudimentary system error calibration parameter after elimination of rough difference according to the distance offsets of the cloud data after correcting with target plate plane equation, obtain final calibration parameter.

The calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes the most according to claim 1, it is characterised in that described step 1) specifically include following steps:

11) by high precision total station, target plate plane is observed, obtains the high-precision three-dimensional space coordinates being uniformly distributed discrete point in plane；

12) utilize method of least square that three dimensional space coordinate matching is obtained target plate plane equation.

The calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes the most according to claim 1, it is characterized in that, described step 2) in pretreatment be by cloud data polar value (x' under laser scanning coordinate system, y', z') rectangular coordinate value (X' based on total powerstation rectangular coordinate system is converted to, Y', Z'), the polar value of described cloud data includes radial distance, horizontal angle and vertical angle, and according to each plane ownership situation of some cloud, cloud data is carried out segmented extraction, sets up identiflication number.

The calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes the most according to claim 3, it is characterised in that the polar value of described cloud data is converted to the formula of rectangular coordinate value (X', Y', Z') and is:

$n=\left[\begin{array}{c}-sin2{{\mathrm{\θ}}_x}^{\′}\\ -cos2{{\mathrm{\θ}}_x}^{\′}\·sin2{{\mathrm{\θ}}_y}^{\′}-cos2{{\mathrm{\θ}}_y}^{\′}\·{\mathrm{tan\θ}}_i\\ \cos 2{{\mathrm{\θ}}_x}^{\′}\·\cos 2{{\mathrm{\θ}}_y}^{\′}-\sin 2{{\mathrm{\θ}}_y}^{\′}\·{\mathrm{tan\θ}}_i\end{array}\right]$

Wherein, (X₀,Y₀,Z₀) it is the translation parameters of laser scanning coordinate system and total station instrument coordinate system,It is referred to as elements of exterior orientation, ρ for the anglec of rotation between laser scanning coordinate system and total powerstation rectangular coordinate system, translation parameters and the anglec of rotation_i' it is the distance measure after correcting, θ_x' it is the horizontal angle surveying value after correcting, θ_y' it is the vertical angle measured value after correcting, θ_iFor the vertical angle between each probe unit of polynary linear array detection imaging laser radar, b and e is known instrument design parameter.

The calibration method of the polynary linear array detection imaging laser radar of a kind of many Normal planes the most according to claim 1, it is characterized in that, described step 3) in the Iterative of systematic error calibration model of polynary linear array detection imaging laser radar comprise the following steps:

31) suppose that the unit normal vector of certain plane j is n under total station instrument coordinate system_j=(a_j,b_j,c_j), the vertical dimension of the initial point of total station instrument coordinate system to this plane j is d_j, any point in this plane can be expressed as:

$\[a_j,b_j,c_j\]\left[\begin{array}{c}{X}^{\′}\\ Y^{\′}\\ Z^{\′}\end{array}\right]-d_j=0;$

32) the observation collection L (ρ of polynary linear array detection imaging laser radar is set₁,ρ₂,...,ρ_k,θ_x,θ_y) and undetermined parameter collectionThen step 31) in equation be expressed as:

$f(\hat{L},\hat{T})=0$

Wherein,For the maximal possibility estimation collection of L,Maximal possibility estimation collection for T；

33) to step 32) in formula carry out linearisation, obtaining the formula after linearisation is:

$f(L_0,T_0)+\frac{\∂f}{\∂\hat{L}}{|}_{L_0,T_0}\·V+\frac{\∂f}{\∂\hat{T}}{|}_{L_0,T_0}\·t=0$

Wherein, V is the correction of observed quantity approximation, and t is the correction of error parameter approximation, L₀ForInitial value, T₀ForInitial value,For the correction of three-dimensional laser scanner k probe unit distance observation altogether, Δ A₁、ΔA₂......ΔA_kFor the correction of k range error parameter approximation, Δ B₁、ΔB₂、ΔB₃、ΔC₁It is respectively the correction of motor offset error of horizontal pendulum mirror, the correction of boresight misalignments, the correction of horizontal axis error, the correction of numerical value pendulum mirror error,Δ ω, Δ κ, Δ X, Δ Y, Δ Z are respectively the correction of 6 elements of exterior orientation error parameter approximations, X₀,Y₀,Z₀,ω, κ are respectively 6 elements of exterior orientation error parameter approximations；

34) setting up Iterative equation, Iterative equation is:

$\underset{m\×n}{A}\underset{n\×1}{V}+\underset{m\×u}{B}\underset{u\×1}{t}-\underset{m\×1}{W}=0$

$\left\{\begin{array}{c}A=\frac{\∂f}{\∂\hat{L}}{|}_{L_0,T_0}\\ B=\frac{\∂f}{\∂\hat{T}}{|}_{L_0,T_0}\\ W=-f\left(L_0,T_0\right)+A\·\left(L_0-L\right)\end{array}\right.$

Wherein, m is the number of the point participating in adjustment, and n is observation number and n=k+2, and u is the number of undetermined parameter, and u=k+10；

35) being iterated Iterative equation resolving, iteration is initial, setsInitial value equal to L,Initial value equal to 0, in adjustment iterative process each time, L₀And T₀It is updated according to the correction after last adjustment, obtains rudimentary system error calibration parameter.