CN110095123B - Method for evaluating and optimizing observation information of road signs on surface of irregular small celestial body - Google Patents

Method for evaluating and optimizing observation information of road signs on surface of irregular small celestial body Download PDF

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CN110095123B
CN110095123B CN201910466275.7A CN201910466275A CN110095123B CN 110095123 B CN110095123 B CN 110095123B CN 201910466275 A CN201910466275 A CN 201910466275A CN 110095123 B CN110095123 B CN 110095123B
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matrix
meteorite
crater
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CN110095123A (en
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朱圣英
修义
崔平远
徐瑞
梁子璇
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Beijing Institute of Technology BIT
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
    • G01C21/20—Instruments for performing navigational calculations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
    • G01C21/24—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 specially adapted for cosmonautical navigation

Abstract

The invention discloses an evaluation optimization method for road sign observation information of an irregular small celestial body surface, belonging to the field of autonomous navigation. The implementation method of the invention comprises the following steps: detecting and extracting meteor crater observation information on the surface of the small celestial body in the navigation camera image by using an image processing algorithm; carrying out ellipse fitting and meteor crater center positioning on the detected and extracted meteor craters, and solving an error uncertainty matrix R of the meteor craters according to uncertainty propagation characteristics by using a fitted ellipse equation; constructing an observation matrix H by using pixel coordinates and image line coordinates of the navigation road sign observed in the navigation image; and constructing an evaluation index function based on R and H, simultaneously considering the observation error and the position configuration distribution of the navigation road signs, optimally selecting the optimal navigation road signs, and determining the position posture of the deep space probe based on the selected optimal meteor crater navigation road signs, thereby improving the navigation precision of the position posture of the deep space probe.

Description

Method for evaluating and optimizing observation information of road signs on surface of irregular small celestial body
Technical Field
The invention relates to an evaluation optimization selection method for observation information of an optical navigation road sign of a deep space probe on the surface of an irregular small celestial body, in particular to an evaluation optimization selection method for a navigation system which is suitable for carrying out autonomous determination on the position and the posture of the deep space probe by using a meteorite crater road sign as the observation information, and belongs to the field of autonomous navigation.
Background
The near-target celestial body flight is one of the most core tasks of deep space exploration in the future, the deep space exploration has long navigation distance and long time, and the traditional measurement and control mode has larger communication delay. In addition, the deep space dynamic environment is complex, the traditional navigation and control mode based on ground remote control cannot meet the requirement of realizing high-precision detection, and the detector is required to have an autonomous navigation function. With the breakthrough of computer hardware technology and the development of optical sensitive devices, the autonomous optical navigation method based on the spaceborne computer and the optical navigation camera becomes a research hotspot. The meteorite crater morphological characteristics on the small celestial body surface are used as natural geographic terrain road signs, the visibility and the distinguishability are high, a detector does not need to additionally carry road sign loads, the task complexity is effectively reduced, and the application prospect is wide.
The autonomous navigation method of the deep space probe based on meteor crater observation information as a navigation road sign has become a research hotspot at present, wherein, how to select a proper road sign from a plurality of navigation road signs and carry out six-degree-of-freedom state estimation of position and attitude through observed navigation road sign pixel information is a key technology based on road sign navigation, which directly influences the calculation efficiency of a software algorithm and the autonomous positioning capability of the probe and determines whether a detection task can be successfully completed, so the autonomous selection method of road sign navigation is one of key problems concerned by current science and technology personnel.
In the developed navigation landmark automatic selection method, in the prior art [1] (S.Zhu, D.Liu, Y.Liu, et al, observer-based visual navigation using landmark measuring and angle for mapping, Acta astronaut.155(2019)313-324), the road landmark navigation measurement degree is discussed through the line-of-sight angle observation matrix, the influence of the navigation landmark spatial distribution on the pose determination precision is analyzed, and the navigation landmark optimal selection method based on the Observability degree is provided. However, the observation matrix in the method is established on the basis of observation angles among navigation road signs, the structure of the observation matrix is more complex along with the increase of the number of the road signs, the resolving time is greatly increased, and the requirement of autonomous navigation real-time performance of the deep space probe cannot be met.
In the prior art [2] (see Chi Pingyuan and the like, an observation matrix-based autonomous navigation road sign selection method for a deep space probe, namely ZL 201010103514.1 [ P ],2012-01-04), aiming at the problem that the current deep space probe based on road sign navigation does not have an accurate and feasible autonomous navigation road sign selection method, the influence of a navigation road sign and a position relationship between the navigation road sign and a detector on navigation precision is considered, pixel information of three road signs is selected to autonomously determine the position and the posture of the deep space probe, and the autonomous navigation road sign selection method for the deep space probe based on the observation matrix is provided. However, the method only considers the configuration of the navigation road sign, and does not evaluate the quality of the navigation road sign, so that the method is only suitable for the condition that the observation states of the navigation road signs are the same.
In the prior art [3] (see Chi Pingyuan and the like, an observation condition number-based autonomous positioning signpost selection method for a deep space probe, China, ZL 201010103515.6 [ P ],2011-11-09) considers the influence of a signpost position on navigation precision, selects two signposts to construct the position of the probe under a target celestial body fixed connection coordinate system based on condition numbers of an observation equation by calculating and comparing condition numbers of an observation matrix, and provides an accurate and feasible positioning signpost autonomous selection method for the deep space probe flying at a low orbit. However, the method neglects the observation errors of different navigation road signs, and is not suitable for selecting the navigation road signs on the surface of the antenna in the actual task of the deep space probe.
In the process of carrying out autonomous navigation on the deep space probe by using meteor crater observation information, the meteor crater detection and identification inevitably have observation errors, so that the error uncertainty of different meteor craters is different. The existing autonomous optical navigation method for the deep space probe does not consider the influence of uncertainty of meteorite pit navigation road signs and does not comprehensively evaluate the observation quality and position distribution of different navigation road signs, so that the autonomous selection method for the navigation road signs of the deep space probe is not accurate enough, and the estimation precision of the position and pose of the probe is low.
Disclosure of Invention
The method aims to solve the problem that the existing deep space probe navigation landmark selection method does not consider the influence of uncertainty of meteorite pit navigation landmark errors, and further the navigation landmark autonomous selection method is not accurate enough. The invention discloses an evaluation optimization method for road sign observation information on the surface of an irregular small celestial body, which aims to solve the technical problems that: meanwhile, the observation error uncertainty and the spatial distribution of different meteorite pits on the surface of the small irregular celestial body are considered, the observation error uncertainty is integrated into an evaluation index, and the navigation road sign with the minimum observation error is selected on the basis of considering the configuration, so that the selection accuracy of the navigation road sign of the deep space detector is improved, and the navigation accuracy of the position posture of the deep space detector is improved. The invention is suitable for a navigation system which uses meteorite crater road signs as observation information to independently determine the position and the posture of the deep space probe.
The invention is realized by the following technical scheme.
The invention discloses an evaluation optimization method for observation information of road signs on the surface of an irregular small celestial body. And carrying out ellipse fitting and meteor crater center positioning on the detected and extracted meteor craters, and solving an error uncertainty matrix R of the meteor craters according to uncertainty propagation characteristics by using a fitted ellipse equation. And constructing an observation matrix H by using the pixel coordinates and the image line coordinates of the navigation road signs observed in the navigation image. And constructing an evaluation index function based on R and H, simultaneously considering the observation error and the position configuration distribution of the navigation road signs, optimally selecting the optimal navigation road signs, and determining the position posture of the deep space probe based on the selected optimal meteor crater navigation road signs, thereby improving the navigation precision of the position posture of the deep space probe.
The invention discloses an evaluation optimization method for road sign observation information of an irregular small celestial body surface, which comprises the following steps:
step 1: detecting and extracting the meteor craters on the small celestial body surface by using an image processing algorithm in the navigation camera image, fitting the detected and extracted meteor crater edge information to obtain an elliptic equation, and realizing the positioning of the meteor craters by a centroid formula.
After reading the topographic image of the surface of the target celestial body shot by the optical camera, detecting and extracting the meteorite crater edge of the image based on an image processing algorithm, and obtaining meteorite crater information of the small celestial body surface, namely the pixel value of the meteorite crater edge point. For each meteorite crater navigation road sign, when not less than five meteorite crater boundary points are observed, determining coefficients B, C, D, E and F of a meteorite crater fitting elliptic equation through an elliptic fitting algorithm, and further obtaining the fitting elliptic equation of the meteorite crater edge as
x2+2Bxy+Cy2+2Dx+2Ey+F＝0 (1)
Determining the center O (x) of the fitted ellipse by centroid equation (2)0,y0) And realizing the positioning of the meteorite crater.
Figure BDA0002079487350000031
Preferably, to facilitate the analytical solution, the coefficients B, C, D, E, F of the merle crate edge fitting ellipse equation are determined by the least squares method.
Step 2: and (4) solving an error uncertainty matrix R by using the fitted elliptic equation in the step 1 according to the error uncertainty propagation characteristic.
Writing n elliptical equations in the form of formula (1) for n edge points for each meteorite crater navigation road sign, solving a covariance matrix P of elliptical equation coefficients through observation errors V, and generating an error covariance matrix of each meteorite crater from the covariance matrix P of elliptical equation coefficients according to covariance propagation law
Figure BDA0002079487350000032
K is a matrix formed by solving partial derivatives of elliptic equation coefficients B, C, D, E and F by the centroid formula (2) in the step 1.
Figure BDA0002079487350000041
Then m meteorite crater navigation signpost pairs of state variables are observed
Figure BDA0002079487350000042
Has an error uncertainty matrix of R
Figure BDA0002079487350000043
Further, the step 2 is realized by the following specific method:
for each meteorite crater navigation road sign, n edge points exist and are xi＝(xi,yi) And i is 1,2,.. n, writing n fitting elliptical equations for the n edge points by using the elliptical equation fitted in the step 1, and expressing an error equation as a matrix
Figure BDA0002079487350000044
Order to
Figure BDA0002079487350000045
The error equation is written as V ═ AX + Y. Observation error v of ith edge pointiHas a variance of
Figure BDA0002079487350000046
Wherein the content of the first and second substances,
Figure BDA0002079487350000047
I2×2is an identity matrix of 2 × 2,
Figure BDA0002079487350000048
is the variance of the ith edge point of the meteorite crater,
Figure BDA0002079487350000049
variance matrix of observation error V
Figure BDA00020794873500000410
Is composed of
Figure BDA00020794873500000411
The covariance matrix P of the elliptic equation coefficients is defined as
Figure BDA0002079487350000051
Wherein A isTA is called autocorrelation matrix, In×nIs the unit matrix of n × n finally, the error covariance matrix of each meteorite crater center is generated from P according to the covariance propagation law
Figure BDA0002079487350000052
Figure BDA0002079487350000053
Wherein K is a matrix formed by solving partial derivatives of elliptic equation coefficients B, C, D, E and F by the centroid formula (2) in the step 1;
Figure BDA0002079487350000054
Figure BDA0002079487350000055
then the error uncertainty matrix of m meteorite crater navigation signposts to the state variable is observed to be R
Figure BDA0002079487350000056
And step 3: pixel coordinate x of m meteorite crater navigation road signs observed in navigation image0jAnd the image line coordinate y0jAnd constructing an observation matrix H.
The position of the jth navigation landmark is rho under the fixed connection coordinate system of the small celestial bodyj＝(Xj,Yj,Zj)TJ-1, 2.. times, m, and r-X (X, Y, Z) coordinate of the detector three-axis positionTThe three-axis attitude is
Figure BDA0002079487350000057
The conversion matrix of the detector body coordinate system relative to the target celestial body fixed coordinate system is CbaThen, under the coordinate system of the detector body, the position of the jth navigation road sign is
Figure BDA0002079487350000058
When the coordinate system of the camera is coincident with the coordinate system of the detector body, the pixel x of the jth navigation road sign is determined according to the collinear equation (14) of the camera0jAnd the image line coordinate y0jIs shown as
Figure BDA0002079487350000061
Wherein X, Y and Z are three-axis position coordinates of the detector in a small celestial body fixed connection coordinate system, and X isj,Yj,ZjThree-axis position coordinates for the jth landmark, cijTo convert matrix CbaAnd f is the focal length of the navigation camera. Then the observed quantity h of the m meteorite crater navigation signposts is
h(r,Cba)＝[x01,y01,...,x0m,y0m]T(15)
The observation matrix of the jth landmark is 1,2
Figure BDA0002079487350000062
All meteorite crater navigation signposts detected and identified are used for observing state variables, and the observation matrix H is
Figure BDA0002079487350000063
And 4, step 4: and constructing an evaluation index function J based on the error uncertainty matrix R and the observation matrix H, and optimizing and selecting the optimal navigation road sign by considering the observation error and the position configuration distribution of the navigation road sign.
The selection criteria are: when m meteorite crater navigation landmarks are detected and extracted in the step 1, the number of expected selected meteorite crater navigation landmarks is N, N meteorite crater landmarks are randomly selected from the m meteorite craters detected and extracted, a structure objective function J is used as an evaluation index of the N meteorite craters, and the N meteorite craters which can enable the J to be minimum are selected, namely the optimal landmarks in the m meteorite crater navigation landmarks. A model of the optimal road sign selection problem is shown below
min J＝tr[(HTΛH)-1HT(ΛR)H(HTΛH)-1](18)
Figure BDA0002079487350000064
Figure BDA0002079487350000065
Wherein, tr [ alpha ], [ alpha ]]Traces of the matrix, wjAnd Λ is a decision matrix used for randomly selecting N meteorite craters from m meteorite craters, and the solution meeting the optimal road sign selection problem is the optimal navigation road sign obtained by simultaneously considering the uncertainty of the observation error and the position distribution of the road sign, so that the accuracy of the navigation road sign selection of the deep space probe is improved.
Further comprising the step 5: and (4) determining the position posture of the deep space detector based on the optimal meteorite pit navigation road sign selected in the step (4), so that the navigation precision of the position posture of the deep space detector is improved.
Has the advantages that:
the invention discloses an evaluation optimization method for observation information of a road sign on the surface of an irregular small celestial body. Carrying out ellipse fitting and meteor crater center positioning on the detected and extracted meteor crater information; solving an error uncertainty matrix R of the meteorite crater by utilizing a fitted elliptic equation according to uncertainty propagation characteristics, and constructing an observation matrix H by utilizing pixel coordinates and image line coordinates of the navigation road sign observed in the navigation image; and constructing an evaluation index function based on the R and the H, and simultaneously considering the observation error and the position configuration distribution of the navigation road signs, optimally selecting the optimal navigation road signs, and improving the accuracy of selecting the navigation road signs of the deep space probe, thereby improving the navigation accuracy of the position posture of the deep space probe.
Drawings
FIG. 1 is a schematic flow chart of an observation information evaluation optimization method for road signs on the surface of an irregular small celestial body according to the invention;
FIG. 2 is a schematic view of the navigation relationship of the deep space probe in the present invention for observing a target celestial body;
FIG. 3 is a schematic diagram of the image processing effect of step 1 in the example of the present invention, in which FIG. 3(a) is reading an original image, FIG. 3(b) is Gaussian noise filtering, FIG. 3(c) is edge detection, FIG. 3(d) is non-edge point rejection, FIG. 3(e) is false edge removal, and FIG. 3(f) is ellipse fitting and positioning;
FIG. 4 is a schematic diagram of the image processing and landmark selection results for the meteor crater landmarks in step 3 in the example of the present invention, where FIG. 4(a) is the original image captured by the navigation camera, FIG. 4(b) is the image of all the meteor crater landmarks detected and extracted after the image processing, FIG. 4(c) is the landmark selection result map considering only the position distribution, and FIG. 4(d) is the selection result map of the method of the present invention;
fig. 5 is a monte carlo simulation result of step 5 in the example of the present invention under the condition of adding 2 noises in the image, wherein fig. 5(a) is a simulation result graph of the attitude error, and fig. 5(b) is a simulation result graph of the position error.
Detailed Description
For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
In order to verify the feasibility of the invention, all the landmarks detected by the meteorite crater through image processing identification are drawn on the original drawing by utilizing the shot meteorite crater image information on the surface of the small celest 433, and adding the image noise of 2 pixels, as shown in fig. 4 (b). Defining the three-dimensional coordinates of each meteorite crater navigation road sign in a small celestial body fixed connection coordinate system, wherein the initial position of a detector in the small celestial body fixed connection coordinate system is [ -300 ℃; 50; 2000 m, initial attitude [ 6; -8; 10 deg. and the detector navigation relationship with the image plane and the planet surface is shown in figure 2. And (5) carrying out simulation verification with the field angle of 30 degrees and the focal length f of the navigation camera of 8 mm.
As shown in fig. 1, the method for evaluating and optimizing observation information of landmarks on the surface of an irregular small celestial body disclosed in this embodiment includes the following specific steps:
step 1: detecting and extracting the meteor craters on the small celestial body surface by using an image processing algorithm in the navigation camera image, fitting the detected and extracted meteor crater edge information to obtain an elliptic equation, and realizing the positioning of the meteor craters by a centroid formula.
After reading the topographic image of the surface of the target celestial body shot by the optical camera, detecting and extracting the meteor crater edge of the image through a Canny operator, and obtaining the meteor crater information of the small celestial body surface, namely the pixel value of the meteor crater edge point. When observing that the meteorite crater boundary points are not less than five, determining coefficients B, C, D, E and F of the meteorite crater fitting elliptic equation by the least square method, and further obtaining the fitting elliptic equation of the meteorite crater edge as
x2+2Bxy+Cy2+2Dx+2Ey+F＝0 (21)
Determining the center O (x) of the fitted ellipse by centroid equation (2)0,y0) And realizing the positioning of the meteorite crater.
Figure BDA0002079487350000081
Taking a single meteorite crater as an example, the processing procedure is shown in FIG. 3, and the processing result is shown in FIG. 3(f) and FIG. 4(b), wherein the yellow dots in FIG. 3(f) and FIG. 4(b) are the edge points extracted by detection, the red ellipse is the fitting ellipse of the meteorite crater edge, and the green dot is the positioning center.
Step 2: and (4) solving an error uncertainty matrix R by using the fitted elliptic equation in the step 1 according to the error uncertainty propagation characteristic.
For each meteorite crater navigation road sign, n edge points exist and are xi＝(xi,yi) And i is 1,2,.. n, writing n fitting elliptical equations for the n edge points by using the elliptical equation fitted in the step 1, and expressing an error equation as a matrix
Figure BDA0002079487350000091
Order to
Figure BDA0002079487350000092
The error equation is written as V ═ AX + Y. Observation error v of ith edge pointiHas a variance of
Figure BDA0002079487350000093
Wherein the content of the first and second substances,
Figure BDA0002079487350000094
I2×2is an identity matrix of 2 × 2,
Figure BDA0002079487350000095
is the variance of the ith edge point of the meteorite crater,
Figure BDA0002079487350000096
variance matrix of observation error V
Figure BDA0002079487350000097
Is composed of
Figure BDA0002079487350000098
The covariance matrix P of the elliptic equation coefficients is defined as
Figure BDA0002079487350000099
Wherein A isTA is called autocorrelation matrix, In×nIs the unit matrix of n × n finally, the error covariance matrix of each meteorite crater center is generated from P according to the covariance propagation law
Figure BDA00020794873500000910
Figure BDA00020794873500000911
Wherein K is a matrix formed by solving partial derivatives of elliptic equation coefficients B, C, D, E and F by the centroid formula (2) in the step 1.
Figure BDA00020794873500000912
Figure BDA0002079487350000101
Then the error uncertainty matrix of m meteorite crater navigation signposts to the state variable is observed to be R
Figure BDA0002079487350000102
And step 3: pixel coordinate x of m meteorite crater navigation road signs observed in navigation image0jAnd the image line coordinate y0jAnd constructing an observation matrix H.
The position of the jth navigation landmark is rho under the fixed connection coordinate system of the small celestial bodyj＝(Xj,Yj,Zj)TJ-1, 2.. times, m, and r-X (X, Y, Z) coordinate of the detector three-axis positionTThe three-axis attitude is
Figure BDA0002079487350000103
The conversion matrix of the detector body coordinate system relative to the target celestial body fixed coordinate system is CbaThen, under the coordinate system of the detector body, the position of the jth navigation road sign is
Figure BDA0002079487350000104
When the coordinate system of the camera is coincident with the coordinate system of the detector body, the pixel x of the jth navigation road sign is determined according to the collinear equation (14) of the camera0jAnd the image line coordinate y0jIs shown as
Figure BDA0002079487350000105
Wherein X, Y and Z are three-axis position coordinates of the detector in a small celestial body fixed connection coordinate system, and X isj,Yj,ZjThree-axis position coordinates for the jth landmark, cijTo convert matrix CbaAnd f is the focal length of the navigation camera. Then the observed quantity h of the m meteorite crater navigation signposts is
h(r,Cba)＝[x01,y01,...,x0m,y0m]T(33)
The observation matrix of the jth landmark is 1,2
Figure BDA0002079487350000106
All meteorite crater navigation signposts detected and identified are used for observing state variables, and the observation matrix H is
Figure BDA0002079487350000111
And 4, step 4: and constructing an evaluation index function J based on the error uncertainty matrix R and the observation matrix H, and optimizing and selecting the optimal navigation road sign by considering the observation error and the position configuration distribution of the navigation road sign.
The selection criteria are: when m meteorite crater navigation landmarks are detected and extracted in the step 1, the number of expected selected meteorite crater navigation landmarks is N, N meteorite crater landmarks are randomly selected from the m meteorite craters detected and extracted, a structure objective function J is used as an evaluation index of the N meteorite craters, and the N meteorite craters which can enable the J to be minimum are selected, namely the optimal landmarks in the m meteorite crater navigation landmarks. A model of the optimal road sign selection problem is shown below
min J＝tr[(HTΛH)-1HT(ΛR)H(HTΛH)-1](36)
Figure BDA0002079487350000112
Figure BDA0002079487350000113
Wherein, tr [ alpha ], [ alpha ]]Traces of the matrix, wjAnd Λ is a decision matrix used for randomly selecting N meteorite craters from m meteorite craters, and the solution meeting the optimal road sign selection problem is the optimal navigation road sign obtained by simultaneously considering the uncertainty of the observation error and the position distribution of the road sign, so that the accuracy of the navigation road sign selection of the deep space probe is improved.
Taking the irregular small celestial body Eros 433 surface image captured in FIG. 4(a) as an example, 24 meteorite craters are detected and extracted by the image processing in step 1, as shown in FIG. 4 (b). If the task needs to select 4 meteorite craters as navigation signposts for subsequent pose determination, 4 meteorite crater navigation signposts which simultaneously meet the requirements of minimum observation error and optimal configuration are optimally selected by the method, preferably the signposts are No. 1,12,18 and 23 meteorite craters as shown in figure 4(d), and the signposts selected only by considering the position distribution of the signposts are No. 1,8,18 and 23 meteorite craters as shown in figure 4(c), and the difference of the selection results can be seen, the method removes the signpost with larger observation uncertainty, namely the No. 8 meteorite crater, and replaces the signpost with the No. 12 meteorite crater with smaller uncertainty at the expense of partial configuration effect.
Further comprising the step 5: and (4) determining the position posture of the deep space detector based on the optimal meteorite pit navigation road sign selected in the step (4), so that the navigation precision of the position posture of the deep space detector is improved.
The 4 meteorite craters selected by the method for evaluating and optimizing the road sign observation information of the small irregular celestial body surface can be used for determining the posture of the position of the detector. To verify the superiority of the meteor crater selected by the method of the present embodiment, the position pose of the probe is estimated using the POSIT algorithm. Through 1000 Monte Carlo simulations, the influence of the meteor crater road signs selected by considering the observation error of the navigation road signs and the position distribution and only considering the position distribution (configuration) of the road signs on the attitude estimation precision is compared, and the Monte Carlo simulation results of the position attitude errors of the two selection methods are shown in FIG. 5. The pose solution results are shown in table 1.
TABLE 1 pose determination results for the method of this example and the method considering only configuration
Figure BDA0002079487350000121
It can be seen through 1000 Monte Carlo simulations that the meteorite crater signpost selected by the method has higher pose estimation accuracy and stability no matter the mean value or the standard deviation, so that the effectiveness of the selection result is verified. Therefore, the influence of the observation uncertainty of the navigation road signs on the pose determination precision is large, and the method disclosed by the invention integrates the observation error uncertainty of the navigation road signs on the basis of considering the distribution configuration of the navigation road signs, so that the selected meteorite navigation road signs not only have good position distribution, but also have higher observation quality, and further the pose estimation precision of the deep space probe is improved.
The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. The method for evaluating and optimizing the road sign observation information of the surface of the irregular small celestial body is characterized by comprising the following steps of: comprises the following steps of (a) carrying out,
step 1: detecting and extracting meteor craters on the small celestial body surface in a navigation camera image by using an image processing algorithm, fitting the detected and extracted meteor crater edge information to obtain an elliptic equation, and realizing the positioning of the meteor craters by using a centroid formula;
step 2: solving an error uncertainty matrix R by using the fitted elliptic equation in the step 1 according to the error uncertainty propagation characteristic;
and step 3: pixel coordinate x of m meteorite crater navigation road signs observed in navigation image0jAnd the image line coordinate y0jConstructing an observation matrix H;
and 4, step 4: constructing an evaluation index function J based on the error uncertainty matrix R and the observation matrix H, and optimizing and selecting an optimal navigation road sign by considering the observation error and the position configuration distribution of the navigation road sign;
wherein, the step 3 is realized by the following steps,
the position of the jth navigation landmark is rho under the fixed connection coordinate system of the small celestial bodyj＝(Xj,Yj,Zj)TJ-1, 2.. times, m, and r-X (X, Y, Z) coordinate of the detector three-axis positionTThe three-axis attitude is
Figure FDA0002488806590000011
Detector body coordinate system is connected with target celestial bodyTransformation matrix of coordinate system to CbaThen, under the coordinate system of the detector body, the position of the jth navigation road sign is
Figure FDA0002488806590000012
When the coordinate system of the camera is coincident with the coordinate system of the detector body, the pixel coordinate x of the jth navigation road sign is determined according to the collinear equation (6) of the camera0jAnd the image line coordinate y0jIs shown as
Figure FDA0002488806590000013
Wherein X, Y and Z are three-axis position coordinates of the detector in a small celestial body fixed connection coordinate system, and X isj,Yj,ZjThree-axis position coordinates for the jth landmark, cijTo convert matrix CbaCorresponding element in the navigation camera, f is the focal length of the navigation camera; then the observed quantity h of the m meteorite crater navigation signposts is
h(r,Cba)＝[x01,y01,...,x0m,y0m]T(7)
Then the observation matrix for the jth landmark is
Figure FDA0002488806590000021
All meteorite crater navigation signposts detected and identified are used for observing state variables, and the observation matrix H is
Figure FDA0002488806590000022
2. The method for evaluating and optimizing observation information of landmarks on the surface of irregular small celestial bodies of claim 1, wherein: and 5, determining the position posture of the deep space probe based on the optimal meteor crater navigation signpost selected in the step 4, thereby improving the navigation precision of the position posture of the deep space probe.
3. The method for evaluating and optimizing observation information of landmarks on the surface of irregular celestial bodies of claim 1 or 2, wherein: the step 1 is realized by the method that,
after reading a topographic image of the surface of a target celestial body shot by an optical camera, detecting and extracting the meteorite crater edge of the image based on an image processing algorithm to obtain meteorite crater information of the small celestial body surface, namely the pixel value of a meteorite crater edge point; for each meteorite crater navigation road sign, when not less than five meteorite crater boundary points are observed, determining coefficients B, C, D, E and F of a meteorite crater fitting elliptic equation through an elliptic fitting algorithm, and further obtaining the fitting elliptic equation of the meteorite crater edge as
x2+2Bxy+Cy2+2Dx+2Ey+F＝0 (1)
Determining the center O (x) of the fitted ellipse by centroid equation (2)0,y0) Realizing the positioning of the meteorite crater;
Figure FDA0002488806590000023
4. the method for evaluating and optimizing the observation information of the road signs on the surface of the irregular small celestial body as claimed in claim 3, wherein: the step 2 is realized by the method that,
writing n elliptical equations in the form of formula (1) for n edge points for each meteorite crater navigation road sign, solving a covariance matrix P of elliptical equation coefficients through observation errors V, and generating an error covariance matrix of each meteorite crater from the covariance matrix P of elliptical equation coefficients according to covariance propagation law
Figure FDA0002488806590000024
K is a matrix formed by solving partial derivatives of elliptic equation coefficients B, C, D, E and F by the centroid formula (2) in the step 1;
Figure FDA0002488806590000031
then m meteorite crater navigation signpost pairs of state variables are observed
Figure FDA0002488806590000032
Has an error uncertainty matrix of R
Figure FDA0002488806590000033
5. The method for evaluating and optimizing observation information of landmarks on the surface of irregular small celestial bodies of claim 4, wherein: step 4, the method is realized by the following steps,
the selection criteria are: when m meteorite crater navigation landmarks are detected and extracted in the step 1, the number of expected selected meteorite crater navigation landmarks is N, N meteorite crater landmarks are randomly selected from the m meteorite craters detected and extracted, a structure target function J is used as an evaluation index of the N meteorite craters, and the N meteorite craters which can enable the J to be minimum are selected, namely the optimal landmarks in the m meteorite crater navigation landmarks; a model of the optimal road sign selection problem is shown below
min J＝tr[(HTΛH)-1HT(ΛR)H(HTΛH)-1](10)
Figure FDA0002488806590000034
Figure FDA0002488806590000035
Wherein, tr [ alpha ], [ alpha ]]Traces of the matrix, wjAnd Λ is a decision matrix used for randomly selecting N meteorite craters from m meteorite craters, and the solution meeting the optimal road sign selection problem is the optimal navigation road sign obtained by simultaneously considering the uncertainty of the observation error and the position distribution of the road sign, so that the accuracy of the navigation road sign selection of the deep space probe is improved.
6. The method for evaluating and optimizing observation information of landmarks on the surface of irregular small celestial bodies of claim 5, wherein: the specific implementation method of the step 2 is that,
for each meteorite crater navigation road sign, n edge points exist and are xi＝(xi,yi) And i is 1,2,.. n, writing n fitting elliptical equations for the n edge points by using the elliptical equation fitted in the step 1, and expressing an error equation as a matrix
Figure FDA0002488806590000041
Order to
Figure FDA0002488806590000042
The error equation is written as V ═ AX + Y; observation error v of ith edge pointiHas a variance of
Figure FDA0002488806590000043
Wherein the content of the first and second substances,
Figure FDA0002488806590000044
I2×2is an identity matrix of 2 × 2,
Figure FDA0002488806590000045
is the variance of the ith edge point of the meteorite crater,
Figure FDA0002488806590000046
variance matrix of observation error V
Figure FDA0002488806590000047
Is composed of
Figure FDA0002488806590000048
The covariance matrix P of the elliptic equation coefficients is defined as
Figure FDA0002488806590000049
Wherein A isTA is called autocorrelation matrix, In×nIs the unit matrix of n × n, and finally, the error covariance matrix of each meteorite crater center is generated by P according to the covariance propagation law
Figure FDA00024888065900000410
Figure FDA00024888065900000411
Figure FDA00024888065900000412
Figure FDA0002488806590000051
7. The method for evaluating and optimizing observation information of landmarks on the surface of irregular small celestial bodies of claim 5, wherein: in step 1, coefficients B, C, D, E and F of the meteorite crater edge fitting elliptic equation are determined through a least square method.
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