CN106885571A - A kind of lunar surface rover method for rapidly positioning of combination IMU and navigation image - Google Patents

Abstract

The lunar surface rover method for rapidly positioning of a kind of combination IMU and navigation image, belongs to field of deep space exploration, including：Build rover zero-bit coordinate system and image space auxiliary coordinates；Extract navigation camera focus, side-play amount, rover luffing angle, yaw angle and IMU three-axis attitudes angle between navigation camera shooting center and rover barycenter and rover zero-bit coordinate origin；Calculate spin matrix between spin matrix between image space auxiliary coordinates and rover zero-bit coordinate system, lander locality vertical coordinate system and rover zero-bit coordinate system；Picture point and its corresponding lunar surface point coordinates are extracted from navigation image；Calculate navigation image photo centre locality vertical coordinate system coordinate；Rover center-of-mass coordinate is calculated, positioning is completed；Cause the problems such as position error is big, positioning precision accumulates decline with mileage instant invention overcomes wheel-slip；Positioned by least only needing at 1 point, when image texture absence of information, characteristic point can also be positioned when few；Realize simply, taking few.

Description

A kind of lunar surface rover method for rapidly positioning of combination IMU and navigation image

Technical field

The invention belongs to field of deep space exploration, and in particular to the lunar surface rover of a kind of combination IMU and navigation image Method for rapidly positioning.

Background technology

The high accuracy navigator fix technology of rover is one of key technology in deep-space detection field, high-precision positioning Result not only may insure the safety of rover, and have preferably finger when rover can be made to be communicated with ground control system To angle, and then to realize that the scientific investigation task such as resource exploration provides basis.At present, the navigation locating method of lunar surface rover Three classes are broadly divided into, including：Localization method based on VLBI, the localization method combined based on odometer and IMU and based on photography The localization method of measurement.

(1) the localization method present Research based on VLBI：

Liu Qinghui etc. (2010) proposes lunar rover Precise Relative Positioning of the superhigh precision multifrequency point with wave beam VLBI technologies Method, after the touch-down zone lunar surface topographic map for obtaining error 10m, using multifrequency point with wave beam VLBI differential phase delays and range finding Data, are expected to realize relative positioning of the lunar rover of error 10m on lunar surface.Wei Erhu etc. (2016) propose joint VLBI and The lunar rover localization method of celestial navigation, positioning result is in latitude deflection error scope in -33 to 31m, longitudinal error model It is trapped among 5.5 to 6.5m.The precision of above-mentioned positioning result cannot meet the demand of rover scientific investigation.

Lunar exploration VLBI results are first switched to general FITS-IDI forms by Tong Fengxian etc. (2014), then to lander and tour Device carries out phase reference imaging, obtains position of the rover antenna relative to lander antenna, positioning precision about 1m.But Need to use the relative height differential of rover and lander antenna in the position fixing process of the method, and the difference in height cannot be obtained accurately Take, therefore, its positioning result needs to obtain the value by other means, when difference in height cannot be obtained accurately, positioning result Precision can be greatly lowered.

Li Peijia etc. (2014) carries out the relative positioning of lunar surface rover and lander using same wave beam VLBI data, nominally Precision is better than 1m.Huang Yong etc. (2014) is calculated relative position of the rover relative to lander using VLBI difference phase delays Put, error is in 1m or so.(2015) such as prosperous victory black horses propose to carry out really the relative position of rover and lander using search method It is fixed, and compare with statistics positioning result, alternate position spike is less than 1m.(2015) are vigorously waited to propose using astronomical with beam phase reference in week The method that deep space probe relative positioning is carried out into diagram technology, rover reaches meter level with respect to lander positioning precision.Guo Li etc. (2016) tracking measurement has been carried out to No. three rovers of the goddess in the moon using the same beam technique of Chinese VLBI Network, has obtained the relative of 1M Positioning precision.

(2) based on IMU combination odometer localization method present Research：

Xia Lingnan etc. (2013) proposes to combine the location algorithm of inertial sensor and visual odometry, is filtered with spreading kalman Ripple (extended Kalman filter, EKF) is framework, and the process mould of EKF is built using the dead reckoning of inertial sensor Type, visual odometry is used for modeling observational equation as relative linear velocity and relative angular-rate sensor, optimizes positioning result. But the above method is not only that wheel-slip in the case of the earth 1/6 causes odometer to be observed to occur for lunar surface gravity The situation of larger error conducts a research.Li Yu etc. (2015) proposes a kind of IMU/ mileage gauge integrated navigations based on federated filter Method, improves integrated navigation and location system precision and robustness.But its experiment is only tested on earth, not Have and tested using the experimental data of the real goddess in the moon No. three.Therefore, its applicability to rover positioning remains to be discussed.Liu Pass triumphant grade (2014) and propose inertial navigation and visual combination and determine appearance localization method, but the method does not have realization truly Inertial navigation and the combination of photogrammetric survey method, but the initial value that only inertial navigation parameter is iterated to calculate as flux of light method, when lunar surface is special When levying a little less, it is impossible to complete positioning.

(3) based on photogrammetric rover localization method present Research：

The comparing that rover localization method based on photogrammetric means is carried out at home is more.Di Kaichang etc. 2015 is proposed A kind of bundle adjustment localization method based on consecutive image sequence.Li Linhui etc. (2011) is for sandy lunar surface simulated environment Propose the matching to the angle point under epipolar-line constraint, and by Optimizing Search window size and estimate the methods such as the direction of search and carry Height matching and the efficiency of tracking.Wang Baofeng etc. (2014) is by SIFT matchings, correlation coefficient matching method, Least squares matching and flux of light method The multinomial technological incorporation such as adjustment, realizes the navigator fix of lunar surface rover between neighbor stations.Xu Xin superfine (2015) proposes base Station localization method is taken the photograph in the rover list of space resection's iterative method, but the control point of needs at least more than 3 could complete Resolve.Ma Youqing etc., proposes that one kind replaces Gauss-Newton Methods using row text Burger-Ma Kuaerte algorithms (LM algorithms), carries out The rover navigation locating method of image beam method adjustment, improves the rate of convergence of iterative process.Liu Zhaoqin etc. (2014) leads to Crossing carries out the consecutive tracking that matching positioning realizes lunar rover to navigation camera raw video, and using the DOM of camera generation of navigating Characteristic matching is carried out with CE-2DOM, the result according to matching realizes positioning of the lunar rover on CE-2 satellite images.Liu creates less (2015) in the controlling filed of ground, accurate camera calibration parameter is obtained using the bundle adjustment method based on control point, so The three-dimensional model structure of image is completed by Pixel matching, forward intersection afterwards, and the connection point sequence between station is taken the photograph according to difference to build Stereo-picture band net is found, finally the Mathematical Modeling to stereo-picture band net carries out least square adjustment, directly obtains lunar surface The position of inspection prober and attitude information.Shi Dele etc. (2006) is proposed with lander as base station, is surveyed using stereoscopic vision The method of amount technology and color images, is tracked the inspection tour prober for moon surface localization method of measurement, to inertial navigation system Plus the localization method of odometer is modified, reduce the amount of calculation of inspection tour prober for moon surface.Ma Youqing etc. (2014) basis The core concept of LM algorithms and the network forming feature of rover image, build bundle adjustment model, overcome Gauss-Newton Methods The weak shortcoming of applicability.Ma Youqing etc. (2014) is based on relative orientation in photogrammetric field and absolute orientation principle, it is proposed that Lunar rover navigation and positioning algorithm based on stereo-picture.And position knot by setting tie point coordinate survey amount right-value optimization Really.

In the above method, the localization method positioning precision based on VLBI is optimal can to reach 1m, relative to photogrammetric light The position error of beam method is larger；It is optimal to reach li and the precision that is based on photogrammetric localization method positioning result is higher Meter level, but substantial amounts of characteristic point is generally required as computing unit based on photogrammetric localization method, when in navigation image When obvious characteristic point is less, then the reduction of the positioning result precision that obtains, or even iterative process occur and do not restrain Situation；Positioning precision higher is had in the starting stage based on IMU and odometer localization method, but with inspection prober Traveling, wheel odometer occurs more slippery conditions, so as to larger mistake occurs in the observed result for causing odometer to obtain Difference, eventually affects the positioning result of inspection prober, and the angle that IMU is measured in the process is not in then above-mentioned feelings Condition.Often solved attitude parameter as unknown number in solution procedure based on photogrammetric method, and pass through IMU and set It is standby can be by certain attitude information for being calculated rover, photogrammetric means combination IMU is observed into data can be real The simplification of existing rover position fixing process.

The content of the invention

For the deficiency that above-mentioned prior art is present, the present invention provides a kind of combination IMU and the lunar surface of navigation image is maked an inspection tour Device method for rapidly positioning.

Technical scheme is as follows：

The lunar surface rover method for rapidly positioning of a kind of combination IMU and navigation image, comprises the following steps：

Step 1：Build rover zero-bit coordinate system；

Step 2：Extract navigation camera focus f, navigate between camera shooting center and rover zero-bit coordinate origin Side-play amount (B_X, B_Y, B_Z), the side-play amount (Δ X, Δ Y, Δ Z) between rover barycenter and rover zero-bit coordinate origin, patrol The three-axis attitude angle that visual organ luffing angle, rover yaw angle and IMU are measured；

Step 3：Image space auxiliary coordinates are built, is calculated as empty according to rover luffing angle and rover yaw angle Between auxiliary coordinates relative to rover zero-bit coordinate system spin matrix R_BowAnd R_Partially；

Step 4：Installation parameter and ground test data according to IMU calculate rover zero-bit coordinate system and exist with IMU device Three angles of change in coordinate axis directionAccording toAnd rover IMU measure three Axle attitude angleObtain three attitudes of the rover zero-bit coordinate system relative to lander locality vertical coordinate system Angle isSimplification is designated asAnd then obtain the rotation under two sets of coordinate systems Matrix R_IMU；

Step 5：The moon millet cake a with obvious characteristic is extracted from selected navigation image, and according to navigation camera calibration Distortion parameter error correction is carried out to picpointed coordinate, obtain picture point a coordinates for (x_a, y_a)；

Step 6：Picture point a is extracted from touch-down zone digital orthoimage DOM and touch-down zone digital complex demodulation corresponding Coordinate (X of moon millet cake A under the vertical coordinate system of lander locality_A, Y_A, Z_A)；

Step 7：According to least square formula X=(A^TA)^-1A^TL is solved, and obtains navigation image photo centre locality lead Hang down coordinate system coordinate (X_S, Y_S, Z_S), wherein：

Step 8：By photo centre (X_S, Y_S, Z_S) following formula is substituted into, obtain rover center-of-mass coordinate (X_C, Y_C, Z_C), complete to patrol Visual organ is positioned：

Beneficial effect：The present invention proposes the lunar surface rover method for rapidly positioning of a kind of combination IMU and navigation image, and existing There is technology to compare, have the following advantages that：

(1) during overcoming using IMU and odometer integrated navigation and location, because wheel-slip causes odometer to be observed Value error increase, so as to the shortcoming for causing position error to increase, simultaneously as IMU angle measurement attitudes are influenceed very by mileage accumulation It is small, the problem for being accumulated with mileage and being declined using IMU and odometer integrated navigation and location precision is overcome, positioning precision is better than IMU and odometer combined positioning method；

(2) relative to the method for traditional photography measurement and positioning, context of methods completes positioning by least only needing to 1 point, The usable condition of method is increased, lunar surface rover is solved in position fixing process is carried out using photogrammetric means, works as image Middle texture information is deficient, and the problem of positioning cannot be completed when characteristic point is less；

(3) attitude for first really measuring IMU device is combined with photogrammetric means, and constituting jointly computation model is carried out The navigator fix of rover, method implementation process is simple, takes few.

Brief description of the drawings

Fig. 1 is the combination IMU of one embodiment of the present invention and the lunar surface rover method for rapidly positioning stream of navigation image Cheng Tu；

Fig. 2 is the rover zero-bit coordinate system schematic diagram of one embodiment of the present invention.

Specific embodiment

One embodiment of the present invention is elaborated below in conjunction with the accompanying drawings.

As shown in figure 1, the lunar surface rover method for rapidly positioning of the combination IMU of present embodiment and navigation image, including：

Step 1：Rover zero-bit coordinate system is built, as shown in Fig. 2 the zero-bit coordinate origin is located at rover mast The intersection point O of driftage rotation axis and head pitching rotation axis, X-axis and head pitching rotation axis coincident, Y-axis are that mast rotates Angle is the zero degree moment, and in the horizontal plane perpendicular to head pitching rotation axis forward, Z axis constitute right-handed system with XY axles；

Step 2：Extract navigation camera focus f, navigate between camera shooting center and rover zero-bit coordinate origin Side-play amount (B_X, B_Y, B_Z), the side-play amount (Δ X, Δ Y, Δ Z) between rover barycenter and rover zero-bit coordinate origin, patrol Visual organ luffing angle, rover yaw angle and rover Inertial Measurement Unit (Inertial measurement unit, IMU the three-axis attitude angle for) measuring；

As shown in Fig. 2 the navigation camera in rover stereo visual system is arranged on the head above mast, Ke Yi Horizontal direction carries out rotation and the pitching of vertical direction around mast.Navigation image shoot when, in order to shoot surrounding terrain, around Mast carries out the rotation of certain angle, referred to as yaw angle, is designated as P；The rotation of certain angle is carried out around horizontal stage rotational axis, referred to as The angle of pitch, is designated as F.

Lunar surface rover navigator fix is as reference with lander locality vertical coordinate system.Land device locality vertical coordinate system is former Point is located at subpoint of the lander barycenter on ground, and for plumb line in downward direction, XY axle positions are in the plane vertical with plumb line for Z axis It is interior, X-axis point to the north to, Y-axis point to east to.Three direction of principal axis are parallel with the direction of principal axis of IMU tri- respectively.The IMU measure three Axle attitude angle, is, when rover somewhere carries out scientific investigation task and needs are positioned, to be carried from IMU device data Take rover current relative to east, north, three attitudes in direction of zenithI.e. current IMU device and lander The angle of three direction of principal axis of local vertical coordinate system.

Step 3：Image space auxiliary coordinates are built, is calculated as empty according to rover luffing angle and rover yaw angle Between auxiliary coordinates relative to rover zero-bit coordinate system spin matrix R_BowAnd R_Partially；

With the navigation camera shooting center S after pitching and driftage as origin, image space auxiliary coordinates, X-axis and Y-axis are set up The x-axis and y-axis of the image plane rectangular coordinate system of navigation image are respectively parallel to, Z axis constitute right-handed system with X-axis and Y-axis.

Step 4：Installation parameter and ground test data according to IMU calculate rover zero-bit coordinate system and exist with IMU device Three angles of change in coordinate axis directionAccording toAnd rover IMU measure three Axle attitude angleObtain three attitudes of the rover zero-bit coordinate system relative to lander locality vertical coordinate system Angle isSimplification is designated asAnd then obtain the rotation under two sets of coordinate systems Matrix R_IMU；

Step 5：The moon millet cake a with obvious characteristic is extracted from selected navigation image, and according to navigation camera calibration Distortion parameter error correction is carried out to picpointed coordinate, obtain picture point a coordinates for (x_a, y_a)；

Step 6：Picture point a correspondences are extracted from touch-down zone digital orthoimage (Digital Orthophoto Map, DOM) Plane coordinates (X of moon millet cake A under the vertical coordinate system of lander locality_A, Y_A), and from the corresponding digital elevation mould in touch-down zone Type (Digital Elevation Model, DEM) extracts the corresponding elevation coordinate Z of picture point a_A；

Step 7：According to least square solution formula X=(A^TA)^-1A^TL, calculates photo centre (X_S, Y_S, Z_S) optimal solution, Wherein：

Above-mentioned least square formula X=(A^TA)^-1A^TL derivations are as follows：

Coordinate of the rover zero-bit coordinate origin under the vertical coordinate system of land device locality is (X₀, Y₀, Z₀), positioning is used Coordinate of the corresponding photo centre's coordinate of navigation image under the vertical coordinate system of land device locality be (X_S, Y_S, Z_S), the navigation phase Side-play amount between machine photo centre and rover zero-bit coordinate origin is (B_X, B_Y, B_Z), then can obtain triangular phase Mutual relation is as follows：

Can obtain rover zero-bit coordinate origin position by above formula is：

By A point coordinates by after rotation and translation, under conversion to rover zero-bit coordinate system, being designated as (X_NA, Y_NA, Z_NA), then Can obtain：

By rotation and translation, moon millet cake A is changed to the auxiliary coordinates of image space by rover zero-bit coordinate system, sat Labeled as (X_SA, Y_SA, Z_SA), then have：

Navigation camera focus are f, by picpointed coordinate (x_a,y_a) its coordinate under the auxiliary coordinates of image space can be obtained It is (x_a,y_a,-f), then by photo centre S (0,0,0), picture point a (x under current image space auxiliary coordinates_a,y_a,-f) and correspondence Moon millet cake A (X_SA, Y_SA, Z_SA) in collinear constraints, can obtain：

Turning to vector form is：

Can be obtained during formula (3), (4) are substituted into formula (6)：

Arrange and be：

Camera shooting center S is can obtain according to picture point and correspondence lunar surface point coordinates, in substitution formula (8) to work as in lander Coordinate (X under ground vertical coordinate system_S, Y_S, Z_S).When being solved according to formula (8), it is only necessary to which millet cake can complete photography within one month The solution of center S coordinates.But to avoid single-point from error occur during practical operation, often using the means of redundant observation, therefore, Need for formula (8) to switch to the form of error equation, optimal solution is solved according to least square method.Order：

Then formula (8) can arrange and be：

In making above formula：

Formula can be decomposed into：

Formula (a) (b) is respectively divided by (c), and further abbreviation is：

Above formula arrange can be obtained：

By unknown number (X_S, Y_S, Z_S) arrange be to equation side：

Formula (13) are rewritten as by the form of error equation according to least square X=(A^TA)^-1A^TL is solved, wherein：

Step 8：By photo centre (X_S, Y_S, Z_S) formula (16) is substituted into, obtain rover centroid position (X_C, Y_C, Z_C), complete Rover is positioned.

The derivation of formula (16) is：

Under rover zero-bit coordinate system, rover barycenter (X is obtained by rover design parameter_C, Y_C, Z_C) relative to tour Device zero-bit coordinate origin (X₀, Y₀, Z₀) being respectively (Δ X, Δ Y, Δ Z) in the side-play amount of three change in coordinate axis direction, then can obtain To relationship below：

With reference to formula (2), arrangement can be obtained：

Result, classical flux of light method before rover 10 positioning result and two of survey station of the context of methods using two-point locating Person's mutual deviation is as shown in table 1：

The positioning result of table 1 and mutual deviation table

Can be drawn by the mutual deviation of table 1, the inventive method can effectively complete lunar surface rover positioning, method is feasible and steady Fixed, positioning precision is higher than VLBI relative positioning results.

Claims (4)

1. the lunar surface rover method for rapidly positioning of a kind of combination IMU and navigation image, it is characterised in that comprise the following steps：

Step 1：Build rover zero-bit coordinate system；

Step 2：Extract navigation camera focus f, the side-play amount (B between navigation camera and rover zero-bit coordinate origin_X, B_Y, B_Z), the side-play amount (Δ X, Δ Y, Δ Z) between rover barycenter and rover zero-bit coordinate origin, rover luffing angle, The three-axis attitude angle that rover yaw angle and IMU are measured；

Step 3：Image space auxiliary coordinates are built, it is auxiliary to calculate image space according to rover luffing angle and rover yaw angle Coordinate system is helped relative to the spin matrix R of rover zero-bit coordinate system_BowAnd R_Partially；

Step 4：Calculate the spin matrix R between lander locality vertical coordinate system and rover zero-bit coordinate system_IMU；

Step 5：The picture point a with obvious characteristic is extracted from selected navigation image, and according to the distortion of navigation camera calibration Parameter carries out error correction to picpointed coordinate, obtains picture point a coordinates (x_a, y_a)；

Step 6：The corresponding lunar surfaces of picture point a are extracted from touch-down zone digital orthoimage DOM and touch-down zone digital complex demodulation Coordinate (Xs of the point A under the vertical coordinate system of lander locality_A, Y_A, Z_A)；

Step 7：Calculate navigation image photo centre coordinate (X under local vertical coordinate system_S, Y_S, Z_S)；

Step 8：According to the side-play amount (Δ X, Δ Y, Δ Z) between rover barycenter and rover zero-bit coordinate origin, rotation Matrix R_IMU, navigation camera and rover zero-bit coordinate origin between side-play amount (B_X, B_Y, B_Z) and photo centre (X_S, Y_S, Z_S), calculate rover center-of-mass coordinate (X_C, Y_C, Z_C), complete rover positioning.

2. the lunar surface rover method for rapidly positioning of combination IMU according to claim 1 and navigation image, its feature exists In the step 4 is specially：

Installation parameter and ground test data according to IMU calculate rover zero-bit coordinate system with IMU device in three reference axis The angle in directionAnd according toAnd the three-axis attitude angle that rover IMU is measuredObtain rover zero-bit coordinate system is relative to three attitude angles of lander locality vertical coordinate systemIt is designated asAnd then obtain the spin matrix R under two sets of coordinate systems_IMU。

3. the lunar surface rover method for rapidly positioning of combination IMU according to claim 1 and navigation image, its feature exists In step 7 specific method is：

According to least square solution formula X=(A^TA)^-1A^TL, calculates coordinate under navigation image photo centre locality vertical coordinate system (X_S, Y_S, Z_S), wherein：

$\begin{array}{ccc}A=\left[\begin{array}{ccc}f\·u1+x_a\·w1& f\·u2+x_a\·w2& f\·u3+x_a\·w3\\ f\·v1+y_a\·w1& f\·v2+y_a\·w2& f\·v3+y_a\·w3\end{array}\right],& X=\left[\begin{array}{c}{X}_S\\ Y_S\\ Z_S\end{array}\right],& L=-\left[\begin{array}{c}{x}_{a}M3+fM1\\ y_{a}M3+fM2\end{array}\right];\end{array}$

$M1=a1X_A+a2Y_A+a3Z_A+B_X^N$

$M2=b1X_A+b2Y_A+b3Z_A+B_Y^N$

$M3=c1X_A+c2Y_A+c3Z_A+B_Z^N;$

4. the lunar surface rover method for rapidly positioning of combination IMU according to claim 1 and navigation image, its feature exists In rover center-of-mass coordinate (X_C, Y_C, Z_C) calculated according to equation below：

$\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]=R_{IMU}^{-1}\left[\begin{array}{c}{B}_X\\ B_Y\\ B_Z\end{array}\right]+\left[\begin{array}{c}{X}_S\\ Y_S\\ Z_S\end{array}\right]-R_{IMU}^{-1}\left[\begin{array}{c}\mathrm{\Δ}X\\ \mathrm{\Δ}Y\\ \mathrm{\Δ}Z\end{array}\right].$