CN102829782B - Geomagnetic aided inertial navigation method - Google Patents

Abstract

The invention relates to the navigation and guidance technologies and provides a technical scheme of a geomagnetic aided inertial navigation method. According to the scheme, at least more than one magnetic measuring apparatus is used for simultaneously measuring real-time geomagnetic information of transporters; and a geomagnetic matching navigation mode is adopted to conduct rough matching, noise reduction and precise matching on the measured real-time geomagnetic information sequentially. The magnetic measuring manner reduces the error of the apparatus and ensures the reliability of the measured value. By adopting the matching mode, the non-matching points with the reference geomagnetic map are eliminated and the range of the noise reduction and the precise matching is reduced, thereby improving the noise reduction efficiency of the real-time geomagnetic information and saving the precise matching time of the non-matching points; and meanwhile, the speed of the precise matching is improved and the precision of the navigation is ensured, thereby further promoting the quality of the geomagnetic aided inertial navigation.

Description

A kind of geomagnetic auxiliary inertia guidance method

Technical field

The present invention relates to navigation, guidance technology, particularly aircraft autonomous navigation technology field, especially a kind of geomagnetic auxiliary inertia guidance method.

Background technology

At present, inertial navigation is one of major way of navigator fix, it can carry out continuous print three-dimensional fix and three dimensions orientation independently, snugly under all weather conditions, in the world with in any media environment, and not by any external information, also not to any information of external radiation, multiple complete navigational parameter completely independently can be provided, all be widely used in a lot of fields, but its navigation error can constantly accumulate in time, be unsuitable for for a long time navigation separately.

For above-mentioned technical matters, the intrinsic geomagnetic field information aided inertial navigation of the current favourable earth carries out the method for integrated navigation, makes up the shortcoming that INS errors accumulates in time, thus improve navigation and positioning accuracy with the long-time stability of earth magnetism.

The mode of the geomagnetic auxiliary inertia guidance that current concern is more is geomagnetic matching aided inertial navigation.Geomagnetic matching, exactly the terrestrial magnetic field characteristic quantity in some region on flight path is depicted as reference map, be stored in carrier computing machine, when carrier is through these regions, measure the terrestrial magnetic field characteristic quantity through point in real time by magnetic survey instrument, to form real-time figure, and in carrier computing machine, carry out relevant matches with reference diagram, calculate the real-time coordinates position of carrier, resolve navigation information for navigational computer.

And geomagnetic auxiliary inertia guidance algorithm conventional is at present a lot, mainly the related notion in terrain match and algorithm are incorporated in geomagnetic matching, as TERCOM, ICCP algorithm etc.This kind of algorithm is length consuming time, poor real not only, and is easily subject to the interference of noise.

In the prior art, actual measurement Geomagnetism Information is utilized to mate the mode of carrying out inertially magnetic navigation with magnetic map, the mode adopted first carries out noise reduction process to actual measurement Geomagnetism Information, carry out coupling navigation separately with single matching algorithm afterwards or adopt two kinds of matching algorithms to carry out combining coupling navigation, the inertially magnetic navigation mode that this navigate mode more only utilizes Geomagnetism Information to carry out, navigation accuracy obtains certain raising, but directly current to the carrier actual measurement Geomagnetism Information of this navigate mode carries out noise reduction process, noise reduction contains much information, match information amount is large, thus noise reduction is large with the calculated amount of mating, considerably increase match strength, while reducing rate matched, also have impact on the precision of coupling.This is the weak point existing for prior art.

Summary of the invention

Technical matters to be solved by this invention, overcome the deficiency of geomagnetic auxiliary inertia guidance method in matching speed and accuracy exactly, by the mode taking the thick coupling before denoising to reduce some non-matching points, reduce the calculating pressure of denoising and essence coupling, make it strengthen denoising effect and improve the matching precision of essence coupling, thus improving the quality of geomagnetic matching.

Technical solution of the present invention is: a kind of geomagnetic auxiliary inertia guidance method, and step is as follows:

(1) obtain the magnetic information in real time of carrier current location by surveying magnetic machine, and determine slightly to mate index and essence coupling index;

(2) read benchmark magnetic chart information, and adopt matching algorithm slightly to be mated with it by actual measurement Geomagnetism Information;

(3) use noise reduction algorithm, remove the Noise and Interference information in the magnetic information in real time after thick coupling;

(4) read benchmark magnetic chart information, and carry out essence with the Geomagnetism Information data after denoising and mate;

(5) according to smart matching result, the position of inertial navigation system is revised.

Survey magnetic machine in described step (1) has more than 1 at least.

Multiple stage in described step (1) is surveyed magnetic machine and is measured simultaneously.

Thick coupling in described step (2), if its matching result meets the thick coupling index that step (1) is determined, then performs step (3), otherwise removes this magnetic information in real time, continues to perform step (2).

Matching algorithm in described step (2) is normalizing eliminate indigestion relevant matches (NProd) algorithm.

Noise reduction algorithm in described step (3) is Hilbert-Huang transform (HHT) algorithm.

When the result of essence coupling meets the essence coupling index determined in step (1) in described step (4), then perform step (5), otherwise continue to perform step (4).

Described step (4) adopts Hausdorff distance method to carry out essence coupling to the Geomagnetism Information data after denoising.

The present invention's advantage is compared with prior art:

(1) the present invention the magnetic information in real time that records is adopted slightly mate successively, the geomagnetic matching pattern of noise reduction and essence coupling.The use of this pattern, eliminate the non-matching point with the part of benchmark magnetic chart, improve the noise reduction efficacy of magnetic information in real time, save the smart match time of non-matching point, improve the speed of essence coupling and ensure that the precision of navigation, and then improve the quality of geomagnetic auxiliary inertia guidance;

(2) NProd algorithm is adopted slightly to mate, this algorithm is the algorithm of a kind of comparative maturity in images match engineer applied, matching precision is high and can work under Low SNR, have not by the advantage that errors of proportional factor affects, and anti-white noise disturbance ability is strong;

(3) compare with existing wavelet de-noising techniques, the present invention adopts HHT algorithm to carry out Geomagnetism Information noise reduction.This algorithm has evaded the problem that wavelet basis is difficult to select, nonlinear and non local boundary value problem can be processed in actual applications, and there is complete adaptivity, and the restriction of the Heisenberg uncertainty principle constraint of a lot of traditional algorithm can be completely free of, thus well noise reduction process is carried out to magnetic information in real time, improve the signal to noise ratio (S/N ratio) of magnetic information in real time;

(4) Hausdorff distance method is adopted to carry out essence coupling to the Geomagnetism Information data after denoising.Hausdorff distance is a kind of method of match point feature, and the similarity degree just between calculating two point sets, overcomes the difficult point of foundation one-to-one relationship between points.The enforcement of thick coupling and denoising process, eliminates its sensible factor, effectively can characterize the dissimilar degree between two point sets, improves the precision of navigation.

The beneficial effect of this programme can be learnt according to describing of such scheme, and the Geomagnetism Information correction inertial navigation system after the above-mentioned high precision obtained being mated, under the prerequisite not reducing navigation accuracy, improves the speed of the navigation of navigational system.As can be seen here, compared with prior art, have outstanding substantive distinguishing features and significant progress, its beneficial effect implemented also is apparent in the present invention.

Accompanying drawing explanation

Fig. 1 is design flow diagram of the present invention.

Fig. 2 is geomagnetic auxiliary inertia guidance system block diagram corresponding to the present invention.

Embodiment

For the technical characterstic of this programme can be clearly demonstrated, below by an embodiment, and in conjunction with its accompanying drawing, this programme is set forth.

As shown in figure 1 and 2, concrete grammar of the present invention is as follows:

(1) obtain the magnetic information in real time of carrier current location by surveying magnetic machine, and determine slightly to mate index and essence coupling index.

For ease of implementation process of the present invention is described, the present embodiment is chosen two identical survey magnetic machines and is measured simultaneously, and by slightly mating, index is set to 10%, essence coupling index is set to 0.5% herein.Thick coupling index and essence coupling index can adjust in actual applications as the case may be.

For implementing the solution of the present invention, the mathematical model of geomagnetic auxiliary navigation system first should be set up.Be applied as example with the land navigation of gimbaled inertial navigation system, system coordinates adopt " east-north-sky " coordinate system, consider the actual conditions that land is applied, during modeling sky to speed be 0, inertia device model simplification is that constant error adds white noise.

A. state equation

The state variable of getting system is platform error angle φ _x, φ _y, φ _z, velocity error δ ν _x, δ ν _y, δ ν _z, site error δ L, δ λ, and accelerometer and gyrostatic constant error, namely system state is:

X＝[φ _x,φ _y,φ _z,δν _x,δν _y,δν _z,δL,δλ,K _gx,K _gy,K _gz,K _ax,K _ay,K _az] ^T,

Then system state equation is:

$\stackrel{\·}{X}\left(t\right)=F\left(t\right)X\left(t\right)+G\left(t\right)w\left(t\right),$ ①

In formula, w is mutual incoherent zero mean Gaussian white noise.

B. observation equation

Magnetic Sensor in the present invention adopts three axis magnetometer, and its measurement output is in the ideal case:

y＝B _m(r,t)+B _a(r)+B _d(r,t)+v ₀

Wherein, v ₀for the measurement noises of magnetometer.

In actual applications, use be similar to and obtain B _m(r, t), B _d(r, t), then the measurement of magnetometer exports and can be written as:

$y=B_m(\tilde{r},t)+B_a\left(r\right)+B_d(\tilde{r},t)+v_0^{\′}$

Wherein, v ' ₀for measurement noises and the approximate error sum of magnetometer.

Geomagnetic anomaly value is extracted from the measurement of above-mentioned magnetometer exports:

$B_a\left(r\right)=y-B_m(\tilde{r},t)-B_d(\tilde{r},t)-v_0^{\′}$

Get estimated position place geomagnetic anomaly value with above-mentioned from measure export the geomagnetic anomaly value B that extracts _ar the difference of (), as observed quantity, obtains observation equation as follows:

$Z\left(t\right)=B_a\left(\tilde{r}\right)-B_a\left(r\right)=H(X\left(t\right),r)+v\left(t\right)$ ②

Then 1., 2. equation is the mathematical model of geomagnetic auxiliary navigation system.

Adopt two to survey measurement that magnetic machines carry out carrier magnetic information in real time simultaneously, reduce equipment error, ensure that the reliability of measured value, its measuring principle is as follows: survey magnetic machine measured value for two and subtract each other the approximate inherent error of the equipment of obtaining and measurement noises, ask for the average that two are surveyed magnetic machine measured value, then deduct approximate inherent error and the measurement noises of the said equipment, the magnetic information in real time of more accurate carrier current location can be obtained.

(2) read benchmark magnetic chart information, and adopt matching algorithm slightly to be mated with it by actual measurement Geomagnetism Information.

Here using the digitally magnetic chart prepared based on IGRF model as benchmark magnetic chart, and adopt Nprod algorithm to carry out actual measurement Geomagnetism Information slightly to mate with benchmark magnetic chart.Wherein, the similarity measurements flow function of Nprod algorithm is:

$P(x,y)=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{X}_{i+x,j+y}{Y}_{i,j}}{{\left(\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{X}_{i+x,j+y}^2{Y}_{i,j}\right)}^{1/2}{\left(\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{Y}_{i,j}^2\right)}^{1/2}}$ ③

In above formula, 0≤x≤M-m, 0≤y≤N-n, the size of benchmark magnetic chart X is M × N, and the size of magnetic chart Y is m × n in real time, and m<M, n<N, (x, y) is the position of magnetic chart in benchmark magnetic chart in real time.When P (x, y) obtains maximal value, if (x, y) meets the thick coupling index that step (1) is determined, the matched position that (x, y) is its best; If (x, y) does not meet the thick coupling index that step (1) is determined, remove this magnetic information in real time, continue to perform step (2).

In order to find Optimum Matching point, Nprod algorithm each point in region of search must carry out similarity matching calculating, it should be noted that, at calculating P (x, y), in process, if distance of certain point is less than threshold value λ in real time sequence and consensus sequence, then directly gets rid of this matching sequence and complete P (x need not be calculated, y), be expressed as follows with mathematical formulae:

P(x,y)<λ ④

The determination of threshold value λ and noise intensity, earth magnetism feature are relevant, can be added up obtain by repeatedly matched data.The data volume of correlation matching algorithm and calculated amount are all very large, and the most of the time is all spent in the calculating of non-matching point, causes matching speed slower.Herein, 4. 3. formula constitute thick matching algorithm with formula, and time between algorithm, complexity is more much smaller than independent Nprod algorithm, thus accelerates matching speed.

(3) the Noise and Interference information in the magnetic information in real time after using noise reduction algorithm to remove thick coupling.

In the magnetic information in real time of the acquisition after thick coupling, there is the impact etc. comprising and taken to the solar disturbance of the earth, the measurement noises of geomagnetic sensor, surrounding environment magnetic interference and other various error by solar wind, can matching precision be had a strong impact on if do not eliminated.The present invention adopts HHT algorithm to carry out noise reduction process to the magnetic information in real time after thick coupling, thus obtains the Geomagnetism Information of high s/n ratio.

Suppose that the above-mentioned magnetic information in real time collected is denoted as x (t), then with HHT algorithm to the process that it carries out denoising be:

1) determine all Local Extremum of magnetic information x (t) in real time, all Local modulus maximas and local minizing point are coupled together respectively and form upper and lower envelope, the mean value of upper and lower envelope is designated as m ₁, have

x(t)-m ₁＝h ₁⑤

2) if h ₁do not meet the condition of IMF, h ₁as original signal, repeat the first step, obtain the mean value m of upper and lower envelope ₁₁, then judge h ₁₁=h ₁-m ₁₁whether meet the condition of IMF, then recirculating k time if do not met, obtaining h _{1 (k-1)}-m _1k=h _1k, make h _1kmeet the condition of IMF.Note c ₁=h _1k, then c ₁for first of signal x (t) meets the component of IMF condition.

3) by c ₁separate from x (t), obtain:

r ₁＝x(t)-c ₁⑥

By r ₁step 1 is repeated as raw data) ~ 2), obtain the component c that second of x (t) meets IMF condition ₂, repetitive cycling n time, obtains the individual component meeting IMF condition of n of signal x (t).Work as r _nbecome a monotonic quantity when therefrom can not extract the component meeting IMF condition again, circulation terminates.

Therefore magnetic information x (t) in real time can be decomposed into following form:

$x\left(t\right)=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{c}_i+r_n$ ⑦

In formula, r _nbe called survival function, the average tendency of representation signal.

Decompose the magnetic information in real time that the complete actual conditions that can require according to precision index can obtain through noise reduction process.

(4) read benchmark magnetic chart information, and carry out essence with the Geomagnetism Information data after denoising and mate.

After thick coupling and noise reduction, Hausdorff distance algorithm is utilized to carry out further essence coupling.Hausdorff distance is a kind of minimax distance, and it is mainly used in the matching degree of measurement two point sets.

Given two finite point set point A and B, note collection A is the set of magnetic information x (t) in real time, and set B is the benchmark magnetic chart information set read, and might as well make A={a ₁, a ₂..., a _pand B={b ₁, b ₂..., b _q, and a _i(i=1,2 ..., p) map one by one with x (t), then the Hausdorff distance definition between A, B is as follows:

H(A,B)＝max(d(A,B),d(B,A)) ⑧

Wherein, $d(A,B)=\underset{a\&Element;A}{\max }\underset{b\&Element;B}{\min }\left|\right|a-b\left|\right|,d(B,A)=\underset{b\&Element;B}{\max }\underset{a\&Element;A}{\min }\left|\right|b-a\left|\right|.$

In formula, definition || || be certain distance norm on point set A and B; D (A, B) is called oriented Hausdorff distance, and its meaning is: a ∈ A that sets up an office is arbitrary element point farthest in set B, and b ∈ B is the point nearest apart from a, then the distance between a and b is exactly d (A, B).Hausdorff distance H (A, B) reflects the not matching degree of collection A and collection B, and Hausdorff distance is larger, and two set differences are far away.Then meet the demands when Hausdorff distance is less than or equal to the essence coupling index that step (1) determines, namely obtain best match position, now perform step (5), otherwise continue to perform step (4).

(5) according to smart matching result, the position of inertial navigation system is revised.

According to expression formula account form 8., the magnetic information in real time after denoising meets essence with the Hausdorff distance of its corresponding benchmark magnetic chart information and mates index, thus the magnetic information in real time that carrier is current, x (t might as well be designated as ₀), the benchmark magnetic chart information corresponding to it is the position of carrier based on this geomagnetic auxiliary inertia guidance method.

The present invention is not limited in above-mentioned embodiment, the change that those of ordinary skill in the art make in essential scope of the present invention, remodeling, interpolation or replacement, also should belong to protection scope of the present invention.

Claims (6)

1. a geomagnetic auxiliary inertia guidance method, is characterized in that comprising the following steps:

(1) obtain the magnetic information in real time of carrier current location by surveying magnetic machine, and determine slightly to mate index and essence coupling index; Adopt two to survey measurement that magnetic machines carry out carrier magnetic information in real time simultaneously, survey magnetic machine measured value for two and subtract each other the approximate inherent error of the equipment of obtaining and measurement noises, ask for the average that two are surveyed magnetic machine measured value, then deduct approximate inherent error and the measurement noises of the said equipment, obtain the magnetic information in real time of carrier current location;

(2) read benchmark magnetic chart information, and adopt matching algorithm slightly to be mated with it by actual measurement Geomagnetism Information, remove the non-matching point differed greatly;

(3) use noise reduction algorithm, remove the Noise and Interference information in the magnetic information in real time after thick coupling;

(4) read benchmark magnetic chart information, and carry out essence with the Geomagnetism Information data after denoising and mate;

(5) according to smart matching result, the position of inertial navigation system is revised.

2. geomagnetic auxiliary inertia guidance method according to claim 1, it is characterized in that: the thick coupling in described step (2), if its matching result meets the thick coupling index that step (1) is determined, then perform step (3), otherwise remove this magnetic information in real time, continue to perform step (2).

3. geomagnetic auxiliary inertia guidance method according to claim 1, is characterized in that: the matching algorithm in described step (2) is normalizing eliminate indigestion relevant matches (NProd) algorithm.

4. geomagnetic auxiliary inertia guidance method according to claim 1, is characterized in that the noise reduction algorithm in described step (3) is Hilbert-Huang transform (HHT) algorithm.

5. geomagnetic auxiliary inertia guidance method according to claim 1, it is characterized in that: when in described step (4), the result of essence coupling meets the essence coupling index determined in step (1), then perform step (5), otherwise continue to perform step (4).

6. geomagnetic auxiliary inertia guidance method according to claim 1, is characterized in that: described step (4) adopts Hausdorff distance method to carry out essence coupling to the Geomagnetism Information data after denoising.