CN103592658A - New method for RAIM (receiver autonomous integrity monitoring) based on satellite selecting algorithm in multimode satellite navigation system - Google Patents

Abstract

The invention discloses a new method for RAIM (receiver autonomous integrity monitoring) based on a satellite selecting algorithm in a multimode satellite navigation system. The method comprises the steps of first determining space position information of satellites according to a navigation message and eliminating satellites with a small elevation angle according to a shielding angle; determining an observation matrix including only one clock correction item according to clock correction conversion factors in the navigation message; selecting p satellites from N visible satellites so as to be used for positioning calculation of a receiver, acquiring a satellite combination, which enables the GDOP (geometric dilution of precision) to be minimum, through the satellite selecting algorithm to act as calculating satellites, and determining a weight matrix in WLS (weighted least squares) according to parameters such as the carrier-to-noise ratio, the loop bandwidth, pre-check integral time and the like of satellite signals; carrying out RAIM availability detection according to a false alarm rate and a missed alarm rate which are preset by the receiver, and calculating a pseudo-range residual error threshold value after positioning according to the false alarm rate and a degree of freedom in Chi-squared distribution; carrying out global detection at first, then carrying out local monitoring in a circumstance that a fault satellite exists, determining calculation satellites again through satellite selection, and finally carrying out positioning calculation through selecting satellite combinations within the threshold value. The method disclosed by the invention is simple, high in fault recognition rate, not only applicable to multi-mode and multi-fault satellite navigation systems, but also applicable to single-mode and multi-fault satellite navigation systems, thereby providing new ideas for carrying out RAIM by a modern GNSS (global navigation satellite system).

Description

RAIM new method based on selecting star algorithm in multimodal satellite navigation system

Technical field

The invention belongs to global navigation satellite field, a kind of based on selecting receiver autonomous integrity monitoring method in the multimodal satellite navigation system of star algorithm specifically.

Background technology

GLONASS (Global Navigation Satellite System) (Global Navigation Satellite System, GNSS) in military and civilian field, all playing the part of extremely important status, the object that GNSS can be sea, land and sky every aspect positions, navigation and time service, comprise boats and ships oceangoing voyage and the diversion of approaching, Automobile automatic navigation and Waypoint guiding and the landing of marching into the arena, electric power, post and telecommunications and communications network system time service and calibrating frequency etc.

Multimodal satellite navigation system, the GPS that mainly comprises the U.S., Muscovite GLONASS, the Galileo in Europe and the Chinese Big Dipper (BD/COMPASS), receiver in each location constantly, visible satellite quantity can reach 30 to 40 conventionally, if all visible satellites are used for to positioning calculation, will cause very big burden to receiver processor, and the ionosphere of lower elevation angle satellite, larger to flow process time delay, multipath effect is stronger, easily cause larger pseudorange deviation, thereby positioning precision is affected, therefore need to be by selecting star algorithm to reduce the computational complexity of processor, and improve user's positioning precision.When tradition the best selects star algorithm to calculate GDOP, large, the length that expends time in of operand, causes larger pressure to receiver processing unit, is difficult to meet the requirement of receiver real-time, continuity positioning calculation.Tradition the best selects the formula that calculates geometric dilution of precision (Geometric Dilution ofPrecision, GDOP) in star algorithm to be:

$\mathrm{GDOP}=\sqrt{\mathrm{trace}\left({\left(G^{T}G\right)}^{-1}\right)}---\left(1\right)$

Wherein G represents that receiver is to the observing matrix of visible satellite, and trace () is the computing of Matrix Calculating mark.

The each computing of process that solves optimum GDOP relates to the larger calculating of complexity such as matrix multiplication, matrix inversion, evolution, and along with the increasing of visible satellite number, operand sharply increases.Although now the result of calculation of best satellite selection method is optimum, its calculated amount is huge, is difficult to meet receiver real-time, successional positioning calculation requirement.

Receiver autonomous integrity monitoring (Receiver Autonomous Integrity Monitoring, RAIM) has been guaranteed accuracy, continuity and the robustness of user location, time service result, and provides assurance for the normal operation of GNSS system.The essence of RAIM algorithm is whether the satellite that judgement participates in resolving comprises erroneous measurements, and detect which satellite measurement and have deviation, a good RAIM algorithm not only should have the higher possibility that correctly detects malfunction, and has again the higher separability energy that correctly identifies erroneous measurements.

In the snapshot algorithm in satellite navigation field, extensively adopt least square method, parity vector method and weighted least-squares method (Weighted Least Squares, WLS), consider least square method and the equivalence of parity vector method positioning result and the accuracy of WLS positioning result, the present invention adopts WLS to carry out receiver positioning calculation.The WLS adopting in RAIM algorithm can be expressed as:

b＝G·x+ε (2)

B ∈ R wherein ^{n * 1}, n is the number of satellite that in multimodal satellite navigation system, participation is resolved, and the rear pseudorange of b representative correction and receiver are poor to satellite geometry distance and clock correction value, and R represents real number field, G ∈ R ^{n * 4}, G represents that receiver is to the observing matrix of satellite direction, x ∈ R ^{n * 1}, representing position coordinates and clock correction value, the clock correction value quantity of receiver is consistent with the constellation number of navigational system, ε ∈ R ^{n * 1}, represent receiver measuring error vector, obeying under normal circumstances average is 0, variance is σ ²gaussian distribution.

The measuring error standard deviation of n satellite in weighted least-squares method is σ _n, weight matrix W can be expressed as a R ^{n * N}diagonal matrix:

$W=\left[\begin{array}{cccc}{w}_1& & & 0\\ & w_2& & \\ & & \·\·\·& \\ 0& & & w_n\end{array}\right]---\left(3\right)$

Wherein

make C=W ^tw, WLS solution is:

x＝(G ^TCG) ^1-G ^TCb (4)

Behind location, residual vector b is:

$\hat{b}=b-G\left[\begin{array}{c}\mathrm{\Δx}\\ \mathrm{\Δy}\\ \mathrm{\Δz}\\ \mathrm{\Δ\δ}{t}_u\end{array}\right]=b-G{\left(G^T\mathrm{CG}\right)}^{-1}{G}^T\mathrm{Cb}=S(b+\mathrm{\ϵ})----\left(5\right)$

Wherein matrix s is defined as: S=I-G (G ^tcG) ^-1g ^tc.

The remaining square weighting of definition pseudorange and (Weighted Sum ofSquares forError, WSSE) ε _wSSE:

${\mathrm{\ϵ}}_{\mathrm{WSSE}}={\left(W\hat{b}\right)}^T\left(W\hat{b}\right)={\hat{b}}^{T}C\hat{b}---\left(6\right)$

By above formula, known ε _wSSEthe length square that represents the residual vector after weighting.Because the positioning solution for being obtained by WLS can make weighting remaining

the quadratic sum ε of each component _wSSEminimum, so ε _wSSEvalue size is embodying the degree of consistency between each measured value, and obedience degree of freedom (Degree ofFreedom, DOF) is the X of N-(mode+3) ²distribute, the number of satellites that wherein N resolves for participation, mode is satellite mode quantity.

In today of satellite navigation system fast development, adopt many constellation combination navigation to become a kind of inexorable trend, yet because the visible satellite quantity of receiver synchronization is more, the single star fault mode of tradition is no longer applicable, ionospheric storm, multipath effect, the generation of the phenomenons such as electromagnetic interference (EMI), cause the probability that multi-satellite breaks down simultaneously greatly to increase, now find out method simple, fault recognition rate is high, be easy to hard-wired many fault satellites error-detecting and eliminating (Fault Detection and Exclusion, FDE) method has become new developing direction.

Summary of the invention

The object of the invention is to overcome the weak point in above-mentioned background, propose the RAIM new method based on selecting star algorithm in a kind of multimodal satellite navigation system.

The method is first by receiver shield angle, reject the visible satellite at the lower elevation angle, and determine by the clock correction conversion factor of various constellations the observing matrix that only comprises a clock correction item, utilize the quick evaluator of GDOP, avoided in classic method the complex calculation such as matrix inversion, guaranteed to determine under optimum GDOP prerequisite to participate in the combinations of satellites resolved.The carrier-to-noise ratio of signal, loop bandwidth and preliminary examination integral time etc., signal processing parameter was determined the weight matrix in WLS via satellite; and distribute for how much and determine the level protection limit value in RAIM by false alarm rate, false dismissed rate and the satellite spatial setting in advance, and then the availability of judgement RAIM.By global detection and the local mode combining that detects, carrying out fault satellites detects and gets rid of, if break down satellite, on the basis of normal operation satellite, again select star, until the satellite WSSE that participates in resolving is less than the card side's dispersal doors limit value based on false alarm rate and degree of freedom, finally by WLS, receiver is positioned and resolved.

To achieve these goals, the present invention proposes the RAIM new method based on selecting star algorithm in a kind of many constellation systems, the method specifically comprises following seven steps:

Step 1: extract satellite information.

According to satellite navigation message, calculate the orbital motion parameter of satellite, and according to receiver location, calculate the elevation angle and the position angle of visible satellite.

Step 2: determine observing matrix.

Receiver shield angle is set, get rid of lower elevation angle satellite, according to the elevation angle, the position angle of the different navigation system time conversion factor in navigation message and satellite, calculate the observing matrix that only comprises a receiver clock correction item, for determining that the optimal spatial of satellite distributes for how much.

Step 3: calculate GDOP.

Consider (G ^tg) ^-1for nonsingular matrix, therefore available feature coefficient lambda ₁, λ ₂, λ ₃, λ ₄be expressed as follows:

$\mathrm{GDOP}=\sqrt{\mathrm{trace}\left({\left(G^{T}G\right)}^{1-}\right)}=\sqrt{{{\mathrm{\λ}}_1}^{-1}+{{\mathrm{\λ}}_2}^{-1}}+{{\mathrm{\λ}}_3}^{-1}+{{\mathrm{\λ}}_4}^{-1}---\left(7\right)$

λ ₁, λ ₂, λ ₃, λ ₄7 values can be solved by system of equations (8).

$\left\{\begin{array}{c}{\mathrm{\λ}}_1+{\mathrm{\λ}}_2+{\mathrm{\λ}}_3+{\mathrm{\λ}}_4=\mathrm{trace}\left(M\right)\\ {\mathrm{\λ}}_1^2+{\mathrm{\λ}}_2^2+{\mathrm{\λ}}_3^2+{\mathrm{\λ}}_4^2=\mathrm{trace}\left(M^2\right)\\ {\mathrm{\λ}}_1^3+{\mathrm{\λ}}_2^3+{\mathrm{\λ}}_3^3+{\mathrm{\λ}}_4^3=\mathrm{trace}\left(M^3\right)\\ {\mathrm{\λ}}_1{\mathrm{\λ}}_2{\mathrm{\λ}}_3{\mathrm{\λ}}_4=\det \left(t\right)\end{array},M=G^{T}G---\left(8\right)\right.$

Definition m ₁, m ₂, m ₃, m ₄as follows:

$\begin{array}{c}{m}_1\&equiv;\mathrm{trace}\left(M\right)\\ {\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">m</figure-callout>}}_2\&equiv;\mathrm{trace}\left(M^2\right)\\ m_3\&equiv;\mathrm{trace}\left(M^3\right)\\ {\mathrm{<figure-callout\; id="4"\; label="m"\; filenames="DEST\_PATH\_HSB0000119199720000022.png,DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">m</figure-callout>}}_4\&equiv;\det \left(M\right)\end{array}---\left(9\right)$

Formula (8) is deformed into:

$\begin{array}{c}{\mathrm{\&lambda;}}_1+{\mathrm{\&lambda;}}_2{\mathrm{\&lambda;}}_3+{\mathrm{\&lambda;}}_4=m_1\\ {\mathrm{\&lambda;}}_1^2+{\mathrm{\&lambda;}}_2^2+{\mathrm{\&lambda;}}_3^2+{\mathrm{\&lambda;}}_4^{2={\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">m</figure-callout>}}_2}\\ {\mathrm{\&lambda;}}_1^3+{\mathrm{\&lambda;}}_2^3+{\mathrm{\&lambda;}}_3^3+{\mathrm{\&lambda;}}_4^3=m_3\\ {\mathrm{\&lambda;}}_1{\mathrm{\&lambda;}}_2{\mathrm{\&lambda;}}_3{\mathrm{\&lambda;}}_4=m_4\end{array}---\left(10\right)$

Association type (7), formula (9), formula (10), through series of complex computing, finally obtain following result:

$\mathrm{GDOP}=\sqrt{\frac{0.5m_1^3-1.5m_1{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">m</figure-callout>}}_2+m_3}{3m_4}}---\left(11\right)$

According to observing matrix G and the number of satellite p that participates in resolving, select to make the combinations of satellites of GDOP numerical value minimum as resolving satellite, wherein altogether need the cycle index of calculating GDOP to be

n is all visible satellite numbers of receiver.

Step 4: determine weight matrix.

The parameters such as, preliminary examination integral time wide according to receiver navigational system classification, the phase detector factor, code endless belt and carrier-to-noise ratio are estimated weight factor.Weight factor computing formula is:

${\mathrm{\&sigma;}}_{\mathrm{\&rho;}}^2={\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="tDLL"\; filenames="DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">tDLL</figure-callout>}}^2+{\mathrm{\&sigma;}}_{\mathrm{atm}}^2---\left(12\right)$

σ wherein _tDLLreceiver delay-locked loop (DLL) thermonoise, σ _atmbe atmosphere time delay, mainly comprise ionosphere time delay and troposphere time delay, σ _tDLLthermonoise can be regarded carrier-to-noise ratio C/N as ₀function:

${\mathrm{\&sigma;}}_{\mathrm{tDLL}}={\mathrm{\&lambda;}}_c\sqrt{\frac{4F_1{d}^2{B}_n}{C{N}_0}[2(1-d)+\frac{4F_{2}d}{T\&CenterDot;C{N}_0}}---\left(13\right)$

Wherein F1 and F2 represent the phase detector factor, and d represents chip related interval, B _nrepresent a code loop noise bandwidth, T represents preliminary examination integral time, λ _crepresent the wavelength of each chip, λ in GPS L1 frequency _c=293.05[m], λ in Big Dipper B1I frequency _c=146.53[m], λ in Galileo E1 frequency _c=293.05[m], the present invention supposes ionosphere and flow process propagated error value is respectively to 5m and 1.5m, and σ _atmvalue is 5.22m.

Step 5: RAIM fault satellites detects and gets rid of.

The first step: RAIM availability detects.

According to false dismissed rate P _mdwith false alarm rate P _fadetermine minimum detection error P _bias, horizontal shutter limit value determine the geometric factor SLOPE to positioning error by measuring error _maxdetermine.

$P_{\mathrm{bias}}=\frac{{\mathrm{\&delta;}}_0}{\sqrt{e^{T}C{Q}_{\underset{v}{~}}\mathrm{Ce}}}---\left(14\right)$

Wherein ${\mathrm{\&delta;}}_0=N_{1-P_{\mathrm{fa}}}\left(\mathrm{0,1}\right)+N_{1-P_{\mathrm{md}}}\left(\mathrm{0,1}\right),Q_{\underset{v}{~}}=C^{-1}-G{\left(G^T\mathrm{CG}\right)}^{-1}{G}^T$ , e ∈ R ^{n * 1}, and corresponding fault satellites value is 1, all the other are that 0, C is weight matrix entirely.

HPL＝SLOPE _max×P _bias (15)

Horizon location error PE _hcomputing formula is as follows:

$P{E}_H=\sqrt{{(A_{11}{\mathrm{\&epsiv;}}_1+A_{12}{\mathrm{\&epsiv;}}_2+...+A_{1n}{\mathrm{\&epsiv;}}_n)}^2+{(A_{21}{\mathrm{\&epsiv;}}_1+A_{22}{\mathrm{\&epsiv;}}_2+...+A_{2n}{\mathrm{\&epsiv;}}_n)}^2}---\left(16\right)$

A wherein _1,1represent the capable and j row of i in A matrix, and A=(G ^tcG) ^-1g ^tc.

$\mathrm{SLOPE}=\frac{P{E}_H}{\mathrm{WSSE}}=\sqrt{\frac{(A_{11}^2+A_{12}^2){\mathrm{\&epsiv;}}_1^2+(A_{12}^2+A_{22}^2){\mathrm{\&epsiv;}}_2^2+...+(A_{1\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">n</figure-callout>}}^2+A_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">n</figure-callout>}2}^2){\mathrm{\&epsiv;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DEST\_PATH\_HSB0000119199720000031.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}{{\mathrm{\&epsiv;}}^T\mathrm{S\&epsiv;}}}---\left(17\right)$

If HPL < is HAL, RAIM has availability, otherwise sends warning information.

Second step: global detection.

The remaining vector of weighting

each component weighted sum of squares ε _wSSEbe the X that degree of freedom is N-(mode+3) ²distribute, and in conjunction with false alarm rate P _fadetermine detection threshold value

if ε _wSSEsurpass threshold value, prove in this combinations of satellites and have fault satellites, and carry out the local detection of the 3rd step, otherwise leap to step 6.

The 3rd step: local detection.

To locating rear remaining pseudorange, carry out normalizing operation, have

$v_1=\left|\frac{\widehat{b_1}}{\sqrt{{\left(C_{\hat{b}}\right)}_n}}\right|,i=\mathrm{1,2}...N---\left(18\right)$

Wherein, $C_{\hat{b}}=C^{-1}-G{\left(G^T\mathrm{CG}\right)}^{-1}{G}^T.$

The temporary transient satellite that comprises maximum pseudorange residual value of rejecting, carries out global detection, afterwards again until meet the combinations of satellites within threshold value.

The 4th step: fault satellites detects and gets rid of.

Because GPS relative positioning is different on the impact of different pseudo-range measurements, therefore after the combinations of satellites of finding out within threshold value, the satellite temporarily excluding is combined with the satellite of step 4 more one by one, if ε in the 3rd step _wSSEbe less than threshold value, the satellite temporarily weeding out reverted in the combinations of satellites that participates in positioning calculation, otherwise thoroughly reject this satellite.

Step 6: re-start and select star on the basis of definite combinations of satellites in step 5, select to meet the satellite that resolves quantity, and carry out RAIM monitoring, until meet the requirement of receiver positioning calculation.

Step 7: WLS positioning calculation.

After the detection of RAIM fault satellites and getting rid of, utilize the weight matrix in step 4, according to formula (4), be weighted least square interative computation, finally calculate position and the clock correction information of receiver.

The invention has the advantages that following five aspects:

1. by selecting star algorithm not only to reduce the computational complexity of receiver processor unit, also improved the positioning precision of receiver, and laid a good groundwork for RAIM.

2. the carrier-to-noise ratio of signal, loop bandwidth and preliminary examination integral time etc., parameter was determined weight matrix via satellite, than conventionally using satellite-signal propagated error as the matrix of weight factor more accurately and robust.

3. by RAIM availability being detected to the reliability that has further improved system health monitoring.

4. after fault satellites detection and eliminating, by selecting star to redefine, resolve combinations of satellites, guarantee accuracy, the stability of final positioning result.

5. RAIM method of the present invention is not only applicable to multimodal satellite navigation system, is applicable to single mode satellite navigation system simultaneously yet, and simple to operate, computational complexity is low, is beneficial to hardware and realizes.

Accompanying drawing explanation

Fig. 1 is that the present invention is for multimodal satellite navigation system RAIM method flow diagram;

Fig. 2 is that Beijing area multimodal satellite navigation system of a certain moment is selected star result figure;

Fig. 3 is receiver positioning precision and resolves number of satellite graph of a relation;

Fig. 4 is positioning result analysis charts corresponding to different carrier-to-noise ratios;

Fig. 5 is single, two fault satellites detection probabilities and pseudorange deviation graph of a relation.

Embodiment

Below in conjunction with accompanying drawing and example, the present invention is described in further detail.

As shown in Figure 1, the RAIM method flow diagram based on selecting star algorithm in the multimodal satellite navigation system realizing to step 7 according to summary of the invention step 1.In a certain epoch of observation, according to navigation message, extract co-ordinates of satellite information, and according to receiver location, calculate the elevation angle and the position angle of all visible satellites; In multimodal satellite navigation system, according to the time conversion factor in navigation message, finally determine the observing matrix that only contains a clock correction item, according to resolving number of satellite and formula (11), calculate best GDOP and combinations of satellites; According to information such as the carrier-to-noise ratio of signal processing and loop bandwidths, determine the weight matrix in WLS, carry out afterwards the detection of RAIM availability; Guaranteeing under the prerequisite that RAIM can use, carrying out respectively global detection and local detection, with the satellite of fixing a breakdown; Exist under the prerequisite of fault satellites, in conjunction with selecting star, reselect the satisfied combinations of satellites of resolving requirement and carry out receiver location.

As shown in Figure 2, Beijing area 0:00 on June 26th, 2013 is GPS, BD and Galileo visible satellite distributed number figure constantly, and shield angle is set to 6 °, wherein carmetta represents BD satellite, totally 11 visible satellites, and the elevation angle and position angle are respectively (36 °, 146 °), (30 °, 229 °), (42 °, 189 °), (25 °, 124 °), (15 °, 247 °), (77 °, 327 °), (42 °, 182 °), (56 °, 265 °), (45 °, 307 °), (68 °, 195 °), (6 °, 238 °), defend asterisk and sort from small to large, No. 1 to No. 11; Green represents gps satellite, totally 12 visible satellites, and the elevation angle and position angle are respectively (67 °, 89 °), (31 °, 108 °), (75 °, 311 °), (11 °, 74 °), (6 °, 102 °), (7 °, 127 °), (38 °, 55 °), (8 °, 35 °), (7 °, 203 °), (9 °, 263 °), (38 °, 176 °), (33 °, 310 °); Blueness represents Galileo satellite, totally 4 visible satellites, and the elevation angle and position angle are respectively (22 °, 279 °), (64 °, 315 °), (33 °, 127 °), (31 °, 72 °), according to formula (11), select 8 satellites for positioning calculation, process after kind of combination, No. 1 satellite of the 3rd, 7,8, No. 10 of final the 4th, 8, No. 10 satellites selecting BD and GPS and Galileo is for receiver positioning calculation, and the best GDOP numerical value now calculating is 1.1635.

As shown in Figure 3, receiver positioning precision with resolve number of satellite graph of a relation, wherein ordinate represents satellite position that WLS calculates and the error ratio of accurate known location under WGS-84 coordinate system, while selecting four satellites to carry out receiver positioning calculation, error mean is 1.2431, and covariance is 0.0038; Select five satellites to position while resolving, error mean is 1.0144, and covariance is 0.0077; Select six satellites to position while resolving, error mean is 0.9586, and covariance is 0.0220.Resolve number of satellite more, it is better that the space geometry of satellite distributes, and receiver positioning precision is higher.

As shown in Figure 4, positioning result analysis chart corresponding to different carrier-to-noise ratios in receiver channel, wherein carrier-to-noise ratio selects to be respectively 30,36 and 42dBHz, carrier-to-noise ratio is higher, under the identical condition of noise bandwidth, the signal to noise ratio (S/N ratio) of satellite-signal is higher, and the precision of carrier wave ring and code ring track loop is higher, the satellite-signal extracting is more accurate launch time, thereby the receiver location calculating is more accurate.

As shown in Figure 5, single, two fault satellites detection probabilities and pseudorange deviation graph of a relation, selecting eight visible satellites under receiver positioning calculation condition, under single fault satellites prerequisite, while there is 20 meters of pseudorange deviations, detection probability is about 40%, while there is 40 meters of pseudorange deviations, detection probability is about 68%, in the time of more than having 60 meters, detection probability is more than 80%, and while there is two satellite pseudorange deviations, fault satellites verification and measurement ratio obviously improves, while there is 10 meters of pseudorange deviations, detection probability is approximately 60%, and while there is 20 meters and above pseudorange deviation, detection probability has approached 100%.

With concrete numerical value, further illustrate the present invention below.

Step 1: extract satellite information.

According to navigation message, extract the spatial information of satellite under WGS-84 coordinate system, and in conjunction with local receiver position, calculate the elevation angle and the position angle of each satellite, as shown in Figure 1.

Step 2: determine observing matrix.

From all visible satellites of BD, GPS, Galileo tri-systems, select 8 satellites to carry out receiver positioning calculation, according to the time conversion factor in navigation message, calculate the observing matrix that only comprises a clock correction item, select the 4th, 8, No. 10 satellites of BD, the 3rd, 7,8, No. 10 and No. 1 satellite of Galileo of GPS, now observing matrix is:

$\left[\begin{array}{cccc}0.9869& 0.0920& 0.1324& 1.0000\\ -0.7628& -0.3823& 0.5216& 1.0000\\ -0.0966& -0.4294& 0.8979& 1.0000\\ -0.0163& 0.9216& 0.3878& 1.0000\\ 0.9548& -0.0211& -0.2964& 1.0000\\ -0.0623& -0.1315& -0.9894& 1.0000\\ -0.7102& 0.5780& -0.4121& 1.0000\\ 0.5661& -0.8243& 0.0089& 1.0000\end{array}\right]$

Step 3: calculate GDOP.

By G matrix, can determine that Metzler matrix is:

$M=\left[\begin{array}{cccc}3.3058& -0.4751& -0.2839& 0.8597\\ -0.4751& 2.2114& -0.3216& -0.2043\\ -0.2839& -0.3216& 2.4828& 0.2506\\ 0.8597& -0.2043& 0.2506& 8.0000\end{array}\right]$

According to formula (9), can obtain m1=16, m2=88.4897, m3=609.1320, m4=131.3303.

According to formula (11), the GDOP finally calculating is 1.1635, and now GDOP numerical value is minimum, and satellite has how much distributions of optimal spatial.

Step 4: determine weight matrix.

According to receiver navigational system classification, the phase demodulation factor, wide, preliminary examination integral time of code endless belt and carrier-to-noise ratio etc. are carried out weight factor estimation.Take GPS navigation system as example, and σ tDLL is receiver delay-locked loop (DLL) thermonoise, σ _atmthe atmosphere time delay that is, wherein F1, F2 value are all 1, chip related interval d=1/2[chips], code loop noise bandwidth B _n=2[Hz], preliminary examination T=2[ms integral time], the wavelength X of each chip of GPS L1 frequency _c=293.05[m], ionosphere and flow process propagated error is respectively to 5m and 1.5m, and σ _atmfor 5.25m.

Step 5: RAIM fault satellites detects and gets rid of.

The first step: RAIM availability detects.

According to false dismissed rate P _md=0.2, false alarm rate P _fa=1 * 10 ^-5, weight factor and observing matrix, determine minimum detection error P _tas, horizontal shutter limit value determine the geometric factor SLOPE to positioning error by measuring error _maxdetermine.

Pass through SlOPE _maxand P _diascan determine horizontal shutter limit value, and then judge the availability of RAIM.

Second step: global detection.

The remaining vector of weighting each component weighted sum of squares ε _wSSEbe the X that degree of freedom is N-(mode+3) ²distribute, and in conjunction with false alarm rate P _fadetermine detection threshold value

if ε _wSSEsurpass threshold value, prove in this combinations of satellites and have fault satellites, and carry out the local detection of the 3rd step, otherwise leap to step 6.

The 3rd step: local detection.

To locating rear remaining pseudorange, carry out normalizing operation, have

The temporary transient satellite that comprises maximum pseudorange residual value of rejecting, carries out global detection, afterwards again until meet the combinations of satellites within threshold value.

The 4th step: fault satellites detects and gets rid of.

Because GPS relative positioning is different on the impact of different pseudo-range measurements, therefore after the combinations of satellites of finding out within threshold value, the satellite excluding is combined with the satellite of step 4 more one by one, if ε in the 3rd step _wSSEbe less than threshold value, the satellite temporarily weeding out reverted in the combinations of satellites that participates in positioning calculation, otherwise thoroughly reject this satellite.

Step 6: re-start and select star on the basis of definite combinations of satellites in step 5, select to meet the satellite that resolves quantity, and carry out RAIM monitoring, until meet the requirement of receiver positioning calculation.

Step 7: WLS positioning calculation.

After the detection of RAIM fault satellites and getting rid of, utilize the weight matrix in step 4, according to formula (4), carry out WLS interative computation, finally calculate position and the clock correction information of receiver.

Claims (8)

1. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system, its feature comprises following seven steps:

Steps A: determine satellite spatial position coordinates according to satellite navigation message;

Step B: determine observing matrix according to navigational system time conversion factor and shield angle;

Step C: according to the quick evaluator of GDOP, select star operation;

Step D: extract the parameters such as satellite-signal carrier-to-noise ratio, determine weight matrix;

Step e: utilize false alarm rate, false dismissed rate, participation to resolve satellite mode and quantity is carried out RAIM;

Step F: exist and again select star in fault satellites situation;

Step G:WLS Position-Solving.

2. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system according to claim 1,

It is characterized in that: steps A is determined satellite spatial position by navigation message, and according to receiver coordinate, calculate the elevation angle and the position angle of all visible satellites.

3. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system according to claim 1,

It is characterized in that: step B excludes lower elevation angle satellite by shield angle and shield angle is made as 6 °, and according to the clock correction conversion factor of different system in navigation message, determines the observing matrix that only contains a clock correction item.

4. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system according to claim 1,

It is characterized in that: step C utilizes the quick evaluator of GDOP, find out best satellite spatial and distribute for how much, by selecting star algorithm to determine, resolve combinations of satellites.

5. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system according to claim 1,

It is characterized in that: step D, by parameters such as carrier-to-noise ratio, loop bandwidth and preliminary examination integral time, determines receiver delay-locked loop thermonoise, and in conjunction with the atmosphere time delay in satellite-signal communication process, determines the weight matrix of receiver.

6. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system according to claim 1,

It is characterized in that: step e completes detection and the eliminating of fault satellites by following four steps.

The first step: by false alarm rate, false dismissed rate, determine minimum detection deviation, and by error geometric factor SLOPE _maxdetermine level protection limit value, and then judgement RAIM availability.

Second step: carry out global detection to obeying the remaining vector of location rear weight of card side's distribution, threshold value is determined jointly by false alarm rate and degree of freedom.

The 3rd step: the satellite that temporary transient rejecting comprises maximum pseudorange residual error, then carry out part and detect, until determine the combinations of satellites meeting within threshold value.

The 4th step: by the satellite after temporarily rejecting again again with step 3 in satellite carry out global detection, if ε _wSSEbe less than threshold value, reduce this satellite participate in resolving, otherwise determine that it is fault satellites.

7. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system according to claim 1,

It is characterized in that: step F, meeting on the satellite basis of integrity monitoring, re-starts and selects star, and again carries out RAIM detection, final selection meets RAIM and resolves the combinations of satellites of requirement.

8. the RAIM new method based on selecting star algorithm in multimodal satellite navigation system according to claim 1,

It is characterized in that: step G is after selecting star and RAIM fault satellites to detect and getting rid of, and according to the weight matrix in step D, employing WLS iterative goes out receiver location and clock correction information.

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