CN105445765B - A kind of pseudo range measurement method of Beidou navigation satellite system hybrid constellation - Google Patents

A kind of pseudo range measurement method of Beidou navigation satellite system hybrid constellation Download PDF

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CN105445765B
CN105445765B CN201510854630.XA CN201510854630A CN105445765B CN 105445765 B CN105445765 B CN 105445765B CN 201510854630 A CN201510854630 A CN 201510854630A CN 105445765 B CN105445765 B CN 105445765B
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CN105445765A (en
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孟骞
曾庆化
刘建业
李荣冰
赵伟
冯邵军
韩志凤
尚斌斌
朱龙泉
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Nanjing University of Aeronautics and Astronautics
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13Receivers
    • G01S19/24Acquisition or tracking or demodulation of signals transmitted by the system
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13Receivers
    • G01S19/23Testing, monitoring, correcting or calibrating of receiver elements
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13Receivers
    • G01S19/35Constructional details or hardware or software details of the signal processing chain
    • G01S19/37Hardware or software details of the signal processing chain

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  • Radar, Positioning & Navigation (AREA)
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  • Computer Networks & Wireless Communication (AREA)
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Abstract

The invention discloses a kind of pseudo range measurement method of Beidou navigation satellite system hybrid constellation, the D2 navigation messages that it broadcasts for Beidou navigation satellite system earth GEO satellite are different from the D1 navigation message speed that non-GEO satellite is broadcast, cause the synchronous head interval of subframe different, at the whole second that can not be in the Big Dipper the problem of synchronism output pseudorange, utilize the thought of fuzzy control, on the basis of the IGSO satellite pseudorange transfer times, fuzzy control rule is set, the output of GEO satellite pseudorange is modified and estimated, realizes that pseudorange synchronism output positions time service with receiver.

Description

Pseudo-range measurement method for mixed constellation of Beidou navigation satellite system
Technical Field
The invention relates to a pseudo-range measurement method, in particular to a pseudo-range measurement method of a mixed constellation of a Beidou navigation satellite system, and belongs to the technical field of satellite navigation.
Background
The Beidou navigation satellite system is a global navigation satellite system integrating basic navigation service and differential integrity service built in China, the space section adopts mixed constellation layout and consists of 5 geostationary orbit satellites (GEO), 3 inclined synchronous orbit satellites (IGSO) and 27 medium and high orbit satellites (MEO), the orbit height of the GEO satellite is 35786 kilometers, and the GEO satellite is respectively fixed at 58.75 degrees E, 80 degrees E, 110.5 degrees E, 140 degrees E and 160 degrees E; the MEO satellite orbit height is 21528 kilometers, and the orbit inclination angle is 55 degrees; the height of the IGSO satellite orbit is 35786 kilometers, and the inclination angle of the orbit is 55 degrees.
In 2012, a regional navigation system consisting of 5 GEO satellites, 5 IGSO satellites and 4 MEO satellites starts to provide positioning and time service for china and surrounding areas, and has generated wide economic and social benefits in many fields such as traffic transportation, marine fishery, hydrological monitoring, weather forecasting, geodetic surveying, intelligent driving investigation, disaster relief and reduction, mobile phone navigation, vehicle-mounted navigation and the like. 3, 30 months in 2015, the first new generation of Beidou navigation satellites are successfully transmitted, the successful transmission of the satellites marks the starting implementation of a Beidou navigation system from regional operation to global expansion, the new generation of Beidou satellites can carry out experimental verification work such as a satellite-borne hydrogen atomic clock, an inter-satellite link, a novel navigation signal system and the like, and the basic service is provided for the country with one path in 2018; the global service capability is formed in 2020, and an international first-class global satellite navigation system is built.
The Beidou IGSO satellite and the MEO satellite broadcast D1 navigation messages, and the D1 navigation messages consist of superframes, main frames and subframes. Each superframe is 36000 bits and lasts for 12 minutes, and each superframe consists of 24 main frames; each main frame is 1500 bits and lasts for 30 seconds, and each main frame consists of 5 subframes; each subframe is 300 bits and lasts for 6 seconds, and each subframe consists of 10 words; each word is 30 bits for 0.6 seconds. The Beidou GEO broadcasts a D2 navigation message, and the D2 navigation message consists of a superframe, a main frame and a subframe. Each superframe is 180000 bits for 6 minutes, and each superframe is composed of 120 main frames; each main frame is 1500 bits and lasts for 3 seconds, and each main frame consists of 5 subframes; each subframe is 300 bits and lasts for 0.6 second, and each subframe consists of 10 words; each word is 30 bits for 0.06 seconds.
Compared with the D2 navigation message, the rising edge of the sub-frame head of the D1 navigation message is aligned with the whole second of the Beidou, and the two sub-frame heads are separated by 6 seconds; the speed of the D2 navigation message is 10 times of that of the D1 navigation message, the time between two adjacent subframe heads is 0.6 second, and the second time corresponding to the second counting in the week is the time corresponding to the first pulse rising edge of the synchronization head of the current main frame 1, which means that the rising edges of the subframe heads are not all aligned with the whole second of the Beidou. The layout of the mixed constellation and the broadcasting of different navigation messages increase the complexity of pseudo range measurement and receiver clock error correction in a real-time receiver, and the traditional pseudo range latch integral second signal aligned with the system time is not directly applicable any more. The solution idea of the hardware level comprises the steps of improving the frequency of pseudo-range latch signals, adopting two sets of pseudo-range latch signals and the like, and increasing the pressure and complexity of hardware operation.
The Beidou GEO satellite is fixed on a geosynchronous orbit above the equator, the IGSO and the GEO orbit have the same height, and the intersatellite point is a big 8-shaped track which takes the equator as a central point and is in the north-south direction. Theoretical analysis and experimental verification of effective coverage areas of the Beidou IGSO and the GEO show that although pseudo-range propagation time changes in real time due to satellite motion, receiver motion and the like, the IGSO close to the GEO position is used as a reference, the difference between the pseudo-range propagation time and the GEO position does not exceed 10ms, and the basis is laid for the application of fuzzy control.
The fuzzy control system is a computer digital control system based on fuzzy aggregation, fuzzy linguistic variable and fuzzy logic reasoning, the fuzzy control belongs to the category of nonlinear control and intelligent control, and the fuzzy controller summarizes experience and experimental results into a plurality of rules and carries out reasoning according to the rules to quickly complete operation. The ideal output result can be obtained by selecting a proper fuzzy model and formulating a proper rule. The principle of the method can be divided into four processes of fuzzification, fuzzy rule, fuzzy reasoning and defuzzification.
Disclosure of Invention
The invention aims to solve the technical problem of providing a pseudo-range measurement method of a Beidou navigation system mixed constellation aiming at the defects of the background technology, which solves the problem of pseudo-range output asynchronism caused by different navigation messages broadcast by a Beidou GEO satellite and a non-GEO satellite, and realizes synchronous output of pseudo-range, receiver positioning and receiver clock error correction.
A pseudo-range measurement method for a mixed constellation of a Beidou navigation satellite system specifically comprises the following steps:
step 1, powering on and resetting a receiver, and randomly generating a pseudo-range latch signal TIC with adjustable rising edge position in the receiver;
step 2, generating a local ranging code and a carrier, capturing a satellite signal, and enabling the successfully captured signal to enter a tracking channel;
step 3, respectively carrying out bit synchronization and subframe synchronization on the GEO satellite, the IGSO satellite and the MEO satellite;
step 4, after sub-frame synchronization of each channel is realized, switching to a pseudo-range output and ephemeris demodulation mode, and further calculating initial pseudo-range propagation time, satellite position and pseudo-range correction parameters, wherein after the IGSO satellite and MEO satellite channels realize bit synchronization, frame synchronization second-integer pulse signals are triggered, and pseudo-range output at the Beidou second-integer position is realized;
step 5, selecting the pseudo-range propagation time of the IGSO satellite calculated in the step 4 as a reference tρ,IGSO_rPseudo-range transmission time t for GEO satellitesρ,GEOCorrecting;
step 6: correcting pseudo-range propagation time of the GEO satellite channel by adopting a fuzzy control rule to obtain pseudo-range propagation time t synchronous with IGSOρ,GEO_cor
Step 7, obtaining an initial pseudo range rho according to the pseudo range propagation time, and smoothing the pseudo range by adopting a carrier phase:
where ρ iss,kFor the smoothed pseudorange, phi, at the current timekIs the carrier phase, p, at the current times,k-1Smoothed by the last time instant of the pseudorange, phik-1Is the carrier phase, p, of the previous time instantkThe pseudo range which is not smoothed at the current moment is M, and the time constant is smoothed;
and 8, calculating the clock error of the receiver by positioning the receiver, calculating the control quantity of the pseudo-range latch signal, and further correcting the position of the pseudo-range latch signal, wherein the specific calculation formula is as follows:
NTIC,k=NTIC,k-1+(Δu-ΔtTIC_frame)*fc/c
in the above formula,. DELTA.uClock error residual, Δ t, obtained for receiver positioningTIC_frameFixed delay for channel frame synchronization, NTIC,kIs the control quantity of TIC at the present moment, NTIC,k-1Control quantity of TIC at the previous time, fcSampling frequency for TIC;
and 9, after the receiver realizes primary positioning, correcting the TIC pulse to be aligned with the Beidou in whole second.
As a further preferable scheme of the pseudo-range measurement method of the mixed constellation of the Beidou navigation satellite system, in the step 4, the subframe head is corrected to the position of the whole second in a soft computing mode, so that pseudo-range synchronous output of all satellites is realized.
As a further preferable scheme of the pseudo-range measurement method of the mixed constellation of the Beidou navigation satellite system, in the step 4, under the premise of not changing the pseudo-range latch signal period, a software correction method is adopted to realize pseudo-range synchronous output of three types of Beidou satellites, namely, two rates of navigation messages.
As a further preferable scheme of the pseudo-range measurement method of the Beidou navigation satellite system mixed constellation, in step 5, the pseudo-range propagation time of one IGSO closest to the equator is selected as a reference, and the pseudo-range propagation time of the GEO is corrected.
As a further preferable scheme of the pseudo-range measurement method of the mixed constellation of the Beidou navigation satellite system, in step 7, the GEO pseudo-range propagation time is corrected by adopting a fuzzy control method.
As a further preferable scheme of the pseudo-range measurement method of the hybrid constellation of the Beidou navigation satellite system, in step 9, the pseudo-range propagation time of the GEO satellite and the IGSO satellite is corrected by adopting a simplified fuzzy control rule.
Compared with the prior art, the invention has the beneficial effects that:
the method is characterized in that the traditional pseudo range latch signal is not changed, pseudo range propagation time output by a channel is corrected on a software level, and pseudo range synchronous output and receiver positioning under three satellites and two navigation message modes of the Beidou are realized by using the fuzzy control idea and utilizing the characteristics that the orbit heights of an IGSO satellite and a GEO satellite are the same and the difference of the pseudo range transmission time is not large. The invention has the advantages of clear purpose, simple technology, easy realization and strong engineering application value, is suitable for the Beidou navigation receiver, and has reference value for other satellite navigation systems adopting mixed constellations or different navigation messages.
Drawings
FIG. 1 is a flow chart of the functional implementation of the present invention;
FIG. 2 is a block diagram of the fuzzy control principle of the present invention;
FIG. 3 is a fuzzy control input membership function curve according to the present invention;
FIG. 4 is a fuzzy control output membership function curve according to the present invention;
FIG. 5 shows the time when tρ,GEO>tρ,IGSO_rThen, positioning a front subframe header and a pseudo range to latch a signal position schematic diagram;
FIG. 6 shows the time when tρ,GEO=tρ,IGSO_rThen, positioning a front subframe header and a pseudo range to latch a signal position schematic diagram;
FIG. 7 shows the time when tρ,GEO<tρ,IGSO_rThen, positioning a front subframe header and a pseudo range to latch a signal position schematic diagram;
FIG. 8 is a schematic diagram of the positions of the positioned subframe header, pseudo-range latch signal, and IGSO frame synchronization second-order signal;
fig. 9 is a schematic diagram of positions of the positioned subframe header, pseudo-range latch signal, and IGSO frame synchronization second signal when a frame decoding failure occurs.
Detailed Description
The technical scheme of the invention is explained in detail in the following with the accompanying drawings:
as shown in fig. 1, a pseudo-range measurement method for a hybrid constellation of a beidou navigation satellite system specifically includes the following steps:
step 1, powering on and resetting a receiver, and randomly generating a pseudo-range latch signal TIC with adjustable rising edge position in the receiver;
step 2, generating a local ranging code and a carrier, capturing a satellite signal, and enabling the successfully captured signal to enter a tracking channel;
step 3, respectively carrying out bit synchronization and subframe synchronization on the GEO satellite, the IGSO satellite and the MEO satellite;
step 4, after sub-frame synchronization of each channel is realized, switching to a pseudo-range output and ephemeris demodulation mode, and further calculating initial pseudo-range propagation time, satellite position and pseudo-range correction parameters, wherein after the IGSO satellite and MEO satellite channels realize bit synchronization, frame synchronization second-integer pulse signals are triggered, and pseudo-range output at the Beidou second-integer position is realized;
step 4.1, after the IGSO satellite and the MEO satellite channel realize sub-frame synchronization, triggering a frame synchronization whole second pulse signal, wherein the period of the frame synchronization whole second pulse signal is 1s, the rising edge lags behind the first 1ms of the sub-frame, so that the position of the frame synchronization whole second pulse is convenient to update when the next sub-frame arrives, and the frame synchronization whole second pulse has the function of realizing pseudo-range output with the frequency of 1 Hz;
4.2, after the sub-frame synchronization of each channel is realized, switching to a pseudo-range output and ephemeris demodulation mode, detecting that a sub-frame head or frame synchronization whole second pulse triggers a high-power code clock counter to count and latch, wherein the frequency of the counter is that the counter at the frame starting moment is cleared, the counting is carried out until the moment of the TIC rising edge, and the value of the counter is synchronously placed in the latch;
step 4.3, each channel reads the frame synchronization count value and calculates the pseudo-range propagation time of the channel, wherein the calculation formula is tρ=1-Nc/fc
Step 5, selecting the pseudo-range propagation time of the IGSO satellite calculated in the step 4 as a reference tρ,IGSO_rPseudo-range transmission time t for GEO satellitesρ,GEOCorrecting;
step 6: correcting pseudo-range propagation time of the GEO satellite channel by adopting a fuzzy control rule to obtain pseudo-range propagation time t synchronous with IGSOρ,GEO_cor
Step 7, obtaining an initial pseudo range rho according to the pseudo range propagation time, and smoothing the pseudo range by adopting a carrier phase:
where ρ iss,kFor the smoothed pseudorange, phi, at the current timekIs the carrier phase, p, at the current times,k-1Smoothed by the last time instant of the pseudorange, phik-1Is the carrier phase, p, of the previous time instantkThe pseudo range which is not smoothed at the current moment is M, and the time constant is smoothed;
and 8, calculating the clock error of the receiver by positioning the receiver, further calculating the control quantity of the pseudo-range latch signal, and further correcting the position of the pseudo-range latch signal, wherein the specific calculation formula is as follows:
NTIC,k=NTIC,k-1+(Δu-ΔtTIC_frame)*fc/c
in the above formula,. DELTA.uClock error residual, Δ t, obtained for receiver positioningTIC_frameFixed delay for channel frame synchronization, NTIC,kIs the control quantity of TIC at the present moment, NTIC,k-1Control quantity of TIC at the previous time, fcSampling frequency for TIC;
and 9, after the receiver realizes primary positioning, correcting the TIC pulse to be aligned with the Beidou in whole second.
In step 4, the period of one sub-frame of the GEO is 0.6 seconds, and the sub-frame head is corrected to the position of the whole second in a soft computing mode to solve the problem that the sub-frame cannot be aligned with the whole second of the Beidou, so that pseudo-range synchronous output of all satellites is achieved.
Under the premise of not changing the pseudo range latch signal period, the method of software correction is adopted to realize pseudo range synchronous output of three types of Beidou satellites, namely under two-rate navigation messages.
And selecting the pseudo-range propagation time of the IGSO closest to the equator as a reference by utilizing the characteristic that the IGSO satellite and the GEO satellite are at the same orbit height, and correcting the pseudo-range propagation time of the GEO.
Before positioning, the pseudo range latch signal TIC, the position of the GEO satellite sub-frame header and the position of the IGSO satellite sub-frame header are different, and the GEO pseudo range propagation time is corrected by adopting a fuzzy control method.
And aiming at the condition that the pseudo-range propagation time of the GEO satellite and the IGSO satellite is only three possible conditions after the receiver realizes positioning, the simplified fuzzy control rule is adopted for correction.
The overall flow chart of the method is shown in fig. 2, and the Beidou intermediate frequency signals are respectively processed. The above process requires the following work to be done:
1. the Beidou navigation receiver realizes the technical scheme and needs to have a baseband signal processing function and a loop tracking and positioning resolving function. The baseband signal processing function comprises carrier NCO generation, code NCO generation, complex phase rotary digital down conversion, local Beidou spread spectrum code generation, a correlator, time base signal generation, observation data measurement, frame synchronization signal generation, navigation message demodulation and the like. The loop tracking and positioning resolving functions mainly complete the functions of prediction of Beidou visible satellites, Doppler prediction, initialization of each channel of the Beidou, reading and storage of an advance, instant and lag correlation value of each channel, loop control of a carrier tracking loop and a code tracking loop, reading of pseudo-range latching moment observation data, carrier phase assisted pseudo-range smoothing processing, tracking Doppler filtering processing, reading of subframe data and navigation message analysis, real-time storage of satellite ephemeris and almanac, Beidou positioning resolving and speed solving, Beidou time service loop control, framing and framing of a serial port protocol and the like.
2. A fuzzy controller is constructed.
And constructing a one-dimensional fuzzy control rule. Setting the difference delta t between the pseudo range propagation time of the GEO latched by the pseudo range latch signal and the reference IGSO satelliteρ,GEO-IGSO_rThe fuzzy subset of the control quantity (i.e. correction quantity) U is { NX, NB, NM, NS, ZO, P }, respectively represents negative, positive, middle, negative, zero, positive, the discrete domain is { -0.8, -0.6, -0.4, -0.2, 0, 0.6}, the output is a discrete precise value, the fuzzy identification rule is 'IfAthen B', and the fuzzy relation R can be written as R A × B
Written as a fuzzy inference sentence:
ifE=N thenU=P
ifE=ZO thenU=ZO
ifE=PS thenU=NS
ifE=PM thenU=NM
ifE=PB thenU=NB
ifE=PX thenU=NX
the input and output membership function curves are shown in fig. 3 and 4, respectively.
For the correction of the GEO pseudo range transmission time by the fuzzy control rule, the three conditions that the GEO pseudo range transmission time is greater than, equal to or less than the reference IGSO pseudo range transmission time are discussed according to two modes before and after the positioning of the receiver, and the main difference of the two modes before and after the positioning is that whether the pseudo range latch signal TIC is aligned with the whole second of the Beidou. It should be noted that all the following fuzzy control rules do not contradict each other, and the set of fuzzy control rules applies to all cases.
2.1 before the receiver is positioned, the position of the TIC rising edge is random, and the GEO pseudo range transmission time is larger than the reference IGSO. As shown in fig. 5, there are three cases as shown in table 1:
TABLE 1
Situation(s) (a) (b) (c)
E ZO PB N
U ZO NB P
In the figure, a transverse arrow is time flow, a longitudinal arrow is the relative position of a subframe header and the rising edge of a pseudo-range latch signal, the highest dotted arrow is the pseudo-range latch signal, the period is 1s, the k-1 moment is before, and the k moment is after, the difference between the two is 1 s; the higher solid arrow is an IGSO sub-frame header, the period is 6s, the lowest solid arrow is a GEO sub-frame header, and the period is 0.6 s; n is a radical ofc1And Nc2And pseudo range count values of the IGSO satellite and the GEO satellite respectively latched by the pseudo range latch signals.
In case (a), two subframe headers latched by pseudo-range latching signals are synchronous subframe headers, the input quantity is suitable for a fuzzy rule ZO, the output quantity is suitable for ZO, and t is not required to be latchedρ,GEOCorrecting; the latched GEO subframe header is one GEO subframe period ahead of the IGSO subframe header under the condition (b), the input quantity is suitable for the fuzzy rule PB, and the output quantity is suitable for NB, tρ,GEOSubtracting 6 s; case (c) the latched IGSO subframe header precedes the GEO subframe header by one GEO subframe period, the input quantity applies the fuzzy rule N, the output quantity applies P, tρ,GEOAnd adding 6 s.
2.2 before the receiver is positioned, the position of the TIC rising edge is random, and the GEO pseudo range transmission time is exactly equal to the reference IGSO. As shown in fig. 6, there are two cases as shown in table 2:
TABLE 2
Situation(s) (a) (b)
E ZO PB
U ZO NB
In case (a), two subframe headers latched by pseudo-range latching signals are synchronous subframe headers, the input quantity is suitable for a fuzzy rule ZO, the output quantity is suitable for ZO, and t is not required to be latchedρ,GEOCorrecting; the latched GEO subframe header is one GEO subframe period ahead of the IGSO subframe header under the condition (b), the input quantity is suitable for the fuzzy rule PB, and the output quantity is suitable for NB, tρ,GEOMinus 6 s.
2.3 before the receiver is positioned, the position of the TIC rising edge is random, and the GEO pseudo range transmission time is less than the reference IGSO. As shown in fig. 7, there are two cases as shown in table 3:
TABLE 3
Situation(s) (a) (b)
E ZO PB
U ZO NB
In case (a), two subframe headers latched by pseudo-range latching signals are synchronous subframe headers, the input quantity is suitable for a fuzzy rule ZO, the output quantity is suitable for ZO, and t is not required to be latchedρ,GEOCorrecting; the latched GEO subframe header is one GEO subframe period ahead of the IGSO subframe header under the condition (b), the input quantity is suitable for the fuzzy rule PB, and the output quantity is suitable for NB, tρ,GEOMinus 6 s.
2.4 after the receiver is positioned, the TIC position is corrected by clock error, and the position of the rising edge is aligned with the whole second of the Beidou. As shown in fig. 8: and triggering the IGSO frame synchronous whole second pulse, and basically fixing the positions of the pseudo-range latch signal, the IGSO subframe head, the GEO subframe head and the IGSO frame synchronous whole second pulse.
TABLE 4
E PM PB PX
U NM NB NX
As shown in Table 4, latched GEO subframe header and IGSThe O sub-frame head has only three position relations, the GEO sub-frame head is advanced than the IGSO sub-frame head, the advanced quantity (namely input quantity) is suitable for the fuzzy control rules PM, PB and PX, the output quantity is correspondingly suitable for NM, NB and NX, tρ,GEOThe corresponding subtraction was 0.4s, 0.6s, 0.8 s. The shorter vertical dotted line in the figure is the IGSO frame synchronization whole second signal, the period is 1s, 1ms later than the IGSO subframe.
2.5 before and after the receiver is positioned, weak signals and strong interference cause possible failure of the GEO satellite in frame decoding. As shown in fig. 9, if the frame decoding of the two sub-frame headers shown in the figure fails, the pseudorange latch signal actually latches the pseudorange count value of the previous GEO sub-frame header, and the pseudorange latch signal can be corrected by using the fuzzy control rule, so as to output the correct pseudorange, and improve the robustness of the receiver, as shown in table 5:
TABLE 5
E ZO PS
U ZO NS
3. The least square method realizes receiver positioning and clock error correction.
And positioning the receiver by using a least square method to obtain a clock error, and returning a clock error parameter to correct the TIC so that the TIC is aligned with the Beidou satellite time (BDT) in whole second. The algorithm is as follows:
the equation of pseudorange is
ρcj=[(xj-xu)2+(yj-yu)2+(zj-zu)2]1/2+tu+vj(1)
Where ρ iscjIs the pseudorange of satellite j to the user, (x)u,yu,zu) And (x)j,yj,zj) Respectively representing the position coordinates, t, of the user and the satellite in the ECEF coordinate systemuEquivalent distance error, v, for user clock errorjThe number of observed satellites is n for the corrected pseudorange error. And writing the receiver position and the clock deviation into two parts of a receiver position coordinate, a receiver clock deviation and a correction quantity.
Wherein,for the receiver position coordinates and receiver clock error, Δ xu,Δyu,Δzu,ΔtuIs the corresponding correction amount.
For pseudo-range observation equation inAnd performing Taylor series expansion, and neglecting high-order terms to obtain:
the constant term of the localization equation is:
the receiver to satellite j observation vector is:
wherein R isjIs the distance of satellite j to the receiver position, the pseudorange residuals may be expressed as:
in the above formula, there are 4 unknowns Δ xu、Δyu、Δzu、ΔtuThe distance measurement can be carried out by using 4 satellites to solve the distance measurement, because the receiver position is used in the equation, an iterative method is required to be adopted for calculation, the receiver position can be randomly selected, the iteration frequency is smaller when the calculated receiver position is close to the real position, and the calculated delta x is calculated twice continuouslyu、Δyu、Δzu、tuThe value difference is very small, the iteration can be stopped, pjThe pseudoranges are corrected through a series of corrections for the actual measured pseudoranges.
Writing the above formula in a matrix form includes:
Δρ=H*Δx (7)
wherein:
when the number of the satellites participating in the calculation is as large as 4, the calculation can be performed by using a least square method, and the calculation result is as follows:
Δx=(HTH)-1HTΔρ (8)
the foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.

Claims (5)

1. A pseudo-range measurement method for a mixed constellation of a Beidou navigation satellite system is characterized by comprising the following steps: the method specifically comprises the following steps:
step 1, powering on and resetting a receiver, and randomly generating a pseudo-range latch signal TIC with adjustable rising edge position in the receiver;
step 2, generating a local ranging code and a carrier, capturing a satellite signal, and enabling the successfully captured signal to enter a tracking channel;
step 3, respectively carrying out bit synchronization and subframe synchronization on the GEO satellite, the IGSO satellite and the MEO satellite;
step 4, after sub-frame synchronization of each channel is realized, switching to a pseudo-range output and ephemeris demodulation mode, and further calculating initial pseudo-range propagation time, satellite position and pseudo-range correction parameters, wherein after the IGSO satellite and MEO satellite channels realize bit synchronization, frame synchronization second-integer pulse signals are triggered, and pseudo-range output at the Beidou second-integer position is realized;
step 5, selecting the pseudo-range propagation time of the IGSO satellite calculated in the step 4 as a reference tρ,IGSO_rPseudo-range transmission time t for GEO satellitesρ,GEOCorrecting;
step 6: correcting pseudo-range propagation time of the GEO satellite channel by adopting a fuzzy control rule to obtain pseudo-range propagation time t synchronous with IGSOρ,GEO_cor
Step 7, obtaining an initial pseudo range rho according to the pseudo range propagation time, and smoothing the pseudo range by adopting a carrier phase:
<mrow> <msub> <mi>&amp;rho;</mi> <mrow> <mi>s</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mi>M</mi> </mfrac> <msub> <mi>&amp;rho;</mi> <mi>k</mi> </msub> <mo>+</mo> <mfrac> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> <mi>M</mi> </mfrac> <mo>&amp;lsqb;</mo> <msub> <mi>&amp;rho;</mi> <mrow> <mi>s</mi> <mo>,</mo> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msub> <mo>+</mo> <mi>&amp;lambda;</mi> <mrow> <mo>(</mo> <msub> <mi>&amp;phi;</mi> <mi>k</mi> </msub> <mo>-</mo> <msub> <mi>&amp;phi;</mi> <mrow> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msub> <mo>)</mo> </mrow> <mo>&amp;rsqb;</mo> </mrow>
where ρ iss,kFor the smoothed pseudorange, phi, at the current timekIs the carrier phase, p, at the current times,k-1Smoothed by the last time instant of the pseudorange, phik-1Is the carrier phase, p, of the previous time instantkThe pseudo range which is not smoothed at the current moment is M, and the time constant is smoothed;
and 8, calculating the clock error of the receiver by positioning the receiver, calculating the control quantity of the pseudo-range latch signal, and further correcting the position of the pseudo-range latch signal, wherein the specific calculation formula is as follows:
NTIC,k=NTIC,k-1+(Δu-ΔtTIC_frame)*fc/c
<mrow> <msub> <mi>N</mi> <mrow> <mi>T</mi> <mi>I</mi> <mi>C</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>=</mo> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>N</mi> <mrow> <mi>T</mi> <mi>I</mi> <mi>C</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>f</mi> <mi>c</mi> </msub> </mrow> </mtd> <mtd> <mrow> <msub> <mi>N</mi> <mrow> <mi>T</mi> <mi>I</mi> <mi>C</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>&lt;</mo> <mn>0</mn> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>N</mi> <mrow> <mi>T</mi> <mi>I</mi> <mi>C</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>f</mi> <mi>c</mi> </msub> </mrow> </mtd> <mtd> <mrow> <msub> <mi>N</mi> <mrow> <mi>T</mi> <mi>I</mi> <mi>C</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>&gt;</mo> <msub> <mi>f</mi> <mi>c</mi> </msub> </mrow> </mtd> </mtr> </mtable> </mfenced> </mrow>
in the above formula,. DELTA.uClock error residual, Δ t, obtained for receiver positioningTIC_frameFixed delay for channel frame synchronization, NTIC,kIs the control quantity of TIC at the present moment, NTIC,k-1Control quantity of TIC at the previous time, fcSampling frequency for TIC;
and 9, after the receiver realizes primary positioning, correcting the TIC pulse to be aligned with the Beidou in whole second.
2. The pseudorange measurement method for a beidou navigation satellite system hybrid constellation according to claim 1, characterized in that: in step 4, the subframe head is corrected to the position of the whole second in a soft computing mode, so that pseudo range synchronous output of all satellites is achieved.
3. The pseudorange measurement method for a beidou navigation satellite system hybrid constellation according to claim 1, characterized in that: in step 4, under the premise of not changing the pseudo range latch signal period, the synchronous output of the pseudo ranges of the Beidou three types of satellites, namely the two-rate navigation message, is realized by adopting a software correction method.
4. The Beidou navigation satellite system mixed constellation pseudorange measurement method of claim 1, characterized in that: in step 5, the pseudorange propagation time of an IGSO closest to the equator is selected as a reference, and the pseudorange propagation time of the GEO is corrected.
5. The Beidou navigation satellite system mixed constellation pseudorange measurement method of claim 1, characterized in that: in step 9, the pseudorange propagation times of the GEO satellite and the IGSO satellite are corrected using a simplified fuzzy control rule.
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