CN108344415B - Combined navigation information fusion method - Google Patents
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- CN108344415B CN108344415B CN201810088309.9A CN201810088309A CN108344415B CN 108344415 B CN108344415 B CN 108344415B CN 201810088309 A CN201810088309 A CN 201810088309A CN 108344415 B CN108344415 B CN 108344415B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/20—Instruments for performing navigational calculations
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
- G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
- G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
- G01C21/165—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO 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
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/33—Multimode operation in different systems which transmit time stamped messages, e.g. GPS/GLONASS
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO 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
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/45—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
- G01S19/47—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
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Abstract
The invention discloses a combined navigation information fusion method which mainly comprises a GNSS satellite signal processing module, an SINS attitude speed position updating module, an SINS error compensation module, an SINS/GNSS information fusion module, an SINS error correction module and a result output module. The method comprises the steps of updating the position of the high-frequency SINS attitude speed and measuring the low-frequency GNSS innovation, adaptively adjusting an SINS/GNSS combined navigation Kalman filter observation noise matrix in real time by combining the elevation angle of each visible satellite tracked by a combined navigation receiver and the carrier-to-noise ratio of a navigation signal, updating a combined navigation Kalman filter state equation and an error covariance matrix by the GNSS, the SINS pseudo range and the pseudo range rate measurement value, and finally correcting the measurement error of an inertial device by the SINS and GNSS information fusion feedback. The integrated navigation information fusion method provided by the invention can realize complete robust information fusion calculation of the integrated navigation receiver in a complex electromagnetic environment, and has stronger design theoretical value and engineering application value of the integrated navigation receiver.
Description
Technical Field
The invention belongs to the technical field of satellite navigation, and particularly relates to a combined navigation information fusion method which can effectively improve the positioning accuracy of a strapdown inertial navigation and satellite navigation receiver.
Background
A Global Navigation Satellite System (GNSS) can provide positioning, Navigation and time service for a receiver, and plays an extremely important role in various industry fields. The global satellite navigation system mainly comprises a GPS in the United states, a BDS in China, GALILEO in Europe and GLONASS in Russia at present, and a signal processing end of a navigation receiver calculates the space position and the speed of a satellite according to Interface Control files (ICDs) of various navigation systems by extracting GNSS navigation messages, so that the positioning and resolving of the receiver are realized. An Inertial Navigation System (INS) is an autonomous dead reckoning Navigation System that determines carrier attitude, velocity, and position using Inertial sensors (gyroscopes and accelerometers), a reference azimuth, and initial position attitude information. The Inertial Navigation systems are classified into a Platform Inertial Navigation System (PINS) and a Strapdown Inertial Navigation System (SINS). The PINS is used for installing a gyroscope and an accelerometer on a solid stable platform and measuring a navigation system of the motion parameters of the carrier by using a platform coordinate system as a reference; SINS mounts gyroscopes and accelerometers directly on a carrier, without the need for a physical platform, with platform alignment done by a processor. The PINS has large volume, heavy mass, complex mechanical structure, poor reliability and maintainability, the system performance is restricted by the inertial sensor, and the system cost is very expensive. The SINS has the advantages of short reaction time, small volume, light weight, simple structure, capability of effectively improving the precision and reliability of the system through proper redundant configuration, autonomy, concealment, interference resistance, continuity, completeness and the like. However, the SINS error is accumulated and increased with time, and usually, the micro-mechanical gyroscope and the accelerometer can reach an error of "hundred seconds and hundred meters", so that the SINS and the GNSS are often complemented in advantages, and the method has a wide application prospect.
Aiming at the situation that the measurement noise in the traditional integrated navigation system is counted roughly and cannot be timely used for the complex electromagnetic environment or the violent change of the mobile carrier, the invention provides the integrated navigation information fusion method which can effectively solve the problem of the reduction of the filtering precision and even the Kalman filtering divergence caused by the violent motion of the mobile carrier and is a new technical requirement at present.
Disclosure of Invention
Technical problem to be solved
In order to solve the problems in the prior art, the invention provides a combined navigation information fusion method which mainly comprises the steps of GNSS navigation message extraction, GNSS navigation signal carrier-to-noise ratio calculation, receiver visible satellite elevation calculation, SINS attitude speed position updating, SINS/GNSS combined navigation Kalman filter design, measurement noise adaptive design and the like.
(II) technical scheme
The invention provides a combined navigation information fusion method, which mainly comprises the following steps:
step 1: the combined navigation receiver carries out down-conversion, capturing and tracking and data synchronization processing on the GNSS satellite signals, and extracts GNSS navigation messages;
step 2: acquiring coherent integration values of in-phase and orthogonal branches through a GNSS signal processing loop, and extracting a GNSS navigation signal carrier-to-noise ratio;
and step 3: calculating the space position and the speed of the visible satellite through the GNSS navigation message and the visible satellite signal emission time, and calculating the elevation angle of the visible satellite according to the position of the combined navigation receiver;
and 4, step 4: updating SINS attitude, speed and position information through SINS gyroscope and accelerometer measurement values;
and 5: designing a state transition matrix and a measurement equation of the integrated navigation Kalman filter through an SINS attitude, speed, position, error propagation model and a GNSS clock error model;
step 6: and designing and measuring a noise matrix through the carrier-to-noise ratio and the elevation angle of the GNSS navigation signal, and performing Kalman filtering updating, SINS error correction and result output.
Preferably, the GNSS in step 1 is GPS.
Optionally, the GNSS in step 1 may be GPS, BDS, GALILEO, or any combination of the three.
Optionally, if the GNSS in step 1 is combined by GLONASS and GPS/BDS/GALILEO, the GPS uses WGS-84 coordinate system, the GALILEO uses GTRF coordinate system, and the BDS uses CGCS2000 coordinate system, and the origins and coordinate axes of the three coordinate systems are substantially the same, and the error between the coordinate systems is very small and can be ignored under non-precise positioning; GLONASS adopts PZ-90 coordinate system, and needs coordinate conversion with GPS/BDS/GALILEO.
Preferably, in step 2, the GNSS navigation signal carrier-to-noise ratio is calculated by a narrow-wide power ratio method in a navigation message data bit period τaNIn the method, coherent accumulation narrowband power P is calculatedNSum non-coherent accumulated wideband power PWThe calculation formula is as follows:
wherein, the navigation message data bit period tauaNDivided into N segments, each segment having a time ofNumber of points of coherent integration time M, IP,iAnd QP,iAre each tauaWAccumulated value over time. Then, the power ratio is calculated, and after n times of accumulation, the average value is taken to reduce noise, and the formula is as follows:
the carrier-to-noise power density ratio measurements are:
finally, the GNSS navigation signal carrier to noise ratio is:
wherein lg represents a base-10 logarithmic operation.
Preferably, in step 2,. tau.aWIs the time for 1ms, and the time for the second time,the average time was 1 s.
Preferably, in step 3, the spatial position and the velocity of the visible satellite are calculated by using the GNSS navigation message and the visible satellite signal transmission time, where the visible satellite signal transmission time is the visible satellite signal transmission time constructed by combining the navigation receiver signal processing tracking loop, and specifically includes the current subframe week inner second, the number of navigation message data code words, the navigation message bit number of the current navigation message data code words, the number of code pieces of the current navigation message bit number, and the phase of the current navigation message code piece.
Preferably, in step 3, the position and the speed of the visible satellite in the geocentric geostationary coordinate system are calculated through the GNSS navigation message and the visible satellite signal emission time according to the official ICD interface document of each satellite navigation system, and the visible satellite elevation angle is calculated according to the position of the combined navigation receiver.
Preferably, the SINS pose, velocity and position information is updated in step 4 by a quadtype method.
Optionally, the update frequency of the SINS in the step 4 is 20-100 Hz.
Preferably, the updating of the attitude of the strapdown inertial navigation system in the step 4 is performed by a quaternion method.
Optionally, the attitude updating algorithm of the strapdown inertial navigation system in the step 4 may adopt a direction cosine method or an euler angle method.
Preferably, the SINS attitude error propagation model in step 5 is:
wherein the content of the first and second substances,and is the attitude error under the SINS navigation coordinate system, "×" represents the matrix cross product,the projection of the rotational angular velocity of the earth relative to the rotational angular velocity of the earth system in a navigation coordinate system is obtained;for rotation of the navigational system relative to the terrestrial systemProjection of the dynamic angular velocity in a navigation coordinate system; δ represents the vector differential;representing a matrix of strapdowns,representing the amount of attitude noise in the carrier coordinate system,the superscript "." denotes the differential, and the same reference signs used in the following text represent the same meanings.
Preferably, the SINS velocity error propagation model in step 5 is:
wherein the content of the first and second substances,representing specific force measurements made by the accelerometer in the navigational coordinate system,representing the specific force measurement noise amount in the carrier coordinate system.
Preferably, the SINS position error propagation model in step 5 is:
wherein, (L, lambda, h) represents the latitude, longitude and elevation of SINS, and RMRepresents the radius of the meridian, RNRepresenting the radius of the unitary mortise ring.
Preferably, the GNSS clock difference model in step 5 is:
wherein, bclkRepresenting combined navigation receiver clock error, omegabRepresenting combined navigation receiver clock error noise, dclkRepresenting combined navigation receiver frequency drift, omegadRepresenting combined navigation receiver frequency drift noise, TclkRepresenting the clock relative time.
Preferably, the state transition matrix of the integrated navigation kalman filter in step 5 is:
wherein, FSINS/CNSSRepresents the combined navigation Kalman filter state transition matrix, wherein 03×30 matrix representing 3 rows and 3 columns, 03×20 matrix representing 3 rows and 2 columns, 02×3Represents a 0 matrix of 2 rows and 3 columns, and
M13=M′+M″
M23=(vn×)(2M′+M″)
preferably, the measurement equation of the integrated navigation kalman filter in step 5 is divided into a pseudorange measurement equation and a pseudorange rate measurement equation.
Preferably, the pseudorange measurement equation in step 5 is as follows:
wherein, deltaρRepresenting a pseudo range obtained by SINS measurement and a pseudo range difference vector obtained by GNSS measurement; li,mi,ni(i ═ 1,2 … N) represents the direction cosine matrix of the ith visible satellite, δxRepresenting the position error of the x axis of the combined navigation receiver under the geocentric geostationary coordinate system; deltayRepresenting the y-axis position error of the combined navigation receiver under the geocentric geostationary coordinate system; deltazRepresenting the position error of the combined navigation receiver on the z axis under the geocentric geostationary coordinate system; bclkRepresenting the clock error of the combined navigation receiver,representing the pseudorange difference noise figure for the ith satellite.
Preferably, the pseudorange rate measurement equation in step 5 is as follows:
wherein the content of the first and second substances,representing a pseudo range rate obtained by SINS measurement and a pseudo range difference vector obtained by GNSS measurement;representing the x-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system;representing the y-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system;representing the z-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system; dclkRepresenting the frequency drift of the combined navigation receiver,representing the pseudorange delta noise magnitude for the ith satellite.
Preferably, the measured noise matrix designed by the carrier-to-noise ratio and the elevation angle of the GNSS navigation signal in step 6 is as follows:
wherein, R represents a measurement noise matrix,represents the square of the elevation of the ith satellite in view, ReferCN0Representing a reference carrier-to-noise ratio of the combined navigation receiver; (C/N)0)i(i-1, 2 … N) represents the carrier to noise ratio at the elevation angle of the ith visible satellite.
(III) advantageous effects
The integrated navigation information fusion method provided by the invention can produce positive beneficial effects, the method can adaptively adjust the observation noise distribution of the SINS/GNSS integrated navigation filter in real time by combining the space distribution of visible satellites and the intensity of navigation signals through the high-frequency SINS attitude speed position updating and the low-frequency GNSS innovation measurement, and timely updates the integrated navigation Kalman filter and corrects the measurement error of an SINS inertial device, can realize complete and robust information fusion resolving of the integrated navigation receiver in a complex electromagnetic environment, and has strong design theoretical value and engineering application value of the integrated navigation receiver.
Drawings
FIG. 1 is a schematic diagram of an integrated navigation information fusion module according to a preferred embodiment of the present invention;
fig. 2 shows a flow chart of the integrated navigation information fusion method according to the preferred embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
Fig. 1 shows a schematic diagram of a combined navigation information fusion module according to a preferred embodiment of the present invention.
As shown in FIG. 1, the integrated navigation information fusion module of the preferred embodiment of the present invention mainly comprises a GNSS satellite signal processing module M1, an SINS attitude velocity and position updating module M2, an SINS error compensation module M3, an SINS/GNSS information fusion module M4, an SINS error correction module M5 and a result output module M6. The GNSS satellite signal processing module M1 extracts a GNSS satellite signal navigation message through capturing, tracking, bit synchronization, and frame synchronization operations in the GNSS satellite signal processing process, which takes GPS as an example in the specific embodiment of the present invention. After a GNSS receiver tracking channel acquires a navigation message of a tracked satellite, calculating the carrier-to-noise ratio of the tracked visible satellite signal by adopting a narrow-wide power ratio method. The SINS attitude velocity position update module M2 obtains the angular velocity and specific force measurement values through the inertial measurement unit gyroscope and accelerometer of the SINS, and follows the new SINS attitude velocity position information, before that, an accurate initial position and attitude of the SINS are needed to be given, and the strapdown inertial navigation coarse alignment and fine alignment operations are performed. The SINS error compensation module M3 corrects the attitude velocity and position errors through a two-subsampled or four-subsampled algorithm, which is used in the preferred embodiment of the present invention. The SINS/GNSS information fusion module M4 obtains the position, speed, elevation angle, carrier-to-noise ratio, pseudo range and pseudo range rate information of the visible satellite through the GNSS, the SINS obtains the pseudo range and pseudo range rate information of the satellite, and performs state transition matrix calculation, measurement noise matrix calculation, combined navigation Kalman filtering state equation and error covariance matrix updating according to the strapdown inertial navigation system error propagation model. The SINS error correction module M5 feeds back the state error amount calculated by the SINS/GNSS information fusion module M4 to the SINS, and performs SINS state error correction. In the result output module M6, the SINS update frequency is faster, which can generally reach 50Hz, and the SINS/GNSS information fusion frequency is lower, which is generally 10Hz, so the SINS update frequency and the SINS/GNSS fusion frequency are adjusted according to the actual requirement of the integrated navigation receiver, and the result after the SINS error correction is output.
Fig. 2 shows a flow chart of the integrated navigation information fusion method according to the preferred embodiment of the present invention.
As shown in fig. 2, the flowchart of the integrated navigation information fusion method according to the preferred embodiment of the present invention mainly includes the following steps:
step 1: the combined navigation receiver carries out down-conversion, capturing and tracking and data synchronization processing on the GNSS satellite signals, and extracts GNSS navigation messages;
step 2: acquiring coherent integration values of in-phase and orthogonal branches through a GNSS signal processing loop, and extracting a GNSS navigation signal carrier-to-noise ratio;
and step 3: calculating the space position and the speed of the visible satellite through the GNSS navigation message and the visible satellite signal emission time, and calculating the elevation angle of the visible satellite according to the position of the combined navigation receiver;
and 4, step 4: updating SINS attitude, speed and position information through SINS gyroscope and accelerometer measurement values;
and 5: designing a state transition matrix and a measurement equation of the integrated navigation Kalman filter through an SINS attitude, speed, position, error propagation model and a GNSS clock error model;
step 6: and designing and measuring a noise matrix through the carrier-to-noise ratio and the elevation angle of the GNSS navigation signal, and performing Kalman filtering updating, SINS error correction and result output.
In the embodiment of the present invention, the GNSS in step 1 is a GPS.
In the step 2, the GNSS navigation signal carrier-to-noise ratio is calculated by adopting a narrow-wide power ratio method, and in the navigation message data bit period tauaNIn the method, coherent accumulation narrowband power P is calculatedNSum non-coherent accumulated wideband power PWThe calculation formula is as follows:
wherein, the navigation message data bit period tauaNDivided into N segments, each segment having a time ofNumber of points of coherent integration time M, IP,iAnd QP,iAre each tauaWAccumulated value over time. Then, the power ratio is calculated, and after n times of accumulation, the average value is taken to reduce noise, and the formula is as follows:
the carrier-to-noise power density ratio measurements are:
finally, the GNSS navigation signal carrier to noise ratio is:
wherein lg represents a base-10 logarithmic operation.
Step 3 said navigation message and visible satellite signal emission time meter by GNSSCalculating the space position and the speed of a visible satellite, wherein the visible satellite signal transmission time is the visible satellite signal transmission time constructed by combining a signal processing and tracking loop of a navigation receiver, and specifically comprises second TOW in the current subframe period, the number omega of navigation message data code words, the navigation message bit number b of the current navigation message data code words, the chip number C of the current navigation message bit number and the phase CP of the current navigation message chips(unit: second) the formula is constructed as follows:
and 3, calculating the position and the speed of the visible satellite under the geocentric geostationary coordinate system according to the GNSS navigation message and the visible satellite signal emission time ts and according to official ICD interface documents of each satellite navigation system, and calculating the elevation angle of the visible satellite according to the position of the combined navigation receiver.
And step 4, updating the SINS attitude, speed and position information by a four-subsample method.
The SINS update frequency in step 4 is 50 Hz.
And 4, updating the attitude of the strapdown inertial navigation system by a quaternion method.
The SINS attitude error propagation model in the step 5 is as follows:
wherein the content of the first and second substances,and is the attitude error under the SINS navigation coordinate system, "×" represents the matrix cross product,the projection of the rotational angular velocity of the earth relative to the rotational angular velocity of the earth system in a navigation coordinate system is obtained;is the projection of the rotation angular speed of the navigation system relative to the earth system in a navigation coordinate system; δ represents the vector differential;representing a matrix of strapdowns,representing the amount of attitude noise in the carrier coordinate system,the superscript ". indicates the differential.
The SINS velocity error propagation model in the step 5 is as follows:
wherein the content of the first and second substances,representing specific force measurements made by the accelerometer in the navigational coordinate system,representing the specific force measurement noise amount in the carrier coordinate system.
The SINS position error propagation model in the step 5 is as follows:
wherein, (L, lambda, h) represents the latitude, longitude and elevation of SINS, and RMRepresents the radius of the meridian, RNRepresenting the radius of the unitary mortise ring.
In step 5, the GNSS clock error model is:
wherein, bclkRepresenting combined navigation receiver clock error, omegabRepresenting combined navigation receiver clock error noise, dclkRepresenting combined navigation receiver frequency drift, omegadRepresenting combined navigation receiver frequency drift noise, TclkRepresenting the clock relative time.
The state transition matrix of the integrated navigation Kalman filter in the step 5 is as follows:
wherein, 03×30 matrix representing 3 rows and 3 columns, 03×20 matrix representing 3 rows and 2 columns, 02×3Represents a 0 matrix of 2 rows and 3 columns, and
M13=M′+M″
M23=(vn×)(2M′+M″)
and 5, dividing the measurement equation of the integrated navigation Kalman filter into a pseudo-range measurement equation and a pseudo-range rate measurement equation. The pseudorange measurement equation is as follows:
wherein, deltaρRepresenting a pseudo range obtained by SINS measurement and a pseudo range difference vector obtained by GNSS measurement; li,mi,ni(i ═ 1,2 … N) represents the direction cosine matrix of the ith visible satellite, δxRepresenting the position error of the x axis of the combined navigation receiver under the geocentric geostationary coordinate system; deltayRepresenting the y-axis position error of the combined navigation receiver under the geocentric geostationary coordinate system; deltazRepresenting the position error of the combined navigation receiver on the z axis under the geocentric geostationary coordinate system; bclkRepresenting the clock error of the combined navigation receiver,representing the pseudorange difference noise figure for the ith satellite.
The pseudorange rate measurement equation in step 5 is as follows:
wherein the content of the first and second substances,representing a pseudo range rate obtained by SINS measurement and a pseudo range difference vector obtained by GNSS measurement;representing the x-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system;representing the y-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system;representing the z-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system; dclkRepresenting the frequency drift of the combined navigation receiver,representing the pseudorange delta noise magnitude for the ith satellite.
The measurement noise matrix designed by the carrier-to-noise ratio and the elevation angle of the GNSS navigation signal in step 6 is as follows:
wherein the content of the first and second substances,represents the square of the elevation of the ith satellite in view, ReferCN0The reference carrier-to-noise ratio of the combined navigation receiver is represented, and is 45dB & Hz in the specific embodiment of the invention; (C/N)0)i(i-1, 2 … N) represents the carrier to noise ratio at the elevation angle of the ith visible satellite.
In the step 6, the update frequency of the SINS/GNSS integrated navigation information fusion Kalman filter is 10Hz, and after each update, the SINS is subjected to error correction and result output.
In summary, the present invention provides a combined navigation information fusion method. According to the method, the SINS/GNSS combined navigation Kalman filter observation noise is adaptively adjusted in real time through high-frequency SINS attitude speed position updating and low-frequency GNSS innovation measurement in combination with the space distribution and navigation signal carrier-to-noise ratio of each visible satellite tracked by the combined navigation receiver, the state equation and the error covariance matrix of the combined navigation Kalman filter are updated through the GNSS, the SINS pseudo range and the pseudo range rate measurement value, the inertial device measurement error is corrected through SINS and GNSS information fusion feedback, complete robust information fusion resolving of the combined navigation receiver in a complex electromagnetic environment can be achieved, and the combined navigation receiver has high design theoretical value and engineering application value. It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modifications and the like made without departing from the spirit and scope of the present invention shall be included in the protection scope of the present invention. It is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (9)
1. A method for fusing combined navigation information is characterized by comprising the following steps:
step 1: the combined navigation receiver carries out down-conversion, capturing and tracking and data synchronization processing on the GNSS satellite signals, and extracts GNSS navigation messages;
step 2: acquiring coherent integration values of in-phase and orthogonal branches through a GNSS signal processing loop, and extracting a GNSS navigation signal carrier-to-noise ratio;
and step 3: calculating the space position and the speed of the visible satellite through the GNSS navigation message and the visible satellite signal emission time, and calculating the elevation angle of the visible satellite according to the position of the combined navigation receiver;
and 4, step 4: updating SINS attitude, speed and position information through SINS gyroscope and accelerometer measurement values;
and 5: designing a state transition matrix and a measurement equation of the integrated navigation Kalman filter through an SINS attitude, speed, position, error propagation model and a GNSS clock error model;
step 6: designing and measuring a noise matrix through a GNSS navigation signal carrier-to-noise ratio and an elevation angle, and performing Kalman filtering updating, SINS error correction and result output;
wherein, the state transition matrix of the integrated navigation kalman filter in step 5 is:
wherein, FSINS/GNSSRepresenting the State transition matrix of the Combined navigation Kalman Filter, 03×30 matrix representing 3 rows and 3 columns, 03×20 matrix representing 3 rows and 2 columns, 02×3Represents a 0 matrix of 2 rows and 3 columns, and
M13=M′+M″
M23=(vn×)(2M′+M″)
wherein the content of the first and second substances,(L, λ, h) represents the latitude, longitude and elevation of the SINS, RMRepresents the radius of the meridian, RNRepresenting radius of unitclkRepresenting the clock correlation time, and dividing the measurement equation of the integrated navigation Kalman filter in the step 5 into a pseudo-range measurement equation and a pseudo-range rate measurement equation; the pseudorange measurement equation is as follows:
wherein, δ ρ represents a pseudorange obtained by SINS measurement and a pseudorange difference vector obtained by GNSS measurement; li,mi,niThe direction cosine matrixes of the ith visible satellite are respectively represented, i is 1, 2.. N, and deltax represents the position error of the x axis of the combined navigation receiver under the geocentric geostationary coordinate system; delta y represents the y-axis position error of the combined navigation receiver under the geocentric geostationary coordinate system; δ z represents the position error of the combined navigation receiver on the z axis under the geocentric geostationary coordinate system; bclkRepresenting combined navigation receiver clock error, thetaρiRepresenting the pseudo range difference noise amount of the ith satellite; the pseudorange rate measurement equation is as follows:
wherein the content of the first and second substances,representing a pseudo range rate obtained by SINS measurement and a pseudo range difference vector obtained by GNSS measurement;representing the x-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system;representing the y-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system;representing the z-axis speed error of the combined navigation receiver under the geocentric geostationary coordinate system; dclkRepresenting the frequency drift of the combined navigation receiver,representing the pseudorange delta noise magnitude for the ith satellite.
2. The combined navigation information fusion method according to claim 1, wherein: the GNSS in the step 1 is GPS or BDS or GALILEO or any combination of the three.
3. The combined navigation information fusion method according to claim 2, wherein: the GNSS adopts GLONASS and GPS/BDS/GALILEO to combine, the GPS adopts a WGS-84 coordinate system, the GALILEO adopts a GTRF coordinate system, the BDS adopts a CGCS2000 coordinate system, the origin and the coordinate axis of the coordinate systems are basically consistent, and the GLONASS adopts a PZ-90 coordinate system and needs to perform coordinate conversion with the GPS/BDS/GALILEO.
4. The combined navigation information fusion method according to claim 1, wherein: in the step 2, the GNSS navigation signal carrier-to-noise ratio is calculated by adopting a narrow-wide power ratio method, and in the navigation message data bit period tauaNIn the method, coherent accumulation narrowband power P is calculatedNSum non-coherent accumulated wideband power PWThe calculation formula is as follows:
wherein, the navigation message data bit period tauaNDivided into N segments, each segment having a time ofNumber of points of coherent integration time M, IP,iAnd QP,iAre all tauaWAccumulated value in time, and then power ratio is calculatedAfter n accumulations, the average is taken to reduce noise, and the formula is:
the carrier-to-noise power density ratio measurements are:
finally, the GNSS navigation signal carrier to noise ratio is:
wherein lg represents a base-10 logarithmic operation.
5. The combined navigation information fusion method according to claim 1, wherein: calculating the space position and the speed of the visible satellite through the GNSS navigation message and the visible satellite signal emission time in the step 3, wherein the visible satellite signal emission time is the visible satellite signal emission time constructed by combining a signal processing and tracking loop of the navigation receiver, and specifically comprises the current subframe week number of seconds, the number of navigation message data code words, the navigation message bit number of the current navigation message data code words, the number of code pieces of the current navigation message bit number and the phase of the current navigation message code pieces; and further, calculating the position and the speed of the visible satellite under the geocentric geostationary coordinate system according to the GNSS navigation message and the visible satellite signal emission time and according to official ICD interface documents of each satellite navigation system, and calculating the visible satellite elevation according to the position of the combined navigation receiver.
6. The combined navigation information fusion method according to claim 1, wherein: and step 4, updating the SINS attitude, speed and position information by a four-subsample method.
7. The combined navigation information fusion method according to claim 1, wherein: the SINS attitude error propagation model in the step 5 is as follows:
wherein the content of the first and second substances,and is the attitude error under the SINS navigation coordinate system, "×" represents the matrix cross product, the projection of the rotational angular velocity of the earth relative to the rotational angular velocity of the earth system in a navigation coordinate system is obtained;is the projection of the rotation angular speed of the navigation system relative to the earth system in a navigation coordinate system; δ represents the vector differential;representing a matrix of strapdowns,representing the amount of attitude noise in the carrier coordinate system,superscript "-" represents differential;
the SINS velocity error propagation model is:
wherein the content of the first and second substances, representing specific force measurements made by the accelerometer in the navigational coordinate system,representing specific force measurement noise amount under a carrier coordinate system;
the SINS position error propagation model is as follows:
wherein, (L, lambda, h) represents the latitude, longitude and elevation of SINS, and RMRepresents the radius of the meridian, RNRepresenting the radius of the unitary mortise ring.
8. The combined navigation information fusion method according to claim 1, wherein: in step 5, the GNSS clock error model is:
wherein, bclkRepresenting combined navigation receiver clock error, omegabRepresenting combined navigation receiver clock error noise, dclkRepresenting combined navigation receiver frequency drift, omegadRepresenting combined navigation receiver frequency drift noise, TclkRepresenting the clock relative time.
9. The combined navigation information fusion method according to claim 1, wherein: the measurement noise matrix designed by the carrier-to-noise ratio and the elevation angle of the GNSS navigation signal in step 6 is as follows:
wherein, R represents a measurement noise matrix,represents the square of the elevation of the ith satellite in view, ReferCN0Representing a reference carrier-to-noise ratio of the combined navigation receiver; (C/N)0)iThe carrier-to-noise ratio representing the elevation angle of the ith visible satellite.
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