CN111427071B - Clock maintenance method for satellite-borne computer navigation filtering - Google Patents
Clock maintenance method for satellite-borne computer navigation filtering Download PDFInfo
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- CN111427071B CN111427071B CN202010112760.7A CN202010112760A CN111427071B CN 111427071 B CN111427071 B CN 111427071B CN 202010112760 A CN202010112760 A CN 202010112760A CN 111427071 B CN111427071 B CN 111427071B
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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
- G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
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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
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
- G06F1/04—Generating or distributing clock signals or signals derived directly therefrom
- G06F1/12—Synchronisation of different clock signals provided by a plurality of clock generators
Abstract
Aiming at the conditions that clocks among different single machines on a 1553B bus in a satellite platform are asynchronous and the data frequency is inconsistent with the calculation period of the satellite-borne computer, the clock maintenance method for the satellite-borne computer navigation filtering ensures the stability and effectiveness of a navigation filtering algorithm by maintaining the time axis of the navigation filtering and constructing a protection mechanism of a navigation measurement data access system. The method can overcome the phenomena of jitter or error data of the GNSS measurement data time stamp, invalid data or no data update. Compared with the method for determining the orbit by directly using the GNSS measurement data, the method has the advantage that the orbit output result of the navigation filtering algorithm is more reliable.
Description
Technical Field
The invention relates to a clock maintenance method for satellite-borne computer navigation filtering. More particularly, the method is a protection mechanism for constructing a navigation measurement data access system by maintaining a time axis of navigation filtering and aiming at the conditions that clocks are not synchronous and data frequency is not consistent with a calculation period among different single machines on a 1553B bus in a satellite platform. The method can overcome the phenomena of jumping or error data of the GNSS measured data timestamp, invalid data or no data updating, and can enable the track output result of the navigation filtering algorithm to be more stable. A clock maintenance method for satellite-borne computer navigation filtering belongs to the technical application field of spacecraft engineering.
Background
In orbit satellites in near earth orbit, autonomous orbit determination relies primarily on positioning measurement data from GNSS receivers. In the satellite platform, the GNSS receiver and the on-board computer are both arranged on a 1553B bus and are subjected to scheduling of a satellite integrated electronic system for data transmission. The GNSS receiver outputs measurement data to the satellite-borne computer, the phenomena of time stamp jumping or error data, data invalidity or data non-updating exist, and the satellite-borne computer is required to design a clock maintenance method of navigation filtering to ensure the stability and the effectiveness of a track determination result. Specifically, the calculation cycles of the spaceborne computer are more in types, and are more commonly 0.5 second; the measurement data update frequency of the GNSS receiver is more commonly 1Hz, which does not match the calculation cycle of the on-board computer. At present, no patent or paper and other research results are published on a clock maintenance method for satellite-borne computer navigation filtering.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the clock maintenance method for satellite-borne computer navigation filtering overcomes the defects of the prior art. The method can overcome the adverse effects on the track determination result caused by the phenomena of time stamp jumping or error data, data invalidity or data non-updating of the measured data output to the satellite-borne computer by the GNSS receiver. The designed clock maintenance method for the satellite-borne computer navigation filtering can effectively improve the stability of the satellite-borne computer orbit determination result.
The technical solution of the scheme is as follows: a clock maintenance method for satellite-borne computer navigation filtering comprises the following steps:
1) the validity judgment is carried out aiming at GNSS measurement data of the satellite-borne GNSS receiver;
2) maintaining the data updating state according to the validity state of the GNSS measurement data;
3) and maintaining a filtering time axis according to the time stamp of the GNSS measurement data, and outputting a track determination result of navigation filtering.
The data validity judgment in the step (1) has three logic criteria 1a), 1b) and 1c), if the three logic criteria are simultaneously met, the data of the GNSS receiver is valid, and the Flag bit is set to be 1; otherwise, setting Flag to be 0; wherein the content of the first and second substances,
1a) judging that the receiver data meet the available requirement when the positioning mark of the GNSS receiver test data is analyzed to be valid; determining that the receiver data is "unavailable" when the locator flag is at another value;
1b) judging whether the effective zone bit of the GNSS measurement data and the orbit data accord with the orbit characteristics; rejecting erroneous measurement data;
1c) the time difference between the time stamp of the GNSS measurement data and the time of the satellite-borne computer is less than 20 seconds, the measurement data "meets the available requirement", otherwise, the measurement data is the "unavailable" data.
The track data conforms to the track characteristics and needs to satisfy a threshold judgment formula, which is specifically as follows:
6.79×106m≤||r||≤7.05×106m
and is
7.46×103m/s≤||v||≤7.75×103m/s
And x, y and z are position data of three axes under the earth fixed system measured by the GNSS receiver, and vx, vy and vz are speed data of three axes under the earth fixed system measured by the GNSS receiver.
The specific process of maintaining the data update state in the step (2) is as follows:
2a) to ensure state continuity of the filtering algorithm, a counter is established: the system comprises a data non-updating counter tn, a data updating counter ty and a data unavailable counter t, wherein default initial values of the three counters are zero;
2b) when each Flag is equal to 1, the accumulated data updating counter ty and the data non-updating counter tn are cleared; when tn is larger than 10, clearing the unavailable data by using the counter t;
2c) when each Flag is equal to 0, the accumulated data does not update the counter tn and the data unavailable counter t; when tn is more than 10, resetting the accumulated data updating counter ty;
2d) when the data unavailable counter t does not exceed the threshold value, performing intermittent Kalman navigation filtering calculation based on GNSS data; when the data unavailable counter t exceeds a threshold value, the navigation quits the filtering calculation, and the autonomous orbit determines to quit the backup scheme;
2e) in the backup scheme state, the data update counter ty is greater than 10, and the GNSS navigation restarts.
The specific process of maintaining the filtering time axis in the step (3) is as follows:
3a) the filtering time of the track navigation takes the time stamp of the GNSS measurement data as the reference;
3b) the calculation cycle of the spaceborne computer is 0.5s, the time interval of GNSS measurement data is 1s, and in the calculation cycle without measurement data, the filtering moment is the filtering moment of the previous beat plus the calculation cycle of the spaceborne computer for 0.5s, so that Kalman intermittent recursive filtering is carried out;
3c) when the GNSS measurement data are not updated for a long time, accumulating by taking the calculation period of the spaceborne computer as 0.5s as a beat on the basis of the valid time of the preorder filtering time, and performing Kalman intermittent recursive filtering;
3d) and (4) carrying out time compensation on the track number obtained by Kalman intermittent recursive filtering under each filtering beat, wherein the track number is consistent with the computing time of the satellite borne computer.
Compared with the prior art, the invention has the advantages that:
1) and judging the validity of the track measurement data, and performing multiple diagnoses on the validity of the data. Aiming at different single machines on a 1553B bus, when a satellite-borne computer applies navigation data, logical and judgment of three conditions of zone bits, track characteristic conformity and time deviation is carried out on GNSS receiver data, validity diagnosis of the GNSS receiver data is completed, and invalid data is removed;
2) maintaining the updating state of the track measurement data, and designing three types of counters for determining the data updating state of the GNSS receiver under the current filtering beat aiming at different single-machine clocks on a 1553B bus, particularly for the inconsistency of the calculation cycle frequency of the satellite-borne computer and the data frequency of the GNSS receiver;
3) and maintaining a filtering time axis, and designing a Kalman intermittent recursive filtering structure and outputting result time compensation aiming at the inconsistency of the calculation cycle frequency (0.5s cycle) of the on-board computer and the data frequency (1s cycle) of the GNSS receiver, so that the inherent frequency deviation does not influence the navigation data application of the on-board computer. At present, no published patent or paper and other research results exist.
Drawings
Fig. 1 is a diagram of a stand-alone access relationship in a satellite platform to which the present invention relates.
FIG. 2 is an on-board computer cycle and GNSS receiver data frequency to which the present invention relates.
FIG. 3 is a logic for determining the update status of data according to the present invention.
Detailed Description
1) Track measurement data validity judgment
The data validity judgment in the step (1) is provided with three logic criteria 1a), 1b) and 1c), if the three logic criteria are simultaneously met, the GNSS receiver data is valid, and the Flag bit is set to be 1; otherwise, set Flag to 0.
1a) Judging that the receiver data meet the available requirement when the positioning mark of the GNSS receiver test data is analyzed to be valid; the receiver data is determined to be "unavailable" when the locator flag is at another value.
1b) Judging whether the effective zone bit of the GNSS measurement data and the orbit data accord with the orbit characteristics; and eliminating error measurement data. The track data meets the requirement of track characteristics, and the requirement of satisfying a threshold judgment formula is as follows
6.79×106m≤||r||≤7.05×106m
And is
7.46×103m/s≤||v||≤7.75×103m/s
And x, y and z are position data of three axes under the earth fixed system measured by the GNSS receiver, and vx, vy and vz are speed data of three axes under the earth fixed system measured by the GNSS receiver. The constant value boundaries on the two sides of the inequality can be flexibly set according to different track heights.
1c) The time difference between the time stamp of the GNSS measurement data and the time of the satellite-borne computer is less than 20 seconds, the measurement data "meets the available requirement", otherwise, the measurement data is the "unavailable" data.
2) Track measurement data update status maintenance
Since the computation cycle of the on-board computer is 0.5s, and the computation cycle is not matched with the update frequency of the GNSS measurement data 1Hz, the effective Flag of the GNSS measurement data collected by the on-board computer appears alternately as 1 and as 0. The connection relationship between the on-board computer and the GNSS receiver on the 1553B bus is shown in FIG. 1, and the data frequency characteristics of the on-board computer and the GNSS receiver are shown in FIG. 2.
2a) To ensure state continuity of the filtering algorithm, a counter is established: the system comprises a data non-updating counter tn, a data updating counter ty and a data unavailable counter t, wherein default initial values of the three counters are zero;
2b) each time Flag is set to 1, the accumulated data update counter ty and the data non-update counter tn are cleared. When the ty is greater than 10, clearing the data unavailable counter t;
2c) every time Flag is set to 0, the accumulated data does not update the counter tn and the data unavailable counter t. When tn is more than 10, resetting the accumulated data updating counter ty;
2d) when the data unavailable counter t does not exceed the threshold value, performing navigation filtering calculation based on GNSS data; if the unavailable counter t of the data exceeds the threshold value, the navigation quits the filtering calculation, and the autonomous orbit determines to quit the backup scheme;
2e) in the backup scheme state, the data update counter ty is greater than 10, and the GNSS navigation restarts.
The logic flow of the counter assignment and data update state is shown in fig. 3.
3) Filtered time axis maintenance
3a) The filtering time of the orbit navigation is based on the time stamp of the GNSS measurement data.
3b) The calculation cycle of the on-board computer is 0.5s, the time interval of GNSS measured data is 1s, and in the calculation cycle without measured data, the filtering time is the filtering time of the previous beat plus the calculation cycle of the on-board computer is 0.5 s;
3c) when the GNSS measurement data is not updated for a long time, accumulating by taking the calculation period of the spaceborne computer as a beat on the basis that the filtering moment is the valid moment of the preorder;
3d) and (3) carrying out time compensation on the track number obtained by Kalman intermittent recursive filtering under each filtering beat, wherein the track number is consistent with the calculation time of the satellite borne computer, and broadcasting a corresponding track determination result on a 1553B bus.
Claims (1)
1. A clock maintenance method for satellite-borne computer navigation filtering is characterized by comprising the following steps:
1) the validity judgment is carried out aiming at GNSS measurement data of the satellite-borne GNSS receiver;
2) maintaining the data updating state according to the validity state of the GNSS measurement data;
3) according to the time stamp of the GNSS measurement data, maintaining a filtering time axis, and outputting a track determination result of navigation filtering;
the data validity judgment in the step (1) has three logic criteria 1a), 1b) and 1c), if the three logic criteria are simultaneously met, the data of the GNSS receiver is valid, and the Flag bit is set to be 1; otherwise, setting Flag to be 0; wherein the content of the first and second substances,
1a) judging that the receiver data meet the available requirement when the positioning mark of the GNSS receiver test data is analyzed to be valid; determining that the receiver data is "unavailable" when the locator flag is at another value;
1b) judging whether the effective zone bit of the GNSS measurement data and the orbit data accord with the orbit characteristics; rejecting erroneous measurement data;
1c) the value of the time difference between the time stamp of the GNSS measurement data and the time difference of the satellite-borne computer is less than 20 seconds, the measurement data meet the available requirement, and otherwise, the measurement data are unavailable data;
the track data conforms to the track characteristics and needs to satisfy a threshold judgment formula, which is specifically as follows:
6.79×106m≤||r||≤7.05×106m
and is
7.46×103m/s≤||v||≤7.75×103m/s
Wherein x, y and z are position data of three shafts under the earth fixed system measured by the GNSS receiver, and vx, vy and vz are speed data of three shafts under the earth fixed system measured by the GNSS receiver;
the specific process of maintaining the data update state in the step (2) is as follows:
2a) to ensure state continuity of the filtering algorithm, a counter is established: the system comprises a data non-updating counter tn, a data updating counter ty and a data unavailable counter t, wherein default initial values of the three counters are zero;
2b) when each Flag is equal to 1, the accumulated data updating counter ty and the data non-updating counter tn are cleared; when tn is larger than 10, clearing the unavailable data by using the counter t;
2c) when each Flag is equal to 0, the accumulated data does not update the counter tn and the data unavailable counter t; when tn is more than 10, resetting the accumulated data updating counter ty;
2d) when the data unavailable counter t does not exceed the threshold value, performing intermittent Kalman navigation filtering calculation based on GNSS data; when the data unavailable counter t exceeds a threshold value, the navigation quits the filtering calculation, and the autonomous orbit determines to quit the backup scheme;
2e) in the state of the backup scheme, the data updating counter ty is larger than 10, and the GNSS navigation is restarted;
the specific process of maintaining the filtering time axis in the step (3) is as follows:
3a) the filtering time of the track navigation takes the time stamp of the GNSS measurement data as the reference;
3b) the calculation cycle of the spaceborne computer is 0.5s, the time interval of GNSS measurement data is 1s, and in the calculation cycle without measurement data, the filtering moment is the filtering moment of the previous beat plus the calculation cycle of the spaceborne computer for 0.5s, so that Kalman intermittent recursive filtering is carried out;
3c) when the GNSS measurement data are not updated for a long time, accumulating by taking the calculation period of the spaceborne computer as 0.5s as a beat on the basis of the valid time of the preorder filtering time, and performing Kalman intermittent recursive filtering;
3d) and (4) carrying out time compensation on the track number obtained by Kalman intermittent recursive filtering under each filtering beat, wherein the track number is consistent with the computing time of the satellite borne computer.
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| CN110553653A (en) * | 2019-08-23 | 2019-12-10 | 上海航天控制技术研究所 | spacecraft orbit determination method based on multi-source data driving |
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| US8456353B2 (en) * | 2011-01-14 | 2013-06-04 | Deere & Company | Method and system for determining clock corrections |
| US11208208B2 (en) * | 2017-10-18 | 2021-12-28 | Geocue Group, Inc. | Systems and methods for synchronizing events in shifted temporal reference systems |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101895383A (en) * | 2010-07-07 | 2010-11-24 | 中国人民解放军国防科学技术大学 | External clock synchronization system and control flow thereof |
| CN103616710A (en) * | 2013-12-17 | 2014-03-05 | 靳文瑞 | Multi-sensor combined navigation time synchronizing system based on field programmable gate array (FPGA) |
| CN108873669A (en) * | 2017-05-10 | 2018-11-23 | 中国航空工业集团公司西安飞行自动控制研究所 | A kind of UTC time calculation method of computer synchronised clock |
| CN110553653A (en) * | 2019-08-23 | 2019-12-10 | 上海航天控制技术研究所 | spacecraft orbit determination method based on multi-source data driving |
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