CN101383653B - Automatic time synchronizing method on satellite - Google Patents

Abstract

The invention relates to an on-board automatic time accounting method which endows with the long and high accuracy punctuality performance and the automatic phase modulation performance of the prior time management unit. A time difference processor uses the latest filtration result estimated in real time by a time difference EKF filter to periodically replace the original stored variable estimation value by the time difference observed quantity; on the one hand, the time difference processor broadcasts the forecast time difference for a user, and judges whether the forecast time difference at the current time enters the phase modulation section or not, if entering the phase modulation section, a second pulse generator is driven to perform the corresponding phase modulation according to the calculated phase modulation quantity through calculating the phase modulation quantity and the name phase modulation residual error, and uses the name phase modulation residual error to replace the start forecast time difference quantity and the time difference prior estimation value in an on-board time difference forecast model, thereby the on-board automatic time unification is realized. The invention can lower the degree of dependence to a land station, helps to reduce the requirements of the on-board clock performance, saves the investment and the maintenance costs of a constellation system, and improves the reliability and the safety of the constellation system.

Description

A kind of automatic time synchronizing method on satellite

Technical field

System method when the present invention relates on a kind of star relates in particular to the autonomous method for synchronous of clock and ground system clock on a kind of star, and system method is compatible when getting involved with the conventional floor station, and the automatic time synchronizing that is particularly suitable for the satellite constellation system is handled.

Background technology

There is main error component such as frequency calibration deviation (being called frequency difference or accuracy), aging phenomenon and random noise in the frequency of clock (or frequency source) output; Thereby; According to always having phase deviation (or time difference) to a certain degree between all kinds of pulse signals synthetic (express time at interval) and the corresponding ideal value to the accumulative total of the frequency source number of oscillation; And As time goes on, this phase deviation becomes increasing.In order to realize some interactive function; The phase place that is arranged between the pulse of exporting in each frequency source in the different system must keep the synchronous of certain precision; Perhaps, needn't adjust real phase difference, adjust accordingly but need that pulse phase difference is broadcast to relevant user.Wherein, the adjustment of impulse phase is a physical process, and it is synchronous to be called physics; Do not carry out the phase place adjustment, just broadcasting phase difference then is a mathematical procedure synchronously, and it is synchronous to be called mathematics.Physics synchronously and mathematics constituted two big contents of time synchronized synchronously.

Clock and ground system clock keep the key of high-precise synchronization to be on the star, to the accurate tracking of the star ground time difference.The method of following the tracks of the star ground time difference mainly contains: 1) time difference observation, and more typical three class methods have: ground station sets up the range finding link with the star that passes by, and records the star ground time difference; To recording the time difference between star, be aided with the observation of the star ground time difference based on the two-way time ratio of inter-satellite link, can amount to and obtain of the time difference observed quantity of each astrology the ground system clock; Based on the time service of GPS Global Navigation System, record the deviation of the relative navigation system clock of clock on ground system clock, the star respectively, amount to and obtain the time difference observed quantity of star ground.2) according to understanding to star ground time difference Changing Pattern; Utilize time difference forecasting model to forecast; As far as high stability crystal oscillator (QZ clock), Long-term forecasting should be adopted the secondary time difference forecasting model that comprises the ageing rate influence, and as far as atomic clock (such as RB or CS clock); Can consider the ageing rate influence, only get final product with once linear time difference forecasting model.All there are pluses and minuses separately in above-mentioned two types of trackings: the former receives the restriction of observation area and time (such as, the distribution limitation of ground station; The constraint of frequency when star ground is surveyed), there is observation error in time difference observation, or the like; The latter can't consider the change at random part (random noise) of clock, seriously relies on the estimated accuracy of model variable (the initial forecast time difference, frequency difference and ageing rate), and long-term time difference prediction error will increase at any time fast.

Based on ground station get involved the time system method major defect be: a little less than the accurate follow-up control to the star ground time difference, cause the excessive demand of hardware performance and the intervention that seriously relies on ground station.Because the distributed areas of China ground station are limited, satellite time of passing by is short, and chronic in non-visible interval; The star ground time difference can only be observed by ground station in the short-term that satellite passes by; And estimate the variable of time difference forecasting model on the star according to this, and in non-visible interval, then can only rely on time difference forecasting model to carry out long-term time difference forecast; Therefore, the trend that can't avoid time difference prediction error to increase fast at any time.In order to reach the high precision time synchronization index request; The high performance clock product of the serious dependence of conventional method; And; When get involved on ground system handle all can't with independent in time the carrying out of time difference observation, and can only be when satellite passes by, by ground station send time service, when concentrating the school, evenly during the school or instruction such as pulse per second (PPS) phase place adjustment accomplish corresponding star ground time synchronizing.

Number of patent application is " a kind of satellite constellation split-second precision unified approach " of 200810074975.3 introductions; The time synchronized that is the small formation satellite system formed of three stars (1 main 2 pairs) provides a kind of solution, has represented when constellation, the unite more recent application achievement in research of technical elements of China.The main purpose of this invention is to realize the time synchronized between 3 stars, and therefore, although propose to utilize domestic ground station that three satellites are carried out star ground time difference observation separately, purpose is for each star time difference is controlled in the index request scope.This method remains a main time system method that relies on ground station's intervention; Reason is that as the key equipment that time on the star unites and handles, time management unit is (as shown in Figure 1 on the star in this invention; Comprised frequently source, frequency synthesis splitter, the time difference signal processor, second pulse generator and communication controler) only play a part the tie surface station administration; And do not possess on the star autonomous accurately punctual ability and autonomous phase modulation ability, and the variable of uploading after can only passive acceptance being handled by ground station is estimated (such as, frequency difference); In order to revise time difference forecast on the star; Rely on ground station to send when the time difference, the school was concentrated in the adjustment instruction or evenly handle during the school, in order to adjust pulse per second (PPS) phase place on the star, the phase modulation that relies on ground station to send instructs.

In addition; This invention also proposes to utilize two inter-satellite links between primary and the secondary star to carry out time difference observation between star; And utilize GPS navigation system time difference between the method observation star of each star time service, and utilize the method for time difference forecast (being used for broadcasting) on these time difference observed quantity correction stars.These two methods have possessed autonomous mathematics synchronizing capacity on certain star; But the geometric distance between the major-minor star is merely several hundred kilometers, and the method for directly utilizing time difference observed quantity (and not doing any Filtering Processing) between star to revise the forecast time difference between star does not satisfy the synchronisation requirement at a distance of the above constellation systems of thousands of kilometers probably.And these two methods do not possess on the star from the primary physical synchronizing capacity yet.The more important thing is that these two methods can't be accomplished the autonomous Synchronous Processing of each star clock and ground system clock.

At present, the time system task of external famous satellite constellation system, the earth station system that all relies on whole world laying is accomplished.Such as, there is the ground station of 11 distribution on global in the Iridium system with inter-satellite link; The Globalstar system is not owing to there is inter-satellite link to need more than 300 ground station; The earth station system that Global Navigation System GPS also relies on the whole world to lay, still, gps system begins to have installed inter-satellite link from Block II R satellite, after 2010, will form automatic time synchronizing ability between certain star.But, show that according to present data this system does not have from the synchronous ability of primary physical equally, and as a navigation system, necessity of system when no star ground is accurate.

System method based on the star of ground station control the time as far as having the constellation systems of tens of satellites, will cause sizable work load and high cost burden to ground station.American-European relatively big country, the limited and ground station of the funds of China development constellation systems lays and limited by the region, therefore, possesses the automatic time synchronizing technology on the star and is very important.

Summary of the invention

Technology of the present invention is dealt with problems: the deficiency that overcomes prior art; A kind of automatic time synchronizing method on satellite is provided; The present invention can independently realize on the star mathematics synchronously and physics synchronous, help to reduce degree of dependence to ground station, reduced requirement to clock performance on the star; Save the input and the maintenance cost of constellation systems, improved reliability, fail safe and the operability of constellation systems simultaneously.

Technical solution of the present invention: a kind of automatic time synchronizing method on satellite may further comprise the steps:

(A) difference signal processor is judged the time difference adjustment sign of current time the time, if time difference adjustment is designated " 0 ", then gets into step (B) and carries out independently punctual; If time difference adjustment is designated " 1 ", then get into ground time service handling process; If time difference adjustment is designated " 2 ", then gets into ground and get involved handling process when concentrating the school;

(B) difference signal processor is judged time difference forecasting model variable replacement sign on the star time; If replacement is designated " 1 "; Then utilize the relevant variable of the up-to-date real-time estimated result replacement current secondary time difference forecasting model of EKF filter on the star; And with this current moment be initial forecast constantly, and time difference forecasting model variable replacement sign reset to " 0 ", get into step (C) then; If replacement is designated " 0 ", then directly change step (C) over to;

(C) difference signal processor judges that ground gets involved the phase modulation sign time, if phase modulation is designated " 1 ", then characterizes current time and carries out the current phase modulation sign that phase modulation handles and be set to " 1 ", and phase modulation is got involved on ground identified and reset to " 0 ", changes step (E) then over to; If phase modulation is designated " 0 ", then change step (D) over to;

(D) difference signal processor is judged autonomous phase modulation sign on the star time, if autonomous phase modulation is designated " 0 " on the star, then current phase modulation sign is set to " 0 ", changes step (G) then over to; If autonomous phase modulation is designated " 1 " on the star, then current phase modulation sign is set to " 1 ", and autonomous phase modulation sign is reset to " 0 ", changes step (E) then over to;

(E) according to the current forecast time difference, calculate phase modulation amount and nominal phase modulation residual error, change step (F) then over to;

(F) difference signal processor sends the instruction of pulse per second (PPS) phase modulation the time; Drive second pulse generator and carry out the respective phase adjustment according to the phase modulation amount of calculating; And residual quantity when unconditionally in the name of the phase modulation residual error replaces initial in the secondary time difference forecasting model; And with current phase modulation be constantly initial forecast constantly, change step (G) then over to;

(G) based on secondary time difference forecasting model on the star, according to the forecast star ground time difference in required moment on the star, forecast that the time difference is broadcast to the user on the one hand, be used for the autonomous phase modulation determining step (H) on opportunity on the other hand;

(H) difference signal processor judges whether next time difference forecast constantly is in the phase modulation interval time, if " being ", then autonomous phase modulation sign on opportunity is set to " 1 ", changes step (I) then over to, otherwise, directly change step (I) over to;

(I) difference signal processor utilizes the EKF filter time residual quantity, frequency difference and the ageing rate of secondary time difference forecasting model to be carried out state upgrades and the time upgrades the time, changes step (J) then over to;

(J) difference signal processor judges based on the replacement cycle whether current time need utilize the state of EKF wave filter to upgrade and time renewal result replaces the variable estimation in the secondary time difference forecasting model time; If current time is the replacement moment; Then replace sign and be set to " 1 "; Otherwise should replace sign and be set to " 0 ", change step (A) then over to.

The handling process of time service is in the said step (A): when carrying out the time service operation, the time difference signal processor when information is accepted as this star during unconditionally with the star in the time service data, and the time residual quantity in the time service data is accepted as forecast time difference of current time.

Handling process when concentrating the school in the said step (A) is: when when concentrating the school, operating; The time difference signal processor disposable when concentrating the school during star in the data during this star of adjustment amount adjustment, and forecast time difference that the disposable adjustment current time of time difference adjustment amount in the data calculates when concentrating the school.

Difference signal processor utilizes the implementation procedure of the relevant variable of the up-to-date real-time estimated result replacement current secondary time difference forecasting model of EKF filter on the star to be in the time of in the said step (B): the time difference signal processor relative reference clock according to the time from this star that communication controler transmits time difference observed quantity sequence; Adopt the EKF filtering algorithm to provide the latest estimated value of secondary time difference forecasting model variable in real time; The time difference signal processor according to the replacement cycle of model variable judge current time whether be replacement constantly; If the variable replacement constantly, then utilize the secondary time difference forecasting model variable estimated value of original storage on the latest estimated value replacement star; Otherwise the secondary time difference forecasting model variable estimated value of original storage on the star is still adopted in the forecast of time difference next time, and described secondary time difference forecasting model is:

$\mathrm{\Δ}{\mathrm{\α}}_k=\mathrm{\Δ}{\mathrm{\α}}_0+{\mathrm{\α}}_1(t_k-t_0)+\frac{1}{2}{\mathrm{\α}}_2{(t_k-t_0)}^2$

Wherein: Δ α _kBe required moment t _kForecast the time residual quantity, Δ α ₀Be initial forecast moment t ₀Time residual quantity estimate α ₁Be the frequency difference estimation of plane system clock relatively of clock on the star, α ₂Be the ageing rate estimation of plane system clock relatively of clock on the star.

The computational methods of phase modulation amount and nominal phase modulation residual error are in the said step (E): the phase modulation amount of pulse per second (PPS) is: Δ α _{K, remove}=-1/f ₀Round (Δ α _k/ (1/f ₀)), corresponding nominal phase modulation residual error is: Δ α _{K, res}=Δ α _k+ Δ α _{K, remove}

Wherein, round () expression rounds operation according to the principle that rounds up, f ₀Be fundamental frequency.

The determination methods that whether next time difference forecast constantly is in the phase modulation interval in the said step (H) is: establishing the phase modulation index is Δ _Lim, the phase modulation threshold value is a Δ _Gate, if the forecast time difference Δ α in the next moment _kSatisfy following condition:

‖Δα _k‖≤Δ _lim-Δ _gate

Think that then this is the autonomous phase modulation moment constantly.

Difference signal processor utilizes the EKF filter that time residual quantity, frequency difference and the ageing rate of secondary time difference forecasting model are carried out the process that state upgrades and the time upgrades to be in the time of in the said step (I):

(1) the EKF filter reads current phase modulation sign, if current phase modulation is designated " 0 ", then gets into step (3); If current phase modulation is designated " 1 ", then get into step (2);

(2) EKF filter utilization name phase modulation residual error replace that EKF filter previous moment provides the time residual quantity prior estimate, get into step (3) then;

(3) difference signal processor is judged the time difference observed quantity sequence of relative reference clock when current time has this star that the communication controler of having no way of transmits the time, if time difference observed quantity sequence is arranged then get into step (4), if do not have time difference observed quantity sequence then directly get into step (5);

(4) the star ground time difference observed quantity that utilizes star ground time difference observation to provide improves the prior estimate of residual quantity when current, frequency difference and ageing rate, gets into step (5) then;

The dynamic rule of residual quantity, frequency difference and ageing rate variable when (5) utilizing is forecast the posterior estimate of these variablees, provides next prior estimate constantly;

Difference signal processor judges based on the replacement cycle whether current time need utilize the state of EKF wave filter to upgrade with time renewal result and replace the variable estimation in the secondary time difference forecasting model when (6) last.

The present invention's advantage compared with prior art is: the present invention has inherited the hardware device and the major function of existing maturation time administrative unit and has divided; Only need to the time difference signal processor the data turnover of software processes function and communication controler suitably revise; Can realize the synchronous and physics simultaneous operation of autonomous mathematics; Can reduce the work load of ground station greatly; And the assurance system is in ground station's fault or ruined the ability of operate as normal in the following regular period of situation, is particularly suitable for the time system task of constellation systems.This automatic time synchronizing method gives that time management unit is long-term, the punctual ability of high accuracy and autonomous phase modulation ability; In order to guarantee long-term time difference accuracy of the forecast on the star; The time difference signal processor utilize the time difference observed quantity between the clock and reference clock on the star as much as possible; When estimating in real time with an EKF filter the up-to-date filtered of these time difference forecasting model variablees of residual quantity, frequency difference and ageing rate periodically replaces the variable estimated value of original storage, thereby has guaranteed that time difference forecast on the star for a long time, accurately follows the tracks of the ability of the true time difference.The time difference signal processor judge forecast time difference of current time; Get in the phase modulation interval when this time difference; Promptly think the autonomous phase modulation of current time constantly,, calculate phase modulation amount and nominal phase modulation residual error according to the minimum principle of phase modulation residual error; Order about second pulse generator and carry out the respective phase adjustment according to calculating the phase modulation amount, and difference component priori Estimation of Mean when residual quantity and EKF filter provide when in the name of the phase modulation residual error replaces on the star the initial forecast in the time difference forecasting model.The present invention has carried out application study and mathematical simulation in the star ground time synchronized task of 24 star Walker constellations.Considered two kinds of different star ground time difference observation programs altogether: a kind of is to utilize ground station and inter-satellite link; A kind of in addition is to utilize gps system to stand earthward and each star time service.Simulation result all shows under these two kinds of different situations; Even if clock adopts the high temperatures typical crystal oscillator on the star; Automatic time synchronizing method can both be strict controlled in pulse per second (PPS) deviation in star ground in the index request scope, has proved absolutely feasibility, validity and the superiority of this automatic time synchronizing method.System method was compatible when the present invention also got involved automatic time synchronizing method and conventional floor station, and the system method had good reliability, fail safe and navigability when this that makes that the present invention provides overlapped.

Description of drawings

Fig. 1 is the structural representation of time management unit on the existing star that adopts of the present invention;

Fig. 2 is that the present invention utilizes the main flow chart that system was handled when time management unit carried out on the star;

Fig. 3 is that the present invention utilizes the flow chart that time management unit carries out EKF filtering on the star;

Fig. 4 is among the embodiment 1 certain residual quantity evaluated error result when representing the star ground on the star;

Fig. 5 is that among the embodiment 1 certain is represented the time difference prediction error result on the star;

Fig. 6 is that among the embodiment 1 certain is represented the true pulse per second (PPS) phase deviation in star ground on the star: the trend that the phase deviation when Fig. 6 A representes not take the phase modulation operation increases in time; The trend that phase deviation when Fig. 6 B representes to take autonomous phase modulation to operate increases in time;

Fig. 7 is the time difference evaluated error result of the relative navigation system clock of ground system clock that provides of the ground EKF filter among the embodiment 2;

Fig. 8 is among the embodiment 2 certain residual quantity evaluated error result when representing the star ground that the EKF filter on the star provides;

Fig. 9 is that among the embodiment 2 certain is represented the time difference prediction error result on the star;

Figure 10 is that among the embodiment 2 certain is represented the true star ground pulse per second (PPS) phase deviation of star; The trend that phase deviation when Figure 10 A representes not take the phase modulation operation increases at any time; The trend that phase deviation when Figure 10 B representes to take the phase modulation operation increases at any time.

Embodiment

Below in conjunction with accompanying drawing and specific embodiment the present invention is done to describe in further detail:

As shown in Figure 1, the existing time management unit that the present invention adopts by high-precision frequency source, frequency synthesis splitter, the time difference signal processor, second pulse generator and 5 functional modules of communication controler form.

The high accuracy frequency source: the stability that the high accuracy frequency source produces frequency can influence the time unification of each satellite in the constellation, and then also can influence the performance of whole constellation.Therefore, the high accuracy frequency source must be able to provide the frequency of precision height, good stability, as the reference frequency of whole star.

The frequency synthesis splitter: the frequency synthesis splitter receives the reference frequency of high accuracy frequency source output; Resolve into the multichannel reference frequency on demand and be provided to the user of high precision time difference clock on the star; And provide the accurate frequency of 1 roadbed to be used to produce the pulse per second (PPS) of multichannel 1PPS benchmark to second pulse generator, the stability of phase equalization between the multichannel reference frequency that the frequency synthesis splitter should guarantee to decomposite and the accurate frequency of each roadbed.

Second pulse generator: second pulse generator receives the accurate frequency of a roadbed that produces along separate routes from the frequency synthesis splitter, and being responsible for its frequency conversion is the pulse per second (PPS) of multichannel 1PPS benchmark, and exports user's use of high precision time difference clock on the star to.The pulse per second (PPS) phase place adjustment instruction that difference signal processor sent when second pulse generator can receive, and comply with this instruction the phase place of the multichannel benchmark pulse per second (PPS) of output is adjusted.The phase place of the benchmark pulse per second (PPS) that second pulse generator should guarantee to export and the reference frequency of input keeps consistency.

The time difference signal processor: the time difference signal processor be the nucleus module of time management unit; Be responsible for resolving and when managing this star and the time difference of fiducial time; The time difference signal processor when time management unit work initially produces split-second precision and is sent to equation clock receiving equipment and equation clock user as this star through communication controler, this split-second precision by the time difference signal processor inner crystal oscillator produce.The time difference signal processor receive through communication controler and gather transmitting apparatus from the time difference and transmit when including this star and the time difference information of fiducial time; And the time difference information that receives carried out the judgement of validity; After rejecting invalid information 5 continuous effective informations are done median operation, delta when it is initial ₀Get median after then sorting and obtain according to 5 time difference observed quantities of uploading, the time difference signal processor can be by following formula basis of calculation time difference Δ:

Δ＝Δ ₀+K(T-T ₀)

When T was this star in the Δ moment basis of calculation time difference in the formula, K was a frequency difference.

The time difference signal processor add that the Δ packing of the standard time difference forms split-second precision information during with this star of current time, outwards be sent to equation clock receiving equipment and equation clock user through communication controler.The time difference signal processor receive the equation clock adjustment instruction of annotating on the ground through communication controler and the standard time difference is adjusted be adjusted to fiducial time when making this star.

Communication controler: communication controler is the interface module of bus on time management unit and the star; Be responsible for to receive the equation clock adjustment instruction that send on time difference of transmitting from bus on the star and ground, and during responsible this star that difference signal processor calculates during bus broadcast on star and the pulse per second (PPS) deviation between fiducial time.

The course of work of time management unit is: the time difference signal processor when time management unit work initially produces split-second precision and is sent to equation clock receiving equipment and equation clock user as this star through communication controler; This split-second precision by the time difference signal processor inner crystal oscillator produce; The high accuracy frequency source produces reference frequency and is sent to the frequency synthesis splitter; By the frequency synthesis splitter reference frequency is resolved into the accurate frequency of n+1 roadbed; N >=1; Wherein the accurate frequency of a roadbed is sent to second pulse generator and generates the accurate pps pulse per second signal of n roadbed; The time difference signal processor receive the time difference through communication controler and gather the time difference information that transmitting apparatus transmits, the time difference signal processor when time difference information is carried out producing this star after the computing and the standard time difference between fiducial time, the time difference signal processor receive the equation clock adjustment instruction of annotating on the ground through communication controler the standard time difference adjusted; The split-second precision information that the accurate frequency of other n roadbed, the accurate pulse per second (PPS) of adjusted n roadbed, the standard time difference and split-second precision constitute is formed equation clock jointly and is sent to equation clock receiving equipment and equation clock user through communication controler, thereby is adjusted to fiducial time during with this star.

This invention adopts identical with it Hardware configuration and major function to divide: the source adopts high stability crystal oscillator or atomic clock that the reference frequency signal of high frequency (being generally 10M Hz) is provided frequently, as task execution on the star time reference; The frequency synthesis splitter uses to relevant user the fundamental frequency signal demultiplexing on demand; Second pulse generator receives the accurate frequency of a roadbed from the frequency synthesis splitter, and being responsible for its frequency conversion is the multichannel pps pulse per second signal, exports to split-second precision user use on the star.Second pulse generator is adjusted according to phase adjustment after receiving the phase modulation instruction accordingly; Communication controler is the interface module of bus on time management unit and the star; Be responsible for to receive the instructions (ground or other star send) and the time difference information that send from bus on the star, and during this star that difference signal processor calculates when being responsible on star bus broadcast and time difference information; The time difference signal processor be the core of time management unit; This invention has been done further expansion to its major function and software content, not only manages the generation and the broadcasting of split-second precision information when forecast (during this star with subtractive combination), and also has suitable instruction judgement and decision-making capability; Can accomplish autonomous punctual and autonomous phase modulation decision-making capability on the star; In addition, also have suitable data-handling capacity, can accomplish the estimation task of time difference forecasting model variable.

Automatic time synchronizing method of the present invention is as shown in Figure 2, and concrete performing step is following:

(1) difference signal processor is judged the time difference adjustment sign of current time the time, if time difference adjustment is designated " 0 ", then gets into autonomous punctual step (2); If time difference adjustment is designated " 1 ", then get into conventional floor time service handling process; If time difference adjustment is designated " 2 ", then gets into conventional floor and get involved handling process when concentrating the school;

(2) difference signal processor is judged time difference forecasting model variable replacement sign on the star time; If the variable replacement is designated " 1 "; Then utilize the relevant variable of the up-to-date real-time estimated result replacement current secondary time difference forecasting model of EKF filter on the star; And with this be constantly initial forecast constantly, also need variable replacement sign is reset to " 0 ", get into step (3) then; If the variable replacement is designated " 0 ", then directly change step (3) over to;

(3) difference signal processor is judged ground intervention phase modulation sign the time; If ground is got involved phase modulation and is designated " 1 "; Then characterize current time and carry out the current phase modulation sign that phase modulation handles and be set to " 1 ", and the phase modulation sign is got involved on ground reset to " 0 ", change step (5) then over to; If ground is got involved phase modulation and is designated " 0 ", then change step (4) over to;

(4) difference signal processor is judged autonomous phase modulation sign on the star time, if autonomous phase modulation is designated " 0 " on the star, then current phase modulation sign is set to " 0 ", changes step (7) then over to; If autonomous phase modulation is designated " 1 " on the star, then current phase modulation sign is set to " 1 ", and with the reset of autonomous phase modulation sign, changes step (5) then over to;

(5) according to the minimum principle of the residual error behind the phase modulation,, calculate phase modulation amount and nominal phase modulation residual error, change step (6) then over to according to the current forecast time difference;

(6) difference signal processor sends the instruction of pulse per second (PPS) phase modulation the time; Drive second pulse generator and carry out the respective phase adjustment according to calculating the phase modulation amount; And residual quantity when unconditionally in the name of the phase modulation residual error replaces initial in the time difference forecasting model; And with current phase modulation be constantly initial forecast constantly, change step (7) then over to;

(7) based on secondary time difference forecasting model on the star, according to the required forecast star ground time difference in the moment on the star.Forecast is used for broadcasting the time difference on the one hand, also is used for the autonomous phase modulation determining step (8) on opportunity on the other hand;

(8) difference signal processor judges whether next time difference forecast constantly is in the phase modulation interval time, if " being ", then autonomous phase modulation sign on opportunity is set to " 1 ", changes step (9) then over to, otherwise, directly change step (9) over to;

(9) difference signal processor utilizes an EKF filter time, time residual quantity, frequency difference and these variablees of ageing rate of star ground time difference forecasting model is estimated to carry out states upgrade and time update processing, changes step (10) then over to;

(10) difference signal processor judges based on the replacement cycle whether current time need utilize the result of EKF wave filter to replace the relevant variable estimation in the secondary time difference forecasting model time; If current time is the replacement moment; Then replace sign and be set to " 1 "; Otherwise should replace sign and be set to " 0 ", change step (1) then over to.

Wherein the adjustment of the time difference in the step (1) sign is a parameter that is stored on the star, and the time difference adjustment instruction that time difference adjustment sign is sent by ground is revised.The relative number of patent application of time difference in this invention adjustment content is that 200810074975.3 corresponding contents is adjusted to some extent: difference signal processor has been introduced autonomous punctual mode when of the present invention; And this mode of phase modulation is got involved on ground from these mathematics Synchronous Processing contents, pick out, mode when also having given up even school.This invention definition time difference adjustment sign default value is " 0 ", adopts autonomous punctual mode on the expression star; When ground decision during with time service or concentrated school mode get involved time difference forecast timing on the star neatly, send instruction and will adjust that sign is revised as " 1 " or " 2 " get final product the time difference, after end was got involved on ground, this sign should be configured to " 0 " again.

All the mathematics method for synchronous that changes time difference forecast on the star when time service in the step (1) or concentrated school.When carrying out time service when operation, the time difference signal processor when information is accepted as this star during unconditionally with the star in the time service data, and the time residual quantity in the time service data is accepted as forecast time difference of current time.This operation is to the influence of time difference forecast, is actually residual quantity when changing initial in the time difference forecasting model.Time difference forecast on the star after the time service, residual quantity when being initial with time service time residual quantity constantly, the time difference forecasting model that original frequency difference and ageing rate estimation are formed is accomplished.The time difference signal processor subtractive combination during with forecast during with the time service star, be broadcast to relevant user through communication controler.When operation when concentrating the school, the time difference signal processor disposable when concentrating the school during star in the data during this star of adjustment amount adjustment, and forecast time difference that the disposable adjustment current time of time difference adjustment amount in the data calculates when concentrating the school.Time difference forecast after when concentrating the school, residual quantity when the time residual quantity in the moment is initial during with the school, the time difference forecasting model that original frequency difference and ageing rate estimation are formed is accomplished.The time be broadcast to relevant user with the forecast time difference through communication controler during difference signal processor this star after when concentrating the school.

Time difference forecasting model variable replacement sign is a parameter that is stored on the star on the star in the step (2), this sign by the time difference signal processor replacement instruction that sends revise.If this is designated " 0 ", then expression needn't be replaced original variable estimation of secondary time difference forecasting model on the star with the real-time estimated result of EKF filter on the star; If this is designated " 1 ", then carry out replacement operation.

Utilize the real-time estimated result of EKF wave filter on the star to replace the process that original variable of secondary time difference forecasting model is estimated on the star to be: the time difference signal processor relative reference clock according to the time from this star that communication controler transmits time difference observed quantity sequence; Adopt the EKF filtering algorithm to provide the latest estimated value of secondary time difference forecasting model variable in real time; The time difference signal processor based on the replacement cycle of model variable judge current time whether be replacement constantly; If the variable replacement constantly, then utilize the secondary time difference forecasting model variable estimated value of original storage on the latest estimated value replacement star; Otherwise the secondary time difference forecasting model variable estimated value of original storage on the star is still adopted in the forecast of time difference next time.Secondary time difference forecasting model is:

$\mathrm{\Δ}{\mathrm{\α}}_k=\mathrm{\Δ}{\mathrm{\α}}_0+{\mathrm{\α}}_1(t_k-t_0)+\frac{1}{2}{\mathrm{\α}}_2{(t_k-t_0)}^2$

Wherein: Δ α _kBe required moment t _kForecast the time residual quantity, Δ α ₀Be initial forecast moment t ₀Time residual quantity estimate α ₁And α ₂Represent on the star clock relatively frequency difference and the ageing rate estimated value of plane system clock respectively.

The phase modulation sign is got involved on ground in the step (3), is a parameter that is stored on the star, and the ground intervention phase modulation that this sign is sent by terrestrial contr instructs to be revised.Phase modulation is got involved on ground; Be the physics simultaneous operation of from original time difference adjustment content, separating; It is " 0 " that phase modulation sign default value is got involved on this invention definition ground, and autonomous phase modulation processing scheme on the expression star is when the ground decision gets involved on the star phase modulation operation, send instruction and phase modulation is got involved on ground identified and be revised as " 1 " and get final product; After end was got involved on ground, this sign was resumed into default " 0 " value again.

Autonomous phase modulation sign and current phase modulation sign on the star in the step (4); Be two parameters that are stored on the star; The two representes that all current time is the phase modulation moment, and just the former representes that current time is the autonomous phase modulation moment, and the latter possibly represent that also current time is that phase modulation is got involved constantly in ground.The default value of autonomous phase modulation sign and current phase modulation sign is " 0 ", and the expression current time is the non-phase modulation moment, and phase modulation is then represented constantly in " 1 ", and after relevant finishing dealing with, these two types of signs should be resumed into default " 0 " value again.

The phase modulation amount in the step (5) and the calculating of nominal phase modulation residual error.The phase modulation strategy is to make nominal phase modulation residual error as far as possible little, because the phase modulation amount can only be 1/f ₀(f ₀The finger fundamental frequency) integral multiple, then the phase modulation amount should be:

Δα _k，remove＝-1/f ₀round(Δα _k/(1/f ₀))

Wherein, round () expression rounds operation according to the principle that rounds up.Corresponding nominal phase modulation residual error does

Δα _k，res＝Δα _k+Δα _k，remove

In the step (7) in order to guarantee the long-term accurately forecast time difference, the time difference signal processor need periodically utilize the latest estimated value of EKF filter to replace.In addition, the ground time service, when concentrating the school or phase modulation handle and all can change the time difference forecast of taking after these measures, the time difference signal processor also need change some model variable and initial forecast automatically constantly, relevant replacement method is mentioned hereinbefore.

The judgement on the constantly autonomous phase modulation of next in the step (8) opportunity.At current time, the time difference signal processor judge whether the next forecast time difference constantly got into the phase modulation interval, should the interval if got into, then autonomous phase modulation sign is arranged to " 1 ".The phase modulation interval is by phase modulation index Δ _LimWith phase modulation threshold value Δ _GateCome common definite.The Rule of judgment on autonomous phase modulation opportunity is described below:

‖Δα _k‖≤Δ _lim-Δ _gate

If satisfy above-mentioned condition, think that then autonomous phase modulation has arrived opportunity.Wherein, Δ _LimBe the system time coincident indicator, initial phase modulation threshold value Δ _GateShould select according to time difference estimated accuracy, but, should utilize emulation finally to confirm for fear of error in judgement.

Time difference forecasting model variable EKF filtering flow process in the step (9) is as shown in Figure 3, compares with other general EKF filtering flow process, has increased step (A), and this step is to handle the Applicable Countermeasure of the EKF filter being estimated influence in order to eliminate phase modulation.Because phase modulation makes the true moment time difference that very big change take place; And the time difference component that general time difference EKF filter provides is estimated to predict this big variation; Therefore; The EKF filter possibly cause filter to get into long state of disturbance because evaluated error is excessive, even possibly cause filter divergence (showing as nonuniformity estimates).Because nominal phase modulation residual error is known, the time difference component priori Estimation of Mean of utilizing that this known quantity replaces that EKF filter previous moment provides can guarantee the smooth working performance of filter.Afterwards, get into general EKF filtering flow process.Comprise one observation step of updating: utilize possible star ground time difference observation airplane meeting (such as; Based on the observation of star ground time difference of ground station, observe based on the star ground time difference observation of ground station and inter-satellite link, based on the star ground time difference of navigation system) the star ground time difference observed quantity that provides; Improve the prior estimate of residual quantity when current, frequency difference and ageing rate; And time step of updating: the dynamic rule of residual quantity, frequency difference and ageing rate variable when utilizing; Posterior estimate to these variablees forecasts, provides next prior estimate constantly.Concrete mathematical description is following:

Quantity of state is defined as

x _k＝[Δα _kα _1，kα _2，k] ^T

Wherein, the time residual quantity of first representation in components current time; Latter two component is represented frequency difference and ageing rate respectively.General EKF filter needs a filter initialization step,, needs given initial priori state Estimation of Mean that is Estimate P with covariance _0|-1, and system noise variance Q _kWith observation noise variance R _k, could start following recursion estimation procedure then:

● (when observed quantity is arranged) upgraded in state estimation observation:

${\tilde{x}}_{k|k}={\tilde{x}}_{k|k-1}+K_k{\mathrm{\υ}}_k$

$P_{k|k}=P_{k|k-1}-K_k{P}_k^{\mathrm{\υ\υ}}{K}_k^T$

Wherein, newly breath and variance battle array thereof do

${\mathrm{\υ}}_k=z_k-H_k{\tilde{x}}_{k|k-1}$

$P_k^{\mathrm{\υ\υ}}=H_k{P}_{k|k-1}{H}_k^T+R_k$

Covariance matrix does

$P_k^{\mathrm{xz}}=P_{k|k-1}{H}_k^T$

Gain matrix does

$K_k=P_k^{\mathrm{xz}}{\left(P_k^{\mathrm{\υ\υ}}\right)}^{-1}$

● the state estimation time upgrades:

${\tilde{x}}_{k+1|k}={\mathrm{\Φ}}_{k+1,k}{\tilde{x}}_{k|k}$

$P_{k+1|k}={\mathrm{\Φ}}_{k+1,k}{P}_{k|k}{\mathrm{\Φ}}_{k+1,k}^T+\mathrm{\Γ}{Q}_k{\mathrm{\Γ}}^T$

Specific descriptions about the Several Parameters in the above-mentioned general time difference EKF filtering formula are following: state-transition matrix does

${\mathrm{\Φ}}_{k,k-1}=\left[\begin{array}{ccc}1& \mathrm{\Δ\τ}& 1/2\mathrm{\Δ}{\mathrm{\τ}}^2\\ 0& 1& \mathrm{\Δ\τ}\\ 0& 0& 1\end{array}\right]$

Δ τ=t _k-t _K-1The expression discrete periodic;

Discrete system noise w _k=[ε _kη _kξ _k] ^TBe by the decision of the performance of clock product self, process noise covariance matrix Q _kBe the amount relevant with Δ τ:

$Q_k=\left[\begin{array}{ccc}{q}_{\mathrm{\α\α}}& q_{\mathrm{\α\α}1}& q_{\mathrm{\α\α}2}\\ q_{\mathrm{\α\α}1}& q_{\mathrm{\α}1\mathrm{\α}1}& q_{\mathrm{\α}1\mathrm{\α}2}\\ q_{\mathrm{\α\α}2}& q_{\mathrm{\α}1\mathrm{\α}2}& q_{\mathrm{\α}2\mathrm{\α}2}\end{array}\right]$

Its each representation in components is following:

$q_{\mathrm{\&alpha;\&alpha;}}=\frac{{\mathrm{<figure-callout\; id="0"\; label="h"\; filenames="H2008102251757E00021.png,H2008102251757E00031.png"\; state="\{\{state\}\}">h</figure-callout>}}_0}{2}\mathrm{\&Delta;\&tau;}+\frac{2{\mathrm{\&pi;}}^2{h}_{-2}}{3}\mathrm{\&Delta;}{\mathrm{\&tau;}}^3+\frac{2{\mathrm{\&pi;}}^4{h}_{-4}}{5}\mathrm{\&Delta;}{\mathrm{\&tau;}}^5$

$q_{\mathrm{\&alpha;}1\mathrm{\&alpha;}1}=2{\mathrm{\&pi;}}^2{h}_{-2}\mathrm{\&Delta;\&tau;}+\frac{8{\mathrm{\&pi;}}^2{h}_{-4}}{3}\mathrm{\&Delta;}{\mathrm{\&tau;}}^3$

q _α2α2＝8π ⁴h _-4Δτ

q _αα1＝π ²h _-2Δτ ²+π ⁴h _-4Δτ ⁴

$q_{\mathrm{\&alpha;\&alpha;}2}=\frac{4{\mathrm{\&pi;}}^4{h}_{-4}\mathrm{\&Delta;}{\mathrm{\&tau;}}^3}{3}$

q _α1α2＝4π ⁴h _-4Δτ ²

H in the above-mentioned formula _aThe expression noise figure is the energy spectrum noise intensity coefficient of a; The system noise distribution matrix does

$\mathrm{\&Gamma;}=\left[\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 1\end{array}\right]$

Observing matrix does

$H_k=\frac{\&PartialD;h}{\&PartialD;x}{|}_{x=x_k}$

Observation noise v _kVariance matrix be R _k

The selection in the model variable replacement cycle in the step (10).The observation that equals the EKF filter when the variable replacement cycle is during the update cycle (the state posteriority of each observation updated time estimates all to be used for the replacement of secondary time difference forecasting model relevant variable), the forecast precision of secondary time difference forecasting model equal the EKF filter the time difference component the prior estimate precision.The variable replacement cycle will cause the decline of secondary time difference forecasting model precision greater than the observation update cycle.Consider the complexity of Project Realization, these two cycles can be different, certainly, should appropriately select according to emulation.

Embodiment 1

Utilize ground station and inter-satellite link to realize that (such as, target is that pulse per second (PPS) synchronous error with clock on each star and ground system clock is controlled in the 1us scope always to the autonomous Synchronous Processing of clock and ground system clock on each star of satellite constellation (24 star Walker constellation).) clock adopts typical high stability crystal oscillator QZ clock on the star, the CS clock is adopted on ground.Each the time system (suppose 5s) in the cycle, ground station records the time residual quantity (supposing that precision is 30ns) of pass by satellite clock and ground system clock, records the time difference between star (supposing that precision is 10ns) through inter-satellite link between adjacent star.Star ground time difference observation data based on the satellite of uploading that passes by; Data during in conjunction with the star intermittent gauging; With the star that passes by is initial star; Convert out the star ground time difference observed quantity of each relative ground station of star according to path, the shortest star ground principle, difference signal processor utilizes that the EKF filter estimates star ground time difference forecasting model variable on the star in the time of on the star.If current time is to the moment (supposing that the replacement cycle is 10s) of replacing secondary time difference forecasting model variable; The time difference signal processor send the model variable replacement instruction; The latest estimated result that filter is provided replaces original variable estimation; Time management unit carries out time difference forecast based on new secondary time difference forecasting model, and will forecast that the time difference is used to broadcast and the judgement on opportunity of autonomous phase modulation, when needs carry out autonomous phase modulation; Calculate phase modulation amount and nominal phase modulation residual error, and send and instruct the driving second pulse generator to adjust accordingly according to calculating the phase modulation amount.The specific descriptions of automatic time synchronizing implementation procedure are following on the above-mentioned star:

(1) difference signal processor is judged the time difference adjustment sign of current time the time, is found to be " 0 ", then gets into autonomous punctual step (2);

(2) judge time difference forecasting model variable replacement sign on the star; " if 1 "; Then utilize the relevant variable of the up-to-date real-time estimated result replacement current secondary time difference forecasting model of EKF filter on the star; And with this be constantly initial forecast constantly, also variable replacement sign is reset to " 0 ", get into step (3) then; If this is designated " 0 ", then directly change step (3) over to;

(3) difference signal processor is judged ground intervention phase modulation sign the time, is found to be " 0 ", directly changes step (4) over to;

(4) difference signal processor is judged autonomous phase modulation sign on the star time, if " 0 ", then current phase modulation sign is set to " 0 ", changes step (7) then over to; " if 1 ", then current phase modulation sign is set to " 1 ", and with the reset of autonomous phase modulation sign, changes step (5) then over to;

(5) according to the minimum principle of the residual error behind the phase modulation,, calculate phase modulation amount and nominal phase modulation residual error, change step (6) then over to according to the current forecast time difference;

(6) difference signal processor sends the instruction of pulse per second (PPS) phase modulation the time; Drive second pulse generator and carry out the respective phase adjustment according to calculating the phase modulation amount; And residual quantity when unconditionally in the name of the phase modulation residual error replaces initial in the time difference forecasting model; And with current phase modulation be constantly initial forecast constantly, change step (7) then over to;

(7) based on secondary time difference forecasting model on the star, according to the required forecast star ground time difference on the star.Forecast is used for broadcasting the time difference on the one hand, also is used for the autonomous phase modulation determining step (8) on opportunity on the other hand;

(8) difference signal processor judges whether next time difference forecast constantly is in the phase modulation interval time, if " being ", then autonomous phase modulation sign on opportunity is set to " 1 ", changes step (9) then over to, otherwise, directly change step (9) over to;

(9) difference signal processor utilizes the EKF filter that state renewal and time update processing are carried out in the estimation of the time difference, frequency difference and these variablees of ageing rate of the secondary time difference forecasting model time.If current phase modulation is designated " 1 ", then need at first carry out extra important operation, that is, utilize the nominal phase modulation residual error of calculating to replace the time difference component Estimation of Mean of priori.Get into common EKF filter process then.If there is star ground time difference observation data (amounting to the back) in current time, then utilize this observation data that the state estimation of priori is upgraded, provide posteriority state estimation result.No matter have or not time difference observation data, all carry out the time update processing of convention, provide next priori state estimation constantly.Change step (10) at last over to;

(10) difference signal processor judges according to the replacement cycle whether needs utilize the result of EKF filter to replace the relevant variable in the secondary time difference forecasting model to current time the time.If current time is the replacement moment, then replace sign and be set to " 1 ", be set to " 0 " otherwise should replace sign, change step (1) then over to;

Optional star is the representative star, adopts one group of mathematical simulation result after system is handled when above-mentioned like Fig. 4,5, shown in 6.Fig. 4 is among the embodiment 1 certain residual quantity evaluated error result when representing the star ground that the EKF filter on the star provides; The result shows that it is that consistency is estimated that the EKF filter is estimated; And the disturbing influence that phase modulation is handled EKF filter on the star also obtains fine inhibition, the time residual quantity stable state estimated accuracy be superior to 10ns; Fig. 5 is that among the embodiment 1 certain is represented the time difference prediction error result of the secondary time difference forecasting model on the star; After the system cycle utilized the estimated result of EKF filter on the star to replace original model variable to estimate when the result showed at interval one, the forecast time difference had been followed the tracks of the time difference estimated result of EKF filter on the star substantially; Fig. 6 is that among the embodiment 1 certain is represented the true pulse per second (PPS) phase deviation in star ground on the star: the trend that the phase deviation when Fig. 6 A representes not take the phase modulation operation increases has at any time exceeded the index request of 1us soon; Fig. 6 B representes to adopt the phase deviation behind the automatic time synchronizing to be controlled in the scope of 1us always, has reached the coincident indicator requirement of expection.

Embodiment 2

Utilize the GPS navigation system realize clock and ground system clock on each star of satellite constellation (24 star Walker constellation) autonomous Synchronous Processing (such as, the pulse per second (PPS) synchronous error of clock on each star and ground system clock is controlled in the 1us scope always.) clock adopts typical QZ clock on the star, the CS clock is adopted on ground.Each the time system (suppose 5s) in the cycle, ground station is through the time service of GPS navigation system, the system's time difference observation sequence that records the relative navigation system clock of ground system clock (suppose that time service precision is 100ns, but available accuracy is higher than this! ); The ground EKF filter of EKF filter on similar star; According to this type observation data, provide system clock the time residual quantity, frequency difference and ageing rate posteriority estimate, and (suppose 1000s) at regular intervals and pass to time management unit on each star through satellite-ground link and inter-satellite link; System was handled when in addition, ground stayed out of on the star.Pass through the time service of GPS navigation system on the star; Record the time difference observation sequence (supposing that time service precision is 100ns) of the relative navigation system clock of clock on the star; And the time difference forecasting model variable that utilizes the cycle to upload to be stored in the relative navigation system clock of ground system clock on the star forecasts system's time difference of current time; These two types of time difference datas amount to the star ground time difference observed quantity of current time, and the EKF filter estimates star ground time difference forecasting model variable in view of the above on the star.If current time is to replacing the moment (supposing that the replacement cycle is 10s) that secondary time difference forecasting model variable is estimated on the star; The time difference signal processor send the model variable replacement instruction; The latest estimated result that EKF filter on the star is provided replaces original variable estimation; Time management unit is then based on the new forecasting model forecast time difference secondary time difference, and is used to broadcast and the judgement on opportunity of autonomous phase modulation, when needs carry out autonomous phase modulation; Calculate phase modulation amount and nominal phase modulation residual error, and send and instruct the driving second pulse generator to adjust accordingly according to calculating the phase modulation amount.The specific descriptions of automatic time synchronizing implementation procedure are following on the above-mentioned star:

(1) difference signal processor is judged the time difference adjustment sign of current time the time, is found to be " 0 ", then gets into autonomous punctual step (2);

(2) judge time difference forecasting model variable replacement sign on the star; " if 1 "; Then utilize the relevant variable of the up-to-date real-time estimated result replacement current secondary time difference forecasting model of EKF filter on the star; And with this be constantly initial forecast constantly, also need variable replacement sign is reset to " 0 ", get into step (3) then; If this is designated " 0 ", then directly change step (3) over to;

(3) difference signal processor is judged ground intervention phase modulation sign the time, is found to be " 0 ", changes step (4) over to;

(4) difference signal processor is judged autonomous phase modulation sign on the star time, if " 0 ", then current phase modulation sign is set to " 0 ", changes step (7) then over to; " if 1 ", then current phase modulation sign is set to " 1 ", and with the reset of autonomous phase modulation sign, changes step (5) then over to;

(5) according to the minimum principle of the residual error behind the phase modulation,, calculate phase modulation amount and nominal phase modulation residual error, change step (6) then over to according to the current forecast time difference;

(6) difference signal processor sends the instruction of pulse per second (PPS) phase modulation the time; Drive second pulse generator and carry out the respective phase adjustment according to calculating the phase modulation amount; And residual quantity when unconditionally in the name of the phase modulation residual error replaces initial in the time difference forecasting model; And with current phase modulation be constantly initial forecast constantly, change step (7) then over to;

(7) based on secondary time difference forecasting model on the star, according to the required forecast star ground time difference on the star.Forecast is used for broadcasting the time difference on the one hand, also is used for the autonomous phase modulation determining step (8) on opportunity on the other hand;

(8) difference signal processor judges whether next time difference forecast constantly is in the phase modulation interval time, if " being ", then autonomous phase modulation sign on opportunity is set to " 1 ", changes step (9) then over to, otherwise, directly change step (9) over to;

(9) difference signal processor utilizes the EKF filter that state renewal and time update processing are carried out in the estimation of the time difference, frequency difference and these variablees of ageing rate of the secondary time difference forecasting model time.If current phase modulation is designated " 1 ", then need at first carry out extra important operation, that is, utilize the nominal phase modulation residual error of calculating to replace the time difference component Estimation of Mean of priori.Get into common EKF filter process then.If there is star ground time difference observation data (amounting to the back) in current time, then utilize this observation data that the state estimation of priori is upgraded, provide posteriority state estimation result.No matter have or not time difference observation data, all carry out the time update processing of convention, provide next priori state estimation constantly.Change step (10) at last over to;

(10) difference signal processor judges according to the replacement cycle whether needs utilize the result of EKF filter to replace the relevant variable in the secondary time difference forecasting model to current time the time.If current time is the replacement moment, then replace sign and be set to " 1 ", be set to " 0 " otherwise should replace sign, change step (1) then over to;

Optional star is the representative star; Adopt one group of mathematical simulation result after above-mentioned time system is handled like Fig. 7,8,9, shown in 10: Fig. 7 is the time difference evaluated error result of the relative navigation system clock of ground system clock that provides of the ground EKF filter among the embodiment 2; The result shows that it is that consistency estimates that its stable state estimated accuracy reaches 1ns that this EKF filter is estimated; Fig. 8 is among the embodiment 2 certain residual quantity evaluated error result when representing the star ground that the EKF filter on the star provides; The result shows that it is that consistency is estimated that this EKF filter is estimated; And the disturbing influence that phase modulation is handled EKF filter on the star also obtains fine inhibition, and its stable state estimated accuracy is about 10ns; Fig. 9 is that among the embodiment 2 certain is represented the time difference prediction error result of the secondary time difference forecasting model on the star; The system cycle utilized the estimated result of EKF filter on the star to replace original model variable when the result showed at interval one, and the forecast time difference has been followed the tracks of the time difference estimated result of EKF filter on the star substantially; Figure 10 is that among the embodiment 2 certain is represented the true star ground pulse per second (PPS) phase deviation of star: the trend that the phase deviation when Figure 10 A representes not take the phase modulation operation increases has at any time exceeded the index request of 1us soon; Figure 10 B representes to adopt the phase deviation behind the automatic time synchronizing to be controlled in the scope of 1us always, has reached the coincident indicator requirement of expection.

Be not difficult to find out that the automatic time synchronizing content of embodiment 1 and embodiment 2 almost is identical.This explanation the present invention has good versatility and adaptability.The simulation result shows of embodiment 1 and embodiment 2; Adopting on the star under the situation of QZ clock; This automatic time synchronizing method will star ground pulse per second (PPS) phase difference be strict controlled in the scope of index request (absolute value is no more than 1us); And this to be conventional method can't realize, prove absolutely feasibility, validity and the superiority of this method.

The content that the present invention does not describe in detail is a technology as well known to those skilled in the art.

Claims (7)

1. automatic time synchronizing method on satellite is characterized in that may further comprise the steps:

(A) difference signal processor is judged the time difference adjustment sign of current time the time, if time difference adjustment is designated " 0 ", then gets into step (B) and carries out independently punctual; If time difference adjustment is designated " 1 ", then get into ground time service handling process; If time difference adjustment is designated " 2 ", then gets into ground and get involved handling process when concentrating the school;

(B) difference signal processor is judged secondary time difference forecasting model variable replacement sign on the star time; If the variable replacement is designated " 1 "; Then utilize the relevant variable of the up-to-date real-time estimated result replacement current secondary time difference forecasting model of EKF filter on the star; And with this current moment be initial forecast constantly, and secondary time difference forecasting model variable replacement sign reset to " 0 ", get into step (C) then; If the variable replacement is designated " 0 ", then directly change step (C) over to;

(C) difference signal processor is judged ground intervention phase modulation sign the time; If ground is got involved phase modulation and is designated " 1 "; Then characterize current time and carry out the current phase modulation sign that phase modulation handles and be set to " 1 ", and the phase modulation sign is got involved on ground reset to " 0 ", change step (E) then over to; If ground is got involved phase modulation and is designated " 0 ", then change step (D) over to;

(D) difference signal processor is judged autonomous phase modulation sign on the star time, if autonomous phase modulation is designated " 0 " on the star, then current phase modulation sign is set to " 0 ", changes step (G) then over to; If autonomous phase modulation is designated " 1 " on the star, then current phase modulation sign is set to " 1 ", and autonomous phase modulation sign is reset to " 0 ", changes step (E) then over to;

(E) according to the current forecast star ground time difference, calculate phase modulation amount and nominal phase modulation residual error, change step (F) then over to;

(F) difference signal processor sends the instruction of pulse per second (PPS) phase modulation the time; Drive second pulse generator and carry out the respective phase adjustment according to the phase modulation amount of calculating; And residual quantity when unconditionally in the name of the phase modulation residual error replaces initial in the secondary time difference forecasting model; And with current phase modulation be constantly initial forecast constantly, change step (G) then over to;

(G) based on secondary time difference forecasting model on the star, according to the forecast star ground time difference in required moment on the star, forecast that the star ground time difference is broadcast to the user on the one hand, be used for the autonomous phase modulation determining step (H) on opportunity on the other hand;

(H) difference signal processor judges whether next star ground time difference forecast constantly is in the phase modulation interval time, if " being ", then autonomous phase modulation sign on opportunity is set to " 1 ", changes step (I) then over to, otherwise, directly change step (I) over to;

(I) difference signal processor utilizes the EKF filter time residual quantity, frequency difference and the ageing rate of secondary time difference forecasting model to be carried out state upgrades and the time upgrades the time, changes step (J) then over to;

(J) difference signal processor judges based on the replacement cycle whether current time need utilize the state of EKF wave filter to upgrade and time renewal result replaces the variable estimation in the secondary time difference forecasting model time; If current time is the replacement moment; Then replace sign and be set to " 1 "; Otherwise should replace sign and be set to " 0 ", change step (A) then over to.

2. a kind of automatic time synchronizing method on satellite according to claim 1; It is characterized in that: the handling process of time service is in the said step (A): when carrying out the time service operation; The time difference signal processor when information is accepted as this star during unconditionally with the star in the time service data, and the time residual quantity in the time service data is accepted as forecast star ground time difference of current time.

3. a kind of automatic time synchronizing method on satellite according to claim 1; It is characterized in that: the handling process when concentrating the school in the said step (A) is: when when concentrating the school, operating; The time difference signal processor disposable when concentrating the school during star in the data during this star of adjustment amount adjustment, and forecast star ground time difference that the disposable adjustment current time of time difference adjustment amount in the data calculates when concentrating the school.

4. a kind of automatic time synchronizing method on satellite according to claim 1; It is characterized in that: difference signal processor utilizes the implementation procedure of the relevant variable of the up-to-date real-time estimated result replacement current secondary time difference forecasting model of EKF filter on the star to be in the time of in the said step (B): the time difference signal processor relative reference clock according to the time from this star that communication controler transmits time difference observed quantity sequence; Adopt the EKF filtering algorithm to provide the latest estimated value of secondary time difference forecasting model variable in real time; The time difference signal processor according to the replacement cycle of model variable judge current time whether be replacement constantly; If the variable replacement constantly, then utilize the secondary time difference forecasting model variable estimated value of original storage on the latest estimated value replacement star; Otherwise the secondary time difference forecasting model variable estimated value of original storage on the star is still adopted in the forecast of the following secondary star ground time difference, and described secondary time difference forecasting model is:

Wherein: Δ α _kBe required moment t _kForecast star ground the time residual quantity, Δ α ₀Be initial forecast moment t ₀Time residual quantity estimate α ₁Be the frequency difference estimation of plane system clock relatively of clock on the star, α ₂Be the ageing rate estimation of plane system clock relatively of clock on the star.

5. a kind of automatic time synchronizing method on satellite according to claim 1 is characterized in that: the computational methods of phase modulation amount and nominal phase modulation residual error are in the said step (E): the phase modulation amount of pulse per second (PPS) is: Δ α _{K, remove}=-1/f ₀Round (Δ α _k/ (1/f ₀)), corresponding nominal phase modulation residual error is: Δ α _{K, res}=Δ α _k+ Δ α _{K, remove}

Wherein, Δ α _kBe required moment t _kForecast star ground the time residual quantity, round () expression rounds operation according to the principle that rounds up, f ₀Be fundamental frequency.

6. a kind of automatic time synchronizing method on satellite according to claim 1 is characterized in that: the determination methods that whether next star ground time difference forecast constantly is in the phase modulation interval in the said step (H) is: establishing the phase modulation index is Δ _Lim, the phase modulation threshold value is a Δ _Gate, if the forecast star ground time difference Δ α in the next moment _kSatisfy following condition:

||Δα _k||≤Δ _lim-Δ _gate

Think that then this is the autonomous phase modulation moment constantly.

7. a kind of automatic time synchronizing method on satellite according to claim 1 is characterized in that: difference signal processor utilizes the EKF filter that time residual quantity, frequency difference and the ageing rate of secondary time difference forecasting model are carried out the process that state upgrades and the time upgrades to be in the time of in the said step (I):

(1) the EKF filter reads current phase modulation sign, if current phase modulation is designated " 0 ", then gets into step (3); If current phase modulation is designated " 1 ", then get into step (2);

(2) EKF filter utilization name phase modulation residual error replace that EKF filter previous moment provides the time residual quantity prior estimate, get into step (3) then;

(3) difference signal processor is judged the time difference observed quantity sequence of relative reference clock when current time has this star that the communication controler of having no way of transmits the time, if time difference observed quantity sequence is arranged then get into step (4), if do not have time difference observed quantity sequence then directly get into step (5);

(4) the star ground time difference observed quantity that utilizes star ground time difference observation to provide improves the prior estimate of residual quantity when current, frequency difference and ageing rate, gets into step (5) then;

The dynamic rule of residual quantity, frequency difference and ageing rate variable when (5) utilizing is forecast the posterior estimate of these variablees, provides next prior estimate constantly.

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