CN102291169B - Onboard high-accuracy time synchronization method for satellite - Google Patents
Onboard high-accuracy time synchronization method for satellite Download PDFInfo
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- CN102291169B CN102291169B CN201110268351.7A CN201110268351A CN102291169B CN 102291169 B CN102291169 B CN 102291169B CN 201110268351 A CN201110268351 A CN 201110268351A CN 102291169 B CN102291169 B CN 102291169B
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Abstract
The invention discloses an onboard high-accuracy time synchronization method for a satellite, which is used for effectively solving the problem of unavailability of meeting time synchronization in the sensitive acting process of the satellite due to low accuracy and poor stability of an onboard time system. By adopting the high-accuracy time synchronization method, the time accuracy (an error between the time accuracy and GPS (Global Positioning System) standard time is less than 25 mus) of a satellite central computer is enhanced, the time synchronization accuracy among subsystems of the entire satellite is higher than 0.1 ms (based on the GPS standard time), and the defect of unavailability of continuing working when a GPS receiver is not positioned existing in a design method in which only GPS second pulse is taken as time synchronization of each subsystem of the entire satellite is overcome. Once one of the GPS receiver and a satellite-to-ground observing and controlling channel exists at the in-orbit flying period of the satellite, time synchronization of the satellite can be realized, so that the risk of functional failure of the system is lowered effectively, the time synchronization mode can be changed in time as required or along with the change of environment, and the time synchronization flexibility, reliability and security of the satellite are enhanced remarkably.
Description
Technical field
The present invention relates to high-precision time synchronization method on a kind of Satellite.
Background technology
Clock on satellite was system clock in the past, system clock is interrupted producing by the remote measurement of Star Service central computer, the remote measurement of Star Service central computer is interrupted every 3.90625ms and is produced once, and software is the cumulative time in remote measurement interrupt service routine, and the time of having no progeny in 256 remote measurements is just in time 1 second.On-Star system clock add up by second and millisecond, and its temporal resolution is 1 millisecond, the time etching system clock zero clearing of reception satellite and the rocket separation signal.Star Service central computer is broadcasted by CAN bus system clock to each subsystem on star, can provide day, time, minute, second and millisecond, its precision and stability is determined by the crystal oscillator of Star Service central computer inside, belongs to the low precision time on star.Raising day by day along with task precision and complexity, increasing task will have been worked in coordination with by a plurality of subsystems on star, the basis of each subsystem collaborative work is exactly on star, to have unified high-precision time synchronization method, therefore the system clock that precision was ms in the past cannot meet the needs of task, need to set up on a kind of Satellite high-precision time synchronization method consistent to guarantee time accuracy inner on star.
Summary of the invention
Technology of the present invention is dealt with problems: overcome the deficiencies in the prior art, high-precision time synchronization method on a kind of Satellite is provided, the problem of low, the poor stability of time precision on original star while adopting the method effectively to solve in orbit, for whole star has been set up high accuracy unified time, make on star each subsystem can collaborative work under unified time coordinate, complete the complex task that satellite cannot complete in the past.
Technical solution of the present invention is:
A high-precision time synchronization method on Satellite, step is as follows:
(1) satellite in orbit during, GPS receiver on star is when positioning states, GPS receiver receives the navigation signal of GPS navigation satellite and calculates the GPS standard time, in the whole second moment of each GPS standard time, GPS receiver sends a GPS pulse per second (PPS) to the Star Service central computer on star; GPS receiver on star is when non-positioning states, and GPS receiver does not send GPS pulse per second (PPS);
(2) judge that whether Star Service central computer receives the GPS pulse per second (PPS) that GPS receiver sends, if receive, enters step (3); If do not receive, Star Service central computer continues to use its internal clocking, enters afterwards step (6);
(3) Star Service central computer sends GPS pulse per second (PPS) and temporal information broadcast to time user on star;
(4) Star Service central computer, according to GPS pulse per second (PPS) calibration internal clocking, makes the internal clocking of Star Service central computer and the deviation of GPS between the standard time be less than 25us;
(5) cycle being stored in Star Service central computer internal register when Star Service central computer obtains its autonomous evenly school, during described autonomous evenly school, the cycle refers to that the internal clocking of Star Service central computer and the deviation of GPS between the standard time reach the 25us time used, return to step (1) afterwards;
(6) judge the cycle while whether having deposited autonomous evenly school in the internal register of Star Service central computer, if deposit in, enter step (7); If do not deposit in, enter step (8);
(7) Star Service central computer is to time user transmitting time broadcast message on star and the inside pulse per second (PPS) that produced by the internal clocking of Star Service central computer, and during the autonomous evenly school of Star Service central computer basis, the cycle is adjusted its internal clocking, make internal clocking and the deviation of GPS between the standard time be less than 25us, return to afterwards step (1);
(8) Star Service central computer, to time user transmitting time broadcast message on star and the inside pulse per second (PPS) that produced by the internal clocking of Star Service central computer, returns to step (1) afterwards.
The present invention compared with prior art has the following advantages:
(1) the present invention utilizes the high accuracy pulse per second (PPS) that on satellite, GPS receiver is exported to Star Service central computer, by Star Service central computer according to GPS pulse per second (PPS) internal clocking is calibrated, make the error < 25us between GPS standard time and the internal clocking of Star Service central computer, and take merely GPS pulse per second (PPS) in the past, as the design of time synchronized benchmark, cannot promote Star Service central computer internal clocking precision (the internal clocking error of gps time and Star Service central computer is ms level).And, Star Service central computer sends pulse per second (PPS) and transmitting time broadcast message in CAN bus in 422 buses, realize the precise synchronization of (time user on star) between each subsystem of whole star, precision is better than 0.1ms (standard time (UTC time) of the GPS of take output is benchmark).
(2) high-precision time synchronization method on star of the present invention, has overcome and has usingd merely the shortcoming that GPS pulse per second (PPS) cannot work on when the delocalization of GPS receiver as each subsystem time synchronized design of whole star in the past.Because original method for designing is only to rely on GPS pulse per second (PPS) as each time user's synchronizing signal, and no longer send pulse per second (PPS) during the delocalization of GPS receiver, between each time user, cannot continue synchronous working.And our rule can be when there is delocalization situation in GPS receiver, Star Service central computer makes the internal clocking error < 25us of GPS standard time and Star Service central computer during by autonomous evenly school, and can export high accuracy pulse per second (PPS) and use to time user, guarantee the needs that each time user time is synchronous.
(3) high-precision time synchronization method on star of the present invention, efficiently solves on star that time system precision is low, poor stability and cannot meet satellite and implement the time synchronization problem in quick mobile process.During satellite reality is flown in-orbit, as long as there is one of GPS receiver, star ground observing and controlling channel, just can realize the time unification of satellite, effectively reduce the risk that systemic-function lost efficacy, and can be as required or the variation of environment for use change in time time unification mode, significantly improved synchronous flexibility, reliability and the fail safe of satellite time.
Accompanying drawing explanation
Fig. 1 is high-precision time synchronization method structural representation of the present invention;
Fig. 2 is high-precision time synchronization method flow chart of the present invention;
Fig. 3 is pulse per second (PPS) output services schematic diagram of the present invention;
Schematic diagram when Fig. 4 is school of the present invention.
Embodiment
Be illustrated in figure 1 high-precision time synchronization method structural representation of the present invention, GPS receiver, Star Service central computer, clock unit and each time user (subsystem on star) are installed on satellite.
Wherein, the navigation signal that GPS receiver receives GPS navigation satellite calculates the GPS standard time, and sends high accuracy pulse per second (PPS) to Star Service central computer.
It is that benchmark accumulative total forms that internal clocking or clock unit are take in the internal clocking that Star Service central computer produces, and in the time of in orbit, the overwhelming majority time is used clock units.Clock unit provides high-precision timing benchmark for Star Service central computer, and has reduced the correction of ground in the face of satellite time.It adopts thermostatic control technology, guarantees that quartz crystal and oscillating circuit are operated at stable temperature, guarantees the stable of output frequency, is output as the square-wave signal of 40kHz.Clock stability is better than 5 * 10
-9/ day, frequency accuracy is 5 * 10
-7.Star Service central computer is counted the 40kHz square-wave signal of the clock unit output receiving, and with this, realizes internal clocking.
Star Service central computer is calibrated the internal clocking of Star Service central computer after receiving GPS pulse per second (PPS), and sends pulse per second (PPS) and time broadcast message to time user on star,
Time user receives pulse per second (PPS) and the temporal information broadcast that Star Service central computer sends, and during as benchmark school, timing.
The invention provides high-precision time synchronization method on a kind of Satellite, as shown in Figure 2, step is as follows:
(1) satellite in orbit during, GPS receiver on star is when positioning states, GPS receiver receives the navigation signal of GPS navigation satellite and calculates the GPS standard time, each GPS standard time whole second constantly, GPS receiver sends one to the Star Service central computer on star and is less than the high-precision GPS pulse per second (PPS) of 1 μ s with GPS standard time error; GPS receiver on star is when non-positioning states, and GPS receiver does not send GPS pulse per second (PPS);
(2) judge that whether Star Service central computer receives the GPS pulse per second (PPS) that GPS receiver sends, if receive, enters step (3); If do not receive, Star Service central computer continues to use its internal clocking, enters afterwards step (6);
(3) Star Service central computer sends GPS pulse per second (PPS) and temporal information broadcast to time user on star;
As shown in Figure 3, Star Service central computer can independently judge the inside pulse per second (PPS) of selecting output GPS pulse per second (PPS) or Star Service central computer to produce according to the positioning states of GPS receiver.
GPS receiver is when positioning states, and Star Service central computer directly forwards to time user the GPS pulse per second (PPS) that GPS receiver is exported to Star Service central computer by 422 buses.
Star Service central computer transfers can be to CAN bus transmitting time broadcast message in 50 milliseconds after GPS pulse per second (PPS).When the GPS pulse per second (PPS) that on star, each time user can transfer according to Star Service central computer and the time broadcast message in CAN bus are carried out school, timing, the internal time of self was alignd with the GPS standard time.
(4) Star Service central computer, according to GPS pulse per second (PPS) calibration internal clocking, makes the internal clocking of Star Service central computer and the deviation of GPS between the standard time be less than 25us;
The inside pulse per second (PPS) that Star Service central computer produces adopts the mode of counter cascade to realize, the first clock signal input using the 40KHz square-wave signal of clock unit output as counter 1, the square-wave signal that generating period is 1ms; Then the input of the clock signal using the square-wave signal of this 1ms as counter 2, generating period is 1 second, the pulse signal that negative pulse width is 1ms.The one-period of 40KHz clock is 25us, can reach that inner pulse per second (PPS) tunes up or the object of the 25us that slows down by increasing or reduce the pulse of 1 40KHz square-wave signal.
Implementation method during according to GPS pulse per second (PPS) school is as shown in Figure 4:
Star Service central computer reads the clock number of the 40KHz signal of inner pulse per second (PPS) trailing edge in the time period from GPS pulse per second (PPS) trailing edge to Star Service central computer, thus error in judgement time (unit of error time is 25us).If clock number is more than or equal to 40001 or be less than or equal to 39999, Star Service central computer sends that pulse adds " 1 " or pulse subtracts a pulse in the corresponding increase and decrease of " 1 " instruction 40KHz pulse train, reach the inner pulse per second (PPS) of Star Service central computer and tune up 25us or the object of the 25us that slows down, thereby make the inner pulse per second (PPS) of Star Service central computer and GPS pulse per second (PPS) error within a clock cycle (25us).
(5) cycle being stored in Star Service central computer internal register when Star Service central computer obtains its autonomous evenly school, during described autonomous evenly school, the cycle refers to that the internal clocking of Star Service central computer and the deviation of GPS between the standard time reach the 25us time used, return to step (1) afterwards;
At GPS receiver during in positioning states, Star Service central computer reads the error between GPS pulse per second (PPS) and inner pulse per second (PPS), record time that each error reaches 25us as cycle during autonomous evenly school on star, and with cycle during autonomous evenly school on the star once obtaining before periodic cover during autonomous evenly school on the last star obtaining, the minimum time equivalent of adjusting during autonomous evenly school is 25us.The method in cycle during autonomous evenly school on the star once obtaining before periodic cover when adopting autonomous evenly school on the last star obtaining, can also ask for mean value that error between GPS pulse per second (PPS) and inner pulse per second (PPS) reaches the 25us time used as cycle during autonomous even school on star through continual statistics.
(6) judge the cycle while whether having deposited autonomous evenly school in the internal register of Star Service central computer, if deposit in, enter step (7); If do not deposit in, enter step (8);
(7) Star Service central computer is to time user transmitting time broadcast message on star and the inside pulse per second (PPS) that produced by the internal clocking of Star Service central computer, and during the autonomous evenly school of Star Service central computer basis, the cycle is adjusted its internal clocking, make internal clocking and the deviation of GPS between the standard time be less than 25us, return to afterwards step (1);
As shown in Figure 3, Star Service central computer independently judges the inside pulse per second (PPS) of selecting output GPS pulse per second (PPS) or Star Service central computer to produce according to the positioning states of GPS receiver.
GPS receiver is when delocalization state, and Star Service central computer sends to time user the inside pulse per second (PPS) that Star Service central computer produces by 422 buses.
Star Service central computer sends can be to CAN bus transmitting time broadcast message in 50 milliseconds after inner pulse per second (PPS).When the inside pulse per second (PPS) that on star, each time user can send according to Star Service central computer and the time broadcast message in CAN bus are carried out school, in time, the internal time of self was alignd with the GPS standard time.
GPS receiver is when delocalization state, Star Service central computer can not be received GPS pulse per second (PPS), in the time of can be according to autonomous evenly school, the cycle be adjusted internal clocking, the a moment that does not receive GPS pulse per second (PPS) from Star Service central computer, every through on a secondary star during autonomous evenly school the cycle just send that pulse adds " 1 " or pulse subtracts a pulse in the corresponding increase and decrease of " 1 " instruction 40KHz pulse train, reach the inner pulse per second (PPS) of Star Service central computer and tune up 25us or the object of the 25us that slows down, thereby keep Star Service central computer internal clocking and the error of GPS standard time within a clock cycle (25us).
(8) Star Service central computer is to time user transmitting time broadcast message on star and the inside pulse per second (PPS) that produced by the internal clocking of Star Service central computer, returns to afterwards step (1) above-mentioned steps that again circulates.
Claims (1)
1. a high-precision time synchronization method on Satellite, is characterized in that step is as follows:
(1) satellite in orbit during, GPS receiver on star is when positioning states, GPS receiver receives the navigation signal of GPS navigation satellite and calculates the GPS standard time, in the whole second moment of each GPS standard time, GPS receiver sends a GPS pulse per second (PPS) to the Star Service central computer on star; GPS receiver on star is when non-positioning states, and GPS receiver does not send GPS pulse per second (PPS);
(2) judge that whether Star Service central computer receives the GPS pulse per second (PPS) that GPS receiver sends, if receive, enters step (3); If do not receive, Star Service central computer continues to use its internal clocking, enters afterwards step (6);
(3) Star Service central computer sends GPS pulse per second (PPS) and temporal information broadcast to time user on star;
(4) Star Service central computer, according to GPS pulse per second (PPS) calibration internal clocking, makes the internal clocking of Star Service central computer and the deviation of GPS between the standard time be less than 25us;
(5) cycle being stored in Star Service central computer internal register when Star Service central computer obtains its autonomous evenly school, during described autonomous evenly school, the cycle refers to that the internal clocking of Star Service central computer and the deviation of GPS between the standard time reach the 25us time used, return to step (1) afterwards;
(6) judge the cycle while whether having deposited autonomous evenly school in the internal register of Star Service central computer, if deposit in, enter step (7); If do not deposit in, enter step (8);
(7) Star Service central computer is to time user transmitting time broadcast message on star and the inside pulse per second (PPS) that produced by the internal clocking of Star Service central computer, and during the autonomous evenly school of Star Service central computer basis, the cycle is adjusted its internal clocking, make internal clocking and the deviation of GPS between the standard time be less than 25us, return to afterwards step (1);
(8) Star Service central computer, to time user transmitting time broadcast message on star and the inside pulse per second (PPS) that produced by the internal clocking of Star Service central computer, returns to step (1) afterwards.
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| CN107092183A (en) * | 2017-05-16 | 2017-08-25 | 上海卫星工程研究所 | Implementation method during high-precision school based on GPS second pulse |
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| WO2021081733A1 (en) * | 2019-10-29 | 2021-05-06 | 中国科学院微小卫星创新研究院 | Navigation satellite time system and autonomous recovery method therefor |
| CN111625327B (en) * | 2020-05-14 | 2023-02-03 | 哈尔滨工业大学 | Automatic satellite time management system |
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