A cluster time synchronization system based on GNSS

Abstract

The present invention discloses a cluster time synchronization system based on GNSS, which can solve the time synchronization problem of cluster systems. The system includes a signal layer, a service layer, a network layer and a terminal layer; the signal layer receives Beidou or GPS satellite information and provides a time signal; the service layer obtains standard time information by processing the time signal sent by the signal layer, and provides timing services for user terminals; the service layer includes a time synchronization server, a secondary time server, a switch and a monitoring device; the network layer is used to realize information transmission and information isolation between user terminals and time synchronization servers, and the network layer includes a network isolation switch; the terminal layer includes user terminals in the cluster, which are users of the timing service, and each user terminal receives time information from the time synchronization server and feeds back the local clock information of the user terminal to the monitoring device.

Description

Technical Field

[0001] The present invention relates to the field of clusters, and in particular to a cluster time synchronization system based on GNSS. Background Art

[0002] With the application of Beidou navigation satellite time and frequency, the cluster system composed of computers has higher and higher requirements for the unified time of the equipment in the system. At present, the internal clock of the system is mostly unified by the computer's own time in the system, and the local self-timekeeping accuracy is poor for a long time; for the system using GPS satellite standard time information, when the satellite time information is unavailable, the local timekeeping accuracy is difficult to guarantee. At the same time, the current time synchronization system lacks the function of managing the health status of the equipment in the system and the closed-loop adjustment of the timing results. Summary of the invention

[0003] In view of this, the present invention provides a GNSS-based cluster time synchronization system, which can solve the time synchronization problem of the cluster system, ensure that the internal time of the cluster system is consistent with the standard time of the satellite (including Beidou and GPS), and adopt a directional automatic timekeeping method to ensure that the time error between devices in the cluster system is better than 50ms without affecting the overall time continuity of the system. It is suitable for long-term time unification between devices in the cluster system.

[0004] In order to solve the above technical problems, the present invention is implemented as follows.

[0005] A GNSS-based cluster time synchronization system, the system comprising a signal layer, a service layer, a network layer and a terminal layer;

[0006] The signal layer receives Beidou or GPS satellite information, and provides a time signal based on the obtained reference frequency and satellite ephemeris information, wherein the time signal is a Beidou time signal or a GPS time signal; the signal layer includes an antenna and a timing receiver, wherein the antenna is used to receive Beidou or GPS satellite information, and the timing receiver is used to process Beidou or GPS satellite information and provide a time signal and a second pulse to a time service module of the service layer;

[0007] The service layer obtains standard time information by processing the time signal sent by the signal layer, and provides timing services for user terminals; the service layer includes a time synchronization server, a secondary time server, a switch and a monitoring device;

[0008] The network layer is used to realize information transmission and information isolation between the user terminal and the time synchronization server, and the network layer includes a network isolation switch;

[0009] The terminal layer includes user terminals in the cluster, which are users of the timing service. Each user terminal receives time information from a time synchronization server and feeds back local clock information of the user terminal to the monitoring device.

[0010] Preferably, the timing receiver is used to receive the time signal transmitted by the signal layer, and based on the time signal, generate standard navigation satellite time, 1PPS and 10M frequency signals, the 1PPS is used to provide a time reference signal, and the 10MHz signal is used for timing clock frequency.

[0011] Preferably, the time synchronization server receives the time signal transmitted by the signal layer, decodes the time information, generates the time information, and has the NTP network timing function; when the time synchronization server cannot obtain the time signal transmitted by the signal layer, the rubidium atomic clock of the time synchronization server itself generates a clock signal, and generates the time information based on the clock signal generated by the rubidium atomic clock;

[0012] The time synchronization server includes a rubidium atomic clock and a time service module; the rubidium atomic clock is used to generate a local standard 10MHz signal when the time signal transmitted by the signal layer cannot be obtained, and the local standard 10MHz signal is used as an internal clock signal to provide time services in conjunction with external clock information; the time service module is used to receive the signal layer time signal, and decode the time signal to provide continuous time services; the external clock is composed of the standard navigation satellite time, 1PPS and 10M frequency signal generated by the timing receiver after demodulating the satellite time information;

[0013] The secondary time server is a private network server, which is used to receive the time service sent by the time synchronization server through the switch, and provide timing service to user terminals within the private network;

[0014] The monitoring device is connected to the time synchronization server and each user terminal in the cluster, and is used to monitor the device information of the time synchronization server and the user terminal, and generate a time synchronization strategy to synchronize the user terminal when the time information of the user terminal deviates.

[0015] Preferably, the time service module internally includes a high-precision time synchronization and management module, and a time sending module; the high-precision time synchronization and management module is used for solving the time signal, and cooperates with 1PPS to correct the local rubidium atomic clock time; the high-precision time synchronization and management module counts the cycle of the external clock signal to generate time information; the time sending module is used for timing clock frequency distribution, and performs second pulse time alignment control by judging the second pulse moment error.

[0016] Preferably, the high-precision time synchronization and management module includes a serial port time receiving submodule, a clock management submodule, a B code receiving submodule and a time synchronization punctuality processing submodule;

[0017] The serial port time receiving submodule maintains the local time of the time synchronization server according to the serial port protocol and the 1PPS signal, supports multiple PPS signal inputs, and automatically selects the next PPS signal according to the priority setting when the PPS signal fails;

[0018] The clock management submodule supports multiple clock signal inputs;

[0019] The clock management submodule uses the clock signal of the local constant temperature crystal oscillator as a backup for the external rubidium atomic clock or other clock signals; when no external clock signal is detected for 10us in a row, it automatically switches to the clock signal of the local constant temperature crystal oscillator when the clock allows automatic switching, and sends the clock switching information to the main control computer through the serial port or network port;

[0020] The B code receiving submodule supports B code time information inputted from a remote optical fiber or cable to synchronize the local time of the time synchronization server;

[0021] The time synchronization and punctuality processing submodule counts the sub-second counter of the time code through an externally input clock, and the counting adopts an incrementing method. When the counter count value reaches the count value of 1s, a second pulse signal is output; when the satellite signal is normal and the second pulse output of the timing receiver is normal, the satellite time is aligned based on the second pulse signal. When the satellite signal is abnormal, the whole second time signal is maintained by the rubidium atomic clock.

[0022] Preferably, the monitoring device is used to perform clock control on the time synchronization server and determine the timing strategy of the user terminal; the clock control on the time synchronization server is: judging the locking state of the timing receiver, if the timing receiver is unlocked, it is determined that the external clock is invalid, and the monitoring device automatically generates a clock switching instruction, and switches the clock signal to the internal clock, thereby ensuring the continuous stability of the clock; when the external clock is restored, the monitoring device automatically generates a clock switching instruction, switches the clock signal to the external clock, and synchronizes the internal clock signal with the external clock; if the timing receiver is in a normal locking state, it is determined that the external clock is valid, and the external clock is continuously output.

[0023] Preferably, the timing strategy of the user terminal is determined based on a directional time synchronization method, and the directional time synchronization method includes:

[0024] Step S1: After the time synchronization server receives the timing request from the monitoring device, the monitoring device calls the timing service of the time synchronization server according to the timing frequency;

[0025] Step S2: the time synchronization server outputs available clock information according to the status of the internal clock and the external clock, wherein the available clock information is a unique and continuous unified time reference in the system and is provided by the internal clock or the external clock;

[0026] Step S3: For each of the user terminals, the monitoring device calculates the clock deviation of the user terminal. The calculation method is to define the clock deviation θ between the time synchronization server and the user terminal, the round-trip delay

[0027]

[0028]

[0029] Among them, T1 is the user terminal time when the user terminal sends the message, T2 is the time synchronization server time when the time synchronization server receives the request message, T3 is the time synchronization server time when the time synchronization server sends the local time information, T4 is the user terminal time updated after the user terminal receives the time synchronization server time, d1 is the delay from the client to the time synchronization server, and d2 is the delay from the time synchronization server to the client;

[0030] Step S4: Determine the compensation time for each of the user terminals, including: for each of the user terminals, determine the clock resolution as the inverse of the local clock frequency of the user terminal, and calculate the clock frequency deviation rate The frequency deviation is estimated using the maximum likelihood estimation method. Determine the exact time of timing t = (1-Δy)(t i-1 -θ); based on the accurate time of the timing and the local time of the user terminal, determine the compensation time of the user terminal; perform time compensation of the user terminal by using the compensation time; wherein y(t) is the clock frequency of the user terminal, i is the i-th timing, n is the statistical result of n timing, Δθ is the deviation change between the time synchronization server and the user terminal clock, Δt is the time difference between two timings, t i-1 The time of the previous time service.

[0031] Beneficial effects:

[0032] (1) The present invention proposes a cluster time synchronization system based on GNSS. By adopting the NTP protocol with high stability, it can provide a high-precision time reference signal for systems that require a standard time scale, and meet the time signal requirements of various automated equipment. The time reference uses GNSS time as a reference, and the frequency reference uses the output signal of a rubidium atomic clock as a reference. The time signal completes the time synchronization of all network computers and application equipment through the NTP time calibration method, and can also be expanded to use IRIG-B code to synchronize the time of specific computers or application equipment. At the same time, through centralized management of the health status of the equipment in the device, real-time monitoring of the terminal device time, and through a directional time synchronization method, automatic time synchronization is achieved; the device provides a wealth of signal interface resources to meet the time interface requirements of different devices and provide conditions for future expansion, with excellent compatibility.

[0033] (2) The receiving antenna of the present invention stably receives Beidou and GPS standard time information, and ensures the stability of time information through the rubidium atomic clock. The overall architecture is flexible, and the modular design and unified time monitoring ensure that the timing service is suitable for application in a variety of scenarios. At the same time, the device has strong scalability and stable timing. At the same time, a closed-loop directional control method is adopted to ensure that the long-term time stability deviation between devices in the system is better than 50ms.

[0034] (3) The GNSS-based cluster time synchronization system of the present invention is used to transmit time signals, including information such as year, month, day, hour, minute, second, and millisecond, so that the time deviation between the devices on the network and the coordinated universal time is within a relatively small range, providing a unified time reference for various computers and application devices of users.

[0035] (4) The GNSS-based cluster time synchronization system of the present invention uses the NTP protocol, which is the most widely used protocol at present, and designs a time and frequency reference system based on satellites and atomic clocks. It can provide a high-precision time reference for systems that require a standard time scale and meet the requirements of various automation equipment for time signals. The time reference uses Beidou time or GPS time as a reference. The time signal completes the time synchronization of all network computers and application equipment through the NTP time calibration method, and can also use IRIG-B code to synchronize the time of specific computers or application equipment. At the same time, automatic time synchronization is achieved by centrally managing the health status of the equipment in the device and monitoring the time of the terminal equipment in real time.

[0036] (5) The GNSS-based cluster time synchronization system of the present invention adopts a relatively reasonable modular structure in design, which can be flexibly configured according to user needs; it uses an excellent processor for control to ensure the processing capability of the system; at the same time, it provides abundant signal interface resources to meet the timing interface requirements of different devices and provide conditions for future expansion, and has excellent compatibility.

[0037] (6) The present invention proposes a GNSS-based cluster time synchronization method, which has been successfully applied to multiple complex systems to provide stable time services. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the structure of the cluster time synchronization system based on GNSS;

[0039] Figure 2 This is a schematic diagram of the northern half signal receiving and processing module;

[0040] FIG3(A) is a schematic diagram of input and output of a time service module;

[0041] FIG3(B) is a schematic diagram showing the composition of a time service module;

[0042] Figure 4 It is a schematic diagram of the communication structure of the time synchronization device;

[0043] Figure 5 This is a schematic diagram of the basic process of directional timing synchronization. DETAILED DESCRIPTION

[0044] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0045] like Figure 1 As shown, the present invention provides a GNSS-based cluster time synchronization system, which includes: a signal layer, a service layer, a network layer and a terminal layer.

[0046] The signal layer receives Beidou or GPS satellite information, and provides a time signal based on the acquired reference frequency and satellite ephemeris information, wherein the time signal is a Beidou time signal or a GPS time signal; the signal layer includes an antenna and a timing receiver, wherein the antenna is used to receive Beidou or GPS satellite information, and the timing receiver is used to process Beidou or GPS satellite information and provide time signals and second pulses to the time service module of the service layer.

[0047] like Figure 2 As shown, the timing receiver is used to receive the time signal transmitted by the signal layer, and based on the time signal, generates standard navigation satellite time, 1PPS and 10M frequency signals. The 1PPS is used to provide a time reference signal to ensure uniform trigger time, and the 10MHz signal is used for timing clock frequency.

[0048] The service layer obtains standard time information by processing the time signal sent by the signal layer, and provides timing services for user terminals; the service layer includes a time synchronization server, a secondary time server, a switch and a monitoring device.

[0049] The time synchronization server receives the time signal transmitted by the signal layer, decodes the time information, generates time information, and has the NTP network timing function; when the time synchronization server cannot obtain the time signal transmitted by the signal layer, the time synchronization server's own rubidium atomic clock generates a clock signal, and generates time information based on the clock signal generated by the rubidium atomic clock.

[0050] The time synchronization server includes a rubidium atomic clock and a time service module. The rubidium atomic clock is used to generate a local standard 10MHz signal when the time signal transmitted by the signal layer cannot be obtained, and the local standard 10MHz signal is used as the internal clock signal to provide time services in conjunction with external clock information. The time service module is used to receive the signal layer time signal, decode the time signal, and provide continuous time services. The external clock is composed of the standard navigation satellite time, 1PPS and 10M frequency signal generated by the timing receiver after demodulating the satellite time information.

[0051] The secondary time server is a private network server, which is used to receive the time service sent by the time synchronization server through the switch, and provide timing service to user terminals within the private network;

[0052] The monitoring device is connected to the time synchronization server and each user terminal in the cluster, and is used to monitor the device information of the time synchronization server and the user terminal, and when the time information of the user terminal deviates, generates a time synchronization strategy to synchronize the time of the user terminal;

[0053] The network layer is used to realize information transmission and information isolation between the user terminal and the time synchronization server, and the network layer includes a network isolation switch;

[0054] The terminal layer includes user terminals in the cluster, which are users of the timing service. Each user terminal receives time information from a time synchronization server and feeds back local clock information of the user terminal to the monitoring device.

[0055] In this embodiment, the signal receiving antenna adopts lightning protection design and electromagnetic shielding, and can receive standard time information. The timing receiver processes the received signal and can be compatible with Beidou and GPS standard time information at the same time.

[0056] As shown in Figure 3(A), the time service module is used to receive the second pulse signal generated by the timing receiver, the 10MHz clock frequency or the 10MHz clock frequency generated by the rubidium atomic clock module; based on the NTP protocol, it generates time information and provides NTP services for the timing terminal equipment, that is, each user terminal.

[0057] As shown in Figure 3(B), the time service module includes a high-precision time synchronization and management module and a time transmission module. The high-precision time synchronization and management module is used for solving the time signal and cooperating with 1PPS to correct the local rubidium atomic clock time; the high-precision time synchronization and management module counts the cycle of the external clock signal to generate time information; the time transmission module is used for timing clock frequency distribution, and performs second pulse time alignment control by judging the second pulse moment error to ensure the normal operation of the external clock and the internal clock. The IRIG-B code in Figure 3(A) is a parallel time code, and this system has the ability to receive and output IRIG-B codes.

[0058] The high-precision time synchronization and management module includes a serial port time receiving submodule, a clock management submodule, a B code receiving submodule and a time synchronization punctuality processing submodule. The serial port time receiving submodule maintains the local time of the time synchronization server according to the serial port protocol and the 1PPS signal, supports the input of multiple PPS signals, and can automatically select the next PPS signal according to the priority setting when the PPS signal fails. The clock management submodule supports the input of multiple clock signals. In order to improve the reliability of the punctuality function of the time service module, the clock management submodule uses the clock signal of the local constant temperature crystal oscillator as a backup for the external rubidium atomic clock or other clock signals. When no external clock signal is detected for 10us continuously, in the state of "clock allows automatic switching", it can automatically switch to the clock signal of the local constant temperature crystal oscillator, and send the clock switching information to the main control computer through the serial port or network port to notify the operation and maintenance personnel. The B code receiving submodule supports the B code time information input by remote optical fiber or cable to synchronize the local time of the time synchronization server. The B code receiving interface can decode the B code time data transmitted from a remote location, synchronize the local time according to the decoded time information, and output a 1PPS pulse signal. The time synchronization and punctuality processing submodule counts the sub-second counter of the time code through an externally input high-stable clock, and the counting adopts an increment counting method. When the counter count value reaches the count value of 1s, a second pulse signal is output; when the satellite signal is normal and the second pulse output of the timing receiver is normal, the satellite time is aligned with the second pulse signal as the reference. When the satellite signal is abnormal, the whole second time signal is maintained by the rubidium atomic clock.

[0059] The secondary time server provides the timing service of the time synchronization server by forwarding and processing, ensuring the special needs of confidentiality of some confidential networks.

[0060] The monitoring device is used to perform clock control on the time synchronization server and determine the timing strategy of the user terminal. The clock control of the time synchronization server is as follows: judging the locking state of the timing receiver. If the timing receiver loses lock, it is determined that the external clock is invalid. The monitoring device automatically generates a clock switching instruction and switches the clock signal to the internal clock, thereby ensuring the clock is continuous and stable; when the external clock is restored, the monitoring device automatically generates a clock switching instruction, switches the clock signal to the external clock, and synchronizes the internal clock signal through the external clock. If the timing receiver is in a normal locking state, it is determined that the external clock is valid and the external clock is continuously output.

[0061] The timing strategy for determining the user terminal is as follows: the monitoring device collects the time of the time synchronization server and the user terminal, adopts a directional time synchronization method, compares the time difference between the user terminal and the time synchronization server, adjusts through alarm monitoring, timing frequency, etc., uses the three-level alarm threshold to generate the corresponding time synchronization strategy, and automatically sets the time synchronization for the user terminal that exceeds the limit.

[0062] The directional time synchronization method dynamically monitors and adjusts the online user terminals in the system in real time. The method adopts a closed-loop feedback strategy to collect time information between user terminals in the system in real time, and calculates the time deviation of the user terminals in the system by comparing it with the time of the standard time synchronization server. According to the calculation result, the time of the over-limit user terminal is synchronized in a directional manner to ensure the uniformity of time between user terminals in the system. The over-limit user terminal determines the timing strategy through the three-level threshold of time deviation. If the time deviation exceeds 500ms, it is level 3, and an automatic alarm prompt is given, and the timing service distribution is prioritized, and the timing frequency is increased to 5s.

[0063] The directional time synchronization method comprises:

[0064] Step S1: After the time synchronization server receives the timing request from the monitoring device, the monitoring device calls the timing service of the time synchronization server according to the timing frequency;

[0065] Step S2: the time synchronization server outputs available clock information according to the status of the internal clock and the external clock, wherein the available clock information is a unique and continuous unified time reference in the system and is provided by the internal clock or the external clock;

[0066] Step S3: For each of the user terminals, the monitoring device calculates the clock deviation of the user terminal. The calculation method is to define the clock deviation θ between the time synchronization server and the user terminal, the round-trip delay

[0067]

[0068]

[0069] Among them, T1 is the user terminal time when the user terminal sends the message, T2 is the time synchronization server time when the time synchronization server receives the request message, T3 is the time synchronization server time when the time synchronization server sends the local time information, T4 is the user terminal time updated after the user terminal receives the time synchronization server time, d1 is the delay from the client to the time synchronization server, and d2 is the delay from the time synchronization server to the client.

[0070] In this embodiment, multiple sets of data statistics may be used to calculate the clock deviation value θ.

[0071] Step S4: Determine the compensation time for each of the user terminals, including: for each of the user terminals, determine the clock resolution as the inverse of the local clock frequency of the user terminal, and calculate the clock frequency deviation rate The frequency deviation is estimated using the maximum likelihood estimation method. Determine the exact time of timing t = (1-Δγ)(t i-1 -θ); based on the accurate time of the timing and the local time of the user terminal, determine the compensation time of the user terminal; perform time compensation of the user terminal by using the compensation time; wherein y(t) is the clock frequency of the user terminal, i is the i-th timing, n is the statistical result of n timing, Δθ is the deviation change between the time synchronization server and the user terminal clock, Δt is the time difference between two timings, t i-1 The time of the previous time service.

[0072] The time of devices in a cluster system is generally maintained by the device's own clock, but long-term operation will cause large time deviations between devices, thereby affecting the stability of system operation. The system of this embodiment is used to transmit time signals, and through a directional time synchronization method, the deviation between the devices on the network and the standard time is kept within a relatively small range of relative values, providing a unified time reference for various computers and application devices of users in the cluster system.

[0073] In normal use, the satellite standard time information is received and the NTP service is provided by the time synchronization server. When the terminal system time drifts and generates a time difference, the terminal operating system time is synchronized at the "next synchronization time". On the monitoring software interface, the current time of each terminal can be monitored at any time through the device connection diagram and list; the clock difference between the terminal and the server can be monitored through the clock difference data and curve. Timing strategies can also be set for different timing terminals according to user needs. Timing strategies are formulated in three levels according to the needs of different terminals. In the timeout alarm mode, when events such as new device access, time drift, or system time being changed by other software occur, the monitoring software will alarm and record the event, and automatically adjust the timing frequency to provide time for the device.

[0074] When the signal receiving antenna does not receive the satellite signal, the time synchronization device automatically switches to the timekeeping mode, the timing accuracy will not be reduced, and stable time information will be provided.

[0075] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in the description may be different and are not limited. Therefore, those skilled in the art in the field of the present invention may modify or replace the technical solutions recorded in the above embodiments; and these modifications and replacements do not deviate from the creative purpose and technical solutions of the present invention and should all fall within the protection scope of the present invention.

Claims

1. A GNSS-based cluster time synchronization system, characterized in that: The system includes a signal layer, a service layer, a network layer, and a terminal layer; The signal layer receives Beidou or GPS satellite information, and provides a time signal based on the obtained reference frequency and satellite ephemeris information, wherein the time signal is a Beidou time signal or a GPS time signal; the signal layer includes an antenna and a timing receiver, wherein the antenna is used to receive Beidou or GPS satellite information, and the timing receiver is used to process Beidou or GPS satellite information and provide a time signal and a second pulse to a time service module of the service layer; The service layer obtains standard time information by processing the time signal sent by the signal layer, and provides timing services for user terminals; the service layer includes a time synchronization server, a secondary time server, a switch and a monitoring device; The network layer is used to realize information transmission and information isolation between the user terminal and the time synchronization server, and the network layer includes a network isolation switch; The terminal layer includes user terminals in the cluster, which are users of the timing service. Each user terminal receives time information from the time synchronization server and feeds back local clock information of the user terminal to the monitoring device. The time synchronization server receives the time signal transmitted by the signal layer, decodes the time information, generates the time information, and has the NTP network timing function; when the time synchronization server cannot obtain the time signal transmitted by the signal layer, the rubidium atomic clock of the time synchronization server itself generates a clock signal, and generates time information based on the clock signal generated by the rubidium atomic clock; The time synchronization server includes a rubidium atomic clock and a time service module; the rubidium atomic clock is used to generate a local standard 10MHz signal when the time signal transmitted by the signal layer cannot be obtained, and the local standard 10MHz signal is used as an internal clock signal to provide time services in conjunction with external clock information; the time service module is used to receive the signal layer time signal, and decode the time signal to provide continuous time services; the external clock is composed of the standard navigation satellite time, 1PPS and 10MHz signal generated by the timing receiver after demodulating the satellite time information; The secondary time server is a private network server, which is used to receive the time service sent by the time synchronization server through the switch, and provide timing service to user terminals within the private network; The monitoring device is connected to the time synchronization server and each user terminal in the cluster, and is used to monitor the device information of the time synchronization server and the user terminal, and when the time information of the user terminal deviates, generates a time synchronization strategy to synchronize the time of the user terminal; The time service module includes a high-precision time synchronization and management module and a time transmission module; the high-precision time synchronization and management module is used for solving the time signal and cooperating with 1PPS to correct the local rubidium atomic clock time; the high-precision time synchronization and management module counts the cycle of the external clock signal to generate time information; the time transmission module is used for timing clock frequency distribution, and performs second pulse time alignment control by judging the second pulse moment error; The high-precision time synchronization and management module includes a serial port time receiving submodule, a clock management submodule, a B code receiving submodule and a time synchronization and punctuality processing submodule; The serial port time receiving submodule maintains the local time of the time synchronization server according to the serial port protocol and the 1PPS signal, supports multiple PPS signal inputs, and automatically selects the next PPS signal according to the priority setting when the PPS signal fails; The clock management submodule supports multiple clock signal inputs; The clock management submodule uses the clock signal of the local constant temperature crystal oscillator as a backup for the external rubidium atomic clock or other clock signals; When no external clock signal is detected for 10μs continuously, the clock will automatically switch to the clock signal of the local constant temperature crystal oscillator under the condition that the clock allows automatic switching, and send the clock switching information to the main control computer through the serial port or network port; The B code receiving submodule supports the B code time information inputted by remote optical fiber or cable to synchronize the local time of the time synchronization server; The time synchronization and punctuality processing submodule counts the sub-second counter of the time code through an externally input clock, and the counting adopts an increment counting method. When the counter count value reaches the count value of 1s, a second pulse signal is output; when the satellite signal is normal and the second pulse output of the timing receiver is normal, the satellite time is aligned based on the second pulse signal. When the satellite signal is abnormal, the whole second time signal is maintained by the rubidium atomic clock. The monitoring device is used to perform clock control on the time synchronization server and determine the timing strategy of the user terminal; The clock control of the time synchronization server is as follows: judging the locking state of the timing receiver, if the timing receiver is unlocked, it is determined that the external clock is invalid, the monitoring device automatically generates a clock switching instruction, and switches the clock signal to the internal clock, thereby ensuring the clock is continuous and stable; When the external clock is restored, the monitoring device automatically generates a clock switching instruction, switches the clock signal to the external clock, and synchronizes the internal clock signal with the external clock; If the timing receiver is in a normal locked state, it is determined that the external clock is valid and the external clock is continuously output.

2. The system according to claim 1, characterized in that The timing receiver is used to receive the time signal transmitted by the signal layer, and based on the time signal, generates standard navigation satellite time, 1PPS and 10MHz signal, the 1PPS is used to provide a time reference signal, and the 10MHz signal is used for timing clock frequency.

3. The system according to claim 1, characterized in that The timing strategy of the user terminal is determined based on a directional time synchronization method, and the directional time synchronization method includes: Step S1: After the time synchronization server receives the timing request from the monitoring device, the monitoring device calls the timing service of the time synchronization server according to the timing frequency; Step S2: the time synchronization server outputs available clock information according to the status of the internal clock and the external clock, wherein the available clock information is a unique and continuous unified time reference in the system and is provided by the internal clock or the external clock; Step S3: For each of the user terminals, the monitoring device calculates the clock deviation of the user terminal. The calculation method is to define the clock deviation θ between the time synchronization server and the user terminal, the round-trip delay Among them, T1 is the user terminal time when the user terminal sends the message, T2 is the time synchronization server time when the time synchronization server receives the request message, T3 is the time synchronization server time when the time synchronization server sends the local time information, T4 is the user terminal time updated after the user terminal receives the time synchronization server time, d1 is the delay from the client to the time synchronization server, and d2 is the delay from the time synchronization server to the client; Step S4: Determine the compensation time for each of the user terminals, including: for each of the user terminals, determine the clock resolution as the inverse of the local clock frequency of the user terminal, and calculate the clock frequency deviation rate The frequency deviation is estimated using the maximum likelihood estimation method. Determine the exact time of timing t = (1-Δγ)(t i-1 -θ); based on the accurate time of the timing and the local time of the user terminal, determine the compensation time of the user terminal; perform time compensation of the user terminal by using the compensation time; wherein y(t) is the clock frequency of the user terminal, i is the i-th timing, n is the statistical result of n timing, Δθ is the deviation change between the time synchronization server and the user terminal clock, Δt is the time difference between two timings, t i-1 The time of the previous time service.

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