Airborne missile group high-precision time self-synchronization method based on network communication

Abstract

The invention discloses an airborne missile group high-precision time self-synchronization method based on network communication, belongs to the field of clock synchronization, realizes nanosecond-level synchronization precision through a layered round-trip timing technology and dynamic combination of autonomous and absolute time synchronization, and is suitable for providing a high-precision space-time reference in an interference environment. Through classification processing of external synchronization and internal synchronization nodes, a mode of combining coarse synchronization and fine synchronization is adopted, and a layered round-trip timing (RTT) mechanism is combined, so that nanosecond-level in-network clock self-synchronization is realized. High-precision time synchronization between platforms is provided through communication link signal interaction. According to the method, high-precision clock synchronization of satellites and atomic clocks is not depended on, high-precision time synchronization among members in a missile group is achieved through network communication, and a high-precision space-time reference is provided for an unmanned aerial vehicle to achieve combat missions such as cooperative relative positioning, cooperative detection and cooperative attack.

Description

Technical Field

[0001] The present invention relates to the technical field of clock synchronization, and in particular to a high-precision time self-synchronization method for airborne missile groups based on network communication. Background Art

[0002] In a combat environment, satellite positioning and timing systems are vulnerable to enemy interference and failure, resulting in the inability to execute satellite-dependent collaborative tasks. Existing technologies usually rely on atomic clocks or external timing sources, which have problems such as high cost, poor anti-interference ability, and large resource occupancy. In addition, traditional synchronization methods are difficult to achieve nanosecond-level synchronization accuracy in non-precise time networks. Therefore, there is an urgent need for a high-precision time self-synchronization technology that does not rely on satellites and atomic clocks to achieve a stable and reliable time reference through dynamic network interaction. Summary of the Invention

[0003] The object of the present invention is to provide a high-precision time self-synchronization method for airborne missile groups based on network communication to solve the problems existing in the background art.

[0004] To achieve the above object, the present invention provides a high-precision time self-synchronization method for airborne missile groups based on network communication, including the following steps:

[0005] S1. Divide the precise time network and the non-precise time network according to the network time reference type. When a user accesses the network, select a synchronization mode according to the time quality level. External synchronization users directly access, and internal synchronization users perform coarse synchronization and fine synchronization;

[0006] S2. Achieve coarse synchronization and fine synchronization of internal synchronization users through the hierarchical round-trip time (RTT) method;

[0007] S3. Combine the Kalman filter to dynamically estimate the time deviation and drift, and optimize the synchronization accuracy of fine synchronization;

[0008] S4. When Beidou is effective, use the combination of absolute synchronization time and autonomous time synchronization to align with UTC time; when Beidou fails, dynamically switch to autonomous time synchronization.

[0009] Preferably, in S1, the precise time network depends on an external precise time, and the non-precise time network depends on an internal time reference; external synchronization users are users with external precise time input, and internal synchronization users are users who depend on the internal time reference.

[0010] Preferably, for the coarse synchronization of in-sync users in the precise time network in S1, the local clock is initially calibrated by the time of arrival (TOA) of the access message, and for the fine synchronization, the hierarchical round-trip time (RTT) method is adopted, combined with Kalman filtering to estimate the time deviation and drift, and the starting point of the time slot is adjusted until the time filter converges; all users in the non-precise time network work in the in-sync user mode, and with the network time reference (NTR) node as the reference, synchronization is achieved through the combination of hierarchical RTT and passive time synchronization.

[0011] Preferably, the synchronization process of the external clock synchronization users in the precise time network includes:

[0012] Load relevant parameters, then input external precise time for precise time delivery, and then select a pattern;

[0013] Judge whether it conforms to the network time reference. If it conforms, send an access message. If it does not conform, wait to receive an access message. After receiving the access message, receive other messages.

[0014] Preferably, the synchronization process of the internal clock synchronization users in the precise time network includes:

[0015] Load relevant parameters for time estimation;

[0016] After selecting a pattern, receive an access message and judge whether the access message is received. If the access message is received, enter the fine synchronization stage;

[0017] In the fine synchronization stage, first perform hierarchical round-trip time (RTT), then perform passive time synchronization, and judge whether the time quality exceeds the set threshold. If it exceeds, return to hierarchical round-trip time (RTT); if it does not exceed, perform passive time synchronization.

[0018] Preferably, the synchronization process of the clock synchronization users in the non-precise time network includes:

[0019] Load relevant parameters and then perform time estimation, and then select a pattern;

[0020] Judge whether it conforms to the network time reference. If it conforms, send an access message; if it does not conform, wait to receive an access message. When the access message is received, enter the fine synchronization stage;

[0021] In the fine synchronization stage, first perform hierarchical round-trip time (RTT), then perform passive time synchronization, and judge whether the time quality exceeds the set threshold. If it exceeds, return to hierarchical round-trip time (RTT); if it does not exceed, perform passive time synchronization.

[0022] Preferably, the NTR node management includes dynamically electing a node with high clock stability as the NTR.

[0023] Preferably, the hierarchical round-trip time (RTT) method includes:

[0024] Divide the cascaded subnet according to the time quality level;

[0025] Measure the propagation time T through two-way message round trips p With the time deviation ε, the calculation formula is:

[0026] ε = (TOA i - TOA r + T d ) / 2

[0027] Among them, TOA i represents the arrival time of the interrogation message measured by the responder; TOA r represents the arrival time of the response message measured by the interrogator; T d represents the sending time of the RTT response message;

[0028] Adopt a competition strategy to allocate RTT time slot resources.

[0029] Preferably, the autonomous time synchronization processing flow is as follows:

[0030] The member to be networked first receives the network access message to complete coarse synchronization, and then constructs the RTT cascaded network after receiving the PPLI message;

[0031] Randomly select n available cascaded networks from the constructed cascaded network, then randomly select n RTT time slots, and then perform RTT operations in 3 specified time slots and specified cascaded networks;

[0032] Check whether the RTT operation is successful. If it is not successful, return to reselect the cascaded network and time slot; if it is successful, continue to judge whether the time is stable. If it is not stable, also return to reselect the cascaded network and time slot; if the time is stable, judge whether it meets the time quality requirements. If it does not meet, still return to reselect the cascaded network and time slot;

[0033] When the time quality requirements are met, perform passive time synchronization.

[0034] Therefore, the present invention adopts the above-mentioned airborne missile group high-precision time self-synchronization method based on network communication, and has the following beneficial effects:

[0035] (1) It does not rely on satellite timekeeping or ground station timekeeping: It can achieve high-precision time synchronization among missiles within the missile group in a complex electromagnetic environment.

[0036] (2) It integrates the autonomous synchronization and absolute synchronization modes: The system has two network synchronization modes, autonomous time synchronization (internal synchronization) and absolute time synchronization (external synchronization), and supports dynamic switching in complex environments to meet different combat requirements.

[0037] (3) Hierarchical round-trip time synchronization: Through the hierarchical round-trip time synchronization technology, the resource allocation and synchronization efficiency are optimized by dynamically dividing the layered subnets. While meeting the system time accuracy, the system resources occupied by time synchronization are minimized as much as possible.

[0038] (4) Dynamic management: Through the dynamic management of the NTR role, the network anti-interference ability and fault tolerance are enhanced. The time quality level and the passive timekeeping mechanism are introduced to reduce resource occupancy and improve robustness.

[0039] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0040] Figure 1 It is the overall flowchart of a high-precision time self-synchronization method for airborne missile groups based on network communication according to an embodiment of the present invention;

[0041] Figure 2 It is the synchronization flowchart of the precise time network external clock synchronization user according to an embodiment of the present invention;

[0042] Figure 3 It is the synchronization flowchart of the precise time network internal clock synchronization user according to an embodiment of the present invention;

[0043] Figure 4 It is the synchronization flowchart of the non-precise time network time synchronization according to an embodiment of the present invention;

[0044] Figure 5 It is the schematic diagram of the principle based on the two-way round-trip time (RTT) according to an embodiment of the present invention;

[0045] Figure 6 It is the schematic diagram of the absolute time synchronization according to an embodiment of the present invention;

[0046] Figure 7 It is the flowchart of the hierarchical RTT processing according to an embodiment of the present invention;

[0047] Figure 8 It is the flowchart of the system autonomous time synchronization processing according to an embodiment of the present invention. Detailed Embodiments

[0048] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0049] Please refer to Figure 1-8 , a high-precision time self-synchronization method for airborne missile groups based on network communication, includes the following steps:

[0050] S1. Divide the precise time network and the non-precise time network according to the network time reference type. When a user accesses the network, select the synchronization mode according to the time quality level. External synchronization users are directly connected, and internal synchronization users perform coarse synchronization and fine synchronization.

[0051] Divide the network into a precise time network (relying on an external standard time) and a non-precise time network (relying on an internal time reference).

[0052] Users are divided into two categories: external synchronization users with an external precise time input, and internal synchronization users relying on an internal time reference.

[0053] Precise time network:

[0054] External synchronization users directly use the external time without synchronization; internal synchronization users achieve synchronization through two stages of coarse synchronization and fine synchronization:

[0055] Coarse synchronization: Initially calibrate the local clock by receiving the arrival time (TOA) of the network access message.

[0056] Fine synchronization: Adopt the hierarchical round-trip time calibration (RTT) technology, combine the Kalman filter to estimate the time deviation and drift, and adjust the starting point of the time slot until the time filter converges.

[0057] Non-precise time network:

[0058] All users work in the internal synchronization user mode, take the network time reference (NTR) node as a reference, and achieve synchronization through the combination of hierarchical RTT and passive timekeeping.

[0059] S2. Implement the coarse synchronization and fine synchronization of internal synchronization users through the hierarchical round-trip time calibration (RTT) method.

[0060] Divide the cascaded subnets according to the user time quality level (0-15 levels), and users with a high time quality participate in the RTT calibration first.

[0061] Measure the propagation time T through the two-way round-trip message p and the time deviation ε, and the calculation formula is:

[0062] ε = (TOA i - TOA r + T d ) / 2

[0063] where TOA i represents the arrival time of the inquiry message measured by the responder; TOA r represents the arrival time of the response message measured by the inquirer; T d represents the sending time of the RTT response message. ε is the time offset between two users.

[0064] Since ε + Tp = TOA i , T d + T p = ε + TOA r , so it can be obtained that ε = (TOA i - TOA r + T d ) / 2.

[0065] S3. Combine the Kalman filter to dynamically estimate the time deviation and drift, and optimize the synchronization accuracy of fine synchronization.

[0066] S4. When Beidou is available, use the combination of absolute synchronization time and autonomous time synchronization to achieve alignment with UTC time; when Beidou fails, dynamically switch to autonomous time synchronization.

[0067] Autonomous time synchronization: Based on the NTR node, maintain the time consistency within the network through hierarchical RTT and passive timekeeping;

[0068] Absolute time synchronization: When Beidou is available, measure the deviation between Beidou time and local time, and combine autonomous synchronization to achieve alignment with UTC time.

[0069] Support dynamic switching mode, and automatically switch to autonomous synchronization when Beidou fails.

[0070] Network Time Reference (NTR) management:

[0071] The NTR node needs to have high clock stability and good line-of-sight connectivity, and the role can be dynamically taken over;

[0072] Before the NTR goes silent, send a PPLI message to mark the RTT status to avoid occupying invalid resources. Specific embodiments:

[0074] A high-precision time self-synchronization method for an unmanned aerial vehicle (UAV) cluster in a satellite-denied environment. During a military exercise, a certain UAV cluster needs to perform cooperative reconnaissance and target strike missions. Due to the enemy's implementation of satellite navigation and timing interference, the UAVs cannot rely on Beidou / GPS to obtain time and position information. To achieve cooperative missions, it is necessary to establish an autonomous high-precision time synchronization network through communication links to ensure that the time deviation between UAVs is less than 10 nanoseconds, and support dynamic networking and anti-jamming communication.

[0075] System composition:

[0076] Network nodes: Include 6 UAVs (UAV1 - UAV6), where UAV1 is used as the initial Network Time Reference (NTR) node and is equipped with a high-stability rubidium atomic clock; the remaining UAVs are internal synchronization users and only rely on local crystal oscillator clocks.

[0077] Communication module: Each UAV is equipped with a frequency-hopping data link, supporting two-way communication and TOA measurement. The operating frequency band is 2.4 GHz, and the bandwidth is 20 MHz.

[0078] Processing unit: Integrates a Kalman filter module, a time quality assessment algorithm, and an RTT scheduling controller.

[0079] Implementation steps:

[0080] 1) Network initialization and NTR election:

[0081] After UAV1 starts, it self-checks the clock stability (frequency drift rate ≤ 1e-10 / second) and automatically becomes an NTR node, broadcasting an access message (including timestamp T0).

[0082] The remaining UAVs (UAV2 - UAV6) receive the access message from UAV1, record the TOA (time of arrival), and enter the coarse synchronization phase.

[0083] 2) Coarse synchronization:

[0084] UAV2 calculates the initial time deviation Δt1 = TOA - T0 based on TOA and adjusts its local clock to T0 + Δt1.

[0085] After all UAVs complete coarse synchronization, the time deviation is initially converged to the microsecond level (≤ 1 μs).

[0086] 3) Hierarchical round-trip time (RTT) calibration and fine synchronization:

[0087] Time quality level division:

[0088] The time quality level of UAV1 (NTR) is 15 (the highest);

[0089] UAV2 - UAV6 dynamically allocate levels according to their local clock stability and historical synchronization errors (for example, UAV2 is 12, UAV3 is 10, and the rest are 8).

[0090] Hierarchical RTT execution:

[0091] Higher-level users initiate RTT requests with priority. For example, UAV2 sends an RTT query message to UAV1 and records the sending time T1;

[0092] After receiving it, UAV1 immediately replies with an acknowledgement message, recording the receiving time T2 and the sending time T3;

[0093] UAV2 receives the acknowledgement message and records the arrival time T4.

[0094] Time deviation calculation:

[0095] Propagation time T p=(T4 - T1 - (T3 - T2)) / 2;

[0096] The time deviation ε = (T2 - T1 + T3 - T4) / 2.

[0097] The Kalman filter (parameters: process noise Q = 1e - 12, observation noise R = 1e - 10) iteratively estimates ε and the frequency drift, and adjusts the time slot start point of UAV2.

[0098] Convergence determination: When the standard deviation of the time deviation ≤ 5 nanoseconds, it is determined that the synchronization is stable, and enter the passive timekeeping stage.

[0099] 4) Passive timekeeping and dynamic switching:

[0100] UAV2 - UAV6 continuously monitor the PPLI (Precise Position and Identity) message of UAV1, measure its TOA, and maintain time synchronization through space transmission time compensation (known relative position);

[0101] If UAV1 fails due to radio silence, trigger the NTR role replacement:

[0102] UAV2 (the second - highest level) broadcasts a competition message, and the other nodes vote to elect a new NTR;

[0103] The new NTR (UAV2) updates the time reference, and the whole network re - executes the hierarchical RTT.

[0104] 5) Absolute time synchronization when Beidou is available:

[0105] When the interference in some areas is lifted (such as UAV4 detects the Beidou signal):

[0106] UAV4 switches to the absolute time synchronization mode, measures the time deviation Δt_GNSS between the Beidou time and the local time;

[0107] Deduct the antenna cable delay (pre - calibrated as 2.3 nanoseconds), input Δt_GNSS into the Kalman filter, and adjust the local clock to align with UTC;

[0108] UAV4 is upgraded to an external synchronization user, provides a calibration reference to other nodes, and optimizes the overall network synchronization accuracy.

[0109] Effect verification, as shown in Table 1:

[0110] Synchronization accuracy: After 10 RTT iterations, the time deviation between UAVs ≤ 8 nanoseconds (meeting the design index);

[0111] Anti - interference ability: When simulating the silence of the NTR node, the whole network completes the role replacement within 200 ms, and the synchronization accuracy fluctuation < 15 nanoseconds;

[0112] Resource Occupancy: The hierarchical RTT time slot competition strategy reduces the communication overhead by 30%, and the CPU occupancy rate in the passive timing stage is <5%.

[0113] Table 1 Key Data Table

[0114]

[0115]

[0116] Therefore, the present invention adopts the above-mentioned airborne missile group high-precision time self-synchronization method based on network communication. In a complex battlefield environment, through hierarchical RTT, dynamic NTR management, and multi-mode synchronization switching, it realizes high-precision and low-resource-occupancy time self-synchronization, providing a reliable spatio-temporal reference for the cooperative operation of UAV clusters.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-precision time self-synchronization method for airborne missile groups based on network communication, characterized in that: The following steps are involved: S1. According to the network time reference type, the network is divided into precise time network and imprecise time network. When users join the network, they select the synchronization mode according to the time quality level. External synchronization users directly access the network, and internal synchronization users perform coarse synchronization and fine synchronization. S2, realize the coarse synchronization and fine synchronization of internal synchronization users through the layered round-trip timing RTT method; S3, combining Kalman filter to dynamically estimate time deviation and drift, and optimize the synchronization accuracy of fine synchronization; S4: When Beidou is valid, use a combination of absolute synchronization time and autonomous time synchronization to achieve alignment with UTC time; when Beidou fails, dynamically switch to autonomous time synchronization.

2. According to claim 1, a high-precision time self-synchronization method for airborne missile groups based on network communication is characterized in that: In S1, the precise time network relies on external precise time, and the imprecise time network relies on the internal time reference; the external synchronization users are users with external precise time input, and the internal synchronization users are users relying on the internal time reference.

3. According to claim 2, a high-precision time self-synchronization method for airborne missile groups based on network communication is characterized in that: In S1, the coarse synchronization of the internally synchronized users in the precise time network preliminarily calibrates the local clock by receiving the arrival time TOA of the network access message. The fine synchronization adopts the hierarchical round-trip time calibration RTT method, combined with the Kalman filter to estimate the time deviation and drift, and adjust the time slot starting point until the time filter converges. All users of the non-precise time network work in the internal synchronization user mode, using the network time reference NTR node as a reference, and achieve synchronization through a combination of hierarchical RTT and passive time synchronization.

4. According to claim 3, a high-precision time self-synchronization method for airborne missile groups based on network communication is characterized in that: The synchronization process of external clock synchronization users in the precise time network includes: Load relevant parameters, then input external precise time for precise timing, and then select the pattern; Determine whether it meets the network time benchmark. If it does, send a network access message. If it does not, wait to receive the network access message. After receiving the network access message, receive other messages.

5. According to claim 4, a high-precision time self-synchronization method for airborne missile groups based on network communication is characterized in that: The synchronization process of internal clock synchronization users in the precise time network includes: Load relevant parameters for time estimation; After selecting the pattern, receive the network access message and determine whether the network access message is received. If the network access message is received, enter the fine synchronization stage; In the fine synchronization stage, layered round-trip time calibration is first performed, followed by passive time synchronization to determine whether the time quality exceeds the set threshold. If so, the system returns to layered round-trip time calibration; if not, passive time synchronization is performed.

6. The high-precision time self-synchronization method for airborne missile groups based on network communication according to claim 5 is characterized in that: The synchronization process of clock synchronization users in an imprecise time network includes: After loading the relevant parameters, make a time estimate and then select the pattern; Determine whether it meets the network time reference. If so, send a network access message. If not, wait to receive a network access message. After receiving the network access message, enter the fine synchronization phase. In the fine synchronization stage, layered round-trip time calibration is first performed, followed by passive time synchronization to determine whether the time quality exceeds the set threshold. If so, the system returns to layered round-trip time calibration; if not, passive time synchronization is performed.

7. The high-precision time self-synchronization method for airborne missile groups based on network communication according to claim 3 is characterized by: NTR node management includes dynamically electing nodes with high clock stability as NTRs.

8. The high-precision time self-synchronization method for airborne missile groups based on network communication according to claim 1 is characterized in that: The hierarchical round-trip timing (RTT) method includes: Divide the overlay subnets by time quality level; The propagation time T is measured by two-way round-trip messages p The time deviation ε is calculated as: ε=(TOA) i -TOA r +T d ) / 2 Among them, TOA i Indicates the arrival time of the inquiry message measured by the answering terminal; TOA r Indicates the arrival time of the response message measured by the inquiry terminal; T d Indicates the time when the RTT response message is sent; A competition strategy is used to allocate RTT time slot resources.

9. The high-precision time self-synchronization method for airborne missile groups based on network communication according to claim 1 is characterized in that: The autonomous time synchronization process is as follows: The member to be connected to the network first receives the network access message and completes the rough synchronization, and then constructs the RTT overlay network after receiving the PPLI message; Randomly select n available overlay networks from the constructed overlay networks, randomly select n RTT time slots, and then perform RTT operations in the three specified time slots and the specified overlay networks; Check whether the RTT operation is successful. If not, return to reselect the overlay network and time slot. If successful, continue to determine whether the time is stable. If not, return to reselect the overlay network and time slot. If the time is stable, determine whether it meets the time quality requirements. If not, return to reselect the overlay network and time slot. When the time quality requirements are met, passive time synchronization is performed.

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