A multi-node high-precision time synchronization method for offshore dynamic platforms

Abstract

The present invention discloses a multi-node high-precision time synchronization method for an offshore mobile platform. The method comprises the following steps: receiving navigation information signals through N slave nodes and one master node to complete the collection of original observation data; a GNSS time and frequency terminal of the master node completes the real-time position solution of the node based on the collected original observation data, obtains the clock difference between the local clock and each satellite based on the position information and information such as the pseudo-range measurement value corresponding to each satellite in the original observation data of the master node, and simultaneously the master station sends the original observation data, position information and the clock difference information between the local clock and each satellite through a communication terminal to each slave station; a GNSS time and frequency terminal of the slave node completes the real-time position solution of the station based on the original observation data collected by the node, the original observation data sent by the master station and the real-time position information of the master station, obtains the clock difference between the local clock and the clocks of each satellite and performs common-view satellite screening, completes the clock difference calculation of the local clocks of the two nodes, adjusts the local clock of the slave node, and realizes high-precision time synchronization among multiple nodes.

Description

Technical Field

[0001] The present invention relates to the technical field of time-frequency synchronization, and in particular to a multi-node high-precision time synchronization method for an offshore mobile platform. Background Art

[0002] To meet the needs of multi-node collaborative networking, such as multi-station passive positioning and multi-station uplink and downlink arrays, high-precision time synchronization between nodes has become a primary issue that these systems must address. Currently, high-precision time synchronization methods between nodes mainly include navigation satellite common view and two-way time and frequency transfer.

[0003] The navigation satellite common view method is mainly divided into two schemes, single-star common view and multi-star common view, depending on the number of common view satellites. The single-star common view method is that two nodes simultaneously receive the downlink signal of a single navigation satellite to complete the time synchronization between nodes. The first prerequisite for the implementation of this method is that each node must be deployed at a known point with precise station address calibration. Therefore, it is only suitable for high-precision time synchronization between fixed stations and does not have high-precision time synchronization between moving platform nodes. Compared with the single-star common view scheme, the multi-star common view scheme completes the time synchronization between nodes by having each node simultaneously receive the downlink signals of multiple navigation satellites. The master and slave nodes can achieve node site measurement by simultaneously receiving multiple satellites (number ≥ 4), and can also complete the clock difference measurement of each node relative to each navigation satellite. The master and slave nodes can achieve time synchronization between nodes by using the station address and clock difference measurement information. Although this scheme does not require prior calibration of the node station address, the station address measurement is obtained by single-point positioning, so its positioning error is low, and the correlation between the single-point positioning results between nodes is poor, resulting in slightly poor synchronization accuracy between nodes. In particular, its performance will be further deteriorated under moving platform conditions.

[0004] Bidirectional time and frequency transfer methods can be broadly categorized into two types, depending on the transmission link: bidirectional microwave time and frequency transfer, bidirectional fiber optic time and frequency transfer, and bidirectional satellite time and frequency transfer. All three methods achieve inter-node time synchronization through bidirectional measurements. Bidirectional microwave time and frequency transfer requires line of sight between nodes, making it suitable for time synchronization between nodes within close proximity and within visual range. Bidirectional fiber optic time and frequency transfer uses optical fiber to interconnect nodes and achieves inter-node time synchronization through bidirectional measurements. Because the bidirectional transmission paths are identical and are less susceptible to external environmental influences, this method offers the highest synchronization accuracy. However, this method requires optical fiber to interconnect nodes, making it suitable only for time synchronization between fixed stations. Furthermore, the need to lay optical cables between nodes leads to high construction costs and makes it unsuitable for achieving high-precision time synchronization between nodes on mobile platforms, particularly offshore platforms. Bidirectional satellite time and frequency transfer uses bidirectional measurement signals transmitted between nodes via satellite to achieve high-precision time synchronization. While this method can also achieve high-precision time synchronization between nodes, its system is more complex, especially for time synchronization requiring a large number of nodes, and its construction costs are high. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a high-precision time synchronization method for multiple nodes on an offshore moving platform. This method can achieve high-precision time synchronization between multiple nodes under the condition of a moving platform by receiving GNSS satellite navigation signals, and is easy to expand the number of nodes.

[0006] The present invention solves the existing technical problems by adopting the following solution: the offshore mobile platform is composed of N+1 independent nodes, including N slave nodes and 1 master node. The time synchronization equipment of each node is composed of a GNSS antenna, a GNSS time and frequency terminal, and a communication terminal. The time synchronization equipment of the master and slave nodes is composed of a GNSS antenna, a GNSS time and frequency terminal, and a communication terminal. The GNSS time and frequency terminal is composed of a rubidium atomic clock module, a navigation signal processing module, a common view processing module, a power module, a time code generation module, and a backplane (bus).

[0007] First, each node receives the navigation signal and completes the collection of raw observation data. The master node GNSS time and frequency terminal completes the real-time position solution of the node based on the raw observation data collection. Based on the position information and the pseudo-range measurement values ​​corresponding to each satellite in the master node's raw observation data, the clock difference between the local clock and each satellite is obtained. At the same time, the master station sends the raw observation data, position information, and the clock difference information between the local clock and each satellite to each slave station through the communication terminal.

[0008] Secondly, the slave GNSS time and frequency terminal completes the real-time position solution of the station based on the original observation data collected by the node, the original observation data sent by the master station, and the real-time position information of the master station. The slave node uses the real-time position of the slave node and the pseudo-range measurement value corresponding to each satellite in the original observation data of the master node to obtain the clock difference between the local clock and the clock of each satellite;

[0009] Then, the slave node GNSS time and frequency terminal performs common view satellite screening on the clock difference between the master node's local clock and each satellite's clock, as well as the corresponding clock difference data of this node, based on the elevation angle and carrier-to-noise ratio constraints. The slave node uses the filtered measurement information to complete the clock difference calculation of the two nodes' local clocks, uses the calculated clock difference results of the two nodes to adjust the slave node's local clock, and outputs the synchronized 1PPS.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] (1) High-precision time synchronization between nodes under dynamic conditions. This invention overcomes the shortcomings of the traditional satellite common view method, which requires each station to be stationary and the station address to be accurately calibrated. Under dynamic conditions, each node receives satellite navigation signals in a unidirectional manner, and achieves high-precision time synchronization between nodes based on satellite common view and high-precision real-time measurement of relative vectors between stations.

[0012] (2) Low cost and easy engineering implementation. Compared with the traditional two-way satellite time and frequency transmission method, the present invention does not require each node to transmit ranging signals to each other to achieve high-precision time synchronization between nodes. It only needs to passively receive satellite navigation signals, which is low cost and easy to implement.

[0013] (3) The number of nodes is easy to expand. Compared with the traditional two-way satellite time and frequency transmission method, the present invention only needs one-way reception of satellite navigation signals to achieve time synchronization between nodes, so the number of synchronized nodes can be easily expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a block diagram of the composition and information flow of the multi-node high-precision time synchronization system for an offshore mobile platform of the present invention;

[0015] Figure 2 This is a block diagram of the GNSS time-frequency terminal of the present invention;

[0016] Figure 3 This is a flowchart of the high-precision time synchronization process for multiple nodes of an offshore mobile platform according to the present invention.

[0017] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0018] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] like Figure 1 As shown in FIG, the multi-node high-precision time synchronization system for offshore mobile platforms of the present invention is composed of one master node and N slave nodes. The time synchronization equipment of each node is composed of a GNSS antenna, a GNSS time and frequency terminal, and a communication terminal.

[0021] like Figure 2 As shown, the GNSS time and frequency terminal of the present invention is composed of a rubidium atomic clock module, a navigation signal processing module, a common view processing module, a power supply module, a time code generation module and a backplane (bus).

[0022] See Figure 1 、 Figure 3First, each node receives the navigation signal and completes the collection of original observation data; the master node GNSS time-frequency terminal completes the real-time position solution of the node based on the original observation data collection, (x m (t m ),y m (t m ),z m (t m )), based on the position information and the distance value ρ measured by the master node relative to each navigation satellite m,i , obtain the clock difference Δt between the local clock and the navigation satellite numbered i m,i :

[0023] Δt m,i =(ρ m,i -R m,i -δ ion -δ tro ) / c

[0024] Where m represents the master node; i represents the navigation satellite number; t m Indicates the local clock of the master node; t i represents the local clock of the navigation satellite numbered i, δ ion represents the ionospheric delay; δ tro represents the tropospheric delay; c represents the speed of light.

[0025]

[0026] Among them, (x i (t i ),y i (t i ),z i (t i )) is the time t at which the satellite navigation signal is transmitted i The exact coordinates of .

[0027] The slave GNSS time-frequency terminal uses the original observation data collected by the node, the original observation data sent by the master station and the real-time position information of the master station to complete the real-time position solution of the station, thereby ensuring the relative vector accuracy of the position coordinates of the slave node and the position coordinates of the master node. At the same time, the slave node uses the position information and the ranging value ρ measured by the slave node relative to each navigation satellite s,j (where s represents the slave node and j represents the navigation satellite number), obtain the clock difference Δt between the local clock of the slave node and the navigation satellite numbered j s,j .

[0028] The slave node GNSS time and frequency terminal performs common view satellite screening on the clock difference between the master node local clock and each satellite clock and the corresponding clock difference data of this node based on the elevation angle and signal-to-noise ratio constraints. The elevation angle constraint is ≥15° and the signal-to-noise ratio constraint is ≥38dBHz. The satellite-to-ground clock difference information of two nodes that meet both the above two conditions and are visible to both the master and slave nodes is screened out, that is, the clock difference Δt between the master node local clock and the navigation satellite numbered k. m,k , the clock difference Δt between the local clock of the slave node and the navigation satellite numbered k s,k , where k represents the satellite number that is commonly viewed by the master and slave nodes, the number of commonly viewed satellites is l, and l ≥ 4.

[0029] The slave node utilizes Δt m,k and Δt s,k Calculate the clock difference Δt between two nodes s,m :

[0030]

[0031] The slave node uses the calculated clock difference between the two nodes to adjust the local clock of the slave node and outputs the synchronized 1PPS.

[0032] The embodiments of the present invention are described in detail above. Specific implementation methods are used herein to illustrate the present invention. The description of the above embodiments is only used to help understand the methods and devices of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

[0033] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or system comprising the element.

[0034] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0035] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better embodiment. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes a number of instructions for enabling a terminal device (which can be a mobile phone, computer, server, or network device, etc.) to execute the methods described in each embodiment of the present invention.

[0036] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-precision time synchronization method for multiple nodes of an offshore mobile platform, characterized in that: The offshore mobile platform includes N slave nodes and one master node. The time synchronization equipment of each node includes a GNSS antenna, a GNSS time and frequency terminal, and a communication terminal. The method includes the following steps: S1: Each node receives the navigation signal and completes the collection of original observation data; S2: The master node GNSS time and frequency terminal completes the real-time position solution of the master node based on the original observation data collection, and obtains the clock difference between the local clock and each satellite based on the position information and the pseudo-range measurement value corresponding to each satellite in the original observation data of the master node. At the same time, the master station sends the original observation data, position information and the clock difference information between the local clock and each satellite to each slave station through the communication terminal; S3: The slave GNSS time and frequency terminal completes the real-time position solution of the station based on the original observation data collected by the node, the original observation data sent by the master station, and the real-time position information of the master station. The slave node uses the real-time position of the slave node and the pseudo-range measurement value corresponding to each satellite in the original observation data of the master node to obtain the clock difference between the local clock and the clock of each satellite; S4: The slave node GNSS time and frequency terminal performs common view satellite screening on the clock difference between the master node's local clock and each satellite's clock, as well as the corresponding clock difference data of the local node, based on the elevation angle and carrier-to-noise ratio constraints. The slave node uses the filtered measurement information to complete the clock difference calculation of the two nodes' local clocks, uses the calculated clock difference result of the two nodes to adjust the slave node's local clock, and outputs the synchronized 1PPS.

2. The method for high-precision time synchronization of multiple nodes of an offshore mobile platform according to claim 1, characterized in that: The GNSS time and frequency terminal of each node consists of a rubidium atomic clock module, a navigation signal processing module, a common view processing module, a power module, a time code generation module and a backplane.

3. The method for high-precision time synchronization of multiple nodes of an offshore mobile platform according to claim 1, characterized in that: The master node receives satellite navigation signals in real time to obtain its own precise location information , based on the location information and the distance measurement values ​​relative to each navigation satellite measured by the master node , get the local clock and number The clock error of the navigation satellite , the expression is: in, Indicates the master node; Indicates the navigation satellite number; Indicates the local clock of the master node; Indicates the number The local clock of the navigation satellite, represents the ionospheric delay; represents the tropospheric delay; represents the speed of light, Satellite navigation signal transmission time The exact coordinates of .

4. The method for high-precision time synchronization of multiple nodes of an offshore mobile platform according to claim 1, wherein: The slave GNSS time-frequency terminal uses the original observation data collected by the node, the original observation data sent by the master station and the real-time position information of the master station to complete the real-time position solution of the station.

5. The method for high-precision time synchronization of multiple nodes of an offshore mobile platform according to claim 1, wherein: The slave node uses the position information and the distance value relative to each navigation satellite measured by the slave node to , get the local clock and number of the slave node The clock error of the navigation satellite ,in Represents a slave node, Indicates the navigation satellite number.

6. The method for high-precision time synchronization of multiple nodes of an offshore mobile platform according to claim 1, characterized in that: The slave node GNSS time and frequency terminal performs common view satellite screening on the clock difference between the master node local clock and each satellite clock and the clock difference data of the corresponding node based on the elevation angle and signal-to-noise ratio constraints, wherein the elevation angle constraint condition is ≥15° and the carrier-to-noise ratio constraint condition is ≥38dBHz, and screens out the satellite-to-ground clock difference information of two nodes that meet both the above two conditions and are visible to both the master and slave nodes, that is, the master node local clock and the clock numbered Navigation satellite clock error , the local clock of the slave node is Navigation satellite clock error ,in Indicates the satellite number that the master and slave nodes view together. The number of satellites that can be viewed together is ,and .

7. The method for high-precision time synchronization of multiple nodes of an offshore mobile platform according to claim 6, characterized in that: The clock difference between the two nodes is calculated using and Calculate the clock difference between two nodes , specifically: 。

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