A train clock synchronization control method and device based on NTP

Abstract

The present disclosure relates to a train clock synchronization control method and device based on NTP, the method comprising: sending an NTP request message to an NTP server every first time interval; receiving an NTP response message to obtain NTP time information; if the NTP time information and the operating system time differ by more than a second time interval, synchronizing the operating system time to the NTP time information; and issuing the operating system time to a subsystem hung under a physical network interface, so that the subsystem synchronizes its own time to the operating system time if the operating system time and the subsystem's own time differ by more than a third time interval. On the one hand, the transmission delay of the clock message in the Ethernet link is eliminated, and on the other hand, the time synchronization control strategy between the central control unit and the switch and the time synchronization control strategy between the switch and the hung subsystem are set, so that the whole vehicle time calibration accuracy can be effectively improved without increasing the complexity of the subsystem function, and the time recorded by different systems in the train is consistent.

Description

Technical Field

[0001] This disclosure relates to the field of rail transit vehicle network technology, and in particular to a train clock synchronization control method and device based on NTP. Background Technology

[0002] Currently, the time source for various systems in rail transit vehicles is the train network control system. These systems are not connected to Beijing time or GPS (Global Positioning System) time, leading to inconsistencies in the time recorded by different systems. Therefore, achieving time consistency across different train systems is a pressing issue that needs to be addressed in this field. Summary of the Invention

[0003] This disclosure provides a train clock synchronization control method and apparatus based on NTP to achieve time consistency between different systems of a train.

[0004] In a first aspect, this disclosure provides an NTP-based train clock synchronization control method, applied to a switch deployed on a train, wherein the switch acts as an NTP client, and the method includes:

[0005] Every first time interval, an NTP request message is sent to the NTP server.

[0006] Receive the NTP response message sent by the NTP server to obtain NTP time information;

[0007] Compare the NTP time information with the operating system time of the NTP client;

[0008] If the NTP time information differs from the operating system time of the NTP client by more than a second duration, then the operating system time of the NTP client will be synchronized with the NTP time information.

[0009] The operating system time of the NTP client is sent to the subsystem connected to the physical network port of the NTP client, so that if the difference between the operating system time and the subsystem's own time exceeds a third time interval, the subsystem will synchronize its own time with the operating system time.

[0010] In some implementations, before comparing the NTP time information with the operating system time of the NTP client, the method further includes:

[0011] Calculate the relative time difference between the NTP server and the NTP client based on the information carried in the NTP response message;

[0012] The NTP time information is adjusted based on the relative time difference.

[0013] In some implementations, the NTP server and the NTP client use a TSN transmission link for message transmission; before comparing the NTP time information with the operating system time of the NTP client, the method further includes:

[0014] The path delay of the TSN transmission link is calculated based on the information carried in the NTP response message.

[0015] The NTP time information is adjusted based on the path delay.

[0016] Secondly, this disclosure provides an NTP-based train clock synchronization control method, applied to a central control unit deployed on a train, wherein the central control unit serves as an NTP server, and the method includes:

[0017] Receive NTP request messages sent by NTP clients;

[0018] After processing the NTP request message, an NTP response message carrying NTP time information is sent to the NTP client, so that if the NTP time information differs from the NTP client's operating system time by more than a second duration, the NTP client will synchronize the NTP client's operating system time with the NTP time information.

[0019] Thirdly, this disclosure provides a switch including a memory, a processor, and a computer program stored in the memory, the processor executing the computer program to implement the steps of the method described in the first aspect.

[0020] Fourthly, this disclosure provides a central control unit, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described in the second aspect.

[0021] Fifthly, this disclosure provides an NTP-based train clock synchronization control device, comprising:

[0022] At least one of the switches described in the third aspect is arranged on the train and used as an NTP client;

[0023] At least one of the central control units described in the fourth aspect is arranged on the train and serves as an NTP server.

[0024] In some implementations, the central control unit supports NTP, TSN, and TRDP protocols, and the switch and the central control unit transmit messages based on NTP and TSN transmission links; the subsystems connected to the physical network ports of the switch support the TRDP protocol.

[0025] In a sixth aspect, this disclosure provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of the method described in the first or second aspect.

[0026] In a seventh aspect, this disclosure provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the method described in the first or second aspect.

[0027] This disclosure provides a train clock synchronization control method and device based on NTP. By transmitting messages between the central control unit and the switch based on the NTP protocol, it eliminates the transmission delay of clock messages in the Ethernet link. Furthermore, it sets time synchronization control strategies between the central control unit and the switch, as well as between the switch and its subordinate subsystems. This effectively improves the overall train time synchronization accuracy without increasing the functional complexity of the subsystems, and achieves time consistency between different systems of the train. Attached Figure Description

[0028] The present disclosure will be described in more detail below based on embodiments and with reference to the accompanying drawings:

[0029] Figure 1 A flowchart illustrating an NTP-based train clock synchronization control method provided in this embodiment of the present disclosure;

[0030] Figure 2 This is a schematic diagram illustrating the principle of calculating the relative time difference offset provided in an embodiment of this disclosure;

[0031] Figure 3 A schematic diagram illustrating the principle of eliminating message transmission delay on the link provided in this embodiment of the disclosure;

[0032] Figure 4 A schematic diagram of the time synchronization process provided in this embodiment of the disclosure, taking a first duration of 100ms as an example;

[0033] Figure 5 A flowchart illustrating another NTP-based train clock synchronization control method provided in this embodiment of the present disclosure;

[0034] Figure 6 A topology diagram of an NTP-based train clock synchronization control device provided in an embodiment of this disclosure.

[0035] In the accompanying drawings, the same parts are referred to by the same reference numerals, and the drawings are not drawn to scale. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solutions of this disclosure, and to fully understand and implement the process of how this disclosure applies technical means to solve technical problems and achieve corresponding technical effects, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. The embodiments of this disclosure and the various features within them can be combined with each other without conflict, and the resulting technical solutions are all within the protection scope of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort should fall within the protection scope of this disclosure.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0038] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0039] Currently, the time source for various systems in rail transit vehicles is the train network control system. These systems are not connected to Beijing time or GPS (Global Positioning System) time, leading to inconsistencies in the time recorded by different systems. Therefore, achieving time consistency across different train systems is a pressing issue that needs to be addressed in this field.

[0040] In related technologies, the common TRDP (Train Real-time Data Protocol) is used to transmit clock information. However, TRDP cannot eliminate link delays, which can introduce errors into the time synchronization of the entire train. The train clock synchronization control method and device based on NTP (Network Time Protocol) provided in this disclosure, by transmitting messages between the central control unit and the switch based on the NTP protocol, eliminates the transmission delay of clock messages in the Ethernet link. Furthermore, it sets time synchronization control strategies between the central control unit and the switch, and between the switch and its subordinate subsystems. This effectively improves the time synchronization accuracy of the entire train without increasing the functional complexity of the subsystems, and achieves time consistency between different systems of the train.

[0041] Example 1

[0042] Figure 1 This is a flowchart illustrating an NTP-based train clock synchronization control method provided in an embodiment of this disclosure. Figure 1 As shown, an NTP-based train clock synchronization control method is applied to a Switch Route Unit (SRU) deployed on the train, where the SRU acts as an NTP client. A Central Control Unit (CCU) is also deployed on the train, which acts as an NTP server. Messages are transmitted between the SRU and CCU based on the NTP protocol.

[0043] The method in this embodiment includes:

[0044] Step S11: Send an NTP request message to the NTP server every first time interval.

[0045] In this embodiment, the first duration is a pre-set window period, which can be set according to actual needs, such as 100ms. The SRU regularly sends NTP request messages to the CCU within this window period to obtain the reference time information obtained by the CCU from the outside. The reference time information can be, but is not limited to, BeiDou time or GPS time.

[0046] Step S12: Receive the NTP response message sent by the NTP server to obtain NTP time information.

[0047] In this embodiment, after receiving the NTP request message sent by the SRU, the CCU processes the message and sends a response message to the SRU. The response message carries reference time information, which is obtained by the SRU as NTP time information after the SRU receives the NTP response message.

[0048] In some implementations, the method further includes comparing the NTP time information with the operating system time of the NTP client before:

[0049] Calculate the relative time difference between the NTP server and the NTP client based on the information carried in the NTP response message; and

[0050] NTP time information is adjusted based on relative time difference.

[0051] by Figure 2 For example, the process for calculating the relative time difference offset is as follows:

[0052] 1. The SRU sends an NTP request message to the CCU, which contains the timestamp t1 of the NTP request message leaving the SRU.

[0053] 2. The NTP request message arrives at the CCU at time t2. After processing the NTP request message, the CCU sends an NTP response message at time t3. The NTP response message carries the timestamps t1 (when the NTP request message left the SRU), t2 (when the NTP request message arrived at the CCU), and t3 (when the NTP response message left the CCU).

[0054] 3. When the SRU receives an NTP response message, it records the timestamp t4 of the arrival of the NTP response message.

[0055] 4. Using the four timestamps mentioned above, SRU can calculate two key parameters:

[0056] 4-1. Round-trip delay of NTP messages from SRU to CCU.

[0057] delay = (t4-t1)-(t3-t2).

[0058] 4-2. The relative time difference offset between SRU and CCU.

[0059] According to the system of equations:

[0060]

[0061] The relative time difference can be calculated:

[0062]

[0063] 5. The SRU eliminates link delay by calculating the relative time difference offset through the NTP protocol, and then achieves clock synchronization with the CCU based on the following clock synchronization control strategy.

[0064] In some implementations, the NTP server and NTP client use a TSN transport link for message transmission; before comparing the NTP time information with the NTP client's operating system time, the following steps are also included:

[0065] Calculate the path delay of the TSN transmission link based on the information carried in the NTP response message; and

[0066] Adjust NTP time information based on path delay.

[0067] Building upon the aforementioned calculation of the relative time difference offset to eliminate time delays during NTP protocol message transmission, this embodiment employs TSN clock synchronization technology to calculate the path delay D between the delay request initiator (CCU) and the delay request responder (SRU), eliminating message transmission delays on the link and thus making the clock information more accurate. Figure 3 As shown, the specific logic is as follows:

[0068] The delay request initiator (SRU) obtained four timestamps, allowing the calculation of the path delay D between the SRU and the CCU.

[0069] t ir =t2-t1

[0070] t ri =t4-t3

[0071]

[0072] Among them, t ir t represents the delay from the initiator of the delay request to the responder of the delay request. ri This indicates the delay from the responder to the initiator of the delay request.

[0073] Based on adjusting the NTP time information according to the relative time difference offset, further adjusting the NTP time information according to the path delay can more effectively eliminate time delay. Then, based on the clock synchronization control strategy below, clock synchronization with CCU can be achieved, improving the time synchronization accuracy of the whole vehicle.

[0074] Step S13: Compare the NTP time information with the operating system time of the NTP client.

[0075] SRU stores the acquired NTP time information in a log and compares the NTP time information with the operating system time of the NTP client.

[0076] Step S14: Determine whether the difference between the NTP time information and the NTP client's operating system time exceeds the second duration. If the difference exceeds the second duration, proceed to step S15. If the difference is less than the second duration, synchronization with NTP time is unnecessary; instead, the NTP client's operating system time is sent to the subsystem connected to the NTP client's physical network port. The second duration is a pre-defined window period that can be set according to actual needs, for example, 100ms.

[0077] Step S15: Synchronize the operating system time of the NTP client with NTP time information.

[0078] Step S16: Send the operating system time of the NTP client to the subsystem connected to the physical network port of the NTP client, so that the subsystem will synchronize its own time with the operating system time if the difference between the operating system time and the subsystem's own time exceeds the third time interval.

[0079] In practical applications, each train set is equipped with at least one switch, and the entire vehicle is equipped with at least two central control units. Each switch only sends the operating system time to its own subordinate subsystems via TRDP messages. For example, SRU1 in vehicle 1 only sends the time to its own subordinate subsystems. Clock information is not transmitted through the ring network. The switches in the entire vehicle synchronize time with the CCU via the NTP protocol. The sending period for sending the NTP client's operating system time to the subsystems connected to the NTP client's physical network port via TRDP messages can be set according to requirements, for example, 20ms. The third duration is a pre-set window period, which can be set according to actual needs, for example, 100ms. If the difference between the operating system time and the subsystem's own time does not exceed the third duration, no time synchronization is performed. The time synchronization process with the first duration of 100ms as an example is as follows: Figure 4 As shown.

[0080] Example 2

[0081] This disclosure provides an NTP-based train clock synchronization control method, applied to a central control unit (CCU) deployed on a train. The CCU acts as an NTP server, and the SRU acts as an NTP client. The SRU and CCU transmit messages based on the NTP protocol.

[0082] like Figure 5 As shown, the method in this embodiment includes:

[0083] Step S21: Receive the NTP request message sent by the NTP client.

[0084] Step S22: After processing the NTP request message, send an NTP response message carrying NTP time information to the NTP client so that the NTP client will synchronize the NTP client's operating system time with the NTP time information if the difference between the NTP time information and the NTP client's operating system time exceeds the second time interval.

[0085] Every first time interval, the SRU sends an NTP request message to the NTP server. After the CCU processes the NTP request message, it sends an NTP response message carrying NTP time information to the NTP client. The SRU receives the NTP response message to obtain the NTP time information and compares it with the operating system time of the NTP client. If the difference between the NTP time information and the SRU's operating system time exceeds the second time interval, the SRU's operating system time is synchronized with the NTP time information. The SRU's operating system time is then sent to the subsystems connected to the physical network interface of the NTP client via a TRDP message, so that if the difference between the subsystem's operating system time and its own time exceeds the third time interval, the subsystem will synchronize its own time with the operating system time.

[0086] Example 3

[0087] This disclosure provides a switch, including a memory, a processor, and a computer program stored in the memory. The processor executes the computer program to implement the steps of the method described in Embodiment 1.

[0088] This disclosure also provides a central control unit, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described in Embodiment 2.

[0089] In some embodiments of this example, a computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the steps of the method described in the above embodiments.

[0090] In some embodiments of this example, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the method described in the above embodiments.

[0091] The processor may include, but is not limited to, one or more processors or microprocessors. Each processor may be implemented as an Application Specific Integrated Circuit (ASIC), Digital Signal Processor (DSP), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field Programmable Gate Array (FPGA), controller, microcontroller, microprocessor, or other electronic component, for executing the methods in the above embodiments.

[0092] Computer-readable storage media can be implemented by any type of volatile or non-volatile storage device or a combination thereof. Computer-readable storage media may include, but are not limited to, random access memory (RAM), read-only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, and computer storage media (e.g., hard disks, floppy disks, solid-state drives, removable disks, CD-ROMs, DVD-ROMs, Blu-ray discs, etc.).

[0093] Computer-readable storage media may also store at least one computer-executable program / instruction, such as computer-readable instructions. Computer-readable storage media include, but are not limited to, volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and / or cache memory. Computer-readable storage media may include, for example, read-only memory (ROM), hard disk, flash memory, etc. For example, a non-transitory computer-readable storage medium may be connected to a computing device such as a computer, and then, when the computing device executes the computer-readable instructions stored on the computer-readable storage medium, the various methods described above can be performed.

[0094] In addition, the computer device may include (but is not limited to) a data bus, an input / output (I / O) bus, a display, and input / output devices (e.g., keyboard, mouse, speakers, etc.).

[0095] The processor can communicate with external devices via the I / O bus through wired or wireless networks.

[0096] In one embodiment, the at least one computer-executable instruction may also be compiled into or comprise a software product / computer program product, wherein one or more computer-executable instructions are executed by a processor to perform the steps of the various functions and / or methods in the embodiments described herein.

[0097] Example 4

[0098] This disclosure provides an NTP-based train clock synchronization control device, comprising:

[0099] At least one switch as described in the above embodiments is deployed on the train and used as an NTP client;

[0100] At least one of the central control units described in the above embodiments is arranged on the train and serves as an NTP server.

[0101] In some implementations, the central control unit supports NTP, TSN, and TRDP protocols, and the switch and the central control unit transmit messages based on NTP and TSN transmission links; the subsystems connected to the physical network ports of the switch support the TRDP protocol.

[0102] If the entire train uses NTP for time synchronization, the requirements for each system are too high, making it unsuitable for all systems. This embodiment only requires the Rear Unit (RSU) and Central Control Unit (CCU) to support NTP, TSN, and TRDP protocols simultaneously, while each subsystem is only required to support TRDP. This solves the problem of using ordinary TRDP for clock information transmission, which cannot eliminate link delays and introduces errors to the overall train clock synchronization, without increasing the functional complexity of the subsystems.

[0103] In one example, such as Figure 6 As shown, the CCU obtains the BeiDou time from an external source. The CCU and SRU1 to SRU10 transmit messages via the NTP protocol. SRU1 to SRU10 then distribute the operating system time to the subsystems via the TRDP protocol. Since the device in this embodiment requires the use of the NTP protocol, and it is not excluded that subsequent subsystems may directly obtain the CCU's time via NTP, the vehicle subsystem must meet the requirements shown in the table below:

[0104]

[0105]

[0106] This disclosure provides a train clock synchronization control method and device based on NTP. By transmitting messages between the central control unit and the switch based on the NTP protocol, it eliminates the transmission delay of clock messages in the Ethernet link. Furthermore, it sets time synchronization control strategies between the central control unit and the switch, as well as between the switch and its subordinate subsystems. This effectively improves the overall train time synchronization accuracy without increasing the functional complexity of the subsystems, and achieves time consistency between different systems of the train.

[0107] In the embodiments provided in this disclosure, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0108] It should be noted that, in this disclosure, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element limited by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0109] While the embodiments disclosed herein are as described above, the foregoing content is merely for the purpose of facilitating understanding of this disclosure and is not intended to limit this disclosure. Any person skilled in the art to which this disclosure pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope of this disclosure; however, the scope of patent protection of this disclosure shall still be determined by the scope defined in the appended claims.

Claims

1. A train clock synchronization control method based on NTP, characterized in that, Each train carriage is equipped with at least one switch, and the entire train is equipped with at least two central control units. The central control unit acts as an NTP server. The switch and the central control unit simultaneously support NTP, TSN, and TRDP protocols. The switch and the central control unit transmit messages based on NTP and TSN transmission links. The subsystems connected to the physical network ports of the switch only support the TRDP protocol. Each switch only sends its operating system time to its own connected subsystems via TRDP messages; clock information is not transmitted through a ring network. This method is applied to switches deployed on the train, which act as NTP clients and synchronize time with the central control unit via the NTP protocol. The method includes: Every first time interval, an NTP request message is sent to the NTP server. The system receives an NTP response message from the NTP server to obtain NTP time information. The NTP response message carries reference time information obtained by the NTP server from an external source. The reference time information serves as NTP time information and includes BeiDou time or GPS time. Calculate the relative time difference between the NTP server and the NTP client based on the information carried in the NTP response message; The NTP time information is adjusted based on the relative time difference; The path delay of the TSN transmission link is calculated based on the information carried in the NTP response message. The NTP time information is adjusted based on the path delay. Compare the NTP time information with the operating system time of the NTP client; If the NTP time information differs from the operating system time of the NTP client by more than a second duration, then the operating system time of the NTP client will be synchronized with the NTP time information. The operating system time of the NTP client is sent to the subsystem connected to the physical network port of the NTP client via TRDP messages, so that the subsystem will synchronize its own time with the operating system time if the difference between the operating system time and the subsystem's own time exceeds a third time interval.

2. A train clock synchronization control method based on NTP, characterized in that, Each train carriage is equipped with at least one switch, and the entire train is equipped with at least two central control units. The switches and central control units simultaneously support NTP, TSN, and TRDP protocols. The switches and central control units transmit messages via NTP and TSN transmission links. Subsystems connected to the physical network ports of the switches only support the TRDP protocol. Each switch only sends its operating system time to its own connected subsystems via TRDP messages; clock information is not transmitted through a ring network. This method is applied to the central control units deployed on the train, which act as NTP servers and synchronize time with the switches via the NTP protocol. The method includes: Receive NTP request messages sent by NTP clients; After processing the NTP request message, an NTP response message carrying NTP time information is sent to the NTP client. This allows the NTP client to calculate the relative time difference between the NTP server and the NTP client based on the information carried in the NTP response message, adjust the NTP time information based on the relative time difference, and calculate the path delay of the TSN transmission link based on the information carried in the NTP response message. The NTP time information is adjusted based on the path delay. If the difference between the NTP time information and the NTP client's operating system time exceeds a second duration, the NTP client's operating system time is synchronized with the NTP time information. Furthermore, the NTP client's operating system time is sent to the subsystem connected to the NTP client's physical network port via a TRDP message, so that if the difference between the operating system time and the subsystem's own time exceeds a third duration, the subsystem synchronizes its own time with the operating system time. The NTP response message carries reference time information obtained by the NTP server from an external source. This reference time information serves as the NTP time information and includes either BeiDou time or GPS time.

3. A switch, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method of claim 1.

4. A central control unit, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method of claim 2.

5. A train clock synchronization control device based on NTP, characterized in that, include: At least one switch as described in claim 3 is arranged on the train and used as an NTP client; At least one central control unit as described in claim 4 is arranged on the train and serves as an NTP server.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method described in claim 1 or 2.

7. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method described in claim 1 or 2.

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