Train clock synchronization control method and device based on NTP

Abstract

The invention relates to a train clock synchronization control method and device based on NTP. The method comprises the steps that NTP request messages are sent to an NTP server side every first duration; receiving an NTP response message to obtain NTP time information; if the difference between the NTP time information and the operating system time exceeds a second duration, synchronizing the operating system time as the NTP time information; and issuing the operating system time to a subsystem hung under the physical network port, so that the subsystem synchronizes the time of the subsystem itself as the operating system time under the condition that the difference between the operating system time and the time of the subsystem itself exceeds a third duration. On one hand, the transmission delay of a clock message in an Ethernet link is eliminated, and on the other hand, a time synchronization control strategy between the central control unit and the switch and a time synchronization control strategy between the switch and a sub-system hung below are set, so that the time calibration precision of the whole vehicle can be effectively improved on the premise of not increasing the functional complexity of the sub-system; and the recorded time of different systems of the train is consistent.

Description

Technical Field

[0001] The present 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 Art

[0002] At present, the time source of each vehicle system in the rail transit field is the train network control system. The vehicle systems are not connected to Beijing time or GPS (Global Positioning System) time, resulting in inconsistent time recorded between different systems of the train. Therefore, how to achieve consistent time recorded between different systems of the train is an urgent problem to be solved in this field. Summary of the invention

[0003] The present disclosure provides a train clock synchronization control method and device based on NTP to achieve consistency in time recorded between different systems of a train.

[0004] In a first aspect, the present disclosure provides a train clock synchronization control method based on NTP, which is applied to a switch arranged on a train, wherein the switch is used as an NTP client, and the method includes:

[0005] Sending NTP request messages to the NTP server at first intervals;

[0006] Receive an 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 difference between the NTP time information and the operating system time of the NTP client exceeds the second time length, synchronizing the operating system time of the NTP client to 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 the subsystem synchronizes its own time with the operating system time when the difference between the operating system time and the subsystem's own time exceeds a third time length.

[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 to transmit messages; before comparing the NTP time information with the operating system time of the NTP client, the method further includes:

[0014] Calculate the path delay of the TSN transmission link based on the information carried by the NTP response message;

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

[0016] In a second aspect, the present disclosure provides a train clock synchronization control method based on NTP, which is applied to a central control unit arranged on a train, and the central control unit is used as an NTP server. The method includes:

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

[0018] After processing the NTP request message, an NTP response message carrying the NTP time information is sent to the NTP client, so that the NTP client synchronizes the operating system time of the NTP client to the NTP time information when the difference between the NTP time information and the operating system time of the NTP client exceeds a second time length.

[0019] In a third aspect, the present disclosure provides a switch, comprising 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 in the first aspect.

[0020] In a fourth aspect, the present disclosure provides a central control unit, comprising 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] In a fifth aspect, the present disclosure provides a train clock synchronization control device based on NTP, comprising:

[0022] At least one switch according to the third aspect, arranged on a train and used as an NTP client;

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

[0024] In some embodiments, the central control unit supports the NTP protocol, the TSN protocol and the TRDP protocol, and the switch and the central control unit perform message transmission based on the NTP protocol and the TSN transmission link; the subsystem hung under the physical network port of the switch supports the TRDP protocol.

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

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

[0027] The present invention provides a train clock synchronization control method and device based on NTP. By transmitting messages between a central control unit and a switch based on the NTP protocol, on the one hand, the transmission delay of the clock message in the Ethernet link is eliminated. On the other hand, a time synchronization control strategy between the central control unit and the switch and a time synchronization control strategy between the switch and the subsystems attached thereto are set. This can effectively improve the time synchronization accuracy of the entire vehicle without increasing the functional complexity of the subsystem, and achieve the consistency of time recorded between different systems of the train. BRIEF DESCRIPTION OF THE DRAWINGS

[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 flow chart of a train clock synchronization control method based on NTP provided in an embodiment of the present disclosure;

[0030] Figure 2 A schematic diagram of the principle of calculating the relative time difference offset provided in an embodiment of the present disclosure;

[0031] Figure 3 A schematic diagram of the principle of eliminating the transmission delay of a message on a link provided by an embodiment of the present disclosure;

[0032] Figure 4 A schematic diagram of a timing calibration process using a first duration of 100ms as an example provided in an embodiment of the present disclosure;

[0033] Figure 5 A flow chart of another NTP-based train clock synchronization control method provided in an embodiment of the present disclosure;

[0034] Figure 6 A topology diagram of a train clock synchronization control device based on NTP provided in an embodiment of the present disclosure.

[0035] In the drawings, the same reference numerals are used for the same components, and the drawings are not drawn to scale. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, and to fully understand and implement how the present disclosure applies technical means to solve technical problems and achieve the corresponding technical effects, the technical solution in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only embodiments of a part of the present disclosure, not all of the embodiments. The embodiments of the present disclosure and the various features in the embodiments can be combined with each other without conflict, and the technical solutions formed are all within the scope of protection of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present disclosure.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

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

[0039] At present, the time source of each vehicle system in the rail transit field is the train network control system. The vehicle systems are not connected to Beijing time or GPS (Global Positioning System) time, resulting in inconsistent time recorded between different systems of the train. Therefore, how to achieve consistent time recorded between different systems of the train is an urgent problem to be solved in this field.

[0040] In the related art, clock information is issued using common TRDP (Train Real-time Data Protocol, train real-time data communication protocol), but TRDP cannot eliminate link delay, and error will be brought to the whole vehicle clock. The train clock synchronization control method and device based on NTP (Network Time Protocol, Network Time Protocol) provided in the present disclosure, by transmitting messages based on NTP protocol between the central control unit and the switch, on the one hand, the transmission delay of the clock message in the Ethernet link is eliminated, 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 subsystems hung below are set, and the whole vehicle time calibration accuracy can be effectively improved without increasing the complexity of subsystem functions, and the time consistency recorded between different systems of the train is realized.

[0041] Embodiment 1

[0042] Figure 1 The following is a flow chart of a train clock synchronization control method based on NTP provided in an embodiment of the present disclosure. Figure 1 As shown, a train clock synchronization control method based on NTP is applied to a switch SRU (Switch Route Unite) arranged on the train, and the SRU is used as an NTP client. A central control unit CCU (Control Center Unit) is also arranged on the train, and the CCU is used as an NTP server. The SRU and the CCU transmit messages based on the NTP protocol.

[0043] The method of this embodiment includes:

[0044] Step S11: Send an NTP request message to the NTP server at a 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 during 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 an 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, and the reference time information is obtained by the SRU as NTP time information after the SRU receives the NTP response message.

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

[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] Adjust NTP time information based on relative time difference.

[0051] by Figure 2 For example, the process of 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 when the NTP request message leaves the SRU.

[0053] 2. The NTP request message arrives at the CCU, and the time at which the CCU arrives is t2. After the CCU processes the NTP request message, it sends an NTP response message at time t3. The NTP response message carries the timestamp t1 when the NTP request message leaves the SRU, the timestamp t2 when the NTP request message arrives at the CCU, and the timestamp t3 when the NTP response message leaves the CCU.

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

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

[0056] 4-1. Round-trip delay of NTP message 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 solved:

[0062]

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

[0064] In some implementations, a TSN transmission link is used between the NTP server and the NTP client for message transmission; before comparing the NTP time information with the operating system time of the NTP client, the method further includes:

[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] Based on the aforementioned calculation of the relative time difference offset to eliminate the time delay in the message transmission process based on the NTP protocol, in order to further eliminate the time delay of the entire link, this embodiment uses the TSN clock synchronization technology to calculate the path delay D between the delay request initiator CCU and the delay request responder SRU, eliminating the transmission delay of the message on the link, thereby making the clock information more accurate, such as Figure 3 As shown, the specific logic is as follows:

[0068] The delay request initiator SRU obtains 4 timestamps and can calculate the path delay D between the delay request initiator SRU and the delay request responder CCU.

[0069] t ir =t2-t1

[0070] t ri =t4-t3

[0071]

[0072] Among them, t ir It represents the delay from the delay request initiator to the delay request responder, t ri Indicates the delay from the delay request responder to the delay request initiator.

[0073] On the basis of adjusting the NTP time information based on the relative time difference offset, further adjusting the NTP time information based on the path delay can more effectively eliminate the time delay, and then achieve clock synchronization with the CCU based on the following clock synchronization control strategy, thereby improving the time synchronization accuracy of the entire vehicle.

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

[0075] The SRU stores the obtained 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 operating system time of the NTP client exceeds the second duration. If the difference between the NTP time information and the operating system time of the NTP client exceeds the second duration, execute step S15. If the difference between the NTP time information and the operating system time of the NTP client does not exceed the second duration, it is not necessary to synchronize to the NTP time information, but the operating system time of the NTP client is sent to the subsystem hanging under the physical network port of the NTP client. Among them, the second duration is a pre-set window period, which can be set according to actual needs, for example, the second duration is 100ms.

[0077] Step S15: Synchronize the operating system time of the NTP client to the 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 synchronizes its own time with the operating system time when the difference between the operating system time and the subsystem's own time exceeds a third time length.

[0079] In actual applications, each marshaling is equipped with at least one switch, and the whole vehicle is equipped with at least two central control units. Each switch only sends the operating system time to the subsystem hanging under itself through the TRDP message. For example, SRU1 set in vehicle 1 only sends the subsystem hanging under itself, and the clock information is not transmitted through the ring network. The switch of the whole vehicle synchronizes the time with the CCU through the NTP protocol. The sending period of sending the operating system time of the NTP client to the subsystem hanging under the physical network port of the NTP client through the TRDP message can be set according to demand, for example, set to 20ms. The third time length is a pre-set window period and can be set according to actual needs, for example, set to 100ms. When the difference between the operating system time and the subsystem's own time does not exceed the third time length, the body time synchronization is not performed. The time calibration process taking the first time length of 100ms as an example is as follows Figure 4 shown.

[0080] Embodiment 2

[0081] The embodiment of the present disclosure provides a train clock synchronization control method based on NTP, which is applied to a central control unit CCU arranged on a train, wherein the central control unit is used as an NTP server, and the SRU is used as an NTP client. Messages are transmitted between the SRU and the CCU based on the NTP protocol.

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

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

[0084] Step S22: after processing the NTP request message, send an NTP response message carrying the NTP time information to the NTP client, so that the NTP client synchronizes the operating system time of the NTP client to the NTP time information when the difference between the NTP time information and the operating system time of the NTP client exceeds the second time length.

[0085] The SRU sends an NTP request message to the NTP server every first time period. After the CCU processes the NTP request message, it sends an NTP response message carrying the NTP time information to the NTP client. The SRU receives the NTP response message to obtain the NTP time information, and compares the NTP time information with the operating system time of the NTP client: if the difference between the NTP time information and the operating system time of the SRU exceeds the second time period, the operating system time of the SRU is synchronized to the NTP time information, and the operating system time of the SRU is sent to the subsystem hung under the physical network port of the NTP client through the TRDP message, so that the subsystem synchronizes its own time to the operating system time when the difference between the operating system time and the subsystem's own time exceeds the third time period.

[0086] Embodiment 3

[0087] An embodiment of the present disclosure provides a switch, 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 first embodiment.

[0088] The embodiment of the present disclosure further provides a central control unit, including a memory, a processor, and a computer program stored in the memory, and the processor executes the computer program to implement the steps of the method described in the second embodiment.

[0089] In some implementations of this embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described in the above embodiment are implemented.

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

[0091] The processor may include, but is not limited to, one or more processors or microprocessors, etc. Each processor may be an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a controller, a microcontroller, a microprocessor or other electronic components to execute the methods in the above embodiments.

[0092] The computer-readable storage medium may be implemented by any type of volatile or non-volatile storage device or a combination thereof, and the computer-readable storage medium may include but is not limited to, for example, random access memory (RAM), read-only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, computer storage media (e.g., hard disk, floppy disk, solid-state drive, removable disk, CD-ROM, DVD-ROM, Blu-ray disc, etc.).

[0093] The computer-readable storage medium may also store at least one computer executable program / instruction, which may be, for example, a computer-readable instruction. The computer-readable storage medium includes, but is not limited to, for example, a volatile memory and / or a non-volatile memory. The volatile memory may include, for example, a random access memory (RAM) and / or a cache memory (cache), etc. The computer-readable storage medium may include, for example, a read-only memory (ROM), a hard disk, a 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 runs the computer-readable instructions stored on the computer-readable storage medium, the various methods described above may be performed.

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

[0095] The processor may communicate with external devices via an I / O bus via a wired or wireless network.

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

[0097] Embodiment 4

[0098] The embodiment of the present disclosure provides a train clock synchronization control device based on NTP, including:

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

[0100] At least one central control unit 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 the NTP protocol, the TSN protocol, and the TRDP protocol, and the switch and the central control unit perform message transmission based on the NTP protocol and the TSN transmission link; the subsystem hung under the physical network port of the switch supports the TRDP protocol.

[0102] If all trains use NTP for time synchronization, the requirements for each system of the train are too high and universality cannot be achieved. This embodiment only requires the switch RSU and the central control unit CCU to support NTP protocol, TSN protocol and TRDP protocol at the same time, and only requires support for TRDP protocol for each subsystem. It solves the problem of using ordinary TRDP to issue clock information, and it is impossible to eliminate link delay, which brings errors to the unified clock of the whole vehicle, and does not increase the complexity of subsystem functions.

[0103] In one example, if Figure 6 As shown, CCU obtains Beidou time from the outside, CCU and SRU1~SRU10 transmit messages through the NTP protocol, and SRU1~SRU10 sends the operating system time to the subsystem through the TRDP protocol. Since the device of the embodiment of the present disclosure needs to use the NTP protocol, and it does not exclude that the subsequent subsystem directly obtains the CCU time through the NTP method, the vehicle subsystem meets the requirements shown in the following table:

[0104]

[0105]

[0106] The present invention provides a train clock synchronization control method and device based on NTP. By transmitting messages between a central control unit and a switch based on the NTP protocol, on the one hand, the transmission delay of the clock message in the Ethernet link is eliminated. On the other hand, a time synchronization control strategy between the central control unit and the switch and a time synchronization control strategy between the switch and the subsystems attached thereto are set. This can effectively improve the time synchronization accuracy of the entire vehicle without increasing the functional complexity of the subsystem, and achieve the consistency of time recorded between different systems of the train.

[0107] In the embodiments provided in the present disclosure, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the above-mentioned module, program segment or a part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0108] It should be noted that in the present disclosure, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element limited by the sentence "includes a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0109] Although the embodiments disclosed in the present disclosure are as above, the above contents are only embodiments adopted for facilitating the understanding of the present disclosure and are not intended to limit the present disclosure. Any technician in the technical field to which the present disclosure belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present disclosure, but the scope of patent protection of the present disclosure shall still be subject to the scope defined in the attached claims.

Claims

1. A train clock synchronization control method based on NTP, characterized in that: Applied to a switch arranged on a train, the switch being used as an NTP client, the method comprising: Sending NTP request messages to the NTP server at first intervals; Receive an NTP response message sent by the NTP server to obtain NTP time information; Compare the NTP time information with the operating system time of the NTP client; If the difference between the NTP time information and the operating system time of the NTP client exceeds the second time length, synchronizing the operating system time of the NTP client to 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, so that the subsystem synchronizes its own time with the operating system time when the difference between the operating system time and the subsystem's own time exceeds a third time length.

2. The method according to claim 1, characterized in that Before comparing the NTP time information with the operating system time of the NTP client, the method further includes: 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.

3. The method according to claim 1 or 2, characterized in that: The NTP server and the NTP client use a TSN transmission link to transmit messages; before comparing the NTP time information with the operating system time of the NTP client, it also includes: Calculate the path delay of the TSN transmission link based on the information carried by the NTP response message; The NTP time information is adjusted based on the path delay.

4. A train clock synchronization control method based on NTP, characterized in that: Applied to a central control unit arranged on a train, the central control unit being used as an NTP server, the method comprising: Receive NTP request messages sent by NTP clients; After processing the NTP request message, an NTP response message carrying the NTP time information is sent to the NTP client, so that the NTP client synchronizes the operating system time of the NTP client to the NTP time information when the difference between the NTP time information and the operating system time of the NTP client exceeds a second time length.

5. 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 according to any one of claims 1 to 3.

6. 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 4.

7. A train clock synchronization control device based on NTP, characterized in that: include: At least one switch according to claim 5, arranged on a train and used as an NTP client; At least one central control unit as claimed in claim 6 is arranged on a train and serves as an NTP server.

8. The NTP-based train clock synchronization control device according to claim 7, characterized in that: The central control unit supports the NTP protocol, the TSN protocol and the TRDP protocol, and the switch and the central control unit perform message transmission based on the NTP protocol and the TSN transmission link; the subsystem hung under the physical network port of the switch supports the TRDP protocol.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

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