Method and system for synchronizing airborne equipment and inertial navigation time

Abstract

The invention discloses an airborne equipment and inertial navigation time synchronization method and system, relates to the field of time synchronization, and aims to improve the synchronization precision of airborne equipment and inertial navigation time. According to the invention, airborne equipment carries out zero setting processing on time less than second in latest analysis absolute time, and distributes the time to each internal node; and the inertial navigation triggers each node in the airborne equipment to update the latest processed absolute time to the absolute time of the whole second level corresponding to the latest second pulse signal receiving when receiving the second pulse signal every time by using the second pulse signal emitted per second, and takes the latest updated absolute time as the latest absolute time. According to the invention, a line of an old existing synchronization system can be utilized, the reconstruction cost is low, and the time synchronization precision of airborne equipment and inertial navigation can be improved from a millisecond magnitude to a hundred nanosecond magnitude.

Description

Technical Field

[0001] The invention relates to the field of time synchronization, and in particular to a method and system for synchronizing airborne equipment with an inertial navigation system. Background Art

[0002] The cross-linking relationship between existing airborne equipment and inertial navigation is as follows: Figure 1 As shown, the airborne equipment is interconnected with the inertial navigation equipment through the avionics bus.

[0003] The INS sends the absolute time (i.e. the time that the INS considers to be absolutely accurate) to the airborne device through the avionics bus. After receiving the absolute time, the airborne device parses the absolute time to obtain the absolute time in the format of year-month-day-hour-minute-second-millisecond (currently to milliseconds, but absolute time to microseconds is not excluded) and applies it to the airborne device to achieve time synchronization between the airborne device and the INS. See the airborne device time synchronization process for details. Figure 2 .

[0004] Since there is a delay in bus transmission, the airborne device needs to parse the bus data after receiving it, and then transmit it to other nodes inside the airborne device after parsing it into absolute time, so as to finally achieve time synchronization between the airborne device and the inertial navigation system. The bus transmission delay, data parsing time, and absolute time transmission time inside the airborne device will affect the accuracy of time synchronization between the airborne device and the inertial navigation system. Moreover, the more nodes involved in data transmission, the longer it takes to achieve time synchronization and the lower the synchronization accuracy. The method of using bus transmission absolute time to achieve time synchronization has an accuracy of milliseconds to tens of milliseconds. Summary of the invention

[0005] The object of the present invention is to provide a method and system for synchronizing airborne equipment with inertial navigation time in order to improve the synchronization accuracy of the airborne equipment with inertial navigation time in order to solve all or part of the above problems.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for synchronizing airborne equipment with inertial navigation time, comprising:

[0008] The airborne device sets the time below the second in the latest resolved absolute time to zero and distributes it to each internal node; the absolute time resolved by the airborne device is continuously sent to the airborne device by the inertial navigation;

[0009] The inertial navigation uses the second pulse signal emitted every second to trigger each node in the airborne device to update the latest processed absolute time to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal each time the second pulse signal is received, and the latest updated absolute time is used as the latest absolute time.

[0010] Furthermore, the airborne device sets the time below the second in the latest resolved absolute time to zero, including:

[0011] The airborne device sets the time below the second in the absolute time to zero only when the time below the second in the latest parsed absolute time is less than the first threshold.

[0012] Furthermore, it is characterized in that the first threshold is 500 milliseconds.

[0013] Furthermore, the first node in the airborne device that receives the absolute time is responsible for parsing and processing the absolute time, and distributing the processed absolute time.

[0014] Furthermore, the first node to receive the absolute time caches the latest processed absolute time and distributes it to other nodes in the airborne device for caching; each node updates the latest cached absolute time each time it receives the second pulse signal.

[0015] Furthermore, the first node in the airborne device that receives the pulse-per-second signal is responsible for forwarding the pulse-per-second signal to other nodes in the airborne device.

[0016] Further, the latest processed absolute time is updated to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal, including:

[0017] Add 1 second to the second value of the most recently processed absolute time.

[0018] Furthermore, the absolute time resolved by the airborne device is periodically sent to the airborne device by the inertial navigation.

[0019] The present invention also provides a system for synchronizing airborne equipment with inertial navigation time, which comprises:

[0020] The first module controls the inertial navigation to continuously send the absolute time to the airborne device; and sends a second pulse signal to the airborne device every second;

[0021] The second module controls the onboard device to parse the absolute time received each time; and resets the time below the second in the latest parsed absolute time to zero, and distributes it to each internal node; and

[0022] Each node in the control airborne device updates the latest processed absolute time to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal each time the second pulse signal is received, and uses the latest updated absolute time as the latest absolute time.

[0023] Further, the second module controls each node in the airborne device to update the latest processed absolute time to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal each time the second pulse signal is received according to the following configuration:

[0024] The second module controls each node in the airborne device to add 1 second to the second value of the latest processed absolute time each time the second pulse signal is received.

[0025] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0026] The synchronization scheme proposed by the present invention can directly utilize the circuits and protocols between the current inertial navigation system and the airborne equipment. Only the transmission line of the second pulse signal needs to be added to the hardware circuit, and the modification cost is relatively low. After executing the synchronization method, the time synchronization accuracy between the airborne equipment and the inertial navigation system can be improved from the millisecond level to the hundred nanosecond level. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0028] Figure 1 : Topological diagram of the cross-linking relationship between existing airborne equipment and inertial navigation.

[0029] Figure 2 :Flowchart of synchronization between existing airborne equipment and inertial navigation time.

[0030] Figure 3 : Topological diagram of the cross-linking relationship between the airborne equipment and the inertial navigation of the present invention.

[0031] Figure 4 : Timing diagram of airborne equipment and inertial navigation time synchronization based on pulse-per-second signals.

[0032] Figure 5 : Flow chart of the airborne equipment and inertial navigation time synchronization of the present invention. DETAILED DESCRIPTION

[0033] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0034] Any feature disclosed in this specification (including any additional claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0035] Example 1

[0036] A method for synchronizing airborne equipment with inertial navigation time, such as Figure 3 As shown, the inertial navigation system is still connected to the airborne equipment through the avionics bus, and continuously sends the planned synchronization absolute time to the airborne equipment through the avionics bus. Usually, the absolute time sent by the inertial navigation system to the airborne equipment is periodic. For example, the inertial navigation system sends the absolute time to the airborne equipment through the avionics bus in a period of 50 milliseconds. There are multiple nodes in the airborne equipment, and there is a link in the airborne equipment to distribute the absolute time to each node.

[0037] On this basis, a differential line is added between the inertial navigation system and the airborne equipment. The inertial navigation system sends a second pulse signal to the airborne equipment through the differential line for time synchronization. The second pulse signal is formed by the inertial navigation system generating a second pulse every full second of absolute time. There is also a link in the airborne equipment to distribute the received second pulse signal to each node.

[0038] It should be noted that the nodes of the airborne equipment mentioned in the present invention all refer to nodes that need to be time synchronized.

[0039] On this basis, the synchronization methods include:

[0040] The airborne device sets the time below the second in the latest resolved absolute time to zero and distributes it to each internal node.

[0041] Since the inertial navigation system continuously sends the absolute time to the airborne device, the airborne device will continuously receive data packets containing the absolute time and continuously parse the absolute time from the data packets. For each latest data packet, the absolute time parsed is the latest parsed absolute time. That is, each time the airborne device parses a data packet, the absolute time parsed from it is regarded as the latest parsed absolute time.

[0042] Assuming that the inertial navigation sends absolute time to the airborne equipment at a period of 50 milliseconds, and assuming that the current time is T, the data packet received by the airborne equipment at the current moment is the latest data packet, and the absolute time parsed at the current moment is the latest parsed absolute time. At T+50 milliseconds (roughly, there may be slight differences due to the influence of the avionics bus transmission delay), the airborne equipment receives the next data packet, and the absolute time parsed from the data packet is regarded as the latest parsed absolute time at the next moment.

[0043] Still taking the frequency of 50 milliseconds as an example, the airborne device will receive 20 data packets carrying absolute time in each full second, and will perform 20 absolute time resolutions. However, according to the concept of the present invention, the absolute time of these 20 resolutions will only update the absolute time that is ultimately used once, so it is possible to consider omitting the zeroing process of a part of the received absolute time (i.e., the zeroing process of the time below the second level). In order to avoid unnecessary zeroing process operation times as much as possible, but it is necessary to prevent the time that the zeroing process operation is not performed from still being in the same full second, in the present embodiment, a time threshold (herein referred to as the first threshold) is set to determine whether the zeroing process is performed or not, that is, the airborne device will perform zeroing process on the time below the second in the absolute time of the latest resolution when the time below the second in the absolute time of the latest resolution is less than the first threshold. If the time below the second in the absolute time of the latest resolution reaches or exceeds the first threshold, it means that the absolute time is already in the same full second, and no additional zeroing process is required. As a representative example, the first threshold is set to 500 milliseconds, or other values ​​between 300 milliseconds and 900 milliseconds, because the same second values ​​of several consecutive absolute times are representative, and the zeroing processing operation of other absolute times in the same full second can be omitted. In this way, the zeroing processing operation of a part of the absolute time can be omitted, reducing the amount of calculation and the frequency of updating the data of the processed absolute time.

[0044] The inertial navigation uses the second pulse signal emitted every second to trigger each node in the airborne device to update the latest processed absolute time to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal each time the second pulse signal is received, and the latest updated absolute time is used as the latest absolute time.

[0045] like Figure 3 As shown, for the airborne device, there is no need to configure facilities for receiving and parsing data packets separately, and a certain node can be directly designated to perform the operation. The first node in the airborne device that receives the absolute time (transmitted by the avionics bus) is responsible for parsing and processing the absolute time (i.e., zeroing the time below the second level), and distributing the processed absolute time (i.e., the absolute time after zeroing the time below the second level) (to other nodes).

[0046] Since the node updates the processed absolute time for use after the triggering of the second pulse signal, and since the inertial navigation sends multiple data packets every full second, the processed absolute time will also change multiple times. Therefore, before this, a cache mechanism can be used to improve the change efficiency and reduce the access time for the processed absolute time. The first node to receive the absolute time caches the latest processed absolute time and distributes it to other nodes in the airborne device for caching; each node updates the latest cached absolute time every time it receives a second pulse signal, that is, updates it to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal.

[0047] For the pulse-per-second signal, its transmission within the airborne device can also directly specify a certain node (such as the node of the absolute time after the analysis and distribution processing in the previous article) to receive and forward it. That is, the first node in the airborne device that receives the pulse-per-second signal (transmitted by the differential line) is responsible for forwarding the pulse-per-second signal to other nodes in the airborne device.

[0048] In the airborne device, the transmission of the processed absolute time and second pulse signal can be forwarded node by node starting from the first node, or can be single-point forwarded by the first node, or a combination of the two methods, that is, the first node forwards it to certain nodes, and then these nodes continue to forward it to other nodes.

[0049] As mentioned above, all processed absolute times within each whole second are eventually updated to the same absolute time of the whole second. Therefore, each node in the airborne device directly adds 1 second to the second value of the latest processed absolute time each time it receives a second pulse signal (i.e., high level), so that it can correspond to the absolute time of the whole second level corresponding to the latest received second pulse signal. Of course, it is not ruled out that the correspondence between the updated absolute time and the latest received second pulse signal can be achieved in other ways, such as adding 1 second to the absolute time of the previous update as the update result of the latest processed absolute time, or rounding the latest resolved absolute time (if the millisecond value reaches 500 milliseconds, it is 1, otherwise it is zero) to the absolute time of the whole second level. But in comparison, it is the simplest and most efficient to directly add 1 second to the second value of the latest processed absolute time.

[0050] For example, Figure 4 As shown in the figure, it is assumed that the inertial navigation sends the absolute time to the airborne equipment through the avionics bus at a period of 50 milliseconds, and sends the second pulse signal to the airborne equipment through the differential line every full second. Figure 5 The process shown in the figure is as follows:

[0051] 1) The absolute time when the airborne device node 1 receives the inertial navigation signal;

[0052] 2) The airborne device node 1 parses the inertial navigation time (i.e. the latest absolute time issued). Assume that the parsing result is T1: Y year M month D day H hour M minute S second MS millisecond;

[0053] 3) When the millisecond value (i.e., time below the second level) of the resolved absolute time T1 is within 500 milliseconds, node 1 sets the millisecond value of T1 to 0, and obtains the processed absolute time T1′, and caches the time value T1′: Y year M month D day H hour M minute S second 0 milliseconds;

[0054] 4) Onboard device node 1 forwards T1′ to node 2 (node ​​2 refers to other nodes);

[0055] 5) Node 2 receives and caches time T′1;

[0056] 6) The inertial navigation sends a second pulse signal to the airborne equipment through the differential line. When node 1 and node 2 receive the second pulse signal, node 1 and node 2 simultaneously add 1 to the cached time T′1 as the absolute time T2 used by the airborne equipment: Y year M month D day H hour M minute S+1 second 0 milliseconds, thereby realizing the time synchronization between the airborne equipment and the inertial navigation.

[0057] Example 2

[0058] This embodiment provides a system for synchronizing airborne equipment with an inertial navigation system, and the system includes a first module and a second module.

[0059] The first module is configured to: control the inertial navigation to continuously send absolute time to the airborne device; and send a second pulse signal to the airborne device every second.

[0060] The second module controls the onboard equipment to parse the absolute time received each time, and resets the time below the second in the latest parsed absolute time to zero, and distributes it to each internal node.

[0061] Each node in the control airborne device updates the latest processed absolute time to the absolute time at the whole second level corresponding to the latest received second pulse signal each time a second pulse signal is received. For example, each time a second pulse signal is received, the second value of the latest processed absolute time is added by 1 second, and the latest updated absolute time is used as the latest absolute time.

[0062] The control strategy of the first module for the inertial navigation system and the control strategy of the second module for the airborne device can refer to the corresponding design scheme in Example 1. For example, the first control module controls how the inertial navigation system performs the absolute time setting; the second module controls under what conditions the airborne device performs the absolute time zeroing processing, controls how the airborne device arranges the reception, analysis, processing, distribution and storage of data packets, controls how the airborne device performs the reception and transmission of second pulse signals, etc., all of which can be configured with reference to the design in Example 1, and will not be repeated here.

[0063] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A method for synchronizing airborne equipment with inertial navigation time, characterized in that: include: The airborne device sets the time below the second in the latest resolved absolute time to zero and distributes it to each internal node; the absolute time resolved by the airborne device is continuously sent to the airborne device by the inertial navigation; The inertial navigation uses the second pulse signal emitted every second to trigger each node in the airborne device to update the latest processed absolute time to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal each time the second pulse signal is received, and the latest updated absolute time is used as the latest absolute time.

2. The method for synchronizing airborne equipment with inertial navigation time according to claim 1, characterized in that: The airborne device sets the time below the second in the latest resolved absolute time to zero, including: The airborne device sets the time below the second in the absolute time to zero only when the time below the second in the latest parsed absolute time is less than the first threshold.

3. The method for synchronizing airborne equipment with inertial navigation time as claimed in claim 2, characterized in that: The first threshold is 500 milliseconds.

4. The method for synchronizing airborne equipment with inertial navigation time according to claim 1, characterized in that: The first node in the airborne device that receives the absolute time is responsible for parsing and processing the absolute time, and distributing the processed absolute time.

5. The method for synchronizing airborne equipment with inertial navigation time as claimed in claim 4, characterized in that: The first node to receive the absolute time caches the latest processed absolute time and distributes it to other nodes in the airborne device for caching; each node updates the latest cached absolute time each time it receives the second pulse signal.

6. The method for synchronizing airborne equipment with inertial navigation time according to claim 1, characterized in that: The first node in the airborne device that receives the pulse-per-second signal is responsible for forwarding the pulse-per-second signal to other nodes in the airborne device.

7. The method for synchronizing airborne equipment with an inertial navigation system according to any one of claims 1 to 6, characterized in that: The latest processed absolute time is updated to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal, including: Add 1 second to the second value of the most recently processed absolute time.

8. The method for synchronizing airborne equipment with inertial navigation time as claimed in claim 1, characterized in that: The absolute time resolved by the airborne device is periodically sent to the airborne device by the inertial navigation.

9. A system for synchronizing airborne equipment with inertial navigation time, characterized in that: include: The first module controls the inertial navigation to continuously send absolute time to the airborne equipment; and sending a pulse-per-second signal to the airborne device every second; The second module controls the onboard equipment to parse the absolute time received each time; and resets the time below the second in the latest parsed absolute time to zero, and distributes it to each internal node; as well as Each node in the control airborne device updates the latest processed absolute time to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal each time the second pulse signal is received, and uses the latest updated absolute time as the latest absolute time.

10. The system for synchronizing airborne equipment with inertial navigation time as claimed in claim 9, characterized in that: The second module controls each node in the airborne device to update the latest processed absolute time to the absolute time at the whole second level corresponding to the latest reception of the second pulse signal each time the second pulse signal is received according to the following configuration: The second module controls each node in the airborne device to add 1 second to the second value of the latest processed absolute time each time the second pulse signal is received.

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