A method for synchronizing high-precision satellite measurement integration with horizontal reference information

Abstract

This invention relates to the field of astronomical navigation technology, and in particular to a high-precision method for synchronizing satellite measurement integration with horizontal reference information. The method includes a calculation system and a calculation method. The calculation system comprises an astronomical navigation calculation unit, a satellite measurement sensor, and an inertial measurement unit. The inertial measurement unit is communicatively connected to both the astronomical navigation calculation unit and the satellite measurement sensor, and the satellite measurement sensor is also communicatively connected to the astronomical navigation calculation unit. This invention achieves high-precision navigation calculation through cross-clock domain synchronization and timestamp synchronization, and can be widely applied in astronomical navigation systems.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of astronomical navigation, and in particular to a high-precision star measurement integration and horizontal reference information synchronization method. BACKGROUND

[0002] An astronomical navigation system is a kind of autonomous navigation means that uses natural or artificial celestial bodies as beacons, and can provide stable position, heading and attitude information for a ship in a complex electromagnetic environment, and is a reliable backup navigation means in wartime. Compared with inertial navigation, the astronomical navigation system can achieve a positioning accuracy of 1 nautical mile per 30 days, and can meet the navigation requirements of the navy for performing tasks in the open sea.

[0003] The astronomical navigation system adopts a design mode in which an astronomical measurement unit is directly and rigidly connected with an inertial measurement unit. In the navigation process, a star measurement sensor tracks and observes multiple stars under the control of a star tracking servo mechanism, realizes multi-position star measurement, and sends a miss distance to an astronomical navigation solution unit. In order to realize astronomical positioning solution, in addition to the need for star measurement to obtain the inertial attitude matrix of the carrier, accurate time information and horizontal reference information are also needed, the time information is provided by a time unit, and the horizontal reference information is provided by the inertial measurement unit. Therefore, in order to ensure the synchronization of the star measurement information and the attitude information, high-precision synchronization between the star measurement integration and the horizontal reference information is one of the key factors for the astronomical navigation system to realize high-precision positioning and orientation.

[0004] In a traditional synchronization mode, the star measurement sensor adopts an internal trigger mode for integration, as shown in FIG. 1, a frame reset signal is generated inside the star measurement assembly, and the middle time point of the star measurement integration cannot be accurately aligned with the 200 Hz horizontal reference information, and there is a time error of Δt, and the maximum time error is close to 2.5 ms. Figure 1 After receiving the miss distance information and the horizontal reference information, the astronomical navigation solution unit needs to push the miss distance information forward by Tdelay time, Tdelay is the delay time from the center point of the integration time to the miss distance output, and then queries the adjacent horizontal reference information to perform navigation solution, the maximum difference between the star measurement information used for solution and the horizontal reference information is 2.5 ms, and the positioning and orientation accuracy of the astronomical navigation system is affected. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a high-precision star measurement integration and horizontal reference information synchronization method, which adopts a combination of cross-clock domain synchronization and time stamp synchronization to align the middle time point of the star measurement sensor integration with the attitude measurement time point of the inertial measurement unit, and the astronomical navigation solution unit pushes back the instantaneous attitude information corresponding to the middle time point of the star measurement integration through the time stamp information, so that the synchronization accuracy of the star measurement integration and the horizontal reference information is better than 0.1 ms, thereby improving the navigation solution accuracy of the astronomical navigation system.

[0006] To achieve the above object, the application provides the following technical scheme: a high-precision star measurement integration and horizontal reference information synchronization method, comprising a solving system and a solving method,

[0007] The solving system comprises an astronomical navigation solving unit, a star measurement sensor and an inertial measurement unit, the inertial measurement unit is in communication connection with the astronomical navigation solving unit and the star measurement sensor respectively, and the star measurement sensor is in communication connection with the astronomical navigation solving unit;

[0008] The solving method based on the solving system is in the following manner:

[0009] (1) the inertial measurement unit transmits a synchronization pulse and timestamp information to the star measurement sensor;

[0010] (2) the star measurement sensor synchronizes the received synchronization pulse and horizontal reference information across the clock domain, and packages the received timestamp information into off-target quantity information and sends it to the astronomical navigation solving unit;

[0011] (3) the inertial measurement unit transmits a synchronization pulse and horizontal reference information to the astronomical navigation solving unit;

[0012] (4) the astronomical navigation solving unit corresponds the star measurement time corresponding to the off-target quantity to the horizontal reference information at this time according to the received off-target quantity information containing the timestamp and the horizontal reference information, and performs high-precision astronomical navigation solving.

[0013] In some embodiments, according to steps (1)-(2) in the solving method, the specific implementation of the star measurement sensor receiving the synchronization pulse is as follows:

[0014] (1) the star measurement sensor receives the synchronization pulse transmitted by the inertial measurement unit, samples it through FPGA, delays 18 sampling clock periods after receiving the frequency period external synchronization signal, avoids the cross-clock domain problem, and takes the falling edge of the synchronization signal;

[0015] (2) according to the frame time and the control command, the effective external synchronization is selected, and the rising edge low-level filtering processing is taken as the frame reset signal;

[0016] (3) the synchronization information after cross-clock domain is counted by 1-8, the counting is triggered by the rising edge of the horizontal reference synchronization signal, and the synchronization information with the count of 8 is taken as the frame reset signal of the star measurement sensor, so as to realize the cross-clock domain synchronization of the star measurement sensor frame period and the horizontal reference information.

[0017] In some embodiments, according to steps (1)-(2) in the solving method, the specific implementation of the star measurement sensor receiving the timestamp information is as follows:

[0018] (1) The star sensor receives the time stamp information transmitted by the inertial measurement unit, and the rising edge trigger is generated by the FPGA at the intermediate time of the star measurement integration to trigger the external interrupt of the DSP;

[0019] (2) The time stamp information transmitted by the inertial measurement unit is cached in the interrupt service sub-function.

[0020] (3) After the star sensor performs image acquisition, image correction, and star target extraction, the cached time stamp information is packaged into the current miss distance information.

[0021] In some embodiments, according to steps (3)-(4) in the solving method, the astronomical navigation solving unit performs astronomical navigation solving in the following specific manner:

[0022] (1) The astronomical navigation solving unit receives the miss distance information containing time stamp transmitted by the star sensor, and simultaneously receives the horizontal reference information transmitted by the inertial measurement unit;

[0023] (2) The horizontal reference information is cached;

[0024] (3) The time stamp information contained in the miss distance is analyzed, and the star measurement time corresponding to the miss distance is corresponded to the horizontal reference information at this time;

[0025] (4) The time stamp synchronization of the star measurement information of the star sensor and the horizontal reference information is realized, and high-precision astronomical navigation solving is performed.

[0026] In some embodiments, the communication mode between the inertial measurement unit and the star sensor is that the differential line is used for signal transmission of the synchronization pulse, and the RS422 serial port is used for data transmission of the time stamp information.

[0027] In some embodiments, the communication mode between the inertial measurement unit and the astronomical navigation solving unit is that the differential line is used for signal transmission of the synchronization pulse, and the RS422 serial port is used for data transmission of the horizontal reference information.

[0028] In some embodiments, the communication mode between the star sensor and the astronomical navigation solving unit is that the RS422 serial port is used for transmission of the miss distance information.

[0029] In some embodiments, the synchronization pulse is a 200Hz synchronization pulse.

[0030] In some embodiments, the integration time of the star sensor is set to an even multiple of the period of the horizontal reference information.

[0031] In some embodiments, the inertial measurement unit outputs horizontal reference information with a period of 5ms, the star measurement sensor frame period is 40ms, and the integration time is 10ms.

[0032] Compared with the prior art, the present application has the following advantages:

[0033] (1) After high-precision synchronization of the star measurement integration and the horizontal reference information, the intermediate time of the star measurement integration is aligned with the instantaneous attitude information, the synchronization time error is reduced from 2.5ms to less than 0.1ms, and the navigation solution accuracy of the celestial navigation system is significantly improved.

[0034] (2) The 200Hz synchronization information and time stamp information are transmitted through a serial port, the electrical interface is simple, the delay is small, and the system is easy to modify.

[0035] The details of one or more embodiments of the present application are presented in the following drawings and description to make the other features, purposes and advantages of the present application more clear, concise and easy to understand. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 For the internal synchronization mode of the star measurement sensor;

[0037] Figure 2 For the internal information flow diagram of the celestial navigation system;

[0038] Figure 3 For the cross-clock domain synchronization diagram;

[0039] Figure 4 For the synchronization method of the present application;

[0040] Figure 5 For the actual measurement diagram of the synchronization method of the present application;

[0041] Figure 6 For the test diagram of the difference between the star measurement image frame start and the external synchronization time. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0043] Embodiment 1

[0044] The present application provides a technical solution: a high-precision star measurement integration and horizontal reference information synchronization method, including a solution system and a solution method,

[0045] As Figure 2 shown in the system hardware connection block diagram, the solving system includes an astronomical navigation solving unit, a star measurement sensor and an inertial measurement unit, the inertial measurement unit is in communication connection with the astronomical navigation solving unit and the star measurement sensor respectively, and the star measurement sensor is in communication connection with the astronomical navigation solving unit;

[0046] The inertial measurement unit transmits 200Hz synchronization pulses through a differential line and transmits time stamp information to the star measurement sensor through an RS422 serial port; the star measurement sensor realizes cross-clock domain synchronization with horizontal reference information according to the received 200Hz synchronization pulses, and packages the received time stamp information into off-target quantity information and sends it to the astronomical navigation solving unit; the inertial measurement unit transmits 200Hz synchronization pulses through a differential line and transmits horizontal reference information to the astronomical navigation solving unit through an RS422 serial port; the astronomical navigation solving unit corresponds the star measurement time corresponding to the off-target quantity with the horizontal reference information at this time according to the received off-target quantity information containing time stamp and horizontal reference information, and performs high-precision astronomical navigation solving.

[0047] The solving method based on the solving system is as follows:

[0048] (1) transmitting synchronization pulses and time stamp information to the star measurement sensor by the inertial measurement unit;

[0049] (2) the star measurement sensor realizes cross-clock domain synchronization with horizontal reference information through the received synchronization pulses, and packages the received time stamp information into off-target quantity information and sends it to the astronomical navigation solving unit;

[0050] (3) transmitting synchronization pulses and horizontal reference information to the astronomical navigation solving unit by the inertial measurement unit;

[0051] (4) the astronomical navigation solving unit corresponds the star measurement time corresponding to the off-target quantity with the horizontal reference information at this time according to the received off-target quantity information containing time stamp and horizontal reference information, and performs high-precision astronomical navigation solving.

[0052] Embodiment 2

[0053] According to steps (1)-(2) in the solving method in embodiment 1, the specific implementation of the star measurement sensor receiving synchronization pulses is as follows:

[0054] (1) the star measurement sensor receives 200Hz synchronization pulses through a differential line, samples through an FPGA, delays 18 sampling clock periods after receiving 200Hz external synchronization signals to avoid cross-clock domain problems, and takes the falling edge of the synchronization signal, as Figure 3 shown;

[0055] (2) According to the frame time and the control command, the effective external synchronization is selected, and the rising edge low-pass filtered processing is taken as the frame reset signal Frame_Rst, as shown in Figure 4

[0056] (3) The star sensor frame period is 40 ms, the integration time is 10 ms, the synchronization pulse period transmitted by the inertial measurement unit is 5 ms, the post-synchronization information across the clock domain is counted by 1-8, the counting is triggered by the rising edge of the horizontal reference synchronization signal, and the synchronization information with the count of 8 is taken as the star sensor frame reset signal, so as to realize the cross-clock-domain synchronization of the star sensor frame period and the horizontal reference information.

[0057] Based on example 2, at this time, the falling edge of the 200 Hz horizontal reference information can be accurately aligned with the middle time of the integration time, and the actual measurement by the oscilloscope is as shown in Figure 5 FSYNC is the integration control signal of the star sensor, the frame period is 40 ms, and the low level at the end of the frame period is the integration time of 10 ms.

[0058] Example 3

[0059] According to steps (1)-(2) in the solving method in example 1, the specific implementation of the time stamp information received by the star sensor is as follows:

[0060] (1) The star sensor receives the time stamp information transmitted by the inertial measurement unit through the RS422 serial port, and the rising edge is generated by the FPGA to trigger the external interrupt of the DSP at the middle time of the star integration;

[0061] (2) In the interrupt service sub-function, the time stamp information transmitted by the inertial measurement unit received last time is cached;

[0062] (3) After the star sensor performs image acquisition, image correction, and star target extraction, the cached time stamp information is packaged into the current off-target information, and is transmitted to the celestial navigation solving unit through the RS422.

[0063] Example 4

[0064] According to examples 1-3, the specific implementation of the celestial navigation solving unit for celestial navigation solving is as follows:

[0065] (1) The celestial navigation solving unit receives the off-target information containing the time stamp transmitted by the star sensor through the RS422 interface;

[0066] (2) The horizontal reference information transmitted by the inertial measurement unit is received through the RS422 interface and the differential synchronization interface, and the 200 Hz horizontal reference information is cached;

[0067] ​(3) Analyzing the time tag information contained in the off-target amount, corresponding the star measurement time of the off-target amount to the horizontal reference information at the time;

[0068] (4) Realizing the time stamp synchronization of the star measurement sensor star measurement information and the horizontal reference information, and performing high-precision celestial navigation calculation.

[0069] After the high-precision star measurement integration and horizontal reference information synchronization method of the application is used, the star measurement integration and horizontal reference information synchronization error can be controlled within 0.1 ms, and the actual measurement by an oscilloscope is 0.048 ms, as shown in FIG. 1. Figure 6

[0070] Embodiment 5

[0071] According to the scheme of Embodiments 1-4, the communication mode between the inertial measurement unit and the star measurement sensor is that the synchronization pulse uses a differential line to transmit signals, and the time stamp information uses an RS422 serial port to transmit data.

[0072] Embodiment 6

[0073] According to the scheme of Embodiments 1-4, the communication mode between the inertial measurement unit and the celestial navigation calculation unit is that the synchronization pulse uses a differential line to transmit signals, and the horizontal reference information uses an RS422 serial port to transmit data.

[0074] Embodiment 7

[0075] According to the scheme of Embodiments 1-4, the communication mode between the star measurement sensor and the celestial navigation calculation unit is that the off-target amount information is transmitted by using an RS422 serial port mode.

[0076] Embodiment 8

[0077] According to the scheme of Embodiments 1-4, the synchronization pulse is a 200Hz synchronization pulse, and the parameter can also be set according to the actual application system.

[0078] Embodiment 9

[0079] According to the scheme of Embodiments 1-4, the star measurement sensor integration time is set to be an even multiple of the horizontal reference information period.

[0080] Preferably, the horizontal reference information period output by the inertial measurement unit is 5ms, the star measurement sensor frame period is 40ms, and the integration time is 10ms.

[0081] In addition, the method of the application is also applicable to a system with a horizontal reference information period of 1ms, and the star measurement sensor integration time is set to be an even multiple of the horizontal reference information period, and the parameter can be set according to the actual application system.

[0082] ​Through the technical solutions of the present application, the core idea of the present application mainly contains two parts, one is cross-clock domain synchronization, and the other is time stamp synchronization.

[0083] Cross-clock domain synchronization: the 200Hz synchronization pulse output by the inertial measurement unit triggers the frame start count of the star measurement sensor, and the integral time center moment of the star measurement sensor is aligned with the 200Hz synchronization pulse output by the inertial measurement unit through cross-clock domain synchronization, so as to realize the sampling synchronization of star measurement integration and horizontal reference information.

[0084] Time stamp synchronization: the star measurement sensor receives the 200Hz time stamp information output by the inertial measurement unit through a serial port, and time marks the output off-target quantity at the middle moment of star measurement integration; the astronomical navigation solving unit buffers the received 200Hz horizontal reference information, and after receiving the off-target quantity information sent by the star measurement sensor, analyzes the time marking information contained therein, then finds the horizontal reference information corresponding to the time in the buffered data according to the time information, and performs high-precision navigation solving.

[0085] The technical features of the above embodiments can be combined arbitrarily, in order to make the description simple, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0086] The above embodiments only express several implementation manners of the present application, the description is more specific and detailed, but it should not be understood as the limitation of the scope of the present application. It should be pointed out that, for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A high-precision star-sensing integration and horizontal reference information synchronization method, characterized in that: The application relates to a solving system and a solving method. The solving method based on the solving system is as follows: (1) transmitting a synchronization pulse and timestamp information to the star sensor by the inertial measurement unit; (2) synchronizing the star sensor with the horizontal reference information across the clock domain through the received synchronization pulse, and sending the received timestamp information into the off-target quantity information to the astronomical navigation solving unit; (3) transmitting the synchronization pulse and the horizontal reference information to the astronomical navigation solving unit by the inertial measurement unit; (4) corresponding the star measurement time corresponding to the off-target quantity to the horizontal reference information at the time according to the received off-target quantity information containing the timestamp and the horizontal reference information, and performing high-precision astronomical navigation solving. The specific implementation of the star sensor receiving the synchronization pulse in the solving method is as follows: The star sensor receives the synchronization pulse transmitted by the inertial measurement unit, samples through FPGA, delays for 18 sampling clock periods after receiving the frequency period external synchronization signal to avoid the cross-clock domain problem, and takes the falling edge of the synchronization signal. According to the frame time and the control command, the effective external synchronization is selected, the rising edge low-level filtering processing is taken as the frame reset signal. The synchronization information after the cross-clock domain is counted by 1-8, the counting is triggered by the rising edge of the horizontal reference synchronization signal, the synchronization information with the count of 8 is taken as the frame reset signal of the star sensor, and the cross-clock domain synchronization of the star sensor frame period and the horizontal reference information is realized.

2. The method of claim 1, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The specific implementation of the star sensor receiving the timestamp information in the solving method is as follows: The star sensor receives the timestamp information transmitted by the inertial measurement unit, generates the rising edge triggered by the FPGA in the middle time of the star measurement integration to trigger the external interruption of the DSP; The timestamp information transmitted by the inertial measurement unit is buffered in the interruption service sub-function; After the star sensor performs image collection, image correction and star target extraction, the buffered timestamp information is packaged into the current off-target quantity information.

3. The method of claim 1, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The specific implementation of the astronomical navigation solving unit performing astronomical navigation solving is as follows: The astronomical navigation solving unit receives the off-target quantity information containing the timestamp transmitted by the star sensor, and simultaneously receives the horizontal reference information transmitted by the inertial measurement unit; The horizontal reference information is buffered; The time label information contained in the off-target quantity is analyzed, and the star measurement time corresponding to the off-target quantity is corresponded to the horizontal reference information at the time; The timestamp synchronization of the star sensor measurement information and the horizontal reference information is realized, and high-precision astronomical navigation solving is performed.

4. The method of claim 1, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The communication mode between the inertial measurement unit and the star sensor is that the synchronization pulse adopts differential line for signal transmission, and the timestamp information adopts RS422 serial port for data transmission.

5. The method of claim 1, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The communication mode between the inertial measurement unit and the celestial navigation solution unit is that the signal is transmitted by using differential line for synchronous pulse and the data is transmitted by using RS422 serial port for horizontal reference information.

6. The method of claim 1, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The communication mode between the star sensor and the celestial navigation solution unit is that the miss distance information is transmitted by using RS422 serial port.

7. The method of claim 1, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The synchronous pulse is 200Hz synchronous pulse.

8. The method of claim 1, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The integration time of the star sensor is set as even times of the horizontal reference information period.

9. The method of claim 8, wherein the high-precision star-sighting integration and horizontal reference information synchronization method is characterized by: The horizontal reference information period output by the inertial measurement unit is 5ms, the frame period of the star sensor is 40ms, and the integration time is 10ms.

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