A confidence prediction method and system

Abstract

The present invention belongs to the technical field of high-orbit satellite orbit determination, and discloses a confidence prediction method and system. After the local state update unit obtains the initial position and almanac information, it starts to traverse and calculate the relationship between the local position and the GPS and BD satellite positions; according to the geometric relationship, the confidence of the satellite on the same side is minimized. The local position after 30 seconds is calculated by the orbit integration unit, and it is judged whether the relative motion direction of the receiver and the satellite beam is reasonable, and the satellite is further screened; for the screened satellite, with 30 seconds as the update cycle, it is traversed to see whether the satellite is inside the main lobe side lobe signal, and the signal strength estimation and Doppler estimation are performed on the signal that meets the signal coverage conditions. The prediction algorithm of the present invention uses a combination of almanac and orbit integration. When the onboard receiver cannot solve the problem, the orbit integration unit can be used to update the local state.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-orbit satellite orbit determination, and in particular relates to a confidence prediction method and system. Background Art

[0002] At present, the orbit determination altitude of high-orbit satellites is generally above 20,000 kilometers, and the general altitude is between 20,000 km and 36,000 km. Therefore, the pseudo-range measurement and orbit determination of the satellite-borne receiver faces problems such as a small number of visible satellites and low satellite signal strength. The average number of visible satellites in the dual system is ten, and the lowest average is only five. At the same time, due to the low signal strength in the high-orbit environment, the coherent integration time required for capturing satellite signals is relatively long. In the absence of prior information, only satellites can be traversed and searched. At present, the number of GPS and BD satellites in orbit is about 80 in total. Linear search for these satellites will take a lot of time. Therefore, the overall time occupied by the receiver from capture to tracking and positioning is very long. At the same time, in the high-orbit environment, the satellite-borne receiver can only receive satellite signals from the opposite side of the earth. These signals are often sidelobe signals and a small number of signals that are not blocked by the earth. When the geometric position of the satellite-borne receiver and the navigation satellite is on the same side of the earth, it will cause the receiver to be unable to use this satellite for a considerable period of time in the future, and the capture and search of this satellite will lose its meaning. If the receiver obtains the local position after completing the first positioning, it can predict the satellites visible in the current arc or in the future, and calculate the Doppler of the satellite, which will greatly reduce the duration of the capture module and the time taken for re-positioning. Therefore, a confidence prediction method combining orbital integration and almanac in a high-orbit environment is proposed to assist in positioning solution. Difficulty of the invention: The navigation signal is weak in a high-orbit environment, and the signal duration is uncertain. In the absence of a forecast system, the capture search time is too long, the positioning is slow, and the receiver consumes a lot of resources.

[0003] Through the above analysis, the problems and defects of the existing technology are: the capture of high-orbit navigation satellites takes a long time and occupies too many on-board resources. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a confidence prediction method and system.

[0005] The present invention is implemented in this way: a confidence prediction method, wherein after a local state update unit obtains an initial position and almanac information, the confidence prediction method starts to traverse and calculate the relationship between the local position and the GPS and BD satellite positions; according to the geometric relationship, the confidence of the satellite on the same side is reduced to the minimum; the local position after 30 seconds is calculated by an orbit integration unit, and whether the relative motion direction between the receiver and the satellite beam is reasonable is judged, and the satellite is further screened; for the screened satellite, with 30 seconds as the update cycle, it is traversed to see whether the satellite is inside the main lobe side lobe signal, and the signal strength estimation and Doppler estimation are performed on the signal that meets the signal coverage condition.

[0006] Further, the confidence prediction method specifically includes:

[0007] Establish an orbital mechanics model in a high-orbit environment and obtain the approximate local position of the receiver at the corresponding time through numerical integration;

[0008] Update the local state. If the onboard receiver meets the positioning conditions at a fixed epoch, use the least square method to solve the local position velocity for orbit prediction update. If the predicted epoch does not meet the positioning conditions, use the local position of the previous epoch to perform orbit integration on the position of the current epoch and update the local state.

[0009] Then, the angles between the receiver, satellite, and the center of the earth at the current moment and 30 seconds later are determined by traversal. If the receiver is about to leave the antenna beam on the satellite, the confidence is d. If it has just entered the beam coverage or is in the middle of the beam, the satellite confidence is increased to level c. For satellites that reach level c or above in the confidence evaluation unit, it is determined that the signal is in the main lobe area or the side lobe area.

[0010] Use the Fouries formula and the classical Doppler formula to estimate signal sensitivity and Doppler shift, and write the calculation results into a confidence table.

[0011] Further including:

[0012] Convert GPS / BD time to mechanical time and Julian day;

[0013] Complete the conversion between ECEF coordinate system and ECI coordinate system;

[0014] Use the fourth-order Runge integral to complete the numerical integration of local position and velocity while taking into account the amount of calculation in the orbital environment;

[0015] By adding the J2 perturbation factor, the perturbation acceleration is calculated and the perturbation equation of the satellite orbital elements is established.

[0016] Further including:

[0017] Obtain satellite almanac information through fixed tracking channels of onboard GNSS receivers;

[0018] If the onboard receiver meets the positioning conditions at a fixed epoch, the least squares method is used to solve the local position velocity for orbit prediction update;

[0019] If the forecast epoch does not meet the positioning conditions, the local position of the previous epoch is used to perform orbital integration on the position of the current epoch.

[0020] Further including:

[0021] All confidence levels are divided into five levels: abcde, with a being the highest and e being the lowest. After the prediction is completed, a confidence evaluation table is formed and provided to the receiver capture module for use;

[0022] When the angle between the receiver, the center of the earth and the navigation satellite is small, it means that the local onboard receiver will not be able to receive the satellite signal for a long time. After traversing all satellites, if the angle between the receiver, the center of the earth and the satellite is acute, the satellite confidence will be the lowest level e.

[0023] The angles between the receiver, satellite, and the center of the earth are determined by traversing at the current time and 30 seconds later. If the receiver is about to leave the antenna beam on the satellite, the confidence level is d. If the receiver has just entered the coverage area of ​​the beam or is in the middle area of ​​the beam, the satellite confidence level is increased to level c.

[0024] For satellites with confidence levels above level c, if the receiver is located in the main lobe signal, the confidence level is increased to a; if it is located in the side lobe signal, the confidence level is increased to b. If the receiver is blocked by the earth or is between the main and side lobe signals, the confidence level remains at level c, and satellites above level c are re-traversed every 30 seconds.

[0025] Further including:

[0026] For satellites with confidence levels above C, the Fouries formula is first used to estimate the received signal strength, and the calculation results are written into the confidence table;

[0027] Using the Doppler formula, estimate the Doppler shift between the receiver and the satellite and write the calculated results into a confidence table.

[0028] Another object of the present invention is to provide a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the confidence prediction method.

[0029] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the confidence prediction method.

[0030] Another object of the present invention is to provide an information data processing terminal, wherein the information data processing terminal is used to implement the confidence prediction method.

[0031] Another object of the present invention is to provide a confidence prediction system for implementing the confidence prediction method, the confidence prediction system comprising:

[0032] The orbital integration unit considers the J2 perturbation, establishes the orbital mechanics model in the high orbit environment, and obtains the local approximate position of the receiver at the corresponding epoch through numerical integration;

[0033] A local status updating unit, used to receive satellite almanac information and update local position information;

[0034] A confidence evaluation unit is used to evaluate the confidence level of the current satellite and exclude satellites that the receiver cannot use for a long period of time;

[0035] A signal estimation unit, used to calculate and predict the sensitivity and Doppler shift of the signal processed by the navigation receiver at the corresponding epoch;

[0036] The track integration unit comprises:

[0037] Time system conversion unit, used to convert GPS / BD time into mechanical time and Julian day;

[0038] Coordinate system conversion unit, used to complete the conversion between ECEF coordinate system and ECI coordinate system;

[0039] Use the fourth-order Runge integral to complete the numerical integration of local position and velocity while taking into account the amount of calculation in the orbital environment;

[0040] The satellite orbit perturbation unit adds the J2 perturbation factor, calculates the perturbation acceleration, and establishes the perturbation equation of the satellite orbit elements.

[0041] In combination with the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solutions to be protected by the present invention from the following aspects:

[0042] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving the problems, the technical solutions to be protected by the present invention and the results and data in the research and development process are closely combined to analyze in detail and deeply how the technical solutions of the present invention solve the technical problems, and some creative technical effects brought about after solving the problems. The specific description is as follows: In the absence of satellite forecasts, high-orbit satellite-borne receivers need to cyclically search all GPS and BD satellites. At present, the number of GPS and BD satellites in the on-orbit environment is about 80 in total, and linear search of these satellites will take up a lot of time. The prediction algorithm of the present invention uses a combination of almanac and orbital integration. When the satellite-borne receiver cannot solve the problem, the orbital integration unit can be used to update the local state. Using the confidence ranking algorithm, the satellites on the same side are first excluded, and they are no longer forecasted for a long time. Only satellites that meet the conditions are processed to save on-board processor resources. The signal is estimated. After simulation verification, the Doppler calculated by the signal estimation unit can converge within ±50kHz. In the absence of a prediction system, the capture search needs to be stepped by 50Hz and a linear search is performed within the range of ±16KHz, which greatly saves the capture search time.

[0043] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are specifically described as follows: The present invention adopts a combination of almanac prediction and local numerical integration to predict the satellites visible to the satellite-borne receiver within a period of time, and uses a confidence evaluation unit to perform a graded evaluation mechanism for the visible satellites, and uses the Fouries formula and the classical Doppler frequency shift formula to calculate the sensitivity and Doppler frequency shift of the visible satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a flow chart of a confidence prediction method provided by an embodiment of the present invention;

[0045] Figure 2 is a schematic diagram of the structure of a confidence prediction system provided by an embodiment of the present invention;

[0046] Figure 3 is a structural block diagram of a confidence evaluation unit provided in an embodiment of the present invention;

[0047] Figure 4 is a geometric relationship diagram of a satellite receiver provided by an embodiment of the present invention;

[0048] Figure 5 It is a sensitivity and Doppler simulation result diagram provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] 1. Explanatory Examples In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an illustrative example that expands and describes the technical solution of the claims.

[0051] like Figure 1 As shown, the confidence prediction method provided by the embodiment of the present invention includes the following steps:

[0052] S101: After the local status update unit obtains the initial position and almanac information, it starts to traverse and calculate the relationship between the local position and the GPS and BD satellite positions;

[0053] S102: According to the geometric relationship, the confidence of the satellite on the same side is reduced to the minimum. The local position after 30 seconds is calculated by the orbit integration unit to determine whether the relative motion direction of the receiver and the satellite beam is reasonable, and further select the satellite;

[0054] S103: For the screened satellites, with an update period of 30 seconds, check whether the satellites are within the main lobe and side lobe signals, and perform signal strength estimation and Doppler estimation on the signals that meet the signal coverage conditions.

[0055] like Figure 2 As shown, the confidence prediction system provided by the embodiment of the present invention includes: a local state updating unit, a track integration unit, a confidence evaluation unit, and a signal estimation unit.

[0056] The local status update is responsible for updating the local status, including using the receiver tracking channel to obtain the almanac information of the GPS / BD satellite, and updating the local position when the positioning conditions are met. At the same time, the orbit integrator is used to update the position and time of the next epoch.

[0057] The orbital integration unit realizes the numerical integration of the local position and velocity, taking into account the orbital perturbations, and completes the coordinate transformation from the inertial coordinate system to the Earth-centered Earth-fixed coordinate system.

[0058] The confidence evaluation unit assigns grades to all satellites and finally forms a confidence table, which is sent to the capture module for use.

[0059] The signal estimation unit estimates the power and Doppler of satellites with confidence levels above level C, stores them in a confidence table, and provides them to the onboard receiver capture module to select satellites with high signal strength for priority capture, thereby reducing the local satellite Doppler search range.

[0060] like Figure 3As shown, the present invention uses a confidence evaluation unit to make a detailed evaluation of the satellite visibility probability. When the local state is updated and satisfies the satellite prediction conditions, the satellites are first traversed to exclude the satellites on the same side as the satellite receiver in the orbit environment, and their confidence is set to the lowest level e. The level e satellites are not processed for a period of time, and other satellites are set to level d. The angles between the receiver, navigation satellite, and the center of the earth are traversed and judged at the current moment and 30 seconds later. If the receiver is about to leave the on-board antenna beam, the confidence is level d. If it just enters the beam coverage range and moves toward each other or is in the middle area of ​​the beam, the satellite confidence is increased to level c. Angle judgment is made for the c-level satellite. If the geometric angle satisfies the requirement of being within the main lobe signal, the confidence is increased to a. If it satisfies the requirement of being within the side lobe signal, the confidence is increased to b. If it is between the main lobe signal and the side lobe signal, or is blocked by the earth, the confidence remains at c. For satellites with confidence levels above level C, signal estimation is performed, approximate sensitivity is calculated based on the Fouries formula, and Doppler frequency shift is calculated based on the classic Doppler formula.

[0061] like Figure 4 As shown in the figure, it is a schematic diagram of the positions of the satellite receiver and the navigation satellite. When the satellite receiver is in a high orbit arc, it can only receive signals from the opposite side of the earth. The essence of orbit prediction is to determine when the satellite receiver is in the main lobe signal or the side lobe signal, and to exclude the situation where it is blocked by the earth.

[0062] 2. Application Examples: In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the technical solution of the claims on specific products or related technologies.

[0063] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0064] 3. Evidence of the effects of the embodiments. The embodiments of the present invention have achieved some positive effects during the development or use process, and indeed have great advantages over the prior art. The following content is described in conjunction with the data, charts, etc. of the test process.

[0065] like Figure 5 As shown, Figure 5 This is a simulation result diagram of the prediction method for the satellite receiver. The figure shows the prediction result of a representative satellite. According to the picture, the satellite has experienced the process of receiving the sidelobe signal, the middle area of ​​the beam, receiving the mainlobe signal, being blocked by the earth, receiving the mainlobe signal again, the middle area of ​​the beam, the sidelobe signal, and finally being lost. In this process, the confidence level changes. When the confidence level is increased to level b or above, the simulation calculates the Doppler frequency shift and sensitivity corresponding to this arc segment.

[0066] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A confidence prediction method, characterized in that: The confidence prediction method starts to traverse and calculate the relationship between the local position and the GPS and BD satellite positions after the local state update unit obtains the initial position and almanac information; According to the geometric relationship, the confidence of the satellite on the same side is reduced to the minimum; the local position after 30 seconds is calculated by the orbit integration unit to determine whether the relative motion direction of the receiver and the satellite beam is reasonable, and further select the satellite; For the screened satellites, with an update period of 30 seconds, check whether the satellite is within the main lobe and side lobe signals, and perform signal strength estimation and Doppler estimation on the signals that meet the signal coverage conditions; The confidence prediction method specifically comprises: Establish an orbital mechanics model in a high-orbit environment and obtain the approximate local position of the receiver at the corresponding time through numerical integration; Update the local state. If the onboard receiver meets the positioning conditions at a fixed epoch, use the least square method to solve the local position velocity for orbit prediction update. If the predicted epoch does not meet the positioning conditions, use the local position of the previous epoch to perform orbit integration on the position of the current epoch and update the local state. Then, the angles between the receiver, satellite, and the center of the earth at the current moment and 30 seconds later are determined by traversal. If the receiver is about to leave the antenna beam on the satellite, the confidence is d. If it has just entered the beam coverage or is in the middle of the beam, the satellite confidence is increased to level c. For satellites that reach level c or above in the confidence evaluation unit, it is determined that the signal is in the main lobe area or the side lobe area. Use the Fouries formula and the Doppler formula to estimate the signal sensitivity and Doppler shift, and write the calculation results into the confidence table.

2. The confidence prediction method according to claim 1, characterized in that: Further including: Convert GPS / BD time to mechanical time and Julian day; Complete the conversion between ECEF coordinate system and ECI coordinate system; Use the fourth-order Runge integral to complete the numerical integration of local position and velocity while taking into account the amount of calculation in the orbital environment; By adding the J2 perturbation factor, the perturbation acceleration is calculated and the perturbation equation of the satellite orbital elements is established.

3. The confidence prediction method according to claim 1, characterized in that: Further including: Obtain satellite almanac information through fixed tracking channels of onboard GNSS receivers; If the onboard receiver meets the positioning conditions at a fixed epoch, the least squares method is used to solve the local position velocity for orbit prediction update; If the forecast epoch does not meet the positioning conditions, the local position of the previous epoch is used to perform orbital integration on the position of the current epoch.

4. The confidence prediction method according to claim 1, characterized in that: Further including: All confidence levels are divided into five levels: abcde, with a being the highest and e being the lowest. After the prediction is completed, a confidence evaluation table is formed and provided to the receiver capture module for use; When the angle between the receiver, the center of the earth and the navigation satellite is small, it means that the local onboard receiver will not be able to receive the satellite signal for a long time. After traversing all satellites, if the angle between the receiver, the center of the earth and the satellite is acute, the satellite confidence will be the lowest level e. The angles between the receiver, satellite, and the center of the earth are determined by traversing at the current time and 30 seconds later. If the receiver is about to leave the antenna beam on the satellite, the confidence level is d. If the receiver has just entered the coverage area of ​​the beam or is in the middle area of ​​the beam, the satellite confidence level is increased to level c. For satellites with confidence levels above level c, if the receiver is located in the main lobe signal, the confidence level is increased to a; if it is located in the side lobe signal, the confidence level is increased to b. If the receiver is blocked by the earth or is between the main and side lobe signals, the confidence level remains at level c, and satellites above level c are re-traversed every 30 seconds.

5. The confidence prediction method according to claim 1, characterized in that: Further including: For satellites with confidence levels above C, the Fouries formula is first used to estimate the received signal strength, and the calculation results are written into the confidence table; Using the Doppler formula, estimate the Doppler shift between the receiver and the satellite and write the calculated results into a confidence table.

6. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the confidence prediction method according to any one of claims 1 to 5.

7. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the confidence prediction method according to any one of claims 1 to 5.

8. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the confidence prediction method described in any one of claims 1 to 5.

9. A confidence prediction system for implementing the confidence prediction method according to any one of claims 1 to 5, characterized in that: The confidence prediction system comprises: The orbital integration unit considers the J2 perturbation, establishes the orbital mechanics model in the high orbit environment, and obtains the local approximate position of the receiver at the corresponding epoch through numerical integration; A local status updating unit, used to receive satellite almanac information and update local position information; A confidence evaluation unit is used to evaluate the confidence level of the current satellite and exclude satellites that the receiver cannot use for a long period of time; A signal estimation unit, used to calculate and predict the sensitivity and Doppler shift of the signal processed by the navigation receiver at the corresponding epoch; The track integration unit comprises: Time system conversion unit, used to convert GPS / BD time into mechanical time and Julian day; Coordinate system conversion unit, used to complete the conversion between ECEF coordinate system and ECI coordinate system; Use the fourth-order Runge integral to complete the numerical integration of local position and velocity while taking into account the amount of calculation in the orbital environment; The satellite orbit perturbation unit adds the J2 perturbation factor, calculates the perturbation acceleration, and establishes the perturbation equation of the satellite orbit elements.

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