Navigation receiver fast positioning method and system based on imu dynamic position keeping

Abstract

The application relates to a navigation receiver rapid positioning method and system based on IMU dynamic position keeping, and belongs to the technical field of satellite navigation positioning. The method comprises the following steps: acquiring auxiliary information initially injected before the navigation receiver is transmitted and performing local time calibration; in flight, continuously and parallelly performing IMU-based dynamic position estimation and visible satellite capture tracking based on the auxiliary information; when five or more satellites are captured, calculating signal transmission time and correcting according to the satellite-ground distance at the local time locking moment and the tracked satellite code phase information; performing rapid AGPS iterative solution based on the corrected signal transmission time; recalibrating the local time according to the local clock difference and the approximate time error output by the solution; and after the calibration, obtaining the accurate position and attitude information of the receiver through loose coupling integrated navigation. The method can improve the positioning accuracy of the navigation receiver.

Description

Technical Field

[0001] This application relates to the field of satellite navigation and positioning technology, and in particular to a method and system for rapid positioning of a navigation receiver based on IMU dynamic position holding. Background Technology

[0002] Navigation receivers typically employ a loosely coupled combination of an IMU (Inertial Measurement Unit) and GPS satellite navigation to continuously provide position and velocity information to the carrier. However, when the carrier is in a high-speed rotating flight state, the navigation receiver cannot quickly complete the bit and frame synchronization of satellite signals, thus failing to achieve initial positioning quickly. A common solution is to use AGPS (Assisted GPS), which, after the navigation receiver is powered on, injects parameters such as the current approximate position (typically with an error of tens of meters), approximate time, ephemeris, ionosphere, and transmission azimuth. AGPS uses this auxiliary information to achieve rapid positioning.

[0003] However, traditional AGPS methods have a tolerance limit for the injected approximate time: existing research shows that there is a critical condition for AGPS methods to solve "millisecond-level time ambiguity": the signal time error caused by position error and local clock bias (which can be understood as equivalent clock bias) must be less than ±0.5ms, that is, it cannot exceed half of one GPS C / A code (coarse acquisition code) cycle (1ms), which corresponds to a distance of approximately 150km (one C / A chip corresponds to half of a distance of 300km). When the receiver is stationary and the approximate position deviation is small (position error is tens of meters, which is equivalent to hundreds of ns in time and can be ignored), based on the theoretical maximum radial velocity of GPS satellites of 800m / s, the receiver's tolerance for injected approximate time is 187.5s. However, in actual operation, if the operating area is interfered with and the GPS receiver cannot acquire satellite signals, the carrier may have already flown tens of kilometers away by the time satellite signal acquisition conditions are met. If the previously injected approximate position is still used for AGPS calculation at this point, the approximate position error will increase, and the algorithm's tolerance for the injection time will be much less than 187.5 seconds. This will seriously affect whether the receiver can successfully locate the target on the first attempt. Furthermore, as the flight progresses, the position error continues to increase, constantly encroaching on the system's total error budget, causing the system's tolerance for time errors to decrease monotonically with increasing flight time. The longer the flight time, the more vulnerable the positioning system becomes, and the lower the positioning accuracy. Summary of the Invention

[0004] Therefore, it is necessary to provide a method and system for rapid positioning of a navigation receiver based on IMU dynamic position keeping to address the above-mentioned technical problems.

[0005] A fast positioning method for a navigation receiver based on IMU dynamic position holding, the method comprising: Acquire the initial auxiliary information injected into the navigation receiver before transmission, including approximate time, approximate position, ephemeris and transmission azimuth, and use the approximate time, which is less than or equal to the actual time, to perform local time synchronization of the navigation receiver; During the flight of the navigation receiver, the IMU-based dynamic position estimation task and the visible satellite acquisition and tracking task are continuously executed in parallel based on auxiliary information; When five or more satellites are captured, the satellite positions at the local time latch time and the dynamic position estimate of the navigation receiver are used to iterate and calculate the satellite-to-ground distance of each satellite. After calculating the signal transmission time of each satellite using the satellite-to-ground distance and the tracked satellite code phase information, the signal transmission time is corrected based on the millisecond integer ambiguity constraint to obtain the corrected signal transmission time of each satellite. Based on the corrected signal transmission time of each satellite, perform fast AGPS iterative calculation until convergence is achieved, outputting the three-dimensional position, local clock error, and approximate time error of the navigation receiver; After recalibrating the local time of the navigation receiver based on the local clock difference and approximate time error, the normal GPS positioning process begins. Based on the GPS positioning results of the navigation receiver, the IMU is re-aligned. The new IMU alignment results and GPS positioning results are used for loosely coupled integrated navigation to finally obtain the precise position and attitude information of the navigation receiver.

[0006] In one embodiment, local time synchronization of the navigation receiver using an approximate time less than or equal to the actual time includes: The navigation receiver's internal clock uses T0+93.75 as the starting point of the local time and continuously updates the local time using an internal crystal oscillator; where T0 is an approximate time that is less than or equal to the actual time.

[0007] In one embodiment, the IMU-based dynamic position estimation task and the visible satellite acquisition and tracking task are continuously executed in parallel based on auxiliary information, including: The IMU-based dynamic position estimation task is as follows: The IMU in the navigation receiver performs coarse alignment based on the transmitted azimuth angle, and starting from the approximate position P0, combines the coarse alignment information to perform inertial navigation calculations in real time, continuously outputting and updating the dynamic position estimate of the navigation receiver at the local time latch time. ,in The time is latched for local time; The visible satellite acquisition and tracking task is as follows: the navigation receiver continuously searches for and attempts to acquire visible satellite signals carrying valid ephemeris based on the local time after the initial time synchronization, and directly locks and tracks the signal when it meets the availability conditions.

[0008] In one embodiment, the satellite-to-ground distance is calculated iteratively based on the satellite position at the local time latch time and the dynamic position estimate of the navigation receiver, including: Calculate the number based on the ephemeris in the auxiliary information. Satellite position at the local time latch time ; according to Dynamic position estimation of the navigation receiver at the local time latch time The distance between the satellite and the Earth is calculated and expressed as: ; in, For the first The distance between the satellite and the ground at the local time latch time of the navigation receiver.

[0009] In one embodiment, the signal transmission time of each satellite is calculated using the satellite-to-ground distance and the tracked satellite code phase information, including: First calculate the distance from the satellite to the Earth. Reverse signal transmission time The expression is: ; in, At the speed of light, The time is latched for local time; Again Take an integer multiple of the C / A code period to obtain the portion of the signal transmission time greater than 1ms. ; final combination and the corresponding tracked number code phase information of each satellite Calculate the first The final signal transmission time of the satellite The expression is: ; in, The size is within one C / A code period, and one C / A code period is 1ms, that is... Greater than 1ms Less than 1ms.

[0010] In one embodiment, the signal transmission time is corrected based on millisecond integer ambiguity constraints to obtain the corrected signal transmission time for each satellite, including: Construct millisecond integer fuzzy constraints, represented as: ; Among them, subscript As the reference star, For reference star The signal transmission time is calculated by inverting the satellite-to-ground distance from the local time latch time of the navigation receiver. As a reference star Final signal transmission time; When the inequality for the millisecond integer fuzziness constraint does not hold, by... A correction of 1ms is made to make the inequality true; the correction process for the signal transmission time is expressed as follows: ; in, For the first The corrected signal transmission time of each satellite.

[0011] In one embodiment, a fast AGPS iterative solution is performed based on the corrected signal transmission time of each satellite, including: Based on the corrected signal transmission times of each satellite, a pseudorange residual equation is constructed and a fast AGPS iterative solution is performed. The AGPS iterative solution process employs least-squares iterative calculation. The pseudorange residual equation is expressed as: ; in For the first The pseudorange residuals of the satellites For the first pseudorange of a satellite, For the first A satellite in Satellite position at any given time This represents the three-dimensional position of the navigation receiver in the Earth-centered, Earth-fixed coordinate system. For the first Measurement error of each satellite The first calculated by the ionospheric delay model Ionospheric delay of a satellite The first calculated by the tropospheric delay model The tropospheric delay of a satellite The first one calculated by ephemeris The clock bias of each satellite; It is the local time latch time of the navigation receiver. A time difference of more than 1ms from the actual time is also called approximate time error; The local clock bias of the navigation receiver; the unknowns in the pseudorange residual equation are: , , The rest are known numbers.

[0012] In one embodiment, when using least squares iterative solution, the approximate time error for each iteration is... The correction signal transmission time needs to be updated for the next iteration, as expressed by the formula: ; Among them, superscript For the first iteration For the first The next iteration The value is set to zero in the first iteration; and The first The satellite in the The second iteration and the first The correction signal transmission time for the next iteration, initial value Pick , For each iteration The sum of .

[0013] In one embodiment, the navigation receiver's local time is calibrated again based on the local clock difference and approximate time error, including: The local clock error of the navigation receiver is calculated based on the least squares iterative solution. and approximate time error for each iteration The sum of Then, perform local time synchronization on the navigation receiver again.

[0014] A navigation receiver rapid positioning system based on IMU dynamic position holding, the system comprising: The auxiliary information injection module is used to obtain the initial auxiliary information injected by the navigation receiver before transmission, including approximate time, approximate position, ephemeris and transmission azimuth angle, and to use the approximate time, which is less than or equal to the actual time, to perform local time synchronization of the navigation receiver. The dynamic position holding and satellite acquisition and tracking module is used to continuously and in parallel perform IMU-based dynamic position estimation and visible satellite acquisition and tracking tasks based on auxiliary information during the flight of the navigation receiver. The signal transmission time calculation and correction module is used to calculate the satellite-to-ground distance of each satellite when five or more satellites are captured, based on the satellite position at the local time latch time and the dynamic position estimate of the navigation receiver. After calculating the signal transmission time of each satellite using the satellite-to-ground distance and the tracked satellite code phase information, the signal transmission time is corrected based on the millisecond integer ambiguity constraint to obtain the corrected signal transmission time of each satellite. The AGPS iterative solution module is used to perform fast AGPS iterative solution based on the transmission time of the corrected signals of each satellite until the three-dimensional position, local clock error and approximate time error of the navigation receiver are converged and output. The loosely coupled integrated navigation module is used to recalibrate the local time of the navigation receiver based on the local clock difference and approximate time error, and then enter the normal GPS positioning process. It also re-aligns the IMU based on the GPS positioning result of the navigation receiver, and uses the new IMU alignment result and GPS positioning result to perform loosely coupled integrated navigation, and finally obtains the precise position and attitude information of the navigation receiver.

[0015] The above-mentioned rapid positioning method and system for navigation receivers based on IMU dynamic position holding has the following advantages compared with existing technologies: 1. By performing IMU-based dynamic position estimation during the flight of the navigation receiver, the real-time approximate position of the receiver can be effectively maintained as a dynamic value that is always very close to the actual position. This ensures that the position error always occupies a very small and stable share in the total error budget of AGPS, thus leaving the majority of the budget to time error. This ensures that even with a large initial time deviation and throughout the entire flight, the AGPS algorithm always has sufficient time tolerance to achieve stable and fast initial positioning.

[0016] 2. Before the AGPS iterative solution, the high-precision dynamic position of the navigation receiver estimated by the inertial measurement unit and the signal transmission time corrected by the millisecond integer ambiguity constraint are used as high-quality initial values. This ensures that the probability of the iterative algorithm converging to the correct global solution is extremely high, and it can converge quickly. This effectively avoids the situation of iterative divergence or convergence to the wrong solution due to the difference in initial values. The reliability of the iterative solution results is significantly enhanced, thereby improving the accuracy of the navigation receiver positioning. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a fast localization method for a navigation receiver based on IMU dynamic position holding in one embodiment. Figure 2 This is a schematic diagram illustrating the implementation steps of a navigation receiver fast positioning method based on IMU dynamic position holding in one embodiment. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] Before providing a more detailed description of the embodiments of this application, let's first introduce the millisecond ambiguity resolution algorithm of AGPS. Its principle is as follows: given the satellite ephemeris and the approximate position of the receiver (P0, with an error typically in the tens of meters) and approximate time (T0, with a potentially larger error), the "integer part deviation of the receiver's local time from the actual time" (i.e., N milliseconds, where N is an unknown integer) is used as a new state variable and solved together with the three-dimensional position and the receiver clock error (in the microsecond range). The key premise for this algorithm is: the initial approximate time error (P0, with an error typically in the tens of meters) is used as the basis for the algorithm. ) and initial approximate position error ( The pseudorange prediction errors for each satellite, caused by all factors, should fall within their true 1-millisecond code period. Theoretical research provides explicit engineering constraints: to satisfy the above premises, it is necessary to ensure that: ; in This represents the satellite's radial velocity, with a maximum value typically taken as 800 m / s. As a constraint, the distance is approximately 150km (the distance corresponding to half a GPS C / A code cycle). Existing solutions all rely on an implicit assumption: It is a fixed value or a slowly changing quantity. When the error of P0 is in the tens of meters, The maximum value is approximately 187.5s.

[0020] In practical applications, due to the high-speed flight of the carrier carrying the navigation receiver, the actual dynamic position error at a given moment in flight is: ; in For dynamic position error, This represents the true position. The dynamic position error increases linearly with flight distance (e.g., flying at Mach 2 for 60 seconds results in an error of approximately 40 km). According to the above formula, A 40km positional error will directly and equally reduce the total error by 150km, leaving the remaining 150km to be used for positioning errors. The distance margin is 110km, according to Calculated based on a maximum value of 800 m / s, then The maximum time cannot exceed 137.5 seconds, meaning the difference between the estimated time and the actual time cannot exceed 137.5 seconds. This increases the accuracy requirement for the estimated time by nearly 50 seconds, which means the system's fault tolerance will be significantly reduced during carrier flight, and the positioning system becomes more vulnerable as the flight time increases.

[0021] To address the above problems, in one embodiment, such as Figure 1 and Figure 2As shown, this application provides a fast positioning method for a navigation receiver based on IMU dynamic position holding, including the following steps: Step 1: Obtain the initial auxiliary information injected into the navigation receiver before transmission, including approximate time, approximate position, ephemeris and transmission azimuth, and use the approximate time, which is less than or equal to the actual time, to perform local time synchronization of the navigation receiver.

[0022] Among them, the approximate time T0 is less than or equal to the actual time, the approximate position P0 is the coordinates of the launch point (the error is generally 0 to tens of meters), the ephemeris is the currently valid satellite orbit parameters, and the launch azimuth angle is used for the initial inertial navigation attitude rough alignment.

[0023] Local time synchronization of the navigation receiver using T0 includes: the internal clock of the navigation receiver uses T0+93.75 as the starting point of the local time and continuously updates the local time using the internal crystal oscillator. It should be understood that using T0+93.75 for local time synchronization can reduce the initial approximate time error. The constraint was changed from less than 187.5s to less than ±93.75s, which narrowed the calculation range for subsequent signal transmission time calculations and improved the accuracy of the local time reference.

[0024] Step 2: During the flight of the navigation receiver, the IMU-based dynamic position estimation task and the visible satellite acquisition and tracking task are continuously executed in parallel based on auxiliary information.

[0025] Specifically, the IMU-based dynamic position estimation task is as follows: the IMU in the navigation receiver performs coarse alignment based on the transmitted azimuth angle, and starting from the approximate position P0, combines the coarse alignment information to perform inertial navigation calculations in real time, continuously outputting and updating the dynamic position estimate of the navigation receiver at the local time latch time. ,in This refers to the local time latching time. It should be understood that the error of IMU-based dynamic position estimation can be controlled within the order of kilometers or even hundreds of meters over a short period (e.g., 1-3 minutes). This ensures that the "approximate position" used for AGPS calculation is always a dynamic value that closely approximates the true position, with its error ΔP_dynamic controlled within an extremely small range (due to the IMU's own zero bias, it may shift by several hundred meters within one minute over time). This task enables the fulfillment of the constraints in the AGPS inequalities... The term is transformed from a variable that increases dramatically over time into a constant that remains extremely small (generally less than 2km). In this way, almost the entire total error budget (150km) of the system can be used to accommodate time errors, ensuring that the AGPS algorithm always has sufficient time tolerance to achieve stable and rapid initial positioning, even with large initial time deviations and throughout the entire flight.

[0026] Specifically, the task of acquiring and tracking visible satellites is as follows: the navigation receiver continuously searches for and attempts to acquire visible satellite signals carrying valid ephemeris based on the local time after the initial time synchronization, and directly locks and tracks the signal when it meets the availability conditions.

[0027] Step 3: When 5 or more satellites are captured, the satellite position at the local time latch time and the dynamic position estimate of the navigation receiver are used to iterate and calculate the satellite-to-ground distance of each satellite. After calculating the signal transmission time of each satellite using the satellite-to-ground distance and the tracked satellite code phase information, the signal transmission time is corrected based on the millisecond integer ambiguity constraint to obtain the corrected signal transmission time of each satellite.

[0028] Specifically, step 3 includes: When five or more satellites are captured, the first step is to calculate the number of satellites based on the ephemeris data in the auxiliary information. Satellite position at the local time latch time and according to Dynamic position estimation of the navigation receiver at the local time latch time The distance between the satellite and the Earth is calculated and expressed as: ; in, For the first The distance between the satellite and the ground at the local time latch time of the navigation receiver.

[0029] Secondly, the signal transmission time is calculated using the satellite-to-ground distance and the phase information of the tracked satellite code. Specifically: First calculate the distance from the satellite to the Earth. Reverse signal transmission time The expression is: ; in, The speed of light is taken as 299,792,458 m / s. The time is latched for local time.

[0030] Again Take an integer multiple of the C / A code period to obtain the portion of the signal transmission time greater than 1ms. .

[0031] final combination and the corresponding tracked number code phase information of each satellite Calculate the first The final signal transmission time of the satellite The expression is: ; in, The size is within one C / A code period, and one C / A code period is 1ms, that is... Greater than 1ms Less than 1ms.

[0032] Finally, the C / A code period (1ms) and above and less than 1ms The signal transmission time obtained by direct addition There may be a difference of ±1ms, so correction is required. The correction steps are as follows: Due to local time latching time There is an error compared to the actual time ( Within ±93.75s), according to Given the conditions, when Dynamic position estimation When using this method for substitution, the error is on the order of kilometers, which translates to a time error on the order of microseconds and is negligible. Take 800 m / s, By taking the maximum value ±93.75s, we can obtain Approximately ±75km, which translates to ±0.25ms in time. Therefore, the signal transmission time error should be within ±0.25ms, i.e.: ; in, This refers to the local clock bias of the navigation receiver.

[0033] In order to eliminate Find a reference star It can be deduced that: ; Subtract the time error inequalities of the two signals to eliminate them. The resulting millisecond integer fuzzyness constraint is represented as: ; in, For reference star The signal transmission time is calculated by inverting the satellite-to-ground distance from the local time latch time of the navigation receiver. As a reference star The final signal transmission time.

[0034] When the inequality for the millisecond integer fuzziness constraint does not hold, by... A correction of 1ms is made to make the inequality true; the correction process for the signal transmission time is expressed as follows: ; in, For the first The corrected signal transmission time of each satellite.

[0035] Step 4: Perform fast AGPS iterative calculation based on the corrected signal transmission time of each satellite until convergence is achieved, outputting the three-dimensional position, local clock error, and approximate time error of the navigation receiver.

[0036] Specifically, fast AGPS iterative calculation is performed based on the corrected signal transmission time of each satellite, including: Based on the corrected signal transmission times of each satellite, a pseudorange residual equation is constructed and a fast AGPS iterative solution is performed. The AGPS iterative solution process employs least-squares iterative calculation. The pseudorange residual equation is expressed as: ; in For the first The pseudorange residuals of the satellites For the first pseudorange of a satellite, For the first A satellite in Satellite position at any given time This represents the three-dimensional position of the navigation receiver in the Earth-centered, Earth-fixed coordinate system. For the first Measurement error of each satellite The first calculated by the ionospheric delay model Ionospheric delay of a satellite The first calculated by the tropospheric delay model The tropospheric delay of a satellite The first one calculated by ephemeris The clock bias of each satellite; It is the local time latch time of the navigation receiver. A time difference of more than 1ms from the actual time is also called approximate time error; The local clock bias of the navigation receiver; the unknowns in the pseudorange residual equation are: , , The rest are known numbers.

[0037] Among them, when using least squares iterative solution, the approximate time error of each iteration is... The correction signal transmission time needs to be updated for the next iteration, as expressed by the formula: ; Among them, superscript For the first iteration For the first The next iteration The value is set to zero in the first iteration; and The first The satellite in the The second iteration and the first The correction signal transmission time for the next iteration, initial value Pick , For each iteration The sum of .

[0038] The iteration and iteration exit process is consistent with the traditional least squares solution, and will not be described again in this paper.

[0039] Based on the above formula, iteration can be performed with 5 or more satellites, and the final converged output is obtained. , , .

[0040] Step 5: After recalibrating the local time of the navigation receiver based on the local clock difference and approximate time error, the normal GPS positioning process is entered. The IMU is re-aligned based on the GPS positioning result of the navigation receiver. The loosely coupled combined navigation is performed using the new IMU alignment result and the GPS positioning result to finally obtain the precise position and attitude information of the navigation receiver.

[0041] Specifically, step 5 includes: calculating the local clock error of the navigation receiver based on the least squares iterative solution. and approximate time error for each iteration The sum of After recalibrating the local time of the navigation receiver, the normal GPS positioning process begins. Based on the GPS positioning results of the navigation receiver, the IMU is re-aligned. Then, the new IMU alignment results and GPS positioning results are used for loosely coupled navigation to finally obtain the precise position and attitude information of the navigation receiver.

[0042] It should be understood that this application does not simply fuse IMU and GPS information at the result level (loose coupling), but rather deeply integrates the dynamic position estimation information provided by the IMU at the core algorithm level of GPS positioning calculation, achieving sensor-level functional complementarity and performance enhancement. Furthermore, GPS can also be replaced by systems such as BD (BeiDou Navigation Satellite System), GLONASS (Global Navigation Satellite System), and Galileo (Galileo Navigation Satellite System).

[0043] In summary, the aforementioned IMU-based dynamic position-keeping method for rapid positioning of navigation receivers effectively maintains the receiver's real-time approximate position as a dynamic value closely approximating the true position by performing IMU-based dynamic position estimation during the receiver's flight. This ensures that the position error consistently accounts for a minimal and stable share of the AGPS total error budget, leaving the majority of the budget for time error. This guarantees that the AGPS algorithm maintains sufficient time tolerance even with significant initial time deviations and throughout the entire flight, achieving stable and rapid initial positioning. Furthermore, before the AGPS iterative calculation, the high-precision dynamic position of the navigation receiver estimated by the inertial measurement unit and the signal transmission time corrected by millisecond integer ambiguity constraints are used as high-quality initial values. This ensures a very high probability of the iterative algorithm converging to the correct global solution and enables rapid convergence, effectively avoiding iterative divergence or convergence to incorrect solutions due to poor initial values. The reliability of the iterative calculation results is significantly enhanced, thereby improving the accuracy of the navigation receiver's positioning.

[0044] In one embodiment, a navigation receiver rapid positioning system based on IMU dynamic position holding is provided, comprising: The auxiliary information injection module is used to obtain the initial auxiliary information injected by the navigation receiver before transmission, including approximate time, approximate position, ephemeris and transmission azimuth angle, and to use the approximate time, which is less than or equal to the actual time, to perform local time synchronization of the navigation receiver. The dynamic position holding and satellite acquisition and tracking module is used to continuously and in parallel perform IMU-based dynamic position estimation and visible satellite acquisition and tracking tasks based on auxiliary information during the flight of the navigation receiver. The signal transmission time calculation and correction module is used to calculate the satellite-to-ground distance of each satellite when five or more satellites are captured, based on the satellite position at the local time latch time and the dynamic position estimate of the navigation receiver. After calculating the signal transmission time of each satellite using the satellite-to-ground distance and the tracked satellite code phase information, the signal transmission time is corrected based on the millisecond integer ambiguity constraint to obtain the corrected signal transmission time of each satellite. The AGPS iterative solution module is used to perform fast AGPS iterative solution based on the transmission time of the corrected signals of each satellite until the three-dimensional position, local clock error and approximate time error of the navigation receiver are converged and output. The loosely coupled integrated navigation module is used to recalibrate the local time of the navigation receiver based on the local clock difference and approximate time error, and then enter the normal GPS positioning process. It also re-aligns the IMU based on the GPS positioning result of the navigation receiver, and uses the new IMU alignment result and GPS positioning result to perform loosely coupled integrated navigation, and finally obtains the precise position and attitude information of the navigation receiver.

[0045] Specific limitations regarding the IMU-based dynamic position-keeping navigation receiver rapid positioning system can be found in the limitations of the IMU-based dynamic position-keeping navigation receiver rapid positioning method described above, and will not be repeated here. Each module in the aforementioned IMU-based dynamic position-keeping navigation receiver rapid positioning system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in the computer device, or stored in software in the computer device's memory, so that the processor can call and execute the corresponding operations of each module.

[0046] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0047] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. A fast positioning method for a navigation receiver based on IMU dynamic position holding, characterized in that, The method includes: Acquire the initial auxiliary information injected into the navigation receiver before transmission, including approximate time, approximate position, ephemeris and transmission azimuth, and use the approximate time, which is less than or equal to the actual time, to perform local time synchronization of the navigation receiver; During the flight of the navigation receiver, the IMU-based dynamic position estimation task and the visible satellite acquisition and tracking task are continuously executed in parallel based on the auxiliary information. When five or more satellites are captured, the satellite positions at the local time latch time and the dynamic position estimation of the navigation receiver are used to iterate and calculate the satellite-to-ground distance of each satellite. After calculating the signal transmission time of each satellite using the satellite-to-ground distance and the tracked satellite code phase information, the signal transmission time is corrected based on the millisecond integer ambiguity constraint to obtain the corrected signal transmission time of each satellite. Based on the corrected signal transmission time of each satellite, perform fast AGPS iterative calculation until convergence is achieved, outputting the three-dimensional position, local clock error, and approximate time error of the navigation receiver; After recalibrating the local time of the navigation receiver based on the local clock difference and approximate time error, the normal GPS positioning process begins. The IMU is then re-aligned based on the GPS positioning results of the navigation receiver. Loosely coupled navigation is then performed using the new IMU alignment results and the GPS positioning results to ultimately obtain the precise position and attitude information of the navigation receiver. The local time synchronization of the navigation receiver using an approximate time that is less than or equal to the actual time includes: The navigation receiver's internal clock uses T0+93.75 as the starting point of the local time and continuously updates the local time using an internal crystal oscillator; where T0 is an approximate time that is less than or equal to the actual time. The signal transmission time of each satellite is calculated using the satellite-to-ground distance and the tracked satellite code phase information, including: First calculate the distance from the satellite to the Earth. Reverse signal transmission time The expression is: ； in, At the speed of light, The time is latched for local time; Again Take an integer multiple of the C / A code period to obtain the portion of the signal transmission time greater than 1ms. ; final combination and the corresponding tracked number code phase information of each satellite Calculate the first The final signal transmission time of the satellite The expression is: ； in, The size is within one C / A code period, and one C / A code period is 1ms, that is... Greater than 1ms Less than 1ms; Specifically, the signal transmission time is corrected based on millisecond integer ambiguity constraints to obtain the corrected signal transmission time for each satellite, including: Construct millisecond integer fuzzy constraints, represented as: ； Among them, subscript As the reference star, For reference star The signal transmission time is calculated by inverting the satellite-to-ground distance from the local time latch time of the navigation receiver. As a reference star Final signal transmission time; When the inequality of the millisecond integer fuzziness constraint does not hold, by... A correction of 1ms is made to make the inequality true; the correction process for the signal transmission time is expressed as follows: ； in, For the first The corrected signal transmission time of each satellite; The fast AGPS iterative solution is performed based on the corrected signal transmission time of each satellite, including: Based on the corrected signal transmission time of each satellite, a pseudorange residual equation is constructed and a fast AGPS iterative solution is performed; wherein, the AGPS iterative solution process adopts least squares iterative solution; the pseudorange residual equation is expressed as: ； in For the first The pseudorange residuals of the satellites For the first pseudorange of a satellite, For the first A satellite in Satellite position at any given time This represents the three-dimensional position of the navigation receiver in the Earth-centered, Earth-fixed coordinate system. For the first Measurement error of each satellite The first calculated by the ionospheric delay model Ionospheric delay of a satellite The first calculated by the tropospheric delay model The tropospheric delay of a satellite The first one calculated by ephemeris The clock bias of each satellite; It is the local time latch time of the navigation receiver. A time difference of more than 1ms from the actual time is also called approximate time error; The local clock bias of the navigation receiver; the unknowns in the pseudorange residual equation are , , All others are known numbers; This includes re-calibrating the local time of the navigation receiver based on the local clock difference and approximate time error, including: The local clock error of the navigation receiver is calculated based on the least squares iterative solution. and approximate time error for each iteration The sum of Then, perform local time synchronization on the navigation receiver again.

2. The fast positioning method for a navigation receiver based on IMU dynamic position holding according to claim 1, characterized in that, Based on the aforementioned auxiliary information, the IMU-based dynamic position estimation task and the visible satellite acquisition and tracking task are continuously executed in parallel, including: The IMU-based dynamic position estimation task is as follows: The IMU in the navigation receiver performs a coarse alignment based on the transmitted azimuth angle, and starting from the approximate position P0, combines the coarse alignment information to perform inertial navigation calculations in real time, continuously outputting and updating the dynamic position estimate of the navigation receiver at the local time latch time. ,in The time is latched for local time; The task of capturing and tracking visible satellites is as follows: the navigation receiver continuously searches for and attempts to capture visible satellite signals carrying valid ephemeris based on the local time after the initial time synchronization, and directly locks and tracks the signal when it meets the availability conditions.

3. The rapid positioning method for a navigation receiver based on IMU dynamic position holding according to claim 2, characterized in that, Based on the satellite positions at the local time latch time and the dynamic position estimation of the navigation receiver, the satellite-to-ground distances of each satellite are calculated iteratively, including: Calculate the number based on the ephemeris in the auxiliary information. Satellite position at the local time latch time ; according to Dynamic position estimation of the navigation receiver at the local time latch time The distance between the satellite and the Earth is calculated and expressed as: ； in, For the first The distance between the satellite and the ground at the local time latch time of the navigation receiver.

4. The fast positioning method for a navigation receiver based on IMU dynamic position holding according to claim 1, characterized in that, When using least squares iterative solution, the approximate time error of each iteration The correction signal transmission time needs to be updated for the next iteration, as expressed by the formula: ； Among them, superscript For the first iteration For the first The next iteration The value is set to zero in the first iteration; and The first The satellite in the The second iteration and the first The correction signal transmission time for the next iteration, initial value Pick , For each iteration The sum of .

5. A rapid positioning system for a navigation receiver based on IMU dynamic position holding, characterized in that, The system includes: The auxiliary information injection module is used to obtain the initial auxiliary information injected by the navigation receiver before transmission, including approximate time, approximate position, ephemeris and transmission azimuth angle, and to use the approximate time, which is less than or equal to the actual time, to perform local time synchronization of the navigation receiver. The dynamic position holding and satellite acquisition and tracking module is used to continuously and in parallel execute the IMU-based dynamic position estimation task and the visible satellite acquisition and tracking task based on the auxiliary information during the flight of the navigation receiver. The signal transmission time calculation and correction module is used to calculate the satellite-to-ground distance of each satellite when five or more satellites are captured, based on the satellite position at the local time latch time and the dynamic position estimation of the navigation receiver. After calculating the signal transmission time of each satellite using the satellite-to-ground distance and the tracked satellite code phase information, the signal transmission time is corrected based on the millisecond integer ambiguity constraint to obtain the corrected signal transmission time of each satellite. The AGPS iterative solution module is used to perform fast AGPS iterative solution based on the transmission time of the corrected signals of each satellite until the three-dimensional position, local clock error and approximate time error of the navigation receiver are converged and output. The loosely coupled integrated navigation module is used to recalibrate the local time of the navigation receiver based on the local clock difference and approximate time error, and then enter the normal GPS positioning process. It also re-aligns the IMU based on the GPS positioning result of the navigation receiver, and uses the new IMU alignment result and GPS positioning result to perform loosely coupled integrated navigation, and finally obtains the precise position and attitude information of the navigation receiver. The local time synchronization of the navigation receiver using an approximate time that is less than or equal to the actual time includes: The navigation receiver's internal clock uses T0+93.75 as the starting point of the local time and continuously updates the local time using an internal crystal oscillator; where T0 is an approximate time that is less than or equal to the actual time. The signal transmission time of each satellite is calculated using the satellite-to-ground distance and the tracked satellite code phase information, including: First calculate the distance from the satellite to the Earth. Reverse signal transmission time The expression is: ； in, At the speed of light, The time is latched for local time; Again Take an integer multiple of the C / A code period to obtain the portion of the signal transmission time greater than 1ms. ; final combination and the corresponding tracked number code phase information of each satellite Calculate the first The final signal transmission time of the satellite The expression is: ； in, The size is within one C / A code period, and one C / A code period is 1ms, that is... Greater than 1ms Less than 1ms; Specifically, the signal transmission time is corrected based on millisecond integer ambiguity constraints to obtain the corrected signal transmission time for each satellite, including: Construct millisecond integer fuzzy constraints, represented as: ； Among them, subscript As the reference star, For reference star The signal transmission time is calculated by inverting the satellite-to-ground distance from the local time latch time of the navigation receiver. As a reference star Final signal transmission time; When the inequality of the millisecond integer fuzziness constraint does not hold, by... A correction of 1ms is made to make the inequality true; the correction process for the signal transmission time is expressed as follows: ； in, For the first The corrected signal transmission time of each satellite; The fast AGPS iterative solution is performed based on the corrected signal transmission time of each satellite, including: Based on the corrected signal transmission time of each satellite, a pseudorange residual equation is constructed and a fast AGPS iterative solution is performed; wherein, the AGPS iterative solution process adopts least squares iterative solution; the pseudorange residual equation is expressed as: ； in For the first The pseudorange residuals of the satellites For the first pseudorange of a satellite, For the first A satellite in Satellite position at any given time This represents the three-dimensional position of the navigation receiver in the Earth-centered, Earth-fixed coordinate system. For the first Measurement error of each satellite The first calculated by the ionospheric delay model Ionospheric delay of a satellite The first calculated by the tropospheric delay model The tropospheric delay of a satellite The first one calculated by ephemeris The clock bias of each satellite; It is the local time latch time of the navigation receiver. A time difference of more than 1ms from the actual time is also called approximate time error; The local clock bias of the navigation receiver; the unknowns in the pseudorange residual equation are , , All others are known numbers; This includes re-calibrating the local time of the navigation receiver based on the local clock difference and approximate time error, including: The local clock error of the navigation receiver is calculated based on the least squares iterative solution. and approximate time error for each iteration The sum of Then, perform local time synchronization on the navigation receiver again.

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