Selection and Anti-interference Methods for Time-Synchronized Inertial Satellite Integrated Navigation Measurements

Abstract

The present application belongs to the field of inertial and integrated navigation, and particularly relates to a time synchronization-based inertial and satellite integrated navigation measurement selection and anti-interference method. The present application first uses satellite navigation second pulse information to realize time synchronization of satellite navigation and inertial data collection time, and realizes high-frequency satellite navigation and inertial navigation velocity and positioning information storage based on satellite navigation output frequency after ensuring satellite navigation and inertial calculation completion. Further, the present application uses satellite navigation data confidence evaluation based on inertial constraint and navigation measurement selection threshold limit considering space boom error isolation to detect data availability, improve measurement selection accuracy, effectively solve measurement error introduced in weak signal, interference signal and complex dynamic situation, and provide a train of thought and solution for the anti-interference problem of integrated navigation algorithm.

Description

Technical Field

[0001] This invention belongs to the field of inertial navigation systems and integrated navigation, and specifically relates to a time-synchronized method for selecting and resisting interference in inertial-satellite integrated navigation measurements. Background Technology

[0002] With the development of navigation technology, Inertial Navigation Systems (INS) and Global Navigation Satellite Systems (GNSS) have been widely used. INS has the advantages of strong autonomy and high short-term accuracy, but it suffers from error accumulation. GNSS has long-term accuracy, but its accuracy drops significantly under weak signal and interference conditions. Therefore, integrated navigation systems have emerged and have become the basic configuration of most carrier navigation systems. Measurement calculation and selection are critical issues in INS / GNSS integrated navigation systems. The accuracy of measurements is related to system performance; measurement failures directly lead to a decrease in system accuracy or even system failure. Traditional measurement failure detection methods are mainly based on statistical tests, such as chi-square tests and residual tests. However, these methods are not very effective under weak signal and interference conditions. Existing technologies do not consider the time and space synchronization issues and the potential measurement errors they may cause, nor do they provide specific implementation methods for measurement calculations. Summary of the Invention

[0003] The purpose of this invention is to overcome the measurement error problem introduced by the spatiotemporal asynchrony of inertial navigation systems and satellite navigation systems in existing technologies. It also aims to effectively isolate the potential non-convergence and accuracy degradation of the integrated navigation system caused by weak satellite signals, interference signals, and conditional observation errors resulting from unstable navigation information output. This invention provides a time-synchronized method for selecting and resisting interference in integrated inertial-satellite navigation measurements, addressing the accuracy degradation or failure of the integrated system caused by measurement errors. Firstly, this invention uses the second pulse information of the satellite navigation system to synchronize the data acquisition time of the satellite navigation system and the inertial navigation system. After ensuring that the satellite navigation system and the inertial navigation system have completed their calculations, it stores the velocity and positioning information of the high-frequency satellite navigation system and the inertial navigation system at the same acquisition time, based on the output frequency of the satellite navigation system. Furthermore, it utilizes methods such as satellite navigation system data confidence assessment based on inertial navigation system constraints and navigation measurement selection threshold restrictions considering spatial lever error isolation to detect data availability, improving the accuracy of measurement selection and effectively solving the measurement errors introduced by weak signals, interference signals, and complex dynamic situations. This provides a concept and solution for the anti-interference problem of integrated navigation algorithms.

[0004] Therefore, the technical solution of the present invention is as follows:

[0005] A time-synchronized inertial satellite integrated navigation measurement selection and anti-interference method, the steps of which are as follows:

[0006] Step S1: Use the second pulse PPS synchronization signal output after GNSS positioning to hardware synchronize the acquisition time of the inertial navigation system, ensuring that the data acquisition time of the inertial navigation system and the satellite navigation system are strictly synchronized;

[0007] Step S2: After the data acquisition time is synchronized, wait for both the satellite navigation system and the inertial navigation system to complete their calculations, i.e., the delay time. After T, the results are stored synchronously at the same sampling frequency, using satellite navigation system and inertial navigation system to calculate positioning and velocity measurement results.

[0008] The stored positioning data at the time of acquisition by the satellite navigation system and the inertial navigation system. and for:

[0009] (1)

[0010]

[0011] in, It is a discrete time series. , This is the initial time for storing data after the previous combined solution cycle is completed. Where N is the sampling time interval, and N is the number of sampling points in the filtering cycle. Geographical latitude, Geographical longitude, The altitude is indicated by the subscripts GNSS and INS, which represent the positioning results from satellite navigation and inertial navigation systems, respectively. This is a specific indicator of position accuracy decay; its value reflects the positioning accuracy, and the lower the value, the higher the positioning accuracy. To locate valid markers for the satellite navigation system.

[0012] Similarly, the positioning data acquired at the time of acquisition is recorded in the navigation storage of satellite navigation and inertial navigation systems. and for:

[0013] (2)

[0014] in, For eastward speed, For northbound speed, The velocity is oriented upwards. The subscripts GNSS and INS indicate the velocity measurement results from satellite navigation and inertial navigation systems, respectively.

[0015] Step S3: Based on step S2, complete the preliminary screening of satellite navigation system data, and check the data integrity and the validity of positioning and velocity measurement; within the combined measurement period with a period of 1 second, that is, within Availability analysis is performed on the positioning and velocity data of the satellite navigation system stored in the previous cycle, with the following constraints:

[0016] (3)

[0017] in, This indicates the integrity of the data, i.e., the frequency of receiving location and speed measurement data packets; , indicating each packet of data All values ​​are less than the threshold val; This indicates that the location data for each packet is valid.

[0018] Step S4: Based on simultaneously satisfying the constraints of formula (3) in step S3, and through the satellite navigation data confidence assessment constrained by the inertial navigation system output parameters and the spatial lever error isolation constraint, the anti-interference analysis before completing the combined navigation quantity measurement calculation is realized.

[0019] (4.1) Confidence assessment of satellite navigation system data based on inertial navigation system constraints

[0020] During the measurement period, the confidence level of the satellite navigation system data is assessed using the short-time stationary characteristics of the inertial navigation system data. The stationarity and accuracy of the satellite navigation system data are evaluated using the stability of the synchronization data differences within the period, as detailed below:

[0021] (4)

[0022] (5)

[0023] (6)

[0024] In the formula, , , , , , These represent the average errors of the inertial navigation system and satellite latitude, longitude, altitude, eastward velocity, northward velocity, and celestial velocity within the measurement period. , , , , , These represent the standard deviations of latitude, longitude, altitude, eastward velocity, northward velocity, and celestial velocity of the inertial navigation system and satellites within the measurement period. The confidence constraint for the satellite navigation system can be set as follows:

[0025] (7)

[0026] If the constraints are met, the satellite navigation system data is considered to be uninterrupted.

[0027] (4.2) Threshold selection for navigation measurements considering spatial lever error isolation

[0028] The spatial lever arm error introduced by large-scale carrier maneuvers is eliminated by using carrier motion constraints. Large-scale carrier maneuver scenarios are determined by analyzing the velocity measurements and angular velocity change thresholds output by inertial devices in the inertial navigation system, thereby isolating spatial lever arm errors and eliminating interference signals.

[0029] During the measurement period, the frequency of the gyroscope and acceleration data output by the inertial navigation system is F, and the output is the three-axis angular increment within the sampling period. and speed increment .

[0030] (8)

[0031] (9)

[0032] In the formula, F is the frequency of the gyroscope and acceleration data output by the inertial navigation system during operation; It is the absolute value of the angle increment within the measurement period. It represents the absolute value of the velocity increment within the measurement period. The angular increment of the inertial navigation system device within the gyroscope sampling period, including , , , which are the angular increments within the sampling period of the three-axis gyroscope of the inertial navigation system device; The velocity increment of the inertial navigation system device within the accelerometer sampling period, including , , , which represent the velocity increments within the sampling period of the three-axis accelerometers of the inertial navigation system device. Therefore, the criteria for excluding high-maneuver scenes are set as follows:

[0033] (10)

[0034] In the formula, This represents the absolute value of the angular velocity of the carrier relative to the inertial navigation system space, calculated so far. This represents the absolute value of the acceleration of the carrier relative to the inertial navigation system space, calculated so far. The sampling time is 1 / F. This is the acceleration due to gravity.

[0035] If the threshold constraints of formulas (7) and (10) are satisfied at the same time, then the measurement calculation can be performed under these conditions.

[0036] Step S5: Based on the anti-interference analysis constraints of step S4, that is, under the threshold constraints of formula (7) and formula (10) in step S4, complete the combined navigation quantity measurement calculation. The quantity measurement adopts the average error of the inertial navigation system and the satellite within the measurement period. Measurement error of inertial navigation system satellite integrated navigation The calculation formula is as follows:

[0037] (11)

[0038] Compared with the prior art, the beneficial effects of this application are as follows:

[0039] 1) Considering the time and space synchronization issues of INS and GNSS: For time synchronization, high-precision pulse-per-second (PPS) output from GNSS is used to achieve strict alignment of the acquisition times of satellites and inertial navigation systems at the hardware level. The synchronization accuracy is at the microsecond or even nanosecond level, ensuring complete time synchronization of the stored inertial navigation system calculations and satellite navigation positioning calculations. For space synchronization, considering the spatial arm errors caused by large maneuvers, interference is eliminated through inertial navigation system measurements, avoiding measurement misjudgments. Both methods directly and effectively improve the accuracy of measurement usage in the combined algorithm.

[0040] 2) Applicable to complex conditions such as weak signals and interference: Under the triggering of the synchronization signal, navigation source data is efficiently collected. The validity of the data is further tested by methods such as the confidence assessment of satellite navigation system data based on inertial navigation system constraints and the selection of navigation measurement thresholds considering spatial lever error isolation. This effectively solves the measurement errors introduced by weak signals, interference signals and complex dynamic situations, and provides ideas and solutions for the anti-interference problem of integrated navigation algorithms. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the process for selecting and resisting interference in an inertial satellite integrated navigation measurement based on time synchronization, according to the present invention.

[0042] Figure 2 This is a schematic diagram of the timing architecture for implementing a time-synchronized inertial satellite integrated navigation measurement selection and anti-interference method according to the present invention.

[0043] Figures 3(a) and 3(b) are schematic diagrams of time and space asynchrony in satellite integrated navigation of inertial navigation systems, respectively. Detailed Implementation

[0044] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0045] like Figure 1As shown, a time-synchronized inertial satellite integrated navigation measurement selection and anti-interference method is described, with the following steps:

[0046] Step S1: Use the second pulse PPS synchronization signal output after GNSS positioning to hardware synchronize the acquisition time of the inertial navigation system, ensuring that the data acquisition time of the inertial navigation system and the satellite navigation system are strictly synchronized;

[0047] Step S2: After the data acquisition time is synchronized, due to limitations in navigation processing capabilities and methods, such as low-pass filtering of the raw navigation data from the inertial navigation system, inertial navigation system calculation, and satellite navigation system calculation, the data acquired at the time of acquisition will be delayed for a short period before navigation information can be obtained at the software level. Therefore, the delay time is until both the satellite navigation system and the inertial navigation system have completed their calculations. T (as) Figure 2 (As shown) After that, the data is stored synchronously at the same sampling frequency, using the satellite navigation system and inertial navigation system to calculate the positioning and velocity results; the typical sampling frequency is 5~20Hz. The following example uses 5Hz sampled static data. The time series is discrete, i.e., t1~t5. Table 1 shows the inertial navigation solution results at sampling times t1~t5, and Table 2 shows the satellite navigation solution results at sampling times t1~t5. Geographical latitude, Geographical longitude, The altitude is indicated by the subscripts GNSS and INS, which represent the positioning results from the satellite navigation system and inertial navigation system, respectively. This is a specific indicator of position accuracy decay; its value reflects the positioning accuracy, and the lower the value, the higher the positioning accuracy. This establishes valid markers for the satellite navigation system. All of these values ​​can be obtained directly from navigation data from satellites and inertial navigation systems. For eastward speed, For northbound speed, The velocity is oriented upwards, with the subscripts GNSS and INS indicating the velocity measurement results from the satellite navigation system and inertial navigation system, respectively.

[0048] Table 1. Inertial navigation calculation results at sampling time.

[0049]

[0050] Table 2 Satellite navigation solution results at sampling time

[0051]

[0052] Step S3, taking the sample data from step S2 as an example, firstly, the preliminary screening of satellite navigation system data is completed to determine the completeness and validity of the satellite navigation data. Through sample data analysis, it is found that...

[0053] (3)

[0054] in, This indicates that the satellite navigation data reception frequency is 5. , indicating each packet of data All values ​​are less than the threshold val, and a typical value for val in this case is 3.5. This indicates that the positioning data for each packet is valid. Therefore, the satellite navigation data is determined to be complete and valid, and the process proceeds to step S3; otherwise, it will not be included in subsequent calculations.

[0055] Step S4: Taking sample data as an example, if the constraint conditions of formula (3) in step S3 are met, then an anti-interference analysis should be performed before the calculation of the combined navigation quantity measurement. This is mainly accomplished by evaluating the confidence of satellite navigation system data based on inertial navigation system constraints and selecting threshold constraints for navigation measurement considering spatial lever error isolation.

[0056] (4.1) Confidence assessment of satellite navigation system data based on inertial navigation system constraints

[0057] During the measurement period, the confidence level of satellite navigation system data is assessed using the short-time stationarity characteristics of inertial navigation system data. Typically, medium-to-high precision inertial navigation systems exhibit high short-time stationarity and continuous output capability, with data that does not fluctuate significantly within a short period. This data can serve as strong constraint information; specifically, the stability of the synchronous data difference within the period is used to evaluate the stationarity and accuracy of the satellite navigation system data, as detailed below:

[0058] (4)

[0059] (5)

[0060] (6)

[0061] In the formula, , , , , , These represent the average errors of the inertial navigation system and satellite latitude, longitude, altitude, eastward velocity, northward velocity, and celestial velocity within the measurement period. , , , , , These represent the standard deviations of latitude, longitude, altitude, eastward velocity, northward velocity, and celestial velocity of the inertial navigation system and the satellite within the measurement period. Typically, the positioning fluctuation of a satellite navigation system does not exceed 10m, and the velocity error does not exceed 0.2m / s. Therefore, the confidence constraint condition for the satellite navigation system can be set as follows:

[0062] (7)

[0063] Substituting the sample data from Table 1-2, we can obtain

[0064]

[0065] Therefore, the data sample satisfies the constraint condition of formula (7) and is determined to be free of interference.

[0066] (2) Threshold selection for navigation measurements considering spatial lever error isolation

[0067] The satellite navigation measurement point is the phase center of the satellite navigation receiver antenna, as shown in Figures 3(a) and 3(b). This measurement point is usually not consistent with the measurement center of the inertial navigation system. The accuracy of the compensation measurement is limited by the measurement method and application scenario. The resulting lever arm error will bring significant position and velocity measurement errors when the equipment moves significantly. Therefore, this invention uses the carrier motion constraint method to eliminate the spatial lever arm error introduced by the large-scale carrier movement. By judging the large-scale carrier movement scenario through the acceleration measurement value and angular velocity change threshold of the inertial navigation system device, the spatial lever arm error isolation is achieved, and the interference signal is eliminated.

[0068] During the measurement period, the frequency of the gyroscope and acceleration data output by the inertial navigation system is F, and the output is the three-axis angular increment within the sampling period. and speed increment .

[0069] (8)

[0070] (9)

[0071] In the formula, F is the frequency of the gyroscope and acceleration data output by the inertial navigation system during operation; It is the absolute value of the angle increment within the measurement period. It represents the absolute value of the velocity increment within the measurement period. The angular increment of the inertial navigation system device within the gyroscope sampling period, including , , , which are the angular increments within the sampling period of the three-axis gyroscope of the inertial navigation system device; The velocity increment of the inertial navigation system device within the accelerometer sampling period, including , , , which are the velocity increments within the sampling period of the three-axis accelerometers of the inertial navigation system. Therefore, the constraint condition for excluding high-maneuver scenes is set as follows:

[0072] (10)

[0073] In the formula, The sampling time is 1 / F. Let gravitational acceleration be the acceleration due to gravity, and its value is... .

[0074] The sample data is static, with a sampling frequency of 200Hz and a sampling time of... The sample data is organized as shown in Table 3:

[0075] Table 3 Sample Data

[0076]

[0077] Calculated:

[0078]

[0079] Therefore, the scenario was determined to be a non-high-speed maneuver scenario, with no interference issues, and the data was valid.

[0080] In summary, the constraints in steps S4 (4.1) and (4.2) are satisfied, and the measurement calculation is performed.

[0081] Step S5: Based on the threshold conditions of formula (7) and formula (10) in step S4, complete the combined navigation quantity measurement calculation. The quantity measurement adopts the average error of the inertial navigation system and the satellite within the measurement period. Moment-based integrated navigation measurement error The calculation formula is as follows:

[0082] (11)

[0083] The final measurement calculation results for this measurement period, after inputting the sample data, are as follows:

[0084]

Claims

1. A time synchronization-based inertial navigation and satellite integrated navigation measurement selection and anti-interference method, characterized in that, The steps are as follows: Step S1, the hardware synchronization inertial navigation system acquisition time is synchronized with the PPS synchronization signal output by GNSS positioning, ensuring that the data acquisition time of the inertial navigation system and the satellite navigation system is strictly synchronized; Step S2, after the synchronization at the acquisition time, after the satellite navigation system and the inertial navigation system are solved, the delay time T is performed, and the positioning and speed measurement results obtained by the satellite navigation system and the inertial navigation system are stored synchronously at the same sampling frequency. Stored positioning data for time instances collected by satellite navigation systems and inertial navigation systems and are: （1）； ； wherein, is a discrete time series, , is the initial time of storing data after the previous integration cycle, is a sampling time interval, N is the number of sampling points in a filtering cycle; is a geographic latitude, is a geographic longitude, is an altitude, and subscripts GNSS and INS represent positioning results of satellite navigation and inertial navigation system navigation, respectively; is a specific index of position accuracy degradation; is a satellite navigation system positioning effective flag bit; Similarly, the positioning data collected at the time of acquisition stored by satellite navigation and inertial navigation systems and is: （2）； wherein, is the eastward velocity, is the northward velocity, is the skyward velocity, the subscripts GNSS and INS denote the velocity measurement results of satellite navigation and inertial navigation system navigation, respectively; Step S3, on the basis of step S2, complete the satellite navigation system data preliminary screening, judge the data integrity and positioning and velocity measurement effectiveness detection; in the combined measurement period of 1s, that is, at the moment, the positioning and velocity measurement data of the satellite navigation system data stored in the last period are analyzed for availability, and the constraint condition is set as: （3）； wherein, represents the integrity of the data, i.e. the positioning and speed data packet reception frequency; represents that each packet of data the values are all less than the threshold value val; represents that each packet of positioning data is valid; Step S4, on the basis of meeting the constraint condition of formula (3) in step S3, the satellite navigation data confidence evaluation and spatial boom error isolation constraint condition are constrained by the inertial output parameters of the inertial navigation system, and the anti-interference analysis before the combined navigation measurement calculation is completed: (4.1) Satellite navigation system data confidence evaluation based on inertial navigation system constraints Within the measurement period, the short-time smoothness of the inertial navigation system data is used to evaluate the confidence of the satellite navigation system data; the stability of the difference value of the synchronous data within the period is used to evaluate the smoothness and accuracy of the satellite navigation system data, as follows: （4）； （5）； （6）； wherein, , , , , , are the mean errors of the inertial navigation system and satellite latitude, longitude, altitude, eastward velocity, northward velocity, and skyward velocity in the measurement period, respectively, , , , , , are the standard deviations of the inertial navigation system and satellite latitude, longitude, altitude, eastward velocity, northward velocity, and skyward velocity in the measurement period, respectively; the satellite navigation system available confidence constraint condition is set as: （7）； If the constraint condition is met, the satellite navigation system data is not disturbed; (4.2) Navigation measurement selection threshold considering spatial boom error isolation The spatial boom error introduced by the large-scale maneuver of the carrier is removed by using the constraint of the carrier motion; the large-scale maneuver scenario of the carrier is judged by the speed measurement value and the angular velocity change threshold value output by the inertial device in the inertial navigation system, and then the spatial boom error isolation is realized, and the interference signal is removed. During the inertial navigation system period, gyro and acceleration data are output at a frequency F during the measurement period, output as three-axis angular increments during the sampling period and velocity increments ; （8）； （9）； where F is the frequency of the gyro and acceleration data output during the inertial navigation system; is the absolute value of the angular increment during the measurement period, is the absolute value of the velocity increment during the measurement period; is the angular increment of the inertial navigation system device during the gyro sampling period, including , , , are the angular increments of the three-axis gyro of the inertial navigation system device during the sampling period, respectively; is the velocity increment of the inertial navigation system device during the accelerometer sampling period, including , , , are the velocity increments of the three-axis accelerometer of the inertial navigation system device during the sampling period, respectively, so the large maneuver scene rejection condition is set as: （10）； wherein is the absolute value of the current calculated angular velocity of the carrier with respect to the inertial navigation system space, is the absolute value of the current calculated acceleration of the carrier with respect to the inertial navigation system space, is the sampling time, with value 1 / F, is the gravitational acceleration; Step S5, on the basis of satisfying the anti-interference analysis constraint condition of step S4, that is, simultaneously satisfying the threshold constraint conditions of formula (7) and formula (10) in step S4, the combined navigation measurement calculation is completed, and the measurement uses the average error of the inertial navigation system and the satellite in the measurement period; Time Inertial navigation system satellite combined navigation measurement error The calculation formula is as follows: （11）。

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