Multi-frequency multi-system integrity monitoring system suitable for eVTOL

Abstract

The invention discloses a multi-frequency multi-system integrity monitoring system suitable for eVTOL, which relates to the technical field of unmanned aerial vehicle application and comprises a plurality of GNSS (Global Navigation Satellite System) signal receiving units, a communication link, a main control processing unit and an eVTOL user unit, the GNSS signal receiving unit comprises a GNSS antenna and a GNSS receiver, supports GNSS signal observation of a plurality of satellite positioning systems and frequency points, and is used for receiving GNSS observation information; and the communication link is used for sending the GNSS observation information received by each GNSS signal receiving unit to the main control processing unit. According to the invention, the potential of multi-frequency multi-system integrity monitoring redundant information application can be broadened, the eVTOL integrity monitoring application cost can be reduced, and the integrity monitoring information between the base station and the service station can be deeply utilized.

Description

Technical Field

[0001] The present application relates to the technical field of UAV applications, and particularly to a multi-frequency and multi-system integrity monitoring system applicable to eVTOL. Background Art

[0002] With the vigorous development of electric vertical take-off and landing aircraft in recent years, eVTOL (electric Vertical Take-off and Landing) has attracted wide attention in the aviation field, and its application fields include urban transportation, medical transportation, logistics distribution, tourism sightseeing, etc. However, at the same time, due to the application and operation scenarios of eVTOL being closely related to safety, it has brought many potential safety hazards. How to effectively guarantee the flight safety of eVTOL is one of the core issues in its application. Guaranteeing the safety of eVTOL during the take-off and landing stages, ensuring its safe and stable operation during the en-route operation stage, and stably controlling its efficient operation can not only ensure the air safety of the passengers on board, but also avoid interfering with people's normal production and life due to safety issues.

[0003] The global satellite navigation system can provide eVTOL with all-weather and uninterrupted absolute position information. Currently, the integrity monitoring for eVTOL is still blank, and the integrity monitoring of the mainstream civil aviation ground-based augmentation system is usually based on single-frequency and single-system. There are relatively few eVTOL integrity monitoring solutions that fully exploit the potential of redundant information of multi-frequency and multi-system; and the mainstream solutions of the receiver autonomous integrity system at the airborne end are usually snapshot-based RAIM (Receiver Autonomous Integrity Monitoring), and there are not many ways to deeply utilize the integrity monitoring information between the observation fields of the reference station. Therefore, how to fill the blank of the current eVTOL integrity detection technology, further broaden the potential of applying redundant information of multi-frequency and multi-system integrity monitoring, reduce the application cost of eVTOL integrity monitoring, and deeply utilize the integrity monitoring information between the reference station and the service station has become an urgent problem to be solved currently. Summary of the Invention

[0004] The present application provides a multi-frequency and multi-system integrity monitoring system applicable to eVTOL, which can broaden the potential of applying redundant information of multi-frequency and multi-system integrity monitoring, reduce the application cost of eVTOL integrity monitoring, and deeply utilize the integrity monitoring information between the reference station and the service station.

[0005] In a first aspect, an embodiment of the present application provides a multi-frequency and multi-system integrity monitoring system applicable to eVTOL. The multi-frequency and multi-system integrity monitoring system applicable to eVTOL includes: a plurality of GNSS signal receiving units, a communication link, a main control processing unit, and an eVTOL user unit;

[0006] The GNSS signal receiving unit includes a GNSS antenna and a GNSS receiver, and supports GNSS signal observations of multiple satellite positioning systems and frequencies. The GNSS signal receiving unit is used to receive GNSS observation information;

[0007] The communication link is used to send the GNSS observation information received by each GNSS signal receiving unit to the main control processing unit;

[0008] The main control processing unit is used to perform performance monitoring on the GNSS observation information at the level of raw observation values to obtain integrity monitoring information;

[0009] The eVTOL user unit includes a GNSS antenna and a GNSS receiver, which supports at least one satellite positioning system and frequency. The eVTOL user unit is used to receive GNSS observation information, differential correction signals, and integrity monitoring information.

[0010] Combined with the first aspect, in an implementation manner, the main control processing unit performs performance monitoring on the GNSS observation information at the level of raw observation values to implement integrity monitoring processing and obtain integrity monitoring information. The specific implementation steps include:

[0011] Perform signal quality monitoring, data quality monitoring, and measurement quality monitoring on the GNSS observation information of the current satellite positioning system at the signal level;

[0012] Enter the processing logic of the first stage of the execution monitor to perform verification in three dimensions of multiple frequencies, multiple satellites, and multiple receivers;

[0013] Enter the processing logic of the second stage of the execution monitor to perform multi-reference consistency verification, information domain pseudorange monitoring, and mean-variance monitoring, and obtain the integrity monitoring information of the GNSS observation information corresponding to the current satellite positioning system.

[0014] Combined with the first aspect, in an implementation manner,

[0015] The signal quality monitoring includes correlation peak symmetry monitoring, receiver signal strength monitoring, and code-carrier deviation monitoring;

[0016] The data quality monitoring includes ephemeris-almanac monitoring, forward and backward ephemeris monitoring, and inter-receiver ephemeris monitoring;

[0017] The measurement quality monitoring includes lock time monitoring, CARST monitoring, and CSC monitoring.

[0018] In one implementation manner in combination with the first aspect,

[0019] The specific related peak symmetry monitoring is as follows: Based on the real-time observation data of the GNSS signal receiving unit, obtain the GNSS observation information and navigation ephemeris data of the current satellite positioning system at the current moment, and perform related peak extraction on both the GNSS observation information and the navigation ephemeris data for symmetry detection;

[0020] The specific receiver signal strength monitoring is as follows: Obtain the receiver signal strength observed by the GNSS receiver on each satellite and each frequency point, and compare it with the threshold value to achieve receiver signal strength detection;

[0021] The specific code carrier deviation monitoring is as follows:

[0022] Obtain the pseudorange observation and carrier phase observation of the GNSS receiver on each satellite and each frequency point;

[0023] Based on the geometric moving average, calculate the code carrier deviation at the current moment. Specifically,

[0024]

[0025] where D m,n (k) represents the code carrier deviation at the current moment, τ d represents the geometric moving average window width, T s represents the time interval, D m,n (k - 1) represents the code carrier deviation at the previous moment, dz m,n (k) represents the difference component of the original code carrier deviation value at the current moment.

[0026] In one implementation manner in combination with the first aspect,

[0027] The specific ephemeris - almanac monitoring is as follows: Extract the broadcast ephemeris file and the almanac file, compare the orbits obtained by solving the broadcast ephemeris and the almanac, and make the comparison difference not exceed the difference limit value;

[0028] The specific front - rear ephemeris monitoring is as follows: Perform orbit solution on the front - rear frame ephemeris, and compare the orbits obtained by the solution, and make the comparison difference not exceed the difference limit value;

[0029] The specific inter - receiver ephemeris monitoring is as follows: Perform orbit solution on the ephemeris received by each GNSS receiver respectively, and compare the orbits obtained by the solution, and make the comparison difference not exceed the difference limit value.

[0030] In one implementation manner in combination with the first aspect,

[0031] The locking time monitoring is specifically as follows: The locking time of the GNSS signal receiving unit is monitored to obtain the continuous observation duration of each satellite. If the continuous observation duration is less than the specified observation time, it indicates that the current satellite is unavailable;

[0032] The CARST monitoring is specifically as follows:

[0033] Calculate the carrier phase observable. Specifically,

[0034]

[0035] Among them, represents the carrier phase observable at the current moment, represents the original carrier phase observable at the current moment, R m,n (k) represents the geometric observation distance at the current moment, τ m,n (k) represents the satellite clock correction at the current moment, represents the carrier phase correction at the initial moment;

[0036] Remove the influence of the GNSS receiver clock error by averaging. Specifically:

[0037]

[0038] Among them, represents the carrier phase observable after removing the GNSS receiver clock error, N m represents the number of carrier phase corrections for averaging, represents the carrier phase correction at the current moment;

[0039] Obtain the carrier phase observable after removing the GNSS receiver clock error within the specified time window, and use the least squares method to perform second-order coefficient fitting on the carrier phase observable after removing the GNSS receiver clock error within the specified time window. Specifically:

[0040]

[0041] Among them, A, B, and C represent fitting coefficients, and t represents a variable;

[0042] The CSC monitoring is specifically as follows:

[0043] Define the monitored phase smoothing correction as,

[0044]

[0045] Among them, Inno m,n (k) represents the phase smoothing stamping quantity at the current moment, P m,n(k) represents the original pseudorange observation value at the current moment, P s,m,n (k - 1) represents the smoothed pseudorange observation value at the previous moment, represents the original carrier phase observation value at the current moment, represents the smoothed carrier phase observation value at the previous moment;

[0046] Calculate the smoothed pseudorange. Specifically,

[0047]

[0048] where, P s,m,n (k) represents the smoothed pseudorange at the current moment, N s represents an intermediate quantity, τ s represents the smoothing interval, T s represents the time interval.

[0049] Combining with the first aspect, in an implementation manner,

[0050] The multi-reference consistency check is specifically:

[0051] First, calculate the pseudorange correction amount after correcting the clock error,

[0052]

[0053] where, P sca,m,n (k) represents the pseudorange correction amount after correcting the clock error, P sc,m,n (k) represents the original pseudorange correction amount without correcting the clock error, N c (k) represents the number of satellites at the current moment, S c (k) represents the satellite set at the current moment, j represents different satellites, P sc,m,j (k) represents the pseudorange correction amount at the current moment;

[0054] Correspondingly, calculate the phase correction amount after correcting the clock error

[0055]

[0056] where, represents the phase correction amount after correcting the clock error, represents the original carrier phase correction amount without correcting the clock error, represents the carrier phase correction amount at the current moment;

[0057] Perform the B value calculation:

[0058]

[0059] where, B ρ,m,n 、 Both represent the B value, M n (k) represents the number of available reference stations at the current moment, S n (k) represents the set of available reference stations at the current moment, i represents different reference stations, m represents the total number of reference stations, P sca,i,n (k) represents the pseudorange correction amount after correcting the clock offset of the ith reference station, represents the phase correction amount after correcting the clock offset of the ith reference station, represents the original phase correction amount of the ith reference station;

[0060] Judge whether the B value exceeds the preset limit. If so, it is determined that the multi-reference consistency check fails;

[0061] The mean-variance monitoring is to judge whether the error distribution of the B value can be broadcast by σ pr_gnd envelope, σ pr_gnd represents the standard deviation of the pseudorange correction error;

[0062] The information field pseudorange monitoring is to check whether the pseudorange correction and the change rate of the pseudorange correction meet the specified range constraints;

[0063] Among them, the calculation method of the pseudorange correction is:

[0064]

[0065] Among them, P corr,n (k) represents the pseudorange correction at the current moment;

[0066] Among them, the calculation method of the change rate of the pseudorange correction is:

[0067]

[0068] Among them, T s represents the time interval, R corr,n (k) represents the change rate of the pseudorange correction at the current moment, P corr,n (k - 1) represents the pseudorange correction at the previous moment.

[0069] Combined with the first aspect, in an implementation manner, after the eVTOL user unit receives the integrity monitoring information, the processing of the integrity monitoring information specifically includes:

[0070] Based on the Kalman filter depending on prior information and the least squares solution depending on the current moment information, perform parameter estimation cross-check on the integrity monitoring information corresponding to the current satellite positioning system to obtain the test result;

[0071] Perform cross-checks between the corresponding test results of each satellite positioning system to ensure the consistency at the solution level of the satellite positioning system.

[0072] Combined with the first aspect, in one implementation, perform parameter estimation cross-checks on the integrity monitoring information corresponding to the current satellite positioning system based on the Kalman filter relying on prior information and the least squares solution relying on the information at the current moment, and obtain the test results, specifically including:

[0073] The eVTOL user unit receives the integrity monitoring information and differential correction numbers, and performs differential positioning;

[0074] Based on the Kalman filter relying on prior information, obtain the Kalman filter positioning solution, and based on the least squares solution relying on the information at the current moment, obtain the least squares solution;

[0075] Compare the obtained least squares solution and the Kalman filter positioning solution. If the difference exceeds the specified limit, the current least squares solution and the Kalman filter positioning solution are unavailable, thereby obtaining the differential positioning result.

[0076] Combined with the first aspect, in one implementation, the cross-checks between the corresponding test results of each satellite positioning system to ensure the consistency at the solution level of the satellite positioning system specifically include:

[0077] Obtain the differential positioning results corresponding to each satellite positioning system;

[0078] Calculate the positioning solution deviation value between the current satellite positioning system and other satellite positioning systems. If the calculated value is greater than the set threshold, it is determined that the differential positioning result of the current satellite positioning system is unavailable.

[0079] The beneficial effects brought by the technical solution provided by the embodiments of the present application include:

[0080] Based on the GNSS observation data of multi-frequency and multi-system, with the integrity of the ground-based augmentation system of the GNSS signal receiving unit and the autonomous integrity monitoring of the eVTOL user unit, jointly construct an integrated eVTOL integrity monitoring system based on multi-frequency and multi-system, which can fill the gap in the current eVTOL integrity detection technology, further broaden the potential application of the redundant information of multi-frequency and multi-system integrity monitoring, reduce the application cost of eVTOL integrity monitoring, and deeply utilize the integrity monitoring information between the reference station and the service station. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 It is a schematic structural diagram of a multi-frequency and multi-system integrity monitoring system applicable to eVTOL of the present application;

[0082] Figure 2 It is a schematic diagram of the eVTOL integrity monitoring architecture. Detailed implementation manners

[0083] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part rather than all of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the protection scope of this application.

[0084] To make the purpose, technical solutions and advantages of this application clearer, the following will further describe the embodiments of this application in detail with reference to the drawings.

[0085] In a first aspect, the embodiments of this application provide a multi-frequency and multi-system integrity monitoring system applicable to eVTOL. Based on the GNSS observation data of multi-frequency and multi-system, the integrity of the ground-based augmentation system of the GNSS signal receiving unit and the autonomous integrity monitoring of the eVTOL user unit are used to jointly construct an integrated eVTOL integrity monitoring system based on multi-frequency and multi-system.

[0086] In one embodiment, referring to Figure 1 , Figure 1 is a schematic structural diagram of the multi-frequency and multi-system integrity monitoring system applicable to eVTOL of this application. As Figure 1 shown, the multi-frequency and multi-system integrity monitoring system applicable to eVTOL includes: a plurality of GNSS signal receiving units, a communication link, a main control processing unit, and an eVTOL user unit. In actual applications, the GNSS signal receiving units are generally set to 3 to 4. GNSS, the full name is Global Navigation Satellite System, that is, the Global Navigation Satellite System.

[0087] The GNSS signal receiving unit includes a GNSS antenna and a GNSS receiver, and supports GNSS signal observations of multiple satellite positioning systems and frequency points. The GNSS signal receiving unit is used to receive GNSS observation information. For the GNSS signal receiving unit, it supports GNSS signal observations of at least 2 satellite positioning systems and 2 frequency points.

[0088] The communication link is used to send the GNSS observation information received by each GNSS signal receiving unit to the main control processing unit.

[0089] The master control processing unit is used to monitor the performance of GNSS observation information at the level of raw observation values to obtain integrity monitoring information. That is, the master control processing unit receives the GNSS observation information observed by each GNSS signal receiving unit, and then monitors the performance of the GNSS observation information at the level of raw observation values and eliminates abnormal data.

[0090] The eVTOL user unit includes a GNSS antenna and a GNSS receiver, which supports at least one satellite positioning system and frequency point. The eVTOL user unit is used to receive GNSS observation information, differential correction signals, and integrity monitoring information. That is, the eVTOL user unit supports GNSS signal observations of at least 1 satellite positioning system and 1 frequency point.

[0091] Furthermore, for the implementation process of the integrity monitoring of the master control processing unit (i.e., the eVTOL master station), that is, the master control processing unit monitors the performance of GNSS observation information at the level of raw observation values to implement integrity monitoring processing and obtain integrity monitoring information. The specific implementation steps include:

[0092] S11: Monitor the signal quality, data quality, and measurement quality of the GNSS observation information of the current satellite positioning system at the signal level;

[0093] S12: Enter the first-stage processing logic of the execution monitor to perform checks in three dimensions: multiple frequency points, multiple satellites, and multiple receivers;

[0094] S13: Enter the second-stage processing logic of the execution monitor to perform multi-reference consistency checks, information field pseudorange monitoring, and mean-variance monitoring to obtain the integrity monitoring information of the GNSS observation information corresponding to the current satellite positioning system.

[0095] Specifically, at the signal level, first perform signal quality monitoring (abbreviated as SQM), data quality monitoring (abbreviated as DQM), and measurement quality monitoring (abbreviated as MQM). Among them, signal quality monitoring mainly includes correlation peak symmetry monitoring, receiver signal strength monitoring, and code-carrier deviation monitoring. Data quality monitoring mainly includes ephemeris-almanac monitoring, forward and backward ephemeris monitoring, and inter-receiver ephemeris monitoring. Measurement quality monitoring mainly includes lock time monitoring, CARST monitoring, and CSC monitoring. CARST monitoring refers to the monitoring and analysis of key parameters such as the Carrier, Amplitude, Ranging code, Signal-to-Noise Ratio, and Time of satellite signals. CSC monitoring refers to the monitoring and analysis of key parameters such as the Carrier, Signal-to-Noise Ratio, and Code of satellite signals.

[0096] After signal quality monitoring, data quality monitoring, and measurement quality monitoring, it enters the first-stage processing logic of the execution monitor (abbreviated as EXM-I), which undergoes verification in three dimensions: multiple frequencies, multiple satellites, and multiple receivers.

[0097] After passing through EXM-I, it enters the second-stage processing logic of the execution monitor (abbreviated as EXM-II), which performs multi-reference consistency check (abbreviated as MRCC), information domain pseudorange monitoring (abbreviated as MFRT), and mean-variance monitoring (abbreviated as u-sigma). That is, GNSS observation information enters MRCC to ensure statistical consistency of GNSS observation information among multiple reference stations. Subsequently, it enters MFRT to check whether the pseudorange correction and the change rate of the pseudorange correction meet the specified range constraints. Then, u-sigma calculation is performed to monitor whether the error distribution of the pseudorange error correction can be enveloped by the broadcast pseudorange variance. The purpose of the EXM-II exclusion logic is to ensure that GNSS observation information can pass through the MRCC, u-sigma, and MFRT monitoring in sequence within the specified number of iterations. Failure to pass through the MRCC, u-sigma monitoring, and MFRT monitoring in sequence beyond the number of iterations is usually regarded as a failure of the EXM-II logic.

[0098] Furthermore, for the integrity monitoring implementation of the eVTOL user unit (i.e., the eVTOL user solution end), specifically, after the eVTOL user unit receives the integrity monitoring information, the processing of the integrity monitoring information includes:

[0099] S21: Based on the Kalman filter relying on prior information and the least squares solution relying on the current moment information, perform parameter estimation cross-check on the integrity monitoring information corresponding to the current satellite positioning system to obtain the test result;

[0100] S22: Perform cross-checks among the test results corresponding to each satellite positioning system to ensure the consistency at the satellite positioning system solution level.

[0101] Specifically, after passing through the EXM-I and EXM-II processing logics, it enters the solution level. Based on the Kalman filter relying on prior information and the least squares solution relying on the current moment information, perform parameter estimation cross-check on the integrity monitoring information to ensure the consistency at the user parameter estimation solution level. After passing through the parameter estimation cross-check, it enters the consistency detection at the system solution level. Through cross-detection among satellite positioning systems, ensure the consistency at the satellite positioning system solution level.

[0102] See Figure 2 shown in the figure, which is a schematic diagram of the eVTOL integrity monitoring architecture. Figure 2Among them, GPS, namely Global Positioning System, represents the Global Positioning System; GLO, namely GLOBAL NAVIGATION SATELLITE SYSTEM, represents the Global Navigation Satellite System; GAL, namely Galileo Satellite Navigation System, represents the Galileo satellite navigation system; BDS, namely Beidou Navigation Satellite System, represents the Beidou satellite navigation system. From Figure 2 It can be seen that for the GNSS observation information of each satellite positioning system, signal quality monitoring, data quality monitoring, measurement quality monitoring, execution of the first-stage processing logic of the monitor, execution of the second-stage processing logic of the monitor, and cross-check of parameter estimation are all required to obtain the test result corresponding to the current satellite positioning system, and then cross-check is performed among the test results corresponding to each satellite positioning system.

[0103] Furthermore, in this application, the correlation peak symmetry monitoring is specifically as follows: Based on the real-time observation data of the GNSS signal receiving unit, the GNSS observation information and navigation ephemeris data at the current moment of the current satellite positioning system are obtained, and correlation peaks are extracted from both the GNSS observation information and the navigation ephemeris data for symmetry detection.

[0104] In this application, the receiver signal strength monitoring is specifically as follows: The receiver signal strength observed by the GNSS receiver on each satellite and each frequency point is obtained and compared with the threshold value to achieve receiver signal strength detection. If it is lower than the threshold value, it is considered that the receiver signal strength detection fails; if it is higher than the threshold value, it is considered that the receiver signal strength detection passes. The setting of the threshold value here can be carried out through a fixed threshold, a statistical model threshold established based on historical data, or a threshold model established based on the elevation angle.

[0105] In this application, the code-carrier deviation monitoring is specifically as follows:

[0106] The pseudorange observation and carrier phase observation of the GNSS receiver on each satellite and each frequency point are obtained;

[0107] Based on geometric moving average, the code-carrier deviation at the current moment is calculated. Specifically,

[0108]

[0109] where D m,n (k) represents the code-carrier deviation at the current moment, τ d represents the geometric moving average window width, T s represents the time interval, D m,n(k - 1) represents the code carrier deviation at the previous moment (for example, if the sampling time interval is 1 second, then D m,n (k - 1) refers to the code carrier deviation in the previous second), dz m,n (k) represents the difference component of the raw code carrier deviation value at the current moment.

[0110] Furthermore, in this application, the ephemeris - almanac monitoring is specifically as follows: extract the broadcast ephemeris file and the almanac file, compare the orbits obtained by resolving the broadcast ephemeris and the almanac, and make the comparison difference not exceed the difference limit value. That is, calculate the difference between the orbits obtained by resolving the broadcast ephemeris and the orbits obtained by resolving the almanac. Here, the difference limit value can be set to 7000 m.

[0111] In this application, the front - back ephemeris monitoring is specifically as follows: perform orbit resolution on the front - back frame ephemeris and compare the resolved orbits, and make the comparison difference not exceed the difference limit value; here, the difference limit value can be set to 250 m.

[0112] In this application, the inter - receiver ephemeris monitoring is specifically as follows: perform orbit resolution on the ephemeris received by each GNSS receiver respectively and compare the resolved orbits, and make the comparison difference not exceed the difference limit value. Here, the difference limit value can be set to 10 m.

[0113] Furthermore, in this application, the lock - time monitoring is specifically as follows: perform lock - time monitoring on the GNSS signal receiving unit, obtain the continuous observation duration of each satellite, and if the continuous observation duration is less than the specified observation time, it means that the current satellite is unavailable. Here, the specified observation time can be set to 30 seconds.

[0114] In this application, the CARST monitoring is specifically as follows:

[0115] Calculate the carrier - phase observable. Specifically,

[0116]

[0117] Among them, represents the carrier - phase observable at the current moment, represents the raw carrier - phase observable at the current moment, R m,n (k) represents the geometric observation distance at the current moment, τ m,n (k) represents the satellite clock correction at the current moment, represents the carrier - phase correction at the initial moment;

[0118] Remove the influence of the GNSS receiver clock error by averaging. Specifically:

[0119]

[0120] Among them, It represents the carrier phase observation after removing the GNSS receiver clock error, N m It represents the number of carrier phase correction amounts for averaging, It represents the carrier phase correction amount at the current moment;

[0121] Obtain the carrier phase observation after removing the GNSS receiver clock error within a specified time window, and use the least squares method to perform second-order coefficient fitting on the carrier phase observation after removing the GNSS receiver clock error within the specified time window. Specifically:

[0122]

[0123] Among them, A, B, and C represent fitting coefficients, and t represents a variable. Specifically, A represents the second-order term coefficient obtained by fitting, B represents the first-order term coefficient obtained by fitting, and C represents the constant term obtained by fitting. The deviation between the observed value and the fitted value is the step detection quantity, and let all three of them not exceed their specified limits, and this limit can be obtained by statistically analyzing the measured observed data and performing an inflation envelope.

[0124] In this application, the CSC monitoring is specifically as follows:

[0125] Define the monitored phase smoothing correction amount as,

[0126]

[0127] Among them, Inno m,n (k) represents the phase smoothing stamping amount at the current moment, P m,n (k) represents the original pseudorange observation value at the current moment, P s,m,n (k - 1) represents the smoothed pseudorange observation value at the previous moment, represents the original carrier phase observation value at the current moment, represents the smoothed carrier phase observation value at the previous moment;

[0128] Calculate the smoothed pseudorange. Specifically,

[0129]

[0130] Among them, P s,m,n (k) represents the smoothed pseudorange at the current moment, N s represents an intermediate quantity, τ s represents the smoothing interval, T s represents the time interval.

[0131] In this application, for the EXM-I processing logic, specifically, obtain the availability (0 or 1) of a specified GNSS receiver for a specified satellite and a specified frequency point, and the determination logic is as follows:

[0132] If it occurs on a single GNSS receiver, a single satellite, and a single frequency point, exclude this single abnormal channel;

[0133] If abnormalities occur in the observations of a single satellite and a single frequency point by multiple GNSS receivers, exclude the results of this satellite and this frequency point on all GNSS receivers;

[0134] If abnormalities occur in multiple satellites and a single frequency point of a single GNSS receiver, exclude the observation results of this GNSS receiver at this frequency point for all satellites;

[0135] If abnormalities occur in a single satellite and multiple frequency points of a single GNSS receiver, exclude the observation results of this GNSS receiver for this satellite at all frequency points;

[0136] In case of a complex situation of multi-dimensional abnormalities, exclude according to the conservative situation and remove all potentially suspicious channel results.

[0137] In this application, the multi-reference consistency check is specifically as follows:

[0138] First, calculate the pseudorange correction amount after correcting the clock bias,

[0139]

[0140] Among them, P sca,m,n (k) represents the pseudorange correction amount after correcting the clock bias, and P sc,m,n (k) represents the original pseudorange correction amount without correcting the clock bias, N c (k) represents the number of satellites at the current moment, S c (k) represents the set of satellites at the current moment, j represents different satellites, and P sc,m,j (k) represents the pseudorange correction amount at the current moment;

[0141] Correspondingly, calculate the phase correction amount after correcting the clock bias

[0142]

[0143] Among them, represents the phase correction amount after correcting the clock bias, represents the original carrier phase correction amount without correcting the clock bias, represents the carrier phase correction amount at the current moment;

[0144] Perform the B value calculation:

[0145]

[0146] Among them, B ρ,m,n 、 both represent the B value, M n(k) represents the number of available reference stations at the current moment, S n (k) represents the set of available reference stations at the current moment, i represents different reference stations, m represents the total number of reference stations, P sca,i,n (k) represents the pseudorange correction amount after correcting the clock bias of the i-th reference station, represents the phase correction amount after correcting the clock bias of the i-th reference station, represents the original phase correction amount of the i-th reference station;

[0147] Determine whether the B value exceeds the preset limit. If so, it is determined that the multi-reference consistency check fails.

[0148] In this application, the mean-variance monitoring is to determine whether the error distribution of the B value can be broadcast by σ pr_gnd envelope, σ pr_gnd represents the standard deviation of the pseudorange correction error; it can be carried out by means of Shewhart control chart, CUSUM control chart, EWMA control chart, etc.

[0149] In this application, the information field pseudorange monitoring is to check whether the pseudorange correction number and the change rate of the pseudorange correction number meet the specified range constraints;

[0150] Among them, the calculation method of the pseudorange correction number is:

[0151]

[0152] Among them, P corr,n (k) represents the pseudorange correction number at the current moment;

[0153] Among them, the calculation method of the change rate of the pseudorange correction number is:

[0154]

[0155] Among them, T s represents the time interval, R corr,n (k) represents the change rate of the pseudorange correction number at the current moment, P corr,n (k - 1) represents the pseudorange correction number at the previous moment.

[0156] Further, in this application, based on the Kalman filter depending on prior information and the least squares solution depending on the current moment information, a parameter estimation cross-check is performed on the integrity monitoring information corresponding to the current satellite positioning system to obtain a test result, which specifically includes:

[0157] S31: The eVTOL user unit receives the integrity monitoring information and the differential correction number, and performs differential positioning;

[0158] S32: Obtain the Kalman filter positioning solution based on the Kalman filter that depends on prior information, and obtain the least squares solution based on the least squares solution that depends on the information at the current moment;

[0159] S33: Compare the obtained least squares solution and the Kalman filter positioning solution. If the difference exceeds the specified limit value, the current least squares solution and the Kalman filter positioning solution are unavailable, thereby obtaining the differential positioning result.

[0160] Furthermore, in this application, cross-checks are performed among the corresponding test results of each satellite positioning system to ensure the consistency at the satellite positioning system solution level, specifically including:

[0161] S41: Obtain the differential positioning results corresponding to each satellite positioning system;

[0162] S42: Calculate the positioning solution deviation value between the current satellite positioning system and other satellite positioning systems. If the calculated value is greater than the set threshold, it is determined that the differential positioning result of the current satellite positioning system is unavailable.

[0163] The following describes the specific monitoring implementation process of the multi-frequency multi-system integrity monitoring system applicable to eVTOL in this application.

[0164] S1: Based on the real-time observation data of 4 reference stations, obtain the GNSS observation information and navigation ephemeris data of the current satellite positioning system at the current moment, and transmit the GNSS observation information and navigation ephemeris data to the master station; The reference stations are the reference stations of the satellite positioning system, including GPS, GLONASS, BDS, and Galileo positioning systems; The reference stations correspond to the above-mentioned GNSS signal receiving units, and the master station corresponds to the above-mentioned master control processing unit;

[0165] S2: The master station obtains the GNSS observation information and navigation ephemeris data of each reference station, and performs symmetry detection on the correlation peaks extracted from the GNSS observation information and navigation ephemeris data of each reference station;

[0166] S3: Obtain the received signal strength of each GNSS receiver observed on each satellite and each frequency point, and compare it with the threshold value to achieve received signal strength detection;

[0167] S4: Obtain the pseudorange observations and carrier phase observations of the GNSS receiver on each satellite and each frequency point;

[0168] S5: Calculate the code-carrier deviation at the current moment based on geometric moving average. Specifically,

[0169]

[0170] S6: Extract the broadcast ephemeris file and almanac file, compare the orbits obtained by solving the broadcast ephemeris and almanac, and make the comparison difference not exceed the difference limit value;

[0171] S7: After the SQM monitoring passes, perform orbit solution on the ephemeris of the front and rear frames, and compare the orbits obtained by the solution, and make the comparison difference not exceed the difference limit value;

[0172] S8: Perform orbit solution on the ephemeris received by each GNSS receiver respectively, and compare the orbits obtained by the solution, and make the comparison difference not exceed the difference limit value;

[0173] S9: After the DQM monitoring passes, monitor the locking time of each reference station, obtain the continuous observation duration of each satellite, and if the continuous observation duration is less than the specified observation time, it means that the current satellite is unavailable;

[0174] S10: After the locking time monitoring passes, the CARST monitoring is to detect impulse, step and ramp faults in the carrier phase observables, and calculate the carrier phase observables. Specifically,

[0175]

[0176] Remove the influence of the GNSS receiver clock error by averaging. Specifically:

[0177]

[0178] Obtain the carrier phase observables after removing the GNSS receiver clock error within the specified time window, and use the least squares method to perform second-order coefficient fitting on the carrier phase observables after removing the GNSS receiver clock error within the specified time window. Specifically:

[0179]

[0180] Furthermore, in the CARST monitoring, compare the monitored quantity with the preset threshold value and make it not exceed the preset threshold value;

[0181] S11: In the CSC monitoring, define the monitored phase smoothing correction amount as

[0182]

[0183] Then calculate the smoothed pseudorange. Specifically,

[0184]

[0185] Furthermore, in the CSC monitoring, compare the monitored quantity with the set threshold value and make it not exceed the set threshold value;

[0186] S12: For the EXM-I processing logic, specifically, obtain the availability (0 or 1) for a specified satellite at a specified frequency point of a specified GNSS receiver. The determination logic is as follows:

[0187] If it occurs on a single GNSS receiver, a single satellite, and a single frequency point, exclude this single abnormal channel;

[0188] If abnormalities occur in the observations of a single satellite and a single frequency point by multiple GNSS receivers, exclude the results of this satellite at this frequency point on all GNSS receivers;

[0189] If abnormalities occur in multiple satellites and a single frequency point of a single GNSS receiver, exclude the observation results of this GNSS receiver at this frequency point for all satellites;

[0190] If abnormalities occur in a single satellite and multiple frequency points of a single GNSS receiver, exclude the observation results of this GNSS receiver for this satellite at all frequency points;

[0191] In case of complex multi-dimensional abnormalities, exclude according to the conservative situation and remove all potentially suspicious channel results.

[0192] S13: Perform the B-value calculation, which is defined as the difference between including and not including this channel. Specifically, it can be expressed as follows. First, calculate the pseudorange correction amount after correcting the clock error,

[0193]

[0194] Then calculate the phase correction amount after correcting the clock error

[0195]

[0196] Then perform the B-value calculation:

[0197]

[0198] Then determine whether the B value exceeds the preset limit. If so, it is determined that the multi-reference consistency check fails, and the maximum abnormal channel is removed and S13 is re-executed. If not, proceed to S14;

[0199] S14: Mean-variance monitoring is to determine whether the error distribution of the B value can be covered by the broadcast σ pr_gnd envelope. If it passes, proceed to S15. If it fails, remove the abnormal channel and proceed to S13;

[0200] S15: Calculate the pseudorange correction number,

[0201]

[0202] Calculate the rate of change of the pseudorange correction number,

[0203]

[0204] Compare the pseudorange correction and the rate of change of the pseudorange correction with a preset threshold. If the threshold is exceeded, exclude the current channel and transfer to S13. If it passes, transfer to the subsequent processing logic. Among them, the total number of exclusion iterations from S13 to S15 does not exceed 3 times;

[0205] S16: Broadcast the integrity monitoring information to the eVTOL airborne receiver through message arrangement; the eVTOL airborne receiver corresponds to the eVTOL user unit of this application;

[0206] S17: After the eVTOL airborne receiver receives the integrity monitoring information and the differential correction, perform differential positioning. Based on the Kalman filter that depends on prior information, obtain the Kalman filter positioning solution. Based on the least squares solution that depends on the current moment information, obtain the least squares solution. Compare the obtained least squares solution and the Kalman filter positioning solution. If the difference exceeds the specified limit, the current least squares solution and the Kalman filter positioning solution are unavailable, thereby obtaining the differential positioning result;

[0207] S18: Compare the differential positioning results of the four systems of GPS, GLONASS, BDS, and Galileo, and calculate the positioning solution deviation value between the current satellite positioning system and other satellite positioning systems. If the calculated value is greater than the set threshold, determine that the differential positioning result of the current satellite positioning system is unavailable;

[0208] S19: After all the above steps, the eVTOL performs the calculation of the differential positioning solution using the full-system observables.

[0209] The multi-frequency multi-system integrity monitoring system applicable to eVTOL in the embodiments of this application is based on the GNSS observation data of multi-frequency multi-systems, and jointly constructs an integrated eVTOL integrity monitoring system based on the integrity of the ground-based augmentation system of the GNSS signal receiving unit and the autonomous integrity monitoring of the eVTOL user unit. It can fill the gap in the current eVTOL integrity detection technology, further broaden the potential of applying redundant information for multi-frequency multi-system integrity monitoring, reduce the application cost of eVTOL integrity monitoring, and make in-depth use of the integrity monitoring information between the reference station and the service station.

[0210] In the description of the specification, claims and the above-mentioned drawings of the present application, the terms "comprising", "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices. The descriptions such as "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit that "first", "second" and "third" are of different types.

[0211] In the description of the embodiments of the present application, terms such as "exemplary", "for example" or "for instance" are used to indicate examples, illustrations or explanations. Any embodiment or design solution described as "exemplary", "for example" or "for instance" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary", "for example" or "for instance" is intended to present relevant concepts in a specific manner.

[0212] In the description of the embodiments of the present application, unless otherwise specified, " / " means "or". For example, A / B may represent A or B; "and / or" in the text is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality of" means two or more than two.

[0213] In some processes described in the embodiments of the present application, there are multiple operations or steps that appear in a specific order. However, it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or may be executed in parallel. The serial numbers of the operations are only used to distinguish different operations, and the serial numbers themselves do not represent any order of execution. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0214] Through the description of the above embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium as described above (such as ROM / RAM, magnetic disk, optical disc), and includes several instructions for causing a terminal device to execute the methods described in the various embodiments of the present application.

[0215] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present application.

Claims

1. A multi-frequency and multi-system integrity monitoring system suitable for eVTOL, characterized in that: The multi-frequency and multi-system integrity monitoring system suitable for eVTOL includes: multiple GNSS signal receiving units, communication links, a main control processing unit, and an eVTOL user unit; The GNSS signal receiving unit includes a GNSS antenna and a GNSS receiver, and supports GNSS signal observation of multiple satellite positioning systems and frequencies, and the GNSS signal receiving unit is used to receive GNSS observation information; The communication link is used to send the GNSS observation information received by each GNSS signal receiving unit to the main control processing unit; The main control processing unit is used to perform performance monitoring on the original observation value level of the GNSS observation information to obtain integrity monitoring information; The eVTOL user unit includes a GNSS antenna and a GNSS receiver, which supports at least one satellite positioning system and frequency point. The eVTOL user unit is used to receive GNSS observation information, differential correction signals and integrity monitoring information.

2. A multi-frequency and multi-system integrity monitoring system suitable for eVTOL according to claim 1, characterized in that: The main control processing unit performs performance monitoring on the original observation value level of the GNSS observation information, implements integrity monitoring processing, and obtains integrity monitoring information. The specific implementation steps include: Conduct signal quality monitoring, data quality monitoring and measurement quality monitoring on the GNSS observation information of the current satellite positioning system at the signal level; Enter the first stage of the monitoring logic and perform verification in three dimensions: multi-frequency, multi-satellite and multi-receiver. Enter the second stage processing logic of the execution monitor to perform multi-reference consistency verification, information domain pseudorange monitoring and mean-variance monitoring to obtain the integrity monitoring information of the current satellite positioning system corresponding to the GNSS observation information.

3. A multi-frequency and multi-system integrity monitoring system suitable for eVTOL as claimed in claim 2, characterized in that: The signal quality monitoring includes correlation peak symmetry monitoring, receiver signal strength monitoring and code carrier deviation monitoring; The data quality monitoring includes ephemeris-almanac monitoring, forward and backward ephemeris monitoring and inter-receiver ephemeris monitoring; The measurement quality monitoring includes lock time monitoring, CARST monitoring and CSC monitoring.

4. A multi-frequency and multi-system integrity monitoring system suitable for eVTOL as claimed in claim 3, characterized in that: The correlation peak symmetry monitoring is specifically as follows: based on the real-time observation data of the GNSS signal receiving unit, the GNSS observation information and navigation ephemeris data of the current satellite positioning system at the current moment are obtained, and the correlation peaks of the GNSS observation information and the navigation ephemeris data are extracted to perform symmetry detection; The receiver signal strength monitoring is specifically as follows: obtaining the receiver signal strength observed by the GNSS receiver on each satellite and each frequency point, and comparing it with the threshold value to realize the receiver signal strength detection; The code carrier deviation monitoring is specifically as follows: Obtain the pseudorange observations and carrier phase observations of the GNSS receiver on each satellite and each frequency point; The code carrier deviation at the current moment is calculated based on the geometric sliding average. Specifically, Among them, D m,n (k) represents the code carrier deviation at the current moment, τ d represents the geometric sliding average window width, T s represents the time interval, D m,n (k-1) represents the code carrier deviation at the previous moment, dz m,n (k) represents the original code carrier deviation value difference at the current moment.

5. The multi-frequency and multi-system integrity monitoring system for eVTOL according to claim 3, characterized in that: The ephemeris-almanac monitoring specifically includes: extracting the broadcast ephemeris file and the almanac file, comparing the orbits obtained by solving the broadcast ephemeris and the almanac, and making the comparison difference not exceed the difference limit; The monitoring of the preceding and following ephemeris specifically includes: performing orbit calculation on the preceding and following frame ephemeris, and comparing the calculated orbits, so that the comparison difference does not exceed the difference limit; The inter-receiver ephemeris monitoring specifically includes: performing orbit calculations on the ephemeris received by each GNSS receiver, and comparing the calculated orbits, so that the comparison difference does not exceed the difference limit.

6. A multi-frequency and multi-system integrity monitoring system suitable for eVTOL as claimed in claim 3, characterized in that: The lock time monitoring is specifically: performing lock time monitoring on the GNSS signal receiving unit to obtain the continuous observation duration of each satellite, and if the continuous observation duration is less than the specified observation time, it means that the current satellite is unavailable; The CARST monitoring is specifically as follows: Calculate the carrier phase observation, specifically, in, represents the carrier phase observation at the current moment, Represents the original carrier phase observation at the current moment, R m,n (k) represents the geometric observation distance at the current moment, τ m,n (k) represents the star clock correction value at the current time, Indicates the carrier phase correction at the initial moment; The influence of GNSS receiver clock error is removed by averaging, specifically: in, N represents the carrier phase observation after removing the GNSS receiver clock error. m Indicates the number of carrier phase corrections to be averaged. Indicates the carrier phase correction at the current moment; Get the carrier phase observation after removing the GNSS receiver clock error in the specified time window, and use the least squares method to perform second-order coefficient fitting on the carrier phase observation after removing the GNSS receiver clock error in the specified time window. Specifically: Among them, A, B, and C represent fitting coefficients, and t represents the variable; The CSC monitoring is specifically as follows: The monitored phase smoothing correction is defined as: Among them, Inno m,n (k) represents the phase smoothing stamping amount at the current moment, P m,n (k) represents the original pseudo-range observation value at the current moment, P s,m,n (k-1) represents the smoothed pseudorange observation value at the previous moment, represents the original carrier phase observation at the current moment, Represents the smoothed carrier phase observation value at the previous moment; Calculate the smoothed pseudorange, specifically, Among them, P s,m,n (k) represents the smoothed pseudorange at the current moment, N s Indicates the intermediate quantity, τ s represents the smoothing interval, T s Indicates a time interval.

7. The multi-frequency and multi-system integrity monitoring system for eVTOL according to claim 2, characterized in that: The multi-reference consistency check is specifically as follows: First, calculate the pseudorange correction after correcting the clock error, Among them, P sca,m,n (k) represents the pseudorange correction after clock error correction, P sc,m,n (k) represents the original pseudorange correction without clock error correction, N c (k) represents the number of satellites at the current moment, S c (k) represents the satellite set at the current moment, j represents different satellites, P sc,m,j (k) represents the pseudorange correction at the current moment; Accordingly, the phase correction after correcting the clock error is calculated in, It indicates the phase correction after the clock error correction. represents the raw carrier phase correction without corrected clock error, Indicates the carrier phase correction at the current moment; Calculate the B value: Among them, B ρ,m,n , Both represent B value, M n (k) represents the number of available reference stations at the current moment, S n (k) represents the set of reference stations available at the current moment, i represents different reference stations, m represents the total number of reference stations, P sca,i,n (k) represents the pseudorange correction after the corrected clock error of the i-th reference station, represents the phase correction after the corrected clock error of the i-th reference station, represents the original phase correction of the i-th reference station; Determine whether the B value exceeds the preset limit, if so, determine that the multi-reference consistency check fails; The mean-variance monitoring is to determine whether the error distribution of the B value can be broadcasted. pr_gnd Envelope, σ pr_gnd represents the standard deviation of the pseudorange correction error; The information domain pseudorange monitoring is to check whether the pseudorange correction number and the pseudorange correction number change rate meet the specified range constraints; The pseudorange correction number is calculated as follows: Among them, P corr,n (k) represents the pseudorange correction number at the current moment; The calculation method of the pseudorange correction rate of change is: Among them, T s Represents the time interval, R corr,n (k) represents the rate of change of pseudorange correction at the current moment, P corr,n (k-1) represents the pseudorange correction number at the previous moment.

8. The multi-frequency and multi-system integrity monitoring system for eVTOL according to claim 2, characterized in that: After the eVTOL user unit receives the integrity monitoring information, the processing of the integrity monitoring information specifically includes: Based on the Kalman filter that depends on the prior information and the least square solution that depends on the current time information, the parameter estimation cross-check is performed on the integrity monitoring information corresponding to the current satellite positioning system to obtain the test result; Cross-check the corresponding test results of each satellite positioning system to ensure the consistency of the satellite positioning system solution level.

9. A multi-frequency and multi-system integrity monitoring system suitable for eVTOL as claimed in claim 8, characterized in that: The Kalman filter based on the prior information and the least square solution based on the current time information is used to perform parameter estimation cross-check on the integrity monitoring information corresponding to the current satellite positioning system to obtain the test result, which specifically includes: The eVTOL user unit receives integrity monitoring information and differential corrections to perform differential positioning; Based on the Kalman filter that depends on the prior information, a Kalman filter positioning solution is obtained, and based on the least squares solution that depends on the current moment information, a least squares solution is obtained; The least squares solution and the Kalman filter positioning solution are compared. If the difference exceeds the specified limit, the current least squares solution and Kalman filter positioning solution are unavailable, thus obtaining a differential positioning result.

10. A multi-frequency and multi-system integrity monitoring system suitable for eVTOL according to claim 9, characterized in that: The cross-checking between the corresponding test results of each satellite positioning system to ensure the consistency of the satellite positioning system solution level specifically includes: Obtain the differential positioning results corresponding to each satellite positioning system; The positioning solution deviation value between the current satellite positioning system and other satellite positioning systems is calculated. If the calculated value is greater than the set threshold, it is determined that the differential positioning result of the current satellite positioning system is unavailable.

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