Hybrid filtering method for improving anti-interference performance of navigation positioning system

Abstract

The invention relates to a hybrid filtering method for improving the anti-interference performance of a navigation positioning system, and the method comprises the steps: designing a GPS detection threshold value by an operator at an offline stage; the designed GPS detection threshold value is configured to a customized configuration file; during actual flight, after the system receives the GPS data, online detection of the GPS data is executed according to set judgment logic, and abnormal GPS data is removed; wherein the GPS detection threshold is determined through comprehensive analysis according to flight envelope and big data statistics on the basis of civil aircraft types and flight stages applying a navigation positioning system.

Description

TECHNICAL FIELD

[0001] The present application relates to civil aircraft navigation positioning system, and particularly to a hybrid filtering method for improving the anti-interference performance of the navigation positioning system. BACKGROUND

[0002] With the deepening application of GPS in the field of civil aviation, the mainstream civil aircraft generally uses performance-based navigation (PBN) operation based on satellite navigation. PBN operation has the characteristics of high navigation accuracy and high flight path repeatability, which improves the air traffic control and operation efficiency of civil aviation.

[0003] However, in recent years, radio frequency interference (RFI) has become increasingly frequent due to various external factors. Specifically, false GPS signal interference affects the normal navigation function of civil aircraft, including the occurrence of GPS unavailability or GPS position jumping during en route, terminal area and other stages, which affects the safety and efficiency of civil aviation operation.

[0004] Therefore, with the increasing frequency of GPS interference problems, research on GPS anti-interference and outlier rejection technology has gradually become a hot topic. Specifically, solutions are proposed at the device level of the GPS receiver, such as the reference CN202010467307.8 "A high-precision anti-interference method and device based on interference bandwidth detection", the reference IN742CHE2011 "Anomaly value detection device, anomaly value detection method and anomaly value detection program for satellite positioning system, and GPS anomaly value rejection in downstream user systems using GPS data". For example, many references for vehicles (CN201710180088.3 "Filtering method and device for abnormal GPS data") and unmanned aerial vehicles (CN201510133960.X "GPS speed and position observation anomaly value detection method for unmanned aerial vehicles") also propose their own solutions to the GPS interference problem. Although the above solutions have certain migration possibilities in the field of civil aircraft, they cannot fully meet the needs of civil aviation navigation positioning systems for GPS anti-interference technology, and there are certain deficiencies in applicability and modification cost.

[0005] Specifically, the current research on GPS anti-interference technology for civil aviation navigation positioning systems mainly has the following problems: GPS anti-interference technology solutions are complex and diverse, and the cost of technology implementation and promotion is high; GPS interference technology is complex and variable, and continues to upgrade, posing challenges to the long cycle and complex process of civil aviation equipment development; the industry has not yet finalized relevant industry standards, resulting in delays in equipment development and certification progress, affecting on-board applications.

[0006] To solve the GPS interference problem, some industries try to identify and remove GPS interference signals by building a GPS signal monitoring network and using authorized signals. This solution requires the construction of a corresponding monitoring system, and the use of authorized signals increases the upgrade cost of the airborne GPS receiver. Some industries provide receivers with certain GPS anti-interference capabilities by upgrading GPS hardware devices only, but this also requires additional upgrade costs and cannot guarantee the same filtering capability for subsequent added interference signals, which is a problem of "one foot taller, one foot taller". Currently, industry standard specification documents have not yet proposed unified and mandatory requirements for the anti-interference capability of GPS airborne receivers / navigational systems, which also reflects the complex and diverse characteristics of GPS interference technology and its continuous evolution. Due to the lag in the release process of industry standards, it has caused great obstacles to the development and certification of major GPS receiver / navigational system manufacturers, leading to the continued occurrence of GPS interference problems for line aircraft.

[0007] Therefore, there is a need to provide a low-cost, simple and flexible solution to improve the anti-interference performance of the navigation and positioning system. SUMMARY

[0008] The hybrid filtering scheme for improving the anti-interference performance of the navigation and positioning system of the present application has strong implementation feasibility, can fully utilize the existing multi-sensor architecture on board, accurately identify the characteristics of GPS interference, and avoid misleading serious consequences of GPS interference on civil aircraft navigation, guidance and control. The existing civil aircraft navigation and positioning system has not yet introduced technical standards and specifications in the field of anti-GPS interference, but there are corresponding GPS interference operation risks in actual operation. The present application can alleviate the impact of GPS interference on civil aircraft navigation and positioning, and avoid false position and speed information caused by GPS interference as much as possible.

[0009] According to a first aspect of the present application, a hybrid filtering method for improving the anti-interference performance of a navigation and positioning system is provided, comprising:

[0010] In the offline phase, an operator designs a GPS detection threshold;

[0011] The designed GPS detection threshold is configured into a customer configuration file;

[0012] During actual flight, the system performs online detection of GPS data according to the set judgment logic after receiving the GPS data, and removes abnormal GPS data;

[0013] Wherein, based on the type of civil aircraft applying the navigation and positioning system and the flight phase, the GPS detection threshold is determined by comprehensive analysis according to the flight envelope and big data statistics.

[0014] This summary is provided to introduce some concepts of the following description in a simplified form. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to describe the manner in which the above-recited and other advantages and features of the application can be obtained, a more particular description of the application briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the application and are not therefore to be considered to be limiting of its scope, the application will be described and explained with additional specificity and detail by the use of the accompanying drawings in which:

[0016] Figure 1 A schematic flow chart of a hybrid filtering method for improving anti-jamming performance of a navigation positioning system is shown according to one embodiment of the present application.

[0017] Figure 2 A schematic diagram of GPS outlier detection threshold generation and judgment logic is shown according to one embodiment of the present application. DETAILED DESCRIPTION

[0018] The object of the present application is civil aircraft navigation positioning system. Compared with the traditional GPS anti-jamming technology through hardware upgrade and additional monitoring network, the present solution mainly starts from the PBN operation and the actual application level of civil aircraft navigation system, focuses on improving through software algorithm, and processes outliers of key signals (not GPS pseudorange, carrier phase measurement value) such as position and speed used by civil aircraft navigation guidance control backend, while fully utilizing the multi-source redundant navigation architecture of civil aircraft, introducing inertial navigation data auxiliary judgment to achieve the purpose of improving the anti-jamming performance of the navigation positioning system. Compared with traditional technology, the solution of the present application has stronger scene applicability, more flexible ability to change and upgrade configuration, and lower development cost.

[0019] Firstly, the present application realizes that the navigation sources that can jump include GPS receivers and GPS / INS combined navigation systems. The reason why GPS / INS combined navigation devices (such as inertial navigation devices that can provide Hybrid IRS signal output) are also included is that there is a possibility in technology that GPS interference can cause GPS processing devices in inertial navigation devices to jump, resulting in errors in the GPS / inertial hybrid positioning results output by the inertial navigation device. Therefore, GPS anti-jamming improvement is also needed for GPS / INS combined navigation systems.

[0020] In general, the present application is mainly divided into three steps: a) offline stage design of GPS detection threshold, b) configuration of GPS detection threshold to the customized configuration file, c) online detection of GPS data using the configured threshold and parameters, and when abnormal GPS data is detected, it is rejected, i.e. not using the GPS data source providing said GPS data.

[0021] It can be seen that the main innovations of the present application include: a scheme for improving the anti-interference performance of the navigation positioning system by removing GPS abnormal values based on flight envelope and big data statistical comprehensive analysis. Compared with the prior art, the present application has stronger pertinence for GPS abnormal value processing of the airborne navigation positioning system, and through analysis and screening of big data samples, it can cover the speed characteristics range of each flight phase in the existing running scene, the speed threshold based on the aircraft type enhances the applicability to the aircraft platform, and the use of speed auxiliary judgment of the difference between GPS positions before and after the time takes into account the detection of GPS position signal, and improves the reliability of detection. At the same time, the present application introduces inertial navigation signals for comparison, and proposes a GPS abnormal value detection method based on pure inertial position drift characteristics and speed measurement accuracy, making the whole detection method more comprehensive, and having strong innovation and comprehensiveness.

[0022] Around the improvement, the present application considers the existing typical navigation architecture of civil aviation aircraft, and proposes a complete set of implementation methods without the need for additional navigation equipment, as shown in Figure 1

[0023] In Figure 1 , a schematic flowchart of a hybrid filtering method for improving the anti-interference performance of the navigation positioning system according to an embodiment of the present application is disclosed. In this figure, the scheme of the present application is mainly described in the form of data and flow direction.

[0024] In step 1.1, in the offline stage, the operator (such as the aircraft designer) designs the GPS detection threshold.

[0025] First, in step 1.1.1, based on the type of civil aircraft applying the navigation positioning system and the flight phase, a method for determining the aircraft speed characteristic value (GPS detection threshold) according to the flight envelope and big data statistical comprehensive analysis is proposed, and the aircraft speed characteristic value is used as the GPS detection threshold for detecting GPS output signal abnormal values, therefore, in the following it is referred to as "GPS detection threshold". The specific design method includes the following five steps:

[0026] a) Calculate the aircraft altitude-velocity flight envelope, which involves the part of Mach number that needs to be converted into airspeed based on standard atmospheric conditions. This step mainly provides the theoretically achievable maximum airspeed range;

[0027] ​b) Obtain the corresponding approach speed of the ABCDE class (approach speed category) aircraft, which provides the lowest airspeed range that can be theoretically achieved;

[0028] c) Calculate the preliminary expected typical ground speed value set of each stage by statistically analyzing the typical wind speed of each stage of the flight and further calculating the airspeed information of the envelope boundary in step a. In theory, the maximum ground speed range (upper limit of the set) should be obtained by vector addition of the maximum airspeed range vector and the wind speed typical value vector. The minimum ground speed range should be obtained by vector addition of the minimum airspeed range vector and the wind speed typical value vector. However, in actual design, considering the direction of the above airspeed, wind speed and ground speed, independent bus parameters (corresponding to heading, wind direction and track angle) need to be introduced, and vector calculation requires more computing resources. After considering the calculation difficulty and the benefits brought by calculation, in actual execution, the maximum ground speed range is generally obtained by scalar addition of the maximum airspeed range and the wind speed typical value, while the minimum ground speed range (lower limit of the set) is generally obtained by scalar subtraction of the minimum airspeed range and the wind speed typical value, thereby simplifying the calculation and saving resources. These two ground speed ranges constitute the preliminary expected typical ground speed value set of each stage, which is used in the next step to combine the statistical analysis of the flight data and to further adjust to finally determine the GPS detection threshold.

[0029] d) Obtain the typical ground speed value provided by the flight data of each stage of the flight by statistically analyzing the flight data of each stage of the flight, including first obtaining the speed components of the aircraft in the take-off, climb, cruise, descent and approach stages, including the east-west direction speed component Vew and the north-south direction speed component Vns, and then obtaining the typical ground speed value of the flight statistics by squaring and taking the square root of the speed components Vew and Vns.

[0030] In some other embodiments, non-representative working condition points such as temporary flight around military control appearing in specific samples are removed, which can be achieved by setting a screening condition, for example, removing the flight stage data of the HDG mode and only adopting the data samples in the LNAV mode to avoid the interference of special cases.

[0031] e) Adjust and generate an updated expected typical ground speed value set by analyzing whether the preliminary expected typical ground speed value set of each stage given in step c can cover the typical ground speed value of the corresponding stage based on the flight data of the flight statistics in step d. The updated expected typical ground speed value set is used as the GPS detection threshold.

[0032] If there is a part that cannot be covered, the preliminary expected typical ground speed value set of the stage should be adjusted to cover the typical ground speed value of the flight statistics.

[0033] If the preliminary expected typical ground speed value set for this phase needs to be adjusted.

[0034] In addition, in some preferred embodiments, if for a specific operating scenario and route (such as a route that often suffers from GPS interference), the GPS detection threshold can be appropriately tightened according to the operating scenario requirements.

[0035] The above adjustment requirements can be achieved by iteratively adjusting the amplification coefficients K and P. The amplification coefficient K is mainly used to adjust the maximum ground speed range of the preliminary expected typical ground speed value set in step c to generate the upper threshold speed Vup of the GPS detection threshold, and the amplification coefficient P is mainly used to adjust the minimum ground speed range of the preliminary expected typical ground speed value set in step c to generate the lower threshold speed Vlo of the GPS detection threshold.

[0036] The specific definitions of Vup and Vlo are as follows:

[0037] 1) Remove the too large GPS speed abnormal value based on the speed characteristics of each phase of the aircraft, that is, define the upper threshold speed Vup = K x V, where V is the result of squaring and taking the square root of the typical speed components Vew and Vns in two directions of the typical ground speed values counted in step d, that is, K is a comprehensive amplification coefficient considering the flight envelope and the statistical value of the route wind speed, which can be defined as a value greater than 1 according to the use scenario and equipment accuracy.

[0038] Example 1: Assuming that for a certain type of aircraft, the upper limit (maximum ground speed range) of the preliminary expected typical ground speed value set of the cruise phase obtained in step c is 350 kt. In step d, the typical ground speed components of a certain route cruise phase are Vew = 370 kt and Vns = 0, so the typical ground speed V of this route is 370 kt (squaring and taking the square root of Vew and Vns). At this time, the preliminary expected typical ground speed value set cannot cover the typical ground speed value of this specific route (the upper limit of the set (350 kt) < the typical ground speed V (370 kt)), so the upper limit of the preliminary expected typical ground speed value set of the cruise phase of this route needs to be amplified to cover the typical ground speed value V (370 kt) counted by the route. On this basis, considering that there is a certain error in GPS speed measurement, it is recommended to use Vup = K x V = 1.1 x 370 kt = 407 kt as the upper threshold speed Vup of the updated expected typical ground speed value set of the cruise phase (i.e. the upper limit of the GPS detection threshold), where K = 1.1 considers that there may be a certain error in GPS speed measurement. Compared with K = 1.1 for the cruise phase, K value can be set to 1.05 when approaching the terminal area, which means that the approach phase tolerates lower GPS error and needs to set a more stringent threshold.

[0039] 2) Eliminate too small GPS speed outliers based on aircraft type. That is, define a threshold speed lower limit Vlo = P x Vat, where Vat is the lower limit of the preliminary expected typical ground speed value set, which is calculated as the maximum indicated airspeed allowed for the aircraft type during approach to the threshold of the runway minus the statistical typical wind speed along the route, and P is a magnification factor defined considering the flight envelope and statistical wind speed along the route, the conversion between indicated airspeed and ground speed, the usage scenario, and the accuracy of the equipment.

[0040] Example 2: Assume a certain D-class aircraft, the lower limit of the preliminary expected typical ground speed value set (the minimum ground speed range) obtained in step c is 150 kt, when applying this speed lower limit to the GPS speed detection during the cruise phase of a certain international route, considering the high possibility of GPS interference when crossing the national boundary, which leads to a large GPS speed error, so set P = 1.5, and the lower limit of the updated expected typical ground speed value set of this cruise phase (i.e. the lower limit of the GPS detection threshold) is: Vlo = Px Vat = 1.5 x 150 kt = 225 kt.

[0041] Compared with this, for domestic routes in the East China region where civil airports are densely covered, the risk of GPS interference is low, so P = 1.2 can be set to relax the detection of GPS ground speed during the cruise phase, and the threshold lower limit should be 1.5 x 150 kt = 180 kt. In addition, the East China region is a plain, so if you need to configure the lower limit of the cruise GPS detection threshold for highland routes, assume that the possibility of GPS interference for highland routes is the same as that for the East China region, but since the cruise altitude of highland routes is higher, the ground speed converted from the same approach speed of the same aircraft type is larger, that is, the reasonable GPS ground speed lower limit value is increased, so P = 1.3 can be set, and 1.3 x 150 kt = 195 kt is obtained as the GPS ground speed detection threshold lower limit for highland routes. Similarly, the upper limit of the GPS ground speed detection threshold can also be adjusted according to the altitude, which will not be repeated here.

[0042] It should be understood that although the values of K and P are set considering various factors, in some scenarios, one iteration adjustment may still not be able to make the expected typical ground speed value set cover the typical ground speed values of the route statistics. Therefore, multiple iteration adjustments based on the magnification factors K and P may be required to obtain an updated expected typical ground speed value set covering the typical ground speed values of the route statistics as the GPS detection threshold.

[0043] Subsequently, step 1.1.2 designs an auxiliary GPS detection threshold based on the redundant information provided by the existing navigation architecture of the civil aircraft (such as pure inertial data) on the basis of step 1.1.1.

[0044] The present application recognizes that the inertial data calculated by the inertial navigation device without the GPS combination can be used as a reference to assist in determining whether there is a jump in the GPS.

[0045] Specifically, for the aircraft equipped with the inertial reference device, the method proposed in this step can be used to further design the auxiliary GPS detection threshold. If not equipped with the inertial reference device, the auxiliary GPS detection threshold based on the inertial navigation comparison can not be designed. This auxiliary GPS detection threshold is independent of the GPS detection threshold generated in step 1.1.1 and does not affect each other.

[0046] Specifically, the auxiliary GPS detection threshold includes four thresholds, Threshold1 to Threshold4, namely:

[0047] a) Threshold1: GPS east-west direction velocity component comparison threshold with inertial navigation east-west direction velocity component:

[0048] Threshold1=amplification factor k1x(GPS east-west speed accuracy+IRS east-west speed accuracy);

[0049] b) Threshold2: GPS north-south direction velocity component comparison threshold with inertial navigation north-south direction velocity component:

[0050] Threshold2=amplification factor k2x(GPS north-south speed accuracy+IRS north-south speed accuracy);

[0051] c) Threshold3: GPS vertical direction velocity component comparison threshold with inertial navigation vertical direction velocity component:

[0052] Threshold3=amplification factor k3x(GPS vertical speed accuracy+IRS vertical speed accuracy);

[0053] Wherein, Threshold1, Threshold2 and Threshold3 can be obtained by adding the speed accuracy index in the GPS receiver device manual and the IRS device manual and then multiplying an amplification factor to obtain the final corresponding Threshold. Considering that the measurement accuracy of the GPS vertical direction is not as high as the horizontal accuracy, Threshold3 should be greater than or equal to Threshold1 and Threshold2.

[0054] The amplification factors k1, k2, and k3 can be appropriately relaxed and tightened according to the degree of tolerance of GPS interference, the frequency of GPS interference problems, and other factors in the running scene. The larger the threshold value, the more tolerant of GPS abnormal values, and vice versa, the more stringent the GPS abnormal value detection.

[0055] For example, the east-west speed measurement accuracy of a certain model of aircraft GPS device is 4 m / s, and the east-west speed measurement accuracy of the IRS is 2 m / s, Threshold1 = amplification factor k1 x (2 m / s + 4 m / s). According to the flight phase, the takeoff and approach require high accuracy of GPS, and the tolerance of GPS abnormal value is low, so the amplification factor k1 = 1, and Threshold1 = 6 m / s. For the cruise phase, the accuracy requirement of GPS is relatively low, and the amplification factor k1 can be set to 1.5, and Threshold1 = 9 m / s. The remaining north-south direction and vertical direction speed threshold values can be obtained in the same way.

[0056] d) Threshold4: GPS position and inertial navigation position comparison threshold.

[0057] Considering that the pure inertial data is not updated externally after ground calibration, this characteristic of not being updated externally reduces the accuracy of the inertial navigation data to some extent, but at the same time avoids the influence of position jump caused by GPS interference. For inertial navigation devices with different accuracy divergence characteristics, different comparison thresholds can be set. Specifically, a GPS position and inertial navigation position comparison threshold Threshold4 is proposed:

[0058] Threshold 4 = GPS POS Error + drift rate x Time + RNP;

[0059] Wherein, GPS POS Error (GPS position error) can use the positioning accuracy promised in the GPS device manual or directly use a fixed value of 36 m; drift rate can refer to the position drift characteristics in the inertial navigation device manual. These two parameters need to be determined in the offline threshold design stage, and can be pre-configured into the customer configuration file according to the characteristics of the existing navigation equipment of the aircraft.

[0060] Time is the flight time since the last calibration, provided by the inertial navigation device; RNP is the RNP accuracy value of the current route, which can be read from the navigation database or use the default value (0.3 NM for approach phase, 1 NM for terminal area, and 2 NM for route). These two parameters are applied in the real-time online detection link, which is used to support online calculation and detection application of Threshold4. Among them, RNP represents the allowed accuracy level of the current route. Introducing RNP value as the detection threshold of the difference between GPS and inertial navigation position is an innovation of the present application, which takes into account that different flight phases have different tolerance levels for GPS abnormalities, that is, the lower the RNP value, the more critical the flight phase, the lower the tolerance of GPS abnormal value, and the lower the GPS detection threshold, and vice versa.

[0061] As mentioned above, the consideration of the GPS detection threshold design method in step 1.1.1 is mainly that when GPS interference occurs, the interference signal can cause the GPS receiver to calculate the wrong latitude and longitude and ground speed (north-south and east-west speed components). Regardless of whether GPS interference occurs, the current aircraft body speed relative to the atmosphere, i.e. airspeed, will not exceed the aircraft design flight envelope. Based on this, it is proposed to judge whether the latitude and longitude and ground speed information of the GPS measurement is reasonable for the aircraft in this scenario based on the flight envelope. However, the definition of the aircraft flight envelope uses airspeed, and there is a certain conversion and calculation relationship between airspeed and ground speed. The indicated airspeed at a certain height defined by the aircraft flight envelope needs to be converted to true airspeed, and then the vector sum of the true airspeed and the wind speed is the ground speed of the aircraft.

[0062] For example, for example, a certain aircraft flight envelope is defined at 30000ft height and can cruise at 300kt indicated airspeed at the fastest, considering a certain temperature condition after conversion, it corresponds to 460kt true airspeed. Even considering a certain maximum wind speed condition (for example, 100kt at 30000ft), the GPS measured ground speed should not exceed 460kt+100kt=560kt. If it exceeds this value, it is considered that the GPS measurement signal is not accurate under this condition. This method correlates and compares the motion characteristics of the aircraft body with the GPS measured ground speed value.

[0063] On this basis, the threshold is also allowed to be adjusted, i.e. controlled by using amplification coefficients K and P, and as mentioned above, the amplification coefficients are related to the GPS abnormal value tolerance degree of the current flight phase and the frequency of GPS interference, allowing for customized configuration and adjustment.

[0064] In addition, regardless of whether GPS interference occurs, the pure inertial position and speed information output by the inertial navigation device is not affected by GPS interference and can also be used as a reference for detection and comparison. Accordingly, the application further proposes the processing process in step 1.1.2.

[0065] It should be understood that the GPS detection threshold designed in step 1.1.1 and the auxiliary GPS detection threshold designed in step 1.1.2 are two independent sets of thresholds for different detection judgment logic, and do not affect each other.

[0066] It should also be understood that the step 1.1.2 of designing the auxiliary GPS detection threshold is an optional step and is not necessary. If the aircraft platform itself has an inertial navigation device, this step can be selected. If the aircraft platform does not have an inertial navigation device, this step and the subsequent 1.3.2 logic judgment part are ignored. In the following embodiments, the scheme including step 1.1.2 is described.

[0067] When the GPS detection threshold (and the auxiliary GPS detection threshold) is designed in step 1.1, the flow enters step 1.2.

[0068] In step 1.2, the designed GPS detection threshold (and the auxiliary GPS detection threshold if step 1.1.2 is performed) is configured to the customized configuration file, that is, the GPS detection threshold is customized and configured. The designed threshold and detection information in step 1.1 is customized for different application scenarios of the aircraft / fleet to improve the detection efficiency.

[0069] The designed threshold and detection information includes the Vup and Vlo finally determined in step 1.1.1, and the Threshold1-3 required for detecting GPS abnormal values based on the inertial navigation comparison and the drift rate required for calculating Threshold4 in step 1.1.2.

[0070] Customization refers to the fact that special airworthiness certification procedures are required due to changes in aviation software. Therefore, if the GPS detection threshold mentioned in this application is directly designed and coded in the code of a detection software, it is more troublesome to change the GPS detection threshold for different aircrafts and routes, and each change requires airworthiness certification. Therefore, the conventional practice is to separate the code and the configurable parameters, make the parameters into a configuration file (which can be understood as a data table) for the software code to read, and then perform logical processing by the software. In this way, different parameters can be easily configured. This is the customization.

[0071] In summary, the customization is a file used to control whether the aircraft option function / device is activated, such as a function of a certain type of aircraft as an option, that is, there are two types of aircraft, A type aircraft with a function, and B type aircraft without a function. For the customization file, a control item is designed, which is set to 0 when the aircraft does not have the a function, and is set to 1 when the aircraft has the a function. The customization file records and controls the configuration information of whether the option function is activated and used on the aircraft. Adjusting the GPS detection threshold using the customization file can simplify the change process, eliminate the need for airworthiness certification, and provide great flexibility.

[0072] Subsequently, in step 1.3, during actual flight (at this time the system has loaded the customization), after receiving GPS data from the GPS data source, online detection of GPS data is performed according to the set judgment logic to eliminate possible abnormal GPS data.

[0073] It should be understood that the receiving GPS data and performing GPS data online detection operation is continuously performed in each flight phase, not just once. And each time the GPS data online detection operation is performed, if one or more of the following judgment logic conditions is GPS jump, the system no longer uses the GPS data of the GPS data source, but if none of the judgment logic conditions detects GPS jump during the next GPS data online detection operation, the system resumes using the GPS data of the GPS data source. Considering the processing capacity, resource efficiency and safety requirements of the system, it is generally recommended that the time interval of each GPS data online detection operation be 1s. Of course, it can also be adjusted according to the actual application requirements.

[0074] In Figure 2 The GPS anomaly value detection threshold generation and judgment logic diagram according to one embodiment of the present application is shown in FIG. 1.3.1. As shown in the figure, the judgment logic flow of the present application can be divided into two parts: 1.3.1 and 1.3.2.

[0075] Figure 1 The following six judgment logic conditions of the online detection shown in FIG. 1.3.1 involve the calculation of some thresholds, such as Vup and Vlo. In the scheme of the present application, these thresholds used in the judgment have been calculated offline (in step 1.1) before the judgment flow is executed. Moreover, the execution of the six judgment logic conditions is independent of each other.

[0076] First, let's look at the judgment logic in part 1.3.1, which is based on comparing the GPS data with the GPS detection threshold determined in step 1.1.1.

[0077] In step 1.3.1.1, the GPS speed in the received GPS data is compared with the threshold speed upper limit Vup in the GPS detection threshold corresponding to the flight phase: if the GPS speed is greater than Vup, it is considered that GPS jump occurs, and the GPS data source providing the GPS data is no longer used.

[0078] The judgment principle is that the updated expected threshold speed upper limit Vup represents the maximum reasonable GPS ground speed value that the detection algorithm considers possible to appear, and if the received GPS ground speed value exceeds the Vup, it is considered that the GPS signal is not reliable and needs to be removed.

[0079] In step 1.3.1.2, the GPS speed in the received GPS data is compared with the threshold speed lower limit Vlo in the GPS detection threshold corresponding to the flight phase: if both horizontal components (Vew, Vns) of the GPS speed are less than Vlo xsin 45°, it is considered that GPS jump occurs, and the GPS data source providing the GPS data is no longer used.

[0080] The judgment principle is that the lower limit of the expected threshold speed Vlo after updating represents the minimum reasonable GPS ground speed value that the detection algorithm considers possible to occur. If both horizontal components (Vew, Vns) of the received GPS ground speed are less than Vlo x sin45°, the GPS horizontal combined ground speed value obtained by combining the two horizontal directions will also be less than 1 x Vlo, that is, it is considered that the received GPS horizontal ground speed is too low and not reliable, and needs to be removed.

[0081] In step 1.3.1.3 (including two judgment logic conditions), based on the GPS positions before and after the time, the speed auxiliary estimation is used to judge the GPS position abnormal value. Assuming that the received GPS longitude and latitude position at time k is X(k), the received GPS longitude and latitude position at the previous time is represented as X(k-1). Define △X as the distance from X(k-1) to X(k). Among them, the most commonly used method to calculate the distance △X between two longitude and latitude points is the Haversine formula. It can very accurately calculate the spherical distance between two points on the earth's surface.

[0082] If any of the following conditions is met, it is judged that the GPS position data jumps and the GPS data source providing the GPS data is no longer used:

[0083] a)△X> △t x Vup;

[0084] b)△X< △t x Vlo;

[0085] Where △t is the time interval from time k-1 to time k, as described above, it is recommended to be 1s.

[0086] The judgment principle is that since GPS also synchronously outputs position information, the GPS detection threshold determined in step 1.1.1 can be used to predict the maximum and minimum position changes within two sampling time intervals (for example, the time interval △t from time k-1 to time k) to detect the difference between the GPS positions received at the two times. Once the GPS position difference is calculated, if it is higher than the expected maximum position change (△t x Vup) or lower than the expected minimum position change (△t x Vlo), it is considered that the GPS position information change is not reliable and needs to be removed, that is, the GPS data source providing the GPS position is no longer used.

[0087] For example, assume cruise phase Vup is set to 420 kt, and a certain category D aircraft has Vlo of 150 kt, the received GPS data rate is 1 Hz, and the detection calculation frequency is 1 Hz, then the GPS position before and after the time should not exceed 420 kt x 1 h / 3600 = 0.11667 NM, nor be less than 150 kt x 1 h / 3600 = 0.041667 NM. Otherwise, it is considered that the GPS is abnormal.

[0088] Next, see the judgment logic in section 1.3.2, which is based on the auxiliary GPS detection threshold (Threshold1-4) determined in step 1.1.2 and the configuration information to compare the GPS data.

[0089] In step 1.3.2.1, the accuracy of the inertial navigation system speed is used to judge the abnormal value of the GPS data. That is, the speed components output by the GPS and the speed components of the inertial navigation device are compared respectively, and if any of the following conditions is met, it is judged that the GPS position data jumps and the GPS data source providing the GPS position is no longer used:

[0090] a) |(GPS N-S speed - IRS N-S speed)| > Threshold1;

[0091] b) |(GPS E-W speed - IRS E-W speed)| > Threshold2;

[0092] c) |(GPS vertical speed - IRS vertical speed)| > Threshold3.

[0093] The judgment principle is: the pure inertial position output by the inertial navigation device has certain drift characteristics, but is not affected by the abnormal value of the GPS. The pure inertial position output value is used to add the position drift error over time, and then the flight accuracy requirement RNP of the current flight phase is used to jointly form the judgment threshold (Threshold1-3 described in step 1.1.2). If the difference between the GPS position and the pure inertial position exceeds the threshold, it is considered that the current GPS position deviates beyond the maximum tolerance of the current flight phase, and the GPS position is not reliable and needs to be removed.

[0094] For example, for a certain aircraft, the horizontal speed threshold after comprehensive consideration is 5 kt, and the vertical speed threshold is 8 kt, then the absolute value of the difference between the GPS speed components in the east, north and vertical directions and the inertial navigation speed components should not exceed the respective thresholds, otherwise it is considered that the GPS is abnormal.

[0095] In step 1.3.2.2, the abnormal value of GPS data is judged based on the inertial navigation position drift characteristics. That is, the GPS position is compared with the inertial navigation position, and if the following conditions are met, it is judged that the GPS position data jumps and the GPS data source providing the GPS position is no longer used:

[0096] GPS position - IRS position > Threshold 4.

[0097] The judgment principle is that the pure inertial velocity measurement value is not interfered by GPS and has accurate measurement accuracy. At the same time, the velocity measurement accuracy indexes of the GPS receiver and the inertial navigation equipment are considered, and the judgment threshold (Threshold 4 described in step 1.1.2) is designed based on the sum of the velocity measurement accuracy of the two devices. When the difference between the GPS velocity and the inertial navigation velocity exceeds the threshold, it is considered that the GPS velocity measurement is inaccurate and needs to be eliminated.

[0098] For example, assuming that the position drift accuracy of a certain inertial navigation equipment can be maintained at 2NM / h within a certain time, and the aircraft has flown for 1h after self-calibration and is in the cruising stage, the threshold value that the GPS position and the pure inertial position output by the IRS should not exceed is 36 / 1852 NM + 2NM / h x 1h + 2NM = 4.02NM. Otherwise, it is considered that the GPS is abnormal.

[0099] Of course, as mentioned earlier, if the aircraft platform does not install an inertial navigation equipment, the determination of the auxiliary GPS detection threshold in step 1.1.2 and the corresponding logic judgment in part 1.3.2 are ignored.

[0100] If all the logic judgments in 1.3.1 and 1.3.2 do not meet the conditions, it can be considered that the GPS is working normally, and the system uses the GPS data.

[0101] In summary, the scheme of the present application has the following advantages:

[0102] 1) A GPS abnormal value detection method considering the flight envelope of the aircraft and big data analysis and statistics is designed, which improves the robustness of the aircraft navigation and positioning system function, improves flight safety, and improves the availability and integrity of the system;

[0103] 2) The civil aviation aircraft navigation sensor redundancy architecture is used, and pure inertial signals are introduced for multi-dimensional comparison and detection, which enhances the detection efficiency;

[0104] 3) The scheme of the present application can be realized by pure software change, and the detection threshold can be customized and changed based on different actual application scenarios and carriers. The cost is lower than that of hardware equipment upgrade, the configuration is flexible, the implementability is high, and the economy is high.

[0105] Although the techniques have been described in language specific to structural features and / or methodological acts, it is to be understood that the appended claims are not necessarily limited to the features or acts described. Rather, the features and acts are described as example implementations for implementing the techniques.

[0106] The operations of example processes are illustrated in individual blocks and summarized with reference to those blocks. The processes are illustrated as logical flow graphs, each operation of which can represent one or more operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the operations represent computer-executable instructions stored on one or more computer-readable media that, when executed by one or more processors, enable the one or more processors to perform the recited operations. Generally, computer-executable instructions include routines, programs, objects, modules, components, data structures, and the like that perform particular functions or implement particular abstract data types. The order in which the operations are described is not intended to be construed as a limitation, and any number of the described operations can be executed in any order, combined in any order, subdivided into multiple sub-operations, and / or executed in parallel to implement the described processes. The described processes can be performed by resources associated with one or more computing devices, such as one or more internal or external CPUs or GPUs, and / or one or more segments of hardware logic, such as FPGAs, DSPs, or other types of accelerators.

[0107] All of the methods and processes described above can be embodied in, and fully automated via, software code modules executed by one or more general purpose computers or processors. The code modules can be stored in any type of computer-readable storage medium or other computer storage device. Some or all of the methods can alternatively be embodied in specialized computer hardware.

[0108] Any routine descriptions, elements or blocks in the flow diagrams described herein and / or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code that include one or more executable instructions for implementing specific logical functions or elements in the routine. Alternate implementations are included within the scope of the examples described herein in which elements or functions can be deleted, or implemented in differing orders or in substantially simultaneous fashion, depending on the functionality involved, as would be understood by one skilled in the art.

[0109] While the foregoing describes different embodiments, it will be appreciated that they are presented as examples only and not limitation. As such, those skilled in the art will appreciate that changes can be made in form and detail without departing from the spirit and scope of the application as defined by the appended claims. Accordingly, the breadth and scope of the application disclosed herein should not be limited by any of the above-described exemplary embodiments, but should be defined in accordance with the following claims and their equivalents.

Claims

1. A hybrid filtering method for improving the anti-interference performance of a navigation and positioning system, comprising: During the offline phase, operators design GPS detection thresholds; Configure the designed GPS detection threshold into the customized configuration file; During actual flight, after receiving GPS data, the system performs online GPS data detection according to the set judgment logic and eliminates abnormal GPS data; Among them, based on the type of civil aircraft and the flight stage of the application navigation and positioning system, the GPS detection threshold is determined through comprehensive analysis of the flight envelope and big data statistics.

2. The hybrid filtering method as described in claim 1, characterized in that, The steps for determining the GPS detection threshold based on the type of civil aircraft and flight phase using the application navigation and positioning system, through comprehensive analysis of the flight envelope and big data statistics, include: a) Calculate the aircraft's altitude-velocity flight envelope; b) Obtain the corresponding approach speeds for aircraft of various approach speed categories; c) Analyze typical wind speed values ​​for each stage of flight using big data statistics, and calculate them with the airspeed information at the envelope boundary in step a to obtain a preliminary set of typical ground speed values ​​for each flight stage; d) Typical ground speed values ​​provided by statistical analysis of flight data for each flight phase of the route using big data; e) By analyzing and confirming whether the preliminary expected typical ground speed value set for each flight stage given in step c covers the typical ground speed value given based on flight data for the corresponding flight stage as statistically analyzed in step d, an updated expected typical ground speed value set is generated as the GPS detection threshold.

3. The hybrid filtering method as described in claim 2, characterized in that, The adjustment is achieved by iteratively adjusting the amplification coefficients K and P, wherein the amplification coefficient K is used to adjust the maximum ground speed range of the typical ground speed value set in step c to generate the upper threshold speed Vup, and the amplification coefficient P is used to adjust the minimum ground speed range of the typical ground speed value set in step c to generate the lower threshold speed Vlo.

4. The hybrid filtering method as described in claim 3, characterized in that, 1) Use the following formula to eliminate excessively large GPS speed anomalies based on the aircraft's speed characteristics at each stage of flight: Vup = K x V; Wherein, Vup is the upper limit of the threshold speed of the GPS detection threshold, K is the amplification factor used to adjust the maximum ground speed range of the typical ground speed value set in step c, and V is the result of taking the square root of the sum of the squares of the typical speed component values ​​Vew and Vns in two directions of the typical ground speed values ​​statistically obtained in step d. 2) Use the following formula to remove excessively small GPS speed outliers based on aircraft type: Vlo = P x Vat; Wherein, Vlo is the lower limit of the threshold speed of the GPS detection threshold, P is the amplification factor used to adjust the minimum ground speed range of the typical ground speed value set in step c, and Vat is the lower limit of the initially expected typical ground speed value set.

5. The hybrid filtering method as described in claim 4, characterized in that, The steps for operators to design GPS detection thresholds also include: designing auxiliary GPS detection thresholds using redundant information provided by the existing navigation architecture of civil aircraft.

6. The hybrid filtering method as described in claim 5, characterized in that, The auxiliary GPS detection thresholds include: - Threshold1: Threshold for comparing the east-west velocity components of GPS and inertial navigation systems. Threshold1 = Amplification factor k1 x (GPS speed measurement accuracy + IRS speed measurement accuracy). - Threshold2: Threshold for comparing the north-south velocity components of GPS and inertial navigation systems. Threshold2 = Amplification factor k2 x (GPS north-south speed measurement accuracy + IRS north-south speed measurement accuracy). - Threshold3: Threshold for comparing GPS vertical velocity components with inertial navigation vertical velocity components: Threshold3 = magnification factor k3 × (GPS vertical velocity measurement accuracy + IRS vertical velocity measurement accuracy). - Threshold4: Threshold for comparing GPS position with inertial navigation position: Threshold 4 = GPS POS Error + drift rate x Time + RNP; The amplification factors k1, k2, and k3 are set according to the tolerance of the operating scenario to the degree of GPS interference and the frequency of GPS interference problems. Among them, GPS POS Error uses the positioning accuracy promised in the GPS device manual or directly uses a fixed value of 36m; drift rate refers to the position drift characteristics in the inertial navigation device manual; Time is the flight time since the most recent calibration, provided by the inertial navigation device; RNP is the RNP accuracy value used for the current route, which is read from the navigation database or uses the default value.

7. The hybrid filtering method as described in claim 5, characterized in that, The redundant information is pure inertial data from an inertial reference device.

8. The hybrid filtering method as described in claim 4, characterized in that, The judgment logic process includes comparing GPS data based on the GPS detection threshold, including: 1) Compare the GPS speed in the received GPS data with the upper limit of the threshold speed Vup in the GPS detection threshold for the corresponding flight phase. If the GPS speed is greater than Vup, it is considered that a GPS jump has occurred, and the GPS data source providing the GPS data is no longer used. 2) Compare the GPS speed in the received GPS data with the lower limit of the threshold speed Vlo in the GPS detection threshold of the corresponding flight phase. If both horizontal components of the GPS speed, Vew and Vns, are less than Vlo xsin 45°, then the GPS is considered to have jumped, and the GPS data source providing the GPS data is no longer used. 3) If any of the following conditions are met, the GPS location data is considered to have changed, and the GPS data source providing the GPS data is no longer used: a) △X > △tx Vup; b) △X < △tx Vlo; Where △t is the time interval from time k-1 to time k, and △X is the distance from the GPS latitude and longitude position received at time one to the GPS latitude and longitude position received at the previous time. Where Vew is the east-west velocity component of the GPS velocity, and Vns is the north-south velocity component of the GPS velocity.

9. The hybrid filtering method as described in claim 6, characterized in that, The judgment logic process also includes comparing GPS data based on the auxiliary GPS detection threshold and configuration information: 1) By comparing the velocity components output by GPS with those of the inertial navigation system, if any of the following conditions are met, it is determined that the GPS position data has changed, and the GPS data source providing the GPS data is no longer used: |(GPS NS speed – IRS NS speed)|>Threshold1; |(GPS EW speed – IRS EW speed)| > Threshold2; |(GPS Vertical Velocity – IRS Vertical Velocity)| >Threshold3; 2) Compare the GPS position with the inertial navigation position. If the following conditions are met, determine that the GPS position data has changed and stop using the GPS data: GPS location – IRS location > Threshold 4.

10. The hybrid filtering method as described in claim 1, characterized in that, The hybrid filtering method is continuously performed during each flight phase. Each time the GPS data online detection operation is performed, if the abnormal GPS data is to be removed according to the set judgment logic, the system will no longer use the GPS data source that provides the GPS data. However, if the GPS jump is not detected according to the set judgment logic during the next GPS data online detection operation, the GPS data source that provides the GPS data will be used again.

Images