Data link relative navigation information fusion method and device

Abstract

The invention discloses a data chain relative navigation information fusion method and device, and the method comprises the steps: firstly building a relative navigation information fusion state equation according to input information, and then building a relative navigation information fusion measurement equation according to the input information to guarantee a relative space-time reference under a satellite navigation denial condition; based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation, selecting a corresponding Kalman filter according to the measurement information to carry out relative navigation information fusion so as to obtain a navigation result, and correcting a navigation error state according to the measurement information after a round of state estimation of relative navigation information fusion is completed. And the corrected relative positioning result is reported to the airborne avionics system. Different types of measurement information are fused, and the information is optimally fused by using a Kalman filter, so that the precision and reliability of relative positioning are improved, the measurement information is quickly processed in a real-time environment, and the robustness and stability of the system are kept by correcting a navigation error state.

Description

Technical Field

[0001] The present application relates to the field of avionics communication technology, and in particular to a method and device for fusing relative navigation information of a data link. Background Art

[0002] With the continuous progress and improvement of information technology, data link plays the role of central nervous system in related fields with its powerful information support capability, and is favored by providing real-time situation sharing and efficient collaboration capabilities. Data link is a data communication system that links various operating platforms according to a unified message format and communication protocol and exchanges key information. Its functions are not limited to the interaction between platforms, but also include voice and data communication, status monitoring, image and other information sharing between different systems.

[0003] The relative position relationship between members is one of the most critical information in collaborative tasks. When external navigation is available, the relative position between groups is usually obtained by distributing positioning information through data links. However, due to the limitations of external signals, it is easily affected in complex electromagnetic environments, making it difficult to ensure the accuracy of the time and space benchmark based on traditional positioning information. To solve this problem, combining the characteristics of platform sensors and building a positioning method through collaborative measurement capabilities has become an effective solution. This technology is based on precise time synchronization of the network, allowing each member to measure each other and obtain relative position data using the principle of geometric positioning. In addition, each member in the system can not only complete its own positioning, but also share relevant data with other members in the entire network to ensure information exchange.

[0004] In order to improve the accuracy and reliability of positioning results, multi-source information fusion is usually used to achieve combined positioning. This method integrates multi-dimensional information (such as distance, motion status, altitude data) to solve the position in the relative coordinate system, aiming to build a local space-time benchmark and output coordinate parameters.

[0005] The relative navigation technology based on data link is mainly divided into two systems: relative navigation based on state sharing and relative navigation based on measurement sharing. The two are distinguished according to the different shared core navigation information. The scheme based on state sharing requires less communication volume but has relatively low navigation accuracy; while the scheme based on measurement sharing can achieve higher positioning accuracy, but requires more communication resources and has limited versatility. In the current relative navigation information fusion algorithm, each member only models its own absolute navigation error and fuses the received state estimation pseudorange measurement to correct its own navigation error, but this may lead to unstable or even divergent estimates, and overconfidence in ignoring source errors, which is not conducive to the rapid recovery of absolute navigation accuracy. Summary of the invention

[0006] The purpose of this application is to provide a data link relative navigation information fusion method and device in order to overcome the existing technical defects, utilize Kalman filter to optimally fuse this information, improve the accuracy and reliability of relative positioning, be able to quickly process measurement information in a real-time environment, and maintain the robustness and stability of the system by continuously correcting the navigation error state.

[0007] The purpose of this application is achieved through the following technical solutions: In a first aspect, the present application proposes a data link relative navigation information fusion method, the method comprising: Establishing a relative navigation information fusion state equation according to the input information, including an absolute navigation error state equation for a navigation controller, an absolute navigation error state equation for a non-navigation controller, and a relative navigation error state equation; Establish a relative navigation information fusion measurement equation based on the input information, and obtain measurement information based on the relative navigation information fusion measurement equation to ensure the relative time and space reference under the satellite navigation denial condition. The relative navigation information fusion measurement equation includes the round-trip timing measurement equation, the geographic pseudo-range measurement equation and the grid pseudo-range measurement equation; Based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation, the corresponding Kalman filter is selected according to the measurement information to perform relative navigation information fusion to obtain the navigation result; After completing a round of state estimation of relative navigation information fusion, the navigation error state is corrected according to the measurement information, and the corrected relative positioning result is reported to the airborne avionics system.

[0008] In a possible implementation, the absolute navigation error state equation of the navigation controller is: ,in is the time derivative of the NC system state vector, is the state equation of NC in the absolute navigation state, is the NC system state vector, is the system noise driving array, is the system noise sequence.

[0009] In one possible implementation, the round trip timing measurement equation is: ,in is the clock difference of node i, is the clock error of NC, To measure noise; The geographic pseudorange measurement equation is: ,in , , are respectively the high estimates of latitude and longitude of node i, , , are the latitude and longitude errors of node i, , , are the estimated values ​​of the latitude and longitude errors of node i, is the clock error of i relative to NC, is the measurement noise of the geographic pseudorange population, is the first parameter; The grid pseudorange measurement equation is: ,in , , is the grid position error of node i; , , is the estimated value of the grid position error of node i; , , is the grid position error of node j; , , is the estimated value of the grid position error of node j; is the random measurement noise, is the first matrix.

[0010] In a possible implementation, when establishing the relative navigation information fusion measurement equation, the source quality information in the message transmitted by the data link is combined to convert the source quality information into measurement noise.

[0011] In a possible implementation, the functional software formed by the relative navigation information fusion method will reside in the data link terminal in the form of a software configuration item.

[0012] In a possible implementation, the input information includes the local inertial navigation solution result, PPLI message, pseudorange information and RTT relative clock error, the local inertial navigation solution result includes position information, speed information and attitude information, the PPLI message includes the other machine's absolute navigation information, relative navigation information, absolute navigation quality and relative navigation quality information, In one possible implementation, the navigation result includes absolute position information, absolute position quality, relative position information and relative position quality. The absolute position information includes the inertial navigation longitude, latitude, and altitude information corrected by the relative navigation information. The absolute position quality information is calculated by the filter covariance matrix in the fusion of relative navigation information. The relative position information includes U, V, and W coordinate information. The relative position quality information is calculated by the filter covariance matrix in the fusion of relative navigation information.

[0013] In a possible implementation, the location of the sea level corresponding to the real absolute position of the navigation controller is used as the origin of the grid coordinate system; The geographic coordinate system where the origin is located is rotated by an angle θ around the celestial axis, and the new three-axis directions are obtained as the U, V, and W axes of the grid coordinate system. The angle θ is the heading angle error output by the inertial navigation of the navigation controller; After rotating around the celestial axis by an angle θ, the V axis of the grid coordinate system deviates from the local north direction, and the U axis deviates from the local east direction, so that the true value of the navigation controller's heading in the grid coordinate system is equal to the erroneous heading indicated by the navigation controller's inertial navigation.

[0014] In a second aspect, the present application proposes a data link relative navigation information fusion device, the device comprising: A state equation building module, used for building a relative navigation information fusion state equation according to input information, including an absolute navigation error state equation for a navigation controller, an absolute navigation error state equation for a non-navigation controller, and a relative navigation error state equation; The measurement equation establishment module is used to establish the relative navigation information fusion measurement equation according to the input information to ensure the relative time and space reference under the satellite navigation denial condition. The relative navigation information fusion measurement equation includes the round-trip timing measurement equation, the geographic pseudo-range measurement equation and the grid pseudo-range measurement equation; A navigation result generation module is used to select a corresponding Kalman filter to perform relative navigation information fusion based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation according to the measurement information to obtain a navigation result; The error correction module is used to correct the navigation error state according to the measurement information after completing a round of state estimation of relative navigation information fusion, and report the corrected relative positioning result to the airborne avionics system.

[0015] The above main scheme of the present application and its further options can be freely combined to form multiple schemes, all of which are schemes that can be adopted and claimed for protection in the present application; and in the present application, (non-conflicting options) options and other options can also be freely combined. After understanding the scheme of the present application, those skilled in the art can understand that there are many combinations based on the existing technology and common knowledge, all of which are technical schemes to be protected by the present application, and they are not exhaustively listed here.

[0016] The present application discloses a data link relative navigation information fusion method and device. First, a relative navigation information fusion state equation is established according to input information. Secondly, a relative navigation information fusion measurement equation is established according to the input information to ensure the relative time and space reference under the satellite navigation denial condition. Based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation, a corresponding Kalman filter is selected according to the measurement information to perform relative navigation information fusion to obtain a navigation result. After completing a round of relative navigation information fusion state estimation, the navigation error state is corrected according to the measurement information, and the corrected relative positioning result is reported to the airborne avionics system. By fusing different types of measurement information and using the Kalman filter to optimally fuse this information, the accuracy and reliability of relative positioning are improved, the measurement information can be quickly processed in a real-time environment, and the robustness and stability of the system can be maintained by continuously correcting the navigation error state. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A flow chart of a data link relative navigation information fusion method proposed in an embodiment of the present application is shown.

[0019] Figure 2 A schematic diagram of input information and navigation results proposed in an embodiment of the present application is shown.

[0020] Figure 3 A schematic diagram of filters and state variables to be corrected for relative navigation information fusion proposed in an embodiment of the present application for different measurement information is shown. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0022] Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of this application.

[0023] In the existing technology, under the condition of satellite navigation denial, when the space-time reference established based on satellite navigation is challenged, the data link relative navigation technology can establish a local space-time reference for the cluster, providing a backup relative positioning and relative timing means for the cluster. The relative navigation information fusion method is essentially distributed information fusion, which is one of the key technologies that directly determines the accuracy and stability of relative navigation fusion. Therefore, it is necessary to carry out systematic research on it.

[0024] Therefore, in order to solve the problem of information fusion instability and overconfidence caused by ignoring navigation source errors in existing information fusion methods, the embodiment of the present application proposes a data link relative navigation information fusion method and device, which fuses different types of measurement information and uses a Kalman filter to optimally fuse this information, thereby improving the accuracy and reliability of relative positioning, being able to quickly process measurement information in a real-time environment, and maintaining the robustness and stability of the system by continuously correcting the navigation error state, which is described in detail below.

[0025] Please refer to Figure 1 , Figure 1 A flow chart of a data link relative navigation information fusion method proposed in an embodiment of the present application is shown, which is based on the actual demand for cluster relative navigation under satellite navigation denial conditions of aviation platforms. The purpose is to improve the existing theoretical research on several problems caused by ignoring navigation source errors through the designed relative navigation information fusion method, and at the same time provide theoretical support for the engineering practice of relative navigation algorithms. The method includes the following steps: Step S1, establishing a relative navigation information fusion state equation according to input information, including an absolute navigation error state equation for a navigation controller, an absolute navigation error state equation for a non-navigation controller, and a relative navigation error state equation.

[0026] In addition to considering its own absolute navigation error, the common members in the state equation also consider the relative navigation error with the NC to ensure the stability of the relative navigation information fusion. Therefore, for the navigation controller (Navigation Controller, NC), a state equation containing only 11-dimensional absolute navigation error is established. For the non-navigation controller, a state equation containing 11-dimensional absolute navigation error state and 7-dimensional relative navigation error state is established. The absolute navigation error state equation of the navigation controller is: ,in is the time derivative of the NC system state vector, is the state equation of NC in the absolute navigation state, is the NC system state vector, is the system noise driving array, is the system noise sequence.

[0027] First, it is divided into two types: NC and non-NC. The navigation state of the node NC is composed only of the absolute navigation state. The absolute navigation error state equation of the navigation controller is as follows: , the subscript NC indicates that the item is the navigation state corresponding to NC, and the superscript a indicates the absolute navigation state; , and They are longitude error, latitude error and altitude error respectively; , and They are eastward velocity error, northward velocity error and celestial velocity error respectively; , and They are pitch angle error, roll angle error and heading angle error respectively; and are the local clock error and clock drift respectively, is the state equation of NC.

[0028] The specific form is: ,in , , , , , , , , The specific forms are: , , , , , , , , , in the above formula and represents the latitude and altitude of NC, , and They represent the eastward, northward and celestial velocities of NC respectively. is the Earth's rotation angular velocity, It is the projection of the specific force information output by the NC inertial navigation accelerometer in the navigation coordinate system. is the NC posture transformation matrix, is the data link clock frequency error process correlation time.

[0029] set up is the radius of the earth, e is the elliptical eccentricity of the earth, and They are the radius of curvature along the meridian and the radius of curvature along the meridian, respectively. The specific forms are as follows: , .

[0030] System Noise Driver The specific form is: ,in is the attitude transformation matrix of NC. Assume that the pitch angle, roll angle and heading angle of NC are , and ,but The specific form is: .

[0031] The specific form is , assuming that the three-axis measurement white noise of the NC accelerometer is , and , the three-axis measurement white noise of the gyroscope is , and , the measured white noise of the clock is , The specific form is: .

[0032] Then the continuous form of the state equation of the NC is converted to a given discrete time Discretize: , , , k is the update time.

[0033] In a possible implementation, the navigation state of node i consists of an absolute navigation state and a relative navigation state. Suppose the system state equation of i is: ,in , the subscript i indicates that the item is the navigation state corresponding to node i, the superscript a indicates the absolute navigation state, and r indicates the relative navigation state; , and They are longitude error, latitude error and altitude error respectively; , and They are eastward velocity error, northward velocity error and celestial velocity error respectively; , and They are pitch angle error, roll angle error and heading angle error respectively; and are the local clock error and clock drift respectively, is the state equation of i, is the system noise driving array, is the system noise sequence.

[0034] The specific form is: , F is the state matrix corresponding to the 18-dimensional absolute navigation state, is the conversion matrix from the 18-dimensional absolute navigation state to the 18-dimensional absolute / relative integrated navigation state. The specific form of F is: ,in The establishment method and The same, the difference is that the position, velocity and other parameters in the matrix are provided by the inertial navigation of node i; is the data link clock error process correlation time of the NC modeled in node i; is the state matrix corresponding to the absolute navigation error of the NC modeled in i, and its specific form is: ,in to The specific form is: , , , , , , , , , , , , .

[0035] The relevant parameters with subscript NC are calculated in node i through the position, velocity, attitude and other information broadcast by NC.

[0036] The specific form is: ,in It means taking the first two rows and the first three columns of the matrix. , , and The specific form is: , , , , is the longitude and latitude of the NC broadcast, , is the longitude and latitude of node i itself.

[0037] The specific form is: , the specific form of G is: , The establishment method and The same, the difference is that the posture information in the matrix is ​​provided by node i; is the system noise driving array corresponding to the absolute navigation error of the NC modeled in i, The specific form is: , Represents the attitude transformation matrix The elements of m rows and n columns, The attitude information broadcast by NC is calculated in i, and the calculation method is the same as The same. Assume that the three-axis measurement white noise of the accelerometer i is , and , the three-axis measurement white noise of the gyroscope is , and , the measured white noise of the clock is , The specific form is: , and then the continuous form of the state equation of i is converted to a given discrete time After discretization, the discrete absolute / relative integrated state equation can be obtained: , , .

[0038] By establishing the state equations for NC and non-NC nodes respectively, the absolute navigation error and relative navigation error are considered, thus ensuring the stability of relative navigation information fusion.

[0039] Step S2: establish a relative navigation information fusion measurement equation based on the input information, obtain measurement information based on the relative navigation information fusion measurement equation, and ensure the relative space-time reference under satellite navigation denial conditions.

[0040] The relative navigation information fusion measurement equations include the round-trip timing measurement equation, the geographic pseudorange measurement equation and the grid pseudorange measurement equation.

[0041] In order to ensure the relative space-time reference under satellite navigation denial conditions, each node regularly measures RTT, geographic pseudorange and grid pseudorange, transmits the measurement data to the central processing unit or distributed processing network, and uses Kalman filtering or other data fusion algorithms to fuse multi-source measurement data to obtain more accurate relative position and time information. By introducing clock synchronization mechanism and environmental parameter compensation, the measurement error is further reduced, and the relative position and time reference of each node are updated in real time according to the latest measurement data to ensure stable operation of the system.

[0042] Round Trip Timing (RTT) refers to the time interval from sending a signal from one node to another and receiving an echo. The round trip timing measurement equation is: ,in is the clock difference of node i, is the clock error of NC, To measure noise. RTT directly measures the difference between the data link clocks of the sending member and the receiving member. Assuming that the time reference is also assumed by NC, the RTT measurement equation is: ,in is the clock difference of node i, is the clock error of NC, is the relative clock difference between node i and NC, is the measurement noise, which obeys Gaussian distribution and satisfies , the measurement matrix is: .

[0043] Geographic pseudorange refers to the estimated value of the distance between nodes calculated based on the geographic location (latitude, longitude, altitude). That is, the geographic pseudorange measures the distance between nodes i and j in the geographic coordinate system. The geographic pseudorange measurement equation is: ,in , , are respectively the high estimates of latitude and longitude of node i, , , are respectively the high estimates of latitude and longitude of node j, , , are the latitude and longitude errors of node i, , , are the estimated values ​​of the latitude and longitude errors of node i respectively; , , is the estimated inertial position error of node j, , , is the estimated inertial navigation position error of node j, is the clock error of i relative to NC, is the clock error of j relative to NC, is the random measurement noise, is the measurement noise of the geographic pseudorange population, is the first parameter.

[0044] First parameter ,matrix , , , The specific form is: , where: , , and , , are the estimated positions of i and j in the earth coordinate system, , , , in , , the measurement matrix of the geographic pseudorange system is: .

[0045] The location quality of the source is given by the measurement noise of the geographic pseudorange population When , the equivalent measurement noise covariance of geographic pseudorange measurement is: ,in represents the absolute horizontal position error covariance matrix of node j; represents the absolute height error covariance of node j; represents the relative clock phase error covariance of node j; represents the geographic pseudorange measurement noise The corresponding covariance. , , Both are calculated based on the error quality transmitted in the PPLI message.

[0046] Assume that in the PPLI message sent by node j to node i, the absolute horizontal position quality, height quality and time quality of node j are , and According to the conversion table of quality level and position error, The corresponding uncertainty range is ( , ), The corresponding uncertainty range is ( , ), The corresponding uncertainty range is ( , ). Take the upper limit value for , and To assign a value: , , , we can get: .

[0047] The grid pseudorange is an estimate of the distance between nodes calculated based on a specific coordinate system (such as the UTM coordinate system). The grid pseudorange measurement equation is: ; ; ,in , , is the grid position error of node i; , , is the estimated value of the grid position error of node i; , , is the grid position error of node j; , , is the estimated value of the grid position error of node j; is the random measurement noise, is the first matrix.

[0048] The form of the matrix M is consistent with that of the matrix M in the state equation. , the first matrix The specific form is: , , the grid pseudorange system measurement matrix is: .

[0049] The measurement noise of the grid pseudorange is obtained from the quality of the source When , the equivalent measurement noise covariance of the grid pseudorange measurement is: ,in represents the relative horizontal position error covariance matrix of node j; represents the absolute height error covariance of node j; represents the relative clock phase error covariance of node j; Represents the grid pseudorange measurement noise The corresponding covariance. , , Both are calculated based on the error quality transmitted in the PPLI message.

[0050] Assume that in the PPLI message sent by node j to node i, the relative horizontal position quality, height quality and time quality of node j are , and According to the conversion table of quality level and position error, The corresponding uncertainty range is ( , ), The corresponding uncertainty range is ( , ), The corresponding uncertainty range is ( , ). Take the upper limit value for , and Assign value and get , , , we can get: .

[0051] Step S3: Based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation, select a corresponding Kalman filter according to the measurement information to perform relative navigation information fusion to obtain a navigation result.

[0052] In order to fuse the state equation and the measurement equation based on relative navigation information, perform relative navigation information fusion through the Kalman filter and obtain navigation results, it is necessary to first establish a system model. The state vector of each node includes parameters such as position, velocity and clock bias, and the state equation describes the evolution of these states over time. At the same time, the measurement equation describes the relationship between the observation value and the system state, which usually involves nonlinear functions such as round-trip timing (RTT), geographic pseudorange and grid pseudorange. According to the linear or nonlinear characteristics of the system, different Kalman filters can be selected, such as linear Kalman filter (LKF), extended Kalman filter (EKF) or unscented Kalman filter (UKF) to predict and update state estimates and covariance.

[0053] The Kalman filter will provide the optimal state estimate for each node, including position, velocity, and clock bias. This information can be used for relative navigation to ensure that the relative time and space reference between nodes is still accurate and reliable under satellite navigation denial conditions. By selecting appropriate state equations, measurement equations, and Kalman filters, the fusion of relative navigation information can be effectively achieved, improving the accuracy and reliability of the navigation system.

[0054] The input information includes the local inertial navigation solution result, PPLI message, pseudorange information and RTT relative clock error. The local inertial navigation solution result includes position information, speed information and attitude information. The PPLI message includes the absolute navigation information of the other machine, relative navigation information, absolute navigation quality and relative navigation quality information. The navigation result includes absolute position information, absolute position quality, relative position information and relative position quality. The absolute position information includes the inertial navigation longitude, latitude and altitude information corrected by the relative navigation information. The absolute position quality information is calculated by the filter covariance matrix in the relative navigation information fusion. The relative position information includes U, V, W coordinate information. The relative position quality information is calculated by the filter covariance matrix in the relative navigation information fusion.

[0055] Please refer to Figure 2 , Figure 2The schematic diagram of the input information and navigation results proposed in the embodiment of the present application is shown. The relative navigation source selection information fusion receives four main input information: the inertial navigation solution result of the aircraft, the PPLI message, the pseudorange information and the RTT relative clock error. The inertial navigation solution result of the aircraft is provided by the avionics inertial group, including position (longitude, latitude, altitude), speed (east, north, celestial speed) and attitude (pitch angle, roll angle, heading angle) information. The PPLI message is sent by the sending aircraft and contains the absolute navigation information, relative navigation information, absolute navigation quality and relative navigation quality information of the other aircraft. The pseudorange information is calculated by signal detection and characterizes the distance between the two aircraft; and the RTT relative clock error reflects the time deviation between the aircraft and the time reference. The output information mainly includes absolute position information and relative position information and their corresponding quality evaluation. The absolute position information is the inertial navigation longitude, latitude and altitude corrected by the relative navigation information, ensuring more accurate absolute positioning. The absolute position quality information is calculated by the filter covariance matrix and is used to evaluate the absolute positioning accuracy. The relative position information is expressed in U, V, and W coordinates to represent the relative position of the aircraft in the coordinate system constructed by the network center. Its quality information is also calculated by the filter covariance matrix to ensure the reliability of relative positioning. Through these processes, the information fusion module significantly improves the accuracy and reliability of the navigation system.

[0056] Figure 3 The diagram shows the filters and state variables that should be corrected for the relative navigation information fusion proposed in the embodiment of the present application for different measurement information, which shows the relationship between different measurement types and filter types and their corrected state variables. Specifically, for RTT (round trip time) measurement, Kalman filtering is used to correct the relative clock; for geographic pseudorange measurement, extended Kalman filtering is used to correct the absolute navigation error and relative clock; and for grid pseudorange measurement, extended Kalman filtering is also used, but the main correction is the relative navigation error and relative clock.

[0057] Step S4: After completing a round of state estimation of relative navigation information fusion, correct the navigation error state according to the measurement information, and report the corrected relative positioning result to the airborne avionics system.

[0058] After completing a round of state estimation of relative navigation information fusion, the system will correct the navigation error state according to the measurement information. Specifically, by fusing the local inertial navigation solution results, PPLI messages, pseudorange information and RTT relative clock error, more accurate absolute and relative position information and quality assessment are calculated. Subsequently, the corrected relative positioning results are reported to the airborne avionics system to ensure that the accuracy and reliability of the navigation system are further improved. Not only does it correct the navigation error, but it also provides more accurate basic data for subsequent navigation operations, thereby ensuring the safety and efficiency of the flight mission.

[0059] When establishing the relative navigation information fusion measurement equation, the source quality information in the message transmitted by the data link is combined to convert the source quality information into measurement noise.

[0060] When establishing the measurement equation for relative navigation information fusion, the system will combine the source quality information in the message transmitted by the data link. The absolute navigation quality information and relative navigation quality information contained in the PPLI message will be used to adjust the measurement model. These quality information reflect the reliability and accuracy of the navigation data. By converting the source quality information into the form of a measurement noise covariance matrix, the statistical characteristics of the measurement error can be more accurately described. This ensures that the measurement equation can more accurately reflect the uncertainty of the actual measurement, thereby improving the accuracy of the state estimation. Finally, the corrected relative positioning results will be reported to the airborne avionics system to ensure the reliability and accuracy of the navigation system.

[0061] The functional software formed by the relative navigation information fusion method will reside in the data link terminal in the form of software configuration items.

[0062] A software configuration item is a software module that has been developed, tested and verified, and has clear functional definitions and interface specifications. These configuration items can be easily versioned, updated and maintained. Residing on the data link terminal means that the software module will be installed and run on the data link terminal to ensure that it can handle the fusion task of relative navigation information in real time during data link communication. The data link terminal is a key device responsible for receiving, processing and transmitting navigation-related information. Deploying it here can ensure the timeliness and accuracy of the information.

[0063] The sea level position corresponding to the real absolute position of the navigation controller is used as the origin of the grid coordinate system; The geographic coordinate system where the origin is located is rotated by an angle θ around the celestial axis, and the new three-axis directions are obtained as the U, V, and W axes of the grid coordinate system. The angle θ is the heading angle error output by the inertial navigation of the navigation controller; After rotating around the celestial axis by an angle θ, the V axis of the grid coordinate system deviates from the local north direction, and the U axis deviates from the local east direction, so that the true value of the navigation controller's heading in the grid coordinate system is equal to the erroneous heading indicated by the navigation controller's inertial navigation.

[0064] The relative positions of all members are represented in the relative coordinate system established by NC. The relative coordinate system is established as follows: At the time of NC broadcast, the sea level corresponding to the true absolute position of NC is used as the origin of the grid coordinate system. The three-axis direction obtained after the angle is used as the UVW axis of the grid coordinate system. Angle is the heading angle error output by the NC inertial navigation system. The V axis of the grid coordinate system slightly deviates from the local north direction, and the U axis slightly deviates from the local east direction, so that the true value of the heading of the NC in the grid coordinate system is the erroneous heading indicated by the NC inertial navigation. Under this coordinate system establishment method, under the constraint of the barometric altimeter elevation, the grid coordinates of the NC can be accurately (0, 0, h).

[0065] Compared with the prior art, the embodiments of the present application have the following beneficial effects: First, low implementation cost and good versatility. The relative navigation function software formed by the relative navigation source information fusion method designed by the present invention is implemented by loading software configuration items in the data link terminal, receiving PPLI messages, pseudoranges, RTT measurement values ​​and local inertial navigation data through the reserved function module interface, executing module functions, and no modification is required to the hardware of the existing data link terminal, which has strong versatility and greatly reduces the implementation cost.

[0066] Second, the relative navigation information fusion algorithm is theoretically complete and the fusion results are stable and reliable. The designed relative navigation information fusion method fully considers the source navigation error, solves the estimation stability problem caused by the existing information fusion method ignoring the source navigation error, and also suppresses the overconfidence problem caused by distributed information fusion.

[0067] Third, the access adaptability is strong. The solution is designed based on the existing data link. It can adapt to the existing data link without modifying the data link message protocol and member role allocation. It is an in-depth exploration and upgrade of the existing data link navigation capability.

[0068] Fourth, the scheme has good real-time operation and meets the requirements of highly dynamic navigation data updates. The requirements for computing power and storage resources relative to the navigation information fusion state modeling dimension are within the capabilities of the existing platform hardware processing resources, and there is a large margin to meet the requirements of algorithm real-time performance under highly dynamic conditions.

[0069] Fifth, the relative navigation technology based on data link under the condition of satellite-guided denial realizes the construction of local space-time reference centered on NC, serving the relative positioning between aircraft in the cluster. The designed relative navigation information fusion method is realized through software algorithm. The designed method has strong versatility and portability, is compatible with the message protocol and member role allocation of the current data link, has low implementation cost, ensures the theoretical completeness of the information fusion method, improves the navigation capability of the existing data link, and has strong engineering application prospects.

[0070] A possible implementation of a data link relative navigation information fusion device is provided below, which is used to execute the various execution steps and corresponding technical effects of the data link relative navigation information fusion method shown in the above embodiment and possible implementation. The device includes: A state equation building module, used for building a relative navigation information fusion state equation according to input information, including an absolute navigation error state equation for a navigation controller, an absolute navigation error state equation for a non-navigation controller, and a relative navigation error state equation; The measurement equation establishment module is used to establish the relative navigation information fusion measurement equation according to the input information to ensure the relative time and space reference under the satellite navigation denial condition. The relative navigation information fusion measurement equation includes the round-trip timing measurement equation, the geographic pseudo-range measurement equation and the grid pseudo-range measurement equation; A navigation result generation module is used to select a corresponding Kalman filter to perform relative navigation information fusion based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation according to the measurement information to obtain a navigation result; The error correction module is used to correct the navigation error state according to the measurement information after completing a round of state estimation of relative navigation information fusion, and report the corrected relative positioning result to the airborne avionics system.

[0071] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A data link relative navigation information fusion method, characterized in that: The method comprises: Establishing a relative navigation information fusion state equation according to the input information, including an absolute navigation error state equation for a navigation controller, an absolute navigation error state equation for a non-navigation controller, and a relative navigation error state equation; Establish a relative navigation information fusion measurement equation based on the input information, and obtain measurement information based on the relative navigation information fusion measurement equation to ensure the relative time and space reference under the satellite navigation denial condition. The relative navigation information fusion measurement equation includes the round-trip timing measurement equation, the geographic pseudo-range measurement equation and the grid pseudo-range measurement equation; Based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation, the corresponding Kalman filter is selected according to the measurement information to perform relative navigation information fusion to obtain the navigation result; After completing a round of state estimation of relative navigation information fusion, the navigation error state is corrected according to the measurement information, and the corrected relative positioning result is reported to the airborne avionics system.

2. The data link relative navigation information fusion method according to claim 1, characterized in that: The absolute navigation error state equation of the navigation controller is: ,in is the time derivative of the NC system state vector, is the state equation of NC in the absolute navigation state, is the NC system state vector, is the system noise driving array, is the system noise sequence.

3. The data link relative navigation information fusion method according to claim 1, characterized in that: The round trip timing measurement equation is: ,in is the clock difference of node i, is the clock error of NC, To measure noise; The geographic pseudorange measurement equation is: ,in , , are respectively the high estimates of latitude and longitude of node i, , , are the latitude and longitude errors of node i, , , are the estimated values ​​of the latitude and longitude errors of node i, is the clock error of i relative to NC, is the measurement noise of the geographic pseudorange population, is the first parameter; The grid pseudorange measurement equation is: ,in , , is the grid position error of node i; , , is the estimated value of the grid position error of node i; , , is the grid position error of node j; , , is the estimated value of the grid position error of node j; is the random measurement noise, is the first matrix.

4. The data link relative navigation information fusion method according to claim 1, characterized in that: When establishing the relative navigation information fusion measurement equation, the source quality information in the message transmitted by the data link is combined to convert the source quality information into measurement noise.

5. The data link relative navigation information fusion method according to claim 1, characterized in that: The functional software formed by the relative navigation information fusion method will reside in the data link terminal in the form of software configuration items.

6. The data link relative navigation information fusion method according to claim 1, characterized in that: The input information includes the local inertial navigation solution result, PPLI message, pseudorange information and RTT relative clock error. The local inertial navigation solution result includes position information, speed information and attitude information. The PPLI message includes the absolute navigation information, relative navigation information, absolute navigation quality and relative navigation quality information of the other machine.

7. The data link relative navigation information fusion method according to claim 1, characterized in that: The navigation results include absolute position information, absolute position quality, relative position information and relative position quality. The absolute position information includes the inertial navigation longitude, latitude and altitude information corrected by the relative navigation information. The absolute position quality information is calculated by the filter covariance matrix in the fusion of relative navigation information. The relative position information includes U, V and W coordinate information. The relative position quality information is calculated by the filter covariance matrix in the fusion of relative navigation information.

8. The data link relative navigation information fusion method according to claim 1, characterized in that: The sea level position corresponding to the real absolute position of the navigation controller is used as the origin of the grid coordinate system; The geographic coordinate system where the origin is located is rotated by an angle θ around the celestial axis, and the new three-axis directions are obtained as the U, V, and W axes of the grid coordinate system. The angle θ is the heading angle error output by the inertial navigation of the navigation controller; After rotating around the celestial axis by an angle θ, the V axis of the grid coordinate system deviates from the local north direction, and the U axis deviates from the local east direction, so that the true value of the navigation controller's heading in the grid coordinate system is equal to the erroneous heading indicated by the navigation controller's inertial navigation.

9. A data link relative navigation information fusion device, characterized in that: The device comprises: A state equation building module, used for building a relative navigation information fusion state equation according to input information, including an absolute navigation error state equation for a navigation controller, an absolute navigation error state equation for a non-navigation controller, and a relative navigation error state equation; The measurement equation establishment module is used to establish the relative navigation information fusion measurement equation according to the input information to ensure the relative time and space reference under the satellite navigation denial condition. The relative navigation information fusion measurement equation includes the round-trip timing measurement equation, the geographic pseudo-range measurement equation and the grid pseudo-range measurement equation; A navigation result generation module is used to select a corresponding Kalman filter to perform relative navigation information fusion to obtain a navigation result based on the relative navigation information fusion state equation and the relative navigation information fusion measurement equation according to the measurement information; The error correction module is used to correct the navigation error state according to the measurement information after completing a round of state estimation of relative navigation information fusion, and report the corrected relative positioning result to the airborne avionics system.

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