A radio direction finding correction method assisted by inertial navigation in complex environment

Abstract

The present invention proposes an inertial navigation-assisted radio direction finding correction method in a complex environment, which can be used for inertial navigation-assisted radio direction finding correction in long-distance complex aviation search and rescue application scenarios. When the carrier aircraft direction finding equipment is blocked or otherwise interfered with, the airborne position information and heading information output by the inertial navigation are combined with the direction finding information measured by the orientation device, and multi-point direction finding information of a single level flight segment is used to perform cross positioning, and the single positioning accuracy is improved by clustering, and then the global target positioning accuracy is gradually improved by using the measurement information of multiple level flight segments, and the direction finding result is corrected, thereby greatly improving the orientation accuracy and reliability of the aviation search and rescue orientation equipment.

Description

Technical Field

[0001] The invention relates to the technical field of radio direction finding, and in particular to an inertial navigation-assisted radio direction finding correction method in a complex environment. Background Art

[0002] Aerial search and rescue is an important part of the emergency rescue system. It uses fixed-wing aircraft, helicopters, drones, etc. to conduct fast and efficient search and rescue operations to respond to emergencies such as battlefield rescue, natural disasters, and shipwrecks. Usually, search and rescue aircraft are equipped with directional equipment to find the direction of the radio distress signal sent by the rescue target and guide the search and rescue aircraft to the rescue. However, radio directional equipment is easily affected by factors such as harsh natural environment, strong electromagnetic confrontation environment, and airborne searchlights, landing gear and other airborne equipment, resulting in large changes in direction finding errors in different directions. Current aerial search and rescue directional equipment does not introduce airborne multi-source information to improve direction finding accuracy. Existing multi-source fusion assisted direction finding methods are mostly aimed at short-range application scenarios such as wireless sensor networks. They use vision, infrared, lidar, inertial and other sensors to correct the direction finding data, which cannot be applied to aerial search and rescue scenarios of tens or even hundreds of kilometers. In addition, most existing fusion methods assume that the direction finding error obeys a certain distribution, such as Gaussian, Ruili, etc., which is not suitable for aerial search and rescue in complex environments. Summary of the invention

[0003] In order to solve the problems existing in the prior art, especially to solve the problem that the existing fusion methods are generally based on the assumption that the direction finding error obeys a certain distribution and are not suitable for aerial search and rescue in complex environments, the present invention provides an inertial navigation-assisted radio direction finding correction method in a complex environment, which combines the airborne position information and heading information output by the inertial navigation with the direction finding information measured by the orientation equipment, uses the multi-point direction finding information of a single level flight segment to perform cross-positioning, improves the single positioning accuracy through clustering, and then uses the measurement information of multiple level flight segments to gradually improve the global target positioning accuracy, corrects the direction finding results, and greatly improves the orientation accuracy and reliability of the aerial search and rescue orientation equipment.

[0004] The technical solution of the present invention is:

[0005] The inertial navigation-assisted radio direction finding correction method under complex environment comprises the following steps:

[0006] Step 1: Obtain the direction-finding data of the airborne radio direction-finding equipment and the inertial navigation data of the carrier aircraft. The direction-finding data is the direction-finding angle of the search and rescue target based on the current heading angle of the carrier aircraft, which is called the reported angle data. ; and determine the stable flight phase based on the inertial navigation data, and report the angle data Convert the true north angle direction finding data of the aircraft during the stable flight phase , the true north angle is a direction-finding angle based on the true north direction;

[0007] Step 2: Direction finding data of true north angle obtained in step 1 Make corrections and obtain the corrected reported angle data based on the corrected true north angle direction finding data , and the corrected reported angle data Normalized to the interval (0°, 360°);

[0008] Step 3: Report angle data corrected according to step 2 , combined with the latitude and longitude coordinates of the carrier aircraft, the target estimated position set is obtained;

[0009] Step 4: Cluster the target estimated positions in the target estimated position set obtained in step 3, and select the cluster center of the cluster with the largest number of clusters as the best target estimated position;

[0010] Step 5: Use the best target estimated position obtained in step 4 and the current aircraft position to calculate the new reported angle data ; and according to the formula

[0011]

[0012] The reported angle data corrected in step 2 and Perform weighted fusion to obtain the reported angle data after weighted fusion ,in To set the threshold, is the weight;

[0013] Step 6: Report the angle data after weighted fusion obtained in step 5 Perform Kalman filter correction to obtain the best reported angle data at the current moment, and realize radio direction finding in complex environments; if the carrier aircraft has not yet passed the stable flight stage during flight, the reported angle data after weighted fusion is not obtained. , the direction-finding data of the airborne radio direction-finding equipment is directly corrected by Kalman filtering and used as the best reported angle data at the current moment.

[0014] Furthermore, step 1 specifically includes the following steps:

[0015] Step 1.1: Obtain the direction finding data of the airborne radio direction finding equipment and the inertial navigation data of the carrier aircraft, the inertial navigation data is real-time heading angle data And the latitude and longitude coordinates of the carrier aircraft;

[0016] Step 1.2: According to the heading angle data obtained in step 1.1, determine the flight status of the carrier aircraft and judge whether it is in a stable flight stage; if it is in a stable flight stage, go to step 1.3, otherwise return to step 1.1 and continue to obtain direction finding data and inertial navigation data;

[0017] Step 1.3: After the aircraft enters the stable flight phase, record the data point number of the reported angle data during the stable flight phase; according to the reported angle data during the stable flight phase, use the formula

[0018]

[0019] Calculate true north angle direction finding data .

[0020] Furthermore, in step 1, the measurement frequency is not less than four measurements per second.

[0021] Furthermore, in step 1.2, the condition for judging that the carrier aircraft is in a stable flight phase is that within a continuous judgment interval, the heading angle change rate at all measurement moments is no greater than 0.8° / s.

[0022] Furthermore, in step 1.3, if the calculated If it is greater than 360°, the calculated value minus 360° is used as the true north angle direction finding data. If the calculated value is less than 0°, the calculated value plus 360° is used as the true north angle direction finding data.

[0023] Furthermore, step 2 specifically includes the following steps:

[0024] Step 2.1: Select a group of due north angle direction finding data of N consecutive measurement points during the stable flight phase of the carrier aircraft, perform least squares linear regression fitting on the group of due north angle direction finding data, and calculate the mean square error between the mean of the fitted due north angle direction finding data and the due north angle direction finding data of the N measurement points. If the mean square error is less than the set threshold, it is considered that the corresponding interval of the group of due north angle direction finding data is a stable interval;

[0025] Step 2.2: For a stable flight phase of the carrier aircraft, obtain several stable intervals of the stable flight phase according to step 2.1, and determine the mean value of the true north angle direction finding data and the slope of the linear expression after linear fitting in each stable interval;

[0026] Step 2.3: Screen the stable intervals of the stable flight stage, remove the stable intervals whose corresponding linear expression slope absolute value is greater than the set threshold, and take the average of the linear expression slopes corresponding to the remaining stable intervals as the change trend of the true north angle direction finding data of the stable flight stage, recorded as C;

[0027] Step 2.4: Calculate the mean of the true north angle direction finding data in each remaining stable interval after screening in step 2.3, and calculate the overall mean of the corresponding means of each remaining stable interval to obtain the stable interval with the mean closest to the overall mean. The mean of the true north angle direction finding data in this stable interval is recorded as , and obtain the data point number i corresponding to the median of the true north angle direction finding data in the stable interval; then the fitted true north angle direction finding data corresponding to each data point in the stable flight stage is:

[0028]

[0029] in is the data point number The corresponding true north angle direction finding data fitting value; then according to the following formula, the corrected true north angle direction finding data is obtained ;

[0030]

[0031] in To set the threshold;

[0032] Step 2.5: Based on the corrected true north angle direction finding data obtained in step 2.4 and the relationship between the true north angle direction finding data and the reported angle data in step 1, the corrected reported angle data is obtained. .

[0033] Furthermore, in step 2.5, if according to the corrected reported angle data If it is determined that the direction finding target is directly in front of or behind the flight heading, only the corrected reported angle data is obtained in the stable flight stage, and subsequent direction finding positioning is not performed, and the process returns to step 1, otherwise it goes to step 3.

[0034] Furthermore, step 3 specifically includes the following steps:

[0035] Step 3.1: After the carrier aircraft has passed a stable flight phase, two sets of consecutive reported angle data are extracted from the reported angle data corrected in step 2, and the time interval between the first set of data and the second set of data meets the set requirements;

[0036] Step 3.2: Each group of reported angle data includes a number of reported angle data. For each reported angle data, the coordinates of the carrier at the corresponding moment and the slope of the target-carrier line in the set two-dimensional plane coordinate system are obtained;

[0037] Step 3.3: Based on the aircraft coordinates at the corresponding moment of each reported angle data obtained in step 3.2 and the slope of the target-aircraft connection line in the set two-dimensional plane coordinate system, use the two sets of reported angle data to perform one-to-one cross direction finding and positioning to obtain several target estimated positions, remove the target estimated positions whose distance from the target estimated position to the aircraft is greater than the actual effective measurement maximum distance, and obtain a set of target estimated positions.

[0038] Furthermore, in step 3.2, the aircraft latitude and longitude coordinates output by the inertial navigation are converted into two-dimensional plane coordinates through Mercator projection; the two-dimensional plane coordinate system is a two-dimensional plane rectangular coordinate system established with the two-dimensional plane coordinate point obtained by converting the first input longitude and latitude coordinates as the origin, the north direction as the y-axis, and the east direction as the x-axis.

[0039] Furthermore, in step 4, the dbscan clustering method is used.

[0040] Beneficial effects:

[0041] The present invention can be used for inertial navigation-assisted radio direction finding correction in long-distance complex aviation search and rescue application scenarios. When the carrier aircraft direction finding equipment is subject to interference such as obstruction, the direction finding accuracy can be significantly improved through multi-source data fusion of direction finding data and inertial navigation data. The search and rescue target can be quickly and roughly located in a short time, and the subsequent direction finding data can be corrected by positioning the target, thus solving the problem of direction finding correction without ranging information. There is no need to require the direction finding error to obey a certain distribution, and the invention is suitable for aviation search and rescue in complex environments.

[0042] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0044] Figure 1 A schematic diagram of the relationship between the reported angle, heading angle and true north angle of the present invention;

[0045] Figure 2 It is a schematic diagram of the inertial navigation assisted direction finding correction method under complex environment of the present invention;

[0046] Figure 3 This is a flow chart of the inertial navigation assisted direction finding correction method in a complex environment of the present invention. DETAILED DESCRIPTION

[0047] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0048] The inertial device is one of the necessary navigation devices for all aircrafts, and can provide position and attitude information for the aircraft without being affected by the outside world. The present invention combines the airborne position information and heading information output by the inertial navigation with the direction finding information measured by the directional device, uses the multi-point direction finding information of a single level flight segment to perform cross positioning, and improves the single positioning accuracy through clustering, and then uses the measurement information of multiple level flight segments to gradually improve the global target positioning accuracy, and corrects the direction finding result, without requiring the direction finding error to obey a certain distribution, and is suitable for aviation search and rescue in complex environments.

[0049] like Figure 3 As shown, the inertial navigation-assisted radio direction finding correction method in a complex environment in this embodiment specifically includes the following steps:

[0050] Step 1: Obtain the direction-finding data of the airborne radio direction-finding equipment and the inertial navigation data of the carrier aircraft. The direction-finding data is the direction-finding angle of the search and rescue target based on the current heading angle of the carrier aircraft, which is called the reported angle data. ; and determine the stable flight phase based on the inertial navigation data, and report the angle data Convert the true north angle direction finding data of the aircraft during the stable flight phase , the true north angle is a direction-finding angle based on the true north direction.

[0051] The specific steps include:

[0052] Step 1.1: Obtain direction finding data from the airborne radio direction finding equipment; Figure 1 As shown, the direction finding data is the search and rescue target direction finding angle based on the current aircraft heading angle direction, hereinafter referred to as the reported angle data ; Obtain the aircraft's inertial navigation data, including real-time heading angle data And the latitude and longitude coordinates of the carrier aircraft; in this embodiment, the measurement frequency is not less than four measurements per second.

[0053] Step 1.2: According to the heading angle data obtained in step 1.1, determine the flight status of the carrier aircraft and judge whether it is in the stable flight stage; if it is in the stable flight stage, go to step 1.3, otherwise return to step 1.1 and continue to obtain direction finding data and inertial navigation data.

[0054] In the present invention, it is assumed that the aircraft's flight altitude remains stable, and the aircraft's flight state is divided into a stable flight stage (referred to as the level flight stage) with a stable heading angle and a non-level flight stage with an unstable heading angle. When the heading angle is unstable, for example, the aircraft is in a large-direction turning state, the aircraft's attitude is unstable, resulting in a significant impact on the reported angle, so the present invention selects the direction-finding data of the level flight stage for subsequent processing.

[0055] According to the previous test flight data, with a measurement frequency of four times per second, it can be roughly determined that during the level flight stage, the change of the heading angle measured each time compared with the last measured heading angle is within 0.2°, and in the non-level flight stage such as turning, the change of the heading angle measured each time compared with the last measured heading angle is more than 0.5°, and after turning, it enters the next level flight stage. Therefore, in this embodiment, the condition for judging that the flight state of the carrier aircraft is the level flight stage is set as follows: within a continuous judgment interval, the change rate of the heading angle at all measurement moments is not greater than 0.8° / s. The time length of the judgment interval is generally 2s~3s.

[0056] Step 1.3: After the aircraft enters the stable flight phase, record the data point number of the reported angle data during the stable flight phase. According to the reported angle data during the stable flight phase, use the formula

[0057]

[0058] Calculate true north angle direction finding data , the true north angle is the direction-finding angle based on the true north direction. If it is greater than 360°, the calculated value minus 360° is used as the true north angle direction finding data. If the calculated value is less than 0°, the calculated value plus 360° is used as the true north angle direction finding data.

[0059] Step 2: Direction finding data of true north angle obtained in step 1 Correction is performed, and based on the corrected true north angle direction finding data, corrected reported angle data is obtained, and the corrected reported angle data is normalized to the interval of (0°, 360°).

[0060] In the present invention, the reason why the reported angle data is converted into the true north angle direction finding data first and then the true north angle direction finding data is corrected instead of using the reported angle data to directly correct it is because when the carrier aircraft is in a stable flight stage, the change of the true north angle direction finding data in a short time tends to be linear, and the reported angle data is based on the heading angle of the current carrier aircraft. Even in the stable flight stage, the heading angle of the carrier aircraft will also change, and it is much greater than the change of the true north angle direction finding data. Therefore, it is more accurate to use the linear characteristics of the true north angle direction finding data for correction.

[0061] The specific steps include:

[0062] Step 2.1: Select a group of due north angle direction finding data of N consecutive measurement points in the stable flight phase of the carrier aircraft. In this embodiment, N=50; perform least squares linear regression fitting on the group of due north angle direction finding data, and calculate the mean square error between the fitted due north angle direction finding data and the due north angle direction finding data of the N measurement points. If the mean square error is less than a set threshold, it is considered that the corresponding interval of the group of due north angle direction finding data is a stable interval. In this embodiment, the number of measurement points N in a stable interval is 50, and the set threshold is 1.5.

[0063] Step 2.2: For a stable flight phase of the carrier aircraft, several stable intervals of the stable flight phase are obtained according to step 2.1, and the mean value of the true north angle direction finding data and the slope of the linear expression after linear fitting of each stable interval are determined. In this embodiment, each stable interval does not overlap.

[0064] Step 2.3: Screen the stable intervals of the stable flight stage. Since the actual rate of change of the true north angle direction finding data is smaller than the rate of change of the heading angle data, a threshold of the absolute value of the slope of the linear expression after linear fitting of the stable interval is set, and the stable intervals whose absolute value of the slope of the linear expression corresponding to the stable interval is greater than the threshold are eliminated. In this embodiment, the threshold is taken as 0.2; then the average of the slopes of the linear expression corresponding to the remaining stable intervals is taken as the change trend of the true north angle direction finding data in the stable flight stage, which is recorded as C.

[0065] Step 2.4: Calculate the mean of the true north angle direction finding data in each remaining stable interval after screening in step 2.3, and calculate the overall mean of the corresponding means of each remaining stable interval to obtain the stable interval with the mean closest to the overall mean. The mean of the true north angle direction finding data in this stable interval is recorded as , and obtain the data point number i corresponding to the median of the true north angle direction finding data in the stable interval; then the fitted true north angle direction finding data corresponding to each data point in the stable flight stage is:

[0066]

[0067] in is the data point number The corresponding true north angle direction finding data fitting value; then according to the following formula, the corrected true north angle direction finding data is obtained ;

[0068]

[0069] in To set the threshold, the value is 7° in this embodiment.

[0070] Step 2.5: Based on the corrected true north angle direction finding data obtained in step 2.4 and the relationship between the true north angle direction finding data and the reported angle data in step 1, the corrected reported angle data is obtained. ; If according to the revised reported angle data If it is determined that the direction finding target is directly in front of or behind the flight heading, only the corrected reported angle data is obtained in the stable flight stage, and subsequent direction finding positioning is not performed, and the process returns to step 1, otherwise it goes to step 3.

[0071] Step 3: Report angle data corrected according to step 2 , combined with the longitude and latitude coordinates of the carrier aircraft, the target estimated position set is obtained.

[0072] The specific steps include:

[0073] Step 3.1: After the carrier aircraft has gone through a stable flight phase, two sets of consecutive reported angle data are extracted from the reported angle data corrected in step 2, and the time interval between the first set of data and the second set of data meets the set requirements.

[0074] Step 3.2: Each set of reported angle data includes several reported angle data. For each reported angle data, the carrier coordinates at the corresponding moment and the slope of the target-carrier line in the set two-dimensional plane coordinate system are obtained; the carrier coordinates are the coordinates in the two-dimensional plane coordinate system obtained by converting the longitude and latitude coordinates.

[0075] In this embodiment, the latitude and longitude coordinates of the carrier output by the inertial navigation are converted into two-dimensional plane coordinates through Mercator projection. The two-dimensional plane coordinate system is a two-dimensional plane coordinate point obtained by converting the first latitude and longitude coordinates input as the origin, the north direction as the y-axis, and the east direction as the x-axis to establish a two-dimensional plane rectangular coordinate system:

[0076]

[0077]

[0078]

[0079]

[0080] The above transformation uses the WGS-84 ellipsoid, a=6378137.0000 is the major semi-axis of the ellipsoid, b=6356752.3142 is the minor semi-axis of the ellipsoid, f=(ab) / a is the flattening, e=0.00669437999013 is the first eccentricity, is the second eccentricity, B is the latitude of the current aircraft position, is the initial latitude position, select the latitude of the carrier at the start time, L is the longitude, is the initial longitude position, is the Mercator projection conversion coefficient, the aircraft longitude at the start time is selected, N is the radius of curvature of the Mercator circle, is the radius of curvature at the location of B0, is the ordinate after coordinate transformation, is the horizontal coordinate after coordinate transformation.

[0081] Step 3.3: Based on the aircraft coordinates at the corresponding moment of each reported angle data obtained in step 3.2 and the slope of the target-aircraft connection line in the set two-dimensional plane coordinate system, use the two sets of reported angle data to perform one-to-one cross direction finding and positioning to obtain several target estimated positions, remove the target estimated positions whose distance from the target estimated position to the aircraft is greater than the actual effective measurement maximum distance, and obtain a set of target estimated positions.

[0082] Step 4: Cluster the target estimated positions in the target estimated position set obtained in step 3, and select the cluster center of the cluster with the largest number after clustering as the best target estimated position.

[0083] In this embodiment, the dbscan clustering method is used; in the dbscan method, the neighborhood radius Eps and the density threshold MinPts (the minimum number of points that meet the requirements within the neighborhood radius) are set to 100 points within a range of 1000m. The specific processing flow is as follows:

[0084] 1. Take each target estimated position in the target estimated position set as a data object point, and arbitrarily select a data object point p as the core point;

[0085] 2. Based on the set neighborhood radius Eps and density threshold MinPts, find all density-reachable data object points with data object point p as the core point to form a cluster;

[0086] 3. If the selected data object point is an edge point, select another data object point;

[0087] 4. Repeat steps 2 and 3 until all points are processed.

[0088] In dbscan clustering, if a data object point has a number of data object points that meet the density threshold MinPts within the neighborhood radius Eps, then the data object point is called a core point; if a data object point does not meet the above conditions, but there are core points within the neighborhood radius, then the data object point is called a boundary point.

[0089] In the data object point set of dbscan clustering, if point X is directly density-reachable by point Y, it means that X is in the neighborhood of Y and Y is a core point. If point X is density-reachable by point Y, that is, X and Y can directly form a point chain with direct density reachability, where X and Y can be core points or boundary points.

[0090] Step 5: Use the best target estimated position obtained in step 4 and the current aircraft position to calculate the new reported angle data ; and according to the formula

[0091]

[0092] The reported angle data corrected in step 2 and Perform weighted fusion to obtain the reported angle data after weighted fusion ,in To set the threshold, in this embodiment, the value is 7°. is the weight, and set The initial value is 0.5. As the direction finding continues, The value is getting smaller and smaller, making the new reported angle data obtained by using the best target estimated position The weight gradually increases.

[0093] Step 6: Report the angle data after weighted fusion obtained in step 5 Perform Kalman filter correction to obtain the best reported angle data at the current moment, and realize radio direction finding in complex environments; if the carrier aircraft has not yet passed the stable flight stage during flight, the reported angle data after weighted fusion is not obtained. , the direction-finding data of the airborne radio direction-finding equipment is directly corrected by Kalman filtering and used as the best reported angle data at the current moment.

[0094] The specific process of Kalman filter correction is:

[0095] Step 6.1: Based on whether there is weighted fusion reported angle data Establish the state equation and observation equation.

[0096] When there is no hour:

[0097]

[0098] When there is hour:

[0099]

[0100] in is the best estimate of the Kalman filter at the previous moment, is the predicted value at the current moment, is the observed value at the current moment, is the process noise, and , that is, it conforms to the Gaussian noise distribution with a mean of 0 and a covariance matrix of Q, and the value range is [10, 16]; represents the measurement noise, similar to The value range is [4, 9], ; , They represent the state transfer matrix and the observation transfer matrix respectively.

[0101] Step 6.2: Calculate the forecast covariance matrix

[0102]

[0103] It represents the posterior error covariance matrix of the true value and the optimal value; It represents the prior error covariance matrix of the true value and the predicted value.

[0104] Step 6.3: Update the Kalman filter gain K:

[0105]

[0106] Step 6.4: Update the best prediction value and the best covariance matrix

[0107]

[0108]

[0109] in is the best estimate of the Kalman filter at the current moment.

[0110] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A radio direction finding correction method assisted by inertial navigation in complex environment, characterized in that: The following steps are involved: Step 1: Obtain the direction-finding data of the airborne radio direction-finding equipment and the inertial navigation data of the carrier aircraft. The direction-finding data is the direction-finding angle of the search and rescue target based on the current heading angle of the carrier aircraft, which is called the reported angle data. ; The stable flight phase is determined based on the inertial navigation data, and the angle data is reported. Convert the true north angle direction finding data of the aircraft during the stable flight phase , the true north angle is a direction-finding angle based on the true north direction; Step 2: Direction finding data of true north angle obtained in step 1 Make corrections and obtain the corrected reported angle data based on the corrected true north angle direction finding data , and the corrected reported angle data Normalized to the range of 0°~360°; Step 3: Report angle data corrected according to step 2 , combined with the latitude and longitude coordinates of the carrier aircraft, the target estimated position set is obtained; Step 4: Cluster the target estimated positions in the target estimated position set obtained in step 3, and select the cluster center of the cluster with the largest number of clusters as the best target estimated position; Step 5: Use the best target estimated position obtained in step 4 and the current aircraft position to calculate the new reported angle data ; and according to the formula The reported angle data corrected in step 2 and Perform weighted fusion to obtain the reported angle data after weighted fusion ,in To set the threshold, is the weight; Step 6: Report the angle data after weighted fusion obtained in step 5 Perform Kalman filter correction to obtain the best reported angle data at the current moment, and realize radio direction finding in complex environments; if the carrier aircraft has not yet passed the stable flight stage during flight, the reported angle data after weighted fusion is not obtained. , the direction-finding data of the airborne radio direction-finding equipment is directly corrected by Kalman filtering and used as the best reported angle data at the current moment.

2. According to the inertial navigation-assisted radio direction finding correction method in a complex environment as described in claim 1, it is characterized in that: Step 1 specifically includes the following steps: Step 1.1: Obtain direction finding data from the onboard radio direction finding equipment and the onboard inertial navigation data, which includes real-time heading angle data. And the latitude and longitude coordinates of the carrier aircraft; Step 1.2: According to the heading angle data obtained in step 1.1, determine the flight status of the carrier aircraft and judge whether it is in a stable flight stage; if it is in a stable flight stage, go to step 1.3, otherwise return to step 1.1 and continue to obtain direction finding data and inertial navigation data; Step 1.3: After the aircraft enters the stable flight phase, record the data point number of the reported angle data during the stable flight phase; according to the reported angle data during the stable flight phase, use the formula Calculate true north angle direction finding data .

3. According to the inertial navigation-assisted radio direction finding correction method in a complex environment as described in claim 1, it is characterized in that: In step 1, the measurement frequency is not less than four measurements per second.

4. According to the inertial navigation-assisted radio direction finding correction method in complex environment as described in claim 2, it is characterized in that: In step 1.2, the condition for judging that the aircraft is in a stable flight phase is that within a continuous judgment interval, the heading angle change rate at all measurement moments is no greater than 0.8° / s.

5. According to the inertial navigation-assisted radio direction finding correction method in complex environment as described in claim 2, it is characterized in that: In step 1.3, if the calculated If it is greater than 360°, the calculated value minus 360° is used as the true north angle direction finding data. If the calculated value is less than 0°, the calculated value plus 360° is used as the true north angle direction finding data.

6. The method for correcting inertial navigation-assisted radio direction finding in a complex environment according to claim 1, characterized in that: Step 2 specifically includes the following steps: Step 2.1: Select a group of due north angle direction finding data of N consecutive measurement points during the stable flight phase of the carrier aircraft, perform least squares linear regression fitting on the group of due north angle direction finding data, and calculate the mean square error between the mean of the fitted due north angle direction finding data and the due north angle direction finding data of the N measurement points. If the mean square error is less than the set threshold, it is considered that the corresponding interval of the group of due north angle direction finding data is a stable interval; Step 2.2: For a stable flight phase of the carrier aircraft, obtain several stable intervals of the stable flight phase according to step 2.1, and determine the mean value of the true north angle direction finding data and the slope of the linear expression after linear fitting in each stable interval; Step 2.3: Screen the stable intervals of the stable flight stage, remove the stable intervals whose corresponding linear expression slope absolute value is greater than the set threshold, and take the average of the linear expression slopes corresponding to the remaining stable intervals as the change trend of the true north angle direction finding data in the stable flight stage, recorded as C ; Step 2.4: Calculate the mean of the true north angle direction finding data in each remaining stable interval after screening in step 2.3, and calculate the overall mean of the corresponding means of each remaining stable interval to obtain the stable interval with the mean closest to the overall mean. The mean of the true north angle direction finding data in this stable interval is recorded as , and obtain the data point number corresponding to the median of the true north angle direction finding data in the stable interval i ; Then the fitting true north angle direction finding data corresponding to each data point in the stable flight phase is: in is the data point number The corresponding true north angle direction finding data fitting value; then according to the following formula, the corrected true north angle direction finding data is obtained ; Wherein is the set threshold; Step 2.5: Based on the corrected true north angle direction finding data obtained in step 2.4 and the relationship between the true north angle direction finding data and the reported angle data in step 1, the corrected reported angle data is obtained. .

7. The method for correcting inertial navigation-assisted radio direction finding in a complex environment according to claim 6, characterized in that: In step 2.5, if the corrected reported angle data If it is determined that the direction finding target is directly in front of or behind the flight heading, only the corrected reported angle data is obtained in the stable flight stage, and subsequent direction finding positioning is not performed, and the process returns to step 1, otherwise it goes to step 3.

8. The method for correcting inertial navigation-assisted radio direction finding in a complex environment according to claim 1, characterized in that: Step 3 specifically includes the following steps: Step 3.1: After the carrier aircraft has passed a stable flight phase, two sets of consecutive reported angle data are extracted from the reported angle data corrected in step 2, and the time interval between the first set of data and the second set of data meets the set requirements; Step 3.2: Each group of reported angle data includes a number of reported angle data. For each reported angle data, the coordinates of the carrier at the corresponding moment and the slope of the target-carrier line in the set two-dimensional plane coordinate system are obtained; Step 3.3: Based on the aircraft coordinates at the corresponding moment of each reported angle data obtained in step 3.2 and the slope of the target-aircraft connection line in the set two-dimensional plane coordinate system, use the two sets of reported angle data to perform one-to-one cross direction finding and positioning to obtain several target estimated positions, remove the target estimated positions whose distance from the target estimated position to the aircraft is greater than the actual effective measurement maximum distance, and obtain a set of target estimated positions.

9. The method for correcting inertial navigation-assisted radio direction finding in a complex environment according to claim 8, characterized in that: In step 3.2, the aircraft latitude and longitude coordinates output by the inertial navigation are converted into two-dimensional plane coordinates through Mercator projection; the two-dimensional plane coordinate system is a two-dimensional plane rectangular coordinate system established with the two-dimensional plane coordinate point obtained by converting the first input longitude and latitude coordinates as the origin, the north direction as the y-axis, and the east direction as the x-axis.

10. The method for correcting inertial navigation-assisted radio direction finding in a complex environment according to claim 1, characterized in that: In step 4, the dbscan clustering method is used.

Images