Pulse radar and strapdown inertial navigation combined positioning method

Abstract

The invention relates to a pulse radar and strapdown inertial navigation combined positioning method, which is used for correcting a strapdown inertial navigation position in a mode of tracking a low-orbit satellite by using a pulse radar when time on shipborne satellite navigation equipment is interfered or the shipborne satellite navigation equipment cannot be used. Satellite orbit data and data with position deviation output by strapdown inertial navigation are used for guiding a pulse radar antenna and a measurement and control antenna to track a target satellite, the pulse radar records a measured distance value in real time in the tracking process, the measurement and control antenna receives telemetry information of the satellite in real time, and the accurate position of the satellite is demodulated through the telemetry information. The distance measurement result of the pulse radar is compared with the calculation result of the relative position of the satellite and the measured ship, the ship position correction value is calculated, and therefore the ship position precision is improved, and the ship can keep high position precision for a long time through combination with strapdown inertial navigation.

Description

Technical Field

[0001] The present application relates to the field of aerospace measurement and control technology, and in particular to a pulse radar and strapdown inertial navigation combined positioning method. Background Art

[0002] At present, the receivers equipped on ships are capable of receiving signals from the three systems of GPS, GLONASS and BeiDou. As long as one system can work properly, the positioning information can be output normally. However, the anti-interference ability of the receiver is weak. Once it is affected by interference, it will not be able to output effective positioning information. Ships can only rely on traditional navigation and positioning methods, such as determining the ship's heading through a magnetic compass, using geographical markers through observation equipment such as sextants, or determining the ship's position based on the relative position of observed celestial bodies. Positioning is limited by observation conditions and has relatively low accuracy. Combined with navigation radar, it can ensure the safe navigation of ships, but it cannot meet the needs of marine measurement tasks.

[0003] At present, the strapdown inertial navigation system of a certain ship can ensure that the ship provides stable, reliable and high-precision ship attitude and position information during the mission. However, the strapdown inertial navigation system requires the satellite navigation system to provide position information for correction or combined navigation mode to provide accurate and reliable position and attitude information continuously and for a long time. When the satellite navigation system is unavailable, the strapdown inertial navigation system can still work normally and maintain high-precision position and attitude accuracy in a short time. However, as time goes on, the position output by the strapdown inertial navigation system will drift. The longer the time, the greater the drift may be, which makes it impossible to meet the needs of performing measurement tasks.

[0004] When the navigation equipment is interfered or damaged, the existing inertial navigation and radio equipment are used to achieve maritime navigation and positioning to meet the needs of safe navigation and measurement tasks of ships. Therefore, in order to ensure that the measurement tasks can still be effectively performed under the condition of satellite navigation interference, it is necessary to combine the combined navigation mode of strapdown inertial navigation and existing equipment to improve the ship's position accuracy for safe navigation and mission execution under the condition of satellite navigation interference. Summary of the invention

[0005] Based on this, it is necessary to provide a pulse radar and strapdown inertial navigation combined positioning method for the above technical problems. This method uses pulse radar and strapdown inertial navigation combined positioning method at sea when the shipborne navigation equipment is interfered with or cannot be used for a long time; since the random difference of the position positioning accuracy of the strapdown inertial navigation in autonomous navigation mode is relatively small, the system difference gradually increases with time. In the arc segment where the pulse radar tracks the low-orbit satellite, it can be approximately considered that the phase difference remains unchanged, and the pulse radar tracking result is used to correct the strapdown inertial navigation position to improve the positioning accuracy.

[0006] A pulse radar and strapdown inertial navigation combined positioning method, the method comprising:

[0007] The transit prediction is carried out according to the satellite orbit parameters, and the satellite position is calculated according to the satellite orbit parameters.

[0008] During the satellite trackable period, the antenna guidance angle is calculated based on the ship's measured position and satellite position in the strapdown inertial navigation autonomous navigation mode. The antenna guidance angle is used to guide the antenna to point to the target, and the target capture and tracking is completed in combination with manual methods.

[0009] The pulse radar system uses reflection tracking to obtain the distance from the target to the antenna, records the measured position of the ship by the strapdown inertial navigation at the corresponding moment in real time, uses a telemetry receiving system to receive the satellite downlink signal, and demodulates it to obtain the satellite's self-positioning information.

[0010] According to the distance from the target to the antenna and the satellite's self-positioning information as the comparison benchmark, the error correction of the ship's measured position by the strapdown inertial navigation is performed to obtain the correction value of the ship's position.

[0011] The measured position of the ship is corrected according to the correction value of the ship's position to obtain the true position of the ship.

[0012] In one embodiment, the satellite is a low-orbit satellite with autonomous positioning function and sends telemetry information; the satellite orbit parameters include: semi-major axis, eccentricity, right ascension of ascending node, orbit inclination, perigee argument and mean anomaly angle.

[0013] Transit forecast refers to the calculation of the target trackable period using the target orbit parameters and observation point location.

[0014] In one of the embodiments, the satellite trackable period refers to a period of time when the elevation angle of the antenna pointing to the target is greater than 0 degrees.

[0015] During the satellite tracking period, the antenna guidance angle is calculated based on the ship's measured position and satellite position in the strapdown inertial navigation autonomous navigation mode, and the antenna guidance angle is used to guide the antenna to point to the target. The target acquisition and tracking is completed in combination with manual methods, including:

[0016] During the satellite trackable period, the azimuth and elevation angles of the target relative to the antenna are calculated based on the ship's measured position and satellite position in the strapdown inertial navigation autonomous navigation mode.

[0017] The pulse radar antenna and telemetry receiving antenna are manually used to search for the target at the same time near the azimuth and elevation angle of the target relative to the antenna. When one antenna searches and finds the target, the other antenna tracks the target through mutual guidance.

[0018] In one embodiment, the distance from the target to the antenna is:

[0019]

[0020] Among them, R i t i The distance from the antenna to the target at the moment, (Δx, Δy, Δz) is the position error of the radar three-axis center, (x i ,y i ,z i ) is the radar three-axis center ground fixed coordinate system coordinate directly calculated from the strapdown inertial navigation data with errors; t i The coordinates of the satellite's position at this moment in the earth's fixed coordinate system.

[0021] In one embodiment, based on the distance from the target to the antenna and the self-positioning information of the satellite as a comparison reference, the error correction of the ship's measured position by the strapdown inertial navigation is performed to obtain a correction value of the ship's position, including:

[0022] The distance from the target to the antenna and the self-positioning position of the satellite are used as the comparison benchmarks. The goal is to minimize the mean square error of the difference between the corrected ship measurement position and the distance value calculated from the satellite position and the distance value measured by the pulse radar. The error correction of the strapdown inertial navigation ship measurement position is obtained as follows:

[0023] ΔX=(A T A) -1 A T ΔR

[0024]

[0025]

[0026] Where ΔX is the correction value of the ship's position, t i Satellite position coordinates at the moment, (x i ,y i ,z i ) is t i Ship position at the moment, R i t i The distance from the antenna to the target at the moment, r 1 Real-time recording for pulse radar i The relative distance value of the target at the moment; ΔR is the difference between the calculated distance value and the pulse radar distance measurement value, α i , β i , γ i t i The angle between the components of the satellite and ship position difference vector in the coordinate axis X, Y, and Z directions and the position difference vector at this moment.

[0027] In one embodiment, the measured position of the ship is corrected according to the correction value of the ship's position to obtain the real position of the ship, including:

[0028] The measured position of the ship is corrected according to the correction value of the ship's position, and the corrected ship's position is converted into a latitude and longitude representation to obtain the ship's true position.

[0029] In one embodiment, the method further includes: a posture correction process; the specific steps of the posture correction process include:

[0030] On the basis of completing the position correction, the theoretical large-scale position and pitch angle calculated by the satellite position and the real position of the ship are taken as the reference values. The theoretical observation values ​​of the large-scale position and pitch angle calculated by using the satellite position and the corrected ship position are compared with the reference values ​​to establish the error correction equation:

[0031] BX=L

[0032] Where X = [γαβ] T is the error component of heading, pitch and roll of the γ, α and β inertial platforms relative to the horizon; L = [ΔA 1 ΔE 1 L LΔA n ΔE n ] T , ΔA i , ΔE i t i The error components of the azimuth and elevation angles of the target relative to the antenna at time i = 1, 2, …, n.

[0033]

[0034] Among them, A i 、E i t i The azimuth and elevation angle of the target relative to the antenna at all times.

[0035] The error correction equation is solved by the least square method to obtain the correction value of the inertial navigation attitude.

[0036] The heading, pitch and roll are corrected using inertial navigation attitude correction values, and the three-axis center position of the radar is further corrected based on the corrected results.

[0037] The pulse radar and strapdown inertial navigation combined positioning method is used to correct the strapdown inertial navigation position by using the pulse radar to track the low-orbit satellite when the time on the ship-borne satellite navigation equipment is disturbed or cannot be used. The pulse radar antenna and the measurement and control antenna are guided to track the target satellite by using the satellite orbit data and the data with position deviation output by the strapdown inertial navigation. The pulse radar records the measured distance value in real time during the tracking process, and the measurement and control antenna receives the satellite's telemetry information in real time, and demodulates the precise position of the satellite through the telemetry information. The pulse radar's ranging result and the calculation result of the relative position of the satellite and the survey ship are compared, and the ship's position correction value is calculated, thereby improving the accuracy of the ship's position. Through the combination with the strapdown inertial navigation, the ship can maintain a high position accuracy for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of a pulse radar and strapdown inertial navigation combined positioning method in one embodiment;

[0039] Figure 2 It is a flow chart of a pulse radar and strapdown inertial navigation combined positioning method in another embodiment;

[0040] Figure 3 It is a principle block diagram of positioning error correction of a combination of strapdown inertial navigation and pulse radar equipment in another embodiment. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0042] The premise for the implementation of this method is: 1) When the satellite navigation is interfered with for a long time and cannot work normally, the strapdown inertial navigation is available and works in autonomous navigation mode; 2) There are certain errors in the position and attitude information output by the strapdown inertial navigation, but it can guide the antenna to find the target; 3) When the ship's satellite navigation receiving system is interfered with or attacked and becomes unavailable, the satellite in the sky can receive navigation signals normally.

[0043] In one embodiment, Figure 1 , Figure 2 As shown, a pulse radar and strapdown inertial navigation combined positioning method is provided, the method comprising the following steps:

[0044] Step 100: Perform transit prediction according to satellite orbit parameters, and calculate satellite positions according to the satellite orbit parameters.

[0045] Specifically, a satellite with an autonomous positioning function and capable of transmitting satellite position information via downlink telemetry is selected, and the satellite position is predicted through its two-line orbital parameters published online.

[0046] Step 102: During the satellite trackable period, the antenna guidance angle is calculated according to the measured position of the ship and the satellite position in the strapdown inertial navigation autonomous navigation mode, and the antenna guidance angle is used to guide the antenna to point to the target, and the target capture and tracking is completed in combination with the manual method.

[0047] Specifically, according to the satellite position prediction results and the current ship position measured by the strapdown inertial navigation, the azimuth angle A(i) and the elevation angle E(i) of the target relative to the antenna at time t(i) are calculated, and the target is searched for near A(i) and E(i) simultaneously using the pulse radar antenna and the telemetry receiving antenna manually. As long as one antenna searches and finds the target, the other antenna can track the target by mutual guidance.

[0048] The trackable period refers to the period of time when the elevation angle of the antenna pointing to the target is greater than 0 degrees.

[0049] Step 104: The pulse radar system uses reflection tracking to obtain the distance from the target to the antenna, records the measured position of the ship by the strapdown inertial navigation at the corresponding time in real time, uses the telemetry receiving system to receive the satellite downlink signal, and demodulates to obtain the satellite's self-positioning information.

[0050] Specifically, during the tracking process, the pulse radar records t in real time. i At this moment, the relative distance value r of the target i At the same time, the strapdown inertial navigation records the ship position X(i) measured at time t(i) in real time, and demodulates the target position X at that time based on the telemetry information. 0 (i) At this moment, the distance value calculated by the satellite self-positioning position and the strapdown inertial navigation measurement ship is R i .

[0051] Step 106: Based on the distance from the target to the antenna and the self-positioning information of the satellite as a comparison reference, the error of the strapdown inertial navigation ship's measured position is corrected to obtain a correction value of the ship's position.

[0052] Specifically, the ship has multiple strapdown inertial navigation systems. In the autonomous navigation mode, the strapdown inertial navigation is not easily affected by external interference, is stable and reliable, and guarantees the measurement accuracy requirements of tracking measurement within 6 hours without the support of satellite navigation equipment, and guarantees the accuracy requirements of safe navigation within a few days. The strapdown inertial navigation system is turned on before leaving the dock. During the sea voyage, at least one device is guaranteed to be in normal working condition. When at least one set of satellite navigation equipment is working normally, the strapdown inertial navigation and the satellite navigation system perform combined navigation. In the context of satellite navigation being interfered with and the satellite navigation equipment is unavailable, the strapdown inertial navigation switches to the autonomous navigation mode. As time goes by, its position error is divergent, but the error will not be too large within a few days, and the error changes little in a short time (more than ten minutes). Assuming that its error remains unchanged in a short time, the position and attitude information with errors provided by the strapdown inertial navigation can be used to guide the antenna or theodolite to point to the approximate angle of the target, and the target can be tracked after manual search. The strapdown inertial navigation position error is corrected according to the tracking distance and the position of the target.

[0053] According to the ship position information obtained by strapdown inertial navigation measurement, the target self-positioning information result is used as a benchmark, and the target distance information obtained by pulse radar measurement is used to correct the strapdown inertial navigation position error.

[0054] It is assumed here that the error value of the strapdown inertial navigation remains unchanged during the tracking period, the longitude error value is Δλ, and the latitude error value is The optimization algorithm is used to estimate the error correction value Δλ and The mean square error of the difference between the distance value calculated from the corrected ship position and satellite position and the distance value measured by the pulse radar is minimized.

[0055] Step 108: Correct the measured position of the ship according to the correction value of the ship's position to obtain the true position of the ship.

[0056] Steps 100 to 108 are repeated at regular intervals to ensure that the strapdown inertial navigation position error does not increase.

[0057] The next position correction time is calculated based on the satellite's transit time and the strapdown inertial navigation autonomous navigation accuracy performance.

[0058] In the pulse radar and strapdown inertial navigation combined positioning method, when the time on the ship-borne satellite navigation equipment is disturbed or unavailable, the method uses the pulse radar to track the low-orbit satellite to correct the strapdown inertial navigation position. By using the satellite orbit data and the data with position deviation output by the strapdown inertial navigation to guide the pulse radar antenna and the measurement and control antenna to track the target satellite, the pulse radar records the measured distance value in real time during the tracking process, the measurement and control antenna receives the satellite's telemetry information in real time, and demodulates the precise position of the satellite through the telemetry information, compares the pulse radar's ranging result with the calculation result of the relative position of the satellite and the survey ship, calculates the ship's position correction value, thereby improving the accuracy of the ship's position, and through the combination with the strapdown inertial navigation, the ship can maintain a high position accuracy for a long time.

[0059] In one embodiment, the satellite is a low-orbit satellite with an autonomous positioning function and transmits via telemetry information; the satellite orbit parameters include: semi-major axis, eccentricity, right ascension of ascending node, orbit inclination, argument of perigee and mean anomaly; transit prediction refers to calculating the target trackable period using the target orbit parameters and the observation point position.

[0060] In one of the embodiments, the satellite trackable period refers to a period of time when the pitch angle of the antenna pointing to the target is greater than 0 degrees; step 102 includes: during the satellite trackable period, according to the measured position of the ship and the satellite position in the strapdown inertial navigation autonomous navigation mode, calculating the azimuth and pitch angle of the target relative to the antenna; manually using a pulse radar antenna and a telemetry receiving antenna to search for the target near the azimuth and pitch angle of the target relative to the antenna, and when one antenna searches and finds the target, the other antenna tracks the target by mutual guidance.

[0061] In one embodiment, the distance from the target to the antenna in step 104 is:

[0062]

[0063] Among them, R i t i The distance from the antenna to the target at the moment, (Δx, Δy, Δz) is the position error of the radar three-axis center, (x i ,y i ,z i ) is the radar three-axis center ground fixed coordinate system coordinate directly calculated from the strapdown inertial navigation data with errors; t i The coordinates of the satellite's position at this moment in the earth's fixed coordinate system.

[0064] In one embodiment, step 106 includes: taking the distance from the target to the antenna and the self-positioning position of the satellite as a comparison reference, and taking the mean square error of the difference between the corrected ship measurement position and the distance value calculated from the satellite position and the distance value measured by the pulse radar as the minimum, performing error correction on the strapdown inertial navigation ship measurement position, and obtaining a corrected value of the ship position as follows:

[0065] ΔX=(A T A) -1 A T ΔR (2)

[0066]

[0067] Where ΔX is the correction value of the ship's position, t i Satellite position coordinates at the moment, (x i ,y i ,z i ) is t i Ship position at the moment, R i t i The distance from the antenna to the target at the moment, r 1 Real-time recording for pulse radar i The relative distance value of the target at the moment; ΔR is the difference between the calculated distance value and the pulse radar distance measurement value, α i , β i , γ i t i The angle between the components of the satellite and ship position difference vector in the coordinate axis X, Y, and Z directions and the position difference vector at this moment.

[0068] Specifically, the satellite navigation system tracks the signals of multiple satellites at the same time, calculates the distance between the observation point and different satellites through the time difference information, and then calculates the position of the observation point through the position of the satellite. The method of using pulse radar to track satellites can directly obtain the distance value between the observation point and the satellite, and the influence of the clock difference can be ignored. However, only one satellite can be tracked at the same time, and the position of the ship is also changing at different times during the marine tracking process. It is impossible to directly use the tracked distance value and satellite position to directly calculate the position of the ship at different times. Since the strapdown inertial navigation system also has high accuracy in autonomous navigation mode, and the change of error value in a short time is relatively small, it can be assumed that the position error of the strapdown inertial navigation system remains unchanged within the tracking arc, and the longitude, latitude and elevation errors are respectively During the tracking process, t i At the moment, the coordinates of the satellite's position in the ground-fixed coordinate system are The geographical coordinates (longitude, latitude and altitude) of the ship position obtained by strapdown inertial navigation measurement are: The ship's attitude angle (heading, roll and pitch) is (K i ,θ i ,Ψ i ), the distance measured by the pulse radar tracking satellite after atmospheric refraction correction is r i After the error correction of the ship position coordinates, the coordinates of the three-axis center position of the pulse radar can be obtained by coordinate transformation:

[0069]

[0070] make:

[0071]

[0072] Since ships mainly sail at low and medium latitudes and the tracking arc time is short, it is assumed that the ship position error remains unchanged during the tracking process. The position error of the radar three-axis center is represented by (Δx, Δy, Δz). i ,y i ,z i ) represents the radar three-axis center ground fixed coordinate system coordinates directly calculated from the strapdown inertial navigation data with errors, then:

[0073] (x i ',y i ',z i ')=(x i -Δx,y i -Δy,z i -Δz) (8) in, Substituting formula (8) into formula (6) yields:

[0074]

[0075] make:

[0076]

[0077] When the position error is zero, R i t i The actual distance from the antenna triaxial center to the target at the moment. The following is an analysis of the distance error caused by the position error in the antenna triaxial center due to the inertial navigation position drift, and its differential equation can be expressed as:

[0078]

[0079] According to formula (10), the differential equation can be rewritten as:

[0080]

[0081] It can be seen that the derivatives are the direction cosines of the meridional distance direction on each coordinate axis. Therefore, these derivatives are also components of the unit vectors of each coordinate axis. Therefore, equation (7) can be further rewritten as

[0082]

[0083] Among them, e i Indicates t i The unit vector along the distance direction at the moment, combined with equation (5), according to the radar measurement values ​​at different moments, the following equation group can be established:

[0084]

[0085] According to formula (3), formula (4) and ΔX = [Δx, Δy, Δz] T , then formula (14) can be expressed as:

[0086] AΔX=ΔR (15)

[0087] When the amount of observation data N is greater than 3, the least squares solution of the position error can be obtained as:

[0088] ΔX=(A T A) -1 A T ΔR

[0089] In practical applications, the satellite positioning calculation idea is adopted, and the iterative method is used to solve it. Δx=0, Δy=0, Δz=0 are set as the initial values ​​for calculation and iteration is performed. The result of each iteration is corrected to the center position of the radar three axes. When the correction amount is less than a certain value, the iteration is stopped. The calculation results of each iteration are accumulated to obtain the error correction amount, and the error correction values ​​of the strapdown inertial navigation longitude and latitude are calculated after coordinate conversion.

[0090] In one embodiment, step 108 includes: correcting the measured position of the ship according to the correction value of the ship's position, converting the corrected ship's position into a latitude and longitude representation to obtain the real position of the ship.

[0091] In one embodiment, the method further includes: an attitude correction process; the specific steps of the attitude correction process include: on the basis of completing the position correction, taking the theoretical large-scale attitude and pitch angle calculated by the satellite position and the real position of the ship as the reference value, comparing the theoretical observation value of the large-scale attitude and pitch angle calculated by using the satellite position and the corrected ship position with the reference value, and establishing an error correction equation:

[0092] BX=L (16)

[0093] Where X = [γαβ] T, the error components of heading, pitch and roll of the γ, α and β inertial platforms relative to the horizon; L = [ΔA 1 ΔE 1 L LΔA n ΔE n ] T , ΔA i , ΔE i t i The error components of the azimuth and elevation angles of the target relative to the antenna at time i = 1, 2, ..., n;

[0094]

[0095] Among them, A i 、E i t i The azimuth and elevation angle of the target relative to the antenna at all times.

[0096] The error correction equation is solved by the least square method to obtain the inertial navigation attitude correction value; the heading, pitch and roll are corrected using the inertial navigation attitude correction value, and the three-axis center position of the radar is further corrected based on the corrected result.

[0097] Specifically, on the basis of completing the position correction, the theoretical general position and pitch angle are calculated based on the satellite position and the corrected ship position as the benchmark. The actual measured angle of the pulse radar is corrected by the axis system and deformation, and then corrected by the ship roll with error. It is compared with the benchmark value, and the error correction equation is established to solve the inertial navigation attitude correction value.

[0098] Assume that (A i ,E i ) represents the actual target observation value after the pulse radar observation angle is corrected by the axis system, the deformation correction and transferred to the inertial navigation horizon system. represents the theoretical observation value calculated using the satellite position and the corrected ship position, where is the value after atmospheric refraction correction. The angle error value can be expressed as

[0099]

[0100] Since the observation time is short, it can be assumed that the attitude angle error of the inertial navigation system is a stable value during the observation period. Assuming that the heading, pitch and roll error components of the inertial platform relative to the horizontal system are γ, α and β respectively, ΔA i , ΔE i The following relationship is approximately expressed with γ, α and β:

[0101]

[0102] According to formula (17), X = [γαβ]T and L = [ΔA 1 ΔE 1 L LΔA n ΔE n ] T , the matrix form of formula (19) is shown in formula (16).

[0103] Solve the equation system composed of formula (19) using the least squares method and obtain:

[0104] X=(B T B) -1 B T L (20)

[0105] The correction values ​​of heading, pitch and roll are obtained, and the corrected results are used to further correct the radar three-axis center position.

[0106] The position of the strapdown inertial navigation system is corrected from the pulse radar ranging results, and the attitude is corrected using the angle measurement information to reduce the drift rate in the autonomous navigation mode and improve the heading accuracy. In practical applications, the position can be corrected using pulse radar ranging and the attitude can be corrected using theodolite star measurement to obtain higher accuracy. The next step will be to consider the changing trend of the strapdown inertial navigation autonomous navigation position error during radar tracking to further improve the position correction accuracy.

[0107] In one embodiment, the principle block diagram of the combined positioning error correction of the strapdown inertial navigation and pulse radar equipment is as follows: Figure 3 As shown. A pulse radar and strapdown inertial navigation combined positioning method is provided. The method uses the orbital parameters of the satellite and the ship position information with position error to calculate the transit time of the satellite to be tracked, as well as the guidance angle calculation, and guides the antenna to find the target during the satellite transit period. After the target is found, the antenna self-tracks and the data is recorded. After the tracking is completed, the satellite position information is extracted by receiving the satellite telemetry signal, or the high-precision position information of the satellite in the tracking arc is calculated by using the precise forecast ephemeris data of the satellite, and the distance between the three-axis center of the antenna and the satellite is calculated in combination with the inertial navigation information with error. The position correction value is calculated by combining the radar ranging result and the position information of the strapdown inertial navigation, and then the theoretical angle value is calculated by using the corrected position, and compared with the measured angle value, the attitude correction value is calculated and provided to the strapdown inertial navigation.

[0108] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0109] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A pulse radar and strapdown inertial navigation combined positioning method, characterized in that: The method comprises: Performing transit prediction based on satellite orbit parameters and calculating satellite positions based on the satellite orbit parameters; During the satellite trackable period, the antenna guidance angle is calculated according to the measured position of the ship in the strapdown inertial navigation autonomous navigation mode and the satellite position, the antenna guidance angle is used to guide the antenna to point to the target, and the target acquisition and tracking is completed in combination with the manual method; The pulse radar system uses reflection tracking to obtain the distance from the target to the antenna, records the measured position of the ship by the strapdown inertial navigation system at the corresponding moment in real time, uses the telemetry receiving system to receive the satellite downlink signal, and demodulates it to obtain the satellite's self-positioning information; Based on the distance from the target to the antenna and the satellite's self-positioning information as the comparison benchmark, the error correction of the strapdown inertial navigation ship's measured position is performed to obtain the correction value of the ship's position; The measured position of the ship is corrected according to the correction value of the ship's position to obtain the true position of the ship.

2. The pulse radar and strapdown inertial navigation combined positioning method according to claim 1, characterized in that: The satellite is a low-orbit satellite with an autonomous positioning function and is transmitted through telemetry information; the satellite orbit parameters include: semi-major axis, eccentricity, right ascension of ascending node, orbit inclination, argument of perigee and mean anomaly; Transit forecast refers to the calculation of the target trackable period using the target orbit parameters and observation point location.

3. The pulse radar and strapdown inertial navigation combined positioning method according to claim 1, characterized in that: The satellite trackable period refers to the period of time when the elevation angle of the antenna pointing to the target is greater than 0 degrees; During the satellite trackable period, the antenna guidance angle is calculated based on the measured position of the ship in the strapdown inertial navigation autonomous navigation mode and the satellite position, and the antenna guidance angle is used to guide the antenna to point to the target, and the target acquisition and tracking is completed in combination with the manual method, including: During the satellite trackable period, the azimuth and elevation angles of the target relative to the antenna are calculated based on the measured position of the ship in the strapdown inertial navigation autonomous navigation mode and the satellite position; The pulse radar antenna and telemetry receiving antenna are manually used to search for the target at the same time near the azimuth and elevation angle of the target relative to the antenna. When one antenna searches and finds the target, the other antenna tracks the target through mutual guidance.

4. The pulse radar and strapdown inertial navigation combined positioning method according to claim 1, characterized in that: The distance from the target to the antenna is: Among them, R i t i The distance from the antenna to the target at the moment, (Δx, Δy, Δz) is the position error of the radar three-axis center, (x i ,y i ,z i ) is the radar three-axis center ground fixed coordinate system coordinate directly calculated from the strapdown inertial navigation data with errors; t i The coordinates of the satellite's position at this moment in the earth's fixed coordinate system.

5. The pulse radar and strapdown inertial navigation combined positioning method according to claim 1, characterized in that: Based on the distance from the target to the antenna and the satellite's self-positioning information as the comparison benchmark, the error correction of the strapdown inertial navigation ship's measured position is performed to obtain the correction value of the ship's position, including: The distance from the target to the antenna and the self-positioning position of the satellite are used as the comparison benchmarks. The goal is to minimize the mean square error of the difference between the corrected ship measurement position and the distance value calculated from the satellite position and the distance value measured by the pulse radar. The error correction of the strapdown inertial navigation ship measurement position is obtained as follows: ΔX=(A T A) -1 A T ΔR Where ΔX is the correction value of the ship's position, t i Satellite position coordinates at the moment, (x i ,y i ,z i ) is t i Ship position at the moment, R i t i The distance from the antenna to the target at time t, r1 is the real-time record of the pulse radar i The relative distance value of the target at the moment; ΔR is the difference between the calculated distance value and the pulse radar distance measurement value, α i , β i , γ i t i The angle between the components of the satellite and ship position difference vector in the coordinate axis X, Y, and Z directions and the position difference vector at this moment.

6. The pulse radar and strapdown inertial navigation combined positioning method according to claim 1, characterized in that: Correcting the measured position of the ship according to the correction value of the ship's position to obtain the real position of the ship includes: The measured position of the ship is corrected according to the correction value of the ship's position, and the corrected ship's position is converted into a longitude and latitude representation to obtain the true position of the ship.

7. The pulse radar and strapdown inertial navigation combined positioning method according to claim 1, characterized in that: The method further includes: a posture correction process; the specific steps of the posture correction process include: On the basis of completing the position correction, the theoretical large-scale position and pitch angle calculated by the satellite position and the real position of the ship are taken as the reference values, and the theoretical observation values ​​of the large-scale position and pitch angle calculated by using the satellite position and the corrected ship position are compared with the reference values ​​to establish the error correction equation: BX=L Where X = [γαβ] T is the error component of heading, pitch and roll of the γ, α and β inertial platforms relative to the horizon; L = [ΔA1ΔE1L LΔA n ΔE n ] T , ΔA i , ΔE i t i The error components of the azimuth and elevation angles of the target relative to the antenna at each moment, i = 1, 2, …, n; Among them, A i 、E i t i The azimuth and elevation angle of the target relative to the antenna at all times; The error correction equation is solved by the least square method to obtain the correction value of the inertial navigation attitude; The heading, pitch and roll are corrected using inertial navigation attitude correction values, and the three-axis center position of the radar is further corrected based on the corrected results.

Images