A radar detection method and system based on a Beidou system

Abstract

The application relates to the field of Beidou system technology, and particularly discloses a radar detection method and system based on a Beidou system, which comprises the following steps: establishing a digital twin model of a ship and determining positions A and B; controlling the posture of the digital twin model to transform from an angle combination i to an angle combination f; determining a compensation set when the posture of the ship transforms from the angle combination i to the angle combination f based on the deviation of the positions A and B; obtaining a calibration set according to an angle combination Z1 of a current moment and an angle combination Z2 of a previous moment; and correcting Beidou positioning data and radar positioning data according to sub-angle combinations J1 and J2 in the calibration set. The application can eliminate the posture deviation of the Beidou and the radar caused by the installation position difference under the condition that the ship body is rocked by wind and waves, and significantly improves the precision and stability of offshore target positioning.

Description

Technical Field

[0001] This invention relates to the field of BeiDou system technology, specifically to a radar detection method and system based on the BeiDou system. Background Technology

[0002] In long-range maritime exploration, most schemes assume that "the installation positions of the Beidou positioning module and the radar detection module are relatively stable," but they ignore the impact of changes in sea conditions (such as rough seas causing ships to pitch and roll).

[0003] The BeiDou and radar modules are mounted in different locations on the ship, and their different swaying angles in rough seas can cause discrepancies in their judgment of the target's location, ultimately leading to incorrect positioning. When the ship is rocking in rough seas, the BeiDou module at the higher position will sway more significantly, for example, tilting 10 degrees to the left; the radar module in the middle will sway less, only tilting 5 degrees to the left. Both will mistakenly interpret this as the target shifting rather than their own swaying, resulting in different judgments of the target's direction: BeiDou will perceive the target as 10 degrees to its right, while the radar will perceive it as 5 degrees to its right.

[0004] When calculating the actual location of the detected target, it is necessary to combine the "ship position + target direction" provided by BeiDou with the "target distance + target direction" provided by radar. However, because the target direction is determined by a difference of 5 degrees between the two methods, the target position calculated using BeiDou data will differ from the position calculated using radar data by several hundred meters, directly causing a positioning error. Summary of the Invention

[0005] The purpose of this invention is to provide a radar detection method and system based on the BeiDou system to solve the above-mentioned technical problems.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A radar detection method based on the BeiDou system includes the following steps:

[0008] Establish a digital twin model of the ship, with the installation positions of the ship's Beidou module and radar module corresponding to positions A and B respectively on the numerical twin model;

[0009] Set several angle combinations, in the virtual physical space, control the posture of the digital twin model to satisfy angle combination i, and control the posture of the digital twin model to change from angle combination i to angle combination f;

[0010] When the attitude of the digital twin model changes to the angle combination f, the deviation between position A and position B is obtained. Based on the deviation, the sub-angle combination of position A and position B is determined. The sub-angle combination of position A and position B constitutes the compensation set when the attitude of the ship changes from angle combination i to angle combination f.

[0011] Obtain the angle combination Z1 satisfied by the ship's attitude at the current moment, and obtain the angle combination Z2 satisfied by the ship's attitude at the previous moment. Obtain the compensation set when the angle combination Z2 is transformed into the angle combination Z1, and denot it as the calibration set.

[0012] Extract sub-angle combinations J1 and J2 from positions A and B in the calibration set. Correct the BeiDou positioning data and radar positioning data based on the sub-angle combinations J1 and J2. The corrected BeiDou positioning data and radar positioning data are used to reflect the position of the detected target.

[0013] As a further aspect of the present invention: several angle combinations are provided, including:

[0014] Set the pitch angle range, yaw angle range, and roll angle range;

[0015] Starting from the beginning of the pitch angle range, yaw angle range, and roll angle range respectively, set several pitch angle nodes, yaw angle nodes, and roll angle nodes at preset angle intervals;

[0016] A single angle combination includes a pitch node, a yaw node, and a roll node, and different angle combinations contain different pitch nodes and / or yaw nodes and / or roll nodes.

[0017] As a further aspect of the present invention: determining the sub-angle combination of position A and position B includes:

[0018] Obtain the roll angle and pitch angle of position A from the initial position, and record them as the first angle and the second angle respectively. The first angle and the second angle constitute the sub-angle combination of position A.

[0019] Obtain the roll angle, yaw angle, and pitch angle of position B as it deviates from the initial position, and record them as the third angle, fourth angle, and fifth angle, respectively. The third angle, fourth angle, and fifth angle constitute the sub-angle combination of position B.

[0020] As a further aspect of the present invention: the correction of BeiDou positioning data includes:

[0021] Extract the sub-angle combination JA at position A in sub-angle combination J1, and extract the first angle j1 and the second angle j2 in sub-angle combination JA;

[0022] Obtain the installation height H of the Beidou module;

[0023] Calculate the first offset distance Second offset distance ;

[0024] Where sign(j1) is the sign function; if j1 > 0, then sign(j1) = 1; if j ≤ 0, then sign(j1) = -1.

[0025] Obtain longitude Y1 and latitude Y2 from the BeiDou positioning data, and correct the longitude Y1 to obtain the longitude. The latitude is obtained by correcting the latitude Y2. η is a preset correction coefficient.

[0026] As a further aspect of the present invention: the correction of radar positioning data includes:

[0027] Extract the sub-angle combination JB at position B in sub-angle combination J2, and extract the third angle j3, the fourth angle j4 and the fifth angle j5 in sub-angle combination JB;

[0028] The distance R between the target and the radar, the azimuth angle ψ of the target relative to the radar, and the elevation angle θ of the target relative to the radar are obtained from the radar positioning data.

[0029] Using the radar's own coordinate system as a reference, construct the direction vector of the detected target relative to the radar module:

[0030] ;

[0031] Among them, VR x VR y VR z These represent the components of the target's orientation along the x-axis, y-axis, and z-axis, respectively.

[0032] Based on the sub-angle combination J2, construct the radar rotation matrix:

[0033] ;

[0034] Rx, Ry, and Rz represent rotation matrices about the X-axis, Y-axis, and Z-axis, respectively.

[0035] Because the radar's installation position sways with the ship's hull, the direction vector vr it measures is defined in the radar's own coordinate system. To obtain the true direction of the detected target in the ship's reference system, the direction vector vr needs to be rotated back to the ship's reference system to obtain the target vector. The specific calculation formula is as follows:

[0036] ;

[0037] Among them, RB -1 This represents the inverse of the radar's rotation matrix, where T denotes the transpose, and vn x vn y vn zThese represent the components of the target on the x-axis, y-axis, and z-axis of the ship's reference frame, respectively.

[0038] The corrected azimuth angle of the target relative to the radar is calculated as ψ'=atan2(vn). y vn x ), and calculate the corrected elevation angle θ' = arcsin(vn) of the target relative to the radar. z ).

[0039] As a further aspect of the present invention, the correction of radar positioning data also includes:

[0040] In the ship's coordinate system, the position vector of the radar module when it is in its original position is rB=[0, 0, H1]. T H1 represents the installation height of the radar module;

[0041] When the hull rotates, the displacement of the radar module is approximated as the cross product of the rotation vector and the arm using a first-order small-angle approximation:

[0042] ;

[0043] Where ε = [j3, j5, j4]T, y1 = (1, 0, 0), y2 = (0, 1, 0), y3 = (0, 0, 1);

[0044] The target vector describes the direction of the target in the ship's reference frame. It is a unit vector (length 1) pointing in the direction the radar reaches the target. If the radar experiences a displacement Δr due to attitude changes, then the equivalent range change along the target direction (i.e., the direction of the target vector vn) is: That is, projecting the displacement Δr of the radar module onto the target direction;

[0045] The distance R between the target and the radar is corrected to obtain a new distance R' = R + D3.

[0046] A radar detection system based on the BeiDou system includes:

[0047] Twin Module: Establish a digital twin model of the ship. The installation positions of the ship's Beidou module and radar module correspond to positions A and B on the numerical twin model, respectively.

[0048] Calibration module: Sets several angle combinations, controls the posture of the digital twin model to satisfy angle combination i in virtual physical space, and controls the posture of the digital twin model to change from angle combination i to angle combination f;

[0049] When the attitude of the digital twin model changes to the angle combination f, the deviation between position A and position B is obtained. Based on the deviation, the sub-angle combination of position A and position B is determined. The sub-angle combination of position A and position B constitutes the compensation set when the attitude of the ship changes from angle combination i to angle combination f.

[0050] Compensation module: Obtain the angle combination Z1 satisfied by the ship's attitude at the current moment, and obtain the angle combination Z2 satisfied by the ship's attitude at the previous moment. Obtain the compensation set when the angle combination Z2 is transformed into the angle combination Z1, denoted as the calibration set.

[0051] Extract sub-angle combinations J1 and J2 from positions A and B in the calibration set. Correct the BeiDou positioning data and radar positioning data based on the sub-angle combinations J1 and J2. The corrected BeiDou positioning data and radar positioning data are used to reflect the position of the detected target.

[0052] The beneficial effects of this invention compared to the prior art are as follows:

[0053] This invention provides unified compensation for the attitude response differences between the BeiDou module and the radar module caused by different installation positions, ensuring that both modules use the same reference standard for spatial target detection even when the ship's attitude changes. After correction, the BeiDou and radar make consistent direction judgments of the detected target, avoiding directional deviations caused by differences in installation positions, thus ensuring the consistency of detection results across different sensors.

[0054] This invention can correct the false displacement of the BeiDou module caused by changes in the ship's attitude, so that the corrected positioning data truly reflects the ship's translational state. Through this correction, the position information output by BeiDou remains consistent with the ship's reference point, avoiding the misinterpretation of attitude changes as position drift, thereby improving the stability and accuracy of positioning data under dynamic sea conditions.

[0055] This invention can correct the direction and distance data measured by radar, making it reflect the true geometric relationship of the detected target relative to a unified reference point. The corrected radar data eliminates the angle and distance deviations caused by attitude changes. After being fused with the corrected BeiDou data under the same coordinate reference, the position of the detected target can accurately correspond to the actual spatial position, improving the overall reliability of detection and positioning. Attached Figure Description

[0056] The invention will now be further described with reference to the accompanying drawings.

[0057] Figure 1 This is a flowchart illustrating a radar detection method based on the BeiDou system according to the present invention. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Please see Figure 1 As shown, this invention is a radar detection method based on the BeiDou system, comprising the following steps:

[0060] Establish a digital twin model of the ship, with the installation positions of the ship's Beidou module and radar module corresponding to positions A and B respectively on the numerical twin model;

[0061] Set several angle combinations, in the virtual physical space, control the posture of the digital twin model to satisfy angle combination i, and control the posture of the digital twin model to change from angle combination i to angle combination f;

[0062] It should be noted that the digital twin model of the ship is established based on the structural parameters of the actual hull and the sensor installation positions. By collecting the ship's external dimensions, center of gravity position, coordinates of the radar and BeiDou modules' installation points, and the spatial relationships of each module relative to the ship's reference coordinate system, a model with realistic geometric constraints is constructed in a three-dimensional virtual space. The ship's coordinate system is defined as a unified reference system in the model, ensuring that the installation points of the BeiDou and radar modules on the model are consistent with those on the actual ship, enabling dynamic control of attitude angles within the model.

[0063] The virtual physical space is used to simulate the attitude changes of a ship under external disturbances. By inputting the changes in roll, pitch, and yaw angles, the digital twin model is driven to achieve an attitude transformation process consistent with that of the real ship. The model's motion is not a simple geometric rotation, but follows the kinematic constraints of the hull, accurately reflecting the relative offset and spatial displacement of the mounting points during attitude changes. In this way, in the virtual space, the motion trajectories and attitude changes of points at different mounting positions in a unified reference frame can be observed and recorded as the ship transitions from one attitude combination to another. The essence of this process is to establish a mapping relationship between the actual hull attitude changes and the motion of the sensor mounting points, so that the deviation of each mounting point under different angle combinations can be expressed in a calculable form, thus providing a data foundation for subsequently determining the sub-angle combinations of each mounting position. The digital twin model constructed in this way allows for accurate acquisition of offset characteristics under attitude changes without relying on experiments with the actual hull in harsh environments when calculating data corrections for BeiDou and radar, ensuring that attitude compensation is established based on real geometric relationships. Its core principle lies in mapping the overall attitude change to the attitude response of local mounting points through motion correlation in virtual space, so that the angle change and displacement of each mounting point are in one-to-one correspondence with the attitude change of the ship. This provides the conditions for subsequently correcting the data of Beidou and radar to the same reference, ensuring that both can still perform target positioning based on the same reference point under different attitude conditions.

[0064] In a preferred embodiment of the present invention, several angle combinations are provided, including:

[0065] Set the pitch angle range, yaw angle range, and roll angle range;

[0066] Starting from the beginning of the pitch angle range, yaw angle range, and roll angle range respectively, set several pitch angle nodes, yaw angle nodes, and roll angle nodes at preset angle intervals;

[0067] A single angle combination includes a pitch node, a yaw node, and a roll node, and different angle combinations contain different pitch nodes and / or yaw nodes and / or roll nodes.

[0068] When the attitude of the digital twin model changes to the angle combination f, the deviation between position A and position B is obtained. Based on the deviation, the sub-angle combination of position A and position B is determined. The sub-angle combination of position A and position B constitutes the compensation set when the attitude of the ship changes from angle combination i to angle combination f.

[0069] In another preferred embodiment of the present invention, determining the sub-angle combination of position A and position B includes:

[0070] Obtain the roll angle and pitch angle of position A from the initial position, and record them as the first angle and the second angle respectively. The first angle and the second angle constitute the sub-angle combination of position A.

[0071] Obtain the roll angle, yaw angle, and pitch angle of position B as it deviates from the initial position, and record them as the third angle, fourth angle, and fifth angle, respectively. The third angle, fourth angle, and fifth angle constitute the sub-angle combination of position B.

[0072] It is understandable that when the ship's attitude changes, the motion effects on modules at different installation positions are not entirely the same; their respective deviation directions and angular magnitudes are determined by their relative positions within the hull. By obtaining the deviations of positions A and B from their initial states when the attitude changes to angle combination f in the digital twin model, the actual attitude response characteristics of the two points can be extracted. After converting this deviation information into angular parameters such as roll, pitch, and yaw, sub-angle combinations reflecting the attitude changes of the installation points themselves can be constructed. These defined sub-angle combinations essentially isolate the local responses of the overall hull attitude change at each installation point, allowing the attitude change of each sensor to be described by specific angular quantities, thus providing a basis for establishing comparable attitude relationships between different installation points. By using the sub-angle combinations of positions A and B together as the compensation set when the attitude changes from angle combination i to angle combination f, the differences between the two locations during the same attitude change can be clearly described. The compensation set reflects the actual response difference of different installation positions to the same hull attitude change. This difference is used as the basis for compensation in subsequent data correction, so that the observation results of the Beidou module and the radar module can be calculated with a unified attitude reference.

[0073] Obtain the angle combination Z1 satisfied by the ship's attitude at the current moment, and obtain the angle combination Z2 satisfied by the ship's attitude at the previous moment. Obtain the compensation set when the angle combination Z2 is transformed into the angle combination Z1, and denot it as the calibration set.

[0074] Extract sub-angle combinations J1 and J2 from positions A and B in the calibration set. Correct the BeiDou positioning data and radar positioning data based on the sub-angle combinations J1 and J2. The corrected BeiDou positioning data and radar positioning data are used to reflect the position of the detected target.

[0075] In another preferred embodiment of the present invention, the correction of BeiDou positioning data includes:

[0076] Extract the sub-angle combination JA at position A in sub-angle combination J1, and extract the first angle j1 and the second angle j2 in sub-angle combination JA;

[0077] Obtain the installation height H of the Beidou module;

[0078] Calculate the first offset distance Second offset distance ;

[0079] Where sign(j1) is the sign function; if j1 > 0, then sign(j1) = 1; if j ≤ 0, then sign(j1) = -1.

[0080] Obtain longitude Y1 and latitude Y2 from the BeiDou positioning data, and correct the longitude Y1 to obtain the longitude. The latitude is obtained by correcting the latitude Y2. η is a preset correction coefficient.

[0081] It is important to note that the BeiDou module is installed at a relatively high position on the hull. When the hull pitches and rolls in wind and waves, this position will experience actual spatial displacement due to the lever effect. This displacement is mistakenly interpreted as overall ship movement in the latitude and longitude coordinates output by the BeiDou system, thus introducing positional deviation. By extracting angle parameters related to attitude changes through sub-angle combinations, the equivalent displacement direction and magnitude caused by pitch and roll can be calculated. The projection of these displacements onto the horizontal plane reflects the offset of the BeiDou antenna in the longitude and latitude directions. The magnitude of this displacement can be obtained using the geometric relationship between installation height and angle change, and then converted into a correction amount in the longitude and latitude directions. This correction is then superimposed with the original longitude and latitude to obtain the corrected ship position. The essence of this correction process is to eliminate the false displacement caused by hull tilt based on attitude angle changes, restoring the position information output by BeiDou to a state consistent with the ship's reference point. This ensures that the BeiDou positioning results no longer contain errors caused by attitude changes, thereby guaranteeing that the position data provided by BeiDou in subsequent fusion shares the same spatial reference with radar data; the meaning of sign(j2) is analogous to that of sign(j1).

[0082] In a preferred embodiment, the correction of radar positioning data includes:

[0083] Extract the sub-angle combination JB at position B in sub-angle combination J2, and extract the third angle j3, the fourth angle j4 and the fifth angle j5 in sub-angle combination JB;

[0084] The distance R between the target and the radar, the azimuth angle ψ of the target relative to the radar, and the elevation angle θ of the target relative to the radar are obtained from the radar positioning data.

[0085] Using the radar's own coordinate system as a reference, construct the direction vector of the detected target relative to the radar module:

[0086] ;

[0087] Among them, VR x VR y VR zThese represent the components of the target's orientation along the x-axis, y-axis, and z-axis, respectively.

[0088] Based on the sub-angle combination J2, construct the radar rotation matrix:

[0089] ;

[0090] Rx, Ry, and Rz represent rotation matrices about the X-axis, Y-axis, and Z-axis, respectively.

[0091] Because the radar's installation position sways with the ship's hull, the direction vector vr it measures is defined in the radar's own coordinate system. To obtain the true direction of the detected target in the ship's reference system, the direction vector vr needs to be rotated back to the ship's reference system to obtain the target vector. The specific calculation formula is as follows:

[0092] ;

[0093] Among them, RB -1 This represents the inverse of the radar's rotation matrix, where T denotes the transpose, and vn x vn y vn z These represent the components of the target on the x-axis, y-axis, and z-axis of the ship's reference frame, respectively.

[0094] The corrected azimuth angle of the target relative to the radar is calculated as ψ'=atan2(vn). y vn x ), and calculate the corrected elevation angle θ' = arcsin(vn) of the target relative to the radar. z ).

[0095] It is worth noting that the corrected radar positioning data includes:

[0096] Extract the sub-angle combination JB at position B in sub-angle combination J2, and extract the third angle j3, the fourth angle j4 and the fifth angle j5 in sub-angle combination JB;

[0097] The distance R between the target and the radar, the azimuth angle ψ of the target relative to the radar, and the elevation angle θ of the target relative to the radar are obtained from the radar positioning data.

[0098] Using the radar's own coordinate system as a reference, construct the direction vector of the detected target relative to the radar module:

[0099] ;

[0100] Among them, VR x VR y VR z These represent the components of the target's orientation along the x-axis, y-axis, and z-axis, respectively.

[0101] Based on the sub-angle combination J2, construct the radar rotation matrix:

[0102] ;

[0103] Rx, Ry, and Rz represent rotation matrices about the X-axis, Y-axis, and Z-axis, respectively.

[0104] Because the radar's installation position sways with the ship's hull, the direction vector vr it measures is defined in the radar's own coordinate system. To obtain the true direction of the detected target in the ship's reference system, the direction vector vr needs to be rotated back to the ship's reference system to obtain the target vector. The specific calculation formula is as follows:

[0105] ;

[0106] Among them, RB -1 This represents the inverse of the radar's rotation matrix, where T denotes the transpose, and vn x vn y vn z These represent the components of the target on the x-axis, y-axis, and z-axis of the ship's reference frame, respectively.

[0107] The corrected azimuth angle of the target relative to the radar is calculated as ψ'=atan2(vn). y vn x ), and calculate the corrected elevation angle θ' = arcsin(vn) of the target relative to the radar. z ).

[0108] Understandably, J1 and J2 respectively depict the actual angular changes at two different mounting points during the same ship attitude change. They can be used to separate the "observation error caused by the sensor's own swaying with the ship" from the measurement, achieving alignment with the same reference standard. First, consider the BeiDou side: BeiDou provides the ship's position, but the antenna is not located at the ship's reference point (such as the center of mass). When the ship pitches and rolls, the antenna shifts in the horizontal plane due to the "lever effect," and this displacement is directly projected onto latitude and longitude, appearing as a false translation of the ship's position. J1 provides the pitch and roll changes of the BeiDou point at this moment. (The goal of BeiDou correction is to compensate for attitude coupling displacement caused by the height of the antenna mounting point, and this type of displacement mainly comes from changes in the pitch and roll angles. These two angles control the tilt of the hull in the vertical plane, causing the antenna to shift in the horizontal plane; while the yaw angle only represents the rotation of the hull around the vertical axis, it does not change the relative position of the antenna with respect to the center of mass of the hull, it only causes the bow direction to rotate in the horizontal plane.) Based on this, the equivalent horizontal displacement of the antenna can be approximated using small angles (essentially, using "angular displacement × arm length" to obtain the linear displacement). Then, the components of these two displacements in the east and north directions are converted into latitude and longitude increments according to geographical proportions (meters corresponding to each degree of latitude and longitude), and superimposed on the original ship position to obtain the "de-leveraged" ship position. The reason for doing this is to return the BeiDou reference point from the "antenna mounting point" to the "unified reference point," eliminate the false displacement caused by attitude, and ensure that the BeiDou data only reflects the true translation of the hull. Looking at the radar side: The original radar echo angle is measured in the radar's own coordinate system. Due to the swaying of the radar mounting point with the ship, its coordinate system rotates, causing the azimuth / elevation of the same target in the radar coordinate system to be "skewed". J2 is the change in the three-axis angle of the radar mounting point due to this swaying. Using it to construct a rotation matrix and inverting it rotates the target line-of-sight unit vector from the "radar's own coordinate system" back to the "unified reference system", obtaining the true direction unaffected by the mounting point's attitude. Rz is a function symbol for a "three-dimensional rotation matrix around the Z-axis". It is a 3×3 matrix specifically used to describe how the coordinate components change when the coordinate system or rigid body rotates around the Z-axis by a certain angle. Rz(j4) represents a three-dimensional rotation matrix of a rotation of j4 angles around the Z-axis. Similarly, Ry(j5) is a three-dimensional rotation matrix of a rotation of j5 angles around the Y-axis, and Rx(j3) is a three-dimensional rotation matrix of a rotation of j3 angles around the X-axis. The reason for inverting it is to cancel out the rotation of the sensor coordinate system relative to the unified reference system (i.e., to reverse the "rotation with the ship"). Then use atan2(vn) y vn x and arcsin(vn zThe azimuth and elevation angles are recovered from the corrected direction vector. atan2 can distinguish quadrants, ensuring that the angles fall within the correct range. Besides direction, the radar measures range. The radar mounting point also has a strut; attitude changes cause a slight linear displacement of the mounting point along a certain direction. This increases or decreases the echo "geometric path" along the target's line of sight, resulting in a systematic bias in the range measurement. Therefore, the displacement of the radar mounting point (derived mathematically as "angle change × strut" - obtained mathematically using the cross product) is multiplied by the target's line of sight unit vector to obtain the range compensation D3 to be added to the measurement. The physical meaning of this step is "projecting the sensor's own movement onto the measurement direction." The corrected range R' = R + D3 is the geometric range with the unified reference point as the origin. After completing these two types of corrections, the "ship position at the unified reference point" given by Beidou and the "target direction and range in the unified reference system" given by the radar are on the same coordinates and the same origin. The target position obtained by fusing the two no longer includes the systematic error caused by the coupling of installation position differences and attitude changes. This is the fundamental purpose of correcting separately from J1 / J2.

[0109] A radar detection system based on the BeiDou system includes:

[0110] Twin Module: Establish a digital twin model of the ship. The installation positions of the ship's Beidou module and radar module correspond to positions A and B on the numerical twin model, respectively.

[0111] Calibration module: Sets several angle combinations, controls the posture of the digital twin model to satisfy angle combination i in virtual physical space, and controls the posture of the digital twin model to change from angle combination i to angle combination f;

[0112] When the attitude of the digital twin model changes to the angle combination f, the deviation between position A and position B is obtained. Based on the deviation, the sub-angle combination of position A and position B is determined. The sub-angle combination of position A and position B constitutes the compensation set when the attitude of the ship changes from angle combination i to angle combination f.

[0113] Compensation module: Obtain the angle combination Z1 satisfied by the ship's attitude at the current moment, and obtain the angle combination Z2 satisfied by the ship's attitude at the previous moment. Obtain the compensation set when the angle combination Z2 is transformed into the angle combination Z1, denoted as the calibration set.

[0114] Extract sub-angle combinations J1 and J2 from positions A and B in the calibration set. Correct the BeiDou positioning data and radar positioning data based on the sub-angle combinations J1 and J2. The corrected BeiDou positioning data and radar positioning data are used to reflect the position of the detected target.

[0115] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A radar detection method based on the BeiDou system, characterized in that, Includes the following steps: A digital twin model of the ship is established, with the installation positions of the ship's Beidou module and radar module corresponding to positions A and B, respectively, on the numerical twin model; Set several angle combinations, in the virtual physical space, control the posture of the digital twin model to satisfy angle combination i, and control the posture of the digital twin model to change from angle combination i to angle combination f; When the attitude of the digital twin model changes to the angle combination f, the deviation between position A and position B is obtained. Based on the deviation, the sub-angle combination of position A and position B is determined. The sub-angle combination of position A and position B constitutes the compensation set when the attitude of the ship changes from angle combination i to angle combination f. Obtain the angle combination Z1 satisfied by the ship's attitude at the current moment, and obtain the angle combination Z2 satisfied by the ship's attitude at the previous moment. Obtain the compensation set when the angle combination Z2 is transformed into the angle combination Z1, and denot it as the calibration set. Extract sub-angle combinations J1 and J2 from positions A and B in the calibration set. Correct the BeiDou positioning data and radar positioning data based on the sub-angle combinations J1 and J2. The corrected BeiDou positioning data and radar positioning data are used to reflect the position of the detected target. The corrections to BeiDou positioning data include: Extract the sub-angle combination JA at position A in sub-angle combination J1, and extract the first angle j1 and the second angle j2 in sub-angle combination JA; Obtain the installation height H of the Beidou module; Calculate the first offset distance Second offset distance ; Where sign(j1) is the sign function; if j1 > 0, then sign(j1) = 1; if j ≤ 0, then sign(j1) = -1. Obtain longitude Y1 and latitude Y2 from the BeiDou positioning data, and correct longitude Y1 to obtain longitude. The latitude is obtained by correcting the latitude Y2. η is a preset correction coefficient; The corrected radar positioning data includes: Extract the sub-angle combination JB at position B in sub-angle combination J2, and extract the third angle j3, the fourth angle j4 and the fifth angle j5 in sub-angle combination JB; The distance R between the target and the radar, the azimuth angle ψ of the target relative to the radar, and the elevation angle θ of the target relative to the radar are obtained from the radar positioning data. Using the radar's own coordinate system as a reference, construct the direction vector of the detected target relative to the radar module: ； Among them, VR x VR y VR z These represent the components of the target's orientation along the x-axis, y-axis, and z-axis, respectively. Based on the sub-angle combination J2, construct the radar rotation matrix: ； Because the radar's installation position sways with the ship's hull, the direction vector vr it measures is defined in the radar's own coordinate system. To obtain the true direction of the detected target in the ship's reference system, the direction vector vr needs to be rotated back to the ship's reference system to obtain the target vector. The specific calculation formula is as follows: ； Among them, RB -1 This represents the inverse of the radar's rotation matrix, where T denotes the transpose, and vn x vn y vn z These represent the components of the target on the x-axis, y-axis, and z-axis of the ship's reference frame, respectively. The corrected azimuth angle of the target relative to the radar is calculated as ψ'=atan2(vn). y vn x ), and calculate the corrected elevation angle θ' = arcsin(vn) of the target relative to the radar. z ); The correction of radar positioning data also includes: In the ship's coordinate system, the position vector of the radar module when it is in its original position is rB=[0, 0, H1]. T H1 represents the installation height of the radar module; When the hull rotates, the displacement of the radar module is approximated as the cross product of the rotation vector and the arm using a first-order small-angle approximation: ； Where ε = [j3, j5, j4] T , y1=(1,0,0), y2=(0,1,0), y3=(0,0,1); The target vector describes the direction of the target in the ship's reference frame. It is a unit vector (length 1) pointing in the direction the radar reaches the target. If the radar experiences a displacement Δr due to attitude changes, then the equivalent range change along the target direction (i.e., the direction of the target vector vn) is: That is, projecting the displacement Δr of the radar module onto the target direction; The distance R between the target and the radar is corrected to obtain a new distance R' = R + D3.

2. The radar detection method based on the BeiDou system according to claim 1, characterized in that, Several angle combinations are available, including: Set the pitch angle range, yaw angle range, and roll angle range; Starting from the beginning of the pitch angle range, yaw angle range, and roll angle range respectively, set several pitch angle nodes, yaw angle nodes, and roll angle nodes at preset angle intervals; A single angle combination includes a pitch angle node, a yaw angle node, and a roll angle node, and different angle combinations contain different pitch angle nodes and / or yaw angle nodes and / or roll angle nodes.

3. The radar detection method based on the BeiDou system according to claim 2, characterized in that, Determining the sub-angle combination of position A and position B includes: Obtain the roll angle and pitch angle of position A from the initial position, and record them as the first angle and the second angle respectively. The first angle and the second angle constitute the sub-angle combination of position A. Obtain the roll angle, yaw angle, and pitch angle of position B as it deviates from the initial position, and record them as the third angle, fourth angle, and fifth angle, respectively. The third angle, fourth angle, and fifth angle constitute the sub-angle combination of position B.

4. A radar detection system based on the BeiDou system, characterized in that, include: Twin Module: Establish a digital twin model of the ship. The installation positions of the ship's Beidou module and radar module correspond to positions A and B on the numerical twin model, respectively. Calibration module: Sets several angle combinations, controls the posture of the digital twin model to satisfy angle combination i in virtual physical space, and controls the posture of the digital twin model to change from angle combination i to angle combination f; When the attitude of the digital twin model changes to the angle combination f, the deviation between position A and position B is obtained. Based on the deviation, the sub-angle combination of position A and position B is determined. The sub-angle combination of position A and position B constitutes the compensation set when the attitude of the ship changes from angle combination i to angle combination f. Compensation module: Obtain the angle combination Z1 satisfied by the ship's attitude at the current moment, and obtain the angle combination Z2 satisfied by the ship's attitude at the previous moment. Obtain the compensation set when the angle combination Z2 is transformed into the angle combination Z1, denoted as the calibration set. Extract sub-angle combinations J1 and J2 from positions A and B in the calibration set. Correct the BeiDou positioning data and radar positioning data based on the sub-angle combinations J1 and J2. The corrected BeiDou positioning data and radar positioning data are used to reflect the position of the detected target. The corrections to BeiDou positioning data include: Extract the sub-angle combination JA at position A in sub-angle combination J1, and extract the first angle j1 and the second angle j2 in sub-angle combination JA; Obtain the installation height H of the Beidou module; Calculate the first offset distance Second offset distance ; Where sign(j1) is the sign function; if j1 > 0, then sign(j1) = 1; if j ≤ 0, then sign(j1) = -1. Obtain longitude Y1 and latitude Y2 from the BeiDou positioning data, and correct longitude Y1 to obtain longitude. The latitude is obtained by correcting the latitude Y2. η is a preset correction coefficient; The corrected radar positioning data includes: Extract the sub-angle combination JB at position B in sub-angle combination J2, and extract the third angle j3, the fourth angle j4 and the fifth angle j5 in sub-angle combination JB; The distance R between the target and the radar, the azimuth angle ψ of the target relative to the radar, and the elevation angle θ of the target relative to the radar are obtained from the radar positioning data. Using the radar's own coordinate system as a reference, construct the direction vector of the detected target relative to the radar module: ； Among them, VR x VR y VR z These represent the components of the target's orientation along the x-axis, y-axis, and z-axis, respectively. Based on the sub-angle combination J2, construct the radar rotation matrix: ； Because the radar's installation position sways with the ship's hull, the direction vector vr it measures is defined in the radar's own coordinate system. To obtain the true direction of the detected target in the ship's reference system, the direction vector vr needs to be rotated back to the ship's reference system to obtain the target vector. The specific calculation formula is as follows: ； Among them, RB -1 This represents the inverse of the radar's rotation matrix, where T denotes the transpose, and vn x vn y vn z These represent the components of the target on the x-axis, y-axis, and z-axis of the ship's reference frame, respectively. The corrected azimuth angle of the target relative to the radar is calculated as ψ'=atan2(vn). y vn x ), and calculate the corrected elevation angle θ' = arcsin(vn) of the target relative to the radar. z ); The correction of radar positioning data also includes: In the ship's coordinate system, the position vector of the radar module when it is in its original position is rB=[0, 0, H1]. T H1 represents the installation height of the radar module; When the hull rotates, the displacement of the radar module is approximated as the cross product of the rotation vector and the arm using a first-order small-angle approximation: ； Where ε = [j3, j5, j4] T , y1=(1,0,0), y2=(0,1,0), y3=(0,0,1); The target vector describes the direction of the target in the ship's reference frame. It is a unit vector (length 1) pointing in the direction the radar reaches the target. If the radar experiences a displacement Δr due to attitude changes, then the equivalent range change along the target direction (i.e., the direction of the target vector vn) is: That is, projecting the displacement Δr of the radar module onto the target direction; The distance R between the target and the radar is corrected to obtain a new distance R' = R + D3.

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