A cloud and fog detection method based on the combination of lidar and microwave radar

Abstract

The present invention relates to a cloud and fog detection method based on a combination of laser radar and microwave radar, belonging to the field of radio. The detection method includes: using the coordinate system where the laser radar radiation antenna is located as a reference and calculating angle tracking parameters based on the installation differences of the laser-microwave radar extension antenna to correct the system pointing angle deviation caused by the installation position of the microwave radar extension, thereby ensuring the synchronization of the scanning space angle; controlling the time when the radar terminal sends the control signal to the laser radar extension and the microwave radar extension to ensure time synchronization so that the radar beam reaches the meteorological particle echo information consistently; after the radar terminal collects the data, feature parameter extraction and data fusion are performed on the composite observation data of the laser radar and cloud and fog radar. The present invention realizes the problem of target angle deviation caused by the spatial distribution differences of the laser radar and microwave radar during the composite observation of the laser-microwave radar system, thereby improving the consistency of the observed target.

Description

Technical Field

[0001] The present invention relates to the field of radio, and in particular to a cloud and fog detection method based on a combination of laser radar and microwave radar. Background Art

[0002] Clouds and fog are common features with distinct seasonal variations, and they significantly impact human production and daily life. Due to differences in the systems of microwave lidar (LiDAR), lidar and microwave radar use different antennas: lidar uses optical lenses, while microwave radar uses parabolic antennas. Therefore, in practical applications, separate microwave and lidar installations are often used for cloud and fog observation. Because cloud and fog meteorological targets are small in diameter and exhibit rapidly changing motion, if the lidar and microwave radar are installed at different locations or antenna heights, the traditional method of using the lidar-microwave radar scanning mechanism to observe at the same angle often suffers from inconsistencies in lidar-microwave radar observation data and inconsistent spatial angles due to deviations in the observed target angle and variations in particle motion characteristics at different times. This makes the application of cloud and fog observation data difficult, and therefore, solutions to these issues are currently under consideration. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a cloud and fog detection method based on the combination of laser radar and microwave radar, which solves the shortcomings of the existing technology.

[0004] The object of the present invention is achieved by the following technical solution: a cloud and fog detection method based on a combination of laser radar and microwave radar, the detection method comprising:

[0005] S1. Using the coordinate system of the laser radar radiation antenna as a reference and calculating the angle tracking parameters based on the installation differences of the laser-microwave radar extension antenna, the system pointing angle deviation caused by the installation position of the microwave radar extension is corrected to ensure the synchronization of the scanning space angle.

[0006] S2. By controlling the time when the radar terminal sends the control signal to the laser radar extension and the microwave radar extension, time synchronization is ensured so that the radar beam reaches the meteorological particle echo information in a consistent manner;

[0007] S3. After the radar terminal collects the data, it extracts feature parameters and fuses the composite observation data of the lidar and cloud radar.

[0008] The S1 includes the following contents:

[0009] S11. Installation subsystem information measurement: Based on the equipment system drawings and measuring tools, with the axis of the laser radar subsystem as the reference coordinate, obtain the spatial height and layout information of the microwave radar subsystem;

[0010] S12. Obtaining particle spatial information: Using the laser radar unit and its mechanical scanner to scan and observe the target area, obtaining accurate information on the distance of the cloud particles and the azimuth and pitch angles of the laser radar unit's scanning mechanism corresponding to the target;

[0011] S13. Calculate radar synchronization angle: Based on the spatial information of the target cloud particles acquired by the laser radar and the difference in height and installation distance between the microwave radar extension and the laser radar extension, calculate the pitch angle and azimuth angle that the microwave radar extension scanning mechanism should adjust with the laser radar extension coordinate system as a reference;

[0012] S14. According to the angle deviation correction result, the scanning mechanism of the microwave radar is controlled to correspond to the scanning angle to achieve angle tracking.

[0013] The calculation of the pitch angle that the microwave radar extension scanning mechanism should adjust in S13 specifically includes:

[0014] A1. The intersection of the azimuth rotation axis of the laser radar unit's scanning mechanism and the rotation center of the pitch mechanism is used as the system reference origin.

[0015] A2. Set the system reference origin to O, the center of the laser radar extension's transceiver window to point A, the cloud and fog weather target to point B, the intersection of the laser radar extension's azimuth axis and the horizontal platform to point K, the center of the microwave radar extension's antenna to point P, the microwave radar extension's elevation axis to point F, and the intersection of the microwave radar extension's azimuth axis and the horizontal platform to point N.

[0016] A3. Input the measurement information of the installation subsystem and draw a relationship diagram between meteorological targets and radar subsystems in the laser-microwave radar composite observation system based on the measurement model for cloud and fog target detection.

[0017] A4. Use the laser radar unit on the scanning mechanism of the laser radar extension to search. When cloud and fog meteorological particles are found, use the distance-time relationship to obtain the radial distance R of the laser radar extension. Also, read the azimuth scanning angle ∠γ and the elevation scanning angle ∠β on the scale of the laser radar extension scanning mechanism.

[0018] A5. Based on the triangular similarity relationship in the relationship diagram between the meteorological target and the radar extension during composite observation by the laser microwave radar, as well as the azimuth scanning angle ∠γ, the elevation scanning angle ∠β, and the radial distance R of the laser radar extension, trigonometric functions are used to obtain the height of the cloud and fog meteorological target in the laser unit window: BG = sin ∠β × R. Similarly, the vertical height difference between the cloud and fog meteorological target and the elevation axis: BH = sin ∠β × (R + a). Furthermore, the distance between the cloud and fog meteorological target projection point I on the installation platform and the elevation axis projection point K on the installation platform: IK = HO = cos ∠β × (R + a), where HO is the distance from the elevation axis to the system reference origin O. Because the distance a1 from the elevation axis of the laser radar extension to the installation platform is known, the relative height between the cloud and fog meteorological target and the installation platform: D1 = BH + HI = sin ∠β × (R + a) + a1, where HI is the distance from the elevation axis to the cloud and fog meteorological target projection point I on the installation platform.

[0019] A6. Since the laser radar extension and microwave radar extension are mounted on a horizontal platform, and the distance b1 from the microwave radar extension's pitch axis to the mounting platform is measured, the relative height between the microwave radar extension's pitch axis and the cloud and fog meteorological target is BQ = D1 - b1 = sin∠β×(R+a) + a1-b1. Furthermore, the distance between the microwave radar extension's pitch axis projection on the ground, N, and the cloud and fog meteorological target's ground projection point, I, is NI = NK + IK = L + IK = L + cos∠β×(R+a), where NK is the distance from the microwave radar extension's pitch axis projection on the ground, N, to its projection point on the mounting platform, K. L is the distance from the laser radar extension's azimuth axis to the microwave radar extension's azimuth axis.

[0020] A7. Express the elevation angle of the microwave radar extension as ∠α, which is the synchronous elevation scanning angle of the microwave radar extension. Then ∠α=arctan(sin∠β×(R+a)+ a1- b1) / (L+ cos∠β×(R+a)).

[0021] The calculation of the azimuth angle that the microwave radar extension scanning mechanism should adjust in S13 specifically includes:

[0022] B1. Set the projection point of the laser radar extension's azimuth rotation center on the horizontal plane to K1, the projection point of the microwave radar extension's azimuth rotation axis on the horizontal plane to N1, and the projection point of the cloud and fog weather target on the horizontal plane to B1. Connect the projection points K1 and N1 to obtain the line segment K1N1 and extend it. At the same time, draw a perpendicular line along the line segment K1N1 to the cloud and fog weather target's projection point B1 on the ground, and make the perpendicular line intersect with the extension line of K1N1. The intersection point is set to B0.

[0023] B2. Based on the triangle similarity relationship between meteorological targets and radar extensions during composite observation by laser microwave radar, assuming that the distance between the horizontal projection of the cloud and fog meteorological targets and the laser radar extension is R1, we can obtain R1 = R × cos ∠β. Furthermore, we can obtain that the distance between points B1 and B0 = the distance between points K0 and K1, that is, B1B0 = K1K0 = R1 × cos ∠γ = R × cos ∠β × cos ∠γ, where K0 is the intersection of point B1 and the distance from the azimuth rotation center of the laser radar extension to point K1.

[0024] B3. Therefore, in the triangle formed by points B1, B0, and N1, tan∠B0N1B1=distance B1B0 / distance N1 B0=distance B1B0 / distance NI=(R×cos∠β×cos∠γ) / (L+ cos∠β×(R+a)), and the angle between distance B1B0 and distance N1 B0 is ∠B0N1B1=arctan(R×cos∠β×cos∠γ) / (L+ cos∠β×(R+a)). According to the relationship ∠B0N1B1+∠B1N1N=90°, the azimuth angle of the synchronous scanning of the microwave radar extension is ∠B1N1N=90°-∠B0N1B1=90°-arctan(R×cos∠β×cos∠γ) / (L+ cos∠β×(R+a)).

[0025] The S2 includes:

[0026] S21. According to sin∠α=distance BQ / radial distance r of microwave radar extension, when the laser radar extension scans the foggy weather target B, the radial distance r between the foggy weather target and the microwave radar extension is distance QB / sin∠α=(D1-b1) / sin∠α=(sin∠β×(R+a)+a1-b1) / sin[arctan(sin∠β×(R+a)+a1-b1) / (L+cos∠β×(R+a))];

[0027] S22. Set the time from the laser radar extension energy output to the foggy weather target receiving the weather echo as t = R / c. Ignoring the distance b between the microwave radar extension antenna feed source and the elevation scanning center, set the time from the microwave radar extension energy output to the foggy weather target receiving the weather echo as T = r / c = (sin∠β×(R+a)+a1-b1) / c×sin[arctan(sin∠β×(R+a)+a1-b1) / (L+cos∠β×(R+a))], and set the time interval between the laser transmission signal and the microwave transmission signal as ∆t. Then, ∆t = tT = R / c-(sin∠β×(R+a)+a1-b1) / c×sin[arctan(sin∠β×(R+a)+a1-b1) / (L+cos∠β×(R+a))], where c is the speed of light.

[0028] S23. Similarly, when the distance b from the microwave radar extension antenna feed source to the elevation scanning center cannot be ignored, the time from the microwave radar extension energy output to the cloud and fog weather target receiving the weather echo is set to T = (rb) / c = {(sin∠β×(R+a)+a1-b1) / sin[arctan(sin∠β×(R+a)+a1-b1) / (L+ cos∠β×(R+a))]-b} / c, and the time interval between the laser transmission signal time and the microwave transmission signal time is set to ∆t, then ∆t = tT = R / c – {(sin∠β×(R+a)+a1-b1) / sin[arctan(sin∠β×(R+a)+a1-b1) / sin[arctan(sin∠β×(R+a)+a1-b1) / (L+ cos∠β×(R+a))]-b} / c.

[0029] When ∆t is a positive value, the radar terminal sends the control signal to the laser radar extension ∆t seconds earlier than the microwave radar extension. When ∆t is a negative value, the radar terminal sends the control signal to the laser radar extension ∆t seconds later than the microwave radar extension.

[0030] The S3 needs to combine radar echoes with different meteorological characteristics during data fusion to switch the dependent data source.

[0031] The present invention has the following advantages: a cloud and fog detection method based on the combination of laser radar and microwave radar, which realizes the problem of target angle deviation caused by the difference in spatial distribution of laser radar and microwave radar during composite observation of laser-microwave radar system, thereby improving the consistency of observed targets; it can realize that the microwave laser radar detection energy signal reaches the observed target at the same time, solving the problem of poor data consistency caused by the asynchronous time of traditional laser microwave radar control energy reaching the target; even if the laser radar extension and the microwave radar extension are not observed in the same field, as long as there is no obstruction between the laser radar extension and the microwave radar extension and the terminal has the feature that can communicate with the extension, after obtaining the relevant installation parameter information of the laser radar and the microwave radar, the angle can be controlled to perform simultaneous and spatial observation, which has application flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process of the present invention;

[0033] Figure 2 A schematic diagram of the process of scanning space angle synchronization;

[0034] Figure 3 This is a schematic diagram of the vertical elevation plane of the relationship between the meteorological target and the radar extension during laser microwave radar composite observation;

[0035] Figure 4 This is a horizontal azimuth diagram of the relationship between meteorological targets and radar extensions during laser microwave radar composite observation. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application provided below in conjunction with the drawings is not intended to limit the scope of protection of the present application for which protection is claimed, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. The present invention is further described below in conjunction with the drawings.

[0037] The present invention relates to a laser-microwave composite cloud and fog observation method, which can enable the microwave / laser irradiation beams of laser-microwave radars at different antenna heights and installation positions to synchronously detect and analyze cloud and fog meteorological targets in the same target area. Since the operating wavelengths of Ka-band microwaves and laser radars are different, simultaneous irradiation of the same cloud and fog meteorological targets will not cause data interference.

[0038] Laser-microwave cloud and fog composite observations typically consist of a laser radar extension, a microwave radar extension, a radar system terminal, and its supporting scanning motion mechanism, as well as communication and power supply facilities. After the control commands of the laser radar extension and microwave radar extension are output by the radar terminal, the system features time synchronization of observation data, spatial angle alignment of observation targets, and good consistency of observation data. After receiving the user's scanning command information, the radar terminal uses this patented technology to calculate angle tracking parameters based on the installation parameters. The time difference caused by the radial distance is calculated based on the spatial difference information between the laser radar and microwave radar antenna centers to obtain the startup timing difference, thereby improving the system's observation accuracy. Because the laser radar and microwave radar use the same terminal, if one radar fails during observation operation, the other radar can be quickly controlled to stop observation, ensuring that the data length of the composite detection system is consistent.

[0039] like Figure 1 As shown, specifically including the following:

[0040] Step 1: Scanning Space Angle Synchronization: Due to differences in aperture size, mounting position, and height between the microwave antenna and the LiDAR lens, the LiDAR and microwave radar units observe the same target at different spatial angles, necessitating laser unit angle tracking synchronization. This method uses the coordinate system of the LiDAR antenna as a reference and calculates angle tracking parameters based on the differences in the installation of the laser and microwave radar antennas to correct for system pointing angle deviations caused by the microwave radar unit's mounting position. This ensures that the microwave and laser data collected represent the same target area.

[0041] Further, if Figure 2 As shown, specifically including the following:

[0042] Step (1) Installation subsystem information measurement: The method of measuring the subsystem installation information is: according to the equipment system drawings and measuring tools, with the axis of the laser radar extension as the reference coordinate, obtain the spatial height and layout information of the microwave radar extension and related units.

[0043] Step (2) Obtaining particle space information: The principle of obtaining target particle space information technology is: using the laser radar extension and its mechanical scanning mechanism to scan and observe the target area. The scanning angle information can be read by the angle scale transmitted back by the laser mechanical scanning, and the distance to the foggy weather target is usually tested by the pulse ranging method. The method is: measuring the target distance information is based on the electromagnetic wave propagating in a straight line at a fixed speed in a uniform medium (the propagation speed in free space is approximately equal to the speed of light c). Assuming that the laser radar is located at point A and the foggy weather target is at point B, it can be known that the straight-line distance R (i.e., radial distance) from the foggy weather target to the laser radar extension antenna can be obtained by measuring the time t required for the electromagnetic wave to travel back and forth once to obtain the distance R between the laser radar extension and the foggy weather target, that is, according to It can be seen that .

[0044] Step (3) Calculate the radar synchronization angle: The principle of calculating the microwave radar synchronization angle is: the radar terminal calculates the angle that the microwave radar extension and the scanning unit should be adjusted synchronously based on the distance of the target cloud and fog meteorological target obtained by the laser radar extension and the difference caused by the height and installation distance between the microwave radar extension and the scanning antenna and the laser radar extension and its scanning unit antenna. Usually, since the distance between the center of the microwave radar extension antenna and the center point of the laser radar extension lens, the height, distance, antenna axis and other parameters between the center of the microwave radar extension antenna and the installation platform can be input using composite observation system drawings or measurement tools, after using the laser radar extension to measure the distance R between the center position of the cloud and fog meteorological target and the laser radar extension, the angle that the microwave radar extension and the mechanical scanning mechanism should be adjusted can be calculated for tracking. The specific calculation method is as follows:

[0045] Step a) The focal point of the azimuth rotation axis of the laser radar unit scanning mechanism and the rotation center of the pitch mechanism is used as the system reference origin;

[0046] Step b) Figure 3 As shown, the system reference origin is set to O, the center of the laser radar extension transceiver window is point A, the cloud and fog weather target is point B, the intersection of the laser radar extension azimuth axis and the horizontal platform is K, the center of the microwave radar extension antenna is point P, the pitch axis point of the microwave radar extension is F, and the intersection of the microwave radar extension azimuth axis and the horizontal platform is N.

[0047] In step c), the installation subsystem measurement information is imported. Based on the cloud and fog target detection measurement model, a relationship diagram between meteorological targets and radar subunits can be drawn in the laser-microwave radar composite observation system. If the distance from the laser radar subunit's pitch axis to the transceiver window plane is a, the distance from the laser radar subunit's pitch axis to the mounting platform is a1, the distance from the microwave radar subunit's pitch axis to the microwave radar subunit's transceiver feed is b, and the distance from the microwave radar subunit's pitch axis to the mounting platform is b1, then the distance from the laser radar subunit's azimuth axis to the microwave radar subunit's azimuth axis is L.

[0048] Step d) Search using the laser radar unit carried by the laser radar unit's scanning mechanism. When cloud and fog meteorological particles are found, the radial distance information R between the target particle and the laser radar unit is obtained using the method described in "Obtaining Particle Spatial Information" (distance and time relationship). The azimuth scanning angle and pitch scanning angle of the laser radar unit's scanning mechanism scale are read and recorded as ∠γ and ∠β, respectively.

[0049] Step e) by Figure 4 It can be seen that in the relationship diagram between meteorological targets and radar extensions during composite observation by laser microwave radar, there are right triangles △ABG, △OBH, and △BQF. The right triangles △ABG and △OBH have similar relationships. Point A represents the laser radar emission window, and point B represents the position of the cloud and fog meteorological target.

[0050] In step f), since the cloud and fog meteorological particle position information has been obtained based on the laser radar extension in step d), including the azimuth scanning angle ∠γ, the elevation scanning angle ∠β, and the radial distance R of the laser radar extension, the height of the cloud and fog meteorological target in the laser unit window can be obtained by using the trigonometric function relationship: BG = sin degrees ∠β × R.

[0051] Step g) Since the right triangle △ABG is similar to the right triangle △OBH and the distance OB from the lidar pitch axis to the foggy weather target is R + a (i.e., the distance AB from the laser transceiver window to the foggy weather target + the distance OA from the lidar extension pitch axis to the transceiver window plane), trigonometric functions can be used to obtain the vertical height difference between the foggy weather target and the pitch axis, BH = sin∠β × (R + a).

[0052] Step h) From the above conditions and the combined diagram, it can be seen that the distance between the projection point I of the cloud and fog meteorological target on the installation platform and the projection point K of the pitch axis on the installation platform is IK=HO=cos∠β×(R+a).

[0053] Step i) Since the distance a1 from the pitch axis of the lidar unit to the mounting platform is known, the relative height between the cloud and fog target and the mounting platform can be calculated as D1 = BH + HI = sin∠β × (R + a) + a1.

[0054] Step j) Since the laser radar extension unit and microwave radar extension unit are usually installed on a horizontal platform, and the distance b1 from the pitch axis of the microwave radar extension unit to the installation platform is measured, the relative height of the pitch axis of the microwave radar extension unit and the cloud and fog meteorological target can be obtained as BQ = D1- b1 = sin∠β×(R+a)+ a1- b1, and the distance NI between the projection N of the microwave radar extension unit's pitch axis on the ground and the projection point I of the cloud and fog meteorological target on the ground exists as NK+IK=L+IK=L+ cos∠β×(R+a).

[0055] Step k) consists of Figure 4 It can be seen that there is a relationship: distance NI = distance QF, that is, distance QF = L + cos∠β×(R+a).

[0056] Step 1) Since there is a right triangle △BQF, trigonometric functions yield: tan = ∠QFB = height BQ / distance QF. Therefore, ∠QFB = arctan(height BQ / distance QF) = arctan((sin∠β×(R+a)+ a1- b1) / (L+cos∠β×(R+a))). Denote the elevation angle of the microwave radar extension by ∠α, then ∠α = arctan(height BQ / distance QF) = arctan(sin∠β×(R+a)+ a1- b1) / (L+ cos∠β×(R+a)).

[0057] Step m) Therefore, in summary, after adopting step (1) to measure the installation distance and combining step (2) to obtain the target particle space information, the synchronous scanning pitch angle of the microwave radar extension can be obtained by using the above-mentioned method of calculating the microwave radar synchronization angle: ∠α=arctan(sin∠β×(R+a)+ a1- b1) / (L+ cos∠β×(R+a)).

[0058] Step n) as Figure 4 As shown, since due north is usually taken as the azimuth 0° position (fixed north) in the radar system, the projection point of the azimuth rotation center of the laser radar extension on the horizontal plane is set as K1, the projection point of the azimuth rotation axis of the microwave radar extension on the horizontal plane is set as N1, and the projection point of the cloud and fog weather target on the horizontal plane is set as B1. The projection point K1 and the projection point N1 can be connected to obtain the line segment K1N1 and then an extension line can be drawn. At the same time, a perpendicular line can be drawn along the line segment K1N1 direction of the cloud and fog weather target at the ground projection point B1 and the perpendicular line can be intersected with the extension line of K1N1. The intersection point is set as B0.

[0059] Step o) consists of Figure 4It can be seen that there are right triangles △B1B0K1 and △B1B0N1. According to the measurement principle of cloud target detection, there is a distance R1 between the cloud meteorological target's projection on the horizontal plane and the actual object of the lidar. From the figure, it is easy to get the relationship between the distance R1 and the radial distance R of the cloud meteorological target measured by the lidar: R1=R×cos∠β, that is, the distance R1 between the cloud meteorological target's projection on the ground and the radar=the radial distance R of the cloud meteorological target multiplied by the cosine COS∠β of the radar's pitch angle in the horizontal plane.

[0060] Step P) Therefore, the distance between point B1 and point B0 = the distance between point K0 and point K1, that is, B1B0 = K1K0 = R1×cos∠γ. Since R1 = R×cos∠β, B1B0 = R1×cos∠γ = R×cos∠β×cos∠γ.

[0061] Step q) consists of Figure 4 It can be seen that the relationship between points B0, N1, and K1 is: the distance between point B0 and point N1 = the distance between point B0 and point K1 + the distance between point N1 and point K1. At the same time, since the laser radar and microwave radar are directly or indirectly installed on the horizontal installation platform, the distance between point B0 and point N1 B0N1 = the distance NI between point I and point N. Therefore, the distance B0N1 = distance NI = L + distance IK = L + cos∠β×(R+a).

[0062] Step r) Using the results from steps p) and q) in the right triangle △B1B0N1, we can obtain: tan∠B0N1B1=distance B1B0 / distance N1 B0=distance B1B0 / distance NI=(R×cos∠β×cos∠γ) / (L+cos∠β×(R+a)), therefore, ∠B0N1B1=arctan(R×cos∠β×cos∠γ) / (L+cos∠β×(R+a)).

[0063] Step s) Since ∠B0N1B1+∠B1N1N=90°, ∠B1N1N=90°-∠B0N1B1=90°-arctan(R×cos∠β×cos∠γ) / (L+cos∠β×(R+a)).

[0064] Step t) Since ∠B1N1N is expressed as the microwave radar azimuth scanning angle in the laser microwave radar system, ∠B1N1N can be expressed by ∠θ. Therefore, the azimuth angle of the microwave radar extension synchronous scanning is ∠θ = 90° - ∠B0N1B1 = 90° - arctan (R × cos ∠β × cos ∠γ) / (L + cos ∠β × (R + a)).

[0065] Step u) In summary, when the laser radar captures a cloud target at a radial distance R at an azimuth scanning angle ∠γ and a pitch scanning angle ∠β, the antenna angle required for the microwave radar mechanical scanning mechanism to synchronize the scans is:

[0066] The pitch angle of synchronous scanning: ∠α=arctan(sin∠β×(R+a)+ a1- b1) / ( L+ cos∠β×(R+a)).

[0067] Azimuth angle of synchronous scanning: ∠θ=90°-∠B0N1B1=90°-arctan(R×cos∠β×cos∠γ) / (L+cos∠β×(R+a)).

[0068] Step (4) controls the angle of the microwave antenna to achieve angle tracking (according to the angle deviation correction result, controls the scanning mechanism of the microwave radar to correspond to the scanning angle).

[0069] Step 2: Time Synchronization: To address the issue of observing cloud and fog meteorological targets by separately setting up microwave radar extensions and lidar extensions, and to resolve the technical issue of data angle deviation during laser and microwave radar acquisition, the laser and microwave radars used in the present invention should share a common system power supply, communication cables, and radar terminals to avoid unexpected errors. The principle of time synchronization is to use the timing of the control signals sent down by the radar terminal to resolve the problem of inconsistent radar beam echo information reaching meteorological particles due to the difference in the radial distance R between the lidar extension and the radial distance r between the microwave radar extension caused by the difference in the installation position of the microwave-lidar extension. The specific calculation method includes the following:

[0070] (1) According to the above results, sin∠α=distance BQ / radial distance r of microwave radar extension. Therefore, when the laser radar extension scans the foggy weather target B, the relationship between the foggy weather target and the radial distance r of the microwave radar extension is: radial distance r=distance QB / sin∠α=(D1- b1) / sin∠α=(sin∠β×(R+a)+ a1- b1) / sin[arctan(sin∠β×(R+a)+ a1- b1) / (L+ cos∠β×(R+a))].

[0071] (2) The distance measurement method of radar is to transmit a high-frequency signal to the target, and then calculate the distance based on the arrival time of the signal and the speed of the signal transmission. The signal propagates in space at the speed of light. The distance after the pulse signal encounters the target is the radar radial distance. Since distance = speed × time, and the speed of microwave and laser propagation in air is the same and constant (usually c = 3 × 10 8m / s), and the time it takes for the laser radar to output energy to the cloud and fog weather target and receive the weather echo is set to t seconds, we can get t=R / (3×10 8 ) in seconds. Similarly, when ignoring the distance b from the antenna feed source of the microwave radar extension to the elevation scanning center, the time from the microwave radar energy output to the cloud and fog weather target receiving the weather echo can be set to T seconds, and we can get: T=r / c=(sin∠β×(R+a)+ a1- b1) / c×sin[arctan(sin∠β×(R+a)+a1- b1) / (L+cos∠β×(R+a))].

[0072] (3) Similarly, when the time interval between the laser emission signal and the microwave emission signal (i.e., the timing of the control signal sent by the radar terminal) is set to ∆t, the above data can be used to obtain:

[0073] Δt= tT= R / c-(sin∠β×(R+a)+a1-b1) / c×sin[arctan(sin∠β×(R+a)+a1-b1) / ( L+cos∠β×(R+a))].

[0074] (4) Therefore, when the distance b between the antenna feed source of the microwave radar extension and the elevation scanning center is ignored, the timing sequence ∆t of the control signal sent by the radar terminal is:

[0075] Δt= tT= R / c-(sin∠β×(R+a)+a1-b1) / c×sin[arctan(sin∠β×(R+a)+a1-b1) / ( L+cos∠β×(R+a))];

[0076] When the distance b between the antenna feed source of the microwave radar extension and the elevation scanning center cannot be ignored, the timing sequence ∆t of the control signal sent by the radar terminal is:

[0077] Δt= tT= R / c –{(sin∠β×(R+a)+a1- b1) / sin[arctan(sin∠β×(R+a)+a1-b1) / ( L+ cos∠β×(R+a))]-b} / c.

[0078] Furthermore, when the value is positive, the laser radar subsystem time sent by the radar terminal is output ∆t seconds ahead of the microwave radar subsystem; when the value is negative, the laser radar subsystem time sent by the radar terminal is output ∆t seconds behind the microwave radar subsystem. This method ensures that the laser signal from the laser radar subsystem and the microwave signal from the microwave radar subsystem arrive at the cloud and fog meteorological target cluster at the same time (i.e., time synchronization). Since the microwave-lidar pulse repetition frequency is typically no higher than 10kHz (pulse interval ≤ 0.1mS / time), the electromagnetic wave propagation rate indicates that even if the laser echo signal and the microwave signal return to the corresponding antenna at different times, both the laser energy and the microwave energy can reach the receiver of the microwave radar composite observation radar before the next energy is emitted, thus not affecting the authenticity of the collected data.

[0079] Step 3: Data fusion: After collecting relevant data, the radar terminal uses traditional multimodal feature fusion technology or neural network-based fusion technology to fuse the laser-microwave cloud and fog composite observation data and extract relevant feature parameters. It should be noted that due to the different penetration capabilities of laser and microwave, data fusion needs to be combined with radar echoes for different meteorological characteristics and rely on data source switching. For example, on foggy days, cloud and fog data relies on millimeter-wave radar observations, and on clear days, it relies on lidar observation data.

[0080] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention is capable of various other combinations, modifications, and improvements, and is capable of modifications within the scope of the concepts described herein, through the above teachings, or through techniques or knowledge in the relevant fields. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A cloud and fog detection method based on a combination of laser radar and microwave radar, characterized by: The detection method comprises: S1. Using the coordinate system of the laser radar radiation antenna as a reference and calculating the angle tracking parameters based on the installation differences of the laser-microwave radar extension antenna, the system pointing angle deviation caused by the installation position of the microwave radar extension is corrected to ensure the synchronization of the scanning space angle. S2. By controlling the time when the radar terminal sends the control signal to the laser radar extension and the microwave radar extension, time synchronization is ensured so that the radar beam reaches the meteorological particle echo information in the same way; S3. After the radar terminal collects the data, it extracts characteristic parameters and fuses the composite observation data of the lidar and cloud radar; The S1 includes the following contents: S11. Installation subsystem information measurement: Based on the equipment system drawings and measurement tools, with the axis of the laser radar extension as the reference coordinate, obtain the spatial height and layout information of the microwave radar extension; S12. Obtaining particle spatial information: Using the laser radar unit and its mechanical scanner to scan and observe the target area, obtaining accurate information on the distance of the cloud particles and the azimuth and pitch angles of the laser radar unit's scanning mechanism corresponding to the target; S13. Calculate radar synchronization angle: Based on the spatial information of the target cloud particles acquired by the laser radar and the difference in height and installation distance between the microwave radar extension and the laser radar extension, calculate the pitch angle and azimuth angle that the microwave radar extension scanning mechanism should adjust with the laser radar extension coordinate system as a reference; S14. According to the angle deviation correction result, the scanning mechanism of the microwave radar is controlled to correspond to the scanning angle to achieve angle tracking.

2. The cloud and fog detection method based on a combination of laser radar and microwave radar according to claim 1, characterized in that: The calculation of the pitch angle that the microwave radar extension scanning mechanism should adjust in S13 specifically includes: A1. The intersection of the azimuth rotation axis of the laser radar unit's scanning mechanism and the rotation center of the pitch mechanism is used as the system reference origin. A2. Set the system reference origin to O, the center of the laser radar extension's transceiver window to point A, the cloud and fog weather target to point B, the intersection of the laser radar extension's azimuth axis and the horizontal platform to point K, the center of the microwave radar extension's antenna to point P, the microwave radar extension's elevation axis to point F, and the intersection of the microwave radar extension's azimuth axis and the horizontal platform to point N. A3. Input the measurement information of the installation subsystem and draw a relationship diagram between meteorological targets and radar subsystems in the laser-microwave radar composite observation system based on the measurement model for cloud and fog target detection. A4. Use the laser radar unit on the scanning mechanism of the laser radar extension to search. When cloud and fog meteorological particles are found, use the distance-time relationship to obtain the radial distance R of the laser radar extension. Also, read the azimuth scanning angle ∠γ and the elevation scanning angle ∠β on the scale of the laser radar extension scanning mechanism. A5. Based on the triangular similarity relationship between the meteorological target and the radar extension during composite observation by the laser microwave radar, as well as the azimuth scanning angle ∠γ, the elevation scanning angle ∠β, and the radial distance R of the laser radar extension, the trigonometric function relationship is used to obtain the height of the cloud and fog meteorological target in the laser unit window BG=sin∠β×R. Similarly, the vertical height difference between the cloud and fog meteorological target and the elevation axis BH=sin∠β×(R+a) is obtained. Then, the distance between the cloud and fog meteorological target projection point I on the installation platform and the elevation axis projection point K on the installation platform is obtained IK=HO=cos∠β×(R+a). HO is the distance from the elevation axis to the system reference origin O. Since the distance a1 from the elevation axis to the installation platform is known, the relative height D1 between the cloud and fog meteorological target and the installation platform is obtained D1=BH+HI=sin∠β×(R+a)+ a1, HI is the distance from the pitch axis to the projection point I of the cloud and fog meteorological target on the installation platform, a is the distance from the pitch axis center of the laser radar extension to the plane of the transceiver window; A6. Since the laser radar extension and microwave radar extension are mounted on a horizontal platform, and the distance b1 from the microwave radar extension's pitch axis to the mounting platform is measured, the relative height between the microwave radar extension's pitch axis and the cloud and fog meteorological target is BQ = D1 - b1 = sin∠β×(R+a) + a1-b1. Furthermore, the distance between the microwave radar extension's pitch axis projection on the ground, N, and the cloud and fog meteorological target's ground projection point, I, is NI = NK + IK = L + IK = L + cos∠β×(R+a), where NK is the distance from the microwave radar extension's pitch axis projection on the ground, N, to its projection point on the mounting platform, K. L is the distance from the laser radar extension's azimuth axis to the microwave radar extension's azimuth axis. A7. Express the elevation angle of the microwave radar extension as ∠α, which is the synchronous elevation scanning angle of the microwave radar extension. Then ∠α=arctan(sin∠β×(R+a)+ a1- b1) / (L+ cos∠β×(R+a)).

3. The cloud and fog detection method based on a combination of laser radar and microwave radar according to claim 2, characterized in that: The calculation of the azimuth angle that the microwave radar extension scanning mechanism should adjust in S13 specifically includes: B1. Set the projection point of the laser radar extension's azimuth rotation center on the horizontal plane to K1, the projection point of the microwave radar extension's azimuth rotation axis on the horizontal plane to N1, and the projection point of the cloud and fog weather target on the horizontal plane to B1. Connect the projection points K1 and N1 to obtain the line segment K1N1 and extend it. At the same time, draw a perpendicular line along the line segment K1N1 to the cloud and fog weather target's projection point B1 on the ground, and make the perpendicular line intersect with the extension line of K1N1. The intersection point is set to B0. B2. Based on the triangle similarity relationship between meteorological targets and radar extensions during composite observation by laser microwave radar, assuming that the distance between the horizontal projection of the cloud and fog meteorological targets and the laser radar extension is R1, we can obtain R1 = R × cos ∠β. Furthermore, we can obtain that the distance between points B1 and B0 = the distance between points K0 and K1, that is, B1B0 = K1K0 = R1 × cos ∠γ = R × cos ∠β × cos ∠γ, where K0 is the intersection of point B1 and the distance from the azimuth rotation center of the laser radar extension to point K1. B3. Therefore, in the triangle formed by points B1, B0, and N1, tan∠B0N1B1=distance B1B0 / distance N1 B0=distance B1B0 / distance NI=(R×cos∠β×cos∠γ) / (L+ cos∠β×(R+a)), and the angle between distance B1B0 and distance N1 B0 is ∠B0N1B1=arctan(R×cos∠β×cos∠γ) / (L+ cos∠β×(R+a)). According to the relationship ∠B0N1B1+∠B1N1N=90°, the azimuth angle of the synchronous scanning of the microwave radar extension is ∠B1N1N=90°-∠B0N1B1=90°-arctan(R×cos∠β×cos∠γ) / (L+ cos∠β×(R+a)).

4. The cloud and fog detection method based on a combination of laser radar and microwave radar according to claim 3, characterized in that: The S2 includes: S21. According to sin∠α=distance BQ / radial distance r of microwave radar extension, when the laser radar extension scans the foggy weather target B, the radial distance r between the foggy weather target and the microwave radar extension is distance QB / sin∠α=(D1- b1) / sin∠α=(sin∠β×(R+a)+ a1- b1) / sin[arctan(sin∠β×(R+a)+ a1- b1) / (L+cos∠β×(R+a))]; S22. Set the time from the laser radar extension energy output to the foggy weather target receiving the weather echo as t = R / c. Ignoring the distance b between the microwave radar extension antenna feed source and the elevation scanning center, set the time from the microwave radar extension energy output to the foggy weather target receiving the weather echo as T = r / c = (sin∠β×(R+a)+a1-b1) / c×sin[arctan(sin∠β×(R+a)+a1-b1) / (L+cos∠β×(R+a))], and set the time interval between the laser transmission signal and the microwave transmission signal as ∆t. Then, ∆t = tT = R / c-(sin∠β×(R+a)+a1-b1) / c×sin[arctan(sin∠β×(R+a)+a1-b1) / (L+cos∠β×(R+a))], where c is the speed of light. S23. Similarly, when the distance b from the microwave radar extension antenna feed source to the elevation scanning center cannot be ignored, the time from the microwave radar extension energy output to the cloud and fog weather target receiving the weather echo is set to T = (rb) / c = {(sin∠β×(R+a)+a1-b1) / sin[arctan(sin∠β×(R+a)+a1- b1) / ( L+ cos∠β×(R+a))]-b} / c, and the time interval between the laser transmission signal time and the microwave transmission signal is set to ∆t, then ∆t = tT = R / c – {(sin∠β×(R+a)+a1- b1) / sin[arctan(sin∠β×(R+a)+a1- b1) / ( L+ cos∠β×(R+a))]-b} / c.

5. The cloud and fog detection method based on a combination of laser radar and microwave radar according to claim 4 is characterized in that: When ∆t is a positive value, the radar terminal sends the control signal to the laser radar extension ∆t seconds earlier than the microwave radar extension. When ∆t is a negative value, the radar terminal sends the control signal to the laser radar extension ∆t seconds later than the microwave radar extension.

6. The cloud and fog detection method based on a combination of laser radar and microwave radar according to claim 1, characterized in that: The S3 needs to combine radar echoes with different meteorological characteristics during data fusion to switch the dependent data source.

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