Cloud detection method based on combination of laser radar and microwave radar

Abstract

The invention relates to a cloud detection method based on combination of a laser radar and a microwave radar, and belongs to the field of radio. The detection method comprises the steps that a coordinate system where a laser radar radiation antenna is located is used as a reference, and system pointing angle deviation caused by the installation position of a microwave radar extension set is corrected in the mode that angle tracking parameters are calculated according to laser-microwave radar extension set antenna installation differences, and scanning space angle synchronization is guaranteed; time synchronization is guaranteed by controlling the time of a radar terminal issuing a control signal to a laser radar extension set and a microwave radar extension set, so that radar beams arrive at meteorological particle echo information to be consistent; after the radar terminal collects data, characteristic parameter extraction and data fusion are carried out on the composite observation data of the laser radar and the cloud radar. According to the method, the problem of target angle deviation caused by spatial distribution difference of the laser radar and the microwave radar during composite observation of the laser-microwave radar system is solved, and the consistency of observed targets is improved.

Description

Technical Field

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

[0002] Clouds and fog are common features with obvious seasonal changes, among which fog has a great impact on human production and life. Due to the difference in the microwave lidar system, the antennas of lidar and microwave radar are not the same. Lidar uses optical lenses and microwave radar uses parabolic antennas. Therefore, in practical applications, microwave radar and lidar are usually set up separately to observe clouds and fog. Since the diameter of cloud and fog meteorological targets is small and the movement characteristics change very quickly, if the lidar and microwave radar are set up at different positions or antenna heights, the traditional method of using the laser-microwave radar scanning mechanism to observe at the same angle is still used. Usually, there will be shortcomings such as poor consistency of lidar-microwave radar observation data and inconsistent observation space angles due to the deviation of the observed target angle and the difference in the movement characteristics of particles at different times, making the application of cloud and fog observation data more difficult. Therefore, how to solve this problem is currently needed to be considered. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a cloud and fog detection method based on a combination of laser radar and microwave radar, thereby solving the shortcomings of the prior art.

[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: S1. Using the coordinate system of the laser radar radiation antenna as a reference and calculating the angle tracking parameters according to the installation difference 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, the time synchronization is ensured so that the radar beam reaches the meteorological particle echo information in a consistent manner; S3. After the radar terminal collects the data, it extracts feature parameters and fuses the composite observation data of the lidar and cloud radar.

[0005] The S1 includes the following contents: S11. Installation subsystem information measurement: According to the equipment system drawings and measuring tools, take the axis of the laser radar extension as the reference coordinate to obtain the height and layout information of the microwave radar extension in space; S12. Obtain particle spatial information: Use the lidar subsystem and its mechanical scanner to scan and observe the target area, and obtain the accurate information of the distance of cloud and fog particles and the azimuth and pitch angles of the scanning mechanism of the lidar subsystem corresponding to the target. S13. Calculate the radar synchronization angle: According to the spatial information of the target cloud and fog particles obtained by the lidar and combined with the differences caused by the height and installation distance of the microwave radar subsystem relative to the lidar subsystem, calculate the pitch angle and azimuth angle that the scanning mechanism of the microwave radar subsystem should adjust with the lidar subsystem coordinate system as the reference. S14. According to the angle deviation correction result, control the scanning mechanism of the microwave radar to the corresponding scanning angle to achieve angle tracking.

[0006] The specific calculation of the pitch angle that the scanning mechanism of the microwave radar subsystem should adjust in S13 includes: A1. Take the intersection point of the azimuth rotation axis and the pitch mechanism rotation center of the lidar subsystem scanning mechanism as the system reference origin. A2. Set the system reference origin as O, the center of the lidar subsystem transceiver window as point A, the cloud and fog meteorological target as point B, the intersection point of the lidar subsystem azimuth axis and the horizontal platform as K, the antenna center of the microwave radar subsystem as point P, the pitch axis center point of the microwave radar subsystem as F, and the intersection point of the azimuth axis of the microwave radar subsystem and the horizontal platform as N. A3. Substitute the information measured by the installation subsystem, and draw the relationship diagram between the meteorological target and the radar subsystem in the laser-microwave radar composite observation system according to the measurement model of the cloud and fog target detection. A4. Use the lidar unit carried by the scanning mechanism of the lidar subsystem to search. When the cloud and fog meteorological particles are searched, obtain the radial distance R of the lidar subsystem using the relationship between distance and time, and read the azimuth scanning angle ∠γ and pitch scanning angle ∠β of the lidar subsystem scanning mechanism scale. A5. According to the similar triangle relationship existing in the relationship diagram between the meteorological target and the radar subsystem during the laser-microwave radar composite observation, as well as the azimuth scanning angle ∠γ, pitch scanning angle ∠β and the radial distance R of the lidar subsystem, use the trigonometric function relationship to obtain the height BG = sin∠β×R of the cloud and fog meteorological target at the laser unit window. Similarly, obtain the vertical height difference BH = sin∠β×(R + a) between the cloud and fog meteorological target and the pitch axis. Then obtain the distance IK = HO = cos∠β×(R + a) between the projection I point of the cloud and fog meteorological target on the installation platform and the projection K point of the pitch axis on the installation platform. HO is the distance from the pitch axis center to the system reference origin O. Also, since the distance a1 from the lidar subsystem pitch axis center to the installation platform is known, the relative height D1 between the cloud and fog meteorological target and the installation platform is obtained as D1 = BH + HI = sin∠β×(R + a)+ a1, where HI is the distance from the pitch axis to the projection I point of the cloud and fog meteorological target on the installation platform. A6. Since the lidar unit and the microwave radar unit are installed on a horizontal platform, and the distance b1 from the pitch axis center of the microwave radar unit to the installation platform is measured, the relative height BQ between the pitch axis of the microwave radar unit and the cloud and meteorological target is obtained as BQ = D1 - b1 = sin∠β×(R + a) + a1 - b1. Also, the distance NI between the projection N of the pitch axis of the microwave radar unit on the ground and the projection point I of the cloud and meteorological target on the ground is obtained as NI = NK + IK = L + IK = L + cos∠β×(R + a), where NK is the distance from the projection N of the pitch axis of the microwave radar unit on the ground to the projection point K of the pitch axis on the installation platform, and L is the distance between the azimuth axis center of the lidar unit and the azimuth axis center of the microwave radar unit. A7. Express the pitch angle of the microwave radar unit as ∠α, which is the synchronous pitch scanning angle of the microwave radar unit. Then ∠α = arctan((sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a))).

[0007] The calculation of the azimuth angle that the scanning mechanism of the microwave radar unit should adjust in S13 specifically includes: B1. Set the projection point of the azimuth rotation center of the lidar unit on the horizontal plane as K1, the projection point of the azimuth rotation axis of the microwave radar unit on the horizontal plane as N1, and the projection point of the cloud and meteorological target on the horizontal plane as B1. After connecting the projection points K1 and N1 to obtain the line segment K1N1 and extending it, at the same time, draw a perpendicular line from the projection point B1 of the cloud and meteorological target on the ground along the direction of the line segment K1N1 so that the perpendicular line intersects the extension of K1N1, and set the intersection point as B0. B2. According to the similar triangle relationship existing in the relationship diagram of the meteorological target and the radar unit during the combined observation of the laser and microwave radars, assume that the distance between the projection of the cloud and meteorological target on the horizontal plane and the lidar unit is R1. Then R1 = R×cos∠β. Furthermore, it is obtained that the distance between point B1 and point B0 = the distance between point K0 and point K1, that is, B1B0 = K1K0 = R1×cos∠γ = R×cos∠β×cos∠γ, where K0 is the intersection point of the distance between point B1 and the azimuth rotation center of the lidar unit to point K1. B3. Therefore, in the triangle formed by point B1, point B0, and point N1, tan∠B0N1B1 = distance B1B0 / distance N1B0 = distance B1B0 / distance NI = (R × cos∠β × cos∠γ) / (L + cos∠β × (R + a)). Furthermore, the included angle between distance B1B0 and distance N1B0 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 sub - unit is ∠B1N1N = 90° - ∠B0N1B1 = 90° - arctan((R × cos∠β × cos∠γ) / (L + cos∠β × (R + a))).

[0008] S2 includes: S21. According to sin∠α = distance BQ / radial distance r, so when the lidar sub - unit scans the cloud and fog meteorological target B, at this time the 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))]; S22. Let the time when the cloud and fog meteorological target receives the meteorological echo of the lidar sub - unit energy output be t = R / c. When ignoring the distance b from the antenna feed of the microwave radar sub - unit to the pitch scanning center, let the time when the microwave radar sub - unit energy output reaches the cloud and fog meteorological target and receives the meteorological echo be T = r / c = (sin∠β × (R + a) + a1 - b1) × c / sin[arctan(sin∠β × (R + a) + a1 - b1) / (L + cos∠β × (R + a))]. Let the time interval between the laser emission signal time and the microwave emission signal be ∆t, then ∆t = t - T = 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 antenna feed of the microwave radar unit to the pitch scanning center cannot be ignored, the time T for the microwave radar unit to output energy to the cloud and fog meteorological target to receive the meteorological echo is set as T = (r - b) / c = [((sin∠β × (R + a) + a1 - b1) × c / sin[arctan(sin∠β × (R + a) + a1 - b1) - b] / (L + cos∠β × (R + a))]. The time interval ∆t between the laser emission signal time and the microwave emission signal time is set as ∆t = t - T = R / c - [((sin∠β × (R + a) + a1 - b1) - b) × c / sin[arctan(sin∠β × (R + a) + a1 - b1) / (L + cos∠β × (R + a))]].

[0009] When ∆t is positive, the radar terminal sends the control signal to the lidar unit ∆t seconds earlier than the microwave radar unit. When ∆t is negative, the radar terminal sends the control signal to the lidar unit ∆t seconds later than the microwave radar unit.

[0010] In step S3, different meteorological features need to be combined with the radar echo for switching the data source on which the dependence is based during data fusion.

[0011] The present invention has the following advantages: A cloud and fog detection method based on the combination of lidar and microwave radar can solve the problem of target angle deviation caused by the spatial distribution difference between the lidar and the microwave radar during the combined observation of the lidar-microwave radar system, improving the consistency of the observed target. It can enable the detection energy signals of the microwave lidar to reach the observation target simultaneously, solving the problem of poor data consistency caused by the asynchronous arrival time of the control energy of the traditional lidar and microwave radar at the target. Even when the lidar unit and the microwave radar unit are not observing at the same site, as long as there is no occlusion between the lidar unit and the microwave radar unit and the terminal has the feature of being able to communicate with the units, after obtaining the relevant erection parameter information of the lidar and the microwave radar, it can also achieve the function of simultaneous spatio-temporal observation by controlling the angle, having application flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic flow chart of the present invention; Figure 2 is a schematic flow chart of the scanning space angle synchronization; Figure 3 is a schematic vertical pitch and roll plane diagram of the relationship between the meteorological target and the radar unit during the combined observation of the lidar and microwave radar; Figure 4 is a schematic horizontal azimuth plane diagram of the relationship between the meteorological target and the radar unit during the combined observation of the lidar and microwave radar. DETAILED DESCRIPTION OF THE INVENTION

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part rather than all of the embodiments of this application. The components of the embodiments of this application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the protection scope of the claimed application, but merely represents the selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative efforts fall within the protection scope of this application. The following further describes the present invention with reference to the accompanying drawings.

[0014] The present invention relates to a laser-microwave cloud and fog composite observation method, which can enable the microwave / laser irradiation beams of lidar and microwave radar at different antenna heights and installation positions to simultaneously detect and analyze cloud and fog meteorological targets in the same target area. Since the microwave in the Ka band and the working wavelength of the lidar are different, simultaneous irradiation of the same cloud and fog meteorological target will not cause data interference.

[0015] The laser-microwave cloud and fog composite observation generally consists of components such as a lidar sub-system, a microwave radar sub-system, a radar system terminal, its supporting scanning and motion mechanism, and communication and power supply facilities. After the control instructions of the lidar sub-system and the microwave radar sub-system are output by the radar terminal, the system can have the characteristics of time synchronization of observation data, spatial angle alignment of observation targets, and good consistency of observation data; after the radar terminal receives the scanning instruction information from the user, the system terminal calculates the angle tracking parameters according to the erection parameters using this patented technology; calculates the time difference caused by the radial distance based on the spatial difference information between the centers of the lidar and microwave radar antennas to obtain the start timing difference and improve the observation accuracy of the system; since the lidar and microwave radar use the same terminal, when one of the radars fails during the observation operation, the other radar can be quickly controlled to stop the observation to ensure that the data lengths of the composite detection system are the same.

[0016] As Figure 1 shown, it specifically includes the following content: Step 1. Scanning space angle synchronization: Due to the differences in the aperture sizes, installation positions, and heights of the microwave antenna and the lidar lens, when observing the same target, the space angles of the lidar subsystem and the microwave radar subsystem are different. Therefore, angle tracking synchronization of the laser unit is required. In the present invention, the coordinate system where the radiation antenna of the lidar subsystem is located is used as a reference, and the angle tracking parameters are calculated based on the antenna installation differences between the lidar and microwave radar subsystems to correct the system pointing angle deviation that may be caused by the installation position of the microwave radar subsystem. Thus, it is ensured that the data collected by the microwave and the laser are from the same target area.

[0017] Further, as Figure 2 shown, it specifically includes the following contents: Step (1) Measurement of subsystem installation information: The method of measuring the subsystem installation information is as follows: Based on the equipment system drawings and measurement tools, with the axis of the lidar subsystem as the reference coordinate, the height and layout information of the microwave radar subsystem and related units in space are obtained.

[0018] Step (2) Obtaining particle space information: The technical principle of obtaining the target particle space information is as follows: The lidar subsystem and its mechanical scanning mechanism are used to scan and observe the target area. Among them, the scanning angle information can be read through the angle scale returned by the laser mechanical scan, and the pulse ranging method is usually used to measure the distance to the cloud and fog meteorological target. The method is as follows: The target distance information is measured based on the fact that electromagnetic waves propagate in a straight line at a fixed speed in a homogeneous medium (the propagation speed in free space is approximately equal to the speed of light c). Assuming that the lidar is at point A and the cloud and fog meteorological target is at point B, then the straight-line distance R (i.e., the radial distance) from the cloud and fog meteorological target to the lidar subsystem antenna can be obtained by measuring the time t required for the electromagnetic wave to travel back and forth once, and the distance R between the lidar subsystem and the cloud and fog meteorological target can be obtained, that is, according to it can be known that .

[0019] Step (3) Calculating the radar synchronization angle: The principle of calculating the microwave radar synchronization angle is as follows: The radar terminal calculates the angle that the microwave radar subsystem and the scanning unit should synchronously adjust based on the distance of the target cloud and fog meteorological target obtained by the lidar subsystem and the differences in height and installation distance between the microwave radar subsystem and the scanning antenna and the lidar subsystem and its scanning unit antenna. Usually, due to the distance between the center of the microwave radar subsystem antenna and the center position point of the lidar subsystem lens, the height, distance, antenna axis, etc. of the center of the microwave radar subsystem antenna and the installation surface of the installation platform can be input after using the composite observation system drawings or measurement tools. Therefore, after measuring the distance R between the center position of the cloud and fog meteorological target and the lidar subsystem by the lidar subsystem, the angle that the microwave radar subsystem and the mechanical scanning mechanism should adjust can be calculated through calculation and then tracking can be carried out. The specific calculation method is as follows: Step a): Take the focus of the azimuth rotation axis of the lidar sub-system scanning mechanism and the rotation center of the pitch mechanism as the system reference origin. Step b): As Figure 3 shown, set the system reference origin as O, the center of the transceiver window of the lidar sub-system as point A, the cloud and fog meteorological target as point B, the intersection of the azimuth axis of the lidar sub-system and the horizontal platform as point K, the center of the antenna of the microwave radar sub-system as point P, the pitch axis point of the microwave radar sub-system as point F, and the intersection of the azimuth axis of the microwave radar sub-system and the horizontal platform as point N.

[0020] Step c): Input the installation sub-system information measurement information, and according to the measurement model for detecting cloud and fog target objects, a relationship diagram of the meteorological target and the radar sub-system can be drawn in the laser-microwave radar composite observation system. If the distance from the pitch axis of the lidar sub-system to the transceiver window plane is a, the distance from the pitch axis of the lidar sub-system to the installation platform is a1, the distance from the pitch axis of the microwave radar sub-system to the transceiver feed of the microwave radar sub-system is b, the distance from the pitch axis of the microwave radar sub-system to the installation platform is b1; the distance between the azimuth axis of the lidar sub-system and the azimuth axis of the microwave radar sub-system is L.

[0021] Step d): Use the lidar carried by the scanning mechanism of the lidar sub-system to search. When cloud and fog meteorological particles are detected, the method described in "Obtaining Particle Spatial Information" (the relationship between distance and time) can be used to obtain the radial distance information R of the target particle from the lidar sub-system, and read the azimuth scanning angle and pitch scanning angle of the lidar sub-system scanning mechanism scale, denoted as ∠γ and ∠β respectively.

[0022] Step e): As Figure 4 known, there are right triangles △ABG, △OBH, and △BQF in the relationship diagram of the meteorological target and the radar sub-system during the laser-microwave radar composite observation. Among them, right triangles △ABG and △OBH have a similarity relationship, where point A represents the laser radar emission window and point B represents the position of the cloud and fog meteorological target.

[0023] Step f): Since in step d), based on the lidar sub-system, the position information of the cloud and fog meteorological particles has been obtained: azimuth scanning angle ∠γ, pitch scanning angle ∠β, and the radial distance R of the lidar sub-system. Therefore, using trigonometric relationships, the height BG of the cloud and fog meteorological target at the laser unit window is BG = sin ∠β × R.

[0024] Step g) Since there is a similarity relationship between the right triangle △ABG and the right triangle △OBH, and the distance OB from the pitch axis of the lidar to the cloud and fog meteorological target is OB = R + a (i.e., the distance AB from the laser transceiver window to the cloud and fog meteorological target plus the distance OA from the pitch axis center of the lidar unit to the transceiver window plane), similarly, using trigonometric functions, we can obtain: the vertical height difference BH between the cloud and fog meteorological target and the pitch axis is BH = sin∠β×(R + a).

[0025] Step h) From the above conditions and in combination with the figure, it can be seen that: the distance IK between the projection I point of the cloud and fog meteorological target on the installation platform and the projection K point of the pitch axis on the installation platform is IK = HO = cos∠β×(R + a).

[0026] Step i) Since the distance a1 from the pitch axis center of the lidar unit to the installation platform is known, therefore, the relative height D1 between the cloud and fog meteorological target and the installation platform can be obtained as D1 = BH + HI = sin∠β×(R + a) + a1.

[0027] Step j) Since the lidar unit and the microwave radar unit are usually installed on a horizontal platform, and the measured distance b1 from the pitch axis center of the microwave radar unit to the installation platform, therefore, the relative height BQ between the pitch axis of the microwave radar unit and the cloud and fog meteorological target can be obtained as BQ = D1 - b1 = sin∠β×(R + a) + a1 - b1, and there is a distance NI between the projection N of the pitch axis of the microwave radar unit on the ground and the projection point I of the cloud and fog meteorological target on the ground, where NI = NK + IK = L + IK = L + cos∠β×(R + a).

[0028] Step k) From Figure 4 it can be seen that there is a relationship: the distance NI = the distance QF, that is, the distance QF = L + cos∠β×(R + a).

[0029] Step l) Since there is a right triangle △BQF, therefore, using trigonometric functions, we can obtain: tan∠QFB = height BQ / distance QF, so ∠QFB = arctan(height BQ / distance QF) = arctan((sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a))). Represent the pitch angle of the microwave radar unit with ∠α, then ∠α = arctan(height BQ / distance QF) = arctan(sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a)).

[0030] Step m) Therefore, in summary, after measuring the installation distance using Step (1) and obtaining the spatial information of the target particles using Step (2), by using the above method for calculating the synchronous angle of the microwave radar, the synchronous scanning pitch angle ∠α of the microwave radar unit can be obtained as ∠α = arctan(sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a)).

[0031] Step n) As Figure 4 shown, since the due north is usually taken as the 0° position of the azimuth (north-fixed) in the radar system, the projection point of the azimuth rotation center of the lidar unit on the horizontal plane is set as K1, the projection point of the azimuth rotation axis of the microwave radar unit on the horizontal plane is set as N1, and the projection point of the cloud and fog meteorological target on the horizontal plane is set as B1. After connecting the projection point K1 and the projection point N1 to obtain the line segment K1N1 and extending it, at the same time, a perpendicular line is drawn from the ground projection point B1 of the cloud and fog meteorological target along the direction of the line segment K1N1 and intersects the extension line of K1N1, and the intersection point is set as B0.

[0032] Step o) From Figure 4 it can be known that there are right triangles △B1B0K1 and right triangle △B1B0N1. According to the measurement principle of cloud and fog target detection, there is a distance R1 between the projection of the cloud and fog meteorological target on the horizontal plane and the lidar entity. It can be easily obtained from the figure that the relationship between the distance R1 and the radial distance R measured by the lidar for the cloud and fog meteorological target is: R1 = R×cos∠β, that is, the distance R1 between the ground projection of the cloud and fog meteorological target and the radar = the radial distance R of the cloud and fog meteorological target multiplied by the cosine COS∠β of the pitch angle of the radar on the horizontal plane.

[0033] 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, then B1B0 = R1×cos∠γ = R×cos∠β×cos∠γ.

[0034] Step q) From Figure 4 it can be known that the relationship between point B0, point N1, and point 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 lidar and the microwave radar are directly or indirectly installed on the horizontal installation platform, the distance B0N1 between point B0 and point N1 = the distance NI between point I and point N. Therefore, the distance B0N1 = the distance NI = L + the distance IK = L + cos∠β×(R + a).

[0035] Step r) Using the results obtained in steps p) and q) in the right triangle △B1B0N1, we can get: tan∠B0N1B1 = distance B1B0 / distance N1B0 = distance B1B0 / distance NI = (R × cos∠β × cos∠γ) / (L + cos∠β × (R + a)), so ∠B0N1B1 = arctan((R × cos∠β × cos∠γ) / (L + cos∠β × (R + a))).

[0036] Step s) Also, because ∠B0N1B1 + ∠B1N1N = 90°, so ∠B1N1N = 90° - ∠B0N1B1 = 90° - arctan((R × cos∠β × cos∠γ) / (L + cos∠β × (R + a))).

[0037] Step t) Since ∠B1N1N represents the microwave radar azimuth scanning angle in the lidar microwave radar system, so ∠B1N1N can be represented by ∠θ. Therefore, the azimuth angle of the microwave radar sub - unit synchronous scanning is ∠θ = 90° - ∠B0N1B1 = 90° - arctan((R × cos∠β × cos∠γ) / (L + cos∠β × (R + a))).

[0038] Step u) In summary, when the lidar captures a cloud target with a radial distance R at the azimuth scanning angle ∠γ and the pitch scanning angle ∠β, the antenna angles that the microwave radar mechanical scanning mechanism needs to synchronously scan are: Synchronous scanning pitch angle: ∠α = arctan((sin∠β × (R + a) + a1 - b1) / (L + cos∠β × (R + a))).

[0039] Synchronous scanning azimuth angle: ∠θ = 90° - ∠B0N1B1 = 90° - arctan((R × cos∠β × cos∠γ) / (L + cos∠β × (R + a))).

[0040] Step (4) Control the microwave antenna angle to achieve angle tracking (control the scanning mechanism of the microwave radar to scan the corresponding angle according to the angle deviation correction result).

[0041] Step 2. Time synchronization: To solve the problem of observing cloud and fog meteorological targets by separately installing microwave radar extenders and lidar extenders, and to solve the technical problem of data angle deviation during the acquisition of lidar and microwave radar, the lidar and microwave radar of the present invention should have the characteristics of sharing a set of system power supply, communication cables, and radar terminals to avoid generating unexpected errors. The time synchronization principle is as follows: By controlling the timing of the downlink control signal of the radar terminal, the problem of inconsistent radar beam arrival at the meteorological particle echo information caused by the difference in the radial distance R of the lidar extender and the radial distance r of the microwave radar extender due to the different installation positions of the separate racks is solved. The specific calculation method includes the following content: (1) According to the foregoing results, it can be known that sin∠α = distance BQ / radial distance r. Therefore, when the lidar extender scans the cloud and fog meteorological target B, the relationship between the radial distance r of the cloud and fog meteorological target and the microwave radar extender at this time 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))].

[0042] (2) The method for measuring the distance of radar ranging is to calculate according to the arrival time of the signal and the transmission speed of the signal when a high-frequency signal is emitted to the target. The signal propagates in space at the speed of light. When the pulse signal encounters the target, the distance is the radar radial distance. Since distance = speed × time, and the propagation speeds of microwave and laser in the air are the same and are constants (usually taken as c = 3×10 8 m / s), when the time for the lidar energy to be output to the cloud and fog meteorological target to receive the meteorological echo is set to t seconds, we can get t = R / (3×10 8 ) unit seconds. Similarly, when ignoring the distance b from the antenna feed of the microwave radar extender to the pitch scanning center, when the time for the microwave radar energy to be output to the cloud and fog meteorological target to receive the meteorological echo is set to T seconds, 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))].

[0043] (3) Similarly, when the time interval between the laser emission signal time and the microwave emission signal time (i.e., the timing of the downlink control signal of the control radar terminal) is set to ∆t, using the above data, we can get: ∆t = t - T = R / c - (sin∠β×(R + a) + a1 - b1) × c / sin[arctan(sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a))].

[0044] (4) Therefore, when ignoring the distance b from the antenna feed of the microwave radar unit to the pitch scanning center, the timing ∆t of the control signal sent by the radar terminal is as follows: ∆t = t - T = R / c - sin∠β×(R + a) + (a1 - b1))×c / sin[arctan(sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a))]; When the distance b from the antenna feed of the microwave radar unit to the pitch scanning center cannot be ignored, the timing ∆t of the control signal sent by the radar terminal is as follows: ∆t = t - T = R / c – [sin∠β×(R + a) + a1 - b1) - b]×c / sin[arctan(sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a))].

[0045] Furthermore, when the value is positive, the lidar subsystem time sent by the radar terminal is output ∆t seconds earlier than the microwave radar subsystem; when the value is negative, the lidar subsystem time sent by the radar terminal is output ∆t seconds later than the microwave radar subsystem; this method can achieve that the laser signal of the lidar unit and the microwave signal of the microwave radar unit reach the cloud and fog meteorological target group simultaneously (i.e., time synchronization). Since the microwave - lidar pulse repetition frequency is usually not higher than 10KHZ (pulse interval ≤ 0.1mS / time), according to the electromagnetic wave propagation rate, even if the laser echo signal and the microwave signal return to the corresponding antennas at different times, it can be ensured that both the laser energy and the microwave energy can reach the receiver of the microwave radar composite observation radar before the next energy emission, so it will not affect the authenticity of the collected data.

[0046] Step 3: Data fusion: After the radar terminal collects relevant data, traditional multi-modal feature fusion technology or fusion technology based on neural networks and other methods are used to achieve the fusion of laser and microwave cloud and fog composite observation data and the extraction of relevant characteristic parameters. It should be noted that due to the different penetration capabilities of lasers and microwaves, when performing data fusion, it is necessary to switch the data sources depending on different meteorological characteristics in combination with the radar echo. For example, in foggy days, rely on the cloud and fog data observed by the millimeter-wave radar, and in sunny days, rely on the lidar observation data.

[0047] The above is only the preferred implementation mode of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and improvements, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A cloud and fog detection method based on the combination of lidar and microwave radar, characterized in that: The detection method includes: S1. Taking the coordinate system where the lidar radiation antenna is located as a reference and calculating the angle tracking parameters according to the installation differences between the lidar and microwave radar sub-system antennas to correct the system pointing angle deviation caused by the installation position of the microwave radar sub-system, and ensuring the synchronization of the scanning space angles; S2. By controlling the time when the radar terminal sends control signals to the lidar sub-system and the microwave radar sub-system, ensuring time synchronization so that the radar beams reach the meteorological particle echo information consistently; S3. After the radar terminal collects data, extracting characteristic parameters and performing data fusion on the composite observation data of the lidar and cloud radar.

2. The cloud and fog detection method based on the combination of lidar and microwave radar according to claim 1, wherein: The S1 includes the following contents: S11. Measuring the installation sub-system information: Taking the axis of the lidar sub-system as the reference coordinate according to the equipment system drawings and measuring tools, and obtaining the height and layout information of the microwave radar sub-system in space; S12. Obtaining the particle space information: Using the lidar sub-system and its mechanical scanner to scan and observe the target area, and obtaining the accurate information of the distance of the cloud particles and the azimuth and elevation angles of the lidar sub-system scanning mechanism corresponding to the target; S13. Calculating the radar synchronization angles: According to the space information of the target cloud particles obtained by the lidar and combining the differences caused by the height and installation distance of the microwave radar sub-system relative to the lidar sub-system, calculating the elevation angle and azimuth angle that the scanning mechanism of the microwave radar sub-system should adjust with the lidar sub-system coordinate system as a reference; S14. According to the angle deviation correction result, controlling the scanning mechanism of the microwave radar to the corresponding scanning angles to achieve angle tracking.

3. A cloud detection method based on the combination of lidar and microwave radar according to claim 2, characterized in that: The calculation of the elevation angle that the scanning mechanism of the microwave radar sub-system should adjust in the S13 specifically includes: A1. Taking the intersection point of the azimuth rotation axis and the elevation mechanism rotation center of the lidar sub-system scanning mechanism as the system reference origin; A2. Setting the system reference origin as O, the center of the lidar sub-system transceiver window as point A, the cloud meteorological target as point B, the intersection point of the lidar sub-system azimuth axis and the horizontal platform as K, the center of the microwave radar sub-system antenna as point P, the elevation axis point of the microwave radar sub-system as F, and the intersection point of the microwave radar sub-system azimuth axis and the horizontal platform as N; A3. Substituting the information measured in the installation sub-system information measurement and drawing the relationship diagram of the meteorological target and the radar sub-system in the lidar-microwave radar composite observation system according to the measurement model of the cloud target detection; A4. Using the lidar unit carried by the scanning mechanism of the lidar sub-system to search. When the cloud meteorological particles are detected, obtaining the radial distance R of the lidar sub-system using the relationship between distance and time, and reading the azimuth scanning angle ∠γ and elevation scanning angle ∠β of the lidar sub-system scanning mechanism scale. A5. According to the triangle similarity relationship in the relationship diagram between the meteorological target and the radar unit during the combined observation of lidar and microwave radar, as well as the azimuth scanning angle ∠γ, the pitch scanning angle ∠β, and the radial distance R of the lidar unit, using trigonometric function relationships, the height BG of the cloud and fog meteorological target at the laser unit window is obtained as BG = sin∠β × R. Similarly, the vertical height difference BH between the cloud and fog meteorological target and the pitch axis is obtained as BH = sin∠β × (R + a). Furthermore, the distance IK 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 obtained as IK = HO = cos∠β × (R + a), where HO is the distance from the pitch axis center of the lidar unit to the system reference origin O. Also, since the distance a1 from the pitch axis center of the lidar unit to the installation platform is known, the relative height D1 between the cloud and fog meteorological target and the installation platform is obtained as D1 = BH + HI = sin∠β × (R + a) + a1, where HI is the distance from the pitch axis to the projection point I of the cloud and fog meteorological target on the installation platform; A6. Since the lidar unit and the microwave radar unit are installed on a horizontal platform, and the measured distance b1 from the pitch axis center of the microwave radar unit to the installation platform is obtained, the relative height BQ between the pitch axis of the microwave radar unit and the cloud and fog meteorological target is obtained as BQ = D1 - b1 = sin∠β × (R + a) + a1 - b1. Also, the distance NI between the projection N of the pitch axis of the microwave radar unit on the ground and the projection point I of the cloud and fog meteorological target on the ground is obtained as NI = NK + IK = L + IK = L + cos∠β × (R + a), where NK is the distance from the projection N of the pitch axis of the microwave radar unit on the ground to the projection point K of the pitch axis on the installation platform, and L is the distance between the azimuth axis center of the lidar unit and the azimuth axis center of the microwave radar unit; A7. The pitch angle of the microwave radar unit is expressed as ∠α, which is the synchronous pitch scanning angle of the microwave radar unit. Then ∠α = arctan((sin∠β × (R + a) + a1 - b1) / (L + cos∠β × (R + a))).

4. A cloud detection method based on the combination of lidar and microwave radar according to claim 3, characterized in that: The calculation of the azimuth angle that the scanning mechanism of the microwave radar unit should adjust in S13 specifically includes: B1. Let the projection point of the azimuth rotation center of the lidar unit on the horizontal plane be K1, the projection point of the azimuth rotation axis of the microwave radar unit on the horizontal plane be N1, and the projection point of the cloud and fog meteorological target on the horizontal plane be B1. After connecting the projection point K1 and the projection point N1 to obtain the line segment K1N1 and extending it, at the same time, draw a perpendicular line from the projection point B1 of the cloud and fog meteorological target on the ground along the direction of the line segment K1N1 so that the perpendicular line intersects the extension of K1N1, and the intersection point is set as B0; B2. According to the similar triangle relationship existing in the relationship diagram between the meteorological target and the radar sub - unit during the combined observation of lidar and microwave radar, assuming the distance between the horizontal projection of the cloud and fog meteorological target and the lidar sub - unit is R1, then R1 = R×cos∠β is obtained. Furthermore, the distance between point B1 and point B0 = the distance between point K0 and point K1, that is, B1B0 = K1K0 = R1×cos∠γ = R×cos∠β×cos∠γ. K0 is the intersection point of the distance from the azimuth rotation center of point B1 and the lidar sub - unit to point K1. B3. Therefore, in the triangle formed by point B1, point B0, and point N1, tan∠B0N1B1 = distance B1B0 / distance N1B0 = distance B1B0 / distance NI = (R×cos∠β×cos∠γ) / (L + cos∠β×(R + a)). Furthermore, the included angle between distance B1B0 and distance N1B0 is ∠B0N1B1 = arctan((R×cos∠β×cos∠γ) / (L + cos∠β×(R + a))). According to the relationship of ∠B0N1B1+∠B1N1N = 90°, the azimuth angle of the synchronous scanning of the microwave radar sub - unit is ∠B1N1N = 90° - ∠B0N1B1 = 90° - arctan((R×cos∠β×cos∠γ) / (L + cos∠β×(R + a))).

5. The cloud and fog detection method based on the combination of lidar and microwave radar according to claim 4, characterized in that: The said S2 includes: S21. According to sin∠α = distance BQ / radial distance r. Therefore, when the lidar sub - unit scans the cloud and fog meteorological target B, at this time, the 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))]; S22. Let the time when the cloud and fog meteorological target receives the meteorological echo of the energy output of the lidar sub - unit be t = R / c. When ignoring the distance b from the antenna feed of the microwave radar sub - unit to the pitch scanning center, let the time when the microwave radar sub - unit outputs energy to the cloud and fog meteorological target and receives the meteorological echo be T = r / c = (sin∠β×(R + a)+ a1 - b1)×c / sin[arctan(sin∠β×(R + a)+ a1 - b1) / (L + cos∠β×(R + a))]. Let the time interval between the laser emission signal and the microwave emission signal be ∆t, then ∆t = t - T = 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 antenna feeder of the microwave radar extension to the pitch scanning center cannot be ignored, the time T for the microwave radar extension to output energy to the cloud and fog meteorological target to receive the meteorological echo is set as T = (r - b) / c = [((sin∠β×(R + a) + a1 - b1)×c / sin[arctan(sin∠β×(R + a) + a1 - b1) - b]) / (L + cos∠β×(R + a))]. The time interval between the laser emission signal time and the microwave emission signal time is set as ∆t. Then, ∆t = t - T = R / c - [((sin∠β×(R + a) + a1 - b1) - b)×c / sin[arctan(sin∠β×(R + a) + a1 - b1) / (L + cos∠β×(R + a))]].

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

7. A cloud and fog detection method based on the combination of lidar and microwave radar according to claim 1, characterized in that: In step S3, when performing data fusion, different meteorological features need to be combined with the radar echo to switch the data source on which the dependence is based.

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