CN115508865A - Wind field inversion method and system based on coherent Doppler continuous wave lidar - Google Patents

Abstract

The invention discloses a wind field inversion method and system based on coherent Doppler continuous wave laser radar, and relates to the technical field of laser radar. The method is based on coherent Doppler laser technology and laser radar to achieve accurate measurement of LOS wind speed. Compared with the DBS mode of pulse laser radar, the present invention uses continuous wave laser radar to scan in VAD mode, and its continuous sequential scanning mode is data. Correction and fitting provide the basis for feasibility. During the inversion process, the present invention adopts the damped Newton method to fit the coordinate-transformed data to obtain a three-dimensional wind field. Compared with the direct inversion method in the prior art, more accurate inversion results are obtained , which improves the inversion ability and calculation accuracy of the three-dimensional wind field.

Description

Wind field inversion method and system based on coherent Doppler continuous wave lidar

technical field

The invention relates to the technical field of laser radar, in particular to a wind field inversion method and system based on coherent Doppler continuous wave laser radar.

Background technique

The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

Coherent Doppler laser technology is a highly reliable wind measurement technology, which uses laser light to irradiate molecules or aerosol particles in the atmosphere, and conducts external detection through the Doppler effect and the coherence between the laser and its echoes. The motion velocity of the detected particles is approximately considered as the radial wind velocity. At present, laser-based working methods are roughly divided into pulse laser radar and continuous wave laser radar. Pulse laser radar calculates the detection distance through the time interval between the pulse signal and the reflected pulse signal. Usually, multiple laser beams are used to scan in DBS (Doppler beam swinging) mode. When the laser radar is not working in a static state, it is difficult to measure the reliability of the results due to the lack of goodness-of-fit information. Therefore, continuous wave lasers are mostly used in the prior art to implement wind measurement technology. Continuous wave laser radar scans in VAD (Velocity-azimuth display) mode through a continuous wave laser. Even if the laser radar is not in a static state, correction and fitting are possible due to its continuous sequential scanning method.

The inventors have found that traditional methods such as the DBS method have the following shortcomings in the inversion of the atmospheric three-dimensional vector wind field:

1. The DBS method has the problem of low detection distance correction accuracy. The DBS method uses the return time of the laser echo to calculate the detection distance. When the laser source is swaying, the DBS method is not easy to use the sway angle to correct the detection distance according to the return time of a single laser beam. If it is corrected, there is also a lack of goodness information of continuous height changes, and there is also the problem of low height accuracy after correction when multi-wave stacking is enhanced.

2. The mathematical formula used for fitting by the DBS method has the problem of theoretical inversion accuracy. The DBS method uses at least 3 laser beams in fixed directions for inversion. Generally, the pulse wave lidar using this system uses 5 fixed directions. Due to the influence of the number of beams, the fitting formula of the DBS method is not completely uniform, and there are multi-directional vectors Theoretical precision issues that arise from superposition.

Contents of the invention

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a wind field inversion method and system based on coherent Doppler continuous wave lidar, based on coherent Doppler laser technology, using VAD mode to scan and measure the line of sight direction (line of sight, LOS) wind speed and wind direction, that is, the wind speed and wind direction in the direction in which the laser is emitted, inverts the actual atmospheric three-dimensional vector wind field.

In order to achieve the above object, the present invention is achieved through the following technical solutions:

The first aspect of the present disclosure provides a wind field inversion method based on coherent Doppler continuous wave lidar, including the following steps:

Obtain the basic information data of the laser echo, and conduct a preliminary screening of the data quality;

Three-dimensional coordinates of the data after the primary screening and transformation from the three-dimensional spherical coordinate system to the three-dimensional Cartesian coordinate system;

The damped Newton method is used to invert the LOS wind speed at the same detection height to obtain the three-dimensional wind field at the detection height.

Further, a complete scanning cycle of the laser radar is used as an inversion cycle, and the basic information of the laser echo is collected with the sampling frequency of the laser radar as the working frequency of the three-dimensional coordinateization of the LOS wind speed.

Further, the specific process of preliminary screening of data quality is: processing the basic information of the laser echo, using the signal-to-noise ratio information provided by coherent detection as the basis for discrimination, and eliminating invalid data through threshold control to complete the data screening.

Furthermore, the basic information of the laser echo includes: LOS wind speed, azimuth angle, elevation angle, laser current working focal length and its corresponding geographic vertical height.

Furthermore, the current working focal length of the laser is used as the laser measurement distance, and its corresponding geographic vertical height is used as the laser detection height, and the laser measurement distance, azimuth and elevation angle are converted from the three-dimensional spherical coordinate system to the three-dimensional rectangular coordinate system.

Furthermore, the inversion process of the LOS wind speed at the same detection height using the damped Newton method is as follows:

Transform the form of LOS wind speed using trigonometric function transformation;

The error objective function is established, and the optimal solution is obtained by using Taylor's formula expansion and iterative algorithm.

The second aspect of the present disclosure provides a wind field inversion system based on coherent Doppler continuous wave lidar, including:

The data acquisition module is configured to acquire the basic information data of the laser echo, and perform preliminary screening on the data quality;

The coordinate conversion module is configured to three-dimensionally coordinate the data after the preliminary screening and convert from the three-dimensional spherical coordinate system to the three-dimensional rectangular coordinate system;

The inversion module is configured to invert the LOS wind speed at the same detection height using the damped Newton method to obtain the three-dimensional wind field at the detection height.

Further, lidar is also included for measuring LOS wind speed based on coherent Doppler laser technology.

The third aspect of the present disclosure provides a medium on which a program is stored, and when the program is executed by a processor, the wind field inversion method based on coherent Doppler continuous wave lidar as described in the first aspect of the present disclosure is implemented. A step of.

The fourth aspect of the present disclosure provides a device, including a memory, a processor, and a program stored on the memory and operable on the processor, when the processor executes the program, the method described in the first aspect of the present disclosure is implemented Steps in a method for wind field inversion based on coherent Doppler continuous wave lidar.

The beneficial effects of the above-mentioned embodiments of the present invention are as follows:

The invention discloses a wind field inversion method, which realizes accurate measurement of LOS wind speed based on coherent Doppler laser technology and laser radar. Compared with the DBS mode of pulse laser radar, the present invention uses continuous wave laser radar to scan in VAD mode , its continuous sequential scanning mode provides a feasible basis for data correction and fitting. In the inversion process, the present invention adopts the damped Newton method to fit the coordinate transformed data to obtain the three-dimensional wind field, and obtains more accurate inversion results compared with the direct inversion method in the prior art , which improves the inversion ability and calculation accuracy of the three-dimensional wind field. In addition, the present invention sets an error objective function, continuously updates the damping coefficient in an iterative manner, corrects the inversion data in real time, and ensures the convergence speed and accuracy of the calculation.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

FIG. 1 is a working diagram of the continuous wave laser radar scanning process in Embodiment 1 of the present invention;

Fig. 2 is a flowchart of inversion using the damped Newton method in Embodiment 1 of the present invention.

detailed description:

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof;

Embodiment one:

Embodiment 1 of the present disclosure provides a wind field inversion method based on coherent Doppler continuous wave lidar, including the following steps:

Step 1: Obtain the basic information data of the laser echo, and conduct a preliminary screening of the data quality.

Step 1.1: Complete a complete scanning cycle of the laser radar as an inversion cycle, and collect the basic information of the laser echo with the sampling frequency of the laser radar as the working frequency of the three-dimensional coordinateization of the LOS wind speed, as shown in Figure 1.

Preferably, the basic information of the laser echo includes: LOS wind speed, azimuth angle, elevation angle, current working focal length of the laser and its corresponding geographic vertical height.

Among them, the LOS wind speed is the projection of the actual three-dimensional wind speed on the direction vector of the laser emission, the azimuth represents the angle of movement along the scanning direction, and the elevation angle is the angle (acute angle) between the direction vector of the emission laser and the horizontal plane. To detect the wind speed at different altitudes, the focal distance is determined by factors such as the curvature of the optical lens and the distance between the laser source and the lens. The focal length on the direction vector of the emitted laser is projected to the vertical direction through the elevation angle, which is its corresponding geographic location. vertical height.

Step 1.2: Preliminary screening of data quality The specific process is: process the basic information of the laser echo, use the signal-to-noise ratio information provided by coherent detection as the basis for discrimination, and eliminate invalid data through threshold control to complete the data screening.

Step 2: Three-dimensional coordinate the data after preliminary screening and transform from three-dimensional spherical coordinate system to three-dimensional rectangular coordinate system.

Step 2.1: Take the current working focal length of the laser as the laser measurement distance, and its corresponding geographic vertical height as the laser detection height, and convert the laser measurement distance r, azimuth θ and elevation angle φ from the three-dimensional spherical coordinate system to the three-dimensional rectangular coordinate system.

Step 2.1.1: In this embodiment, the northeast sky coordinate system is used as the three-dimensional rectangular coordinate system, and the spherical coordinate system (r, θ, φ) is used to directly calculate the rectangular coordinate system values (x′, y′, z′), Then project the Cartesian coordinate system into the northeast sky coordinate system (x, y, z), and the formula is as follows.

Among them, in the spherical coordinate system, r is the detection distance, θ is the rotation angle, and φ is the elevation angle. In the Cartesian coordinate system, x', y', and z' are the distances to the north, east, and vertically upward, respectively.

Step 3: Invert the LOS wind speed at the same detection height using the damped Newton method to obtain the three-dimensional wind field at the detection height.

Step 3.1: After coordinate transformation, the laser detection height corresponds to z in formula (2), and the z value within a reasonable deviation range can be regarded as the same detection height. The three-dimensional wind field can be obtained by fitting the measured wind speed values within this height using the damped Newton (Levenberg-Marquadt) method.

In step 3.2, the inversion process of the LOS wind speed at the same detection height using the damped Newton method is as follows:

Transform the form of LOS wind speed using trigonometric function transformation;

The error objective function is established, and the optimal solution is obtained by using Taylor's formula expansion and iterative algorithm.

Step 3.2.1: For the convenience of numerical calculation, the LOS wind speed (that is, V _r ) is transformed using trigonometric functions.

V _r =acos(θ-b)+c (3)

c＝w·sinφ。u、v、w分别为三维风矢量在经纬度方向和垂直方向上的分量，即风在水平面上的分量u-component of wind、v-component of wind和风在垂直方向上的分量w-component of wind，以P＝(a,b,c)将公式简写为有关于θ和P的方程f(θ,P)，则有in

c=w sin φ. u, v, and w are the components of the three-dimensional wind vector in the latitude and longitude direction and the vertical direction, respectively, that is, the components of the wind on the horizontal plane u-component of wind, v-component of wind and the component of the wind on the vertical direction w-component of wind , using P=(a,b,c) to abbreviate the formula as an equation f(θ,P) about θ and P, then we have

f(θ,P)=acos(θ-b)+c (4)

According to the working principle of the continuous wave lidar VAD method, there are m focus positions (m≥3) for a single height wind field, so it can be regarded as an m-dimensional vector space R ^m in the inversion process.

为残量函数r:R³→R^m的分量，其中

为三维风场在LOS方向上的分量，即V_r在m维空间中各个矢量方向上的投影，i＝1,2,3…m。According to the property definition of the least squares method, let the residual

is the component of the residual function r:R ³ →R ^m , where

is the component of the three-dimensional wind field in the LOS direction, that is, the projection of V _r on each vector direction in the m-dimensional space, i=1, 2, 3...m.

Step 3.2.2: So there is an error objective function:

即使用雅克比矩阵J(P^*)表示为J^T(P^*)r(P^*)＝0。Find the optimal solution P ^* so that the value of φ(P) is the smallest. According to the necessary condition of extremum, the optimal solution P=P ^* should satisfy:

That is, the Jacobian matrix J(P ^* ) is used to represent ^JT (P ^* )r(P ^* )=0.

Using Taylor's formula to expand J ^T (P ^* ) and r (P) around the initial value P = P ^* , and turn it into a linear equation system to solve iteratively with S _k as the step size, we can get

P _k+1 =P _k +S _k (6)

J ^T (P _k )J(P _k )S _k ＝-J ^T (P _k )r(P _k ) (7)

Appropriately increase the main diagonal elements of the matrix, that is, perform regularization processing

(J ^T (P _k )J(P _k )+μ _k I)S _k ＝-J ^T (P _k )r(P _k ) (8)

Where μ _k is the set damping factor, and I is the unit matrix, then the optimal solution P ^* iterative formula is:

P _k+1 ＝P _k -(J ^T (P _k )J(P _k )+μ _k I) ^-1 J ^T (P _k )r(P _k ) (9)

Step 3.2.3: Cycle through the following steps:

Step 3.a set allowable error ∈ ₁ , adjustment factor ∈ ₂ , initial damping μ ₀ and constant H;

Step 3.b sets the maximum number of iterations t, and gives the initial guess P ₀ ;

Step 3.c uses formula (5) and the Jacobian matrix to obtain φ(P _k ), J(P _k );

返回步骤3.c；否则增大阻尼系数μ＝μ·H，返回步骤3.d。Step 3.d judges whether φ(P _k ) is less than the allowable error ∈ ₁ or does not exceed the maximum number of iterations, if not, the iteration is ended directly. If it is satisfied, continue to iterate, obtain P _k+1 according to formula (9), and then obtain φ(P _k+1 ) through formula (5), if the error objective function decreases, that is, φ(P _k+1 ) <φ(P _k ), then reduce the damping coefficient

Return to step 3.c; otherwise, increase the damping coefficient μ=μ·H, and return to step 3.d.

Step 4: Repeat step 3 to obtain the three-dimensional wind field at all detection heights.

Embodiment two:

Embodiment 2 of the present disclosure provides a wind field inversion system based on coherent Doppler continuous wave lidar, including:

The data acquisition module is configured to acquire the basic information data of the laser echo, and perform preliminary screening on the data quality;

The coordinate conversion module is configured to three-dimensionally coordinate the data after the preliminary screening and convert from the three-dimensional spherical coordinate system to the three-dimensional rectangular coordinate system;

The inversion module is configured to invert the LOS wind speed at the same detection height using the damped Newton method to obtain the three-dimensional wind field at the detection height.

Preferably, in this embodiment, continuous wave laser radar is used to measure LOS wind speed based on coherent Doppler laser technology. Specifically, the laser transmitter of the lidar is placed on a platform with a linear motion motor, and the focal length is controlled by controlling the distance through the motor. The emitted laser light is reflected to the outside of the radar by a movable plane mirror, so parameters such as azimuth and elevation are obtained. The geographic vertical height can be derived directly mathematically from the focal length position and elevation angle.

Embodiment three:

Embodiment 3 of the present disclosure provides a medium on which a program is stored. When the program is executed by a processor, the wind field inversion method based on coherent Doppler continuous wave lidar as described in Embodiment 1 of the present disclosure is implemented. A step of.

Embodiment four:

Embodiment 4 of the present disclosure provides a device, including a memory, a processor, and a program stored on the memory and operable on the processor. Steps in a method for wind field inversion based on coherent Doppler continuous wave lidar.

The steps involved in the devices of the above embodiments 2, 3 and 4 correspond to the method embodiment 1, and for specific implementation, please refer to the relevant description of the embodiment 1. The term "computer-readable storage medium" shall be construed to include a single medium or multiple media including one or more sets of instructions; and shall also be construed to include any medium capable of storing, encoding, or carrying A set of instructions to execute and cause the processor to execute any method in the present invention.

Those skilled in the art should understand that each module or each step of the present invention described above can be realized by a general-purpose computer device, optionally, they can be realized by a program code executable by the computing device, thereby, they can be stored in The device is executed by a computing device, or they are made into individual integrated circuit modules, or multiple modules or steps among them are made into a single integrated circuit module for realization. The invention is not limited to any specific combination of hardware and software.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (10)

1. A wind field inversion method based on coherent Doppler continuous wave laser radar, is characterized in that, comprises the following steps: Obtain the basic information data of the laser echo, and conduct a preliminary screening of the data quality; Three-dimensional coordinates of the data after the primary screening and transformation from the three-dimensional spherical coordinate system to the three-dimensional Cartesian coordinate system; The damped Newton method is used to invert the LOS wind speed at the same detection height to obtain the three-dimensional wind field at the detection height. 2. the wind field inversion method based on coherent Doppler continuous wave laser radar as claimed in claim 1, is characterized in that, completes a complete scan cycle as an inversion cycle with laser radar, takes laser radar sampling frequency as LOS wind speed three-dimensional coordinate working frequency for basic information collection of laser echo. 3. the wind field inversion method based on coherent Doppler continuous wave laser radar as claimed in claim 1, is characterized in that, the specific process of preliminary screening to data quality is: the basic information of laser echo is processed, by The signal-to-noise ratio information provided by coherent detection is used as the basis for discrimination, and invalid data is eliminated through threshold control to complete data screening. 4. The wind field inversion method based on coherent Doppler continuous wave lidar as claimed in claim 1, wherein the basic information of the laser echo includes: LOS wind speed, azimuth, elevation angle, laser current working focal length and Its corresponding geographic vertical height. 5. The wind field inversion method based on coherent Doppler continuous wave lidar as claimed in claim 4, wherein the current working focal length of the laser is used as the laser measurement distance, and its corresponding geographic vertical height is used as the laser detection height, Convert the three-dimensional spherical coordinate system to the three-dimensional rectangular coordinate system for the laser measurement distance, azimuth angle and elevation angle. 6. The wind field inversion method based on coherent Doppler continuous wave lidar as claimed in claim 5, is characterized in that, the specific process of using the damped Newton method to invert the LOS wind speed at the same detection height is: Transform the form of LOS wind speed using trigonometric function transformation; The error objective function is established, and the optimal solution is obtained by using Taylor's formula expansion and iterative algorithm. 7. A wind field inversion system based on coherent Doppler continuous wave lidar, characterized in that it comprises: The data acquisition module is configured to acquire the basic information data of the laser echo, and perform preliminary screening on the data quality; The coordinate conversion module is configured to three-dimensionally coordinate the data after the preliminary screening and convert from the three-dimensional spherical coordinate system to the three-dimensional rectangular coordinate system; The inversion module is configured to invert the LOS wind speed at the same detection height using the damped Newton method to obtain the three-dimensional wind field at the detection height. 8. The wind field inversion system based on coherent Doppler continuous wave laser radar as claimed in claim 7, further comprising a laser radar for measuring LOS wind speed based on coherent Doppler laser technology. 9. A computer-readable storage medium, wherein a plurality of instructions are stored, and the instructions are adapted to be loaded by a processor of a terminal device and execute the coherent multiple-based Wind Field Inversion Method for Puller CW LiDAR. 10. A terminal device, characterized in that it includes a processor and a computer-readable storage medium, the processor is used to implement instructions; the computer-readable storage medium is used to store multiple instructions, and the instructions are suitable for being loaded by the processor and Executing the wind field inversion method based on coherent Doppler continuous wave lidar described in any one of claims 1-6.

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