A 4D millimeter wave radar flow velocity measurement method and system

Abstract

The present invention belongs to the field of flow velocity measurement technology, and relates to a 4D millimeter wave radar flow velocity measurement method and system. The method comprises: using a 4D millimeter wave radar to transmit a frequency modulated continuous wave to illuminate the water surface; receiving the water surface transmission signal and mixing it to obtain a difference frequency signal; processing the difference frequency signal through a two-dimensional FFT to obtain the distance information from the transmission point to the river surface reflection point, the mirror velocity information of the reflection point relative to the radar, and the angle information of the reflection point relative to the transmission point; establishing a coordinate system; converting the distance information and the angle information into coordinate data; determining the angle of the transmission wave of the radar normal corresponding to the river surface and the reflection point; determining the flow velocity of several reflection points located on the same straight line of the river surface, and taking the average value to obtain the river surface flow velocity. The present invention uses a 4D millimeter wave radar to construct a three-dimensional river surface plane, avoiding errors caused by installation errors or equipment aging, and achieving the effect of accurate measurement; through information in four dimensions, complete four-dimensional spatial information is constructed.

Description

Technical Field

[0001] The present invention belongs to the technical field of flow velocity measurement, and in particular, relates to a 4D millimeter wave radar flow velocity measurement method and system. Background Art

[0002] Existing millimeter wave radars for measuring flow velocity generally use traditional 3D millimeter wave radars, which are installed on crossbars or bridges, and are aimed at the river surface at a specific installation angle. The radial velocity and installation angle measured by the radar are used to calculate the river velocity. However, due to installation angle errors, or after a period of wind and sun exposure, the radar deviates from the installation angle more and more, resulting in a larger and larger deviation in the calculated velocity, which cannot be discovered in a short time. If it is corrected, it needs to be rebuilt, wasting manpower and material resources.

[0003] The basic principle of using millimeter waves is to use the Doppler effect to measure the speed of water flow. The specific working mechanism is: the millimeter wave radar emits a beam of microwave radar waves, usually toward the surface of the river, and the radar waves propagate at a certain frequency; when the radar waves encounter the water surface or tiny particles floating in the water, such as mud or bubbles, reflection will occur, and the reflected waves will be received by the receiver; if the water flow is moving, the frequency of the reflected radar waves will change, which is the Doppler effect; the radar flow meter calculates the speed of the water flow through a formula based on the Doppler frequency offset.

[0004] Assuming that the angle between the radar normal and the water surface is known and fixed, when the radar is offset due to installation error or the installation angle over time, the measured speed will deviate from the true speed, and this error is generally difficult to detect. Correcting this error requires reinstallation, which is time-consuming and laborious. The angle between the radar normal and the river surface is measured using a gyroscope, but the gyroscope measures the angle between the radar normal and the horizontal plane. Generally, the river surface is not horizontal, so the angle measured by the gyroscope is inaccurate, making it difficult to calculate the true angle. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a 4D millimeter wave radar flow velocity measurement method and system.

[0006] In a first aspect, the present invention provides a 4D millimeter wave radar flow velocity measurement method, comprising:

[0007] Use 4D millimeter wave radar to emit frequency modulated continuous waves to illuminate the water surface;

[0008] The 4D millimeter wave radar is used to receive the surface transmission signal and mix it to obtain the difference frequency signal;

[0009] The difference frequency signal is processed by two-dimensional FFT to obtain the distance information from the 4D millimeter wave radar emission point to the river surface reflection point, the image velocity information of the reflection point relative to the radar, and the angle information of the reflection point relative to the 4D millimeter wave radar emission point; the angle information includes azimuth and elevation;

[0010] A coordinate system is established with the 4D millimeter-wave radar as the origin, the straight line where the radar normal of the 4D millimeter-wave radar with an azimuth angle of 0 degrees and an elevation angle of 0 degrees is located as the y-axis, the direction perpendicular to the y-axis and parallel to the river surface is the x-axis, and the plane perpendicular to the x-axis and the y-axis is located as the z-axis;

[0011] Convert the distance and angle information from the 4D millimeter wave radar emission point to the river surface reflection point into coordinate data;

[0012] According to the coordinate data corresponding to the distance information and the angle information, determine the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point;

[0013] The image velocity information of the reflection point relative to the 4D millimeter-wave radar and the angle between the transmitted wave of the river surface straight line with the same direction of the water flow and the radar normal are used to determine the flow velocity of several reflection points located on the river surface straight line, and the river surface flow velocity is obtained by taking the average value.

[0014] In a second aspect, the present invention provides a 4D millimeter wave radar flow velocity measurement system, including a radar transmitting unit, a frequency mixing unit, a first data processing unit, a coordinate system establishment unit, a conversion unit, a second data processing unit and a third data processing unit;

[0015] A radar transmitting unit, used for transmitting frequency modulated continuous waves to illuminate the water surface using a 4D millimeter wave radar;

[0016] A mixing unit, used to receive the surface transmission signal using the 4D millimeter wave radar and perform mixing to obtain a difference frequency signal;

[0017] The first data processing unit is used to process the difference frequency signal through two-dimensional FFT to obtain the distance information from the 4D millimeter wave radar emission point to the river surface reflection point, the image velocity information of the reflection point relative to the radar, and the angle information of the reflection point relative to the 4D millimeter wave radar emission point; the angle information includes azimuth and elevation;

[0018] A coordinate system establishing unit, for establishing a coordinate system with the 4D millimeter wave radar as the origin, a straight line where the radar normal line of the 4D millimeter wave radar at an azimuth angle of 0 degrees and an elevation angle of 0 degrees is located as the y-axis, and a direction perpendicular to the y-axis and parallel to the river surface as the x-axis;

[0019] A conversion unit, used to convert the distance information and angle information from all 4D millimeter wave radar emission points to the river surface reflection points into coordinate data;

[0020] A second data processing unit is used to determine the angle between the river surface straight line which is the same as the water flow direction and the transmitted wave of the radar normal corresponding to the reflection point according to the coordinate data corresponding to the distance information and the angle information;

[0021] The third data processing unit is used to determine the flow velocity of several reflection points located on the river surface straight line by using the mirror velocity information of the reflection point relative to the 4D millimeter wave radar and the transmission wave angle between the river surface straight line with the same direction of water flow and the radar normal, and take the average value to obtain the river surface flow velocity.

[0022] Based on the above technical solution, the present invention can also be improved as follows.

[0023] Further, let A be the reflection point, is the water velocity at the reflection point A, and the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point is , c is the propagation speed of radar wave, is the frequency difference between the transmitted wave and the reflected wave at reflection point A, is the original frequency of the radar wave, is the incident angle of the radar wave at the reflection point A, is the azimuth angle of the reflection point A relative to the 4D millimeter-wave radar emission point, then:

[0024] ;

[0025] Assume the number of reflection points is N, and the river flow velocity is , Indicates The water velocity at the reflection point is:

[0026] .

[0027] Further, according to the coordinate data corresponding to the distance information and the angle information, the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point is determined, including: setting the angle between the straight line on the river surface and the transmitted wave of the radar normal corresponding to the reflection point to be , determine the first reflection point where the y-axis intersects the river surface straight line, determine the second reflection point on the river surface straight line that is perpendicular to the line connecting the radar emission points, and use the ratio of the distance from the radar emission point to the first reflection point to the distance from the radar emission point to the first reflection point as The cosine value of The cosine value of The value of .

[0028] The beneficial effects of the present invention are as follows: the present invention constructs the river surface in three dimensions through the 4D millimeter-wave radar, and then can accurately calculate the angle between the river surface and the radar transmission wave, avoiding errors caused by installation errors or equipment aging, achieving the effect of accurate measurement, and having the advantages of easy use and low maintenance cost; the present invention can provide information in four dimensions, including distance, speed, horizontal angle and vertical angle. Compared with traditional 3D millimeter-wave radar, it can not only detect the distance, speed and azimuth of the target, but also accurately measure the vertical angle of the target, thereby constructing complete four-dimensional spatial information of the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a 4D millimeter wave radar flow velocity measurement method provided in Example 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of the angle between the radar normal and the straight line where the reflection point on the river surface is located;

[0031] Figure 3 It is a schematic diagram of the angle formed by the straight line where several reflection points on the river surface are located and the difference frequency signal;

[0032] Figure 4 A schematic diagram of a 4D millimeter wave radar flow velocity measurement system provided in Example 2 of the present invention.

[0033] In the figure: R-radar emission point; H-horizontal plane; L1-radar normal; L2-river surface straight line. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0035] Example 1

[0036] As an example, Figure 1 As shown, in order to solve the above technical problems, this embodiment provides a 4D millimeter wave radar flow velocity measurement method, including:

[0037] Use 4D millimeter wave radar to emit frequency modulated continuous waves to illuminate the water surface;

[0038] The 4D millimeter wave radar is used to receive the surface transmission signal and mix it to obtain the difference frequency signal;

[0039] The difference frequency signal is processed by two-dimensional FFT to obtain the distance information from the 4D millimeter wave radar emission point to the river surface reflection point, the image velocity information of the reflection point relative to the radar, and the angle information of the reflection point relative to the 4D millimeter wave radar emission point; the angle information includes azimuth and elevation;

[0040] A coordinate system is established with the 4D millimeter-wave radar as the origin, the straight line where the radar normal of the 4D millimeter-wave radar with an azimuth angle of 0 degrees and an elevation angle of 0 degrees is located as the y-axis, the direction perpendicular to the y-axis and parallel to the river surface is the x-axis, and the plane perpendicular to the x-axis and the y-axis is located as the z-axis;

[0041] Convert the distance and angle information from the 4D millimeter wave radar emission point to the river surface reflection point into coordinate data;

[0042] According to the coordinate data corresponding to the distance information and the angle information, determine the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point;

[0043] The image velocity information of the reflection point relative to the 4D millimeter-wave radar and the angle between the transmitted wave of the river surface straight line with the same direction of the water flow and the radar normal are used to determine the flow velocity of several reflection points located on the river surface straight line, and the river surface flow velocity is obtained by taking the average value.

[0044] Optionally, let A be the reflection point, is the water velocity at the reflection point A, and the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point is , c is the propagation speed of radar wave, is the frequency difference between the transmitted wave and the reflected wave at reflection point A, is the original frequency of the radar wave, is the incident angle of the radar wave at the reflection point A, is the azimuth angle of the reflection point A relative to the 4D millimeter-wave radar emission point, then:

[0045] ;

[0046] Assume the number of reflection points is N, and the river flow velocity is , Indicates The water velocity at the reflection point is:

[0047] .

[0048] As attached Figure 2 As shown, the four reflection points A, B, C and D on the river surface are located on the same river surface straight line L2, and the river surface straight line L2 has the same velocity as the water flow. Point C is located at the intersection of the river surface and the radar normal line L1. The angle between the transmitted wave of the river surface straight line L2 and the radar normal corresponding to the reflection point C is The angle between the radar normal L1 and the horizontal plane H measured by the traditional gyroscope is set to , It is not equal to the angle between the radar normal and the river surface. .

[0049] Optionally, according to the coordinate data corresponding to the distance information and the angle information, determining the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point, comprising: setting the angle between the straight line on the river surface and the transmitted wave of the radar normal corresponding to the reflection point to be , determine the first reflection point where the y-axis intersects the river surface straight line, determine the second reflection point on the river surface straight line that is perpendicular to the line connecting the radar emission points, and use the ratio of the distance from the radar emission point to the first reflection point to the distance from the radar emission point to the first reflection point as The cosine value of The cosine value of The value of .

[0050] In actual application, Figure 3 As shown in the figure, the four reflection points A, B, C and D on the river surface are located on the same river surface straight line L2, and the river surface straight line L2 has the same velocity as the water flow. The river surface straight line L2 where the reflection points are located on the river surface forms an angle with the difference frequency signal, and the angle between the line connecting the radar transmitting point R and the reflection point A and the radar normal line L1 is The angle between the line connecting the radar transmitting point R and the reflection point A and the line connecting the four reflection points A, B, C and D on the same straight line on the river surface is equal and The sum of . Assume that the water velocity at reflection point A is , the water velocity at reflection point B is , the water velocity at the reflection point C is , the water velocity at the reflection point D is , the river flow rate is ,but:

[0051] .

[0052] The present invention uses a 4D millimeter-wave radar to construct a river surface in three dimensions, and then can accurately calculate the angle between the river surface and the radar transmission wave, avoiding errors caused by installation errors or equipment aging, achieving accurate measurement results, and has the advantages of easy use and low maintenance cost; the present invention can provide information in four dimensions, including distance, speed, horizontal angle and vertical angle. Compared with traditional 3D millimeter-wave radars, it can not only detect the distance, speed and azimuth of the target, but also accurately measure the vertical angle of the target, thereby constructing complete four-dimensional spatial information of the target.

[0053] Example 2

[0054] Based on the same principle as the method shown in Example 1 of the present invention, as shown in the attached Figure 4 As shown, a 4D millimeter wave radar flow velocity measurement system is also provided in an embodiment of the present invention, including a radar transmitting unit, a frequency mixing unit, a first data processing unit, a coordinate system establishing unit, a conversion unit, a second data processing unit and a third data processing unit;

[0055] A radar transmitting unit, used for transmitting frequency modulated continuous waves to illuminate the water surface using a 4D millimeter wave radar;

[0056] A mixing unit, used to receive the surface transmission signal using the 4D millimeter wave radar and perform mixing to obtain a difference frequency signal;

[0057] The first data processing unit is used to process the difference frequency signal through two-dimensional FFT to obtain the distance information from the 4D millimeter wave radar emission point to the river surface reflection point, the image velocity information of the reflection point relative to the radar, and the angle information of the reflection point relative to the 4D millimeter wave radar emission point; the angle information includes azimuth and elevation;

[0058] A coordinate system establishing unit, for establishing a coordinate system with the 4D millimeter wave radar as the origin, a straight line where the radar normal line of the 4D millimeter wave radar at an azimuth angle of 0 degrees and an elevation angle of 0 degrees is located as the y-axis, and a direction perpendicular to the y-axis and parallel to the river surface as the x-axis;

[0059] A conversion unit, used to convert the distance information and angle information from all 4D millimeter wave radar emission points to the river surface reflection points into coordinate data;

[0060] A second data processing unit is used to determine the angle between the river surface straight line which is the same as the water flow direction and the transmitted wave of the radar normal corresponding to the reflection point according to the coordinate data corresponding to the distance information and the angle information;

[0061] The third data processing unit is used to determine the flow velocity of several reflection points located on the river surface straight line by using the mirror velocity information of the reflection point relative to the 4D millimeter wave radar and the transmission wave angle between the river surface straight line with the same direction of water flow and the radar normal, and take the average value to obtain the river surface flow velocity.

[0062] Optionally, let A be the reflection point, is the water velocity at the reflection point A, and the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point is , c is the propagation speed of radar wave, is the frequency difference between the transmitted wave and the reflected wave at reflection point A, is the original frequency of the radar wave, is the incident angle of the radar wave at the reflection point A, is the azimuth angle of the reflection point A relative to the 4D millimeter-wave radar emission point, then:

[0063] ;

[0064] Assume the number of reflection points is N, and the river flow velocity is , Indicates The water velocity at the reflection point is:

[0065] .

[0066] Optionally, according to the coordinate data corresponding to the distance information and the angle information, determining the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point, comprising: setting the angle between the straight line on the river surface and the transmitted wave of the radar normal corresponding to the reflection point to be , determine the first reflection point where the y-axis intersects the river surface straight line, determine the second reflection point on the river surface straight line that is perpendicular to the line connecting the radar emission points, and use the ratio of the distance from the radar emission point to the first reflection point to the distance from the radar emission point to the first reflection point as The cosine value of The cosine value of The value of .

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A 4D millimeter wave radar flow velocity measurement method, characterized in that: include: Use 4D millimeter wave radar to emit frequency modulated continuous waves to illuminate the water surface; The 4D millimeter wave radar is used to receive the surface transmission signal and mix it to obtain the difference frequency signal; The difference frequency signal is processed by two-dimensional FFT to obtain the distance information from the 4D millimeter wave radar emission point to the river surface reflection point, the image velocity information of the reflection point relative to the radar, and the angle information of the reflection point relative to the 4D millimeter wave radar emission point; the angle information includes azimuth and elevation; A coordinate system is established with the 4D millimeter-wave radar as the origin, the straight line where the radar normal of the 4D millimeter-wave radar with an azimuth angle of 0 degrees and an elevation angle of 0 degrees is located as the y-axis, the direction perpendicular to the y-axis and parallel to the river surface is the x-axis, and the plane perpendicular to the x-axis and the y-axis is located as the z-axis; Convert the distance and angle information from the 4D millimeter wave radar emission point to the river surface reflection point into coordinate data; According to the coordinate data corresponding to the distance information and the angle information, determine the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point; Using the image velocity information of the reflection point relative to the 4D millimeter-wave radar and the angle between the river surface straight line with the same direction of the water flow and the radar normal, the flow velocity of several reflection points located on the river surface straight line is determined, and the average value is taken to obtain the river surface flow velocity; let A be the reflection point, is the water velocity at the reflection point A, and the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point is , c is the propagation speed of radar wave, is the frequency difference between the transmitted wave and the reflected wave at reflection point A, is the original frequency of the radar wave, is the incident angle of the radar wave at the reflection point A, is the azimuth angle of the reflection point A relative to the 4D millimeter-wave radar emission point, then: ； Assume the number of reflection points is N, and the river flow velocity is , Indicates The water velocity at the reflection point is: 。 2. A 4D millimeter wave radar flow velocity measurement method according to claim 1, characterized in that: According to the coordinate data corresponding to the distance information and the angle information, the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point is determined, including: setting the angle between the straight line on the river surface and the transmitted wave of the radar normal corresponding to the reflection point to be , determine the first reflection point where the y-axis intersects the river surface straight line, determine the second reflection point on the river surface straight line that is perpendicular to the line connecting the radar emission points, and use the ratio of the distance from the radar emission point to the first reflection point to the distance from the radar emission point to the first reflection point as The cosine value of The cosine value of The value of .

3. A 4D millimeter wave radar flow velocity measurement system, characterized in that: It includes a radar transmitting unit, a frequency mixing unit, a first data processing unit, a coordinate system establishing unit, a conversion unit, a second data processing unit and a third data processing unit; A radar transmitting unit, used for transmitting frequency modulated continuous waves to illuminate the water surface using a 4D millimeter wave radar; A mixing unit, used to receive the surface transmission signal using the 4D millimeter wave radar and perform mixing to obtain a difference frequency signal; The first data processing unit is used to process the difference frequency signal through two-dimensional FFT to obtain the distance information from the 4D millimeter wave radar emission point to the river surface reflection point, the image velocity information of the reflection point relative to the radar, and the angle information of the reflection point relative to the 4D millimeter wave radar emission point; the angle information includes azimuth and elevation; A coordinate system establishing unit, for establishing a coordinate system with the 4D millimeter wave radar as the origin, a straight line where the radar normal line of the 4D millimeter wave radar at an azimuth angle of 0 degrees and an elevation angle of 0 degrees is located as the y-axis, and a direction perpendicular to the y-axis and parallel to the river surface as the x-axis; A conversion unit, used to convert the distance information and angle information from all 4D millimeter wave radar emission points to the river surface reflection points into coordinate data; A second data processing unit is used to determine the angle between the river surface straight line which is the same as the water flow direction and the transmitted wave of the radar normal corresponding to the reflection point according to the coordinate data corresponding to the distance information and the angle information; The third data processing unit is used to determine the flow velocity of several reflection points located on the river surface straight line by using the image velocity information of the reflection point relative to the 4D millimeter wave radar and the transmission wave angle between the river surface straight line with the same direction of the water flow and the radar normal line, and take the average value to obtain the river surface flow velocity; let A be the reflection point, is the water velocity at the reflection point A, and the angle between the straight line on the river surface in the same direction as the water flow and the transmitted wave of the radar normal corresponding to the reflection point is , c is the propagation speed of radar wave, is the frequency difference between the transmitted wave and the reflected wave at reflection point A, is the original frequency of the radar wave, is the incident angle of the radar wave at the reflection point A, is the azimuth angle of the reflection point A relative to the 4D millimeter-wave radar emission point, then: ； Assume the number of reflection points is N, and the river flow velocity is , Indicates The water velocity at the reflection point is: 。

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