A method and device for measuring water surface flow velocity in adverse weather conditions

Abstract

The application belongs to the technical field of water flow velocity measurement, and provides a water surface flow velocity measurement method under severe weather conditions, which comprises a first radio frequency chip and a second radio frequency chip, the first radio frequency chip emits a first electromagnetic wave to the water surface and receives a return signal of the first electromagnetic wave reflected by the water surface, the second radio frequency chip emits a second electromagnetic wave to the unobstructed sky and receives a return signal of the second electromagnetic wave, a master control chip uses the return signal of the second electromagnetic wave as a local oscillator signal of the first electromagnetic wave, performs frequency mixing, and obtains a Doppler frequency shift signal of the first electromagnetic wave with respect to the water surface after low-pass filtering, so as to obtain flow velocity information of the water surface. The method can improve the accuracy and reliability of the millimeter wave radar flow meter in wind and rainy weather conditions, reduce the influence of wind and rain on the millimeter wave radar flow velocity and flow measurement, and according to the method, a device is designed, which can measure real water flow velocity data.

Description

Technical Field

[0001] This invention belongs to the field of water flow velocity measurement technology, and specifically relates to a method and device for measuring water surface velocity under adverse weather conditions. Background Technology

[0002] Non-contact Doppler radar current meter is a flow measurement device that calculates the frequency difference between the received echo signal and the transmitted electromagnetic wave signal, based on the Doppler principle, to determine the surface flow velocity. It is simple to operate, can be remotely controlled and communicated, is unaffected by silt and sewage corrosion, has a long service life, and low maintenance costs. In recent years, it has been widely used in hydrology and water conservancy fields.

[0003] Currently, Doppler radar current meters are typically installed at the centerline in applications such as canals and rivers, emitting pulses in the direction of water flow and collecting echo signals for calculation. Since the wavelength of K-band radar is approximately 1 cm, the distance the radar wave can penetrate below the water surface is no more than one wavelength, so the measured velocity value can be considered the surface velocity of the water body. Influenced by factors such as wind speed, the surface velocity of the water body often deviates from the average velocity, making it impossible for the radar current meter to obtain an accurate velocity value. Furthermore, rainfall and snowfall can also affect the measurement of water velocity, leading to measurement errors.

[0004] There is an urgent need for a method and device for measuring water surface velocity under severe weather conditions, to eliminate the influence of rainfall, snowfall and wind speed, and to measure the true water flow velocity data. Summary of the Invention

[0005] The purpose of this invention is to remove the influence of rainfall, snowfall, and wind speed to measure the true water flow velocity data. This is mainly achieved from two aspects. The first aspect is a method for measuring water surface velocity under adverse weather conditions, including a first radio frequency chip 21 and a second radio frequency chip 22. The first radio frequency chip 21 emits a first electromagnetic wave 3 towards the water surface 6 and receives the echo signal of the first electromagnetic wave 3 reflected by the water surface 6. The second radio frequency chip 22 emits a second electromagnetic wave 4 towards the unobstructed sky and receives the echo signal of the second electromagnetic wave 4. The main control chip uses the echo signal of the second electromagnetic wave 4 as the local oscillator signal of the first electromagnetic wave 3, performs frequency mixing, and after low-pass filtering, obtains the Doppler frequency shift signal of the first electromagnetic wave 3 with respect to the water surface 6, thereby obtaining the water surface velocity information of the water surface 6.

[0006] Furthermore, it includes an ultrasonic probe 23, which consists of two diagonally opposite probes forming a group to transmit and receive ultrasonic waves 5. The main control chip uses the time difference between the transmission and reception of ultrasonic waves 5 to calculate the wind speed.

[0007] Furthermore, the mixing formula is:

[0008] Furthermore, the main control chip 2 converts the signal into discrete digital form, removes the DC component of the discrete signal, and calculates the Doppler frequency through Fourier transform.

[0009] Furthermore, the formula for the surface velocity of water affected by wind speed is: x(t)=Acos[(ω d +ω w )t+θ].

[0010] Furthermore, the formula for water flow velocity after eliminating the influence of wind speed is: v(t)=αv1(t)±βv2(t).

[0011] Secondly, a water surface velocity measuring device for coping with severe weather conditions is provided, including a radar current meter, an ultrasonic anemometer and a main control chip. The radar current meter has a built-in first radio frequency chip 21 and a second radio frequency chip 22; the ultrasonic anemometer has a built-in ultrasonic probe 23.

[0012] Furthermore, the ultrasonic probe 23 is configured with two or more groups, consisting of a transmitting end and a receiving end.

[0013] Furthermore, the device also includes a mounting bracket 1 and a housing 2, wherein the housing 2 integrates a radar current meter and an ultrasonic anemometer, and is suspended at a fixed downward angle on the mounting bracket 1 on the shore.

[0014] Beneficial effects:

[0015] This method can improve the accuracy and reliability of flow velocity and flow rate information of millimeter-wave radar flowmeters under windy and rainy weather conditions, and reduce the impact of wind and rain on millimeter-wave radar flow velocity and flow rate measurement. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0017] Figure 1 Flow chart of water flow velocity measurement process;

[0018] Figure 2 Schematic diagram of wind speed measurement principle;

[0019] Figure 3 Mixer schematic diagram;

[0020] Figure 4 Structural diagram of a water surface velocity measuring device;

[0021] Figure 5 Structural diagram of an ultrasonic anemometer.

[0022] The attached diagram lists the components represented by each number as follows:

[0023] 1. Mounting bracket; 2. Housing; 3. First electromagnetic wave; 4. Second electromagnetic wave; 5. Ultrasonic wave; 6. Water surface; 21. First radio frequency chip; 22. Second radio frequency chip; 23. Ultrasonic probe. Detailed Implementation

[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0025] like Figure 1 As shown, the main control chip triggers the operation of the first electromagnetic wave radar 3, the second electromagnetic wave radar 4, and the ultrasonic anemometer 5 on the circuit board, causing them to simultaneously emit CW narrow-band electromagnetic wave signals at 45° downwards and 45° upwards in the direction of the water flow, as well as ultrasonic signals. The first electromagnetic wave 3 is received by the first radio frequency chip 21 after reflection from the water surface, and the second electromagnetic wave 4 is received by the second radio frequency chip 22 after reflection from airborne dust particles, rain, snow, and other particulate matter. The received signals of the second electromagnetic wave 4 and the first electromagnetic wave 3 are respectively input to the input and local oscillator terminals of the radio frequency mixer, as shown below. Figure 3 As shown, by utilizing the common source of the first electromagnetic wave 3 and the second electromagnetic wave 4, and the fact that they are in the same frequency and direction as the noise signal, the mixer output signal can eliminate the interference of rain and snow and obtain the surface flow velocity of the water.

[0026] The mixing formula is:

[0027] The expression for the first electromagnetic wave 3 emission signal is: x(t) = Acos(ω) c t)

[0028] Where ω c ω is the angular frequency of the local oscillator signal, and A is the amplitude of the transmitted signal.

[0029] Echo signal under ideal conditions (no wind, no rain, actual surface velocity of water):

[0030] x(t)=Acos[(ω c +ω d )t+θ]

[0031] Where ω d Let θ be the Doppler frequency shift of the water surface velocity, and θ represent the time delay of the returned signal.

[0032] The transmitted signal and the echo signal are mixed using the following mixing formula:

[0033]

[0034] According to the mixing formula, we have

[0035]

[0036] After mixing, the signal passes through a low-pass filter and amplifier circuit to filter out 2ω. c +ω d A high-frequency signal is obtained, with a frequency of ω. d The frequency offset signal.

[0037] The echo signal under rain conditions is: x(t)=Acos[(ω c +ω d +ω r )t+θ]

[0038] Where ω r The Doppler frequency shift angle of the rainwater flow velocity.

[0039] If the transmitted signal is still used as the local oscillator signal of the mixer, then the result is:

[0040]

[0041] After mixing, the signal passes through a low-pass filter and amplifier circuit to filter out 2ω. c +ω d +ω r A high-frequency signal is obtained, with a frequency of ω. d +ω r The frequency offset signal, ω d With ω r The signal could not be further separated, and ultimately only surface flow velocity information containing rain velocity information could be obtained.

[0042]

[0043] However, if the echo signal of the second electromagnetic wave 4 is used as the local oscillator signal of the mixer, then the result is:

[0044] The echo signal of the second electromagnetic wave 4 is:

[0045] x(t)=A cos[(ω c +ω r )t+θ]

[0046]

[0047] After mixing, the signal passes through a low-pass filter and amplifier circuit to filter out 2ω. c +ω d +2ω r High-frequency signals, yielding results containing only frequencies of ω d The frequency offset signal, ω, contains information about rainwater flow velocity. rThe signal was filtered out by the mixer, and the true surface velocity information of the water body was finally obtained.

[0048] The main control chip samples the signal, converts it into discrete digital form, removes the DC component of the discrete signal, and calculates the Doppler frequency through Fourier transform.

[0049] like Figure 2 As shown, the echo signal of wind speed measured by the ultrasonic wave 5 is detected, filtered, amplified, and the wind speed components on the x and y axes are obtained after the time delay is calculated. Then, by superimposing the wind speed-water surface influence factor, it is combined with the water surface velocity to finally obtain the true water surface velocity value after eliminating the influence of wind speed and rain speed.

[0050] The expression for the surface velocity of water affected by wind speed is: x(t)=A cos[(ω d +ω w )t+θ]

[0051] Wind speed sensors use ultrasonic waves as carriers, which have a different carrier frequency than radar waves, so frequency mixing cannot be used.

[0052] v(t)=αv1(t)±βv2(t)

[0053] Where v1(t) is the surface velocity obtained from radar waves, v2(t) is the wind speed measured by ultrasound, and α and β are the influence factors of the two velocities, respectively. Based on on-site calibration, the corresponding relationship is obtained, thus yielding the water velocity v(t) after eliminating the influence of wind speed.

[0054] like Figure 2 As shown, the outer casing 2 is suspended at a fixed angle from the mounting bracket 1 on the shore. The angle is determined by the bracket height, the width of the water area, and specific application requirements, with the aim of ensuring the radar can illuminate the effective water area. The radar contains two transceiver RF chips, each facing a different angle. Under the control of the main control chip, the first RF chip 21 and the second RF chip 22 simultaneously transmit a first electromagnetic wave 3 and a second electromagnetic wave 4 towards the water surface 6 and the unobstructed sky. The first electromagnetic wave 3 is reflected by the water surface 6, and the echo signal is received. The echo signal of the second electromagnetic wave 4 is used as the local oscillator signal of the first electromagnetic wave 3, mixed, and then low-pass filtered to obtain the Doppler frequency shift signal of the first electromagnetic wave 3 with respect to the water surface 6, thereby determining the flow velocity information of the water surface 6.

[0055] Ultrasonic 5 is a beam diagram of an ultrasonic anemometer, typically consisting of 4 to 6 ultrasonic probes. Taking a 4-probe ultrasonic anemometer as an example, the two diagonally opposite probes form a transmit-receive pair. Figure 5As shown. The working principle of an ultrasonic anemometer is to measure wind speed using the ultrasonic time-of-flight method. Since the speed of sound in air is superimposed on the airflow speed in the direction of the wind, if the ultrasonic wave propagates in the same direction as the wind, its speed will be faster; conversely, if the ultrasonic wave propagates in the opposite direction to the wind, its speed will be slower. Therefore, under fixed detection conditions, the speed of ultrasonic waves in air can correspond to a function of wind speed. Two sets of four probes can calculate and measure the x and y vectors of the plane wind speed, thus obtaining the wind speed and direction. Furthermore, due to the complementary effect of a set of diagonally opposite probes, the influence of temperature on the speed of sound can be ignored.

[0056] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring water surface velocity under adverse weather conditions, characterized in that, It includes a first radio frequency chip (21) and a second radio frequency chip (22). The first radio frequency chip (21) emits a first electromagnetic wave (3) toward the water surface (6) and receives the echo signal of the first electromagnetic wave (3) reflected by the water surface (6); The second radio frequency chip (22) emits a second electromagnetic wave (4) into the unobstructed sky and receives the echo signal of the second electromagnetic wave (4); The main control chip uses the echo signal of the second electromagnetic wave (4) as the local oscillator signal of the first electromagnetic wave (3) for mixing. After low-pass filtering, the Doppler frequency shift signal of the first electromagnetic wave (3) about the water surface (6) is obtained, and the flow velocity information of the water surface (6) is obtained. The severe weather described refers to wind, rain, and snow.

2. The method for measuring water surface velocity under adverse weather conditions according to claim 1, characterized in that, Includes an ultrasonic probe (23), wherein two diagonally opposite probes form a pair to transmit and receive ultrasonic waves (5), and the main control chip uses the time difference between the transmission and reception of ultrasonic waves (5) to calculate the wind speed.

3. The method for measuring water surface velocity under adverse weather conditions according to claim 2, characterized in that, The mixing formula is: ; in It is an influencing factor on surface flow rate. It is a factor affecting wind speed.

4. The method for measuring water surface velocity under adverse weather conditions according to claim 1, characterized in that, The main control chip (2) converts the signal into discrete digital form, removes the DC component of the discrete signal, and calculates the Doppler frequency through Fourier transform.

5. The method for measuring water surface velocity under adverse weather conditions according to claim 3, characterized in that, The formula for the surface velocity of water affected by wind speed is: ; in The amplitude of the transmitted signal, The Doppler frequency shift of the water surface velocity. The additional Doppler frequency shift caused by wind on the water surface is denoted by t, where t is time. Indicates the delay of the return signal. It refers to the water flow velocity affected by wind speed.

6. The method for measuring water surface velocity under adverse weather conditions according to claim 5, characterized in that, The formula for water flow velocity that eliminates the influence of wind speed is: ; in It is the surface velocity obtained from radar waves. It is the wind speed measured by ultrasound. It is the water flow velocity that eliminates the influence of wind speed.

7. The apparatus of the method according to any one of claims 1-6, characterized in that, It includes a radar flow meter, an ultrasonic anemometer, and a main control chip. The radar flow meter has a built-in first radio frequency chip (21) and a second radio frequency chip (22). The ultrasonic anemometer has a built-in ultrasonic probe (23).

8. A water surface velocity measuring device for coping with severe weather conditions according to claim 7, characterized in that, The ultrasonic probe (23) is set up in two or more groups, with the transmitting end and the receiving end as one group.

9. A water surface velocity measuring device for coping with severe weather conditions according to claim 7, characterized in that, The device also includes a mounting bracket (1) and a housing (2), wherein the housing (2) integrates a radar current meter and an ultrasonic anemometer and is suspended at a fixed angle on the mounting bracket (1) on the shore.

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