Pulse energy self-adaptive laser Doppler wind finding radar device and adjusting method thereof

Abstract

The invention provides a laser wind finding radar device and an adjusting method. The laser wind finding radar device can adaptively adjust emitted laser pulse energy according to the carrier-to-noise ratio of an echo signal to complete wind speed measurement. On one hand, under the condition of weak back scattering echo signals caused by thin aerosol signals in good weather or severe attenuation of laser pulse energy along with distance propagation caused by sharp increase of atmospheric extinction coefficient in severe weather, the emitted laser pulse energy can be adaptively improved, and the detection capability of the laser wind finding radar is improved; on the other hand, the energy of emitted laser pulses can be properly reduced under the high-quality working condition, the detection capacity of the radar is guaranteed, meanwhile, the assembly loss is reduced, the service life of the radar is prolonged, the overall power consumption is reduced, and the good self-adaptive adjustment capacity is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of laser Doppler wind speed measurement and meteorological radar, and in particular to a pulse energy adaptive laser Doppler wind measurement radar device for measuring wind in a wind turbine cabin and an adjustment method thereof. Background Art

[0002] At present, clean energy mainly includes wind power generation, photovoltaic power generation and hydropower. Among them, wind power generation occupies an important position. In wind power generation technology, the kinetic energy of wind is mainly used to drive the generator to rotate to generate electricity. If you want to maximize the utilization of wind energy, the blades of the wind turbine usually need to be facing the wind direction. Therefore, there is an urgent need for the application of forward wind measurement in the nacelle of wind turbines. Traditional wind turbine control pitch and rudder usually give the next stage of control targets based on the current state of the wind turbine and the output data of the wind speed and direction meter loaded on the nacelle. However, the control process under this scheme lags behind the change of wind conditions, and the controller is always in a state of local optimization, which will cause the wind turbine to move more frequently and the load is relatively large. At the same time, the traditional wind vane is easily disturbed by the wind turbine impeller, resulting in an error of 4 to 10 degrees, resulting in a decrease in power generation efficiency.

[0003] Laser wind radar has the advantages of early perception, non-contact long-distance measurement, high-precision points, and is not affected by aerodynamic shape and wake. It can provide effective information for early prediction of wind turbines and has become a good solution for cabin feedforward control. However, in actual installation, the effective data output rate of the laser wind radar did not meet expectations due to the variability of meteorological conditions. On the one hand, complex meteorological conditions such as sand and dust cause strong attenuation of the laser during propagation along the path, and on the other hand, under good clear sky atmospheric conditions, the laser backscatter signal is extremely weak in the case of thin aerosols. The former can be compensated by using microwave synchronous detection with stronger penetration, and for the latter, how to improve the detection capability of wind radar in the case of thin aerosols is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The basic working principle of the laser wind radar is to use the local oscillator light signal of a single-frequency laser and the backscattered signal of the laser by the aerosol in the atmosphere for coherent heterodyne detection, calculate the radial wind speed by detecting its Doppler frequency shift information, obtain wind speed information in multiple directions by multi-beam scanning, and further invert to obtain real-time wind field data. For example, a nacelle-type wind laser radar can be installed on the top of a wind turbine nacelle, and detect the wind profile information in front of the wind turbine blades by measuring the Doppler frequency shift of the pulsed laser atmospheric echo. It can be applied to the feedforward control of the wind turbine, providing a reliable and efficient solution for wind turbine efficiency improvement and load reduction. The purpose of the present invention is to provide a laser wind radar device with adaptive transmission capability, improve the detection capability of the wind radar in the case of thin aerosols, and at the same time ensure the durability of the components and increase the life of the equipment.

[0005] In order to achieve the above-mentioned purpose, the present invention starts from the principle of Doppler coherent detection, analyzes the relationship between the Doppler echo signal intensity, laser pulse energy and aerosol backscattering coefficient caused by wind speed according to the wind measurement laser radar equation; analyzes the influence of the echo signal carrier-to-noise ratio on the wind measurement accuracy, and provides a laser wind measurement radar device with adaptive pulse energy adjustment and an adaptive adjustment method, which can adaptively adjust the emission laser pulse energy according to the high or low echo signal carrier-to-noise ratio to complete wind speed measurement.

[0006] The present invention relates to a laser wind measurement radar device with self-adaptive emission capability, comprising a narrow line width laser seed source (1), a beam splitter (2), a first-stage optical fiber amplifier (3), an amplifier driver (4), an acousto-optic modulator (5), a second-stage optical fiber amplifier (6), an amplifier driver (7), an optical fiber circulator (8), an optical antenna (9), a 2×2 coupler (10), a balanced detector (11), an analog-to-digital converter (12) and an embedded SoC processing board (13), wherein the narrow line width laser seed source (1) is used to generate a single-frequency continuous laser as seed light, the beam splitter (2) is used to split the single-frequency continuous laser into two beams A and B according to energy ratio; the first-stage optical fiber amplifier (3) is used to amplify optical power; the acousto-optic modulator (5) is used to shift the frequency and chop the laser signal; the second-stage optical fiber amplifier (6) is used to amplify optical power; the amplifier driver (7) is used to adjust the emission laser pulse intensity; the optical fiber circulator (8) is used to transmit the laser signal; the optical antenna (9) is used to transmit and receive the laser signal;

[0007] The transmission link is composed of a first-stage optical fiber amplifier (3), an acousto-optic modulator (5), a second-stage optical fiber amplifier (6), an optical fiber circulator (8) and an optical antenna (9);

[0008] The receiving link is composed of an optical antenna (9), a fiber circulator (8), a 2×2 coupler (10), a balanced detector (11), an analog-to-digital converter (12) and an embedded SoC processing board (13);

[0009] The feedback link is composed of an embedded SoC processing board (13), an amplifier driver (7), a secondary optical fiber amplifier (6), an acousto-optic modulator (5), an amplifier driver (4) and a primary optical fiber amplifier (3);

[0010] The light beam A sequentially enters the first-stage optical fiber amplifier (3), the acousto-optic modulator (5), the second-stage optical fiber amplifier (6), the optical fiber circulator (8) and the optical antenna (9) in the transmission link;

[0011] The light beam B, as local oscillator light, sequentially enters the 2×2 coupler (10), the balanced detector (11), the analog-to-digital converter (12) and the embedded SoC processing board (13) in the receiving link.

[0012] Furthermore, the wavelength of the single-frequency continuous laser is 1550 nm; and the energy ratio is (95:5) to (99:1).

[0013] Furthermore, the first-stage optical fiber amplifier (3) is composed of an isolator (301), a pump signal combiner (302), a photodetector (303), a pump source (304) and a polarization-maintaining erbium-ytterbium co-doped optical fiber (305).

[0014] Furthermore, the isolator (301) has taps, one of which is used by the photodetector (303) to monitor the input power of the first-stage optical fiber amplifier (3); the other tap is combined with the light of the pump source (304) through the pump signal combiner (302) and then enters the erbium-ytterbium co-doped optical fiber (305), and the power of the input signal light is amplified by forward pumping; the composition of the second-stage optical fiber amplifier (6) is the same as that of the first-stage optical fiber amplifier (3).

[0015] Furthermore, the output currents of the amplifier driver (4) and the amplifier driver (7) are both controlled by the embedded SoC processing board (13), and the embedded processing board of the embedded SoC processing board (13) collects the output signal of the analog-to-digital converter (12) and performs radial wind speed calculation.

[0016] Furthermore, the pump source (304) includes a plurality of 940nm 10W multi-mode laser diodes. When the input current of the amplifier drive (4) is 2000mA-2600mA, the output continuous laser power of the first-stage optical fiber amplifier (3) is 200mW-400mW; when the output current of the amplifier drive (7) is 3200mA, the second-stage optical fiber amplifier (6) outputs a laser pulse of 10 microjoules.

[0017] The present invention relates to a method for adaptively adjusting the transmission capability of a laser wind radar device, the method comprising the following steps:

[0018] Step 1: After the components of the device are powered on, the narrow linewidth laser seed source (1) outputs 1550nm continuous laser;

[0019] Step 2: The embedded processing board loads pre-configuration settings, wherein the pre-configuration settings include laser output parameter configuration and acquisition processing parameter configuration; the laser output parameter configuration includes: output laser pulse repetition rate, laser pulse width, first-stage optical fiber amplifier (3) driving current, second-stage optical fiber amplifier (6) driving current; the acquisition processing parameter configuration includes: detection distance layer number H and distance segment range D of each layer, incoherent accumulation number N;

[0020] Step 3: The embedded processing platform sets the amplifier drive according to the loaded laser configuration parameters, and sequentially provides 2000mA driving current to the first-stage optical fiber amplifier (3) and 3200mA driving current to the second-stage optical fiber amplifier (6); at the same time, the acousto-optic modulator is controlled to output the frequency-shifted laser pulse according to the set repetition rate and pulse width;

[0021] Step 4: After the laser pulse is scattered by the air and aerosol particles in the irradiated area, the Doppler information of the particles in the irradiated area is collected by the optical antenna (9) and enters the receiving link. After being converted to digital by the analog-to-digital converter (12), the data enters the embedded processing board for data processing.

[0022] Step 5: The embedded processing board divides the time domain data collected in each cycle into segments according to the set detection distance layer number H and the distance segment range D of each layer. The length of each data segment includes 100 sampling points; and determines the center point position M of each data segment. n ; The starting and ending positions of each data segment are based on the center point position N of the data segment n Sure;

[0023] Step 6: Take the first 100 sampling points of each cycle as the noise sampling data segment;

[0024] Step 7: The embedded processing board performs zero padding on each data segment containing 100 sampling points. The length of each data segment after zero padding is 512, that is, 412 zeros are added after 100 valid data sampling points.

[0025] Step 8: The embedded processing board performs fast Fourier transform on the zero-filled data segment to obtain the power spectrum signal of each distance segment signal With the noise power spectrum signal Pn 1 ; Where D1 represents the distance range of the first layer, D H Indicates the distance range of the Hth layer; The power spectrum signal of the distance range of the Hth layer obtained by the first measurement;

[0026] Step 9: Repeat steps 5 to 8 for multiple times, and accumulate the power spectrum data output in step 8, complete N repeated accumulations in total, and obtain the power spectrum after incoherent accumulation of each distance segment, that is:

[0027]

[0028] …

[0029]

[0030] Pn=Pn 1 +Pn 2 +…+Pn N ;

[0031] Step 10: Calculate the carrier-to-noise ratio, CNR, for each distance segment D =Ps D / Pn

[0032] Step 11: Determine the final distance segment D H Carrier-to-noise ratio value: if the terminal carrier-to-noise ratio is greater than 1.2 and less than 1.5, maintain the current configuration; if the carrier-to-noise ratio is greater than 1.5, reduce the current two-stage amplifier drive current by 100mA each, and repeat steps 3 to 11; if the carrier-to-noise ratio is less than 1.2, reduce the current two-stage amplifier drive current by 200mA each;

[0033] Step 12: Locate the peak position f of each power spectrum according to the power spectrum of each distance segment d , and according to v = f d / 2λ, calculate the radial wind speed for each distance segment, and give the validity of the radial wind speed according to the carrier-to-noise ratio of the current distance segment. If the carrier-to-noise ratio is greater than 1.2, the valid position is 1, otherwise the valid position is 0;

[0034] Step 13: Repeat steps 3 to 11.

[0035] Furthermore, the laser pulse repetition rate is set to 30kHz, the laser pulse width is 200ns, the first-stage optical fiber amplifier (3) driving current is 2000mA, and the second-stage optical fiber amplifier (6) driving current is 3200mA; the number of detection distance layers H is selected to be 10-20 layers; the distance range D of each layer is selected to be any integer value in the range of 50 to 500m; and the number of incoherent accumulation times N is selected to be 1 to 65536.

[0036] Furthermore, the center point position M n It is obtained by converting the current distance segment to the corresponding distance layer. The conversion formula is:

[0037]

[0038] Where D n is the distance layer position, f s is the sampling rate of the analog-to-digital converter, which is selected to be 100MSps-500MSps; c is the speed of light; t 0 The delay between the trigger signal of the embedded processing board driving the acousto-optic modulator to trigger the laser pulse and the actual light emission of the laser pulse, t 0 Usually 500 to 800ns.

[0039] Furthermore, the number of detection distance layers H is set to 15 layers; the distance segment range D of each layer is set to 50m, and the number of incoherent accumulation times N is set to 30,000 times.

[0040] Compared with the prior art, the technical solution conceived by the present invention can, on the one hand, adaptively increase the energy of emitted laser pulses and improve the detection capability of the laser wind measuring radar when the aerosol signal is thin in good weather, resulting in a weak backscattered echo signal, or when the aerosol extinction coefficient surges in bad weather, resulting in a sharp attenuation of the laser pulse energy with distance propagation. On the other hand, it can appropriately reduce the energy of emitted laser pulses under high-quality working conditions, while ensuring the detection capability of the radar, reducing component loss, increasing the life of the radar, and reducing the power consumption of the entire machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0042] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.

[0043] Figure 1 The present invention is a block diagram of the Doppler laser wind measurement device with adaptive pulse energy regulation.

[0044] Figure 2 This is a block diagram of the optical fiber amplifier of the present invention.

[0045] in:

[0046] 1 Narrow linewidth laser seed source 2 Beam splitter

[0047] 3-stage fiber amplifier 4-amplifier driver

[0048] 5Acousto-optic modulator6Second-stage fiber amplifier

[0049] 7 amplifiers driving 8 fiber optic circulators

[0050] 9 Optical antenna 10 2×2 coupler

[0051] 11 Balanced detector 12 Analog-to-digital converter

[0052] 13Embedded SoC Processing Board 301 Isolator

[0053] 302 pump source 303 photodetector

[0054] 304 Pump signal combiner 305 Erbium-ytterbium co-doped fiber DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0056] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0057] Laser wind radar uses laser Doppler velocity measurement technology to obtain wind speed information by measuring the frequency change of laser and photons scattered in the air. The laser beam passes through the air within the measurement range and is scattered back. The frequency of the laser beam changes after scattering. The frequency difference is proportional to the speed, so wind field information can be obtained.

[0058] In order to understand the technical solution of this application more clearly, Figure 1-2 The testing method of the present invention is described in detail.

[0059] like Figure 1 As shown, it is a block diagram of a Doppler laser wind measurement device for adaptively adjusting pulse energy according to the present invention, wherein the connection relationship of each component is as follows:

[0060] The narrow linewidth laser seed source 1 generates a 1550nm single-frequency continuous laser, which is transmitted to the beam splitter 2 through an optical fiber and is divided into two paths at a ratio of 95:1 to 99:1, of which 95-99% of the energy enters the first-stage fiber amplifier 3 in the transmitting link, and 1-5% of the energy enters the input port 10 of the 2×2 coupler 10 in the receiving link as the local oscillator light. The first-stage fiber amplifier 3 is composed of an isolator 301, a pump signal combiner 302, a photodetector 303, a pump source 304 and a section of polarization-maintaining erbium-ytterbium co-doped fiber 305. The isolator 301 has a tap, one of which is used for the photodetector 303 to monitor the input power of the fiber amplifier; the other path is combined with the pump source 304 light through the pump signal combiner 302 and then enters the polarization-maintaining erbium-ytterbium co-doped fiber 305, and the seed light is power amplified by forward pumping. After amplification, the continuous light is transmitted to the acousto-optic modulator 5.

[0061] The acousto-optic modulator 5 shifts the frequency of the continuous optical signal and generates a 120MHz frequency-shifted laser pulse after chopping. The generated laser pulse is amplified by the secondary optical amplifier 6, input from port 1 of the optical fiber circulator 8, and output from port 2 to the optical antenna 9. The composition of the secondary optical amplifier 6 can be the same as that of the primary optical amplifier 3, or different.

[0062] The optical antenna 9 expands and shapes the laser beam and then emits the laser pulse to the area to be measured. The backscattered echo signal after the Doppler shift generated by the laser pulse and the aerosol blown by the wind is collected by the optical antenna 9, input by the port of the optical fiber circulator 8, and output by the port 3 to the input port 2 of the 2×2 coupler 10 to beat the local oscillator light signal, and then output to the balanced detector 11 for photoelectric conversion. The converted electrical signal is converted into a voltage analog signal by the analog-to-digital converter 12, and then the signal is collected and the radial wind speed is resolved by the embedded SoC processing board (13). The embedded SoC processing board (13) controls the acousto-optic modulator 5 to complete the frequency shift and chopping of the optical signal, and at the same time controls the amplifier driver 4 and the amplifier driver 7 according to the strength of the echo signal carrier-to-noise ratio to complete the adjustment of the intensity of the emitted laser pulse.

[0063] The narrow linewidth laser seed source 1 used in the embodiment of the present invention generates a single-frequency continuous laser of 1550nm with a power of 40-80mW, usually 50mW;

[0064] The fraction ratio of the beam splitter 2 used in the embodiment of the present invention is 99:1-95:5, wherein 1%-5% of the energy is used as local oscillator light to avoid saturation of the optical signal entering the detector.

[0065] In the embodiment of the present invention, a first-stage optical fiber amplifier 3 and a second-stage optical fiber amplifier 6 are integrated, and an isolator 301 is used to isolate the return light of the optical fiber amplifier from entering the front stage and damaging the narrow linewidth laser seed source 1 or the acousto-optic modulator 5; at the same time, ASE noise (amplifier spontaneous emission noise) in the amplification process is filtered out.

[0066] The pump source 304 used in the embodiment of the present invention is a plurality of 940nm 10W multimode laser diodes, which, together with the pump signal combiner 302 and the erbium-ytterbium co-doped fiber 305, form an amplifier stage. When the amplifier driver 4 inputs a current of 2000mA, the first-stage fiber amplifier 3 can achieve an output continuous laser power of 200mW after amplification. When the maximum input current is 2600mA, the first-stage fiber amplifier 3 can achieve an output continuous laser power of 400mW. When the amplifier driver 7 outputs a current of 3200mA, the second-stage fiber amplifier 6 can achieve an output laser pulse of 10 microjoules.

[0067] The output currents of the amplifier driver 4 and the amplifier driver 7 in the embodiment of the present invention are both controlled by the embedded processing board 13 .

[0068] The acousto-optic modulator 5 used in the embodiment of the present invention is cascaded by a first-stage 80MHz analog acousto-optic modulator and a first-stage 40MHz digital acousto-optic modulator. The two-stage acousto-optic modulator is controlled by an embedded processing board 13 to perform waveform distortion compensation, and finally generates a Gaussian type, 120MHz shift frequency, 200ns pulse width laser pulse, and the output pulse repetition rate is 30kHz.

[0069] The optical fiber circulator 8 selected in the embodiment of the present invention is a polarization-maintaining optical fiber circulator, and the length of the circulator pigtail is not more than 40 cm to avoid nonlinear effects.

[0070] The balanced detector 11 used in the embodiment of the present invention has a bandwidth of 200 MHz, a maximum saturated optical power of 140 μW, and a transimpedance gain of 30 kV / A.

[0071] The analog-to-digital converter used in the embodiment of the present invention has a sampling bit number of 12 bits and a sampling rate of 100MSps to 500MSps.

[0072] The embedded SoC processing board (13) used in the embodiment of the present invention has a main processing chip composed of a programmable logic gate array and an ARM core, wherein the logic end mainly completes the FFT transformation of the collected signal and the pulse generation timing control, and the ARM core completes the radial wind speed solution, wind direction calculation, and carrier-to-noise ratio calculation functions.

[0073] The specific working process of this device is as follows:

[0074] Step 1: After the device is started, each component is powered on, and the laser seed source outputs 1550nm continuous laser after power is turned on;

[0075] Step 2: The embedded processing board loads the pre-configured settings, including the laser output parameter configuration: output laser pulse repetition rate, laser pulse width, first-level fiber amplifier drive current, second-level fiber amplifier drive current; acquisition and processing parameter configuration: detection distance layer number H and each layer's distance segment range D, non-coherent accumulation times N; by default: laser pulse repetition rate is set to 30kHz, laser pulse width is 200ns, first-level fiber amplifier drive current is 2000mA, and second-level fiber amplifier drive current is 3200mA. Default detection distance layer position (default 15 layers): 50m, 80m, 110m, 140m, 170m, 200m, 230m, 260m, 290m, 320m, 350m, 380m, 410m, 440m, 470m. The detection distance layer can be set to 10 layers, 15 layers, or 20 layers; each layer's distance segment can be configured to any integer value in the range of 50 to 500m. The default setting of the non-coherent accumulation times is 30000 times, and the setting range is 1 to 65536.

[0076] Step 3: The embedded processing platform sets the amplifier drive according to the loaded laser configuration parameters, providing 2000mA for the first-stage fiber amplifier and 3200mA for the second-stage fiber amplifier. At the same time, the acousto-optic modulator outputs the frequency-shifted laser pulse according to the set repetition rate and pulse width. To protect the two-stage amplifier from damage, the photodetector detects that the optical power is not less than the threshold before loading the drive current. The threshold is usually 20mA. After the laser configuration parameters are executed, the laser wind radar continuously outputs the amplified laser pulses through the optical antenna.

[0077] Step 4: After the laser pulse is scattered by the air and aerosol particles in the irradiated area, the Doppler information of the particles in the irradiated area is collected by the optical antenna and enters the receiving channel. After analog-to-digital conversion, it enters the embedded processing board to complete data processing.

[0078] Step 5: The embedded processing board divides the time domain data collected in each cycle into segments according to the set distance layer number and distance layer position. The length of each data segment is 100 sampling points. The start and end of each data segment is determined by its center point (the 50th point); the center point position is converted from the current distance segment to the distance layer. The conversion process is as follows:

[0079] Assume the distance layer position is D n , then the center point position Mn is where f s is the sampling rate of the analog-to-digital converter, which is 500MSps; c is the speed of light; t 0 The delay between the trigger signal of the embedded processing board driving the acousto-optic modulator to trigger the laser pulse and the actual light emission of the laser pulse, t 0 Usually 500 to 800ns.

[0080] Step 6: Take the first 100 sampling points of each cycle as the noise sampling data segment;

[0081] Step 7: The embedded processing board performs zero padding on each data segment containing 100 sampling points. The length of each data segment after zero padding is 512, that is, 412 zeros are added after 100 valid data sampling points.

[0082] Step 8: The embedded processing board performs fast Fourier transform on the zero-filled data segment to obtain the power spectrum signal Ps of each distance segment signal 1,50m ,Ps 1,80m ,…,Ps 1,470m , and the noise power spectrum signal Pn 1 .

[0083] Step 9: Repeat steps 5 to 8, and accumulate the power spectrum data output in step 8, and complete 30,000 repetitions of accumulation to obtain the power spectrum after incoherent accumulation in each distance segment, that is:

[0084] Ps 50m =Ps 1,50m +Ps 2,50m +…+Ps 30000,50m

[0085] …

[0086] Ps 470m =Ps 1,470m +Ps 2,470m +…+Ps 30000,470m

[0087] Pn=Pn 1 +Pn 2 +…+Pn 30000

[0088] Step 10: Calculate the carrier-to-noise ratio of each distance segment, taking the 50m distance segment as an example.

[0089] CNR 50m =Ps 50m / Pn;

[0090] Step 11: Determine the carrier-to-noise ratio value of the last distance segment (the default is 470m segment). If the carrier-to-noise ratio at the end is greater than 1.2 and less than 1.5, maintain the current configuration; if the carrier-to-noise ratio is greater than 1.5, reduce the current two-stage amplifier drive current by 100mA each, and repeat steps 3 to 11; if the carrier-to-noise ratio is less than 1.2, reduce the current two-stage amplifier drive current by 200mA each;

[0091] Step 12: Locate the peak position f of each power spectrum according to the power spectrum of each distance segment d , and according to v = f d / 2λ calculates the radial wind speed for each distance segment, and gives the validity of the radial wind speed according to the carrier-to-noise ratio of the current distance segment. If the carrier-to-noise ratio is greater than 1.2, the valid position is 1, otherwise it is set to 0;

[0092] Step 13: Repeat steps 3 to 11.

[0093] In good weather, the aerosol signal of the laser wind measuring radar is thin, resulting in a weak backscattered echo signal; in bad weather, the aerosol extinction coefficient surges, resulting in a sharp attenuation of the laser pulse energy with distance propagation. At this time, the carrier-to-noise ratio of the long-distance echo signal will be greatly reduced, and the measurement effectiveness will decrease. By adopting the scheme proposed in the present invention, the laser wind measuring radar can adaptively increase the energy of the emitted laser pulse according to the carrier-to-noise ratio, thereby improving the detection capability of the laser wind measuring radar to a certain extent; on the other hand, it can appropriately reduce the energy of the emitted laser pulse under high-quality working conditions, while ensuring the detection capability of the radar, reducing component loss, increasing the life of the radar, and reducing the power consumption of the whole machine.

[0094] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, and two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0095] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

[0096] In this specification, each embodiment is described in a progressive, parallel, or progressive and parallel manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0097] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.

[0098] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A laser wind measurement radar device with adaptive transmission capability, characterized in that: The invention comprises a narrow linewidth laser seed source (1), a beam splitter (2), a first-stage optical fiber amplifier (3), an amplifier driver (4), an acousto-optic modulator (5), a second-stage optical fiber amplifier (6), an amplifier driver (7), an optical fiber circulator (8), an optical antenna (9), a 2×2 coupler (10), a balanced detector (11), an analog-to-digital converter (12) and an embedded SoC processing board (13), wherein the narrow linewidth laser seed source (1) is used to generate a single-frequency continuous laser as a seed light, and the beam splitter (2) is used to split the single-frequency continuous laser into a beam A and a beam B according to an energy ratio; The light beam A sequentially enters the first-stage optical fiber amplifier (3), the acousto-optic modulator (5), the second-stage optical fiber amplifier (6), the optical fiber circulator (8) and the optical antenna (9) in the transmission link; The light beam B, as a local oscillator light, sequentially enters a 2×2 coupler (10), a balanced detector (11), an analog-to-digital converter (12) and an embedded SoC processing board (13) in the receiving link; The transmission link is composed of a first-stage optical fiber amplifier (3), an acousto-optic modulator (5), a second-stage optical fiber amplifier (6), an optical fiber circulator (8) and an optical antenna (9); The receiving link is composed of an optical antenna (9), a fiber circulator (8), a 2×2 coupler (10), a balanced detector (11), an analog-to-digital converter (12) and an embedded SoC processing board (13); The feedback link is composed of an embedded SoC processing board (13), an amplifier driver (7), a secondary optical fiber amplifier (6), an acousto-optic modulator (5), an amplifier driver (4) and a primary optical fiber amplifier (3).

2. The device according to claim 1, characterized in that: The wavelength of the single-frequency continuous laser is 1550 nm; the energy ratio is (95:5) to (99:1).

3. The device according to claim 1, characterized in that: The first-stage optical fiber amplifier (3) is composed of an isolator (301), a pump signal combiner (302), a photodetector (303), a pump source (304) and a polarization-maintaining erbium-ytterbium co-doped optical fiber (305).

4. The device according to claim 3, characterized in that: The isolator (301) has taps, one of which is used by the photodetector (303) to monitor the input power of the first-stage optical fiber amplifier (3); the other tap is combined with the light of the pump source (304) through the pump signal combiner (302) and then enters the erbium-ytterbium co-doped optical fiber (305), and the power of the input signal light is amplified by forward pumping; the composition of the second-stage optical fiber amplifier (6) is the same as that of the first-stage optical fiber amplifier (3).

5. The device according to claim 1, characterized in that: The output currents of the amplifier driver (4) and the amplifier driver (7) are both controlled by the embedded SoC processing board (13); the embedded processing board of the embedded SoC processing board (13) collects the output signal of the analog-to-digital converter (12) and performs radial wind speed calculation.

6. The device according to claim 3, characterized in that: The pump source (304) includes a plurality of 940nm 10W multi-mode laser diodes. When the input current of the amplifier drive (4) is 2000mA-2600mA, the output continuous laser power of the first-stage optical fiber amplifier (3) is 200mW-400mW; when the output current of the amplifier drive (7) is 3200mA, the second-stage optical fiber amplifier (6) outputs a laser pulse of 10 microjoules.

7. A method for adaptively adjusting the transmission capability of a laser wind radar device according to claim 1, characterized in that: The steps include: Step 1: After the components of the device are powered on, the narrow linewidth laser seed source (1) outputs 1550nm continuous laser; Step 2: The embedded processing board loads pre-configured settings, wherein the pre-configured settings include laser output parameter configuration and acquisition processing parameter configuration; The laser output parameter configuration includes: output laser pulse repetition rate, laser pulse width, first-stage optical fiber amplifier (3) driving current, second-stage optical fiber amplifier (6) driving current; the acquisition processing parameter configuration includes: detection distance layer number H and distance segment range D of each layer, incoherent accumulation number N; Step 3: The embedded processing platform sets the amplifier drive according to the loaded laser configuration parameters, and sequentially provides 2000mA driving current to the first-stage optical fiber amplifier (3) and 3200mA driving current to the second-stage optical fiber amplifier (6); at the same time, the acousto-optic modulator (5) is controlled to output the frequency-shifted laser pulse according to the set repetition rate and pulse width; Step 4: After the laser pulse is scattered by the air and aerosol particles in the irradiated area, the Doppler information of the particles in the irradiated area is collected by the optical antenna (9) and enters the receiving link. After being converted to digital by the analog-to-digital converter (12), the data enters the embedded processing board for data processing. Step 5: The embedded processing board divides the time domain data collected in each cycle into segments according to the set detection distance layer number H and the distance segment range D of each layer. The length of each data segment includes 100 sampling points; and determines the center point position M of each data segment. n ; The starting and ending positions of each data segment are based on the center point position M of the data segment n Sure; Step 6: Take the first 100 sampling points of each cycle as the noise sampling data segment; Step 7: The embedded processing board performs zero padding on each data segment containing 100 sampling points. The length of each data segment after zero padding is 512, that is, 412 zeros are added after 100 valid data sampling points. Step 8: The embedded processing board performs fast Fourier transform on the zero-filled data segment to obtain the power spectrum signal of each distance segment signal and the noise power spectrum signal Pn1; where D1 represents the distance range of the first layer, D H Indicates the distance range of the Hth layer; The power spectrum signal of the distance range of the Hth layer obtained by the first measurement; Step 9: Repeat steps 5 to 8 for multiple times, and accumulate the power spectrum data output in step 8, complete N repeated accumulations in total, and obtain the power spectrum after incoherent accumulation of each distance segment, that is: Pn=Pn1+Pn2+…+Pn N ; Step 10: Calculate the carrier-to-noise ratio, CNR, for each distance segment D =Ps D / Pn Step 11: Determine the final distance segment D H The carrier-to-noise ratio value, if the terminal carrier-to-noise ratio is greater than 1.2 and less than 1.5, maintain the current configuration; if the carrier-to-noise ratio is greater than 1.5, reduce the current two-stage amplifier drive current by 100mA each, and repeat steps 3 to 11; if the carrier-to-noise ratio is less than 1.2, reduce the current two-stage amplifier drive current by 200 m A; Step 12: Locate the peak position f of each power spectrum according to the power spectrum of each distance segment d , and according to v = f d / 2λ, calculate the radial wind speed for each distance segment, and give the validity of the radial wind speed according to the carrier-to-noise ratio of the current distance segment. If the carrier-to-noise ratio is greater than 1.2, the valid position is 1, otherwise the valid position is 0; Step 13: Repeat steps 3 to 11.

8. The method according to claim 7, characterized in that: in, The laser pulse repetition rate is set to 30kHz, the laser pulse width is 200ns, the first-stage optical fiber amplifier (3) driving current is 2000mA, and the second-stage optical fiber amplifier (6) driving current is 3200mA; the number of detection distance layers H is selected to be 10-20 layers; the distance range D of each layer is selected to be any integer value within the range of 50 to 500m; and the number of incoherent accumulation times N is selected to be 1 to 65536.

9. The method according to claim 8, characterized in that: The center point position M n It is converted according to the distance layer position corresponding to the current distance. The conversion formula is: Where D n is the distance layer position, f s is the sampling rate of the analog-to-digital converter, which is selected to be 100MSps-500MSps; c is the speed of light; t0 is the delay between the sending of the trigger signal of the embedded processing board driving the acousto-optic modulator to trigger the laser pulse and the actual emission of the laser pulse, and t0 is usually 500-800ns.

10. The method according to claim 9, characterized in that: In the pre-configuration setting, the number of detection distance layers H is set to 15 layers; the distance segment range D of each layer is set to 50m, and the number of incoherent accumulation times N is set to 30,000 times.

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