CN117805792A - Doppler laser wind-finding radar radial wind speed calibration method - Google Patents
Doppler laser wind-finding radar radial wind speed calibration method Download PDFInfo
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Abstract
The invention aims to provide a Doppler laser wind-finding radar radial wind speed calibration method which meets the high-precision requirement and has low uncertainty of target calibration. The method comprises the following steps: a. establishing a calibration device of a pulse coherent Doppler laser wind-finding radar; b. modeling is carried out based on the calibration device established in the step a; c. inclination angle of light beamCalibrating; d. establishing the diameter of the light spot and the radius of the discPerforming uncertainty calculations; e. according to the calibrated beam inclination angleSweep angleRadius of discAnd angular frequency of rotation of the discFinally, the radial wind speed is obtained. The method is applied to the technical field of laser radars.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a Doppler laser wind-finding radar radial wind speed calibration method.
Background
Laser wind radars are commonly referred to as instruments for measuring absolute values, given only the laser wavelengthAnd the frequency shift value of the backscattered laser light +.>We can go through the equation->Calculate the speed of view (++>) This illustrates to some extent that laser wind radars are also not calibrated. However, if the laser radar is not calibrated, it cannot be known whether the measurement result of the laser radar is accurate, and in the actual measurement process, small errors easily penetrate into frequency analysis, or the laser wavelength may drift along with the change of the external temperature.
Current practice for calibrating lidar is to use a cup or ultrasonic anemometer as the reference instrument, but calibration is often limited by uncertainty of the reference instrument itself. Even with ultrasonic anemometers as a reference, the overall calibration uncertainty of lidar is typically on the order of 1% -2%. In fact, the accuracy of the lidar is far higher than this, so a new calibration method is needed to meet the accuracy requirement of the lidar.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of the prior art and providing the Doppler laser wind finding radar radial wind speed calibration method which meets the high-precision requirement and has low uncertainty of target calibration.
The technical scheme adopted by the invention is that the method comprises the following steps:
a. establishing a calibration device of a pulse coherent Doppler laser wind-finding radar: the device comprises a disc, a motor, a speed reducer and a supporting frame, wherein the disc is arranged on the supporting frame and driven by the motor, the speed reducer is used for controlling the rotating speed, the laser wind-finding radar is arranged outside an observation distance L, a laser beam of the laser wind-finding radar points to the tangential direction of the disc in a plane perpendicular to the rotating shaft of the disc, and the laser beam is inclined up and down along the vicinity of the disc, so that the projection value of the tangential speed is measured;
b. modeling is carried out on the basis of the calibration device established in the step a: let the view direction speed detected by the laser radar beThe disk circumferential velocity projected in the beam direction at the intersection point of the disk surface and the laser beam is:
， （1）
wherein V is Disc Is the circumferential velocity of the wheel and,is glancing angle +.>Is the beam tilt angle +.>Is angular frequency, +.>Is the radius of the disc;
c. inclination angle of light beamCalibrating: inclination angle of light beam->Accurately measuring by total station or estimating the beam tilt angle by means of trigonometric function from the height difference>Is a value of (2);
d. establishing the diameter of the light spot and the radius of the discIs subjected to uncertainty calculation: different sweep angles +.>The corresponding tangential projection speeds are not consistent, when all the light spots are hit on the disc, the diameter of the light spots is set asThe corresponding sweep angle range +.>There is the following relationship:
（2）
the trigonometric function Taylor expansion is finally obtained
，
By increasing the sweep angle according to the above formulaOr reducing the diameter of the spot +.>Or increasing the radius of the disc +.>Further reducing the measurement calibration error, whereby the spot diameter is determined +.>And disc radius->Is a relationship of (2);
e. according to the calibrated beam inclination angleGlancing angle->Disc radius->And the angular frequency of rotation of the disc->Finally, radial wind speed +.>。
Further, in the step d, the sweep angle rangeThe specific calculation process of (2) is as follows:
the trigonometric function Taylor expansion is performed according to the formula (2) to obtain
（3），
Only take into accountTerm, at this time, formula (3) becomes:
（4）
finally can be obtainedThe method comprises the following steps:
（5）。
in addition, in the step c, the inclination angle of the light beam is estimated by utilizing a trigonometric function according to the height differenceThe process of the values of (2) is:
the radar and the disc are placed on the same horizontal plane, and the height between the center of the telescope and the ground is measured to beThe difference in height between the center of the light spot irradiated to the turntable and the ground is set to +.>The inclination angle of the light beam is
（6）。
The beneficial effects of the invention are as follows: in the laser wind-finding radar calibration process, a laser beam is directed to the tangential direction of the disc in a plane perpendicular to the rotation axis of the disc, and can tilt up and down along the vicinity of the disc, so that the projection value of the tangential speed is measured.The speed accuracy of the disk is ensured by a servo motor and is recorded synchronously with the laser radar measurement data. The geometric model is built to show that the measured visual direction speed is [ ]) And beam tilt +.>The method has a trigonometric function relation and is used for deducing the tangential velocity measured by the laser radar, and the uncertainty analysis based on the model shows that about 0.2% of standard measurement uncertainty can be realized, so that the method can effectively improve the measurement accuracy, reduce the uncertainty and ensure the reliability.
Drawings
FIG. 1 is a diagram of a geometric model corresponding to the calibration device;
FIG. 2 is a graph comparing radial velocity data for two radars simultaneously measuring upper and lower tangential surfaces of a disk;
FIG. 3 is a schematic diagram of the signal-to-noise ratio of two test radars measuring radial wind speed;
FIG. 4 is a partial enlarged view of two test radars measuring radial wind speed;
FIG. 5 is a schematic diagram of radial wind speed and signal to noise ratio measurements;
FIG. 6 is a schematic illustration of the correlation between calibration means and radial wind speed.
Detailed Description
As shown in fig. 1, the method of the present invention includes the steps of,
a. establishing a calibration device of a pulse coherent Doppler laser wind-finding radar: the device comprises a disc, a motor, a speed reducer and a supporting frame, wherein the disc is arranged on the supporting frame and driven by the motor, the speed reducer is used for controlling the rotating speed, the laser wind-finding radar is arranged outside an observation distance L, a laser beam of the laser wind-finding radar points to the tangential direction of the disc in a plane perpendicular to the rotating shaft of the disc, the laser beam is inclined up and down along the vicinity of the disc, and the pointing direction of the laser beam can be adjusted by using a screw on a radar bracket, so that the projection value of the tangential speed is measured;
b. modeling is carried out on the basis of the calibration device established in the step a: let the view direction speed detected by the laser radar beThe disk circumferential velocity projected in the beam direction at the intersection point of the disk surface and the laser beam is:
， （1）
wherein V is Disc Is the circumferential velocity of the wheel and,is glancing angle +.>Is the beam tilt angle +.>Is angular frequency, +.>Is the radius of the disc;
c. inclination angle of light beamCalibrating: inclination angle of light beam->Accurately measuring by total station or estimating the beam tilt angle by means of trigonometric function from the height difference>Is a value of (2);
d. establishing the diameter of the light spot and the radius of the discIs subjected to uncertainty calculation: different sweep angles +.>The corresponding tangential projection speeds are not consistent, when all the light spots are hit on the disc, the diameter of the light spots is set asThe corresponding sweep angle range +.>There is the following relationship:
（2）
the trigonometric function Taylor expansion is performed according to the formula (2) to obtain
（3），
With the glancing angleIncreasing from 0 to->In the course of (2), the radial wind speed value in formula (1) is smaller and smaller, and therefore +.>Cannot be too large, when->When (I)>The term and higher order small amounts are negligible. Therefore only consider->Term, at this time, formula (3) becomes:
（4）
finally can be obtainedThe method comprises the following steps:
（5）。
by appropriately increasing the sweep angle according to the above formulaOr reducing the diameter of the spot +.>Or increasing the radius of the disc +.>Further reducing the measurement calibration error, whereby the spot diameter is determined +.>And disc radius->Is a relationship of (2);
e. according to the calibrated beam inclination angleGlancing angle->Disc radius->And the angular frequency of rotation of the disc->Finally, radial wind speed +.>. In the calibrating process, two radars can be used for calibrating simultaneously, one radar telescope can irradiate an upper tangential plane, the other radar telescope can irradiate a lower tangential plane, and two measuring results are respectively +.>=/>And->=. Only acquire +.>When the position of the spot in the disc is determined, the +.>Values. After aligning the laser and fixing the telescope height, measuring the arc length of the light spot and the highest point and the arc length of the light spot and the lowest point to obtain
Wherein l arc Indicating the arc length between the spot and the tangent point on the disc.
In the step c, the inclination angle of the light beam is estimated by utilizing a trigonometric function according to the height differenceThe process of the values of (2) is:
the radar and the disc are placed on the same horizontal plane, and the height between the center of the telescope and the ground is measured to beThe difference in height between the center of the light spot irradiated to the turntable and the ground is set to +.>The inclination angle of the light beam is
（6）。
Specifically, since the laser wind-finding radar has a blind area, the distance is observed in the actual measurement processLarger, aiming is required, here 100m is chosen as the observation distance. Normally beam tilt +.>The measurement can be performed accurately by means of a total station, or the beam tilt angle can be estimated from the height difference>Is a value of (2). According to the actual measurement field L of about 100m, the height difference between the height of the turntable at the high point and the telescope height is calculated to be less than 0.2m, and the inclination angle can be estimated according to the trigonometric functionAbout->When the wind speed reaches 16m/s,/s>When (rad is an angular unit, referring to radians), the absolute value of the introduced error is about 0.01m/s,/L>The value calculation is negligible.
When the sweep angleWhen (I)>The maximum value of (5) is 2mm in spot diameter and 300mm in disk radius, and +.>When the radial wind speed is 16m/s, the extremely bad of the measured data is 0.7m/s; when->At this time +.>The range of the measured data was 0.1m/s. Since the outgoing laser is Gaussian light, the intensity of the light beam is distributed in a normal way in space, the corresponding measurement data error is distributed in a normal way, and the relative error of the measurement standard deviation introduced by the measuring device is about 0.11%.
In addition, to simulate the intensity of atmospheric backscatter, the laser pulse energy is attenuated to a level equivalent to the measured wind field radial wind speed, where the intensity of the attenuated signal is measured in terms of signal-to-noise ratio. The signal-to-noise ratio is defined as the ratio of the intensity of the signal to the intensity of the noise. Fig. 2 shows that two radars simultaneously measure radial velocity data of an upper tangential plane and a lower tangential plane of a disc, and the signal to noise ratios of the two radars are different to a certain extent through signal attenuation, as shown in fig. 3, standard deviations of the corresponding measured data are inconsistent, as shown in fig. 4, which shows that the dispersion of the measured data is directly related to the signal to noise ratio. The corresponding signal to noise ratio is shown in fig. 5, and the result shows that the higher the wind speed is, the lower the corresponding signal to noise ratio is. The higher the signal-to-noise ratio of the measurement data, the less the measurement data dispersion. In addition, the offset of the measured data can be corrected, a certain section of measured result is shown in fig. 6 (the abscissa is the theoretical value of the disc, the ordinate is the average value of radar measured values), and the radial wind speed of the device is corrected and calibrated through the coefficient fitted by the measured data of the reference device and the radar.
According to the novel calibration method provided by the invention, the uncertainty of target calibration can be 0.2%. The result of the order of magnitude improvement of precision is expected to be popularized in the wind energy industry, and according to the fact that the power generation power of the wind driven generator is highly correlated with the windward angle, higher wind speed precision brings remarkable economic benefit.
It should be emphasized that the above description is only a preferred embodiment of the present invention, and not intended to limit the present invention, and that various changes and modifications (e.g. number of laser radar beams, angle of beam pointing) can be made by those skilled in the art, and any modifications, equivalent substitutions, improvements, etc. are included in the scope of the present invention within the spirit and principle of the present invention.
Claims (3)
1. A Doppler laser wind-finding radar radial wind speed calibration method is characterized by comprising the following steps,
a. establishing a calibration device of a pulse coherent Doppler laser wind-finding radar: the device comprises a disc, a motor, a speed reducer and a supporting frame, wherein the disc is arranged on the supporting frame and driven by the motor, the speed reducer is used for controlling the rotating speed, the laser wind-finding radar is arranged outside an observation distance L, a laser beam of the laser wind-finding radar points to the tangential direction of the disc in a plane perpendicular to the rotating shaft of the disc, and the laser beam is inclined up and down along the vicinity of the disc, so that the projection value of the tangential speed is measured;
b. modeling is carried out on the basis of the calibration device established in the step a: let the view direction speed detected by the laser radar beThe disk circumferential velocity projected in the beam direction at the intersection point of the disk surface and the laser beam is:
， （1）
wherein V is Disc Is the circumferential velocity of the wheel and,is glancing angle +.>Is the beam tilt angle +.>Is angular frequency, +.>Is the radius of the disc;
c. inclination angle of light beamCalibrating: inclination angle of light beam->Accurately measuring by total station or estimating the beam tilt angle by means of trigonometric function from the height difference>Is a value of (2);
d. establishing the diameter of the light spot and the radius of the discIs subjected to uncertainty calculation: different sweep angles +.>The corresponding tangential projection speeds are not uniform, when the light spot is totally hit on the disk, the diameter of the light spot is set to be +.>The corresponding sweep angle range +.>There is the following relationship:
（2）
the trigonometric function Taylor expansion is finally obtained
，
By increasing the sweep angle according to the above formulaOr reducing the diameter of the spot +.>Or increasing the radius of the disc +.>Further reducing the measurement calibration error, whereby the spot diameter is determined +.>And disc radius->Is a relationship of (2);
e. according to the calibrated beam inclination angleGlancing angle->Disc radius->And the angular frequency of rotation of the disc->Finally, radial wind speed +.>。
2. The method for calibrating the radial wind speed of the Doppler laser wind finding radar according to claim 1, wherein in the step d, the sweep angle range isThe specific calculation process of (2) is as follows:
the trigonometric function Taylor expansion is performed according to the formula (2) to obtain
（3），
Only take into accountTerm, at this time, formula (3) becomes:
（4）
finally can be obtainedThe method comprises the following steps:
（5）。
3. the method according to claim 1, wherein in the step c, the beam tilt angle is estimated by using trigonometric function according to the altitude differenceThe process of the values of (2) is:
the radar and the disc are placed on the same horizontal plane, and the height between the center of the telescope and the ground is measured to beThe difference in height between the center of the light spot irradiated to the turntable and the ground is set to +.>The inclination angle of the light beam is
（6）。
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101833089A (en) * | 2010-04-30 | 2010-09-15 | 西安理工大学 | Doppler anemometry laser radar sensitivity calibrating system and method |
| CN102508222A (en) * | 2011-11-18 | 2012-06-20 | 中国科学技术大学 | Middle and upper atmospheric wind field retrieval method |
| CN106019303A (en) * | 2016-04-28 | 2016-10-12 | 中国科学技术大学 | Doppler anemometry laser radar radial wind speed real-time correction system |
| CN108717195A (en) * | 2018-05-24 | 2018-10-30 | 远景能源（江苏）有限公司 | A kind of coherent Doppler wind-observation laser radar system and its control method |
| CN113311436A (en) * | 2021-04-30 | 2021-08-27 | 中国人民解放军国防科技大学 | Method for correcting wind measurement of motion attitude of laser wind measuring radar on mobile platform |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101833089A (en) * | 2010-04-30 | 2010-09-15 | 西安理工大学 | Doppler anemometry laser radar sensitivity calibrating system and method |
| CN102508222A (en) * | 2011-11-18 | 2012-06-20 | 中国科学技术大学 | Middle and upper atmospheric wind field retrieval method |
| CN106019303A (en) * | 2016-04-28 | 2016-10-12 | 中国科学技术大学 | Doppler anemometry laser radar radial wind speed real-time correction system |
| CN108717195A (en) * | 2018-05-24 | 2018-10-30 | 远景能源（江苏）有限公司 | A kind of coherent Doppler wind-observation laser radar system and its control method |
| CN113311436A (en) * | 2021-04-30 | 2021-08-27 | 中国人民解放军国防科技大学 | Method for correcting wind measurement of motion attitude of laser wind measuring radar on mobile platform |
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