CN114594278B - Method and system for inverting wind speed based on Moire measurement technology - Google Patents
Method and system for inverting wind speed based on Moire measurement technology Download PDFInfo
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- CN114594278B CN114594278B CN202210326299.4A CN202210326299A CN114594278B CN 114594278 B CN114594278 B CN 114594278B CN 202210326299 A CN202210326299 A CN 202210326299A CN 114594278 B CN114594278 B CN 114594278B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/26—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The invention discloses a method and a system for inverting wind speed based on a Moire measurement technology, comprising the following steps: the moire fringe distance and the moire fringe displacement under the action of wind force are acquired by using a pre-established moire fringe acquisition system; and calculating according to the moire fringe spacing and the moire fringe displacement to obtain the wind speed. The advantages are that: according to the invention, a Moire measurement technology is introduced into wind speed measurement, and the wind speed is inverted by correlating the tiny displacement of the grating with wind pressure, so that the wind speed measuring device has the characteristics of real time, stability, non-contact and high precision.
Description
Technical Field
The invention relates to a method and a system for inverting wind speed based on a Moire measurement technology, and belongs to the technical field of optical detection.
Background
Wind is a common phenomenon in nature, and wind speed is required to be measured in the fields of meteorology, military, ship navigation, aerospace, new energy, fire protection and the like. In addition, the wind speed is closely related to the intensity of atmospheric turbulence, and the method has non-negligible influence on the aspects of atmospheric detection, optical imaging detection of an aircraft, atmospheric laser communication and the like. With the increasing development of science and technology, the requirements on wind speed measurement accuracy are also higher and higher.
Existing manners for measuring wind speed mainly include mechanical, ultrasonic and hot wire anemometers. The mechanical anemometer is easy to be disturbed by severe environments; temperature compensation is needed to be considered during measurement of the ultrasonic anemometer, so that the influence of temperature change on a measurement result is reduced; the hot wire anemometer heating element is easily damaged, affecting the final measurement. The moire measurement technology has the advantages of wide application range, difficult damage, high precision, no interference by the ambient temperature and the like, and has unique advantages in wind speed measurement.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method and a system for inverting wind speed based on a Moire measurement technology.
In order to solve the technical problems, the invention provides a method for inverting wind speed based on Moire measurement technology, comprising the following steps:
the moire fringe distance and the moire fringe displacement under the action of wind force are acquired by using a pre-established moire fringe acquisition system;
and calculating according to the moire fringe spacing and the moire fringe displacement to obtain the wind speed.
Further, the moire fringe acquisition system comprises: moire fringe acquisition device and wind speed sensing device;
the moire fringe acquisition device is used for acquiring moire fringes;
the wind speed sensing device is used for changing the grating position change in the moire fringe collecting device according to the wind power change so as to change the moire fringe position.
Further, the moire fringe acquisition device comprises: the device comprises a laser, a beam expanding and collimating system, a grating group, a first imaging lens, a filter, a second imaging lens and a receiving screen;
the laser is used for generating laser, and moire fringes are obtained on the receiving screen through the beam expanding collimation system, the grating group, the first imaging lens, the filter and the second imaging lens in sequence.
Further, the grating group includes: a first grating and a second grating;
the wind speed sensing device includes: the wind screen, the fixed platform and the translation;
the fixed bench is fixed the first grating, the translation platform is equipped with the spout, the one end fixed connection spring of spout, the other end fixed connection second grating of spring, second grating and spout sliding connection, second grating fixed connection wind screen.
Further, the screen surface of the wind screen is perpendicular to the chute groove direction.
Further, the wind force magnitude F is equal to the force of the spring, expressed as:
wherein v is wind speed, ρ is air mass density, A is stress area of the wind screen, and C D And k is the elastic coefficient of the spring, and s is the moving displacement of the second grating in the chute.
Further, the wind speed v is calculated using the following formula,
wherein, p' is the moire fringe spacing, w is the moire fringe displacement, ρ is the air mass density, A is the stress area of the wind screen, and C D Representing the air resistance coefficient;
θ is an included angle between the first grating and the second grating;
d is the distance between adjacent grating lines on the first grating and the second grating.
A system for inverting wind speed based on moire measurement techniques, comprising:
the first calculation module is used for acquiring moire fringe spacing and moire fringe displacement under the action of wind power by utilizing a pre-established moire fringe acquisition system;
and the second calculation module is used for calculating the wind speed according to the moire fringe spacing and the moire fringe displacement.
The invention has the beneficial effects that:
according to the invention, a Moire measurement technology is introduced into wind speed measurement, and the wind speed is inverted by correlating the tiny displacement of the grating with wind pressure, so that the wind speed measuring device has the characteristics of real time, stability, non-contact and high precision.
Drawings
FIG. 1 is a schematic view of a moire fringe acquisition device of the present invention;
FIG. 2 is a schematic view of a wind speed sensing device;
fig. 3 (a) is a moire pattern in a windless state, fig. 3 (b) is a moire pattern of 300 th frame, fig. 3 (c) is a moire pattern of 600 th frame, and fig. 3 (d) is a moire pattern of 900 th frame;
fig. 4 (a) is a truncated moire pattern of the windless state, fig. 4 (b) is a truncated moire pattern of the 300 th frame, fig. 4 (c) is a truncated moire pattern of the 600 th frame, and fig. 4 (d) is a truncated moire pattern of the 900 th frame;
fig. 5 (a) is a thinned fringe pattern in a windless state, fig. 5 (b) is a thinned fringe pattern of a 300 th frame taken, fig. 5 (c) is a thinned fringe pattern of a 600 th frame taken, and fig. 5 (d) is a thinned fringe pattern of a 900 th frame taken;
FIG. 6 is a graph of wind speed measured by two methods.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.
A method of inverting wind speed using moire measurement techniques, comprising:
the moire fringe distance and the moire fringe displacement under the action of wind force are acquired by using a pre-established moire fringe acquisition system;
and calculating according to the moire fringe spacing and the moire fringe displacement to obtain the wind speed.
As shown in fig. 1, the moire fringe acquisition device comprises a laser 1; a beam expansion collimation system consisting of a small lens 2 and a large lens 3; a Ronchi grating group; a first imaging lens 6 and a second imaging lens 8; a filter 7; a receiving screen 9; the Ronchi grating group comprises a first grating 4 and a second grating 5.
The laser 1 is used for generating laser, sequentially passes through a beam expanding and collimating system, a Ronchi grating group, a first imaging lens 6, a filter 7 and a second imaging lens 8, and collects moire fringes from a receiving screen by using a CCD camera on the receiving screen 9 and transmits the moire fringes to a computer.
As shown in fig. 2, the wind speed sensing device is assembled with the Ronchi grating and the wind speed is inverted by using the amplification of moire fringes.
The wind speed sensing device includes: a wind screen 10, a fixed table 11 and a translation table 12;
the first grating 4 is fixed on the fixed table 11, the translation table 12 is provided with a chute, one end of the chute is fixedly connected with a spring, the other end of the spring is fixedly connected with the second grating 5, the second grating 5 is in sliding connection with the chute, and the second grating is fixedly connected with the air screen 10.
As can be seen from fig. 2, we fix the second grating 5 and the wind screen 10 on a displacement table with springs, and can know that the acting force of wind on the wind screen 10 is:
where v denotes the air velocity relative to the wind screen 10, i.e. wind speed, ρ is the air mass density, and typically 1.21Kg/m at room temperature 3 A represents the stress area of the wind screen 10, C D Representing air resistance coefficient ] 。
The contact surface of the translation stage 12 uses roller guides with low friction. The force of the wind on the wind screen 10 can extend the spring of the translation stage and correspondingly the position of the second grating 5 is also changed. For ease of calculation, we will have the magnitude of F approximately equal to the magnitude of the force of the spring extension, the amount of spring extension, i.e. the amount of grating displacement. Therefore, the displacement of the grating can be expressed as:
where k is the spring rate of the spring.
When the displacement of the grating in the x-axis direction is s, the moire fringes will move by a distance w in the y-axis direction, the relationship between the two can be approximated as [4] :
Wherein θ is the angle between the two gratings.
Because the included angle of the two gratings is not easy to measure, the relation between the fringe spacing p ', p' and the included angle theta of the gratings is introduced as follows [5] ：
Where d is the two grating period, tg (θ/2) ≡sin (θ/2) since θ is small.
Combining formulas (1) - (4), we can obtain:
based on the principle described by the formula (5), we can invert the wind speed by obtaining moire fringes and obtaining the moire fringe pitch p' through the moire measurement technique and measuring the displacement w of the fringes under the action of wind force.
The invention also provides a system for inverting wind speed based on the Moire chromatography technology, comprising:
the first calculation module is used for acquiring moire fringe spacing and moire fringe displacement under the action of wind power by utilizing a pre-established moire fringe acquisition system;
and the second calculation module is used for calculating the wind speed according to the moire fringe spacing and the moire fringe displacement.
Principle experiment 1
Based on fig. 1, an experimental apparatus was set up and a principle experiment was performed. The experiment uses a fan as a wind source, the wavelength of a laser is 532nm, the focal length of the small lens 2 is 3mm, the diameter is 4mm, the focal length of the large lens 3 is 300mm, the diameter is 50mm, and the fan and the small lens form a beam expanding and collimating system. 4 and 5 are a pair of Ronchi gratings with an effective size of 50mm x 50mm, with a grating period d=0.02 mm. The diameter and focal length of the imaging lens are 75mm and 300mm, respectively. The spring constant of the spring in the translation stage is k= 766.4N/m. The area of the wind screen is a=0.031 m 2 The vertical distance to the wind source is l=0.82 m.
First, moire was recorded in a windless state. Then, the wind source is opened, after the wind speed is stable, the CCD is set to collect moire fringes at the speed of 1 frame/second and store the moire fringes into the computer, and the wind speed is unchanged in the collecting process, so that 900 frames are collected in total. In order to verify the feasibility of the method provided by the invention, in the experimental process, the anemometer synchronously records the wind speed, and 900 data are recorded in total. Among them, 300 th, 600 th, 900 th and no moire patterns in case of wind are shown in fig. 3 (a), 3 (b), 3 (c) and 3 (d).
The actual size of the moire pattern is 5cm×5cm, the pixel size is 600×600, the fringe pitch corresponds to 36 pixels in the pattern, and by pixel ratio we can calculate the moire pitch p' =0.3 cm as shown in fig. 3 (a). In the measuring process, the spacing between adjacent grating lines of the grating and the grating included angle are not changed, so the stripe spacing is always unchanged. For ease of processing we have truncated the same positions for all 900 frames of moire patterns. The region with a pixel size of 320×320 is cut down and right from the red dot position shown in fig. 3 (a), and the result is shown in fig. 4 (a), 4 (b), 4 (c), and 4 (d).
Binarization and thinning processing are carried out on the truncated moire pattern, wherein 300 frames, 600 frames and 900 frames when wind exists and thinning stripes when no wind exists are shown in fig. 5 (a), 5 (b), 5 (c) and 5 (d).
As can be seen from fig. 5 (a), 5 (b), 5 (c) and 5 (d), the streak f significantly moves down when there is wind. Taking one of the points as an example (the yellow point marked in the figure), 300 th, 600 th and 900 th frames in windy state are respectively shifted down by 16, 17 and 15 pixels compared with windless state. Respectively calculating w by pixel ratio 1 ＝0.133cm，w 2 =0.142 cm and w 3 =0.125 cm. In the same way, we can calculate the amount of downshifting of other points and thus find how much the stripe has downshifted on average. Finally, lead toThe wind speed was inverted by equation (5), and the result is shown in fig. 6.
As can be seen from fig. 6, compared with the anemometer measurement, the moire measurement technique is inverted to have smaller fluctuation of wind speed, and the wind speed is unchanged in the measurement process, so that the stability of the wind speed measured by the moire measurement technique is better, the error is smaller, and the moire measurement technique is feasible to be introduced into the inversion of the wind speed. However, this method also has certain errors, mainly because of the following: firstly, in theoretical deduction, we neglect the action of other forces by considering only the action of wind on the wind screen and the elasticity of the spring. Secondly, we assume that the wind is blowing evenly onto the wind screen, in fact the wind is not uniform, and the inverted wind speed is the average wind speed of all blowing onto the wind screen.
The present invention uses moire fringes to have a magnifying effect, i.e. when one of the gratings is moved, the fringes are moved in a direction perpendicular to the direction of movement of the grating, by a much greater distance than the movement of the grating. The invention introduces the moire measurement technology into wind speed measurement, links tiny displacement of the grating with wind pressure, inverts wind speed, and provides a feasible method for measuring wind speed.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.
Claims (4)
1. A method of inverting wind speed based on moire measurement techniques, comprising:
the moire fringe distance and the moire fringe displacement under the action of wind force are acquired by using a pre-established moire fringe acquisition system;
calculating to obtain wind speed according to the moire fringe spacing and the moire fringe displacement;
the moire fringe acquisition system comprises: moire fringe acquisition device and wind speed sensing device;
the moire fringe acquisition device is used for acquiring moire fringes;
the wind speed sensing device is used for changing the grating position change in the moire fringe acquisition device according to the wind power change so as to change the moire fringe position;
the moire fringe acquisition device comprises: the device comprises a laser, a beam expanding and collimating system, a grating group, a first imaging lens, a filter, a second imaging lens and a receiving screen;
the laser is used for generating laser, and moire fringes are obtained on the receiving screen through the beam expanding collimation system, the grating group, the first imaging lens, the filter and the second imaging lens in sequence;
the grating group includes: a first grating and a second grating;
the wind speed sensing device includes: the wind screen, the fixed platform and the translation;
the first grating is fixed on the fixed table, the translation table is provided with a chute, one end of the chute is fixedly connected with a spring, the other end of the spring is fixedly connected with a second grating, the second grating is in sliding connection with the chute, and the second grating is fixedly connected with the air screen;
the screen surface of the wind screen is perpendicular to the chute groove direction.
2. The method for inverting wind speed based on moire measurement technique as defined in claim 1, wherein,
the wind force magnitude F is equal to the force of the spring, expressed as:
wherein v is wind speed, ρ is air mass density, A is stress area of the wind screen, and C D And k is the elastic coefficient of the spring, and s is the moving displacement of the second grating in the chute.
3. The method for inverting wind speed based on moire measurement technique according to claim 2, wherein,
the wind speed v is calculated using the following formula,
wherein, p' is the moire fringe spacing, w is the moire fringe displacement, ρ is the air mass density, A is the stress area of the wind screen, and C D Representing the air resistance coefficient;
θ is an included angle between the first grating and the second grating;
d is the distance between adjacent grating lines on the first grating and the second grating.
4. A system for inverting wind speed based on moire measurement techniques, comprising:
the first calculation module is used for acquiring moire fringe spacing and moire fringe displacement under the action of wind power by utilizing a pre-established moire fringe acquisition system;
the second calculation module is used for calculating the wind speed according to the moire fringe spacing and the moire fringe displacement;
the moire fringe acquisition system comprises: moire fringe acquisition device and wind speed sensing device;
the moire fringe acquisition device is used for acquiring moire fringes;
the wind speed sensing device is used for changing the grating position change in the moire fringe acquisition device according to the wind power change so as to change the moire fringe position;
the moire fringe acquisition device comprises: the device comprises a laser, a beam expanding and collimating system, a grating group, a first imaging lens, a filter, a second imaging lens and a receiving screen;
the laser is used for generating laser, and moire fringes are obtained on the receiving screen through the beam expanding collimation system, the grating group, the first imaging lens, the filter and the second imaging lens in sequence;
the grating group includes: a first grating and a second grating;
the wind speed sensing device includes: the wind screen, the fixed platform and the translation;
the first grating is fixed on the fixed table, the translation table is provided with a chute, one end of the chute is fixedly connected with a spring, the other end of the spring is fixedly connected with a second grating, the second grating is in sliding connection with the chute, and the second grating is fixedly connected with the air screen;
the screen surface of the wind screen is perpendicular to the chute groove direction.
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