CN117805431A - Laser Doppler instantaneous rotating speed measuring device and method - Google Patents
Laser Doppler instantaneous rotating speed measuring device and method Download PDFInfo
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- CN117805431A CN117805431A CN202311857389.7A CN202311857389A CN117805431A CN 117805431 A CN117805431 A CN 117805431A CN 202311857389 A CN202311857389 A CN 202311857389A CN 117805431 A CN117805431 A CN 117805431A
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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
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/36—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light
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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
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Abstract
The invention relates to the field of laser and precise measurement, in particular to a device and a method for measuring the instantaneous rotation speed of laser Doppler, which comprises a laser, a collimating lens, a beam splitter, an attenuation sheet, a total reflection lens, an optical filter, a small aperture diaphragm, a photoelectric detector, a double-spectrum peak processing circuit, an aplanatic parallel beam splitter prism and a measured rotator. The invention measures the instantaneous rotating speed of the tested rotating body by utilizing the Doppler frequency difference corresponding to the two parallel light beams which are incident to different positions of the tested rotating body and the distance between the light beams.
Description
Technical Field
The invention relates to the field of laser and precise measurement, in particular to a laser Doppler instantaneous rotating speed measuring device and method.
Background
The usual methods for measuring the rotational speed of a rotating object are: hardware counting, software counting and spectrum analysis methods are most widely used in current metering, including frequency measurement, period measurement and frequency period measurement, and all the methods need to be realized by photoelectric or magneto-electric sensors, such as photoelectric encoders or Hall sensors. Some of these sensors need to be coaxially connected to the motor, and some need to be directly rotated by the motor, which is a typical contact measurement method, and in some applications, the sensor cannot be or is not allowed to be mounted on the rotating shaft.
In the prior art, a laser Doppler speed measurement technology can be adopted to measure the linear velocity and then indirectly calculate the rotating speed, so that a new step is provided on the non-contact rotating speed measurement method, and the overall schematic block diagram of a measurement system is shown in fig. 1.
Laser emitted by the HE-NE laser passes through the acousto-optic modulator, 0-order and 1-order diffraction light is generated due to anomalous Bragg diffraction, the 1-order diffraction light is reflected by the reflecting mirror M1 to pass through the half wave plate, and the half wave plate is regulated to enable the fast axis of the half wave plate to form 45 degrees with the vibration direction of the 1-order diffraction light, so that the vibration direction of the 1-order diffraction light is changed by 90 degrees. The M1 is adjusted so that the 0 th order diffracted light and the 1 st order diffracted light are parallel to each other. The two beams of light are converged on the surface of the measured object after passing through the lens L1, and scattered light generated by the surface of the measured object is converged on the surface of the photoelectric receiver through the lens L2 by the reflector M2. And processing the obtained electric signals by a hardware circuit to obtain the linear velocity of the surface to be measured. As can be seen from the formula v=ω·r, the rotational speed of the object to be measured can be obtained when the radius of the rotating object is known.
The system adopts a double-beam differential Doppler model, the model irradiates the surface of a measured object with light of two beams with different propagation directions, and then uses a lens to collect scattered light in the same direction, namely the observation direction, on the surface of a photoelectric detector for heterodyning to obtain Doppler frequency. The light path diagram is shown in figure 2;
the included angle between the two beams of light is alpha, and the object to be measured performs tangential motion at a speed v. The included angles between the light beam 1, the light beam 2 and the movement direction are respectively theta 1 、θ 2 The included angle between the observation direction and the movement direction is theta 3 . As known from the Doppler principle, the Doppler shift of two light beams is respectively
The difference frequency generated after mixing the two beams of light in the observation direction is
When the light beam 1 irradiates the surface to be measured at the same incident angle as the light beam 2, θ 1 And theta 2 Complementary, the above can be simplified into
It can be seen from the above that after the parameters of the optical path system are determined, f 0 The speed of the object to be measured can be obtained by measuring the difference frequency signal of the two light beams, and the rotation speed ω of the object to be measured can be obtained from v=ω·r by combining the radius of the object to be measured.
The measuring method has the advantages of high precision, quick dynamic response, large measuring range, non-contact measurement, capability of conducting remote measurement and the like, but has several obvious defects in practical application: (1) This method requires high installation requirements for the system measurement. The dual-beam differential system is sensitive to the transverse (the direction perpendicular to the bisector of the included angle of the two beams), and in the practical application process, it is difficult to ensure that the bisector of the included angle of the two beams is perpendicular to the tangential direction of the point to be measured on the rotator. If the system is not vertically installed, the measurement accuracy of the system is affected; (2) The method is to indirectly calculate the rotation speed from the tangential linear velocity of the edge of the tested rotor, so that the radius of the tested rotor must be measured first. In some applications (such as foundation-mounted rollers), the radius of the rotor (roller) being measured is inconvenient or not precisely measured, which greatly affects the accuracy of the measurement of the rotational speed. (3) The roundness of the tested rotating body (roller) is also high in the method, because the rotating speed is directly related to the radius, and fluctuation of the radius can lead to fluctuation of the measured rotating speed.
Therefore, a device and a method for measuring the instantaneous rotation speed of laser doppler are provided by a person skilled in the art to solve the above-mentioned problems in the background art.
Disclosure of Invention
In order to solve the technical problems, the invention provides a laser Doppler instantaneous rotation speed measuring device and a method thereof,
the utility model provides a laser Doppler instantaneous rotational speed measuring device, includes laser instrument, collimating mirror, beam splitter, attenuation piece, total reflection mirror, light filter, aperture diaphragm, photoelectric detector, dual spectral peak processing circuit, aplanatic parallel beam splitter prism and the measured rotator, laser instrument, collimating mirror, beam splitter, aplanatic parallel beam splitter prism, the measured rotator are in the same direction, just total reflection mirror, attenuation piece, beam splitter, light filter, aperture diaphragm, photoelectric detector and dual spectral peak processing circuit are in same direction.
The laser Doppler instantaneous rotation speed measuring method includes that laser emitted by a laser is collimated by a collimating lens and then split into two beams of light with equal intensity by a beam splitter, one beam returns along the original direction by an attenuation sheet and a total reflection lens, and then is incident on a photoelectric detector through the beam splitter, an optical filter and a small aperture diaphragm to be used as reference light; the other beam of light passes through the aplanatic parallel beam splitting prism to form two beams of light which are parallel to each other and are incident on the surface of the tested rotating body, the two beams of light are an emergent beam 1 and an emergent beam 2 respectively, and scattered light returned along the original direction of the two beams of light are combined together to form signal light.
Preferably, the outgoing beam 1 and the outgoing beam 2 are both located at the upper half part of the tested rotor, and the outgoing beam 1 and the outgoing beam 2 are both located at the same side of the tested rotor.
Preferably, the included angles between the outgoing beam 1 and the outgoing beam 2 and the tangential direction of the respective to-be-measured points are different, so that the signal light contains two different frequencies, and the system adopts a double-spectrum peak processing circuit, so that two Doppler frequencies can be extracted accurately, and then speed calculation is performed;
after mixing the signal light and the reference light on the photosensitive surface of the photodetector, two different Doppler frequencies are generated
Wherein f D1 The difference frequency is the Doppler frequency corresponding to the emergent beam 1 after the scattered light returned by the emergent beam 1 along the original direction is mixed with the reference light;
f D2 the difference frequency is the Doppler frequency corresponding to the outgoing beam 2 after the scattered light returned by the outgoing beam 2 along the original direction is mixed with the reference light;
wherein v is 1 And v 2 All represent speed, λ represents wavelength;
the schematic structure of the two light beams irradiating the surface of the tested rotator is shown in fig. 4, and then the formulas (1) and (2) can be expressed as
Wherein alpha and beta are included angles of the emergent light beam 1, the emergent light beam 2 and the tangential linear velocity of the measured point, r is the radius of the measured rotator, and omega is the angular velocity of the measured rotator.
Further deriving the formula (3) and the formula (4) according to the geometric relationship shown in the figure
Wherein A is the intersection point of the emergent beam 1 and the tested rotating body, C is the intersection point of the emergent beam 2 and the tested rotating body, O is the center point of the tested rotating body, B is the symmetrical point of A about O, D is the symmetrical point of B about O, E is the midpoint between AB, F is the midpoint between CD, and H is the perpendicular point between C and AB;
the difference frequency signal of Doppler frequency generated by the two beams of light is
Thus the rotation speed is
Wherein d is the distance between two parallel beams;
by measuring the parallel distance between the emergent light beam 1 and the emergent light beam 2 and the difference value between Doppler frequencies corresponding to the emergent light beam and the emergent light beam, and combining the wavelength of the laser, the angular velocity of the tested rotator can be directly obtained.
The method adopted by the system can be used for calculating the instantaneous angular velocity of the tested swivel in real time, and the installation angle of the system or the radius measurement precision of the tested swivel can not influence the measurement of the angular velocity.
The invention has the technical effects and advantages that:
first, directly measuring the rotation speed without passing throughThe linear velocity conversion is determined by equation (8) using λ, Δf D And d, directly settling the angular speed of the tested rotating body. The radius of the measured swivel is not required to be measured indirectly by v=omega·r;
secondly, outputting the rotating speed in real time, wherein the average rotating speed of the tested rotating body in a certain time is obtained by removing the number of turns by the traditional target pasting method, and the rotating speed measuring error caused by the error of +/-1 of the number of turns does not exist in the method;
and thirdly, the installation is convenient, the coaxial installation like the encoder method is not needed, and the installation angle of the system does not influence the measurement accuracy of the rotating speed. Only the two emergent beams are ensured to be positioned in the same area of the tested rotator;
and (IV) the roundness of the tested swivel is not required. As can be seen from the principle formula (12) of system measurement, the rotating speed has no relation with the radius, and the fluctuation of the radius does not influence the measuring precision of the rotating speed.
Drawings
FIG. 1 is a schematic block diagram of a differential laser Doppler rotational speed measurement system provided in an embodiment of the present application;
figure 2 is an optical path diagram of a differential doppler system provided in an embodiment of the present application;
fig. 3 is a general structure of a laser doppler instantaneous rotation speed measurement device provided in an embodiment of the present application;
fig. 4 is a schematic diagram of dual parallel beam laser doppler instantaneous rotation speed measurement according to an embodiment of the present application.
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description. The embodiments of the invention have been presented for purposes of illustration and description, and are not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
Example 1
Referring to fig. 3 to 4, in this embodiment, a laser doppler instantaneous rotation speed measurement device is provided, which includes a laser, a collimator, a beam splitter, an attenuation sheet, a total reflection mirror, an optical filter, a small aperture diaphragm, a photoelectric detector, a dual-spectral peak processing circuit, an aplanatic parallel beam splitter prism, and a measured rotator, where the laser, the collimator, the beam splitter, the aplanatic parallel beam splitter prism, and the measured rotator are in the same direction, and the total reflection mirror, the attenuation sheet, the beam splitter, the optical filter, the small aperture diaphragm, the photoelectric detector, and the dual-spectral peak processing circuit are in the same direction.
A laser Doppler instantaneous rotation speed measuring method includes that an aperture diaphragm is incident on a photoelectric detector and is used as reference light; the other beam of light passes through the aplanatic parallel beam splitting prism to form two beams of light which are parallel to each other and are incident on the surface of the tested rotating body, the two beams of light are an emergent beam 1 and an emergent beam 2 respectively, and scattered light returned along the original direction of the two beams of light are combined together to form signal light.
Preferably, the outgoing beam 1 and the outgoing beam 2 are both located at the upper half part of the tested rotor, and the outgoing beam 1 and the outgoing beam 2 are both located at the same side of the tested rotor.
Preferably, the included angles between the outgoing beam 1 and the outgoing beam 2 and the tangential direction of the respective to-be-measured points are different, so that the signal light contains two different frequencies, and the system adopts a double-spectrum peak processing circuit, so that two Doppler frequencies can be extracted accurately, and then speed calculation is performed;
after mixing the signal light and the reference light on the photosensitive surface of the photodetector, two different Doppler frequencies are generated
Wherein f D1 Is the scattered light and the scattered light returned by the emergent beam 1 along the original directionThe corresponding difference frequency after mixing the reference light, namely the Doppler frequency corresponding to the emergent light beam 1;
f D2 the difference frequency is the Doppler frequency corresponding to the outgoing beam 2 after the scattered light returned by the outgoing beam 2 along the original direction is mixed with the reference light;
wherein v is 1 And v 2 All represent speed, λ represents wavelength;
the schematic structure of the two light beams irradiating the surface of the tested rotator is shown in fig. 4, and then the formulas (1) and (2) can be expressed as
Wherein alpha and beta are included angles of the emergent light beam 1, the emergent light beam 2 and the tangential linear velocity of the measured point, r is the radius of the measured rotator, and omega is the angular velocity of the measured rotator.
Further deriving the formula (3) and the formula (4) according to the geometric relationship shown in the figure
Wherein A is the intersection point of the emergent beam 1 and the tested rotating body, C is the intersection point of the emergent beam 2 and the tested rotating body, O is the center point of the tested rotating body, B is the symmetrical point of A about O, D is the symmetrical point of B about O, E is the midpoint between AB, F is the midpoint between CD, and H is the perpendicular point between C and AB;
the difference frequency signal of Doppler frequency generated by the two beams of light is
Thus the rotation speed is
Wherein d is the distance between two parallel beams;
by measuring the parallel distance between the emergent light beam 1 and the emergent light beam 2 and the difference value between Doppler frequencies corresponding to the emergent light beam and the emergent light beam, and combining the wavelength of the laser, the angular velocity of the tested rotator can be directly obtained.
In summary, the method adopted by the scheme can calculate the instantaneous angular velocity of the tested rotating body in real time, and the installation angle or the radius measurement precision of the tested rotating body can not influence the measurement of the angular velocity.
It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art and which are included in the embodiments of the present invention without the inventive step, are intended to be within the scope of the present invention. Structures, devices and methods of operation not specifically described and illustrated herein, unless otherwise indicated and limited, are implemented according to conventional means in the art.
Claims (4)
1. The device is characterized by comprising a laser, a collimating mirror, a beam splitter, an attenuation sheet, a total reflection mirror, an optical filter, a small aperture diaphragm, a photoelectric detector, a dual-spectrum peak processing circuit, an aplanatic parallel beam splitter prism and a tested rotating body, wherein the laser, the collimating mirror, the beam splitter, the aplanatic parallel beam splitter prism and the tested rotating body are in the same direction, and the total reflection mirror, the attenuation sheet, the beam splitter, the optical filter, the small aperture diaphragm, the photoelectric detector and the dual-spectrum peak processing circuit are in the same direction.
2. The method for measuring the instantaneous rotation speed of laser Doppler is characterized in that laser emitted by the laser is collimated by the collimating lens and then split into two beams of light with equal intensity by the beam splitter, one beam returns along the original direction by the attenuation sheet and the total reflection lens, and then is incident on the photoelectric detector by the beam splitter, the optical filter and the aperture diaphragm to be reference light; the other beam of light passes through an aplanatic parallel beam splitting prism to form two beams of light which are parallel to each other and are incident on the surface of the tested rotating body, the two beams of light are an emergent beam 1 and an emergent beam 2 respectively, and scattered light of the two beams of light respectively returns along the original direction and are combined together to form signal light.
3. The method according to claim 2, wherein the outgoing beam 1 and the outgoing beam 2 are located at the upper half part of the tested rotor, and the outgoing beam 1 and the outgoing beam 2 are located at the same side of the tested rotor.
4. The method for measuring the instantaneous rotational speed of laser Doppler according to claim 2, wherein the angles between the outgoing beam 1 and the outgoing beam 2 and the tangential direction of the respective points to be measured are different, so that the signal light contains two different frequencies, and the system adopts a dual-spectral peak processing circuit, so that two Doppler frequencies can be extracted accurately, and then the speed calculation is performed;
after mixing the signal light and the reference light on the photosensitive surface of the photodetector, two different Doppler frequencies are generated
Wherein f D1 The difference frequency is the Doppler frequency corresponding to the emergent beam 1 after the scattered light returned by the emergent beam 1 along the original direction is mixed with the reference light;
f D2 the difference frequency is the Doppler frequency corresponding to the outgoing beam 2 after the scattered light returned by the outgoing beam 2 along the original direction is mixed with the reference light;
wherein v is 1 And v 2 All represent speed, λ represents wavelength;
the schematic structure of the two light beams irradiating the surface of the tested rotator is shown in fig. 4, and then the formulas (1) and (2) can be expressed as
Wherein alpha and beta are included angles of an outgoing light beam 1, an outgoing light beam 2 and a tangential linear speed of a measured point, r is a radius of a measured rotator, and omega is an angular speed of the measured rotator;
further deriving the formula (3) and the formula (4) according to the geometric relationship shown in the figure
Wherein A is the intersection point of the outgoing light beam 1 (light beam 1) and the tested rotating body, C is the intersection point of the outgoing light beam 2 (light beam 2) and the tested rotating body, O is the center point of the tested rotating body, B is the point of symmetry of A about O, D is the point of symmetry of B about O, E is the midpoint between AB, F is the midpoint between CD, and H is the perpendicular point between C and AB;
the difference frequency signal of the doppler frequency generated by the two beams of light is:
thus the rotation speed is
Wherein d is the distance between two parallel beams;
by measuring the parallel distance between the emergent light beam 1 and the emergent light beam 2 and the difference value between Doppler frequencies corresponding to the emergent light beam and the emergent light beam, and combining the wavelength of the laser, the angular velocity of the tested rotator can be directly obtained.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311857389.7A CN117805431A (en) | 2023-12-29 | 2023-12-29 | Laser Doppler instantaneous rotating speed measuring device and method |
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| CN202311857389.7A CN117805431A (en) | 2023-12-29 | 2023-12-29 | Laser Doppler instantaneous rotating speed measuring device and method |
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