CN207528750U - A kind of vehicle-mounted laser Doppler anemometer - Google Patents

Abstract

A vehicle-mounted laser Doppler velocimeter. The laser light emitted by the laser is divided into two parallel beams of equal intensity and equal optical path by a beam splitter. The two beams of parallel light are respectively incident on the first and second half mirrors. The two parallel light beams transmitted by the first and second half mirrors enter the two symmetrical optical paths of the dual beam differential system; the two beams reflected from the first and second half mirrors are respectively incident into the optical path of two 1D reference photonic systems arranged symmetrically. The dual-beam differential system outputs the Doppler signal S3 with the Doppler frequency _fD , and the two one-dimensional reference photonic systems output the Doppler signal S1 with the Doppler frequency _fD1 and the Doppler signal S1 with the Doppler frequency _fD2 respectively. Doppler signal S2; use S1, S2 and S3 to complete the solution of the current vehicle speed. The utility model can adapt to the bumping and swaying of the vehicle on the uneven road surface, and the whole speed measuring system is installed on the vehicle carrier to provide accurate speed parameters for the vehicle in real time.

Description

A vehicle-mounted laser Doppler velocimeter

technical field

The utility model relates to a high-precision and high-reliability novel laser speed measuring instrument, which is mainly used to provide accurate speed parameters for vehicles in different application environments, and belongs to the technical field of laser and precision measurement.

Background technique

At present, the speed parameters of the vehicle are mainly acquired in two ways. One is to use the on-board accelerometer to measure the acceleration of the carrier relative to the reference coordinate system, calculate the carrier velocity change, and combine the initial value to obtain the carrier velocity parameters. The other is to obtain the velocity of the carrier by means of the Global Positioning System (GPS). Both speed measurement methods have their own disadvantages.

The current vehicle-mounted accelerometer speed measurement is based on the principle of measuring specific force. Although it is an autonomous test device, it measures the apparent acceleration of the moving body, not the absolute acceleration; in addition, it is necessary to calculate the acceleration generated by the gravitational field. In order to obtain the absolute acceleration of the moving body. Since it is measured through a mass, there is an error term affected by the overload. However, there are many error items in the measurement, which require complex calculations for correction.

The speed of the carrier is obtained by means of the Global Positioning System (GPS). Although GPS has the advantages of globalization, all-weather, high precision, and real-time positioning system, it is the second-generation satellite navigation system developed by the US Department of Defense and belongs to non-autonomous. The system has poor dynamic performance and anti-interference ability.

The laser Doppler velocimeter is based on the laser Doppler effect, using the Doppler frequency shift of light scattered by moving particles to obtain velocity information. The research on laser Doppler velocimetry technology began in 1964. After decades of development, it has become increasingly mature. At the same time, the development of signal processing technology, modern laser technology and micro-manufacturing technology has provided favorable conditions for the research of laser Doppler velocimetry. . Laser Doppler velocimeter, as a new type of velocity sensor, has gradually become a hotspot in velocity measurement research at home and abroad.

In some existing laser Doppler velocimeters, due to the defects of their optical path design (such as the small control body of the probe), the measurement range is far from being able to adapt to the environment such as the up and down vibration of the vehicle and the fluctuation of the ground height. However, because the Doppler speedometer is sensitive to the emission inclination (the angle between the emission beam and the direction of motion), the bumps and swaying of the vehicle will cause measurement errors and cannot provide accurate speed measurement information for the vehicle in real time.

Utility model content

Aiming at the defects of various existing speedometers, especially the existing laser Doppler speedometers cannot adapt to the bumps and swaying of vehicles, and cannot provide accurate speed measurement information for vehicles in real time. The purpose of this utility model is to provide a vehicle-mounted laser Doppler speedometer, which can adapt to the bumps and swings of the vehicle on uneven roads, install the entire speed measurement system on the vehicle carrier, and provide accurate speed for the vehicle in real time parameter.

In order to realize the purpose of this utility model, adopt following technical scheme to realize:

A vehicle-mounted laser Doppler velocimeter includes two one-dimensional reference photon systems, a dual beam differential system, a signal discriminator and a signal processor.

The laser light emitted by the laser is divided into two parallel beams of equal intensity and equal optical path by the beam splitter. The two beams of parallel light are respectively incident on the first half mirror and the second half mirror. The two parallel light beams transmitted by the mirror and the second half-mirror enter into the two symmetrical optical paths of the double-beam differential system; the beams reflected from the first half-mirror and the second half-mirror The two light beams are symmetrically incident on the optical paths of the two symmetrically arranged one-dimensional reference photonic systems respectively.

The dual-beam differential system outputs Doppler signal S3 with Doppler frequency _fD , and the two one-dimensional reference photonic systems output Doppler signal S1 with Doppler frequency _fD1 and Doppler frequency _fD2 respectively Doppler signal S2; Doppler signal S1, Doppler signal S2 and Doppler signal S3 are all input to the signal discriminator used to distinguish the current driving state of the vehicle, the signal discriminator is connected with the signal processor, and the signal The discriminator transmits the received Doppler signal and the current driving state information of the vehicle to the signal processor, and the signal processor performs signal processing to complete the calculation of the current vehicle driving speed.

Among them: the signal discriminator can judge the current driving state of the vehicle through the received Doppler signal (the Doppler frequency f _D1 is the same as f _D2 , and the change amount Δθ of the emission inclination is zero, and the vehicle is driving on a smooth road at this time ; Doppler frequency f _D1 is not the same as f _D2 , and the variation of the launch inclination is Δθ, and the vehicle is running on the uneven ground at this time.), when the vehicle is running on the flat ground, when running smoothly, the signal processing The device extracts the corresponding Doppler frequency f _D from the Doppler signal S3, uses the Doppler frequency f _D to realize the calculation of the current vehicle speed, and obtains the current vehicle real speed; when the vehicle is on the uneven ground When driving, when the vehicle bumps and sways, the signal processor extracts the corresponding Doppler frequency f _D1 from the Doppler signal S1 and the corresponding Doppler frequency f _D2 from the Doppler signal S2, and uses the Doppler The frequencies f _D1 and f _D2 realize the calculation of the current vehicle speed, and obtain the current real speed of the vehicle.

Among them, the laser, the dichroic prism, the first half-mirror, the second half-mirror, the third diaphragm, the fourth diaphragm, the first converging lens, the ground, the second converging lens, the fifth diaphragm and the first Three avalanche diode modules form a dual-beam differential system;

Laser, splitter prism, first half mirror, second half mirror, first attenuation sheet, second attenuation sheet, first total reflection mirror, second total reflection mirror, first narrow light filter , the second narrow light filter, the first aperture, the second aperture, the first avalanche diode module and the second avalanche diode module constitute two one-dimensional reference beam type subsystems, in which: the laser, the beam splitter, the first The half-transparent mirror, the first attenuator, the first total mirror, the first narrow light filter, the first aperture, and the first avalanche diode module form a one-dimensional reference beam type subsystem, the laser, the beam splitter The prism, the second half mirror, the second attenuation plate, the second total mirror, the second narrow filter, the second diaphragm and the second avalanche diode module form a one-dimensional reference beam type subsystem.

The laser light emitted by the laser is divided into two parallel beams of equal intensity and equal optical path by a dichroic prism. The light beam transmitted by the half-mirror is incident on the ground through the third aperture and the first converging lens, and the light velocity transmitted from the second half-mirror is incident on the ground through the fourth aperture and the first converging lens. Part of the scattered light is incident on the photosensitive surface of the third avalanche diode module through the first converging lens, the second converging lens, and the fifth aperture, and undergoes heterodyne interference to obtain a Doppler signal S3 with a Doppler frequency of f _D .

Part of the scattered light on the ground will go back the same way, that is, a part of the scattered light on the ground will pass through the first converging lens and the third diaphragm to the first half mirror, and the light beam reflected from the first half mirror will pass through the first half mirror. A narrow light filter, the first aperture is incident on the photosensitive surface of the first avalanche diode module, and the light beam incident on the photosensitive surface of the first avalanche diode module according to this optical path is 1# signal light; similarly, the ground Part of the scattered light passes through the first converging lens and the fourth aperture to the second half mirror, and the light beam reflected from the second half mirror enters through the second narrow filter and the second aperture To the photosensitive surface of the second avalanche diode module, the light beam incident on the photosensitive surface of the second avalanche diode module according to this optical path is 2# signal light.

The two beams of parallel light hit the first half-mirror and the second half-mirror respectively; the light beams reflected from the first half-mirror pass through the first attenuation sheet to the first full-mirror and are reflected again After being attenuated by the first attenuator, it enters the first half-mirror, and the light beam transmitted from the first half-mirror enters the first avalanche diode module through the first narrow light filter and the first diaphragm. 1# reference light on the photosensitive surface; similarly, the light beam reflected from the second half-mirror passes through the second attenuation sheet to the second total reflection mirror, and then is reflected to the second attenuation sheet for attenuation. To the second half-mirror, the light beam transmitted from the second half-mirror is incident on the photosensitive surface of the second avalanche diode module through the second narrow light filter and the second aperture, which is 2# reference Light.

The 1# reference light and 1# signal light incident on the first avalanche diode module interfere on its photosensitive surface, and the Doppler signal S1 with Doppler frequency f _D1 is obtained; the 2# signal light incident on the second avalanche diode module The #reference light and the 2# signal light interfere on the photosensitive surface, and the Doppler signal S2 with the Doppler frequency f _D2 is obtained. The Doppler signal S1 obtained by the first avalanche diode module, the Doppler signal S2 obtained by the second avalanche diode module and the Doppler signal S3 obtained by the third avalanche diode module are all discriminated by the signal discriminator and then sent to the signal Processor, which performs signal processing. The signal discriminator can judge the current driving state of the vehicle through the received Doppler signal. When the vehicle is running on a flat ground and runs smoothly, the signal processor extracts the corresponding Doppler frequency from the Doppler signal S3 f _D , use the Doppler frequency f _D to realize the calculation of the current vehicle speed, and obtain the current vehicle's real speed; The Doppler signal S1 extracts its corresponding Doppler frequency f _D1 , and the Doppler signal S2 extracts its corresponding Doppler frequency f _D2 , and uses the Doppler frequency f _D1 and f _D2 to realize the calculation of the current vehicle speed, Through the two Doppler signals S1 and S2, the measurement error caused by the change of the launch inclination angle can be reduced or eliminated, and the real moving speed of the vehicle can be obtained.

The longitudinal axis of the laser emitted by the laser, the fifth diaphragm, the second converging lens and the first converging lens are on the same straight line. The first half-mirror and the second half-mirror take the laser light emitted by the laser, the fifth aperture, the second converging lens and the longitudinal central axis of the first converging lens as the axis of symmetry, and the third aperture and the second aperture take the laser light emitted by the laser, the fifth aperture, the second converging lens and the longitudinal central axis of the first converging lens as symmetrical axes, and the longitudinal central axis of the first half mirror and the The longitudinal central axis of the third diaphragm coincides, and the longitudinal central axis of the second half mirror coincides with the longitudinal central axis of the second diaphragm. The longitudinal direction in the present invention refers to the direction perpendicular to the moving direction of the vehicle. Lateral means a direction parallel to the direction of motion of the vehicle.

The lateral central axis of the first total reflection mirror, the first attenuation sheet, the first half mirror, the first narrow light filter, and the first diaphragm is on the same straight line, and the same, the second total reflection The transverse central axes of the anti-mirror, the second attenuation sheet, the second half-mirror, the second narrow light filter and the second aperture are on the same straight line.

The laser is a single longitudinal mode solid-state laser. In the utility model, a beam of wavelength emitted by the single longitudinal mode solid-state laser is 532nm, and the power is 50mW laser.

(1) In the utility model, the angle between the light beam incident on the ground and the ground through the third aperture and the first converging lens is the 1# emission inclination angle; The angle between the light beam and the ground is 2# launch inclination. When the vehicle is running on a flat ground and running smoothly, the two emission inclination angles of the on-board laser Doppler velocimeter installed on the vehicle do not change and the angles are both θ. θ is the launch inclination when the vehicle runs smoothly on a flat road. The Doppler frequency f _D1 obtained by interfering the 1# reference light and 1# signal light incident on the photosensitive surface of the first avalanche diode module with the 2# reference light and 2# signal light incident on the second avalanche diode module The Doppler frequency f _D2 obtained by interference on the photosensitive surface is the same, and Δθ (the variation of the launch inclination angle) is zero, so the vehicle speed solution formula is formula (1). At the same time, because the carrier runs smoothly and the ground is located in the intersection area of the two beams, the dual-beam differential system works, and the signal dropout rate of the system can be reduced due to the strong signal of the dual-beam differential system.

Where v is the moving speed of the vehicle, λ is the laser wavelength of the laser emitted by the laser, θ is the angle between the beam and the ground, that is, the emission inclination, and f _D is the Doppler frequency.

For the speed calculation when the vehicle is running on a flat ground and the vehicle is running smoothly, the above formula (1) uses the launch angle θ when the vehicle is running smoothly on a smooth road, that is, the 1# launch angle can be used, or Using the 2# emission angle, this is a speed measurement method based on a single-beam optical path. This speed measurement method based on a single-beam optical path is suitable for speed measurement when the vehicle is running smoothly on a flat road. At this time, the launch inclination does not change. The Doppler frequency f _D1 is the same as f _D2 , and the change amount Δθ of the emission inclination is zero, and the vehicle speed solution formula is formula (1).

In addition, for the speed calculation when the vehicle is running on a flat ground and the vehicle is running smoothly, since the vehicle is running smoothly, the ground is located in the intersection area of the two beams of light. The dual-beam differential system works normally. At this time, the angle between the two beams can also be used, that is, the beam incident on the ground through the third aperture and the first converging lens and the incident beam on the ground through the fourth aperture and the first converging lens. The angle α between the beams and the Doppler frequency f _D collected by the dual-beam differential system are used to calculate the speed of the vehicle when it is running smoothly. At this time, the speed of the vehicle when it is running smoothly is calculated by the dual-beam differential system, and the vehicle's speed calculation formula is formula (2):

Due to the strong signal of the dual-beam differential system, the signal dropout rate of the system can be reduced by using the dual-beam differential system to calculate the speed of the vehicle when it is running smoothly.

(2) When the vehicle is running on uneven ground, the vehicle is bumpy and swaying. The 1# launch inclination and the 2# launch inclination change, and the change of the launch inclination is Δθ, then the vehicle’s moving speed is calculated by the Doppler frequency f _D1 and the Doppler frequency f _D2 collected by two one-dimensional reference photon systems , calculate the moving speed of the vehicle through formula (3) and formula (4), and reduce the speed measurement error caused by the change of launch inclination angle.

in

In this way, no matter what kind of ground the vehicle is driving on, it can ensure that the speed measurement will not be affected by the change of the launch inclination, that is, this compact and symmetrical laser Doppler speedometer can effectively measure the speed of the vehicle, and at the same time under appropriate conditions It is also possible to obtain a signal with a lower disengagement rate.

Compared with the existing laser Doppler velocimeter, the utility model has the following advantages:

(1) Using the optical path arrangement of symmetrical structure, two one-dimensional reference beam-type subsystems are set up, and the Doppler frequency obtained by each other is corrected through the two symmetrical one-dimensional reference beam-type subsystems, which solves the problem of ordinary velocimeter Difficulty sensitive to launch tilt. The utility model can ensure that the speed measurement will not be affected by the change of the launch inclination angle no matter what kind of ground the vehicle is running on, and can effectively measure the speed of the vehicle. When the vehicle is bumping and swaying, since two symmetrical one-dimensional reference beam-type subsystems are arranged, the two one-dimensional reference beam-type subsystems can compensate the launch inclination angle, so the speedometer provided by the utility model is not sensitive to the bumping and swaying of the vehicle. sensitive. The output signals of the two avalanche diode modules in the two one-dimensional reference beam subsystems are sent to the signal processor for signal processing, and the two-way Doppler frequency can reduce or eliminate the effect caused by the change of the launch inclination angle. The measurement error is obtained to obtain the real speed of the vehicle at this time.

(2) two beams of light (i.e. the light beam incident on the ground through the beam splitting prism, the first half mirror, the third aperture and the first converging lens through the beam splitting prism, the second half mirror through the beam splitting prism, and the second half mirror) are cleverly used The light beam incident on the ground by the mirror, the fourth diaphragm and the first converging lens is symmetrical). When the vehicle is running smoothly, the ground is located in the area where the two beams intersect, and the dual-beam differential system is working normally. The speed of the vehicle can be calculated through the dual-beam differential system. Due to the strong signal of the dual-beam differential system, the signal dropout of the system can be reduced Rate.

(3) By using the dichroic prism and the converging lens, the requirement that the emission direction of the two beams of light is symmetrical along the vertical direction of the movement of the vehicle-type carrier is cleverly realized.

(4) Replace the traditional He-Ne laser or semiconductor laser diode with a single longitudinal mode solid-state laser, so that the laser has many advantages such as narrow line width, high power and small volume, which is conducive to improving the signal-to-noise ratio and detection of Doppler signals distance.

Description of drawings

Fig. 1 is a structural representation of the utility model

In the figure: single longitudinal mode solid-state laser 1, dichroic prism 2, first half mirror 3, second half mirror 4, first attenuator 5, second attenuator 6, first total mirror 7 , the second total mirror 8, the first narrow light filter 9, the second narrow light filter 10, the first aperture 11, the second aperture 12, the first avalanche diode module 13, the second avalanche diode module 14. The third diaphragm 15, the fourth diaphragm 16, the first converging lens 17, the second converging lens 18, the fifth diaphragm 19, the third avalanche diode module 20, the signal discriminator 21, the signal processor 22, on-board Laser Doppler Velocimeter23, Surface24.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the accompanying drawings in the embodiments of the present invention, and further detailed descriptions will be given, but the embodiments of the present invention are not limited thereto.

Referring to Fig. 1, it is a structural representation of the utility model. The vehicle-mounted laser Doppler velocimeter 23 includes a single longitudinal mode solid-state laser 1, a beam splitter 2, a first half mirror 3, a second half mirror 4, a first attenuation sheet 5, a second attenuation sheet 6, First total reflection mirror 7, second total reflection mirror 8, first narrow light filter 9, second narrow light filter 10, first aperture 11, second aperture 12, first avalanche diode module 13 , the second avalanche diode module 14, the third aperture 15, the fourth aperture 16, the first converging lens 17, the second converging lens 18, the fifth aperture 19, the third avalanche diode module 20, the signal discriminator 21 and signal processor 22 .

Among them, single longitudinal mode solid-state laser 1, dichroic prism 2, first half mirror 3, second half mirror 4, third diaphragm 15, fourth diaphragm 16, first converging lens 17, ground 24 , the second converging lens 18, the fifth diaphragm 19 and the third avalanche diode module 20 form a dual-beam differential system. The optical paths of the two beams in the dual-beam differential system are arranged symmetrically.

Single longitudinal mode solid-state laser 1, dichroic prism 2, first half-mirror 3, second half-mirror 4, first attenuation sheet 5, second attenuation sheet 6, first total reflection mirror 7, second half-mirror Total mirror 8, the first narrow light filter 9, the second narrow light filter 10, the first aperture 11, the second aperture 12, the first avalanche diode module 13 and the second avalanche diode module 14 form Two one-dimensional reference beam subsystems, including: single longitudinal mode solid-state laser 1, beam splitter 2, first half mirror 3, first attenuator 5, first total mirror 7, first narrow filter The light sheet 9, the first diaphragm 11, and the first avalanche diode module 13 form a one-dimensional reference beam type subsystem, the single longitudinal mode solid-state laser 1, the beam splitting prism 2, the second half mirror 4, and the second attenuation The sheet 6, the second total reflection mirror 8, the second narrow light filter 10, the second aperture 12 and the second avalanche diode module 14 form a one-dimensional reference beam type subsystem. The optical paths of the two beams in the two one-dimensional reference beam subsystems are symmetrical.

Specifically, the longitudinal central axes of the laser light emitted by the single longitudinal mode solid-state laser 1 , the fifth aperture 19 , the second converging lens 18 , and the first converging lens 17 are on the same straight line. The first half-mirror 3 and the second half-mirror 4 take the laser light emitted by the laser, the fifth aperture 19, the second converging lens 18 and the longitudinal central axis of the first converging lens 17 as symmetrical axes left and right. , the third diaphragm 15 and the second diaphragm 12 are left-right symmetrical with the longitudinal central axis of the laser emitted by the laser, the fifth diaphragm 19, the second converging lens 18 and the first converging lens 17 as the axis of symmetry, and the first The longitudinal central axis of the half mirror 3 coincides with the longitudinal central axis of the third diaphragm 15 , and the longitudinal central axis of the second half mirror 4 coincides with the longitudinal central axis of the second diaphragm 12 . The longitudinal direction in the present invention refers to the direction perpendicular to the moving direction of the vehicle. Lateral means a direction parallel to the direction of motion of the vehicle.

The lateral central axis of the first total mirror 7, the first attenuation sheet 5, the first half-mirror 3, the first narrow light filter 9, and the first aperture 11 is on the same straight line, and the same, The lateral central axes of the second total reflection mirror 8 , the second attenuation sheet 6 , the second half mirror 4 , the second narrow light filter 10 and the second aperture 12 are on the same straight line.

The basic principle of the utility model is that two symmetrically arranged laser beams are mainly used to form a reference light type subsystem, and at the same time, the two beams are skillfully intersected at a certain point to form a double-beam differential system. Specifically, two beams of light arranged symmetrically to the vertical direction of motion are respectively incident on the ground. Based on these two symmetrical laser beams, on the one hand, two sets of one-dimensional reference beam subsystems are respectively formed. Due to the symmetrical structural arrangement, the error caused by the bumping and swaying of the car carrier on a single reference optical circuit can be passed through two The Doppler frequency obtained by two symmetrical subsystems is corrected to obtain the real speed of the vehicle; on the other hand, these two beams also constitute two intersecting beams in the dual-beam differential technology. At the same time, if the ground is located in the intersecting area (measuring body) of the two beams, then the dual-beam differential system can also calculate the real speed of the vehicle-type carrier, and it is not affected by the carrier's turbulence and tilt.

The single longitudinal mode solid-state laser 1 emits a beam of laser light with a wavelength of 532nm and a power of 50mW. The beam splitter 22 divides it into two parallel beams of equal intensity and equal optical path. The two beams of parallel light hit the first half mirror 3 and the second half mirror 4 respectively; the light beam transmitted from the first half mirror 3 passes through the third aperture 15 and the first converging lens 17 Incident to the ground 24, the light velocity transmitted from the second half mirror 4 enters the ground 24 through the fourth aperture 16, the first converging lens 17, and a part of the scattered light on the ground 24 passes through the first converging lens 17, the second converging lens 17 The converging lens 18 and the fifth aperture 19 are incident on the photosensitive surface of the third avalanche diode module 20 and undergo heterodyne interference to obtain a Doppler signal S3 with a Doppler frequency f _D .

A part of the scattered light on the ground will go back the same way, that is, a part of the scattered light on the ground will be sent to the first half-mirror 3 through the first converging lens 17 and the third aperture 15, and will be reflected from the first half-mirror 3 The light beam incident on the photosensitive surface of the first avalanche diode module 13 through the first narrow light filter 9 and the first aperture 11, the light beam incident on the photosensitive surface of the first avalanche diode module 13 according to this optical path is 1 #Signal light; Similarly, a part of scattered light on the ground is projected to the second half-mirror 4 through the first converging lens 17, the fourth aperture 16, and the light beam reflected from the second half-mirror 4 passes through the second half-mirror 4 The second narrow light filter 10 and the second aperture 12 are incident on the photosensitive surface of the second avalanche diode module 14, and the light beam incident on the photosensitive surface of the second avalanche diode module 14 according to this optical path is 2# signal light.

The two beams of parallel light hit the first half-mirror 3 and the second half-mirror 4 respectively; the light beams reflected from the first half-mirror 3 pass through the first attenuation sheet 5 to the first total reflection After the mirror 7 is reflected again to the first attenuation sheet 5 and is attenuated, the first half-mirror 3 is shot, and the light beam transmitted from the first half-mirror 3 passes through the first narrow light filter 9, the first half-mirror The aperture 11 is incident on the photosensitive surface of the first avalanche diode module 13, which is 1# reference light; similarly, the light beam reflected from the second half mirror 4 is incident on the second total reflection through the second attenuation sheet 6 After the mirror 8 is reflected to the second attenuation sheet 6 again after attenuation, it is impinged on the second half-mirror 4, and the light beam transmitted from the second half-mirror 4 passes through the second narrow light filter 10, the second half-mirror. The aperture 12 is incident on the photosensitive surface of the second avalanche diode module 14, which is 2# reference light.

The 1# reference light incident on the first avalanche diode module 13 and the 1# signal light interfere on its photosensitive surface, and the obtained Doppler frequency is the Doppler signal S1 of f _D1 ; incident on the second avalanche diode module 14 The 2# reference light and the 2# signal light interfere on the photosensitive surface, and the Doppler signal S2 with the Doppler frequency f _D2 is obtained. The Doppler signal S1 obtained by the first avalanche diode module 13, the Doppler signal S2 obtained by the second avalanche diode module 14, and the Doppler signal S3 obtained by the third avalanche diode module 20 all pass through the signal discriminator 21 for signal discrimination. After that, it is sent to the signal processor 22 for signal processing. The signal discriminator 21 can judge the current driving state of the vehicle through the received Doppler signal. When the vehicle is running on a flat ground and runs smoothly, the signal processor extracts the corresponding Doppler signal from the Doppler signal S3. frequency f _D , use the Doppler frequency f _D to realize the calculation of the current vehicle speed, and obtain the current real speed of the vehicle; Extract the corresponding Doppler frequency f _D1 from the Doppler signal S1, extract the corresponding Doppler frequency f _D2 from the Doppler signal S2, and use the Doppler frequency f _D1 and f _D2 to realize the calculation of the current vehicle speed , through the two Doppler signals S1 and S2 can reduce or eliminate the measurement error caused by the change of the launch inclination angle, and obtain the real speed of the vehicle.

(1) In the utility model, the angle between the light beam incident on the ground and the ground through the third aperture 15, the first convergent lens 17 is the 1# emission angle; through the fourth aperture 16, the first convergent lens 17 The angle between the light beam incident on the ground and the ground is 2# launch inclination angle. Where θ is the launch inclination when the vehicle runs smoothly on a flat road. α is the angle between the light beam incident on the ground through the third diaphragm and the first converging lens and the light beam incident on the ground through the fourth diaphragm and the first converging lens. When the vehicle is running on a flat ground and running smoothly, the two emission inclination angles of the on-board laser Doppler velocimeter installed on the vehicle do not change and the angles are both θ. The Doppler frequency f _D1 obtained by the interference of the 1# reference light and the 1# signal light incident on the photosensitive surface of the first avalanche diode module 13 and the 2# reference light and 2# incident on the second avalanche diode module 14 The Doppler frequency f _D2 obtained by the interference of the signal light on the photosensitive surface is the same, and Δθ (the variation of the emission inclination angle) is zero, so the vehicle speed solution formula is formula (1). At the same time, because the carrier runs smoothly and the ground is located in the intersection area of the two beams, the dual-beam differential system works, and the signal dropout rate of the system can be reduced due to the strong signal of the dual-beam differential system.

Where v is the moving speed of the vehicle, λ is the laser wavelength of the laser emitted by the laser, θ is the angle between the beam and the ground, that is, the emission inclination, and f _D is the Doppler frequency.

For the speed calculation when the vehicle is running on a flat ground and the vehicle is running smoothly, the above formula (1) uses the launch angle θ when the vehicle is running smoothly on a smooth road, that is, the 1# launch angle can be used, or Using the 2# emission angle, this is a speed measurement method based on a single-beam optical path. This speed measurement method based on a single-beam optical path is suitable for speed measurement when the vehicle is running smoothly on a flat road. At this time, the launch inclination does not change. The Doppler frequency f _D1 is the same as f _D2 , and the change amount Δθ of the emission inclination is zero, and the vehicle speed solution formula is formula (1).

In addition, for the speed calculation when the vehicle is running on a flat ground and the vehicle is running smoothly, since the vehicle is running smoothly, the ground is located in the intersection area of the two beams of light. The dual-beam differential system works normally. At this time, the angle between the two beams can also be used, that is, the beam incident on the ground through the third aperture and the first converging lens and the incident beam on the ground through the fourth aperture and the first converging lens. The angle α between the beams realizes the speed calculation when the vehicle is running smoothly. At this time, the speed of the vehicle when it is running smoothly is calculated by the dual-beam differential system, and the vehicle's speed calculation formula is formula (2):

Due to the strong signal of the dual-beam differential system, the signal dropout rate of the system can be reduced by using the dual-beam differential system to calculate the speed of the vehicle when it is running smoothly.

(2) When the vehicle is running on uneven ground, the vehicle is bumpy and swaying. The 1# launch inclination and the 2# launch inclination change, and the change of the launch inclination is Δθ, then the vehicle’s moving speed is calculated by the Doppler frequency f _D1 and the Doppler frequency f _D2 collected by two one-dimensional reference photon systems , calculate the moving speed of the vehicle through formula (3) and formula (4), and reduce the speed measurement error caused by the change of launch inclination angle.

in

In this way, no matter what kind of ground the vehicle is driving on, it can ensure that the speed measurement will not be affected by the change of the launch inclination, that is, this compact and symmetrical laser Doppler speedometer can effectively measure the speed of the vehicle, and at the same time under appropriate conditions It is also possible to obtain a signal with a lower disengagement rate.

In summary, although the present utility model has been disclosed as above with preferred embodiments, it is not intended to limit the present utility model, any person of ordinary skill in the art, without departing from the spirit and scope of the present utility model, should be able to use it as Various changes and modifications, so the scope of protection of the utility model should be determined by the scope defined in the claims.

Claims (8)

1. A vehicle-mounted laser Doppler velocimeter, characterized in that: comprise two one-dimensional reference photon systems, a two-beam differential system, signal discriminator and signal processor; The laser light emitted by the laser is divided into two parallel beams of equal intensity and equal optical path by the beam splitter. The two beams of parallel light are respectively incident on the first half mirror and the second half mirror. The two parallel light beams transmitted by the mirror and the second half-mirror enter into the two symmetrical optical paths of the double-beam differential system; the beams reflected from the first half-mirror and the second half-mirror The two light beams are symmetrically incident into the optical paths of the two one-dimensional reference photonic systems arranged symmetrically; The dual-beam differential system outputs Doppler signal S3 with Doppler frequency _fD , and the two one-dimensional reference photonic systems output Doppler signal S1 with Doppler frequency _fD1 and Doppler frequency _fD2 respectively Doppler signal S2; Doppler signal S1, Doppler signal S2 and Doppler signal S3 are all input to the signal discriminator used to distinguish the current driving state of the vehicle, the signal discriminator is connected with the signal processor, and the signal The discriminator transmits the received Doppler signal and the current driving state information of the vehicle to the signal processor, and the signal processor performs signal processing to complete the calculation of the current vehicle driving speed. 2. The vehicle-mounted laser Doppler velocimeter according to claim 1, characterized in that: laser device, dichroic prism, first half-mirror, second half-mirror, the third aperture, the fourth light The diaphragm, the first converging lens, the ground, the second converging lens, the fifth diaphragm and the third avalanche diode module form a dual-beam differential system; Laser, splitter prism, first half mirror, second half mirror, first attenuation sheet, second attenuation sheet, first total reflection mirror, second total reflection mirror, first narrow light filter , the second narrow light filter, the first aperture, the second aperture, the first avalanche diode module and the second avalanche diode module constitute two one-dimensional reference beam type subsystems, in which: the laser, the beam splitter, the first The half-transparent mirror, the first attenuator, the first total mirror, the first narrow light filter, the first aperture, and the first avalanche diode module form a one-dimensional reference beam type subsystem, the laser, the beam splitter The prism, the second half mirror, the second attenuation plate, the second total mirror, the second narrow filter, the second diaphragm and the second avalanche diode module form a one-dimensional reference beam type subsystem. 3. vehicle-mounted laser Doppler velocimeter according to claim 2, is characterized in that: the longitudinal central axis of the laser light that laser device emits, the fifth aperture, the second converging lens, and the first converging lens are on the same straight line; The first half-mirror and the second half-mirror are left-right symmetrical with respect to the longitudinal axis of the laser emitted by the laser, the fifth diaphragm, the second converging lens, and the first converging lens; The third aperture and the second aperture take the laser light emitted by the laser, the fifth aperture, the second converging lens and the longitudinal central axis of the first converging lens as the axis of symmetry, and the first half-mirror The longitudinal central axis coincides with the longitudinal central axis of the third diaphragm, and the longitudinal central axis of the second half mirror coincides with the longitudinal central axis of the second diaphragm; The longitudinal direction refers to the direction perpendicular to the moving direction of the vehicle; the transverse direction refers to the direction parallel to the moving direction of the vehicle. 4. vehicle-mounted laser Doppler velocimeter according to claim 3, is characterized in that: described first total reflection mirror, the first attenuation sheet, the first half mirror, the first narrow light filter, The transverse central axis of the first aperture is on the same straight line; Likewise, the lateral central axes of the second total reflection mirror, the second attenuation sheet, the second half mirror, the second narrow light filter and the second diaphragm are on the same straight line. 5. vehicle-mounted laser Doppler velocimeter according to claim 4, is characterized in that: the light beam that transmits from the first half-mirror is incident on the ground through the third aperture, the first converging lens, from the second The light velocity transmitted by the half mirror enters the ground through the fourth aperture and the first converging lens, and part of the scattered light on the ground enters the third avalanche diode module through the first converging lens, the second converging lens and the fifth aperture and heterodyne interference occurs on the photosensitive surface, and the obtained Doppler signal S3 with Doppler frequency _fD ; Part of the scattered light on the ground will go back the same way, that is, a part of the scattered light on the ground will pass through the first converging lens and the third diaphragm to the first half mirror, and the light beam reflected from the first half mirror will pass through the first half mirror. A narrow light filter, the first aperture is incident on the photosensitive surface of the first avalanche diode module, and the light beam incident on the photosensitive surface of the first avalanche diode module according to this optical path is 1# signal light; similarly, the ground Part of the scattered light passes through the first converging lens and the fourth aperture to the second half mirror, and the light beam reflected from the second half mirror enters through the second narrow filter and the second aperture To the photosensitive surface of the second avalanche diode module, the light beam incident on the photosensitive surface of the second avalanche diode module according to this optical path is 2# signal light; The light beam reflected from the first half-mirror passes through the first attenuation sheet to the first total reflection mirror and then reflects to the first attenuation sheet for attenuation and then hits the first half-mirror, from the first half-mirror The light beam transmitted by the half mirror is incident on the photosensitive surface of the first avalanche diode module through the first narrow light filter and the first aperture, which is 1# reference light; similarly, it is reflected from the second half mirror The light beam emitted by the second attenuation sheet is sent to the second full reflection mirror, and then reflected to the second attenuation sheet for attenuation, and then sent to the second half-mirror, and the light beam transmitted from the second half-mirror passes through the second half-mirror. The second narrow light filter and the second aperture are incident on the photosensitive surface of the second avalanche diode module, which is 2# reference light. 6. vehicle-mounted laser Doppler velocimeter according to claim 5, is characterized in that: 1# reference light and 1# signal light incident to the first avalanche diode module interfere on its photosensitive surface, and the obtained Doppler The Doppler signal S1 with a Le frequency of f _D1 ; the 2# reference light and the 2# signal light incident on the second avalanche diode module interfere on its photosensitive surface, and the obtained Doppler frequency is a Doppler of f _D2 Signal S2. 7. The vehicle-mounted laser Doppler velocimeter according to any one of claims 1 to 6, wherein the laser is a single longitudinal mode solid-state laser. 8. The vehicle-mounted laser Doppler velocimeter according to claim 7, characterized in that: a single longitudinal mode solid-state laser emits a beam of laser light with a wavelength of 532nm and a power of 50mW.