Vehicle dynamic measurement sensing device and method based on fiber annular cavity attenuation and vibration technique
Technical field
The present invention relates to a kind of fiber annular cavity ring-down spectroscopy technologies and the dynamic of vehicle dynamic weighing and speed monitoring to survey
Measure sensing device, and in particular to a kind of vehicle dynamic measurement sensing device and method based on fiber annular cavity attenuation and vibration technique belongs to
In Fibre Optical Sensor and vehicle dynamic fields of measurement;The device of the invention is dynamic based on fiber annular cavity ring-down spectroscopy technology, vehicle
The dynamic that state weighing technology and speed monitoring technology combine measures sensing device.
Background technique
The highway economic lifeline important as a country, the informationization of traffic transport industry are currently under high speed development
Stage.Realize that the automatic detection of motor vehicle and real-time monitoring be to realize the essential means of transport information.And for
The weighing of vehicle, traditional method all carry out in the quiescent state, although this vehicle measurement method precision is very high, exist
Very big defect cannot measure axis again etc. such as price height respectively.And highway communication is just towards high speed and Informatization Development, this
Time-consuming, expensive conventional method will be eliminated gradually for kind.
Piezoelectric film sensor is newer vehicle comprehensive information acquisition sensor a kind of at present, is domestic and international research application
A hot spot.Piezoelectric membrane utilizes the principle of piezoelectric effect (piezoelectric effect), when automobile tire is through over-voltage
When conductive film, sensor, which is hit, generates charge signal, impacts charge signal by demodulation, can obtain the speed of vehicle, weight,
The signals such as vehicle can also be easily obtained information of vehicle flowrate.Although this technology can be realized speed, car weight, vehicle flowrate, vehicle
The measurement of type, but there is also distinct disadvantage, such as the distance that piezoelectric signal can be transmitted directly are short, therefore signal processing centre distance
Sensor must not be too far away, and system conformance is poor, and product technology is mainly import at present, piezoelectric film material price used
Valuableness is unsuitable for promoting and applying.
Optical fiber vehicle information sensor not yet obtains practical application in traffic, and research at present it is most hot be no more than optical fiber
Bragg grating sensor.The basic principle of optical fiber Bragg grating sensor is: temperature, strain, stress around grating or
When other measured physical quantity change, the variation of screen periods or fiber core refractive index will lead to, to generate grating Bragg
The wave length shift Δ λ of signal can be obtained the situation of change of measured physical quantity by detecting the drift situation of Bragg wavelength.Light
The most significant advantage of grid Bragg sensor is exactly quite high sensitivity, can detect the variation of tiny signal.Meanwhile and by
In to the too sensitive of small-signal, to can not obviously be distinguished to some extraneous variations, proposed to experimental facilities higher
Requirement.Therefore, fiber-optic grating sensor price is more expensive, and from functionization, there are also quite long a distances with industrialization.
In addition to this, in recent years, the fibre optic compression sensor based on principle of interference also comes into being, such as: F-P (method cloth
In Perot) interference, Michelson interference, Mach increases to obtain interference etc., principle is all by acquisition interference figure to analyze
To outer signals.But since the application environment of the sensor requirements based on principle of interference is harsher, it is difficult in outdoor popularization
And application.
Summary of the invention
The present invention is directed to shortcoming and defect of the existing technology, proposes a kind of vehicle based on fiber annular cavity attenuation and vibration technique
Dynamic measurement sensing device and method.The device is novel, and design is simple, and cost is relatively low, is suitable for road traffic vehicle
Dynamic measures.
In order to solve the above technical problems, the present invention provides following technical scheme:
It is a kind of based on fiber annular cavity attenuation and vibration technique vehicle dynamic measurement sensing device, be characterized in that including
Light-pulse generator 1, import optical fiber 2, coupler, sensing head, transmission fiber 5, export optical fiber 6, photodetector 7, oscillograph 8 and
Computer 9 for data processing;
Coupler includes No.1 coupler 3a and No. two coupler 3b, and sensing head includes No.1 sensing head 4a and No. two sensings
Head 4b;
The sensing head includes optical fiber and two buffer boards, and optical fiber is arranged between two buffer boards, buffer board and optical fiber
Contact surface is corrugated surface (i.e. sensing head sensing head that Microbend structures can be used);
No.1 coupler 3a, No.1 sensing head 4a, No. two coupler 3b and No. two sensing head 4b are connected by transmission fiber
Constitute ring resonator;
The light-pulse generator is connected by importing optical fiber with No.1 coupler 3a, No. two coupler 3b by export optical fiber and
Photodetector 7 is connected, and photodetector 7 is connected by oscillograph 8 with computer 9;
The pulse width of light-pulse generator is t2, pulse interval t1, the light beam of light-pulse generator is in ring resonator inner ring
The one week time of shape is τr;Light-pulse generator is transmitted to photodetector, the light that photodetector will receive through ring resonator
Signal is converted to electric signal, and electric signal is shown on oscillograph, and the spectrum of display is ring-down spectroscopy, and declining for ring-down spectroscopy is swung
Time is τ, wherein t2< τr, t1> τ.
Ring resonator is in rectangle, and four angles of rectangular loop resonant cavity use arc transition;Coupler and sensing head are equal
The straightway of rectangular loop resonant cavity is set.
The position face of No.1 sensing head 4a and No. two sensing head 4b.
Above-mentioned sensing head can be substituted by special optical fiber.
Above-mentioned special optical fiber is D-type optical fiber, photonic crystal fiber or bare fibre.
Above-mentioned transmission fiber uses multimode vitreous silica optical fiber or single mode vitreous silica optical fiber.
The length of ring resonator is 10m, and the distance between No.1 sensing head 4a and No. two sensing head 4b are 1m.
The repetition rate of light-pulse generator is 1MHZ, pulsewidth 10ns.
Above-mentioned coupler is 2 × 2 couplers, and the coupling ratio of coupler is 1: 99,12: 88,0.1: 99.9 or 8: 92.
The coupling ratio of coupler meets following principle:
Peak light intensity is the bigger the better in the ring-down spectroscopy of No. two couplers output, in the ring-down spectroscopy of No. two couplers output
Decline that swing peak number amount The more the better.
The method for carrying out vehicle dynamic measurement using above-mentioned sensing device includes the steps that measuring vehicle weight M, specifically such as
Under:
1) k is calculated, the unit of k is kgs
1.1) light intensity attenuation of ring resonator output is to being input to needed for the 1/e of ring resonator light intensity when obtaining unloaded
Time τ0
When unloaded, the light beam that light-pulse generator generates enters ring resonator via optical fiber 2 is imported, and repeatedly passes through sensing head,
Part light wave into ring resonator enters photodetector through exporting optical fiber, and photodetector converts optical signal into electricity
Signal, and corresponding ring-down spectroscopy is shown on oscillograph, time τ is directly obtained by ring-down spectroscopy0;τ0Unit be s;
1.2) unit under test of multiple known weights is chosen;
1.3) unit under test is individually positioned on one of sensing head of the invention, according to the method for step 1.1),
The different ring-down time τ of each unit under test is obtained respectivelyn;
1.4) using the weight of unit under test as ordinate, withLinear curve fit is carried out for abscissa, by quasi-
It closes formula and obtains k;
2) obtain wheel when passing through the pressure act on the light intensity attenuation of lower ring resonator output to being input to annular resonance
τ the time required to the 1/e of chamber light intensity
When wheel passes through, the light beam that light-pulse generator generates enters ring resonator via optical fiber 2 is imported, repeatedly by sensing
Head, the part light wave into ring resonator enter photodetector through exporting optical fiber, and photodetector converts optical signal
For electric signal, and corresponding ring-down spectroscopy is shown on oscillograph, time τ is directly obtained by ring-down spectroscopy;The unit of τ is s;
3) the weight M for pressing through the vehicle of sensing head according to the following formula, is calculated:
Wherein, the unit of M is kg.
In step 1), unit under test uses counterweight, and the quantity of unit under test is 10;In order to reduce measurement vehicle weight
The error of M, when calculating k, the unit under test of selection is The more the better.
Further include the steps that obtaining speed:
The distance between two sensing heads are d,
When wheel presses through sensing head, record wheel is by time interval corresponding to No.1 sensing head and No. two sensing heads
τd, pass through publicityObtain corresponding speed.
The present invention has following technical effect that
1, the present invention combines cavity attenuation and vibration technique with pressure sensing technology, thus by the measurement of power signal convert when
Measurement on domain facilitates signal detection and processing;
2, the present invention uses all optical fibre structure, is greatly reduced the loss of conventional optical arrangement bring;
3, the present invention utilizes fiber annular resonant cavity, so that light wave multipass sensing head, increases absorption light path, quite
It is amplified in by outer signals, greatly improves the monitoring sensitivity of the system, be suitble to the measurement of small-signal;
4, the present invention uses " racetrack " ring resonator, is on the one hand conducive to the coupling of light beam, reduces coupling bring
Amplitude loss and phase difference;On the other hand be conducive to the installation of sensing head, reduce because optical fiber itself is bent bring loss;
5, sensing head of the present invention uses Microbend structures, for explaining that light beam transmits the sound to ambient pressure in multimode fibre
There should be stronger theoretical foundation;
6, the present invention combines pressure monitor system with speed detection system together, realizes the real-time survey of speed and car weight
Amount;
7, the present invention be not easy to be influenced by light source fluctuation, decline swing spectrometry be light ring-down time, it is a light
Strong ratio is a relative quantity, will not be because of the unstable and impacted of light source intensity;
8, the present invention has very strong flexibility, and according to different measurands, different sensing heads can be used, realize not
With the measurement of physical quantity;
9, the structural system is simple, compact-sized, and performance is stablized, low in cost;
10, the present invention can be realized vehicle dynamic monitoring, alleviates the measurement bring that needs to stop at present and has inconvenient traffic.
Detailed description of the invention
Fig. 1 is the structural diagram of the present invention;
Fig. 2 (has for ring resonator unloaded (i.e. no wheel presses through sensing head) in the present invention and under having pressure to act on
Wheel presses through sensing head) ring-down spectroscopy schematic diagram;
Fig. 3 be the present invention in different weight vehicle act on sensing head ring-down spectroscopy schematic diagram, in figure P1, P2, P3, P4 and
P5 indicates the pressure that the vehicle of different weight generates;
Fig. 4 is the corresponding ring-down time linear fit curve synoptic diagram of different weight counterweight in the present invention;
Fig. 5 is light-pulse generator schematic diagram in the present invention.
Appended drawing reference: 1 is light-pulse generator, and 2 is import optical fiber, and 3a is No.1 coupler, and 3b is No. two couplers, 4a mono-
Number sensing head, 4b are No. two sensing heads, 5 are transmission fiber, 6 are export optical fiber, 7 are photodetector, 8 are oscillograph, and 9 be meter
Calculation machine, 10 be buffer board, and 11 be the optical fiber in sensing head, and 12 be corrugated surface.
Specific embodiment
Such as Fig. 1, the present invention provides a kind of, and the vehicle dynamic based on fiber annular cavity attenuation and vibration technique measures sensing device, should
Device is mainly by light-pulse generator 1, importing optical fiber 2,2 × 2 coupler 3a of No.1, No.1 sensing head 4a, No. two sensing head 4b, transmission
5, No. two 2 × 2 coupler 3b of optical fiber, export optical fiber 6, photodetector 7, oscillograph 8 and the computer 9 for data processing
Composition.Microbend structures, Microbend structures partial enlarged view such as Fig. 1 can be used in No.1 sensing head 4a and No. two sensing head 4b;No.1 2
× 2 coupler 3a, No.1 sensing head 4a, No. two 2 × 2 coupler 3b and No. two sensing head 4b connect and compose light by transmission fiber
Fine " racetrack " ring resonator;
Light-pulse generator is connected by importing optical fiber with 2 × 2 coupler 3a of No.1, and No. two 2 × 2 coupler 3b pass through export light
Fibre is connected with photodetector 7, and photodetector 7 is connected by oscillograph 8 with computer 9;
The pulse width of light-pulse generator is t2, pulse interval t1, the light beam of light-pulse generator is in ring resonator inner ring
The one week time of shape is τr;Light-pulse generator is transmitted to photodetector, the light that photodetector will receive through ring resonator
Signal is converted to electric signal, and electric signal is shown on oscillograph, and the spectrum of display is ring-down spectroscopy, and declining for ring-down spectroscopy is swung
Time is τ, wherein t2< τr, t1> τ.
Ring resonator is in rectangle, and four angles of rectangular loop resonant cavity use arc transition;Coupler and sensing head are equal
The straightway of rectangular loop resonant cavity is set.
In zero load, (zero load refers to the present invention by the state of extra pressure, i.e., no vehicle does not press through sensing head
State), the light beam that light-pulse generator generates through No.1 coupler 3a enters optical fiber " racetrack " annular resonance via optical fiber 2 is imported
Chamber, into ring resonator light beam intracavitary repeatedly round-trip, by using the coupler of different coupling ratios, when light beam passes through two
When number coupler, have sub-fraction light wave and be exported into export optical fiber, the overwhelming majority be reflected back toward it is intracavitary, repeatedly by passing
Feel head, this process moves in circles.
Through exporting the lightwave signal of optical fiber, electric signal is converted optical signal by photodetector, and on oscillograph
Figure displaying is carried out, data processing system is eventually arrived at, carries out corresponding data processing;Computer can be used in data processing system
9。
It observes to obtain by oscillograph, exponential damping, and die-away time and coupler is presented in the light intensity for reaching detector
Coupling ratio, fiber lengths and annular resonance it is intracavitary loss it is related.Then, by measuring ring-down spectroscopy, so that it may obtain ring
Light intensity changes with time relationship in shape resonant cavity:
In above formula, I0For incident intensity, c is the light velocity in vacuum, and n is transmission fiber core refractive rate, and L is that transmission fiber is long
Degree, A represent the light beam loss intracavitary in annular resonance, including fiber absorption loss, fiber coupling insertion loss and light beam exist
Inside of optical fibre scattering loss.
Ring-down time τ0It is the light intensity attenuation that is exported as ring resonator to being input to needed for the 1/e of ring resonator light intensity
Time meets following formula:
It is τ that light beam, which is defined, in the annular resonance intracavitary time for propagating one weekr, expression are as follows:
Contrast equation (2) and formula (3), then the intracavitary loss A of annular resonance can be indicated are as follows:
When wheel acts on No.1 sensing head 4a, additional loss, but light wave will be generated annular resonance is intracavitary at this time
It declines and swings signal e index attenuated form is still presented, as shown in Fig. 2 curve b, as can be seen that additional loss will be led from curve
Induced attenuation speed is accelerated, and ring-down time is reduced.
At this point, the intracavitary light intensity of annular resonance changes over time relationship and meets following formula:
Wherein, B are as follows: the wheel in movement presses through the loss of sensing head generation, the contact length of B and wheel and sensing head and
Contact area is related, expression are as follows:
B=η 1SP (6)
Wherein η is defined as loss coefficient, and the unit of η is m-3pa-1, 1 is the length of sensing head buffer board, and S is in sensing head
Buffer board and optical fiber contact area, P be wheel press through sensing head generation pressure.
At this point, will lead to ring-down time τ in ring-down spectroscopy0Change, change later ring-down time be τ, embody
Formula are as follows:
When the automobile of different weight presses through No.1 sensing head 4a, different attenuation curves will be obtained, as shown in figure 3, together
Reason, will also obtain different ring-down time τ1, τ2, τ3, τ4……
Contrast equation (2) and (7), it may be found that:
WhereinFor the present invention, β is a constant, can be found from formula (7),It is full with P
The good linear relationship of foot, ring-down time τ when unloaded by the measurement present invention0And the ring-down time under different pressures effect
τ, so that it may determine the pressure size acted on sensing head.
In above formula, M indicates the weight of tested vehicle, S0The area of sensing head is represented, g indicates local acceleration of gravity;It is a constant for proportionality coefficient.
The measuring method of k:
1.1) ring-down time τ when zero load is measured0;
1.2) counterweight (M of 10 known weights is sequentially placed on sensing head of the present invention0), obtain different ring-down times
τn;
1.3) then using counterweight weight as ordinate, withLinear curve fit, matched curve are carried out for abscissa
As shown in figure 4, passing through the available k of fitting formula.
For the present invention, can be obtained by measuring the ring-down time that a certain vehicle presses through sensing head using formula (9)
The weight M of the vehicle.
Meanwhile when wheel again passes by No. two sensing head 4b with certain speed, for the present invention, two sensing heads it
Between distance be it is fixed, be set as d, record wheel is by time interval τ corresponding to No.1 sensing head and No. two sensing headsd,
Pass through publicityThe real-time monitoring to speed can be easily achieved.
Further, in the device two sensing heads position face, can be realized vehicle bidirectional test, meanwhile, in ring
When increasing different sensing heads or the different types of sensing head of use in shape resonant cavity, multimetering and unlike signal can be realized
Measurement.
To can be good at being differentiated on oscillograph, following principle should be met when choosing light-pulse generator:
If pulse width is t2, pulse interval t1, as shown in Figure 5.
①t2< τr, i.e. pulse width t2Time τ less than light wave at ring resonator annular one weekr;
②t1> τ, i.e. pulse interval are greater than ring-down time.
Since the coupling ratio of two couplers will will affect ring-down time of the light wave in optical fibre ring, thus in selection coupling
When the coupling ratio of clutch, need to meet following principle:
1. peak light intensity is the bigger the better from the ring-down spectroscopy that No. two couplers export;
2. it is The more the better to swing peak number amount from declining in the ring-down spectroscopy that No. two couplers export;
Embodiment
Light-pulse generator repetition rate 1MHZ of the invention, pulsewidth 10ns, sensing head use Microbend structures, are also possible to other
Special optical fiber, such as D-type optical fiber, photonic crystal fiber, bare fibre etc.;Ring resonator uses " racetrack " fiber annular resonance
Chamber, two coupler coupling ratios are all 1: 99, and transmission fiber uses multimode vitreous silica optical fiber (core refractive rate 1.58), entirely
Ring resonator length 10m, distance 1m between two sensing heads;Other further include importing, exporting optical fiber, photodetector, oscillography
Device and computer.
Light-pulse generator generates the light wave that repetition is 1MHz (period 1us) and enters " racetrack " fiber annular through importing optical fiber
Resonant cavity, light wave are about 53ns in the one week time of ring resonator annular, and ring-down time is about several hundred a nanoseconds, work as vapour
When vehicle wheel presses through sensing head, optical fiber is caused to bend, mode leaks, and additional loss is generated, so as to cause entire
Ring-down time is reduced, and by being analyzed above, can be obtained by the driving vehicle weight for pressing through sensing head by the measurement of ring-down time
Measure size.Meanwhile recording the time interval that wheel passes through two sensing heads, so that it may obtain the speed of vehicle driving.