CN104792364A - Dynamic bridge parameter extracting system and dynamic bridge parameter extracting method based on laser Doppler - Google Patents

Abstract

The invention discloses a dynamic bridge parameter extracting system and a dynamic bridge parameter extracting method based on laser Doppler and relates to the technical field of bridge detection. The dynamic bridge parameter extracting method includes the steps of S1, collecting photoelectric signals of a photoelectric detector by a high-frequency signal collector, and converting the photoelectric signals into voltage values to obtain a photoelectric signal discrete sequence ; S2, by the aid of a computer, subjecting the photoelectric signal discrete sequence to fast Fourier transform so as to obtain a frequency movement sequence, seeking the specific position of the photoelectric signal corresponding to a peak value of the frequency movement sequence, subjecting a frequency-subdivided interval to further subdivision to compute a frequency spectrum within the frequency-subdivided interval, seeking the specific position of the photoelectric signal corresponding to a peak value of a frequency spectrum sequence, and computing a Doppler frequency shift; S3, computing moving speed of an object; S4, judging whether vibrating frequency of the object needs to be computed or not; S5, computing the vibrating frequency of the object according to a speed sequence. The dynamic bridge parameter extracting system and the dynamic bridge parameter extracting method based on the laser Doppler are high in extracting precision and used for measuring the low moving speed and the vibrating frequency of an engineering structure like a bridge.

Description

The dynamic parameter extraction system and method for bridge based on laser-Doppler

Technical field

The present invention relates to Bridge Inspection field, be specifically related to the dynamic parameter extraction system and method for a kind of bridge based on laser-Doppler.

Background technology

In recent years, the sensor technology for bridge detection of dynamic is flourish, comprises the acceleration transducer of the principles such as based semiconductor material piezoresistive effect, material piezoelectric effect, but is substantially all touch sensor.Touch sensor drawback is very large, and installing touch sensor wastes time and energy, and can cause damage in various degree to bridge structure, can hinder site traffic after installation.Utilize contactless bridge dynamic detection technology can solve above-mentioned drawback, wherein, the knotmeter based on laser Doppler principle is a Typical Representative of contactless technique of dynamic measurement.Knotmeter based on laser Doppler principle has the excellent properties such as rate accuracy is high, dynamic range large, response of testing the speed is fast, be widely used in measuring atomic flowing velocity in fluid, and the flowing velocity etc. of various types of cells in measurement biological blood, be also applied to the dynamic parameter measuring bridge.

Shown in Figure 1, a kind of bridge vibration detection device based on laser, comprise interconnective test box 1 and computing machine 14, the inside of described test box 1 is provided with optical-fiber laser transmitter 5, first fiber coupler 4, first fiber optic collimator mirror 2, second fiber optic collimator mirror 9, second fiber coupler 11, photodetector 12, high-frequency signal Acquisition Instrument 13 and laser pen 10; Described laser pen 10 is between the first fiber optic collimator mirror 2 and the second fiber optic collimator mirror 9; Described optical-fiber laser transmitter 5, first fiber coupler 4 is connected in turn with the first fiber optic collimator mirror 2, and described second fiber optic collimator mirror 9, second fiber coupler 11, photodetector 12 are connected in turn with high-frequency signal Acquisition Instrument 13; Described first fiber coupler 4 is connected with the second fiber coupler 11, and described high-frequency signal Acquisition Instrument 13 is connected with the computing machine 14 being provided with laser Doppler signal disposal system.The principle of work of this pick-up unit: optical-fiber laser transmitter 5 Emission Lasers, laser is by being divided into the first laser and the second laser after the first fiber coupler 4, first laser can change frequency because of Doppler effect through the body surface of vibration, therefore, the frequency diffused and the first laser, the frequency of the second laser is different, vibration velocity due to incident light and radiative difference on the frequency and object has a fixing analytic relationship, laser Doppler signal disposal system is provided with in computing machine 14, can by diffusing and the difference on the frequency of the first laser, calculate the vibration information of determinand.

Different target movement velocity scope to the requirement very different of laser Doppler signal disposal system, because bridge structure movement velocity is less, therefore flashlight and reference light difference on the frequency very little, signal to noise ratio (S/N ratio) decline, the extraction accuracy of light frequency is lower.For the engineering structure of the low-speed motions such as bridge, current laser Doppler signal disposal system is difficult to the dynamic parameter in measuring-signal to extract, and therefore, is difficult to the low-speed motion measuring bridge structure, such as speed is 100m/s ~ 1mm/s, even the measurement of 100m/s ~ 0.1mm/s.

Summary of the invention

For the defect existed in prior art, the object of the present invention is to provide the dynamic parameter extraction system and method for a kind of bridge based on laser-Doppler, the extraction accuracy of light frequency is high, for measuring low-speed motion speed and the vibration frequency of the engineering structures such as bridge.

For reaching above object, the technical scheme that the present invention takes is: the dynamic parameter extraction system of a kind of bridge based on laser-Doppler, and this system comprises:

Photodetector, for detecting photosignal;

High-frequency signal Acquisition Instrument, for gathering the photosignal of certain length in photodetector, and being converted into magnitude of voltage, obtaining photosignal discrete series;

Computing machine, for carrying out Fast Fourier Transform (FFT) to photosignal discrete series, obtains frequency movement sequence; Find the particular location of the photosignal corresponding to frequency movement sequence peaks, obtain frequency fine by stages; Segmented further frequency fine by stages, the frequency spectrum on calculated rate subdivided interval, obtains spectrum sequence; Find the particular location of the photosignal corresponding to peak value of spectrum sequence, calculate Doppler shift; According to Doppler shift, calculate target speed; Judge whether the vibration frequency needing to calculate target, judge whether the vibration frequency needing to calculate target, if not, then calculate movement velocity corresponding to different length photosignal; If so, then formed according to movement velocity and obtain the vibration frequency that velocity series calculates target; Fast Fourier Transform (FFT) is carried out to velocity series, obtains frequency vibration sequence; Find the particular location of the photosignal corresponding to frequency vibration sequence peaks, obtain vibration frequency subdivided interval; Frequency fine by stages is segmented further, calculates the rumble spectrum on vibration frequency subdivided interval, obtain rumble spectrum sequence, find the particular location of the photosignal corresponding to rumble spectrum sequence peaks, calculate the vibration frequency of target;

The dynamic parameter extracting method of the bridge based on laser-Doppler for described system, comprises the following steps:

S1. high-frequency signal Acquisition Instrument gathers the photosignal of certain length in photodetector, and is converted into magnitude of voltage, obtains photosignal discrete series;

S2. computing machine carries out Fast Fourier Transform (FFT) to photosignal discrete series, obtains frequency movement sequence; Find the particular location of the photosignal corresponding to frequency movement sequence peaks, obtain frequency fine by stages; Segmented further frequency fine by stages, the frequency spectrum on calculated rate subdivided interval, obtains spectrum sequence; Find the particular location of the photosignal corresponding to peak value of spectrum sequence, calculate Doppler shift; According to Doppler shift, calculate target speed;

S3. judge whether the vibration frequency needing to calculate target, if not, then repeat step S1 ~ S2, calculate the movement velocity that different length photosignal is corresponding; If so, then step S4 is forwarded to;

S4. corresponding according to different length photosignal movement velocity, obtains velocity series;

S5. Fast Fourier Transform (FFT) is carried out to velocity series, obtain frequency vibration sequence; Find the particular location of the photosignal corresponding to frequency vibration sequence peaks, obtain vibration frequency subdivided interval; Frequency fine by stages is segmented further, calculates the rumble spectrum on vibration frequency subdivided interval, obtain rumble spectrum sequence, find the particular location of the photosignal corresponding to rumble spectrum sequence peaks, calculate the vibration frequency of target.

On the basis of technique scheme, the detailed process of step S1 is: in a period of time △ t, high-frequency signal Acquisition Instrument is according to voltage sample rate FS, gather the photosignal in photodetector, and being converted into magnitude of voltage, the length of described photosignal is N, N is positive integer, photosignal is at the corresponding magnitude of voltage x in each position of length direction, obtain photosignal discrete series X={x (n), n=0,1 ... N-1}, the resolution of frequency is Δ f

On the basis of technique scheme, step S2 specifically comprises the following steps:

S201. computing machine is to photosignal discrete series X={x (n), n=0, and 1 ... N-1} carries out Fast Fourier Transform (FFT), obtain frequency movement sequence Z=T (X)={ z (n), n=0,1 ... N-1}, wherein, T is Fourier transform operator;

S202. photosignal discrete series X={x (n) that collects at every batch of frequency movement sequence Z=T (X), n=0,1 ... simple spike value is there is in the scope of N-1}, find the photosignal particular location k in the longitudinal direction corresponding to frequency movement sequence Z=T (X) peak value, k ∈ [1, N], obtaining frequency fine by stages is

S203. according to accuracy class M ₁, by frequency fine by stages be further subdivided into 2M ₁equal portions, M ₁for positive integer, further frequency analysis be spaced apart △, adopt the frequency spectrum on following formula calculated rate subdivided interval, obtain spectrum sequence Y (f):

$Y\left(f\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)e^{-j2\mathrm{\πfn}},$

Wherein, Doppler shift e is natural constant, and j is imaginary unit;

S204. there is simple spike value in spectrum sequence Y (f) within the scope of f, finds the position p in the longitudinal direction of the photosignal corresponding to peak value of spectrum sequence Y (f), p ∈ [1,2M ₁], adopt following formula to calculate photosignal discrete series X={x (n), n=0,1 ... the Doppler shift f of N-1}:

$f=\frac{\mathrm{FS}}{N}\×(k-1)+\frac{\mathrm{FS}}{N\×2M_1}p;$

S205. according to following formula, target speed v is calculated:

$v=\frac{1}{2}f{\mathrm{\λ}}_0,$

Wherein, λ ₀for the wavelength of transmitted light of optical-fiber laser transmitter.

On the basis of technique scheme, in step S3, if not, then repeat step S1 ~ S2, computational length is the movement velocity that the photosignal of l is corresponding respectively, wherein, l=0,1 ..., L-1, L be positive integer.

On the basis of technique scheme, the detailed process of step S4 is: be the movement speed v that the photosignal of l is corresponding according to length, forms velocity series V={v (l), l=0,1 ... L-1}, wherein, the sampling rate of speed is Fs, the resolution of speed in frequency is new △ f, newly $\mathrm{\Δf}=\frac{\mathrm{Fs}}{L}.$

On the basis of technique scheme, step S5 specifically comprises the following steps:

S501. to velocity series V={v (l), l=0,1 ... L-1} carries out Fast Fourier Transform (FFT), obtain frequency vibration sequence W=T (V)=w (l), l=0,1...L-1}, wherein T is Fourier transform operator;

S502. frequency vibration sequence W=T (V) is at velocity series V={v (l), l=0,1 ... there is simple spike value in the scope of L-1}, find the particular location k of the photosignal corresponding to frequency vibration sequence W=T (V) peak value at length direction _i, k _i∈ [1, L], obtains vibration frequency subdivided interval: wherein, m is vibration exponent number, and m is positive integer;

S503. according to accuracy class M ₂, by vibration frequency subdivided interval be further subdivided into 2M ₂equal portions, M ₂for positive integer, further vibration Frequency Analysis be spaced apart Δ ₂, adopt the frequency spectrum on following formula calculating vibration frequency subdivided interval, obtain rumble spectrum sequence U (f _i):

$U\left(f_i\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}v\left(l\right)e^{-j2\mathrm{\π}{f}_{i}l},$

Wherein e is natural constant, and j is imaginary unit;

S504. rumble spectrum sequence U (f _i) at f _ithere is simple spike value in scope, find rumble spectrum sequence U (f _i) the position q in the longitudinal direction of the photosignal corresponding to peak value, q ∈ [1,2M ₂], adopt following formula to calculate every rank vibration frequency f of target _i:

$f_i=\frac{\mathrm{Fs}}{L}\×(k_i-1)+\frac{\mathrm{Fs}}{L\×2M_2}q.$

On the basis of technique scheme, described voltage sample rate FS=625KHz, accuracy class M ₁=20, M ₂=40.

On the basis of technique scheme, when the movement velocity estimating bridge test position is 0 ~ 15mm/s, the length N=65536 of setting photosignal, the sampling rate Fs=5Hz of speed; When to estimate bridge test position movement velocity be 16 ~ 50mm/s, the length N=32768 of setting photosignal, the sampling rate Fs=10Hz of speed; When to estimate bridge test position movement velocity be 51 ~ 100mm/s, the length N=16384 of setting photosignal, the sampling rate Fs=15Hz of speed; When to estimate bridge test position movement velocity be 101 ~ 250mm/s, the length N=8192 of setting photosignal, the sampling rate Fs=20Hz of speed.

Beneficial effect of the present invention is:

The present invention adds the further high precision computation of frequency on the basis of conventional fast Fourier transform algorithm, the extraction accuracy of light frequency is high, can when laser Doppler frequencies signal and noise ratio lower accurately extract frequency values, finally can meet the demand of bridge structure dynamic test; For the accuracy class value of low-speed motion different sample frequency, sampling number and the optimization by test target classification setting further again of bridge, ensure that the precision of the dynamic parameter extraction of bridge and the computing velocity of on-line measurement simultaneously, reduce the requirement to hardware computing power, reduce cost, for measuring low-speed motion speed and the vibration frequency of the engineering structures such as bridge.

Accompanying drawing explanation

Fig. 1 is the structural representation based on the bridge vibration detection device of laser in background technology of the present invention;

Fig. 2 is the schematic flow sheet of the dynamic parameter extracting method of bridge that the present invention is based on laser-Doppler.

In figure: 1-test box, 2-first fiber optic collimator mirror, 3-adjustable type clamper, 4-first fiber coupler, 5-optical-fiber laser transmitter, 6-first laser port, 7-second laser port, 8-the 3rd laser port, 9-second fiber optic collimator mirror, 10-laser pen, 11-second fiber coupler, 12-photodetector, 13-high-frequency signal Acquisition Instrument, 14-computing machine.

Embodiment

Below in conjunction with accompanying drawing, embodiments of the invention are described in further detail.

The embodiment of the present invention provides a kind of bridge based on laser-Doppler dynamic parameter extraction system, and this system comprises:

Photodetector 12, for detecting photosignal.

High-frequency signal Acquisition Instrument 13, for gathering the photosignal of certain length in photodetector, and being converted into magnitude of voltage, obtaining photosignal discrete series.

Computing module, for carrying out Fast Fourier Transform (FFT) to photosignal discrete series, obtains frequency movement sequence; Find the particular location of the photosignal corresponding to frequency movement sequence peaks, obtain frequency fine by stages; Segmented further frequency fine by stages, the frequency spectrum on calculated rate subdivided interval, obtains spectrum sequence; Find the particular location of the photosignal corresponding to peak value of spectrum sequence, calculate Doppler shift; According to Doppler shift, calculate target speed; Judge whether the vibration frequency needing to calculate target, judge whether the vibration frequency needing to calculate target, if not, then calculate movement velocity corresponding to different length photosignal; If so, then formed according to movement velocity and obtain the vibration frequency that velocity series calculates target; Fast Fourier Transform (FFT) is carried out to velocity series, obtains frequency vibration sequence; Find the particular location of the photosignal corresponding to frequency vibration sequence peaks, obtain vibration frequency subdivided interval; Frequency fine by stages is segmented further, calculates the rumble spectrum on vibration frequency subdivided interval, obtain rumble spectrum sequence, find the particular location of the photosignal corresponding to rumble spectrum sequence peaks, calculate the vibration frequency of target.

Shown in Figure 2, the embodiment of the present invention also provides a kind of bridge based on laser-Doppler for said system dynamic parameter extracting method, comprises the following steps:

S1. high-frequency signal Acquisition Instrument 13 gather certain length in photodetector 12 photosignal, and be converted into magnitude of voltage, obtain photosignal discrete series, detailed process is: in a period of time △ t, high-frequency signal Acquisition Instrument 13 is according to voltage sample rate FS, gather the photosignal in photodetector 12, and be converted into magnitude of voltage, the length of described photosignal is N, photosignal is at the corresponding magnitude of voltage in each position of length direction, obtain photosignal discrete series X={x (n), n=0, 1 ... N-1}, N is positive integer, the resolution of frequency is Δ f,

S2. computing machine carries out Fast Fourier Transform (FFT) to photosignal discrete series, obtains frequency movement sequence; Find the particular location of the photosignal corresponding to frequency movement sequence peaks, obtain frequency fine by stages; Segmented further frequency fine by stages, the frequency spectrum on calculated rate subdivided interval, obtains spectrum sequence; Find the particular location of the photosignal corresponding to peak value of spectrum sequence, calculate Doppler shift; According to Doppler shift, calculate target speed.

Step S2 specifically comprises the following steps:

S201. computing machine is to photosignal discrete series X={x (n), n=0, and 1 ... N-1} carries out Fast Fourier Transform (FFT), obtain frequency movement sequence Z=T (X)={ z (n), n=0,1 ... N-1}, wherein, T is Fourier transform operator;

S202. photosignal discrete series X={x (n) that collects at every batch of frequency movement sequence Z=T (X), n=0,1 ... simple spike value is there is in the scope of N-1}, find the photosignal particular location k in the longitudinal direction corresponding to frequency movement sequence Z=T (X) peak value, k ∈ [1, N], obtaining frequency fine by stages is

S203. according to accuracy class M ₁, by frequency fine by stages be further subdivided into 2M ₁equal portions, M ₁for positive integer, further frequency analysis be spaced apart △, adopt the frequency spectrum on following formula calculated rate subdivided interval, obtain spectrum sequence Y (f):

$Y\left(f\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)e^{-j2\mathrm{\πfn}},$

Wherein, Doppler shift e is natural constant, and j is imaginary unit;

S204. there is simple spike value in spectrum sequence Y (f) within the scope of f, finds the position p in the longitudinal direction of the photosignal corresponding to peak value of spectrum sequence Y (f), p ∈ [1,2M ₁], adopt following formula to calculate photosignal discrete series X={x (n), n=0,1 ... the Doppler shift f of N-1}:

$f=\frac{\mathrm{FS}}{N}\×(k-1)+\frac{\mathrm{FS}}{N\×2M_1}p;$

S205. according to following formula, target speed v is calculated:

$v=\frac{1}{2}f{\mathrm{\λ}}_0,$

Wherein, λ ₀for the wavelength of transmitted light of optical-fiber laser transmitter 5.

S3. judge whether the vibration frequency needing to calculate target, if not, then repeat step S1 ~ S2, calculate the movement velocity that different length photosignal is corresponding, that is, computational length is the movement velocity that the photosignal of l is corresponding respectively, wherein, l=0,1 ..., L-1, L be positive integer; If so, then step S4 is forwarded to.

S4. corresponding according to different length photosignal movement velocity, obtains velocity series, and detailed process is: be the movement speed v that the photosignal of l is corresponding according to length, forms velocity series V={v (l), l=0,1 ... L-1}, wherein, the sampling rate of speed is Fs the resolution of speed in frequency is new △ f, newly

S5. Fast Fourier Transform (FFT) is carried out to velocity series, obtain frequency vibration sequence; Find the particular location of the photosignal corresponding to frequency vibration sequence peaks, obtain vibration frequency subdivided interval; Frequency fine by stages is segmented further, calculates the rumble spectrum on vibration frequency subdivided interval, obtain rumble spectrum sequence, find the particular location of the photosignal corresponding to rumble spectrum sequence peaks, calculate the vibration frequency of target.

Step S5 specifically comprises the following steps:

S501. to velocity series V={v (l), l=0,1 ... L-1} carries out Fast Fourier Transform (FFT), obtain frequency vibration sequence W=T (V)=w (l), l=0,1...L-1}, wherein T is Fourier transform operator;

S502. frequency vibration sequence W=T (V) is at velocity series V={v (l), l=0,1 ... there is simple spike value in the scope of L-1}, find the particular location k of the photosignal corresponding to frequency vibration sequence W=T (V) peak value at length direction _i, k _i∈ [1, L], obtains vibration frequency subdivided interval: wherein, m is vibration exponent number, and m is positive integer;

S503. according to accuracy class M ₂, by vibration frequency subdivided interval be further subdivided into 2M ₂equal portions, M ₂for positive integer, further vibration Frequency Analysis be spaced apart Δ ₂, adopt the frequency spectrum on following formula calculating vibration frequency subdivided interval, obtain rumble spectrum sequence U (f _i):

$U\left(f_i\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}v\left(l\right)e^{-j2\mathrm{\π}{f}_{i}l},$

Wherein e is natural constant, and j is imaginary unit;

S504. rumble spectrum sequence U (f _i) at f _ithere is simple spike value in scope, find rumble spectrum sequence U (f _i) the position q in the longitudinal direction of the photosignal corresponding to peak value, q ∈ [1,2M ₂], adopt following formula to calculate every rank vibration frequency f of target _i:

$f_i=\frac{\mathrm{Fs}}{L}\×(k_i-1)+\frac{\mathrm{Fs}}{L\×2M_2}q.$

In said process, voltage sample rate FS=625KHz, accuracy class M ₁=20, M ₂=40.

When the movement velocity estimating bridge test position is 0 ~ 15mm/s, the length N=65536 of setting photosignal, the sampling rate Fs=5Hz of speed; When to estimate bridge test position movement velocity be 16 ~ 50mm/s, the length N=32768 of setting photosignal, the sampling rate Fs=10Hz of speed; When to estimate bridge test position movement velocity be 51 ~ 100mm/s, the length N=16384 of setting photosignal, the sampling rate Fs=15Hz of speed; When to estimate bridge test position movement velocity be 101 ~ 250mm/s, the length N=8192 of setting photosignal, the sampling rate Fs=20Hz of speed.

Below in conjunction with embodiment, embodiments of the invention are described in further detail.

Example is measured as, sampling rate FS=625KHz, accuracy class M with the span centre vertical displacement of certain bridge ₁=20, M ₂=40, according to design feature, the vertical displacement speed in estimation bridge span, at 101 ~ 250mm/s, sets N=8192, Fs=20Hz.The dynamic parameter extracting method of bridge based on laser-Doppler comprises the following steps:

S1. every △ t=50ms, signal in high-frequency signal Acquisition Instrument 13 pairs of photodetectors 12 carries out once batch sampling, in 50ms at front 13ms according to sampling rate FS=625KHz, gather N=8192 data, obtain photosignal discrete series X={x (1), x (2) ... x (8192) }, the resolution of frequency

S2. to X={x (1), x (2) ... x (8192) } carry out Fast Fourier Transform (FFT) (FFT conversion), calculate frequency movement sequence Z=T (X)={ z (1), z (2) ... z (8192) }, the peak k=3277 of Z=T (X), obtain the subdivided interval of frequency for [249052Hz, 255606Hz]; Accuracy class M ₁=20, interval △=3.8Hz that cline frequency is analyzed, adopt the frequency spectrum on formulae discovery frequency fine by stages: wherein f ∈ [249052Hz, 255606Hz], goes forward one by one and is spaced apart △=3.8Hz, and e is natural constant, and j is imaginary unit; Find the peak value to Y (f) sequence, find the p=15 that crest frequency is corresponding; Calculate Doppler shift $f=\frac{\mathrm{FS}}{N}\×(k-1)+\frac{\mathrm{FS}}{N\×2M_1}p=249052+3.8\×15=249109\mathrm{Hz};$ Calculate target speed $v=\frac{1}{2}f{\mathrm{\λ}}_0=\frac{1}{2}\×249109\mathrm{Hz}\×1550\mathrm{nm}=190\mathrm{mm}/s,$ Vertical displacement speed so within the sampling time of △ t=50ms in bridge span is 190mm/s.

S3. judge whether the vibration frequency needing to calculate target, if not, then repeat step S1 ~ S2, calculate the movement velocity that different length photosignal is corresponding, that is, computational length is the movement velocity that the photosignal of l is corresponding respectively, wherein, l=0,1 ..., L-1, L be positive integer; If so, then step S4 is forwarded to.

S4. corresponding according to different length photosignal movement velocity, obtains velocity series V={v (l), l=0,1 ... L-1}, wherein, the sampling rate of speed the resolution of speed in frequency is

S5. Fast Fourier Transform (FFT) is carried out to velocity series, obtain frequency vibration sequence; Find the particular location of the photosignal corresponding to frequency vibration sequence peaks, obtain vibration frequency subdivided interval; Frequency fine by stages is segmented further, calculates the rumble spectrum on vibration frequency subdivided interval, obtain rumble spectrum sequence, find the particular location of the photosignal corresponding to rumble spectrum sequence peaks, calculate the vibration frequency of target.

The present invention is not limited to above-mentioned embodiment, and for those skilled in the art, under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications are also considered as within protection scope of the present invention.The content be not described in detail in this instructions belongs to the known prior art of professional and technical personnel in the field.

Claims (9)

1., based on the dynamic parameter extraction system of bridge of laser-Doppler, it is characterized in that, this system comprises:

Photodetector, for detecting photosignal;

High-frequency signal Acquisition Instrument, for gathering the photosignal of certain length in photodetector, and being converted into magnitude of voltage, obtaining photosignal discrete series;

Computing machine, for carrying out Fast Fourier Transform (FFT) to photosignal discrete series, obtains frequency movement sequence; Find the particular location of the photosignal corresponding to frequency movement sequence peaks, obtain frequency fine by stages; Segmented further frequency fine by stages, the frequency spectrum on calculated rate subdivided interval, obtains spectrum sequence; Find the particular location of the photosignal corresponding to peak value of spectrum sequence, calculate Doppler shift; According to Doppler shift, calculate target speed; Judge whether the vibration frequency needing to calculate target, judge whether the vibration frequency needing to calculate target, if not, then calculate movement velocity corresponding to different length photosignal; If so, then formed according to movement velocity and obtain the vibration frequency that velocity series calculates target; Fast Fourier Transform (FFT) is carried out to velocity series, obtains frequency vibration sequence; Find the particular location of the photosignal corresponding to frequency vibration sequence peaks, obtain vibration frequency subdivided interval; Frequency fine by stages is segmented further, calculates the rumble spectrum on vibration frequency subdivided interval, obtain rumble spectrum sequence, find the particular location of the photosignal corresponding to rumble spectrum sequence peaks, calculate the vibration frequency of target.

2., for the dynamic parameter extracting method of the bridge based on laser-Doppler of system described in claim 1, it is characterized in that, comprise the following steps:

S1. high-frequency signal Acquisition Instrument gathers the photosignal of certain length in photodetector, and is converted into magnitude of voltage, obtains photosignal discrete series;

S2. computing machine carries out Fast Fourier Transform (FFT) to photosignal discrete series, obtains frequency movement sequence; Find the particular location of the photosignal corresponding to frequency movement sequence peaks, obtain frequency fine by stages; Segmented further frequency fine by stages, the frequency spectrum on calculated rate subdivided interval, obtains spectrum sequence; Find the particular location of the photosignal corresponding to peak value of spectrum sequence, calculate Doppler shift; According to Doppler shift, calculate target speed;

S3. judge whether the vibration frequency needing to calculate target, if not, then repeat step S1 ~ S2, calculate the movement velocity that different length photosignal is corresponding; If so, then step S4 is forwarded to;

S4. corresponding according to different length photosignal movement velocity, obtains velocity series;

S5. Fast Fourier Transform (FFT) is carried out to velocity series, obtain frequency vibration sequence; Find the particular location of the photosignal corresponding to frequency vibration sequence peaks, obtain vibration frequency subdivided interval; Frequency fine by stages is segmented further, calculates the rumble spectrum on vibration frequency subdivided interval, obtain rumble spectrum sequence, find the particular location of the photosignal corresponding to rumble spectrum sequence peaks, calculate the vibration frequency of target.

3. as claimed in claim 2 based on the dynamic parameter extracting method of bridge of laser-Doppler, it is characterized in that, the detailed process of step S1 is: in a period of time Δ t, high-frequency signal Acquisition Instrument is according to voltage sample rate FS, gather the photosignal in photodetector, and be converted into magnitude of voltage, the length of described photosignal is N, N is positive integer, and photosignal, at the corresponding magnitude of voltage x in each position of length direction, obtains photosignal discrete series X={x (n), n=0,1 ... N-1}, the resolution of frequency is Δ f

4., as claimed in claim 3 based on the dynamic parameter extracting method of bridge of laser-Doppler, it is characterized in that, step S2 specifically comprises the following steps:

S201. computing machine is to photosignal discrete series X={x (n), n=0, and 1 ... N-1} carries out Fast Fourier Transform (FFT), obtain frequency movement sequence Z=T (X)={ z (n), n=0,1 ... N-1}, wherein, T is Fourier transform operator;

S202. photosignal discrete series X={x (n) that collects at every batch of frequency movement sequence Z=T (X), n=0,1 ... simple spike value is there is in the scope of N-1}, find the photosignal particular location k in the longitudinal direction corresponding to frequency movement sequence Z=T (X) peak value, k ∈ [1, N], obtaining frequency fine by stages is

S203. according to accuracy class M ₁, by frequency fine by stages be further subdivided into 2M ₁equal portions, M ₁for positive integer, further frequency analysis be spaced apart Δ, adopt the frequency spectrum on following formula calculated rate subdivided interval, obtain spectrum sequence Y (f):

Wherein, Doppler shift e is natural constant, and j is imaginary unit;

S204. there is simple spike value in spectrum sequence Y (f) within the scope of f, finds the position p in the longitudinal direction of the photosignal corresponding to peak value of spectrum sequence Y (f), p ∈ [1,2M ₁], adopt following formula to calculate photosignal discrete series X={x (n), n=0,1 ... the Doppler shift f of N-1}:

S205. according to following formula, target speed v is calculated:

Wherein, λ ₀for the wavelength of transmitted light of optical-fiber laser transmitter.

5., as claimed in claim 4 based on the dynamic parameter extracting method of bridge of laser-Doppler, it is characterized in that: in step S3, if not, then repeat step S1 ~ S2, computational length is the movement velocity that the photosignal of l is corresponding respectively, wherein, l=0,1 ..., L-1, L be positive integer.

6. as claimed in claim 5 based on the dynamic parameter extracting method of bridge of laser-Doppler, it is characterized in that, the detailed process of step S4 is: be the movement speed v that the photosignal of l is corresponding according to length, form velocity series V={v (l), l=0,1, ... L-1}, wherein, the sampling rate of speed is Fs the resolution of speed in frequency is new Δ f, newly

7., as claimed in claim 6 based on the dynamic parameter extracting method of bridge of laser-Doppler, it is characterized in that, step S5 specifically comprises the following steps:

S501. to velocity series V={v (l), l=0,1 ... L-1} carries out Fast Fourier Transform (FFT), obtain frequency vibration sequence W=T (V)=w (l), l=0,1...L-1}, wherein T is Fourier transform operator;

S502. frequency vibration sequence W=T (V) is at velocity series V={v (l), l=0,1 ... there is simple spike value in the scope of L-1}, find the particular location k of the photosignal corresponding to frequency vibration sequence W=T (V) peak value at length direction _i, k _i∈ [1, L], obtains vibration frequency subdivided interval: wherein, m is vibration exponent number, and m is positive integer;

S503. according to accuracy class M ₂, by vibration frequency subdivided interval be further subdivided into 2M ₂equal portions, M ₂for positive integer, further vibration Frequency Analysis be spaced apart Δ ₂, adopt the frequency spectrum on following formula calculating vibration frequency subdivided interval, obtain rumble spectrum sequence U (f _i):

Wherein e is natural constant, and j is imaginary unit;

S504. rumble spectrum sequence U (f _i) at f _ithere is simple spike value in scope, find rumble spectrum sequence U (f _i) the position q in the longitudinal direction of the photosignal corresponding to peak value, q ∈ [1,2M ₂], adopt following formula to calculate every rank vibration frequency f of target _i:

8., as claimed in claim 7 based on the dynamic parameter extracting method of bridge of laser-Doppler, it is characterized in that: described voltage sample rate FS=625KHz, accuracy class M ₁=20, M ₂=40.

9. as claimed in claim 7 based on the dynamic parameter extracting method of bridge of laser-Doppler, it is characterized in that: when the movement velocity estimating bridge test position is 0 ~ 15mm/s, the length N=65536 of setting photosignal, the sampling rate Fs=5Hz of speed; When to estimate bridge test position movement velocity be 16 ~ 50mm/s, the length N=32768 of setting photosignal, the sampling rate Fs=10Hz of speed; When to estimate bridge test position movement velocity be 51 ~ 100mm/s, the length N=16384 of setting photosignal, the sampling rate Fs=15Hz of speed; When to estimate bridge test position movement velocity be 101 ~ 250mm/s, the length N=8192 of setting photosignal, the sampling rate Fs=20Hz of speed.