CN110044399A - Prevent the optic fiber grating wavelength demodulating system and demodulation method of piezo actuator creep - Google Patents
Prevent the optic fiber grating wavelength demodulating system and demodulation method of piezo actuator creep Download PDFInfo
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Abstract
The invention discloses a kind of optic fiber grating wavelength demodulating system for preventing piezo actuator creep and methods, the light that system middle width strip light source issues successively is divided into two-way after optoisolator, tunable TEA CO2 laser and photo-coupler, wherein all the way by F-P etalon, another way is reflected after circulator by fiber grating；The optical signal of above-mentioned two passes is acquired by data collecting card after photoelectric conversion and signal conditioning circuit and is sent into host computer；The analog output voltage all the way of data collecting card drives tunable TEA CO2 laser by summing circuit with another way analog output voltage after ratio circuit.The input voltage of host computer procedure one side monitoring data capture card, on the other hand Wavelength demodulation sensitivity and controlling feature value are calculated using the data of monitoring, and the output voltage of data collecting card is controlled, the influence of piezo actuator creep in tunable TEA CO2 laser is eliminated, optic fiber grating wavelength demodulation is completed.
Description
Technical field
The invention belongs to the wavelength interrogation techniques of fiber grating, and in particular to a kind of optical fiber for preventing piezo actuator creep
Grating wavelength demodulating system and demodulation method.
Background technique
Fiber grating (fiber Bragg grating, FBG) will be by that will strain, the information such as temperature are converted into its back wave
Long offset realizes the sensing measurement to physical quantity.Therefore, in the measuring system using FBG as sensing unit, Wavelength demodulation
It is core link.Currently, what is be widely used is the Wavelength demodulation side based on length scanning in the wavelength demodulation device of commercialization
Method.One outstanding advantages of this method are easy for realizing the Wavelength demodulation of large capacity, Distributed FBG.However carrying out high speed
When Wavelength demodulation, the measuring system cost based on this method will become very high.In contrast, the wavelength based on edge filter
Demodulation method more economical can must realize high speed Wavelength demodulation from principle.The principle of edge filter type FBG Wavelength demodulation system
Can be summarized as follows: the light that wideband light source issues is successively after optical filter and FBG, the reflective light intensity of FBG and its back wave
Long offset has corresponding relationship, therefore can be realized by the reflected light intensity values of detection FBG (utilizing photoelectric conversion device)
The Wavelength demodulation of FBG.In recent years, researcher the field research emphasis fixed optical filter exploitation using upper,
Common fixed optical filter mainly has: FBG, long-period fiber grating, chirped fiber grating, array waveguide grating, wavelength-division
Multiplexer, Fabry-Perot (F-P) chamber etc..Although the optical filter using this fixed can reduce cost, due to
Filtering characteristic is fixed, so the wave band that can be demodulated is very limited.The method for solving problem above is adjustable using filtering characteristic
The optical filter of section, in this way can be according to the filtering characteristic of the wavelength regulation optical filter of practical grating.Tunable F-P interferometer is
A kind of common filtering characteristic adjustable type optical filter.Tunable TEA CO2 laser, which can be regarded as, is coated with highly reflecting films by two
Glass plate composition, one of youngster's glass plate fixes, together with another piece and glass plate are connected firmly with piezo actuator.In this way,
One of youngster's glass plate can be made mobile by applying different voltage to piezo actuator, thus tunable TEA CO2 laser
Chamber length change, and then its transmission peak wavelength changes.
When carrying out Wavelength demodulation, it is desirable that the chamber of tunable TEA CO2 laser long (transmission peak wavelength) is constant, and such FBG's is anti-
The offset of its reflection wavelength can be reacted by penetrating intensity signal.But piezo actuator has creep properties, i.e., when piezoelectricity executes
When the driving voltage of device is steady state value, still can occur slow change in displacement, and this change in displacement can change it is tunable
The transmissison characteristic of F-P filter in turn results in the drift of demodulating system quiescent point.If quiescent point is in the mistake of drift
Without departing from linear measurement section in journey, then it still can use a high-pass filter and carry out dynamic wavelength demodulation (because creep is
One slow process), but due to the influence of creep, static Wavelength demodulation will be unable to complete at this time；Once and quiescent point is super
Linear surveying range (in its natural state, this moment always will appear) out, due to the variation of sensitivity, Wavelength demodulation necessarily goes out
Existing large error.
Summary of the invention
In order to solve the problems, such as that above-mentioned static Wavelength demodulation failure and quiescent operation point drift lead to demodulating error, the present invention
Purpose be to provide a kind of edge filter type optic fiber grating wavelength demodulating system with piezo actuator creep compensation function and
Method.
To achieve the goals above, the technical scheme is that, the optic fiber grating wavelength of piezo actuator creep is prevented
Demodulating system, including ratio circuit and summing circuit, the ratio circuit and summing circuit are connected to data collecting card and adjustable
Between humorous F-P filter, in which: data collecting card is provided with two-way analog output voltage altogether, wherein all the way (set this channel as
AO0) analog output voltage inputs summing circuit after ratio circuit, and another way (sets this channel as AO1) analog output voltage
Directly input summation operation circuit, the output end output drive signal of the summation operation circuit to tunable TEA CO2 laser into
Row driving.
Further, further include wideband light source and be successively set on the wideband light source output end optoisolator, can
Tune F-P filter and photo-coupler；The light that the wideband light source issues successively passes through optoisolator, tunable TEA CO2 laser
Be divided into two-way after photo-coupler, wherein this channel is defined as feedback channel all the way by F-P etalon, another way is passed through
It is reflected after circulator by fiber grating, this channel is defined as Measurement channel；
The transmitted light of the F-P etalon and the reflected light of fiber grating after photoelectric conversion and signal conditioning circuit,
Two-way voltage signal is acquired by data collecting card and is sent into host computer；It is logical for monitoring feedback channel and measurement in the host computer
The voltage value in road, and control the analog output voltage value of data collecting card.
Further, wherein the proportionality coefficient absolute value of ratio circuit is proper fraction.
The invention also discloses the optic fiber grating wavelength demodulation methods for preventing piezo actuator creep, comprising the following steps:
Step 1 determines Wavelength demodulation sensitivity and controlling feature value
Step 1.1, tunable TEA CO2 laser is driven using triangle wave voltage, wavelength scanning range is made to cover the bandwidth of FBG
Range；The a cycle of optional triangle wave voltage obtains feedback channel and Measurement channel during the periodic voltage rises
Voltage with the change curve of sampled point, choose one section of linearly interval on Measurement channel voltage wave crest, utilize two, the section
The corresponding sampled point of two feedback channel voltage wave crests and F-P mark at left and right sides of extreme coordinates and Measurement channel voltage wave crest
The transmission peak wavelength data of quasi- tool calculate Wavelength demodulation sensitivity；
Step 1.2, using the voltage curve of the feedback channel and Measurement channel that obtain in step 1.1, Measurement channel is determined
The corresponding feedback channel voltage value in linearly interval midpoint (i.e. the corresponding control reference voltage of FBG) and feedback channel voltage wave crest side
The position (i.e. the corresponding wave crest edge number of FBG) of edge；
Step 1.3, the driving voltage of tunable TEA CO2 laser is gradually increased since 0V, and is set rule and enable program
The wave crest amount of edge that feedback channel occurs during enough identification rises on the drive voltage.
Further, demodulation method of the invention is further comprising the steps of:
Step 2, when carrying out list FBG Wavelength demodulation, steps are as follows:
Step 2.1, the driving voltage that tunable TEA CO2 laser is started to step up from 0V, in voltage uphill process, prison
The voltage value for surveying feedback channel and Measurement channel counts feedback channel voltage wave crest edge according to the rule set in step 1.3
The quantity of appearance；
Step 2.2, when wave crest number of edges wave crest edge number corresponding with FBG is equal, driving voltage is controlled, it will be practical
The voltage value of feedback channel controls on the corresponding control reference voltage of FBG；After control result is stablized, counted using step 1.1
The work of FBG Wavelength demodulation is carried out in the Wavelength demodulation sensitivity of calculating.
Further, demodulation method of the invention is further comprising the steps of:
Step 3, when carrying out the demodulation of FBG array wavelength, steps are as follows:
Step 3.1, the driving voltage that tunable TEA CO2 laser is started to step up from 0V, rises process on the drive voltage
In, the voltage value of feedback channel and Measurement channel is monitored, according to the rule set in step 1.3, counts feedback channel voltage wave
The quantity that peak edge occurs；
Step 3.2, when feedback channel voltage wave crest number of edges wave crest edge number corresponding with first FBG is equal,
Stop wave crest edge to count, control driving voltage, the voltage value in actual feedback channel is controlled into the control benchmark in first FBG
On voltage value；After control result is stablized, i.e., carry out first FBG using the calculated Wavelength demodulation sensitivity of step 1.1
Wavelength demodulation work；
Step 3.3, when carrying out subsequent FBG Wavelength demodulation, stop control, and continue growing tunable TEA CO2 laser
Driving voltage, and continue wave crest edge and count, utilize the corresponding control reference voltage value of subsequent FBG and feedback channel wave crest edge
Number carries out creep control according to the method in step 3.2, and carries out the Wavelength demodulation of corresponding FBG after control result is stablized；
Step 3.4, after completing all FBG Wavelength demodulations, the driving voltage of tunable TEA CO2 laser is set as 0V, and
Repeat the above steps 3.
Further, in the present invention, specific step is as follows for the step 1.1:
(1) all transmitted wave long values of the measurement F-P etalon in wideband light source wave-length coverage；
(2) channel the AO0 output voltage of data collecting card is set as 0V, and the channel AO1 exports triangle wave voltage, it is desirable that triangular wave
The valley value of voltage is 0V, and the wavelength scanning range under the triangular wave driving voltage covers the bandwidth range of FBG, one
In secondary complete driving voltage uphill process, the voltage of feedback channel and Measurement channel is obtained with the change curve of sampled point；
(3) one section of linearly interval of Measurement channel voltage peak upslope or descending is taken, if the linearly interval left end point coordinate
For (nFBGL,UFBGL), the coordinate of right endpoint is (nFBGR,UFBGR)；If left and right two feedback adjacent with Measurement channel voltage wave crest
Sampled point corresponding to channel voltage wave crest is respectively nFPIL、nFPIR, corresponding F-P etalon transmission wavelength is respectively λFPIL、
λFPIR；Then the Wavelength demodulation sensitivity table of FBG is shown as:
Specific step is as follows for step 1.2:
(1) it is selected for the voltage of the feedback channel and Measurement channel obtained in step 1.1 with the change curve of sampled point
The voltage threshold U of feedback channelFPIth, it is desirable that in addition to several wave crests on boundary, the voltage peak voltage of other all feedback channels
Value is all larger than the threshold value；
(2) the voltage threshold U of Measurement channel is selectedFBGth, it is desirable that the threshold value is located near the midpoint in linear measurement section；If
The corresponding sampling number of Measurement channel threshold value is nFBGth, and when reaching the sampling number, the voltage value of feedback channel is
UFPI-FBG, this voltage value is named as control reference voltage value；
It (3) include U by the 1st from left numberFPIthFeedback channel voltage wave crest top edge number be 1, lower edge number
It is 2, includes U by the 2ndFPIthFeedback channel voltage wave crest top edge number be 3, lower edge number be 4, with such
It pushes away, if nFBGthCorresponding wave crest edge number is NFPI-FBG；
Specific step is as follows for step 1.3:
(1) data collecting card AO0 channel voltage is set as 0V, and AO1 channel voltage is gradually increased since 0V, increased every time
Amplitude is the minimum resolution voltage of data collecting card, carries out following work on the basis of walking herein；
(2) two parameters: feedback channel threshold interval half-breadth Δ U are setFPIth, driving voltage variation delta Udrive；It is located at
In AO1 voltage uphill process, certain once detects that the voltage value of feedback channel reaches threshold interval (UFPIth-ΔUFPIth, UFPIth+
ΔUFPIth) when, the driving voltage of tunable TEA CO2 laser is Udrive-now, the preceding voltage value arrival for once detecting feedback channel
When the threshold interval, the driving voltage of tunable TEA CO2 laser is Udrive-pre；Set up rule: when the voltage value of feedback channel arrives
Up to threshold interval (UFPIth-ΔUFPIth, UFPIth+ΔUFPIth), and Udrive-now-Udrive-pre>ΔUdriveWhen, threshold marker
flagFPIthAdd 1；
(3) Δ U is adjustedFPIthWith Δ UdriveSize, make feedback channel voltage per pass UFPIth, flagFPIthAdd and
Only plus 1.
Specific step is as follows for step 2.1:
Data collecting card AO0 channel voltage is set as 0V, and AO1 channel voltage is gradually increased since 0V, each increased width
Degree is the minimum resolution voltage of data collecting card；In AO1 voltage uphill process, using the rule set up in step 1.3, open
Beginning flagFPIthIt counts, flagFPIthInitial value be 0；
Specific step is as follows for step 2.2:
(1) work as flagFPIthReach NFPI-FBGWhen, the voltage in the channel AO1 remains unchanged, and stops flagFPIthIt counts；With this
Control is started simultaneously at, control target is to make feedback channel voltage stabilization to UFPI-FBG, controller is write by upper computer software
PID controller, output are AO0 channel voltage value, and input divides following four situation, wherein UFPIFor the real-time electricity of feedback channel
Pressure value:
1) work as NFPI-FBGIt is numbered to go up a slope, and the proportionality coefficient of ratio circuit is timing, the input of controller is UFPI-FBG-
UFPI；
2) work as NFPI-FBGFor number of going up a slope, and when the proportionality coefficient of ratio circuit is negative, the input of controller is UFPI-
UFPI-FBG；
3) work as NFPI-FBGIt is numbered for descending, and the proportionality coefficient of ratio circuit is timing, the input of controller is UFPI-
UFPI-FBG；
4) work as NFPI-FBGFor descending number, and when the proportionality coefficient of ratio circuit is negative, the input of controller is UFPI-FBG-
UFPI；
(2) after control result is stablized, the wavelength shift Δ λ of FBGFBGWith the voltage variety Δ U of Measurement channelFBG's
Relationship is expressed as:
Specific step is as follows for the step 3.1:
Data collecting card AO0 channel voltage is set as 0, AO1 channel voltage and gradually increases since 0V, each increased amplitude
It, using the rule set up in step 1.3, is opened during rising on the drive voltage for the minimum resolution voltage of data collecting card
Beginning flagFPIthIt counts, flagFPIthInitial value be 0；
Specific step is as follows for the step 3.2:
If the number of FBG is followed successively by 1,2,3 ... n in FBG array, the Wavelength demodulation sensitivity of n-th of FBG is SFBGn, right
The control reference voltage value answered is UFPI-FBGn, corresponding wave crest edge number is NFPI-FBGn；
Work as flagFPIthEqual to NFPI-FBG1When, keep that AO1 channel voltage is constant (sets voltage value at this time as UAO1-FBG1), stop
Only flagFPIthCounting, start simultaneously at according to the method in step 2.2, with UFPI-FBG1The defeated of AO0 is controlled for control a reference value
Voltage out utilizes Wavelength demodulation sensitivity S after control result is stablizedFBG1, wavelength solution is carried out to the 1st FBG according to formula (2)
It adjusts；
Specific step is as follows for the step 3.3:
(1) when carrying out subsequent FBG Wavelength demodulation, if the output voltage in the channel AO0 has reached U at this timeAO0-FBG1, ratio electricity
The proportionality coefficient on road is k, and enabling the voltage in the channel AO1 is UAO1-FBG1+kUAO0-FBG1, the voltage in the channel AO0 is reset and stopping control,
The voltage for being stepped up the channel AO1 is started simultaneously at, each increased amplitude is the minimum resolution voltage of data collecting card；With this
Meanwhile if NFPI-FBG1For number and the U of going up a slopeFPI-FBG1<UFPIthOr NFPI-FBG1For descending number and UFPI-FBG1>UFPIth, enable
flagFPIthFirst subtract 1 and then proceed to count, otherwise flagFPIthIt continues directly to count；
(2) strategy for using step 3.2 utilizes the corresponding control reference voltage of other FBG, wave crest edge number and wavelength
Demodulation sensitivity completes the demodulation of corresponding FBG；After completing the Wavelength demodulation of n-th of FBG, the voltage in the channel AO1 is enabled to be
UAO1-FBGn+kUAO0-FBGn, the voltage in the channel AO0 resets, and starts simultaneously at the voltage for being stepped up the channel AO1, each increased width
Degree is the minimum resolution voltage of data collecting card；
Specific step is as follows for the step 3.4:
(1) when AO1 channel voltage reaches the maximum drive voltage U of settingAO1maxWhen, by the voltage in the channel AO1 and
flagFPIthClear 0, and repeat the above steps 3；
It (2), only need to be by control reference voltage and wave crest edge when expectation demodulates discontinuous FBG wavelength in FBG array
The corresponding value of FBG that number is sequentially arranged as expectation demodulation, the load and the same above-mentioned steps of control strategy of driving voltage
3。
Compared with prior art, the present invention at least has the advantages that
The present invention can prevent the static work of the edge filter type FBG Wavelength demodulation system based on tunable TEA CO2 laser
Make point and exceed linearly interval, and realizes static and dynamic wavelength while demodulating.
In attached system shown in FIG. 1, when gradually increasing the driving voltage of tunable TEA CO2 laser, transmission peak wavelength
It will change, in the process, according to tunable F-P interferometer transmission peak wavelength and FBG reflection wavelength and F-P etalon transmission wavelength
Matching degree, the voltage waveform in collected two channels of data collecting card is as shown in Fig. 2, in attached drawing 2 abscissa be adopt
Sampling point (represents the time), and the transmission peak wavelength with tunable TEA CO2 laser is linear relationship.The voltage peak upslope of Measurement channel
(or descending) there are the sections of one section of approximately linear, if showing, the reflection wavelength of the FBG in the section is constant, tunable F-P filter
The transmission peak wavelength (sampled point) of wave device and the voltage swing of Measurement channel are linear relationships.It is easy to reason out based on this: above-mentioned
In linearly interval, if the transmission peak wavelength of tunable TEA CO2 laser is constant, the reflection wavelength of FBG and the electricity of Measurement channel
Press size in a linear relationship, this is the basis of Wavelength demodulation.But the premise that should be noted that the demodulation principle is set up is: can
The transmission peak wavelength for tuning F-P filter is constant.However, due to the creep of piezo actuator, even if under constant drive voltage, it can
The transmission peak wavelength of F-P filter is tuned also slowly varying, the voltage change for being just hard to tell Measurement channel in this way is by tunable
Caused by the transmission peak wavelength variation of F-P filter or as caused by the variation of FBG reflection wavelength.Under draw, work as measurement
The voltage in channel is still located at linearly interval, can carry out dynamic wavelength demodulation, because creep is relatively slow process, however one
The voltage of denier Measurement channel exceeds linearly interval, and calculating wavelength according to the result demarcated in advance necessarily will appear large error, this
For the necessity of creep control.
The voltage in channel where F-P etalon is realized creep control by the present invention, and control principle can
Illustrated by attached drawing 2.Some voltage value U in Measurement channel linearly intervalFBGthA corresponding sampled point nFBGth, i.e., one can
Tune the transmission peak wavelength λ of F-P filterFBGth, also correspond to a point (n on feedback channel voltage curveFBGth,UFPI-FBG),
If making the voltage stabilization of feedback channel in (n by the driving voltage of control tunable TEA CO2 laserFBGth,UFPI-FBG) point,
So the transmission peak wavelength of tunable TEA CO2 laser is necessarily stable in λ at this timeFBGth, the voltage of Measurement channel will be located at linearly interval,
And since the transmission peak wavelength of tunable TEA CO2 laser is constant, the demodulation of static and dynamic wavelength just can carry out.
The present invention realizes a wide range of, high-resolution Wavelength demodulation using compared with the data collecting card of lower-order digit: in reality
In demodulating process, after control result stabilization, the transmission peak wavelength federation of tunable TEA CO2 laser upper and lower wave near some value
Dynamic, which will affect Wavelength demodulation resolution ratio.And an important determinant of degree of fluctuation is the resolution ratio of driving voltage,
When the resolution ratio of driving voltage is lower, then degree of fluctuation is big, and when the high resolution of driving voltage, then degree of fluctuation is small.Using height
Though position data collecting card can improve wavelength resolution, system cost will increase.The present invention increases after the output of data collecting card
Ratio circuit (proportionality coefficient is proper fraction) is added, data acquisition can not increased by reducing data collecting card driving voltage value
The resolution ratio of tunable TEA CO2 laser driving voltage is improved in the case where detent number, but so, the maximum of driving voltage becomes
Changing range can also decline therewith, be unfavorable for distributed wavelength demodulation, and therefore, the present invention is defeated using the simulation of two paths of data capture card
Out, tunable TEA CO2 laser is directly controlled all the way, this road is coarse adjustment, it is therefore an objective to which larger range adjusts tunable TEA CO2 laser
Transmission peak wavelength, thus the FBG that " tracking " needs to demodulate to some, another way controls tunable F-P filtering after passing through ratio circuit
Device, this road are fine tuning, are controlled for creep.In this way by using the two-way simulation output of data collecting card, and combine ratio electricity
Road and add circuit can utilize and realize a wide range of, high-resolution Wavelength demodulation compared with the data collecting card of lower-order digit.
Detailed description of the invention
Fig. 1 is optic fiber grating wavelength demodulating system structure chart of the invention；
Fig. 2 is the present invention when carrying out list FBG Wavelength demodulation, each characteristic parameter schematic diagram；
Fig. 3 is the present invention when carrying out the demodulation of FBG array wavelength, the control reference voltage schematic diagram of each FBG；
Fig. 4 is the present invention when carrying out the demodulation of FBG array wavelength, Measurement channel voltage, feedback channel voltage and driving electricity
The correspondence diagram of pressure；
In attached drawing: 1, wideband light source, 2, optoisolator, 3, tunable TEA CO2 laser, 4, coupler, 5, circulator, 6, light
Fine grating, 7, F-P etalon, 8, photoelectric conversion and signal conditioning circuit, 9, data collecting card, 10, host computer, 11, ratio electricity
Road, 12, summing circuit.
Specific embodiment
Below in conjunction with attached drawing, the present invention is described in further detail.
As shown in Figure 1, the light that wideband light source 1 issues successively passes through optoisolator 2, tunable TEA CO2 laser 3 and optical coupling
Be divided into two-way after device 4: wherein all the way by F-P etalon 7, this channel is defined as feedback channel；Another way passes through circulator 5
It is reflected afterwards by fiber grating 6, this channel is defined as Measurement channel.The transmitted light of F-P etalon 5 and the reflection of fiber grating 6
Light passes through photoelectric conversion and signal conditioning circuit 8, and two-way voltage signal is acquired by data collecting card 9 and is sent into host computer later
10, host computer 10 sends control instruction to data collecting card 9 simultaneously.Data collecting card 9 wherein (sets this channel all the way as AO0)
Analog output voltage (sets this channel and is carried out as AO1) analog output voltage by circuit 12 after ratio circuit 11 with another way
Summation operation, the voltage signal after final summation drive tunable TEA CO2 laser 3, wherein the ratio of ratio circuit 11
Absolute coefficient is proper fraction.
Demodulation method of the invention the following steps are included:
Step 1: determining Wavelength demodulation sensitivity and controlling feature value
(1) channel data collecting card AO0 output voltage is set as the channel 0, AO1 output triangle wave voltage and drives tunable F-P
Filter, triangle wave voltage minimum value are 0.Under triangular wave driving voltage, the transmission peak wavelength of tunable F-P interferometer changes,
Transmission peak wavelength variation range is known as wavelength scanning range.It is required that wavelength scanning range at this time covers the bandwidth range of FBG.When can
Tune F-P cavity transmission peak wavelength it is equal with the reflection wavelength of the transmission peak wavelength of F-P etalon or FBG when, can make feedback channel or
There is maximum in the voltage of Measurement channel.Therefore, in a complete driving voltage uphill process, feedback channel and measurement are logical
The voltage in road should be form as indicated with 2 with the typical curve that sampled point changes.
Being set in sampled point corresponding to two feedback channel voltage wave crests of Measurement channel voltage wave crest two sides is respectively
nFPIL、nFPIR, corresponding F-P etalon transmission wavelength is respectively λFPIL、λFPIR.Take Measurement channel voltage peak upslope (under or
Slope) one section of linearly interval, if the coordinate of the linear zone left end point be (nFBGL,UFBGL), the coordinate of right endpoint is (nFBGR,
UFBGR).Then shown in the Wavelength demodulation sensitivity such as formula (1) of fiber grating.The sensitivity indicates, when demodulating system work exists
When linearly interval, the variable quantity and Measurement channel voltage change of the difference of the reflection wavelength of the transmission peak wavelength and FBG of tunable F-P interferometer
The relationship of amount.
The voltage threshold U of selected feedback channelFPIth, in addition to several wave crests on boundary, it is desirable that other all feedback channels
Voltage wave crest includes the threshold value；The voltage threshold U of selected Measurement channelFBGth, which is located at the midpoint in linear measurement section
Near.If the corresponding sampling number of Measurement channel threshold value is nFBGth, and when reaching the sampling number, the voltage value of feedback channel
For UFPI-FBG, this voltage value is control reference voltage value.Position of the above each value on voltage waveform is as shown in Figure 2.By the 1st
It include UFPIthFeedback channel voltage wave crest top edge number be 1, lower edge number be 2, include U by the 2ndFPIth's
The top edge number of feedback channel voltage wave crest is 3, and lower edge number is 4, and so on, if nFBGthIt compiles at the wave crest edge at place
Number be NFPI-FBG.According to above-mentioned coding rule, N in Fig. 2FPI-FBGValue should be 4.
(2) data collecting card AO0 channel voltage is set as 0V, and AO1 channel voltage is gradually increased since 0V, increased every time
Amplitude is the minimum resolution voltage of data collecting card.In AO1 channel voltage uphill process, host computer monitor feedback channel and
The voltage value of Measurement channel.Given threshold section (UFPIth-ΔUFPIth, UFPIth+ΔUFPIth), if the electricity of certain feedback channel
When pressure value reaches the threshold interval, the driving voltage of tunable TEA CO2 laser is Udrive-now, the voltage of a preceding feedback channel
When value reaches the threshold interval, the driving voltage of tunable TEA CO2 laser is Udrive-pre.Set the changing value Δ of driving voltage
Udrive.When the voltage value of feedback channel reaches the threshold interval, and Udrive-now-Udrive-pre>ΔUdriveWhen, threshold marker
flagFPIthAdd 1.Adjust Δ UFPIthWith Δ UdriveSize, so that each feedback channel voltage is passed through UFPIthWhen, flagFPIthAdd
And only add 1.
This step is to calculate during tunable TEA CO2 laser driving voltage rises, and feedback channel voltage is logical
Cross UFPIthNumber.The strategy why determined using above-mentioned threshold interval and driving voltage difference joint, is because collecting
Feedback channel voltage be in amplitude it is discrete, U can not be exactly equal toFPIth, therefore the voltage of feedback channel can not be directlyed adopt
Value directly determines.However if determined only with threshold interval, can also there be problem: when threshold interval is excessive, feedback
Channel voltage per pass UFPIth, will do it multiple counting；When threshold interval is too small, feedback channel voltage per pass
UFPIth, it may be without counting, this problem is also to be caused by feedback channel voltage magnitude is discrete.Reach only by adusting threshold interval
Desired effects are more difficult.
Step 2: FBG Wavelength demodulation
1, list FBG Wavelength demodulation
Data collecting card AO0 channel voltage is set as 0V, and AO1 channel voltage is gradually increased since 0V, each increased width
Degree is the minimum resolution voltage of data collecting card.flagFPIth(initial value 0) is counted according to the rule in step 1, when
flagFPIthReach NFPI-FBGWhen, the voltage in the channel AO1 stops increasing, and starts to control, and control target is the electricity for making feedback channel
Pressure value is stabilized to UFPI-FBG, controller is the PID controller write by upper computer software, and output is AO0 channel voltage value, defeated
Enter a point following four situation and (sets the real-time voltage value of feedback channel as UFPI):
1) work as NFPI-FBGIt is numbered to go up a slope, and the proportionality coefficient of ratio circuit is timing, the input of controller is UFPI-FBG-
UFPI；
2) work as NFPI-FBGFor number of going up a slope, and when the proportionality coefficient of ratio circuit is negative, the input of controller is UFPI-
UFPI-FBG；
3) work as NFPI-FBGIt is numbered for descending, and the proportionality coefficient of ratio circuit is timing, the input of controller is UFPI-
UFPI-FBG；
4) work as NFPI-FBGFor descending number, and when the proportionality coefficient of ratio circuit is negative, the input of controller is UFPI-FBG-
UFPI。
After control result is stablized, the voltage variety Δ U of Measurement channelFBGWith the wavelength shift Δ λ of FBGFBGPass
System may be expressed as:
The emphasis of the above demodulating process is to control feedback voltage level in wave crest edge NFPI-FBGOn UFPI-FBGPlace, at this point,
According to the voltage corresponding relationship of Measurement channel and feedback channel, the voltage value of Measurement channel should be U in the initial stateFBGth, i.e.,
The voltage of Measurement channel will not be slowly varying because of the creep of piezo actuator again, in this case, can carry out static state
With the demodulation of dynamic wavelength.
On the other hand, directly adopt data collecting card output voltage theoretically also can achieve control piezo actuator it is compacted
The effect of change, but due to the output voltage limited resolution of data collecting card, so measurement is logical after waiting control results to stablize
The voltage fluctuation in road will be larger, so that the resolution ratio of Wavelength demodulation can be reduced, therefore a ratio circuit is increased in system
Improve the resolution ratio of piezo actuator driving voltage.But if only with driving voltage all the way in this way, tunable TEA CO2 laser
Transmission peak wavelength variation range will reduce, and then the FBG wavelength that can be demodulated is limited, so using data in system
The two-way of capture card exports, wherein output directly controls tunable TEA CO2 laser (piezo actuator) all the way, its object is to
" tracking " FBG, another output control tunable TEA CO2 laser after passing through ratio circuit, and its object is to creep compensations.
2, FBG array wavelength demodulates
FBG array is composed in series by multiple FBG, if the number of FBG is followed successively by 1,2,3 ... n.First, in accordance in step 1
Method acquires the Wavelength demodulation sensitivity and corresponding controlling feature value of each FBG.If the Wavelength demodulation sensitivity of n-th of FBG
For SFBGn, corresponding control reference voltage value is UFPI-FBGn, corresponding wave crest edge number is NFPI-FBGn.As worked as some FBG gusts
When column are containing 3 FBG, Fig. 3 show Measurement channel voltage and feedback channel voltage rise on the drive voltage during with sampling
The change curve of point, the control reference voltage value of three FBG mark in figure, the corresponding wave crest edge number point of three FBG
Not are as follows: 3,9,15.
The demodulation of all gratings is completed according to the following steps:
(1) AO0 channel voltage is set as 0, AO1 channel voltage and gradually increases since 0V, and each increased amplitude is data
The minimum resolution voltage of capture card.flagFPIth(initial value 0) is counted according to the rule in step 1, works as flagFPIthDeng
In NFPI-FBG1When, keep that AO1 channel voltage is constant (sets voltage value at this time as UAO1-FBG1), stop flagFPIthCounting, together
When start according to the method in single FBG Wavelength demodulation, with UFPI-FBG1The output voltage that AO0 is controlled for control a reference value, is controlling
After stabilization, it can utilize SFBG1Wavelength demodulation is carried out to the 1st FBG according to formula (2).After controlling a period of time, if at this time
The output voltage in the channel AO0 is UAO0-FBG1, the proportionality coefficient of ratio circuit is k, and enabling the voltage in the channel AO1 is UAO1-FBG1+
kUAO0-FBG1, the voltage in the channel AO0 resets, and starts simultaneously at the voltage for being stepped up the channel AO1, each increased amplitude is data
The minimum resolution voltage of capture card.At the same time, if NFPI-FBG1For number and the U of going up a slopeFPI-FBG1<UFPIthOr NFPI-FBG1
For descending number and UFPI-FBG1>UFPIthEnable flagFPIthFirst subtract 1 and then proceed to count, otherwise flagFPIthIt continues directly to count.
(2) work as flagFPIthEqual to NFPI-FBG2When, keep AO1 channel voltage it is constant (set voltage value at this time as
UAO1-FBG2), stop flagFPIthCounting, start simultaneously at according to the method in single FBG Wavelength demodulation, with UFPI-FBG2To control base
The output voltage of quasi- value control AO0, after control is stablized, it can Wavelength demodulation is carried out to the 2nd FBG according to formula (2).Work as control
After a period of time processed, if the output voltage in the channel AO0 is U at this timeAO0-FBG2, enabling the voltage in the channel AO1 is UAO1-FBG2+
kUAO0-FBG2, the voltage in the channel AO0 resets, and starts simultaneously at the voltage for being stepped up the channel AO1, each increased amplitude is data
The minimum resolution voltage of capture card.At the same time, if NFPI-FBG2For number and the U of going up a slopeFPI-FBG2<UFPIthOr NFPI-FBG2
For descending number and UFPI-FBG2>UFPIthEnable flagFPIthFirst subtract 1 and then proceed to count, otherwise flagFPIthIt continues directly to count.It presses
According to driving voltage identical with above method load and control strategy, the demodulation of other FBG is completed.
(3) after completing the Wavelength demodulation of n-th of FBG, enabling the voltage in the channel AO1 is UAO1-FBGn+kUAO0-FBGn, AO0
The voltage in channel is reset, and starts simultaneously at the voltage for being stepped up the channel AO1, and each increased amplitude is the minimum of data collecting card
Resolution voltage.When AO1 channel voltage reaches the maximum drive voltage U of settingAO1maxWhen, AO1 voltage clear 0, and repeat (1)-
(3) process.
Assuming that a FBG array contains 4 FBG, then in the manner described above, feedback channel voltage, Measurement channel voltage, can
The driving voltage for tuning F-P cavity is as shown in Figure 4.
It (4) is that Wavelength demodulation, used control reference voltage successively are carried out to FBG all in FBG array with upper type
Vector is (UFPI-FBG1,UFPI-FBG2,…,UFPI-FBGn), wave crest edge number vector is (NFPI-FBG1,NFPI-FBG2,…,
NFPI-FBGn).The several FBG of certain in FBG array can also only be demodulated using system of the invention, and at this moment only need to be by control benchmark electricity
Element in pressure vector sum wave crest edge number vector is set as the selected corresponding element of FBG, other processing modes are constant.
Such as it is expected demodulation the 2nd and the 4th FBG, then (U should be set as by controlling reference voltage vectorFPI-FBG2,UFPI-FBG4), wave crest edge
Number vector should be set as (NFPI-FBG2,NFPI-FBG4)。
Claims (9)
1. preventing the optic fiber grating wavelength demodulating system of piezo actuator creep, it is characterised in that: including ratio circuit (11) and
Summing circuit (12), the ratio circuit (11) and summing circuit (12) are connected to data collecting card (9) and tunable F-P filtering
Between device (3), in which: data collecting card (9) is provided with two-way analog output voltage altogether, wherein analog output voltage passes through all the way
Ratio circuit (11) inputs summing circuit (12) afterwards, and another way analog output voltage directly inputs summation operation circuit (12), institute
Output end output drive signal to the tunable TEA CO2 laser (3) for stating summation operation circuit (12) is driven.
2. the optic fiber grating wavelength demodulating system according to claim 1 for preventing piezo actuator creep, it is characterised in that:
Further include wideband light source (1) and be successively set on the optoisolator (2) of the wideband light source (1) output end, tunable F-P filter
Wave device (3) and photo-coupler (4)；The light that the wideband light source (1) issues successively passes through optoisolator (2), tunable F-P filtering
It is divided into two-way after device (3) and photo-coupler (4), wherein this channel is defined as feedback channel all the way by F-P etalon (7),
Another way is reflected after circulator (5) by fiber grating (6), this channel is defined as Measurement channel；
The transmitted light of the F-P etalon (7) and the reflected light of fiber grating (6) pass through photoelectric conversion and signal conditioning circuit
(8) after, two-way voltage signal is acquired by data collecting card (9) and is sent into host computer (10)；The host computer (10) is for monitoring
The voltage value of feedback channel and Measurement channel, and control the analog output voltage value of data collecting card (9).
3. the optic fiber grating wavelength demodulating system according to claim 1 for preventing piezo actuator creep, it is characterised in that:
Wherein the proportionality coefficient absolute value of ratio circuit (11) is proper fraction.
4. preventing the optic fiber grating wavelength demodulation method of piezo actuator creep, which comprises the following steps:
Step 1 determines Wavelength demodulation sensitivity and controlling feature value
Step 1.1, tunable TEA CO2 laser is driven using triangle wave voltage, wavelength scanning range is made to cover the bandwidth model of FBG
It encloses；The a cycle of optional triangle wave voltage obtains feedback channel and Measurement channel during the periodic voltage rises
Voltage chooses one section of linearly interval on Measurement channel voltage wave crest with the change curve of sampled point, utilizes two, section end
The corresponding sampled point of two feedback channel voltage wave crests and F-P standard at left and right sides of point coordinate and Measurement channel voltage wave crest
The transmitted wave long value of tool calculates Wavelength demodulation sensitivity；
Step 1.2, using the voltage curve of the feedback channel and Measurement channel that obtain in step 1.1, determine that Measurement channel is linear
The position of the corresponding feedback channel voltage value of interval midpoint and feedback channel voltage wave crest edge；
Step 1.3, the driving voltage of tunable TEA CO2 laser is gradually increased since 0V, and is set rule and enabled a program to know
The wave crest amount of edge that feedback channel occurs during not rising on the drive voltage.
5. the optic fiber grating wavelength demodulation method according to claim 4 for preventing piezo actuator creep, which is characterized in that
It is further comprising the steps of:
Step 2, when carrying out list FBG Wavelength demodulation, steps are as follows:
Step 2.1, the driving voltage that tunable TEA CO2 laser is started to step up from 0V, in voltage uphill process, monitoring is anti-
The voltage value in feedthrough road and Measurement channel counts feedback channel voltage wave crest edge and occurs according to the rule set in step 1.3
Quantity；
Step 2.2, when wave crest number of edges wave crest edge number corresponding with FBG is equal, driving voltage is controlled, by actual feedback
The voltage value in channel controls on the corresponding control reference voltage of FBG；After control result is stablized, calculated using step 1.1
Wavelength demodulation sensitivity carry out FBG Wavelength demodulation work.
6. the optic fiber grating wavelength demodulation method according to claim 4 for preventing piezo actuator creep, which is characterized in that
It is further comprising the steps of:
Step 3, when carrying out the demodulation of FBG array wavelength, steps are as follows:
Step 3.1, the driving voltage of tunable TEA CO2 laser is started to step up from 0V, during rising on the drive voltage, prison
The voltage value for surveying feedback channel and Measurement channel counts feedback channel voltage wave crest edge according to the rule set in step 1.3
The quantity of appearance；
Step 3.2, when feedback channel voltage wave crest number of edges wave crest edge number corresponding with first FBG is equal, stop
Wave crest edge counts, and controls driving voltage, and the voltage value in actual feedback channel is controlled the control reference voltage in first FBG
In value；After control result is stablized, i.e., carry out first FBG wavelength using the calculated Wavelength demodulation sensitivity of step 1.1
Demodulate work；
Step 3.3, when carrying out subsequent FBG Wavelength demodulation, stop control, and continue growing the driving of tunable TEA CO2 laser
Voltage, and continue wave crest edge and count, it is compiled using the corresponding control reference voltage value of subsequent FBG and feedback channel wave crest edge
Number, creep control is carried out according to the method in step 3.2, and the Wavelength demodulation of corresponding FBG can be carried out after control result is stablized；
Step 3.4, after completing all FBG Wavelength demodulations, the driving voltage of tunable TEA CO2 laser is set as 0V, and repeat
Above-mentioned steps 3.
7. the optic fiber grating wavelength demodulation method according to claim 4 for preventing piezo actuator creep, which is characterized in that
Specific step is as follows for the step 1.1:
(1) all transmitted wave long values of the measurement F-P etalon in wideband light source wave-length coverage；
(2) channel the AO0 output voltage of data collecting card is set as 0V, and the channel AO1 exports triangle wave voltage, it is desirable that triangle wave voltage
Valley value be 0V, and the wavelength scanning range under the triangular wave driving voltage covers the bandwidth range of FBG, primary complete
In whole driving voltage uphill process, the voltage of feedback channel and Measurement channel is obtained with the change curve of sampled point；
(3) one section of linearly interval of Measurement channel voltage peak upslope or descending is taken, if the linearly interval left end point coordinate is
(nFBGL,UFBGL), the coordinate of right endpoint is (nFBGR,UFBGR)；If left and right two feedback adjacent with Measurement channel voltage wave crest is logical
Sampled point corresponding to road voltage wave crest is respectively nFPIL、nFPIR, corresponding F-P etalon transmission wavelength is respectively λFPIL、
λFPIR；Then the Wavelength demodulation sensitivity table of FBG is shown as:
Specific step is as follows for step 1.2:
(1) feedback is selected with the change curve of sampled point for the voltage of the feedback channel and Measurement channel obtained in step 1.1
The voltage threshold U in channelFPIth, it is desirable that in addition to several wave crests on boundary, the voltage peak voltage value of other all feedback channels is equal
Greater than the threshold value；
(2) the voltage threshold U of Measurement channel is selectedFBGth, it is desirable that the threshold value is located near the midpoint for the linearly interval chosen；If surveying
Measuring the corresponding sampling number of channel threshold value is nFBGth, and when reaching the sampling number, the voltage value of feedback channel is UFPI-FBG,
This voltage value is named as control reference voltage value；
It (3) include U by the 1st from left numberFPIthFeedback channel voltage wave crest top edge number be 1, lower edge number be 2,
It include U by the 2ndFPIthFeedback channel voltage wave crest top edge number be 3, lower edge number be 4, and so on, if
nFBGthCorresponding wave crest edge number is NFPI-FBG；
Specific step is as follows for step 1.3:
(1) data collecting card AO0 channel voltage is set as 0V, and AO1 channel voltage is gradually increased since 0V, each increased amplitude
For the minimum resolution voltage of data collecting card, carry out following work on the basis of walking herein；
(2) two parameters: feedback channel threshold interval half-breadth Δ U are setFPIth, driving voltage variation delta Udrive；It is located at AO1 electricity
It presses in uphill process, certain once detects that the voltage value of feedback channel reaches threshold interval (UFPIth-ΔUFPIth, UFPIth+Δ
UFPIth) when, the driving voltage of tunable TEA CO2 laser is Udrive-now, the preceding voltage value for once detecting feedback channel reaches should
When threshold interval, the driving voltage of tunable TEA CO2 laser is Udrive-pre；Set up rule: when the voltage value of feedback channel reaches
Threshold interval (UFPIth-ΔUFPIth, UFPIth+ΔUFPIth), and Udrive-now-Udrive-pre>ΔUdriveWhen, threshold marker
flagFPIthAdd 1；
(3) Δ U is adjustedFPIthWith Δ UdriveSize, make feedback channel voltage per pass UFPIth, flagFPIthAdd and only adds
1。
8. the optic fiber grating wavelength demodulation method according to claim 5 for preventing piezo actuator creep, which is characterized in that
Specific step is as follows for step 2.1:
Data collecting card AO0 channel voltage is set as 0V, and AO1 channel voltage is gradually increased since 0V, and each increased amplitude is
The minimum resolution voltage of data collecting card；In AO1 voltage uphill process, using the rule set up in step 1.3, start
flagFPIthIt counts, flagFPIthInitial value be 0；
Specific step is as follows for step 2.2:
(1) work as flagFPIthReach NFPI-FBGWhen, the voltage in the channel AO1 remains unchanged, and stops flagFPIthIt counts；At the same time
Start to control, control target is to make feedback channel voltage stabilization to UFPI-FBG, controller is the PID control write by upper computer software
Device processed, output are AO0 channel voltage value, and input divides following four situation, wherein UFPIFor the real-time voltage value of feedback channel:
1) work as NFPI-FBGIt is numbered to go up a slope, and the proportionality coefficient of ratio circuit is timing, the input of controller is UFPI-FBG-UFPI；
2) work as NFPI-FBGFor number of going up a slope, and when the proportionality coefficient of ratio circuit is negative, the input of controller is UFPI-UFPI-FBG；
3) work as NFPI-FBGIt is numbered for descending, and the proportionality coefficient of ratio circuit is timing, the input of controller is UFPI-UFPI-FBG；
4) work as NFPI-FBGFor descending number, and when the proportionality coefficient of ratio circuit is negative, the input of controller is UFPI-FBG-UFPI；
(2) after control result is stablized, the wavelength shift Δ λ of FBGFBGWith the voltage variety Δ U of Measurement channelFBGRelationship
It indicates are as follows:
9. the optic fiber grating wavelength demodulation method according to claim 6 for preventing piezo actuator creep, which is characterized in that
Specific step is as follows for the step 3.1:
Data collecting card AO0 channel voltage is set as 0, AO1 channel voltage and gradually increases since 0V, and each increased amplitude is number
According to the minimum resolution voltage of capture card, during rising on the drive voltage, using the rule set up in step 1.3, start
flagFPIthIt counts, flagFPIthInitial value be 0；
Specific step is as follows for the step 3.2:
If the number of FBG is followed successively by 1,2,3 ... n in FBG array, the Wavelength demodulation sensitivity of n-th of FBG is SFBGn, corresponding control
Reference voltage value processed is UFPI-FBGn, corresponding wave crest edge number is NFPI-FBGn；
Work as flagFPIthEqual to NFPI-FBG1When, keep AO1 channel voltage constant, if voltage value at this time is UAO1-FBG1, stop
flagFPIthCounting, start simultaneously at according to the method in step 2.2, with UFPI-FBG1The output of AO0 is controlled for control a reference value
Voltage utilizes Wavelength demodulation sensitivity S after control result is stablizedFBG1, Wavelength demodulation is carried out to the 1st FBG according to formula (2)；
Specific step is as follows for the step 3.3:
(1) when carrying out subsequent FBG Wavelength demodulation, if the output voltage in the channel AO0 has reached U at this timeAO0-FBG1, ratio circuit
Proportionality coefficient is k, and enabling the voltage in the channel AO1 is UAO1-FBG1+kUAO0-FBG1, the voltage in the channel AO0 is reset and stopping control, simultaneously
The voltage in the channel AO1 is started to step up, each increased amplitude is the minimum resolution voltage of data collecting card；It is same with this
When, if NFPI-FBG1For number and the U of going up a slopeFPI-FBG1<UFPIthOr NFPI-FBG1For descending number and UFPI-FBG1>UFPIth, enable
flagFPIthFirst subtract 1 and then proceed to count, otherwise flagFPIthIt continues directly to count；
(2) strategy for using step 3.2 utilizes the corresponding control reference voltage of other FBG, wave crest edge number and Wavelength demodulation
The demodulation of corresponding FBG is completed in sensitivity；After completing the Wavelength demodulation of n-th of FBG, enabling the voltage in the channel AO1 is UAO1-FBGn
+kUAO0-FBGn, the voltage in the channel AO0 resets, and starts simultaneously at the voltage for being stepped up the channel AO1, each increased amplitude is data
The minimum resolution voltage of capture card；
Specific step is as follows for the step 3.4:
(1) when AO1 channel voltage reaches the maximum drive voltage U of settingAO1maxWhen, by the voltage and flag in the channel AO1FPIthClearly
0, and repeat the above steps 3；
(2) when expectation demodulates discontinuous FBG wavelength in FBG array, control reference voltage and wave crest edge need to only be numbered
It is sequentially arranged the corresponding value of FBG for expectation demodulation.
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