CN106771347A - A kind of frequency sweep type ultrasonic wind measurement method - Google Patents
A kind of frequency sweep type ultrasonic wind measurement method Download PDFInfo
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- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/24—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting acoustical wave
- G01P5/241—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting acoustical wave by using reflection of acoustical waves, i.e. Doppler-effect
- G01P5/242—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting acoustical wave by using reflection of acoustical waves, i.e. Doppler-effect involving continuous, e.g. modulated or unmodulated, waves
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Abstract
The invention discloses a kind of frequency sweep type ultrasonic wind measurement method, belong to technical field of wind power generation.The method, using the sine signal source of frequency consecutive variations, corresponding wind vector is calculated by the requency sampling fjlter for gathering from signal source, is effectively prevented from the influence to certainty of measurement such as temperature, noise.This method, using the sine signal source of frequency consecutive variations, corresponding wind speed is calculated by the requency sampling fjlter for gathering from signal source, and the method effectively reduces the difficulty and cost of wind velocity measurement system, improves the certainty of measurement of wind speed.The time for avoiding time difference method from surveying picosecond in wind speed circuit gathers, it is often more important that avoid the influence to certainty of measurement such as the introduced error of the very important time delay of ultrasonic drive circuit in time difference method and temperature, noise.Measure the cycle of the present invention is shorter, response speed very fast, and eliminates influence of the velocity of sound to certainty of measurement.
Description
Technical field
The present invention relates to a kind of frequency sweep type ultrasonic wind measurement method, belong to technical field of wind power generation.
Background technology
With developing rapidly for wind power industry, the introducing of adjustable-pitch wind energy conversion system group.Wind velocity signal is used as control system
The input variable of system carries out rotating speed and Power Control, and when wind speed is less than rated wind speed, unit can track best power curve,
Make unit that there is highest wind energy conversion efficiency；And when wind speed is higher than rated wind speed, the flexibility of transmission system should be increased, make machine
Group power output is more stablized.Because wind energy has uncertainty very high, therefore, want to control wind turbine power generation well, make
Follow the change of wind speed and obtain maximum power generation and reduces cost, just must accurately and timely measure wind speed, and to wind
Machine is controlled accordingly, therefore the accurate measurement of wind speed is basic link that wind-driven generator is controlled and optimizes.
The measuring instrumentss of wind speed, it is conventional to have mechanical and non-mechanical, wherein it is mechanical it is main have cup-shaped airspeedometer,
Wing airspeedometer, cup-shaped airspeedometer and wing airspeedometer are easy to use, but this class air speed measuring apparatus mechanical device volume compared with
Greatly, rotator inertia can cause hesitation, and response speed is slow, be adapted to the relatively low occasion of required precision；There are rotatable parts, easily
Produce abrasion；Mechanical structure may be subject to boisterous infringement, and sand and dust and salt fog can also cause corrosion to it；Due to friction
In the presence of, propeller or vane can not be driven to be rotated less than the wind speed of initiation value, therefore, less than the gentle breeze of threshold wind velocity
Measurement is will be unable to, larger measuring wind speed is only suitable for.The anemometer of non-mechanical mainly has temperature-sensitive anemometer and ultrasonic wave
Formula anemometer, wherein temperature-sensitive anemometer thermosensitive probe, the heat on thermal element is taken away based on cold shock gas, by a tune
The constant of switch element keeping temperature is saved, now electric current is adjusted and flow velocity is directly proportional.This adjusting method is in all directions air-flow
It is the accuracy that can influence measurement result to impact thermal element simultaneously, ultrasonic wind speed meter using ultrasonic wave in communication process, meeting
The flow rate information of fluid is loaded, these information separating treatments can be obtained into the flow velocity of fluid this feature surveys to wind speed
Amount.The current method of ultrasonic wind speed meter mainly has Doppler method, misfortune street method, time difference method.
The measuring method of ultrasonic wind speed meter is described in detail below：
(1) measuring principle of Doppler method is measured using the Doppler effect of sound wave, and Doppler effect is when hair
When having relative motion between emitter and receiver, the difference of the acoustic frequency for receiving acoustic frequency and transmitter of receiver and between the two
Relative velocity be directly proportional.When the rate of flow of fluid containing suspended particles or bubble is measured, launch many of ultrasonic signal
It is general Le frequency displacement be：
Δ f=fr-fs=2 × v × f × sin θ/C
Wherein Δ f：Doppler frequency shift
fr：Emission signal frequency
fs：Receive signal frequency
θ：Incidence angle
C:Ultrasonic signal spread speed in a fluid
V：Gas flow rate
Gas velocity can be obtained is：
Found out by above formula, gas flow rate is directly proportional to the spread speed of ultrasonic wave, and ultrasonic wave is in communication process, its speed
Degree is influenceed by external environment, can influence the accuracy of the measuring method.The method is only applicable to unpurified fluid measurement,
Be applied to measuring wind speed aspect and there is certain limitation, but this kind of method to the remolding sensitivity other method of change in flow well very
It is many.
(2) ultrasonic wave misfortune street flowmeter using ultrasonic wave phase demodulating mode detect toll bar misfortune street alternating change in flow this
One is theoretical and be made.When being measured to flow with phase difference, if transducer transmitting continuous ultrasound wave impulse or pulse
The cycle wave train more long, then just will produce phase difference when following current and adverse current are launched between receiver received signalWherein w=2 π f, w are angular frequency, and f is ultrasonic frequency, and Δ t is that two receivers are successively respectively received
The time difference.Phase difference method is conducive to improving the precision for measuring, because this method is micro- so as to avoid measurement by measuring phase difference
The small time difference, but the presence due to velocity of sound C in flow equation, therefore sonic velocity change will cause flow measurement error.
This kind of metering system is only applicable to pipeline gas flow-speed measurement, has certain office for open measuring wind speed
It is sex-limited.
(3) time difference method be the difference according to ultrasonic signal propagation time and adverse current propagation time come calculating speed,
Different expression form for the time difference can be divided into direct time difference method, phase difference method.In early stage ultrasonic flowmeter with direct
Time difference method is measured, and this method is applied to the larger duct survey of relative aperture, but temperature change influences than larger on it,
The development trend of direct time difference method is to improve accuracy of timekeeping and reduce certainty of measurement temperature influence.With entering for scientific and technological level
Step with development, and brand-new signal processing method research, the gas flow rate based on time difference method measure oneself through reach well
Highly.The continuous measurement ultrasonic waves of phase difference Bian receive signal when following current and adverse current are propagated between time difference, then by the time
Difference is converted to phase and measures.The method deficiency is affected by environment big, job insecurity.
Frequency sweep circuit be divided into frequency consecutive variations sine wave signal occur module, frequency difference acquisition module, frequency difference show and
Three parts of computing module.(1) wherein frequency consecutive variations sinusoidal signal occur module by master controller (SCM system or
ARM embedded systems) circuit is controlled, the part such as including 16 digit analog conversion circuits (DAC), voltage-frequency conversion circuit,
Major function produces the sine wave signal of frequency consecutive variations；(2) frequency difference acquisition module is by mixting circuit and bandwidth-limited circuit
Constitute, major function be by two different signals of amplitude equal frequencies by mixing and bandpass filtering after, finally give this two
The frequency difference signal of individual signal, the i.e. signal frequency are the difference on the frequency of the two signals, and amplitude is the amplitude product of the two signals；
(3) frequency difference to show and gather timing circuit, frequency difference pulse-scaling circuit, collection startup control circuit group by frequency difference with computing module
It is the beginning and end moment for controlling frequency difference to calculate into, major function, and calculates frequency difference value to be converted to wind speed information.
In general, the main operational principle of frequency sweep type ultrasonic air speed measuring apparatus be by frequency consecutive variations just
String ripple signal generating circuit produces the sinusoidal signal of frequency consecutive variations in the range of 90KHZ-110KHZ, amplitude to keep constant,
The signal is put on into ultrasonic wave transmitting terminal drive circuit so that the frequency signal that ultrasonic wave sends and receives no longer is intrinsic frequency
Rate but with the frequency signal of time consecutive variations.Afterwards, in synchronization collection ultrasonic receiver frequency different from transmitter
The signal of rate, and send into mixting circuit (multiplier) and band logical (or low pass) wave filter, can finally obtain ultrasonic transmitter with
Difference on the frequency between two signals of receiver, can be calculated by difference on the frequency and obtain wind vector (size and Orientation).
The air speed measuring apparatus commonly used in wind-driven generator at present mainly have cup anemometer, Pitot tube (or Pitot tube)
Anemobiagraph, hot line hot film anemometer, ultrasonic wind meter, LDV and particle imaging velocimetry etc..Wherein
It is relatively low, easy to use that cup anemometer possesses cost, and rotating speed and wind speed are substantially linear relationship, strong excellent of anti-high wind ability
Point.But because its mechanical device volume is larger, rotator inertia can cause hesitation, and response speed is slow, and precision is low, and rotatable parts
Abrasion is easily produced, mechanical structure may be subject to boisterous infringement, and sand and dust and salt fog can also cause corrosion to it.Due to rubbing
The presence of wiping, can not drive propeller or vane to be rotated less than the wind speed of initiation value, therefore, less than threshold wind velocity
Gentle breeze will be unable to measurement.After pipeline is connected, the pressure limit according to estimation is selected Pitot tube (or Pitot tube) anemobiagraph
The suitable Pitot tube of range.Pitot tube total head joint connects the high-pressure side of pressure sensor, and static pressure inlet connects the low of pressure sensor
Pressure side, air intake, leaving air temp are measured in the current stabilization area of airduct cross-section center.By the differential manometer test system of Pitot tube one
The ram compression value of wind speed is measured, then further according to wind speed and the relational expression of ram compression, corresponding air speed value is obtained.Based on its structure and work
Make principle, Pitot tube anemobiagraph has the advantages that simple structure, manufacture/easy to use, cheap, and is measuring wind higher
When fast, accuracy is high and good resolution.But it there is also obvious shortcoming, surveyed because it belongs to single-point, permanent contact
Amount, pitot hole is needed just to wind direction when using, and because its baroport size is smaller, instrument can produce disturbance to wind field in itself.
Secondly Pitot tube needs to measure the density of fluid surveying wind speed, and the change of the density with temperature of fluid and change, therefore to temperature
Output and the wind speed of the stricter Pitot tube of measurement request square be directly proportional, in addition when wind speed is relatively low, the pressure difference of generation
Small, the sensitivity of low wind speed section (being less than 10m/s) is low, it is difficult to accurate measurement, and it is not suitable for the measuring wind speed containing fume gases, makes
With by a definite limitation.The operation principle of hot line hot film anemometer is the thin metal much larger than thermal anemometer diameter by a length
Silk probe or the layer of metal thin-film component spread on glass material support are placed in wind field as sensing element, by electric current
Wire or metallic film are heated.When wind speed changes, the temperature of wire or metallic film also changes therewith, so as to change
Become its resistance value, the output signal that can obtain being monotonically correlated with wind speed using Wheatstone bridge.Due to its structure and specific reason
By the limitation hot line hot film anemometer of principle as a kind of contact type measurement, probe can be to the certain disturbance of measured stream field flow movable property life
And be must assure that in measurement to preferably orthogonal with airflow direction in the certain angle before probe of wind direction, if wind speed direction and spy
Pin measurement direction cannot measure reverse flow conversely, cannot then measure.Because there is oxidized and pollution asking in heater strip
Inscribe, and hot line is easily broken off, and to ensure the accuracy of its measurement, periodic maintenance need to be carried out to anemobiagraph with calibration.Metering system
It is a measurement, it is helpless to dynamic structure change information.Sensitivity reduces with the increase of wind speed, with obvious non-thread
Property.
For the development that some shortcomings of above air speed measuring apparatus are measured with ultrasonic wave fluid flow rate, ultrasonic wind speed
Measuring instrument because of it there is following advantage to be introduced in wind power industry：1. non-contact measurement is used, is not done substantially
Wind field is disturbed, no pressure loss, the scope of application is wider；2. due to no mechanical component, in the absence of mechanical wear, obstruction, ice
The problems such as jelly, long service life is lightweight；3. due to not having " machinery inertial ", sensitivity is high, can catch instantaneous wind speed small
Change.The dither composition in wind speed can be measured, the upper limit is not measured in theory, not require threshold wind velocity；4. it is easily achieved
The calculating of Digital output and flow, and time difference method overcomes the error that the velocity of sound is brought with change of fluid, the degree of accuracy is higher；⑤
It is convenient to install and maintain, it is not necessary to special valve, flange and bypass conduit etc., it is not necessary to interrupt wind field flowing.It is domestic at present ultrasonic
Method applied in ripple air speed measuring apparatus is time difference method, and time difference method is being propagated with contrary wind path with the wind using ultrasonic wave
Speed difference determines wind speed size, and speed difference is unable to direct measurement, be typically translated into ultrasonic wave with the wind with contrary wind path on
The time difference of propagation, but because this time difference is picosecond, therefore existing time module essence can be subject to when to time measurement
The influence of degree, and the circuit delay of ultrasonic drive circuit be can not ignore, it is necessary to accurate measurement and calculating, otherwise draw in time difference method
The error for entering can cause larger interference to measurement result, further, since measured value belongs to tiny signal, therefore temperature, noise etc.
Certainty of measurement is had a certain impact.In general, time difference method is relatively costly, and technical difficulty is big.
Therefore, the present invention proposes sweep-frequency Békésy audiometer measuring wind speed, measuring wind speed is really realized using difference on the frequency.By monolithic
The digital signal modulated DAC of machine output sixteen bit is changed into the voltage signal of consecutive variations, from piezo-electric effect, consecutive variations
Voltage signal is converted into the frequency of consecutive variations through voltage to frequency converter.At this moment ultrasonic sensor receive and send it is super
Sound wave is no longer the ultrasonic signal of fixed frequency, but the swept-frequency signal of 90KHZ to 110KHZ, a certain moment frequency acquisition is poor
Wind vector can be measured.Wind speed is surveyed by difference on the frequency, measure the cycle is short, fast response time, and eliminate the velocity of sound to measurement
The influence (identical with time difference method) of precision, because measured value is larger, therefore can well avoid temperature, noise etc. to measurement result
Influence, than by the time difference survey wind speed it is more accurate, error is smaller, and interference free performance is more preferable.Further, since not needing picosecond
Time measurement module, therefore, also than time difference method measuring circuit low cost on cost.
The content of the invention
It is an object of the invention to propose a kind of frequency sweep type ultrasonic wind measurement method, the method profit from signal source
With the sine signal source of frequency consecutive variations, corresponding wind vector is calculated by the requency sampling fjlter for gathering, the method is a kind of
The brand-new wind measurement method based on sweep method.It is effectively prevented from the influence to certainty of measurement such as temperature, noise.This method
Measure the cycle is short, fast response time, eliminates influence of the velocity of sound to certainty of measurement；Frequency sweeping method is in ultrasonic wind speed measuring instrument
Application.Method of the present invention utilizes the sine signal source of frequency consecutive variations from signal source, by the frequency for gathering
Difference calculates corresponding wind speed, and the method effectively reduces the difficulty and cost of wind velocity measurement system, improves the certainty of measurement of wind speed.
The time for avoiding time difference method (current ultrasonic surveys wind speed method) from surveying picosecond in wind speed circuit gathers, it is often more important that when avoiding
The shadow to certainty of measurement such as the introduced error of the very important time delay of ultrasonic drive circuit and temperature, noise in difference method
Ring.
The present invention realizes real frequency domain measurement, it is not necessary to measure picosecond time difference Δ t collections, its measure the cycle is shorter,
Response speed is very fast, and eliminates influence of the velocity of sound to certainty of measurement.
To achieve the above object, the technical solution adopted by the present invention is a kind of frequency sweep type ultrasonic wind measurement method, should
The implementation process of method is as follows：
Assuming that ultrasonic wave in atmosphere spread speed be VC, it is V to be tested wind speedf.The aerial spread speed meeting of ultrasonic wave
The air velocity superposition upward with air, if the direction of propagation of ultrasonic wave is identical with the direction of wind speed, then the speed of ultrasonic wave
Can accelerate be：Vc+Vf, otherwise if the direction of propagation of ultrasonic wave is in opposite direction with wind speed, the speed of ultrasonic wave can slow down, and be
VC-Vf, fixed by the distance between two ultrasonic sensors：
Wherein, L is the distance between ultrasonic wave reception and transmitter module, t1And t2Respectively down wind and upwind measurement
When transmitter module propagation time and receiver module propagation time.By VfUnderstand to obtain wind speed notice t1、t2, due to right
Time is measured as picosecond, therefore the difficulty of measurement is high, and common survey method precision is low, error is big.This method is by measurement
Difference on the frequency realizes wind speed measurement, it is to avoid picosecond time measurement.
If a pair of signals of ultrasonic sensor are C1 and C2, the signal C1 of ultrasonic sensor is made to send first, C2 connects
Receive.Now, the frequency signal that ultrasonic wave sends and receives is no longer using intrinsic frequency signal but uses with time consecutive variations
Swept-frequency signal.There is circuit (frequency sweep circuit) by the sine wave signal of frequency consecutive variations and produce frequency in 90KHZ-
The sinusoidal signal of consecutive variations in the range of 110KHZ, amplitude keeps constant, and the signal is put on into ultrasonic wave C1 for transmitting terminal drives
Dynamic circuit, it is transmission signal to drive ultrasonic wave C1.
As shown in figure 1, dotted line is C1 transmission signals, solid line is that C2 receives signal；t1For transmission signal C1 is sent to reception
The time difference of signal C2, f1It is any instant transmission signal C1, the instantaneous frequency difference f of reception signal C21=f '1-f′2, f '1,f′2
Be this moment transmission signal C1, receive the instantaneous frequency of signal C2, due to swept-frequency signal consecutive variations, its slope is K, K by
Signal generating circuit is set, and is known quantity, therefore, by K=f1/t1, obtain t1=f1/K。
Similarly, when ultrasonic sensor C2 is sent, and C1 is received, t is known2=f2/ K, as shown in Figure 2.Afterwards, by t1=f1/
K, t2=f2/ K is brought into formula (1)
Wherein f1, f2It is that down wind and upwind transmitting are poor with receives frequency, the difference on the frequency is surveyed by following methods
Amount.The signal feeding frequency mixer that synchronization will be gathered on ultrasonic sensor C1 and C2 carries out signal multiplication, there is sinusoidal signal
Productization and difference understand, mixer output signal is superimposed for C1 with the frequency of C2 and with frequency difference signal, afterwards, by mixed signal
Low-pass filtered device rejection frequency and signal, then obtain corresponding frequency difference signal f1Or f2, gathered back when C1 is sent when C2 is received
The frequency difference come is f1, it is f when C2 sends the frequency difference that collection is returned when C1 is received2。
Wind measurement method is to produce a digital triangular signal using singlechip CPU control counter, and DAC is realized will
Digital triangular wave is converted into the voltage signal of simulation triangular wave；The gradient of voltage triangles waveform is turned down, connected by voltage regulator circuit
It is continuous intensive；Voltage signal is converted to triangular wave frequency signal, i.e. swept-frequency signal by frequency-voltage conversion circuit, by ultrasonic wave
Drive circuit makes supersonic generator normal work；The ultrasonic signal that ultrasonic receiver is received filters sky through bandpass filtering
Clutter in gas, and frequency mixing circuit is sent into together with swept-frequency signal now after signal amplifies enhancing, then through low pass filtered
Ripple device be obtain ultrasonic wave from be transmitted into receive this period in difference on the frequency.
Brief description of the drawings
Fig. 1 ultrasonic wave forward direction transmission difference on the frequencies.
The reverse tranmitting frequency of Fig. 2 ultrasonic waves is poor.
Fig. 3 sweep-frequency Békésy audiometer flow rate measuring device structural representations.
Fig. 4 swept-frequency signals occur and frequency measuring block logic diagram.
Specific embodiment
It is an object of the invention to provide a kind of circuit structure is simple, simple installation, measurement result more precisely, need not enter
The ultrasonic wind speed detection means (sensor) of row picosecond time measurement.Another object of the present invention is to provide a kind of wind speed
The measuring method of wind direction, the method measurement process is easy, result is accurate.
In order to solve the problems existing in background technology, the present invention uses following technical scheme：
A kind of sweep-frequency Békésy audiometer wind speed measuring device, the device is made up of frequency sweep circuit and main controller circuit two parts, wherein
There is module, frequency difference acquisition module, frequency difference and show and computing module in sine wave signal of the frequency sweep circuit comprising frequency consecutive variations
Three modules.As shown in Figure 3.
Main controller circuit includes single-chip microcomputer (or ARM/STM32) controller, power control circuit, serial communication circuit.
The effect of main controller circuit be control swept-frequency signal module corresponding actions, the transmitting-receiving to ultrasonic wave module switch over control,
Difference on the frequency to obtaining is calculated to wind vector and external equipment is communicated.Instruction is powered and sent through master board,
Swept-frequency signal module sends the frequency sweep ultrasonic ripple that continuous sawtooth voltage signal sends sinusoidal waveform into supersonic generator
Signal, the ultrasonic signal that ultrasonic receiver is received has frequency with the ultrasonic signal that now supersonic generator sends
Difference, desired frequency difference signal is obtained by the two ultrasonic signals feeding mixing of synchronization and low-pass filter circuit, by
This can indirectly calculate the time difference of ultrasonic propagation, so that calculation of wind speed.
Single-chip microcomputer/ARM/STM32 controllers are used to carry out logic control with data calculating.
Power control circuit is each module for power supply.
Serial communication circuit realizes the communication (RS485 interfaces) with host computer.
Swept-frequency signal part
The specific module of swept-frequency signal circuit is as shown in figure 4, swept-frequency signal circuit includes the sine of frequency consecutive variations respectively
Ripple signal generating circuit, frequency difference Acquisition Circuit, frequency difference show and counting circuit.Effect is the sine wave by frequency consecutive variations
Signal generating circuit produces sinusoidal signal and its frequency consecutive variations in 90KHZ-110KHZ, and amplitude keeps constant so that super
The frequency signal that sound wave sends and receives no longer is intrinsic frequency but with the frequency signal of time consecutive variations.Synchronization is adopted
The ultrasonic frequency that collection ultrasonic receiver is received sends into frequency mixing circuit with the ultrasonic frequency of ultrasonic transmitter transmitting,
It is final to show that signal reaches the difference on the frequency in ultrasonic receiver this period from ultrasonic transmitter.
Circuit design of the embodiment with single-chip microcomputer as CPU
(1) there is circuit design in the sine wave signal of frequency consecutive variations
The major function that this partial circuit is realized is (STC15W408AS monolithics to be used in embodiment by single-chip microcomputer
Machine) digital analog converter (in embodiment use DAC8562) of control 16 carries out digital-to-analogue conversion final output sawtooth voltage letter
Number, original voltage signal is amplified and is raised by instrument amplifier amplifying circuit (AD620 is used in embodiment), coordinate
Linear voltage controlled oscillator (ICl8038 is used in embodiment) output frequency is the sine wave signal of 90KHZ-110KHZ, output frequency
Rate is directly proportional with corresponding input voltage size, and is driven into ultrasonic wave drive module.
Specific design circuit includes singlechip minimum system circuit, D/A change-over circuits, voltage amplifier circuit, V/F conversions
Circuit.
In embodiment, control circuit CPU selection single-chip microcomputer STC15W408AS, the single-chip microcomputer has strong interference immunity, height
The advantages of speed, reliability, low-power consumption, and crystal oscillator, reset circuit have been integrated with inside single-chip microcomputer, so STC15W408AS is only
Need normal work, the high speed SPI synchronous serial communication Interface Controller DAC8562 in controller STC15W408AS by power supply
Output.D/A converting circuit selects the voltage signal output of high-precision 16 DAC8562 chip sawtooth waveforms performance period.16
D/A conversion output be voltage saw tooth ripple signal, using sawtooth voltage signal now as V/F input voltage, it is defeated
Go out within the incomplete frequency range required for us of frequency.So needing to enter the output voltage of 16 D/A translation circuits
Row regulation.Voltage-regulation is carried out with amplifying circuit AD620 using instrument in the present embodiment.Finally, voltage-frequency conversion (V/F) circuit
Main Function be that the sine wave signal for linearly controlling as control signal frequency to change within the specific limits by voltage is exported.This
From ICL8038 as linear voltage controlled oscillator in embodiment, output sine wave, triangular wave, three kinds of signals of square wave may be selected, this
Ultrasonic wave drive module signal is sinusoidal signal in example.
(2) frequency difference Acquisition Circuit design
This partial circuit is mainly realized ultrasonic wave transmitting and is gathered while receiving signal, and two signals are sent into multiplication
Device carries out product and difference operation, and then low-pass filtered device obtains frequency difference signal, then obtains pulse signal through waveform shaping circuit
Iting has been shown that, and send into single-chip microcomputer carries out wind vector calculating.Specific design circuit include multiplier circuit, low-pass filter circuit,
Waveform shaping circuit.
In embodiment, multiplier only needs outer member trimming precision and stabilization using analog multiplier AD633JN, the chip
Property, X and Y input of the output overall error in the 2% of full scale, AD633JN are the inputs of difference high impedance, while there is the mark of 10V
Determine reference value and Z inputs carries out summation operation as gain.Low-pass filter circuit has selected low-pass filter MAX291,
MAX291 is 8 rank Butterworth type switched capacitor active low-pass filters of MAXIM companies production, and filtering performance is good, can
Make filtering characteristic closer to ideal.Afterwards, it is necessary to LPF output sinusoidal signal is converted into pulse signal, after facilitating
Continuous frequency counting and wind speed are calculated.Waveform shaping is realized using single limit comparator in embodiment.
(3) frequency difference Acquisition Circuit logic control
Frequency difference collection mainly realizes that the beginning and end sequential logic of frequency signal collection is very heavy with pulse counting method
Will.Come from the sawtooth voltage signal of DAC outputs in view of ultrasonic wave transmission signal in this example, using the decline of sawtooth waveforms
Edge starts to trigger, and the end time can just be controlled with single-chip microcomputer timer, and the T triggers in this example using digital circuit decline
Along triggering.Trigger is necessarily inverted to the state opposite with original state after each CLK clock signals effect, also just makes ultrasonic wave
Receiver module carries out a frequency counting every a sawtooth waveforms.
(4) frequency difference collection signal analysis
At present, the available wind speed of large-scale wind driven generator is in 7-25m/s, it is now assumed that the measurable most strong wind of ultrasonic sensor
Speed is 50m/s.The distance between two ultrasonic sensors are set as 30cm in this example.Swept frequency range L 90~110KHz it
Between change.The input range of 16 D/A conversion is 0-65535.
The duration for making the signal corresponding to each frequency is 1 μ s, the speed V of ultrasonic wavec=340m/s, then slope K
Can be calculated by formula (1)：
Transmitting (reception) signal period T is calculated by formula (2)：
T=1us × 66536=66.536ms (2)
As down wind wind speed VfDuring=50m/s, transmission time t1For：
At this moment the frequency difference for producing is just:
As upwind wind speed VfDuring=50m/s, transmission time t2For：
At this moment the frequency difference for producing is just:
Then checking inverse understands：Result is correct.
Among these, signal transmission time is 1ms or so (0.769~1.034ms), the remaining time for leaving signal acquisition for
For:
tc=T-t=66.5-1=65.5ms (7)
Namely at least t in the entire systemcThe time of=65ms can be used to gather signal.
Frequency difference signal now is the sinusoidal signal of 234.5~315.4Hz, and the counting to frequency can use cycle test method or survey
Frequency method is capable of achieving accurate measurement, is expanded as a example by 10 times by cycle test method, then in acquisition time tcIt is capable of achieving to collect in=65ms
The pulse number of frequency difference signal is 155~205.
Part material object has been carried out to foregoing circuit to build, test result has been obtained using oscillograph.Existing similar technique is
Ultrasonic wind speed measuring instrument based on time difference method, compared to the air speed measuring apparatus of time difference method, frequency sweep method proposed by the present invention surveys wind speed
Measuring method has certainty of measurement higher, and can eliminate influence of the extraneous factors such as temperature, noise to certainty of measurement.From
The sinusoidal signal of original fixed frequency is changed into the sinusoidal signal of frequency consecutive variations in fixed interval in signal source, is so led to
Cross frequency acquisition difference higher compared to the certainty of measurement of the measurement frequency difference of time difference using the measuring wind speed that frequency difference carries out correlation, this
Sample just improves certainty of measurement from signal source, and the transmitting of signal ultrasonic wave and reception signal additionally, due to collection are difference on the frequency
The interference signal in signal can thus be eliminated by subtraction, the frequency difference signal for so finally giving is also for relatively clearly
Clear sine wave, it is convenient to calculate display.
The present invention is also adopted by Multisim softwares and has carried out circuit simulation, frequency difference Acquisition Circuit is emulated, by pulse module
The count frequency of 74LS160 is controlled, the output of 74LS160 counter is connected with 138 decoders so that 138 being translated while counting
Thus code device Y0-Y7 ports are sequentially output useful signal to control variable connector per break-make all the way, realize the sinusoidal letter of output
Number frequency be in ladder propradation, and amplitude keeps constant, and thus as launching and receiving signal, the closure for switching J1 is controlled
System reception time standard, system acquisition frequency difference signal carries out product and difference operation and then will mix through multiplier when pressing switch J1
The frequency signal of conjunction filters high-frequency signal and has just obtained frequency difference by second-order low-pass filter, can also convert into pulse signal with side
Just count operation.
Frequency difference shows and counting circuit：The Main Function of this partial circuit is to carry out frequency difference to calculate display, and controls its
Start and terminate.Frequency is shown in the Multisim artificial circuits with calculating, because the frequency signal for receiving is a sawtooth
Ripple signal, the beginning of frequency counting circuit and timing circuit is triggered using the trailing edge for receiving signal, because work as receiving letter
Number when, frequency difference signal also just start produce.So triggered with trailing edge starting, this hour counter is started counting up, at the same time
Timer also begins to carry out subtracting counting and timing from 9, terminates and keeps count results to show when subtracting to count down to be counted when counting 3,
Timing proceeds to subtract counting until next trailing edge of the reception signal in the receiving circuit of ultrasonic wave module is come also just
It is to receive signal cut-off hour counter all to be reset with timer.Control section uses T triggers, often carrys out a trailing edge
Clock signal output signal overturns once, that is, shows once current frequency difference every a cycle.What counting circuit was used
It is two 74LS160 set associatives, count range is 0-99, can also be changed by changing the number of the chip of set associative as needed
Count range.Timing circuit is subtract counting timing by 74LS190 and additional pulse signal, specific timing time be by
Pulse frequency and count number and determine, this circuit does not terminate but when utilizing remaining subtracting at the end of timing to count
Between carry out display counting result, so convenient observation and record.
Claims (7)
1. a kind of frequency sweep type ultrasonic wind measurement method, it is characterised in that：The implementation process of the method is as follows, it is assumed that ultrasonic wave
Spread speed is V in atmosphereC, it is V to be tested wind speedf；The aerial spread speed of ultrasonic wave can be with the upward gas velocity of air
Degree superposition, if the direction of propagation of ultrasonic wave is identical with the direction of wind speed, then the speed of ultrasonic wave can accelerate be：Vc+Vf, instead
If ultrasonic wave the direction of propagation it is in opposite direction with wind speed, the speed of ultrasonic wave can slow down, and be VC-Vf, by two supersonic sensings
The distance between device is fixed：
Wherein, L is the distance between ultrasonic wave reception and transmitter module, t1And t2Respectively down wind and send out during upwind measurement
Penetrate the propagation time of module and the propagation time of receiver module；By VfUnderstand to obtain wind speed notice t1、t2；
If a pair of signals of ultrasonic sensor are C1 and C2, the signal C1 of ultrasonic sensor is made to send first, C2 is received；This
When, the frequency signal that ultrasonic wave sends and receives is no longer using intrinsic frequency signal but uses with the frequency sweep of time consecutive variations
Signal；Circuit occurs by the sine wave signal of frequency consecutive variations produces frequency continuously to become in the range of 90KHZ-110KHZ
The sinusoidal signal of change, amplitude keeps constant, and the signal is put on into ultrasonic wave C1 for transmitting terminal drive circuit, drives ultrasonic wave C1
It is transmission signal；
t1For transmission signal C1 is sent to the time difference for receiving signal C2, f1For any instant transmission signal C1, receive signal C2's
Instantaneous frequency difference f1=f1′-f2', f1′,f2' it is this moment transmission signal C1, the instantaneous frequency of reception signal C2, due to frequency sweep
Signal consecutive variations, its slope is K, and K is set by signal generating circuit, is known quantity, therefore, by K=f1/t1, obtain t1=f1/
K；
Similarly, when ultrasonic sensor C2 is sent, and C1 is received, t is known2=f2/K；Afterwards, by t1=f1/ K, t2=f2/ K brings into
In formula (1)
Wherein f1, f2It is that down wind and upwind transmitting are poor with receives frequency, the difference on the frequency is measured by following methods；
The signal feeding frequency mixer that synchronization will be gathered on ultrasonic sensor C1 and C2 carries out signal multiplication, there is the product of sinusoidal signal
Change and difference understands that mixer output signal is superimposed for C1 with the frequency of C2 and with frequency difference signal, afterwards, by mixed signal through low
Bandpass filter rejection frequency and signal, then obtain corresponding frequency difference signal f1Or f2, when C1 sends what collection when C2 is received was returned
Frequency difference is f1, it is f when C2 sends the frequency difference that collection is returned when C1 is received2。
2. a kind of frequency sweep type ultrasonic wind measurement method according to claim 1, it is characterised in that：Wind measurement method
It is to produce a digital triangular signal, DAC to realize for digital triangular wave being converted into simulation using singlechip CPU control counter
The voltage signal of triangular wave；Voltage regulator circuit turns the gradient of voltage triangles waveform down, continuous intensive；Voltage signal is through overfrequency
Rate voltage conversion circuit is converted to triangular wave frequency signal, i.e. swept-frequency signal, by ultrasonic drive circuit ultrasonic wave occurs
Device normal work；The ultrasonic signal that ultrasonic receiver is received filters clutter in air through bandpass filtering, and by signal
Frequency mixing circuit is sent into together with swept-frequency signal now after amplifying enhancing, then low-pass filtered device is to obtain ultrasonic wave from hair
It is mapped to the difference on the frequency received in this period.
3. a kind of frequency sweep type ultrasonic wind measurement method according to claim 1, it is characterised in that：Realize the method
Device is a kind of sweep-frequency Békésy audiometer wind speed measuring device, and the device is made up of frequency sweep circuit and main controller circuit two parts, wherein sweeping
There is module, frequency difference acquisition module, frequency difference and show and computing module three in sine wave signal of the frequency circuit comprising frequency consecutive variations
Individual module；
Main controller circuit includes singlechip controller, power control circuit, serial communication circuit；The effect of main controller circuit
Be control swept-frequency signal module corresponding actions, the transmitting-receiving to ultrasonic wave module to switch over control, to the difference on the frequency of acquisition to wind
Fast vector is calculated and external equipment is communicated；Instruction is powered and sent through master board, and swept-frequency signal module sends company
Continuous sawtooth voltage signal sends the frequency sweep ultrasonic ripple signal of sinusoidal waveform into supersonic generator, and ultrasonic receiver connects
The ultrasonic signal that receives has difference on the frequency with the ultrasonic signal that now supersonic generator sends, by synchronization the two
The mixing of ultrasonic signal feeding and low-pass filter circuit obtain desired frequency difference signal, thus can indirectly calculate ultrasonic wave biography
The time difference broadcast, so that calculation of wind speed.
4. a kind of frequency sweep type ultrasonic wind measurement method according to claim 3, it is characterised in that：Singlechip controller
It is used to carry out logic control with data calculating.
5. a kind of frequency sweep type ultrasonic wind measurement method according to claim 3, it is characterised in that：Power control circuit
It is each module for power supply.
6. a kind of frequency sweep type ultrasonic wind measurement method according to claim 3, it is characterised in that：Serial communication circuit
Realize the communication with host computer.
7. a kind of frequency sweep type ultrasonic wind measurement method according to claim 3, it is characterised in that：Swept-frequency signal circuit
The sine wave signal generation circuit including frequency consecutive variations, frequency difference Acquisition Circuit, frequency difference show and counting circuit respectively；Effect
It is to be connected in 90KHZ-110KHZ by the sine wave signal generation circuit generation sinusoidal signal of frequency consecutive variations and its frequency
Continuous change, amplitude keeps constant so that the frequency signal that ultrasonic wave sends and receives no longer is intrinsic frequency but connects with the time
The frequency signal of continuous change；The ultrasonic frequency that synchronization collection ultrasonic receiver is received and ultrasonic transmitter transmitting
Ultrasonic frequency sends into frequency mixing circuit, finally show that signal reaches ultrasonic receiver this period from ultrasonic transmitter
Interior difference on the frequency.
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