CN102636252A - Method and device for detecting precise arrival moment of ultrasonic wave - Google Patents

Abstract

The invention relates to a method and a device for detecting the precise arrival moment of an ultrasonic wave, and the method and the device are suitable for the application field of the high-precision ultrasonic detections, such as distance measurement, target tracking and positioning and flow detection. The method is based on a digital processing technology, and comprises the following steps: utilizing an A/D (analog to digital) converter to collect ultrasonic data, dynamically determining decision threshold levels reached by ultrasonic signals according to the characteristics of ultrasonic waveforms, and accurately calculating the arrival moment of the ultrasonic wave by utilizing a linear fitting method. The detection on the nanosecond stage precision can be realized through simple research and arithmetical operation at the low sampling rate. The invention provides the detection method with low calculation amount and high precision for high-precision ultrasonic detections, such as distance measurement, target tracking and positioning and flow detection.

Description

A kind of ultrasound wave arrives method and the device that accurately detects constantly

Technical field

The present invention relates to a kind of ultrasound wave and arrive method and the device that accurately detects constantly, be specifically related to a kind of method and device that needs to detect the ultrasound wave due in based on hyperacoustic range finding, track and localization, flow detection etc.

Background technology

In based on parameter measurements such as the distance of ultrasonic technology, flow, location, liquid level, temperature, need accurate the measurement transmission time of ultrasound wave in medium usually, realize measured measurement thereby convert directly or through engineering.Transmission time is the travel-time that transmitter ultrasonic waves transmitted signal arrives receiver, and ultrasonic emitting can be passed through inner synchronousing signal, infrared signal or radiofrequency signal constantly and produce.Traditional fixed threshold relative method comprise single threshold method and dual threshold method; The basic thought of fixed threshold is that fixing threshold level (threshold value) is set, and when the ultrasonic signal that receives surpasses this threshold level, thinks that then ultrasound wave arrives; It is thus clear that; The threshold value relative method is based on the method that amplitude of ultrasonic detects, and guarantee its accuracy of detection, needs to guarantee that the ultrasonic signal amplitude that receives is constant basically.And in the practical application, receive the density, temperature of transmission medium, the influence of factor such as flow, bigger to the decay of ultrasonic signal; Its changes in amplitude is bigger; Even adopt automatic gain adjustment circuit, also be difficult to realize high Precision Detection, therefore lower based on the detection method precision of fixed threshold.Based on transit time (TOF:time of flight) algorithm for estimating such as related function, wavelet transformation and two indexes, calculated amount is big, and sampling rate of having relatively high expectations and processing capability in real time, and precision is difficult to guarantee.In practical engineering application, the amplitude factor that influences ultrasound wave reception signal is more, causes the changes in amplitude of ultrasonic signal bigger, studies a kind of ultrasound wave due in detection method and device that has nothing to do with the variation of reception signal amplitude and has actual application value.

Summary of the invention

Based on this; The present invention utilizes digital processing technology; Receive the signal waveform characteristic based on ultrasound wave, in ultrasound data, find the invariant feature point of ultrasound wave waveform, confirm that dynamically ultrasound wave arrives the judgement threshold level; Utilize line fitting method accurate Calculation ultrasound wave due in, the detection method that a kind of calculated amount is low, precision is high is provided for high-precision ultrasonics such as range finding, target following location, flow detection detect.

The purpose of this invention is to provide a kind of high-precision ultrasound wave due in detection method and device, in based on practical applications such as ultrasonic ranging, track and localization, flow measurement, level gaugings, improve the accuracy of detection of ultrasound wave due in.

The present invention adopts infrared signal as synchronizing signal, receive receive infrared signal with treating apparatus after, by receiving with the processor control A/D converter continuous acquisition data of treating apparatus and be stored in the storer, and carry out the calculating of ultrasonic signal due in.

The present invention provides a kind of ultrasound wave to arrive the device that accurately detects constantly, comprising:

(1) ultrasonic infrared launcher

Comprise ultrasound-driven device, ultrasound emission sensor, infrared driving device, infrared transmitting tube, first microprocessor (MCU) and power supply.

Infrared and ultrasound emission all adopts pulsed drive, and infrared pulse adopts burst pulse, and pulse width range is 5～10 μ s, adopts the triode current drives.

The ultrasound-driven device adopts pulse transformer to drive; The ultrasonic pulse width is the half the of ultrasonic signal cycle; The ultrasound emission sensor is a capacitance type transducers, constitutes the shunt-resonant circuit with transformer secondary output, requires the inductance of transformer secondary output and the electric capacity of sonac to satisfy condition of resonance.

First microprocessor mainly produces infrared pulse signal, ultrasonic pulsative signal and timing signal, adopts low pin, low performance single-chip microcomputer, like 8 pin single-chip microcomputers such as PIC12F508, PIC12F629.

Infrared and ultrasound wave transmit simultaneously, because infrared with light velocity propagation, the travel-time can be ignored, therefore with infrared signal as the reception synchronizing signal, begin to gather ultrasonic signal after receiving infrared signal.

Power supply adopts single-unit AA battery, produces the 5V direct supply to other device power supplies with booster circuit.

(2) reception and treating apparatus

Comprise ultrasonic reception and amplification, infrared reception and amplification, A/D converter, power supply, second microprocessor and storer.

Ultrasonic reception and amplification comprise ultrasonic receiving sensor, ultrasonic multiplying arrangement, ultrasonic gain control.

The centre frequency of ultrasonic receiving sensor is 40KHz, and ultrasonic multiplying arrangement adopts the single supply low noise operational amplifier.Ultrasonic gain control is according to the ultrasonic signal amplitude that receives; Produce control signal and control the parameter of ultrasonic multiplying arrangement; Realization prevents because of the excessive or too small accuracy of detection that influences the ultrasound wave due in of ultrasonic signal the automatic control of the gain of ultrasonic signal.

Infrared reception and amplification comprise infrared receiving tube, infrared multiplying arrangement, infrared gain control.

Second microprocessor to infrared sampling, receives the center of data through judging infrared pulse through A/D converter, confirms infrared due in, with the synchronizing signal of this due in as the ultrasonic signal collection.

Infrared multiplying arrangement adopts the single supply low noise operational amplifier.Infrared gain control produces the parameter that control signal is controlled infrared multiplying arrangement according to the infrared signal amplitude that receives, and realizes the automatic control of the gain of infrared signal is prevented because of the excessive or too small accuracy of detection that influences system of infrared signal.

A/D converter adopts two A/D converters or a double channel A/D converter, and the highest SF reaches 1MSPS, single power supply.

Second microprocessor adopts DSP, ARM, FPGA or high-performance single-chip microcomputer, and instruction execution speed surpasses 10MIPS.

Supply unit can adopt powered battery or 220V Alternating Current Power Supply, needs to produce 5V power supply and the required supply voltage of microprocessor, like 3.3V, and 1.8V etc.

Infrared and the ultrasonic signal that memory stores is gathered, capacity is confirmed according to the distance of emitter and reception and treating apparatus and the sampling rate of setting.

The present invention provides a kind of ultrasound wave to arrive the method that accurately detects constantly, comprising:

After (1) second microprocessor (DSP, ARM, FPGA or high-performance single-chip microcomputer) is received infrared signal; Control A/D converter continuous acquisition ultrasonic signal; Obtain required ultrasound data, said ultrasound data is stored in the data-carrier store, storage space is Buf;

(2) the continuous acquisition ultrasound data and store after, in whole storage space Buf,, find the peak point in each ultrasound wave cycle by in the past backward sequential search, set storage space B _High, numerical value and this numerical value of each peak point is stored in storage space B in the address of storage space _HighIn;

(3) at B _HighInterior maximum of points by the past sequential search ultrasonic signal backward, its numerical value is designated as V _Max, the address is designated as V _Maxad

(4) at B _HighInterior by the past sequential search backward, judging before the maximum of points has several ultrasonic signal peak points, and the peak point number scale is N _h, N wherein _hContain maximum of points, N _hThe expression peak value is counted;

(5) threshold level value V is set _Th=V _Max/ N _h, in storage space Buf, search for first greater than V _ThPeak point, be designated as V _Com

(6) in storage space Buf, from V _ComSearch obtains former and later two sampled points of first zero crossing backward, uses P respectively ₁, P ₂Expression, the numerical value and the memory address of preserving two sampled points are designated as V respectively ₁, V ₂And AD ₁, AD ₂, AD ₂=AD ₁+ 1, be expressed as with the time: P ₁(t ₁, V ₁), P ₂(t ₁+ T _s, V ₂), wherein, t ₁Expression P ₁The point due in, T _sThe expression sampling period, t ₁=AD ₁T _s, V ₁>=0, V ₂＜0 or V ₁＞0, V ₂≤0;

(7) P is passed through in definition ₁, P ₂2 the straight line and the intersection point of time shaft are the ultrasound wave due in, are designated as t _Com, utilize P ₁, P ₂2 sampled value and memory address adopt line fitting method to get

$\frac{t_{\mathrm{com}}-t_1}{T_S}=\frac{V_1}{V_1-{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000697861700032.png"\; state="\{\{state\}\}">V</figure-callout>}}_2}$

T wherein _ComExpression ultrasound wave due in is with t ₁=AD ₁T _sBringing following formula into gets

$t_{\mathrm{com}}=({\mathrm{AD}}_1+\frac{V_1}{V_1-V_2})\&CenterDot;T_s=({\mathrm{AD}}_1+\frac{1}{1-{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000697861700032.png"\; state="\{\{state\}\}">V</figure-callout>}}_2/V_1})\&CenterDot;T_s$

Through step (1)～(7), only, just can detect ultrasound wave due in t through search and simple calculating to storage space _Com

The invention has the advantages that: it is relative value that ultrasound wave arrives decision threshold level, is directly proportional with ultrasonic signal is peaked, avoids the use of the influence that the fixed threshold level receives signal amplitude.The method that the present invention proposes is only through simple search and mathematical operation; Under 6 times of signal sampling rate conditions; Detect error and be lower than 100 nanoseconds (ns), a kind of calculated amount is low, the high-precision test method for the detection of high-precision ultrasonics such as range finding, target following location, flow detection provides.

Description of drawings

Figure 1A is ultrasonic infrared launcher synoptic diagram

Figure 1B is for receiving and the treating apparatus synoptic diagram

Fig. 2 A reaches peaked ultrasound wave waveform at 6 cycles

Fig. 2 B reaches peaked ultrasound wave waveform at 5 cycles

Fig. 3 A reaches the accurate detection method constantly of peaked ultrasound wave arrival 6 cycles to describe oscillogram

Fig. 3 B reaches the accurate detection method constantly of peaked ultrasound wave arrival 5 cycles to describe oscillogram

Fig. 4 calculates synoptic diagram for due in

Fig. 5 is the error analysis oscillogram

Fig. 6 is the error change curve

Embodiment

The present invention provides a kind of ultrasound wave to arrive the method that accurately detects constantly, and its key step comprises:

(1) required ultrasound data and the storage of microprocessor (single-chip microcomputer, DSP, ARM) control A/D converter continuous acquisition;

(2) at whole ultrasonic signal storage space search, find the peak point in each ultrasound wave cycle, open up the numerical value and its address of each peak point of storage space storage at storage space;

(3) in step (2), search for the maximum of points that obtains ultrasonic signal in the storage space of peak point;

(4) search in the storage space of peak point in step (2) confirms to arrive maximum of points previous peaks point number (containing maximum of points);

(5) according to the peak point number before peaked amplitude and the arrival maximal value, confirm the threshold level value, first memory location of search in the data space that step (1) is stored greater than threshold level;

(6) search for backward from first memory location, confirm former and later two ultrasound datas of first zero crossing greater than threshold level;

The numerical value and the memory address of two ultrasound datas that (7) obtain according to step (6) are utilized line fitting method, just can accurately calculate the ultrasound wave due in.

In conjunction with accompanying drawing 1～6 embodiment of the present invention is described.

(1) ultrasonic data acquisition and storage

Ultrasound data is through acquisition system collection and storage, and data acquisition system (DAS) is a core with microprocessor MCU (single-chip microcomputer, DSP, ARM, FPGA etc.), and theory diagram is as shown in Figure 1, and Figure 1A is the emitter synoptic diagram, and Figure 1B is for receiving and the harvester synoptic diagram.Among Figure 1A, infrared and ultrasonicly transmit simultaneously, because infrared signal is with light velocity propagation, the travel-time can be ignored, therefore, in the system with infrared signal as the reception synchronizing signal, begin to gather ultrasonic signal after receiving infrared signal.A/D converter is the parallel A/D converters of 4 path 10 bit among Figure 1B, and the high sampling rate of single channel is 4MSPS (million samples per second), and the signal input voltage scope is 0～5V.A/D converter is configured to dual channel mode, handles ultrasonic respectively and infrared signal.Infrared and ultrasound emission all adopts pulsed drive; Infrared pulse adopts burst pulse, and pulse width range is 5～10 μ s, and drive unit adopts the triode current drives; Acquisition Circuit is passed through A/D converter to infrared sampling; The second microprocessor MCU in reception and the harvester receives the center of data through judging infrared pulse, confirms infrared due in, with the benchmark of this moment as the ultrasonic signal timing.Ultrasonic transmitter adopts pulse transformer to drive, and the ultrasonic pulse width is the half the of ultrasonic signal cycle.When taking multiple measurements; The second microprocessor MCU in reception and the harvester obtains the amplitude of ultrasonic signal through A/D converter; During follow-up measurement; According to amplitude the self-adaptation adjustment is carried out in the gain of ultrasonic circuit, signal too little (signal to noise ratio (S/N ratio) is low) saturation distortion appears or in the signal of avoiding receiving.

Data acquisition system (DAS) shown in Figure 1, emitter are launched ultrasonic and infrared signal simultaneously, and the ultrasonic signal frequency is 40KHz, and the infrared signal that receiver receives is a single pulse signal, and the typical waveform that receives ultrasonic signal is shown in Fig. 2 A, Fig. 2 B.Under the prerequisite that ultrasonic receiving sensor sensitivity is confirmed; The waveform that receives is different because of the incident angle that transmits, and excited vibration arrives the asynchronism(-nization) of peak-peak, and Fig. 2 provides two kinds of typical ultrasonic signals; Fig. 2 A is the ultrasonic oscillogram that 6 cycles reaches peak-peak; Peak-to-peak value is about 2.7V, and Fig. 2 B is the ultrasonic oscillogram that 5 cycles reaches peak-peak, and peak-to-peak value is about 1.6V.

Because the amplitude and the waveform character of the ultrasonic signal that receives receive ultrasonic propagation distance, temperature, humidity and receiving angle to influence bigger.Traditional single threshold and dual threshold relative method judgement ultrasound wave due in only basis signal amplitude are judged, fixing level is set, and when the signal that receives surpasses this level, think that then ultrasound wave arrives, and signal amplitude is different, and its due in is also different.Obviously; Signal amplitude has directly determined the accuracy of detection of ultrasound wave due in; And in the practical application, be difficult to guarantee that the amplitude of ultrasonic signal remains unchanged, like the ultrasonic signal waveform among Fig. 2; Therefore, adopt the single threshold of fixed threshold level and the high Precision Detection that the dual threshold relative method can't realize the ultrasound wave due in.

If the sampling period of A/D converter is T _s, SF is f _s, ultrasonic signal is f frequently _c=40KHz.After the second microprocessor MCU in reception and the harvester received infrared synchronizing signal, continuous acquisition was also stored ultrasonic signal, and storage space is Buf.

Search in order in whole ultrasonic signal storage space, find the peak point in each ultrasound wave cycle, in Fig. 3, represent, and set storage space B with " " _HighStore the numerical value and its address of each peak point at storage space.

At B _HighIn search in order, find the maximum of points of ultrasonic signal, be designated as V _Max, its address is designated as V _Maxad, as shown in Figure 3.

At B _HighIn search in order, judge to arrive that several peak points, peak point number scale to be arranged before the ultrasonic signal maximum of points be N _h, peak value points N wherein _hComprise maximum of points.

Ultrasonic signal waveform among Fig. 2 A is handled N by above-mentioned steps _h=6.

Ultrasonic signal waveform among Fig. 2 B is handled N by above-mentioned steps _h=5.

Ultrasound wave arrives judges confirming of threshold level: adopt the threshold level of fixed proportion a ultrasound wave cycle even bigger error can occur surpassing; Like two ultrasonic waveforms of typical case among Fig. 2; If adopt the identical ratio of signal amplitude peak relatively separately, the error of one-period will appear.Therefore, the ratio of confirming dynamic threshold is a key of problem.

In Fig. 2, the peak point in each ultrasound wave cycle is with " " expression, and " * " representes the changing value (being equivalent to velocity variations) in each last relatively cycle of cycle peak point among the figure.Because first cycle ultrasonic signal amplitude is less, and change lessly, characteristic is not obvious.Second period ultrasonic signal characteristic is obvious, and present embodiment is realized the detection of ultrasound wave due in through the ultrasonic signal that detects second period.Changing largest peaks among Fig. 2 A is the peak value in the 4th cycle; Changing minimum peak point is the peak value and the peak-peak place in the 1st cycle; Waveform among Fig. 2 A arrives the peak-peak place need can extrapolate the 1st peak value less than 1/6 of peak-peak, and the 2nd cycle peak value be greater than 1/6 of peak-peak through 6 cycles; Therefore, 1/6 threshold level as the ultrasound wave due in of peak-peak is set.

Ultrasonic signal wave form varies largest peaks is the peak value in the 3rd cycle among Fig. 2 B; Changing minimum peak point is the peak value and the peak-peak place in the 1st cycle; Ultrasonic signal waveform arrival peak-peak place need can extrapolate the 1st peak value less than 1/5 of peak-peak, and the 2nd cycle peak value be greater than 1/5 of peak-peak through 5 cycles among the 2B; Therefore, 1/5 threshold level as the ultrasound wave due in of peak-peak is set.

General rule is: if ultrasonic vibration is to the N that needs of peak-peak _hIn the individual cycle (containing the maximal value cycle), peak-peak is V _Max, threshold level value V then is set _Th=V _Max/ N _h

N in Fig. 2 A _h=6, threshold level V then _Th=V _Max/ 6.

N in Fig. 2 B _h=5, threshold level V then _Th=V _Max/ 5.

The 1st zero crossing that defines all after dates of the 2nd ultrasound wave utilizes two sampled datas of zero crossing front and back as the ultrasound wave due in, calculates due in through following method.

(6) in the Buf storage space, from V _ComSearch obtains former and later two neighbouring sample points of first zero crossing backward, uses P ₁, P ₂Expression, the numerical value and the memory address of preserving two sampled points are designated as V respectively ₁, V ₂And AD ₁, AD ₂, AD wherein ₂=AD ₁+ 1.Represent P with the time ₁(t ₁, V ₁), P ₂(t ₁+ T _s, V ₂), t wherein ₁=AD ₁T _s, V ₁＞0, V ₂＜0, as shown in Figure 4, P among Fig. 4 ₀Zero crossing for actual signal.

(7) P is passed through in definition ₁, P ₂2 the straight line and the intersection point of time shaft are the ultrasound wave due in, are designated as t _ComUtilize P ₁, P ₂2 sampled value and memory address are calculated due in through following method.

$\frac{t_{\mathrm{com}}-t_1}{T_S}=\frac{V_1}{V_1-V_2}---\left(1\right)$

With t ₁=AD ₁T _sBringing following formula into gets

$t_{\mathrm{com}}=({\mathrm{AD}}_1+\frac{V_1}{V_1-V_2})\&CenterDot;T_s=({\mathrm{AD}}_1+\frac{1}{1-{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HSA00000697861700032.png"\; state="\{\{state\}\}">V</figure-callout>}}_2/V_1})\&CenterDot;T_s---\left(2\right)$

Through step (1)～(7), only, just can detect ultrasound wave due in t through search and simple calculating to storage space _Com

If known T _s=1/680KSPS=1.470588 μ s is to the ultrasonic signal waveform of Fig. 2 A, N _h=6, through above-mentioned steps, calculate t _Com=998.8649*T _s=1468.9190 μ s, accurate detecting method describe oscillogram shown in Fig. 3 A.

If known T _s=1/680KSPS=1.470588 μ s is to the ultrasonic signal waveform of Fig. 2 B, N _h=5, through above-mentioned steps, calculate t _Com=1330.6105*T _s=1956.7798 μ s, accurate detecting method describe oscillogram shown in Fig. 3 B.

Can know ultrasonic propagation time t by formula (2) _ComWith P ₁Memory address, V ₂/ V ₁And the sampling rate of system decision.Because V ₁And V ₂The error that causes has same nature, and being divided by through the two (is V ₂/ V ₁), the t that causes thus _ComError can be offset, below among the embodiment, calculate P ₁With the influence of the variable in distance of zero crossing and different sample rate to the due in error of calculation.

Easy for analyzing, ultrasonic signal is represented with first sinusoidal wave periodic waveform, as shown in Figure 5.Former and later two neighbouring sample points of zero crossing P ₁, P ₂Being expressed as the displacement form is P ₁(x ₁, V ₁), P ₂(x ₂, V ₂), through P ₁, P ₂The intersection point of 2 straight line and x axle is P (x, 0), is defined as the zero crossing that calculates.Easy for computational analysis, suppose the coordinate P of actual zero crossing ₀π-2 π f can be known in (π, 0) _cT _s≤x ₁≤π, π≤x ₂≤π+2 π f _cT _s, T wherein _sBe the sampling period.

Based on formula (2), can get

$x=x_1+\frac{V_1\&CenterDot;{2\mathrm{\&pi;f}}_c{T}_s}{V_1-V_2}---\left(3\right)$

Wherein, x ₁Be P ₁The point displacement, x ₂Be P ₂The point displacement, x is P ₁And P ₂The displacement of some line and x axle intersection point, f _cBe the ultrasonic signal frequency.

Because P ₁, P ₂Also be the point on the ultrasonic signal curve (sinusoidal waveform among Fig. 5) simultaneously, can get

V ₁＝sin(x ₁) (4)

V ₂＝sin(x ₂)＝sin(x ₁+2πf _cT _s) (5)

Formula (4), (5) are brought in the formula (3), can get

$x=x_1+\frac{\sin \left(x_1\right)\&CenterDot;{2\mathrm{\&pi;f}}_c{T}_s}{\sin \left(x_1\right)-\sin (x_1+{2\mathrm{\&pi;f}}_c{T}_s)}$

$=x_1-\frac{\sin \left(x_1\right)\&CenterDot;{\mathrm{\&pi;f}}_c{T}_s}{\cos (x_1+{\mathrm{\&pi;f}}_c{T}_s)\&CenterDot;\sin \left({\mathrm{\&pi;f}}_c{T}_s\right)}---\left(6\right)$

The zero crossing that calculates according to formula (6) and the error delta of actual zero crossing do

$\mathrm{\&Delta;}=\mathrm{\&pi;}-x=\mathrm{\&pi;}-x_1+\frac{\sin \left(x_1\right)\&CenterDot;{\mathrm{\&pi;f}}_c{T}_s}{\cos (x_1+{\mathrm{\&pi;f}}_c{T}_s)\&CenterDot;\sin \left({\mathrm{\&pi;f}}_c{T}_s\right)}---\left(7\right)$

If ultrasonic signal frequencies is f _c=40KHz establishes sample rate f _s=N*f _c, N is an integer.As N ∈ [4,8], x ₁∈ [0, π] obtains Δ with sampling period T according to formula (7) _sAnd x ₁The curve that changes, as shown in Figure 6.

Can know the last sampled point P of zero crossing from Fig. 6 ₁Apart from the zero crossing distance is π, pi/2, and 0 time error Δ is 0.When N=4, error delta is less than 0.3 μ s, and when N=7, then error delta is less than 50ns, and the detection algorithm precision that visible present embodiment proposes is higher, and along with the increase of sampling rate, error reduces gradually, and precision increases gradually.

The present invention utilizes the A/D sampled data, through search ultrasonic signal maximal value, reaches the periodicity of maximal value process according to ultrasonic signal, confirms the threshold level that ultrasonic arrival is judged, and then calculates the ultrasound wave due in through line fitting method.The threshold level that this method adopts is a relative value, is directly proportional with ultrasonic signal is peaked, avoids the use of the influence that the hyperacoustic arrival of fixed threshold level judging receives signal amplitude, is defined as the dynamic threshold method.The method that the present invention proposes is only through simple search and mathematical operation; Under 6 times of signal sampling rate conditions; Detect error and be lower than 100 nanoseconds (ns), a kind of calculated amount is low, the high-precision test method for the detection of high-precision ultrasonics such as range finding, target following location, flow detection provides.

The above is merely preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of within spirit of the present invention and principle, being made, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. a ultrasound wave arrives the method that accurately detects constantly, it is characterized in that, comprising:

(1) microprocessor control A/D converter continuous acquisition ultrasound data is set the ultrasound data storage space, and said ultrasound data is stored in the said ultrasound data storage space;

(2) search in order at whole ultrasonic wave datum storage space, find the peak point in each ultrasound wave cycle, set the peak point storage space, the numerical value and its address of said each peak point of peak point storage space storage at storage space;

(3) in step (2), search in the peak point storage space, obtain the maximum of points of ultrasonic signal;

(4) search in the peak point storage space in step (2), definite number that arrives maximum of points previous peaks point;

(5) according to the amplitude of said maximum of points and the number of said arrival maximum of points previous peaks point, confirm the threshold level value, first ultrasound data memory location of search in said ultrasound data storage space greater than said threshold level value;

(6) from said first ultrasound data memory location search backward in order, obtain first zero crossing greater than said threshold level value, and former and later two ultrasound datas that close on said first zero crossing most;

The numerical value and the memory address of said two ultrasound datas that (7) will obtain calculate the ultrasound wave due in line fitting method.

2. the method for claim 1 is characterized in that: adopt dynamic threshold level judging ultrasound wave due in.

3. the method for claim 1 is characterized in that: confirm dynamically according to the number in ultrasound wave cycle of the maximum of points that arrives said ultrasonic signal that ultrasound wave arrives and judge threshold level.

4. the method for claim 1, it is characterized in that: first zero crossing that calculates and the error delta between the actual zero crossing do

$\mathrm{\&Delta;}=\mathrm{\&pi;}-x=\mathrm{\&pi;}-x_1+\frac{\sin \left(x_1\right)\&CenterDot;{\mathrm{\&pi;f}}_c{T}_s}{\cos (x_1+{\mathrm{\&pi;f}}_c{T}_s)\&CenterDot;\sin \left({\mathrm{\&pi;f}}_c{T}_s\right)},$

Wherein, x ₁Be zero crossing P ₀First sampled point P before ₁The point displacement, x ₂Be zero crossing P ₀First sampled point P afterwards ₂The point displacement, x is P ₁And P ₂The displacement of some line and time shaft intersection point, f _cBe ultrasonic signal frequency, T _sBe the sampling period.

5. the method for claim 1, it is characterized in that: said ultrasonic signal frequency is greater than 20KHz.

6. a data acquisition system (DAS) is characterized in that, comprising:

Emitter and reception and treating apparatus;

Said emitter comprises first microprocessor, ultrasound-driven device, ultrasound emission sensor, infrared driving device and infrared transmitting tube;

Said reception and treating apparatus comprise second microprocessor, ultrasonic A/D converter, infrared A/D converter, ultrasonic gain control, infrared gain control, ultrasonic multiplying arrangement, infrared multiplying arrangement, ultrasonic receiving sensor, infrared receiving tube and storer;

Said second microprocessor is controlled ultrasonic A/D converter continuous acquisition ultrasound data, in storer, sets the ultrasound data storage space, and said ultrasound data is stored in the ultrasound data storage space; Second microprocessor finds the peak point in each ultrasound wave cycle in the search of whole ultrasonic wave datum storage space, sets the peak point storage space, the numerical value and its address at storage space of said each peak point of peak point storage space storage; Second microprocessor is searched in the peak point storage space, obtains the maximum of points and the number of confirming to arrive maximum of points previous peaks point of ultrasonic signal; According to the amplitude of said maximum of points and the number of said arrival maximum of points previous peaks point, confirm the threshold level value, first ultrasound data memory location of search in said ultrasound data storage space greater than said threshold level value; From said first ultrasound data memory location search backward in order greater than said threshold level value, obtain first zero crossing, and former and later two ultrasound datas that close on said first zero crossing most; The numerical value and the memory address of said two ultrasound datas that obtain are calculated ultrasound wave arrival accurately constantly with line fitting method.

7. system as claimed in claim 6 is characterized in that: adopt dynamic threshold level judging ultrasound wave due in.

8. system as claimed in claim 6 is characterized in that: confirm dynamically according to the number in ultrasound wave cycle of the maximum of points that arrives said ultrasonic signal that ultrasound wave arrives and judge threshold level.

9. system as claimed in claim 6 is characterized in that: first zero crossing that calculates and the error delta between the actual zero crossing do

$\mathrm{\&Delta;}=\mathrm{\&pi;}-x=\mathrm{\&pi;}-x_1+\frac{\sin \left(x_1\right)\&CenterDot;{\mathrm{\&pi;f}}_c{T}_s}{\cos (x_1+{\mathrm{\&pi;f}}_c{T}_s)\&CenterDot;\sin \left({\mathrm{\&pi;f}}_c{T}_s\right)},$

Wherein, x ₁Be zero crossing P ₀First sampled point P before ₁The point displacement, x ₂Be zero crossing P ₀First sampled point P afterwards ₂The point displacement, x is P ₁And P ₂The displacement of some line and time shaft intersection point, f _cBe ultrasonic signal frequency, T _sBe the sampling period.

10. system as claimed in claim 6 is characterized in that: said ultrasonic signal frequency is greater than 20KHz.

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