CN101813515B - Method and device for precisely measuring ultrasonic wave transmission time - Google Patents

Abstract

The invention relates to a method and a device for precisely measuring ultrasonic wave transmission time. The method adopts two ultrasonic wave transducers A and B, a hardware circuit and a software subdivision algorithm. The hardware circuit mainly comprises an ultrasonic wave transducer drive circuit, an ultrasonic wave return signal filter circuit, an amplification circuit and a signal processing circuit. The signal processing circuit comprises an analog-to-digital (A/D) converter, an FPGA and a CPU. The CUP control the FPGA to start the ultrasonic wave transducer drive circuit to drive the transducer A to send an ultrasonic wave signal; the filter circuit filters and amplifies an ultrasonic wave return signal received by the ultrasonic wave transducer B; the A/D converter samples the wave return signal and stores the sampled data in a storage region constructed in the FPGA; and after the sampling is completed, the CPU reads the sampled data from the FPGA and accurately calculates the transmission time of the ultrasonic wave between the two transducers A and B by adopting the software subdivision algorithm. As the FPGA-based hardware circuit and the special software subdivision algorithm are adopted, the method and the device can realize the measurement of the ultrasonic wave transmission time with nanosecond precision and ensure good real-time.

Description

The method in a kind of precisely measuring ultrasonic wave transmission time and device

Technical field

The invention belongs to sophisticated sensor and detection technique field, be specifically related to the Technology of Precision Measurement of a kind of ultrasonic transmission time.

Background technology

Hyperacoustic notable feature is that frequency is high, thereby wavelength is short, and the diffraction phenomenon is little, and good directionality can direction propagation.At liquid, decay is little in the solid, penetration capacity is strong, runs into impurity or interphase and just has significant reflection.Along with development of electronic technology, the increasing precision measurement that is applied to distance, flow etc. of ultrasonic technology.

When ultrasound wave is propagated in fluid, downbeam and countercurrent direction transmission time different, suitable, therefore the adverse current mistiming is relevant with flow velocity, can suitable, adverse current mistiming when measuring ultrasound wave and in fluid, propagate measure flow.For example, the velocity of propagation of ultrasound wave in clean water is about 1450m/s, at caliber D=300mm; Under the condition of rate of flow of fluid v=1.33m/s; The concurrent-countercurrent mistiming is about 1 microsecond, guarantee to measure to reach 0.5% measuring accuracy, and the resolution of the mistiming that requirement is measured will reach and could realize 1～2 nanosecond; The Measurement Resolution in suitable, adverse current travel-time also should be in nanosecond, and even picosecond.If with conventional timer counter circuit, the frequency of clock circuit will reach 1G at least, this obviously is difficult to realize for instrument development.

Summary of the invention

The present invention is directed to the problems referred to above, disclose the method and the device in a kind of precisely measuring ultrasonic wave transmission time, adopt FPGA circuit and software segmentation interpolation algorithm, can under the prerequisite that guarantees the measurement real-time, realize nanosecond, and even picosecond is measured.

The technical scheme that the present invention adopts is:

The precision measurement method of a kind of ultrasonic transmission time is used for the precision measurement in transmission time between two ultrasonic transducers of ultrasound wave.Said method adopts A, two ultrasonic transducers of B, hardware circuit and software segmentation interpolation algorithm three parts.Hardware circuit mainly comprises ultrasonic transducer drive circuit, ultrasonic echo signal filter circuit, amplifying circuit and signal processing circuit.Signal processing circuit mainly contains analog to digital converter (A/D), FPGA (FPGA) and CPU (CPU) and forms.

Said transducer A is a piezoelectric transducer, can be the electrical signal conversion with certain energy mechanical vibration, and when the frequency of signal was in the frequency of ultrasonic scope, transducer A was electrical signal conversion a ultrasonic signal.Transducer B also is a piezoelectric transducer, converts mechanical vibration into electric signal, and when ultrasonic signal affacted on the ultrasonic transducer B, it converted ultrasonic signal into electric signal, and this signal can be referred to as the ultrasonic echo signal.

Said ultrasonic transducer drive circuit comprises digital-to-analog conversion (D/A) and power amplification circuit.The digital sine conversion of signals that D/A converter is used for sending FPGA is an analog sinus signals, and power amplification circuit is used to amplify the power of this sinusoidal signal, makes it enough energy drives ultrasonic transducer A.It is digital signal that said A/D converter is mainly used in a ultrasonic echo analog signal conversion, and the figure place of A/D converter and SF are the key factors that influences ultrasonic transmission time measurement precision.

Said FPGA circuit major function has two, and first function is under the control of CPU, to produce the digital sine signal, and second function is to accomplish the ultrasonic echo signals sampling, and has data in the memory block that is configured in FPGA inside.

The sinusoidal ultrasonic signal of periodicity of ultrasonic transducer A emission some; After this signal is propagated in medium and is arrived transducer B; Excitation transducer B produces the ultrasonic echo signal, and the continuous pump of the ultrasonic signal that the amplitude of echoed signal receives along with transducer and increasing gradually is when pumping signal stops; The mechanical vibration of transducer still can continue under action of inertia and decay gradually; The amplitude of echoed signal also reduces gradually, so the ultrasonic echo signal is a luffing cyclical signal, and its cycle is corresponding to the cycle of ultrasonic signal.That cycle of echoed signal amplitude maximum is corresponding to the cycle of last sent that ultrasonic signal of transducer A.

Hyperacoustic travel-time is exactly the corresponding time interval between that a bit and on the echoed signal that receives of transducer B arbitrarily on the ultrasonic signal that sends of transducer A.The key of ultrasonic transmission time measurement is to confirm the starting point and the terminal point in travel-time.The starting point in travel-time can be the specific pairing moment on the ultrasonic signal that sends of transducer A, the terminal point of time be on the echoed signal with corresponding that pairing moment of ultrasonic signal unique point.

Echoed signal is a Variable Amplitude cyclical signal, and the most characteristic ripple is that maximum ripple of amplitude in its waveform, can be referred to as characteristic wave, and characteristic wave is corresponding to last ripple of ultrasonic signal.In characteristic wave, the most characteristic point is zero crossing and peak point, can select the unique point of zero crossing as echoed signal.The unique point moment corresponding is exactly the terminal point in travel-time, and is corresponding with it, and the pairing moment of zero crossing of last that ripple can be confirmed as the starting point in travel-time in the ultrasonic signal waveform.

Because ultrasonic signal is that FPGA produces under the control of CPU, the starting point in travel-time, just the zero crossing moment corresponding of last that ripple of ultrasonic signal is easy to confirm accurately that by CPU its precision depends on the running frequency of FPGA.

The terminal point in travel-time, just the pairing moment of zero crossing is confirmed through the segmentation interpolation algorithm in the echoed signal characteristic wave.The segmentation interpolation algorithm is according to the waveform in that cycle of peak amplitude maximum in the at first definite echoed signal of the A/D sampled signal of the ultrasonic echo of storing among the FPGA; Confirm former and later two sampled points of zero crossing (ratio zero is big, and a ratio zero is little) pairing moment then; Be benchmark with former and later two sampled points of zero crossing at last, with fit method sampled point segmented, confirm the pairing moment of echoed signal zero crossing, i.e. in the pairing moment of ultrasonic propagation time terminal point, its precision depends primarily on the resolution of A/D sampling.

In sum; The precision measurement method of the ultrasonic transmission time that the present invention proposes is ultrasonic transducer A and ultrasonic transducer B to be kept at a certain distance away be oppositely arranged; Adopt central processing unit CPU control on-site programmable gate array FPGA sine wave output drive signal; Let signal input to said ultrasonic transducer A through D/A change-over circuit and power amplification circuit successively, this ultrasonic transducer A converts said this input signal to mechanical vibration and produces ultrasonic signal.

Said ultrasonic transducer B receives the ultrasonic signal that said ultrasonic transducer A sends; And output ultrasonic wave echoed signal; By filtering circuit the ultrasonic echo signal that ultrasonic transducer B sends is carried out filtering; After being amplified by amplifying circuit, by the A/D change-over circuit echoed signal is sampled, sampled data is stored in earlier in the memory block that is configured in the FPGA again.

After sampling is accomplished; Central processing unit CPU is at first launched hyperacoustic data according to FPGA and is confirmed the pairing moment of ultrasonic propagation time starting point; Read the A/D sampled data of ultrasonic echo signal then in the FPGA; Employing accurately calculates the pairing moment of ultrasonic propagation time terminal point through the segmentation interpolation algorithm, and then accurately confirms the transmission time of ultrasound wave between two transducer A, B.

Thus, the device of the realization said method of the present invention's proposition comprises ultrasonic transducer A, ultrasonic transducer B, power amplification circuit, amplifying circuit, filtering circuit, A/D change-over circuit, D/A change-over circuit, on-site programmable gate array FPGA and central processing unit CPU;

Said ultrasonic transducer A and ultrasonic transducer B keep at a certain distance away and are oppositely arranged, exist between two transducers can propagate ultrasound waves medium;

Said central processing unit CPU connects on-site programmable gate array FPGA; Control on-site programmable gate array FPGA sine wave output drive signal; One tunnel output of on-site programmable gate array FPGA connects the D/A change-over circuit, by crossing the D/A change-over circuit said sine wave drive signal is changed, and the D/A change-over circuit connects power amplification circuit again; Signal is amplified; Power amplification circuit is connected with ultrasonic transducer A, and signal is inputed to said ultrasonic transducer A, and this ultrasonic transducer A converts said this input signal to mechanical vibration and produces ultrasonic signal;

Said ultrasonic transducer B receives the ultrasonic signal that said ultrasonic transducer A sends; Convert mechanical vibration into electric signal; The output ultrasonic wave echoed signal; And through with its amplifying circuit that is connected successively, filtering circuit and A/D change-over circuit, make said ultrasonic echo signal after amplification, filtering and A/D conversion, input to on-site programmable gate array FPGA successively;

Said on-site programmable gate array FPGA sample simultaneously sine wave drive signal and the ultrasonic echo signal of input of output, and sampled data left in the internal memory;

Said central processing unit CPU reads sampled data from the on-site programmable gate array FPGA internal memory; Sine wave drive signal according to output is confirmed the pairing moment of ultrasonic propagation time starting point; Ultrasonic echo signal according to input; Employing accurately calculates the pairing moment of ultrasonic propagation time terminal point through the segmentation interpolation algorithm, and then the transmission time of accurate Calculation ultrasound wave between ultrasonic transducer A and ultrasonic transducer B.

The present invention can realize the measurement of the ultrasonic transmission time of nanosecond precision owing to adopted based on the hardware circuit of FPGA and special software algorithm of subdivision, and guarantees good real-time.The present invention can be widely used in adopt ultrasonic technology realize flow, apart from fields such as precision measurements.

Description of drawings

Fig. 1 is a kind of hardware block diagram of precisely measuring ultrasonic wave transmission time method;

Fig. 2 is the drive signal synoptic diagram that is added on the transducer A;

Fig. 3 is the ultrasonic echo signal schematic representation that receives on the transducer B;

Fig. 4 is a kind of working principle of hardware synoptic diagram of precisely measuring ultrasonic wave transmission time method;

Fig. 5 a-5b is a synoptic diagram of confirming the corresponding moment of ultrasonic propagation time terminal point institute.

Embodiment

Below in conjunction with Figure of description technical scheme of the present invention is done further explain.

Referring to Fig. 1, the hardware circuit of this method is mainly by ultrasonic transducer A 11, transducer B 12, central processing unit CPU 19; FPGA FPGA 18, A/D change-over circuit 17, filtering circuit 16; Amplifying circuit 15, power amplification circuit 14 and D/A change-over circuit constitute.Exist between ultrasonic transducer A 11, transducer B 12 separated by a distance the placing on same the straight line, two transducers can propagate ultrasound waves medium, such as air, water, steel etc.Ultrasonic transducer is a piezoelectric transducer.

Referring to Fig. 2; Be the drive signal on the ultrasonic transducer A, it is that the digital sine signal that in FPGA, produces converts analog sinus signals to through the D/A change-over circuit, and then forms through the power amplification circuit amplification; The voltage of the V representation signal among the figure, t represents the time.The frequency of this signal is 1MHz, the about 10V of maximum voltage, and the about 1.5A of maximum current has about 15 watts electric energy, is enough to drive ultrasonic transducer A and converts electrical energy into mechanical energy, sends ultrasonic signal.

Referring to Fig. 3, be the ultrasonic echo signal of on transducer B, exporting, the voltage of the V representation signal among the figure, t represents the time.When the ultrasonic signal that transducer A sends was gone up through propagating into transducer B after certain travel-time, transducer B converted the mechanical energy of ultrasonic signal into electric energy, the output ultrasonic wave echoed signal.The electric signal of transducer B output is not before ultrasound wave propagates on the transducer B; Amplitude is zero; After transducer B received ultrasonic signal, the electric signal amplitude of output increased gradually, reduced to decay to zero then gradually; Be a luffing periodic signal, that ripple of amplitude maximum is corresponding to last ripple of ultrasonic signal.The frequency of ultrasonic echo signal depends on the frequency of ultrasonic signal, also is 1MHz.

Referring to Fig. 4, after the synchronizing circuit 432 of CPU19 in FPGA18 sent the beginning sample command, FPGA18 started to the driving of ultrasonic transducer A11 with to ultrasonic transducer B12 output signals sampling simultaneously.

The digital sine signal generator 431 transmission frequencies that are implemented in the FPGA are the sinusoidal signal in 8 cycles of 1MHz; This signal converts simulating signal into through D/A change-over circuit 13; After power amplification circuit 14 amplifies, be carried on the transducer A11 again, send ultrasonic signal.After the electric signal of transducer B12 output amplifies through operational amplification circuit 15, through being connected to A/D change-over circuit 17 after filtering circuit 16 filtering.The inner sample circuit 433 control A/D change-over circuits 443 of FPGA are digital signal with analog signal conversion, and deposit sampled value one by one in the RAM memory block 434 that is implemented in the FPGA.After sampling was accomplished, FPGA430 sent sampling done state information to CPU 19, and CPU19 finishes once sampling after receiving sampling done state information.

After sampling finished, CPU19 at first accurately confirmed the pairing moment T of starting point in the ultrasonic signal according to the data of the digital sine signal generator 431 in the FPGA _QD

CPU19 sends the read data order then, reads the data that are temporary in the RAM memory block 434, the pairing moment of accurate Calculation ultrasonic propagation time terminal point.

The pairing moment of ultrasonic transmission end time is through analyzing and calculate and realize with the segmentation interpolation algorithm all sampled datas of echoed signal.Referring to Fig. 5 a, analyze the ultrasonic echo signal of ultrasonic transducer B output and can know, be the repeatability that guarantees measurement, should in the waveform of peak amplitude maximum, extract the terminal point of ultrasonic transmission time.In the complete cycle of this waveform, the most tangible two unique points are peak point and zero crossing, and the time reference of confirming as zero crossing echoed signal obtains high precision more easily.

Referring to Fig. 5 a, the computing method in the pairing moment of ultrasonic transmission end time of the present invention are:

At first the A/D sampled point is compared in pointwise, finds out the maximal value of sampled point and just can confirm the waveform that amplitude is maximum easily, can be referred to as the eigenwert waveform to this waveform;

Secondly, participate in Fig. 5 b, confirm the pairing zero crossing P of ultrasonic transmission end time ₀Sampled point P+1 of sampled point P in front and back, obviously the sampled value of sampled point P is greater than zero in characteristic wave, and the sampled value of sampled point P+1 is less than zero;

At last, as benchmark, can accurately calculate zero crossing P with sampled point P and 2 moment corresponding of P+1 with the segmentation interpolation algorithm ₀In the pairing moment, concrete computing method are following:

If the SF of A/D is F _A/D, the time between adjacent two sampled points is to be T in the sampling period _A/DIs N from first sampled point to the hits the sampled point P, and the sampled value that sampled point P is corresponding is V1, and the pairing moment of sampled point P is T1; The sampled value that sampled point P+1 is corresponding is V2; The pairing moment of sampled point P is T1, sampled point P and zero crossing P ₀Between time be T2, zero crossing P ₀Moment corresponding is T _ZD, hyperacoustic transmission time is T, then:

$T_{A/D}=\frac{1}{F_{A/D}}$

$T1=N\×\frac{1}{F_{A/D}}$

In the less zone of near zero-crossing point, sinusoidal wave waveform approaches straight line, can confirm T2 according to the method for linear interpolation:

$T2=\frac{1}{V2-V1}\×V1\×T_{A/D}$

Then the pairing moment of zero crossing, promptly the pairing moment of ultrasonic transmission end time is:

$T_{\mathrm{ZD}}=T1+T2=N\×\frac{1}{F_{A/D}}+\frac{1}{V2-V1}\×T_{/\mathrm{AD}}\×V1$

Can know from following formula, the ultrasonic transmission end time corresponding resolution constantly be:

$R=\frac{1}{V2-V1}\×T_{/\mathrm{AD}}$

Participate in Fig. 5 b, the frequency of supposing the ultrasonic echo signal is 1M, and then the cycle is 1us; The resolution of A/D is 12; Can the amplitude of signal be divided into 4096 parts so; If the SF of A/D is 32MHz, then arrive in the negative peaked half period in the positive maximal value of sine wave, can adopt 16 points at most; If regard sinusoidal wave positive maximal value as straight line to the waveform in the negative peaked half period, then obviously can know:

$V2-V1=\frac{4096}{16}=256$

Observe sinusoidal wave positive maximal value and can find out that to the waveform in the negative peaked half period near zero-crossing point slope of a curve is much larger than near the slope of a curve peak value, then

V2-V1＞256

$R=\frac{1}{V2-V1}\&times;T_{/\mathrm{AD}}<\frac{1}{256}\&times;T_{/\mathrm{AD}}=\frac{1}{256}\&times;\frac{1}{32}\&times;1\mathrm{\&mu;s}=0.122\mathrm{ns}$

Referring to Fig. 5, hyperacoustic transmission time is:

$T=T_{\mathrm{ZD}}-T_{\mathrm{QD}}=N\&times;\frac{1}{F_{A/D}}+\frac{1}{V2-V1}\&times;T_{/\mathrm{AD}}\&times;V1-T_{\mathrm{QD}}$

Because the pairing moment of ultrasonic transmission start time can accurately confirm, then the resolution of ultrasonic transmission time measurement depends on the resolution in the corresponding moment of ultrasonic transmission end time institute.Then the resolution of ultrasonic transmission time measurement if adopt more high-resolution A/D change-over circuit, can also realize more high-resolution measurement less than 0.122 nanosecond.

Claims (2)

1. the method in a precisely measuring ultrasonic wave transmission time; Be used for the precision measurement in transmission time between two ultrasonic transducers of ultrasound wave; It is characterized in that: said method is ultrasonic transducer A and ultrasonic transducer B to be kept at a certain distance away be oppositely arranged; Exist between two transducers can propagate ultrasound waves medium; Adopt central processing unit CPU control on-site programmable gate array FPGA sine wave output drive signal, let signal input to said ultrasonic transducer A through D/A change-over circuit and power amplification circuit successively, this ultrasonic transducer A converts input signal to mechanical vibration and produces ultrasonic signal;

Said ultrasonic transducer B receives the ultrasonic signal that said ultrasonic transducer A sends; And output ultrasonic wave echoed signal; By filtering circuit the ultrasonic echo signal that ultrasonic transducer B sends is carried out filtering; After being amplified by operational amplification circuit, by the A/D change-over circuit echoed signal is sampled, sampled data is stored in earlier in the memory block that is configured in the FPGA again;

After sampling is accomplished; Central processing unit CPU is at first launched hyperacoustic data according to FPGA and is confirmed the pairing moment of ultrasonic propagation time starting point; Read the A/D sampled data of ultrasonic echo signal then in the FPGA; Accurately calculate the pairing moment of ultrasonic propagation time terminal point through the segmentation interpolation algorithm, and then accurately confirm the transmission time of ultrasound wave between two transducer A, B;

The said pairing moment of acoustic transit time starting point is got the zero crossing moment corresponding of last that ripple of FPGA emission ultrasonic signal;

The segmentation interpolation algorithm that calculates the terminal point in travel-time is: according to the A/D sampled signal of the ultrasonic echo of storing among the FPGA, at first confirm the maximum interior waveform of that cycle of peak amplitude in the echoed signal; Confirm the pairing moment of former and later two sampled points of zero crossing then; Be benchmark with former and later two sampled points of zero crossing at last, sampled point segmented, confirm the pairing moment of echoed signal zero crossing, i.e. the pairing moment of ultrasonic propagation time terminal point with fit method.

2. device of realizing the precisely measuring ultrasonic wave transmission time of the said method of claim 1; Said device comprises ultrasonic transducer A, ultrasonic transducer B, power amplification circuit, operational amplification circuit, filtering circuit, A/D change-over circuit, D/A change-over circuit, on-site programmable gate array FPGA and central processing unit CPU, it is characterized in that:

Said ultrasonic transducer A and ultrasonic transducer B keep at a certain distance away and are oppositely arranged, exist between two transducers can propagate ultrasound waves medium;

Said central processing unit CPU connects on-site programmable gate array FPGA; Control on-site programmable gate array FPGA sine wave output drive signal; One tunnel output of on-site programmable gate array FPGA connects the D/A change-over circuit, by the D/A change-over circuit said sine wave drive signal is changed, and the D/A change-over circuit connects power amplification circuit again; Signal is amplified; Power amplification circuit is connected with ultrasonic transducer A, and signal is inputed to said ultrasonic transducer A, and this ultrasonic transducer A converts input signal to mechanical vibration and produces ultrasonic signal;

Said ultrasonic transducer B receives the ultrasonic signal that said ultrasonic transducer A sends; Convert mechanical vibration into electric signal; The output ultrasonic wave echoed signal; And through with its operational amplification circuit that is connected successively, filtering circuit and A/D change-over circuit, make said ultrasonic echo signal after amplification, filtering and A/D conversion, input to on-site programmable gate array FPGA successively;

Said on-site programmable gate array FPGA sample simultaneously sine wave drive signal and the ultrasonic echo signal of input of output, and sampled data left in the internal memory;

Said central processing unit CPU reads sampled data from the on-site programmable gate array FPGA internal memory; Sine wave drive signal according to output is confirmed the pairing moment of ultrasonic propagation time starting point; Ultrasonic echo signal according to input; Employing accurately calculates the pairing moment of ultrasonic propagation time terminal point through the segmentation interpolation algorithm, and then accurately confirms the transmission time of ultrasound wave between two transducer A, B;

The said pairing moment of acoustic transit time starting point is got the zero crossing moment corresponding of last that ripple of FPGA emission ultrasonic signal;

The segmentation interpolation algorithm of the terminal point in said calculating travel-time is: according to the A/D sampled signal of the ultrasonic echo of storing among the FPGA, at first confirm the maximum interior waveform of that cycle of peak amplitude in the echoed signal; Confirm the pairing moment of former and later two sampled points of zero crossing then; Be benchmark with former and later two sampled points of zero crossing at last, sampled point segmented, confirm the pairing moment of echoed signal zero crossing, i.e. the pairing moment of ultrasonic propagation time terminal point with fit method.

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