CN103995262B - MIMO sparse array ultrasonic measurement methods and system for fluctuation interface - Google Patents

Abstract

The invention discloses two ultrasonic measurement methods and system for coded signal transmission on the basis of MIMO sparse array elements, and belongs to the technical field of ultrasonic measurement. The methods are used for measuring irregular fluctuation interfaces similar to fluctuation liquid levels and snow depths, and accuracy of distance measurement under the situation of the fluctuation interface is effectively improved. According to the methods, the sparse array is utilized for conducting ultrasonic measurement on the fluctuation interface at different angles, and two signal transmission modes, namely the time-sharing transmission mode and the simultaneous transmission mode, are adopted. According to the two transmission modes, signals are transmitted through the sparse array, and beam forming processing is carried out after channel separation of the signals is achieved. According to the methods, the echo signals of different virtual array elements can be effectively distinguished, the beam forming processing is facilitated, and accuracy of distance measurement of the fluctuation interface is improved; in addition, the simultaneous transmission mode is adopted to be applied to measurement of rapid changes of the fluctuation interface, distance ambiguity generated by the rapid changes of the fluctuation interface is avoided, and therefore the accuracy of the measurement is improved.

Description

Ultrasonic measurement method for the mimo thinned array at the interface that rises and falls and system

Technical field

The invention belongs to ultrasonic measurement technical field, especially relate to two kinds for measurement fluctuation liquid level, snow depth etc. The ultrasonic measurement method of mimo thinned array at fluctuating interface and the measuring system being capable of these methods.

Background technology

Ultrasonic measurement is a kind of measuring method of high performance-price ratio, is widely used in all trades and professions.For example in meteorological field, energy Enough measurements realizing rainfall and evaporation capacity by ultrasonic liquid-level measurement, realize the survey of snow depth by ultrasonic range measurement Amount.However, while obtaining these meteorological elements with ultrasonic measurement method, due to the fluctuation of liquid level or the fluctuating at interface, passing The point ultrasonic measurement method of system is likely to produce larger measure error.

In order to reduce measure error in such applications, a simple method is to use spatial sampling, then carries out sky Between sample mean.Phase-array scanning method is a kind of method therein, but the port number that the method needs is larger, system cost Higher, thus can not be widely adopted.Ultrasonic measurement method is in transition time (tof) estimation, transmission signal, echo signal processing Etc. aspect studied, and obtain certain progress.In terms of tof estimation, angrisani l in 2006 etc. is in " ieee Transactions on instrumentation and measurement " on " the ultrasonic time-of- that delivers Flight eatimation through unscented kalman filter ", processed ultrasonic using lossless Kalman filtering Echo-signal, obtains the envelope of echo-signal, and compared with discrete EKF, tof estimated accuracy is improved Decrease amount of calculation simultaneously；In terms of transmission signal, Zang Huai has just waited that delivers on " sensor and instrument and meter " " to answer within 2010 Intelligence Ultrasound tank gage with linear FM signal ", linear frequency modulation ripple is applied in ultrasonic liquid-level measurement, and combines coupling filter Wave technology improves the accuracy of level gauging；In terms of echo signal processing, yellow newly-built grade in 2011 is delivered on " hydrology " " improving the discussion of aerosphere type ultrasonic water level gauge certainty of measurement ", compensates the echo frontier of ultrasonic wave using digital sampling techniques, Improve the accuracy of Precipitation measurement.However, above method is mainly made up of one or two ultrasonic transducer, it is that single channel is visited Examining system, these conventional methods only estimate the distance value of one of whole liquid level fixed point, for the range measurement at fluctuating interface, with Upper method all easily produces larger measure error, at present, still lacks a kind of ultrasonic survey being more accurately directed to fluctuating interface Amount method.

Content of the invention

For solving the above problems, the invention discloses the ultrasonic survey of two kinds of encoded signal transmittings based on the sparse array element of mimo Amount method and the ultrasound measurement system being capable of these methods, such not for measuring similar fluctuation liquid level, snow depth Regular fluctuating interface, effectively increases the accuracy of range measurement under fluctuating interface conditions.

In order to achieve the above object, the following technical scheme of present invention offer:

A kind of ultrasonic measurement method of the mimo thinned array for the interface that rises and falls, using mimo Sparse Array element array, by m Individual transmitting array element with n receive array element equivalent become the uniform Virtual array arranged of m × n；Comprise the steps:

Step a, using m transmitting array element time division emission identical linear frequency modulation ripple, transmission signal is:

S1 (t)=exp { j (2 π f₀t+πμt²)},0≤t≤t

Wherein, f₀For the initial frequency of linear frequency modulation ripple, μ=b/t is the chirp rate of linear frequency modulation ripple, and wherein b is to adjust Bandwidth, t is signal duration；

Step b, n receives array element and receives corresponding Virtual array echo-signal, and echo-signal is:

R1 (m, n, t)=α_mns1(t-δt_mn),1≤m≤m,1≤n≤n

Wherein, α_mnFor echo-signal attenuation coefficient, m, n represent m-th transmitting array element and n-th reception array element, δ respectively t_mnFor transmission signal from m-th transmitting array element to target, then the propagation time by target to n-th reception array element；

Step c, carries out Wave beam forming process, acquisition echo data matrix to signal:

Step c-1, corresponding for each echo-signal Virtual array is reassembled into the echo-signal of m × n autonomous channel；

Step c-2, using r1 in echo data matrix, (2,1, t) (3,4, data t) carries out matched filtering process with r1 Obtain corresponding transition time δ t1 and δ t2；

Step c-3, goes out, by computing formula (δ t1+ δ t2) c/2, the distance at interface that rises and falls according to a preliminary estimate；

Step c-4, enters line delay summation Wave beam forming and processes to echo-signal:

$y\left(t\right)=\underset{m,n}{\mathrm{\σ}}{\mathrm{\α}}_{\mathrm{mn}}s1(t-\mathrm{\δ}{t}_{\mathrm{mn}}^c),1\≤m\≤m,1\≤n\≤n$

WhereinFor time delay after Wave beam forming for the different Virtual arrays, τ_mnFor different Virtual arrays Delay compensation value with respect to reference point；

Step c-5, whether the echo-signal in the predetermined orientation of detection has all carried out Wave beam forming process, to untreated Orientation proceed Wave beam forming and process, until all signals have all carried out after Wave beam forming processes, obtaining new echo letter Number matrix；

Step d, carries out tiltedly processing to the signal after Wave beam forming, output signal is:

Y1 (m, n, t)=aexp { j2 π φ (m, n, t) }

In formula, phase function φ is $\mathrm{\φ}(m,n,t)=(\mathrm{\μ\δ}{t}_{\mathrm{mn}}^{c}t+f_0\mathrm{\δ}{t}_{\mathrm{mn}}^c-\mathrm{\μ}{\left(\mathrm{\δ}{t}_{\mathrm{mn}}^c\right)}^2/2),$ A is range coefficient；

After trying to achieve process, signal frequency composition isFft process is carried out to signal, obtain away from From information:

$d_{\mathrm{mn}}=\mathrm{c\δ}{t}_{\mathrm{mn}}^c=\frac{{\mathrm{cf}}_{\mathrm{mn}}}{\mathrm{\μ}}.$

Further, also include self adaptation focus setting procedure after described step c-3:

Determine the focus position of the Wave beam forming of each scanning direction by the distance and bearing angle at fluctuating interface according to a preliminary estimate Put.

Present invention also offers second is used for the ultrasonic measurement method of the mimo thinned array at interface that rises and falls, using mimo Sparse Array element array, by m transmitting array element with n receive array element equivalent become the uniform Virtual array arranged of m × n；Including such as Lower step:

Step a, m transmitting array element launches the linear frequency modulation ripple of different balance gold pscudo-random codc modulation, transmitting simultaneously Signal is:

$\begin{array}{c}s{2}_i\left(t\right)=\underset{n=0}{\overset{p-1}{\mathrm{\σ}}}{\mathrm{\κ}}_n^i\mathrm{\δ}(t-n{\mathrm{\τ}}_c)\&circletimes;v\left(t\right)\exp \left[j2\mathrm{\π}(f_{0}t+\frac{1}{2}{\mathrm{\μt}}^2)\right]\\ =s_{\mathrm{gold}}^i\left(t\right)\&circletimes;s_{\mathrm{lfm}}\left(t\right),i=\mathrm{1,2}...m\end{array}$

In formula, p, τ_cIt is respectively code length and the symbol width of balance gold code； For balancing gold code；f₀、 μ=b/ τ_c, b be respectively chirped initial frequency, chirp rate, modulating bandwidth；V (t) is τ for length_cRectangular function；Represent convolution algorithm；s_goldT () represents the impulse function of balance gold code, s_lfmT () represents linear FM signal；

The echo-signal receiving array element k is:

$r{2}_k\left(t\right)=\underset{i=1}{\overset{m}{\mathrm{\σ}}}{\mathrm{\α}}_{i}s{2}_i(t-{\mathrm{\τ}}_{\mathrm{ki}}),k=\mathrm{1,2}...n$

In formula, α_iFor ultrasound echo signal attenuation amplitude, τ_kiLaunch the signal of array element transmitting for i-th to target, then warp Target is to the propagation time receiving array element k；

Step b, each echo-signal receiving array element reception is carried out related operation respectively with m transmission signal and realizes leading to Road separates, and obtains the signal of m × n autonomous channel:

$y{2}_{\mathrm{jk}}\left(\mathrm{\τ}\right)=\underset{0}{\overset{t}{\&integral;}}r{2}_k\left(t\right)s{2}_j^{*}(t-\mathrm{\τ})\mathrm{dt}={\mathrm{\α}}_i{r}_{\mathrm{ii}}+\underset{i\&notequal;j}{\overset{m}{\mathrm{\σ}}}{\mathrm{\α}}_i{r}_{\mathrm{ij}}$

In formula, * represents and seeks complex conjugate；r_iiFor signal autocorrelation output；For the output of signal all possible cross-correlation Sum；Cross-correlation output expression formula is:

$\begin{array}{c}{r}_{\mathrm{ij}}\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\&integral;}}s{2}_i\left(t\right)s{2}_j^{*}(t-\mathrm{\τ})\mathrm{dt}=s{2}_i\left(\mathrm{\τ}\right)\&circletimes;s{2}_j^{*}(-\mathrm{\τ})\\ =[s_{\mathrm{gold}}^i\left(\mathrm{\τ}\right)\&circletimes;s_{\mathrm{lfm}}\left(\mathrm{\τ}\right)]\&circletimes;[s_{\mathrm{gold}}^{j*}(-\mathrm{\τ})\&circletimes;s_{\mathrm{lfm}}^{*}(-\mathrm{\τ})]\\ =\underset{m=-(p-1)}{\overset{p-1}{\mathrm{\σ}}}{r}_{\mathrm{gold}}^{\mathrm{ij}}\left(m{\mathrm{\τ}}_c\right)\·r_{\mathrm{lfm}}(\mathrm{\τ}-m{\mathrm{\τ}}_c)\end{array}$

Wherein,

$r_{\mathrm{gold}}^{\mathrm{ij}}\left(m{\mathrm{\τ}}_c\right)=\left\{\begin{array}{cc}\underset{n=0}{\overset{p-1+m}{\mathrm{\σ}}}{\mathrm{\κ}}_n^i{\mathrm{\κ}}_{n-m}^j,& -(p-1)\≤m\≤0\\ \underset{n=m}{\overset{p-1}{\mathrm{\σ}}}{\mathrm{\κ}}_n^i{\mathrm{\κ}}_{n-m}^j,& 0\≤m\≤(p-1)\end{array}\right.,$

$r_{\mathrm{lfm}}(\mathrm{\τ}-m{\mathrm{\τ}}_c)=\left\{\begin{array}{cc}\exp \left[j2\mathrm{\π}(f_0+\frac{1}{2}\mathrm{\μ}{\mathrm{\τ}}_c)(\mathrm{\τ}-m{\mathrm{\τ}}_c)\right]\·& \\ ({\mathrm{\τ}}_c-|\mathrm{\τ}-m{\mathrm{\τ}}_c\left|\right)\sin c\left[\mathrm{\π\μ}{\mathrm{\τ}}_c(\mathrm{\τ}-m{\mathrm{\τ}}_c)(1-\frac{|\mathrm{\τ}-m{\mathrm{\τ}}_c|}{{\mathrm{\τ}}_c})\right],& |\mathrm{\τ}-m{\mathrm{\τ}}_c|\≤{\mathrm{\τ}}_c\\ 0,& |\mathrm{\τ}-m{\mathrm{\τ}}_c|\&greaterequal;{\mathrm{\τ}}_c\end{array}\right.,$

In formula,For balancing the cross-correlation function of gold code；r_lfm(τ) for the cross-correlation function of linear FM signal.

Step c, carries out Wave beam forming process, acquisition range information to signal:

Step c-1, using r1 in the echo data matrix of m × n autonomous channel (2,1, t) and r1 (3,4, data t) Carry out matched filtering process and obtain corresponding transition time δ t1 and δ t2；

Step c-2, goes out, by computing formula (δ t1+ δ t2) c/2, the distance at interface that rises and falls according to a preliminary estimate；

Step c-3, then enters line delay summation Wave beam forming and processes to the signal after channel separation；

Step c-4, proceeds Wave beam forming and processes, until all signals have all carried out wave beam shape to untreated orientation After one-tenth is processed, obtain new echo-signal matrix；

Step c-5, the peak value of the echo-signal after being processed by channel separation and Wave beam forming obtains target echo signal Transition time δ t, calculates δ t c and obtains target distance measurement information.

Further, also include self adaptation focus setting procedure after described step c-2:

Determine the focus position of the Wave beam forming of each scanning direction by the distance and bearing angle at fluctuating interface according to a preliminary estimate Put.

A kind of ultrasound measurement system of the mimo thinned array for the interface that rises and falls, launch including supersonic array and signal and Process model,

Described supersonic array by m transmitting array element with n receive array element equivalent become the uniform Virtual array arranged of m × n；

Described signal transmitting and process model and include time division emission model and Launching Model simultaneously, described time division emission model Including time division emission unit, beam forming unit, remove oblique processing unit, fft converter unit；

In described time division emission unit, m transmitting array element time division emission linear frequency modulation ripple, real by the time division emission of signal The channel separation of existing Virtual array echo-signal, n receives array element and receives corresponding Virtual array echo-signal；

Described beam forming unit is used for, after all echo signal reception terminate, each echo-signal being corresponded to virtual array Unit reassembles into the echo-signal of m × n autonomous channel, carries out Wave beam forming process to it；

Described remove oblique processing unit for carrying out tiltedly processing to composite signal；

Described fft converter unit is used for going the signal after tiltedly processing to carry out fft process, is calculated corresponding distance letter Breath；

Described Launching Model simultaneously includes transmitter unit, channel separation unit, beam forming unit simultaneously；

In described transmitter unit simultaneously, m transmitting array element launches the linear of different balance gold pscudo-random codc modulation simultaneously Frequency-modulated wave, n receives array element and receives simultaneously；

The echo-signal that described channel separation unit is used for receiving array element reception to each is carried out with m transmission signal respectively Related operation realizes channel separation, obtains the signal of m × n autonomous channel,

Described beam forming unit is used for carrying out Wave beam forming process to the signal that above-mentioned separation obtains, obtain corresponding away from From information.

Further, described time division emission model and simultaneously in Launching Model, beam forming unit is entering traveling wave to signal Bundle is formed when processing, using self adaptation focusing method.

Beneficial effect:

Compared with traditional point ultrasonic measurement, the anti-interference of ultrasonic measurement method and accuracy of measurement that the present invention provides Significantly improve, can accurately measure fluctuating interface, even if in the case of the amplitude of the interfacial wave of about 4cm, remain able to obtain pole High accuracy.Simultaneously by the use of big when wide bandwidth signals as transmission signal, and combine pulse compression technique, have preferably away from High Resolution；When the present invention is using emission mode simultaneously, in the case of signal to noise ratio as little as -30db, remain to reliably working.Additionally, Employ self adaptation focusing method it is ensured that focus changes with the change at interface, thus ensureing the accuracy measuring.This The bright application being not limited only to meteorological field, and other field can be widely popularized, the such as phase such as chemical industry, cement, coal, hydrology The measurement of related parameter, has the value of high application and wide variety of prospect.

Brief description

Fig. 1 is the ultrasound measurement system structural representation of the mimo thinned array for the interface that rises and falls；

Fig. 2 is 4 transmitting array elements and the array junctions composition of 4 reception array elements；

Fig. 3 is using 4 transmitting array element transmission signal pie graphs during time division emission pattern；

Fig. 4 is the signal processing flow figure carrying out fluctuating interface distance measurement using time division emission pattern；

Fig. 5 is linear FM signal excitation in embodiment one, balance gold-lfm composite signal excitation is linear with point measurement Pulse pressure result figure in the case of single scattering son measurement for the frequency modulation on pulse；

Fig. 6 is that the impact offseting to certainty of measurement taking Wave beam forming focus during different signal to noise ratio in embodiment two is illustrated Figure；

Fig. 7 is the point target measure error figure taking two kinds of emission modes during different signal to noise ratio in embodiment three, wherein schemes (b) For scheming the vertical magnification figure of (a)；

Fig. 8 is the Error Graph of fluctuating interface level measurement under time division emission pattern in example IV, and wherein figure (a) is fluctuating circle Face, figure (b) is the Error Graph that measurement obtains.

Specific embodiment

The technical scheme present invention being provided below with reference to specific embodiment is described in detail it should be understood that following concrete Embodiment is only illustrative of the invention and is not intended to limit the scope of the invention.

A kind of the invention provides ultrasound measurement system of the mimo thinned array for the interface that rises and falls, as shown in figure 1, bag Include supersonic array and signal transmitting and process model,

Described supersonic array by m transmitting array element with n receive array element equivalent become the uniform Virtual array arranged of m × n；

Described signal transmitting and process model and include time division emission model and Launching Model simultaneously, described time division emission model Including time division emission unit, beam forming unit, remove oblique processing unit, fft converter unit；

In described time division emission unit, m transmitting array element time division emission linear frequency modulation ripple, real by the time division emission of signal The channel separation of existing Virtual array echo-signal, n receives array element and receives corresponding Virtual array echo-signal；

Described beam forming unit is used for, after all echo signal reception terminate, each echo-signal being corresponded to virtual array Unit reassembles into the echo-signal of m × n autonomous channel, carries out Wave beam forming process to it；

Described remove oblique processing unit for carrying out tiltedly processing to composite signal；

Described fft converter unit is used for going the signal after tiltedly processing to carry out fft process, is calculated corresponding distance letter Breath；

Described Launching Model simultaneously includes transmitter unit, channel separation unit, beam forming unit simultaneously；

In described transmitter unit simultaneously, m transmitting array element launches the linear of different balance gold pscudo-random codc modulation simultaneously Frequency-modulated wave, n receives array element and receives simultaneously；

The echo-signal that described channel separation unit is used for receiving array element reception to each is carried out with m transmission signal respectively Related operation realizes channel separation, obtains the signal of m × n autonomous channel,

Described beam forming unit is used for carrying out Wave beam forming process to the signal that above-mentioned separation obtains, obtain corresponding away from From information.

Deviation due to Wave beam forming focus can produce impact to measurement accuracy, therefore in time division emission model with simultaneously In beam forming unit in Launching Model all using a kind of self adaptation focusing method it is ensured that focus with interface change and Change, thus ensure that the accuracy of measurement.

The present invention carries out ultrasonic measurement using thinned array from different perspectives to fluctuating interface, employs two kinds of transmission signals Pattern: time division emission pattern and simultaneously emission mode, can effectively distinguish the echo-signal of different Virtual arrays, be conducive to into Row Wave beam forming is processed, and improves the degree of accuracy of fluctuating interface distance measurement, in addition, can apply using transmission signal pattern simultaneously To in the fast-changing measurement in fluctuating interface, it is to avoid range ambiguity is produced by the quick change at fluctuating interface, thus improving survey The accuracy of amount.Both emission modes, all by thinned array transmission signal, after realizing the channel separation of signal, carry out wave beam shape One-tenth is processed.The channel separation of signal is realized by time division emission signal, pass through under emission mode will simultaneously under time division emission pattern The different echo-signals receiving array element carry out, with m transmission signal, the channel separation that relevant treatment to realize signal respectively.When adopting During with time division emission pattern, Wave beam forming also needs to carry out tiltedly processing and FFT (fft) after processing.

Specifically, the time division emission method that the present invention provides, using mimo Sparse Array element array, by m transmitting array element With n receive array element equivalent become the Virtual array uniformly arranged of m × n；Comprise the steps:

Step a, using m transmitting array element time division emission identical linear frequency modulation ripple of timesharing, transmission signal is:

S1 (t)=exp { j (2 π f₀t+πμt²)},0≤t≤t (1)

Wherein, f₀For the initial frequency of linear frequency modulation ripple, μ=b/t is the chirp rate of linear frequency modulation ripple, and wherein b is to adjust Bandwidth, t is signal duration；

Step b, n receives array element and receives corresponding Virtual array echo-signal, and echo-signal is:

R1 (m, n, t)=α_mns1(t-δt_mn),1≤m≤m,1≤n≤n (2)

Wherein, α_mnFor echo-signal attenuation coefficient, m, n represent m-th transmitting array element and n-th reception array element, δ respectively t_mnFor transmission signal from m-th transmitting array element to target, then the propagation time by target to n-th reception array element；

Step c, corresponding for each echo-signal Virtual array is reassembled into the echo-signal of m × n autonomous channel；Using return In ripple data matrix, (2,1, t) (3,4, data t) carries out matched filtering process and obtains corresponding transition time δ t1 r1 with r1 With δ t2；The distance at interface that rises and falls is gone out according to a preliminary estimate by computing formula (δ t1+ δ t2) c/2；Due to Wave beam forming focus Deviate and can produce impact to measurement accuracy, therefore as improving, we adopt self adaptation focusing method, first by tentatively estimating The distance and bearing angle at the fluctuating interface of meter determines each " to be scanned " direction (scanning direction refers to coordinate origin to Wave beam forming The direction of focus.Scanning to be realized generally by the direction changing ultrasonic wave acoustic beam, and the present invention passes through to change Wave beam forming The position of focus, to change synthesis ultrasound echo signal sound beam direction, play the effect of " scanning ") Wave beam forming focus Position, then echo-signal is entered with line delay summation Wave beam forming process:

$y\left(t\right)=\underset{m,n}{\mathrm{\σ}}{\mathrm{\α}}_{\mathrm{mn}}s1(t-\mathrm{\δ}{t}_{\mathrm{mn}}^c),1\≤m\≤m,1\≤n\≤n---\left(3\right)$

WhereinFor time delay after Wave beam forming for the different Virtual arrays, τ_mnFor different Virtual arrays Delay compensation value with respect to reference point；

Whether the echo-signal in the predetermined orientation of detection has all carried out Wave beam forming process, if result is negative , then untreated orientation is proceeded with Wave beam forming and processes, conversely, obtaining new echo-signal matrix；

Step d, carries out tiltedly processing to the signal after Wave beam forming, output signal is:

Y1 (m, n, t)=aexp { j2 π φ (m, n, t) } (4)

In formula, phase function φ is $\mathrm{\φ}(m,n,t)=(\mathrm{\μ\δ}{t}_{\mathrm{mn}}^{c}t+f_0\mathrm{\δ}{t}_{\mathrm{mn}}^c-\mathrm{\μ}{\left(\mathrm{\δ}{t}_{\mathrm{mn}}^c\right)}^2/2),$ A is range coefficient；

After trying to achieve process, signal frequency composition isTherefore, the letter after " going tiltedly " being processed Number carry out fft process, range information can be obtained by following formula:

$d_{\mathrm{mn}}=\mathrm{c\δ}{t}_{\mathrm{mn}}^c=\frac{{\mathrm{cf}}_{\mathrm{mn}}}{\mathrm{\μ}}---\left(5\right)$

The launching technique while present invention provides, using mimo Sparse Array element array, by m transmitting array element and n reception The array element equivalent one-tenth m × n Virtual array uniformly arranged；Comprise the steps:

Step a, m transmitting array element launches the linear frequency modulation ripple of different balance gold pscudo-random codc modulation, transmitting simultaneously Signal is:

$\begin{array}{c}s{2}_i\left(t\right)=\underset{n=0}{\overset{p-1}{\mathrm{\σ}}}{\mathrm{\κ}}_n^i\mathrm{\δ}(t-n{\mathrm{\τ}}_c)\&circletimes;v\left(t\right)\exp \left[j2\mathrm{\π}(f_{0}t+\frac{1}{2}{\mathrm{\μt}}^2)\right]\\ =s_{\mathrm{gold}}^i\left(t\right)\&circletimes;s_{\mathrm{lfm}}\left(t\right),i=\mathrm{1,2}...m\end{array}---\left(6\right)$

In formula, p, τ_cIt is respectively code length and the symbol width of balance gold code； For balancing gold code；f₀、μ =b/ τ_c, b be respectively chirped initial frequency, chirp rate, modulating bandwidth；V (t) is τ for length_cRectangular function； Represent convolution algorithm；s_goldT () represents the impulse function of balance gold code, s_lfmT () represents linear FM signal；

The echo-signal receiving array element k is:

$r{2}_k\left(t\right)=\underset{i=1}{\overset{m}{\mathrm{\σ}}}{\mathrm{\α}}_{i}s{2}_i(t-{\mathrm{\τ}}_{\mathrm{ki}}),k=\mathrm{1,2}...n$

In formula, α_iFor ultrasound echo signal attenuation amplitude, τ_kiLaunch the signal of array element transmitting for i-th to target, then warp Target is to the propagation time receiving array element k.

Step b, each echo-signal receiving array element reception is carried out related operation respectively with m transmission signal and realizes leading to Road separates, and obtains the signal of m × n autonomous channel:

$y{2}_{\mathrm{jk}}\left(\mathrm{\τ}\right)=\underset{0}{\overset{t}{\&integral;}}r{2}_k\left(t\right)s{2}_j^{*}(t-\mathrm{\τ})\mathrm{dt}={\mathrm{\α}}_i{r}_{\mathrm{ii}}+\underset{i\&notequal;j}{\overset{m}{\mathrm{\σ}}}{\mathrm{\α}}_i{r}_{\mathrm{ij}}$

In formula, * represents and seeks complex conjugate；r_iiFor signal autocorrelation output；Defeated for all possible cross-correlation of signal Go out sum；Cross-correlation output expression formula is:

$\begin{array}{c}{r}_{\mathrm{ij}}\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\&integral;}}s{2}_i\left(t\right)s{2}_j^{*}(t-\mathrm{\τ})\mathrm{dt}=s{2}_i\left(\mathrm{\τ}\right)\&circletimes;s{2}_j^{*}(-\mathrm{\τ})\\ =[s_{\mathrm{gold}}^i\left(\mathrm{\τ}\right)\&circletimes;s_{\mathrm{lfm}}\left(\mathrm{\τ}\right)]\&circletimes;[s_{\mathrm{gold}}^{j*}(-\mathrm{\τ})\&circletimes;s_{\mathrm{lfm}}^{*}(-\mathrm{\τ})]\\ =\underset{m=-(p-1)}{\overset{p-1}{\mathrm{\σ}}}{r}_{\mathrm{gold}}^{\mathrm{ij}}\left(m{\mathrm{\τ}}_c\right)\·r_{\mathrm{lfm}}(\mathrm{\τ}-m{\mathrm{\τ}}_c)\end{array}$

$r_{\mathrm{gold}}^{\mathrm{ij}}\left(m{\mathrm{\τ}}_c\right)=\left\{\begin{array}{cc}\underset{n=0}{\overset{p-1+m}{\mathrm{\σ}}}{\mathrm{\κ}}_n^i{\mathrm{\κ}}_{n-m}^j,& -(p-1)\≤m\≤0\\ \underset{n=m}{\overset{p-1}{\mathrm{\σ}}}{\mathrm{\κ}}_n^i{\mathrm{\κ}}_{n-m}^j,& 0\≤m\≤(p-1)\end{array}\right.$

$r_{\mathrm{lfm}}(\mathrm{\τ}-m{\mathrm{\τ}}_c)=\left\{\begin{array}{cc}\exp \left[j2\mathrm{\π}(f_0+\frac{1}{2}\mathrm{\μ}{\mathrm{\τ}}_c)(\mathrm{\τ}-m{\mathrm{\τ}}_c)\right]\·& \\ ({\mathrm{\τ}}_c-|\mathrm{\τ}-m{\mathrm{\τ}}_c\left|\right)\sin c\left[\mathrm{\π\μ}{\mathrm{\τ}}_c(\mathrm{\τ}-m{\mathrm{\τ}}_c)(1-\frac{|\mathrm{\τ}-m{\mathrm{\τ}}_c|}{{\mathrm{\τ}}_c})\right],& |\mathrm{\τ}-m{\mathrm{\τ}}_c|\≤{\mathrm{\τ}}_c\\ 0,& |\mathrm{\τ}-m{\mathrm{\τ}}_c|\&greaterequal;{\mathrm{\τ}}_c\end{array}\right.$

In formula,For balancing the cross-correlation function of gold code；r_lfm(τ) for the cross-correlation function of linear FM signal. The channel separation of echo-signal is achieved, the sharp nature of auto-correlation function is conducive to improving the accurate of measurement after relevant treatment Property.

Step c, using r1 in the echo data matrix of m × n autonomous channel, (2,1, t) (3,4, data t) is entered with r1 Row matched filtering processes and obtains corresponding transition time δ t1 and δ t2, and by computing formula (δ t1+ δ t2), c/2 is according to a preliminary estimate Go out the distance at interface that rises and falls. as improvement, we adopt self adaptation focusing method, first by fluctuating interface according to a preliminary estimate Distance and bearing angle determines that each " scans " focal position of the Wave beam forming in direction, then the signal after channel separation is prolonged Shi Qiuhe Wave beam forming is processed, and whether the echo-signal in the predetermined orientation of detection has all carried out Wave beam forming process, if Result is negative, then untreated orientation is proceeded with Wave beam forming and processes, conversely, obtaining new echo-signal matrix. The peak value of the echo-signal after being processed by channel separation and Wave beam forming obtains the transition time δ t of target echo signal, calculates δ t c obtains target distance measurement information.

Embodiment one:

As shown in Fig. 2 the criterion of the ultrasonic Sparse Array element array arrangement in the present embodiment is: if setting between Virtual array Away from for d, then the array element distance of every group of emission array is d^t=2 × d, the array element distance of receiving array is d^r=m × d, every group of transmitting Array is d with the spacing at receiving array edge.Embodiment of the present invention all using 4 transmitting array elements, its coordinate be respectively (- 135,0), (- 105,0), (105,0), (135,0) (unit: mm), 4 reception array elements, its coordinate is respectively (- 90,0), (- 30,0), (30,0), (90,0) (unit: mm).

The centre frequency of linear FM signal is set to 300khz, carries a width of 60khz, and balance gold code adopts in table 1 below Coding.

Table 1 optimizes the balance gold code that the code length obtaining is 127

Be respectively adopted linear FM signal excitation carry out time division emission pattern, balance gold-lfm composite signal excitation carry out Emission mode and point measurement chirp carry out single channel emission mode simultaneously.

When the measurement of fluctuating interface distance is carried out using time division emission pattern, using the 44 ultrasonic thinned arrays of receipts in Fig. 2 Obtain the echo data of 16 autonomous channels, 4 transmitting array element transmission signal pie graphs are as shown in Figure 3；It is organized into echo data After matrix, follow-up signal processing procedure comprises the following steps (as shown in Figure 4): 1. utilize echo data matrix in r1 (2,1, t) (3,4, data t) goes out the distance at interface that rises and falls according to a preliminary estimate, then by distance and the side at fluctuating interface according to a preliminary estimate with r1 Parallactic angle geometry determines that 2. the focal position of Wave beam forming is calculated according to the position coordinates of ultrasound element and Wave beam forming focus Time delay and the corresponding relative delay of each Virtual array, correspond to each echo-signal in echo data matrix Time delay equalization, then carry out the composite signal obtaining that this side up of suing for peace, change focus orientation repeat processed above Until obtaining, 3. directive composite signal carries out tiltedly processing and fft journey to a directive composite signal, obtains corresponding On direction, supersonic array center, to the distance at fluctuating interface, can obtain fluctuating interface shape sample distance letter according to azimuth Breath, is averaged to it and obtains accurate range information.

When carrying out the measurement of fluctuating interface distance using emission mode simultaneously, 4 transmitting array elements launch different balances simultaneously The linear frequency modulation ripple of gold pscudo-random codc modulation, 4 receive array element and receive simultaneously, and the echo-signal that each receives array element reception is divided Do not carry out related operation with 4 transmission signals and realize channel separation, obtain the signal of 4 × 4=16 autonomous channel, then carry out Wave beam forming is processed, and obtains corresponding range information.

Aforementioned three kinds of emission modes in the case of single scattering son measurement the pulse compression result figure that obtains as shown in figure 5, From figure 5 it can be seen that main secondary lobe ratio after pulse compression for the transmitted waveform under two kinds of emission modes of present invention offer Higher, there is preferable range resolution ratio, the pulsewidth after balance gold-lfm composite signal pulse pressure compares linear FM signal Narrower but secondary lobe slightly improves, and Range resolution effect in the case of multiple scattering measurement for the point measurement chirp is relatively Difference.

Embodiment two:

Ultrasound element array arrangement as shown in Fig. 2 take array center's point be reference axis initial point, the center of linear FM signal Frequency is set to 300khz, carries a width of 60khz, and point target position is located at (14 °, 1.2m), by changing the position of Wave beam forming focus Put the impact that the deviation of inspection Wave beam forming focus produces to measurement accuracy, the skew of wherein Wave beam forming focus be divided into along Synthesis wave beam axially offsets with azimuth both direction.When Wave beam forming focus is 20mm along synthesis wave beam axle offset scope, When echo signal to noise ratio is higher than 5, measure error is stablized in 0.6mm, however, azimuthal displacement can lead to sizable Wave beam forming Focal shift, causes serious measure error, corresponding emulation (using time division emission pattern) result such as Fig. 6.From Fig. 6 we As can be seen that echo signal to noise ratio is 15, when the azimuth of Wave beam forming focus is 0.245 radian (14 °), measure error is less than 0.5mm, when the azimuth of Wave beam forming focus is reduced to 0.241 radian (13.45 °) or increases to 0.253 radian (14.55 °) When, measure error increases to 1.2mm；Echo signal to noise ratio is reduced to 5, and the azimuth of Wave beam forming focus is reduced to 0.242 radian (13.85 °) or when increasing to 0.247 radian (14.2 °), measure error is more than 1.2mm.It can also be seen that wave beam shape from Fig. 6 Become focus along azimuth direction offset when, measure error near symmetrical, with the reduction of echo signal to noise ratio, Wave beam forming focus It is limited in a small range along azimuth direction deviation range and may insure desired measure error.Although, the wave beam in method Formed focus deviation can on measurement accuracy produce impact, but, the present invention due to employing self adaptation focusing method, Ensure that focus changes with the change at interface, thus ensureing the accuracy measuring.

Embodiment three:

Ultrasound element array arrangement such as Fig. 2, takes array center's point to be reference axis initial point, the centre frequency of linear FM signal Be set to 300khz, carry a width of 60khz, balance gold code adopts the coding in table 1, be respectively adopted timesharing, simultaneously emission mode exist Carry out single-point target measurement under different state of signal-to-noise, the scope of signal to noise ratio takes -30～15db, point target position be located at (0 °, 0.5m), steps flow chart, with embodiment one, obtains the Error Graph (Fig. 7) of two kinds of emission modes under different state of signal-to-noise.

As can be seen that the method for the invention accurately can measure target range in the case of low signal-to-noise ratio from Fig. 7 (a), Especially at the same time under emission mode, in the case of signal to noise ratio as little as -30db, remain to reliably working.Fig. 7 (b) is the longitudinal direction of Fig. 7 (a) Enlarged drawing it can be seen that at the same time under emission mode measure error within 0.1mm, the method has preferable noiseproof feature.

Example IV:

Ultrasound element array arrangement such as Fig. 2, takes array center's point to be reference axis initial point, the centre frequency of linear FM signal It is set to 300khz, carries a width of 60khz, shown in the such as Fig. 8 (a) of fluctuating interface, carry out the survey at fluctuating interface using time division emission pattern Amount, steps flow chart, with embodiment one, obtains measure error figure such as Fig. 8 (b).

Using r1 in echo data matrix, (2,1, t) (3,4, data t) goes out the distance at interface that rises and falls according to a preliminary estimate with r1 For 1.0063m, the distance finally giving fluctuating interface is 1.0002, and maximum error of measuring is 0.1867mm, therefore, institute of the present invention State that method is not only feasible, and the degree of accuracy of fluctuating interface level measurement can be improved further.

Technological means disclosed in the present invention program is not limited only to the technological means disclosed in above-mentioned embodiment, also includes By the formed technical scheme of above technical characteristic any combination.It should be pointed out that for those skilled in the art For, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications are also considered as Protection scope of the present invention.

Claims (4)

1. a kind of ultrasonic measurement method of the mimo thinned array for the interface that rises and falls is it is characterised in that adopt mimo Sparse Array Element array, by m transmitting array element with n receive array element equivalent become the uniform Virtual array arranged of m × n；Comprise the steps:

Step a, using m transmitting array element time division emission identical linear frequency modulation ripple, transmission signal is:

S1 (t)=exp { j (2 π f₀t+πμt²)},0≤t≤t

Wherein, f₀For the initial frequency of linear frequency modulation ripple, μ=b/t is the chirp rate of linear frequency modulation ripple, and wherein b is frequency modulation band Width, t is signal duration；

Step b, n receives array element and receives corresponding Virtual array echo-signal, and echo-signal is:

R1 (m, n, t)=α_mns1(t-δt_mn),1≤m≤m,1≤n≤n

Wherein, α_mnFor echo-signal attenuation coefficient, m, n represent m-th transmitting array element and n-th reception array element, δ t respectively_mnFor Transmission signal launches array element to target from m-th, then the propagation time by target to n-th reception array element；

Step c, carries out Wave beam forming process, acquisition echo data matrix to signal:

Step c-1, corresponding for each echo-signal Virtual array is reassembled into the echo-signal of m × n autonomous channel；

Step c-2, using r1 in echo data matrix, (2,1, t) (3,4, data t) carries out matched filtering process and obtains with r1 Corresponding transition time δ t1 and δ t2；

Step c-3, goes out, by computing formula (δ t1+ δ t2) c/2, the distance at interface that rises and falls according to a preliminary estimate；

Step c-4, enters line delay summation Wave beam forming and processes to echo-signal:

$y\left(t\right)=\underset{m,n}{\&sigma;}{\mathrm{\&alpha;}}_{mn}s1(t-{\mathrm{\&delta;t}}_{mn}^c),1<m\&le;m,1\&le;n\&le;n$

WhereinFor time delay after Wave beam forming for the different Virtual arrays, τ_mnFor different Virtual arrays relatively Delay compensation value in reference point；

Step c-5, whether the echo-signal in the predetermined orientation of detection has all carried out Wave beam forming process, to untreated side Position proceeds Wave beam forming and processes, until after all signals have all carried out Wave beam forming process, obtaining new echo-signal square Battle array；

Step d, carries out tiltedly processing to the signal after Wave beam forming, output signal is:

Y1 (m, n, t)=aexp { j2 π φ (m, n, t) }

In formula, phase function φ isA is range coefficient；

After trying to achieve process, signal frequency composition isFft process is carried out to signal, obtains distance letter Breath:

$d_{mn}={\mathrm{c\&delta;t}}_{mn}^c=\frac{{\mathrm{cf}}_{mn}}{\mathrm{\&mu;}}.$

2. the mimo thinned array for the interface that rises and falls according to claim 1 ultrasonic measurement method it is characterised in that Self adaptation focus setting procedure is also included after described step c-3:

Determine the focal position of the Wave beam forming of each scanning direction by the distance and bearing angle at fluctuating interface according to a preliminary estimate.

3. a kind of ultrasound measurement system of the mimo thinned array for the interface that rises and falls it is characterised in that: include supersonic array and Signal transmitting and process model,

Described supersonic array by m transmitting array element with n receive array element equivalent become the uniform Virtual array arranged of m × n；

Described signal transmitting and process model and include time division emission model and Launching Model simultaneously, described time division emission model includes Time division emission unit, beam forming unit, remove oblique processing unit, fft converter unit；

M transmitting array element time division emission linear frequency modulation ripple in described time division emission unit, is realized empty by the time division emission of signal The channel separation of matroid unit echo-signal, n receives array element and receives corresponding Virtual array echo-signal；

Described beam forming unit is used for, after all echo signal reception terminate, each echo-signal being corresponded to Virtual array weight The echo-signal of m × n autonomous channel of composition, carries out Wave beam forming process to it；

Described remove oblique processing unit for carrying out tiltedly processing to composite signal；

Described fft converter unit is used for going the signal after tiltedly processing to carry out fft process, is calculated corresponding range information；

Described Launching Model simultaneously includes transmitter unit, channel separation unit, beam forming unit simultaneously；

The linear frequency modulation that array element launches different balance gold pscudo-random codc modulation simultaneously is launched for m in described transmitter unit simultaneously Ripple, n receives array element and receives simultaneously；

Described channel separation unit carries out related respectively for the echo-signal that each is received with array element reception to m transmission signal Channel separation is realized in computing, obtains the signal of m × n autonomous channel,

Described beam forming unit is used for carrying out Wave beam forming process to the signal that above-mentioned separation obtains, and obtains corresponding distance letter Breath.

4. the mimo thinned array for the interface that rises and falls according to claim 3 ultrasound measurement system it is characterised in that: In described time division emission model and simultaneously Launching Model, beam forming unit, when signal is carried out with Wave beam forming process, adopts Self adaptation focusing method.