CN104267403A - Rapid dynamic focusing method for shallow-water multi-beam echo sounder - Google Patents

Abstract

The invention discloses a rapid dynamic focusing method for a shallow-water multi-beam echo sounder. The method comprises the steps that underwater acoustic transducer array elements collect echo sound signals of the multi-beam echo sounder, and the sound signals are converted into electric signals and then processed to obtain digital signals; the digital signals are converted to obtain the plural form V<m> of the echo sound signals; a preset angle theta <k> is selected, and a phase shift parameter tau<mki> of the ith array element is rapidly figured out according to the sampling point number N and the array element number m; the plural form of the phase shift parameters of the array elements and the plural form V<m> of the echo sound signals are correspondingly multiply-accumulated according to the channel number and the sampling point number, and a single-beam dynamic focusing result is obtained; whether a preset angle which is not selected exists or not is judged, if yes, the third step and the fourth step are executed again, and if not, all single-beam dynamic focusing results are output. The rapid dynamic focusing method has the rapid calculating ability with no reduction of the precision of dynamic focusing carried out during multi-beam sounding, and is high in precision, simple in structure and easy to implement.

Description

A kind of quick dynamic focusing method of shallow water multibeam echosounder

Technical field

The invention belongs to multibeam echosounding field, particularly relate to and can solve near-field effect, a kind of shallow water multibeam echosounder quick dynamic focusing method.

Background technology

China has large-area marine site and inland river, rivers and lakes, and major part belongs to shallow-water environment, and for understanding water-bed landform fully, shallow water multibeam echosounder plays irreplaceable effect.Along with the continuous progress of science and technology, people have more and more higher requirement to the precision obtaining water-bed landform, and calculate for simplifying in conventional multibeam echosounder, the normal far-field approximation model that adopts, and are meeting r > > D ²can ensure high precision during/λ, wherein r is the distance of target from array element center, and D is the pore size of basic matrix, and λ is the wavelength of Received signal strength, and for not meeting the near field situation of this condition, total accuracy of sounding sharply declines.In whole investigative range, all ensure total accuracy of sounding in order to ensure multibeam echosounder, near field situation does not allow ignorance, and particularly in occasions such as the river courses that shallow water is main, this problem is particularly outstanding.

For solving Near-field Problems In Civil Engineering, domestic and international experts and scholars have carried out many theoretical researches, but are limited to theoretical simulation or segmentation focus approach more.Wherein theoretical simulation is only limitted to total accuracy of sounding analysis, cannot be applied in the Quick Measurement of shallow water multibeam echosounder; Although segmentation focus approach can realize but fast to lose measuring accuracy for cost.The people such as Chen Ying propose in its article delivered the quick acoustic imaging algorithm of focused beamforming " adopt classification ", Chen Ying, Ye Qinghua, the Huanghai Sea is peaceful. adopt the quick acoustic imaging algorithm [J] of classification focused beamforming, applied acoustics, 2008,27 (3): 207-210.Although computing velocity improves, dynamic beam focusing error is larger.Therefore, a kind of new quick high accuracy dynamic beam focus method is badly in need of.

Summary of the invention

The object of this invention is to provide have high-precision, a kind of quick dynamic focusing method of shallow water multibeam echosounder.

The present invention is achieved by the following technical solutions:

A kind of quick dynamic focusing method of shallow water multibeam echosounder, comprises following step:

Step one: underwater acoustic transducer array element gathers the echo acoustical signal of multibeam echosounder, acoustical signal is converted to electric signal, then obtains digital signal through process;

Step 2: plural form V digital signal being obtained echo acoustical signal through orthogonal transformation _m;

Step 3: select a predetermined angle θ _k, according to sampling period N and array element m, calculate the phase shift parameters τ of i-th array element _mki,

Wherein angle item factor of influence distance terms factor of influence c is the velocity of sound, f _sfor sampling rate, π is circular constant, and d is array element distance, and λ is wavelength, and k is numbers of beams;

By the phase shift parameters τ of i-th array element _mkicalculated by Coordinate Rotation Digital, obtain the phase shift parameters τ of i-th array element _mkiplural form;

Step 4: by the plural form V of the plural form of the phase shift parameters of each array element and echo acoustical signal _m, by channel number and the corresponding multiply accumulating of sampling period, obtain the dynamic focusing result of single beam wherein M is array element sum;

Step 5: judge whether to there is non-selected predetermined angle, if existed, repeats step 3 ~ step 4, otherwise, export the dynamic focusing result of all single beams.

Beneficial effect of the present invention:

Provide one dynamic focus technology fast, according to the difference of goal-selling from the difference of basic matrix distance and array element number, calculate the phase shift parameters of corresponding each array element, then plural form phase shift parameters being converted to plural form and echoed signal, by the corresponding multiply accumulating of channel number, obtains quick dynamic focusing result.Introducing area and speed exchange principle simultaneously, solve the quick computational problem of dynamic focusing.The effect that the present invention is useful is: when not losing dynamic focusing precision in multibeam echosounding, has the ability calculated fast, and structure is simple, is easy to realize, can be widely used in the near field Quick Measurement precision improving shallow water multibeam echosounder.

Accompanying drawing explanation

Fig. 1 method flow diagram of the present invention,

The connected system block diagram of Fig. 2 specific embodiment of the invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further details.

1, the quick dynamic focusing method of shallow water multibeam echosounder, comprises step as follows:

Step one: gather the echoed signal of multibeam echosounder with underwater acoustic transducer, carry out acoustic-electric conversion, then through amplification, filtering, time-varying gain control with analog to digital conversion is down-sampled obtains digital signal;

Step 2: the plural form V result of step one being obtained echoed signal through orthogonal transformation _m;

Step 3: according to the predetermined angle θ of dynamic focusing Wave beam forming _k, sampling period N and array element m, calculate the phase shift parameters of each array element fast wherein angle item factor of influence distance terms factor of influence c is the velocity of sound, f _sfor sampling rate, π be circular constant, d is array element distance, λ is wavelength, k is numbers of beams;

By phase shift parameters result τ _mkcalculated by quick Coordinate Rotation Digital, produce the sinusoidal result sin (τ of phase shift parameters respectively _mk) and cosine result cos (τ _mk);

Step 4: by the predetermined angle θ of dynamic focusing Wave beam forming _kphase shift parameters be converted to the plural form V of plural form and the multibeam echosounding echoed signal after orthogonal transformation _m, press corresponding θ by channel number and sampling period _km multiplication result of angle adds up, and obtains the dynamic focusing result of single wave beam namely be the focus beam output of k θ angle of Wave beam forming, wherein M is array element sum, V _mrepresent the plural form of the echoed signal of array element m, j represents the imaginary part of plural number;

Step 5: by different θ _kangle repeats step 4, can obtain the result of the quick dynamic focusing of arranging by isogonism or equidistant pattern.

2, aforesaid step 3, comprises step as follows:

The first step: utilize and produce array element m from adding device circulation, its value is from 0 to (M-1), and wherein M is element number of array, and resets when launching multi-beam echo sounding signal;

Second step: previous step result is input to squarer and produces m ², and by result and parameter the result correspondence that storer exports is multiplied, wherein parameter c is the velocity of sound, f _sfor sampling rate, π be circular constant, d is array element distance, λ is wavelength, θ _kfor a kth focus wave beam angle;

3rd step: by first step result and parameter γ _kthe result correspondence that storer exports is multiplied, wherein π is circular constant, d is array element distance, λ is wavelength, θ _kfor a kth focus wave beam angle;

4th step: to launch multi-beam echo sounding signal for starting point, take sampling period as interval, produces sampling period count value N with from adding device, and produces (2 with divider ^p)/N, wherein 16≤p≤64, and p is integer;

5th step: the result of step 2 is multiplied by step 4 result and divided by (2 ^p) or p position that fixed point results is moved to right, producing near-field effect affects item;

6) result of step 3 and step 5 is added up by totalizer, obtain phase shift parameters result wherein τ _mkfor a kth focus wave beam angle is in the phase shift of array element m.

The quick dynamic focusing method of a kind of shallow water multibeam echosounder of the present invention, comprise fast dynamically phase shift computing module 1 and quick phase shift to add up summation module 2 two parts, be connected to the quick phase shift summation module 2 that adds up by electric signal after wherein dynamically phase shift computing module 1 dynamically calculates corresponding phase shift fast according to the change of sampling period and array element number fast and calculate the result exporting dynamic focusing.At this with implementation example explanation in programmable gate array.

Dynamic phase shift computing module 1, comprises array element m counter 4, array element m squarer 3, parameter fast with parameter γ _kstorer 5,10, sampling period N counter 7, divider 8, two multipliers 6,9, a totalizer 11 and phase shift result memory 12; For calculating dynamic phase shift fast, need internal logic Resource Design array element m counter 4 be used, realize array element m squarer 3 by multiplier resources, by internal storage Resource Design parameter with parameter γ _kstorer 5,10, with internal logic Resource Design sampling period N counter 7, with internal multiplier Resource Design two multipliers 6,9, with internal logic Resource Design divider 8, use internal logic Resource Design totalizer 11 again, finally with memory resource design phase shift result memory 12, wherein parameter with parameter γ _kmeet wherein c is the velocity of sound, f _sfor sampling rate, π be circular constant, d is array element distance, λ is wavelength, θ _kfor a kth focus wave beam angle.Wherein array element m counter 4 circulates and produces channel number, by array element m squarer 3 and parameter the pre-stored data of storer is multiplied, and then divided by sampling period N counter, can obtain the output of array element m counter 4 simultaneously, direct and parameter γ _kthe pre-stored data of storer is multiplied and can obtains m γ _kpart, two parts are added can obtain dynamic phase shift concrete structure is as shown in Fig. 21:

Wherein m is array element number, N is sampling period, for custom parameter, the γ of a kth focus wave beam angle _kfor the custom parameter of a kth focus wave beam angle.Often receive one group of hyperchannel raw data, sampling period N counter 7, from increasing 1, then delivers to divider 8 as electronic signals; Array element m counter 4 Zi increasing to array number M, is then transferred to array element m squarer 3 and multiplier 9 from 1 in electrical signal form;

Array element m squarer 3 completes square operation after receiving array element m value, then delivers to multiplier 6;

Multiplier 9 is address lookup parameter γ with array element number after receiving the change of array element number _kstorer 10, and be multiplied number corresponding with Query Result for array element, result is outputted to totalizer 11 in electrical signal form; Multiplier 6 is address lookup parameter with array element number after receiving the change of array element number square storer 5, and be multiplied square corresponding with Query Result for array element number, result is outputted to divider 8 in electrical signal form;

Divider 8 uses the result of multiplier 6 divided by sampling period N counter 7 result, and outputs to totalizer 11 in electrical signal form; The result correspondence of divider 8 and multiplier 9 is added by totalizer 11, can obtain fast dynamically phase shift result of calculation.

Quick phase shift adds up summation module 2, comprises Coordinate Rotation Digital computing module 13, raw storage 14, complex multiplier 15, totalizer 16 and dynamic beam focusing results storer 17.

Result V (θ is formed for calculating dynamic near field focused beam fast _k), wherein

$V\left({\mathrm{\&theta;}}_k\right)=\underset{m=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{V}_m(\cos \left({\mathrm{\&tau;}}_{\mathrm{mk}}\right)-j\sin \left({\mathrm{\&tau;}}_{\mathrm{mk}}\right))$

In formula: V (θ _k) represent k θ angle of Wave beam forming focus beam export, V _mrepresent the raw data input signal of array element m, M represents the overall channel number of raw data, and j represents the imaginary part of plural number.Internal logic Resource Design Coordinate Rotation Digital computing module 13 need be used, with internal storage Resource Design raw storage 14, with internal multiplier and totalizer Resource Design complex multiplier 15, with internal additions device Resource Design totalizer 16 with internal storage Resource Design dynamic beam focusing results storer 17.Wherein Coordinate Rotation Digital computing module 13 is considering fast and the problem of precision, and the Coordinate Rotation Digital of 18 iteration can be adopted to calculate.By dynamic phase shift τ _mkresult is sent in Coordinate Rotation Digital computing module 13, corresponding sine and cosine is produced through interative computation, then complex multiplier 15 is passed through with the raw data of raw storage 14, finally obtaining dynamic near field focused beam by totalizer 16 forms result, and concrete structure is as shown in Fig. 22.

Wherein Coordinate Rotation Digital computing module 13 receives the phase shift result of calculation from quick dynamically phase shift computing module 1, and calculates output sine and cosine result; Coordinate Rotation Digital computing module 13 and raw storage 14 export electric signal respectively and are connected to the complex multiplication that complex multiplier 15 completes raw data and phase shift parameters, reach the object of phase shift; Complex multiplier 15, totalizer 16 and dynamic beam focusing results storer 17, press electric signal successively and connect, by by the raw data of each passage after the phase shift of correspondence is cumulative, dynamic focusing result is stored in storer.Coordinate Rotation Digital computing module 13 receives the phase-shift value from quick dynamically phase shift computing module 1 in electrical signal form, calculated by Coordinate Rotation Digital, obtain sine and the cosine result of corresponding phase shift, and be combined into the plural form of phase shift, and be sent to complex multiplier 15 in electrical signal form; Corresponding for data in the result of calculation of Coordinate Rotation Digital computing module 13 and raw storage 14 complex multiplication is obtained complex result by complex multiplier 15, transfers to totalizer 16 in electrical signal form; Totalizer 16 obtains dynamic focusing result by cumulative for complex multiplier 15 result of corresponding array element number 1 to M, and is stored in dynamic beam focusing results storer 17.

The invention provides one dynamic focus technology fast, according to the difference of goal-selling from the difference of basic matrix distance and array element number, calculate the phase shift parameters of corresponding each array element, then plural form phase shift parameters being converted to plural form and echoed signal, by the corresponding multiply accumulating of channel number, obtains quick dynamic focusing result.Introducing area and speed exchange principle simultaneously, approximate due to what do not adopt classification focusing and segmentation to focus on, relative classification focused beamforming and segmentation focused beamforming have the high feature of focus beam precision, solve the problem of traditional shallow water multibeam echosounder near field high precision depth measurement, reach the object calculating near field dynamic beam focused beamforming fast.

Claims (1)

1. the quick dynamic focusing method of shallow water multibeam echosounder, is characterized in that, comprise following step:

Step one: underwater acoustic transducer array element gathers the echo acoustical signal of multibeam echosounder, acoustical signal is converted to electric signal, then obtains digital signal through process;

Step 2: plural form V digital signal being obtained echo acoustical signal through orthogonal transformation _m;

Step 3: select a predetermined angle θ _k, according to sampling period N and array element m, calculate the phase shift parameters τ of i-th array element _mki,

Wherein angle item factor of influence distance terms factor of influence c is the velocity of sound, f _sfor sampling rate, π is circular constant, and d is array element distance, and λ is wavelength, and k is numbers of beams;

By the phase shift parameters τ of i-th array element _mkicalculated by Coordinate Rotation Digital, obtain the phase shift parameters τ of i-th array element _mkiplural form;

Step 4: by the plural form V of the plural form of the phase shift parameters of each array element and echo acoustical signal _m, by channel number and the corresponding multiply accumulating of sampling period, obtain the dynamic focusing result of single beam wherein M is array element sum;

Step 5: judge whether to there is non-selected predetermined angle, if existed, repeats step 3 ~ step 4, otherwise, export the dynamic focusing result of all single beams.