CN105137394A - Super-short baseline water sound positioning system based on maximum likelihood estimation and positioning algorithm - Google Patents

Abstract

The invention discloses a super-short baseline water sound positioning system based on maximum likelihood estimation and a positioning algorithm, which solves the technical problem that the long-distance positioning accuracy of the super short baseline positioning system is low. The super-short baseline water sound positioning system consists of an under-water responder and a sound reception basic matrix, wherein the under water responder is capable of generating and emitting ultrasonic wave positioning signals and the sound reception basic matrix capable of receiving and processing ultrasonic positioning signals; the positioning algorithm utilizes internal geometry relations among all basic matrix member signals, does not need the ultrasonic signal to reach the azimuth of array element of the matrix array and improves the accuracy of the position solution. The maximum likelihood estimation is utilized to perform integral processing on the signal reaching all the array members after summation in order to obtain a global optimal positioning result. Unified resolving is performed on the ultrasonic signals, which is equivalent to improving integration time. As a result, when the signal to noise ratio of the signals is relatively low, the super-short baseline water sound positioning system based on maximum likelihood estimation can effectively improves the signal-to-noise ratio and further guarantee the accuracy of the signals.

Description

Based on ultra-short baseline acoustic positioning system and the location algorithm thereof of Maximum-likelihood estimation

Technical field

The invention belongs to ultrasonic positioning techniques field, relate to long distance and high precision ultra-short baseline ultrasonic positioning techniques under water, specifically refer to a kind of ultra-short baseline acoustic positioning system based on Maximum-likelihood estimation and location algorithm thereof.

Background technology

For to the exploitation of ocean resources or military demand, usually the real-time position information knowing submarine target carrier is needed, but because light wave and radiowave can produce larger decay when water transmission, cause traditional radio and optical positioning system normally to work.And the rate of decay of sound wave in water is very slow, can propagate at a distance, therefore, the acoustic positioning technique based on sound wave is widely used in the engineering field such as operation and ocean petroleum developing under water.Classify according to acoustic receiver basic matrix base length, acoustic positioning technique can be divided into Long baselines, Short baseline and ultra-short baseline three kinds.Long baselines and Short baseline acoustic positioning technique positioning precision is high, distance, but because of its baseline longer, there is the problem of installation and deployment difficulty.Ultra-short baseline acoustic positioning technique is generally only several centimetres because of its base length, and have the advantage that equipment volume is little, can carry out rapid deployment, the field such as operation and ocean petroleum developing is widely applied under water.But, because the location baseline of ultra short base line is short, therefore when localizing objects distance basic matrix is comparatively far away or ultrasonic signal signal to noise ratio (S/N ratio) is lower, be difficult to obtain high-precision positioning result, and positioning error can increase along with the increase of distance.

Summary of the invention

For above-mentioned technical matters, the invention provides a kind of ultra-short baseline acoustic positioning system based on Maximum-likelihood estimation and location algorithm thereof, solve the technical matters that ultra short baseline locating system long distance positioning precision is low; Utilize the inherent geometric relationship between each base array element signals, by the position of Maximum-likelihood estimation direct solution localizing objects, effectively prevent direction of arrival of signal angle error and range error to the impact of positioning precision, effectively improve the precision of location compute.

The present invention is achieved through the following technical solutions above-mentioned purpose:

Based on a ultra-short baseline acoustic positioning system for Maximum-likelihood estimation, described positioning system is made up of reception acoustic array two parts of the transponder under water and reception and process ultrasound locating signal that produce and launch ultrasound locating signal;

Wherein, under water transponder by forming with lower unit of connecting successively:

Hydraulic pressure depthometer: the depth data being positioned at below surface level for measuring transponder;

Distance measuring signal generation module: generating the spread spectrum ultrasonic ranging signal waveform for locating, the depth data that hydraulic pressure depthometer records being modulated in this signal waveform simultaneously;

Transducer power amplifier: power amplification is carried out, to drive ultrasonic piezo-transducer work to the ultrasonic ranging signal generated;

Ultrasonic piezo-transducer: produce ultrasonic ranging signal and be transmitted to reception acoustic array;

Power module: for transponder running under water provides required power supply;

Described reception acoustic array is by forming with lower unit of connecting successively:

Transducer array: for comprising the orthogonal matrix of 5 transducer array elements, for tentatively receiving the ultrasound locating signal that transponder is under water launched;

Low noise amplifier: for amplifying the positioning signal that in transducer array, each array element exports;

Bandpass filter: carry out filtering to the positioning signal of amplifying via low noise amplifier, to reduce in water noise signal to the interference of positioning signal;

Analog-to-digital conversion module: digitized sampling is carried out to the simulating signal exported by bandpass filter;

Matched filter and signal receiving module: carry out demodulation to the ultrasonic ranging signal after digitized sampling, obtain the transponder depth information modulated in signal;

Positioning calculation module: for resolving the positional information of Underwater Navigation target;

Positioning result display module: be human-computer interaction interface, for showing locating result information for user.

As prioritization scheme of the present invention, described reception acoustic array also comprises acoustic array position and attitude reference module, the gyrocompass built-in by module and RTK system, for positioning calculation module provides accurate position and attitude reference information.

As prioritization scheme of the present invention, 5 transducer array elements of described transducer array use B respectively ₀, B ₁, B ₂, B ₃and B ₄represent, wherein, array element B ₀be positioned at the initial point of carrier coordinate system, array element B ₁, B ₂be positioned in the x-axis of carrier coordinate system, array element B ₃, B ₄be positioned in the y-axis of carrier coordinate system, and B ₁, B ₂, B ₃and B ₄to initial point B ₀distance C be less than or equal to the half of ultrasonic ranging signal wavelength, i.e. C≤λ/2.

As prioritization scheme of the present invention, described transducer is piezoelectric transducer.

The location algorithm of described ultra-short baseline acoustic positioning system, comprises the following steps:

(1) laying comprises 5 array element B ₀, B ₁, B ₂, B ₃and B ₄reception acoustic array, install acoustic responder at localizing objects point S place, it sends modulated the spread spectrum underwater sound signal of depth data to receiving acoustic array in a pulsed fashion, wherein, the coordinate of localizing objects point S is (x, y, z), z value is the depth data value measured by hydraulic pressure depthometer;

(2) adopt the incident horn cupping of traditional ultra-short baseline localization method oblique distance-sound ray, Primary Location is carried out to Underwater Navigation impact point S, obtains the initial value (x of localizing objects position ₀, y ₀);

(3) with (x ₀, y ₀) as estimating position, search for the coordinate (x, y) of localizing objects S in the search volume of Maximum-likelihood estimation, hunting zone is determined by the uncertainty of (x, y) value;

A), particularly, the process of a Maximum-likelihood estimation can be equivalent to:

$L=\underset{i=0}{\overset{4}{\Σ}}\[{\left|\underset{T_0}{\overset{T_0+T}{\∫}}{r}_i\left(t\right)S_i\left(t\right)dt\right|}^2\]---\left(1\right)$

Wherein, r _it () is array element B _iwhat (i=0,1,2,3,4) received contains noisy underwater sound signal; T ₀it is the initial time of each array element Received signal strength; T is the integral time of signal; S _it ()=f [t, (x, y, z)] is array element B _inot Noise this locality reproduction signal, it is a function being independent variable with (x, y, z);

B) the underwater sound signal model that, localizing objects S place acoustic responder sends is:

r(t)＝AC(t)D(t)cos(2πf _IFt)(2)

Wherein, A is signal amplitude, C (t) for being modulated at the pseudo-random code on signal, the positioning signal that D (t) is the localizing objects point S that modulates depth data, f _iFfor the centre frequency of ultrasonic signal carrier wave;

When localizing objects point S and the distance R that receives between acoustic array is much larger than acoustic array dimension D, during R/D>20, the S in formula (1) _it () can be expressed as:

Wherein, df is the Doppler shift of ultrasonic signal; τ _ifor ultrasonic signal sends rear arrival array element B from S point _itravel-time; for r ₀the phase differential of (t) signal and r (t) signal; for signal r _i(t) and signal r ₀the phase differential of (t);

C), following relation can be obtained according to the positioning principle figure of localizing objects S:

$\stackrel{\‾}{{\mathrm{SB}}_0}=R=\sqrt{x^2+y^2+z^2}$

cosα＝x/R

cosβ＝y/R

$\stackrel{\‾}{{\mathrm{SB}}_1}-\stackrel{\‾}{{\mathrm{SB}}_0}=D\frac{x}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_2}-\stackrel{\‾}{{\mathrm{SB}}_0}=-D\frac{x}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_3}-\stackrel{\‾}{{\mathrm{SB}}_0}=D\frac{y}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_4}-\stackrel{\‾}{{\mathrm{SB}}_0}=-D\frac{y}{R}---\left(4\right)$

Wherein, represent localizing objects S and acoustic array B _ithe distance of (i=0,1,2,3,4);

α is vector with the angle of x-axis positive dirction, β is vector with the angle of y-axis positive dirction, θ is the deflection of the projection S ‵ of localizing objects point S in carrier coordinate system in XOY plane;

D), by the corresponding relation in formula (3) and (4), S can be obtained _it () and localizing objects point S coordinate (x, y, z) have following relation:

The above-mentioned S drawn _it the relational expression between () Yu localizing objects point S coordinate (x, y, z) is a step the most key in location algorithm of the present invention; Wherein, the size of signal amplitude A can't have an impact to the estimated result of MLE, is set to 1; Velocity of sound c accurately can be measured by sound velocimeter; Carrier phase difference can by being arranged on basic matrix B with the exact value of Doppler frequency df ₀in phaselocked loop obtain; Localizing objects S directly measures by hydraulic pressure depthometer at the coordinate z of depth direction, and sends to acoustic array by ultrasonic signal; The centre frequency f of ultrasonic signal carrier wave _iFknown; Therefore A, c, z and df is known quantity; Therefore, this locality reproduction signal S of acoustic array _it () (i=0,1,2,3,4) are the function only containing parameter (x, y);

E), formula (5), (6), (7), (8), (9) are brought in formula (1), algorithm model localizing objects S coordinate (x, y) being carried out to Maximum-likelihood estimation can be used for:

$(\hat{x},\hat{y})=MLE(\underset{i=0}{\overset{4}{\Σ}}\[{|\underset{T_0}{\overset{T_0+T}{\∫}}{r}_i\left(t\right)S_i\[t,(x,y)\]dt|}^2\])---\left(10\right)$

Wherein, for the maximum likelihood estimation of localizing objects point coordinate; MLE () is Maximum-likelihood estimation computing;

(4) by the different coordinate (x of the localizing objects S of search _k, y _l) substitute into formula (10), r _i(t) and B _icorrelation integral computing is carried out in integration period T, and using the summation of the integral result of different array element as L _k,l, work as L _k,lwhen obtaining maximal value, corresponding (x _k, y _l) be both the position of required localizing objects S.

As prioritization scheme of the present invention, described in the search volume of Maximum-likelihood estimation, localizing objects S estimates position (x ₀, y ₀) and search radius R _searchcan be calculated as follows:

$(x_0,y_0)=\[x(n-1)+\mathrm{\Δ}\hat{x}\left(n\right),y(n-1)+\mathrm{\Δ}\hat{y}\left(n\right)\]$

$R_{search}=2\sqrt{{\left(\mathrm{\Δ}\hat{x}\right(n\left)\right)}^2+{\left(\mathrm{\Δ}\hat{y}\right(n\left)\right)}^2}$

$\mathrm{\Δ}\hat{x}\left(n\right)=x(n-1)-x(n-2)$

$\mathrm{\Δ}\hat{y}\left(n\right)=y(n-1)-y(n-2)$

Wherein, [x (n-1), y (n-1)] estimates the coordinate of ground point that obtains for last locating periodically by MLE; [x (n-2), y (n-2)] estimates the coordinate of ground point that obtains for locating periodically upper last time by MLE; for the variable quantity of the first two locating periodically localizing objects point coordinate.

As prioritization scheme of the present invention, described step (4) (x, the y) that try to achieve estimates position (x as next locating periodically ₀, y ₀), for the positioning calculation in next new cycle.

The invention has the beneficial effects as follows:

1, classic method is when carrying out the clearing of ultra-short baseline location, does not make full use of the inherent geometric relationship between each array element, causes " effective information " loss, therefore can not obtain optimum positioning result; And the method for the invention can utilize the inherent geometric relationship information between each array element more fully, do not need to solve the position angle that ultrasonic signal arrives acoustic array array element, avoid solving the impact of azimuth angle error on positioning precision, improve the precision of location compute;

2, calculate respectively when classic method calculates the angle of arrival of acoustical signal on all directions component, therefore result of calculation is locally optimal solution, and algorithm provided by the invention is when carrying out location compute, bulk treatment is carried out after being sued for peace by the signal arriving all array element, and utilize Maximum-likelihood estimation direct solution localizing objects position, the positioning result of global optimum can be obtained;

3, the ultrasonic signal that all array element receives by the present invention carries out unifying to resolve, and is equivalent to add integral time, therefore when the signal to noise ratio (S/N ratio) of signal is lower, effectively can improve signal to noise ratio (S/N ratio) by the method for the invention, ensures signal accuracy;

4, based on Maximum-likelihood estimation criterion as theoretical foundation, the reliability resolved of under extreme conditions positioning system can be ensured.

Accompanying drawing explanation

Fig. 1 is system architecture diagram of the present invention;

Fig. 2 is location algorithm FB(flow block) of the present invention;

Fig. 3 is transducer array schematic diagram in the present invention;

Fig. 4 is the positioning principle figure of localizing objects;

Fig. 5 is the search module schematic diagram of Maximum-likelihood estimation;

Fig. 6 is the search volume schematic diagram of Maximum-likelihood estimation.

Embodiment

Below in conjunction with drawings and Examples, the present invention and effect thereof are further elaborated.

Maximum-likelihood estimation location algorithm for ultra-short baseline acoustic positioning system of the present invention, belong to long distance, high precision ultra-short baseline ultrasonic positioning techniques field under water, solve the technical matters that ultra-short baseline underwater positioning system long distance positioning is accurately low.The orthogonal matrix comprising five array elements is adopted to receive basic matrix as ultrasonic signal, and do not need calculate ultrasonic signal and receive the distance of basic matrix and the arrival direction angle of ultrasonic signal, but utilize the internal relation between each base array element signals, utilize maximum likelihood estimation algorithm directly to solve the locus of localizing objects, therefore can effectively avoid deflection error and range error on the impact of positioning precision.

As shown in Figure 1, a kind of ultra-short baseline acoustic positioning system based on Maximum-likelihood estimation, described positioning system is made up of reception acoustic array two parts of the transponder under water and reception and process ultrasound locating signal that produce and launch ultrasound locating signal;

Wherein, under water transponder by forming with lower unit of connecting successively:

Hydraulic pressure depthometer: the depth data being positioned at below surface level for measuring transponder;

Distance measuring signal generation module: generating the spread spectrum ultrasonic ranging signal waveform for locating, the depth data that hydraulic pressure depthometer records being modulated in this signal waveform simultaneously;

Transducer power amplifier: power amplification is carried out, to drive ultrasonic piezo-transducer work to the ultrasonic ranging signal generated;

Ultrasonic piezo-transducer: produce ultrasonic ranging signal and be transmitted to reception acoustic array;

Power module: for transponder running under water provides required power supply;

Described reception acoustic array is by forming with lower unit of connecting successively:

Transducer array: for comprising the orthogonal matrix of 5 transducer array elements, for tentatively receiving the ultrasound locating signal that transponder is under water launched; Transducer adopts piezoelectric transducer;

Low noise amplifier: for amplifying the positioning signal that in transducer array, each array element exports;

Bandpass filter: carry out filtering to the positioning signal of amplifying via low noise amplifier, to reduce in water noise signal to the interference of positioning signal;

Analog-to-digital conversion module: digitized sampling is carried out to the simulating signal exported by bandpass filter;

Matched filter and signal receiving module: carry out demodulation to the ultrasonic ranging signal after digitized sampling, obtain the transponder depth information modulated in signal;

Positioning calculation module: for resolving the positional information of Underwater Navigation target;

Positioning result display module: be human-computer interaction interface, for showing locating result information for user.

Receive acoustic array and also comprise acoustic array position and attitude reference module, the gyrocompass built-in by module and RTK system, for positioning calculation module provides accurate position and attitude reference information.

5 transducer array elements of transducer array use B respectively ₀, B ₁, B ₂, B ₃and B ₄represent, wherein, array element B ₀be positioned at the initial point of carrier coordinate system, array element B ₁, B ₂be positioned in the x-axis of carrier coordinate system, array element B ₃, B ₄be positioned in the y-axis of carrier coordinate system, and B ₁, B ₂, B ₃and B ₄to initial point B ₀distance C be less than or equal to the half of ultrasonic ranging signal wavelength, i.e. C≤λ/2.

As shown in Figure 2, the location algorithm of ultra-short baseline acoustic positioning system, comprises the following steps:

(1) laying comprises 5 array element B ₀, B ₁, B ₂, B ₃and B ₄reception acoustic array, as shown in Figure 3, wherein, array element B ₀be positioned at the initial point of carrier coordinate system, array element B ₁, B ₂be positioned in the x-axis of carrier coordinate system, array element B ₃, B ₄be positioned in the y-axis of carrier coordinate system, and B ₁, B ₂, B ₃and B ₄to initial point B ₀distance C be less than or equal to the half of ultrasonic ranging signal wavelength, i.e. C≤λ/2; Install acoustic responder at localizing objects point S place, it sends the spread spectrum underwater sound signal of having modulated depth data to receiving acoustic array in a pulsed fashion, wherein, the coordinate of localizing objects point S is (x, y, z), z value is the depth data value measured by hydraulic pressure depthometer;

(2) adopt the incident horn cupping of traditional ultra-short baseline localization method oblique distance-sound ray, Primary Location is carried out to Underwater Navigation impact point S, obtains the initial value (x of localizing objects position ₀, y ₀);

(3) with (x ₀, y ₀) as estimating position, search for the coordinate (x, y) of localizing objects S in the search volume (as shown in Figure 6) of Maximum-likelihood estimation, hunting zone is determined by the uncertainty of (x, y) value; Ultra-short baseline location algorithm of the present invention uses the position (x, y, z) of the direct compute location target S of Maximum-likelihood estimation (MaximumLikelihoodEstimation, MLE);

A), particularly, the process of a Maximum-likelihood estimation can be equivalent to:

$L=\underset{i=0}{\overset{4}{\Σ}}\[{\left|\underset{T_0}{\overset{T_0+T}{\∫}}{r}_i\left(t\right)S_i\left(t\right)dt\right|}^2\]---\left(1\right)$

Wherein, r _it () is array element B _iwhat (i=0,1,2,3,4) received contains noisy underwater sound signal; T ₀it is the initial time of each array element Received signal strength; T is the integral time of signal; S _it ()=f [t, (x, y, z)] is array element B _inot Noise this locality reproduction signal, it is a function being independent variable with (x, y, z);

B) the underwater sound signal model that, localizing objects S place acoustic responder sends is:

r(t)＝AC(t)D(t)cos(2πf _IFt)(2)

Wherein, A is signal amplitude, C (t) for being modulated at the pseudo-random code on signal, the positioning signal that D (t) is the localizing objects point S that modulates depth data, f _iFfor the centre frequency of ultrasonic signal carrier wave;

When localizing objects point S and the distance R that receives between acoustic array is much larger than acoustic array dimension D, during R/D>20, the S in formula (1) _it () can be expressed as:

Wherein, df is the Doppler shift of ultrasonic signal; τ _ifor ultrasonic signal sends rear arrival array element B from S point _itravel-time; for r ₀the phase differential of (t) signal and r (t) signal; for signal r _i(t) and signal r ₀the phase differential of (t);

C), following relation can be obtained according to positioning principle figure Fig. 4 of localizing objects S:

$\stackrel{\‾}{{\mathrm{SB}}_0}=R=\sqrt{x^2+y^2+z^2}$

cosα＝x/R

cosβ＝y/R

$\stackrel{\‾}{{\mathrm{SB}}_1}-\stackrel{\‾}{{\mathrm{SB}}_0}=D\frac{x}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_2}-\stackrel{\‾}{{\mathrm{SB}}_0}=-D\frac{x}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_3}-\stackrel{\‾}{{\mathrm{SB}}_0}=D\frac{y}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_4}-\stackrel{\‾}{{\mathrm{SB}}_0}=-D\frac{y}{R}---\left(4\right)$

Wherein, represent localizing objects S and acoustic array B _ithe distance of (i=0,1,2,3,4);

α is vector with the angle of x-axis positive dirction, β is vector with the angle of y-axis positive dirction, θ is the deflection of the projection S ‵ of localizing objects point S in carrier coordinate system in XOY plane;

D), by the corresponding relation in formula (3) and (4), S can be obtained _it () and localizing objects point S coordinate (x, y, z) have following relation:

Wherein, the size of signal amplitude A can't have an impact to the estimated result of MLE, is set to 1; Velocity of sound c accurately can be measured by sound velocimeter; Carrier phase difference can by being arranged on basic matrix B with the exact value of Doppler frequency df ₀in phaselocked loop obtain; Localizing objects S directly measures by hydraulic pressure depthometer at the coordinate z of depth direction, and sends to acoustic array by ultrasonic signal; The centre frequency f of ultrasonic signal carrier wave _iFknown; Therefore A, c, z and df is known quantity, this locality reproduction signal S of acoustic array _it () (i=0,1,2,3,4) are the function only containing parameter (x, y);

E), formula (5), (6), (7), (8), (9) are brought in formula (1), algorithm model localizing objects S coordinate (x, y) being carried out to Maximum-likelihood estimation can be used for:

$(\hat{x},\hat{y})=MLE(\underset{i=0}{\overset{4}{\Σ}}\[{|\underset{T_0}{\overset{T_0+T}{\∫}}{r}_i\left(t\right)S_i\[t,(x,y)\]dt|}^2\])---\left(10\right)$

Wherein, for the maximum likelihood estimation of localizing objects point coordinate; MLE () is Maximum-likelihood estimation computing;

(4) as shown in Figure 5, by the different coordinate (x of the localizing objects S of search _k, y _l) substitute into formula (10), r _i(t) and B _icorrelation integral computing is carried out in integration period T, and using the summation of the integral result of different array element as L _k,l, work as L _k,lwhen obtaining maximal value, corresponding (x _k, y _l) be both the position of required localizing objects S.

Above-mentioned steps (4) (x, the y) that try to achieve estimates position (x as next locating periodically ₀, y ₀), for the positioning calculation in next new cycle.

As shown in Figure 6, in the search volume of Maximum-likelihood estimation, localizing objects S estimates position (x ₀, y ₀) and search radius R _searchcan be calculated as follows:

$(x_0,y_0)=\[x(n-1)+\mathrm{\Δ}\hat{x}\left(n\right),y(n-1)+\mathrm{\Δ}\hat{y}\left(n\right)\]$

$R_{search}=2\sqrt{{\left(\mathrm{\Δ}\hat{x}\right(n\left)\right)}^2+{\left(\mathrm{\Δ}\hat{y}\right(n\left)\right)}^2}$

$\mathrm{\Δ}\hat{x}\left(n\right)=x(n-1)-x(n-2)$

$\mathrm{\Δ}\hat{y}\left(n\right)=y(n-1)-y(n-2)$

Wherein, [x (n-1), y (n-1)] estimates the coordinate of ground point that obtains for last locating periodically by MLE; [x (n-2), y (n-2)] estimates the coordinate of ground point that obtains for locating periodically upper last time by MLE; for the variable quantity of the first two locating periodically localizing objects point coordinate.

Above embodiment is only exemplary, can't limit to the present invention, should be understood that for a person skilled in the art, and under technology enlightenment provided by the present invention, other equivalent modifications made and improvement, all should be considered as protection scope of the present invention.

Claims (7)

1. based on a ultra-short baseline acoustic positioning system for Maximum-likelihood estimation, it is characterized in that, described positioning system is made up of reception acoustic array two parts of the transponder under water and reception and process ultrasound locating signal that produce and launch ultrasound locating signal;

Wherein, under water transponder by forming with lower unit of connecting successively:

Hydraulic pressure depthometer: the depth data being positioned at below surface level for measuring transponder;

Distance measuring signal generation module: generating the spread spectrum ultrasonic ranging signal waveform for locating, the depth data that hydraulic pressure depthometer records being modulated in this signal waveform simultaneously;

Transducer power amplifier: power amplification is carried out, to drive ultrasonic piezo-transducer work to the ultrasonic ranging signal generated;

Ultrasonic piezo-transducer: produce ultrasonic ranging signal and be transmitted to reception acoustic array;

Power module: for transponder running under water provides required power supply;

Described reception acoustic array is by forming with lower unit of connecting successively:

Transducer array: for comprising the orthogonal matrix of 5 transducer array elements, for tentatively receiving the ultrasound locating signal that transponder is under water launched;

Low noise amplifier: for amplifying the positioning signal that in transducer array, each array element exports;

Bandpass filter: carry out filtering to the positioning signal of amplifying via low noise amplifier, to reduce in water noise signal to the interference of positioning signal;

Analog-to-digital conversion module: digitized sampling is carried out to the simulating signal exported by bandpass filter;

Matched filter and signal receiving module: carry out demodulation to the ultrasonic ranging signal after digitized sampling, obtain the transponder depth information modulated in signal;

Positioning calculation module: for resolving the positional information of Underwater Navigation target;

Positioning result display module: be human-computer interaction interface, for showing locating result information for user.

2. ultra-short baseline acoustic positioning system according to claim 1, it is characterized in that: described reception acoustic array also comprises acoustic array position and attitude reference module, the gyrocompass built-in by module and RTK system, for positioning calculation module provides accurate position and attitude reference information.

3. ultra-short baseline acoustic positioning system according to claim 1, is characterized in that: 5 transducer array elements of described transducer array use B respectively ₀, B ₁, B ₂, B ₃and B ₄represent, wherein, array element B ₀be positioned at the initial point of carrier coordinate system, array element B ₁, B ₂be positioned in the x-axis of carrier coordinate system, array element B ₃, B ₄be positioned in the y-axis of carrier coordinate system, and B ₁, B ₂, B ₃and B ₄to initial point B ₀distance C be less than or equal to the half of ultrasonic ranging signal wavelength, i.e. C≤λ/2.

4., according to the arbitrary described ultra-short baseline acoustic positioning system of claim 1-3, it is characterized in that: described transducer is piezoelectric transducer.

5., according to the location algorithm of the arbitrary described ultra-short baseline acoustic positioning system of claim 1-3, it is characterized in that, comprise the following steps:

(1) lay the reception acoustic array comprising 5 array elements, install acoustic responder at localizing objects point S place, it sends the spread spectrum underwater sound signal of having modulated depth data to receiving acoustic array in a pulsed fashion, wherein, the coordinate of localizing objects point S is (x, y, z);

(2) adopt the incident horn cupping of traditional ultra-short baseline localization method oblique distance-sound ray, Primary Location is carried out to Underwater Navigation impact point S, obtains the initial value (x of localizing objects position ₀, y ₀);

(3) with (x ₀, y ₀) as estimating position, search for the coordinate (x, y) of localizing objects S in the search volume of Maximum-likelihood estimation, hunting zone is determined by the uncertainty of (x, y) value;

A), particularly, the process of a Maximum-likelihood estimation can be equivalent to:

$L=\underset{i=0}{\overset{4}{\Σ}}\[{\left|\underset{T_0}{\overset{T_0+T}{\∫}}{r}_i\left(t\right)S_i\left(t\right)dt\right|}^2\]---\left(1\right)$

Wherein, r _it () is array element B _iwhat (i=0,1,2,3,4) received contains noisy underwater sound signal; T ₀it is the initial time of each array element Received signal strength; T is the integral time of signal; S _it ()=f [t, (x, y, z)] is array element B _inot Noise this locality reproduction signal, it is a function being independent variable with (x, y, z);

B) the underwater sound signal model that, localizing objects S place acoustic responder sends is:

r(t)＝AC(t)D(t)cos(2πf _IFt)(2)

Wherein, A is signal amplitude, C (t) for being modulated at the pseudo-random code on signal, the positioning signal that D (t) is the localizing objects point S that modulates depth data, f _iFfor the centre frequency of ultrasonic signal carrier wave;

When localizing objects point S and the distance R that receives between acoustic array is much larger than acoustic array dimension D, during R/D>20, the S in formula (1) _it () can be expressed as:

Wherein, df is the Doppler shift of ultrasonic signal; τ _ifor ultrasonic signal sends rear arrival array element B from S point _itravel-time; for r ₀the phase differential of (t) signal and r (t) signal; for signal r _i(t) and signal r ₀the phase differential of (t);

C), following relation can be obtained according to the positioning principle figure of localizing objects S:

$\stackrel{\‾}{{\mathrm{SB}}_0}=R=\sqrt{x^2+y^2+z^2}$

cosα＝x/R

cosβ＝y/R

$\stackrel{\‾}{{\mathrm{SB}}_1}-\stackrel{\‾}{{\mathrm{SB}}_0}=D\frac{x}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_2}-\stackrel{\‾}{{\mathrm{SB}}_0}=-D\frac{x}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_3}-\stackrel{\‾}{{\mathrm{SB}}_0}=D\frac{y}{R}$

$\stackrel{\‾}{{\mathrm{SB}}_4}-\stackrel{\‾}{{\mathrm{SB}}_0}=-D\frac{y}{R}---\left(4\right)$

Wherein, represent localizing objects S and acoustic array B _ithe distance of (i=0,1,2,3,4);

α is vector with the angle of x-axis positive dirction, β is vector with the angle of y-axis positive dirction, θ is the deflection of the projection S ‵ of localizing objects point S in carrier coordinate system in XOY plane;

D), by the corresponding relation in formula (3) and (4), S can be obtained _it () and localizing objects point S coordinate (x, y, z) have following relation:

Wherein, the size of signal amplitude A can't have an impact to the estimated result of MLE, is set to 1; Velocity of sound c accurately can be measured by sound velocimeter; Carrier phase difference can by being arranged on basic matrix B with the exact value of Doppler frequency df ₀in phaselocked loop obtain; Localizing objects S directly measures by hydraulic pressure depthometer at the coordinate z of depth direction, and sends to acoustic array by ultrasonic signal; The centre frequency f of ultrasonic signal carrier wave _iFgiven value; Therefore A, c, z and df is known quantity, this locality reproduction signal S of acoustic array _it () (i=0,1,2,3,4) are the function only containing parameter (x, y);

E), formula (5), (6), (7), (8), (9) are brought in formula (1), algorithm model localizing objects S coordinate (x, y) being carried out to Maximum-likelihood estimation can be used for:

$(\hat{x},\hat{y})=MLE(\underset{i=0}{\overset{4}{\Σ}}\[{|\underset{T_0}{\overset{T_0+T}{\∫}}{r}_i\left(t\right)S_i\[t,(x,y)\]dt|}^2\])---\left(10\right)$

Wherein, for the maximum likelihood estimation of localizing objects point coordinate; MLE () is Maximum-likelihood estimation computing;

(4) by the different coordinate (x of the localizing objects S of search _k, y _l) substitute into formula (10), r _i(t) and B _icorrelation integral computing is carried out in integration period T, and using the summation of the integral result of different array element as L _k,l, work as L _k,lwhen obtaining maximal value, corresponding (x _k, y _l) be both the position of required localizing objects S.

6. the location algorithm of ultra-short baseline acoustic positioning system according to claim 5, it is characterized in that: described in the search volume of Maximum-likelihood estimation, localizing objects S estimates position (x ₀, y ₀) and search radius R _searchcan be calculated as follows:

$(x_0,y_0)=\[x(n-1)+\mathrm{\Δ}\hat{x}\left(n\right),y(n-1)+\mathrm{\Δ}\hat{y}\left(n\right)\]$

$R_{search}=2\sqrt{{\left(\mathrm{\Δ}\hat{x}\right(n\left)\right)}^2+{\left(\mathrm{\Δ}\hat{y}\right(n\left)\right)}^2}$

$\mathrm{\Δ}\hat{x}\left(n\right)=x(n-1)-x(n-2)$

$\mathrm{\Δ}\hat{y}\left(n\right)=y(n-1)-y(n-2)$

Wherein, [x (n-1), y (n-1)] estimates the coordinate of ground point that obtains for last locating periodically by MLE; [x (n-2), y (n-2)] estimates the coordinate of ground point that obtains for locating periodically upper last time by MLE; for the variable quantity of the first two locating periodically localizing objects point coordinate.

7. the location algorithm of ultra-short baseline acoustic positioning system according to claim 5, is characterized in that: described step (4) (x, the y) that try to achieve estimates position (x as next locating periodically ₀, y ₀), for the positioning calculation in next new cycle.