CN101369021A - Two-dimension scattering property measuring method for underwater movement objective - Google Patents

Abstract

The invention belongs to the target two-dimension scattering property measurement field, which relates to a two-dimension scattering property measuring method for the underwater moving target. The measuring method is characterized in that an active sonar receiving array and an emission array are firmly fixed, the emission array transmits signals, the receiving array receives echo of the underwater rectilinear moving target of which the moving direction and the moving speed are known, the received echo signal can be treated through the synthetic aperture imaging, so as to obtain the two-dimension high resolution scattering property of the target in distance and direction. The measuring method has the advantages that utilizing small-size array can obtain the two-dimension high resolution scattering property of the underwater target, the equipment is simple, and the underwater part can be easily arranged.

Description

The two-dimension scattering property measuring method of underwater movement objective

Technical field

The invention belongs to submarine target two-dimension scattering property fields of measurement, relate to a kind of two-dimension scattering property measuring method that utilizes the synthetic aperture principle to measure underwater movement objective.

Background technology

At present, the scattering properties measurement Research of submarine target mainly adopts the method based on true aperture.This method is when practical application, and there are the following problems:

(1), need set up large-sized true aperture sonar array, the difficulty of bringing the raising on the cost and laying in order to improve the Measurement Resolution of submarine target scattering properties;

(2) the true hole routing method is difficult to obtain the two-dimentional high resolving power scattering properties of distant object.

Adopt synthetic aperture technique, can address the above problem well.At present, imaging mainly contains two kinds of methods to submarine target to adopt synthetic aperture technique, comprises synthetic aperture sonar and contrary synthetic aperture sonar.

Synthetic aperture sonar utilizes sonar transducer array to do linear uniform motion along the space and forms big aperture, and the submarine target transfixion to the echoed signal that the receives processing that is concerned with, obtains the high-resolution two-dimension scattering property of target.Synthetic aperture sonar is mainly used in seabed mapping, sinks to the bottom and bury physical prospecting survey etc.Because target is hovered in water and is difficult to accomplish, thereby synthetic aperture sonar is difficult to use in actual submarine target two-dimension scattering property is measured.

Contrary synthetic aperture sonar utilizes the displacement of target to form the aperture, target is done noncooperative motion, its kinetic characteristic and unknown parameters, usually need carry out motion compensation to echoed signal based on echo, it is compensated for as the turntable imaging model, promptly utilizes static sonar transducer array that the target that rotates around certain reference point is carried out imaging.This method needs high s/n ratio, is difficult to move towards practical.

Summary of the invention

The objective of the invention is in order to solve the deficiency that the above-mentioned background technology exists, a kind of two-dimension scattering property measuring method of cooperative moving targets under water based on the synthetic aperture principle is proposed, make it can make things convenient for the scattering properties of measuring underwater kit exactly, thereby reach the acoustic scattering intensity of reduction underwater kit.

For achieving the above object, the present invention adopts following scheme:

The two-dimension scattering property measuring method of underwater movement objective, it is characterized in that active sonar receives battle array and the emission battle array maintains static, signal is penetrated in the emission paroxysm, receive the echo of the known target of rectilinear motion under water of battle array reception direction of motion and movement velocity, the echoed signal that receives is carried out synthetic aperture imaging handle, obtain the two-dimentional high resolving power scattering properties of target in the distance and bearing dimension.

In such scheme, in the synthetic aperture imaging processing procedure, at first echoed signal is carried out pulse compression and obtain distance images, the paired pulses compressed echo signal is carried out the orientation and is obtained the orientation picture to focus on handling then, thereby obtains the two-dimension scattering property of target.

In such scheme, before echoed signal being carried out the synthetic aperture imaging processing, utilize heave, sidesway, surging, pitching, driftage and the roll motion error of motion sensor measurement target, according to the geometric shape of kinematic error that records and combining target, echoed signal is carried out Radial Motion Error compensation and angular movement error compensation.

The present invention adopts the pointwise motion compensation process that echoed signal is carried out Radial Motion Error compensation and angular movement error compensation.

Compensation of above-mentioned Radial Motion Error and angular movement error compensation are to be that target is done the echoed signal under the linear uniform motion with echo compensated signal.The Radial Motion Error of target and angular movement error can be described with six-freedom degree, comprise heave, sidesway, surging, pitching, driftage and roll, as shown in Figure 2.Among the figure, I, II, III, IV, V, VI represent heave, sidesway, surging, pitching, driftage and roll respectively.Radial Motion Error is caused by heave, sidesway and the motion of surging line that mainly the angular movement error is mainly caused by pitching, driftage and roll angle motion.

Above-mentioned Radial Motion Error compensation and angular movement error compensation adopt the pointwise motion compensation process based on motion sensor or kinematic error measurement mechanism.By the kinematic error measurement mechanism, as attitude sensor etc., can record certain some attitude angle at any time on the target, by motion sensor,, can record reference point position coordinates at any time on the target as inertial navigation equipment that target self disposed etc.Reference point transient posture angle and position coordinates on the geometric shape of combining target and the measured target are done necessary compensation to the motion of target.

Above-mentioned pointwise kinematic error compensation method will, synoptic diagram based on motion sensor or kinematic error measurement mechanism as shown in Figure 3,1 expression sonar transducer array among the figure, 2 expression targets, 3 expressions receive battle array, 4 expression emission battle arrays, k represents to receive array element.With certain scattering point M on the target is example, at the situation that transmits to narrow band signal, and the phase error that the compensation of this motion compensation process causes because of the Radial Motion Error and the angular movement error of target, concrete formula is:

$\mathrm{\Δ\Φ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}[r_{1e}+r_{2e}^k-(r_1+r_2^k)]---\left(1\right)$

Wherein, ΔΦ is the phase error that causes because of radial target motion sum of errors angular movement error that should compensate, r _1eWith

Be respectively that certain launches the distance value that array element and k receive array element scattering point M on the target, r constantly in conjunction with motion sensor obtains ₁With

Be respectively that this launches the distance value that array element and k receive array element scattering point M on the linear uniform motion target constantly, λ is the wavelength that transmits, k 〉=1.

Concrete steps of the present invention are:

1, sonar receives battle array and launches battle array and maintains static, and big bandwidth signal is penetrated in the emission paroxysm;

2, target to be measured is with the zone of approximate straight line motion mode by sonar emission array beam and the covering of reception array beam;

3, sonar receives the echoed signal of battle array receiving target, through passing to data collecting card after amplification and the filtering;

4, after data collecting card receives synchronizing signal, gather isometric target echo signal through fixing time-delay with certain frequency acquisition, and store computing machine into;

5, data acquisition the time, gather the data of motion sensor or kinematic error measurement mechanism;

6, computing machine carries out motion compensation and imaging processing to echoed signal, obtains the two-dimension scattering property of target.

The present invention utilizes the small size basic matrix can obtain the two-dimentional high resolving power scattering properties of submarine target, and it is simple to have equipment, and underwater portion lays advantage easily.

This method can be used for the scattering properties of underwater kit and measures.Under water Zhuan Bei the development demonstration stage, its two-dimension scattering property is measured, indicated the two-dimensional position of strong scattering point, control, thereby reach the acoustic scattering intensity of the full ship of reduction by scattering strength to strong scattering point.

Description of drawings

Fig. 1 synoptic diagram of the present invention.

The 6DOF motion of Fig. 2 target.

Fig. 3 pointwise kinematic error compensation method will synoptic diagram.

Fig. 4 embodiment synoptic diagram.

Embodiment

Synoptic diagram of the present invention as shown in Figure 1, among the figure, 1 the expression sonar transducer array, 2 the expression targets.

Present embodiment adopts single receiving array, and sonar transducer array is fixed, and there is the three dimensional angular motion in target when making linear uniform motion with speed V, comprise pitching, driftage and roll.The linear movement direction of target is parallel with sonar transducer array.Suppose that sonar transducer array transmitting-receiving puts altogether, its bee-line with target is r, the geometric position synoptic diagram of basic matrix and target as shown in Figure 4, among the figure, 1 represents sonar transducer array, 2 represent targets, I, II and III represent pitching, driftage and roll respectively.

With certain scattering point P on the target is example, and the idiographic flow of this embodiment is as follows:

(1) modelled signal source produces gate-control signal and chirp narrow band signal according to predetermined pulse recurrence interval PRI, and its expression formula is:

$s_T\left(\mathrm{\&tau;}\right)=\mathrm{rect}\left(\frac{\mathrm{\&tau;}}{T}\right)\exp (\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A200810197185E00111.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_0\mathrm{\&tau;}+\mathrm{j\&pi;K}{\mathrm{\&tau;}}^2)---\left(2\right)$

Wherein, rect

The expression rect.p., T is a pulse width, τ is a time variable, f ₀Be carrier frequency, K is a chirp rate, exp ( ) the expression exponential function, j represents imaginary unit.

(2) linear FM signal is launched battle array through passing to sonar behind the power amplifier;

(3) chirp pulse signal is penetrated in sonar emission paroxysm, shines aforementioned moving target;

(4) sonar receives the echoed signal that battle array receives scattering point P, through passing to data collecting card after amplification and the filtering;

(5) after data collecting card receives synchronizing signal, gather isometric target echo signal through fixing time-delay with certain frequency acquisition, and store computing machine into, target echo s _R(t, τ; R) expression formula is:

$s_R(t,\mathrm{\&tau;};r)=A\&CenterDot;\mathrm{rect}\left(\frac{\mathrm{\&tau;}-2R(t,r)/C}{T}\right)\exp [\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A200810197185E00111.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_0(\mathrm{\&tau;}-2R(t,r)/C)$

(3)

$+\mathrm{j\&pi;K}{(\mathrm{\&tau;}-2R(t,r)/C)}^2]$

Wherein, A is an echo signal amplitude, and (t r) is the instantaneous distance of scattering point P to sonar transducer array to R, and t represents that C is the velocity of sound constantly.

(6) data acquisition the time, gather the data that the kinematic error measurement mechanism records;

(7) echoed signal is carried out motion compensation and signal Processing, obtain the two-dimension scattering property of target.

In the present embodiment, when the echoed signal that receives was handled, the echoed signal after at first utilizing matched filtering method to coherent demodulation was done process of pulse-compression, obtained the echoed signal after the pulse compression $s_R^{\&prime;}(t,\mathrm{\&tau;};r)$ For:

$s_R^{\&prime;}(t,\mathrm{\&tau;};r)=A\&prime;\sin c\left\{\mathrm{\&pi;KT}[\mathrm{\&tau;}-\frac{2R(t;r)}{C}]\right\}\exp [-j\frac{4\mathrm{\&pi;}{f}_0}{C}R(t;r)]---\left(4\right)$

Wherein, A ' is the echo signal amplitude maximal value after the pulse compression,

Secondly the phase error of generation because the three dimensional angular of target scattering point is moved makes the orientation to focusing on, and the compensation of must taking exercises is made a concrete analysis of as follows:

The three dimensional angular motion of hypothetical target is followed successively by driftage, pitching and roll.As Fig. 4, set up the sonar coordinate system (u, v, w) and target-based coordinate system (x, y, z).Sonar transducer array is positioned at sonar coordinate origin o, on the target coordinate of scattering point P in target-based coordinate system be (x, y, z).In the t=0 moment, the coordinate of scattering point P in the sonar coordinate system is respectively (u on the initial point O of target-based coordinate system and the target ₀, v ₀, w ₀), (u ₀+ x, v ₀+ y, w ₀+ z).T at any time, the coordinate of initial point O in the sonar coordinate system of target-based coordinate system is (u ₀(t), v ₀(t), w ₀(t))=(u ₀+ Vt, v ₀, H), H is a constant, the coordinate (u (t), v (t), w (t)) of scattering point P in the sonar coordinate system is

$\left[\begin{array}{c}u\left(t\right)\\ v\left(t\right)\\ w\left(t\right)\end{array}\right]=\mathrm{Rot}\left(t\right)\left[\begin{array}{c}x\\ y\\ z\end{array}\right]+\left[\begin{array}{c}{u}_0\left(t\right)\\ v_0\left(t\right)\\ w_0\left(t\right)\end{array}\right]---\left(5\right)$

Wherein, Rot (t) is the rotation matrix in this moment, Rot (t)=Yaw[θ _z(t)] Pitch[θ _y(t)] Roll[θ _x(t)], θ _z(t), θ _y(t) and θ _x(t) be driftage, pitching and three angles that rotative component turned over of roll respectively, Yaw[θ _z(t)], Pitch[θ _yAnd Roll[θ (t)] _x(t)] be the rotation matrix of this driftage constantly, pitching and three rotative components of roll respectively, satisfy

$\mathrm{Yaw}\left[{\mathrm{\&theta;}}_z\left(t\right)\right]=\left[\begin{array}{ccc}\cos \left({\mathrm{\&theta;}}_z\left(t\right)\right)& -\sin \left({\mathrm{\&theta;}}_z\left(t\right)\right)& 0\\ \sin \left({\mathrm{\&theta;}}_z\left(t\right)\right)& \cos \left({\mathrm{\&theta;}}_z\left(t\right)\right)& 0\\ 0& 0& 1\end{array}\right]---\left(6\right)$

$\mathrm{Pitch}\left[{\mathrm{\&theta;}}_y\left(t\right)\right]=\left[\begin{array}{ccc}\cos \left({\mathrm{\&theta;}}_y\left(t\right)\right)& 0& \sin \left({\mathrm{\&theta;}}_y\left(t\right)\right)\\ 0& 1& 0\\ -\sin \left({\mathrm{\&theta;}}_y\left(t\right)\right)& 0& \cos \left({\mathrm{\&theta;}}_y\left(t\right)\right)\end{array}\right]---\left(7\right)$

$\mathrm{Roll}\left[{\mathrm{\&theta;}}_x\left(t\right)\right]=\left[\begin{array}{ccc}1& 0& 0\\ 0& \cos \left({\mathrm{\&theta;}}_x\left(t\right)\right)& -\sin \left({\mathrm{\&theta;}}_x\left(t\right)\right)\\ 0& \sin \left({\mathrm{\&theta;}}_x\left(t\right)\right)& \cos \left({\mathrm{\&theta;}}_x\left(t\right)\right)\end{array}\right]---\left(8\right)$

Then rotation matrix is

$\mathrm{Rot}\left(t\right)=\left[\begin{array}{ccc}{a}_{11}\left(t\right)& a_{12}\left(t\right)& a_{13}\left(t\right)\\ a_{21}\left(t\right)& a_{22}\left(t\right)& a_{23}\left(t\right)\\ a_{31}\left(t\right)& a_{32}\left(t\right)& a_{33}\left(t\right)\end{array}\right]---\left(9\right)$

Wherein,

a ₁₁(t)＝cos(θ _z(t))cos(θ _y(t))

a ₁₂(t)＝cos(θ _z(t))sin(θ _y(t))sin(θ _x(t))-sin(θ _z(t))cos(θ _x(t))

a ₁₃(t)＝cos(θ _z(t))sin(θ _y(t))cos(θ _x(t))+sin(θ _z(t))sin(θ _x(t))

a ₂₁(t)＝sin(θ _z(t))cos(θ _y(t))

a ₂₂(t)＝sin(θ _z(t))sin(θ _y(t))sin(θ _x(t))+cos(θ _z(t))cos(θ _x(t))

a ₂₃(t)＝sin(θ _z(t))sin(θ _y(t))cos(θ _x(t))-cos(θ _z(t))sin(θ _x(t))

a ₃₁(t)＝-sin(θ _y(t))

a ₃₂(t)＝cos(θ _y(t))sin(θ _x(t))

a ₃₃(t)＝cos(θ _y(t))cos(θ _x(t))

For the sake of simplicity, make z=0, w (t) ≡ H.Suppose to transmit constantly at t, then pass through the Δ t time, at t+ Δ t constantly promptly, receive the echoed signal that battle array receives scattering point P, at this moment, the coordinate (u (t+ Δ t), v (t+ Δ t), w (t+ Δ t)) of this scattering point in the sonar coordinate system is

$\left[\begin{array}{c}u(t+\mathrm{\&Delta;t})\\ v(t+\mathrm{\&Delta;t})\\ w(t+\mathrm{\&Delta;t})\end{array}\right]=\mathrm{Rot}(t+\mathrm{\&Delta;t})\left[\begin{array}{c}x\\ y\\ z\end{array}\right]+\left[\begin{array}{c}{u}_0(t+\mathrm{\&Delta;t})\\ v_0(t+\mathrm{\&Delta;t})\\ w_0(t+\mathrm{\&Delta;t})\end{array}\right]---\left(10\right)$

Wherein, (u ₀(t+ Δ t), v ₀(t+ Δ t), w ₀(t+ Δ t)) be the t+ Δ t coordinate of center of rotation O in the sonar coordinate system constantly, u ₀(t+ Δ t)=u ₀+ V (t+ Δ t), v ₀(t+ Δ t)=v ₀, w ₀(t+ Δ t) ≡ H,

$\mathrm{Rot}(t+\mathrm{\&Delta;t})=\left[\begin{array}{ccc}{a}_{11}(t+\mathrm{\&Delta;t})& a_{12}(t+\mathrm{\&Delta;t})& a_{13}(t+\mathrm{\&Delta;t})\\ a_{21}(t+\mathrm{\&Delta;t})& a_{22}(t+\mathrm{\&Delta;t})& a_{23}(t+\mathrm{\&Delta;t})\\ a_{31}(t+\mathrm{\&Delta;t})& a_{32}(t+\mathrm{\&Delta;t})& a_{33}(t+\mathrm{\&Delta;t})\end{array}\right].$

Think that Δ t is that linear uniform motion by target causes, through the simple geometric relation derivation, can get herein,

$\mathrm{\&Delta;t}=\frac{V^{2}t+(u_0+x)\&CenterDot;V\&PlusMinus;\sqrt{C^2{[(u_0+x)+\mathrm{Vt}]}^2+(C^2-V^2)[{(v_0+y)}^2+H^2]}}{C^2-V^2}---\left(11\right)$

Formula (11) substitution formula (10) just can be obtained the instantaneous coordinate of scattering point, thereby this scattering point receives the distance of battle array apart from sonar $R(t+\mathrm{\&Delta;t})=\sqrt{{\left[u(t+\mathrm{\&Delta;t})\right]}^2+{\left[v(t+\mathrm{\&Delta;t})\right]}^2+{\left[w(t+\mathrm{\&Delta;t})\right]}^2}.$ Convolution (4) makes R that (t, r)=R (t+ Δ t), corresponding phase is $\mathrm{\&phi;}=-\frac{4\mathrm{\&pi;}{f}_0}{C}\&CenterDot;R(t;r).$

From the derivation of front as can be seen, being used for follow-up orientation causes to focusing on the phase term exp (j φ) that handles linear uniform motion and three dimensional angular motion two parts by target.Wherein, the phase term that the target linear uniform motion partly causes is useful to the orientation to focus on handling, and to handle be unhelpful to focusing on and the kinetic phase term of three dimensional angular is to the orientation, in addition can have a strong impact on the orientation to focusing handle, make the orientation to defocusing.Therefore the compensation of must the paired pulses compressed echo signal taking exercises.

Wood embodiment adopts the pointwise motion compensation process based on the kinematic error measurement mechanism, and the phase error that diagonal motion causes compensates, and is phase place under the linear uniform motion with phase compensation, as the formula (12),

$\mathrm{\&Delta;\&phi;}=\frac{4\mathrm{\&pi;}{f}_0}{C}[R_e(t;r)-R_t(t;r)]---\left(12\right)$

Wherein, Δ φ is the phase error that causes because of the angle on target kinematic error that should compensate, R _e(t; R) be the measured value that arrives the sonar transducer array distance in conjunction with the scattering point that the kinematic error measurement mechanism obtains, R _t(t; R) be the distance value that scattering point arrives sonar transducer array under the linear uniform motion.

Echoed signal after the motion compensation as the formula (13),

$s_R^{\&prime;\&prime;}(t,\mathrm{\&tau;};r)=s_R^{\&prime;}(t,\mathrm{\&tau;};r)\&CenterDot;\exp \left\{j\frac{4\mathrm{\&pi;}{f}_0}{C}[R_e(t;r)-R_t(t;r)]\right\}---\left(13\right)$

At last the echoed signal after the motion compensation is done the orientation to focus on handling, suc as formula (14), obtain target two-dimension scattering property f (r, x),

$f(r,x)={\&Integral;}_{R(t;r)}{s}_R^{\&prime;\&prime;}(t,\mathrm{\&tau;};r)\exp [j\frac{4\mathrm{\&pi;}{f}_0}{C}\&CenterDot;\mathrm{\&Delta;R}(t;r)]\mathrm{dl}---\left(14\right)$

Wherein, R (t; R) be path of integration, Δ R (t; R)=R _t(t; R)-r.

Claims (4)

1. the two-dimension scattering property measuring method of underwater movement objective, it is characterized in that active sonar receives battle array and the emission battle array maintains static, signal is penetrated in the emission paroxysm, receive the echo of the known target of rectilinear motion under water of battle array reception direction of motion and movement velocity, the echoed signal that receives is carried out synthetic aperture imaging handle, obtain the two-dimentional high resolving power scattering properties of target in the distance and bearing dimension.

2. the two-dimension scattering property measuring method of underwater movement objective according to claim 1, it is characterized in that in the synthetic aperture imaging processing procedure, at first echoed signal is carried out pulse compression and obtain distance images, the paired pulses compressed echo signal is carried out the orientation and is obtained the orientation picture to focus on handling then, thereby obtains the two-dimension scattering property of target.

3. the two-dimension scattering property measuring method of underwater movement objective according to claim 1, it is characterized in that before echoed signal being carried out the synthetic aperture imaging processing, utilize heave, sidesway, surging, pitching, driftage and the roll motion error of motion sensor measurement target, according to the geometric shape of kinematic error that records and combining target, echoed signal is carried out Radial Motion Error compensation and angular movement error compensation.

4. according to the two-dimension scattering property measuring method of claim 1 or 2 or 3 described underwater movement objectives, it is characterized in that adopting the pointwise motion compensation process that echoed signal is carried out Radial Motion Error compensation and angular movement error compensation.

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