1. A new underwater sonar positioning method with average sound velocity is characterized by comprising the following steps:

s1, acquiring a three-dimensional space position of a sea surface survey ship and an approximate coordinate of an underwater unknown target transponder;

back-calculating the sound ray incidence angle by the approximate coordinate;

s2, measuring a sound velocity profile of the sea area where the underwater unknown point is located through a sound velocity profiler;

calculating the precise coordinates of the underwater unknown point under the sound ray incidence angle by using a sound ray tracking and positioning algorithm;

s3, positioning by adopting an average sound velocity least square positioning algorithm, and searching for the optimal average sound velocity;

the optimal average sound velocity meets the error requirements of the average sound velocity least square positioning result and the sound ray tracking positioning result;

s4, changing the sound ray incidence angle, repeating the steps from S1 to S3 to obtain a functional relation between the sound ray incidence angle and the average sound velocity, and establishing a new average sound velocity positioning model based on the sound ray incidence angle;

and S5, positioning under the new average sound velocity positioning model to obtain the accurate position of the underwater unknown point, and completing the rapid and accurate positioning of the underwater target.

2. The new underwater sonar positioning method according to claim 1, wherein step S1 includes the following substeps:

s1.1, obtaining accurate three-dimensional position information (X) of sea surface survey ship through POS positioning and orientation system_b,Y_b,Z_b)；

S1.2, obtaining the three-dimensional position (X) of the ship bottom transducer through coordinate conversion_i,Y_i,Z_i)；

S1.3. unknown target Transponder approximate coordinates (X) under known Water₀,Y₀,Z₀) On the basis of the above formula, the sound ray incidence angle theta at the moment is obtained through coordinate back calculation_iThe formula is as follows:

3. the new underwater sonar positioning method according to claim 1, wherein step S2 includes the following substeps:

s2.1, acquiring water temperature, salinity and pressure hydrological data of an underwater unknown point through a sound velocity profiler, and inverting a sound velocity profile of a sea area where the underwater unknown point is located, wherein the sound velocity profile refers to the relation of sound velocity with respect to water depth;

s2.2, on the basis of obtaining the sound velocity profile, dividing the sea area into N layers, and calculating the time t of sound signal propagation of the ith layer by adopting an equal-gradient sound ray tracking algorithm_iThe formula is as follows:

wherein the content of the first and second substances,representing sound velocity gradient, alpha representing sound ray grazing angle, v representing sound velocity, and z representing water depth;

s2.3. time t of propagation by accumulation_iObtaining the total propagation time of sound ray

S2.4, obtaining the known actual measurement acoustic signal propagation time T, and obtaining a coordinate correction value dx by a least square method, wherein the formula is as follows:

dx＝(A^TPA)^-1A^TPb，

wherein, A represents a Jacobian matrix, P represents an observation weight matrix, and b represents a ranging residual error;

s2.5. step S2.4 is iterated, and the sound ray incidence angle theta is obtained through dx coordinate correction_iNext, the precise location (X, Y, Z) of the unknown point of the underwater target.

4. The new underwater sonar positioning method according to claim 1, wherein step S3 includes the following substeps:

s3.1, after a sound velocity profile is measured, calculating an average sound velocityThe formula is as follows:

wherein the content of the first and second substances,representing average sound velocity, N representing the number of sound velocity profile layers, v_iRepresenting the layer i sound velocity value;

s3.2, when the sound velocity is the average sound velocityThen, positioning is carried out by adopting an average sound velocity least square positioning algorithm to obtain a sound ray incidence angle theta_iRough coordinates (X ', Y ', Z ') of the underlying underwater unknown point;

s3.3. varying average speed of soundFinding the optimal average speed of soundAnd enabling the average sound velocity least square positioning result (X ', Y ', Z ') and the sound ray tracking positioning result (X, Y, Z) to meet the tolerance requirement.

5. The new underwater sonar positioning method according to claim 1, wherein step S4 includes the following substeps:

s4.1, obtaining the sound ray incidence angle theta through the steps of S1, S2 and S3_iOptimum average speed of soundObtaining the accurate position of the unknown point of the underwater target under the sound velocity;

s4.2, changing the position of the sea surface survey ship and changing the incident angle theta of sound rays_i；

S4.3, repeating the steps of S1, S2 and S3, and establishing a functional relation between the sound ray incidence angle and the average sound velocity, wherein the formula is as follows:

wherein a, b and c represent undetermined parameters;

s4.4, according to the average sound velocity positioning principle, on the basis of the functional relation between the sound ray incidence angle and the average sound velocity, establishing a new average sound velocity positioning model, wherein the formula is as follows:

wherein the content of the first and second substances,a distance observation value is represented by a distance measurement value,representing a new established sound speed function, t_iRepresenting the propagation time of the acoustic signal, epsilon_LIndicating a range error.

6. The new underwater sonar positioning method according to claim 1, wherein step S5 includes the following substeps:

s5.1, carrying out linearization according to the new average sound velocity positioning model provided by S4, wherein the formula is as follows:

wherein e is_iDenotes the direction cosine, r_iRepresenting the linearized residual term,. epsilon.representing other errors, e_i＝(x₀-x_i)/d_i(x₀)；

S5.2, carrying out least square positioning calculation, wherein the formula is as follows:

dx＝(A^TPA)^-1A^TPb；

s5.3, obtaining the accurate position (X, Y, Z) of the underwater unknown point, wherein the formula is as follows:

(X,Y,Z)″＝(X₀,Y₀,Z₀)+dx；

the underwater target can be quickly and accurately positioned by the steps.

Background

The average sound velocity positioning mode is that the single sound velocity average value of the region is directly used for distance measurement positioning, and the model is simplest and most efficient, but the influence of sound velocity errors is ignored. The sound ray tracking algorithm adopts a layer adding method to calculate a sound ray propagation path, reduces the influence of sound ray bending errors on the basis of accurately measuring the sound velocity, and obtains the three-dimensional coordinates of the high-precision underwater target point. Although the accuracy of the sound ray tracking algorithm is improved compared with that of the average sound velocity positioning algorithm, the problems of complex positioning model, low calculation efficiency and the like exist. The incidence angle related error of the sound ray is an important error source for influencing and positioning, and comprises a noise error, a sound velocity error, a control point error and the like of a ranging system. When the observation pattern is not good, the change range of the sound ray incidence angle is large, the influence of the average sound velocity model error is obvious, and the positioning result is inaccurate. The relationship between the sound ray incidence angle and the average sound velocity is established, so that a new average sound velocity positioning model is established, and the problem of sound velocity errors caused by a single average sound velocity can be effectively replaced.

Disclosure of Invention

Aiming at the problems of complexity, low calculation efficiency and the like of a positioning model in the prior art, the invention provides a new underwater sonar positioning method with average sound velocity, and a new positioning model with average sound velocity is established by establishing the relationship between the sound ray incidence angle and the average sound velocity.

The invention specifically adopts the following technical scheme:

a new underwater sonar positioning method with average sound velocity comprises the following steps:

s1, acquiring a three-dimensional space position of a sea surface survey ship and an approximate coordinate of an underwater unknown target transponder;

back-calculating the sound ray incidence angle by the approximate coordinate;

s2, measuring a sound velocity profile of the sea area where the underwater unknown point is located through a sound velocity profiler;

calculating the precise coordinates of the underwater unknown point under the sound ray incidence angle by using a sound ray tracking and positioning algorithm;

s3, positioning by adopting an average sound velocity least square positioning algorithm, and searching for the optimal average sound velocity;

the optimal average sound velocity meets the error requirements of the average sound velocity least square positioning result and the sound ray tracking positioning result;

s4, changing the sound ray incidence angle, repeating the steps from S1 to S3 to obtain a functional relation between the sound ray incidence angle and the average sound velocity, and establishing a new average sound velocity positioning model based on the sound ray incidence angle;

and S5, positioning under the new average sound velocity positioning model to obtain the accurate position of the underwater unknown point, and completing the rapid and accurate positioning of the underwater target.

Preferably, the step S1 includes the following sub-steps:

s1.1, obtaining accurate three-dimensional position information (X) of sea surface survey ship through POS positioning and orientation system_b,Y_b,Z_b)；

S1.2, obtaining the three-dimensional position (X) of the ship bottom transducer through coordinate conversion_i,Y_i,Z_i)；

S1.3. unknown target Transponder approximate coordinates (X) under known Water₀,Y₀,Z₀) On the basis of the above formula, the sound ray incidence angle theta at the moment is obtained through coordinate back calculation_iThe formula is as follows:

preferably, the step S2 includes the following sub-steps:

s2.1, acquiring water temperature, salinity and pressure hydrological data of an underwater unknown point through a sound velocity profiler, and inverting a sound velocity profile of a sea area where the underwater unknown point is located, wherein the sound velocity profile refers to the relation of sound velocity with respect to water depth;

s2.2. obtaining the base of sound velocity profileOn the basis, the sea area is divided into N layers, and the time t of sound signal propagation of the ith layer is calculated by adopting an equal gradient sound ray tracking algorithm_iThe formula is as follows:

wherein the content of the first and second substances,representing sound velocity gradient, alpha representing sound ray grazing angle, v representing sound velocity, and z representing water depth;

s2.3. time t of propagation by accumulation_iObtaining the total propagation time of sound ray

S2.4, obtaining the known actual measurement acoustic signal propagation time T, and obtaining a coordinate correction value dx by a least square method, wherein the formula is as follows:

dx＝(A^TPA)^-1A^TPb，

wherein, A represents a Jacobian matrix, P represents an observation weight matrix, and b represents a ranging residual error;

s2.5. step S2.4 is iterated, and the sound ray incidence angle theta is obtained through dx coordinate correction_iNext, the precise location (X, Y, Z) of the unknown point of the underwater target.

Preferably, the step S3 includes the following sub-steps:

s3.1, after a sound velocity profile is measured, calculating an average sound velocityThe formula is as follows:

wherein the content of the first and second substances,means average ofSound velocity, N represents the number of sound velocity profile layers, v_iRepresenting the layer i sound velocity value;

s3.2, when the sound velocity is the average sound velocityThen, positioning is carried out by adopting an average sound velocity least square positioning algorithm to obtain a sound ray incidence angle theta_iRough coordinates (X ', Y ', Z ') of the underlying underwater unknown point;

s3.3, changing the average sound velocity V to search the optimal average sound velocityAnd enabling the average sound velocity least square positioning result (X ', Y ', Z ') and the sound ray tracking positioning result (X, Y, Z) to meet the tolerance requirement.

Preferably, the step S4 includes the following sub-steps:

s4.1, obtaining the sound ray incidence angle theta through the steps of S1, S2 and S3_iObtaining the accurate position of an unknown point of the underwater target at the sound velocity;

s4.2, changing the position of the sea surface survey ship and changing the incident angle theta of sound rays_i；

S4.3, repeating the steps of S1, S2 and S3, and establishing a functional relation between the sound ray incidence angle and the average sound velocity, wherein the formula is as follows:

wherein a, b and c represent undetermined parameters;

s4.4, according to the average sound velocity positioning principle, on the basis of the functional relation between the sound ray incidence angle and the average sound velocity, establishing a new average sound velocity positioning model, wherein the formula is as follows:

wherein the content of the first and second substances,a distance observation value is represented by a distance measurement value,representing a new established sound speed function, t_iRepresenting the propagation time of the acoustic signal, epsilon_LIndicating a range error.

Preferably, step S5 includes the following sub-steps:

s5.1, carrying out linearization according to the new average sound velocity positioning model provided by S4, wherein the formula is as follows:

wherein e is_iDenotes the direction cosine, r_iRepresenting the linearized residual term,. epsilon.representing other errors, e_i＝(x₀-x_i)/d_i(x₀)；

S5.2, carrying out least square positioning calculation, wherein the formula is as follows:

dx＝(A^TPA)^-1A^TPb；

s5.3, obtaining the accurate position (X, Y, Z) of the underwater unknown point, wherein the formula is as follows:

(X,Y,Z)″＝(X₀,Y₀,Z₀)+dx；

the underwater target can be quickly and accurately positioned by the steps.

Compared with the prior art, the invention has the following beneficial effects:

the new average sound velocity underwater sonar positioning algorithm is used for replacing the traditional average sound velocity positioning algorithm, the default sound velocity of the traditional average sound velocity positioning algorithm is a certain fixed value, the sound ray is considered to be propagated along a straight line, and actually, the propagation of the sound ray is bent under the influence of factors such as temperature, salinity and pressure in seawater. The influence of the sound ray bending error increases the distance measurement error, and the deeper the water depth, the greater the influence, and the difficulty in realizing high-precision positioning.

The new average sound velocity positioning model is adopted, the influence of the sound velocity profile is fully considered, the positioning accuracy which is equivalent to a sound ray tracking algorithm is achieved, and when the change range of the sound ray incidence angle is large, the positioning accuracy is improved more obviously; in addition, when a certain region on the sea is repeatedly measured for multiple times, the positioning efficiency can be effectively improved, and compared with a sound ray tracking algorithm, the calculation cost can be greatly reduced.

Drawings

Fig. 1 is a flow chart of a technique for positioning by using a new average sound velocity underwater acoustic positioning model.

Detailed Description

The invention will be further illustrated with reference to specific examples:

a new underwater sonar positioning method with average sound velocity is disclosed, the technical flow chart is shown in figure 1, and the method comprises the following steps:

s1, on the basis of obtaining the three-dimensional space position of a sea surface survey ship and the approximate coordinates of an underwater unknown target transponder, calculating the incident angle of sound rays through coordinate back;

s2, measuring a sound velocity profile of a sea area where the underwater unknown point is located through a sound velocity profiler (CTD), and calculating the accurate coordinate of the underwater unknown point under the incident angle through a sound ray tracking algorithm;

s3, positioning by adopting an average sound velocity least square method, and finding an optimal average sound velocity to enable an average sound velocity least square positioning result and a sound ray tracking positioning result to meet error requirements;

s4, changing the sound ray incidence angle, repeating the steps to obtain a functional relation between the incidence angle and the average sound velocity, and establishing a new average sound velocity positioning model based on the sound ray incidence angle;

and S5, positioning under the new average sound velocity positioning model to obtain the accurate position of the underwater unknown point, and completing the rapid and accurate positioning of the underwater target.

Step S1 includes the following sub-steps:

s1.1, a POS positioning and orientation system is arranged on a ship survey carrier, a GNSS receiver and an IMU respectively receive GNSS observation data, IMU observation data and precision correction information, and the GNSS observation data, the GNSS precision correction information and the IMU observation information are received according to the received GNSS observation data, the received IMU precision correction information and the received IMU observationData, performing high-precision GNSS/INS integrated navigation positioning to obtain high-precision and accurate three-dimensional position information (X) of the ship survey_b,Y_b,Z_b)；

S1.2, after high-precision three-dimensional position information of the ship is obtained, the three-dimensional position (X) of a transducer arranged at the bottom of the ship can be obtained through coordinate conversion_i,Y_i,Z_i)；

S1.3. the approximate coordinate of the plane position of the underwater transponder can be measured by defense arrangement, the depth can be measured by a pressure gauge, and the approximate coordinate (X) of the underwater unknown target transponder is known₀,Y₀,Z₀) On the basis of the acoustic wave propagation method, the incident angle theta of the sound ray propagation at the moment can be obtained through coordinate back calculation_iThe formula is as follows:

step S2 includes the following sub-steps:

s2.1, before positioning, the ship can place the carried sound velocity profiler CTD underwater, the sound velocity profiler CTD can obtain the temperature, salinity and pressure hydrological data of an underwater target point water area, and can invert the sound velocity profile of the area where the target point is located, wherein the sound velocity profile refers to the relation of sound velocity with water depth and can reflect the change condition of the sound velocity with the water depth in a specified area within a period of time;

s2.2, on the basis of obtaining the sound velocity profile, dividing the water area where the target point is located into N layers, and calculating the time t of sound signal propagation of the ith layer by adopting an equal-gradient sound ray tracking algorithm_iThe equal-gradient sound ray tracking algorithm is an algorithm which is more accurate in underwater positioning at present, corrects the influence of sound ray bending errors caused by sound velocity change, and has the following formula:

wherein the content of the first and second substances,representing sound velocity gradient, alpha representing sound ray grazing angle, v representing sound velocity, and z representing water depth;

s2.3. time t of propagation by accumulation_iThe total propagation time of the sound ray can be obtained

S2.4. the transducer can measure the propagation time of the acoustic signal from transmitting to feedback receiving, and on the premise of knowing the actual measured acoustic signal propagation time T, the distance measurement difference can be calculated, and the formula is as follows:

then, the coordinate correction value dx is obtained by the least square method, and the formula is as follows:

dx＝(A^TPA)^-1A^TPb，

wherein, A represents a Jacobian matrix, P represents an observation weight matrix, and b represents a ranging residual error;

s2.5. by iterating step S2.4, by dx coordinate correction, the sound ray incidence angle theta can be obtained_iNext, the precise position (X, Y, Z) of the unknown point of the underwater target can be obtained.

Step S3 includes the following sub-steps:

s3.1, by averaging the sound velocity profiles, the average sound velocity can be calculatedThe formula is as follows:

wherein the content of the first and second substances,representing average sound velocity, N representing the number of sound velocity profile layers, v_iRepresenting the value of sound velocity of the i-th layer；

S3.2, when the sound velocity is the average sound velocity V, positioning is carried out by adopting an average sound velocity least square method to obtain the sound ray incidence angle theta_iThe lower target point is given rough coordinates (X ', Y ', Z ');

s3.3. by varying the average speed of soundFinding an optimal average speed of soundThe positioning result (X ', Y ', Z ') under the average sound velocity least square model and the positioning result (X, Y, Z) under the sound ray tracking model meet the tolerance requirement, namely delta_(X,Y,Z)＜δ。

Step S4 includes the following sub-steps:

s4.1, the incident angle theta can be obtained through the steps of S1, S2 and S3_iNext, the optimal average sound velocity V' is such that the precise position of the unknown point of the underwater target at this sound velocity;

s4.2, by changing the position of the sea surface survey ship, the propagation incident angle theta of the sound ray can be changed_i；

S4.3, repeating the steps of S1, S2 and S3, a functional relationship between the incident angle and the average sound velocity can be established, and the formula is as follows:

wherein a, b and c represent undetermined parameters, and the mode is obtained by MATLAB fitting according to the functional relation between the incident angle and the average sound velocity;

s4.4, according to the average sound velocity positioning principle, on the basis of the functional relation between the incident angle and the average sound velocity, establishing a new average sound velocity positioning model, wherein the formula is as follows:

wherein the content of the first and second substances,a distance observation value is represented by a distance measurement value,representing a new established sound speed function, t_iRepresenting the propagation time of the acoustic signal, epsilon_LIndicating a range error.

Step S5 includes the following sub-steps:

s5.1, linearization can be carried out according to the new average sound velocity positioning model provided by S4, wherein the formula is as follows:

wherein e is_iDenotes the direction cosine, r_iWhich represents a linearized residual term, which is generally negligible, epsilon represents other errors,

e_i＝(x₀-x_i)/d_i(x₀)；

s5.2, carrying out least square positioning calculation to obtain a coordinate correction value, wherein the formula is as follows:

dx＝(A^TPA)^-1A^TPb，

s5.3, through correction of the coordinate correction value and iterative calculation, the accurate position (X, Y, Z) "of the underwater unknown point can be obtained, and the formula is as follows:

(X,Y,Z)″＝(X₀,Y₀,Z₀)+dx，

the underwater target can be quickly and accurately positioned by the steps.