A method for measuring array receiving signals during the turning process of towed array sonar platform

Abstract

The present invention provides a method for measuring array receiving signals during the steering process of a towed array sonar platform, and belongs to the technical field of underwater acoustic detection and sonar signal processing. The present invention establishes an array steering model around a circular arc trajectory, and for large-angle steering and small-angle steering, left steering and right steering conditions, uses the center angle of the circle corresponding to the array position arc to decompose the steering process into five steering stages, gives the time point values ​​of four adjacent moments in the five stages, and for each steering stage, takes the first array element as a reference, gives the receiving signals of all array elements at the current moment, which has great application value for improving the performance of array signal processing algorithms.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater acoustic detection and sonar signal processing, and relates to a method for measuring array receiving signals during the steering process of a towed array sonar platform. Background Art

[0002] Towed array sonar is an important tool for detecting low-frequency and concealed targets. During the detection process, hydrophones are needed to receive array data to estimate the target's time-frequency information and the target's incident azimuth. During the detection process, the towed array sonar platform often needs to change its course, and the flexible towed array also turns accordingly. Affected by the platform's turning, the position of each array element in the array is offset from the position of the ideal linear array element, and the received array data is significantly different from the received array data of the ideal linear array. Therefore, establishing an array signal reception model during the platform's turning process and mastering the signal change law during the turning process have great application value for improving the performance of the array data processing algorithm of the towed array sonar. Summary of the invention

[0003] The invention provides a method for measuring array receiving signals during the steering process of a towed array sonar platform, and solves the technical problem of providing signals received by each array element in real time according to known transmitting signals when the array is steering.

[0004] The technical solution of the present invention is:

[0005] A method for measuring array receiving signals during the steering process of a towed array sonar platform, comprising the following steps:

[0006] Step 1: Build a sound source model

[0007] Assume that the signal emitted by the sound source is s0(t) = Acos(ω0t+φ0), where A, ω0, and φ0 are the amplitude, frequency, and initial phase of the signal, respectively. R is the distance from the emitted signal to the origin O, and c is the speed of sound. The first element of the array is 1, the last element is N, d is the element spacing, θ is the incident direction of the sound source as a far-field plane wave, and s m (t) is the signal received by array element m, and K is the amplitude attenuation coefficient of the sound source signal reaching the receiving array.

[0008] Assume that the array steering angle is α, the turning radius is r, and the array aperture is L = (N-1)d. Define αr < L as a small angle steering, and αr ≥ L as a large angle steering. During the array steering process, the center angle β corresponding to the length of the array on the ring changes with time. According to the value of the center angle β, the array steering is divided into 5 time stages, and the intersection points of each time stage are defined as time t0, t1, t2, and t3 respectively. β mIt represents the center angle of the turning arc from the array element m to the origin O.

[0009] Step 2: Give the received signals at five time stages under small angles, large angles, and left and right turns. The details are as follows:

[0010] (I) Small angle steering

[0011] When the array turns at a small angle, the array formation diagrams at each stage are as follows Figure 2 , Figure 3 As shown, Figure 2 It's turning right. Figure 3 is to turn left. Figure 2 , Figure 3 It can be seen that t0 is the reference time, corresponding to the time when the first array element reaches the turning ring. where v is the platform (array) velocity.

[0012] Case 1: Turn right at a small angle

[0013] (1) When 0≤t≤t0, the array has not yet reached the turning ring and is arranged in a standard linear array. The received signal at this time is:

[0014]

[0015] (2) When t0<t≤t1, part of the array is located on the turning circle, and the other part is tangent to the turning circle in a straight line. represents rounding down, and k represents the last number of array elements on the turning circle. The received signal is:

[0016]

[0017] (3) When t1<t≤t2, the first array element of the array is out of the ring, and the last array element is not in the ring. k represents the number of the last array element in the front ring of the array; q represents the last number of array elements on the turning circle. The received signal is:

[0018]

[0019] in, Represents the phase difference between array element m and the origin O.

[0020] (4) When t2<t≤t3, the first array element is located on the tangent line of the ring, and the last array element is on the turning ring. k represents the last array element number of the front ring of the array. The received signal at this time is:

[0021]

[0022] in,

[0023] (5) When t>t3, the last array element has left the ring, and all array elements are located on the tangent of the ring, forming a uniform linear array. At this time, the received signal is:

[0024]

[0025] in,

[0026] Case 2: Small left turn

[0027] (1) When 0≤t≤t0, the array has not yet reached the turning ring and is arranged in a standard linear array. The received signal at this time is:

[0028]

[0029] (2) When t0<t≤t1, part of the array is located on the turning circle, and the other part is tangent to the turning circle in a straight line. At this time, the received signal is:

[0030]

[0031] in, k represents the last element number of the array on the turning circle.

[0032] (3) When t1<t≤t2, the first array element of the array is out of the ring, and the last array element is not in the ring. At this time, the received signal is:

[0033]

[0034] in, represents the phase difference between array element m and the origin O; k represents the number of the last array element in the front ring of the array; q represents the last number of array elements on the turning circle.

[0035] (4) When t2<t≤t3, the first array element is located on the tangent of the ring, and the last array element is on the turning ring. At this time, the received signal is:

[0036]

[0037] in, k represents the number of the last array element in the front ring of the array;

[0038] (5) When t>t3, the last array element has moved out of the ring, and all array elements are located on the tangent of the ring, forming a uniform linear array. At this time, the received signal is:

[0039]

[0040] in,

[0041] (II) Large-angle steering

[0042] When the array turns at a large angle, the array formation diagrams at each stage are as follows: Figure 4 , Figure 5 As shown, Figure 4 It's turning right. Figure 5 is to turn left. Figure 4 , Figure 5 It can be seen that t0 is the reference time, corresponding to the time when the first array element reaches the turning ring. where v is the platform (array) velocity.

[0043] Case 3: Large right turn

[0044] (1) When 0≤t≤t0, the array has not yet reached the turning ring and is arranged in a standard linear array. The received signal at this time is:

[0045]

[0046] (2) When t0<t≤t1, part of the array is located on the turning circle, and the other part is tangent to the turning circle in a straight line. k represents the last element number of the array on the turning circle. The received signal at this time is:

[0047]

[0048] (3) When t1<t≤t2, the first and last elements of the array are both inside the ring. The received signal is:

[0049]

[0050] (4) When t2<t≤t3, the first array element is located on the tangent line of the ring, and the last array element is on the turning ring. k represents the last array element number of the front ring of the array. The received signal at this time is:

[0051]

[0052] in, Represents the phase difference between array element m and the origin O.

[0053] (5) When t>t3, the last array element has moved out of the ring, and all array elements are located on the tangent of the ring, forming a uniform linear array. At this time, the received signal is:

[0054]

[0055] in,

[0056] Case 4: Large left turn

[0057] (1) When 0≤t≤t0, the array has not yet reached the turning ring and is arranged in a standard linear array. The received signal at this time is:

[0058]

[0059] (2) When t0<t≤t1, part of the array is located on the turning circle, and the other part is tangent to the turning circle in a straight line. At this time, the received signal is:

[0060]

[0061] in, k represents the last element number of the array on the turning circle.

[0062] (3) When t1<t≤t2, the first and last elements of the array are both inside the ring. The received signal is:

[0063]

[0064] (4) When t2<t≤t3, the first array element is located on the tangent of the ring, and the last array element is on the turning ring. At this time, the received signal is:

[0065]

[0066] in, k represents the number of the last array element in the front ring of the array; Represents the phase difference between array element m and the origin O.

[0067] (5) When t>t3, the last array element has moved out of the ring, and all array elements are located on the tangent of the ring, forming a uniform linear array. At this time, the received signal is:

[0068]

[0069] in,

[0070] Beneficial effects of the present invention: The present invention establishes a steering model of an array around an arc trajectory, and for large-angle steering and small-angle steering, left steering and right steering conditions, uses the center angle corresponding to the array position arc to decompose the steering process into five steering stages, gives the time point values ​​of four adjacent moments in the five stages, and for each steering stage, takes the first array element as a reference, gives the receiving signals of all array elements at the current moment, which has great application value for improving the performance of array signal processing algorithms. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 Indicates the change of the center angle β corresponding to the length of the array ring during the array steering process; the value of β divides the array steering into 5 time stages, and the intersection points of each stage are defined as time t0, t1, t2, and t3, respectively. α is the platform or array steering angle. When the array is turned at a small angle, β max =α, when the array turns at a large angle,

[0072] Figure 2 It shows the positional relationship between the array formation and the turning circle in the five stages when the array turns right at a small angle. Among them, O(0,0) is the position where the array enters the turning circle, P is the position where the array exits the turning circle, and the coordinate system x0y0 is established at this point. The angle that the platform needs to turn is α. Figure 3 , Figure 4 , Figure 5 The corresponding coordinate origin and parameters in are also set in the same way.

[0073] Figure 3 It shows the positional relationship between the array formation and the turning circle in the five stages when the array turns left at a small angle.

[0074] Figure 4 It shows the positional relationship between the array formation and the turning circle in the five stages when the array turns right at a large angle.

[0075] Figure 5 It shows the positional relationship between the array formation and the turning ring in the five stages when the array turns left at a large angle. DETAILED DESCRIPTION

[0076] The specific implementation examples of the present invention are described in detail below in conjunction with the invention content and the accompanying drawings.

[0077] A method for measuring array receiving signals during the steering process of a towed array sonar platform, comprising the following steps:

[0078] Step 1: Determine the platform steering direction, steering angle α, turning radius r, number of array elements N, and array element spacing d. Calculate L = (N-1)d. If αr < L, it is defined as a small angle steering, and αr ≥ L is defined as a large angle steering.

[0079] Step 2: When the platform and array are turning at a small angle, let t0 be the reference time when the first array element enters the turning circle, When the platform and array are turning at a large angle, let t0 be the reference time,

[0080] Four possible situations of judging the steering direction and steering angle are given, and the received signals of the five stages of the steering process are given for each situation.

[0081] Situation 1. Small right turn

[0082] (1) When 0≤t≤t0, the received signal is:

[0083]

[0084] (2) When t0<t≤t1, the received signal is:

[0085]

[0086] in, means round down,

[0087] (3) When t1<t≤t2, the received signal is:

[0088]

[0089] in,

[0090] (4) When t2<t≤t3, the received signal is:

[0091]

[0092] in,

[0093] (5) When t>t3, the received signal is:

[0094]

[0095] in,

[0096] Case 2: Small left turn

[0097] (1) When 0≤t≤t0, the received signal is:

[0098]

[0099] (2) When t0<t≤t1, the received signal is:

[0100]

[0101] in,

[0102] (3) When t1<t≤t2, the received signal is:

[0103]

[0104] in,

[0105] (4) When t2<t≤t3, the received signal is:

[0106]

[0107] in,

[0108] (5) When t>t3, the received signal is:

[0109]

[0110] in,

[0111] Case 3: Large right turn

[0112] (1) When 0≤t≤t0, the received signal is:

[0113]

[0114] (2) When t0<t≤t1, the received signal is:

[0115]

[0116] in,

[0117] (3) When t1<t≤t2, the received signal is:

[0118]

[0119] in

[0120] (4) When t2<t≤t3, the received signal is:

[0121]

[0122] in,

[0123] (5) When t>t3, the received signal is:

[0124]

[0125] in,

[0126] Situation 4: Large left turn

[0127] (1) When 0≤t≤t0, the received signal is:

[0128]

[0129] (2) When t0<t≤t1, the received signal is:

[0130]

[0131] in,

[0132] (3) When t1<t≤t2, the received signal is:

[0133]

[0134] in,

[0135] (4) When t2<t≤t3, the received signal is:

[0136]

[0137] in,

[0138] (5) When t>t3, the received signal is:

[0139]

[0140] in,

Claims

1. A method for measuring array receiving signals during the steering process of a towed array sonar platform, characterized in that: The specific steps are as follows: Step 1: Build a sound source model Assume that the signal emitted by the sound source is s0(t)=Acos(ω0t+φ0), where A, ω0, φ0 are the amplitude, frequency and initial phase of the signal respectively; R is the distance from the emitted signal to the origin O, c is the speed of sound; the first element of the array is 1, the last element is N, d is the element spacing, θ is the incident direction of the sound source as a far-field plane wave, s m (t) is the signal received by array element m, K is the amplitude attenuation coefficient of the sound source signal reaching the receiving array; Determine the platform's steering direction, steering angle α, turning radius r, number of array elements N, and array element spacing d, and calculate L = (N-1)d; if αr < L, it is defined as a small-angle steering, and αr ≥ L is defined as a large-angle steering; Step 2: During the array steering process, the center angle β corresponding to the length of the array on the ring changes with time; according to the value of the center angle β, the array steering is divided into 5 time stages, and the intersection points of each stage are defined as time t0, t1, t2, and t3 respectively; when the platform and the array belong to small angle steering, let t0 be the reference time when the first array element enters the steering ring, When the platform and array are turning at a large angle, let t0 be the reference time when the first array element enters the turning circle. β m represents the central angle of the turning arc from the array element m to the origin O; v represents the platform and array speed; There are four situations for judging the steering direction and steering angle, and the array receiving signals at five stages of the steering process are given in each situation, as follows: Situation 1. Small right turn (1) When 0≤t≤t0, the received signal is: (2) When t0<t≤t1, the received signal is: in, Indicates rounding down; (3) When t1<t≤t2, the received signal is: in, (4) When t2<t≤t3, the received signal is: in, (5) When t>t3, the received signal is: in, Case 2: Small left turn (1) When 0≤t≤t0, the received signal is: (2) When t0<t≤t1, the received signal is: in, (3) When t1<t≤t2, the received signal is: in, (4) When t2<t≤t3, the received signal is: in, (5) When t>t3, the received signal is: in, Case 3: Large right turn (1) When 0≤t≤t0, the received signal is: (2) When t0<t≤t1, the received signal is: in, (3) When t1<t≤t2, the received signal is: (4) When t2<t≤t3, the received signal is: in, (5) When t>t3, the received signal is: in, Situation 4: Large left turn (1) When 0≤t≤t0, the received signal is: (2) When t0<t≤t1, the received signal is: in, (3) When t1<t≤t2, the received signal is: (4) When t2<t≤t3, the received signal is: in, (5) When t>t3, the received signal is: in,

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