A full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance

Abstract

The present invention relates to the technical field of underwater acoustic engineering and provides a full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance. The method realizes the full-process target echo signal simulation of "transmit-channel-Doppler-target-channel-Doppler-receive", further provides a set of intelligent solutions for meeting underwater target countermeasure and avoidance based on a single computing device, and makes up for the serious deficiency of existing integrated sonar signal simulators that cannot control the target motion state. The method uses the equivalent bright spot structure parameters of the target to control the echo signal waveform structure and uses the target intensity TS curve to control the target echo intensity characteristics, so that the simulated target echo signal characteristics are more accurate. The target echo signal is simulated according to the signal process, which truly reflects the physical process of echo signal generation and makes the channel characteristics and Doppler characteristics of the simulated signal more realistic. The method also proposes a reconnaissance sonar signal detection azimuth estimation method and an avoidance heading decision method based on reconnaissance information.

Description

Technical Field

[0001] The present invention relates to the field of underwater acoustic engineering technology, and in particular to a full-process simulation method for underwater target echo signals for intelligent simulation reconnaissance and avoidance. Background Art

[0002] The sonar array signal simulator can quickly calculate and simulate sonar array signal data through a computer or signal processor under any setting of the ocean acoustic environment and target situation. It can provide important data support for the testing of acoustic signal processing algorithms, the deduction and evaluation of sonar detection performance, and the training and assessment of sonar operators, greatly saving the cost of sonar technology development, sonar operation training and detection performance evaluation. As a digital twin technology in the field of underwater acoustics, it has very important application prospects.

[0003] The sonar signal simulator is a relatively independent device, which is generally an integrated device consisting of a computer (industrial computer) or DSP signal processor to complete the simulation background setting, array signal simulation, and array simulation signal storage or output, and provide it to subsequent sonar signal processing and sonar display and control console.

[0004] Currently, sonar signal simulators are run before signal simulation begins, based on the simulation task. These parameters include ocean environment parameters, sonar array and operating parameters, as well as the heading and speed of the sonar and target platforms. After the simulation begins, the simulator simulates array data according to the preset simulation state. The motion state of the target or sonar platform cannot be changed during the simulation.

[0005] However, in actual maritime confrontations, underwater target platforms are equipped with reconnaissance and long-range warning sonars. Once a surface anti-submarine vessel activates its active sonar, it can detect and locate the surface vessel at a relatively long distance, determine its position, and then take evasive measures to counter the active sonar detection. Based on the detected position of the surface vessel, the platform changes its course, aiming towards the anti-submarine vessel at an angle (bow angle) that minimizes echo intensity, minimizing the range of active sonar detection. When the underwater target takes countermeasures, the active detection sonar array signal changes significantly, significantly altering the sonar detection effectiveness. If a sonar array signal simulator fails to reflect this common countermeasure capability, its signal simulation functionality and effectiveness will be significantly impacted, limiting its scope of application.

[0006] In addition, the existing active sonar target echo signal simulation methods have the following deficiencies: (1) Most of the existing active sonar target echo signal simulations are based on one-way underwater acoustic channel simulation and Doppler characteristic simulation, taking into account twice the propagation delay and Doppler frequency shift. They do not take into account the changes in the relative motion posture of the platform during the round-trip propagation of the active sonar signal and the reception signal errors caused by the different round-trip channels. As a result, the waveform characteristics, Doppler characteristics, and target echo intensity characteristics of the target echo cannot reflect the real signal generation effect and the simulation is inaccurate. (2) In addition to meeting the attenuation characteristics of the ocean channel propagation, the waveform characteristics and target intensity characteristics of the target echo signal received by the sonar are also related to the shape, structure and material of the target and the change in the signal incident direction (i.e., the target intensity TS curve). These echo signal characteristics are one of the core of active sonar signal simulation. To well reflect these signal characteristics, it is very important and difficult for real-time simulation simulators with extremely high computing speed requirements. This is also an important problem that the current active sonar target echo signal simulation technology has not yet solved. Summary of the Invention

[0007] The present invention mainly solves the technical problems faced by an integrated simulation system (simulator) of active sonar array signals under the background of dynamic confrontation at sea, namely, autonomous reconnaissance and reconnaissance information simulation of underwater platforms, autonomous avoidance decision simulation, and dynamic simulation of the entire process of active sonar signals from "transmission-transmission channel propagation-Doppler influence-target reflection-receiving ocean channel-Doppler influence-reception". A full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance is proposed to improve the accuracy and reliability of the simulation of underwater target echo waveform characteristics, intensity characteristics and Doppler characteristics. By intelligently simulating the reconnaissance and avoidance maneuvering decisions of underwater target platforms for active sonar signals, the output signal of the integrated simulator based on a single computing device is more in line with the actual confrontation background at sea, and can better meet the actual needs of confrontation effect deduction and evaluation.

[0008] The present invention provides a full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance, comprising:

[0009] 1. A full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance, characterized in that the simulation method comprises:

[0010] S1. Setting simulation background parameters; the simulation background parameters include: ocean acoustic environment parameters, motion status of the sonar platform and underwater target platform, as well as active sonar parameters and underwater target platform reconnaissance sonar parameters;

[0011] S2. Calculate the position coordinates of the sonar platform and the underwater target platform; calculate the distance and side angle between the sonar platform and the underwater target platform for each simulation moment;

[0012] S3. Based on the principle of solution encounter, calculate the sound wave propagation direction, arrival time, propagation distance, incident side angle of the active sonar signal reaching the underwater target, as well as the target distance and target side angle when the signal reaches the target;

[0013] S4. Calculating, based on the ocean acoustic environment parameters, an acoustic channel impulse response function of the active sonar signal transmitted to the target, and a propagation loss of the transmitted signal along the ocean propagation direction to the target distance;

[0014] S5. Convolutionally calculating the incident signal when the active sonar signal reaches the target based on the impulse response function of the transmitting underwater acoustic channel, and performing time-domain Doppler processing on the incident signal to complete signal simulation including transmitting channel propagation and Doppler effects;

[0015] S6. For the incident signal including the Doppler effect of the transmitting segment, the target reflection signal is calculated based on the bright spot characteristics and the target intensity characteristics of the underwater target;

[0016] S7, calculating the sound wave propagation direction, arrival time and sound wave incident angle of the reflected signal returning to the sonar platform, as well as the side angle of the sonar platform at the target when the reflected signal returns to the sonar platform; calculating the return section underwater acoustic channel impulse response function; convolution calculation of the echo signal of the target reflected signal arriving at the sonar platform receiving point, performing time domain Doppler processing on the echo signal, and completing one cycle of underwater target echo signal simulation;

[0017] S8, intelligently simulate the detection and azimuth estimation of the active sonar signal by the reconnaissance sonar of the underwater target platform, and independently determine whether the reconnaissance sonar can detect the active sonar signal. If so, perform reconnaissance azimuth simulation of the reconnaissance sonar; if not, re-execute steps S2 to S7 to perform the next simulation cycle;

[0018] S9. Determine whether the underwater target platform is in a special reflection area based on the reconnaissance azimuth simulation. If so, calculate the underwater target avoidance heading and determine the new track coordinates. If not, re-execute steps S2 to S8 to perform the next simulation cycle.

[0019] Furthermore, the setting of simulation background parameters includes: ocean acoustic environment parameter setting including: simulating the seabed topography of the sea area, the sea area depth z(x,y) of the sea area location point (x,y), bottom parameters, and ocean sound velocity profile c(z). Estimating the ocean environment noise NL based on the working frequency band of the reconnaissance sonar; underwater target platform motion situation setting including: the preset initial heading h of the underwater target platform T , speed vT , the initial side angle θ of the underwater target relative to the sonar platform s0 , initial distance R0, underwater platform depth D q ; Strength curve TS(θ T ); the bright spot structure and reflection parameters of the underwater target platform; the high-intensity reflection area Ψg, the medium-intensity reflection area Ψz, and the weak reflection area Ω of the underwater target platform; the linear velocity v of the underwater platform T The radius of rotation is r x ; Sonar platform and its active sonar parameter settings include: sonar platform heading h s , speed v s Active sonar emission source level SL, emission signal s(t), pulse width ΔT, pulse emission repetition period T; transmit and receive array depth D s ; Assume that the active sonar transmits pulse signals omnidirectionally; the underwater target platform reconnaissance sonar parameter settings include: reconnaissance array directivity index DI, detection threshold DT, azimuth estimation error δ θ .

[0020] Furthermore, the position coordinates of the sonar platform and the underwater target platform are calculated, and the position coordinates include: initial position coordinates, dynamic simulation moment position coordinates updated according to the simulation step size; and the distance and side angle between the sonar platform and the underwater target platform are calculated at each simulation moment:

[0021] Assume that the simulation starts at t = 0 and the initial rectangular coordinate of the sonar platform is x s (0)=0,y s (0)=0;

[0022] Calculate the initial coordinates of the underwater target platform T0 according to the initial situation:

[0023]

[0024] Calculate the position coordinates of the sonar platform and the underwater target platform according to the simulation time step Δt, t i =t i-1 At time +Δt, the coordinates of the sonar platform and the underwater target platform can be calculated by the following formula:

[0025] Sonar platform location coordinates:

[0026] The location coordinates of the underwater target platform:

[0027] The calculation of the distance and side angle between the sonar platform and the underwater target platform at each simulation moment includes:

[0028] t iThe distance between the underwater target platform and the sonar platform at this moment is:

[0029]

[0030] t i The side angle between the underwater target platform and the sonar platform at this moment is:

[0031] Side angle of underwater target platform:

[0032] Side angle of sonar platform:

[0033] Furthermore, the step S3 includes:

[0034] Assume that the active sonar transmits pulse signals in an omnidirectional manner at time t0. Since the underwater target moves in a uniform straight line, the side angle of the sound wave when it reaches the target will deviate in the direction of the target's movement. The deviation angle Δθ is q Size:

[0035]

[0036] Assume that the acoustic propagation delay of the transmitted signal to the target is τ I ,but:

[0037] cτ I cos△θ q +v T τ I cosθ q0 =R0 (8)

[0038] Then, from S0 to T t The sound propagation delay τ of a point I for:

[0039]

[0040] Therefore, the time it takes for the transmitted signal to reach the underwater target and the distance it travels are:

[0041] t=t0+τ I =τ I (10-1)

[0042] R I =cτ I (10-2)

[0043] At this time, the sonar platform position S1 and the underwater target platform T t The coordinates are:

[0044]

[0045]

[0046] The distance between the sonar platform and the underwater target platform is:

[0047]

[0048] The incident angle θ of the sound wave reaching the underwater target qi for:

[0049] θ qi =θ q0 +Δθ q (14)

[0050] The side angle of the underwater target relative to the sonar platform is:

[0051]

[0052] Furthermore, the step S4 includes: calling the ocean sound propagation model according to the ocean topography data, the seabed geological data, the sound velocity profile data and the sonar operating frequency, and calculating the propagation direction of the transmitted sound wave in the direction S0-T t The underwater acoustic channel impulse response function h1(t) and the propagation distance R in the ocean direction I The propagation loss TL(R I ); The ocean sound propagation model may be one of Bellhop, Kraken, Ram, and For3d.

[0053] Furthermore, the step S5 includes:

[0054] Calculate the incident signal s when the active transmission signal reaches the target I (t);

[0055] The incident wave signal of the transmitted signal reaching the target is the convolution of the transmitted signal and the channel impulse response function:

[0056]

[0057] Perform time domain Doppler processing on the incident signal;

[0058] The Doppler frequency shift caused by the motion of both platforms corresponds to the change of the signal waveform in the time domain. The Doppler effect causes the waveform of the incident wave to change to:

[0059] s I (t) = s I1 [(1+△ Id )t] (16-2)

[0060] where Δ Id is the Doppler factor:

[0061]

[0062] Furthermore, the step S6 includes: assuming that the echo characteristics of the underwater target are equivalent to a linear structure of N bright spots, and the reflection coefficient of each bright spot is A i , the curve of underwater target intensity and water incident angle change is TS(θ), then the reflected wave of the incident sound signal from the underwater target is:

[0063]

[0064] Among them, τ i is the time delay of the i-th bright spot relative to the reference bright spot, is a random phase uniformly distributed from 0 to 2π; assuming that the reference bright spot is located at the head of the target, the incident angle is based on the target heading, and the distance between the i-th bright spot and the reference bright spot is d i , then:

[0065] τ i (θ qi )=d i cosθ qi / c,0≤θ qi ≤π (19)

[0066] Where, Normalizes the amplitude of the echo signal.

[0067] Furthermore, the step S7 includes:

[0068] The step of calculating the sound wave propagation direction, arrival time, and sound wave incident angle of the target reflected signal reaching the sonar platform, as well as the side angle of the sonar platform at the target when the reflected signal returns to the sonar platform, includes:

[0069]

[0070] The target reflected wave from T t Sound propagation delay τ of point-return sonar platform R for:

[0071]

[0072] At this time, the sonar platform S r The coordinates are:

[0073]

[0074] The incident angle θ of the target echo reaching the sonar platform sr for:

[0075] θ sr =θ s1 +Δθ s(twenty three)

[0076] At this time, the side angle of the sonar platform relative to the target is:

[0077]

[0078] The method of calculating the return section underwater acoustic channel impulse response function; convolutionally calculating the echo signal of the target reflected signal arriving at the sonar platform receiving point, and performing time domain Doppler processing on the echo signal includes:

[0079] According to the ocean topography data, seabed geological data, sound velocity profile data and sonar working frequency, the ocean sound propagation model is called to calculate the propagation direction S of the transmitted sound wave. t —T r The underwater acoustic channel impulse response function h2(t) on ;

[0080] Calculate the target reflection signal s r (t) T t —S r The target echo signal returned by the underwater acoustic channel to the sonar platform

[0081]

[0082] Considering the Doppler effect of the return process, the waveform of the target echo signal received by the sonar changes to:

[0083] r(t)=r R [(1+△ Rd )t] (25-2)

[0084] where Δ Rd is the Doppler factor of the active signal return phase, which is expressed by the following formula:

[0085]

[0086] Furthermore, the step S8 includes:

[0087] According to the passive sonar equation:

[0088] SL-(NL-DI+DT)=TL (27)

[0089] Where SL is the sound source level of the active sonar transmission signal, TL is the propagation loss of the transmission signal to the underwater target platform, NL is the background noise level, DI is the directivity index of the reconnaissance sonar, and DT is the detection threshold of the reconnaissance sonar. The left side of the above formula is the quality factor representing the sonar detection performance, expressed as FOM.

[0090] If FOM ≥ TL(R I ), then the reconnaissance sonar can detect the active sonar signal;

[0091] The reconnaissance sonar bearing estimation simulation includes:

[0092] Assume that the bearing estimation error of the reconnaissance sonar is δ θ , the incident side angle θ when the active transmission signal reaches the target qi It has been calculated by formula (14), so the incident direction of the active sonar signal detected by the reconnaissance sonar, that is, the side angle is:

[0093] θ I =θ qi +δ θ (28).

[0094] Furthermore, the step S8 includes: autonomously determining whether the reconnaissance sonar can detect the active sonar transmission signal. The method includes: according to the passive sonar equation:

[0095] SL-(NL-DI+DT)=TL (27)

[0096] Where SL is the sound source level of the active sonar transmission signal, TL is the propagation loss of the transmission signal to the underwater target platform, NL is the background noise level, DI is the directivity index of the reconnaissance sonar, and DT is the detection threshold of the reconnaissance sonar. The left side of the above formula is the quality factor representing the sonar detection performance, expressed as FOM.

[0097] According to step 4 in claim 5, the propagation loss TL (R I ), if FOM≥TL(R I ), the reconnaissance sonar can detect the active sonar signal, otherwise the reconnaissance sonar does not detect the active sonar signal;

[0098] If the reconnaissance sonar detects an active sonar signal, the method for autonomously simulating the direction of arrival (side angle) of the active sonar signal detected by the reconnaissance sonar includes:

[0099] Assume that the bearing estimation error of the reconnaissance sonar is δ θ , the incident side angle θ when the active transmission signal reaches the target qi It has been calculated by formula (14), so the incident side angle of the active sonar transmission signal that the reconnaissance sonar estimates actually arrives is:

[0100] θ I =θ qi +δ θ (28).

[0101] Furthermore, the step S9 includes: dividing the area where the underwater target platform is located into a high-intensity reflection area, a medium-intensity reflection area and a weak reflection area according to the reflection intensity TS, and then judging whether the underwater target platform is in the "high-intensity reflection area" when the reconnaissance sonar of the underwater target platform detects the active sonar signal; if the incident angle θ of the signal is I Located in the high-intensity reflection area g and medium-intensity reflex zone Ψ z , an evasive course should be taken to ensure that the incident angle of the next active sonar detection signal is located in the weak intensity reflection area Ω, thereby improving the concealment of the underwater target platform; otherwise, the original course should be maintained and no evasive maneuver should be performed; according to the incident angle θ of the active sonar signal obtained by reconnaissance I , the central angle θ of the weak intensity reflection area is determined according to the following o , considering the sign of the incident angle, i.e., whether the signal comes from the starboard or port side, the avoidance steering angle is calculated as follows:

[0102] △h T =|θ0-|θ I || (29)

[0103] (1) If the active sonar signal is located in the high-intensity reflection area Ψ g

[0104] With the minimum steering angle, the vehicle will move away from the weak reflection area of ​​the detection signal, that is, the tail area, and face the direction of the active sonar signal. At this time, the central angle θ of the weak reflection area Ω o =180°; the avoidance heading is:

[0105] h Tg =h T ±Δh T (30-1)

[0106] In the above formula, when the active sonar signal comes from the port side, take "+" (turn right); when it comes from the starboard side, take "-" (turn left);

[0107] (2) If the active sonar signal is located in the medium-intensity reflection area Ψ z , and the detected active sonar signal is located at a small side angle, that is, from the side and front of the underwater platform, θ o =0°; the avoidance heading is:

[0108] h Tg =h T ±Δh T (30-2)

[0109] In the above formula, when the active sonar signal comes from the port side, take "-" (turn left), and when it comes from the starboard side, take "+" (turn right);

[0110] (3) If the active sonar signal is located in the medium-intensity reflection area Ψ z , and the detected active sonar signal is at a large side angle, that is, from the side and rear of the underwater platform, θ o =180°; the avoidance heading is:

[0111] h Tg =h T ±Δh T (30-3)

[0112] In the above formula, when the active sonar signal comes from the port side, take "+" (turn right), and when it comes from the starboard side, take "-" (turn left);

[0113] Considering the reconnaissance signal detection processing time t cl , the time delay between requesting and issuing steering decision instructions t jc , and the control delay t from issuing a steering command to the platform actually turning cz , so the actual turning moment of the platform is when it receives the incident signal t i After that, delay t cl , t jc , t cz Just started, that is, t zx =t i +t cl +t jc +t cz Only then does the platform actually start to turn, before which the platform still moves in a straight line;

[0114] Determining the new track coordinates includes:

[0115] (1) Coordinate calculation in the turning phase:

[0116] If the underwater platform is turning at a speed v T unchanged, and its gyration radius is r x , the steering angle is Δh T , then the total rotation time is:

[0117]

[0118] Assuming that the rotation is uniform circular motion, the angular velocity ω is:

[0119]

[0120] Assume that the turning moment is t zx , the coordinates of the underwater platform position at this time are [x T (t zx ),y T (t zx )], then the coordinates of the center of the circle of the right-turn uniform circular motion (xx0 ,y x0 )for:

[0121]

[0122] The coordinates of the center of the circle of the left-turn uniform circular motion (x x0 ,y x0 )for:

[0123]

[0124] Then at the i-th rotation time t after the start of the turn i =t zx +i·Δt, when it is regarded as clockwise (right turn) uniform circular motion, its motion trajectory coordinates are:

[0125]

[0126] When the motion is in counterclockwise (left turn) uniform circular motion, the coordinates of its motion trajectory are:

[0127]

[0128] (2) The coordinate calculation for turning to end the straight flight phase includes:

[0129] Assume that the coordinates of the underwater platform at the end of the turn are (x Tj ,y Tj ), follow the avoidance heading h Tg If the flight is straight and at a constant speed, then at the simulation time t i =iΔt, i=1, 2, ..., the track coordinates of the subsequent direct flight phase are:

[0130]

[0131] in:

[0132]

[0133] The present invention provides a full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance, which has the following beneficial effects:

[0134] 1. An autonomous simulation method for the reconnaissance and countermeasure avoidance functions of underwater target platforms is proposed. Underwater target (especially submarine) platforms are equipped with reconnaissance sonars, which are used to detect and analyze enemy active sonar or communication sonar signals, and to provide information support for further underwater acoustic confrontation. Once active sonar detection is detected, maneuvering and evasive measures will be taken to reduce the detection capability of active sonar and better conceal itself. This is the normal state adopted by underwater target platforms when active sonar is used for submarine search. The active sonar signal simulator currently developed by a single computing device does not have this simulation function, which greatly affects the authenticity of the sonar signal simulation and also limits the scope of application of the active sonar signal simulator. The patent of this invention, based on a single computing device, provides a set of intelligent solutions for realizing the underwater target countermeasure avoidance function, which makes up for the serious deficiencies of the existing integrated sonar signal simulator.

[0135] 2. A target reflection signal simulation method based on the target bright spot structure and target intensity TS characteristics is proposed. The key to target echo signal simulation is that the waveform characteristics of the target echo signal conform to the actual target shape structure. In addition to conforming to the attenuation characteristics of the ocean channel propagation, the target echo signal intensity received by the sonar also has to conform to the target echo intensity's variation characteristics with the signal incident direction, that is, it must conform to the target intensity curve TS(θ). For real-time simulation simulators with extremely high computing speed requirements, this is both very important and very difficult. To this end, the patent of this invention proposes a method of controlling the echo signal waveform structure with the target's equivalent bright spot structure parameters and controlling the target echo intensity characteristics with the target intensity TS curve. It simulates the waveform characteristics (bright spot structure) and intensity characteristics of the target echo very well, and the calculation is simple and convenient, making it very suitable for engineering applications with extremely high requirements for fast calculations.

[0136] 3. A full-function system simulation model of the target echo signal is proposed, which reflects the underwater acoustic propagation characteristics and the relative motion characteristics of the platform based on the entire process of active sonar signal "transmission-transmission segment channel-target-reception segment channel-reception". Most existing active sonar target echo signal simulations are based on one-way underwater acoustic channel simulation and Doppler characteristic simulation, taking into account twice the propagation delay and Doppler frequency shift. They do not take into account the changes in the relative motion posture of the platform and the errors in the received signal caused by the different round-trip channels during the round-trip propagation of the active sonar signal, resulting in inaccurate simulation of the target echo waveform characteristics, Doppler characteristics, and target echo intensity characteristics. The patent of this invention proposes a channel and Doppler segmented simulation idea. The target reflection wave simulation simulates the signal generated by the transmission channel propagation and Doppler frequency shift, which more realistically restores the process of marine signal propagation and the generation of target reflection waves, making the target echo simulation signal more realistic, accurate, and reliable.

[0137] 4. An intelligent simulation method for reconnaissance sonar signal detection and azimuth estimation, suitable for a single computing device simulator, is proposed. This method eliminates the need to know the specific sonar array, number of elements, or signal processing methods. Instead, the detection range of the reconnaissance signal is determined by solving the passive sonar equation. Furthermore, the sonar's direction-finding error and the dynamically simulated reconnaissance signal azimuth are used to estimate the sonar's signal incidence angle (azimuth). The resulting data meets the sonar's performance specifications and can meet the platform's needs for simulated avoidance decisions.

[0138] 5. An intelligent simulation method for underwater platform avoidance decision-making suitable for a single computing device simulator is proposed. According to the target intensity (TS) distribution characteristics of the underwater platform at different incident angles, the platform reflection intensity is divided into "high-intensity reflection area", "medium-intensity reflection area" and "weak-intensity reflection area". Based on the two principles of concealment safety and steering speed, a platform avoidance decision-making method suitable for autonomous simulation is proposed. First, the regional range of the platform's reflection intensity is estimated based on the incident azimuth (port angle) of the reconnaissance signal reaching the platform; further, according to the size of the incident angle and the port and starboard directions of the active signal, the size of the steering angle and the direction of the left turn or right turn are determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0139] Figure 1 This is a flow chart for implementing the full-process simulation method of underwater target echo signals for simulating reconnaissance and avoidance according to the present invention;

[0140] Figure 2 This is a flow chart of underwater target echo simulation calculation in the present invention;

[0141] Figure 3 It is a schematic diagram of the platform movement and active sonar echo signal propagation process in the present invention;

[0142] Figure 4 It is a schematic diagram of the underwater target intensity TS curve and its strong and weak reflection area division in the present invention;

[0143] Figure 5 This is a simulation example motion situation diagram in the embodiment;

[0144] Figure 6 1. The target bright spot position and the bright spot structure diagram at different incident angles obtained from the echo simulation signal in the embodiment;

[0145] Figure 7 1 is a comparison diagram of the TS curve of the simulation setting in the embodiment and the TS curve calculated using the target echo simulation signal;

[0146] Figure 8 This is an underwater target echo history diagram without intelligent decision-making and avoidance in the embodiment;

[0147] Figure 9 It is an underwater target echo history diagram for intelligent decision-making and avoidance in the embodiment;

[0148] Figure 10 These are example diagrams of the echo waveforms of underwater targets received by the sonar in a simulated avoidance situation in the embodiment (the upper left diagram is the waveform of the echo signal of the first target; the upper right diagram is the waveform of the echo signal of the third target; the lower left diagram is the waveform of the echo signal of the fourth target; and the lower right diagram is the waveform of the echo signal of the sixth target;). DETAILED DESCRIPTION

[0149] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, rather than all of the contents.

[0150] like Figure 1 、 Figure 2 As shown, the full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance provided by an embodiment of the present invention includes:

[0151] S1. Setting simulation background parameters; the simulation background parameters include: ocean acoustic environment parameters, underwater target platform motion status, sonar platform and its active sonar parameters, underwater target platform reconnaissance sonar parameters;

[0152] Specifically, the ocean acoustic environment parameter settings include: simulated seabed topography, the sea depth z(x,y) at a sea location (x,y), bottom sediment parameters, and the ocean sound velocity profile c(z). The ocean ambient noise (NL) is estimated based on the reconnaissance sonar operating frequency band. In this example, the sea depth is 550 meters, the bottom sediment parameters are muddy and sandy, the ocean sound velocity profile has a positive gradient, and the ocean ambient noise (NL) is 87 dB.

[0153] The motion situation setting of the underwater target platform includes: the preset initial heading h of the underwater target platform T , speed v T , the initial side angle θ of the underwater target relative to the sonar platform s0 , initial distance R0, underwater platform depth D q ; Strength curve TS(θ T ); the bright spot structure and reflection parameters of the underwater target platform; the high-intensity reflection area Ψg, the medium-intensity reflection area Ψz, and the weak reflection area Ω of the underwater target platform; the linear velocity v of the underwater platform T The radius of rotation is r x In this embodiment, the initial heading of the underwater target platform h T=270°, speed v T = 12 knots, the initial side angle θ of the underwater target relative to the sonar platform s0 =-90° (port side), initial distance R0 = 15km, underwater platform depth D q = 150 meters; the intensity curve TS of the underwater target is as follows Figure 2 As shown, it can be seen that: high-intensity reflection side angle interval Ψ g The range of the port side angle is -70° to -110° and the starboard side angle is 70° to 110°; the medium-strong reflection side angle range is Ψ z The port side is -8 to -70°, -110° to -172°; the starboard side is 8 to 70°, 110° to 172°; the weak reflection side angle range Ω is -8° to 0° to 8° in the bow area and -172° to 180° to 172° in the stern area. The underwater target length is 100 meters, and the 11 bright spots are located at 1, 7, 12, 25, 32, 37, 40, 65, 70, 90, and 95 meters from the bow. The specific distribution is as follows: Figure 5 The corresponding reflection coefficients are: 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 0.8, 0.7, 0.6, 0.5, 0.4.

[0154] Sonar platform and its active sonar parameter settings include: sonar platform heading h s , speed v s Active sonar emission source level SL, emission signal s(t), pulse width ΔT, pulse emission repetition period T; transmit and receive array depth D s ; Assume that the active sonar transmits pulse signals omnidirectionally. The heading of the sonar platform in this embodiment is h s =90°, speed v s =10 knots; sonar array depth D s =150 meters, transmitting sound source level SL = 210dB, transmitting signal s(t) is HFM signal, pulse width is 3 seconds, pulse transmission repetition period T = 24 seconds; omnidirectional transmission.

[0155] The parameters of underwater target platform reconnaissance sonar include: reconnaissance array directivity index DI, detection threshold DT, azimuth estimation error δ θ In this embodiment, the reconnaissance sonar directivity index DI = 5dB, the detection threshold DT = 12dB, and the azimuth estimation error δ θ In [-2°~+2°], it obeys random uniform distribution.

[0156] S2. Calculate the position coordinates of the sonar platform and the underwater target platform; calculate the distance and side angle between the sonar platform and the underwater target platform for each simulation moment;

[0157] Specifically, the position coordinates of the sonar platform and the underwater target platform are calculated, including: calculating the position coordinates of the sonar platform and the underwater target platform according to the simulation time step Δt=1 second; establishing Figure 3 The rectangular coordinate system shown in the figure has the y-axis direction as the true north direction. Assume that the simulation starts at t = 0 and the initial rectangular coordinate of the sonar platform is x s (0)=0,y s (0) = 0; calculate the initial coordinates of the underwater target platform T0 according to the initial situation:

[0158]

[0159] Then t i =t i-1 At time +Δt, the coordinates of the sonar platform and the underwater target platform can be calculated by the following formula:

[0160] Sonar platform location coordinates:

[0161] The location coordinates of the underwater target platform:

[0162] The distance and side angle between the sonar platform and the underwater target platform are calculated at each simulation moment, including:

[0163] t i The distance between the underwater target platform and the sonar platform at this moment is:

[0164]

[0165] t i The side angle between the underwater target platform and the sonar platform at this moment is:

[0166] Side angle of underwater target platform:

[0167] Side angle of sonar platform:

[0168] S3. Based on the principle of solution encounter, calculate the sound wave propagation direction, arrival time, propagation distance, incident side angle of the active sonar signal reaching the underwater target, as well as the target distance and target side angle when the signal reaches the target;

[0169] Specifically, at t0 = 4 seconds, the active sonar transmits a pulse signal in an omnidirectional manner. Since the underwater target moves in a uniform straight line, the side angle of the sound wave when it reaches the target will deviate in the direction of the target's movement, and the deviation angle Δθ q Size:

[0170]

[0171] Assume that the acoustic propagation delay of the transmitted signal to the target is τ I ,according to Figure 3 have:

[0172] cτ I cos△θ q +v T τ I cosθ q0 =R0 (8)

[0173] Then, from S0 to T t The sound propagation delay τ of a point I for:

[0174]

[0175] Therefore, the time it takes for the transmitted signal to reach the underwater target and the distance it travels are:

[0176] t=t0+τ I =τ I (10-1)

[0177] R I =cτ I (10-2)

[0178] At this time, the sonar platform position S1 and the underwater target platform T t The coordinates are:

[0179]

[0180]

[0181] The distance between the sonar platform and the underwater target platform is:

[0182]

[0183] The incident angle θ of the sound wave reaching the underwater target qi for:

[0184] θ qi =θ q0 +Δθ q (14)

[0185] The side angle of the underwater target relative to the sonar platform is:

[0186]

[0187] According to the above formula, the incident side angle θ of the first active sonar pulse reaching the underwater target is calculated qi =87.6°(port side).

[0188] S4. Calculating, based on the ocean acoustic environment parameters, an acoustic channel impulse response function of the active sonar signal transmitted to the target, and a propagation loss of the transmitted signal along the ocean propagation direction to the target distance;

[0189] Specifically, according to the ocean topography data, seabed geological data, sound velocity profile data and sonar operating frequency, the ocean sound propagation model is called to calculate the propagation direction of the transmitted sound wave S0-T t The underwater acoustic channel impulse response function h1(t) and the propagation distance R in the direction of arrival of the first pulse are I The propagation loss TL(R I )=72dB.

[0190] The propagation model in this embodiment adopts the Bellhop model.

[0191] S5. Based on the impulse response function of the transmitting underwater acoustic channel, convolution is performed to calculate the incident signal when the active sonar signal reaches the target. The incident signal is subjected to time domain Doppler processing to complete the signal simulation including the transmitting channel propagation and Doppler effect.

[0192] The incident wave signal of the transmitted signal reaching the target is the convolution of the transmitted signal and the channel impulse response function:

[0193]

[0194] The Doppler frequency shift caused by the movement of both platforms is manifested as a stretching or compression of the waveform in the time domain signal. The waveform of the incident wave signal after Doppler processing changes to:

[0195] s I (t) = s I1 [(1+△ Id )t] (16-2)

[0196] where Δ Id is the Doppler factor:

[0197]

[0198] S6. For the incident signal including the Doppler effect of the transmitting segment, the target reflection signal is calculated based on the bright spot characteristics and the target intensity characteristics of the underwater target;

[0199] According to the set underwater target echo characteristic equivalent bright spot number N, the reflection coefficient of each bright spot is A i The curve of underwater target intensity changing with incident angle is TS(θ), and the reflected signal of the incident sound signal from the underwater target is:

[0200]

[0201] Among them, τi is the time delay of the i-th bright spot relative to the reference bright spot, is a random phase uniformly distributed from 0 to 2π; according to the distance d between the i-th bright spot and the reference bright spot i , then:

[0202] τ i (θ qi )=d i cosθ qi / c,0≤θ qi ≤π (19)

[0203] Where, Normalizes the amplitude of the echo signal.

[0204] S7, calculating the sound wave propagation direction, arrival time and sound wave incident angle of the reflected signal returning to the sonar platform, as well as the side angle of the sonar platform at the target when the reflected signal returns to the sonar platform; calculating the impact response function of the return section underwater acoustic channel; convolution calculation of the echo signal of the target reflected signal arriving at the sonar platform receiving point, performing time domain Doppler processing on the echo signal, and completing one cycle of underwater target echo signal simulation;

[0205] Specifically, the calculation of the sound wave propagation direction, arrival time, and sound wave incident angle of the target reflection signal reaching the sonar platform includes:

[0206]

[0207] The target reflected wave from T t Sound propagation delay τ of point-return sonar platform R for:

[0208]

[0209] At this time, the sonar platform S r The coordinates are:

[0210]

[0211] The incident angle θ of the target echo reaching the sonar platform sr for:

[0212] θ sr =θ s1 +Δθ s (twenty three)

[0213]

[0214] Calculate the underwater target echo reception signal, including the echo band ocean propagation characteristics and platform motion Doppler characteristics, including:

[0215] According to the ocean topography data, seabed geological data, sound velocity profile data and sonar working frequency, the ocean sound propagation model is called to calculate the propagation direction S of the transmitted sound wave. t —T r The underwater acoustic channel impulse response function h2(t) on ;

[0216] Calculate the target reflection signal s r (t) T t —S r The target echo signal returned by the underwater acoustic channel to the sonar platform:

[0217]

[0218] Considering the Doppler effect of the return process, the waveform of the target echo signal received by the sonar changes to:

[0219] r(t)=r R [(1+△ Rd )t] (25-2)

[0220] where Δ Rd is the Doppler factor of the active signal return phase, which is expressed by the following formula:

[0221]

[0222] S8, intelligently simulate the detection and azimuth estimation of the active sonar signal by the reconnaissance sonar of the underwater target platform, and autonomously determine whether the reconnaissance sonar can detect the active sonar signal. If so, perform reconnaissance azimuth simulation of the reconnaissance sonar; if not, re-execute steps S2 to S7 to perform the next simulation cycle, including:

[0223] Based on the previously set values: the sound source level SL of the active sonar transmission signal, the directivity index DI of the reconnaissance sonar, the detection threshold DT of the reconnaissance sonar, and the background noise level NL, FOM=116dB is calculated.

[0224] According to the simulation background set in this example, when the first pulse reaches the underwater target platform, the propagation loss TL (R I )=72dB.

[0225] Obviously FOM≥TL(R I ), so the first active sonar pulse can be captured by the reconnaissance sonar of the underwater target platform.

[0226] Then we further simulate the direction of arrival (bow angle) of the active sonar signal detected by the reconnaissance sonar: the incident bow angle θ when the active transmission signal reaches the target has been calculated by formula (14): qi=87.6° (port side), the reconnaissance sonar direction-finding error is 1.8°, then the actual detected active sonar transmission signal incident side angle is:

[0227] θ I =θ qi +δ θ =90.4° (28)

[0228] S9: Determine whether the underwater target platform is in a special reflection area based on the reconnaissance azimuth simulation. If so, calculate the underwater target avoidance heading and determine the new track coordinates. If not, re-execute steps S2 to S8 to perform the next simulation cycle, including:

[0229] (1) Decision-making on whether the underwater platform should take evasive maneuvers

[0230] The area where the underwater target platform is located is divided into: a high-intensity reflection area, a medium-intensity reflection area and a weak reflection area according to the reflection intensity TS, and then it is judged whether the underwater target platform is in the "high-intensity reflection area" when the reconnaissance sonar of the underwater target platform detects the active sonar signal; according to the following Figure 4 The “reflection zone” divided by the TS “butterfly diagram” of the underwater platform shown.

[0231] At this time, the active sonar includes the incident signal side angle θ I Located on the port side of the underwater platform is the "high intensity reflection area" g ”, hence the need for an evasive maneuver.

[0232] (2) Decision-making on underwater platform’s avoidance course

[0233] Because the active sonar signal is located in the high-intensity reflection area on the port side, the aircraft should turn right and turn the "weak-intensity reflection area" (i.e., the tail area) away from the detection signal toward the active sonar signal. At this time, the central angle θ of the "weak-intensity reflection area Ω" is o =180°.

[0234] Calculate the steering angle to avoid:

[0235] △h T =|θ0-|θ I ||=90.4° (29)

[0236] The avoidance heading is:

[0237] h Tg =h T ±Δh T =270+90.4=360.4°, or 0.4° (30-1)

[0238] In the above formula, the active sonar signal comes from the port side, so take "+" (turn right).

[0239] Determining the new track coordinates includes:

[0240] 1) Coordinate calculation in the steering phase:

[0241] If the underwater platform is turning at a speed v T unchanged, and its gyration radius is r x , the steering angle is Δh T , the total rotation time is:

[0242]

[0243] Assuming that the rotation is uniform circular motion, the angular velocity ω is:

[0244]

[0245] Assume that the turning moment is t zx , the coordinates of the underwater platform position at this time are [x T (t zx ),y T (t zx )], then the coordinates of the center of the circle of the right-turn uniform circular motion (x x0 ,y x0 )for:

[0246]

[0247] The coordinates of the center of the circle of the left-turn uniform circular motion (x x0 ,y x0 )for:

[0248]

[0249] Then at the i-th rotation time t after the start of the turn i =t zx +i·Δt, when it is regarded as clockwise (right turn) uniform circular motion, its motion trajectory coordinates are:

[0250]

[0251] When the motion is in counterclockwise (left turn) uniform circular motion, the coordinates of its motion trajectory are:

[0252]

[0253] 2) The coordinate calculation for the turning and ending straight flight phase includes:

[0254] Assume that the coordinates of the underwater platform at the end of the turn are (x Tj ,y Tj ), follow the avoidance heading h Tg If the flight is straight and at a constant speed, then at the simulation time ti =iΔt, i=1, 2, ..., the track coordinates of the subsequent direct flight phase are:

[0255]

[0256] in:

[0257]

[0258] The effect of the above simulation embodiment is as follows:

[0259] Figure 5 The motion situation diagram of the above simulation embodiment is given. Figure 6 The bright spot location of the target and the bright spot structure at different incidence angles obtained from the simulated echo signal are shown. The horizontal axis shows the bright spot location and the vertical axis shows the incidence angle. The bright spot structure of the echo signal calculated based on the target parameters and active sonar parameters of this simulation shows that the bright spot structure of the underwater target signal obtained by this technology is very close to the echo structure obtained by current testing methods. The echo bright spot location closely matches the physical equivalent bright spot of the actual target, demonstrating that the simulation technology of this invention can well simulate the waveform structure characteristics of the target echo signal. Figure 7 This is a comparison chart of the TS curve of the simulation setting and the TS curve calculated by the target echo simulation signal. The figure shows the target echo signal intensity (TS) curve of different incident angles calculated by the present invention and the target TS curve of the simulation setting. In order to facilitate comparison, the TS curve obtained by the simulation calculation and the TS curve of the simulation setting are normalized in the figure. Figure 7 It can be seen that the two are in very good agreement, indicating that the sonar target echo signal intensity simulation method of the present invention can well reflect the reflection intensity characteristics of the target. Figure 8 This is a target echo history diagram without intelligent decision-making and avoidance. Based on the motion of the sonar platform and the underwater target platform, taking into account the ocean noise environment, and assuming the underwater target platform does not make intelligent decisions or avoidance, this target echo history diagram (the horizontal axis is target direction, the vertical axis is time) is obtained after beamforming the active sonar array signal. Figure 9 It is an underwater target echo history diagram for intelligent decision-making and avoidance. Based on the motion situation of the sonar platform and the underwater target platform, taking into account the ocean environment noise, the target echo history diagram (the horizontal axis is the target direction, the vertical axis is the time) is obtained after the active sonar array signal is beamformed when the underwater target platform makes intelligent judgment and avoidance. Figure 8 、 Figure 9It can be seen that when there is no evasive decision-making, the target echo detected by active sonar beamforming is very strong. However, in the simulated signal with intelligent decision-making and evasive maneuvers, the third echo is significantly weakened due to the evasive maneuver, and the target echo signals from the sixth echo onward are undetectable. This demonstrates that the array signal generated by this innovative technology truly reflects the actual changes in the maritime situation. Moreover, this simulation technology can well reflect the actual confrontation situation at sea. Figure 10 This is an example diagram of the echo waveform of an underwater target received by the sonar in a simulated evasive situation. The intensity (amplitude) of the echo signal of each target in the figure changes (gradually decreases) according to the TS curve as the incident angle changes.

[0260] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications to the technical solutions described in the above embodiments, or equivalent replacement of some or all of the technical features therein, do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance, characterized in that: The simulation method comprises: S1. Setting simulation background parameters; the simulation background parameters include: ocean acoustic environment parameters, motion status of the sonar platform and underwater target platform, as well as active sonar parameters and underwater target platform reconnaissance sonar parameters; S2. Calculate the position coordinates of the sonar platform and the underwater target platform; calculate the distance and side angle between the sonar platform and the underwater target platform for each simulation moment; S3. Based on the principle of solution encounter, calculate the sound wave propagation direction, arrival time, propagation distance, incident side angle of the active sonar signal reaching the underwater target, as well as the target distance and target side angle when the signal reaches the target; S4. Calculating, based on the ocean acoustic environment parameters, an acoustic channel impulse response function of the active sonar signal transmitted to the target, and a propagation loss of the transmitted signal along the ocean propagation direction to the target distance; S5. Convolutionally calculating the incident signal when the active sonar signal reaches the target based on the impulse response function of the transmitting underwater acoustic channel, and performing time-domain Doppler processing on the incident signal to complete signal simulation including transmitting channel propagation and Doppler effects; S6. For the incident signal including the Doppler effect of the transmitting segment, the target reflection signal is calculated based on the bright spot characteristics and the target intensity characteristics of the underwater target; S7, calculating the sound wave propagation direction, arrival time and sound wave incident angle of the reflected signal returning to the sonar platform, as well as the side angle of the sonar platform at the target when the reflected signal returns to the sonar platform; calculating the return section underwater acoustic channel impulse response function; convolution calculation of the echo signal of the target reflected signal arriving at the sonar platform receiving point, performing time domain Doppler processing on the echo signal, and completing one cycle of underwater target echo signal simulation; S8, intelligently simulate the detection and azimuth estimation of the active sonar signal by the reconnaissance sonar of the underwater target platform, and independently determine whether the reconnaissance sonar can detect the active sonar signal. If so, perform reconnaissance azimuth simulation of the reconnaissance sonar; if not, re-execute steps S2 to S7 to perform the next simulation cycle; S9. Determine whether the underwater target platform is in a special reflection area based on the reconnaissance azimuth simulation. If so, calculate the underwater target avoidance heading and determine the new track coordinates. If not, re-execute steps S2 to S8 to perform the next simulation cycle.

2. The full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance according to claim 1 is characterized in that: The setting of simulation background parameters includes: The ocean acoustic environment parameter settings include: simulating the seabed topography of the sea area, the sea area depth z(x,y) of the sea area location point (x,y), bottom parameters, and ocean sound speed profile c(z); estimating the ocean environmental noise NL based on the reconnaissance sonar working frequency band; The motion situation setting of the underwater target platform includes: the preset initial heading h of the underwater target platform T , speed v T , the initial side angle θ of the underwater target relative to the sonar platform s0 , initial distance R0, underwater platform depth D q ; Strength curve TS(θ T ); the bright spot structure and reflection parameters of the underwater target platform; the high-intensity reflection area Ψg, the medium-intensity reflection area Ψz, and the weak reflection area Ω of the underwater target platform; the linear velocity v of the underwater platform T The radius of rotation is r x ; Sonar platform and its active sonar parameter settings include: sonar platform heading h s , speed v s Active sonar emission source level SL, emission signal s(t), pulse width ΔT, pulse emission repetition period T; transmit and receive array depth D s ; Assume that the active sonar transmits pulse signals omnidirectionally; The parameters of underwater target platform reconnaissance sonar include: reconnaissance array directivity index DI, detection threshold DT, azimuth estimation error δ θ .

3. The full-process simulation method for underwater target echo signal for simulating reconnaissance and avoidance according to claim 2 is characterized in that: The position coordinates of the sonar platform and the underwater target platform are calculated, and the position coordinates include: initial position coordinates, dynamic simulation moment position coordinates updated according to the simulation step size; and the distance and side angle between the sonar platform and the underwater target platform are calculated at each simulation moment: Assume that the simulation starts at t = 0 and the initial rectangular coordinate of the sonar platform is x s (0)=0,y s (0)=0; Calculate the initial coordinates of the underwater target platform T0 according to the initial situation: Calculate the position coordinates of the sonar platform and the underwater target platform according to the simulation time step Δt, t i =t i-1 At time +Δt, the coordinates of the sonar platform and the underwater target platform can be calculated by the following formula: Sonar platform location coordinates: The location coordinates of the underwater target platform: The calculation of the distance and side angle between the sonar platform and the underwater target platform at each simulation moment includes: t i The distance between the underwater target platform and the sonar platform at this moment is: t i The side angle between the underwater target platform and the sonar platform at this moment is: Side angle of underwater target platform: Side angle of sonar platform:

4. The full-process simulation method for underwater target echo signal for simulating reconnaissance and avoidance according to claim 3 is characterized in that: The step S3 comprises: Assume that the active sonar transmits pulse signals in an omnidirectional manner at time t0. Since the underwater target moves in a uniform straight line, the side angle of the sound wave when it reaches the target will deviate in the direction of the target's movement. The deviation angle Δθ is q Size: Assume that the acoustic propagation delay of the transmitted signal to the target is τ I ,but: c I cos△θ q +v T t I cosθ q0 =R0 (8) Then, from S0 to T t The sound propagation delay τ of a point I for: Therefore, the time it takes for the transmitted signal to reach the underwater target and the distance it travels are: t=t0+τ I =τ I (10-1) R I =cτ I (10-2) At this time, the sonar platform position S1 and the underwater target platform T t The coordinates are: The distance between the sonar platform and the underwater target platform is: The incident angle θ of the sound wave reaching the underwater target qi for: i qi =θ q0 +Δθ q (14) The side angle of the underwater target relative to the sonar platform is:

5. The full-process simulation method for underwater target echo signal for simulating reconnaissance and avoidance according to claim 4 is characterized in that: The step S4 comprises: According to the ocean topography data, seabed geological data, sound velocity profile data and sonar working frequency, the ocean sound propagation model is called to calculate the propagation direction of the transmitted sound wave S0-T t The underwater acoustic channel impulse response function h1(t) and the propagation distance R in the ocean propagation direction are I The propagation loss TL(R I ); The ocean sound propagation model may be one of Bellhop, Kraken, Ram, and For3d.

6. The full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance according to claim 5 is characterized in that: The step S5 comprises: Calculate the incident signal s when the active transmission signal reaches the target I (t); The incident wave signal of the transmitted signal reaching the target is the convolution of the transmitted signal and the channel impulse response function: Perform time domain Doppler processing on the incident signal; The Doppler frequency shift caused by the motion of both platforms corresponds to a change in the signal waveform in the time domain. The Doppler effect causes the waveform of the incident wave to change to: s I (t)=s I1 [(1+△ Id )t] (16-2) where Δ Id is the Doppler factor:

7. The full-process simulation method for underwater target echo signal for simulating reconnaissance and avoidance according to claim 6 is characterized in that: The step S6 comprises: Assume that the echo characteristics of the underwater target are equivalent to a linear structure of N bright spots, and the reflection coefficient of each bright spot is A i , the curve of underwater target intensity and water incident angle change is TS(θ), then the reflected wave of the incident sound signal from the underwater target is: Among them, τ i is the time delay of the i-th bright spot relative to the reference bright spot, is a random phase uniformly distributed from 0 to 2π; assuming that the reference bright spot is located at the head of the target, the incident angle is based on the target heading, and the distance between the i-th bright spot and the reference bright spot is d i , then: t i (i qi )=d i cosθ qi / c,0≤θ qi ≤π (19) Where, Normalizes the amplitude of the echo signal.

8. The full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance according to claim 7 is characterized in that: The step S7 comprises: The step of calculating the sound wave propagation direction, arrival time, and sound wave incident angle of the target reflected signal reaching the sonar platform, as well as the side angle of the sonar platform at the target when the reflected signal returns to the sonar platform, includes: The target reflected wave from T t Sound propagation delay τ of point-return sonar platform R for: At this time, the sonar platform S r The coordinates are: The incident angle θ of the target echo reaching the sonar platform sr for: i sr =θ s1 +Δθ s (23) At this time, the side angle of the sonar platform relative to the target is: The method of calculating the return section underwater acoustic channel impulse response function; convolutionally calculating the echo signal of the target reflected signal arriving at the sonar platform receiving point, and performing time domain Doppler processing on the echo signal includes: According to the ocean topography data, seabed geological data, sound velocity profile data and sonar working frequency, the ocean sound propagation model is called to calculate the propagation direction S of the transmitted sound wave. t —T r The underwater acoustic channel impulse response function h2(t) on ; Calculate the target reflection signal s r (t) T t —S r The target echo signal returned by the underwater acoustic channel to the sonar platform Considering the Doppler effect of the return process, the waveform of the target echo signal received by the sonar changes to: where Δ Rd is the Doppler factor of the active signal return phase, which is expressed by the following formula:

9. The full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance according to claim 8 is characterized in that: The step S8 comprises: According to the passive sonar equation: SL-(NL-DI+DT)=TL (27) Where SL is the sound source level of the active sonar transmission signal, TL is the propagation loss of the transmission signal to the underwater target platform, NL is the background noise level, DI is the directivity index of the reconnaissance sonar, and DT is the detection threshold of the reconnaissance sonar. The left side of the above formula is the quality factor representing the sonar detection performance, expressed as FOM. If FOM ≥ TL(R I ), then the reconnaissance sonar can detect the active sonar signal; The reconnaissance sonar bearing estimation simulation includes: Assume that the bearing estimation error of the reconnaissance sonar is δ θ , the incident side angle θ when the active transmission signal reaches the target qi It has been calculated by formula (14), so the incident direction of the active sonar signal detected by the reconnaissance sonar, that is, the side angle is: i I =θ qi +d θ (28)。 10. The full-process simulation method for underwater target echo signals for simulating reconnaissance and avoidance according to claim 9 is characterized in that: The step S9 includes: The area where the underwater target platform is located is divided into a high-intensity reflection area, a medium-intensity reflection area, and a weak reflection area according to the reflection intensity TS. Then, when the underwater target platform's reconnaissance sonar detects an active sonar signal, it is determined whether the underwater target platform is in the "high-intensity reflection area"; If the incident angle of the signal is θ I Located in the high-intensity reflection area g and medium-intensity reflex zone Ψ z , then an evasive course should be taken to ensure that the incident angle of the next active sonar detection signal is within the weak intensity reflection area Ω, thereby improving the concealment of the underwater target platform; otherwise, the original course should be maintained and no evasive maneuver should be performed; According to the incident angle θ of the active sonar signal obtained by reconnaissance I , the central angle θ of the weak intensity reflection area is determined according to the following o , considering the sign of the incident angle, i.e., whether the signal comes from the starboard or port side, the avoidance steering angle is calculated as follows: △h T =|θ0-|θ I || (29) (1) If the active sonar signal is located in the high-intensity reflection area Ψ g With the minimum steering angle, the vehicle will move away from the weak reflection area of ​​the detection signal, that is, the tail area, and face the direction of the active sonar signal. At this time, the central angle θ of the weak reflection area Ω o =180°; the avoidance heading is: h Tg =h T ±Δh T (30-1) In the above formula, when the active sonar signal comes from the port side, take "+" (turn right); when it comes from the starboard side, take "-" (turn left); (2) If the active sonar signal is located in the medium-intensity reflection area Ψ z , and the detected active sonar signal is located at a small side angle, that is, from the side and front of the underwater platform, θ o =0°; the avoidance heading is: h Tg =h T ±Δh T (30-2) In the above formula, when the active sonar signal comes from the port side, take "-" (turn left), and when it comes from the starboard side, take "+" (turn right); (3) If the active sonar signal is located in the medium-intensity reflection area Ψ z , and the detected active sonar signal is at a large side angle, that is, from the side and rear of the underwater platform, θ o =180°; the avoidance heading is: h Tg =h T ±Δh T (30-3) In the above formula, when the active sonar signal comes from the port side, take "+" (turn right), and when it comes from the starboard side, take "-" (turn left); Considering the reconnaissance signal detection processing time t cl , the time delay between requesting and issuing steering decision instructions t jc , and the control delay t from issuing a steering command to the platform actually turning cz , so the actual turning moment of the platform is when it receives the incident signal t i After that, delay t cl , t jc , t cz Just started, that is, t zx =t i +t cl +t jc +t cz Only then does the platform actually start to turn, before which the platform still moves in a straight line; Determining the new track coordinates includes: (1) Coordinate calculation in the steering phase: If the underwater platform is turning at a speed v T unchanged, and its gyration radius is r x , the steering angle is Δh T , then the total rotation time is: Assuming that the rotation is uniform circular motion, the angular velocity ω is: Assume that the turning moment is t zx , the coordinates of the underwater platform position at this time are [x T (t zx ),y T (t zx )], then the coordinates of the center of the circle of the right-turn uniform circular motion (x x0 ,y x0 )for: The coordinates of the center of the circle of the left-turn uniform circular motion (x x0 ,y x0 )for: Then at the i-th rotation time t after the start of the turn i =t zx +i·Δt, when it is regarded as clockwise (right turn) uniform circular motion, its motion trajectory coordinates are: When the uniform circular motion is counterclockwise (left turn), the coordinates of its motion trajectory are: (2) The coordinate calculation for turning to end the straight flight phase includes: Assume that the coordinates of the underwater platform at the end of the turn are (x Tj ,y Tj ), follow the avoidance heading h Tg If the flight is straight and at a constant speed, then at the simulation time t i =iΔt, i=1, 2, ..., the track coordinates of the subsequent direct flight phase are: in:

Images