Multi-state active sonar decoy generation method and system

Abstract

The present invention provides a multi-state active sonar decoy generation method and system, which uses a time-domain plate element method based on physical acoustics to calculate the impulse response of scattered sound fields in different directions of a predetermined target. At this time, the output decoy signal will be overlapped with the opponent's self-guided torpedo detection signal, causing distortion of our sonar decoy input signal. Therefore, echo isolation technology is used to filter our distorted sonar decoy input signal in real time, and self-feedback suppression is performed while filtering in real time to offset the influence of our output signal on our input signal. The input signal is convolved with the impulse response of scattered sound fields in different directions of the predetermined target to obtain an ideal sonar decoy output signal, which is used as a false target to confuse the opponent. The present invention provides a false target for the opponent by generating an echo signal of the opponent's detection signal in real time, which plays a role in covering our ships to buy time for escape, thereby avoiding large losses at the lowest cost.

Description

Technical Field

[0001] The present invention relates to the field of underwater acoustic engineering technology, and in particular to a multi-state active sonar decoy generation method and system. Background Art

[0002] For targets with weak electromagnetic or acoustic radiation, radar or sonar emits high-power electromagnetic or acoustic waves and uses the electromagnetic and acoustic signals scattered by the target to detect and identify them. In order to counter the needs of radar or sonar detection, people have proposed active decoy technology that can simulate the electromagnetic and acoustic scattering characteristics of the target. Compared with active radar decoys, active sonar decoy technology started late and is relatively backward.

[0003] At present, the working mode of active sonar decoys is mainly fixed gain and delay forwarding, where gain and delay are calculated based on rough empirical formulas or bright spot models. However, the acoustic scattering characteristics of underwater targets change with the direction of the sound wave incident, that is, gain and delay are functions of the direction of the sound wave incident. Existing active sonar decoys can only simulate the echo of underwater targets in a single state, which is easy to be identified by the opponent's active sonar, or can form a certain simulated scale echo, but cannot simulate the scattered echo of underwater targets in a refined manner.

[0004] At present, no description or report of similar technology to the present invention has been found, and similar information at home and abroad has not been collected yet. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a multi-state active sonar decoy generation method and system.

[0006] According to one aspect of the present invention, a multi-state active sonar decoy generation method is provided, comprising:

[0007] The time-domain plate element method based on physical acoustics is used to calculate the impulse response of the scattered acoustic field of the predetermined target in different directions.

[0008] The detection signal of the enemy's homing torpedo is used as the input signal of our sonar decoy, and the input signal of our sonar decoy is convolved with the impulse response of the scattered sound field of the predetermined target in different directions to obtain a preliminary sonar decoy output signal;

[0009] Simulating the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal, and filtering the sonar decoy output signal from the input signal of the sonar decoy to obtain an ideal input signal;

[0010] Convolving the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal;

[0011] Repeat the above steps to continuously output the ideal sonar decoy output signal to obtain a multi-state active sonar decoy.

[0012] Preferably, the method of calculating the impulse responses of scattered sound fields of predetermined targets in different directions by using a time-domain plate element method based on physical acoustics includes:

[0013] A group of planar plate elements are used to approximate the target surface, and the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave is obtained. The scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave is superimposed to obtain the approximate value of the scattered sound field impulse response of the predetermined target.

[0014] Preferably, for the mth plate element, its scattered sound field impulse response p s,m (t) is:

[0015]

[0016] Among them, - is the soft sound field boundary; + is the hard sound field boundary; is the incident wave vector, is the outgoing wave vector, is the unit normal vector, k is the acoustic wave number; are all the edge vectors of the plate element in the counterclockwise direction; is the field point; s i is the unit impulse response and t is the time.

[0017] Preferably, an adaptive filter is used to simulate the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal.

[0018] Preferably, the adaptive filter uses the least mean square algorithm to adjust the filter coefficients with the goal of minimizing the evaluation function J(n), then:

[0019] J(n)=E[E 2 (n)]

[0020] Where n is the time point and E[·] is the mathematical expectation.

[0021] Preferably, the method further comprises forwarding the obtained multi-state active sonar decoy in real time.

[0022] According to another aspect of the present invention, there is provided a multi-state active sonar decoy generating system, comprising:

[0023] Target scattered sound field impulse response module, which uses the time domain plate element method based on physical acoustics to calculate the scattered sound field impulse response of the predetermined target in different directions;

[0024] A preliminary sonar decoy signal generation module, which uses the opponent's homing torpedo detection signal as the input signal of our sonar decoy, convolves the input signal of our sonar decoy with the impulse response of the scattered sound field in different directions of the predetermined target, and obtains a preliminary sonar decoy output signal;

[0025] an echo isolation module, which simulates the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal, and filters the sonar decoy output signal from the input signal of the sonar decoy to obtain an ideal input signal;

[0026] The multi-state active sonar decoy generation module convolves the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal and a multi-state active sonar decoy.

[0027] Preferably, the target scattered sound field impulse response module uses a group of planar plate elements to approximate the target surface, obtains the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave, and superimposes the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave to obtain an approximate value of the scattered sound field impulse response of the predetermined target, thereby simulating the echo characteristics of the predetermined target.

[0028] Preferably, the preliminary sonar decoy signal generating module comprises:

[0029] A multi-channel A / D unit, which uses an acquisition module of the NI CompactRIO embedded measurement and control platform to convert the opponent's homing torpedo detection signal from an analog signal to a digital signal;

[0030] A pre-formed multi-beam unit, the unit is used to determine the direction of the incoming wave of the opponent's homing torpedo detection signal;

[0031] A preliminary sonar decoy generation unit convolves the input signal of our sonar decoy with the impulse response of the scattered sound field in different directions of the predetermined target to obtain a preliminary sonar decoy output signal.

[0032] Preferably, the echo isolation module comprises:

[0033] a signal simulation unit, the unit using an adaptive filter to simulate the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal;

[0034] An echo cancellation unit filters out the sonar decoy output signal from the input signal of our sonar decoy to obtain an ideal input signal.

[0035] Preferably, the multi-state active sonar decoy generation module comprises:

[0036] An ideal sonar decoy generation unit, which convolves the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal;

[0037] The D / A conversion unit uses the output module of the NI CompactRIO embedded measurement and control platform to convert the ideal sonar decoy output signal from a digital signal to an analog signal, thereby obtaining a multi-state active sonar decoy.

[0038] Preferably, the preliminary sonar decoy generation unit, the echo cancellation unit and the ideal sonar decoy generation unit use a common FPGA programmer.

[0039] Due to the adoption of the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art:

[0040] The multi-state active sonar decoy generation method and system provided by the present invention provides a false target for the opponent by generating an echo signal of the opponent's detection signal in real time, thereby playing a role in covering our ships to buy time for escape, thereby avoiding greater losses at a minimum cost.

[0041] The multi-state active sonar decoy generation method and system provided by the present invention can simulate the target scattered sound waves under the conditions of sound wave incidence from different directions based on the multi-state scattering characteristics of underwater targets, thereby improving the decoy effect.

[0042] The multi-state active sonar decoy generation method and system provided by the present invention use a more accurate physical acoustic method to replace the traditional empirical formula or bright spot model to calculate the impulse response of scattered sound fields in different azimuths, determine the incident direction of the sound wave according to the multi-channel phased array technology, use FPGA technology to generate forwarding signals in real time, and introduce echo cancellation technology to improve the transmission / reception isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0044] Figure 1 The present invention is a flowchart of a multi-state active sonar decoy generation method in one embodiment of the present invention.

[0045] Figure 2Schematic diagram of the components of a multi-state active sonar decoy generating system in one embodiment of the present invention.

[0046] Figure 3 This is a working diagram of a multi-state active sonar decoy generating system in a preferred embodiment of the present invention.

[0047] Figure 4 It is a schematic diagram of a plate element in a preferred embodiment of the present invention.

[0048] Figure 5 This is a connection block diagram of a multi-state active sonar decoy generating system in a preferred embodiment of the present invention.

[0049] Figure 6 Schematic diagram of a typical adaptive filter structure in a preferred embodiment of the present invention.

[0050] Figure 7 Schematic diagram of the system identification process of the adaptive filter in a preferred embodiment of the present invention.

[0051] Figure 8 Schematic diagram of an FIR adaptive filter in a preferred embodiment of the present invention.

[0052] Fig. 9 It is a schematic diagram of an FPGA module in a preferred embodiment of the present invention.

[0053] Fig.10 This is a functional module block diagram of the system in a preferred embodiment of the present invention.

[0054] Fig.11 The waveform diagram of the response signal d(n) of our sonar decoy in a specific application example of the present invention.

[0055] Fig.12 This is a waveform diagram of the simulated echo signal y(n) of our sonar decoy in a specific application example of the present invention.

[0056] Fig.13 The figure is a waveform diagram of an ideal sonar decoy input signal x(n) in a specific application example of the present invention.

[0057] Fig.14 It is a schematic diagram of a predetermined target in a specific application example of the present invention.

[0058] Fig.15 The figure is a waveform diagram of the output signal of our sonar decoy at the azimuth of a predetermined target in a specific application example of the present invention.

[0059] Fig.16 The figure is a waveform diagram of the output signal of our sonar decoy at the predetermined target bow position in a specific application example of the present invention.

[0060] Fig.17The figure is a waveform diagram of the output signal of our sonar decoy at the predetermined target bow position in a specific application example of the present invention. DETAILED DESCRIPTION

[0061] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0062] Figure 1 A flow chart of a multi-state active sonar decoy generation method provided by one embodiment of the present invention.

[0063] like Figure 1 As shown, the multi-state active sonar decoy generation method provided by this embodiment may include the following steps:

[0064] S100 uses the time-domain plate element method based on physical acoustics to calculate the impulse response of the scattered sound field of the predetermined target in different directions;

[0065] S200, using the enemy's homing torpedo detection signal as the input signal of our sonar decoy, convolving the input signal of our sonar decoy with the impulse response of the scattered sound field in different directions of the predetermined target, and obtaining a preliminary sonar decoy output signal;

[0066] S300, simulating the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal, and filtering the sonar decoy output signal from the input signal of our sonar decoy to obtain an ideal input signal;

[0067] S400, convolving the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal;

[0068] S500, repeating steps S100 to S400, continuously outputting the ideal sonar decoy output signal, and obtaining a multi-state active sonar decoy.

[0069] In S100 of this embodiment, as a preferred embodiment, using a time domain plate element method based on physical acoustics to calculate the impulse response of scattered sound fields of a predetermined target in different directions may include the following steps:

[0070] A group of planar plate elements are used to approximate the target surface, and the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave is obtained. The scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave is superimposed to obtain the approximate value of the scattered sound field impulse response of the predetermined target.

[0071] In S100 of this embodiment, as a preferred embodiment, for the mth plate element, its scattered sound field impulse response p s,m (t) may be:

[0072]

[0073] Among them, - is the soft sound field boundary; + is the hard sound field boundary; is the incident wave vector, is the outgoing wave vector, is the unit normal vector, k is the acoustic wave number; are all the edge vectors of the plate element in the counterclockwise direction; is the field point; s i is the unit impulse response and t is the time.

[0074] In S300 of this embodiment, as a preferred embodiment, an adaptive filter may be used to simulate the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal.

[0075] In S300 of this embodiment, as a preferred embodiment, the adaptive filter may use a least mean square algorithm to adjust the filter coefficients with the goal of minimizing the evaluation function J(n), then:

[0076] J(n)=E[E 2 (n)]

[0077] Where n is the time point and E[·] is the mathematical expectation.

[0078] In this embodiment, as a preferred embodiment, the method may further include the following steps:

[0079] The obtained multi-situation active sonar decoy is forwarded in real time.

[0080] In some embodiments of the present invention:

[0081] The enemy homing torpedo detection signal received by us is taken as the input signal x(n), and the excitation signal x(n) is passed through the adaptive filter, that is, the convolution operation of the input signal x(n) and the impulse response of the scattered sound field of the predetermined target in different directions is completed, and the ideal sonar decoy output signal y(n) is obtained. The aliasing signal of the enemy homing torpedo detection signal x(n) received by us and the decoy signal y(n) output by our sonar decoy is the response signal d(n) of our sonar decoy. The role of the adaptive filter is to simulate the echo signal y(n) as much as possible and eliminate it from d(n) to obtain the ideal input signal x(n). Among them, the filter coefficient is adjusted by the adaptive filter to minimize the error signal e(n).

[0082] The enemy homing torpedo detection signal we receive is the input signal of our sonar decoy; the excitation signal of our sonar decoy is convolved with the impulse response of the scattered sound field in different directions of the predetermined target, and the influence of our sonar decoy output signal on our sonar decoy input signal is filtered out to generate a false target of our sonar decoy, thereby confusing the enemy.

[0083] The multi-state active sonar decoy generation method provided in this embodiment can simulate the target scattered sound waves as false targets under the condition of sound wave incidence in different directions, thereby improving the decoy effect. The enemy homing torpedo detection signal is used as the input signal of our sonar decoy, and the input signal is convolved with the impulse response of the scattered sound field in different directions of the predetermined target to obtain the ideal sonar decoy output signal. Among them, the time domain plate element method based on physical acoustics is used to calculate the impulse response of the scattered sound field in different directions of the predetermined target to obtain the echo characteristics of the target. However, the output decoy signal will be overlapped with the enemy homing torpedo detection signal, causing the input signal of our sonar decoy to be distorted. Therefore, the echo isolation technology is used to filter the distorted sonar decoy input signal of our side in real time, and self-feedback suppression is performed while filtering in real time to offset the influence of our output signal on our input signal. The output signal is forwarded in real time by FPGA, and used as a false target to confuse the opponent. The present invention provides a false target for the opponent by generating an echo signal of the opponent's detection signal in real time, thereby playing a role in covering our ships to buy time for escape, thereby achieving the goal of avoiding greater losses at a minimum cost.

[0084] Figure 2 A schematic diagram of the components of a multi-state active sonar decoy generating system provided in one embodiment of the present invention.

[0085] like Figure 2 As shown, the multi-state active sonar decoy generation system provided by this embodiment may include the following modules:

[0086] Target scattered sound field impulse response module, which uses the time domain plate element method based on physical acoustics to calculate the scattered sound field impulse response of the predetermined target in different directions;

[0087] A preliminary sonar decoy signal generation module, which uses the opponent's homing torpedo detection signal as the input signal of our sonar decoy, convolves the input signal of our sonar decoy with the impulse response of the scattered sound field in different directions of the predetermined target, and obtains a preliminary sonar decoy output signal;

[0088] An echo isolation module, which simulates the preliminary sonar decoy output signal, generates a simulated sonar decoy output signal, and filters the sonar decoy output signal from the input signal of our sonar decoy to obtain an ideal input signal;

[0089] The multi-state active sonar decoy generation module convolves the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain the ideal sonar decoy output signal and obtain the multi-state active sonar decoy.

[0090] In this embodiment, as a preferred embodiment, the target scattered sound field impulse response module can use a group of planar plate elements to approximate the target surface, obtain the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave, and superimpose the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave, so as to obtain an approximate value of the scattered sound field impulse response of the predetermined target, thereby simulating the echo characteristics of the predetermined target.

[0091] In this embodiment, as a preferred embodiment, the preliminary sonar decoy signal generation module may include the following units:

[0092] A multi-channel A / D unit, which uses the acquisition module of the NI CompactRIO embedded measurement and control platform to convert the enemy's homing torpedo detection signal from analog to digital;

[0093] Pre-formed multi-beam unit, which is used to determine the direction of the incoming wave of the enemy's homing torpedo detection signal;

[0094] The preliminary sonar decoy generation unit convolves the input signal of our sonar decoy with the impulse response of the scattered sound field in different directions of the predetermined target to obtain a preliminary sonar decoy output signal.

[0095] In this embodiment, as a preferred embodiment, the echo isolation module may include the following units:

[0096] A signal simulation unit, which uses an adaptive filter to simulate the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal;

[0097] The echo cancellation unit filters out the sonar decoy output signal from the input signal of our sonar decoy to obtain the ideal input signal.

[0098] In this embodiment, as a preferred embodiment, the multi-state active sonar decoy generation module may include the following units:

[0099] An ideal sonar decoy generation unit, which convolves an ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal;

[0100] The D / A conversion unit uses the output module of the NI CompactRIO embedded measurement and control platform to convert the ideal sonar decoy output signal from a digital signal to an analog signal, thereby obtaining a multi-state active sonar decoy.

[0101] In this embodiment, as a preferred embodiment, the preliminary sonar decoy generation unit, the echo cancellation unit and the ideal sonar decoy generation unit can use a common FPGA programmer.

[0102] It should be noted that the steps in the method provided by the present invention can be implemented by using corresponding modules, devices, units, etc. in the system. Those skilled in the art can refer to the technical solution of the method to realize the composition of the system, that is, the embodiments in the method can be understood as preferred examples for constructing the system, which will not be elaborated here.

[0103] The acoustic scattering characteristics of underwater targets change with the direction of the sound wave, that is, the gain and delay are functions of the direction of the sound wave. Existing active sonar decoys can only simulate the echo of underwater targets in a single state, which can be easily identified by enemy active sonar. Therefore, the multi-state active sonar decoy generation method and system provided by the above-mentioned embodiment of the present invention can be understood as mainly including two parts, wherein the first part is the simulation of the impulse response of the target scattered sound field, that is, the use of accurate physical acoustic methods instead of traditional empirical formulas or bright spot models to calculate the impulse response of the scattered sound field in different directions; the second part is the real-time output of the active sonar decoy forwarding signal, in which echo cancellation technology is introduced to improve the transmission / reception isolation, such as Figure 3 As shown. Among them:

[0104] Part 1: The time-domain plate element method based on physical acoustics is used to calculate the impulse response of the scattered sound field of the predetermined target in different directions.

[0105] Part II: using the enemy's homing torpedo detection signal as the input signal of our sonar decoy, convolving the input signal of our sonar decoy with the impulse response of the scattered sound field in different directions of the predetermined target to obtain a preliminary sonar decoy output signal; simulating the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal, and filtering the sonar decoy output signal from the input signal of our sonar decoy to obtain an ideal input signal; convolving the ideal input signal with the impulse response of the scattered sound field in different directions of the predetermined target to obtain an ideal sonar decoy output signal;

[0106] Through the first part and the second part, the ideal sonar decoy output signal is continuously output to obtain a multi-state active sonar decoy.

[0107] The technical solutions of the multi-state active sonar decoy generation method and system provided by the above-mentioned embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0108] 1. Impulse response of target scattered sound field

[0109] The time-domain plate element method based on the physical acoustic method is used to calculate the impulse response of the scattered sound field of the predetermined target in different directions. The specific method is as follows:

[0110] Use a group of planar plate elements to approximate the target surface, find the impulse response of the scattered sound field of each plate element in the bright area, sum the impulse responses of the scattered sound field of all plate elements in the bright area to get the approximate value of the impulse response of the target scattered sound field, and thus get the echo characteristics of the target. Figure 4 As shown, its far-field scattered sound field is:

[0111]

[0112] Among them, - is the soft sound field boundary; + is the hard sound field boundary; is the incident wave vector, is the outgoing wave vector, is the unit normal vector, k is the acoustic wave number; are all the edge vectors of the plate element in the counterclockwise direction; is the field point; s i is the unit impulse response and t is the time.

[0113] 2. Real-time output of active sonar decoy forwarding signals

[0114] The main function of this part is to filter and output the collected input signal in real time. In addition, the system self-feedback suppression can be turned on during real-time filtering to offset the impact of its own output on the input signal. The system connection is as follows: Figure 5 shown.

[0115] In this section, the generation system can select the following hardware and implement the steps in the corresponding generation method.

[0116] 1. System hardware

[0117] The system selected the NI CompactRIO embedded measurement and control platform. The NI CRIO platform provides the required high performance and high reliability as well as the flexibility of customization for industrial and embedded control applications. NI CompactRIO provides an open embedded architecture, including a built-in embedded real-time controller, a programmable FPGA, and hot-swappable I / O modules. The RIO (FPGA) core of NI CompactRIO has a built-in data transmission mechanism, which is responsible for transmitting data to the embedded processor for real-time analysis, data processing, data logging, or communication with a networked host. Using the basic I / O functions of LabVIEW FPGA, signal acquisition and output can be performed directly at the hardware level, and the real-time controller has high stability.

[0118] The hardware configuration of the system is cRIO 9033+NI 9215+NI 9269, and NI 9215 is installed in slot 1 of the chassis, and NI9269 is installed in slot 2 of the chassis. If the controller or board is changed, the FPGA program needs to be recompiled. Use a 9V-30V DC power supply and connect the PC-cRIO chassis with a network cable or USB. The specific introduction is as follows:

[0119] (a) Controller (cRIO-9033)

[0120] The cRIO-9033 is an embedded controller for advanced control and monitoring applications. The controller features an FPGA and a real-time processor running the NI Linux Real-Time operating system. Embedded user interface capabilities and MiniDisplayPort allow for the addition of a local human-machine interface (HMI) to simplify application development. This rugged fanless controller provides an SDHC slot and a variety of connection ports, including two Gigabit Ethernet, two USB hosts, one USB device, and two serial ports.

[0121] ●1.33GHz dual-core CPU

[0122] 2GB DRAM

[0123] 8GB storage capacity

[0124] Kintex-7 160T FPGA

[0125] Real-time filter and system self-feedback suppression algorithm runs in the FPGA:

[0126] ●Large-capacity programmable logic array, 40MHz reference clock, can meet complex high-speed parallel processing requirements (FPGA processor has inherent parallel processing capabilities, so it is suitable for MIMO multi-channel control algorithms,

[0127] It does not reduce the overall performance and determinism of the application).

[0128] ●Execute timing, triggering and custom control loops with 25ns time resolution to achieve highly deterministic and reliable hardware decision making

[0129] ●FPGA is directly interconnected with I / O modules. It can perform high-speed data acquisition, calculation and control operations. The I / O speed of this system can reach 100KHz

[0130] (b) Acquisition module (NI-9215)

[0131] NI 9215 is a 4-channel C series voltage signal acquisition module with technical specifications shown in Table 1.

[0132] Table 1 Main technical indicators of voltage acquisition card 9215

[0133] Number of differential input channels 4-channel simultaneous input Sampling rate 100kS / s / ch Analog input resolution 16 bits Maximum voltage range ±10V isolation Channel-to-ground isolation

[0134] (c) Output Module (NI-9269)

[0135] NI 9269 is a synchronous update analog output module for CompactRIO. Its technical specifications are shown in Table 2:

[0136] Table 2 Main technical indicators of voltage output card 9269

[0137] Number of differential output channels 4 Synchronous sampling rate per channel 100kS / s / ch Analog input resolution 16 bits Maximum voltage range ±10V isolation Channel-to-channel isolation

[0138] NI CompactRIO is designed for applications in harsh environments and small areas. In many similar embedded applications, size, weight, and I / O channel density are key design requirements. With the top performance and compact size of FPGA devices, NI CompactRIO not only has a lightweight and rugged package with top industrial certifications and ratings, but also provides extraordinary control and acquisition capabilities in harsh industrial environments. NI CompactRIO has a wide operating temperature range of -40°C to 70°C, a 50g shock rating, and international certifications and ratings for various safety, electromagnetic compatibility (EMC), and environmental indicators.

[0139] 2. Working Principle of Technical Solution

[0140] The technical solution in the above example of the present invention mainly consists of two parts: system self-feedback transmission relationship identification and FPGA real-time forwarding. Before real-time forwarding, the self-feedback transmission relationship of the system transmission-reception must be obtained first, that is, the transmission response relationship of our acoustic decoy system itself.

[0141] (a) Self-feedback transmission relationship identification

[0142] The purpose of self-feedback transfer relationship identification is to establish a mathematical model of the system's own output-input using the excitation signal and response signal generated by the system itself. Figure 8 The system identification process using adaptive filter is given. Where x(n) is the excitation signal and d(n) is the response signal of the system we want to identify. y(n) is the output signal of the adaptive filter. e(n) is the error signal representing the difference between d(n) and y(n).

[0143] During each iteration, the adaptive filter adjusts the filter coefficients to minimize the power of e(n). Eventually, the power of e(n) becomes small, and the coefficients of the adaptive filter become close to the coefficients h(n) of the system's self-feedback.

[0144] An adaptive filter is a filter that uses an adaptive algorithm to change the parameters and structure of the filter according to changes in environmental parameters. The coefficients of the adaptive filter are time-varying coefficients updated by the adaptive algorithm. That is, its coefficients automatically and continuously adapt to the given signal according to the iteration of the signal to obtain the expected response. The most important feature of the adaptive filter is that it can work effectively in an unknown environment and can track the time-varying characteristics of the input signal. The structure of a typical adaptive filter is as follows: Figure 6 shown.

[0145] x(n) is the input signal;

[0146] y(n) is the output signal;

[0147] ●d(n) is the desired output signal;

[0148] ●e(n) is the error signal which is the difference between the desired output signal d(n) and the filter output signal y(n).

[0149] In the above-mentioned embodiment of the present invention, an adaptive filter is adopted, such as Figure 7 As shown. Figure 7 In the adaptive algorithm, the coefficients of the linear filter are iteratively adjusted to minimize e(n). The input and output signals x(n), d(n), y(n), and e(n) can be selected in different ways for different applications.

[0150] The difference between traditional digital filters and adaptive filters:

[0151] ● Traditional digital filters have only one input signal x(n) and one output signal y(n). Adaptive filters require an additional input signal d(n) and return an additional output signal e(n).

[0152] ●The filter coefficients of traditional digital filters do not change over time, while the coefficients of adaptive filters change over time. Therefore, adaptive filters have self-learning capabilities that traditional digital filters do not have.

[0153] ●Compared with traditional digital filters, adaptive filters have the following advantages:

[0154] ● Adaptive filters can accomplish some signal processing tasks that traditional digital filters cannot. For example, you can use adaptive filters to eliminate noise that traditional digital filters cannot eliminate, such as noise whose power spectrum changes over time.

[0155] ● Adaptive filters can accomplish some real-time or online modeling tasks that traditional digital filters cannot accomplish. For example, you can use adaptive filters to identify unknown systems in online mode. Generally, adaptive filters are useful when performing real-time or online signal processing applications.

[0156] Each adaptive filter consists of two parts: a linear filter and an adaptive algorithm. You can use linear filters with different filter types, such as finite impulse response (FIR) and infinite impulse response (IIR) filters. The schematic diagram of the FIR adaptive filter is shown in Figure 8 As shown. Among them, x(n) is the input signal of the linear filter at time point n, y(n) is the corresponding output signal, d(n) is another input signal of the adaptive filter, e(n) is the error signal representing the difference between d(n) and y(n), z -1 is the unit delay, w i (n) is the filter coefficient, and i is an integer with a value in the range [0, n–1].

[0157] Different adaptive filter algorithms can be applied to the FIR adaptive filter according to the situation. The adaptive algorithm adjusts the filter coefficients with the goal of minimizing the evaluation function J(n):

[0158] J(n)=E[E 2 (n)]

[0159] Among them, E[E 2 (n)] is E 2 (n) expectation, E 2 (n) is the square of the error signal at time point n.

[0160] According to how the adaptive filter algorithm calculates the evaluation function J(n), these algorithms are generally divided into the following two groups: I. Least Mean Square (LMS) Algorithm

[0161] The calculation formula of LMS algorithm J(n): J(n) = E[E 2 (n)].

[0162] This equation shows that the LMS algorithm uses E at time point n. 2 The instantaneous value of (n) is taken as E[E 2 (n)] is estimated. II. Recursive Least Squares (RLS) Algorithm

[0163] The calculation formula of RLS algorithm J(n) is:

[0164] N is the filter length, and γ is the forgetting (decaying) factor. This algorithm not only calculates E 2 (n) instantaneous value, and at the same time, E is accumulated2 (n-1),E 2 (n-2),…,E 2 (n-N+1). The forgetting factor ranges from (0,1]. When the forgetting factor is less than 1, this factor specifies that the algorithm places greater weight on current values ​​and less weight on past values. The result of the RLS algorithm estimation E[E 2 (n)] is more accurate than the result of LMS algorithm.

[0165] Compared with the RLS algorithm, the LMS algorithm requires less computational resources and memory. However, the eigenvalue expansion of the correlation matrix of the input signal may affect the convergence speed of the resulting adaptive filter. The convergence speed of the RLS algorithm is faster than that of the LMS algorithm. However, the RLS algorithm requires more computational resources than the LMS algorithm.

[0166] In summary, this system uses LMS adaptive filter to identify self-feedback transfer relations.

[0167] (b) FPGA real-time forwarding

[0168] FPGA uses the concept of logic cell array LCA (Logic Cell Array), which includes three parts: configurable logic block CLB (Configurable Logic Block), input and output block IOB (Input Output Block) and internal connection (Interconnect). Fig. 9 As shown. Field Programmable Gate Array (FPGA) is a programmable device. Compared with traditional logic circuits and gate arrays (such as PAL, GAL and CPLD devices), FPGA has a different structure. FPGA uses a small lookup table (16×1 RAM) to implement combinational logic. Each lookup table is connected to the input of a D flip-flop, which then drives other logic circuits or drives I / O, thus forming a basic logic unit module that can implement both combinational logic functions and sequential logic functions. These modules are connected to each other or to I / O modules using metal wires. The logic of FPGA is implemented by loading programming data into the internal static storage unit. The value stored in the memory unit determines the logic function of the logic unit and the connection between modules or between modules and I / O, and ultimately determines the functions that FPGA can implement. FPGA allows unlimited programming.

[0169] The main real-time forwarding program of this system runs on FPGA, which mainly realizes three functions: self-feedback transmission path filtering, self-feedback echo signal elimination and FIR real-time filtering. Fig.10 shown.

[0170] like Fig.10 As shown in the figure, the active emission signal of the enemy homing torpedo received by us is used as the input signal. After the active emission signal passes through the system self-feedback transmission path h(n), it will be mixed with the enemy homing torpedo target detection signal emitted by our sonar decoy. At this time, the FIR adaptive filter is required to simulate the echo signal as much as possible and eliminate it from the aliased signal to obtain the ideal input signal, that is, the enemy homing torpedo active emission signal without interference.

[0171] The technical solution of the above embodiment of the present invention is further described in detail below with reference to the accompanying drawings and a specific application example.

[0172] In this specific application example, the experimental operation process mainly consists of two parts: system self-feedback transmission relationship identification and FPGA real-time filtering and forwarding.

[0173] Implementation example:

[0174] 1. Before real-time forwarding, we must first obtain the ideal bait input signal through the self-feedback transmission relationship.

[0175] The response signal d(n) of our sonar decoy is mixed with our sonar decoy echo signal y(n). This problem is handled through the self-feedback transmission relationship (that is, the transmission response relationship of our acoustic decoy system itself), and our sonar decoy input signal x(n) is restored to the maximum extent, as shown in Figure 11 to Figure 13 shown.

[0176] 2. After the self-feedback relationship identification is completed, the real-time filtering experiment can begin.

[0177] The restored sonar decoy input signal x(n) is convolved with the impulse response of the scattered sound field of the predetermined target in different directions to obtain the output signal y(n) of the sonar decoy. Fig.14 As shown; the output signal of our sonar decoy is as follows Figure 15 to Figure 17 shown.

[0178] The multi-state active sonar decoy generation method and system provided in the above-mentioned embodiment of the present invention provide a false target for the opponent by generating the echo signal of the opponent's detection signal in real time, which plays the role of covering our ship to buy time for escape, thereby avoiding greater losses with the minimum cost; based on the multi-state scattering characteristics of underwater targets, it can simulate the target scattered sound waves under the conditions of sound wave incidence in different azimuths to improve the deception effect; a more accurate physical acoustic method is used to replace the traditional empirical formula or bright spot model to calculate the impulse response of scattered sound fields in different azimuths, the sound wave incidence direction is determined according to the multi-channel phased array technology, the FPGA technology is used to generate the forwarding signal in real time, and the echo cancellation technology is introduced to improve the transmission / reception isolation.

[0179] All matters not covered in the above embodiments of the present invention are well known in the art.

[0180] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A multi-state active sonar decoy generation method, characterized in that: include: The time-domain plate element method based on physical acoustics is used to calculate the impulse response of the scattered acoustic field of the predetermined target in different directions. The detection signal of the enemy's homing torpedo is used as the input signal of our sonar decoy, and the input signal of our sonar decoy is convolved with the impulse response of the scattered sound field of the predetermined target in different directions to obtain a preliminary sonar decoy output signal; Simulating the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal, and filtering the preliminary sonar decoy output signal from the input signal of the sonar decoy to obtain an ideal input signal; Convolving the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal; Repeat the above steps to continuously output the ideal sonar decoy output signal to obtain a multi-state active sonar decoy.

2. The multi-state active sonar decoy generation method according to claim 1, characterized in that: The method of using a time-domain plate element method based on physical acoustics to calculate the impulse response of scattered sound fields of predetermined targets in different directions includes: A group of planar plate elements are used to approximate the target surface, and the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave is obtained. The scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave is superimposed to obtain the approximate value of the scattered sound field impulse response of the predetermined target.

3. The multi-state active sonar decoy generation method according to claim 2, characterized in that: For the mth plate element, its scattered sound field impulse response p s,m (t) is: Among them, - is the soft sound field boundary; + is the hard sound field boundary; is the incident wave vector, is the outgoing wave vector, is the unit normal vector, k is the acoustic wave number; are all the edge vectors of the plate element in the counterclockwise direction; is the field point; s i is the unit impulse response and t is the time.

4. The multi-state active sonar decoy generation method according to claim 1, characterized in that: The preliminary sonar decoy output signal is simulated by using an adaptive filter to generate a simulated sonar decoy output signal.

5. The multi-state active sonar decoy generation method according to claim 4, characterized in that: The adaptive filter uses the least mean square algorithm to adjust the filter coefficients with the goal of minimizing the evaluation function J(n), then: J(n)=E[E 2 (n)] Where n is the time point, E[·] is the mathematical expectation, E[E 2 (n)] is E 2 (n) expectation, E 2 (n) is the square of the error signal at time point n.

6. The multi-state active sonar decoy generation method according to any one of claims 1 to 5, characterized in that: The method also includes forwarding the obtained multi-state active sonar bait in real time.

7. A multi-state active sonar decoy generation system, characterized in that: include: Target scattered sound field impulse response module, which uses the time domain plate element method based on physical acoustics to calculate the scattered sound field impulse response of the predetermined target in different directions; A preliminary sonar decoy signal generation module, which uses the opponent's homing torpedo detection signal as the input signal of our sonar decoy, convolves the input signal of our sonar decoy with the impulse response of the scattered sound field in different directions of the predetermined target, and obtains a preliminary sonar decoy output signal; an echo isolation module, which simulates the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal, and filters the preliminary sonar decoy output signal from the input signal of the sonar decoy to obtain an ideal input signal; The multi-state active sonar decoy generation module convolves the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal and a multi-state active sonar decoy.

8. The multi-state active sonar decoy generating system according to claim 7, characterized in that: The target scattered sound field impulse response module uses a group of planar plate elements to approximate the target surface, obtains the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave, and superimposes the scattered sound field impulse response of each plate element in the target area illuminated by the incident sound wave to obtain an approximate value of the scattered sound field impulse response of the predetermined target, thereby simulating the echo characteristics of the predetermined target.

9. The multi-state active sonar decoy generating system according to claim 7, characterized in that: Also includes: -The preliminary sonar decoy signal generation module comprises: A multi-channel A / D unit, which uses an acquisition module of the NI CompactRIO embedded measurement and control platform to convert the opponent's homing torpedo detection signal from an analog signal to a digital signal; A pre-formed multi-beam unit, the unit is used to determine the direction of the incoming wave of the opponent's homing torpedo detection signal; A preliminary sonar decoy generation unit, which convolves the input signal of the sonar decoy with the impulse response of the scattered sound field of the predetermined target in different directions to obtain a preliminary sonar decoy output signal; -The echo isolation module comprises: a signal simulation unit, the unit using an adaptive filter to simulate the preliminary sonar decoy output signal to generate a simulated sonar decoy output signal; An echo cancellation unit, which filters out the sonar decoy output signal from the input signal of the sonar decoy to obtain an ideal input signal; -The multi-situation active sonar decoy generation module includes: An ideal sonar decoy generation unit, which convolves the ideal input signal with the impulse response of the scattered sound field of the predetermined target in different directions to obtain an ideal sonar decoy output signal; The D / A conversion unit uses the output module of the NI CompactRIO embedded measurement and control platform to convert the ideal sonar decoy output signal from a digital signal to an analog signal, thereby obtaining a multi-state active sonar decoy.

10. The multi-state active sonar decoy generating system according to claim 9, characterized in that: The preliminary sonar decoy generating unit, the echo cancellation unit and the ideal sonar decoy generating unit adopt a common FPGA programmer.

Images