29 results about "Target strength" patented technology

The invention provides an underwater weak target integrated detection and positioning method using a deep sea distributed MIMO sonar, the distributed MIMO sonar is used to suppress channel fluctuation and target intensity fluctuation, and at the same time, the signal waveform of each detection node and the two-way propagation characteristic of a seabed ejection channel are combined, so that the underwater weak target integrated detection and positioning method based on the deep sea distributed MIMO sonar can be realized. A joint matching filter for simultaneously realizing signal waveform matching and channel structure matching is designed, a multipath cumulative gain is obtained on the basis of obtaining a traditional space-time processing gain, the signal-to-mix ratio and the signal-to-noise ratio are synchronously improved, and finally, a peak value fused and output by each node of the distributed MIMO sonar is used as a test statistic, so that the test accuracy is improved. And meanwhile, the peak value position is used as a target positioning result, so that integrated detection and positioning of the weak target in the deep-sea shadow area are realized. Compared with a traditional target detection method using multipath arrival feature matching, the method provided by the invention makes full use of the seabed ejection channel gain, and has better target detection and positioning effects under the conditions of low signal-to-mix ratio and low signal-to-noise ratio.

The invention belongs to the technical field of underwater acoustic measurement, and relates to an indirect-coherent measurement method for the forward acoustic scattering target intensity of an underwater object. The method comprises the following steps: respectively carrying out background field measurement when an underwater object does not exist and target field measurement when the underwater object exists, and storing and recording receiving signals of an observation channel and a reference channel; based on the measurement signals of the background field and the target field, through time delay estimation and signal coherence subtraction processing, forward sound scattering signals of the underwater object are extracted; and calculating the forward sound scattering target intensity of the underwater object by using the extracted forward sound scattering signal based on the sound propagation loss estimation and the signal power. According to the method, after the forward sound scattering wave signal of the object is extracted, the definition formula of the target intensity in the sonar equation is directly used for measuring and calculating the forward sound scattering target intensity, the number of calculation links is small, and the calculation efficiency is high.

The application relates to a weak underwater target azimuth detection pre-tracking method based on belief propagation, which comprises the following steps: converting a weak target tracking problem into solving a joint posterior probability density function (pdf) based on a Bayesian rule; factorizing the joint posterior pdf, constructing a corresponding factor graph through a graph model; solving the transmitted information in the factor graph by using a belief propagation (BP) algorithm, and converting multiple integrals into ordinary integrals by using a Goodman variable substitution principle; constructing a likelihood function by using a complex Wishart distribution to describe the relationship between original sonar data and target states, and simplifying the remaining pdf by using a Gaussian distribution to obtain a confidence approximation of a target state edge posterior pdf; and calculating the number of weak targets and corresponding states by using a minimum mean square error (MMSE) estimator. The application can simultaneously track multiple weak targets without a complex clustering algorithm, has fewer preset parameters, and can accurately and efficiently track target state information including an azimuth, an azimuth angular velocity and target intensity.

The invention relates to a land slope sea area weak signal passive detection performance limit analysis method based on space-frequency focusing processing, and the method comprises the following steps: 1, dividing a receiving array into two sub-arrays, and obtaining sub-array receiving signals; step 2, constructing steering vectors of the two sub-arrays; step 3, calculating beam output of the two sub-arrays, and constructing a frequency domain vector; and step 4, constructing a frequency domain steering vector based on the arrival time delays of the four main sound rays arriving at the sound shadow area. The method is suitable for underwater acoustic transponder target intensity measurement lake / sea tests, the far-field condition is easily met, the measurement method is convenient and efficient, and the method conforms to the actual use scene.

The application belongs to the technical field of target detection, and relates to a small target real-time detection method based on a sonar image, which comprises the following steps: 1) performing enhancement and segmentation on the sonar image to obtain target intensity, target position and target diffusion range; 2) restoring the target shape of the target in the sonar image based on the target position; and 3) based on the target shape and the target intensity, target position and target diffusion range, adopting target multi-frame detection to realize real-time detection of small targets. The method does not depend on large parallel computing devices, is easy to deploy, has small computing amount and fast running speed, can meet the run-time detection of the device on a CPU, has few preset parameters and clear meanings, can be adjusted in time according to the use effect, and is convenient to use. The method adopts multi-frame detection, retains historical target records, can retain target positions when the image is subjected to temporary interference, and has strong anti-interference capability.

In order to solve the problem that the detection performance of an active sonar is seriously reduced due to channel fluctuation, target intensity fluctuation and strong reverberation backgrounds, the invention provides a single-frame and multi-frame integrated reverberation suppression and target enhancement method for a distributed MIMO sonar, which comprises the following steps: firstly, carrying out space-time processing on all receiving ends of the distributed MIMO sonar to obtain transmitting-receiving channel output; carrying out incoherent delay summation on all transmitting-receiving channel outputs to obtain single-frame detection output; then, single-frame detection output serves as input of multi-frame processing, and a multi-frame Gaussian mixture model is used for restraining reverberation background and enhancing moving target bright spots; and finally, processing the output of the multi-frame Gaussian mixture model by using the multi-frame high-order nonlinear cumulant. Compared with a traditional method, the method has the advantages that under the conditions of channel fluctuation, target intensity fluctuation and strong reverberation background, the strong reverberation background can be effectively inhibited, and more stable and higher-quality target bright spot detection output is obtained.

Disclosed in the present invention is a method for predicting characteristics of multiple acoustic scattering of an underwater vehicle, comprising a preprocessing step: constructing an underwater vehicle geometric model for subsequent acoustic simulation and calculation, generating a underwater vehicle mesh model: on the basis of the geometric model, generating meshes to divide the model of the underwater vehicle into smaller units so as to facilitate numerical calculation, and establishing an underwater vehicle multi-layer grouped surface element model: dividing the surface of the underwater vehicle into a plurality of surface elements so as to simulate a complex structure of the underwater vehicle; a solving step comprising: using an iterative algorithm for accelerating a physical acoustic simulation process, and calculating scattering sound fields of different orders so as to obtain an accurate simulation result for multiple scattering phenomena of the underwater vehicle; and a post-processing step comprising: analyzing acoustic characteristics, comprising multiple acoustic scattering time domain echoes and target strength of the underwater vehicle, of the underwater vehicle in an underwater environment.

The invention provides a wave glider high-frequency sound scattering characteristic forecasting method which comprises the following steps: dividing a wave glider into an overwater floating body ship, a connecting rod and an underwater tractor, obtaining three-dimensional geometric models of the overwater floating body ship, the connecting rod and the underwater tractor, and carrying out structure simplification; respectively establishing a grid model; the grid model is imported into Matlab, the scattering sound pressure of the grid model is obtained through a plate meta-algorithm, and then the target intensity is obtained; extracting target intensity distribution under different conditions to obtain sound scattering characteristics of the target intensity distribution; a simplified geometric model is constructed based on the actual shape of the wave glider, a high-quality triangular mesh is generated through surface discretization, and then target strength distribution under different conditions is obtained by adopting a plate element method.

The present invention relates to a corner reflector, a reflector and an intensity assessment method with an acoustic metasurface, wherein the metasurface is a narrow well acoustic metasurface with a specific gradient, and the corner reflector is a combination of multiple "concave" surfaces. The target intensity assessment method of this article, based on the existing plate element method, combines ray tracing theory to establish a plate element acoustic target intensity calculation model based on ray tracing theory, and develops a fast calculation method for "concave" surface targets of underwater corner reflectors based on improved plate elements. This method can calculate the scattered sound field of underwater corner reflectors, study their acoustic scattering characteristics, and carry out structural design technology of corner reflector groups, echo field reconstruction technology based on spatial strong scattering target characteristics, passive interference and simulation body confrontation effect assessment technology research based on corner reflectors, solve the basic problems of passive interference and simulation body design and application, and realize typical passive interference and model design.

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.

The invention relates to a digital simulation model method for a typical target, and the method is based on the construction of a mine detection environment in underwater acoustic engineering, and comprises the following steps: collecting data, building a mathematical simulation model of the typical target, building a target image and posture, and carrying out the application. And applying the constructed typical target digital simulation model to a sonar simulation model. According to the digital simulation model method, a digital simulation model of a typical target is constructed, a sinking mine, an anchoring mine and other small targets are integrated, shapes and materials of the targets are collected, and the digital simulation model of the typical target is constructed according to different laying postures; a mathematical simulation model for a typical mine target is established according to a column method, and simulation analysis is performed on a waveform structure, target strength and the like.

The invention belongs to the field of underwater acoustic engineering, and particularly relates to a target strength adjustable underwater target reflector and a construction method thereof.The target strength adjustable underwater target reflector comprises a pressure-resistant shell, a target adjusting layer, a lifting interface, a lifting interface and a counterweight cabin, the pressure-resistant shell is of a spherical shell structure, and the target adjusting layer is arranged on the outer surface of the pressure-resistant shell; a balance weight cabin is arranged in the center of the pressure-resistant shell, and an enclosure bulkhead of the pressure-resistant shell is arranged on the outer side of the balance weight cabin. According to the underwater target reflector acoustic target intensity adjusting device, the adjustment of the underwater target reflector acoustic target intensity is realized by replacing the acoustic material of the target adjusting layer or compounding the acoustic material with different acoustic characteristics in different directions or adjusting the water / gas proportion of the inner cavity; a large number of target reflectors do not need to be manufactured, the target strength of the target reflectors can be flexibly adjusted according to requirements to meet test simulation requirements, the test cost is reduced, and the test equipment storage space is reduced.

The invention discloses a fish body target strength measuring system and method, and relates to the field of aquaculture intelligent monitoring. The system comprises a transducer, a signal control system, a data processing unit and a calibration module, the transducer transmits sound wave signals to a fish body at different rotation angles and different sound wave incidence angles, the signal control system processes echo signals of the fish body at different rotation angles and different sound wave incidence angles, and the data processing unit sequentially performs pulse compression, main lobe detection and resampling processing on the echo signals processed by the signal control system. The target intensity values of different parts of the fish body under different sound wave incidence angles are calculated according to the echo signals after resampling and system response, and the system response is determined based on the calibration module. According to the method and the device, partitioned measurement of the target strength of the fish body can be accurately and efficiently realized in real time.

The present invention discloses an intelligent underwater acoustic signal processing system and method based on multi-sensor data fusion, belonging to the field of underwater signal processing. Acoustic signals, linear acceleration, angular velocity and other information of underwater targets are collected by multiple sensors and continuous analog signals are output, and then transmitted to a signal conditioning module to dynamically adjust the gain according to the target strength, and the amplified differential signal is output to an analog-to-digital conversion module. High-precision digitization is performed through a 24-bit Δ-Σ ADC and a digital signal is output to a main control unit, which performs multi-sensor data fusion and target azimuth calculation; finally, the main control unit uploads the underwater acoustic signal and device attitude information data to a host computer through an RS485 bus for human-computer interaction. Based on multi-sensor data fusion, this solution can achieve high-precision target detection and positioning in a dynamic underwater environment and has wide popularization and application value.

The application discloses a confidence degree calculation method of a water acoustic target intensity simulation model based on orthogonal design, and comprises the following steps: S1, determining the calculation result and the uncertainty of the water acoustic target intensity simulation model; S2, determining the test result and the uncertainty of the water acoustic target intensity test; S3, determining the upper limit and the lower limit of the simulation model result and the upper limit and the lower limit of the test result, drawing a water acoustic target intensity simulation model confidence degree evaluation diagram, and calculating the confidence degree of the water acoustic target intensity simulation model. In view of the actual test difficulties of the water acoustic material component target intensity evaluation, such as far-field test limitation, low signal-to-noise ratio and accurate positioning difficulty, the simulation technology is used to make up for the deficiency of the actual test, the confidence degree of the simulation result is mainly considered, the calculation method improves the reliability of the simulation result, and belongs to an innovative method applied to the field of underwater electric acoustic parameter simulation and test.

The invention relates to an underwater component target strength measurement method and device based on a near-field scanning mode, and the method comprises the following steps: 1, placing an underwater component in a far field of a transducer, and guaranteeing that no other sound sources influence a sound field at the measurement device and near the underwater component; 2, dispersing the measurement surface of the underwater component into grid units, and determining the size and number of the grid units according to the measurement frequency wavelength and the irregularity degree of the shape of the underwater component; according to the invention, the problem that the far-field condition cannot be met in the target intensity measurement can be solved, the space required by the measurement is greatly reduced, and a new direction is provided for the target intensity measurement.

The invention relates to the technical field of underwater acoustic detection, in particular to an equivalent target strength evaluation method for a target wake flow field induced sound field, and the method comprises the steps: building an underwater acoustic environment, respectively calculating receiving end sound fields before and after target intrusion in the underwater acoustic environment, and calculating receiving end sound field abnormal components based on the receiving end sound fields before and after target intrusion; the sound field abnormal component of the receiving end is pushed back to the position 1 m away from the internal wave equivalent sound center, and therefore the target wake flow field induction sound field is converted into an equivalent scattering sound field; based on a path superposition principle, calculating an incident sound field at an internal wave equivalent sound center; based on the equivalent scattering sound field and the incident sound field, constructing the equivalent target intensity of the target wake flow field induction sound field; and embedding the equivalent target strength of the target wake flow field induced sound field into the sonar equation to carry out detection efficiency evaluation. According to the method, statistical measurement of the acoustic effect of the target wake flow field is realized, and the method has very high engineering availability.

This invention provides an underwater target echo detection method and system based on amplitude fluctuation characteristics, comprising: Step S1: establishing a target detection model according to preset rules; Step S2: acquiring an echo image, performing sliding window processing on the waveform data in the echo image, and establishing a probability density function model; Step S3: calculating the likelihood ratio function of the waveform data based on the target detection model and the probability density function model; Step S4: calculating a threshold based on the probability density function model and the likelihood ratio function; Step S5: updating the echo image using the threshold as a criterion to obtain the target detection result. This invention provides a dynamic threshold detection method that adapts to target intensity fluctuations and background changes through constant false alarm rate detection and the Neyman-Pearson criterion, detecting echo images and forming new echo images.

The invention discloses an underwater weak target intelligent detection method based on time-frequency feature fusion. The method comprises the following steps: firstly, obtaining underwater acoustic signal data, then obtaining modal decomposition signals of signal time domain information and frequency domain information corresponding to original sonar signal data through variational modal decomposition, and obtaining a time-frequency domain modal feature data set after combination; and then, a deep neural network based on a cross attention mechanism is constructed, the deep neural network comprises a convolution module, a bidirectional gating circulation unit module, a cross attention mechanism module, a full connection layer and a classifier which are connected in sequence, and after the deep neural network is trained, an underwater weak target detection network is obtained. Finally, the high-accuracy, high-efficiency and high-generalization detection effect on the input signal is realized. The method can effectively detect single-frequency signals and broadband signals with weak target intensity in the ocean, and has high detection probability and good generalization performance.

The application relates to the technical field of underwater acoustic detection, in particular to a method for evaluating equivalent target strength of a target wake-induced sound field, which comprises the following steps: establishing an underwater acoustic environment; calculating a receiving-end sound field before and after target intrusion in the underwater acoustic environment; calculating a receiving-end sound field anomaly component based on the receiving-end sound field before and after target intrusion; back-propagating the receiving-end sound field anomaly component to a position 1 m away from an internal wave equivalent sound center, so as to convert the target wake-induced sound field into an equivalent scattering sound field; calculating an incident sound field at the internal wave equivalent sound center based on a path superposition principle; constructing equivalent target strength of the target wake-induced sound field based on the equivalent scattering sound field and the incident sound field; and embedding the equivalent target strength of the target wake-induced sound field into a sonar equation to carry out detection efficiency evaluation. The method realizes statistical measurement of the acoustic effect of the target wake field and has strong engineering usability.

The invention relates to the technical field of jellyfish detection, and discloses a device and method for underwater observation of target intensities of different attitude angles of a large jellyfish, the device comprises a net cage, a constraint assembly and an attitude adjusting assembly are arranged in the net cage, the constraint assembly comprises a support and two connecting lines, the two connecting lines penetrate through umbrella parts of the jellyfish, and the support is connected with the attitude adjusting assembly. And the end parts of the two connecting wires are fixedly connected with the bracket. According to the jellyfish posture adjusting device, the restraining assembly composed of the steel pipe and the connecting line is arranged, the jellyfish is fixed underwater through the restraining assembly to pull the first pulling rope or the second pulling rope, the angle of the restraining assembly is adjusted through the posture adjusting assembly, and therefore the purpose that the jellyfish posture angle is more convenient to adjust is achieved; conditions are provided for the underwater sonar to observe the target intensities of different attitude angles of the jellyfish, and the relative positions of the constraint assemblies are relatively fixed, so that the target intensities of the different attitude angles of the jellyfish can be measured repeatedly, and the measurement result is more accurate and reliable.

The application discloses a large-scale flat plate type underwater component target strength measurement method and device, which comprises a high-frequency transducer for acoustic ranging and lateral measurement; a signal generator for generating specific acoustic signals; a low-frequency power amplification module for amplifying low-frequency electric signals; a high-frequency power amplification module for amplifying radio frequency signals; a low-frequency transducer for generating acoustic signals for testing; a hydrophone for measuring acoustic signals; and a lifting and rotating mechanism for lifting and rotating the underwater component. The application breaks the original underwater target strength measurement and underwater acoustic signal processing thought, can greatly reduce the lower limit of the free field test frequency of the large-scale flat plate type underwater component, and facilitates the measurement of the target strength of the large-scale flat plate type underwater component.

The invention relates to an underwater weak target azimuth track-before-detect method based on belief propagation. The method comprises the following steps: converting a weak target tracking problem into solving of a joint posterior probability density function (pdf) based on a Bayesian rule; factorization is carried out on the joint posteriori pdf, and a corresponding factor graph is constructed through a graph model; solving information transmitted in the factor graph by using a belief propagation (BP) algorithm, and converting multiple integrals into common integrals by using a Goodman variable substitution principle; constructing a likelihood function through complex Wishart distribution to describe the relationship between the original sonar data and the target state, and simplifying the residual pdf by using Gaussian distribution to obtain confidence approximation of the target state edge posteriori pdf; and calculating by using a minimum mean square error (MMSE) estimator to obtain the number of weak targets and corresponding states. According to the method, multiple weak targets can be tracked at the same time without a complex clustering algorithm, the number of preset parameters is small, and target state information including the orientation, the azimuth angle speed and the target intensity can be tracked accurately and efficiently.

The application discloses a test device for testing fish target strength by using a suspension control method, which comprises a net cage, a winding wheel, an angle adjusting ruler, a transducer, a fish body suspension system and an underwater video monitoring system and an underwater camera arranged in the net cage from top to bottom in sequence, two equal-length first fish lines output by the winding wheel are connected with the upper and lower ends of the stainless steel rods of the fish body suspension system through the threading holes in the angle adjusting ruler; the lifting system is composed of the winding wheel and the two equal-length first fish lines, the first fish lines are connected with the winding wheel and the fish body suspension system respectively, the winding wheel is fixed to the top end of a fourth steel pipe, the fourth steel pipe is connected with a first steel pipe through a fourth fastener, and the first steel pipe is connected with the net cage through a first fastener. The test device is simple in structure and reasonable in design, can eliminate the influence of the fish body posture and the inclination angle on the fish target strength test, and can accurately measure the target strength of the fish body under different sound wave incident angles.

The present application belongs to the technical field of underwater acoustic channel and physical field, and relates to a numerical hybrid calculation method of forward scattering acoustic field of a regular shape object underwater. The method comprises: obtaining an initial projection profile of a three-dimensional geometric model of the regular shape object under a specified projection plane and an incident direction; dividing discrete points of the initial projection profile into upper boundary points and lower boundary points; interpolating and completing the upper boundary points and the lower boundary points, so that the upper boundary points and the lower boundary points have the same number and share the same horizontal coordinates; discretizing the completed projection profile by using trapezoidal plane elements; calculating a forward scattering far field pattern function based on the discretization result; and calculating a forward scattering target strength of the object. The method provided by the present application can cover the shape range of the scattering object applicable to the analytical method, and does not need to calculate complex series expressions composed of special functions such as Bessel functions and spherical harmonic waves, thereby obviously improving the calculation efficiency.

The application relates to a multi-base station detection efficiency evaluation method based on marine environment data, the algorithm calculates propagation loss based on actual marine environment data and sound propagation characteristics, the error of the propagation loss calculated by an empirical formula method is reduced, and the influence of specific sea area conditions on the detection efficiency can be reflected. The algorithm adopts a Monte Carlo simulation and a cumulative detection probability mode, simulates the changes of target intensity and detection probability caused by changes in target motion posture, and increases the reliability of the multi-base station detection efficiency evaluation result.

This invention provides a method for analyzing and synthesizing the acoustic scattering echo characteristics of underwater target substructures, comprising: Step S1: Dividing the underwater model into substructures according to preset rules, and forming substructure mesh data in surface element and point element format; Step S2: Calculating the target intensity of the unobstructed substructures using the plate element method based on the mesh data and the sound source orientation; Step S3: Calculating the angular range of obstruction of the substructures based on the mesh data and the sound source orientation; Step S4: Calculating the synthesized target intensity of the substructures based on the angular range of obstruction; Step S5: Selecting the target intensity and synthesized target intensity corresponding to the substructures according to preset rules to form the overall target intensity. This invention discusses the calculation method of the target intensity of each substructure of a rigid target during synthesis using the synthesis theory of target intensity and the plate element theory, thereby revealing the contribution of each substructure to the overall structural target intensity.

The present application belongs to the technical field of underwater acoustic measurement, and relates to an indirect-coherent measurement method of forward acoustic scattering target strength of an underwater object. The method comprises: respectively performing background field measurement when the underwater object does not exist and target field measurement when the underwater object exists, and storing the received signals of an observation channel and a reference channel; based on the measurement signals of the background field and the target field, the forward acoustic scattering signal of the underwater object is extracted through time delay estimation and signal coherent subtraction processing; and based on sound propagation loss estimation and signal power, the forward acoustic scattering target strength of the underwater object is calculated by using the extracted forward acoustic scattering signal. After the forward acoustic scattering wave signal of the object is extracted, the definition formula of the target strength in the sonar equation is directly used to calculate the forward acoustic scattering target strength, so that the calculation links are less and the calculation efficiency is high.

The application provides an underwater weak target integrated detection and positioning method using a deep sea distributed MIMO sonar, utilizes the distributed MIMO sonar to suppress channel fluctuation and target intensity fluctuation, simultaneously, combines the signal waveform of each detection node and the double-path propagation characteristics of the sea bottom bounce channel, designs a joint matching filter which simultaneously realizes signal waveform matching and channel structure matching, obtains a multi-path cumulative gain on the basis of traditional space-time processing gain, synchronously improves the signal-to-clutter ratio and the signal-to-noise ratio, finally, takes the peak value of the fusion output of each node of the distributed MIMO sonar as a test statistic, simultaneously takes the peak position as a target positioning result, so that the integrated detection and positioning of the weak target in the deep sea shadow area are realized. Compared with the traditional target detection method using the multi-path arrival characteristics matching, the method fully utilizes the sea bottom bounce channel gain, and has better target detection and positioning effect under the condition of low signal-to-clutter ratio and low signal-to-noise ratio.