16 results about "Target strength" patented technology

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 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 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.

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 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.

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.