CN113866771B - Underwater target detection method - Google Patents
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- CN113866771B CN113866771B CN202111395611.7A CN202111395611A CN113866771B CN 113866771 B CN113866771 B CN 113866771B CN 202111395611 A CN202111395611 A CN 202111395611A CN 113866771 B CN113866771 B CN 113866771B
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- 238000007781 pre-processing Methods 0.000 claims abstract description 9
- 238000004364 calculation method Methods 0.000 claims abstract description 8
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 4
- 238000003491 array Methods 0.000 claims abstract description 3
- 238000002592 echocardiography Methods 0.000 claims description 3
- 238000012937 correction Methods 0.000 claims description 2
- 238000005259 measurement Methods 0.000 description 8
- 238000005562 fading Methods 0.000 description 4
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- 238000003672 processing method Methods 0.000 description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
- G01S15/04—Systems determining presence of a target
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
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- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
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- Acoustics & Sound (AREA)
- Computer Networks & Wireless Communication (AREA)
- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
Abstract
The invention discloses a method for detecting an underwater target, belongs to the field of ocean detection methods, and solves the technical problem that the method in the prior art is low in detection and calculation efficiency of the target. The buoy is provided with a vertical linear array and a horizontal expansion array and is provided with a compass auxiliary system; the horizontal expansion arrays are arranged in a bi-orthogonal and symmetrical array; the vertical line array transmits a double-pulse detection signal for measuring state parameters of the underwater target by the horizontal expansion array, wherein the state parameters are at least the distance, the azimuth and the speed of the target; the double pulse detection signals received by the horizontal expansion array are subjected to signal preprocessing, and the preprocessing signals are subjected to wave beam formation and matched filtering so as to generate a two-dimensional spectrogram of the azimuth and the distance of the underwater target; performing constant false alarm processing on the two-dimensional spectrogram to determine an active detection spectrogram; and the active detection spectrogram determines the current target state parameters of the detection target through a coordinate method. The invention is used for submitting the precision of ocean target detection.
Description
Technical Field
The invention belongs to the field of ocean detection methods, and particularly relates to a method for detecting an underwater target.
Background
The aviation sonar buoy has good platform noise performance, can detect radiation noise and active detection echo of an underwater target, realizes passive detection and active detection, obtains azimuth, distance and speed information of the target, and has wide application prospects in anti-diving, underwater target detection and ocean monitoring.
Currently, aviation sonobuoys mainly adopt the form of transmitting a single detection pulse, and commonly used pulse forms include CW pulse, HFM pulse, LFM pulse, cw+lfm (linear frequency modulation signal, insensitive signal) combined pulse, wherein:
The CW signal is a Doppler sensitive signal for target velocity measurement, but because the underwater acoustic channel is slowly time-varying and has severe frequency selective fading, the CW pulse has a failure condition in practical use;
The HFM pulse and the LFM pulse are used for suppressing reverberation and simultaneously carrying out high-precision ranging on the target, but the HFM pulse and the LFM pulse belong to Doppler insensitive signals, so that speed information of the target cannot be provided;
In order to make up for the defect that the Doppler insensitive signal cannot measure the target speed, a learner in the active detection field puts forward a CW+LFM combined pulse form, but the situation that the CW signal is influenced by channel fading is also faced.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a method for detecting an underwater target, which solves the technical problem that the method in the prior art has low detection and calculation efficiency on the target. The technical scheme of the scheme has a plurality of technical advantages, and the following description is provided:
the method is suitable for active detection of the buoy on the underwater moving object, and comprises the following steps:
S101: the buoy is provided with a vertical linear array and a horizontal expansion array, wherein: the vertical line array is used for detecting the emission of signals, the horizontal expansion array is used for receiving target echoes, and a compass auxiliary system is arranged;
S102: the horizontal expansion arrays are arranged in a bi-orthogonal and symmetrical array; the vertical line array transmits a double-pulse detection signal for measuring state parameters of the underwater target by the horizontal expansion array, wherein the state parameters are at least the distance, the azimuth and the speed of the target;
S103: the double pulse detection signals received by the horizontal expansion array are subjected to signal preprocessing, (analog amplification and data acquisition) and the preprocessing signals are subjected to wave beam formation and matched filtering so as to generate a two-dimensional spectrogram of the azimuth and the distance of the underwater target; two-dimensional map of non-velocity and distance
S104: and performing constant false alarm processing on the two-dimensional spectrogram to determine an active detection spectrogram so as to improve the echo signal-to-noise ratio of the target object, reduce false alarm interference and background noise and improve the detection probability of the target. Compared with the traditional CFAR method-constant false alarm processing method, the method reduces the hardware operand and saves the cost. The traditional CFAR method carries out noise calculation on the whole area of the two-dimensional spectrogram, and the method only carries out two-dimensional constant false alarm treatments on the distance dimension and the azimuth dimension.
S105: and the active detection spectrogram is used for detecting the current target state parameters of the target through a coordinate method.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
The invention adopts a double LFM pulse form, and the measurement of the target radial velocity is completed by measuring the time delay interval of two pulses. The method overcomes the defect that the target speed cannot be provided by adopting a single HFM pulse and an LFM pulse, and avoids the problem of new ratio loss caused by channel fading of CW pulses.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from them without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of a buoy active signal processing flow;
FIG. 2 is a schematic illustration of a horizontally extending array of buoys;
FIG. 3 is a schematic diagram of a dual LFM probe pulse;
Fig. 4 is a schematic diagram of an improved constant false alarm processing method.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It is noted that various aspects of the embodiments are described below within the scope of the following claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the present disclosure, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspect, and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented and/or a method practiced using any number of the aspects set forth herein. In addition, such apparatus may be implemented and/or such methods practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.
It should also be noted that the illustrations provided in the following embodiments merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.
In addition, in the following description, specific details are provided in order to provide a thorough understanding of the examples. However, it will be understood by those skilled in the art that aspects may be practiced without these specific details. In order to better understand the aspects of the present invention, the present invention will be described in further detail with reference to the accompanying drawings and detailed description. The terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
The method for detecting the underwater target shown in fig. 1 is suitable for actively detecting the underwater moving target object by the buoy, and comprises the following steps:
S101: the buoy is provided with a vertical linear array and a horizontal expansion array, wherein: the vertical line array is used for detecting the emission of signals, the horizontal expansion array is used for receiving target echoes, and a compass auxiliary system is arranged, the products and the system adopt the prior art products, and the model of the compass auxiliary system is TCM5 electronic compass of PNI company in U.S.;
s102: the horizontal expansion array is arranged in a bi-orthogonal and symmetrical array, the vertical line array transmits a double pulse detection signal, and the double pulse detection signal is used for measuring underwater target state parameters by the horizontal expansion array, wherein the state parameters at least comprise the distance, the azimuth and the speed of a target object, and specifically:
as shown in fig. 2, the horizontal extension array is arranged in a bi-orthogonal and symmetrical array, preferably, a m-shaped structure is arranged, for example, the horizontal extension array includes 8 extension arms, an included angle between any adjacent extension arms is 45 degrees, each extension arm has 4 receiving hydrophone elements, and total 32 receiving hydrophones are used for receiving target echo signals, the reference numerals in fig. 1 are defined by serial numbers of the receiving hydrophones, and signals received by the elements are respectively xi (t), i=1, 2, …,32, and the purpose of the bi-orthogonal and symmetrical array is that: the horizontal expansion array adopts the double orthogonal symmetrical array, so that the azimuth measurement ambiguity of the underwater target can be effectively avoided, the azimuth measurement precision and the distance measurement precision of the underwater target are improved, and the stability and the reliability of the measurement result are ensured.
The vertical line array transmits double pulse detection signals in the form of transmitting linear frequency modulation signals with consistent two parameters, the pulse width is T, the bandwidth is B, a protection interval T is arranged between the two linear frequency modulation signals, the selection of T is larger than the channel expansion length of a target and a buoy, the initial value is generally, the default value is 0.5s, preferably, the double pulse detection signals are in the form of double LFM pulses, the measurement of the radial speed of the target is completed by measuring the time delay interval of the two pulses, the double LFM pulse forms are applied to the ocean detection field technology, and the situation that single pulse signals are easy to fail is overcome, or HFM pulses and LFM pulses belong to Doppler insensitive signals and cannot provide speed information of the target is avoided, and the detection is aimed at adopting sensitive signals to detect the target in ocean.
S103: the double pulse detection signals received by the horizontal extension array are subjected to signal preprocessing, such as analog amplification and data acquisition. Carrying out wave beam forming and matched filtering on the preprocessed signals to generate a two-dimensional spectrogram of the azimuth and the distance of the underwater target object, wherein the two-dimensional spectrogram is a non-speed and distance two-dimensional image, and specifically:
The buoy collects the horizontal extension array primitive signals in real time; preprocessing echo signals received by the horizontal expansion array and carrying out beam forming processing; and performing matched filtering processing on the data of the beam forming processing.
The processing method of the matched filtering comprises the following steps:
FD_Sig_Bi＝FFT[Bi(t)]
FD_Sig_Ref＝FFT[Sig_Ref]
Wherein FFT [ ] represents the fourier transform; IFFT [ ] represents an inverse fourier transform; /(I) Representing a dot product of data. Td_sig_xcorr_bi represents the matched filtering result of the ith beam.
S104: and the two-dimensional spectrogram is subjected to constant false alarm processing to determine an active detection spectrogram so as to improve the echo signal-to-noise ratio of the target object, reduce false alarm interference and background noise and improve the detection probability of the target. The traditional CFAR method carries out noise calculation on the whole area of the two-dimensional spectrogram, and the method only carries out two-dimensional constant false alarm treatments on the distance dimension and the azimuth dimension, and is specific:
Performing distance dimension one-dimensional constant false alarm processing on an underwater target object in a two-dimensional spectrogram, performing one-dimensional constant false alarm processing on azimuth dimension after processing, and obtaining a two-dimensional spectrogram after constant false alarm processing, wherein the purpose is to reduce the number of interference points of the target object in the two-dimensional spectrogram, and the method is specifically implemented as follows:
as shown in fig. 4, a protection window P1 and a reference window R1 are set in a distance dimension, and a protection window P2 and a reference window R2 are set in an azimuth dimension, wherein the size of P1 is 3 times the inverse of the bandwidth of the chirp signal, and the size of R1 is 2 times the inverse of the bandwidth of the chirp signal;
calculating the speed of an underwater target, and calculating the time T' of two peaks according to the matched filtering peak value result at the position with the maximum target strength and azimuth, wherein the calculation formula of the target speed is approximately as follows:
Wherein c is the sound velocity value of the buoy at the horizontal expansion array;
furthermore, the true position of the ground coordinate of the underwater target is required to be calculated, the target position theta' calculated by the horizontal expansion array is utilized for correction, and the following conditions are met:
θ out =θ' - ε, where: epsilon is the horizontal course angle of the horizontal expansion array recorded by the roc-still auxiliary system, the value is the north-east included angle, and theta out is the final corrected target azimuth.
S105: the active detection spectrogram is used for detecting the current target state parameters of the targets through a coordinate method.
And calculating the distance of the underwater target object by using a conventional method in the prior art to obtain a two-dimensional spectrogram subjected to constant false alarm treatment, for example, calculating target state parameters including speed, azimuth, distance parameters and the like by using a coordinate method.
The invention adopts a double LFM pulse form, and the measurement of the target radial velocity is completed by measuring the time delay interval of two pulses. The method overcomes the defect that the target speed cannot be provided by adopting a single HFM pulse and an LFM pulse, and avoids the problem of new ratio loss caused by channel fading of CW pulses. Because the method only carries out the matched filtering processing on the data after the wave beam formation once, compared with the traditional CW+LFM combined pulse method, the calculation efficiency of the whole algorithm is improved. In addition, under the condition that the buoy active detection signal is determined, the traditional two-dimensional constant false alarm detection mostly adopts a 'field character grid' form, and the calculated amount is large. Compared with the conventional two-dimensional constant false alarm detection, the improved constant false alarm technology is adopted, only two dimensions are considered, and the calculation efficiency is improved.
The product provided by the invention is described in detail above. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the core concepts of the invention. It should be noted that it will be apparent to those skilled in the art that several improvements and modifications can be made to the invention without departing from the inventive concept, and these improvements and modifications fall within the scope of the appended claims.
Claims (7)
1. A method of underwater target detection adapted for active detection of moving objects underwater by a buoy, comprising:
S101: the buoy is provided with a vertical linear array and a horizontal expansion array, wherein: the vertical line array is used for detecting the emission of signals, the horizontal expansion array is used for receiving target echoes, and a compass auxiliary system is arranged;
s102: the horizontal expansion arrays are arranged in a bi-orthogonal and symmetrical array; the vertical line array transmits a double-pulse detection signal for measuring the state parameters of the underwater target by the horizontal expansion array, wherein the state parameters at least comprise the distance, the azimuth and the speed of the target;
S103: the double pulse detection signals received by the horizontal expansion array are subjected to signal preprocessing, and the preprocessing signals are subjected to wave beam formation and matched filtering so as to generate a two-dimensional spectrogram of the azimuth and the distance of the underwater target;
S104: performing constant false alarm processing on the two-dimensional spectrogram to determine an active detection spectrogram;
s105: and the active detection spectrogram determines the current target state parameters of the detection target through a coordinate method.
2. The method according to claim 1, characterized by S103: the method for preprocessing the double pulse detection signals received by the horizontal extension array comprises the following steps:
the buoy collects the primitive signals of the horizontal expansion array in real time, and pre-processes the echo signals received by the horizontal expansion array and performs beam forming processing;
and performing matched filtering processing on the data of the beam forming processing.
3. The method according to claim 1, wherein the method in S104 comprises:
performing one-dimensional constant false alarm processing on the distance dimension of the underwater target object in the two-dimensional spectrogram;
And carrying out one-dimensional constant false alarm processing on the azimuth dimension after processing to determine a two-dimensional spectrogram after the constant false alarm processing.
4. A method according to claim 3, wherein the vertical line array transmits the double pulse detection signal in S102 in the form of transmitting a chirp signal with consistent two parameters, the pulse width of the chirp signal is T, the bandwidth B, and a guard interval T is set between the two chirp signals, and the guard interval T should be selected to be greater than the channel extension length of the target and buoy.
5. A method according to claim 3, wherein the method for performing the one-dimensional constant false alarm processing of the distance dimension of the underwater target in the two-dimensional spectrogram, and performing the one-dimensional constant false alarm processing of the azimuth dimension after the processing comprises the following steps:
the protection window P1 and the reference window R1 are set in the distance dimension, and the protection window P2 and the reference window R2 are set in the azimuth dimension, wherein:
the P1 size is 3 times of the inverse of the bandwidth of the linear frequency modulation signal, and the R1 size is 2 times of the inverse of the bandwidth of the linear frequency modulation signal.
6. The method of claim 5, wherein S105: the method for determining the current target state parameters of the detection target through the active detection spectrogram by a coordinate method comprises the following steps:
calculating the speed of an underwater target, and calculating the time T' of two peaks according to the matched filtering peak value result at the position with the maximum target strength and azimuth, wherein the calculation formula of the target speed meets the following conditions:
where c is the sound velocity value at the buoy level expansion array.
7. The method according to claim 6, wherein: the method also comprises a method for calculating the true position of the geodetic coordinates of the underwater target, wherein the target position theta' calculated by the horizontal expansion array is corrected and meets the requirement of correction: θ out =θ' - ε, where: epsilon is the horizontal course angle of the horizontal expansion array recorded by the compass auxiliary system, and theta out is the final corrected target azimuth.
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