JP2010190682A - Method and apparatus for exploring and classifying object in the bottom of water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for exploring and classifying objects in the bottom of water and capable of easily selecting a frequency having a high level of scattering waves and suitable for classification and accurately classifying objects in the bottom of water. <P>SOLUTION: A transmitter 3 transmits sound waves having a frequency being changed within a prescribed band during a round trip, and a receiver 4 receives their scattered waves to create a distribution of frequency scattering levels having the azimuth angle to an object in the bottom of water as a vertical axis and the frequency as a horizontal axis. On the basis of a created distribution of frequency scattering levels, a frequency having a high intensity of scattering waves and suitable for classification is selected, and a direction level pattern of scattering waves at a selected frequency is extracted and verified with a database in which direction level patterns of the scattering waves are accumulated to classify the object in the bottom of water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an underfloor object exploration classification method and apparatus used for classifying the shape, size, and the like of an object buried under a water bottom.

  Conventionally, as a means for measuring the size and shape of an object existing in water or at the bottom of the water, exploration using an acoustic image has been widely used.

  In sound image exploration, a high-frequency sound wave (for example, several tens to several hundreds of kHz) is converged into a highly directional beam and transmitted from a transmitter (sound source), and the reflected wave is transmitted to the transmitter. By receiving at a receiver at the same position, the distance to the reflection point is measured based on the time information from the transmission of the sound wave to the reception of the reflected wave, and a lot of position information of this reflection point is accumulated. By doing so, an acoustic image is created, and an object existing in the water or at the bottom of the water is searched, and information about the size and shape of the object is obtained visually.

  However, since high-frequency sound waves are difficult to penetrate below the bottom of the water, exploration of objects (for example, artificial objects) buried under the bottom of the water, that is, sand, mud, gravel, etc. It was difficult to do.

  In view of this, a method has been proposed in which a low-frequency object that penetrates under the water bottom is used to search for an object under the water bottom buried in the water bottom. However, since the low frequency has a long wavelength, the resolution is lowered, and there is a problem that it is difficult to visually grasp the shape of the object to be searched like an acoustic image using the high frequency.

  Therefore, as a method for enabling discovery of an underwater resource having a desired shape regardless of the shape or the state of being buried in the bottom of the water, the present applicant has a low frequency of 20 kHz or less toward the underwater exploration direction. Of sound waves, received scattered waves from unknown underwater resources at multiple locations around the exploration direction, and arrival times of scattered waves received by multi-static measurements at these multiple locations, Based on the level (intensity) and scattering pattern, an underwater resource exploration method for estimating the location of an unknown underwater resource causing the scattering, and the shape and posture of the underwater resource has been proposed (for example, Patent Documents) 1).

  Further, the present applicant uses an underwater vehicle equipped with a transmitter and a receiver, and makes the underwater vehicle travel around the underwater object to be explored, while the underwater vehicle is underwater. A sound wave is transmitted to an object, a scattered wave from an object under the water is received by a receiver, and a direction level pattern (scattering pattern) of the scattered wave is generated based on the level of the scattered wave received by the receiver. Proposing a submarine object exploration classification method that classifies the shape, size, etc. of a submarine object by creating and collating the direction level pattern of the scattered wave with a previously stored database (for example, patents) Reference 2).

JP 2004-184268 A JP 2008-76294 A

  By the way, when the underwater object to be searched is a hollow elastic object made of, for example, FRP or metal, the underwater object has a natural vibration corresponding to its shape, size, material, plate thickness, and the like. Therefore, it has a characteristic that the level (intensity) of the scattered wave is higher than the sound wave of a specific frequency. That is, the level of the scattered wave to be received increases or decreases depending on the frequency of the sound wave to be transmitted.

  For this reason, when measurement is performed using a frequency at which the level of the scattered wave is low, no clear feature appears in the direction level pattern of the generated scattered wave, and there is a possibility that the object under the water bottom cannot be classified. Therefore, in order to classify the underwater object to be searched with high accuracy, it is desirable to use a frequency at which the level of the scattered wave is high in accordance with the natural vibration of the underwater object.

  However, in the above-described conventional method, the frequency of the sound wave transmitted from the transmitter is determined empirically. Therefore, for submerged objects where the level of the scattered wave is low with respect to the empirically determined frequency, the direction level pattern of the scattered wave with clear characteristics cannot be obtained, and the classification cannot be performed with high accuracy. There was a problem.

  In order to solve this problem, prior to actual measurement, it may be possible to change the frequency in advance and perform preliminary measurement to determine the frequency at which the level of the scattered wave becomes high. However, since the frequency at which the level of the scattered wave increases for each underwater object changes, it is necessary to perform pre-measurement every time for each underwater object to be explored, and there is a problem that it takes time and effort.

  Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide a search method and apparatus for submarine object search and classification that can easily select a frequency with a high scattered wave level and suitable for classification, and that can classify submerged objects with high accuracy. It is to provide.

  The present invention was devised to achieve the above-described object, and includes a transmitter and a receiver mounted on an underwater vehicle, and circulates around an underwater object to be explored. While navigating, the sound wave is transmitted from the transmitter to the underwater object, the scattered wave from the underwater object is received by the receiver, and the scattered wave received by the receiver is received. In the submerged object exploration classification method, a circulatory level level pattern of a scattered wave is created based on intensity, and the direction level pattern of the scattered wave is collated with a previously stored database. While transmitting a sound wave having a frequency changed in a predetermined band from the transmitter, the scattered wave is received by the receiver, and the azimuth angle with respect to the object under the water is a vertical axis, and the frequency is Create a distribution of frequency scattering levels on the horizontal axis and create Based on the distribution of several scattering levels, the frequency of the scattered wave is high and suitable for classification, and the direction level pattern of the scattered wave at the selected frequency is extracted, and the direction level pattern of the scattered wave is extracted from the database. This is an under-floor object exploration classification method for classifying the under-floor object by collating.

  A wideband pulse wave whose frequency is continuously changed in a predetermined band is transmitted from the transmitter, the scattered wave is received by the receiver, and the scattered wave received by the receiver The frequency scattering level distribution may be created based on wave intensity.

  You may obtain | require the intensity | strength for every frequency of a scattered wave by frequency-analyzing the scattered wave received with the said receiver.

  In addition to measuring scattered waves at every predetermined azimuth angle interval, gradually moving the azimuth angle for measuring scattered waves for each lap of the underwater vehicle to measure scattered waves at all azimuth angles. You may do it.

  The frequency scattering level distribution may be created by rotating the underwater vehicle a plurality of times and transmitting by gradually changing the frequency of the sound wave transmitted from the transmitter.

  The sound wave transmitted from the transmitter may be transmitted by changing in a band of several kHz to 20 kHz.

  The present invention also provides an underwater vehicle that orbits around an underwater object to be explored, a transmitter that is mounted on the underwater vehicle and transmits sound waves to the underwater object, and the underwater vehicle. A receiver mounted on the traveling body for receiving the scattered wave from the object under the water bottom, and creating a directional level pattern of the scattered wave based on the intensity of the scattered wave received by the receiver, the scattered wave In the submarine object exploration classification apparatus, which comprises analyzing means for classifying the shape and size of the underwater object by collating the direction level pattern of Frequency modulation means for transmitting a sound wave having a frequency changed in a predetermined band from the vessel, and the analysis means is based on the intensity of the scattered wave received by the wave receiver, and the azimuth angle with respect to the object under the seabed The vertical axis and the horizontal axis the frequency scatter level. Based on the distribution of the generated scattered frequency level, the frequency selection unit that selects a frequency with high scattered wave intensity and a suitable classification, and the direction level pattern of the scattered wave at the selected frequency A submarine object exploration classification apparatus including a classification determination unit that extracts and classifies the submarine object by collating the direction level pattern of the scattered wave with the database.

  According to the present invention, it is possible to easily select a frequency that has a high scattered wave level and is suitable for classification, and it is possible to classify objects under the seabed with high accuracy.

It is a general | schematic cut side view of the search classification apparatus of the underwater object of this invention. It is a schematic top view which shows the state which is searching the underwater object by the search classification apparatus of the underwater object of FIG. It is a schematic rear view which shows the state which is exploring the underwater object by the underwater object exploration classification apparatus. FIG. 4A is a diagram showing an example of a broadband pulse wave transmitted from the transmitter and the level for each frequency, and FIG. 4B is a diagram of the broadband pulse wave of FIG. It is a figure which shows an example of the scattered wave received by a receiver, and the level for every frequency when transmitting. FIG. 5A is an example of the distribution of the frequency scattering level created in the present invention, and FIG. 5B is the direction level pattern of the scattered wave at the frequency indicated by the broken line in FIG.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  The method for searching for an underwater object according to the present invention is a method for searching for an object buried under the waterbed.

  First, the underfloor object exploration classification apparatus used for the underfloor object exploration classification method according to the present embodiment will be described.

  FIG. 1 is a schematic cut-away side view of the underfloor object exploration classification apparatus according to the present embodiment.

  As shown in FIG. 1, an underfloor object exploration classification apparatus 1 includes an underwater vehicle 2 as a traveling body, a low-frequency sound source 3 as a transmitter that transmits sound waves to the underwater object, A receiver 4 that receives a scattered wave from a bottom object, an amplifier 5 that amplifies a signal received by the receiver 4, and a signal processor as an analysis unit that analyzes the received signal amplified by the amplifier 5 6 is mounted. The underwater vehicle 2 has a propulsion mechanism, a steering mechanism, and a hovering mechanism (not shown), and controls these so as to control the underwater vehicle 2 to navigate according to a predetermined route (not shown). ), And a navigation device (not shown) that can identify the positional relationship between the own position in water and the underwater object to be searched.

  As shown in FIG. 2, the underwater vehicle 2 searches the underwater object 21 while navigating around the underwater object to be searched. Although FIG. 2 shows the case where the underwater vehicle 2 circulates around the underwater object 21 in a substantially circular shape, the present invention is not limited to this, and it circulates in an ellipse, a square, a rectangle, or a polygon. May be.

  The low frequency sound source 3 is configured to transmit a low frequency sound wave having a frequency changed in a predetermined band as a directional beam 7. In FIG. 1, the angle θ indicates the directivity width of the directional beam 7. Further, as shown in FIG. 3, the directional beam 7 has a central axis C inclined with respect to the water bottom when viewed from the rear in the navigation direction.

  The low frequency sound source 3 is provided with frequency modulation means (not shown) for modulating the frequency of the sound wave transmitted from the low frequency sound source 3, and the frequency modulation means allows the frequency from the low frequency sound source 3 to be a predetermined band. It is configured to transmit a changed low-frequency sound wave.

  In the present embodiment, a broadband pulse wave is transmitted from the low-frequency sound source 3. Here, a broadband pulse wave is a pulsed sound wave whose frequency is continuously changed in a predetermined frequency band, and continuously changes from a low frequency to a high frequency or from a high frequency to a low frequency. This is a pulsed sound wave (see FIG. 5A). The frequency band of the sound wave to be transmitted may be a band of 20 kHz or less, and in this embodiment, the frequency band is a few kHz to 20 kHz.

  A plurality of receivers 4 are arranged side by side in the navigation direction to form a receiving array. By performing synthetic aperture processing on the received signals from the plurality of receivers 4 according to a known algorithm, scattered waves from a narrow range in the navigation direction can be detected.

  The signal processor 6 performs frequency analysis, for example, FFT (Fast Fourier Transformation) analysis of the scattered wave received by the receiver 4 to obtain the intensity for each frequency of the scattered wave, and based on the analysis result. In addition, the scattered wave analysis unit that creates a distribution of the frequency scattering level with the azimuth angle with respect to the object under the water as the vertical axis and the frequency as the horizontal axis, and the intensity of the scattered wave based on the created distribution of the frequency scattering level The frequency selection unit for selecting a frequency suitable for the target and the direction level pattern of the scattered wave at the selected frequency are extracted, and the direction level pattern of the scattered wave is collated with a previously stored database, thereby classifying the underwater object 21 And a classification determination unit that performs the above.

  Next, a method for classifying underwater objects according to this embodiment will be described.

  First, the underwater vehicle 2 is thrown into the water, and while the underwater vehicle 2 travels straight forward, the irradiation and measurement of sound waves are intermittently performed to search the underwater object 21 in a wide water area (wide area). Roller exploration mode). At this time, for example, if a U-turn is made after moving forward by an appropriate distance, a wide water area can be explored throughout.

  When the underwater object 21 is detected in the wide area roller exploration mode, the underwater vehicle 2 is made to circulate around the underwater object 21 to be explored, and the area around the place where the underwater object 21 is expected is concentrated. Exploring (Narrow-area exploration mode).

  In the narrow-area intensive search mode, a broadband pulse wave is transmitted from the low-frequency sound source 3 while the underwater vehicle 2 travels around the underwater object 21 to be searched, and the scattered wave from the underwater object 21 is transmitted. Is received by the receiver 4.

  When the underwater object 21 is a hollow elastic object made of FRP, metal, or the like, the level of the scattered wave increases at a specific frequency depending on the shape, size, material, plate thickness, etc. of the underwater object 21. Or lower. Therefore, the receiver 4 receives scattered waves having different levels for each frequency.

  For example, as shown in FIG. 4 (a), when a broadband pulse wave having a constant level at each frequency is transmitted from the low-frequency sound source 3, the receiver 4 is as shown in FIG. 4 (b). Scattered waves having different levels for each frequency are received.

  The received signal received by the receiver 4 is amplified by the amplifier 5 and input to the signal processor 6. The scattered wave analysis unit of the signal processor 6 performs FFT analysis on the received signal to obtain the intensity for each frequency of the scattered wave, and stores this in the memory in association with the azimuth angle with respect to the underwater object 21 that has been measured. Keep it.

  Similarly, a wide-band pulse wave is transmitted from the low-frequency sound source 3 at predetermined time intervals while the underwater vehicle 2 is traveling around, and scattered waves are measured at predetermined azimuth angle intervals. If sufficient data cannot be obtained in one lap, the underwater vehicle 2 circulates multiple times, and the azimuth angle (a wideband pulse wave is measured for each lap of the underwater vehicle 2). It is preferable to measure the scattered wave at all azimuth angles by gradually moving the transmission position).

  After measurement of scattered waves at all azimuth angles (or after sufficient data has been obtained), the scattered wave analysis unit of the signal processor 6 analyzes the results stored in the memory (scattering for each frequency with respect to the azimuth angle). Based on the wave level, a distribution of frequency scattering levels is created. An example of the created distribution of frequency scattering levels is shown in FIG.

  As shown in FIG. 5A, the frequency scattering level distribution is a stepwise display of scattered wave levels in color, with the azimuth angle as the vertical axis and the frequency as the horizontal axis. The frequency selection unit of the signal processor 6 selects a frequency having a high scattered wave intensity and suitable for classification based on the created distribution of frequency scattering levels.

  The method for selecting the frequency is not particularly limited. For example, a frequency including the peak value of the scattered wave level may be selected, and the value obtained by integrating the scattered wave level at each azimuth angle is the most. You may make it select the frequency which becomes large. In addition, considering the effects of noise such as background noise and reverberation from the bottom of the water, the data with extremely high levels can be removed, and the frequency with a high scattered wave level can be selected. Good. As an example, in the frequency scattering level distribution of FIG. 5A, the frequency indicated by the broken line is selected.

  The category determination unit of the signal processor 6 extracts the direction level pattern of the scattered wave at the frequency selected by the frequency selection unit. As an example, FIG. 5B shows a directional level pattern of scattered waves at the frequency indicated by the broken line in the frequency scattering level distribution of FIG. Data necessary for creating the scattered wave direction level pattern (data of the scattered wave level with respect to the azimuth angle at the selected frequency) is already measured and stored in the memory when creating the distribution of the frequency scattered level. Therefore, it is not necessary to perform measurement again.

  The classification determination unit of the signal processor 6 classifies the underwater object 21 by comparing the extracted scattered wave direction level pattern with a previously stored database. The database used for classification is a database of scattered wave direction level patterns obtained in advance by measurement or numerical calculation for various objects whose shape, size, material, plate thickness, etc. are known.

  As described above, in the underfloor object exploration classification method according to the present embodiment, a sound wave having a frequency changed in a predetermined band is transmitted from the low-frequency sound source 3 during the lap of the underwater vehicle 21, The receiver 4 receives the scattered wave, creates a distribution of frequency scattering levels with the azimuth angle with respect to the underwater object 21 as the vertical axis and the frequency as the horizontal axis, and based on the generated frequency scattering level distribution. In addition to selecting a frequency with high intensity of the scattered wave and suitable for the classification, the direction level pattern of the scattered wave at the selected frequency is extracted, and the direction level pattern of the scattered wave is collated with a pre-stored database. Classification of objects under the bottom.

  As a result, it is possible to easily select a frequency that has a high scattered wave level and is suitable for classification without taking time and effort such as prior measurement. Further, since the classification is performed using the direction level pattern of the scattered wave at the frequency suitable for the classification, the classification performance can be improved.

  Furthermore, when creating the frequency scatter level distribution, the data necessary to create the scattered wave direction level pattern has already been measured and stored in the memory, so there is no need to perform another measurement, saving time and time. It is possible to create a direction level pattern to be used without class.

  In the present embodiment, a broadband pulse wave whose frequency is continuously changed in a predetermined band is transmitted from the low-frequency sound source 3 and the scattered wave is received by a receiver, and the frequency scattering is performed. Creating a level distribution. Thus, once the scattered wave is measured, the level of the scattered wave for each frequency at the azimuth angle can be obtained at a time, and the distribution of the frequency scattered level can be created in a short time. It becomes possible. Therefore, it is possible to classify the underwater objects without taking time.

  In the above embodiment, FFT (Fast Fourier Transformation) analysis is used as the frequency analysis method. However, as other frequency analysis methods, a method such as a wavelet using a wavelet function as a basis function may be used. .

  Moreover, in the said embodiment, although the broadband pulse wave which changed the frequency continuously in the predetermined band was transmitted from the low frequency sound source 3, it is not limited to this, but the underwater vehicle 2 The frequency scattering level distribution may be created by rotating around a plurality of times and gradually changing the frequency of the sound wave transmitted from the transmitter. In this case, compared with the case of using a wideband pulse wave, the time for creating the distribution of the frequency scattering level becomes longer, but the work of determining the frequency by prior measurement as in the past can be omitted, and the determination of the frequency Since the underwater vehicle 2 can be made to perform a series of operations from classification to classification, there is an advantage that it does not take time.

  In the above embodiment, the signal processor 6 mounted on the underwater vehicle 2 analyzes the scattered wave received by the receiver 4, creates a distribution of frequency scattering levels, and determines the frequency suitable for the classification. The directional level pattern of the scattered wave at that frequency is extracted and the steps of the classification of the underwater object 21 are performed. However, the present invention is not limited to this, and the scattered wave data received by the receiver 4 It may be sent to an analysis device provided on the mother ship or the like of the underwater vehicle 2 or an analysis device provided on the ground, and the above-described steps may be performed by the analysis device on the ship or the ground.

  Furthermore, in the said embodiment, although the underwater vehicle 2 was used as a navigation body, you may make it use the ship etc. which are the navigation bodies on the water. However, it can be said that it is preferable to use the underwater vehicle 2 from the viewpoint that it is easy to specify the position with respect to the underwater object 21.

  It goes without saying that various changes can be made without departing from the scope of the present invention.

1 Exploration and classification equipment for underwater objects 2 Underwater vehicle 3 Low-frequency sound source (transmitter)
4 receiver 5 amplifier 6 signal processor (analysis means)
7 Directional beam 21 Underwater object

Claims (7)

A transmitter and receiver are mounted on the underwater vehicle, and sound waves are transmitted from the transmitter to the underwater object while the underwater vehicle is orbiting around the underwater object to be explored. And receiving a scattered wave from the object under the seabed with the receiver, creating a direction level pattern of the scattered wave based on the intensity of the scattered wave received by the receiver, and the scattered wave In the exploration classification method of the underwater object, which classifies the underwater object by comparing the direction level pattern of
During the lap, the transmitter transmits a sound wave whose frequency is changed in a predetermined band, and receives the scattered wave by the receiver. Create a frequency scatter level distribution with the horizontal axis as the horizontal axis, and select a frequency that is suitable for each category with high scattered wave intensity based on the created frequency scatter level distribution, and the direction level of the scattered wave at the selected frequency. A submarine object exploration classification method, wherein a pattern is extracted and the direction level pattern of the scattered wave is collated with the database to classify the submarine object.   A wideband pulse wave whose frequency is continuously changed in a predetermined band is transmitted from the transmitter, the scattered wave is received by the receiver, and the scattered wave received by the receiver The method according to claim 1, wherein the distribution of the frequency scattering level is created based on wave intensity.   The method according to claim 2, wherein the intensity for each frequency of the scattered wave is obtained by frequency analysis of the scattered wave received by the receiver.   In addition to measuring scattered waves at every predetermined azimuth angle interval, gradually moving the azimuth angle for measuring scattered waves for each lap of the underwater vehicle to measure scattered waves at all azimuth angles. The method for exploring and classifying underwater objects according to claim 2 or 3 as described above.   The underwater bottom according to claim 1, wherein the frequency scattering level distribution is created by rotating the underwater vehicle a plurality of times and gradually changing the frequency of a sound wave transmitted from the transmitter. Object exploration classification method.   The method for exploring and classifying underwater objects according to any one of claims 1 to 5, wherein a sound wave transmitted from the transmitter is transmitted by changing in a band of several kHz to 20 kHz. An underwater vehicle that circulates around an underwater object to be explored, a transmitter that is mounted on the underwater vehicle and that transmits sound waves to the underwater object, and is mounted on the underwater vehicle and Based on the receiver that receives the scattered wave from the object under the seabed, and the intensity of the scattered wave received by the receiver, the direction level pattern of the scattered wave is created in advance. In the underfloor object exploration classification apparatus comprising an analysis means for performing classification such as the shape and size of the underwater object by collating with the accumulated database,
A frequency modulation means for transmitting a sound wave having a frequency changed in a predetermined band from the transmitter during the circulation, the analysis means based on the intensity of the scattered wave received by the receiver, Based on the scattered wave analysis unit that creates a distribution of frequency scattering levels with the azimuth angle with respect to the object under the water as the vertical axis and the frequency as the horizontal axis, and the created distribution of frequency scattering levels, the scattered wave intensity is high and suitable for classification A classification determination that classifies the underwater objects by extracting a direction level pattern of the scattered wave at the selected frequency and collating the direction level pattern of the scattered wave with the database. And an apparatus for exploring and classifying underwater objects.

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