JPH04501316A - sonar exploration system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] sonar exploration system The present invention relates to a sonar exploration system for exploring the ocean and the like.

Unprecedented progress has been made in recent years in the exploitation of the marine environment for commercial, social and scientific purposes. product This, along with the trend towards larger ships carrying cargo, has increased the demand for accurate offshore exploration. Ta.

Commercial development purposes require precise measurements of the seabed, and large ships require accurate depth measurements when approaching a port. create a need for Objects located on the ocean floor are located where they are to be detected. requires the use of high-resolution seafloor profilers.

Sonar exploration systems for mapping the ocean floor or objects therein are known.

These systems are basically of three types: echo acoustic sonar, and side It consists of scanning sonar and fan scanning sonar.

Echo acoustic sonar systems use active elements that beam pulses of sound vertically downward. A single transmit/receive converter is used. Sending pulses and receiving signals reflected from the ocean floor The measurement of the time delay between the two points indicates the depth of the ocean at that point.

The Zyde scanning sonar system has a pair of sonar on each side of the exploration vessel to obtain the seafloor profile. Use a converter. Each transducer transmits short acoustic pulses laterally and downwardly. these sona - Each converter consists of many active elements arranged in a linear array as shown in Figure 1(a). Consists of children lO. Each return acoustic signal caused by backscatter of the transmitted pulse is The element produces a signal output. Adding signals from each element to provide output signal S This results in an overall increased sensitivity - this is wider at the depression angle (Figure 2), Narrow in azimuth (Fig. 1). This is called the beam pattern of transducer 12. Therefore The transducer only receives data from a narrow azimuth angle that is perpendicular to the plane of the transducer .

Therefore, each transmission transmits a line of seafloor data that is perpendicular to the transducer plane of the side-scan system. It will collect up to a maximum range depending on frequency and power.

Therefore, ships follow known trajectories to scan large areas of the ocean floor. The return signal is used to form the shape of the seafloor based on the amplitude of the return.

The transducer should not be subjected to sudden changes to avoid problems due to sudden changes in temperature or salinity. The fish is placed underwater or under a layer of water.

Fan-scan sonar systems use a similar transducer arrangement as side-scan systems. death However, by introducing the time delay of the signals from the individual elements of the transducer, The narrow beam pattern (in azimuthal angle) can result in an angle that the narrow beam pattern makes in the plane of the transducer. This is a beam pattern This is known as "orienting" the direction. 10 elements per sonar transmission Their output signals are each subjected to a time delay before being summed, resulting in a predetermined angle to the transducer plane. In the next transmission, different time delays result in data from different directions. produces a line of data. As shown in Figure 3, different times for Kl to KN in each direction A sector of seafloor data is formed using the interdelays KI to KN.

The main drawback of the last two systems is that the ocean depth at a known location from the received data is It is not possible to perform precise measurements of Get accurate depth at a fixed point Therefore, echo acoustic techniques must be used.

However, this method is very time consuming and expensive. The reason is that the predetermined area A In order to explore the Must be oriented in a grid pattern.

The inventor devised a sonar exploration system that provides both depth and position information. Ta. This system can be used in side scan mode or fan scan mode.

According to the invention, an array of sensor elements whose outputs are connected to multiple banks of delay elements a receiver transducer consisting of a receiver transducer, and each bank representing a received sonar beam from each direction. The outputs of the delay elements in each bank are configured to simultaneously provide multiple corresponding output signals from each bank. and means for summing.

Desirably, a parallel processing system is provided that processes multiple output signals simultaneously.

Preferably, this parallel processing system is manufactured and sold by Inmos, Bristol, UK. It consists of one or more parallel processing elements, such as commercially available transputers.

For side-scan or fan-scan sonar sounding systems, a second transducer is connected to the first transducer. located at a predetermined distance on the transducer and whose output is connected to a second plurality of banks of delay elements. a second array of sensor elements from each direction from each bank of the second plurality; a corresponding second plurality representing the sonar beams received by the second receiving transducer; summing the outputs of the delay elements of each bank of the second plurality to simultaneously provide output signals of It consists of a means to

Preferably the processing system represents the sonar beam received from a predetermined direction and from one bank of delay elements to the other of a pair of banks of delay elements of a second plurality. Process the force signal and determine the phase difference between the several pairs of output signals and the received sonar processed to determine the amplitude of the beam.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: FIG.

Figure 1 shows the diagram of a transducer consisting of a linear array of active sensor elements whose output signals are summed together. It is a front view.

Figure 2 is a side view showing the sonar pulses transmitted from the transducer and reflected from the ocean floor. Ru.

Figure 3 shows that the output passes through each delay element and then moves in a direction predetermined by the delay element. A matrix consisting of a linear array of active sensor elements summed to represent the beam received from FIG. 3 is a plan view of the lance deuser.

Figure 4 shows that when the normal depth is necessary to determine the depth of the seabed below the exploration vessel, It shows a typical course followed by an exploration vessel.

FIG. 5 shows a transducer of the exploration system according to the invention.

Figure 6a shows a side-scan or fan-scan sonar search system and an angle a to the vertical. Figure 2 shows two transducers of sonar return approaching them at

FIG. 6b shows the depth to the point of reflection and the horizontal distance thereto.

Figure 7 shows the phase difference relationship between the signals from the two transducers of Figure 6a with respect to the depression angle a. It is a diagram.

Figure 8 is a diagram showing the different posture changes that occur in the "fish" to which the transducer is attached. It is.

FIG. 9 is a schematic block diagram of a sonar exploration system according to the present invention.

FIG. 1O is a block diagram of the electronics system attached to the fish.

FIG. 11 is an index table used to convert the measured phase angle to the depression angle.

Figure 12 shows a parallel processing system in a fish that processes signals from two transducers. It is a block system diagram.

The sonar exploration system consists of two parts, one contained within a watertight pressure vessel; Others are kept on board. The two parts of the system are linked by a high-speed data link be done. The pressure vessel may be installed directly on the exploration vessel or attached to a towing fish or It may also be installed in a device capable of submersible operation. Sea units are for all systems. Provides control and recording equipment and online VDU table of attitude, sonar amplitude and seafloor shape Includes equipment with indicators.

The transducer of the system is shown in FIG. 5 and consists of a linear array of active sensor elements 10.

The outputs from these sensor elements are passed through sequential banks of delay elements through KN. , the output of each bank corresponds to the sonar return beam received from the respective direction DI-DN. are summed to provide corresponding respective output signals 5l-3N. Output by the present invention The signals 5l-SN are processed simultaneously so that the visual A display can be generated that represents a visual image of the ocean floor over a wide range of angles. the system, Two such transducers Tri and Tr, as explained with reference to Figures 6a and 6b. 2: converter Tr1. Each of Tr2 is as shown in FIG. 5, and each is a delay element. Output signal pairs associated with return beams received from each direction in several banks of children ( one from Tri and the other from Tr2).

Referring to Figures 6a and 6b, the main principle of a side-scan sonar interferometer will be explained.

Transducers Tri and Tr2 are arranged one above the other and are separated by a short distance Nλ (here where λ is the wavelength of the transmitted wave. ) Sonar pulses are sent from one transducer, e.g. Tr2. be believed.

The sonar return is determined by the depth D of the reflection point and the horizontal distance Ds to it, RCosa and R5. The depression angle a is given by 1na, respectively. where R is the absolute range of reflection It is. The sonar return is reduced by the lower transducer because the path length to the upper transducer is greater by an amount The upper transducer Tr2 is reached a little after the transducer Tri. Therefore, the outputs of the two converters The phase difference between signals is given by: Q=2N%Cos a From the above equation, the phase angle Q is '0 to 3606 phase for the change in depression angle from 0 to 90. You can see that you will be shifted N times. This means that for a value of N=3 there are a large number of phase shown in FIG. 7 as "ringe". For N>1, in the phase angle versus depression angle relationship: There is something wrong. To eliminate this anomaly, the transducer is first used after the sonar transmit pulse. Therefore, it is necessary to first detect the absolute phase of the signal from the seabed that is detected from the seabed.

The system may use two methods.

In one, the first return phase detector detects the absolute time delay of the first return. Ru. Others use vertical depth data obtained from precision echo sounders, seafloor shape data in front of the transducer. data and beam pattern used to estimate the position and absolute phase of the first return. It will be done. These two methods can be used in auxiliary inspection mode or stand-alone mode, and can be used in operation mode. The mode is selected via the main shipboard operations interface.

The first returned data is then used to place a pointer into the phase-to-depression index table. It will be done. The sequential phase data is then used for the orbit phase/depression angle pair via this index table. The conversion to depression angle ensures that the correct phase fringes are used. This will be explained later do.

The phase is determined digitally using a zero-crossing detector that starts and stops a high-speed counter. Measured by a barrel phase meter. This information is obtained by performing a moving average of the phase angle values. and organize data from the starboard transducer, attitude, and situation.

Add information from echo sounders, pressure data, etc. and send the results to the main onboard parallel processing system. It is fed to an online parallel processing system for output. used by the averager The number of phase angle values to be entered is set by the operator.

Errors due to changes in the attitude of the transducers as they scan the seafloor are be retroactively removed by software running on the system.

This software has six possible posture changes: roll, pitch.

Yaw, heap, surge and sway measurements are required and these are shown in FIG.

The attitude detection package, which consists of a gyro and an accelerometer, is equipped with a field that measures these values. incorporated into the flash.

Figure 9 shows the main components of the exploration system, these are the Fish electronics FE, operational components. Interface (control/analysis parallel processing system) PE.

High-resolution graphic display CD, digital large-capacity medium ST and position determination device PF (main ship (including a system for measuring fish displacement from a position determination device). Fit The ship's data is sent to the sea unit SU via a high-speed bidirectional link LN. child It stores all incoming data from both fish positioning devices on a digital recording medium. Accumulates in the body. Online analysis of the data is performed to yield a sample of the seafloor shape. and the quality of exploration data is monitored. System PE is also fish used to communicate with a parallel processing system housed in a global exploration system. Allows online changes to be made to operating parameters.

FIG. 10 shows a fish electronic equipment block system. This fish electronic device is Preamplifiers PRE1 and PRE2. Automatic gain control amplifier AGC1 and AGC2 , parallel processing signal acquisition element P2. Sonar pulse generator SP, data acquisition system D A, digital phase meter DP, first return phase meter FD, system status and alarms From circuit SSA, parallel processing control and communication element Pi, and envelope detector ED Become. The system shown in Figure 1O only has one signal from each of Tri and Tr2. is simplified to give:. Multiplexed signals Sl to SN from each converter are handled. A method for doing this will be explained with reference to FIG.

Under the operator's control, the power period and repetition rate of sonar pulses are set by the set pulse plate S. P, via a power amplifier PA that generates the power necessary to drive converter Tr2. Set by Pi. The accurate lock pulse is also initiated at the transmit time. Sona Immediately after the pulse (or “bin”) is sent, a data acquisition sequence under the control of the Pi begins. Stem DA multiplexes attitude data onto the surface and receives data from status and alarm circuit SSA. data is sent at this time. The system waits for the detection of the first return, at which time the absolute position The phase is determined by the first return phase meter FD and this data is stored for later reference. It will be done.

The time is determined by a precision clock and recorded on the first return detection.

Both clock and absolute phase data are sent to the plane for use in later analysis. 1st The return detector FD sends phase data to the digital phase meter DP to the processing element P2. make it possible to

The digital phase meter DP performs zero-cross detection to start or stop the digital counter. Use a device. −These counters maintain their signal output at a constant level Supplied from automatic gain control amplifiers AGCI and AGC2. PREl and AGC A zero-crossing detector connected to the transducer Tri via The other detectors are connected to Tr2 in order so that they are always in phase with Tr2. used to enable

The phase difference is the difference between a positive and a negative voltage when the signal level passes from a negative to a positive voltage (positive state detection). Measured between zero-crossing detections that occur for signals passing through pressure (detection of negative conditions) .

The phase values for rain detection in positive and negative states are sent to parallel processing element P2 (one data A digital sample consists of a pair of these phase values). Then R2 Performs a running average of the digital samples, and the number of values used in this averaging process is determined by the operator. Preset by. This eliminates the DC drift of the preamplifier and AGC. Ru.

An envelope detector consisting of an A/D converter ED (Fig. 10) processes multiple amplitude data in parallel. It is supplied to the physical element P2. Here it sends the average phase angle data to the surface unit combined. This will help the analysis of exploration data from equipment to traditional sites. generate a scanned sonar plot. This data detects areas of return to incomplete signals. It is also used for serving.

The system will be described for scanning as an example. Generate information from port side to starboard side of fish The circuit below is again used to create a preamplifier as shown in Figure 1O. , AGC, envelope detector, digital phase meter.

First return detector and microcomputer signal and analyzer.

The final signal processing is carried out in parallel on board using a series of algorithms to process the data. It is executed by the processing system PE. Raw data is stored in large digital capacity for later analysis. It is first stored in the medium ST. Next, the phase data is obtained using the index table shown in Figure 11. converted to depression angle. The first returned value positions the pointer P at the exact position in this table. The next value of the phase is the value of the area surrounding the pointer P for the conversion value to the depression angle. It is used to find the search window W, and the pointer P is updated by the last converted phase value. will be updated to the new location.

The signal level is such that its amplitude (as detected by an envelope detector) A predetermined minimum set by the number of values of the averaging process that fall below a set level above the minimum value. When the value is less than or equal to the value, conversion is prohibited. This means that the signal level is below the general noise level. Eliminates errors caused by underlying dead areas. Last part of available data The depression angle value equal to the one extracted from minutes is used as the latest value, and the flag is Attached to this data is used to indicate incomplete data areas on the upper display. Next The roll error is corrected.

Next, a conversion is made from the depression angle range R to a depth/distance matrix.

Absolute range R measures the sea speed in the exploration area and then determines the range of the first return This is determined by using data from the clock. The next range here is The speed of the system is predetermined by digitizing it. The location data is Yaw to generate a depth/position matrix.

Corrects pitch, hip, surge, sway, and fish deviation from the main ship position. Added. Finally, this data can be stored in different formats as required by the worker. It is displayed on the mat's graphic display GD. Hard copies are proprietary graphs if necessary. obtained from the graphic plotter GP.

Since the initial signal processing is essentially performed by a software system, this processing The special price is converted into a field by the main computer on board. Therefore, the average algorithm The range of values for the system depends on the particular type of ocean floor being explored, the digital Transducer separation and/or altered transducer speed and/or new cable directed downwards from the ship May be changed to suit the reference table.

Other modifications such as fine tuning of the power, duration and repetition of the transmitted pulses are also available. . Finally, the transducer can be changed as different sonar transmit frequencies are used. Often system parameters are changed thereby.

Therefore, the system performance depends on the seabed shape, the fish running height above the seabed, and the desired All areas covered are optimized with respect to the desired measurement accuracy.

Therefore, the above monitoring system may be implemented with different transmission frequencies and digitization speeds. I understand that it is okay. Furthermore, the number of formed beams can be changed to 20 or more. It's okay to be hit. The system then uses one or more beam patterns. Any one of the directions of transport or the phase using one or more beam patterns It may be used to obtain data looking in the direction of.

As shown in Fig. 12, the above matters (from the preamplifier, AGC, phase meter, etc.) This is achieved by expanding the parallel processing elements and associated interferometers. parallel A first group of processing elements (transputers) is provided, each element of the group having one T One receives a pair of signals, one from rl, the other from Tr2. The element Tll is, for example, Tri The summed output S1. from the first delay bank Kl of S1. From the first delay bank of Tr2 receives the corresponding addition output, etc. Tll for each return beam direction and for this return beam direction. Determine the phase difference between Tri and Tr2 with respect to the amplitude of the wave. This data is such element along with corresponding data from two other elements of the group T21 and Ta2. It is passed through a second group of parallel processing elements T12. Each setting of the three elements of the second group The output of is further passed to a parallel processing element or the like. a number of processing elements are in a first group; Each of the three settings is connected to one element in the second group, so that the data of the lower order elements are all passed through. = (as indicated by T in Figure 12) The last element is transferred to the onboard equipment. Passes phase and amplitude data from all channels to the final output for transmission.

After reception by Tri (Fig. 6(a)): time delay between reception of the same signal in Tr2 The detection of may be altered by using correlation techniques. Here, two converters signal time delay between the two received signals using parallel processing elements to perform correlation of the two received signals. It can be determined by Signal received from the transducer Tri closest to the seabed Correlating the signals from transducer Tr2 furthest from the seabed with respect to yields the maximum correlation. This results in a time delay introduced into the signal from Tri to make it happen. Therefore, the maximum correlation point results in a signal time delay between Tri and Tr2=X”c, where C is the underwater sound It's speed. Therefore, the path difference X and the depression angle a are calculated. Sona for correlation technology – The transmitted signal can be a single frequency, a chirp, a pseudo-random binary sequence, or a frequency modulated The sweep may be linear or non-linear.

Special table Hei 4-501316 (5) international search report international search report GB 9001291 S^　39180

Claims (6)

[Claims] 1. A receiver whose output consists of an array of sensor elements connected to multiple banks of delay elements transducer and corresponding from each bank representing the sonar beams received from each direction. means for summing the outputs of the delay elements of each bank to provide multiple output signals simultaneously; and a sonar exploration system. 2. Claim 1 further comprising a parallel processing system that processes the plurality of output signals simultaneously. sonar exploration system. 3. a second receiving transducer disposed at a predetermined distance above the first transducer; a second array of sensor elements connected to a second bank of the second plurality of sensors; sonar received by the second receiving transducer from each direction, one from each bank; the second plurality to simultaneously provide corresponding second plurality of output signals representative of the beams; 3. The sonar search system according to claim 2, further comprising means for adding the outputs of the delay elements of each bank. stem. 4. The processing system represents the received sonar beam from a predetermined direction and a second bank of delay elements, the other from a second bank of delay elements; Process the signals, determine the phase difference between the output signals of the pair, and determine the phase difference between them. 4. The sonar sounding system of claim 3, wherein the sonar search system is processed to determine the amplitude of the beam. 5. The processing system includes a first group in which each element of the first group processes the output signal in pairs. Parallel processing elements and a second group of parallel processing where each element receives the output of three elements of the first group. the elements and at least one further parallel processing receiving the outputs of the three elements of the second group. 5. The sonar exploration system according to claim 4, comprising: an element. 6. receiving and probing the output from the final parallel processing element of the first processing system; further comprising a second processing system for processing the output to provide a visual image of the terrain. 6. The sonar exploration system of claim 5.