RU2484499C1 - Method of determining depth of water body using side-scanning sonar and side-scanning sonar for realising said method - Google Patents

Abstract

FIELD: physics.SUBSTANCE: in the method of determining the depth of a water body using a side-scanning sonar, involving emission of a hydroacoustic signal towards the bottom and receiving reflected signals from two points lying on the vertical at a given distance, measuring the time delay of arrival of in-phase, the angle of roll of the antenna carrier and determining, based on the obtained data, the direction of arrival of in-phase signals and the unknown depth of the water body, there is further determining of coordinates of the reflecting (or scattering) layers on each "emit-receive" cycle; measurement results in neighbouring cycles are synchronised when receiving reflected signals differing on frequency characteristics; when determining the angle of roll, successive correction of angular and vertical displacements is performed for each measurement cycle. The side-scanning sonar for determining the depth of a water body, having operably connected first and second antenna, and operably connected transmitting unit, receiving and measuring unit, control unit, computer and recorder, the transmitting unit includes a pumping signal generator, the receiving and measuring unit includes a compensator, the transmitting unit is in form of a parametric radiating channel capable of correcting phase and amplitude of received signals.EFFECT: high reliability of surveying the bottom of a water body.2 cl, 6 dwg

Description

A method for determining the depths of the water with a side-scan sonar and a side-scan sonar for its implementation

The invention relates to the field of hydrography, in particular to methods and technical means for determining depths of a water area with a side-scan phase sonar, and can be used to take pictures of the relief of the bottom of the water area.

A known method of determining the depths of the water phase side-scan sonar (Shipbuilding abroad, Edition Central Research Institute Rumb, 1987, 76-80. [1]), including the radiation of the hydroacoustic signal to the bottom and receiving the reflected signals at two points located at a distance d along vertical, measuring the delay time ts of the reflected signals and their phase shift φ at these points, determining the direction ( a ) of receiving the reflected signals by the formula

$$\alpha =\arcsin \frac{C}{fd}\cdot \frac{\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="00000027.png"\; state="\{\{state\}\}">\phi </figure-callout>}}{2\pi },\left(\mathrm{one}\right)$$

where f is the frequency of the sonar signal;

C is the speed of sound propagation in water.

The device measures the angle β of the side rolling of the antenna carrier and calculates the depths (Z) of the water area according to the formula

$$Z=\frac{\mathrm{<figure-callout\; id="2"\; label="C\; t\; s"\; filenames="00000027.png"\; state="\{\{state\}\}">C\; </figure-callout>}{t}_s{}_{}}{2}\sin \gamma ,\left(2\right)$$

.Where $$\gamma =\alpha +\beta$$

.

However, this method has insufficient accuracy.

This is because when it is used, there is a significant error (m _γ ) in determining the direction (γ) of arrival of the reflected signals from the measured values of their phase shift φ at the receiving points.

,The value of m _γ , based on formula (1), can be calculated by the formula $$m_{\gamma }=\mathrm{one}/\mathrm{one}-{\left(\varphi /2\pi \right)}^2{m}_{\varphi }$$

,

where m _φ is the measurement error φ.

Since a reliable determination of the direction of y (without resolving the ambiguity) is possible only in the case of a small separation of d antennas not exceeding two wavelengths (λ), the possible range of phase shift φ at d = λ will be 0-2 π.

The error m _γ , as can be seen from formula (3), varies nonlinearly for φ = 0 m _γ = -m _φ , and for φ = 2π it reaches a maximum and can be 2 m _φ .

This circumstance causes a significant error (m _z ) for determining the depth of the water area z when using the known method.

где $$\gamma =\alpha +\beta .$$

Например, когда С=1500 м/с, tз=0,7 с, γ=30°, cos φ=87, m_γ=2, m_φ=2·0,0017 (m_φ у современных фазовых гидролокаторов бокового обзора не превышает 1°). Тогда m_z составит 13 м или около 4% от величины. Допустимая погрешность определения глубины акватории в соответствии с нормативными документами по съемке рельефа дна составляет 1% от глубины Z.The value of m _z , based on formula (2), can be calculated by the formula $$m_z=C{t}_s/2\cos \phi m_{\phi },$$

Where $$\gamma =\alpha +\beta .$$

For example, when C = 1500 m / s, tz = 0.7 s, γ = 30 °, cos φ = 87, m _γ = 2, m _φ = 2 · 0.0017 (m _φ in modern phase side-scan sonars does not exceeds 1 °). Then m _z will be 13 m or about 4% of the value. The permissible error in determining the depth of the water area in accordance with regulatory documents for surveying the bottom topography is 1% of the depth Z.

There is also a method for determining the depths of a water area with a side-scan phase sonar (Stubbs AK: Telesounding a merhod of wide swathe a depth measurement International Hydrographic Review 1974, 51 Ns 1, pp23-59 [2]), including simultaneous radiation to the bottom of the main and auxiliary sonar signals differing in frequency by a small amount, and receiving the reflected main and auxiliary signals at two points disposed vertically at a predetermined distance d, the measurement time t _c inphase delay joining the main and auxiliary signals using two of many priemoizmeritelnyh channel two-frequency blocks, the measurement device the angle of roll support antennas, determining from the data arrival directions of the main-phase signal and the desired depth of the water area by calculation.

Also known is a side-view phase sonar, which contains the first and second two-frequency antennas located vertically at a given distance (d), the transmitting unit, the first and second two-frequency multi-channel receiving and measuring units, a control unit, a calculator and a recorder, while the outputs of the first and second two-frequency antennas are connected respectively to the inputs of the first and second two-frequency multi-channel receiving and measuring units, the output of the transmitting unit is connected to the radiating antenna, the outputs of the first and second of multi-channel dual-frequency priemoizmeritelnyh units connected to the output of the calculator, the latest output is connected to the DVR.

The disadvantage of this method and device (phase sonar side view) is that they are difficult to use.

This is because in order to increase the accuracy of determining the depths of the water area in these technical solutions, reflected hydroacoustic signals are received at two points located vertically at a large distance (d = n λ) of several wavelengths compared to the analogue, and the signal delay time is measured , that is, signals in which the phase shift is absent or a multiple of an integer 2π.

The implementation of this action provides high accuracy in determining the depths of the water area, since with a phase shift of φ = 0, as can be seen from formula (3), the error m _γ will be minimal and equal to m _φ .

However, in this case, there is a need to solve a complex problem - the elimination of ambiguity in determining the directions of arrival of common-mode signals. To solve this problem, when using the first known known method, it is necessary, in addition to the main ones, to perform the following complex steps: take in the third point, located vertically on an auxiliary base at a given distance from the common point, the reflected sonar signals; measure in the third and main points the delay time of the arrival of common-mode signals.

To carry out these actions, it is necessary to equip the side-view phase sonar with a receiving antenna and a receiving-measuring unit, that is, significantly complicate the structural diagram and increase the weight and size characteristics of the side-view phase sonar.

When using the known method for solving the same problem, it is necessary to perform, in addition to the main ones, the following additional steps:

- emit an auxiliary hydroacoustic signal at a given frequency that differs from the fundamental frequency;

- receive reflected auxiliary signals (common mode) in the same cases where the main common mode signal is received;

- measure the arrival delay time of auxiliary common-mode signals.

To carry out these actions, it is necessary to use an auxiliary phase sonar side view. That is, to implement this method, it is necessary to use almost two phase side-scan sonars operating at different frequencies, which causes considerable difficulty in using known methods and devices.

There is also a method for determining the depths of the water with a side-scan phase sonar and a side-view phase sonar for its implementation (patent RU No. 1829019 A1, 07/23/1993 [3], in which the technical result consists in simplifying the process of determining the depth of the water area with a side-scan phase sonar.

In this case, the technical result is achieved by the fact that in the method for determining water depths by a side-scan phase sonar, which includes emitting a hydroacoustic signal to the bottom and receiving reflected signals at two points located vertically at a given distance, measuring the delay time of arrival of common-mode signals, the pitch angle carrier antennas and determining from the data arrival directions θ _n in-phase signal and the desired depth of the waters by calculation, measurement of time delay _of arrival t the reflected sonar signal vertically, the time delays (t _p ) of the arrival of the common-mode signals are separated if they are reflected from the flat bottom surface in each calculated (θ _p ) direction according to the formula

$$\begin{array}{l}{t}_{p_n}=\frac{t_b}{\sin \left({\theta }_{p_n}+\beta \right)}+\\ \left(3\right)\\ +\frac{t_b\cdot \cos \left({\theta }_{p_n}+\beta \right)\cdot \sin \xi }{\sin \left({\theta }_{p_n}+\beta \right)\sin \left({\theta }_{p_n}+\beta -\xi \right)},\end{array}$$

where n = 1,2,3 ... N;

N = d / λ is the number of calculated directions θ _p ;

ξ is the general angle of inclination of the bottom in the sensing strip;

вычисленному по формулеThen, the convergence of the calculated t _n and measured t _p values is determined by the criterion $$(\stackrel{2}{\delta }),$$

calculated by the formula

$$\begin{array}{l}{\mathrm{<figure-callout\; id="2"\; label="\sigma "\; filenames="00000027.png"\; state="\{\{state\}\}">\sigma </figure-callout>}}^2={\displaystyle \sum _{m=\mathrm{one}}^{M-\mathrm{one}}[\left(t_{p_{n+\mathrm{one}}}-t_{p_n}\right)}-\\ {-\left(t_{c_{m+\mathrm{one}}}-t_{c_m}\right)]}^2,\left(\mathrm{four}\right)\end{array}$$

where M is the number of measured values of t _c for each number M of design directions θ _p .

In this case, the initial value of n is successively changed from 1 to K = N-M, and M calculated directions θ _p , characterized by a minimum value of δ, are taken for the sought-after directions of arrival of common-mode signals.

The known side-scan sonar for determining the depths of the water area [3] contains a functionally connected first and second antenna, one of which is a receiving-emitting, transmitting unit, first and second receiving-measuring units, a control unit, a unit for determining the arrival delay time of common-mode signals reflected from a flat bottom surface for each the calculated direction, the calculator and the recorder, in which the outputs of the first and second antennas are connected respectively to the inputs of the first and second receiving and measuring units, the output the giving unit is connected to the receiving-radiating antenna, the outputs of the first and second receiving-measuring units are connected to the inputs of the calculator, the output of the last is connected to the registrar, and the control unit is connected to the first and second receiving-measuring blocks, the transmitting unit, the calculator and the registrar, the input of the unit determining the arrival delay time reflected from a flat bottom surface of common-mode signals in each design direction, the input of which is connected to the output of the control unit, and the output is connected to the input of the calculator. A significant disadvantage of this device is that to achieve the technical result stated in the method, the control unit and the calculator must be made in the form of a computer of type SM-4 due to the greater number of calculation and computational operations, which limits its use only when used for measuring work of large-capacity carriers (ships) equipped with a powerful computer.

However, despite the achievement of simplifying the known method, it is burdened by substantial calculations and time-consuming computational operations.

In addition, the selection of reflected signals from a flat bottom surface and their mathematical processing are associated with a number of assumptions, which significantly reduces the reliability of obtaining the final measurement results.

So, for example, studies of the distortion of the spectra of linear frequency-modulated (LFM) signals in sea soil depending on the depth of penetration into sea soil showed that the first reflection is recorded in the bottom layer at the upper frequencies of the spectrum. As the depth increases (below the bottom surface), the spectrum expands toward lower frequencies, the low-frequency part of the spectrum increases and begins to prevail, and with a further increase in depth, the remaining low-frequency part gradually decreases. The maximum value of the intensity is achieved in the low-frequency part of the spectrum. For thick bottom sediments, features in the nature of the change are sometimes observed. These features consist in a relative increase in a certain depth range of the high-frequency part of the spectrum and are manifested in the appearance of a low-frequency spectrum between high-frequency spectra. Moreover, the predominance of the low-frequency part in this range is less significant for this type of soil. The spectrum forms become equalized and only then does the high-frequency part decrease, and the low-frequency part decays. This feature is associated with a layered structure of sediments and weak absorption in individual layers. This circumstance limits the application of the known method [3], since its implementation requires the selection of discrete measurements from the general series, the selection of discrete measurements with the presence of a flat bottom surface, free from bottom sediments.

A significant disadvantage of the device for implementing the known method is the fact that when calculating the time delays of the arrival of reflected waves, only the change in the pitching angles is taken into account, while the measurement results will also be burdened by the influence of pitching.

In addition, one of the tasks of the secondary processing of recorded signals is the task of identifying the structure of the probe space. For this, it is necessary to localize layers reflecting or scattering acoustic waves, i.e. detect and determine the coordinates of these layers on each radiation-reception cycle. In addition, it is necessary to synchronize the measurement results in adjacent discrete measurement cycles to obtain cartographic material from the results of bathymetric surveys of the water area. This circumstance is due to the fact that the angles in the vertical plane of the radiation and the vertical coordinates of the points "radiation-reception" change in time and in the presence of excitement.

Compensation for these changes is necessary when revealing a layered medium. And also when “stitching” responses of signals that differ in frequency characteristics. This situation occurs when it is impossible to emit a frequency-modulated signal of the necessary deviation. One of the ways to perform this compensation is the well-known method [3], which requires knowledge with high accuracy of determining the change in the radiation angles in the vertical plane and the vertical coordinates of the radiation-receive points. And if, under the conditions of installing a side-scan sonar on a hydrographic vessel equipped with the appropriate equipment (a satellite navigation system receiver combined with an inertial navigation system), a positive result in compensating for changes in the angles in the vertical plane of radiation can be achieved, then if the side-scan sonar is installed on underwater vehicle, towed by a vessel, and even more so, taking into account changes in the vertical coordinates of the radiation-reception points, which change in time and in the presence of unrest, the achievement of a technical result in the prototype, it is practically impossible.

In addition, in the vertical direction, the marine aquatic environment is a horizontally heterogeneous medium with a variable speed of sound. When passing in a vertical direction from the surface to the bottom, the emitted sound pulse will partially reflect on the internal inhomogeneities of the aquatic environment and these signals, as well as signals reflected from the bottom, will be recorded by the receiving device. As a result, after the moment of emission of a sound pulse until the moment of receiving a signal reflected from the bottom, signals reflected from the bottom and from internal inhomogeneities of the aquatic environment will be recorded. As a result, the device records the time series of the density of sound energy reflected from the bottom and from the internal inhomogeneities of the aquatic environment.

In known methods and devices, signals received from internal heterogeneities of the aqueous medium are subjected to complex processing in order to reduce their effect on the final measurement results. However, intense sound waves in water do not propagate independently, but due to non-linear effects interact with each other. Usually, in acoustics, dispersion is practically absent and waves of close frequencies in the quadratic approximation effectively interact only when collinear propagation, when the synchronism condition is satisfied (see, for example, Aredov A.A., Dronov PM, Okhrimenko N.N., Furduev A.V. Experimental Estimates of the Stationarity of Underwater Ocean Noise. // Acoustic Journal, 1994, v.40, No. 3, p. 357-361. BM Kuryanov, AA Moiseev, A Study of the Dependence of the Low-Frequency Ocean Noise Using a Controlled Buoyancy Buoy // Acoustic Journal. 1994, v.40 , No. 3, p. 487-488. Derevyankina PI, Kapielson BG, Lyubchenko A.Yu. Vertical structure of the intensity of the low-frequency noise field of the shallow sea // Acoustic journal. 1994, v.40, No. 3, p. 380-384). However, in the interaction of waves that differ significantly in frequency, for example, if an intense high-frequency sound beam propagates in a medium perturbed by a low-frequency wave, a modulation effect of the high-frequency beam is possible, the degree of which will depend on the magnitude of the nonlinear parameter of the aqueous medium and the angle between the wave propagation vectors. The objective of the proposed technical solution is to expand the functionality of the method for determining the depths of the water area, while increasing the reliability of shooting the bottom of the water area.

The problem is solved due to the fact that in the method for determining water depths with a side-scan sonar, which includes emitting a hydroacoustic signal to the bottom and receiving reflected signals at two points located vertically at a given distance, measuring the delay time of arrival of common-mode signals, the pitch angle of the carrier antennas and determining from the received data the directions of arrival of common-mode signals and the desired depths of the water, in contrast to the prototype, they additionally determine the coordinates of the reflecting (or scattering) layers on each radiation-receive cycle, the measurement results in adjacent cycles are synchronized when receiving reflected signals that differ in frequency characteristics, in determining the roll angle, sequential correction of angular and vertical movements for each measurement cycle is performed, and in the side radar review to determine the depths of the water area, containing functionally connected first and second antennas and functionally connected transmitting unit, receiving and measuring unit, control unit Lenia, computer and recorder, unlike the prototype, the transmitting unit introduced shaper pump signals in priemoizmeritelny introduced compensator unit, the transmitting unit is designed as a parametric radiating path, with the phase correction of the amplitudes of the received signals.

The technical implementation of the claimed invention is illustrated by drawings.

Figure 1. Structural block diagram of a side-scan sonar.

The side-scan sonar includes a pump driver 1 for generating two-frequency probing pump signals with a given duration and a given modulation, generating synchronization pulses and gating signals for the receiving path, a parametric radiating path 2, designed to amplify the pump signals at both frequencies to the nominal level (at this in separate channels can be the correction of the phases of the amplitudes), the emitting pump Converter 3, designed for the formation of electrical signals into acoustic signals with the necessary directivity characteristics, an emitting antenna of signals of a difference frequency 4, intended for generating a directivity pattern, a receiving antenna 5 for receiving and converting acoustic waves of a difference frequency into electric signals, a receiving path 6, intended for preliminary processing of received signals and amplification them to the level necessary to register the received signals, the compensator 7, the control unit 8, the calculator 9 and the register Op 10.

Figure 2. Functional diagram of the pump driver. The pump signal generator 1 consists of a reference frequency crystal oscillator 11, a generator 12 of the period of the emitted pump pulses, a device 13 for generating the duration of the emitted pulse, two channels for generating radio pulses with pump frequencies, which are based on phase storage devices 14 and 15, which are accumulating adders and constant storage devices 16 and 17, digital-to-analog converters 18 and 19, power amplifiers 20 and 21, low-pass filters 22 and 23, arithmetic-logic devices Stv 24, 25, 26 and 27, a counter 28, accumulating adders 29 and 30, a phase code generator 31, an analog-to-digital converter 32.

Power amplifiers 20, 21 consist of four identical broadband units, including preamplifiers and power amplifiers with a power of up to 4000 W each, divided into two groups of two blocks to enhance the pump frequencies f ₁ and f ₂ . Four amplifiers are installed in front of the amplifiers. The output amplifier is made according to a two-contact circuit on powerful transistors TK-152. The preamplifier consists of an operational amplifier and two pairs of complementary medium-power transistors.

Figure 3. Block diagram of the receiving path. The receiving path is designed to receive, amplify and frequency select the scattered signals of the differential frequency wave in the frequency band 5-50 kHz. Its sensitivity to acoustic pressure is at least 0.001 Pa. The receiver is made according to the direct amplification scheme. The receiver consists of a receiving antenna 5, designed to convert acoustic signals into electrical signals, bandpass filters 33 and 34, antenna amplifier 35, main amplifier 36, drivers 37, 38 control codes, filter unit 39, amplitude detector 40, low pass filter 41, switch 42, output amplifier 43.

Figure 4 Change in the coordinates of the points of radiation and signal reception. Vessel 44, A, B are the radiation-receive points in the jth and j + 1th cycles, respectively, θ _j , θ _{j + 1} are the angles in the vertical plane, H _j H _{j + 1} are the vertical coordinates of the points radiation-reception ”, h _n - vertical coordinate of the n-th layer.

Figure 5. Implementation of a sequential correction algorithm for angular and vertical movements. In a graphic form are shown:

- the initial sequence {S _ji } (figa);

- the sequence {S _ji } after compensating for changes in the angle (Fig.5b);

- the final result (figv).

In the figures, dots indicate the maxima corresponding to the reflective layers.

6. Algorithm for detecting weak signals (detection of layers with a low reflection coefficient) against a background of interference. On figa in graphical form displays the original sequence {S _ji }. On figb presents the coordinates of the detected maxima. In Fig.6b, the signal-to-noise ratio is 2; in Fig. 6d, the signal-to-noise ratio is 0.8.

The pump signal pump 1 (figure 2) works as follows. The reference frequency crystal oscillator 11 generates pulses with a repetition rate of 2.04 MHz. The pulses of the reference frequency are fed to the input of the shaper 12 of the repetition period of the emitted pump pulses, at the input of which short pulses are formed with a given repetition period. These pulses are fed to the input of the device 13 forming the duration of the emitted pulse. The output of the device 13 is removed rectangular pulses, the duration of which can be changed using binary codes from the control unit 8.

The rectangular pulses thus formed with a given duration and repetition rate are fed to two channels for generating radio pulses with pump frequencies. The basis of both channels of the shaper are phase drives 14 and 15 and read-only memory devices 16 and 17. Phase drives are controlled by the clock pulses of the reference frequency generator 11 and the pulses from the device 13. Eight-bit codes from the phase drives 14 and 15 are fed to the address inputs of the corresponding read-only memory devices 16 and 17, in which the samples of the period of the sine wave are recorded. These samples are selected in the form of eight-bit codes, fed to the inputs of the corresponding digital-to-analog converters 18 and 19, from the outputs of which, through the low-pass filters 20 and 21, the radio pulses with a rectangular envelope and the selected filling frequencies are fed to the inputs of the power amplifiers 22 and 23.

Changing the pump frequencies f ₁ and f _{2 is} performed using binary codes supplied to the inputs of phase drives 14 and 15 from arithmetic-logic devices 24 and 25, respectively. The radiation frequency can be automatically changed through each radiation pulse, after two, four, eight or sixteen pulses. The number of pulses of one frequency is set by the counter 28. The resolution of the tuning (62.5, 125, 200, 500, or 1000 Hz) is selected by the control unit 8, which sets the corresponding code at the inputs of the accumulating adders 29 and 30. The analog-to-digital converter 32 with its output codes supplied to the lower inputs of the arithmetic-logic devices 26 and 27, determines the initial difference frequency. The codes are changed by changing the reference voltage at the input of the analog-to-digital converter 18. Codes determined by the resonant frequency of each of the two channels of the pump antenna are constantly set on the upper inputs of the devices 26 and 27. In the pump signal driver 1, it is possible to form an in-pulse linear frequency modulation with fixed frequencies. In this case, the signal is generated by applying phase codes to phase drives 14 and 15 from the phase code generator 31.

In the receiving path 5 (figure 3) bandpass filters 33 and 34 are used to suppress the frequencies of the pump signals, as well as interference below the frequencies of the operating range. They are passive high and low pass filters connected in series. The suppression of the pump frequency signals is not worse than 60 dB. Antenna amplifier 35 is a broadband low noise preamplifier. To attenuate common mode interference, the last stage is made in differential switching. The gain is 26 dB. The main amplifier 36 is three-stage with manual gain control. Gain control is performed by digital codes. The adjustment range is 0-80 dB. Filter block 39 is a set of low and high frequency filters that are switched by bandpass filters with a variable passband. The management of the switches, and therefore the bandwidth, is done by digital codes. Code generators 37 and 38 are used to generate control codes for the gain of the main amplifier 36 and the passband of the filter unit 39. The linear detector consists of an amplitude detector 40 and a low-pass filter 41 and serves to isolate the envelope of the scattered signals of the difference frequency wave in the dynamic range of 40 dB. The switch 42 is designed to select the reflected signal or its envelope. The output amplifier 43 serves to match the receiver with external devices.

The calculator 9 includes a controller, an integrated 8-channel 16-bit ADC type AD 7715 with external inputs for connecting the receiving and emitting channels and external devices, a linear prediction filter, an autonomous supply voltage control system, an internal temperature sensor based on a silicon diode pn junction , two comparators with programmable reference voltage, a multiplexer, an RS-232 standard serial interface, three timers that provide frequency measurement relative to the reference crystal oscillator, and represent It is a processor with a separate 14-bit bus command and an 8-bit data bus. A two-stage converter allows the execution of up to 35 commands in one machine cycle. An analog is a microprocessor type PJC 14000.

The control unit 8 includes a central module that organizes the mode of measuring signals, processing the measurement results, generating exchange signals with external devices and a data packet in a given format, and storing it in memory for subsequent processing. The main functions that determine the operation algorithm are sequentially turning on the power supply and polling the output signals of the function blocks in accordance with a given program, averaging the measurement results for each channel in accordance with the specified time intervals, introducing amendments to the measurement results taking into account the ADC zero drift, and the deviation of the conversion characteristics from the source, temperature dependence of the characteristics of the sensors with the representation of data in the form of conditional codes, reduction of conditional codes the measured values to the measured values of physical parameters in accordance with the data processing algorithms including coefficients, recording and storing the received data in the buffer memory of the microprocessor generating the message set format, for transmission to the external communication channels. The software includes a powerful microassembler, intrasystem and debugging emulators, a universal programmer and compiler. Plotter 6 is a plotter.

The operation of the receiving path is as follows. The reflected acoustic signals are fed to the receiving antenna 5, which converts the acoustic pressure into electrical voltage. The signals converted by antenna 5 are fed to bandpass filters 33 and 34, in which the frequency selection of the difference frequency wave signals is performed. From the outputs of the filters 33 and 34, the signals are fed to the input of a two-channel differential antenna amplifier 35, in which the signals are pre-amplified and common mode noise is suppressed, and the output of which is fed to the input of the main amplifier 36, the gain of which depends on the codes received at the digital inputs of the amplifier from the code generator 37. The main amplifier is locked at the time of sending by an inverted sending pulse from the code generator 37. The output of the main amplifier 36 is amplified the signal is input to the filter unit 39 with an adjustable passband. At the digital inputs of the filter unit 39, the necessary code is received from the code generator 41. From the output of the filter unit 39, the signal is fed to the input of the amplitude detector 40, which selects an alternating signal module. The detected signal from the output of the amplitude detector 40 is fed to a low-pass filter 41, in which the envelope of this signal is extracted. The extracted envelope of the reflected signal from the amplitude detector 40 and the reflected signal from the filter unit 39 are fed to the input of the switch 42. The signal type selected by the switch 42 through the matching output amplifier 43 is fed to external devices of the receiving path.

The parametric radiating path 2 includes a pump antenna, which is a multi-element array, consisting of two two-frequency channels each. Elements in each sublattice are arranged in an alternating order of types with different frequencies and are designed so as to ensure the greatest uniformity of the acoustic field at both frequencies. The active part of the dual-frequency mosaic antenna is made of rod-type piezoceramics. Dividing the antenna into four channels allows you to achieve the necessary power and high reliability during the operation of transistor power amplifiers. The pump antenna has a circular shape with a diameter of the active surface of 300 mm. The average operating pump frequency is 180 kHz. The range of difference frequencies is 5-50 kHz. The estimated width of the directivity pattern at 3 dB is two degrees and is constant in the range of operating frequencies.

The method is implemented as follows. When the carrier of the depth measuring equipment, for example, a vessel 44, is equipped with standard navigation aids: sonar lag, heading meters, satellite and radio navigation systems receiver, side-scan sonar, depth determination is performed.

In this case, one of the goals of secondary signal processing is the task of identifying the layered structure of the probe space. To do this, localize layers reflecting or scattering acoustic waves, i.e. detect and determine the coordinates of these layers on each radiation-reception cycle. In addition, it is necessary to “link” the measurement results in adjacent cycles to obtain an averaged map of the environment. At this stage of processing, a number of problems arise.

The result of the primary processing (filtering) of the received signals are sequences of the form

$$\left\{S_{ji}\right\}=\left\{{\displaystyle \sum _{n=\mathrm{one}}^N{X}_n\left(l_{nj}-i\right)}+{\xi }_{ji}\right\}\left(5\right),$$

where S _ji is the value of the member of the jth sequence at the output of the compression filter at the time i = E (t / Δt);

Δt is the sampling step;

t is the time from the start of radiation;

N is the number of reflective layers;

X _n (i) - samples of the response from the n layer at the filter output, taking into account the reflective properties of the layer;

l _nj is the time coordinate of the n layer in the j sequence;

ξ is the value of noise interference at time i.

As a result of joint processing of the values of the given sequence, it is necessary to determine the coordinates of the reflecting layers and evaluate their reflective properties. A number of factors associated with field measurements may interfere with this task. These include work on waves, which leads to a random nature of the coordinate values l _nj , the presence of interference, “masking” the layers with a small reflection coefficient.

Consider the features of revealing the layered structure of the medium when working in waves and in the absence of spatial stabilization of the receiving and emitting devices (antennas 4,5). Let the cycles of "radiation-reception" occur sequentially with the period T. Under the conditions of excitement for the period T, the coordinates of the points of radiation and reception of signals (Fig.4).

Figure 5. Change of coordinates of points of radiation and reception of signals. Ship 47, A, B are the radiation-reception points in the jth and j + 1th cycles, respectively, θ _j , θ _{j + 1} are the angles in the vertical plane, H _j H _{j + 1} are the vertical coordinates of the points radiation-reception ”, H _n is the vertical coordinate of the nth layer.

.For accepted designations $$l_{nj}=H_j-H_n/C\cos {\theta }_j\left(6\right)$$

.

.The quantities H _j and θ _j are random functions of time (i.e., they are random sequences). The change in the time coordinate of the nth layer in neighboring cycles is described by the expression $$\Delta {\ln }_{n,j,j+\mathrm{one}}={\ln }_j-{\ln }_{nj+\mathrm{one}}=H_j-h_n/C\cos {\theta }_j-H_{j+\mathrm{one}}-h_n/C\cos {\theta }_{j+\mathrm{one}}\left(7\right)$$

.

Compensation of these changes is necessary when revealing the layered structure of the medium, as well as when “linking” the responses of signals that differ in frequency characteristics. This situation occurs when it is impossible to emit a frequency-modulated signal of the necessary deviation. One of the methods of compensation requires knowledge with high accuracy θ _j , θ _{j + 1} and H _j H _{j + 1} , i.e. sensors are needed that measure these values, which is not always possible, especially when placing a side-scan sonar on towed underwater vehicles, and which also requires a translation of the coordinates of the spatial location of the towed vehicle relative to the vessel.

When using known methods of processing the received sequences of reflected hydroacoustic signals, there are no operations that can compensate for distortions in the coordinates of the layers that do not require additional information about the changes in θ and H. This is explained by the difficulties encountered in creating such algorithms due to the inability to separate Δln _n , _j , _{j + 1} into two partial components, one of which is due to a change in the angle, and the other due to the height, i.e. the impossibility of representing Δln _n , _j , _{j + 1} as a product or the sum of partial errors.

Under some assumptions about the characteristics of the medium and the conditions for the measurements, it is possible to take these displacements into account.

Assume that the vertical coordinates H _n do not change sharply during the time between adjacent receive-emission cycles. Under the assumptions made, we consider the following difference

. $$\Delta {\ln }_{n,n=\mathrm{one,}j}={\ln }_j-{\ln }_{nj+\mathrm{one}}=H_j-h_n/C\cos {\theta }_j-H_{j+\mathrm{one}}-h_n/C\cos {\theta }_{j+\mathrm{one}}=n_{n+\mathrm{one}}-h_n/C\cos {\theta }_j\left(7\right)$$

.

The above expression is the product of two factors 1 / cosθ _j and h _{n + 1} -h _n / С, the first of which depends only on the angle θ _j , the second on the difference in the coordinates of neighboring layers. This circumstance allows us to propose an algorithm for processing sequences {S _ji }, with the help of which it is possible to track the change in θ and H in neighboring study-receive cycles. The essence of the algorithm is the sequential correction of angular and vertical movements. For this, the coordinates of the maxima ln _j are determined from the initial sequence {S _ji } and the estimate of the mathematical expectation of the differences Δln _{n, j, j + 1 is} calculated

$$\Delta l_j=\mathrm{one}/N-l{\displaystyle \sum _{n=\mathrm{one}}^{N-\mathrm{one}}{\ln }_j-l_{\left(n+\mathrm{one}\right),j}}\left(8\right).$$

Given the expression for $$\Delta {\ln }_{n,j+\mathrm{one,}j}$$

$$\Delta l_j=\mathrm{one}/C\cos {\theta }_j{\displaystyle \sum _{n=\mathrm{one}}^{N-\mathrm{one}}\Delta h_n=l/C\cos {\theta }_j\cdot \Delta H_j/C}\left(9\right).$$

In the obtained expression, Δh _j is a formal estimate of the mathematical expectation of the distances between the layers in the jth measurement cycle.

If Δh _j and Δh _{j + 1} are close, then we can form the following relation

или $$C=\cos {\theta }_{j+1}/\cos {\theta }_j=\Delta l_{j+1}/\Delta l_j\left(10\right)$$

. $$\Delta l_j\cos {\theta }_j=\Delta l_{j+\mathrm{one}}\cos {\theta }_{j+\mathrm{one}}$$

or $$C=\cos {\theta }_{j+\mathrm{one}}/\cos {\theta }_j=\Delta l_{j+\mathrm{one}}/\Delta l_j\left(10\right)$$

.

The obtained value C allows you to compensate for the change in the angle in adjacent measurement cycles. For this, the coordinates of the sequences {S _ji } in the j + 1-th cycle are changed by C ^-1 times, forming a new sequence {S _ji }. In the newly formed sequence, the coordinates of the layers have the following meanings

. $${\ln }_{n,n=\mathrm{one}}=H_{j+\mathrm{one}}-h_n/C\cos {\theta }_{j+\mathrm{one}}\cdot \cos {\theta }_{j+\mathrm{one}}/\cos \theta =H_{j+\mathrm{one}}-h_n/C\cos {\theta }_j\left(\mathrm{eleven}\right)$$

.

It can be noted that at this stage, the angle θ was compensated.

.Really $$\Delta {\ln }_{n,j,j+\mathrm{one}}={\ln }_j-{\ln }_{n\left(j+\mathrm{one}\right)}=H_j-h_n-H_{j+\mathrm{one}}+h_n/C\cos {\theta }_j=H_j-H_{j+\mathrm{one}}/C\cos {\theta }_j\left(12\right)$$

.

The second part of the algorithm allows you to compensate for a random change in the vertical coordinate of the point "radiation-reception". For this, it is enough to introduce such a shift of coordinates in the sequence {S _{j + 1, j} } in order to minimize the difference

$$p_{j+\mathrm{one}}=\sqrt{{\displaystyle \sum _{i=\mathrm{one}}\left[S_{j,i}-S_{j,}n{,}_j+{\delta }_{j+\mathrm{one}}\right]}}\left(13\right),$$

those. δ _{j + 1} → min p _{j + 1} .

To test the operability of the described algorithm, a program was created that implements the proposed algorithm and a simulator program generating sequences {S _ji }.

The results of this algorithm are shown in figure 5, which shows in graphical form:

- the initial sequence {S _ji } (figa);

- the sequence {S _ji } after compensating for changes in the angle (Fig.5b);

- the final result (figv).

In Fig. 5, dots indicate the maxima corresponding to the reflective layers. The conditions of the depicted experiment are as follows: the number of implementations is 60, the number of samples in the implementation is 600, the sampling step is 1 ms, the number of layers detected is 50, the mean square error of changes in the vertical angle is 0.175 rad, the mean square error of changes in the vertical coordinate is 2 m.

The second algorithm is designed to detect weak signals (detection of layers with a low reflection coefficient) against a background of interference. Detection occurs by increasing the signal-to-noise ratio of a weak signal in the output sequence.

For this, a temporary accumulation of responses belonging to individual layers is performed. The main difficulty in organizing the accumulation is caused by the variability of the coordinates of the layer. If these changes occur rather slowly, then we can assume that in the averaging interval, the change in the coordinates of the layers occurs according to a linear law. This makes it easy to implement the accumulation algorithm.

Figure 6 presents the results of the operation of such an algorithm. On figa in graphical form displays the original sequence {S _ji }. On figb presents the coordinates of the detected maxima. On figv - the signal-to-noise ratio is 2, on fig.6g - 0.8.

These operations are performed on the compensator 7.

The control unit 8 is based on the Intel Core2Duo processor.

Registrar 10 is a hardware-software unit and consists of a processor, graphics accelerators, an object-graphics engine such as OGRE, software modules such as PhysX, Hydrax, Skyx and ANSYS AQWA. As a graphic engine, it is also possible to use commercial engines such as CRY ENGINE, VALVE or similar.

Calculator 9 is based on a computing platform in the form of a system on a chip of the System on Chip (SoC) type and consists of a general-purpose processor, the functions of which are to solve navigation equations to ensure the movement of the vessel on surveying tacks during bathymetric surveying of the seabed and servicing interfaces, and two processors with vector-matrix coprocessors, which are designed for full software processing in real time of registered signals.

A significant advantage of the proposed method for determining water depths with a side-scan sonar and a side-scan sonar for its implementation is the ability to accurately measure the coordinates of the scattering layers, which, when using 9 algorithms of the well-known deconvolution method in time series processing, also allows estimating the coefficients of the autoregressive model with minimal error dispersion , and the use of the Levinson algorithm to solve the problem of deconvolution of the observed temporarily on a number makes it possible with minimal computational cost to determine the unknown parameters of the model complex heterogeneous medium. The procedure for determining the parameters of a complex inhomogeneous medium is implemented using a linear prediction filter made in the form of an optimal lattice filter.

The current trend in the construction of underwater pipelines at great depths necessitates the use of remotely controlled underwater vehicles with installed on them, including side-scan sonars to obtain a detailed picture of the bottom. Given the limited carrying capacity of remotely controlled underwater vehicles, the proposed method for determining water depths with a side-scan sonar and a side-scan sonar make it possible to perform bathymetric surveys in deep-sea waters with the required accuracy.

The implementation of the proposed method does not present technical difficulties, since standard measuring devices (speed meter, receiver-indicator of a satellite or radio navigation system) installed on the carrier (vessel) of measuring equipment are used for its implementation, and the device for implementing the method is implemented on an accessible element base, which allows to conclude that the claimed technical solution meets the condition of patentability "industrial applicability".

Information sources.

1. Shipbuilding abroad, Edition of the Central Research Institute Rumb, 1987, pp. 76-80.

2. Stubbs A.K. Telesounding a merhod of wide swathe a depth measurement International Hydrographic Review 1974, 51 Ns 1, p. P. 23-59.

3. Patent RU No. 1829019 A1, 07.23.1993.

Claims (2)

1. A method for determining the depths of the water area with a side-scan sonar, including emitting a hydroacoustic signal to the bottom and receiving reflected signals at two points vertically at a given distance, measuring the delay time of arrival of common-mode signals, the pitch angle of the antenna carrier, and determining the directions from the received data the arrival of common-mode signals and the desired depths of the water area, characterized in that they additionally determine the coordinates of the reflecting (or scattering) layers on each cycle "radiation s-reception ", the results of measurements in neighboring cycles synchronized with the reception of the reflected signals with different frequency characteristics, in determining the angle of roll is performed consistent correction of angular and vertical displacements of each measurement cycle. 2. The side-scan sonar for determining the depths of the water area contains functionally connected first and second antennas and functionally connected a transmitting unit, a receiving-measuring unit, a control unit, a calculator and a recorder, characterized in that a pump signal driver is inserted into the transmitting unit, a compensator is inserted into the receiving-measuring unit, the transmitting unit is made in the form of a parametric radiating path with the ability to correct the phases of the amplitudes of the received signals.

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