RU2796238C1 - Method for measuring target strength on a scale model - Google Patents

Abstract

FIELD: hydroacoustics.

SUBSTANCE: hydroacoustic measurements, used to measure the magnitude of the target strength (TS) of underwater objects (UO) on their scale models.

Calibration of the receiving-emitting path is carried out in two stages, namely, at the first stage, the amplitude of the signal reflected from the standard is determined; at the second stage, the signal amplitude is measured by an additional receiver installed above the scale model at a distance equal to the vertical size of the scale model; then, by adjusting the gain of the receiving path, equality of the amplitudes of the signals measured by the additional receiver and reflected from the standard is achieved, then, in the measurement process, the difference between the measured amplitudes of the signals of the additional receiver and the standard obtained during calibration is determined; then the current value of the amplitude of the signal reflected from the reference is determined; next, the amplitude of the signal reflected from the scale model is measured; then the equivalent radius is determined; then the magnitude of the target strength is determined by the formula

EFFECT: improving the accuracy of the results of measuring the magnitude of the target force of an underwater object.

1 cl, 3 dwg

Description

The present invention relates to the field of hydroacoustics, namely, hydroacoustic measurements and can be used to measure the magnitude of the target force (SC) of underwater objects (PO) on their scale models.

The magnitude of the sonar reflection from an underwater object is estimated by the strength of the target, defined as the ratio of the amplitude of the signal reflected from the underwater object to the amplitude of the signal reflected from the standard. Also in domestic technical literature, the value of the equivalent radius R _eq is often used, determined by the ratio of the amplitude of the signal reflected from underwater objects - A _m , to the value of the amplitude of the signal reflected from a sphere with a radius

A known method of measuring the strength of the target scale model of an underwater object, described in the monograph (V.P. Peresada "Radar visibility of marine objects" State Union Publishing House of the shipbuilding industry, Leningrad, 1961, p. 98). In this method, the measurement of the target force of underwater objects is performed by comparing the amplitudes of the signals reflected from the scale model of the underwater object - A _m and the standard - A _floor . A metal sphere is most often chosen as a standard. Measurement of the amplitude of the reflected signal from the standard is performed at the stage of equipment calibration before and after the end of each series of experiments.

The disadvantage of this method is the need to measure the standard before and after measurements and, as a result, the accuracy of the results obtained is reduced due to changes in hydrological conditions during the measurement process.

As the closest prototype, a method for measuring the magnitude of the target strength of an underwater object, described in the book (G.V. Abramov "Fundamentals of hydroacoustic modeling", Saratov University Publishing House, 1976, p. 13) was adopted. According to this method, to determine the target strength of a scale model of an underwater object, before and at the end of each series of measurements, the transceiver path is calibrated using the amplitude of the signal reflected from the standard - A _floor . To do this, the model is removed from the rod, and a reference reflector is installed in its place. Measurements are made of the amplitude of the signal A _floor reflected from the standard. By comparing the amplitudes of the signals obtained as a result of measurements, reflected from the model of the underwater object - A _m and the standard - A _et , the magnitude of the target strength is calculated.

In the known method, measurements of the reference signal are performed with a long time interval between the beginning and end of a series of experiments, including measurements of the amplitudes of reflected signals from an underwater object at different durations of probing signals, various types of probing signals (tonal, complex), as well as in multistatic and bistatic radiation modes and reception.

The disadvantage of the prototype is that during the time between two successive series of measurements lasting 5-6 hours, the amplitude of the signals reflected from the standard received by the receiver as a result of calibration before and after the end of the measurement series differ by 3-4 dB. The reason for the change in the amplitudes of the reference signals between two adjacent series of measurements is the change in the speed of sound with depth in the measurement area and, as a result, the change in the amplitudes of the signals reflected from the measured underwater object (V.B. Zhukov "Modern technologies in the field of hydroacoustic antennas." Collection "Actual problems of piezoelectric instrumentation and nanotechnology" - Proceedings of NKTB "Piezopribor" Rostov State University, 2016). Such a significant change in signal amplitudes when measuring the target strength of an underwater object on its scale model significantly reduces the accuracy of the measurement results.

The technical result of the invention is to increase the accuracy of the measurement results of the magnitude of the target force of an underwater object.

The technical result is achieved due to the fact that in the method of determining the target strength of underwater objects on their scale models, which consists in irradiating the standard and the scale model with a probing signal, receiving the reflected signal amplitudes from the standard and the scale model and determining the target strength, it has the following differences: - the radiating path is carried out in two stages, namely, at the first stage, the amplitude of the signal _And reflected from the standard is determined; at the second stage, the signal amplitude A _pr is measured by an additional receiver installed above the scale model at a distance equal to the vertical size of the scale model; then, by adjusting the gain of the receiving path, equality of the amplitudes of the signal measured by the additional receiver A _pr and reflected from the standard A _et is achieved, then in the measurement process, the difference between the measured signal amplitudes ΔA _et of the additional receiver and the standard obtained by calibrating according to the formula is determined:

then the current value of the amplitude of the signal reflected from the standard is determined by the formula:

далее определяется величина силы цели по формуле:then the equivalent radius is determined by the formula:

then the magnitude of the target strength is determined by the formula:

Where:

ΔΑ _et - the value of the difference between the measured amplitudes of the signals of the additional receiver and reflected from the standard;

And _et - the amplitude of the signal reflected from the standard;

A _pr - signal amplitude measured by an additional receiver;

R _eq - equivalent radius;

A _m is the amplitude of the signal reflected from the scale model of the underwater object;

And _e - the current value of the amplitude of the signal reflected from the standard;

SP - target strength.

The essence of the invention is illustrated by drawings, where in Fig. 1 shows the scheme for measuring the amplitude of the signal reflected from the standard; in fig. 2 is a scheme for measuring the target strength of a scale model; in fig. 3 shows a graph of the change in the speed of sound with depth with a time interval of 6 hours between successive measurements,

Where:

1 - floating laboratory;

2 - electronic unit;

3 - acoustic signal receiver;

4 - acoustic signal emitter;

5 - lifting - turning device;

6 - standard;

7 - scale model of an underwater object;

8 - additional receiver installed above the model;

9 - time interval morning;

10 - evening time interval.

The device for determining the magnitude of the target force includes a floating laboratory 1 containing an electronic unit 2 connected to a receiver 3 and an emitter 4 (Fig. 1), a receiver 3 and an emitter 4 installed at a predetermined depth, as well as a lifting and turning device 5 for installation standard 6 and scale model 7 with an additional receiver 8 installed above it and connected to the electronic unit 2. (see Fig. 2). Receiver 3, transmitter 4, reference 6, and scale model 7 are set to the same depth.

Initially, in the proposed method for determining the magnitude of the target strength of a scale model of an underwater object, the receiving-radiating path (not shown in the drawing) of the electronic unit 2 is calibrated in two stages:

At the first stage, with the help of the lifting-turning device 5, the standard 6 is installed. The acoustic signal receiver 3 measures the amplitude of the signal emitted by the emitter 4 and reflected from the standard 6 - And _floor . The received amplitude of the signal A _floor reflected from the standard 6 is fed to the input of the electronic unit 2 installed on the floating laboratory 1.

After that, the standard 6 is removed with the help of the lifting-turning device 5.

At the second stage, with the help of a lifting and turning device 5, a scale model 7 is installed at the same depth as the standard 6, above which an additional receiver 8 is installed at a distance h _pr equal to the vertical size of the model 4 h _m . Further, an additional receiver 8 measures the amplitude of the signal A _pr radiated by the emitter 4.

The measured amplitude of the signal A _CR from the receiver 8 is fed to the input of the electronic unit 2, installed on the floating laboratory 1, and compared with the amplitude of the signal reflected from the reference 6 And _floor .

By adjusting the gain of the receiving path (not shown in Fig.) of the electronic unit 2, equality of the amplitudes of the signal received by the additional receiver 8 and the signal reflected from the standard 6 and received by the receiver 3 A _et =A _pr at the first stage of calibration is achieved.

Further, in the process of measurement, the receiver 3 measures the amplitude of the signal A _m emitted by the emitter 4 and reflected from the scale model 7, at the same time, the additional receiver 8 measures the amplitude of the signal emitted by the emitter 4 - A _pr . When changing the amplitude of the signal And _CR is determined by the difference between the current value of the amplitude of the signal And _CR and the amplitude of the signal A _floor .

Where:

And _et - the amplitude of the signal reflected from the standard;

A _pr is the amplitude of the signal measured by an additional receiver.

Due to the fact that the additional receiver 8 measures the amplitude of the signal A _pr that has passed the distance from the emitter 4 to the additional receiver 8, and the receiver 3 measures the amplitude of the signal A _et that has passed the distance from the emitter 4 to the reference 6 and back, then the value of the difference ΔA _et increases by 2 times and the current value of the reference signal is formed.

Where:

And _e - the current value of the amplitude of the signal reflected from the standard;

This amplitude of the reference signal A _e is used in determining the magnitude of the target force. When changing the acoustic-hydrological conditions of measurement, they will be automatically taken into account by the value of A _e .

Equivalent radius R _equiv is determined by the formula

Where:

A _m is the amplitude of the signal reflected from the scale model of the underwater object;

And _e - the current value of the amplitude of the signal reflected from the standard;

SP - target strength.

The magnitude of the target strength is determined by the formula

Where:

SP - target strength.

When performing measurements, knowledge of the sensitivity of the receivers 3 and 8 is not required. The sensitivity of the receiver 8 is calibrated in the process of equating the amplitudes of the signals A _CR and the signal reflected from the standard A _floor . Sensitivity equalization is achieved by the fact that the signal reflected from the standard 6 and model 7 are received by one receiver 3.

As can be seen from FIG. 3, the depth distribution of sound velocity with a time interval of 8 hours (morning-evening) has changed significantly. As a result of refraction (rotation) of the beams, the amplitude of the signal irradiating the model and the reference sphere change by ΔА. If the measurements of the amplitudes of the signals from the sphere A _floor and the model A _m are performed simultaneously, then changes in the amplitude of the irradiation signal will not lead to an error in determining the value of the target force. In the case of measurements of the values of A _et and A _m at different times, there will be an error in calculating the magnitude of the target force, because measurements of the amplitudes of the signal reflected from the standard A _et and the signal reflected from the scale model of the underwater object A _m are performed at different times.

Thus, due to the fact that the calibration of the receiving-emitting path is carried out in two stages and at the second stage an additional receiver is installed above the scale model; and also by taking into account the change in the amplitude level incident on the scale model of the signal throughout the experiment, an increase in the accuracy of measuring the target force value due to changes in hydrological conditions during the measurement process is achieved.

Claims (13)

A method for determining the target strength of underwater objects on their scale models, which consists in irradiating the standard and the scale model with a probing signal, receiving the reflected signal amplitudes from the standard A _et and the scale model A _m and determining the target strength, characterized in that the calibration of the receiving-radiating path is carried out in two stages, namely the first stage is determined by the amplitude of the signal A _floor reflected from the standard; at the second stage, the signal amplitude A _pr is measured by an additional receiver installed above the scale model at a distance equal to the vertical size of the scale model; then, by adjusting the gain of the receiving path, equality of the amplitudes of the signals measured by the additional receiver A _pr and reflected from the standard A _et is achieved, then in the measurement process, the difference between the measured signal amplitudes ΔA _{et of} the additional receiver and the standard obtained during calibration is determined by the formula

, then the current value of the amplitude of the signal reflected from the reference is determined by the formula

, then the equivalent radius is determined by the formula

, then the value of the target strength is determined by the formula

, where ΔA _et - the value of the difference between the measured amplitudes of the signals of the additional receiver and reflected from the standard; And _et - the amplitude of the signal reflected from the standard; A _pr - signal amplitude measured by an additional receiver; R _eq - equivalent radius; A _m is the amplitude of the signal reflected from the scale model of the underwater object; And _e - the current value of the amplitude of the signal reflected from the standard; SP - target strength.

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