RU2806876C1 - Method for classifying underwater object - Google Patents

Abstract

FIELD: hydroacoustics.

SUBSTANCE: method comprises emitting a probing signal by a sonar, receiving an echo signal from an object, measuring the time delay between the moment of emission and reception of the echo signal, determining distance D to the object based on the delay value and the known speed of sound propagation, and determining the immersion depth of an underwater object. Next, the angle Q° is measured, that is the direction to the underwater object in the vertical plane and the distance from the sonar to the bottom H_b is measured using the echo sounder, estimates of which are remembered during the time between the emission of the sounding signal and the reception of the echo signal. If H_b>D, then decision is made that the object is “above the bottom”. If H_b<D, then the average value of N_bavg is determined from several consecutive measurements of N_b, the calculated estimate of the depth N_bc is determined, and a decision is made that the detected underwater object is “at the bottom” for N_bc<N_bavg, and the underwater object is “above the bottom” for N_bc≥N_bavg, and the distance between the object and the bottom is determined.

EFFECT: increased probability of correct classification according to the measured parameters.

1 cl, 2 dwg

Description

The present invention relates to the field of hydroacoustics and can be used to classify an underwater object using a short-range sonar mounted on a moving underwater carrier.

The well-known work [Timoshenkov V.G. Assessing the effectiveness of classification of underwater stationary objects // Hydroacoustics Founders: Joint Stock Company “Concern “Okeanpribor”. - No. 47. - P. 5-8.], where the possibility of classifying objects into classes is shown: an object located “at the bottom” and an object located “above the bottom”. The classification is confirmed by modeling using the depth measurement method described in [Pat. No. 2350983 Russian Federation, IPC G01S 15/00. Method for determining the immersion depth of an object / V.G. Timoshenkov, A.A. Voitov; applicant and patent holder OJSC Concern Okeanpribor. - No. 2007105779/28; application 02/15/2007; published 03/27/2009, Bulletin. No. 9]. The material presented in the article by Timoshenkov V.G. is the closest analogue to the proposed method

The prototype method contains emitting a probing signal, receiving an echo signal and measuring distance D ₁ at time t ₁ , while repeating the procedure for measuring the distance to object D ₂ at time t ₁ +Δt, determining the speed of movement of the carrier V _sov and the depth of immersion of the object relative to The carrier movement horizon is determined by the formula:

, Where

, Where

D ₁ - distance to the object at time t ₁ , D ₂ - distance to the object at time t ₂ +Δt,

Nob. - object immersion depth

V _comp. - speed of movement of the sonar emitter.

In the above article, the measured depth estimate is compared to thresholds of 30 m and 50 m, which are chosen arbitrarily. Classification was carried out into classes: an object “at the bottom”, upon receiving an assessment of H less than 50 m and H less than 30 m. Otherwise, a decision was made on the object above the bottom.

The disadvantages of this method include the fact that the classification probability significantly depends on the selected thresholds, which are chosen arbitrarily and are not determined by the real standard.

As a rule, the distance D to an object is determined by a sonar regardless of the spatial position of detected objects, the class of which is unknown. Therefore, the task of measuring the depth of a detected object faces every underwater lighting sonar. All measurements are made in conditions where the position of the object is not determined. Since the slant range determined the position of the object at the slant distance, it did not answer the question of where it was “at the bottom” or “above the bottom.” If “above the bottom,” then at what distance from the bottom the object is located. The whole issue was that there was no standard that would allow us to determine the spatial position of the resulting distance estimate. The proposed technical solution eliminates this uncertainty.

The objective of the invention is to increase the probability of correct classification based on the measured parameters.

To solve the problem, a method containing emission of a probing signal by a sonar, reception of an echo signal from an object, measurement of the time delay between the moment of emission and reception of the echo signal, determination of the distance D to the object based on the delay value and the known speed of sound propagation, determination of the immersion depth of an underwater object, new features are introduced, namely, they measure the angle Q ⁰ of the direction towards the underwater object in the vertical plane, measure with an echo sounder the distance from the sonar to the bottom H _dn , during the time between the emission of the sounding signal and the reception of the echo signal, remember the estimates H _dn , if H _dn > D, then make a decision that the object “above the bottom”, if N _dn <D, then determine the average value of N _dnr from several consecutive measurements N _dnr , determine the estimated depth H _dnr using the formula H _dnr = D COS Q ⁰ , make a decision that the detected underwater object is “at the bottom » for N _dnr <N _dnsr , and for N _dnr ≥N _dnsr , the underwater object is “above the bottom”, while the distance of the object from the bottom P _ob is determined by the formula P _ob = N _dn - D COS Q ⁰ .

The technical result from the use of the proposed technical solution is to increase the reliability of classification, since classification can be carried out using a standard, which is the depth H _bottom , determined by an echo sounder with a small error.

Let us explain the achievements of the result obtained.

Sonars have long been known and developed, which make it possible to determine the depth of the sonar. These are so-called echo sounders, which are equipped with all surface and underwater vehicles.

In all short-range illumination sonars, measuring the distance along the vertical and horizontal channels determines the slant range to the detected object. The only reliable measurement is the depth of the Hdn sonar, which is measured automatically using an echo sounder. This is a well-known device that is mass-produced and installed on all ships. Depth H _bottom , measured by an echo sounder, the directional characteristic of which is located directly in the direction of the bottom, provides a measurement error of the order of 5-10 cm at shallow depths and up to 1 m at great depths [Evtyutov A.P. and others. Handbook on hydroacoustics //L.: Shipbuilding. - 1988. - p. 38.]. The echo sounder operates continuously perpendicular to the direction of movement with a high frequency of emission of the sounding signal in the direction of the bottom, therefore the measured depth values H _bottom correspond to each moment of depth change. The time between emitted echo sounder signals is significantly less than the time between emitted signals of the near-field illumination sonar, since this emission time is determined by the selected range scale. It is known that the bottom area may have some variability, therefore the resulting estimate of H _day corresponds to bottom irregularities and bottom slopes, which must be taken into account when making a decision. For this purpose, several successive estimates of the sonar depth are used, for which N _dnsr is determined

The essence of the invention is illustrated in Fig. 1, which shows a diagram that explains the procedure for solving the problem, and FIG. 2, which shows a block diagram of a device that implements the method in question.

Reliable measurement of the distance from the sonar to the bottom H _dn , measured by an echo sounder (Fig. 1), which corresponds to the leg of a right triangle, and the angle Q ⁰ , which is obtained by measuring the distance D with a sonar. However, it is not known exactly whether D is the hypotenuse of this right triangle, which must reach the bottom or only part of the hypotenuse. At this stage, a clear decision is made. If D ₁ ≤H, then the object is “above the bottom”. For further decision-making, it is necessary to determine the calculated estimate of the depth H _races from the measured distance and angle Q ⁰ and compare it with a standard, the error of which is significantly less than the error in determining the heading angle Q ⁰ and the unknown position of the estimate D. Thus, there is a fairly accurate estimate of H _dn , as the average value of the last several measurements and the calculated estimate of the depth H _dnr based on the measured distance D and the measured angle Q ⁰ . From these data, it is possible to determine the error ΔН=Н _ras -Н _day . If the calculated estimate is less than N _day , then the object is “above the bottom”. If the calculated estimate is equal to or greater than N _day , then the object is “at the bottom”.

A block diagram of a device that implements the method under consideration is shown in Fig. 2.

The sonar 1, through the distance meter 2, through the first input of the target depth determination block 3, is connected to the first input of the control and display unit 4, the output of which is connected to the input of the sonar 1. The second output of the sonar 1 is connected through the vertical angle meter block 5, through the first input of block 6 calculating the depth, through block 7 for making a decision on the class with the second input of block 3 for determining the depth of the target. The echo sounder block 8, through the block 9 for determining the average and standard H, is connected to the block 10 for determining the depth estimation error H, the second input of which is connected to the second output of the depth calculation block 6. The first output of block 10 is connected to the second input of block 7 for making a class decision, and the second output of block 10 is connected to the third input of block 3 for determining the target depth.

The proposed scheme works as follows.

From the control and display unit 4, a signal is sent to the sonar 1, which generates a sounding signal and emits it. Based on the received reflected echo signal, the distance to the detected object in block 2 and the vertical angle in block 5, along which the signal with maximum amplitude arrived, are determined. The sonar and the angle of arrival meter 5 of the echo signal are known devices that are used in the above analogues. The measured value of the angle enters block 6 for calculating the depth, the second input of which receives an estimate of the measured distance. In block 6, the depth H _{of the races} to the bottom is calculated using the measured distance D ₁ and the measured angle Q ⁰ . The resulting depth estimate H _av is sent to block 10 for determining the depth estimation error, which receives the average value of H _av and sc N _av measured from the echo sounder data of block 8. The resulting error measurements are sent to block: making a decision about class 7.

An echo sounder is a well-known device that is installed on all ships and submarines [Khrebtov A.A., Vinogradov K.A., Osyukhin B.A. Ship echo sounders //L.: Shipbuilding. - 1982. - T. 232.]. Measurement echo sounders provide depth measurement with high accuracy of the order of 5-10 cm [Evtyutov A.P. and others. Handbook on hydroacoustics //L.: Shipbuilding. - 1988]. During the emission of sounding signals by the sonar, the echo sounder manages to make several emissions to measure the depth to the bottom. As a rule, the horizontal distance of the sonar operating scale, which determines the radiation sequence, is greater than the vertical distance to the bottom. The measured estimates of successive distances to the bottom are sent to block 9 for determining the average H _avg . These procedures are known operations performed in all sonars. The resulting estimates are transmitted to block 10 for determining the depth estimation error and then to decision-making block 7, the output of which is connected to block 3, where the depth of the target is determined.

Thus, the proposed decision-making procedure allows making a decision on the class of the detected object over several emission-reception cycles.

Claims (1)

A method for classifying an underwater object by a short-range sonar installed on a moving underwater carrier, containing the emission of a probing signal by the sonar, the reception of an echo signal from the object, the measurement of the time delay between the moment of emission and reception of the echo signal, the determination of the distance D to the object based on the delay value and the known speed of sound propagation, determination immersion depth of an underwater object, characterized in that they measure the direction angle Q° to the underwater object in the vertical plane, measure with an echo sounder the distance from the sonar to the bottom H _dn , during the time between the emission of the sounding signal and the reception of the echo signal, the estimates H _dn are stored if H _dn >D , then they make a decision that the object is “above the bottom”, if N _dn <D, then determine the average value of N _dnr over several successive measurements of N _dn , determine the estimated depth N _dnr using the formula N _dnr = D COS Q°, make a decision, that the detected underwater object is “at the bottom” when N _dnr <N _dnsr , and when N _dnr ≥N _dnsr the underwater object is “above the bottom”, while the distance of the object from the bottom P _ob is determined by the formula P _ob = N _dn -D COS Q° .

Images