RU2350983C2 - Method for determination of object submersion depth - Google Patents

Abstract

FIELD: physics, measurement.

SUBSTANCE: invention is related to the field of hydraulic acoustics and may be used for measurement of object submersion depth. Method is designed for measurement of object submersion depth with application of short-range hydraulic locator installed on moving carrier relative to horizon of its motion. For this purpose in two moments of time distance to object is determined with the help of hydraulic locator, and speed of carrier motion is measured. Depth of object submersion relative to horizon, where carrier is located, is determined solving system of equations for distance to object in the first and second moments of time.

EFFECT: higher accuracy of object submersion depth measurement relative to horizon of carrier motion and simplification of method realisation.

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Description

The present invention relates to the field of hydroacoustics and can be used to measure the immersion depth of an object using a short-range sonar mounted on a moving medium relative to the horizon of movement of the medium.

Known methods for detecting an object located in the vicinity of a mobile carrier in an aqueous medium using a sonar mounted on this carrier. Using these methods allow you to detect an object, measure the distance to it and measure the direction to the object (Yakovlev AN, Kablov GP Short-range sonars. L., Shipbuilding, 1983).

This method includes: radiation of the probe signal, measuring the delay time between the emitted signal and the received echo signal from the object, determining the distance to the detected object from the value of the time delay and the known speed of sound propagation and determining the direction of arrival of the reflected signal in the horizontal direction.

However, the method does not allow to determine the immersion depth of the object. A known method for determining the depth of immersion of a target using a sonar (A.P. Stashkevich, “Acoustics of the Ocean”, Shipbuilding, Leningrad, 1966, p. 263). The method includes measuring the distance to the target and the angle determined by the direction of the directivity in the vertical plane.

The well-known "Method and device for determining the depth of an underwater object" authors SATO KAZUO and others according to patent JP 02708109 B2 dated 02/04/98 G01S 15 \ 10 HITACYI LTD, which is based on the same principle as the previous method, but the direction is determined using a scan of the directivity in the vertical plane when the probe signal is emitted by a narrow directivity.

The disadvantage of these methods is that it is necessary to know exactly the direction to the target, which is determined using a narrow directivity characteristic (XI) in the vertical plane. The result of evaluating the depth for an object is the value that is obtained when solving a right triangle by hypotenuse, which is determined by estimating the distance and angle determined by the direction of the directivity.

Such a procedure for determining the depth of immersion depends on the correctness of obtaining an estimate of the direction to the target, which depends on the width of the directivity in the vertical plane. The narrower the CN, the more accurately you can determine the direction to the target. Existing echo detection systems have a narrow directivity pattern in the horizontal plane and a wide directivity pattern in the vertical plane. The width of the directivity characteristic in the vertical plane is a finite value and in existing systems is about 20 ° at a level of 0.7 from the maximum, and therefore, the error in determining the angle will have a value of about 20 ° -25 °, since the echo can be received not in the center of the characteristic focus, and one of its edges. In this case, the total error in determining the depth can reach 50%. In addition, it should be borne in mind that even if by means of hardware costs it is possible to provide a narrow CN in the vertical plane, then target detection with a narrow directivity characteristic will be significantly more complicated.

The complexity of the formation of a narrow directivity pattern in the vertical plane and the difficulty of detecting a target with such a directivity pattern limit the possibilities of practical use of the known method.

The closest analogue is the method described in the book by A.P. Stashkevich, “Acoustics of the Ocean”, which we choose as a prototype.

The method contains the following operations:

radiation of the probe signal at time t ₁ ,

receiving an echo from an object,

measuring the time delay between the moments of radiation of the probe signal and the reception of the echo signal,

determining at time t _{1 the} distance D ₁ to the object by the value of the time delay and the known speed of sound propagation,

measuring the direction to the target in a vertical plane;

determination of the depth of immersion by the formula H = D Sin (α),

where D is the measured distance to the target,

α is the angle between the direction of movement of the carrier and the direction to the target in a vertical plane.

These shortcomings are eliminated by the fact that in the known method comprising emitting a sounding signal, receiving an echo signal and measuring a distance D ₁ at time t ₁ , additional operations are introduced, namely:

at time t ₁ + Δt repeat the procedure for measuring the distance to the object, determine the distance D ₂ to the object at time t ₁ + Δt,

determine the speed of the carrier V _sob ;

and the depth of immersion of the object relative to the horizon of movement of the medium is determined by the formula

где

Where

где

Where

D ₁ - distance to the object at time t ₁ ,

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

h _rad - the depth of immersion of the radiator,

V ² _sob - the speed of the emitter.

The technical result of the proposed method is to increase the accuracy of measuring the depth of immersion of the object relative to the horizon of movement of the medium and simplifying the implementation of the method.

Let us explain the achievement of the specified technical result.

The proposed technical solution uses estimates of the distance to the detected object, obtained from two points spaced a certain distance. This distance can be determined if the intrinsic speed of movement and the time interval between the signal emission are known. The accuracy of measuring its own speed at medium speeds does not exceed 0.2-0.5 knots. It follows that the accuracy of measuring the depth of immersion at distances of the order of 2 kilometers will be within ± 20% of the measured depth. In addition, there is no need to form a narrow directivity characteristic, scan this characteristic vertically and determine the exact angular position of the object, which greatly simplifies the implementation of the method.

The invention is illustrated in figure 1, which shows a block diagram of a device that implements the method.

A device that implements this method contains a short-range sonar 1 connected through a distance meter 2 to a computer 3, the second input of which is connected to a self-speed meter 4, and the third input to a control unit 5. The second output of block 5 is connected to the input of sonar 1, and the third output with a 2 distance meter.

Using the proposed device, the method is as follows.

Sonar 1 emits sounding signals at time t ₁ , receives the echo signal reflected from the object, which enters the distance meter 2. In meter 2, the distance to the object D ₁ is determined by the delay time between the emitted signal and the received signal and the known speed of sound propagation. The measured distance estimate D ₁ at time t ₁ enters the calculator 3. The ship's own speed log lag 4 measures the speed of the carrier, the value of which goes to the second input of the calculator 3. When the next package is emitted by sonar 1, a subsequent distance measurement is made at the next time, and the distance D ₂ corresponding to the time t ₁ + Δt is determined. From the difference of the radiation times Δt, the measured estimates of the distance D ₁ and D ₂ estimates of the own speed V in the calculator 3 determine the distance traveled V Δt by the sonar carrier 1 between packages, the system of 2 equations is solved

from which we can obtain the estimate ΔD, the knowledge of which allows us to calculate the desired immersion depth of the location object relative to the carrier:

Where

The accuracy of measuring the depth of immersion is determined by the time of measuring the distance and the accuracy of measuring the carrier’s own speed. As a rule, the accuracy of distance measurement is determined by the resolution of the probing signal used and is about 1-2 meters. The accuracy of measuring its own speed at medium speeds does not exceed 0.2-0.5 knots. It follows that the accuracy of measuring the depth of immersion at distances of about 2 kilometers will be within ± 20% of the measured depth. If the immersion depth of the object is small, then the relations between D ₁ and D ₂ will differ only by the value of V Δt. Short-range sonar (short-range lighting) is characterized by the use of short-duration signals or complex signals that have good distance resolution. The range of short-range sonar is limited to distances of several kilometers. As a rule, at these distances the multipath propagation does not have a significant effect.

Thus, the proposed method allows to increase the accuracy of measuring the depth of the object relative to the horizon of movement of the carrier on which the sonar is mounted, and to simplify the implementation of the method, since there are no requirements for the width and accuracy of forming the directivity characteristics of the sonar antenna of the sonar in the vertical plane in this method. This allows us to consider the claimed technical result achieved.

Claims (1)

A method for determining the immersion depth of an object using a sonar mounted on a movable medium relative to the horizon of movement of the medium, containing the radiation of the sounding signal at time t ₁ , receiving an echo from the object, measuring the time delay between the moments of radiation of the sounding signal and receiving an echo, determining at a time t ₁ distance D ₁ to the object in the direction of arrival of the reflected signal in terms of the time delay and the known speed of sound propagation, differing in those m, that at time t ₁ + Δt, repeat the procedure for determining the distance to the object and find the distance D ₂ to the object at time t ₁ + Δt, measure the speed of the carrier V; and the depth H of immersion of the object relative to the horizon of movement of the medium is determined by the formula

Where