RU2650839C1 - Low-frequency vector acoustic receiver - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention is a low-frequency vector acoustic receiver the inertial mass of which is common for the three recording channels and is connected to three molecular-electronic converters and three feedback elements. At least one of the feedback elements is an electrodynamic system of interacting conductors with current and magnet, combined with a hydraulic amplifier, increasing the impact on the inertial mass.

EFFECT: improved data accuracy.

6 cl, 7 dwg, 1 tbl

Description

Measurement of low-frequency acoustic signals in the aquatic environment is one of the most important ways to monitor the movement of surface and submarine vessels, marine fauna objects, obtain information about the structure of the seabed (seismic exploration), and detect natural and man-caused, including dangerous, phenomena in the aquatic environment that are accompanied by acoustic effects, etc.

To measure sonar signals developed many technical means. The most common are hydrophones of various designs [RF Patent 2368099, RF Patent 2393643, RF Patent 2392767, US Patent 6549488]. Regardless of the technology used to create the hydrophones, the ability to measure weak signals using hydrophones is limited by the level of recorded noise that is not related to the useful signal and represents noise in terms of measurement processes. One way to improve the signal-to-noise ratio is to use a vector (combined) signal reception method (A. Nehorai & E. Paldi, "AcousticVectorSensorArrayProcessing," IEEETransactionsonSignalProcessing, vol. 42, no. 9, p. 2481-2491, September 1994.) . In this case, not only the pressure in the acoustic wave is recorded, as in the case of a hydrophone, but also the vector component — the particle velocity in the medium. An accelerometer is most often used to measure particle velocity. As a result, during processing, it is possible to separate the signals in the direction of polarization of particle motion, and hence in the direction of wave arrival at the receiving point. Thus, it is possible to locate the signal source and, in addition, increase the signal-to-noise ratio, since it becomes possible, by analyzing polarization, to isolate signal components related to well-defined directions of wave arrival. A similar technical effect is achieved when instead of a triaxial sensor an accelerometer is used - a triaxial pressure gradient sensor.

A number of technical solutions are known for the instrumental implementation of the vector signal registration method. Most of them are based on the use of piezoelectric transducers.

Thus, a three-component piezoelectric sensor is known, which is three one-component sensors combined in one housing. This is a complex and expensive device with significant weight and dimensions [ed. St. N 1057910]. In addition, a three-component piezoelectric seismometer is known that contains three pairs of piezoelectric elements, the sensitivity axes of which are located in three mutually perpendicular directions, an inertial mass centering system with pushers and springs. This device is difficult to manufacture and when configured, unstable in operation, has low measurement accuracy (ed. St. N 397868).

To reduce the dimensions of the device and simplify the design, a three-component piezoelectric acceleration sensor is proposed, containing a housing, a liquid inert mass, in this device piezoelectric plates are arranged in pairs normal to three orthogonal axes, limiting the cavity filled with liquid under pressure (ed. St. N 188767).

A method for expanding the temperature and frequency ranges is proposed for a three-component Vinfranco-low frequency piezoelectric acceleration sensor [RF Patent 2129290], a housing containing a liquid inert mass is used and piezoelectric transducers are placed along the normals to three orthogonal axes, temperature compensators are introduced, and the liquid inert mass is inert, and the liquid is inert in mass made in the housing along three orthogonal axes, each cavity being bounded on one side by a piezoelectric transducer, yaschim of the piezoelectric element mounted on the membrane and on the opposite - temperature compensator, formed as a resilient member.

To reduce the lateral sensitivity of a vector acoustic receiver, a digital method for its compensation is proposed (RF Patent 2509320).

In any case, the above technical solutions do not imply the introduction of feedback, and therefore do not provide high measurement accuracy. In addition, the piezoelectric transducers used in the considered devices are characterized by sufficiently high low-frequency noise.

The lowest noise during measurements in the low-frequency region is provided by accelerometers built using a capacitive-type converting element (Sercel 508XT Brochure (English). Available online: http://www.sercel.com/products/Lists/ProductSpecification/508XT_brochure_Sercel.pdf, KinemetricsEpiSensorensi ES-T Force Balance Accelerometer Datasheet. Available online: http://www.kinemetrics.com/uploads/PDFs/ES-T%20Datasheet.pdf, CMG-5T Strong Motion Feedback Accelerometer. Availableonline: http: //www.guralp .com / documents / DAS-050-0001.pdf). Such accelerometers are built on the principle of force compensation of external influences using electrodynamic feedback and are known as force-balanced accelerometers in the English literature. Devices belong to the category of precision mechanics and their disadvantages include a very high cost price, as well as insufficient mechanical strength with respect to shock and vibration. Known methods of using such sensors in vector acoustic receivers, however, this approach is not widespread due to these disadvantages.

A converter based on the principles of molecular electron transfer (electrochemical accelerometer) (Lidorenko N.S., Ilyin B.I., Zaydenman I.A. et al. Introduction to molecular electronics 1984. 320 pp., N. Huang, V. Agafonov, and N. Yu, "Molecular electric transducers as motion sensors: A review", Sensors (Switzerland), vol. 13, no. 4, p. 4581-4597, 2013), like capacitive, provides high conversion efficiency in the low frequency range . At the same time, the advantages of such sensors are significantly greater mechanical strength.

A low-frequency vector acoustic receiver based on the principles of molecular-electron transfer is presented in the inventions (RF Patent, 2128850, RF Patent for Utility Model 53459) and is the closest analogue of the claimed invention. This device includes three transducers located in common or separate casings, each transducer being a hollow casing sealed at both ends with elastic elastic membranes and filled with an electrochemical redox system. The internal volume of the hollow body is divided into two compartments connected by a channel. The channel contains a system of four electrodes for converting the fluid flow into an electrical signal.

The disadvantages of this solution are the large enough volume needed to accommodate all three converters, and the low conversion accuracy associated with the absence of a feedback mechanism in the device.

Finally, we note that based on molecular-electronic transducers, pressure gradient sensors can be built (V.G. Dmitriev. Experience in the construction and study of a combined acoustic antenna. Acoustic journal. 2013, vol. 59, No. 4, pp. 494-501, RF patent 2403684).

Thus, the main disadvantages of the known technical solutions used to create a low-frequency acoustic receiver of the vector type are excessive noise at low frequencies, large dimensions and low measurement accuracy. The last drawback is associated with the lack of elements in the design that form the feedback signal. It is known that the use of negative feedback makes it possible to improve a number of characteristics of the converter, which directly affect the accuracy of measurements carried out with its help. Such characteristics include the working bandwidth, dynamic range, temperature and time stability of the output parameters.

The task of the invention is the creation of a low-frequency vector acoustic receiver, which eliminates the noted drawbacks.

The solution to the problem is achieved in that in a low-frequency vector acoustic receiver, the inertial mass of which is common to three recording channels and connected to three molecular-electronic transducers and three elements forming feedback, at least one of the feedback elements is an electrodynamic system of a conductor interacting with each other with a current and a magnet, combined with a hydraulic booster that increases the effect on the inertial mass. The total inertial mass is a solid attached to the membranes of three molecular electronic converters, and the specified hydraulic booster is a chamber filled with liquid and bounded on both sides by membranes of different sizes, with the larger side of the membrane connected to the specified inertial mass, and the smaller to the coil of the electrodynamic system.

The total inertial mass is a liquid connected by channels to the working volumes of three molecular-electronic converters, and the specified hydraulic booster consists of a pair of electrodes in a magnetic field placed in a channel through which fluid flows under the action of inertia forces, and the cross section of the specified channel in the region where the interaction of the current flowing between the electrodes with the magnetic field is much smaller than the cross section of the rest of the channel.

In special cases of execution, the low-frequency vector acoustic receiver is characterized by the following: placed in a sealed enclosure; suspended on a soft elastic suspension on a support with a base fixed on the seabed; suspended on a soft elastic suspension on a support with a base frozen in ice cover.

To reduce the intrinsic noise, a molecular-electronic converting element with a significant attached inertial mass is used, since it is known that the amplitude of the inertial mass displacements associated with random, Brownian type motion decreases with increasing inertial mass. The inertial mass may be in the form of a solid or liquid.

To reduce the dimensions, it is proposed to use the inertial mass common to all three measuring channels. This design can significantly reduce the weight and dimensions of the proposed measuring device.

An increase in inertial mass requires the creation of a large effort from the feedback side, compensating for the action of inertia forces:

When using a solid-state inertial mass, a feedback mechanism is used, consisting of interacting coils and a magnet. The coil is attached to the inertial mass, and the magnet is attached to the receiver body. The magnitude of the effort created by such a system can be determined by the formula:

раз, где S₁ и S₂ - площади большей и меньшей мембран, соответственно.where B is the magnetic field, I is the current in the coil, A is a coefficient that increases with the number of turns in the coil, which also depends on the geometry and relative position of the coil and magnet. Thus, with a fixed magnetic field, an increase in the force requires an increase in the current flowing through the coil or in the number of turns in the coil (hence, the resistance of the coil). In any of these cases, power consumption increases. Therefore, in the proposed technical solution, the electrodynamic device for creating a feedback signal is proposed to be supplemented with a hydraulic booster consisting of a liquid chamber bounded on both sides by membranes of different diameters, with a large membrane connected to an inertial mass, and a smaller one to the coil of the electrodynamic device. In this case, the hydraulic booster provides an increase in the impact from the side of the electrodynamic device in

times, where S ₁ and S ₂ are the areas of the larger and smaller membranes, respectively.

When using a liquid inertial mass, the fluid flow through the converting molecular-electronic element is determined by the pressure drop created by the inertia forces:

where L is the length of the liquid column in the direction of action of inertia forces.

The compensating force on the feedback side is provided by a magnetohydrodynamic cell, consisting of a pair of electrodes located on opposite sides of the channel through which the working fluid flows under the action of inertia forces. When a feedback signal is generated, an electric current is passed through the electrodes, the magnitude of which is proportional to the output current of the molecular-electronic converter. The intersection of the streamlines and the specified channel is in a magnetic field perpendicular to the plane containing the streamlines and the axis of the specified channel. In this case, the compensating pressure difference from the feedback mechanism is:

раз.where S _mhd is the cross-sectional area of the channel in the region where the interaction of the electric current flowing between the electrodes of the magnetohydrodynamic cell and the magnetic field occurs. Thus, to increase the compensating pressure differential, the region of the channel adjacent to the magnetohydrodynamic cell must be made in the form of a narrowing in the channel, which provides an increase in the compensating effect in

time.

The invention is illustrated by drawings.

FIG. 1. The block diagram of the invention.

FIG. 2. Photograph (example implementation) of the invention.

Fig 3. A schematic representation of a low-frequency vector acoustic receiver with a liquid inertial mass.

FIG. 4. Schematic illustration of a feedback signal amplifying device for use in a low-frequency vector acoustic receiver with a liquid inertial mass.

Fig 5. The structure of the channels inside the magnetohydrodynamic cell for an example implementation of the invention.

FIG. 6. Schematic representation of a low-frequency vector acoustic receiver with a solid inertial mass.

FIG. 7. Schematic representation of a feedback signal amplifying device for use in a low-frequency vector acoustic receiver with a solid inertial mass.

An example implementation of the invention.

A block diagram of an implementation is shown in FIG. one.

A practical implementation example of the invention is shown in FIG. 2 and structurally corresponds to the circuit shown in FIG. 3. In this implementation, the receiver has the form of a three-dimensional cross, in the center of which is a chamber 1 with a total liquid inertial mass. In the protruding parts of the cross, lateral liquid chambers 2 are arranged, in which one magnetohydrodynamic cell 3 is placed. Each such chamber is connected by a channel 4 to the central chamber, and on the outside it is closed by a flexible rubber membrane 5 deformed by the inertia forces acting on the liquid.

The structure of the channels inside the magnetohydrodynamic cell is shown in FIG. 4 and 5. The channels 6 have a circular cross section, the diameter of the narrow part is 1 mm, the main part is 3 mm. This provides a nine-fold gain of the feedback signal. The magnet 7 is adjacent to the walls of the channel, the electrodes 8 of the cell are located on the sides of the channel (Fig. 5). Molecular-electronic transducer 9 is placed in the channel between the Central chamber and one of the side. The electronic board converts the output currents of the molecular-electronic converter into voltage, frequency correction, feedback closure, and filtering the output signal.

Due to the long length of each of the three channels filled with liquid and oriented along the sensitivity axes of the sensor, bounded on both ends by flexible membranes, the developed design ensures, according to formula (3), a large pressure drop across the converting element, which means high sensitivity and low noise. A significant part of the channels falls on the total inertial mass, which reduces the dimensions of the device. The narrowing in the channel of the magnetohydrodynamic cell ensures the effective operation of deep negative feedback in a wide frequency and dynamic ranges.

The main technical characteristics of the converter are given in table 1.

Another embodiment is illustrated in FIG. 6. Here, the total inertial mass 10 is connected to the large hydraulic booster membranes 11. A feedback mechanism drive consisting of a coil 12 and a magnet 13 is connected to the smaller hydraulic booster membranes. The inertial mass is connected to the large membranes by means of suspensions 14. The whole structure is fixed to the receiver body 15.

Claims (6)

1. A low-frequency vector acoustic receiver, the inertial mass of which is common to three recording channels and is connected to three molecular-electronic transducers and three elements forming feedback, characterized in that at least one of the feedback elements is an electrodynamic system of interacting between a conductor with a current and a magnet, combined with a hydraulic booster that increases the effect on the inertial mass. 2. The low-frequency vector acoustic receiver according to claim 1, characterized in that the total inertial mass is a solid body attached to the membranes of three molecular-electronic converters, and said hydraulic booster is a chamber filled with liquid and bounded on both sides by membranes of different sizes, moreover, the larger side of the membrane is connected to the indicated inertial mass, and the smaller to the coil of the electrodynamic system. 3. The low-frequency vector acoustic receiver according to claim 1, characterized in that the total inertial mass is a liquid connected by channels to the working volumes of three molecular-electronic converters, and said hydraulic amplifier consists of a pair of electrodes in a magnetic field placed in a channel through which the fluid flows under the action of inertia forces, and the cross section of the specified channel in the region where the interaction of the current flowing between the electrodes with the magnetic field is much smaller transversely section of the rest of the channel. 4. The low-frequency vector acoustic receiver according to claim 1, characterized in that it is placed in a sealed enclosure. 5. The low-frequency vector acoustic receiver according to claim 4, characterized in that it is arranged to be suspended by a soft elastic suspension on a support with a base fixed on the seabed. 6. The low-frequency vector acoustic receiver according to claim 4, characterized in that it is arranged to be suspended by a soft elastic suspension on a support with a base frozen into the ice sheet.

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