An underwater acoustic measurement device and method based on angular motion

Abstract

The present invention discloses an underwater acoustic measurement device and method based on angular motion. The steps of the method include: 1) placing an inertial body in the water area to be measured, and respectively arranging an angular motion sensor on one or more surfaces of the inertial body for measuring the angular acceleration β in the corresponding direction of each surface when the inertial body is disturbed by water flow; the inertial body is an inertial cube with a mass of m and a side length of L; 2) when the inertial body is disturbed by water flow, each of the angular motion sensors respectively sends the measured angular acceleration β in the corresponding direction to the data processing unit; 3) the data processing unit calculates the corresponding underwater acoustic pressure difference ΔP according to #imgabs0#. The present invention completes the sensing of underwater acoustic based on the angular motion of the inertial body, has high sensitivity to underwater acoustic, and breaks through the problems existing in the existing sensors for observing underwater acoustic based on the deformation of the inertial body, such as inconsistent responses in each direction and relatively high low-frequency self-noise level.

Description

Technical Field

[0001] The present invention relates to an underwater acoustic measurement device and method based on angular motion, which can be used in the field of underwater acoustic observation, and can be applied to fields such as underwater vibration monitoring and ground acoustic observation. Background Art

[0002] Underwater acoustic observation can obtain the kinematic characteristics of water bodies, so as to directly obtain hydrological information or indirectly obtain information on underwater vibration sources. Underwater acoustic observation technology is widely used in military monitoring, biological observation, and ship monitoring.

[0003] The physical quantity measured by underwater acoustics is generally the underwater acoustic pressure difference. The existing underwater acoustic measurement principle is essentially that the pressure difference generated by underwater acoustic vibration drives the inertial body inside the sensor to deform, and this deformation of the inertial body is observed through a certain measurement technology to obtain the underwater acoustic pressure difference. Currently, interferometric fiber optic hydrophones, piezoelectric hydrophones, and MEMS piezoelectric hydrophones all belong to this type. However, the hydrophones manufactured based on this principle have directivity, that is, they have inconsistent responses in different directions, and the low-frequency self-noise level is relatively high, making it difficult to achieve high-sensitivity low-frequency underwater acoustic detection. Summary of the Invention

[0004] The present invention provides an underwater acoustic measurement device and method based on angular motion. The complete forms of medium motion include translational motion, rotational motion (angular motion), and deformation. In traditional underwater acoustic measurement, only deformation is used for underwater acoustic sensing. The present invention proposes to use angular motion to complete underwater acoustic sensing.

[0005] Figure 1 is the schematic diagram of underwater acoustic measurement based on angular motion, where the inertial cube is used to sense underwater acoustic signals, L is the side length, and the inertial cube generates angular motion under the action of underwater acoustic signals. For the Figure 1 inertial cube in water shown, its moment of inertia is:

[0006]

[0007] where m is its mass and L is its side length.

[0008] When the inertial cube is disturbed by water flow, the angular motion of the water flow will cause an equivalent rotational force ΔF to exist on the paired faces of the inertial cube, thereby generating an inertial rotational torque

[0009] According to the law of rotation:

[0010]

[0011] where β represents the angular acceleration of angular motion.

[0012] Considering the relationship between the pressure difference ΔP and the rotational force, it can be obtained that:

[0013]

[0014] Through the above formula, the pressure difference of underwater sound can be observed by measuring the angular acceleration of angular motion, and underwater sound measurement can be realized.

[0015] The technical solution of the present invention is as follows:

[0016] An underwater sound measurement method based on angular motion, the steps of which include:

[0017] 1) Place an inertial body in the water area to be measured, and respectively set an angular motion sensor on one or more surfaces of the inertial body for measuring the angular acceleration β in the corresponding direction of each surface when the inertial body is disturbed by water flow; the inertial body is an inertial cube, and the mass of the inertial cube is m and the side length is L;

[0018] 2) When the inertial body is disturbed by water flow, each of the angular motion sensors respectively sends the measured angular acceleration β in the corresponding direction to the data processing unit;

[0019] 3) The data processing unit calculates the corresponding underwater sound pressure difference ΔP according to

[0020] Furthermore, an angular motion sensor is respectively set on three orthogonal surfaces of the inertial cube for respectively measuring the angular acceleration β in three orthogonal directions.

[0021] Furthermore, the angular motion sensor is realized by an interferometric fiber optic gyro based on the Sagnac effect; by taking the derivative of the Sagnac phase shift φ measured by the interferometric fiber optic gyro based on the Sagnac effect, and through the angular acceleration β is obtained; then through the underwater sound pressure difference ΔP is obtained; where, the length of the fiber optic loop in the interferometric fiber optic gyro is T, the diameter of the fiber optic loop is D, γ represents the light wavelength in vacuum, and c represents the speed of light in vacuum.

[0022] Furthermore, the angular motion sensor is an angle sensor, an angular velocity sensor or an angular acceleration sensor.

[0023] An underwater sound measurement device based on angular motion, characterized in that it includes an inertial body, several angular motion sensors and a data processing unit;

[0024] An angular motion sensor is respectively set on one or more surfaces of the inertial body for measuring the angular acceleration β in the corresponding direction of each surface when the inertial body is disturbed by water flow; the inertial body is an inertial cube, and the mass of the inertial cube is m and the side length is L;​

[0025] The described data processing unit is used to calculate the underwater acoustic pressure difference ΔP in the corresponding direction according to

[0026] Compared with the prior art, the positive effects of the present invention are as follows:

[0027] The present invention completes the sensing of underwater acoustics based on the angular motion of the inertial body and has high sensitivity to underwater acoustics. The sensor implemented based on the present invention can overcome the problems existing in the existing sensors for observing underwater acoustics based on the deformation of the inertial body, such as inconsistent responses in different directions and relatively high low-frequency self-noise levels. The present invention can achieve measurement based on the Sagnac effect, which is insensitive to translational motion and suppresses the influence of other motion forms; the Sagnac effect has no directivity in its sensitivity to angular motion and has the same response in different directions, which can solve the problem of non-uniform directivity in current underwater acoustic measurements; the use of the fiber optic Sagnac interferometer can increase the sensitivity by increasing the fiber length and loop diameter, and can obtain the low self-noise characteristics in the full frequency band, meeting the requirements of high stability and high sensitivity for underwater acoustic measurements. Description of the Drawings

[0028] Figure 1 FIG. is the schematic diagram of underwater acoustic measurement based on angular motion.

[0029] Figure 2 FIG. is the flowchart of underwater acoustic measurement based on angular motion.

[0030] Figure 3 FIG. is the schematic diagram of the implementation of underwater acoustic measurement based on angular motion. Detailed Embodiment

[0031] The present invention will be further described in detail below with reference to the drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0032] Figure 2 FIG. is the flowchart of underwater acoustic measurement based on angular motion. The underwater acoustic signal drives the inertial body to generate angular motion. The angular motion is measured by angular motion sensors (including angle sensors, angular velocity sensors, angular acceleration sensors, etc.) and converted into an underwater acoustic pressure difference, thereby completing the underwater acoustic measurement. For example, if an angle sensor is used, the angular acceleration can be obtained by taking the second derivative of time after measuring the angular quantity of the angular motion; if an angular velocity sensor is used, the angular acceleration can be obtained by taking the first derivative of time after measuring the angular velocity quantity of the angular motion. The angular acceleration is converted into an underwater acoustic pressure difference through Equation (3), thereby completing the underwater acoustic measurement.

[0033] Figure 3 ​Schematic diagram for implementing underwater acoustic measurement based on angular motion. On each of the three orthogonal faces of an inertial cube architecture, an angular motion sensor (including angle sensor, angular velocity sensor, angular acceleration sensor, etc.) is installed to sense the corresponding directional angular motion generated by the inertial cube architecture under the action of underwater acoustic signals. The monitoring value of the angular motion sensor is used to obtain the underwater acoustic pressure difference in this direction through the aforementioned method.

[0034] Among them, the underwater acoustic pressure differences in the corresponding measurement directions are obtained by angular motion sensors in different directions; the underwater acoustic pressure differences in three orthogonal directions are obtained by three angular motion sensors arranged orthogonally; the angular motion sensor can be implemented by an interferometric fiber optic gyro based on the Sagnac effect. In an interferometric fiber optic gyro, generally, a relatively long fiber is wound into a fiber loop to make it the core sensing component to sense angular motion. If the length of the fiber loop is T and the loop diameter is D, the expression of the Sagnac phase shift φ can be written as:

[0035]

[0036] where λ represents the optical wavelength in vacuum, c represents the speed of light in vacuum, and Ω is the angular velocity. The Sagnac effect is only sensitive to angular motion and insensitive to translational motion, so the influence of other motion forms can be suppressed. The angular acceleration β can be obtained by differentiating the Sagnac phase shift φ measured by the fiber optic gyro. Specifically: differentiating the Sagnac phase shift φ gives and through the angular acceleration β is obtained. Then, the underwater acoustic pressure difference ΔP can be calculated through Equation (3). If it is necessary to increase the detection sensitivity of this scheme, the sensitivity can be increased by increasing the fiber length and loop diameter.

[0037] Although specific embodiments of the present invention are disclosed for illustrative purposes, the purpose is to help understand the content of the present invention and implement it accordingly. Those skilled in the art can understand that: without departing from the spirit and scope of the present invention and the appended claims, various substitutions, changes, and modifications are possible. Therefore, the present invention should not be limited to the content disclosed in the best embodiments, and the scope of protection required by the present invention is defined by the scope of the claims.

Claims

1. An underwater acoustic measurement method based on angular motion, the steps of which include: 1) Place an inertial body in the water area to be measured, and respectively set an angular motion sensor on one or more surfaces of the inertial body for measuring the angular acceleration β in the corresponding direction of each surface when the inertial body is disturbed by water flow; the inertial body is an inertial cube with a mass of m and a side length of L; 2) When the inertial body is disturbed by water flow, each of the angular motion sensors respectively sends the measured angular acceleration β in the corresponding direction to the data processing unit; 3) The data processing unit, according to calculates the underwater acoustic pressure difference ΔP in the corresponding direction.

2. The method according to claim 1, wherein Set an angular motion sensor on each of the three orthogonal planes of the inertial cube for respectively measuring the angular accelerations β in three orthogonal directions.

3. The method according to claim 1, wherein The angular motion sensor is implemented by an interferometric fiber optic gyroscope based on the Sagnac effect; the angular acceleration β is obtained by taking the derivative of the Sagnac phase shift φ measured by the interferometric fiber optic gyroscope based on the Sagnac effect and is obtained by to obtain the angular acceleration β; then by the underwater acoustic pressure difference ΔP is obtained; where, in the interferometric fiber optic gyroscope, the length of the fiber loop is T, the diameter of the fiber loop is D, λ represents the light wavelength in vacuum, and c represents the speed of light in vacuum.

4. The method according to claim 1 or 2 or 3, characterized in that, The angular motion sensor is an angle sensor, an angular velocity sensor or an angular acceleration sensor.

5. An underwater acoustic measurement device based on angular motion, characterized in that, Comprising an inertial body, a plurality of angular motion sensors and a data processing unit; One or more surfaces of the inertial body are respectively provided with one of the angular motion sensors for measuring the angular acceleration β in the corresponding direction of each surface when the inertial body is disturbed by water flow; the inertial body is an inertial cube with a mass of m and a side length of L; The data processing unit is configured to calculate, according to the underwater acoustic pressure difference ΔP in the corresponding direction.

6. The underwater acoustic measurement device according to claim 5, wherein Set an angular motion sensor on each of the three orthogonal planes of the inertial cube for respectively measuring the angular accelerations β in three orthogonal directions.

7. The underwater acoustic measurement device according to claim 5, wherein The angular motion sensor is implemented by an interferometric fiber optic gyroscope based on the Sagnac effect; the angular acceleration β is obtained by taking the derivative of the Sagnac phase shift φ measured by the interferometric fiber optic gyroscope based on the Sagnac effect and through the angular acceleration β is obtained; then through the underwater acoustic pressure difference ΔP is obtained; where, in the interferometric fiber optic gyroscope, the length of the fiber loop is T, the diameter of the fiber loop is D, λ represents the optical wavelength in vacuum, and c represents the speed of light in vacuum.

8. The underwater acoustic measurement device according to claim 5 or 6 or 7, characterized in that, The angular motion sensor is an angle sensor, an angular velocity sensor or an angular acceleration sensor.

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