Four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of piston transducer

Abstract

The present invention relates to the field of metrology and testing technology, and in particular to a four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of a piston transducer. The method utilizes the phase distribution characteristics of the acoustic field radiated by the piston transducer to extract variables that affect the acoustic axis direction of the piston transducer, finds the extreme points of the acoustic field phase by differential iteration, and further determines the acoustic axis direction of the transducer. The present invention can effectively improve the efficiency of acoustic field layout, enhance the acoustic field quality, and improve the reliability of experimental data.

Description

Technical Field

[0001] The invention relates to the field of measurement and testing technology, and specifically relates to a four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of a piston transducer. Background Art

[0002] This application is based on the hydrophone complex sensitivity calibration technology, underwater target intensity measurement technology, and underwater sound source level measurement technology. In the process of measuring underwater acoustic components and equipment acoustic parameters such as hydrophone complex sensitivity, target intensity, and sound source level, the sound field layout is a very important preliminary preparation for the experiment. The quality of the sound field layout determines whether the sound field boundary conditions meet the measurement requirements during the measurement process, which will greatly affect the accuracy of the measurement.

[0003] In previous transducer calibration experiments, the number of experimental equipment was relatively small. For example, the reciprocity calibration method of hydrophones only involved three hydrophones and transducers. The equipment under test was small and easy to adjust its position and posture. The sound field layout requirements were relatively simple and the difficulty of sound field layout was relatively low. However, with the continuous development of the field of hydroacoustics, acoustic instruments such as the measured targets, receiving arrays, and transmitting arrays have gradually become more complex and refined, and the difficulty of sound field layout has become increasingly greater, and the debugging time has also increased accordingly. Among them, the relative position of the transducer and hydrophone is the main factor affecting the efficiency of the on-site layout of the sound field in the hydroacoustic experiment.

[0004] In almost all distance-pulling experiments, the acoustic axis position of the piston transducer has a significant impact on the measurement results. The far-field distance correction of the measurement results in hydrophone sensitivity calibration, target intensity measurement, and underwater sound source level measurement are all based on the premise that "under far-field conditions, the propagation loss of the radiated sound pressure of the piston transducer in the direction of the acoustic axis is the same as the propagation loss of the spherical wave sound pressure". If the hydrophone position cannot be guaranteed to be on the acoustic axis of the piston transducer during the distance-pulling process, then as the distance increases, the directivity factor of the transducer will affect the measurement results.

[0005] In a deep pool (more than 5m deep), natural light decays quickly. During the experiment, the position and posture of the transducer and hydrophone cannot be observed with the naked eye. It is necessary to adjust the underwater positioning system and compare the readings of the hydrophone on the oscilloscope to confirm whether the sound field layout meets the standards. The debugging process lacks a unified standard, and the experimenter often relies on experience and patience to repeatedly confirm and adjust the equipment parameters. Different experimenters have different debugging times and effects, which will affect the efficiency of the measurement work and bring greater measurement uncertainty. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of a piston transducer.

[0007] To achieve the above object, the present invention provides the following technical solution: a four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of a piston transducer, comprising the following steps:

[0008] S101: Under far-field conditions, the phase of the piston transducer is distributed in a spherical wave pattern. Therefore, according to the formula, the sound pressure phase difference between any two points of equal distance in space under far-field conditions is the largest when the straight line between the two points coincides with the transducer acoustic axis.

[0009] S102: When the positions of the two hydrophones are fixed, the phase difference between the hydrophone signals is only related to the piston transducer posture and transducer position;

[0010] S103: Among the six degrees of freedom that affect the posture and position of the piston transducer, the translation and rotation in the direction of the normal vector of the radiation surface will not affect the phase difference between the hydrophone signals, so the phase difference function between the hydrophone signals is related to only four degrees of freedom;

[0011] S104: Since the phase difference function between hydrophone signals has a maximum value, the value of the four degrees of freedom when the total differential of the function is zero is the target value;

[0012] S105: Using a partial differential iteration method to adjust the attitude and position of the transducer, the two target hydrophones and the transducer acoustic axis are adjusted to the same straight line.

[0013] Preferably, according to step S101, under far-field conditions, the polar coordinate complex sound pressure distribution formula of the piston transducer is as follows:

[0014]

[0015] Where A is a constant, which is related to the radiation surface area, vibration velocity and radiation distance of the transducer; J 1 is the first-order Bessel function; k is the wave number; r is the radiation distance; θ is the directivity variable; p is the complex sound pressure. It can be seen from formula (1) that the modulus of the complex sound pressure is directional, but the phase is only related to the propagation distance and has nothing to do with the propagation direction.

[0016] Preferably, according to step S101, the formula for the sound pressure phase difference between any two points with equal distance in space under the far field condition is:

[0017] Select any two points (r 1 ,θ 1 ) and (r 2 ,θ 2 ), if the distance d between two points is a constant, then:

[0018]

[0019] The phase difference of the sound pressure between the two points for:

[0020]

[0021] Substituting formula (2) into formula (3) yields:

[0022]

[0023] It is easy to obtain that if and only if θ 1 -θ 2 = 0, If the acoustic pressure modulus of any of the two points changes with θ at this time reaches the maximum value, then it can be considered that both points are on the acoustic axis of the piston transducer.

[0024] Preferably, the piston transducer can translate on the plane xoy, and the translation amount is recorded as dx, dy; it can rotate along the x-axis and y-axis directions, and the rotation amount is recorded as dθ x , dθ x , and r 1 ,θ 1 、r 2 ,θ 2 It's all about x, y, θ x ,θ y function, then the phase difference It is also about x, y, θ x ,θ y The function of

[0025]

[0026] In the formula, d is the total differential operator. According to the above argument, when the hydrophone is on the acoustic axis of the transducer at the same time, and Δp have maximum values ​​and are continuous functions that vary with position and posture variables. Therefore, as long as x is found 0 ,y 0 ,θ x0 ,θ y0 Satisfy the phase difference The value of the total differential of the sound pressure difference Δp being 0 can determine the direction of the acoustic axis of the transmitting transducer.

[0027] Preferably, the position and posture of the transducer before adjustment are recorded as (x 1 ,y 1 ,θ x1 ,θ y1 ) According to formula (1), the phase difference is only related to the relative position between the transducer and the hydrophone, so formula (5) can be simplified to

[0028]

[0029] Since the x and y coordinates are determined by the phase difference The change of the sound pressure difference Δp is only θ x1 ,θ y1 If the variable is controlled, formula (6) can be simplified as follows:

[0030]

[0031] Due to the phase difference There is only one maximum value for the sound pressure difference Δp. Therefore, when an extreme point appears in the partial differential of any variable, it can be determined that the current variable value is the optimal solution when the other three variables remain unchanged.

[0032] Preferably, by adjusting the variables in turn, the extreme point of the total differential can be found through partial differential iteration, and the position and posture of the transducer can be finally determined.

[0033] Compared with the prior art, the beneficial effects of the present invention are: utilizing the phase distribution characteristics of the acoustic field radiated by the piston transducer, extracting the variables that affect the acoustic axis direction of the piston transducer, finding the extreme point of the acoustic field phase by differential iteration, and then determining the acoustic axis direction of the transducer. By using this method, the efficiency of acoustic field layout can be effectively improved, the quality of the acoustic field can be enhanced, and the reliability of experimental data can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a polar coordinate diagram under the perspective of the circular transducer;

[0035] Figure 2 Schematic diagram of the transducer's four degrees of freedom. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] See also Figures 1 to 2 The present invention provides a technical solution: a four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of a piston transducer, characterized in that it includes the following steps:

[0038] S101: Under far-field conditions, the phase of the piston transducer is distributed in a spherical wave pattern. Therefore, according to the formula, the sound pressure phase difference between any two points of equal distance in space under far-field conditions is the largest when the straight line between the two points coincides with the transducer acoustic axis.

[0039] S102: When the positions of the two hydrophones are fixed, the phase difference between the hydrophone signals is only related to the piston transducer posture and transducer position;

[0040] S103: Among the six degrees of freedom that affect the posture and position of the piston transducer, the translation and rotation in the direction of the normal vector of the radiation surface will not affect the phase difference between the hydrophone signals, so the phase difference function between the hydrophone signals is related to only four degrees of freedom;

[0041] S104: Since the phase difference function between hydrophone signals has a maximum value, the value of the four degrees of freedom when the total differential of the function is zero is the target value;

[0042] S105: Using a partial differential iteration method to adjust the attitude and position of the transducer, the two target hydrophones and the transducer acoustic axis are adjusted to the same straight line.

[0043] Under far-field conditions, the polar coordinates of the piston transducer are as follows: Figure 1 As shown, the complex sound pressure distribution formula is as follows:

[0044]

[0045] Where A is a constant, which is related to the radiation surface area, vibration velocity and radiation distance of the transducer; J 1 is the first-order Bessel function; k is the wave number; r is the radiation distance; θ is the directivity variable; and p is the complex sound pressure. From formula (1), it can be seen that the modulus of the complex sound pressure is directional, but the phase is only related to the propagation distance and has nothing to do with the propagation direction.

[0046] At this time, select any two points (r 1 ,θ 1 ) and (r 2 ,θ 2 ), if the distance d between two points is a constant, then:

[0047]

[0048] The phase difference of the sound pressure between the two points for:

[0049]

[0050] Substituting formula (2) into formula (3) yields:

[0051]

[0052] It is easy to obtain that if and only if θ 1 -θ 2 = 0, If the acoustic pressure modulus of any of the two points changes with θ at this time reaches the maximum value, then it can be considered that both points are on the acoustic axis of the piston transducer.

[0053] Assume that the piston transducer can translate on the plane xoy, and the translation amount is recorded as dx and dy; it can rotate along the x-axis and y-axis, and the rotation amount is recorded as dθ x , dθ x , as shown in Figure (2). And r 1 ,θ 1 、r 2 ,θ 2 It's all about x, y, θ x ,θ y function, then the phase difference It is also about x, y, θ x ,θ y The function of

[0054]

[0055] In the formula, d is the total differential operator. According to the above argument, when the hydrophone is on the acoustic axis of the transducer at the same time, and Δp have maximum values ​​and are continuous functions that vary with position and posture variables. Therefore, as long as x is found 0 ,y 0 ,θ x0 ,θ y0 Satisfy the phase difference The value of the total differential of the sound pressure difference Δp being 0 can determine the direction of the acoustic axis of the transmitting transducer.

[0056] The position and posture of the transducer before adjustment are recorded as (x 1 ,y 1 ,θ x1 ,θ y1 ) According to formula (1), the phase difference is only related to the relative position between the transducer and the hydrophone, so formula (5) can be simplified to

[0057]

[0058] Since the x and y coordinates are determined by the phase difference The change of the sound pressure difference Δp is only θ x1 ,θ y1 If the variable is controlled, formula (6) can be simplified as follows:

[0059]

[0060] Due to the phase difference There is only one maximum value for the sound pressure difference Δp. Therefore, when the partial differential of any variable has an extreme value, it can be determined that the current variable value is the optimal solution when the other three variables remain unchanged. By adjusting the variables in turn, the extreme value of the total differential can be found through partial differential iteration, and the position and posture of the transducer can be finally determined.

[0061] Through this technical solution,

[0062] 1. To Change the x-axis coordinate to the negative direction. Stop when it changes from negative to positive, and record the transducer position and posture (x 2 ,y 1 ,θ x1 ,θ y1 );

[0063] 2. To Change the y-axis coordinate in the negative direction. Stop when it changes from negative to positive, and record the transducer position and posture (x 2 ,y 2 ,θ x1 ,θ y1 );

[0064] 3. To The negative direction changes the transducer attitude. Stop when it changes from negative to positive, and record the transducer position and posture (x 2 ,y 2 ,θ x2 ,θ y1 );

[0065] 4. To The negative direction changes the transducer attitude. Stop when it changes from negative to positive, and record the transducer position and posture (x 2 ,y 2 ,θ x2 ,θ y2 );

[0066] 5. Finally, (x 2 ,y 2 ,θ x2 ,θ y2 ) as the starting point, repeat the above adjustment until the minimum change of the four variables does not cause phase difference The sound pressure difference Δp changes.

[0067] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A four-degree-of-freedom differential iterative method for adjusting the acoustic axis direction of a piston transducer, characterized in that: The following steps are involved: S101: Under far-field conditions, the phase of the piston transducer is distributed in a spherical wave pattern. Therefore, according to the formula, the sound pressure phase difference between any two points of equal distance in space under far-field conditions is the largest when the straight line between the two points coincides with the transducer acoustic axis. S102: When the positions of the two hydrophones are fixed, the phase difference between the hydrophone signals is only related to the piston transducer posture and transducer position; S103: Among the six degrees of freedom that affect the posture and position of the piston transducer, the translation and rotation in the direction of the normal vector of the radiation surface will not affect the phase difference between the hydrophone signals, so the phase difference function between the hydrophone signals is related to only four degrees of freedom; S104: Since the phase difference function between hydrophone signals has a maximum value, the value of the four degrees of freedom when the total differential of the function is zero is the target value; S105: using a partial differential iteration method to adjust the attitude and position of the transducer so that the two target hydrophones and the transducer acoustic axis are aligned on the same straight line; According to step S101, under far-field conditions, the polar coordinate complex sound pressure distribution formula of the piston transducer is as follows: In the formula, A is a constant, which is the amplitude of the piston vibration and is related to the transducer radiation surface area, vibration velocity and radiation distance; a is the acoustic effective vibration size of the piston; J1 is the first-order Bessel function; k is the wave number; r is the radiation distance; θ is the directivity variable; p is the complex sound pressure. From formula (1), it can be seen that the modulus of the complex sound pressure has directivity, but the phase is only related to the propagation distance and has nothing to do with the propagation direction; According to step S101, the formula for the sound pressure phase difference between any two points with equal distance in space under far field conditions is: Select any two points (r1, θ1) and (r2, θ2) in the sound field. If the distance d between the two points is a constant, then: The phase difference of the sound pressure between the two points for: Substituting formula (2) into formula (3) yields: It is easy to find that if and only if θ1-θ2=0, has a maximum value, If the acoustic pressure modulus of any of the two points changes with θ at this time reaches the maximum value, then both points are considered to be on the acoustic axis of the piston transducer; Assume that the piston transducer translates on the plane xoy, and the translation is recorded as dx and dy; it rotates along the x-axis and y-axis, and the rotation is recorded as dθ x , dθ x , and r1, θ1, r2, θ2 are all about x, y, θ x ,θ y function, then the phase difference It is also about x, y, θ x ,θ y The function of In the formula, d is the total differential operator. According to the above argument, when the hydrophone is on the acoustic axis of the transducer at the same time, and Δp have maximum values ​​and are continuous functions that vary with position and posture variables. Therefore, as long as x0, y0, θ are found x0 ,θ y0 Satisfy the phase difference The value of the total differential of the sound pressure difference Δp being 0 determines the direction of the acoustic axis of the transmitting transducer.

2. The four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of a piston transducer according to claim 1, characterized in that: The position and posture of the transducer before adjustment are recorded as (x1, y1, θ x1 ,θ y1 ) According to formula (1), the phase difference is only related to the relative position between the transducer and the hydrophone, so formula (5) is simplified to Since the x and y coordinates are determined by the phase difference The change of the sound pressure difference Δp is only θ x1 ,θ y1 Variable control, then formula (6) is simplified to: Due to the phase difference There is only one maximum value for the sound pressure difference Δp. Therefore, when an extreme point appears in the partial differential of any variable, it can be determined that the current variable value is the optimal solution when the other three variables remain unchanged.

3. The four-degree-of-freedom differential iteration method for adjusting the acoustic axis direction of a piston transducer according to claim 2, characterized in that: The variables are adjusted in turn, and the extreme points of the total differential are found through partial differential iteration to finally determine the position and posture of the transducer.

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