Concentric ring-shaped acoustic-magnetic composite sensor and underwater measuring system comprising same

Abstract

The disclosure provides a concentric annular acoustic-magnetic composite sensor and an underwater measuring system formed by the same. The composite sensor comprises: a piezoceramic ring for responding to an external acoustic field and generating a first electric signal, and responding to a magnetostrictive strain transmitted through an interface and generating a second electric signal; a magnetostrictive ring concentrically sleeved outside the piezoceramic ring for responding to an external magnetic field and generating a magnetostrictive strain; and an excitation coil wound on an outer circumference of the magnetostrictive ring in a circumferential direction for generating a high-frequency bias magnetic field to frequency-modulate the external magnetic field; wherein the piezoceramic ring and the magnetostrictive ring are combined through a composite packaging process to realize transmission of the magnetostrictive strain, so that the piezoceramic ring synchronously outputs the first electric signal and the second electric signal.

Description

Technical Field

[0001] This disclosure relates to the field of underwater acoustic and magnetic field detection technology, specifically to a concentric ring acoustic-magnetic composite sensor and an underwater measurement system thereof. Background Technology

[0002] Underwater acoustic and magnetic field detection are two core methods for marine scientific research and underwater target detection. Acoustic sensors (such as hydrophones) can acquire rich underwater sound field information, but are susceptible to interference from marine environmental noise and multipath effects. Magnetic sensors (such as fluxgate magnetometers and magnetoelectric sensors) are unaffected by hydrological conditions, but their detection signals attenuate rapidly with distance and have limited information content. The two technologies are naturally complementary in their physical characteristics, thus "acoustomagnetic joint detection," which integrates acoustic and magnetic detection methods, has become a research hotspot.

[0003] However, existing acoustic-magnetic joint detection systems typically employ a combination of discrete sensors. This approach suffers from problems in practical applications, including difficulties in data spatiotemporal registration, large system size and power consumption, and poor adaptability to dynamic environments. Furthermore, traditional magnetoelectric sensors used for magnetic field measurement often employ a sheet-like stacked structure with a single sensing axis, classifying them as single-axis vector sensors. When the platform's attitude changes underwater, the sensor's output signal fluctuates drastically with the change in the angle between the magnetic field's incident direction and the sensing axis, introducing additional attitude coupling noise. This severely limits their reliability in complex marine dynamic environments. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above problems, this disclosure provides a concentric ring acoustomagnetic composite sensor and an underwater measurement system thereof, so as to at least partially solve the technical problems of spatiotemporal registration difficulties, large system size and power consumption, and poor dynamic environment adaptability caused by the directional sensitivity of traditional magnetoelectric sensors in existing acoustomagnetic joint detection.

[0006] (II) Technical Solution

[0007] This disclosure provides a concentric ring acoustomagnetic composite sensor, comprising: a piezoelectric ceramic ring for responding to an external sound field and generating a first electrical signal, and responding to magnetostrictive strain transmitted through an interface and generating a second electrical signal; a magnetostrictive ring concentrically disposed outside the piezoelectric ceramic ring for responding to an external magnetic field and generating magnetostrictive strain; and an excitation coil wound around the outer circumference of the magnetostrictive ring along the circumferential direction for generating a high-frequency bias magnetic field to frequency modulate the external magnetic field; wherein the piezoelectric ceramic ring and the magnetostrictive ring are combined through a composite packaging process to achieve the transmission of magnetostrictive strain, so that the piezoelectric ceramic ring synchronously outputs the first electrical signal and the second electrical signal.

[0008] According to embodiments of this disclosure, the piezoelectric ceramic ring is tangentially polarized, with the polarization direction along the circumference of the piezoelectric ceramic ring.

[0009] According to embodiments of this disclosure, the inner and outer surfaces of the piezoelectric ceramic ring are plated with silver electrodes to serve as a common output terminal for the first and second electrical signals.

[0010] According to embodiments of this disclosure, the magnetostrictive ring is made of an iron-based amorphous alloy.

[0011] According to embodiments of this disclosure, the composite encapsulation process is an interference fit combined with epoxy resin bonding, and the interference between the piezoelectric ceramic ring and the magnetostrictive ring is 0.01mm-0.03mm; the interface gap between the piezoelectric ceramic ring and the magnetostrictive ring is filled with epoxy resin, and the interface coupling coefficient is greater than or equal to 0.85.

[0012] According to embodiments of this disclosure, the concentric ring acoustomagnetic composite sensor has a concentric ring structure to provide an isotropic response to an external magnetic field in any direction parallel to the plane of the sensor.

[0013] A second aspect of this disclosure provides an underwater measurement system, comprising: a concentric ring acousto-magnetic composite sensor; a signal conditioning and demodulation circuit electrically connected to the output end of a piezoelectric ceramic ring for receiving and processing a first electrical signal and a second electrical signal; and a data acquisition module for acquiring acoustic field data of an external sound field and magnetic field data of an external magnetic field.

[0014] According to embodiments of this disclosure, the signal conditioning and demodulation circuit includes: a sound field baseband amplifier for amplifying a first electrical signal to obtain sound field data; a magnetic field lock-in amplification and demodulation circuit for performing phase-sensitive detection on a second electrical signal based on a high-frequency bias magnetic field of an excitation coil to demodulate magnetic field data; and a filtering and analog-to-digital conversion unit for filtering and converting the amplified sound field data and the demodulated magnetic field data into analog-to-digital data, respectively.

[0015] According to embodiments of this disclosure, it further includes: a weak magnetic alloy housing for encapsulating a concentric ring acousto-magnetic composite sensor to form a pressure-resistant, watertight probe.

[0016] According to embodiments of this disclosure, it further includes: a power management module for supplying power to the concentric ring acoustomagnetic composite sensor and the signal conditioning and demodulation circuit.

[0017] (III) Beneficial Effects

[0018] The concentric ring acousto-magnetic composite sensor and the underwater measurement system thereof disclosed herein have at least the following technical advantages:

[0019] 1. Achieve synchronous acquisition of the physical sources of sound field and magnetic field: By designing an integrated structure that concentrically combines a piezoelectric ceramic ring and a magnetostrictive ring, the sound field signal (i.e., the first electrical signal) and the magnetic field signal (i.e., the second electrical signal) are both synchronously output from the electrodes of the same piezoelectric ceramic ring, fundamentally solving the problem of spatiotemporal registration error caused by different installation positions in existing discrete sensor combination schemes.

[0020] 2. Achieving in-plane isotropic response for magnetic field measurement. By utilizing the rotational symmetry of the concentric ring structure, the sensor exhibits consistent response sensitivity to magnetic field components in any direction parallel to the ring plane. This overcomes the inherent limitation of traditional sheet-like magnetoelectric sensors being sensitive to magnetic field direction, enabling the sensor to stably measure the magnetic field amplitude even when the platform rotates.

[0021] 3. Achieving system miniaturization and low power consumption: Integrating acoustic detection and magnetic field detection functions into a single probe significantly reduces system size and power consumption, meeting the requirements for miniaturized underwater platforms.

[0022] 4. Provide a data foundation for the coordinated suppression of noise from the same source: By synchronously acquiring sound field and magnetic field signals at the same spatiotemporal point, a physical prerequisite is provided for the subsequent establishment of a spatiotemporal correlation model of background noise in the sound field and magnetic field and the realization of coordinated suppression of related noise. Attached Figure Description

[0023] To gain a more complete understanding of this disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1 This schematic diagram illustrates the overall structure of the concentric ring acousto-magnetic composite sensor provided in an embodiment of the present disclosure.

[0025] Figure 2 This illustration schematically shows a diagram illustrating the acoustic magnetic field sensing principle provided in an embodiment of the present disclosure.

[0026] Figure 3 A schematic diagram illustrating the sensor orientation response characteristics provided in an embodiment of this disclosure is shown.

[0027] Figure 4 A schematic diagram illustrating the frequency modulation principle provided in an embodiment of this disclosure is shown.

[0028] Figure 5 A schematic diagram of an underwater measurement system provided in an embodiment of this disclosure is shown.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1-Piezoelectric ceramic ring;

[0031] 2-Magnetostrictive ring;

[0032] 3-Excitation coil. Detailed Implementation

[0033] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0035] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0036] The inventors discovered that existing acoustic-magnetic joint detection systems typically employ a combination of discrete sensors to achieve "system-level fusion." This approach suffers from the following inherent problems in practical applications: First, due to the different installation locations of the discrete sensors, there are inherent spatial offsets and time synchronization errors between the acoustic and magnetic field data, making spatiotemporal registration difficult. Second, the combined system is bulky and consumes a lot of power, making it difficult to meet the integration requirements of miniaturized platforms such as autonomous underwater vehicles and buoys. Third, the discrete sensors exhibit inconsistent response characteristics to common-mode interference such as platform vibration and attitude changes, making collaborative compensation and noise suppression difficult. Fourth, fusion processing can only be performed at the signal processing layer, failing to achieve synchronous acquisition and collaborative optimization of acoustic-magnetic information from the physical source. Therefore, there is an urgent need for an integrated sensor solution capable of synchronizing and acquiring acoustic and magnetic fields from the same physical source.

[0037] In view of this, this disclosure provides a concentric ring acoustomagnetic composite sensor and the underwater measurement system thereof, which can acquire underwater low-frequency acoustic and magnetic field signals synchronously and at the same location, and can be widely used in the fields of marine dynamic process observation, underwater target detection and deep-sea resource exploration.

[0038] Figure 1 The schematic diagram illustrates the overall structure of the concentric ring acousto-magnetic composite sensor provided in the embodiments of this disclosure.

[0039] like Figure 1 As shown, the concentric ring acoustomagnetic composite sensor includes: a piezoelectric ceramic ring 1, a magnetostrictive ring 2, and an excitation coil 3.

[0040] The piezoelectric ceramic ring 1 is used to respond to an external sound field and generate a first electrical signal, and to respond to magnetostrictive strain transmitted through the interface and generate a second electrical signal.

[0041] In some exemplary embodiments, the piezoelectric ceramic ring 1 is made of lead-based textured piezoelectric ceramic, such as PZT-5H piezoelectric ceramic. To further improve the piezoelectric response performance, template grain growth technology (TGG) can be used to orient the ceramic grains along a specific direction, thereby obtaining excellent piezoelectric performance similar to that of a piezoelectric single crystal.

[0042] It should be noted that the material of the piezoelectric ceramic ring 1 is not limited to PZT-5H mentioned above. In practical applications, PZT-5A piezoelectric ceramic, PZT-8 piezoelectric ceramic, lead magnesium niobate-lead titanate (PMN-PT) piezoelectric single crystal, or other materials with piezoelectric effect can be selected according to actual requirements such as sensitivity, temperature stability, or impedance matching.

[0043] The piezoelectric ceramic ring 1 is tangentially polarized, meaning its polarization direction is set tangentially along the circumference of the piezoelectric ceramic ring 1, giving it the highest response sensitivity to radial strain. Specifically, when an external sound field acts on the sensor or the strain generated by the magnetostrictive ring 2 is transmitted to the piezoelectric ceramic ring 1 through the interface, it can cause radial deformation of the piezoelectric ceramic ring 1. Since the tangentially polarized piezoelectric ceramic ring 1 has the highest response sensitivity to radial strain, it can effectively improve the overall detection sensitivity of the sensor to sound field and magnetic field signals.

[0044] The inner and outer surfaces of the piezoelectric ceramic ring 1 are coated with silver electrodes. These silver electrodes can serve as a common output terminal for the first and second electrical signals, enabling the acoustic field response signal and the magnetic field response signal to be output synchronously through the same physical port, thus ensuring the spatiotemporal consistency of the acoustic-magnetic data from the physical source.

[0045] Magnetostrictive ring 2 is concentrically fitted around the piezoelectric ceramic ring to respond to an external magnetic field and generate magnetostrictive strain. When an external low-frequency magnetic field acts on magnetostrictive ring 2, the ring body generates micro-strain through the magnetostrictive effect. This strain can be transmitted to piezoelectric ceramic ring 1 through the interface between piezoelectric ceramic ring 1 and magnetostrictive ring 2, and then converted into a second electrical signal output through the piezoelectric effect.

[0046] The magnetostrictive ring 2 is made of a high-permeability iron-based amorphous alloy. Iron-based amorphous alloys possess high initial permeability (≥10,000), low coercivity (≤1.6 A / m), and a moderate saturation magnetostriction coefficient (approximately 27 ppm), enabling them to generate considerable magnetostrictive strain under weak, low-frequency magnetic fields, making them ideal sensitive materials for ultra-low-frequency magnetic field measurements. To further optimize material properties, the iron-based amorphous ring (i.e., magnetostrictive ring 2) undergoes microstructure optimization through a vacuum magnetic field heat treatment process after processing. After this process, the magnetic domains within the amorphous ring tend to be more ordered, and the internal stress distribution is more uniform, thereby ensuring that its magnetostrictive performance approaches or reaches the theoretical value.

[0047] In other embodiments, the material of the magnetostrictive ring 2 is not limited to the iron-based amorphous alloys described above, but may also be Terfenol-D rare earth super magnetostrictive material, Metglas amorphous alloy strip, or other soft magnetic materials with magnetostrictive effect.

[0048] The excitation coil 3 is wound around the outer circumference of the magnetostrictive ring along the circumferential direction to generate a high-frequency bias magnetic field for frequency modulation of the external magnetic field. Specifically, by passing a high-frequency alternating current through the excitation coil 3, a high-frequency alternating bias magnetic field can be generated in the circumferential direction of the magnetostrictive ring 2. This high-frequency bias magnetic field modulates the operating point of the magnetostrictive ring 2 to near its mechanical resonant frequency. The external low-frequency magnetic field to be measured interacts with the high-frequency carrier wave as a modulation wave, thereby generating a modulation sideband component containing the information of the magnetic field to be measured in the output signal of the piezoelectric ceramic ring 1.

[0049] It should be noted that the number of turns of the excitation coil 3 can be optimized according to impedance matching requirements and the required excitation magnetic field strength. Furthermore, the specific winding method of the excitation coil 3 is not limited to uniform close winding; rather, it can be adjusted according to the geometry of the magnetostrictive ring 2, the requirements for magnetic field distribution uniformity, and the overall packaging space limitations of the sensor. This allows for adjustments to the number of winding layers, their arrangement density, or the segmented winding method to achieve the optimal magnetic field modulation effect.

[0050] The piezoelectric ceramic ring 1 and the magnetostrictive ring 2 are combined through a composite packaging process to achieve a tight physical bond between the two rings. This ensures that the magnetostrictive strain generated by the magnetostrictive ring 2 under the action of an external magnetic field can be efficiently and with low loss transmitted to the piezoelectric ceramic ring 1, so that the piezoelectric ceramic ring can synchronously output the first electrical signal and the second electrical signal.

[0051] Specifically, the composite encapsulation process involves an interference fit combined with epoxy resin bonding. Regarding the interference fit, the tolerance between the outer diameter of the piezoelectric ceramic ring 1 and the inner diameter of the magnetostrictive ring 2 is strictly controlled through precision machining, resulting in a physical press-fit with an interference of 0.01mm to 0.03mm. For interface filling, the micro-gaps between the piezoelectric ceramic ring 1 and the magnetostrictive ring 2 can be filled with epoxy resin with low elastic modulus and high shear strength. Its high shear strength ensures efficient transmission of magnetostrictive strain along the tangential direction of the interface, while its low elastic modulus effectively buffers the rigid contact stress between the two rings, avoiding the introduction of additional stress noise and thus improving the signal-to-noise ratio of the sensor. Finite element simulation and experimental verification show that after adopting the above composite encapsulation process, the interface coupling coefficient k between the piezoelectric ceramic ring 1 and the magnetostrictive ring 2 is [value missing]. c It can reach above 0.85.

[0052] Understandably, compared to existing discrete sensor combinations (such as sonar + magnetometer), the concentric ring acousto-magnetic composite sensor provided in this disclosure achieves a shift from "system-level fusion" to "sensor-level fusion." This is achieved through an integrated structural design that concentrically combines a piezoelectric ceramic ring and a magnetostrictive ring, allowing both acoustic and magnetic field signals to be synchronously output from the same piezoelectric ceramic ring electrode. This fundamentally solves the problems of spatiotemporal registration errors and volumetric power consumption redundancy. Furthermore, this disclosure represents a technological leap from "single-function" to "dual-capability," integrating scientific observation (synchronous acquisition of acoustic-magnetic signals from the same source) with target detection (cooperative suppression of noise from the same source), thus providing a novel technological means for marine scientific research and engineering applications.

[0053] The concentric ring acoustomagnetic composite sensor provided in this embodiment achieves synchronous sensing of sound field and magnetic field based on magnetostrictive-piezoelectric composite effect. The two signals generate responses through two different physical paths, do not interfere with each other in terms of physical generation mechanism, and are ultimately output by the same piezoelectric ceramic ring 1 electrode, thus naturally ensuring the spatiotemporal synchronization of sound field data and magnetic field data from the physical source.

[0054] Figure 2 The schematic diagram illustrates the acoustic magnetic field sensing principle provided in the embodiments of this disclosure.

[0055] like Figure 2 As shown, in the sound field sensing path (piezoelectric effect), when an external sound field (0.01Hz~100kHz) acts on the sensor, the sound pressure directly acts on the surface of the inner piezoelectric ceramic ring 1, causing radial deformation of the piezoelectric ring. According to the piezoelectric effect, this radial deformation generates charge accumulation in the tangential polarization direction of the piezoelectric ceramic ring 1, thereby forming the first electrical signal corresponding to the sound field. For small signal excitation conditions, the open-circuit output voltage of the piezoelectric ceramic ring 1 is... The relationship with sound pressure P can be expressed as:

[0056]

[0057] in, The piezoelectric voltage coefficient, The stress induced by the sound pressure in the piezoelectric ceramic ring 1 is denoted as , and t is the wall thickness of the piezoelectric ring. Through tangential polarization design, the piezoelectric ceramic ring 1 can improve the response sensitivity to radial sound pressure by approximately 12 dB compared to traditional radial polarization structures, thereby effectively enhancing the sensor's ability to detect weak sound field signals.

[0058] Continue to refer to Figure 2 In the magnetic field sensing path (magnetostrictive-piezoelectric composite effect), when an external low-frequency magnetic field (0.01Hz~100Hz) acts on the sensor, the magnetic field penetrates and acts on the magnetostrictive ring 2, causing microscopic strain in the ring through the magnetostrictive effect. This strain is transmitted to the inner piezoelectric ceramic ring 1 through the interface, and then converted into a second electrical signal output through the piezoelectric effect. The sensor's magnetoelectric voltage coefficient... It can be represented as:

[0059]

[0060] in, is the interface coupling coefficient, which characterizes the efficiency of magnetostrictive strain transfer to the piezoelectric ceramic ring 1 through the interface; is the piezomagnetic coefficient of magnetostrictive ring 2, which characterizes the ability to convert magnetic field into strain; Let be the piezoelectric voltage coefficient of piezoelectric ceramic ring 1, characterizing the ability to convert strain into electric field. The product of these three factors is the physical essence of the magnetoelectric conversion effect, i.e., "magnetic field → strain ( → Interface transfer ( → Electric field The cascade conversion process of ").

[0061] It should be noted that although the operating frequency bands of the sound field signal and the magnetic field signal partially overlap within the range of 0.01 Hz to 10 Hz, they generate responses through two fundamentally different physical paths: "sound pressure → piezoelectric effect" and "magnetic field → magnetostrictive effect → piezoelectric effect," respectively. Furthermore, they exhibit distinguishable differences in phase, polarization response characteristics, and time constants. This provides a physical basis for subsequent separation of the sound field signal and the magnetic field signal through signal processing methods.

[0062] The concentric ring acoustomagnetic composite sensor is a concentric ring structure that integrates acoustic detection and magnetic field detection functions into a single probe. By utilizing the rotational symmetry geometry of the concentric ring structure, it achieves an isotropic response to magnetic field measurement, that is, an isotropic response to an external magnetic field in any direction parallel to the plane of the sensor. This fundamentally overcomes the inherent defect of traditional sheet-like magnetoelectric sensors being sensitive to the direction of the magnetic field.

[0063] Specifically, traditional magnetoelectric sensors mostly employ a sheet-like stacked structure, where the magnetostrictive layer and piezoelectric layer are flatly stacked. They only exhibit high response sensitivity to the magnetic field component perpendicular to the lamination interface, classifying them as single-axis vector sensors. In practical underwater applications, when the onboard platform (such as an autonomous underwater vehicle or buoy) undergoes attitude changes, the sensor's sensitive axis direction changes accordingly. This causes the output signal to vary according to the cosine of the angle between the external magnetic field direction and the sensitive axis, introducing severe attitude coupling fluctuation noise. This significantly limits the measurement stability and data reliability in dynamic marine environments.

[0064] To address the aforementioned issues, this embodiment employs a concentric ring structure design, utilizing the rotational symmetry of the magnetostrictive ring 2 to achieve isotropic response in the plane. Based on the linear small-signal theoretical model of magnetoelectric composite materials, when the magnetostrictive ring's geometry is rotationally symmetric, its volumetric strain under an external magnetic field... It is independent of the direction of the magnetic field in the plane, that is, it satisfies the following relationship:

[0065]

[0066] In the formula, This represents the components of the strain tensor before and after rotation. Since coordinate rotation does not change the value of the volumetric strain, and the sensor's output voltage V is proportional to the amplitude of the volumetric strain, i.e. Therefore, the output voltage of the sensor is only related to the amplitude of the external magnetic field, and is independent of the incident direction of the magnetic field in the plane of the sensor.

[0067] Figure 3 The diagram illustrates the sensor orientation response characteristics provided in an embodiment of this disclosure.

[0068] like Figure 3As shown, the sensor disclosed herein exhibits consistent response sensitivity to magnetic field components in any direction parallel to the toroidal plane, displaying "quasi-scalar" magnetic field measurement characteristics. When the sensor rotates or changes attitude with the underwater platform at any angle, the magnetic field measurement output signal remains stable, effectively avoiding additional measurement noise introduced by platform attitude changes. Experimental data shows that the magnetic field response anisotropy ratio K (defined as the ratio of the maximum output voltage to the minimum output voltage of the sensor in different magnetic field directions under the same magnetic field amplitude) of the sensor disclosed herein can be as low as 3.1, far superior to the anisotropy ratio of traditional sheet-like stacked structures. ).

[0069] It is understood that the embodiments of this disclosure realize the transformation of magnetic field measurement from "anisotropic" to "isotropic", overcome the defect of traditional sheet magnetoelectric sensors being sensitive to the direction of the magnetic field, realize isotropic measurement in the plane, and greatly improve the measurement stability on the dynamic platform.

[0070] To address the physical bottleneck of achieving high-sensitivity detection of ultra-low frequency magnetic fields in the 0.01Hz~100Hz range, this disclosure introduces active frequency modulation technology to overcome the severe limitation of 1 / f noise in traditional direct detection schemes. This technology modulates the ultra-low frequency magnetic field signal to be measured onto a high-frequency carrier band, effectively avoiding the influence of low-frequency 1 / f noise, while simultaneously utilizing mechanical resonance gain to significantly improve the detection sensitivity of weak magnetic field signals.

[0071] Figure 4 A schematic block diagram illustrating the frequency modulation principle provided in an embodiment of this disclosure is shown.

[0072] like Figure 4 As shown, a frequency of is supplied through excitation coil 3. A high-frequency alternating current of kHz generates a high-frequency bias magnetic field of corresponding frequency in the magnetostrictive ring 2. The bias magnetic field modulates the operating point of the magnetostrictive ring 2 to near its mechanical resonant frequency. The ultra-low frequency magnetic field to be measured can be expressed as... The frequency of the signal under test The ultra-low frequency magnetic field to be measured, acting as a modulation wave, interacts nonlinearly with a high-frequency bias magnetic field as a carrier wave within the magnetostrictive ring 2. This interaction generates a modulation sideband component containing information about the magnetic field to be measured in the output signal of the piezoelectric ceramic ring 1. The frequency of this sideband component is... .

[0073] To extract the ultra-low frequency magnetic field information to be measured from the output signal of the piezoelectric ceramic ring 1, lock-in amplification technology can be used to demodulate and detect the modulation sideband signal. Specifically, using the high-frequency excitation signal supplied to the excitation coil 3 as a reference signal, the output signal of the piezoelectric ceramic ring 1 is subjected to phase-sensitive detection, and after low-pass filtering, a DC signal proportional to the amplitude of the ultra-low frequency magnetic field to be measured can be extracted.

[0074] Understandably, the aforementioned frequency modulation and lock-in amplification demodulation scheme can effectively avoid 1 / f noise. That is, the measured ultra-low frequency magnetic field signal is shifted to a high-frequency band of approximately 20kHz, which is far removed from the ultra-low frequency region dominated by 1 / f noise, thus significantly reducing the adverse impact of system background noise on measurement accuracy. Simultaneously, by setting the operating point of the magnetostrictive ring 2 near its mechanical resonant frequency, the gain generated by the mechanical resonance effect amplifies the weak magnetostrictive strain signal, thereby increasing the sensor's detection sensitivity to ultra-low frequency magnetic fields by one to two orders of magnitude.

[0075] Based on previous experience in low-noise circuit design, a closed-loop self-excited frequency modulation and demodulation circuit can be designed to achieve the above modulation and demodulation process.

[0076] Specifically, the circuit may include a high-frequency bias excitation module, a weak sideband signal preamplifier module, a phase-sensitive detector, and a low-pass filter. The high-frequency bias excitation module generates a stable, amplitude-controllable ~20kHz sinusoidal excitation signal to drive the excitation coil 3 to generate a high-frequency bias magnetic field. The weak sideband signal preamplifier module amplifies the weak sideband signal output from the piezoelectric ceramic ring 1. It can use a low-noise junction field-effect transistor (JFET) as the input stage to achieve high impedance matching and low current noise (≤5 fA / √Hz), thereby maximizing the preservation of weak magnetic field information in the sideband signal. The phase-sensitive detector uses the excitation signal generated by the high-frequency bias excitation module as a reference signal to perform phase-sensitive detection on the preamplified sideband signal, extracting the signal component related to the amplitude of the magnetic field to be measured. The low-pass filter filters out high-frequency components and residual carrier components from the output signal of the phase-sensitive detector, ultimately outputting a DC voltage signal proportional to the amplitude of the ultra-low frequency magnetic field to be measured.

[0077] After processing by the frequency modulation and demodulation circuit described above, the measurement system disclosed herein is expected to achieve a magnetic field detection resolution of ≤10 pT / √Hz at a frequency of 1 Hz and a magnetic field detection resolution of ≤50 pT / √Hz at a frequency of 0.1 Hz.

[0078] Although both the sound field and magnetic field signals are output from the same piezoelectric ceramic ring 1, and their operating frequency bands partially overlap (0.01Hz~100Hz), they have fundamentally different physical paths and response characteristics. Specifically, the sound field signal is generated by the direct application of external sound pressure to the piezoelectric ceramic ring, resulting in a short response path and small phase delay. In contrast, the magnetic field signal must first pass through a magnetostrictive ring, where it is converted into microscopic strain via the magnetostrictive effect, and then transmitted through the interface to the piezoelectric ceramic ring, where it is converted into an electrical signal via the piezoelectric effect. This results in a longer response path and a certain phase lag. Furthermore, the sound field primarily induces radial strain in the piezoelectric ceramic ring 1, while the magnetic field, transmitted through the interface, primarily induces thickness strain. These differences also lead to variations in their polarization response characteristics. These fundamental differences in phase, polarization direction, and time constant provide the physical basis for subsequent signal processing methods to clearly separate the sound field and magnetic field signals.

[0079] This embodiment enables the simultaneous acquisition of sound and magnetic fields at the same location and time. In actual marine environments, sound and magnetic field signals often originate from the same hydrodynamic process; their overlapping frequency bands reflect their physical homology, meaning that sound and magnetic fields originating from the same hydrodynamic process inevitably change at similar spatiotemporal scales. By simultaneously acquiring this pair of "twin signals," a spatiotemporal correlation model between the sound and magnetic fields can be established, thereby extracting mutual information. This provides "additional information" that cannot be obtained from single physical field observations, thus offering a new perspective for cutting-edge research on ocean vortex dynamics, internal wave propagation mechanisms, and other related fields.

[0080] Based on the different physical paths and response characteristics of acoustic and magnetic field signals, signal separation can be achieved using the following methods. For example, blind source separation based on phase characteristics utilizes the phase difference caused by the different transmission paths of the acoustic and magnetic fields, employing blind source separation algorithms such as Independent Component Analysis (ICA) to extract their respective features. Another example is signal identification based on polarization characteristics: the acoustic signal mainly causes radial strain in the piezoelectric ceramic ring 1, while the magnetic field signal causes thickness strain in the piezoelectric ceramic ring 1 through interface transmission; their polarization responses differ, therefore, they can be distinguished and separated by analyzing the polarization characteristics of the output signals. Yet another example is feature extraction based on statistical properties: acoustic and magnetic field signals generated by ocean dynamic processes have different statistical distribution characteristics, which can be distinguished using higher-order statistics.

[0081] In other embodiments, the synchronously acquired acoustic and magnetic field data can support the following scientific applications and engineering practices. For example, establishing a spatiotemporal correlation model between acoustic and magnetic fields: by performing cross-correlation function analysis and coherence spectrum analysis on the synchronously acquired acoustic and magnetic field data, the response law of the same ocean dynamic process in the acoustic and magnetic fields can be revealed, and a quantitative model of the spatiotemporal correlation between the two can be established; another example is the joint inversion of seawater motion parameters: by utilizing the coupling relationship of acoustic and magnetic signals, key dynamic parameters such as seawater velocity, vorticity, and turbulent energy dissipation rate can be jointly inverted, providing richer and more accurate observation data for marine environmental monitoring; yet another example is the identification of ocean process characteristics: different ocean processes (internal waves, turbulence, vortices) exhibit different characteristic patterns in the acoustic and magnetic fields, and synchronous observation can improve the accuracy and reliability of process identification; yet another example is the synergistic suppression of background noise: by utilizing the homogeneity of the acoustic and magnetic fields, a spatiotemporal correlation model of background noise can be established to achieve correlation cancellation and improve the detection capability of weak target signals.

[0082] Another aspect of this disclosure provides an underwater measurement system that integrates the aforementioned concentric ring acoustic-magnetic composite sensor and its associated modules to form a complete marine low-frequency acoustic-magnetic co-source observation system.

[0083] like Figure 5 As shown, the underwater measurement system provided in this disclosure includes: a concentric ring acousto-magnetic composite sensor, a signal conditioning and demodulation circuit, a data acquisition module, a power management module, and a sealed alloy shell (i.e., a weak magnetic alloy shell). The signal conditioning and demodulation circuit and the data acquisition module together constitute the signal processing and data acquisition module.

[0084] The concentric ring-shaped acoustomagnetic composite sensor, as the core sensing element of the system, is used to simultaneously sense the external sound field and the external magnetic field, and output corresponding first and second electrical signals. The specific structure, materials, and working principle of this sensor have been described in detail in the foregoing embodiments, and will not be repeated here.

[0085] The signal conditioning and demodulation circuit is electrically connected to the output terminal of the piezoelectric ceramic ring, and is used to receive and process the first electrical signal and the second electrical signal respectively.

[0086] Furthermore, the signal conditioning and demodulation circuit includes a sound field baseband amplifier, a magnetic field lock-in amplifier demodulation circuit, and a filtering and analog-to-digital conversion unit. Specifically, the sound field baseband amplifier is used to perform low-noise amplification processing on the first electrical signal to obtain sound field data. Since the sound field signal operates over a wide frequency band (0.01Hz to 100kHz), this amplifier can possess wide-bandwidth, low-noise amplification characteristics to completely preserve the frequency domain information of the sound field signal. The magnetic field lock-in amplifier demodulation circuit is used to perform phase-sensitive detection processing on the second electrical signal based on the high-frequency bias magnetic field of the excitation coil to demodulate the magnetic field data. This circuit uses the high-frequency excitation signal supplied to the excitation coil as a reference signal to demodulate the modulation sideband component in the second electrical signal, ultimately outputting a DC signal proportional to the amplitude of the ultra-low frequency magnetic field to be measured. The filtering and analog-to-digital conversion unit is used to filter and perform analog-to-digital conversion on the amplified sound field data and the demodulated magnetic field data, respectively. This unit can set appropriate filter parameters according to the different frequency band characteristics of the sound field signal and the magnetic field signal to further suppress out-of-band noise and convert the analog signal into a digital signal for subsequent storage and analysis.

[0087] The data acquisition module is used to acquire sound field data and magnetic field data after signal conditioning and demodulation circuitry. This module can adopt a multi-channel synchronous sampling architecture to perform strictly synchronized analog-to-digital conversion and data recording of the sound field data channel and the magnetic field data channel, thereby further ensuring the spatiotemporal consistency of the sound field data and magnetic field data from the circuit and data acquisition level.

[0088] The power management module provides operating power to the concentric ring acousto-magnetic composite sensor, signal conditioning and demodulation circuits, and data acquisition module. This power management module employs a low-noise power supply design to minimize the interference of power ripple and switching noise on weak acoustic and magnetic field signals. Furthermore, to meet the application requirements of long-term underwater deployment, the power management module features low-power management capabilities, keeping the overall power consumption of the underwater measurement system below 300mW.

[0089] A weak magnetic alloy housing is used to encapsulate a concentric ring-shaped acousto-magnetic composite sensor to form a pressure-resistant, watertight probe. The weak magnetic alloy housing is preferably made of materials with low magnetic permeability and high pressure resistance, such as titanium alloy, to avoid interference with magnetic field measurements from the housing itself, while providing sufficient mechanical strength to meet the pressure resistance requirements of deep-sea deployment. For example, the housing's pressure resistance rating is greater than or equal to a water depth of 1000 meters. Furthermore, the housing can be designed with standardized mechanical and electrical interfaces to facilitate the mounting of the underwater measurement system onto various marine observation platforms such as buoys, autonomous underwater vehicles, and seabed observation nodes.

[0090] Through the system integration of the above modules, a complete prototype of a "Marine Low-Frequency Acoustomagnetic Co-source Observation System" can be formed. This system can be flexibly deployed on diverse platforms such as buoys, autonomous underwater vehicles, and seabed observation nodes to achieve synchronous, simultaneous, and long-term continuous observation of acoustic and magnetic field signals in the marine environment, providing new technical means and data support for marine scientific research and underwater target detection.

[0091] It is understood that the concentric ring acoustomagnetic composite sensor provided in this disclosure adopts a concentric ring integrated structure, concentrically combining a piezoelectric ceramic ring and a magnetostrictive ring. This allows both the acoustic and magnetic field signals to be synchronously output from the electrodes of the same piezoelectric ceramic ring, achieving synchronous and simultaneous acquisition of the acoustic and magnetic fields from the physical source. This solves the inherent spatiotemporal registration error problem in existing discrete sensor combination schemes. Simultaneously, utilizing the rotational symmetry geometry of the concentric ring structure, isotropic in-plane response is achieved for magnetic field measurement. The sensor exhibits consistent response sensitivity to magnetic field components in any direction parallel to the ring plane, overcoming the sensitivity of traditional sheet-like magnetoelectric sensors to magnetic field direction and effectively avoiding additional measurement noise introduced by changes in the platform's attitude. Furthermore, by applying a high-frequency bias magnetic field through the excitation coil, the ultra-low frequency magnetic field signal to be measured is modulated to the high-frequency sideband. Combined with lock-in amplification and demodulation technology for signal detection, the detection sensitivity of the ultra-low frequency magnetic field is significantly improved. Finally, based on the essential differences between acoustic field signals and magnetic field signals in terms of physical effects and response characteristics, the synchronous acquisition and subsequent separation of acoustic field signals and magnetic field signals on the same probe were realized, providing a unique physical premise for the joint interpretation of acoustic and magnetic data and the coordinated suppression of noise from the same source.

[0092] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0093] Although this disclosure has been shown and described with reference to specific exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made to this disclosure without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Therefore, the scope of this disclosure should not be limited to the above embodiments, but should be defined not only by the appended claims, but also by their equivalents.

Claims

1. A concentric ring acousto-magnetic composite sensor, characterized in that, include: A piezoelectric ceramic ring is used to respond to an external sound field and generate a first electrical signal, and to respond to magnetostrictive strain transmitted through the interface and generate a second electrical signal. The piezoelectric ceramic ring is tangentially polarized, with the polarization direction along the circumference of the piezoelectric ceramic ring. A magnetostrictive ring is concentrically fitted around the outside of the piezoelectric ceramic ring to respond to an external magnetic field and generate the magnetostrictive strain. An excitation coil is wound around the outer circumference of the magnetostrictive ring along the circumferential direction to generate a high-frequency bias magnetic field to modulate the frequency of the external magnetic field. The piezoelectric ceramic ring and the magnetostrictive ring are combined through a composite packaging process to realize the transmission of magnetostrictive strain, so that the piezoelectric ceramic ring synchronously outputs the first electrical signal and the second electrical signal. The concentric ring acoustomagnetic composite sensor has a concentric ring structure to provide an isotropic response to an external magnetic field in any direction parallel to the plane of the sensor.

2. The composite sensor according to claim 1, characterized in that, The inner and outer surfaces of the piezoelectric ceramic ring are plated with silver electrodes to serve as the common output terminal for the first and second electrical signals.

3. The composite sensor according to claim 1, characterized in that, The magnetostrictive ring is made of an iron-based amorphous alloy.

4. The composite sensor according to claim 1, characterized in that, The composite encapsulation process is an interference fit combined with epoxy resin bonding, and the interference between the piezoelectric ceramic ring and the magnetostrictive ring is 0.01mm-0.03mm. The interface gap between the piezoelectric ceramic ring and the magnetostrictive ring is filled with epoxy resin, and the interface coupling coefficient is greater than or equal to 0.

85.

5. An underwater measurement system, characterized in that, include: The concentric ring acousto-magnetic composite sensor as described in any one of claims 1 to 4; The signal conditioning and demodulation circuit is electrically connected to the output terminal of the piezoelectric ceramic ring and is used to receive and process the first electrical signal and the second electrical signal. The data acquisition module is used to acquire the sound field data of the external sound field and the magnetic field data of the external magnetic field.

6. The underwater measurement system according to claim 5, characterized in that, The signal conditioning and demodulation circuit includes: A sound field baseband amplifier is used to amplify the first electrical signal to obtain the sound field data; A magnetic field lock-in amplifier demodulation circuit is used to perform phase-sensitive detection on the second electrical signal based on the high-frequency bias magnetic field of the excitation coil, so as to demodulate the magnetic field data. The filtering and analog-to-digital conversion unit is used to filter and convert the amplified sound field data and the demodulated magnetic field data into digital data, respectively.

7. The underwater measurement system according to claim 5, characterized in that, Also includes: A weak magnetic alloy housing is used to encapsulate the concentric ring acousto-magnetic composite sensor to form a pressure-resistant and watertight probe.

8. The underwater measurement system according to claim 5, characterized in that, Also includes: The power management module is used to supply power to the concentric ring acoustomagnetic composite sensor and the signal conditioning and demodulation circuit.

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