A marine towed vector magnetometer gradiometer

Abstract

The application discloses a marine towed vector magnetic gradient instrument, which comprises a deck unit and a towed body, the towed body comprises a non-magnetic pressure-bearing shell, a non-magnetic mounting framework and a tail wing fixedly arranged at the tail of the non-magnetic pressure-bearing shell, the non-magnetic pressure-bearing shell is fixedly sleeved outside the non-magnetic mounting framework and cooperatively forms a closed chamber, the non-magnetic mounting framework in the closed chamber is fixedly connected with a magnetic gradient measuring module for measuring magnetic data, an acquisition module for acquiring magnetic data and a power module for supplying power to the magnetic gradient measuring module and the acquisition module, the deck unit is electrically connected with the acquisition module and the power module through a tension cable, the deck unit obtains electricity through an external power supply, and the deck unit is further provided with a data output end for data interaction. The application simultaneously realizes the functions of magnetic force vector measurement, scalar measurement, vector gradient measurement and scalar gradient measurement.

Description

Technical Field

[0001] The present invention belongs to the field of underwater magnetic signal detection, and in particular relates to an ocean towed vector magnetic gradiometer. Background Art

[0002] Marine magnetic signal detection is an important means of marine geophysical exploration. It reflects the magnetic topography of the detection area by obtaining the magnetic signal characteristics of the marine geological environment, or locates and identifies magnetic targets by obtaining magnetic anomaly signals.

[0003] Conventional magnetic field measurements include vector and scalar measurements. Scalar measurements generally refer to the total field measurement of the Earth's magnetic field, which can only reflect the magnitude of the measured field but not its direction. Mature devices include cesium optically pumped magnetometers, helium optically pumped magnetometers, or proton magnetometers. Two or more scalar measurement devices, arranged according to a certain pattern, can form a scalar gradient measurement device. Scalar magnetic gradient information is obtained from the scalar magnetic field values ​​synchronously acquired by multiple magnetometers. Vector measurements generally refer to component measurements of the Earth's magnetic field, which can reflect both the magnitude and direction of the measured field. Common devices include vector fluxgate magnetometers, high-temperature superconducting magnetometers, and vector magnetoresistive magnetometers. These devices typically consist of three magnetic component sensors, each perpendicular to the other. Each component acquires magnetic field data along its axis, and the resulting total field is the total geomagnetic field data. Two or more sets of vector measurement devices, arranged according to a certain pattern, can form a vector gradient measurement device. Both vector and total field gradient information can be obtained from the magnetic field vector values ​​synchronously acquired by multiple magnetometers.

[0004] Compared with the scalar gradient measurement device, the vector gradient measurement device can obtain not only the total field magnetic information, but also the component magnetic information. The reflected magnetic field information is richer, the inversion mapping of geological magnetic features is more comprehensive and rich, and the positioning and identification of magnetic target characteristics is more accurate and efficient.

[0005] The invention patent "A Cesium Optically Pumped Magnetometer Probe CN106772158A" proposes the fabrication of a cesium optically pumped magnetometer probe, comprising an atomic absorption chamber, a photocell, a light-transmitting window, and a cesium spectral lamp. This optically pumped magnetometer probe features a narrow working area, a compact size, and low energy consumption. However, the probe is a scalar magnetometer, providing only scalar data on the total geomagnetic field, not geomagnetic vector or geomagnetic gradient data, and its intended operating environment is not specified. The invention patent "A Deep-Sea Towed Proton Precession Magnetometer" proposes a deep-sea towed proton precession magnetometer system, comprising a deck unit and a submersible unit connected to the submersible unit's ballast via an optoelectronic composite cable and a bearing head. The ballast is connected to the magnetometer towfish via a magnetic cable, and the deck unit and submersible unit communicate via optical fiber. This invention emphasizes an engineering application method for use in marine environments, but the magnetometer used is still a scalar magnetometer and cannot provide magnetic field gradient information. The journal "An Array-Type Marine Magnetism Measurement System" proposes an array-type marine magnetism measurement system based on multiple marine magnetometers, depth sounders, and GPS. The system consists of three G882 total-field magnetometers arranged in a specific sequence to form a total-field gradient array, enabling simultaneous acquisition of multiple data channels and gradient data. While the system can measure gradient data in an ocean environment, it can only measure total geomagnetic field gradients, not geomagnetic vector data or vector gradient data. Summary of the Invention

[0006] One of the objectives of the present invention is to provide a marine towed vector magnetic gradiometer to solve the problem that the existing magnetometers in the background art cannot obtain geomagnetic vector data and vector gradient data at the same time.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A marine towed vector magnetic gradiometer includes a deck unit and a towed body, wherein the towed body includes a non-magnetic pressure-bearing shell, a non-magnetic mounting frame, and a tail fin fixedly arranged at the tail of the non-magnetic pressure-bearing shell. The non-magnetic pressure-bearing shell is fixedly sleeved outside the non-magnetic mounting frame and cooperates to form a closed chamber. The non-magnetic mounting frame in the closed chamber is fixedly connected to a magnetic gradient measurement module for measuring magnetic data, an acquisition module for acquiring magnetic data, and a power supply module for supplying power to the magnetic gradient measurement module and the acquisition module; the power supply module and the acquisition module are commonly connected to an interface, the deck unit and the interface are electrically connected via a tension cable, the deck unit is powered by an external power supply, and the deck unit is also provided with a data output terminal for data exchange.

[0009] Preferably, the magnetic gradient measurement module includes two vector magnetometers, which are arranged at a certain distance. Each vector magnetometer includes three magnetic component sensors that are perpendicular to each other, and the components of the two vector magnetometers are arranged in the same direction.

[0010] Preferably, the vector magnetometer is a vector fluxgate magnetometer.

[0011] Preferably, a heading attitude sensor is further connected to the non-magnetic mounting frame in the sealed chamber, the power module supplies power to the heading attitude sensor, and the acquisition module acquires navigation data of the heading attitude sensor.

[0012] Preferably, the head of the non-magnetic mounting skeleton is the sealing end face of the closed chamber, the head of the non-magnetic pressure-bearing shell is matched with the sealing end face to set an opening, a pressure sensor is fixedly connected to the non-magnetic skeleton outside the closed chamber, the power module supplies power to the pressure sensor, and the acquisition module collects water depth data of the pressure sensor.

[0013] Preferably, the dragging body further comprises a deflector fixedly mounted on the head of the non-magnetic pressure-bearing shell, the deflector is provided with a water inlet in cooperation with the pressure sensor, and the deflector is provided with a mounting hole in cooperation with the tension cable.

[0014] Preferably, the maximum bearing force of the tension cable is 1000kg, the maximum power supply is 220V, and the RS485 serial port is used, and the maximum signal transmission distance is ≥1000m.

[0015] Preferably, the outer diameter of the drag body is ≤90.0 mm, the weight is ≤10.0 kg, and the length is ≤1.5 m.

[0016] Preferably, the maximum withstand pressure of the magnetic gradiometer is ≥10MPa. Working principle:

[0017] The marine towed vector magnetic gradiometer of the present invention adopts a magnetic gradient measurement module. The magnetic gradient measurement module uses two vector fluxgate magnetometers arranged in the same order of components. The measured data include six sets of magnetic component data, two sets of total magnetic field data, three sets of magnetic component gradient data, and one set of total magnetic field gradient data.

[0018] The present invention uses a pressure sensor to measure the water depth and assist in magnetic field error correction and compensation; uses a heading sensor to measure the roll angle, pitch angle and heading angle, and assist in magnetic field error correction and compensation; uses a non-magnetic pressure-resistant shell with a tail fin for system sealing and deep-sea use; uses a tension cable for signal transmission and towing; uses a deck unit for signal switching and communication; and uses a collection system for data acquisition and processing.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention simultaneously realizes the functions of magnetic vector measurement, scalar measurement, vector gradient measurement, and scalar gradient measurement; adopts a pressure-resistant structural design, making deep-sea magnetic measurement at a water depth of more than 500m possible; adopts a tension cable that can simultaneously bear force, supply power, and transmit signals, and adopts RS485 communication method, realizing long-distance signal transmission of more than 500m; the towing body adopts a compact, small, and lightweight design, with a towing body length of no more than 1.5m, an outer diameter of no more than 90.0mm, and an underwater part weight of no more than 10.0kg, which is convenient for retraction and deployment operations in marine environments and does not require a special retraction and deployment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the overall structure of the ocean towed vector magnetic gradiometer provided in an embodiment of the present invention.

[0022] Figure 2 for Figure 1 Schematic diagram of the structure of the non-magnetic mounting frame.

[0023] Markings in the figure: 1. Towed body; 2. Tail; 3. Fairing; 4. Tension cable; 5. Deck unit; 6. Power cord; 7. Deck cable; 8. Acquisition system; 9. Magnetic gradient measurement module; 10. Non-magnetic mounting frame; 11. Attitude and heading sensor; 12. Power module; 13. Acquisition module; 14. Pressure sensor. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Reference Figure 1 , a marine towed vector magnetic gradiometer, including a deck unit 5 and a towing body 1, the towing body 1 is a towing carrier of the underwater wet end, which undertakes the functions of pressure-resistant sealing, magnetic gradient data acquisition and transmission, and its outer diameter is ≤90.0mm, length ≤1.5m, and total weight ≤10.0kg. The towing body 1 has the advantages of being light and easy to operate, and the underwater system does not need to be equipped with a special retraction system, which is convenient for application in the marine environment. The towing body 11 includes a non-magnetic pressure-bearing shell, a non-magnetic mounting frame 10 and a tail wing 2. The non-magnetic pressure-bearing shell and the non-magnetic mounting frame 10 are both made of non-magnetic aluminum alloy (model: TC4). The non-magnetic nature of the material prevents the entire device from introducing system magnetic interference, ensuring the accuracy of the magnetic field measurement. The non-magnetic pressure-bearing shell is a sleeve with a closed rear end, an open front end and a receiving cavity for mounting the non-magnetic mounting frame 10; refer to Figure 2The non-magnetic mounting frame 10 is a support frame for the entire circuit system inside the tow body 1. A magnetic gradient measurement module 9, an acquisition module 13, and a power module 12 are fixed to the non-magnetic mounting frame 10. The power module 12 is electrically connected to the magnetic gradient measurement module 9 and the acquisition module 13, respectively, for supplying power to the magnetic gradient measurement module 9 and the acquisition module 13. The acquisition module 13 is electrically connected to the magnetic gradient measurement module 9 for collecting magnetic data measured by the magnetic gradient measurement module 9. The non-magnetic pressure-bearing housing is fixedly sleeved on the non-magnetic mounting frame 10, and the front end face of the non-magnetic mounting frame 10 cooperates with the front portion of the non-magnetic pressure-bearing housing to form a sealed end face, thereby making the accommodating cavity a sealed chamber under the action of the sealed end face. The magnetic gradient measurement module 9, the acquisition module 13, and the power module 12 are all arranged in the sealed chamber. For example, a sealing ring can be provided between the non-magnetic pressure-bearing housing and the non-magnetic mounting frame 10 to achieve the formation of a sealed end face by the front end face of the non-magnetic mounting frame 10 and the front portion of the non-magnetic pressure-bearing housing. This is common knowledge in the art, and those skilled in the art can set it according to actual conditions. The tail wing 2 is fixedly arranged at the rear end of the non-magnetic pressure-bearing shell, and the tail wing 2 is used for balance and stability during the towing process.

[0026] The deck unit 5 is equipped with an RS485 serial port. The acquisition module 13 and the power module 12 are connected to a common interface. The RS485 serial port in this interface is connected to the RS485 serial port of the deck unit 5 via a tension cable 4. The non-magnetic pressure-bearing housing has a mounting hole for the tension cable 4. A sealing ring is fixedly installed in the mounting hole, which cooperates with the tension cable 4 to prevent liquid media from entering the sealed chamber through the mounting hole. The deck unit 5 is connected to a 220VAC / 50Hz external power supply via a power cable 6. After converting the 220VAC to 28VDC, the power module is supplied via the cable, thereby powering the entire marine towed vector magnetometer, achieving voltage conversion and voltage stabilization for the entire system. The deck unit 5 also has a data output terminal for data exchange. The deck unit 5 is connected to the input terminal of the acquisition system 8 via a deck cable 7 to enable data exchange. The acquisition system 8 includes a human-computer interaction main interface, which enables command transmission and data acquisition, display, storage, and playback.

[0027] In this invention, the tension cable 4 performs load-bearing, power supply, and signal transmission functions. It can be 500 meters or longer, bear a maximum load of 1000 kg, and is powered by 28V. It utilizes RS485 communication, with a maximum signal transmission distance of 1000 meters or more. The deck unit 5 serves as a power and signal relay, uploading data from the towed vehicle 1, distributing commands from the data acquisition system 8, and providing a stable voltage.

[0028] In the present invention, the magnetic gradient measurement module 9 is the core module for magnetic measurement, realizing the functions of magnetic vector measurement, scalar measurement, vector gradient measurement, and scalar gradient measurement. The magnetic gradient measurement module 9 includes two three-component fluxgate magnetometers, which are arranged in a corresponding order and a certain distance apart. Specifically, each three-component fluxgate magnetometer includes three magnetic component sensors, each of which is perpendicular to the other. The three components represent the X component, Y component, and Z component respectively. The X component direction of the two magnetometers is consistent, the Y component direction is consistent, and the Z component direction is consistent, so as to measure the component, total field, component gradient, and total field gradient.

[0029] In the present invention, since each magnetic field component of the magnetometer can measure the magnetic field projection of the total geomagnetic field along its axial direction, the three magnetic components are used to obtain a composite total field value by taking the square root of the square root. Two vector magnetometers are arranged in a corresponding order and a certain distance apart, i.e., the components are arranged in the same direction. The magnetic gradient measurement module 9 can simultaneously measure the six magnetic field component data and the two composite total field data. Components in the same direction are subtracted to obtain the component gradient value, and the two composite total fields are subtracted to obtain the total field gradient value.

[0030] In the present invention, the vector magnetic gradiometer is operated in a towing manner. Since the length of the tension cable 4 is ≥500m, the maximum towing length of the vector magnetic gradiometer is ≥500m, the maximum deployment water depth is ≥500m, and the maximum pressure resistance of the vector magnetic gradiometer is ≥10MPa.

[0031] Furthermore, the front end of the non-magnetic pressure-bearing shell is fixedly connected to the deflector 3, and the tension cable 4 is led out from the deflector 3. The deflector 3 is used to guide the fluid during the towing process and plays a role of balance and stability.

[0032] Furthermore, a pressure sensor 14 is installed between the deflector 3 and the non-magnetic mounting frame 10. This pressure sensor 14 is fixedly mounted on the front surface of the non-magnetic mounting frame 10 and is located outside the sealed chamber. The pressure sensor 14 is electrically connected to the acquisition module 13 and the power module 12. The acquisition module 13 acquires water depth data measured by the pressure sensor 14, and the power module 12 supplies power to the pressure sensor 14. The deflector 3 is equipped with a water inlet to accommodate this pressure sensor 14. The pressure sensor 14 is used to measure the submerged depth of the towed body 1. Its maximum operating depth is 500 meters and its maximum range is 5 MPa. Furthermore, a heading sensor 11 is fixedly mounted on the non-magnetic mounting frame 10 within the sealed chamber. This heading sensor 11 is a navigation unit used to measure the roll, pitch, and heading angles of the towed vehicle 1. Its roll range is 0-360°, its pitch range is ±90°, and its heading range is 0-360°, providing real-time information on the attitude and heading of the towed vehicle 1. The heading sensor 11 is connected to the acquisition module 13 and power module 12. The power module 12 not only supplies power to the pressure sensor 14, the magnetic gradient measurement module 9, and the acquisition module 13, but also to the heading sensor 11. The acquisition module 13 collects magnetic and water depth data, as well as navigation data from the heading sensor 11.

[0033] In the present invention, the power module 12 serves as the power supply for the internal circuit system of the towed body 1. It converts the 28VDC provided by the deck unit into ±12VDC to power the various electronic modules on the non-magnetic mounting frame 10. The acquisition module 13 is used to synchronously collect, fuse, and package magnetic data, navigation data, and water depth data from the magnetic gradient measurement module 9, the heading and attitude sensor 11, and the pressure sensor 14, processing them into complete data packets for upload via the tension cable 4, with a maximum upload frequency of 10Hz. It also receives command information from the acquisition system 8 and responds to command control.

[0034] In the present invention, water depth, attitude, and heading information are acquired through an external pressure sensor 14 and a heading attitude sensor 11, and incorporated into a magnetic field error correction algorithm to correct and compensate for magnetic field errors. This magnetic field error correction algorithm uses the content disclosed in Application No. 202110752476.0, entitled "A Method for Correcting Steering Errors in a Vector Magnetic Gradiometer."

Claims

1. A marine towed vector magnetic gradiometer, characterized in that: The towing device comprises a deck unit and a towing body, wherein the towing body comprises a non-magnetic pressure-bearing shell, a non-magnetic mounting frame, and a tail wing fixedly arranged at the rear of the non-magnetic pressure-bearing shell. The non-magnetic pressure-bearing shell is fixedly sleeved on the non-magnetic mounting frame and cooperates to form a closed chamber. The non-magnetic mounting frame in the closed chamber is fixedly connected to a magnetic gradient measurement module for measuring magnetic data, an acquisition module for acquiring magnetic data, and a power supply module for supplying power to the magnetic gradient measurement module and the acquisition module. The power supply module and the acquisition module are commonly connected to an interface. The deck unit and the interface are electrically connected via a tension cable. The deck unit obtains power via an external power supply. The deck unit is also provided with a data output terminal for data exchange. The magnetic gradient measurement module includes two vector magnetometers, which are arranged at a certain distance from each other, and each vector magnetometer includes three magnetic component sensors that are perpendicular to each other. The components of the two vector magnetometers are arranged in the same direction, and the vector magnetometers are vector fluxgate magnetometers; the non-magnetic mounting frame in the closed chamber is also connected to a heading sensor, the power module supplies power to the heading sensor, and the acquisition module collects navigation data from the heading sensor; the head of the non-magnetic mounting frame is the sealing end face of the closed chamber, the head of the non-magnetic pressure-bearing shell is provided with an opening to cooperate with the sealing end face, and a pressure sensor is fixedly connected to the non-magnetic frame outside the closed chamber; The power module supplies power to the pressure sensor, and the acquisition module collects water depth data from the pressure sensor; the towing body also includes a deflector fixedly mounted on the head of the non-magnetic pressure-bearing shell, the deflector is provided with a water inlet in conjunction with the pressure sensor, and the deflector is provided with an installation hole in conjunction with the tension cable.

2. The ocean towed vector magnetic gradiometer according to claim 1, characterized in that: The maximum bearing force of the tension cable is 1000kg, the power supply is 28VDC, and it uses an RS485 serial port. The maximum signal transmission distance is ≥1000m.

3. The ocean towed vector magnetic gradiometer according to claim 1, characterized in that: The outer diameter of the drag body is ≤90.0 mm, the weight is ≤10.0 kg, and the length is ≤1.5 m.

4. The ocean towed vector magnetic gradiometer according to claim 1, characterized in that: The maximum pressure resistance of the magnetic gradiometer is ≥10 MPa.

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