A sink-float vertical gravity gradiometer

Abstract

The application belongs to the technical field of gravity gradient measurement, and specifically discloses a sinking and floating type vertical gravity gradiometer. The gravity gradiometer mainly comprises a fluid container, a fluid medium, a sensing unit and a measurement module. The sensing unit is designed in an integrated coaxial straight-line structure, and is composed of a partially submerged displacement probe, a fully submerged floating cabin body, a rigid force transmission shaft and a sinking weight, which are rigidly connected from top to bottom. The sensing unit is placed in the fluid medium, and a spatial asymmetric straight-line structure with a high floating center and a low gravity center is constructed. The working of the gravity gradiometer is based on a sinking force and a floating force difference mechanism. When the external vertical gravity gradient changes, the original balance of the sinking force and the floating force of the sensing unit is broken, and a net force difference drives the system to produce a small displacement in the vertical direction. The vertical displacement of the displacement probe is monitored by the measurement module, and the relative vertical gravity gradient value can be accurately calculated. The application has the advantages of simple structure, high integration, easy field operation and the like under the condition of high sensitivity.

Description

Technical Field

[0001] This application belongs to the field of gravity gradient measurement technology, specifically relating to a sinking-floating vertical gravity gradient meter. Background Technology

[0002] Gravity gradiometers, as high-precision instruments for measuring the spatial rate of change of the Earth's gravitational field, have extremely important applications in fields such as geological resource exploration and space mapping. Common gravity gradiometers are usually based on differential acceleration measurement or superconducting technology.

[0003] The mainstream gravity gradiometer technologies mainly include the traditional electromechanical differential accelerometer scheme and the quantum or superconducting scheme based on new technologies. Although the former attempts to cancel common-mode noise by using symmetrical distribution, it has extremely high requirements for the scaling factor matching accuracy of the accelerometer and the system structure is complex. The latter, although highly sensitive, must rely on an extremely complex cold atom system or liquid helium cryogenic system, which results in a large instrument size, extremely high power consumption, and extremely difficult field maintenance, making it difficult to leave the laboratory environment for field use.

[0004] Therefore, existing gravity gradiometers still face the problem of not being able to achieve both high sensitivity and portability, and insufficient environmental adaptability. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this application is to provide a sinking and floating vertical gravity gradiometer, which aims to solve the problems that existing gravity gradiometers face, such as the difficulty in achieving both high sensitivity and portability, and insufficient environmental adaptability.

[0006] The first aspect of this application relates to a sinking-floating vertical gravity gradient meter, comprising: a fluid container filled with a fluid medium; a sensing unit suspended and immersed in the fluid medium, comprising: a partially submerged displacement probe, a fully submerged floating chamber, a rigid force transmission shaft, and a weight connected in series from top to bottom; and a measurement module for monitoring the displacement change of the displacement probe in the vertical direction to obtain the change in the vertical gravity gradient.

[0007] In one embodiment, the geometric center of buoyancy of the floating hull, the geometric axis of the rigid force transmission shaft, and the geometric center of mass of the lower weight are all coaxially arranged on the same vertical measurement baseline to construct an integrated linear force transmission path without lateral deflection moment.

[0008] In one embodiment, the average density of the floating hull is less than the density of the fluid medium; the average density of the lower weight is greater than the density of the fluid medium.

[0009] In one embodiment, the displacement probe, the floating hull, the rigid force transmission shaft, and the lower weight are integrated into a single configuration to maintain a constant relative position.

[0010] In one embodiment, there is a preset height difference between the center of mass of the lower weight and the upper buoyancy chamber, so that the sensing unit can construct a spatial asymmetric structure with a high center of buoyancy and a low center of gravity in the fluid medium.

[0011] In one embodiment, the cross-sectional area of ​​the displacement probe is smaller than a preset threshold to amplify the displacement change caused by the change in gravitational gradient.

[0012] In one embodiment, the sinking-floating vertical gravity gradiometer is configured such that, under a preset gravity gradient environment, the sinking force and buoyancy force on the sensing unit are in equilibrium; when the external vertical gravity gradient changes, a net resultant force is generated to drive the sensing unit to move vertically until the restoring force generated by the change in the depth of the displacement probe immersed in the fluid medium causes it to reach a new equilibrium position.

[0013] In one embodiment, the change in vertical gravity gradient and the change in depth of the displacement probe satisfy a linear proportional relationship, and the linear proportionality coefficient is obtained by calibration using determined structural parameters and fluid medium parameters.

[0014] In one embodiment, the measurement module includes a capacitive displacement sensor, a magnetic sensor, or a photoelectric sensor.

[0015] In one embodiment, the displacement probe is a measuring probe with a thin rod-shaped body and a head that cooperates with the measuring module; the floating chamber is a sealed chamber with a cylindrical, conical, spherical, square, or irregular shape with a sealed cavity inside; the rigid force transmission shaft is a rigid straight rod; and the lower weight is a mass block with a cylindrical, conical, spherical, square, or irregular shape.

[0016] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: The sinking-floating vertical gravity gradiometer proposed in this application employs a fluid container filled with fluid medium, a suspended and submerged sensing unit, and a measurement module above the liquid surface. By using the fluid medium to provide buoyancy support and damping buffer, the sensing unit can sensitively generate vertical displacement when the gravity gradient changes, thus solving the problem of difficulty in achieving both high sensitivity and portability in the prior art.

[0017] Specifically, the sensing unit couples the sinking force of the lower object with the buoyancy of the upper hull through a rigid force transmission shaft, forming a dynamic system that is extremely sensitive to vertical gradients. When the gravity gradient changes slightly, the balance between the sinking force on the lower object and the buoyancy of the upper hull is broken. This change is transmitted losslessly to the partially submerged displacement probe through the rigid force transmission shaft. Since the displacement probe is only damped by the fluid medium and has no other mechanical friction, a small force difference can be converted into a large vertical displacement. The measurement module directly monitors this displacement change, thereby amplifying the weak gravity gradient signal, which is difficult to measure directly, into a geometric displacement signal that is easy to measure accurately. This ultimately achieves highly sensitive measurement, avoids complex mechanical structures, and enhances portability.

[0018] In addition, while maintaining a compact structure, the design also reduces the impact of environmental vibration and temperature fluctuations by isolating the fluid medium, thus achieving a balance between high sensitivity and strong environmental adaptability, enabling the instrument to operate stably under variable conditions such as in the field. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the submerged and floating vertical gravity gradiometer provided in the embodiments of this application; Figure 2 This is an enlarged schematic diagram of the sensing unit provided in the embodiments of this application; Figure 3 This is a flowchart illustrating the gravity gradient measurement method provided in the embodiments of this application.

[0020] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is the measurement module; 2 is the displacement probe; 3 is the fluid container; 4 is the floating hull; 41 is the floating center of the floating hull; 5 is the fluid medium; 6 is the rigid force transmission shaft; 61 is the center of mass of the rigid force transmission shaft; 7 is the lower weight; 71 is the center of mass of the lower weight. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0023] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0024] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0025] Currently, existing gravity gradiometers face the problem of not being able to achieve both high sensitivity and portability, as well as insufficient environmental adaptability.

[0026] Based on this, this application proposes an embodiment of a sinking-to-floating vertical gravity gradiometer. Please refer to... Figure 1 , Figure 1 This is a schematic diagram of the submerged and floating vertical gravity gradiometer provided in the embodiments of this application.

[0027] In this embodiment, the sinking-floating vertical gravity gradient meter includes: a fluid container 3 filled with a fluid medium 5; a sensing unit suspended and submerged in the fluid medium 5, including: a partially submerged displacement probe 2 connected in series from top to bottom, a fully submerged floating chamber 4, a rigid force transmission shaft 6, and a weight 7; and a measurement module 1, which can be set above the liquid surface of the fluid medium 5, for monitoring the displacement change of the displacement probe 2 in the vertical direction to obtain the vertical gravity gradient change.

[0028] It should be noted that this application proposes a sinking-floating vertical gravity gradiometer for measuring the gradient change of the Earth's gravitational field in the vertical direction. It senses the gravity gradient by detecting changes in the suspension state of a sensing unit in a fluid medium, and the measurement module monitors the displacement to obtain data.

[0029] It should be noted that the fluid container 3 is a rigid shell filled with a fluid medium 5, which provides a buoyancy and damping environment, such as deionized water or silicone oil, to support the suspension of the sensing unit.

[0030] It should be noted that the sensing unit consists of a displacement probe 2, an upper buoyancy chamber 4, a rigid force transmission shaft 6, and a lower weight 7 connected in series from top to bottom. The series connection refers to the fact that these components are mechanically linked to form a vertical chain structure, suspended and submerged in the fluid medium 5. The displacement probe 2 is partially submerged, with its tip exposed above the liquid surface, for direct displacement detection; the upper buoyancy chamber 4 is fully submerged and designed as a sealed hollow structure to provide buoyancy (the buoyancy force on the upper buoyancy chamber minus its weight is related to the gravitational acceleration at the chamber's location); the lower weight 7 is a high-density mass block that provides sinking force (the weight of the lower weight minus buoyancy is related to the gravitational acceleration at the lower weight's location); the rigid force transmission shaft 6 is a rod-shaped component that transmits the sinking force and buoyancy force differentially.

[0031] It should be noted that the measurement module 1 is positioned above the liquid surface and monitors the displacement probe 2 in the vertical direction using non-contact methods, such as capacitive displacement sensing, magnetic sensing, photoelectric sensing, etc., to obtain the vertical gravity gradient change.

[0032] To achieve the above, this application provides a feasible implementation method: Specifically, the fluid container 3 can be made of cylindrical glass or stainless steel to ensure chemical inertness and structural stability; the fluid medium 5 can be deionized water, glycerin, etc., to adjust the density and viscosity to adapt to different environments.

[0033] Specifically, the displacement probe 2 can be implemented as a displacement sensor probe that can be used with various types of sensors such as capacitive displacement sensing, magnetic sensing, and photoelectric sensing. For example, a measuring probe with a thin rod-shaped body and a head that cooperates with the measuring module. The buoyancy chamber 4 can be made of materials such as carbon steel or polyvinyl chloride plastic into a sealed chamber, and its shape can be cylindrical, conical, spherical, square, or irregular, filled with air or inert gas to control buoyancy. The rigid force transmission shaft 6 can be a rigid straight rod made of materials such as brass or ordinary carbon steel to ensure that the force transmission is free from elastic deformation. The lowering weight 7 can be made of materials such as iron blocks or copper blocks into cylindrical, conical, spherical, square, or irregular shaped mass blocks, and the initial sinking position can be finely adjusted by adjusting the mass.

[0034] Specifically, the measurement module 1 can be a sensor of various forms, such as capacitive displacement sensing, magnetic sensing, and photoelectric sensing, which can record displacement data in real time and output digital signals.

[0035] Regarding alternative options, the fluid medium 5 can be replaced with other known types of oil or other liquid fluids as needed; the floating hull 4 can adopt a multi-hull combination structure or an adjustable buoyancy structure; the lower weight 7 can be replaced with other forms of counterweight systems; and the displacement probe 2 and measurement module 1 can also be replaced with other conventional displacement and signal acquisition components. In addition, the connection method of the entire sensing unit can also be conventionally modified according to actual needs, provided that the vertical force transmission path is maintained.

[0036] Understandably, based on the above structure, the sinking and floating vertical gravity gradient meter is configured such that, under a preset gravity gradient environment, the sinking force and the buoyancy force on the sensing unit are in equilibrium; when the external vertical gravity gradient changes, a net resultant force is generated to drive the sensing unit to move vertically until the restoring force generated by the change in the depth of the displacement probe 2 immersed in the fluid medium 5 causes it to reach a new equilibrium position.

[0037] It should be noted that the sinking force refers to the weight of the lower object minus the buoyancy it experiences, and is related to the gravitational acceleration at its location; the buoyancy force refers to the upward buoyancy of the upper hull minus its downward weight, and is also related to the gravitational acceleration at its location. When the buoyancy and sinking forces are balanced, the sensing unit is stationary. When the external vertical gravity gradient changes, the changes in gravitational acceleration at different depths of the upper hull and the lower object are different, disrupting the force balance and generating a net resultant force driving vertical movement. This causes the depth to which the displacement probe 2 is immersed in the fluid medium 5 to change, resulting in a change in the submerged volume and generating additional buoyancy as a restoring force. The restoring force refers to the increase in buoyancy caused by the change in depth, and its direction is opposite to the displacement, prompting the sensing unit to reach a new equilibrium position. This process realizes the conversion of the change in gravity gradient into mechanical displacement.

[0038] It is understandable that the change in vertical gravity gradient and the change in depth of displacement probe 2 satisfy a linear proportional relationship.

[0039] For example, the preset calculation model for vertical gravity gradient change is: .

[0040] In the formula, This represents the vertical gravity gradient change information, where k is a linear scaling factor. This indicates the amount of depth change.

[0041] It should be noted that the coefficient k is obtained through calibration using defined structural and fluid medium parameters. Here, calibration refers to a process of measuring the depth change of the displacement probe of the sensing unit under a known and precisely controllable gravity gradient environment. h, and calculate the specific value of the proportional coefficient k based on the preset model.

[0042] To ensure measurement accuracy, calibration must be performed under high-standard conditions. The required structural parameters mainly include the total mass of the sensing unit, the mass and dimensions of its individual components, and the fluid medium parameters, primarily its density at the calibration ambient temperature and its viscosity, which affects the system's dynamic response.

[0043] It is understandable that there is a one-to-one correspondence between the defined combination of structural parameters and fluid medium parameters and the coefficient k. This one-to-one correspondence means that a specific set of parameter values ​​uniquely determines a single k value. Therefore, when any parameter affecting the force balance changes—for example, by changing the fluid medium to a different density, adjusting the mass of the load, or by changes in fluid density and sensor unit size due to temperature variations—the value of coefficient k will change. To ensure the accuracy of subsequent measurements, the above calibration procedure must be repeated under this new parameter combination.

[0044] Understandably, this linear model simplifies data processing and supports real-time gradient calculation: First, after obtaining the calibration coefficient k, the measurement module 1 only needs to collect the depth change of the displacement probe in real time, and can directly calculate the vertical gravity gradient change through simple multiplication, without the need for complex nonlinear iterative calculations or real-time force field modeling. This reduces the computing power requirements of the data processing unit.

[0045] Secondly, it is precisely based on this simple mathematical relationship that the system can support real-time gradient calculation. The displacement signal collected by measurement module 1, after analog-to-digital conversion, can be converted into gradient values ​​and output by the processor with almost no delay, realizing rapid and continuous monitoring of changes in the gravity gradient field. This feature is of key value for applications requiring real-time feedback, such as gravity gradient measurement on dynamic carriers (ships, aircraft) or real-time monitoring and early warning of geological disasters.

[0046] In summary, the effects and benefits of this submerged-floating vertical gravity gradiometer include: the sensing unit is suspended and immersed in the fluid medium 5, significantly reducing mechanical friction and interference from the support structure, and avoiding the displacement sensing dead zone caused by static friction of the solid; the viscous damping effect provided by the fluid medium 5 effectively suppresses environmental vibrations and enhances measurement stability. By directly monitoring the vertical displacement change of the displacement probe 2, the instrument can acquire high-precision gravity gradient data in real time and continuously, making it suitable for geophysical exploration, resource detection, or gravity field mapping.

[0047] Furthermore, based on the above embodiments, specific components are optimized to propose new embodiments. Please refer to... Figure 2 , Figure 2 This is an enlarged schematic diagram of the sensing unit provided in the embodiments of this application.

[0048] In this embodiment, the geometric center of buoyancy of the upper hull 4, the geometric axis of the rigid force transmission shaft 6, and the geometric center of mass of the lower weight 7 are all coaxially arranged on the same vertical measurement baseline to construct an integrated linear force transmission path without lateral deflection moment. That is, the buoyancy center 41 of the upper hull, the center of mass 61 of the rigid force transmission shaft, and the center of mass 71 of the lower weight in the figure are coaxial.

[0049] It is understandable that the geometric center of buoyancy refers to the shape center of the fluid volume displaced by the floating hull 4, i.e., the equivalent point of buoyancy; the geometric center of mass refers to the center point of the mass distribution of the lower weight 7; and the vertical measurement baseline is an ideal reference straight line perpendicular to the local horizontal plane. Arranging them on the same axis directly results in the construction of an integrated linear force transmission path without lateral deflection moment.

[0050] It is understandable that lateral flexural moment refers to the moment that attempts to bend a component due to the deviation of the point of force application from the axis; the integrated straight force transmission path means that all longitudinal forces generated by gravity and buoyancy can be transmitted along the same straight line, avoiding bending stress, friction or viscoelastic energy loss caused by axis deviation, and ensuring the highest fidelity correspondence between vertical displacement and net resultant force.

[0051] To achieve the aforementioned coaxial configuration, the following specific components and manufacturing examples can be adopted: The upper buoy 4 can be designed as a strictly axisymmetric rotating structure, such as a perfect cylinder or sphere, and manufactured using a material of uniform density. Precision machining ensures that its geometric center coincides with the center of buoyancy. A counterweight cavity can be set inside the buoy, and the center of buoyancy can be finely adjusted by adding micro-counterweights. The rigid force transmission shaft 6 can be made of materials such as stainless steel bars, precision ground to ensure that its geometric axis is consistent with the physical axis. It can be connected to the upper and lower components through high-precision coaxial threads or flanges at both ends. The lower weight 7 should be made of a material of uniform density and machined into an axisymmetric shape, such as a cylinder, and its geometric center of mass should be located on the axis through dynamic balancing calibration. The final assembly needs to be carried out on a precision platform, using an optical level and a laser alignment instrument to align and fix the designated axes of the above three components with the plumb line.

[0052] In this embodiment, the average density of the floating chamber 4 is less than the density of the fluid medium 5; the average density of the lower weight 7 is greater than the density of the fluid medium 5. This is the core physical condition for achieving stable suspension of the sensing unit in the fluid medium and establishing a sensitive force balance state.

[0053] It is understandable that average density refers to the ratio of an object's total mass to its total volume.

[0054] For the buoyancy chamber 4, its structure is typically non-solid, so its average density is determined by the density of the chamber shell material, the volume of the internal cavity, and any possible internal gas, and is always less than the density of the fluid medium 5. This relationship, according to Archimedes' principle, ensures that the buoyancy force on the buoyancy chamber in the fluid is greater than its own weight, thus generating a net upward buoyancy force related to the gravitational acceleration at that location.

[0055] The lower weight 7 is typically a solid or highly packed mass with an average density greater than that of the fluid medium 5. This results in the weight acting on it in the fluid being greater than the buoyancy, thus generating a net downward sinking force related to the gravitational acceleration at that location. The sensing unit connects these two parts into a whole via a rigid force transmission shaft 6. Under the combined action of the upward buoyancy and the downward sinking force, the entire sensing unit can achieve a stable suspended equilibrium position in the fluid.

[0056] In this embodiment, the displacement probe 2, the floating hull 4, the rigid force transmission shaft 6, and the lower weight 7 are integrated into one unit to maintain a constant relative position.

[0057] Understandably, integrated configuration refers to the rigid connection of these key mechanical components in a way that prevents relative movement, forming a single integrated structure. Specifically, they can be fixed together through welding, high-strength bonding, interference fits with pins, or directly machined as a single unit. For example, probes, force transmission shafts, and weight components can be precision-machined from a single metal blank and then fixed to a separately manufactured cabin. The direct purpose of this design is to maintain a constant relative position, ensuring that no minute relative displacement, torsion, or angular change occurs between these four components during instrument operation.

[0058] Understandably, this design eliminates micro-motion or deformation at internal connection points. If non-rigid connections are used between components, unpredictable and uncalibrated minute displacements may occur under stress or temperature changes, introducing measurement errors. The integrated configuration solidifies the entire sensing unit into a rigid body, permanently locking its internal geometry and ensuring the rigidity and determinism of the force transmission path. Secondly, it complements the aforementioned optimization of the coaxial configuration. The integrated structure permanently maintains the precisely calibrated vertical measurement baseline and coaxial relationship established during assembly and debugging, preventing the optimal alignment from being compromised due to component loosening or misalignment caused by long-term use or environmental vibration. Finally, it simplifies the system's mechanical model. Since there is no relative motion internally, the entire sensing unit can be considered a single rigid body during force analysis, with its mass, center of mass, and moment of inertia remaining stable. This makes the theoretical model based on force balance more accurate and reliable, and the long-term stability of the calibration coefficient k is also higher.

[0059] In this embodiment, there is a preset height difference between the center of mass of the heavy object 7 and the floating hull 4, so that the sensing unit can construct a spatial asymmetric structure with a high buoyancy center and a low center of gravity in the fluid medium 5.

[0060] It is understood that the preset height difference refers to a vertical distance value that is pre-set and precisely controlled during the design phase. It ensures that the center of mass of the floating hull 4, which provides the main buoyancy, is higher in space than the center of mass of the lower weight 7, which provides the main gravity. In specific implementation, the preset height difference is set according to the overall size of the gradient instrument. Preferably, the preset height difference is 30cm to 60cm.

[0061] Understandably, this spatial asymmetric structure breaks the symmetry between the center of buoyancy and the center of gravity, creating a stable torque balance condition. According to the principles of rigid body statics, when the center of buoyancy is above the center of gravity, after the sensing unit is subjected to a slight tilting disturbance in the fluid, the buoyancy and gravity will generate a restoring torque, causing it to tend to return to its original vertical attitude, thereby significantly enhancing its attitude stability.

[0062] It should be noted that obtaining the preset height difference is a systematic design process combining theoretical calculations, simulation optimization, and experimental calibration. Its core objective is to achieve an optimal balance between attitude stability and measurement sensitivity. For example: First, based on the geometric parameters and material density of the buoyant hull and the submerged weight, the positions of their centers of mass are theoretically calculated. The vertical difference between them is the initial height difference, which must satisfy the static stability condition that the center of buoyancy is higher than the center of gravity. Next, through multiphysics coupling simulation, the restoring torque and vertical displacement sensitivity under different height differences are analyzed in fluid dynamics and structural mechanics models, thereby optimizing and determining the design values ​​between stability and sensitivity. Finally, based on a physical prototype, experimental verification and fine-tuning are conducted in a controlled environment. By measuring the center of mass, applying disturbances and observing the recovery response, or locally adding or removing counterweights, the optimal height difference is finally calibrated. This method ensures the attitude stability of the sensing unit in complex environments, thereby guaranteeing measurement accuracy.

[0063] In this embodiment, the cross-sectional area of ​​the displacement probe 2 is smaller than a preset threshold to amplify the displacement change caused by the change in gravity gradient. Specifically, the preset threshold can be set to 20 mm², and preferably, the preset threshold is set to no more than 2% of the maximum cross-sectional area of ​​the floating hull 4.

[0064] It should be noted that the cross-sectional area refers to the cross-sectional area of ​​displacement probe 2 in the direction perpendicular to its axis. The preset threshold is a critical value determined through theoretical calculation, simulation analysis, or experimental calibration based on the overall system performance requirements. The core physical principle is that when displacement probe 2 moves vertically in fluid medium 5, the change in buoyancy it experiences is inversely proportional to its cross-sectional area. By reducing the cross-sectional area below the threshold, a sufficient mechanical amplification factor can be obtained. This allows displacement probe 2 to produce a larger displacement amplitude under the same net resultant force generated by the change in gravitational gradient, or in other words, enables the system to detect smaller changes in net resultant force.

[0065] It should be noted that the final sinking and floating vertical gravity gradiometer, which integrates all technical features, can achieve: a high-precision and high-stability vertical gravity gradient measurement based on the principle of force balance and displacement detection.

[0066] Specifically, through the synergistic effect of an integrated coaxial sensing unit, a spatial asymmetric stability design (high-position buoyancy center and low-position gravity center), and sensitivity optimization of the displacement probe (small cross-sectional area), a mechanical sensing system with good attitude stability in fluids, low internal friction and interference, and sensitivity to changes in vertical net net force was constructed. This system can efficiently, intuitively, and linearly convert minute changes in vertical gravity gradient into vertical displacements easily detectable by the displacement probe. Combined with a pre-set linear mathematical model and calibration techniques, the instrument ultimately achieves direct measurement of vertical gravity gradient changes with high sensitivity, high resolution, and rapid response. Simultaneously, it boasts a simple and reliable structure, good environmental adaptability, and is suitable for fine gravity field detection on long-term, continuous, and dynamic platforms.

[0067] In addition, this application proposes a method for measuring gravity gradient. This method defines the standard operating procedure for the instrument to quantify the changes in vertical gravity gradient between different locations. Please refer to... Figure 3 , Figure 3 This is a flowchart illustrating the gravity gradient measurement method provided in the embodiments of this application.

[0068] Specifically, the measurement range is first determined and grid points are divided. Then, multiple points are measured sequentially according to the grid points: the gradiometer is moved to the measurement position 1, and after equilibration, the output signal 1 of the measurement module reflecting the displacement probe depth information is recorded; the gradiometer is moved to the measurement position 2, and after equilibration, the output signal 2 of the measurement module reflecting the displacement probe depth information is recorded; ...; the gradiometer is moved to the measurement position n, and after equilibration, the output signal n of the measurement module reflecting the displacement probe depth information is recorded. The changes in the output signals of the measurement module between these different measurement positions reflect the changes in the gravitational gradient.

[0069] Understandably, this process combines high-precision instrument hardware with standardized operating procedures, enabling on-site, quantitative, and rapid measurement of vertical gravity gradient changes. The method is clear in its steps, highly operable, and effectively utilizes the instrument's linear response characteristics, avoiding complex real-time force field modeling. Furthermore, it inherits the same beneficial effects as the sinking-floating vertical gravity gradiometer provided in the aforementioned embodiments, which will not be elaborated upon here.

[0070] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0071] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0072] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0073] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0074] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A sinking-floating vertical gravity gradiometer, characterized in that, include: A fluid container, filled with a fluid medium; The sensing unit, suspended and submerged in the fluid medium, includes: a partially submerged displacement probe connected in series from top to bottom, a fully submerged floating hull, a rigid force transmission shaft, and a weight below. The measurement module is used to monitor the displacement change of the displacement probe in the vertical direction in order to obtain the change of the vertical gravity gradient.

2. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that: The geometric center of buoyancy of the floating hull, the geometric axis of the rigid force transmission shaft, and the geometric center of mass of the lower weight are all coaxially arranged on the same vertical measurement baseline to construct an integrated linear force transmission path without lateral deflection moment.

3. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that: The average density of the floating hull is less than the density of the fluid medium; the average density of the lower weight is greater than the density of the fluid medium.

4. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that: The displacement probe, the floating hull, the rigid force transmission shaft, and the lower weight are integrated into a single configuration to maintain a constant relative position.

5. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that: There is a preset height difference between the center of mass of the lower weight and the center of mass of the upper buoyancy chamber, so that the sensing unit can construct a spatial asymmetric structure of a high buoyancy center and a low center of mass in the fluid medium.

6. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that: The cross-sectional area of ​​the displacement probe is smaller than a preset threshold to amplify the displacement change caused by the change in gravity gradient.

7. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that, The sinking-floating vertical gravity gradiometer is configured as follows: Under a preset gravity gradient environment, the sinking force and buoyancy force experienced by the sensing unit are in equilibrium. When the external vertical gravity gradient changes, a net resultant force is generated that drives the sensing unit to move vertically until the restoring force generated by the change in the depth of the displacement probe immersed in the fluid medium causes it to reach a new equilibrium position.

8. The sinking-floating vertical gravity gradiometer as described in claim 1 or 7, characterized in that: The change in vertical gravity gradient and the change in depth of the displacement probe satisfy a linear proportional relationship, and the linear proportionality coefficient is obtained by calibration using determined structural parameters and fluid medium parameters.

9. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that, The measurement module includes a capacitive displacement sensor, a magnetic sensor, or a photoelectric sensor.

10. The sinking-floating vertical gravity gradiometer as described in claim 1, characterized in that, The displacement probe is a measuring probe with a thin rod-shaped body and a head that cooperates with the measuring module; The floating hull is a cylindrical, conical, spherical, or square sealed hull with a sealed cavity inside. The rigid force transmission shaft is a rigid straight rod; The lower weight is a cylindrical, conical, spherical, or square mass block.

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