Magnetic-liquid mixed suspension gravimeter

Abstract

A magnetic-liquid mixed suspension gravimeter comprises a shell, a magnetic confinement unit, a suspension oscillator unit and a displacement detection unit, the shell is filled with a liquid medium, the magnetic confinement unit and the suspension oscillator unit are located in the shell, the magnetic confinement unit provides suspension force for the suspension oscillator unit, the suspension oscillator unit comprises an oscillator and a displacement component, and the displacement component is located in the shell. The density of the liquid medium is smaller than that of the vibrator material, the displacement component moves along with the vibrator, and the displacement detection unit detects the displacement of the displacement component and is used for calculating a gravity measurement result. The reliability of the gravimeter in a complex environment is improved, the sensitivity to environment temperature change is reduced, the structure is simplified, the size is small, maintenance is easy, and high precision and long-term stability are achieved.

Description

Technical Field

[0001] This invention belongs to the field of gravity measurement technology, and relates to antimagnetic levitation technology, specifically a magnetic-liquid hybrid levitation gravimeter. Background Technology

[0002] Gravity measurement is a key technology in geophysics, resource exploration, and fundamental physics research. Currently, high-precision gravimeters are mainly divided into two categories: absolute gravimeters and relative gravimeters. Absolute gravimeters play an important role in many fields due to their superior accuracy, but their large size, high cost, and complex operational requirements limit their application in portable, commercial, and large-scale deployments. Relative gravimeters, such as quartz spring gravimeters or microelectromechanical systems (MEMS) gravimeters, compensate for some of the shortcomings of absolute gravimeters due to their more compact design and relatively lower cost. However, they generally face the problem of long-term linear drift, mainly because quartz or MEMS materials undergo irreversible deformation under long-term loads, causing gravity measurement results to gradually shift over time, affecting the reliability of the data and the effectiveness of long-term monitoring.

[0003] In recent years, levitation systems have received widespread attention as an innovative means of acceleration measurement. For example, Chinese patent document CN113484538A discloses an acceleration measurement method based on antimagnetic levitation. Gravity measurement is an important branch of acceleration measurement. Chinese patent document CN119960071A discloses a small-sized, high-precision gravimeter based on the principle of antimagnetic levitation. It uses permanent magnets to construct a magnetic confinement potential well, allowing the antimagnetic material oscillator to be stably suspended in the air, avoiding direct contact with any material. However, these methods require operation in a vacuum to reduce mechanical impact damage and long-term linear drift caused by device corrosion. However, these technical solutions and similar levitation gravimeters face several significant technical challenges:

[0004] First, for gravity measurement applications in complex environments, gravimeters face mechanical shocks during transportation and other processes. When mechanical oscillators under vacuum conditions are subjected to mechanical shocks, the mechanical properties and magnetic structure of the oscillators will be damaged and aged due to the lack of a buffer mechanism. These damages will be reflected in changes in the magnetic performance of the system, leading to the accumulation of measurement errors and even directly causing damage to the oscillator, thus directly limiting the core performance indicators of its portable measurement applications.

[0005] Secondly, for applications requiring gravity measurement in the field and complex environments, the vacuum system necessitates maintenance of the vacuum pump, airtightness checks of the chamber, and long-term maintenance of the vacuum level. Especially in long-term field monitoring and unattended applications, the stability of the vacuum system is difficult to guarantee, requiring regular maintenance. This undoubtedly increases the system's size and power consumption, ultimately increasing operating costs.

[0006] Furthermore, the requirement for a strong magnetic field limits the choice of magnet design and oscillator materials. Suspending high-density diamagnetic materials in air requires extremely strong magnetic fields and magnetic field gradients. This not only places stringent demands on the design and manufacture of the magnet but may also introduce additional magnetic noise, affecting the accuracy of the measurement. In addition, the limited selection of high-density diamagnetic materials makes it difficult to achieve higher thermal noise suppression, thus affecting the sensitivity of the measurement.

[0007] In summary, while existing levitation gravimeters can theoretically provide high-precision gravity measurements, they still face numerous technical bottlenecks in practical applications, particularly in terms of portability, long-term stability, and ease of maintenance. Therefore, there is an urgent need to develop a novel gravity measurement device that can maintain high accuracy and long-term stability while reducing sensitivity to temperature fluctuations, eliminating dependence on a vacuum environment, and lowering magnetic field requirements. Summary of the Invention

[0008] The technical problem to be solved by the present invention is that existing suspended gravimeters are easily affected by ambient temperature, have high requirements for the operating environment, and cannot meet the usage requirements in terms of stability and ease of maintenance.

[0009] The technical solution of the present invention is as follows: a magnetic-liquid hybrid suspension gravimeter, comprising a shell, a magnetic confinement unit, a suspension oscillator unit, and a displacement detection unit. The shell is filled with a liquid medium. The magnetic confinement unit and the suspension oscillator are located inside the shell. The magnetic confinement unit provides levitation force for the suspension oscillator. The density of the liquid medium is less than the density of the suspension oscillator material. The displacement detection unit detects the displacement of the suspension oscillator in the vertical direction and is used to calculate the gravity measurement result.

[0010] Furthermore, the displacement detection unit includes an LED light source, an imaging lens, a moving light-blocking component, a fixed light-blocking component, and a camera. The fixed light-blocking component is fixed in position relative to the magnetic confinement unit, while the moving light-blocking component moves vertically with the levitating oscillator. Under the illumination of the LED light source, the moving light-blocking component and the fixed light-blocking component are magnified by the imaging lens and imaged in the camera. The displacement of the moving light-blocking component is detected with the position of the fixed light-blocking component as a reference.

[0011] Furthermore, the moving light-blocking component is fixed above the oscillator by a vertical rod, and the fixed light-blocking component is fixed above the magnetic confinement unit by a vertical rod. Both are set on the focal plane of the imaging lens. The moving light-blocking component and the fixed light-blocking component do not overlap in the area of ​​the light beam blocked in the direction of the optical axis of the imaging lens, and do not interfere with each other in space.

[0012] Furthermore, the moving light-blocking component and the fixed light-blocking component are light-transmitting sheets containing light-blocking patterns, with the light-blocking pattern of the fixed light-blocking component located on one or both sides of the light-blocking pattern of the moving light-blocking component.

[0013] Furthermore, a pair of light path windows are provided on both sides of the housing, with the LED light source and camera located outside the light path windows respectively.

[0014] Furthermore, it also includes a temperature control unit, which comprises a temperature probe, an electric heater, and a PID controller, used to control the temperature of the liquid medium inside the housing.

[0015] Furthermore, the oscillator is made of PMMA, SiO2, or metallic bismuth.

[0016] Furthermore, the oscillator is a cylinder with a regular polygonal cross-section, and the bottom portion contracts relative to the top portion.

[0017] Furthermore, the magnetic confinement unit includes two layers of permanent magnets, with the lower magnet pointing towards the center and the upper magnet pointing outward from the center. The permanent magnets are made of samarium cobalt or neodymium iron boron. The upper magnet has a cavity structure in the center to accommodate the oscillator.

[0018] Furthermore, the housing is a multi-layered nested housing, including an inner housing, a magnetic shielding housing, and an outer housing. The bottom of the housing is equipped with leveling screws for adjusting the gravimeter so that its tilt angle is less than 10°. -5 radian.

[0019] Existing technologies rely entirely on magnetic levitation, limiting their application to materials with strong antimagnetic properties, such as graphite. Graphite exhibits low temperature stability, necessitating stringent temperature control. In contrast, the magnetic-fluid hybrid levitation method of this invention can levy materials with relatively low antimagnetic properties but low temperature sensitivity, such as PMMA and silica, thus reducing the system's temperature stability requirements. Furthermore, this invention eliminates the need for a vacuum environment and vacuum equipment, including a vacuum chamber and an outer vacuum pump, further reducing the size of the gravimeter.

[0020] The present invention has the following beneficial effects:

[0021] 1) The magnetic-liquid hybrid suspension scheme proposed in this invention provides a buffer, which can prevent mechanical impact from damaging the oscillator and improve the reliability of the gravimeter in complex environments; the liquid provides better thermal uniformity, reduces the impact of external temperature changes on the gravimeter, and facilitates the temperature control unit to control the working environment temperature of the suspension oscillator unit; in addition, by selecting the liquid medium, corrosion resistance can be achieved without the aid of an external vacuum system.

[0022] 2) This invention utilizes the combination of magnetic confinement unit and liquid medium to achieve stable suspension not only in the vertical direction, but also to provide additional damping in the horizontal direction to improve lateral stability.

[0023] 3) The displacement detection unit of the present invention uses CCD detection, which reduces the linear drift of the optical path and increases the detection range compared with the existing technology that uses laser for photoelectric conversion. This increases the measurable gravity fluctuation range of the system, enables the precise capture of the small displacement changes of the oscillator, improves the measurement sensitivity, and realizes high-precision measurement of small gravity changes.

[0024] 4) The magnetic-liquid hybrid suspension gravimeter of the present invention is advantageous for small-size design, improves portability, reduces the requirements for the working environment, and is beneficial for field operations.

[0025] 5) The magnetic-liquid hybrid suspension gravity detection scheme proposed in this invention provides auxiliary suspension force through the liquid, which is conducive to expanding different design schemes of the magnetic confinement unit. By adjusting the position of the permanent magnet, the characteristics of the magnetic confinement potential well can be flexibly controlled to adapt to different application requirements. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an embodiment of the gravimeter of the present invention.

[0027] Figure 2 This is a schematic diagram of the displacement detection unit of the present invention performing displacement measurement.

[0028] Figure 3 This is a schematic diagram of the displacement detection sensitivity of the present invention. The single-light-blocking component represents the prior art method of measuring a single moving light-blocking component using a laser, while the dual-light-blocking component represents the present invention method of performing differential measurement using a moving light-blocking component and a fixed light-blocking component.

[0029] Figure 4 This is a schematic diagram illustrating the displacement of the moving light-blocking component and the fixed light-blocking component of the present invention.

[0030] Figure 5 This is a schematic diagram of the second displacement method between the moving light-blocking component and the fixed light-blocking component of the present invention.

[0031] Figure 6 This is a curve showing the change of gravitational acceleration measurement results with temperature in the embodiments of the present invention.

[0032] The components shown in the diagram are: upper magnet 1, lower magnet 2, oscillator 3, displacement detection unit 4, motion light-blocking component 401, LED light source 402, camera 403, fixed light-blocking component 404, imaging lens 405, temperature control unit 5, temperature probe 501, electric heater 502, temperature controller 503, housing 6, liquid inlet 7, liquid medium 8, optical path window 9, heat insulation pad 10, and machine foot screws 11. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0036] This invention provides a small-sized gravimeter with magnetic-liquid hybrid suspension, comprising a shell, a magnetic confinement unit, a suspension oscillator unit, and a displacement detection unit. The shell is filled with a liquid medium, and the magnetic confinement unit and the suspension oscillator are located inside the shell. The magnetic confinement unit provides levitation force for the suspension oscillator. The density of the liquid medium is less than the density of the suspension oscillator material. The displacement detection unit detects the vertical displacement of the suspension oscillator and is used to calculate the gravity measurement result.

[0037] Existing technologies, such as CN119960071A, disclose a method for detecting oscillator displacement through photoelectric conversion using lasers. This invention further investigates a method for detecting oscillator displacement using camera imaging. Figure 1As shown in the figure, in a specific embodiment of the present invention, the housing 6 is injected with liquid medium 8 through the injection port 7. The magnetic confinement unit includes two layers of permanent magnets, an upper magnet 1 and a lower magnet 2. The magnetic confinement unit is used to generate a magnetic confinement potential well to ensure that the antimagnetic material oscillator is stably suspended in the cavity. The suspended oscillator 3 is located in the magnetic confinement potential well. The displacement detection unit 4 includes a moving light-blocking component 401, an LED light source 402, a CCD camera 403, a fixed light-blocking component 404, and an imaging lens 405. A pair of optical path windows 9 are provided on both sides of the housing 6. The LED light source and the camera are located outside the optical path windows respectively. The moving light-blocking component 401 is fixed above the suspended oscillator 3 and moves with the suspended oscillator in the vertical direction. The fixed light-blocking component 404 is fixed above the magnetic confinement unit. Both are set in the plane of the focal point of the imaging lens to ensure clear imaging. The moving light-blocking component 401 and the fixed light-blocking component 404 do not overlap in the area of ​​the light beam blocked in the direction of the optical axis of the imaging lens, and the two do not interfere with each other in space. This can be adjusted during the initial configuration of the gravimeter. The light beam emitted by the LED light source is blocked by both moving and fixed light-blocking components, and then imaged in the camera after passing through the imaging lens, thereby enabling real-time detection of the displacement of the moving light-blocking component. ,pass The gravity result was calculated, where This indicates the frequency of the oscillator in the vertical direction. This indicates the change in environmental gravity in the vertical direction. In this embodiment, the displacement detection unit 4 can also be located below the levitation oscillator 3. For example, a through hole can be opened at the center of the lower magnet 2 of the magnetic confinement unit, corresponding to the position of the levitation oscillator 3. An optical fiber or thin rod can be passed through the through hole, and a moving light-blocking component 401 can be suspended below the lower magnet. A fixed light-blocking component 404 can be fixed below the lower magnet 2. The two images are then used to detect displacement.

[0038] As one embodiment, the moving light-blocking component 401 is connected to the top of the suspended oscillator 3 via a vertical rod, and the fixed light-blocking component 404 is connected to the top of the upper permanent magnet 1 via a vertical rod. Both are located on the focal plane of the imaging lens 405, preferably in the focal region, to achieve clear imaging. This design ensures that when the oscillator shifts due to gravity, the moving light-blocking component can accurately block or transmit the light beam emitted by the LED light source. After being focused by the lens group, the light beam is received by the camera. Figure 2As shown, since the moving light-blocking component is located at the focal point of the imaging lens, any minute displacement will significantly affect the beam transmission path, thereby altering the imaging result on the camera's image plane. Similarly, when the moving light-blocking component shifts, the fixed light-blocking component, acting as a stationary reference, images onto the camera's image plane along the same path. By simultaneously performing differential measurements on both the moving and fixed light-blocking components, displacement measurement errors caused by camera drift and imaging noise can be reduced in the time domain. Through precise machining of the geometric dimensions of both the fixed and moving light-blocking components, the displacement of the oscillator caused by changes in gravity can be accurately inverted, thus accurately measuring minute fluctuations in gravitational acceleration. According to experimental results, this method can achieve a linear dynamic range for displacement measurement better than ±100 micrometers, corresponding to a relative gravity detection range of kilo-migars. Furthermore, the connection method of the vertical rod is not only stable and reliable but also minimizes the impact of external disturbances on the oscillator, ensuring the stability and accuracy of the measurement. In other embodiments not shown in the figures, if the shape or size of the oscillator is adjusted, the positions of the moving and fixed light-blocking components can be changed accordingly to ensure that they are always located near the focal point of the imaging lens, thereby maintaining the system's high sensitivity and response characteristics. This invention uses a differential imaging method to detect displacement by simultaneously imaging the oscillator and a reference object with a camera. Compared to existing single-light-blocking detection methods that use lasers for photoelectric conversion, this reduces linear drift in the optical path, such as... Figure 3 As shown, the horizontal axis represents the displacement detection noise frequency, and the vertical axis represents the displacement detection accuracy. The measurement system of this invention is based on the differential measurement technology of dual-stage optical components. It can achieve a measurement accuracy of up to 6 nm / √Hz within a dynamic measurement range of ±100 micrometers. Compared with the method of measuring the displacement of only a single moving optical component, it improves the detection accuracy and suppresses time-domain drift.

[0039] In a preferred embodiment, the moving light-blocking component 401 and the fixed light-blocking component 404 are light-transmitting sheets containing a light-blocking pattern. The specific shape of the light-blocking pattern can be set to a sphere, a cross, or other shapes as needed. Figure 4 and Figure 5 The diagram illustrates two displacement methods for the moving and fixed light-blocking components of the present invention. Red indicates the fixed light-blocking component, and blue indicates the moving light-blocking component. A particularly preferred method is... Figure 5 As shown, the fixed light-blocking components are placed on both sides of the moving light-blocking component. The moving light-blocking component moves vertically under the influence of gravity, and the fixed light-blocking components provide displacement references on both sides, thus avoiding any shading problem.

[0040] As one example, by suspending a levitation oscillator 3 made of materials such as PMMA, SiO2, or bismuth in a liquid medium, the gravimeter's sensitivity to temperature fluctuations is significantly reduced. In this configuration, the oscillator's diamagnetism is almost unaffected by temperature changes, and the only remaining temperature-sensitive element in the system is the magnetic component of the magnet. The liquid medium not only provides the necessary buoyancy to assist the oscillator's suspension, but its high heat capacity also helps stabilize the internal temperature and reduce thermal noise caused by air molecule movement. Furthermore, the presence of the liquid medium eliminates the need for a high-vacuum environment, greatly simplifying system maintenance and improving the device's convenience and applicability.

[0041] As an example, the gravimeter of the present invention is also provided with a temperature control unit, which includes a temperature control probe 501, an electric heater 502 and a PID temperature controller 503, for controlling the temperature inside the housing, providing a suitable temperature environment, and ensuring that the magnetic-liquid hybrid suspension gravimeter maintains high accuracy during measurement. The temperature control probe monitors the temperature of the liquid environment and sends the signal to the PID controller. The PID controller adjusts the working state of the electric heater according to the signal. Compared with a vacuum environment, the liquid medium is more conducive to ensuring the temperature stability of the working environment of the magnetic confinement unit and the suspension oscillator unit.

[0042] By applying the technical solution of this embodiment, the small-sized gravimeter with magnetic-liquid hybrid suspension achieves a technological innovation that combats temperature fluctuations and reduces dependence on vacuum environments and magnetic field requirements. Under the combined action of the magnetic confinement potential well constructed by the magnetic confinement unit and the liquid medium, the diamagnetic material oscillator is stably suspended, avoiding measurement errors caused by excessive system temperature sensitivity. The displacement detection unit maps the relative displacement changes of the moving and fixed light-blocking components onto the image plane through the interaction of the light beam with the moving and fixed light-blocking components. The relative position is directly calculated from the camera's image, obtaining the actual displacement of the diamagnetic material oscillator, achieving sub-microgal level gravitational acceleration measurement accuracy. The PID controller in the temperature control unit adjusts the power of the electric heater based on feedback information from the temperature control probe, effectively controlling temperature fluctuations within the cavity and further ensuring that the device maintains measurement accuracy over a wide temperature range. In summary, this technical solution not only reduces the stringent environmental requirements for gravity measurement but also improves the long-term stability and measurement accuracy of the system, opening up new avenues for high-precision gravity measurement technology.

[0043] In this invention, the magnetic-fluid hybrid gravimeter introduces a liquid medium with a density lower than that of the oscillator material, achieving stable levitation of the oscillator under the combined action of the magnet and the liquid buoyancy. The presence of the liquid medium not only provides additional buoyancy support, reducing the required magnetic field strength for levitation of the diamagnetic oscillator, but also, due to its excellent thermal properties, effectively stabilizes the internal temperature, significantly reducing the impact of temperature fluctuations on the levitation system. This design avoids the dependence on extreme temperature control inherent in traditional levitation systems and eliminates the need for a vacuum environment, greatly simplifying the gravimeter's structure and enabling long-term, stable gravity measurements. Furthermore, the liquid medium absorbs external noise, improving the overall anti-interference capability of the system, thereby enhancing the accuracy and stability of gravity measurements. This embodiment uses electronic fluorinated liquid FC-40 as the liquid medium, whose density matches that of diamagnetic oscillator materials such as PMMA, SiO2, or metallic bismuth, enabling high-quality oscillator levitation under lower magnetic field requirements, reducing thermal noise, and improving measurement sensitivity.

[0044] In this embodiment, the levitation oscillator 3 is made of PMMA, SiO2, or metallic bismuth. This choice is based on the diamagnetic properties of these materials, and their diamagnetic properties are independent of temperature changes. The material and design of the oscillator enable the magnetofluid hybrid gravimeter to maintain stable levitation in environments with temperature fluctuations, significantly reducing the impact of ambient temperature changes on measurement accuracy. By using these temperature-stable diamagnetic materials, even under conditions of temperature fluctuations of 1 mK, the measurement fluctuation of gravitational acceleration can be reduced to approximately 4 × 10⁻⁶ mK. -7 Compared to materials more sensitive to temperature, such as graphite, the effect of temperature is reduced by at least one-third, enabling the gravimeter to maintain high-precision measurements under a wider range of environmental conditions. Furthermore, this design simplifies the system structure, eliminating the need for vacuum equipment, improving the overall portability and long-term operational stability of the device, and providing greater convenience for field monitoring and commercial applications.

[0045] Furthermore, as an example, the cross-section of the suspended oscillator 3 is a regular polygon, and the bottom is relatively constricted.

[0046] In this embodiment, the oscillator's cross-section is designed as a regular polygon with a relatively constricted bottom. This design ensures the stability of the oscillator in a magnetic-fluid hybrid suspension state, preventing the risk of tipping over due to the bottom shape. The regular polygonal cross-section helps the oscillator distribute magnetic and buoyant forces evenly in all directions, keeping it stably suspended, while the constricted bottom design further enhances this stability, ensuring accurate and unwavering position of the oscillator even under slight changes in external conditions. This improvement is crucial for enhancing the gravimeter's measurement accuracy because it reduces the influence of non-gravitational factors on the oscillator's displacement, enabling the system to detect gravity changes more accurately and reliably. Furthermore, the constricted bottom structure contributes to the dynamic stability of the oscillator during ascent or descent, avoiding unstable vibrations that may occur during rapid movement, thereby improving the sensitivity and accuracy of displacement detection. In the overall design, this detailed optimization works synergistically with other components to achieve high accuracy and long-term stability of the gravimeter in complex environments.

[0047] Furthermore, as an embodiment, the magnetic confinement unit includes two layers of permanent magnets, with the magnetization direction of the lower magnet 2 pointing towards the center and the magnetization direction of the upper magnet 1 pointing outward from the center.

[0048] In this embodiment, the magnetic fluid hybrid gravimeter further optimizes the design of the magnetic confinement unit, comprising upper and lower layers of permanent magnets. The magnetization direction of the lower magnet 2 is precisely pointed towards the center, aiming to converge magnetic field lines in the central region and form a strong vertical magnetic field gradient to overcome gravity and provide the necessary vertical antimagnetic force for the levitation of the antimagnetic material. The magnetization direction of the upper magnet 1 is from the center outward, achieving horizontal magnetic confinement through the central cavity structure, ensuring the stable position of the suspended oscillator in three-dimensional space. This magnet arrangement not only effectively controls the levitation state of the oscillator but also adjusts the vertical frequency of the magnetic confinement potential well by adjusting the relative distance between the upper and lower permanent magnets. This adjustment mechanism allows the gravimeter to operate at different frequencies to adapt to specific measurement needs or environmental conditions. Simultaneously, by fine-tuning the relative distance between each layer of permanent magnets and its enclosing center, the confinement position of the magnetic confinement potential well can be precisely controlled, ensuring the levitation unit stably resides at the optimal levitation point, thereby optimizing measurement accuracy. This design enhances the adjustability and adaptability of the gravimeter, enabling it to achieve high-precision gravity measurements under various working conditions and environments, thus improving the system's long-term stability and measurement accuracy. In practical operation, these adjustments can be made through built-in precision mechanical devices, eliminating the need to disassemble the instrument, simplifying maintenance procedures, and improving operational efficiency. Of course, similar effects can also be achieved by adjusting other physical quantities, such as adjusting the magnetic field distribution of the electromagnet using current intensity. Furthermore, by selecting a suitable liquid medium, the dependence of the levitation oscillator on the magnetic field is further reduced, broadening the range of oscillator materials, reducing thermal noise, and achieving more accurate and continuous monitoring of gravity changes. Further, in this embodiment, the vertical frequency of the magnetic confinement potential well is changed by adjusting the relative distance between the upper and lower layers of permanent magnets; the confinement position of the magnetic confinement potential well is adjusted by adjusting the relative distance between the permanent magnets in each layer and their enclosing center.

[0049] Furthermore, as an example, the upper magnet has a cavity structure in the center.

[0050] In this embodiment, a cavity structure is provided in the center of the upper magnet. The purpose of this design is to provide horizontal magnetic confinement, ensuring the stable positioning of the suspended oscillator in three-dimensional space. Since the magnetization direction of the upper magnet points from the center outwards, the presence of the cavity not only does not weaken the effect of the magnetic confinement potential well, but also helps to optimize the magnetic field distribution, making the oscillator less prone to lateral displacement or rotation in the suspended state, thus enhancing the stability and reliability of the system. Furthermore, the cavity structure also helps to reduce the weight of the magnet unit, simplifying the design of the overall device and improving portability and deployability. Of course, in other embodiments, the cavity structure of the upper magnet can also be adjusted according to actual needs, such as changing the shape or size of the cavity to adapt to different oscillator materials and suspension requirements. The liquid medium of the gravimeter of this invention provides additional damping in the horizontal direction to improve lateral stability. The cavity structure combined with the liquid medium provides design flexibility that allows the magnetofluid hybrid gravimeter to better adapt to various measurement environments and meet diverse application needs.

[0051] Furthermore, as an example, the permanent magnets of the magnetic confinement unit are made of samarium cobalt (SmCo) or neodymium iron boron (NdFeB) materials. These types of magnets exhibit extremely low magnetic decay over time, ensuring long-term stability.

[0052] Furthermore, as an embodiment, the housing 6 is a multi-layered nested housing, including an inner housing, a magnetic shielding housing, and an outer housing, with the innermost housing filled with a liquid medium 8. In this embodiment, the magnetic shielding housing is located outside the inner housing to isolate external magnetic field interference, ensuring the purity and stability of the magnetic field generated by the internal magnet unit and improving measurement accuracy. The outer housing, as the outermost protective housing, not only provides physical protection but also isolates the system from external environmental influences, further enhancing system stability and anti-interference capabilities. Through the multi-layered housing design, effective isolation of the magnet unit, the levitation oscillator unit, and the displacement detection unit is achieved, optimizing the working environment of each component and reducing the impact of external factors on system performance. In addition, the space between the housings can be kept in a vacuum state, enhancing insulation and magnetic shielding effects. Even under non-vacuum conditions, the thermal stability of the liquid medium and the magnetic field isolation of the magnetic shielding housing enable long-term stable operation, improving the accuracy and reliability of gravity measurements. The multi-layered housing structure further enhances the system's isolation and stability, reducing the stringent requirements of traditional gravimeters for complex external environments, making it suitable for field operations and commercial applications, and providing a solid foundation for long-term, continuous, high-precision gravity measurements.

[0053] Furthermore, as an embodiment, the bottom of the housing 6 is provided with a heat insulation pad 10 and a leveling screw 11 for adjusting the device. The heat insulation pad 10 is used to prevent heat exchange between the housing 6 and the tilting platform below, further ensuring the control of the temperature inside the housing. The leveling screw 11 is used to adjust the tilt angle of the gravimeter to be less than 10 degrees.-5 The use of arc angle effectively reduces gravity measurement errors caused by equipment tilt, ensuring the gravimeter maintains high measurement accuracy in any environment. The fine-tuning function of the mounting screws allows for on-site leveling of the gravimeter after deployment, adapting to various complex ground conditions and enhancing the instrument's practicality and reliability. Of course, in other embodiments, the leveling mechanism can take different forms, such as a built-in automatic leveling system, to further improve operational convenience and accuracy. By controlling the equipment's tilt angle, the uniformity of the magnetic field generated by the magnet unit is ensured, avoiding changes in magnetic field strength and direction caused by tilt, which could affect the stability of the suspended oscillator. This guarantees the displacement detection unit's accurate capture of oscillator displacement changes, achieving high-precision measurement of gravity changes.

[0054] The following further analyzes the improvement of temperature fluctuation sensitivity achieved by the magnetic-fluid hybrid suspension mechanism employed in this invention. By comparing the impact of temperature fluctuations in the graphite suspension system, it can be seen that in the magnetic-fluid hybrid gravimeter of this embodiment, as... Figure 6 As shown, a temperature fluctuation of 1 mK results in a change of only 4 × 10⁻⁶ gravitational acceleration. -7 g, far lower than 1.5 × 10 g in traditional graphite suspension systems. -6 Compared to the graphite levitation scheme, the impact is reduced by about one-third, thanks to the combined effect of the more temperature-stable antimagnetic material and the liquid medium. The antimagnetic material used for levitation in this invention is made of materials with extremely low temperature sensitivity, such as PMMA, SiO2, or metallic bismuth, whose magnetic susceptibility is almost unaffected by temperature changes. Simultaneously, the presence of the liquid medium further reduces the requirements for magnetic field strength, allowing the magnet unit to be levied using a smaller or weaker magnetic field, thereby reducing the magnet's sensitivity to temperature changes and improving the overall temperature stability of the system. This improvement not only reduces the stringent requirements for temperature control but also lessens the dependence on the magnetic field, paving the way for the long-term stable operation and commercial application of the gravimeter.

[0055] In the process of gravity measurement using the magnetic-fluid hybrid gravimeter of this application, firstly, a magnetic confinement potential well is constructed by two layers of permanent magnets in the magnet unit. The magnetization direction of the lower magnet points towards the center, while the magnetization direction of the upper magnet is from the center outwards. Their combined action stabilizes the oscillator in the suspension oscillator unit within the liquid medium. Next, the displacement detection unit is activated, and a beam of light emitted from an LED light source illuminates a moving light-blocking component on top of the oscillator. The camera records the displacement information of the oscillator. Simultaneously, the temperature control unit operates, with a temperature probe monitoring the temperature inside the cavity in real time and transmitting the data to a PID controller. The PID controller adjusts the power of the electric heater based on the feedback signal to maintain a constant temperature inside the shell, ensuring the stability of the magnet unit and further reducing the impact of temperature fluctuations on the measurement results. The magnetic-fluid hybrid gravimeter of this invention can continuously measure changes in gravitational acceleration with sub-microgal precision. Even in environments with temperature fluctuations of 1 mK, the fluctuation in gravitational acceleration can be controlled within approximately 4 × 10⁻⁶ mK. -7 This significantly improves the system's long-term stability and measurement accuracy. Throughout the process, key aspects such as the stable levitation of the oscillator, displacement detection, and temperature control are closely integrated and work together to ensure the accuracy and reliability of gravity measurements.

[0056] In the workflow of implementing a small-sized gravimeter with magnetic-liquid hybrid suspension, the magnetic confinement unit adjusts the relative positions of the upper and lower layers of permanent magnets to form a suitable magnetic confinement potential well, ensuring the stable suspension of the oscillator within the cavity. Throughout the entire workflow, the integrated use of magnetic confinement, displacement detection, temperature control, and the liquid medium ensures high measurement accuracy and long-term stability.

[0057] The gravimeter designed in this invention eliminates the need to maintain a high vacuum environment, simplifying the system structure and enhancing its long-term stability and portability. It achieves high-precision gravity measurement, and by combining high-precision optical displacement detection and PID temperature control technology, it can stably measure gravity changes over long periods with micro-gallon-level accuracy. The above description is merely a preferred embodiment of the invention and is not intended to limit the invention. Various modifications and variations can be made to this invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A magnetic-fluid hybrid suspension gravimeter, characterized in that: It includes a shell, a magnetic confinement unit, a levitation oscillator unit, and a displacement detection unit. The shell is filled with a liquid medium. The magnetic confinement unit and the levitation oscillator are located inside the shell. The magnetic confinement unit provides levitation force for the levitation oscillator. The density of the liquid medium is less than the density of the levitation oscillator material. The displacement detection unit detects the vertical displacement of the levitation oscillator and uses it to calculate the gravity measurement result.

2. The magnetic-fluid hybrid levitation gravimeter according to claim 1, characterized in that: The displacement detection unit includes an LED light source, an imaging lens, a moving light-blocking component, a fixed light-blocking component, and a camera. The fixed light-blocking component is fixed in position relative to the magnetic confinement unit, while the moving light-blocking component moves vertically with the levitating oscillator. Under the illumination of the LED light source, the moving light-blocking component and the fixed light-blocking component are magnified by the imaging lens and imaged in the camera. The displacement of the moving light-blocking component is detected with the position of the fixed light-blocking component as a reference.

3. A magnetic-fluid hybrid levitation gravimeter according to claim 2, characterized in that: The moving light-blocking component is fixed above the oscillator by a vertical rod, and the fixed light-blocking component is fixed above the magnetic confinement unit by a vertical rod. Both are set on the focal plane of the imaging lens. The moving light-blocking component and the fixed light-blocking component do not overlap in the area of ​​the light beam blocked in the direction of the optical axis of the imaging lens, and do not interfere with each other in space.

4. A magnetic-fluid hybrid levitation gravimeter according to claim 3, characterized in that: The moving light-blocking component and the fixed light-blocking component are light-transmitting sheets containing light-blocking patterns, with the light-blocking pattern of the fixed light-blocking component located on one or both sides of the light-blocking pattern of the moving light-blocking component.

5. A magnetic-fluid hybrid levitation gravimeter according to claim 2, characterized in that: The housing has a pair of light path windows on both sides, with the LED light source and camera located outside the light path windows respectively.

6. A magnetic-fluid hybrid levitation gravimeter according to claim 1, characterized in that... It also includes a temperature control unit, which consists of a temperature probe, an electric heater, and a temperature controller, used to control the temperature of the liquid medium inside the housing.

7. A magnetic-fluid hybrid levitation gravimeter according to claim 1, characterized in that... The oscillator is made of PMMA, SiO2 or metallic bismuth.

8. A magnetic-fluid hybrid levitation gravimeter according to claim 1, characterized in that: The oscillator is a cylinder with a regular polygonal cross-section, and the bottom is contracted relative to the top.

9. A magnetic-fluid hybrid levitation gravimeter according to claim 1, characterized in that: The magnetic confinement unit includes two layers of permanent magnets. The magnetization direction of the lower magnet is towards the center, and the magnetization direction of the upper magnet is from the center outward. The permanent magnets are made of samarium cobalt or neodymium iron boron. The upper magnet has a cavity structure in the center to accommodate the oscillator.

10. A magnetic-fluid hybrid levitation gravimeter according to claim 1, characterized in that... The housing is a multi-layered nested housing, including an inner housing, a magnetic shielding housing, and an outer housing. The bottom of the housing is equipped with leveling screws for adjusting the gravimeter so that its tilt angle is less than 10°. -5 radian.

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