Radial correction coil stabilizing control device and method for superconducting gravity measurement

Abstract

This invention discloses a radial correction coil stabilization control device and method for superconducting gravity measurement, belonging to the field of gravity measurement technology. The device includes: an upper suspension coil frame, a lower suspension coil frame, a superconducting levitation sphere, multiple correction coil frames and correction coils with identical structural parameters, a levitation power supply, a PID controller, a current source, and a radial displacement detector. Suspension coils are wound on the two suspension coil frames, forming a Helmholtz coil structure, and are symmetrically distributed on the upper and lower sides of the superconducting levitation sphere. The levitation power supply is electrically connected to the two suspension coils. Multiple correction coil frames are symmetrically distributed radially around the superconducting levitation sphere, each with a correction coil wound on it. The radial displacement detector is electrically connected to the correction coil frames, transmitting the detected radial offset of the superconducting levitation sphere to the PID controller. The PID controller is connected to the current source. This invention can improve radial support stiffness and dynamic measurement stability.

Description

Technical Field

[0001] This invention belongs to the field of gravity measurement technology, specifically relating to a radial correction coil stabilization control device and method for superconducting gravity measurement. Background Technology

[0002] High-precision gravity measurements are of great significance for in-depth research in fields such as geodynamics, resource exploration, and geodesy. Superconducting gravimeters, developed based on the zero-resistance characteristics of superconductors and the Meissner effect, are recognized as the most accurate gravity measurement instruments. The need for high-precision gravity measurements in dynamic environments is becoming increasingly urgent in fields such as airborne geophysical exploration and marine gravity measurement.

[0003] Existing superconducting gravimeter magnetic levitation systems typically consist of only a pair of coaxially arranged upper and lower levitation coils. While these provide axial levitation and restoring forces, the radial (horizontal) support stiffness of the suspended test mass is relatively low due to the divergent magnetic field distribution, resulting in insufficient radial restoring force. When affected by external temperature changes and tilting interference factors, the superconducting sphere is prone to radial displacement during operation, even touching the cavity wall, leading to measurement failure. Furthermore, due to manufacturing and assembly errors, the superconducting suspended test mass is also prone to lateral displacement, causing gravity measurement failure or reduced accuracy, severely restricting the application of superconducting gravimeters in dynamic measurement scenarios. Therefore, effectively improving the radial support stability of the suspended test mass in superconducting gravity measurement devices has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A radial correction coil stabilization control device for superconducting gravity measurement includes: an upper suspension coil frame, a lower suspension coil frame, a superconducting suspension sphere, multiple correction coil frames with identical structures and parameters, and the same number of multiple correction coils with identical structures and parameters, a suspension power supply, a PID controller, a current source, and a radial displacement detector.

[0006] An upper levitation coil is wound on the upper levitation coil skeleton, and a lower levitation coil is wound on the lower levitation coil skeleton. The upper and lower levitation coils form a Helmholtz coil structure and are symmetrically distributed on the upper and lower sides of the superconducting levitation sphere. The levitation power supply is electrically connected to the upper and lower levitation coils and is used to inject current into the upper and lower levitation coils to levitate the superconducting levitation sphere.

[0007] Multiple correction coil frames are symmetrically distributed radially around the superconducting levitation sphere. Correction coils are wound on the correction coil frames respectively. The correction coils are used to provide radial correction force for the superconducting levitation sphere. The correction coil frames also serve as radial displacement sensing elements. The radial displacement detector is electrically connected to the correction coil frames to detect the radial offset of the superconducting levitation sphere and transmits the detected radial offset of the superconducting levitation sphere to the PID controller.

[0008] The PID controller is electrically connected to the current source and is used to control the current source to inject current into the correction coil in the direction of radial displacement according to the offset direction and radial offset of the superconducting levitation ball, so that the superconducting levitation ball returns to the suspension center.

[0009] The present invention has the following beneficial effects:

[0010] This invention utilizes radially symmetrically distributed correction coils to provide radial correction force for a superconducting levitation sphere. The radial displacement of the sphere is detected in real time by the correction coil frame, and closed-loop stable control is achieved in conjunction with a PID controller. This effectively suppresses lateral displacement of the superconducting levitation sphere caused by processing and assembly errors, external temperature changes, or tilting, significantly increasing radial support stiffness and improving radial support stability. This effectively solves the problem of poor suspension stability caused by insufficient radial support stiffness in current superconducting gravity measuring instruments. Furthermore, the correction coil frame simultaneously serves as a radial displacement sensing element and coil support structure, exhibiting high integration and a compact structure, which is beneficial for device miniaturization. This invention is easy to operate, has good implementation results, and a simple structure, significantly improving the measurement accuracy and stability of superconducting gravity measuring devices under external interference environments. Attached Figure Description

[0011] Figure 1 The exploded view of the overall structure of the radial correction coil stabilization control device for superconducting gravity measurement of the present invention is shown below: 1-Upper suspension coil frame, 2-Lower suspension coil frame, 3-X-axis negative direction correction coil frame, 4-X-axis positive direction correction coil frame, 5-Y-axis negative direction correction coil frame, 6-Y-axis positive direction correction coil frame, 7-Superconducting suspension ball;

[0012] Figure 2 This is a schematic diagram of the radial correction coil skeleton of the present invention, 6 - correction coil skeleton in the positive Y-axis direction, 8 - correction coil wiring hole;

[0013] Figure 3 This is an electromagnetic structure diagram of the device for radial correction coil stabilization control for superconducting gravity measurement according to the present invention. 9 - X-axis negative direction correction coil, 10 - X-axis positive direction correction coil, 11 - Y-axis negative direction correction coil, 12 - Y-axis positive direction correction coil, 13 - upper suspension coil, 14 - lower suspension coil.

[0014] Figure 4 This is a schematic diagram illustrating the actual control process of the radial correction coil stabilization control device for superconducting gravity measurement according to the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0016] This invention employs radially symmetrically distributed correction coils to perform radial correction and stabilization control on the superconducting suspended sphere 7, thereby improving the support stiffness of the non-sensitive shaft. The correction coil frame also serves as a displacement detection element, enabling real-time detection of radial offset. Through the combination of the above two aspects, the radial correction coil stabilization control device of this invention for superconducting gravity measurement is suitable for high-precision dynamic gravity measurement.

[0017] like Figure 1 As shown, the radial correction coil stabilization control device (hereinafter referred to as the device) for superconducting gravity measurement of the present invention includes: an upper levitation coil frame 1, a lower levitation coil frame 2, a superconducting levitation sphere 7, and multiple correction coil frames and correction coils with identical structures and parameters, symmetrically distributed radially along the superconducting levitation sphere 7. An upper levitation coil 13 is wound on the upper levitation coil frame 1, and a lower levitation coil 14 is wound on the lower levitation coil frame 2. The upper levitation coil 13 and the lower levitation coil 14 constitute a Helmholtz coil structure, symmetrically distributed on the upper and lower sides of the superconducting levitation sphere 7. The lower levitation coil 14 is used to provide the main levitation force, and the upper levitation coil 13 is used to adjust the magnetic gradient.

[0018] Preferably, the upper suspension coil frame 1 and the lower suspension coil frame 2 are made of insulating material, which is G10 (a high-performance composite material made of glass fiber and epoxy resin).

[0019] Preferably, each correction coil frame is made of aluminum alloy. The correction coil frame is used to sense changes in radial displacement. A capacitance is formed between the correction coil frame and the superconducting levitation sphere 7. When the superconducting levitation sphere 7 undergoes radial displacement, the capacitance between the correction coil frame and the superconducting levitation sphere 7 will change.

[0020] like Figure 1 and Figure 3As shown, the correction coil frames are symmetrically distributed radially around the superconducting levitation sphere 7. Correction coils are wound on the correction coil frames, providing radial correction force to the superconducting levitation sphere 7. Preferably, there are four correction coil frames, symmetrically distributed at 90° intervals along the circumference, respectively positioned in the positive X-axis direction, negative X-axis direction, positive Y-axis direction, and negative Y-axis direction, i.e., X-axis negative direction correction coil frame 3, X-axis positive direction correction coil frame 4, Y-axis negative direction correction coil frame 5, and Y-axis positive direction correction coil frame 6. Four correction coils are wound on each of the four correction coil frames: X-axis negative direction correction coil 9, X-axis positive direction correction coil 10, Y-axis negative direction correction coil 11, and Y-axis positive direction correction coil 12. The four correction coils are symmetrically distributed and positioned at 90° intervals to provide radial correction force to the superconducting levitation sphere 7.

[0021] Preferably, the upper levitation coil 13, the lower levitation coil 14, and each correction coil are all wound with superconducting niobium (Nb) wire. The upper levitation coil 13 and the lower levitation coil 14 are arranged in a Helmholtz pattern to form a uniform magnetic field gradient region. The lower levitation coil 14 provides the main electromagnetic levitation force for the superconducting levitation sphere 7, while the upper levitation coil 13 is used to adjust the magnetic force gradient.

[0022] In this embodiment, Figure 1 Each correction coil frame in the structure also serves as a radial displacement sensing element, used to detect the radial offset of the superconducting levitated sphere 7. For example... Figure 2 As shown, taking the Y-axis positive direction correction coil frame 6 as an example (other correction coil frames have the same structure), the correction coil frame is a spherical support structure, which provides spherical support for the correction coil wound on it. A correction coil routing hole 8 is provided at the center of the sphere. The correction coil routing hole 8 is provided with threaded holes at the top and bottom for threaded connection with the upper suspension coil frame 1 and the lower suspension coil frame 2.

[0023] like Figure 4 As shown, the device also includes a radial displacement detector, a levitation power supply, a PID (Proportional-Integral-Derivative) controller, and a current source. The levitation power supply is electrically connected to the upper levitation coil 13 and the lower levitation coil 14, and is used to inject current into the upper levitation coil 13 and the lower levitation coil 14 to levitate the superconducting levitation sphere 7. The correction coil frame is electrically connected to the radial displacement detector, and is used to detect the radial offset of the superconducting levitation sphere 7 and transmit the detected radial offset signal of the superconducting levitation sphere 7 to the PID controller. The PID controller is electrically connected to the current source, and is used to control the current source to inject current into the correction coil in the direction of radial offset, so that the superconducting levitation sphere 7 returns to the levitation center, based on the offset direction and magnitude of the superconducting levitation sphere 7.

[0024] like Figure 4As shown, the radial correction and stabilization control principle of this invention is as follows: Current is injected into the upper suspension coil 13 and the lower suspension coil 14 by the levitation power supply, causing the superconducting levitation sphere 7 to levitate. The radial displacement of the superconducting levitation sphere 7 is detected jointly by the frame of each correction coil and the radial displacement detector. Based on the offset direction of the superconducting levitation sphere 7, a PID controller controls the current source to inject appropriate current into the correction coil in the corresponding direction, causing the superconducting levitation sphere 7 to return to the levitation center. In practical applications, the PID controller corrects the radial offset of the superconducting levitation sphere 7 by controlling the current in each correction coil in real time, ensuring it remains in the levitation center position and improving the support stability of the non-sensitive shaft.

[0025] As an alternative, six or eight correction coil frames are used, evenly distributed around the 7-axis of the superconducting levitation sphere to achieve higher radial correction isotropy and higher control accuracy. When using six correction coil frames, the angle between adjacent frames is 60°; when using eight frames, the angle is 45°. Increasing the number of correction coil frames improves the spatial resolution of radial displacement detection and the uniformity of correction force, but also increases system complexity and cost. The specific number can be determined based on actual application requirements.

[0026] As an alternative, the displacement detection function of the correction coil frame can also be achieved by independently installing other, more precise displacement sensors around the radial periphery of the superconducting levitation sphere 7. For example, a superconducting quantum interference device (SQUID) correction coil frame can be used to convert changes in sensitive magnetic flux into changes in displacement. This approach offers higher displacement detection sensitivity, thus enabling higher correction control accuracy, but it increases the complexity and cost of the device, making it suitable for applications requiring higher precision.

[0027] The present invention further provides a radial correction coil stabilization control method for superconducting gravity measurement, which is used in the aforementioned radial correction coil stabilization control device for superconducting gravity measurement, and includes:

[0028] Step 1: Inject current into the upper suspension coil 13 and the lower suspension coil 14 through the suspension power supply to levitate the superconducting suspension ball 7.

[0029] Step 2: The radial offset of the superconducting levitated ball 7 is detected by using the correction coil frame and the radial displacement detector.

[0030] Step 3: Based on the offset direction and radial offset of the superconducting levitated ball 7, use a PID controller to control the current source and inject appropriate current into the correction coil in the corresponding direction to generate radial correction force, so that the superconducting levitated ball 7 returns to the levitation center.

[0031] Step 4: Monitor the radial displacement of the superconducting levitated ball 7 in real time, and continuously maintain the stable levitation state of the superconducting levitated ball 7 at the levitation center through closed-loop control of the PID controller.

[0032] In step 3, when the superconducting levitation sphere 7 shifts laterally, the correction coil frame detects the direction of shift. If the levitation sphere 7 shifts in the positive X-axis direction, the PID controller injects current into the correction coil 10 in the positive X-axis direction, generating or increasing the correction force pointing in the negative X-axis direction, causing the levitation sphere 7 to return to the levitation center. If the levitation sphere 7 shifts in other directions, current is injected into the correction coil in the corresponding direction according to the same principle, generating or increasing the reverse correction force, causing the levitation sphere 7 to return to the levitation center. Optionally, when the levitation sphere 7 shifts, correction can also be assisted by removing or reducing the current in the correction coil in the opposite direction of the shift; both methods can be performed simultaneously. When the levitation sphere 7 returns to the levitation center, current adjustment stops, and the controller completes one control process for the levitation sphere 7.

[0033] The radial correction coil stabilization control method of the present invention for superconducting gravity measurement requires ensuring the normal operation of the cryogenic system of the superconducting gravimeter before conducting the power-on experiment. Liquid helium is generated by using a helium liquefaction device or directly filled into the superconducting gravimeter, immersing the entire device in liquid helium to a liquid helium bath temperature of about 4.2K. This ensures that all superconducting components (including the upper suspension coil 13, the lower suspension coil 14, the superconducting suspension ball 7, and each correction coil) are in a fully superconducting state and maintains a stable liquid helium temperature environment.

[0034] The above description is merely an embodiment of the present invention and does not limit the scope of the invention. Any equivalent structural or procedural transformations made based on the description and drawings of this invention, or direct or indirect applications in other related system fields, are similarly included within the protection scope of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A radial correction coil stabilization control device for superconducting gravity measurement, characterized in that, include: The upper suspension coil frame, the lower suspension coil frame, the superconducting suspension ball, multiple correction coil frames with the same structure and parameters, the same number of correction coils with the same structure and parameters, the suspension power supply, the PID controller, the current source, and the radial displacement detector. An upper levitation coil is wound on the upper levitation coil skeleton, and a lower levitation coil is wound on the lower levitation coil skeleton. The upper and lower levitation coils form a Helmholtz coil structure and are symmetrically distributed on the upper and lower sides of the superconducting levitation sphere. The levitation power supply is electrically connected to the upper and lower levitation coils and is used to inject current into the upper and lower levitation coils to levitate the superconducting levitation sphere. Multiple correction coil frames are symmetrically distributed radially around the superconducting levitation sphere. Correction coils are wound on the correction coil frames respectively. The correction coils are used to provide radial correction force for the superconducting levitation sphere. The correction coil frames also serve as radial displacement sensing elements. The radial displacement detector is electrically connected to the correction coil frames to detect the radial offset of the superconducting levitation sphere and transmits the detected radial offset of the superconducting levitation sphere to the PID controller. The PID controller is electrically connected to the current source and is used to control the current source to inject current into the correction coil in the direction of radial displacement according to the offset direction and radial offset of the superconducting levitation ball, so that the superconducting levitation ball returns to the suspension center.

2. The radial correction coil stabilization control device for superconducting gravity measurement according to claim 1, characterized in that, There are four correction coil frames, which are symmetrically distributed at 90° intervals along the circumference and are respectively set in the positive X-axis direction, the negative X-axis direction, the positive Y-axis direction, and the negative Y-axis direction.

3. The radial correction coil stabilization control device for superconducting gravity measurement according to claim 1, characterized in that, There are six correction coil frames, and the angle between adjacent correction coil frames is 60°.

4. The radial correction coil stabilization control device for superconducting gravity measurement according to claim 1, characterized in that, There are eight correction coil frames, and the angle between adjacent correction coil frames is 45°.

5. The radial correction coil stabilization control device for superconducting gravity measurement according to claim 1, characterized in that, The upper and lower suspension coil frames are made of insulating material, which is G10.

6. The radial correction coil stabilization control device for superconducting gravity measurement according to claim 1, characterized in that, Each correction coil frame is made of aluminum alloy.

7. The radial correction coil stabilization control device for superconducting gravity measurement according to claim 1, characterized in that, The displacement detection function of the correction coil skeleton is realized by a superconducting quantum interference device (SQU). The SQU is independently installed around the radial periphery of the superconducting levitation sphere and is used to convert changes in sensitive magnetic flux into changes in displacement.

8. The radial correction coil stabilization control device for superconducting gravity measurement according to claim 1, characterized in that, Each correction coil frame is a spherical support structure, providing spherical support for the correction coil wound on it. A correction coil routing hole is provided at the center of the sphere, and threaded holes are provided above and below the correction coil routing hole for threaded connection with the upper and lower suspension coil frames.

9. A radial correction coil stabilization control method for superconducting gravity measurement, used in any one of the radial correction coil stabilization control devices for superconducting gravity measurement as described in claims 1 to 8, characterized in that, include: Step 1: Inject current into the upper and lower suspension coils through the suspension power supply to levitate the superconducting suspension ball; Step 2: The radial offset of the superconducting levitation sphere is detected by using the correction coil frame and the radial displacement detector together; Step 3: Based on the offset direction and radial offset of the superconducting levitated ball, use a PID controller to control the current source to inject current into the correction coil in the corresponding direction, generating radial correction force to make the superconducting levitated ball return to the suspension center. Step 4: Monitor the radial displacement of the superconducting sphere in real time, and continuously maintain the stable suspension state of the superconducting sphere at the suspension center through closed-loop control of the PID controller.

10. The radial correction coil stabilization control method for superconducting gravity measurement according to claim 9, characterized in that, In step 3, when the superconducting levitated ball deviates in the positive X-axis direction, the PID controller controls the current source to inject current into the correction coil in the positive X-axis direction, generating a correction force pointing in the negative X-axis direction, so that the superconducting levitated ball returns to the center of suspension. When the superconducting levitated ball deviates in other directions, current is injected into the correction coil in the corresponding direction according to the same principle to generate a reverse correction force, so that the superconducting levitated ball returns to the center of levitation.

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