A three-axis gradient magnetic compensation coil system of a micro nuclear magnetic resonance gyroscope

Abstract

The application discloses a three-axis gradient magnetic compensation coil system of a micro nuclear magnetic resonance gyroscope, which is composed of an inner-layer cylindrical coil framework, an axial first-order gradient magnetic compensation coil, an axial second-order gradient magnetic compensation coil and a radial first-order gradient compensation coil; wherein the inner-layer cylindrical coil framework is a hollow cylindrical tube, the outer surface of the hollow cylindrical tube is provided with an annular groove, the axial first-order gradient magnetic compensation coil is pasted in the annular groove and is composed of a plurality of coaxial first circular coils; the axial first-order gradient magnetic compensation coil is pasted outside the axial first-order gradient magnetic compensation coil and is composed of a plurality of coaxial second circular coils; and the radial first-order gradient compensation coil is pasted outside the axial second-order gradient magnetic compensation coil. Compared with the prior art, the three-axis gradient magnetic compensation coil system has a smaller length-diameter ratio, is suitable for the miniaturization development of the micro nuclear magnetic resonance gyroscope, can compensate the magnetic field gradient caused by the residual magnetism of a shielding barrel, internal active devices and the like, and improves the magnetic field uniformity in a prototype; and the three-axis gradient magnetic compensation coil system is composed of a coil framework and a flexible circuit board, and is convenient to install and replace.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro nuclear magnetic resonance gyroscopes, and in particular to a three-axis gradient magnetic compensation coil system for a micro nuclear magnetic resonance gyroscope. BACKGROUND

[0002] Micro nuclear magnetic resonance gyroscopes have small volume, low cost and high precision, and have become a research focus and hotspot for new inertial navigation. Micro nuclear magnetic resonance gyroscopes are suitable for strapdown inertial navigation systems and can be applied to fields such as tactical weapons and small aircraft.

[0003] A nuclear magnetic resonance gyroscope polarizes inert gas atomic nuclei through polarized alkali metal, and detects the spin precession frequency of the atomic nuclei to calculate the angular rate of the carrier. The nuclear magnetic resonance gyroscope not only needs a magnetic shielding system to shield the interference of external magnetic fields, but also needs an internal magnetic compensation coil to generate a uniform axial magnetic field to compensate for the three-axis residual magnetic field. The accuracy of the measured gyroscope rotation signal is mainly related to the uniformity of the environmental magnetic field in which the working gas chamber is located. Therefore, the nuclear magnetic resonance gyroscope needs a magnetic field compensation system with excellent performance to make the internal magnetic field of the gyroscope uniform.

[0004] Small magnetic shielding can introduce residual magnetic field gradients, and internal active devices can introduce active magnetic fields, which can cause magnetic field gradients and result in non-uniformity of the axial magnetic field, thereby affecting the performance of the nuclear magnetic resonance gyroscope. If the magnetic field gradient is large, it will bring large errors to the measurement results.

[0005] The traditional magnetic compensation system for micro nuclear magnetic resonance gyroscopes uses three-axis coils to generate a uniform magnetic field to compensate for the uniform distribution of residual magnetic field inside the gyroscope, but it cannot compensate for the non-uniform distribution of gradient magnetic field in the internal residual magnetic field, so the existence of non-uniform three-axis gradient magnetic field inside the gyroscope leads to a decrease in performance. At the same time, the magnetic compensation coils currently used are usually cylindrical and have a height-to-base radius ratio greater than 2, which limits the miniaturization of the nuclear magnetic resonance gyroscope and is not conducive to the expansion of the application scenarios of the micro nuclear magnetic resonance gyroscope. In addition, the magnetic compensation coils currently used are usually formed by winding enameled wire, and their positioning accuracy is limited. Positioning and dimensional errors are introduced during the winding process, resulting in a certain gap between the accuracy and uniformity of the generated magnetic field and the theoretical design, which is not conducive to generating a high-uniformity magnetic field. SUMMARY

[0006] The present application provides a new three-axis gradient magnetic compensation coil system for a micro nuclear magnetic resonance gyroscope, which has a compact structure, is easy to install and replace, and significantly improves the performance of the gyroscope.

[0007] To achieve the above-mentioned purposes, the technical solutions provided by the present application are as follows:

[0008] The application discloses a three-axis gradient magnetic compensation coil system of a novel micro nuclear magnetic resonance gyroscope, which is composed of an inner layer cylindrical coil framework, an axial first-order gradient magnetic compensation coil, an axial second-order gradient magnetic compensation coil and a radial first-order gradient compensation coil from inside to outside.

[0009] The inner layer cylindrical coil framework is a hollow cylindrical tube, and the ratio of the height of the inner layer cylindrical coil framework to the radius of the bottom surface of the inner layer cylindrical coil framework is 2-2.5; the outer surface of the inner layer cylindrical coil framework is provided with an annular groove for pasting a plurality of flexible circuit boards.

[0010] The axial first-order gradient compensation coil is pasted in the annular groove and is composed of a plurality of coaxial first circular coils for generating an axial first-order gradient magnetic field.

[0011] The axial second-order gradient compensation coil is pasted in the annular groove and is pasted on the outer layer of the axial first-order gradient compensation coil and is composed of a plurality of coaxial second circular coils for generating an axial second-order gradient magnetic field.

[0012] The radial first-order gradient compensation coil is pasted in the annular groove and is pasted on the outer layer of the axial second-order gradient compensation coil and is composed of eight identical saddle-shaped coils for generating a radial first-order gradient magnetic field.

[0013] Further, the inner layer cylindrical coil framework is made of polyether ether ketone material.

[0014] Further, the diameter of the inner layer cylindrical coil framework is 1-2.5 cm, the height of the inner layer cylindrical coil framework is 1-3 cm, and the ratio of the height to the radius is less than 3.

[0015] Further, the axial first-order gradient compensation coil is composed of eight first circular coils with the same radius and concentric with each other, the first circular coils are connected in series and are symmetrical about a center plane of the inner layer cylindrical coil framework, the center plane is parallel to the bottom surface of the inner layer cylindrical coil framework, the height of the center plane is half of the height of the inner layer cylindrical coil framework, the ratio of the height of the first circular coil to the radius of the bottom surface of the inner layer cylindrical coil framework is less than 2, and the ratio of the height of the axial first-order gradient compensation coil to the radius of the bottom surface of the inner layer cylindrical coil framework is less than 2.

[0016] Further, the axial second-order gradient compensation coil is composed of 10 concentric second circular coils with the same radius, the second circular coils are connected in series, and are symmetrical about a center plane of the inner cylindrical coil framework, the center plane is parallel to the bottom surface of the inner cylindrical coil framework, and the height of the center plane is half of the height of the inner cylindrical coil framework; the ratio of the height of the second circular coil to the radius of the bottom surface of the inner cylindrical coil framework is less than 2, and the ratio of the height of the axial second-order gradient compensation coil to the radius of the bottom surface of the inner cylindrical coil framework is less than 2.

[0017] Further, the radial first-order gradient compensation coil is composed of two groups of eight saddle-shaped coils, and the eight saddle-shaped coils are expanded into eight rectangular coils when the eight saddle-shaped coils are arranged in a plane; each group of saddle-shaped coils is composed of four saddle-shaped coils, the four saddle-shaped coils in the same group are connected in series, the four saddle-shaped coils in the same group are rotated by 90 degrees counterclockwise or clockwise about the longitudinal axis of the inner cylindrical coil framework to obtain the four saddle-shaped coils in the other group; the positions of the saddle-shaped coils are uniformly distributed at an angle of 90 degrees along the circumference of the inner cylindrical coil framework, and the saddle-shaped coils are symmetrical about a center plane, the center plane is parallel to the bottom surface of the inner cylindrical coil framework, the height of the center plane is half of the height of the inner cylindrical coil framework, the ratio of the length of the straight edge of the saddle-shaped coil to the radius of the bottom surface of the inner cylindrical coil framework is less than 1, the ratio of the height of the radial first-order gradient compensation coil to the radius of the bottom surface of the inner cylindrical coil framework is less than 2, and the central angle of the arc segment of the saddle-shaped coil is 60-90 degrees.

[0018] Compared with the prior art, the technical effects of the present application are:

[0019] Compared with the prior art, the present application has the advantages that:

[0020] (1) The present application uses flexible circuit board technology to replace enameled wire, which has high size and position precision and avoids size errors caused by winding, and the generated magnetic field has higher precision, thereby improving the uniformity of the magnetic field generated by the coil.

[0021] (2) The ratio of the height of all coils to the radius of the inner coil framework is designed to be within 1:2, which reduces the volume of the entire magnetic compensation system, and is suitable for the small volume requirement and further miniaturization trend of the miniature nuclear magnetic resonance gyroscope.

[0022] (3) The present application has a simple structure, and only needs to paste the flexible circuit board on the groove of the coil framework during installation, which saves space and is convenient to replace, and the design of the multi-layer flexible circuit board leaves space for introducing new coils in the future.

[0023] (4) The present application introduces a gradient magnetic compensation coil system into a miniature nuclear magnetic resonance gyroscope, which can compensate for the three-axis magnetic field gradient introduced by the environment, and is conducive to improving the uniformity of the actual magnetic field sensed by the internal chamber of the gyroscope. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0025] Figure 1 A schematic diagram of the inner cylindrical coil skeleton provided in an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of an axial first-order gradient magnetic compensation coil provided in an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of an axial second-order gradient magnetic compensation coil provided in an embodiment of the present invention;

[0028] Figure 4 A schematic diagram of a radial first-order gradient magnetic compensation coil provided in an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of annular grooves provided in an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the planar unfolding of the axial first-order gradient magnetic compensation coil provided in an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the axial second-order gradient magnetic compensation coil planar unfolding provided in an embodiment of the present invention;

[0032] Figure 8 This is a schematic diagram of the radial first-order gradient magnetic compensation coil as provided in an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Inner cylindrical coil frame; 2. Axial first-order gradient compensation coil; 3. Axial second-order gradient magnetic compensation coil; 4. Radial first-order gradient magnetic compensation coil. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] See Figures 1-4As shown, the application provides a novel miniature nuclear magnetic resonance gyroscope three-axis gradient magnetic compensation coil system, which is composed of an inner cylindrical coil framework 1, an axial first-order gradient magnetic compensation coil 2, an axial second-order gradient magnetic compensation coil 3, and a radial first-order gradient compensation coil 4 from inside to outside. The inner cylindrical coil framework 1 is made of a special engineering plastic polyether ether ketone (PEEK) material with high temperature resistance, self-lubrication, easy processing, and high mechanical strength. The axial first-order gradient magnetic compensation coil 2, the axial second-order gradient magnetic compensation coil 3, and the radial first-order gradient compensation coil 4 all use polyimide or polyester film as the base material, which has high reliability.

[0037] As shown in Figure 5 The inner cylindrical coil framework 1 is a hollow cylindrical cylinder, and the ratio of its height to the radius of its bottom circle is 2-2.5. The diameter of the inner cylindrical coil framework 1 is less than 3 cm, and the height is less than 5 cm. For example, the diameter of the inner cylindrical coil framework 1 is 1-2.5 cm, and the height is 1-3 cm. The atom gas chamber, heating assembly, and optical path structure of the miniature nuclear magnetic resonance gyroscope are placed in the hollow cylindrical cylinder. The outer surface of the inner cylindrical coil framework 1 has an annular groove for pasting multiple layers of flexible circuit boards. The depth of the annular groove is 1-2 mm, and multiple coils made of flexible circuit boards can be pasted in it, which is convenient to install and replace, and leaves space for introducing new coils. The annular groove is perpendicular to the axis of the inner cylindrical coil framework 1 and parallel to the circular bottom surface of the inner cylindrical coil framework 1. The axial first-order gradient magnetic compensation coil 2, the axial second-order gradient magnetic compensation coil 3, and the radial first-order gradient magnetic compensation coil 4 are sequentially pasted and fixed in the annular groove. The axial first-order gradient magnetic compensation coil 2, the axial second-order gradient magnetic compensation coil 3, and the radial first-order gradient magnetic compensation coil 4 are all manufactured by flexible circuit board technology. The flexible circuit board is rectangular, and after being wrapped around the inner cylindrical coil framework, the coils on the flexible circuit board become cylindrical or saddle-shaped. The circular arc of the cylindrical coil and the saddle-shaped coil is concentric with the bottom surface of the inner cylindrical coil framework. In engineering implementation, the axial first-order gradient magnetic compensation coil 2, the axial second-order gradient magnetic compensation coil 3, and the radial first-order gradient compensation coil 4 are sequentially wrapped and pasted in the annular groove 101 of the inner cylindrical coil framework 1, and a three-axis gradient compensation magnetic field is generated when they are energized.

[0038] As shown in Figure 6As shown, the axial first-order gradient compensation coil 2 is attached within the annular groove 101. It consists of multiple coaxial first circular coils and is used to generate an axial first-order gradient magnetic field. Specifically, the axial first-order gradient compensation coil 2 consists of eight concentric first circular coils of the same radius, connected in series and symmetrical about the central plane of the inner cylindrical coil frame 1. The central plane is parallel to the bottom surface of the inner cylindrical coil frame 1, and its height is half the height of the inner cylindrical coil frame 1. The ratio of the height of the first circular coils to the radius of the bottom surface of the inner cylindrical coil frame 1 is 0.2 to 1.8. The magnetic field generated by the axial first-order gradient compensation coil 2 is an axial first-order gradient magnetic field. In this example, the thickness of the flexible circuit board is approximately 0.1mm-0.15mm, and the magnetic field gradient generated by passing a 1mA current in the axial direction is on the order of approximately 100pT / mm.

[0039] like Figure 7 As shown, the axial first-order gradient compensation coil 3 is pasted inside the annular groove 101 and on the outer layer of the axial first-order gradient compensation coil 2. It consists of multiple coaxial second circular coils and is used to generate an axial second-order gradient magnetic field. Specifically, the axial first-order gradient compensation coil 3 consists of 10 concentric circular second-order coils of the same radius. The second circular coils are connected in series and are symmetrical about the central plane of the inner cylindrical coil skeleton 1. The central plane is parallel to the bottom surface of the inner cylindrical coil skeleton 1, and the height of the central plane is half the height of the inner cylindrical coil skeleton 1. The ratio of the height of the first circular coil to the radius of the bottom surface of the inner cylindrical coil skeleton 1 is 0.2-2.0. The magnetic field generated by the axial second-order gradient compensation coil 3 is an axial second-order gradient magnetic field. In this example, the flexible circuit board is approximately 0.1mm-0.15mm thick, and a 1mA current flowing through it generates an axial magnetic field gradient of approximately 10pT / mm. 2 Order of magnitude.

[0040] like Figure 8 As shown, the radial first-order gradient compensation coil 4 is pasted inside the annular groove 101 and on the outer layer of the axial second-order gradient compensation coil 3. It consists of eight identical saddle-shaped coils and is used to generate a radial first-order gradient magnetic field. Specifically, the radial first-order gradient compensation coil 4 consists of two groups of eight saddle-shaped coils. When the eight saddle-shaped coils are unfolded into a plane, they form eight rectangular coils. Each group of saddle-shaped coils consists of four saddle-shaped coils (…). Figure 8The 4 saddle-shaped coils in the same group are connected in series, and the longitudinal axis of the inner cylindrical coil framework 1 is the rotation axis, and the 4 saddle-shaped coils in the same group are rotated counterclockwise or clockwise by 90 degrees to obtain the 4 saddle-shaped coils in the other group; the positions of the saddle-shaped coils are uniformly distributed along the circumference of the inner cylindrical coil framework 1 by 90 degrees, and are symmetrical about the center plane, the center plane is parallel to the bottom surface of the inner cylindrical coil framework 1, and the position height of the center plane is half of the height of the inner cylindrical coil framework 1; the 2 groups of 8 saddle-shaped coils are realized on a flexible circuit board, and the ratio of the straight edge length of the saddle-shaped coil to the radius of the bottom surface of the inner cylindrical coil framework 1 is 1:0.3-1:1. The central angle of the arc segment of the saddle-shaped coil is 60-90 degrees. The magnetic field generated by the radial first-order gradient compensation coil 4 is a radial first-order gradient magnetic field and In the present example, the thickness of the flexible circuit board of the saddle-shaped coil 3 is about 0.1-0.15 mm, and the magnetic field gradient generated in the radial direction by passing 1 mA current is about 100 pT / mm.

[0041] Compared with the prior art, the micro nuclear magnetic resonance gyroscope three-axis gradient magnetic compensation coil system designed by the present application has a smaller length-diameter ratio, is suitable for the miniaturization development of the micro nuclear magnetic resonance gyroscope, can compensate the magnetic field gradient caused by the residual magnetism of the shielding barrel, internal active devices and the like, and thus improves the magnetic field uniformity in the prototype; the magnetic compensation system is composed of a coil framework and a flexible circuit board, and is convenient to install and replace.

[0042] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and thus cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus cannot be understood as limiting the present application. In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium; can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. The part not described in detail in the present application belongs to the known technology of those skilled in the art.

[0043] The foregoing merely illustrates some exemplary embodiments of the application, and no doubt numerous modifications and alterations thereto will be apparent to those skilled in the art. Accordingly, the above description is intended for purposes of illustration only and should not be construed as limiting the scope of the application.

Claims

1. A three-axis gradient magnetic compensation coil system for a miniature nuclear magnetic resonance gyroscope, characterized in that, The system consists of an inner cylindrical coil frame (1), an axial first-order gradient magnetic compensation coil (2), an axial second-order gradient magnetic compensation coil (3), and a radial first-order gradient compensation coil (4) from the inside out; wherein: the axial first-order gradient magnetic compensation coil (2), the axial second-order gradient magnetic compensation coil (3), and the radial first-order gradient magnetic compensation coil (4) are all manufactured by flexible circuit board technology, using polyimide or polyester film as the substrate; The inner cylindrical coil frame (1) is a hollow cylindrical tube, and the ratio of its height to the radius of its bottom circle is 2 to 2.5; the outer surface of the inner cylindrical coil frame (1) has an annular groove for attaching multilayer flexible circuit boards. The axial first-order gradient compensation coil (2) is pasted in the annular groove. It is composed of multiple coaxial first circular coils and is used to generate an axial first-order gradient magnetic field. The axial first-order gradient compensation coil (2) is composed of 8 concentric first circular coils with the same radius. The first circular coils are connected in series and are symmetrical about the central plane of the inner cylindrical coil skeleton (1). The central plane is parallel to the bottom surface of the inner cylindrical coil skeleton (1), and the height of the central plane is half the height of the inner cylindrical coil skeleton (1). The ratio of the height of the first circular coil to the bottom radius of the inner cylindrical coil skeleton (1) is less than 2, and the ratio of the height of the axial first-order gradient compensation coil to the bottom radius of the inner cylindrical coil skeleton is less than 2. The axial second-order gradient compensation coil (3) is pasted in the annular groove and on the outer layer of the axial first-order gradient compensation coil (2). It is composed of multiple coaxial second circular coils and is used to generate an axial second-order gradient magnetic field. The axial second-order gradient compensation coil (3) is composed of 10 concentric second circular coils with the same radius. The second circular coils are connected in series and are symmetrical about the central plane of the inner cylindrical coil skeleton (1). The central plane is parallel to the bottom surface of the inner cylindrical coil skeleton (1), and the height of the central plane is half the height of the inner cylindrical coil skeleton (1). The ratio of the height of the second circular coil to the bottom radius of the inner cylindrical coil skeleton (1) is less than 2, and the ratio of the height of the axial second-order gradient compensation coil to the bottom radius of the inner cylindrical coil skeleton is less than 2. The radial first-order gradient compensation coil (4) is pasted inside the annular groove and on the outer layer of the axial second-order gradient compensation coil (3). It consists of 8 identical saddle-shaped coils and is used to generate a radial first-order gradient magnetic field. The radial first-order gradient compensation coil (4) consists of 2 groups of 8 saddle-shaped coils. When the 8 saddle-shaped coils are unfolded into a plane, they are 8 rectangular coils. Each group of saddle-shaped coils consists of 4 saddle-shaped coils. The 4 saddle-shaped coils in the same group are connected in series. With the longitudinal axis of the inner cylindrical coil skeleton (1) as the rotation axis, the 4 saddle-shaped coils in the same group rotate 90° counterclockwise or clockwise. This yields another set of four saddle-shaped coils. The saddle-shaped coils are evenly distributed at 90° along the circumference of the inner cylindrical coil skeleton (1) and are symmetrical about the central plane. The central plane is parallel to the bottom surface of the inner cylindrical coil skeleton (1). The height of the central plane is half the height of the inner cylindrical coil skeleton (1). The ratio of the straight side length of the saddle-shaped coil to the bottom radius of the inner cylindrical coil skeleton (1) is less than 1. The ratio of the radial first-order gradient compensation coil height to the bottom radius of the inner cylindrical coil skeleton is less than 2. The central angle of the arc segment of the saddle-shaped coil is 60° to 90°.

2. The three-axis gradient magnetic compensation coil system of the miniature nuclear magnetic resonance gyroscope according to claim 1, characterized in that, The inner cylindrical coil skeleton (1) has a diameter of 1 to 2.5 cm and a height of 1 to 3 cm, with a height-to-radius ratio of less than 3.

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