A multi-degree-of-freedom sensing system for a magnetic levitation rotor based on eddy current shape detection

Abstract

The present invention discloses a multi-degree-of-freedom sensing system for a magnetic levitation rotor based on eddy current shape detection. The present invention includes an electromagnetic levitation-driving system, a rotor, 3 lateral sensing coils and 2 bottom sensing coils. The rotor is arranged inside the upper part of the electromagnetic levitation-driving system. The 3 lateral sensing coils are fixedly installed on the outer circumferential side of the rotor at intervals along the circumference. The 3 lateral sensing coils are all arranged at intervals with the rotor. The 2 bottom sensing coils are fixedly installed at intervals below the aluminum sheet of the rotor. The present invention can realize the measurement of a total of 4 degrees of freedom including 2 radial displacements, axial displacement and rotation angle only with 5 sensing coils, and realizes the temperature compensation of the coil part of the pre-stage circuit. When measuring the same number of degrees of freedom, this non-contact measurement system greatly reduces the number of sensors and reduces the measurement cost.

Description

Technical Field

[0001] The present invention relates to a magnetic levitation rotor multi-degree-of-freedom sensing system in the field of magnetic levitation rotor multi-degree-of-freedom sensing, and particularly to a magnetic levitation rotor multi-degree-of-freedom sensing system based on eddy current shape detection. Background Art

[0002] In fields such as semiconductor manufacturing, high-purity chemical engineering, and biopharmaceuticals, magnetic levitation pumps are required in many occasions. Due to the special measurement requirements of these magnetic levitation systems, their measurement and positioning methods must achieve non-contact sensing.

[0003] In current measurement methods, a combination of multiple sensing methods is required to obtain information on the key degrees of freedom of the levitated rotor. For example, in the practical application of an electromagnetic levitation drive system, sensors such as laser type, inductive type, or capacitive type are usually used to obtain rotor displacement information. And sensors such as optoelectronic encoding or magnetic encoding are used to obtain angle information. These sensors of different measurement types, due to different measurement principles, result in redundant measurement and compensation of some information (such as temperature drift and temperature compensation), causing redundant sensor quantity and increasing the measurement cost.

[0004] Currently, the measurement method based on coil impedance is a scheme with high usage rate and low cost in displacement measurement methods, which only includes a measurement coil and a post-processing circuit. However, the impedance value of the measurement coil is greatly affected by temperature changes, which has a great impact on subsequent calibration and measurement. And currently, there is no scheme to inversely calculate multi-degree-of-freedom information using the relationship between multiple coils and the shape of the measured object. If all key degrees of freedom can be measured using the same principle, then this scheme will effectively solve the problem of redundant sensor quantity in multi-degree-of-freedom measurement and save costs. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a magnetic levitation rotor multi-degree-of-freedom sensing system based on eddy current shape detection. The rotor part includes a permanent magnet rotor and an aluminum sheet. Coils distributed on the side of the permanent magnet are used to measure the radial displacement of the rotor and achieve temperature compensation, and coils distributed under the aluminum sheet are used to measure the axial displacement and angle of the rotor. A measurement method for the change in coil impedance and the change in the output voltage of the measurement circuit caused by the change in rotor displacement or rotation angle is proposed through theoretical derivation. This measurement system can achieve the measurement of a total of 4 degrees of freedom, including 2 radial displacements, axial displacement, and rotation angle, with only 5 sensing coils, and realizes temperature compensation for the coil part of the front-stage circuit. This non-contact measurement system greatly reduces the number of sensors and lowers the measurement cost when measuring the same number of degrees of freedom.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention includes an electromagnetic suspension-drive system, a rotor, three lateral sensing coils, and two bottom sensing coils. The rotor is disposed inside the upper part of the electromagnetic suspension-drive system. The three lateral sensing coils are fixedly installed at intervals along the circumference on the outer circumferential side of the rotor in the electromagnetic suspension-drive system. The two bottom sensing coils are disposed inside the electromagnetic suspension-drive system, and the two bottom sensing coils are fixedly installed at intervals below the rotor.

[0008] The rotor includes aluminum sheets, permanent magnets, and non-metallic connectors. The permanent magnets are connected to the aluminum sheets through the non-metallic connectors. The aluminum sheets are annular aluminum sheets with a positive circular hole in the middle. There is a linear relationship between the radial width and the axial rotation angle of the annular aluminum sheets.

[0009] The three lateral sensing coils are denoted as the first-third lateral sensing coils. The central axes of the first-third lateral sensing coils are perpendicular to the axis of the electromagnetic suspension-drive system. The central axes of the first lateral sensing coil and the second lateral sensing coil are perpendicular. The third lateral sensing coil is disposed between the first lateral sensing coil and the second lateral sensing coil.

[0010] Taking the intersection point of the central axes of the three lateral sensing coils as the origin, an xy coordinate system is established in the plane where the central axes of the three lateral sensing coils are located. The axis of the electromagnetic suspension-drive system is the z-axis. The central axes of the three lateral sensing coils are respectively disposed on the x-axis, the y-axis, and y = ax, where y represents the y-axis coordinate value, x represents the x-axis coordinate value, and a represents the first coefficient.

[0011] The two bottom sensing coils have the same structure. The first bottom sensing coil and the second bottom sensing coil are in the same plane and are spaced apart. The central axes of the first bottom sensing coil and the second bottom sensing coil are parallel to the axis of the electromagnetic suspension-drive system. The coil cross-sections of the two bottom sensing coils are slender. There is an angle γ between the long symmetry lines of the two bottom sensing coils. The intersection point of the extension lines of the long symmetry lines of the coil cross-sections of the two bottom sensing coils is denoted as the center of the circle and is on the axis of the rotor. The two bottom sensing coils are denoted as the first and second bottom sensing coils. The first bottom sensing coil coincides with the second bottom sensing coil after rotating counterclockwise by the angle γ around the center of the circle; both the first bottom sensing coil and the second bottom sensing coil are disposed below the rotor.

[0012] The stator part of the electromagnetic levitation-drive system includes a 7-shaped silicon steel group, a levitation drive winding, and a bottom circular silicon steel. The 7-shaped silicon steel group is fixedly installed on the bottom circular silicon steel. The rotor is arranged in the middle inside the upper end of the 7-shaped silicon steel group. The levitation drive winding is wound around the 7-shaped silicon steel group. The rotor is arranged in the 7-shaped silicon steel group above the levitation drive winding. Three lateral sensing coils are fixedly installed in the tooth grooves of the 7-shaped silicon steel group on the levitation drive winding. Two bottom sensing coils are fixedly installed inside the space surrounded by the 7-shaped silicon steel group below the rotor.

[0013] The 7-shaped silicon steel group includes multiple 7-shaped silicon steels, and the multiple 7-shaped silicon steels are fixedly installed on the bottom circular silicon steel at equal intervals along the circumference. In each 7-shaped silicon steel, the levitation drive winding is wound around the 7-shaped silicon steel. The rotor is arranged between the inner side surfaces of the upper ends of the multiple 7-shaped silicon steels. The levitation drive winding is composed of all the levitation drive coils in the 7-shaped silicon steel group.

[0014] Collect and obtain the voltages of the three lateral sensing coils and the two bottom sensing coils, and calculate the displacements Δx, Δy, Δz and the deflection angle Δθ of the rotor on the xyz axes. The calculation formulas are as follows:

[0015]

[0016] Among them, U1 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the x-axis direction, U2 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the y-axis direction, U3 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the y = ax direction, U4 is the output voltage of the processing circuit corresponding to the first bottom sensing coil, U5 is the output voltage of the processing circuit corresponding to the second bottom sensing coil, and k r is the voltage-displacement coefficient of the lateral sensing coil 3, b is the slope of the linearized inductance-displacement curve, c is the intercept of the linearized inductance-displacement curve, U T represents the temperature drift variable, U 01 represents the initial output voltage of the lateral sensing coil, U 02 represents the initial output voltage of the bottom sensing coil.

[0017] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects.

[0018] The present invention can realize non-contact measurement of multiple key degrees of freedom and can be used in a super-clean environment. The pre-stage circuit of the coil in the present invention adopts a differential bridge measurement circuit, which has good stability and high output sensitivity. The present invention can realize the measurement of 4 degrees of freedom, namely 2 radial displacements, axial displacement and rotation angle, and complete the temperature drift compensation of the coil with only 5 sensing coils. Compared with the solutions for measuring the same number of degrees of freedom, the measurement cost is greatly reduced.

[0019] Compared with the measurement of displacement by a single sensor, this measurement method compensates for the temperature drift in the coil through theoretical calculation, improving the measurement accuracy. The present invention can decouple two voltage signals on the axial coil into axial displacement and rotation angle, and can be used for measurement. The method is novel and has high measurement accuracy. Description of the Drawings

[0020] Figure 1 It is the equivalent circuit of the load model of the single-coil measurement system.

[0021] Figure 2 It is the impedance measurement circuit of the differential AC bridge.

[0022] Figure 3 It is the diagram of the spatial position distribution relationship between the multi-degree-of-freedom sensing system and the suspension drive system.

[0023] Figure 4 It is the schematic diagram of the relative positions of the various parts of the multi-degree-of-freedom sensing system.

[0024] Figure 5 It is the top view of the relative position of the sensing system.

[0025] Figure 6 It is the relative position diagram of the aluminum sheet and the coil.

[0026] Figure 7 It is the front view of the relative position of the sensing system.

[0027] Figure 8 It is the linear relationship diagram of the axial position, rotation angle and impedance of the rotor on the lower coil.

[0028] In the figure: rotor 1, aluminum sheet 11, permanent magnet 12, non-metallic connector 13, 7-shaped silicon steel 2, lateral sensing coil 3, suspension drive winding 5, bottom circular silicon steel 7, bottom sensing coil 8. Detailed Embodiment

[0029] The present invention will be further described below in conjunction with the drawings.

[0030] As Figure 3As shown in the figure, the system includes an electromagnetic suspension-drive system, a rotor 1, three lateral sensing coils 3, and two bottom sensing coils 8. The structures of the three lateral sensing coils 3 and the two bottom sensing coils 8 are the same. The rotor 1 is arranged inside the upper part of the electromagnetic suspension-drive system. The three lateral sensing coils 3 are fixedly installed at intervals along the circumference on the outer circumferential side of the rotor 1 in the electromagnetic suspension-drive system. The three lateral sensing coils 3 are arranged on the sides of the rotor 1. The axial movement range of the rotor 1 does not exceed the axial length of the lateral sensing coils 3. The three lateral sensing coils 3 are all arranged at intervals with the rotor 1. When the rotor 1 does not move, the distances between the three lateral sensing coils 3 and the surface of the permanent magnet 12 are equal. The two bottom sensing coils 8 are arranged inside the electromagnetic suspension-drive system. The two bottom sensing coils 8 are fixedly installed at intervals below the aluminum sheet 11 of the rotor 1. The two bottom sensing coils 8 are arranged at intervals with the rotor 1.

[0031] The rotor 1 includes an aluminum sheet 11, a permanent magnet 12, and a non-metallic connector 13. The permanent magnet is connected to the aluminum sheet 11 through the non-metallic connector 13. The permanent magnet 12 and the aluminum sheet 11 are arranged at intervals up and down. The aluminum sheet 11 is an annular aluminum sheet with a positive round hole in the middle. There is a linear relationship between the radial width and the axial rotation angle of the annular aluminum sheet.

[0032] The three lateral sensing coils 3 are denoted as the first - third lateral sensing coils. The central axes of the first - third lateral sensing coils intersect at the same point, and this point is on the axis of the electromagnetic suspension-drive system. The central axes of the first - third lateral sensing coils are perpendicular to the axis of the electromagnetic suspension-drive system. The central axes of the first lateral sensing coil and the second lateral sensing coil are perpendicular. The third lateral sensing coil is arranged between the first lateral sensing coil and the second lateral sensing coil.

[0033] Taking the intersection point of the central axes of the three lateral sensing coils 3 as the origin, an xy coordinate system is established in the plane where the central axes of the three lateral sensing coils 3 are located. The axis of the electromagnetic suspension-drive system is the z-axis. The central axes of the three lateral sensing coils 3 are respectively arranged on the x-axis, the y-axis, and y = ax, where y represents the y-axis coordinate value, x represents the x-axis coordinate value, and a represents the first coefficient.

[0034] The two bottom sensing coils 8 have the same structure. The first bottom sensing coil and the second bottom sensing coil are in the same plane and are arranged at intervals. The central axes of the first bottom sensing coil and the second bottom sensing coil are parallel to the axis of the electromagnetic levitation-driving system. The coil cross-sections of the two bottom sensing coils 8 are slender. There is an included angle γ (the included angle is 90° in this embodiment) between the long symmetry lines of the two bottom sensing coils 8, that is, the short symmetry lines of the two bottom sensing coils 8 are perpendicular to each other. The intersection point of the extension lines of the long symmetry lines of the coil cross-sections of the two bottom sensing coils 8 is denoted as the center of the circle and is on the axis of the rotor 1. The two bottom sensing coils 8 are denoted as the first and second bottom sensing coils. The first bottom sensing coil coincides with the second bottom sensing coil after rotating counterclockwise by γ around the center of the circle when viewed from the negative z-axis direction; both the first bottom sensing coil and the second bottom sensing coil are arranged below the rotor 1. Specifically, the two long ends in the coil cross-sections of the first bottom sensing coil and the second bottom sensing coil are respectively arranged inside the positive circular hole and outside the outer contour of the annular aluminum sheet.

[0035] The stator part of the electromagnetic levitation-driving system includes a 7-shaped silicon steel group, a levitation driving winding 5, and a bottom circular silicon steel 7; the 7-shaped silicon steel group is fixedly installed on the bottom circular silicon steel 7. The rotor 1 is arranged in the middle inside the upper end of the 7-shaped silicon steel. The levitation driving winding 5 is wound on the 7-shaped silicon steel group. The rotor 1 is arranged in the 7-shaped silicon steel group above the levitation driving winding 5. Three lateral sensing coils 3 are fixedly installed in the tooth grooves of the 7-shaped silicon steel group on the levitation driving winding 5. Two bottom sensing coils 8 are fixedly installed inside the space surrounded by the 7-shaped silicon steel group below the rotor 1;

[0036] The 7-shaped silicon steel group includes multiple 7-shaped silicon steels 2, and the multiple 7-shaped silicon steels 2 are fixedly installed on the bottom circular silicon steel 7 at equal intervals along the circumference; in each 7-shaped silicon steel 2, the levitation driving winding 5 is wound on the 7-shaped silicon steel 2. The rotor 1 is arranged between the inner side surfaces of the upper ends of the multiple 7-shaped silicon steels 2; the levitation driving winding 5 is composed of all the levitation driving coils in the 7-shaped silicon steel group. The six levitation driving coils are fed with the superimposed levitation current and driving current, and the set levitation force and driving torque are generated by an independent control method.

[0037] The described multi-degree-of-freedom sensing system includes the measured rotor 1, lateral sensing coils 3, and bottom sensing coils 8, as well as a post-processing circuit connecting the coils. The pre-stage circuit of each sensing coil adopts a differential bridge measurement circuit. The measured distance of the coil is linearly related to its impedance, and the change in impedance in the coil is approximately linearly related to the potential difference in the bridge. And the above linear relationships are all verified by theoretical derivation, so the measurement requirements can be met.

[0038] The high-frequency excitation current passed through the coil generates a high-frequency alternating magnetic field, and the high-frequency induced current excited on the surface of the measured object further excites a reverse magnetic field, causing the impedance of the coil to change. Different shapes of the measured object or the coil can induce eddy currents of different shapes on the surface of the measured object. By designing the shape of the measured object or the coil, various information can be extracted and applied to multi-degree-of-freedom measurement. According to the principle of induced current, the displacement of the measured object is related to the equivalent impedance of the detection coil. Therefore, the equivalent impedance Z of the detection coil can be written as:

[0039] Z = f(d)

[0040] where f(d) represents the mapping relationship between the coil impedance and the distance d between the coil and the surface of the measured object.

[0041] Therefore, in this measurement process, the sensing system and the measured conductor can be equivalent to a transformer model, and its load equivalent circuit is as Figure 1 shown. The load equivalent impedance of the sensing coil is:

[0042]

[0043] In the formula, represents the input alternating voltage, represents the alternating current in the sensing coil, R1 is the resistance of the coil itself. The envelope of the eddy current path generated on the surface of the measured conductor can be regarded as a single-turn coil, and its resistance and inductance can be represented by R2 and L2 respectively, ω represents the frequency of the alternating voltage; L1 is the inductance of the coil itself; M is the mutual inductance between the coil and the measured conductor, and its magnitude is where k is the coupling coefficient, and 0 < k < 1. Figure 2 is the pre-stage circuit of the measurement system, which adopts a differential AC bridge circuit. The sensing coil is generally used as a branch in the bridge circuit. This pre-stage circuit generally has good system stability and output sensitivity. Under the balanced state, the potential difference between node 1 and node 2 in the bridge is zero, that is, ΔU0 is equal to zero. When the measured conductor approaches the sensing coil, the coil impedance Z x changes, the AC bridge loses balance, and the output voltage of the bridge circuit is not zero, that is, the conversion from coil impedance to voltage quantity is realized. At this time, the potential difference ΔU0 between node 1 and node 2 is:

[0044]

[0045] where Z1 represents Figure 2 the impedance of the upper left bridge arm coil already set in the pre-stage circuit, Z2 represents the impedance of the upper right bridge arm coil, Z3 represents the impedance of the lower left bridge arm coil, and U i represents the voltage of the input excitation source.

[0046] The voltage output by the pre-stage circuit still needs to be amplified and filtered by the post-stage circuit later. The potential difference ΔU0 output by the pre-stage circuit and the final output voltage U of the processing circuit out show a linear relationship. Therefore, in this measurement system, within a certain measurement range, the equivalent impedance Z x and the final output voltage U of the processing circuit out show an approximately linear relationship and can be reflected by the displacement change.

[0047] U out = KΔd + U0

[0048] where, U out represents the final output voltage of the processing circuit, Δd represents the actual displacement of the measured object. The initial output voltage of the measurement circuit is U0. The initial output voltages of the 3 lateral sensing coils are the same, all denoted as U 01 . The initial output voltages of the 2 bottom sensing coils are the same, all denoted as U 02 .

[0049] Figure 3 is the position distribution relationship diagram of the multi-degree-of-freedom sensing system and the suspension drive system in space.

[0050] Figure 4 is the schematic diagram of the relative position distribution of each part of the multi-degree-of-freedom sensing system in space.

[0051] As Figure 5 shown, the 3 coils on the side in the sensing system are respectively located on the x-axis, y-axis and y = ax (a = 1). The resistance in the coil will change with temperature, so the temperature drift variable U T is introduced separately. The output voltages of the processing circuits of the 3 side coils can be expressed as U1 to U3 in the formula,

[0052] As Figure 6 shows the radial position relationship between the 2 sensing coils below and the aluminum sheet. Here, the 2 coils below are respectively located on the x-axis and y-axis, separated by 90°, that is, γ = 90°. The maximum width of the aluminum sheet is less than the length of the coil to ensure that when the rotor is at each angle, the coil has a unique impedance value corresponding to it. As the rotor rotates, the width of the intersection of the aluminum sheet and the coil will increase linearly, and then the rotor rotation angle and the coil output voltage will show a linear relationship. In the sensing system. After introducing the temperature drift variable, the output voltages of the processing circuits of the 2 bottom coils can be expressed as U4 to U5 in the formula.

[0053] Figure 7It shows the positional relationship between the permanent magnet rotor and the three sensing coils on the side, as well as the axial positional relationship between the two sensing coils below and the aluminum sheet. The change in the axial position of the rotor needs to be within the axial length of the side sensing coils. Therefore, the change in the axial position of the rotor will not cause a change in the impedance of the side sensing coils. The expression of the linear rotation angle-width contour line in the plane polar coordinate system is r = r0 + kθ. It can be seen from the expression that the width r and the rotation angle θ are linearly related. Therefore, when the rotation angle changes, the width of the eddy current region induced in the aluminum sheet will also change linearly. The change in the width of the eddy current region causes a change in the impedance of the coil, and finally it is reflected in the output voltage of the processing circuit, that is, the output voltage of the two bottom sensing coils 8 and the rotation angle are linearly related. The change in the axial position of the rotor will also cause a change in the impedance of the coil below. Therefore, in this system, the processing circuit outputs a voltage signal that is mutually coupled between the axial position Δz and the rotation angle Δθ of the rotor. Therefore, through the calculation method proposed by the present invention, the axial displacement and the rotation angle can decouple and solve these two parts of information from the voltage value respectively.

[0054] Figure 8 is the linear relationship diagram of the axial position Δz, rotation angle Δθ of the rotor and the impedance Z collected on the lower sensing coil x The k θ (Δz) function is the voltage-rotor rotation angle relationship function on the measurement coil when the axial displacement of the rotor is Δz. The slope coefficient in this function will change with the change of the axial position. Because the impedance Z x will be linearly related to the distance d, so the impedance Z x can be regarded as a first-order function of the distance d, and the parameters b and c are both constants that can be obtained through measurement.

[0055] Through the above-derived relationships, five voltage equations of the measurement coil and the voltage-rotation angle relationship function k θ (Δz) can be obtained. The equations are as follows, where k r is the voltage-displacement coefficient of the measurement coil in the radial direction, and a is the tangent value of the arbitrary installation angle of the measurement coil in the Cartesian coordinate system. The above parameters can all be obtained through measurement and the installation design process.

[0056]

[0057] By solving the above equations, a unique set of solutions can be determined according to the voltage values of U1~U5.

[0058] Collect and obtain the voltages of the three lateral sensing coils 3 and the two bottom sensing coils 8, calculate and obtain the displacements Δx, Δy, Δz of the rotor 1 on the xyz axes and the deflection angle Δθ, and record them as the four key degrees of freedom of the rotor 1. The calculation formulas are as follows:

[0059]

[0060] Among them, U1 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the x-axis direction, U2 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the y-axis direction, U3 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the y = ax direction, U4 is the output voltage of the processing circuit corresponding to the first bottom sensing coil, U5 is the output voltage of the processing circuit corresponding to the second bottom sensing coil, k r is the voltage-displacement coefficient of the lateral sensing coil 3, b is the slope of the linearized inductance-displacement curve, c is the intercept of the linearized inductance-displacement curve, U T represents the temperature drift variable, U 01 represents the initial output voltage of the lateral sensing coil, U 02 represents the initial output voltage of the bottom sensing coil.

Claims

1. A multi-degree-of-freedom sensing system for a magnetic levitation rotor based on eddy current shape detection, characterized in that, It includes an electromagnetic levitation-drive system, a rotor (1), three lateral sensing coils (3) and two bottom sensing coils (8). The rotor (1) is arranged inside the upper part of the electromagnetic levitation-drive system. The three lateral sensing coils (3) are fixedly installed at intervals along the circumference on the outer circumferential side of the rotor (1) in the electromagnetic levitation-drive system. The two bottom sensing coils (8) are arranged inside the electromagnetic levitation-drive system, and the two bottom sensing coils (8) are fixedly installed at intervals below the rotor (1). The rotor (1) includes an aluminum sheet (11), a permanent magnet (12) and a non-metallic connector (13). The permanent magnet is connected to the aluminum sheet (11) through the non-metallic connector (13). The aluminum sheet (11) is an annular aluminum sheet with a positive circular hole in the middle, and there is a linear relationship between the radial width and the axial rotation angle of the annular aluminum sheet. The three lateral sensing coils (3) are denoted as the first - third lateral sensing coils. The central axes of the first - third lateral sensing coils are perpendicular to the axis of the electromagnetic levitation-drive system. The central axes of the first lateral sensing coil and the second lateral sensing coil are perpendicular. The third lateral sensing coil is arranged between the first lateral sensing coil and the second lateral sensing coil. The displacements Δx, Δy, Δz and the deflection angle Δθ of the rotor (1) on the xyz axes are calculated based on the voltages of the three lateral sensing coils (3) and the two bottom sensing coils (8).

2. The multi-degree-of-freedom sensing system for a magnetic levitation rotor based on eddy current shape detection according to claim 1, wherein Taking the intersection point of the central axes of the three lateral sensing coils (3) as the origin, an xy coordinate system is established in the plane where the central axes of the three lateral sensing coils (3) are located. The axis of the electromagnetic levitation-drive system is the z axis. The central axes of the three lateral sensing coils (3) are respectively arranged on the x axis, the y axis and y = ax, where y represents the y-axis coordinate value, x represents the x-axis coordinate value, and a represents the first coefficient.

3. A multi-degree-of-freedom sensing system for a magnetic levitation rotor based on eddy current shape detection according to claim 1, characterized in that, The two bottom sensing coils (8) have the same structure. The first bottom sensing coil and the second bottom sensing coil are in the same plane and are arranged at intervals. The central axes of the first bottom sensing coil and the second bottom sensing coil are parallel to the axis of the electromagnetic levitation-drive system. The coil cross-sections of the two bottom sensing coils (8) are slender. There is an included angle γ between the long symmetry lines of the two bottom sensing coils (8). The intersection point of the extension lines of the long symmetry lines of the coil cross-sections of the two bottom sensing coils (8) is denoted as the center of the circle and is on the axis of the rotor (1). The two bottom sensing coils (8) are denoted as the first and second bottom sensing coils. The first bottom sensing coil coincides with the second bottom sensing coil after rotating counterclockwise by an angle γ around the center of the circle. Both the first bottom sensing coil and the second bottom sensing coil are arranged below the rotor (1).

4. A multi-degree-of-freedom sensing system for a magnetic levitation rotor based on eddy current shape detection according to claim 1, wherein The stator part of the electromagnetic suspension-drive system includes a 7-shaped silicon steel group, a suspension drive winding (5), and a bottom circular silicon steel (7); the 7-shaped silicon steel group is fixedly installed on the bottom circular silicon steel (7), the rotor (1) is arranged in the middle of the upper end of the 7-shaped silicon steel group, the suspension drive winding (5) is wound on the 7-shaped silicon steel group, the rotor (1) is arranged in the 7-shaped silicon steel group above the suspension drive winding (5), and 3 lateral sensing coils (3) are fixedly arranged in the tooth grooves of the 7-shaped silicon steel group on the suspension drive winding (5), and 2 bottom sensing coils (8) are fixedly installed inside the space surrounded by the 7-shaped silicon steel group below the rotor (1); The 7-shaped silicon steel group includes multiple 7-shaped silicon steels (2), and the multiple 7-shaped silicon steels (2) are fixedly installed on the bottom circular silicon steel (7) at equal intervals along the circumference; in each 7-shaped silicon steel (2), the suspension drive winding (5) is wound on the 7-shaped silicon steel (2), and the rotor (1) is arranged between the inner side surfaces of the upper ends of the multiple 7-shaped silicon steels (2); the suspension drive winding (5) is composed of all the suspension drive coils in the 7-shaped silicon steel group.

5. A multi-degree-of-freedom sensing system for a magnetic levitation rotor based on eddy current shape detection according to claim 3, characterized in that, Collect and obtain the voltages of the 3 lateral sensing coils (3) and the 2 bottom sensing coils (8), and calculate the displacements Δx, Δy, Δz and the deflection angle Δθ of the rotor (1) on the xyz axes. The calculation formulas are as follows: Among them, U1 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the x-axis direction, U2 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the y-axis direction, U3 is the output voltage of the processing circuit corresponding to the lateral sensing coil 3 in the y = ax direction, U4 is the output voltage of the processing circuit corresponding to the first bottom sensing coil, U5 is the output voltage of the processing circuit corresponding to the second bottom sensing coil, k r is the voltage-displacement coefficient of the lateral sensing coil 3, b is the slope of the inductance-displacement curve after linearization, c is the intercept of the inductance-displacement curve after linearization, U T represents the temperature drift variable, U 01 represents the initial output voltage of the lateral sensing coil, U 02 represents the initial output voltage of the bottom sensing coil.

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