A radial self-inductive displacement sensor for magnetic levitation bearing systems

Abstract

This invention discloses a radial and axial self-inductive displacement sensor for a magnetic levitation bearing system, belonging to the field of sensor technology. The structure of the radial and axial self-inductive displacement sensor includes a rotor core, a stator core, a shaft, and coils. The stator core is a circular core with magnetic poles on its inner ring. Coils are wound around the magnetic poles, which are aligned with the rotor's stepped surface. There are a total of four sets of magnetic poles, evenly distributed circumferentially. Two coils on each set of poles are connected in series, and adjacent poles form closed magnetic circuits, generating a total of four inductors. Each of the four inductors is connected in series with a fixed resistor, one end of which is grounded, and the other end receives an excitation signal. By measuring the voltage across the four inductors, the axial and radial displacements of the rotor can be obtained. This invention can detect axial displacement from the radial direction of the rotor, solving the problem of limited axial space in conventional axial displacement measurement, and can simultaneously measure the axial and radial displacements of the rotor, improving the integration of the rotor system.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a radial self-inductive displacement sensor for a magnetic levitation bearing system. Background Technology

[0002] In a magnetic levitation bearing system, the controller controls the current in the magnetic levitation bearing coil in real time based on the rotor displacement signal to achieve stable rotor levitation. Therefore, obtaining the rotor displacement signal is a key factor in a magnetic levitation bearing system.

[0003] Currently, eddy current sensors are mainly used to measure rotor displacement in magnetic levitation bearing systems. One eddy current sensor probe is installed at the end of the shaft to detect axial displacement, four eddy current sensor probes are evenly distributed along the circumference of the shaft to detect radial displacement, two sensor probes are symmetrically installed in one radial direction to detect displacement in that direction, and two more sensor probes are installed at a 90-degree angle to detect rotor displacement. This detection method is complex to install and occupies a lot of space. However, with the increasing integration of rotor systems, the power output and testing devices are concentrated in the axial direction of the shaft. Furthermore, to reduce the critical speed and improve system stability, the rotor length is shortened. In addition, the magnetic levitation bearing is integrated into the axial direction of the rotor, resulting in insufficient space for sensors. Therefore, a new displacement detection method is urgently needed. Summary of the Invention

[0004] To address the shortcomings of the prior art, the present invention aims to provide a self-inductive axial displacement sensor for a magnetic levitation bearing system. This sensor can detect axial displacement from the radial direction of the rotor, solving the problem of limited axial space in conventional axial displacement measurement. Furthermore, it can simultaneously measure the axial and radial displacements of the rotor, thereby improving the integration of the rotor system.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A radial and axial self-inductive displacement sensor for a magnetic levitation bearing system includes a rotor core, a stator core, a shaft, and coils. The stator is a circular iron core with magnetic poles on its inner ring. The coils are wound around the magnetic poles, which are aligned with the rotor's stepped surface. There are a total of four sets of magnetic poles, evenly distributed circumferentially. Each set has two magnetic poles, and the two coils on each set are connected in series. When an excitation signal is applied to the coils, the magnetic circuits of adjacent magnetic poles close, generating four inductors. Each of the four inductors is connected in series with a fixed resistor, one end of which is grounded, and the other end receives the excitation signal. The voltages across the four inductors are added to obtain the output voltage in the axial z-direction. The voltages across the two inductors in the y-direction are subtracted to obtain the output voltage in the radial y-direction, and the voltages across the two inductors in the x-direction are subtracted to obtain the output voltage in the radial x-direction.

[0007] Furthermore, the rotor core and stator core are made of silicon steel or permalloy; each coil has the same number of turns; and each magnetic pole has the same cross-sectional area.

[0008] Furthermore, the rotor step surface does not exceed the magnetic pole detection range.

[0009] Furthermore, the four fixed resistors connected in series with each of the four inductors have equal resistance values.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0011] (1) The sensor of the present invention can detect axial displacement from the radial direction of the rotor, which solves the problem of limited space for axial sensor in conventional axial displacement measurement.

[0012] (2) The sensor of the present invention realizes the synchronous measurement of rotor axial and radial displacement, which improves the integration of rotor system. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the overall structure of the sensor of the present invention.

[0014] Figure 2 This is a partial structural schematic diagram of the sensor of the present invention.

[0015] Figure 3 This is a schematic diagram of the modulation circuit structure of the sensor of the present invention.

[0016] The attached figures are labeled as follows: stator core 1, rotor core 2, shaft 3, coil 4. Detailed Implementation

[0017] The invention will now be described in further detail with reference to the accompanying drawings and specific examples, but the invention is not limited to these embodiments. In the following detailed description of the invention, certain specific details are described in detail. Those skilled in the art will fully understand the invention even without these detailed descriptions. To avoid obscuring the essence of the invention, well-known methods, processes, flows, elements, and circuits are not described in detail.

[0018] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

[0019] like Figure 1 , Figure 2 and Figure 3As shown, this invention provides a radial and axial self-inductive displacement sensor for a magnetic levitation bearing system, comprising a rotor core 2, a stator core 1, a shaft 3, and a coil 4. The stator core 1 is a circular core with magnetic poles on its inner ring. The coils are wound around the magnetic poles, which are aligned with the rotor step surface. There are a total of 4 sets of magnetic poles, evenly distributed circumferentially. Each set has 2 magnetic poles, and the 2 coils on each set of magnetic poles are connected in series. When an excitation signal is applied to the coils, the magnetic circuits of adjacent magnetic poles close, generating 4 inductors L1, L2, L3, and L4. Each of the 4 inductors L1, L2, L3, and L4 is connected in series with a fixed resistor, with one end grounded and the other end receiving the excitation signal. The voltages across the 4 inductors are added to obtain the output voltage in the axial z-direction. The voltages across the two inductors in the y-direction are subtracted to obtain the output voltage in the radial y-direction, and the voltages across the two inductors in the x-direction are subtracted to obtain the output voltage in the radial x-direction.

[0020] In this invention, the rotor core and stator core are made of silicon steel or permalloy. Each coil has the same number of turns. Each magnetic pole has the same cross-sectional area.

[0021] like Figure 2 As shown, in this invention, the rotor step surface remains within the magnetic pole detection range of the sensor within the rotor displacement range. When the rotor undergoes axial or radial displacement, the inductance of the coil also changes accordingly.

[0022] like Figure 3 As shown, when the magnitudes of inductors L1, L2, L3, and L4 change, the voltage across the inductors will also change accordingly. When the rotor displacement range is small, the relationship between the voltage across inductor L1 and the displacement can be approximated linearly as follows:

[0023] U1=k a Δz+k r Δy+U0

[0024] Where, k a To determine the sensitivity of displacement detection along the axial direction of the sensor, k r To determine the radial displacement detection sensitivity along the sensor, k a and k r With the value fixed, U0 is the voltage across the inductor when the rotor displacement is 0 (the rotor is suspended in the middle position), and Δy and Δz are the rotor displacements along the y and z directions, respectively. Since the number of turns, magnetic pole cross-sectional area, and air gap length (when the rotor is in the equilibrium position) of the four sets of coils are the same and uniformly distributed circumferentially, the output characteristics of the four sets of inductors are identical. Therefore, the relationship between the voltage across inductors L2, L3, and L4 and the displacement is as follows:

[0025] U2=k a Δz+k r Δx+U0

[0026] U3=ka Δz-k r Δy+U0

[0027] U4=k a Δz-k r Δx+U0

[0028] Where Δx is the displacement of the rotor along the x-direction.

[0029] Adding U1, U2, U3, and U4 together, we can obtain the axial output voltage as follows:

[0030] U z =U1+U2+U3+U4=k a Δz+k r Δy+U0

[0031] Subtracting U1 from U3, we can obtain the output voltage in the radial y-direction as follows:

[0032] U y =U1-U3=2k r Δy

[0033] Subtracting U2 from U4 yields the output voltage in the radial x-direction:

[0034] U x =U2-U4=2k r Δx

[0035] Therefore, the output voltage U x U y U z The axial and radial displacements of the rotor are linearly related to the displacements in the x, y, and z directions, respectively. By detecting the magnitude of the output voltage, the magnitude and direction of the rotor's axial and radial displacements can be determined.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A shaft radial self-induction displacement sensor for a magnetic bearing system, characterized by: The structure of the shaft radial self-induction displacement sensor comprises a rotor core, a stator core, a rotating shaft and a coil; the stator is an inner ring annular core with magnetic poles; the coil is wound on the magnetic poles; the magnetic poles are aligned with the rotor step surface; the magnetic poles are totally 4 groups; the 4 groups of magnetic poles are evenly distributed along the circumference; each group has 2 magnetic poles; the 2 coils on each group of magnetic poles are connected in series; after the coil is connected with the excitation signal, the magnetic circuit of adjacent magnetic poles is closed to generate 4 inductances; the 4 inductances are respectively connected with a fixed resistance in series; one end is grounded and the other end is connected with the excitation signal; the output voltage in the axial z direction can be obtained by adding the voltages at the two ends of the 4 inductances; the output voltage in the radial y direction can be obtained by subtracting the voltages at the two ends of the 2 inductances in the y direction; the output voltage in the radial x direction can be obtained by subtracting the voltages at the two ends of the 2 inductances in the x direction.

2. A shaft radial self-induction displacement sensor for a magnetic bearing system according to claim 1, characterized in that: The materials of the rotor core and the stator core are silicon steel or permalloy; the number of turns of each coil is the same; the cross-sectional area of each magnetic pole is the same.

3. A shaft radial self-induction displacement sensor for a magnetic bearing system according to claim 1, characterized in that: The rotor step surface does not exceed the detection range of the magnetic poles.

4. A shaft radial self-induction displacement sensor for a magnetic bearing system according to claim 1, characterized in that: The 4 fixed resistances connected with the 4 inductances respectively have the same resistance value.

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