A differential self-inductive axial displacement sensor

Abstract

This invention relates to a differential self-inductive axial displacement sensor, belonging to the field of displacement sensor technology. The invention comprises: two coaxially arranged stator core rings and a mover. The mover consists of a mover spindle, an annular mover core mounted thereon, and two mover retaining rings, supporting axial movement within a certain range. Each stator core ring has four sets of magnetic pole pairs symmetrically and uniformly arranged circumferentially, and each set of magnetic pole pairs has a winding, which is two coils wound in series and then twisted in opposite directions. Two windings from two symmetrical sets of magnetic pole pairs on one stator core ring are connected in series with two windings at the same position on the other stator core ring to form a branch. The eight windings form two branches, which are connected in parallel to the same sinusoidal AC voltage source. The potential difference at the midpoint of the two branches is extracted as the output voltage signal characterizing the axial displacement of the mover. This application aims to improve the sensitivity and signal-to-noise ratio of the self-inductive axial displacement sensor.

Description

Technical Field

[0001] This invention relates to the field of inductive displacement sensor technology, and more particularly to a differential self-inductive axial displacement sensor. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] In modern industrial automation, precision manufacturing, aerospace, and high-end equipment, the demand for high-precision and high-reliability measurement of minute displacements is increasing. Self-inductive displacement sensors are widely used in axial displacement detection due to their simple structure, fast response, and non-contact measurement capabilities. Among them, the differential structure, by introducing symmetrical inductance changes, can effectively improve linearity and sensitivity while suppressing common-mode interference, and has become one of the mainstream technologies for high-precision displacement sensing.

[0004] However, existing differential self-inductance displacement sensors still face several technical bottlenecks. Traditional solutions typically employ a single stator core structure with two sets of symmetrical windings, reflecting displacement by detecting the difference in inductance between the two windings. While this structure possesses certain differential characteristics, its sensitivity is limited by the air gap variation range of a single magnetic circuit, and the output signal amplitude is relatively small, making it susceptible to power fluctuations and external electromagnetic noise, resulting in a low signal-to-noise ratio and failing to meet the stringent requirements of higher-precision displacement detection. Therefore, there is an urgent need to propose a novel differential self-inductance axial displacement sensor structure that achieves efficient coupling and noise suppression of displacement signals, thereby significantly improving the sensor's sensitivity and signal-to-noise ratio to meet the core requirements of high-precision displacement sensing in high-end applications. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, or at least partially solve the above-mentioned technical problems, the present invention provides a differential self-inductive axial displacement sensor.

[0006] The present invention provides two stator core rings and one mover arranged coaxially. The mover consists of a mover spindle, an annular mover core assembled thereon, and two mover retaining rings. The mover supports movement within a certain range along its axial direction. Each stator core ring has four sets of magnetic pole pairs symmetrically and uniformly arranged in the circumferential direction, and each set of magnetic pole pairs is provided with a winding, which is two coils wound in opposite directions in series.

[0007] Two windings on two symmetrical pairs of magnetic poles on one stator core ring are connected in series with two windings at the same position on another stator core ring to form a branch. The eight windings form two branches, which are connected in parallel to the same sinusoidal AC voltage source. The potential difference at the midpoint of the two branches is extracted as the output voltage signal characterizing the axial displacement of the mover.

[0008] When the mover core is in the axial balance position between the two stator core rings, the inductance is balanced, the midpoint potentials of the two branches are equal, and the output voltage signal is 0. When the mover spindle undergoes axial displacement, the mover core moves accordingly, the inductance becomes unbalanced, the midpoint potential of one branch increases, and the midpoint potential of the other branch decreases, creating a potential difference between the midpoints of the two branches, thereby outputting a voltage signal corresponding to the axial displacement of the mover.

[0009] Furthermore, the two stator core rings are two identical coaxially arranged first stator core rings and second stator core rings;

[0010] A moving mandrel is provided at the central axis of the first stator core ring and the second stator core ring. The moving mandrel supports movement within a certain range along its axial direction. An annular moving core and a first moving retaining ring and a second moving retaining ring are provided on both sides of the moving core.

[0011] The first stator core ring and the second stator core ring each have eight magnetic poles whose center lines pass through the center of the outer circle of the stator core ring. The magnetic poles are paired up to form four sets of magnetic pole pairs that are symmetrically distributed along the circumference. The magnetic pole pairs are opposite to each other. Each magnetic pole is wound with a coil of the same number of turns. The two coils in a set of magnetic pole pairs are wound in opposite directions and connected in series to form a winding.

[0012] Furthermore, the first stator core ring, the second stator core ring, and the mover core are made of high magnetic permeability materials, while the first mover retaining ring and the second mover retaining ring are made of non-magnetic materials.

[0013] Furthermore, when the mover spindle is in the axial equilibrium position, the center lines of each magnetic pole of the first stator core ring and the second stator core ring are aligned with the end faces on both sides of the mover core.

[0014] Furthermore, the four windings on the first stator core ring 1 are winding W1, winding W2, winding W3 and winding W4 respectively, with winding W1 and winding W3 facing each other, and winding W2 and winding W4 facing each other.

[0015] The four windings on the second stator core ring 2 are windings W5, W6, W7 and W8 respectively. Windings W5 and W7 are opposite each other, and windings W6 and W8 are opposite each other.

[0016] The windings W1, W2, W3, and W4 on the first stator core ring 1 and the windings W5, W6, W7, and W8 on the second stator core ring 2 are respectively aligned one-to-one;

[0017] Windings W1, W3, W5 and W7 are connected in series to form one branch, and windings W6, W8, W2 and W4 are connected in series to form another branch.

[0018] The potential difference between the nodes of windings W3 and W5, and between the nodes of windings W8 and W2, is used as the output voltage signal.

[0019] Furthermore, when the mover spindle 6 moves along the stator core ring axis, the relationship between the winding inductance and the axial displacement of the mover spindle is as follows: The equivalent inductances of windings W1, W2, W3, W4, W5, W6, W7, and W8 are respectively:

[0020] ;

[0021] ;

[0022] in, The permeability of free space, N The total number of turns of the coil on a set of magnetic pole pairs. a and b These represent the circumferential width and axial thickness of a magnetic pole, respectively. δ The length of the air gap between the stator poles and the mover core; z 0 represents the moving spindle along the axis. z The distance in the positive direction from the equilibrium position.

[0023] Furthermore, at the operating frequency of the sensor's sinusoidal AC voltage source, since the DC resistance of the winding is much smaller than its inductive reactance, the impedance of the winding can be approximated as its inductive reactance. When the mover spindle 6 moves along the stator core ring axis, the impedance of each winding can be expressed as:

[0024] ;

[0025] ;

[0026] Where j is the imaginary unit, ω ω is the angular frequency of the sinusoidal AC voltage source.

[0027] Furthermore, the sensitivity of the differential self-inductive axial displacement sensor is:

[0028] ;

[0029] in, This is the effective voltage value of the sinusoidal AC voltage source for the sensor.

[0030] Furthermore, the maximum magnetic flux of the differential self-inductance axial displacement sensor is:

[0031] ;

[0032] in, The frequency of the sinusoidal AC voltage source for the sensor. This represents the maximum voltage of the sinusoidal AC voltage source for the sensor.

[0033] The maximum magnetic flux through the sensor's magnetic poles to the winding from external interference magnetic fields is Φ EIM The signal-to-noise ratio of the differential self-inductance axial displacement sensor to external interference magnetic fields can be expressed as:

[0034] .

[0035] Furthermore, the frequency of the sinusoidal AC voltage source for the differential self-inductance axial displacement sensor is between 20 and 100 kHz.

[0036] The technical solutions provided in the embodiments of the present invention have the following advantages compared with the prior art:

[0037] In this invention, the mover spindle drives the mover core to move axially, changing the inductance of the windings on the two stator core rings. The inductance of the winding on one stator core ring increases, while the inductance of the winding on the other stator core ring decreases. Two windings at symmetrical positions of the magnetic pole pairs on one stator core ring are connected in series with two windings at the same positions on the other stator core ring to form a branch. The eight windings form two branches, which are connected in parallel to the same sinusoidal AC voltage source. After the mover spindle undergoes axial displacement, the inductance of the windings on the two stator core rings changes accordingly. The potential at the midpoint of one branch increases, while the potential at the midpoint of the other branch decreases. The difference between the potentials at the two midpoints is taken as the sensor output voltage signal to reflect the axial displacement of the mover spindle. In this invention, by selecting the winding connection method and the output position, higher sensitivity and a larger signal-to-noise ratio are achieved for displacement measurement. Higher sensitivity means that even a small displacement can produce a more significant change in output voltage, greatly improving detection accuracy. A larger signal-to-noise ratio means stronger anti-interference capability. This makes the solution of this application have measurement advantages in high-precision measurement scenarios. Attached Figure Description

[0038] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A view along the vertical axis of a differential self-inductive axial displacement sensor provided in an embodiment of the present invention;

[0041] Figure 2 This is an axial view of side A of the differential self-inductive axial displacement sensor provided in an embodiment of the present invention.

[0042] Figure 3 This is an axial view of side B of the differential self-inductive axial displacement sensor provided in an embodiment of the present invention.

[0043] Figure 4 A circuit diagram showing the coil connection method of a differential self-inductive axial displacement sensor provided in an embodiment of the present invention;

[0044] Figure 5 The equivalent circuit diagram of the coil of the differential self-inductive axial displacement sensor provided in the embodiment of the present invention;

[0045] Figure 6 A circuit diagram of the coil connection method for a comparative scheme provided in an embodiment of the present invention;

[0046] Figure 7 The equivalent circuit diagram of the coil of the comparative scheme provided in the embodiment of the present invention.

[0047] The labels and their meanings in the diagram are as follows:

[0048] 1. First stator core ring; 2. Second stator core ring; 3. Rotor core; 4. First rotor retaining ring; 5. Second rotor retaining ring; 6. Rotor spindle. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] Example 1

[0052] The present invention provides a differential self-inductive axial displacement sensor, comprising: two stator core rings coaxially arranged and a mover, the mover consisting of a mover spindle, an annular mover core mounted thereon and two mover retaining rings, the mover supporting movement within a certain range along its axial direction; each stator core ring has four sets of magnetic pole pairs symmetrically and uniformly arranged circumferentially, and each set of magnetic pole pairs is provided with a winding, the winding being two coils wound in opposite directions in series.

[0053] Specifically, such as Figures 1 to 3 As shown, the differential self-inductive axial displacement sensor includes:

[0054] Two identical coaxially arranged first stator core rings 1 and 2 are provided. A mover spindle 6 is located at the central axis of the first stator core rings 1 and 2. An annular mover core 3 and first and second mover retaining rings 4 and 5 respectively are mounted on the mover spindle 6. The mover spindle 6 supports movement within a certain range along its axial direction. The first stator core rings 1, 2, and 3 are made of high magnetic permeability materials, such as silicon steel sheets. The first and second mover retaining rings 4 and 5 are made of non-magnetic materials.

[0055] The first stator core ring 1 and the second stator core ring 2 each have eight magnetic poles whose center lines pass through the center of the outer circle of the stator core ring. The magnetic poles are paired, and the angle between the paired magnetic poles is smaller than the angle between the unpaired magnetic poles. The eight magnetic poles form four sets of magnetic pole pairs that are symmetrically distributed along the circumference and are opposite to each other. Each magnetic pole is wound with a coil of the same number of turns. The two coils in a pair of magnetic poles are wound in opposite directions and connected in series to form a winding. The four windings on the first stator core ring 1 are windings W1, W2, W3, and W4, with impedances Z1 to Z4 respectively. Windings W1 and W3 are opposite each other, and windings W2 and W4 are opposite each other. The four windings on the second stator core ring 2 are windings W5, W6, W7, and W8, with impedances Z5 to Z8 respectively. Windings W5 and W7 are opposite each other, and windings W6 and W8 are opposite each other. The windings W1, W2, W3, and W4 on the first stator core ring 1 and the windings W5, W6, W7, and W8 on the second stator core ring 2 are opposite each other.

[0056] There is a certain air gap between the inner diameter end face of the magnetic pole and the moving core 3. The coil is made of enameled wire.

[0057] When the mover core 6 is in the axial equilibrium position, the magnetic pole center lines of the first stator core ring 1 and the second stator core ring 2 are aligned with the end faces on both sides of the mover core 3, that is, at this time, the axial distance between the inner end faces of the magnetic poles of the first stator core ring 1 and the second stator core ring 2 and the end faces of the mover core 3 is half of the axial thickness of the magnetic pole.

[0058] The eight windings are connected in a set manner and then connected to a high-frequency sinusoidal AC voltage source, thereby generating a high-frequency alternating magnetic field in the stator core, the mover core and the air gap between them.

[0059] Specifically, such as Figure 4 and Figure 5 As shown in this application, windings W1, W3, W5, and W7 are connected in series to form one branch, and windings W6, W8, W2, and W4 are connected in series to form another branch. The extended ends of windings W1 and W6, and the extended ends of windings W4 and W7 are connected to the sensor's sinusoidal AC voltage source. The potential difference between the junctions of windings W3 and W5 and the junctions of windings W8 and W2 is used as the sensor's output voltage signal.

[0060] When the mover core is in the axial balance position between the two stator core rings, the inductance is balanced, the midpoint potentials of the two branches are equal, and the output voltage signal is 0. When the mover spindle undergoes axial displacement, the mover core moves, the inductance becomes unbalanced, the midpoint potential of one branch increases, and the midpoint potential of the other branch decreases, creating a potential difference between the midpoints of the two branches, thus outputting a voltage signal corresponding to the axial displacement of the mover.

[0061] The relationship between winding inductance and the displacement of the mover core is as follows: When the mover core 6 moves along the axis z The displacement in the positive direction from the axial equilibrium position is z At time 0, without considering core reluctance, pole edge effect, and leakage flux, the equivalent inductances of windings W1, W2, W3, W4, W5, W6, W7, and W8 are as follows:

[0062] ;

[0063] ;

[0064] in, The permeability of free space, N The total number of turns of the coil on a set of magnetic pole pairs. a and b These represent the circumferential width and axial thickness of a magnetic pole, respectively. δ The length of the air gap between the stator poles and the mover core; z 0 is the moving spindle 6 along the axis z The distance in the positive direction from the equilibrium position.

[0065] According to electromagnetic field theory and circuit theory, the equivalent impedance of the winding can be expressed as:

[0066] ;

[0067] ;

[0068] in, ω and These are the angular frequency and frequency of the sinusoidal AC voltage source of the sensor, respectively. and The first k The equivalent resistance and equivalent inductance of each winding. Under ideal conditions, neglecting sensor core losses and the skin effect of the enameled wire, the equivalent resistance of each winding is only the wire resistance (i.e., DC resistance). ),Right now .

[0069] Due to the frequency of the sensor's sinusoidal AC voltage source Between 20 and 100 kHz, at the operating frequency of the sensor's sinusoidal AC voltage source, the DC resistance of the windings is much smaller than the inductive reactance of the windings. Therefore, the impedance of each winding is approximately equal to the inductive reactance, expressed as:

[0070] ;

[0071] ;

[0072] Where j is the imaginary unit.

[0073] The sensitivity and maximum magnetic flux of the differential self-inductance axial displacement sensor are calculated based on the impedance of the winding.

[0074] The voltage of the sensor's sinusoidal AC voltage source can be expressed as:

[0075] ;

[0076] in, This represents the effective voltage value of a sinusoidal AC voltage source. t For time, φ This is the initial phase.

[0077] The total impedance, voltage, and current of the two branches are the same.

[0078] make , ;

[0079] The current phasor of each branch is then:

[0080] ;

[0081] in, This is the voltage phasor of the sinusoidal AC voltage source for the sensor.

[0082] The voltage phasors to ground at the midpoints of the two branches are as follows:

[0083] ;

[0084] ;

[0085] The output voltage phasor of this application is:

[0086] ;

[0087] The sensitivity of the output voltage to relative displacement change in this application is:

[0088] ;

[0089] The maximum magnetic flux in the magnetic circuit of this application is:

[0090] ;

[0091] in, This represents the maximum voltage of the sinusoidal AC voltage source for the sensor.

[0092] Assume the maximum magnetic flux through the sensor's magnetic poles to the winding of the external interference magnetic field is Φ EIM The signal-to-noise ratio of the differential self-inductance axial displacement sensor to external interference magnetic fields can be expressed as:

[0093] .

[0094] The comparative scheme connects W1-W8 in series and uses the junction voltage between windings W4 and W5 as the sensor's output voltage, such as... Figure 6 As shown, its equivalent phasor form circuit diagram is as follows: Figure 7 As shown.

[0095] The output voltage phasor of the comparison scheme is:

[0096] ;

[0097] The sensor sensitivity of the comparison scheme is:

[0098] ;

[0099] The maximum magnetic flux in the magnetic circuit of the comparison scheme is:

[0100] .

[0101] The signal-to-noise ratio of the comparative scheme against external interfering magnetic fields is:

[0102] .

[0103] Comparing the sensitivity, maximum magnetic flux, and signal-to-noise ratio of the two schemes, it can be seen that the sensitivity of this application is twice that of the comparative scheme; the maximum magnetic flux of this application is twice that of the comparative scheme. When the interference magnetic field remains unchanged, the proportion of interference magnetic flux to the main magnetic flux of the sensor decreases by 50%. Therefore, the signal-to-noise ratio of this application is twice that of the comparative scheme, which significantly improves the anti-interference performance of the sensor of this application.

[0104] The circuit is essentially a combination of two parallel branches: one branch consists of impedances (Z1+Z3) and (Z5+Z7), and the other branch consists of (Z6+Z8) and (Z2+Z4). The output voltage is actually the difference in potential between the midpoints of the two bridge arms. When the mover is displaced... z When the impedance of the bridge arm changes, the impedance of the bridge arm will change differentially, disrupting the balance of the bridge. According to the voltage divider formula, the imbalance of the bridge arm impedance will be converted into a linear voltage output, thus accurately mapping the mechanical displacement into a voltage signal.

[0105] In the embodiments provided by this invention, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, structures, or units, and may be electrical, mechanical, or other forms.

[0106] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0107] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0108] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A differential self-inductive axial displacement sensor, characterized in that, include: Two stator core rings and one mover are coaxially arranged. The mover consists of a mover spindle, an annular mover core mounted on it, and two mover retaining rings. The mover supports movement within a set range along its axial direction. Four sets of magnetic pole pairs are symmetrically and evenly arranged in the circumferential direction in each stator core ring, and a winding is provided on each set of magnetic pole pairs. The winding consists of two coils wound in opposite directions in series. Two windings on two symmetrical pairs of magnetic poles on one stator core ring are connected in series with two windings at the same position on another stator core ring to form a branch. The eight windings form two branches, which are connected in parallel to the same sinusoidal AC voltage source. The potential difference at the midpoint of the two branches is extracted as the output voltage signal characterizing the axial displacement of the mover. The four windings on one stator core ring are, in order, windings W1, W2, W3, and W4, with windings W1 and W3 opposite each other, and windings W2 and W4 opposite each other. The four windings on the other stator core ring are, in order, windings W5... Windings W6, W7, and W8 are connected in series, with W5 and W7 facing each other, and W6 and W8 facing each other. Windings W1, W2, W3, and W4 on one stator core ring and W5, W6, W7, and W8 on another stator core ring are connected in series, one-to-one. Windings W1, W3, W5, and W7 are connected in series to form one branch, and windings W6, W8, W2, and W4 are connected in series to form another branch. The potential difference between the junctions of windings W3 and W5, and between the junctions of windings W8 and W2, is used as the output voltage signal. When the mover core is in the axial balance position between the two stator core rings, the inductance is balanced, the midpoint potentials of the two branches are equal, and the output voltage signal is 0. When the mover spindle undergoes axial displacement, the mover core moves accordingly, the inductance becomes unbalanced, the midpoint potential of one branch increases, and the midpoint potential of the other branch decreases, creating a potential difference between the midpoints of the two branches, thereby outputting a voltage signal corresponding to the axial displacement of the mover.

2. The differential self-inductive axial displacement sensor according to claim 1, characterized in that, The two stator core rings are two identical coaxially arranged first stator core ring (1) and second stator core ring (2); A moving core shaft (6) is provided at the central axis of the first stator core ring (1) and the second stator core ring (2). The moving core shaft (6) supports movement within a certain range along its axial direction. An annular moving core (3) and a first moving retaining ring (4) and a second moving retaining ring (5) are provided on both sides of the moving core (3). The first stator core ring (1) and the second stator core ring (2) each have eight magnetic poles whose center lines pass through the center of the outer circle of the stator core ring. The magnetic poles are paired up to form four sets of magnetic pole pairs that are symmetrically distributed along the circumference. The magnetic pole pairs are opposite to each other. Each magnetic pole is wound with a coil of the same number of turns. The two coils on a set of magnetic pole pairs are wound in opposite directions and connected in series to form a winding.

3. The differential self-inductive axial displacement sensor according to claim 2, characterized in that, The first stator core ring (1), the second stator core ring (2), and the mover core (3) are made of high magnetic permeability material, while the first mover retaining ring (4) and the second mover retaining ring (5) are made of non-magnetic permeability material.

4. The differential self-inductive axial displacement sensor according to claim 2, characterized in that, When the mover core (6) is in the axial equilibrium position, the center lines of each magnetic pole of the first stator core ring (1) and the second stator core ring (2) are aligned with the end faces on both sides of the mover core (3).

5. The differential self-inductive axial displacement sensor according to claim 1, characterized in that, When the moving spindle (6) moves along the axis of the stator core ring, the relationship between the winding inductance and the axial displacement of the moving core is as follows: The equivalent inductances of windings W1, W2, W3, W4, W5, W6, W7, and W8 are respectively: ； ； in, The permeability of free space, N The total number of turns of the coil on a set of magnetic pole pairs. a and b These represent the circumferential width and axial thickness of a magnetic pole, respectively. δ The length of the air gap between the stator poles and the mover core; z 0 is the moving mandrel (6) along the axis z The distance in the positive direction from the equilibrium position.

6. The differential self-inductive axial displacement sensor according to claim 5, characterized in that, At the operating frequency of the sensor's sinusoidal AC voltage source, since the DC resistance of the winding is much smaller than the inductive reactance of the winding, the impedance of the winding can be approximated as its inductive reactance. When the mover spindle (6) moves along the axis of the stator core ring, the impedance of each winding can be expressed as: ； ； Where j is the imaginary unit, ω ω is the angular frequency of the sinusoidal AC voltage source.

7. The differential self-inductive axial displacement sensor according to claim 6, characterized in that, The sensitivity of the differential self-inductive axial displacement sensor is: ； in, This is the effective voltage value of the sinusoidal AC voltage source for the sensor.

8. The differential self-inductive axial displacement sensor according to claim 6, characterized in that, The maximum magnetic flux of the differential self-inductive axial displacement sensor is: ； in, The frequency of the sinusoidal AC voltage source for the sensor. This represents the maximum voltage of the sinusoidal AC voltage source for the sensor. The maximum magnetic flux through the sensor's magnetic poles to the winding from external interference magnetic fields is Φ EIM The signal-to-noise ratio of the differential self-inductance axial displacement sensor to external interference magnetic fields is expressed as: 。 9. The differential self-inductive axial displacement sensor according to claim 1, characterized in that, The frequency of the sinusoidal AC voltage source for the differential self-inductance axial displacement sensor is between 20 and 100 kHz.

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