A method for measuring the air gap between the stator and rotor of a magnetic bearing based on flexible circuit coils.

Abstract

This invention relates to the field of motor state sensing and monitoring technology, and discloses a method for measuring the air gap between the stator and rotor of a magnetic bearing based on flexible circuit coils. Taking the rotor as the origin, mutually perpendicular X-axis and Y-axis are defined. Several flexible circuit coils are symmetrically arranged on the inner surface of the stator core around the X-axis or Y-axis, and the magnetic flux formed by the magnetic bearing windings passing through a single flexible circuit coil is made close to zero. Two flexible circuit coils symmetrically arranged around the X-axis or Y-axis are connected in series to form an inductor. The rotor displacement is detected by detecting changes in the inductance value of this inductor. This invention, a method for measuring the air gap between the stator and rotor of a magnetic bearing based on flexible circuit coils, effectively reduces the cost and size of the magnetic bearing system. Furthermore, since the sensor and actuator are located in the same position, the phase deviation between bearing rotor displacement detection and execution can be reduced, further improving rotor control stability.

Description

Technical Field

[0001] This invention relates to the field of magnetic bearing condition sensing and monitoring technology, specifically to a method for measuring the air gap between the stator and rotor of a magnetic bearing based on a flexible circuit coil. Background Technology

[0002] Magnetic bearings are a new type of high-performance bearing that uses magnetic force to suspend the rotor, achieving frictionless support between the rotor and stator without mechanical contact. As a novel high-performance bearing, magnetic bearings offer significant advantages such as no lubrication required, low power consumption, high speed, high precision, high temperature resistance, long lifespan, simple use and maintenance, and no environmental pollution. A key characteristic of magnetic bearings is that their active feedback requires a highly sensitive and high-resolution displacement sensor to detect the rotor position in real time. Currently, eddy current displacement sensors are commonly used in magnetic bearing systems, but they are complex in structure, expensive, and their installation position is misaligned with the actuator position. This means the rotor position change measured by the sensor cannot accurately reflect the rotor position change at the actuator, reducing the stability of the system control. Other types of displacement sensors, such as inductive, capacitive, and optical sensors, all face the fundamental problem of misaligned sensor and actuator positions, which limits the further widespread application of magnetic bearings.

[0003] To address this issue, some scholars have proposed a method for measuring the air gap between the stator and rotor of a magnetic bearing based on a probe coil. This method involves winding a probe coil on the stator core teeth of the magnetic bearing and measuring the change in inductance of the probe coil caused by the change in rotor position directly or indirectly to achieve in-situ displacement measurement.

[0004] However, the commonly used method for winding the detection coil is to use a strong or weak coupling method between the detection coil and the magnetic bearing. That is, the magnetic flux circuit formed by the detection coil and the magnetic flux circuit formed by the magnetic bearing share the same iron core. In this scheme, the inductance value of the detection coil is affected not only by the change of rotor position, but also by the change of magnetic reluctance of the magnetic bearing iron core, resulting in a strong nonlinear or even non-monotonic output response, which is not conducive to high-precision measurement of rotor displacement. In addition, due to the non-ideal factors of the winding coil construction, this type of detection coil is greatly affected by end leakage magnetic flux and is greatly affected by the switching subharmonic interference of the magnetic bearing winding. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the aforementioned technologies by providing a method for measuring the air gap between the stator and rotor of a magnetic bearing based on a flexible circuit coil. This method effectively reduces the cost and size of the magnetic bearing system. Furthermore, since the sensor and actuator are located in the same position, it can reduce the phase deviation between bearing rotor displacement detection and execution, thereby further improving rotor control stability.

[0006] To achieve the above objectives, the present invention provides a method for measuring the air gap between a stator and rotor of a magnetic bearing based on flexible circuit coils. The method defines mutually perpendicular X-axis and Y-axis with the rotor as the origin. Several flexible circuit coils are symmetrically arranged on the inner surface of the stator core with the X-axis or Y-axis as the center. The magnetic flux formed by the magnetic bearing windings passing through a single flexible circuit coil is made close to zero. Two flexible circuit coils symmetrically arranged with the X-axis or Y-axis as the center are connected in series to form an inductor. The rotor displacement is detected by detecting changes in the inductance value of this inductor.

[0007] Preferably, the flexible circuit coil is wound in a figure-eight pattern in reverse.

[0008] Preferably, when the flexible circuit coil is arranged on the inner surface of the stator core, it forms a radial magnetic circuit of the core.

[0009] Preferably, two inductors symmetrical about the X-axis or Y-axis are connected in series to form a variable air gap differential inductive displacement sensor along the X-axis or Y-axis direction, which is used to detect the displacement of the rotor in that direction.

[0010] Preferably, the change in inductance value is measured using a full-bridge inductance detection circuit.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] 1. Effectively reduces the cost and size of the magnetic bearing system, and the sensor and actuator are in the same position, which can reduce the phase deviation between bearing rotor displacement detection and execution, and further improve rotor control stability;

[0013] 2. The coil is not wound on the stator teeth and does not occupy the winding space of the magnetic bearing winding in the stator slot. During operation, a closed magnetic circuit is formed locally in the stator and rotor cores. The length of the core magnetic circuit is greatly reduced, and the influence of the core magnetic reluctance on the air gap measurement can be ignored, thus obtaining an excellent linearity response curve.

[0014] 3. There is no limit to the number of teeth in the magnetic bearing, and there are no requirements for the number of pole pairs in the magnetic bearing. Displacement measurement in a single direction can be achieved on only a single stator tooth of the magnetic bearing.

[0015] 4. The flexible circuit coil is wound in a figure-eight pattern in reverse, which can cancel the local main magnetic flux of the magnetic bearing stator core. Therefore, the magnetic circuit coupling with the core is very low, and the magnetic flux formed by the magnetic bearing winding passing through a single flexible circuit coil approaches zero. Attached Figure Description

[0016] Figure 1 This is an embodiment of a method for arranging flexible circuit coils in a magnetic bearing stator and rotor air gap measurement.

[0017] Figure 2Another arrangement method for flexible circuit coils

[0018] Figure 3 A schematic diagram illustrating the principle of a full-bridge inductance detection circuit in the X-axis direction for detecting changes in inductance value;

[0019] Figure 4 A schematic diagram illustrating the principle of a full-bridge inductance detection circuit in the Y-axis direction for detecting changes in inductance value;

[0020] Figure 5 This is a schematic diagram of a flexible circuit coil wound in a figure-eight reverse configuration. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] This invention discloses a method for measuring the air gap between a stator and rotor of a magnetic bearing based on flexible circuit coils. Taking the rotor as the origin, mutually perpendicular X-axis and Y-axis are defined. Several flexible circuit coils are symmetrically arranged on the inner surface of the stator core with the X-axis or Y-axis as the center. The magnetic flux formed by the magnetic bearing winding passing through a single flexible circuit coil is made close to zero. Two flexible circuit coils symmetrical with the X-axis or Y-axis as the center are connected in series to form an inductor. The displacement of the rotor is detected by detecting the change in the inductance value of this inductor.

[0023] Two inductors symmetrical about the X-axis or Y-axis can be connected in series to form a variable air gap differential inductive displacement sensor along the X-axis or Y-axis direction, which is used to detect the displacement of the rotor in that direction.

[0024] In this method, when the flexible circuit coil is arranged on the inner surface of the stator core, it forms a radial magnetic circuit of the core.

[0025] like Figure 1 As shown, flexible circuit coils C1, C2, C3, C4, C5, C6, C7, and C8 are arranged sequentially on the inner surface of the stator core. Alternatively, when the inner surface area of ​​the stator core is large, as shown... Figure 2 As shown in the diagram, in use, flexible circuit coils C1 and C6 are connected in series to form an inductor, and flexible circuit coils C5 and C2 are connected in series to form another inductor, forming a structure as shown in the diagram. Figure 3 The full-bridge inductor detection circuit shown constitutes a variable air gap differential inductor displacement sensor along the X-axis, which realizes displacement detection in the X-axis direction by detecting changes in inductance value.

[0026] Similarly, flexible circuit coils C3 and C8 are connected in series to form an inductor, and flexible circuit coils C4 and C7 are connected in series to form an inductor, forming an inductor as shown in the figure. Figure 4The full-bridge inductance detection circuit shown constitutes a variable air gap differential inductance displacement sensor along the Y-axis, which realizes displacement detection in the Y-axis direction by detecting changes in inductance value.

[0027] In this embodiment, a full-bridge inductance detection circuit is used to measure changes in inductance. Taking X-axis displacement detection as an example, as follows... Figure 3 As shown, a high-frequency AC current is first supplied to the bridge circuit. When the rotor is at the center of the stator, the inductance values ​​of the four inductors C1, C2, C5, and C6 are equal, and the bridge output voltage is almost zero. When the rotor moves in the positive X-axis direction, the inductances of C1 and C2 will increase, while the inductances of C5 and C6 will decrease. The magnitude of the output voltage thereafter is positively correlated with the magnitude of the X-axis displacement. By detecting the magnitude and direction of this voltage amplitude, the X-axis displacement can be obtained. Similarly, the Y-axis displacement detection is performed in a similar manner. Figure 4 This is a full-bridge inductor detection circuit in the Y-axis direction. Furthermore, the voltage amplitude detection method employs amplitude acquisition techniques including envelope detection, peak detection, and quadrature lock-in amplifier demodulation.

[0028] Finally, this method can also be applied to the field of rotor eccentricity monitoring in large motors, by arranging flexible circuit coils on the inner surface of the motor stator core, combined with... Figure 5 As shown, the flexible circuit coil is wound in a figure-eight pattern in reverse, so that the total magnetic flux formed by the main magnetic field of the motor passing through the flexible circuit coil approaches zero.

[0029] This invention presents a method for measuring the air gap between the stator and rotor of a magnetic bearing based on a flexible circuit coil. This method effectively reduces the cost and size of the magnetic bearing system. Furthermore, since the sensor and actuator are located in the same position, the phase deviation between rotor displacement detection and execution can be reduced, further improving rotor control stability. In addition, the coil is not wound on the stator teeth, thus not occupying the winding space of the magnetic bearing winding in the stator slot. During operation, a closed magnetic circuit is formed locally in the stator and rotor core, significantly reducing the length of the core magnetic circuit. This allows the influence of the core magnetic reluctance on the air gap measurement to be ignored, resulting in an excellent linearity response curve. Moreover, there are no restrictions on the number of teeth or pole pairs of the magnetic bearing; displacement measurement in a single direction can be achieved on only a single stator tooth of the magnetic bearing. Finally, the flexible circuit coil can be wound in a figure-eight pattern in reverse, which can cancel the local main magnetic flux of the magnetic bearing stator core. Therefore, the coupling degree with the magnetic circuit of the core is very low, and the magnetic flux formed by the magnetic bearing winding passing through a single flexible circuit coil approaches zero.

Claims

1. A method for measuring the air gap between the stator and rotor of a magnetic bearing based on a flexible circuit coil, characterized in that: With the rotor as the origin, define mutually perpendicular X-axis and Y-axis, arrange several flexible circuit coils symmetrically on the inner surface of the stator core with the X-axis or Y-axis as the center, and make the magnetic flux formed by the magnetic bearing winding passing through a single flexible circuit coil approach zero. Connect two flexible circuit coils symmetrical with the X-axis or Y-axis as the center in series to form an inductor, and realize the rotor displacement detection by detecting the change of the inductance value of the inductor. The flexible circuit coil is wound in a figure-eight pattern in reverse. When the flexible circuit coil is arranged on the inner surface of the stator core, it forms a radial magnetic circuit of the core. Two inductors symmetrical about the X-axis or Y-axis are connected in series to form a variable air gap differential inductive displacement sensor along the X-axis or Y-axis direction, which is used to detect the displacement of the rotor in that direction.

2. The method for measuring the air gap between the stator and rotor of a magnetic bearing based on a flexible circuit coil according to claim 1, characterized in that: The change in inductance value is measured using a full-bridge inductance detection circuit.

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