CN1210507C - Method for measuring axial displacement of electromagnet bearing rotor - Google Patents

Abstract

The invention relates to a method for measuring the axial displacement of an electromagnetic bearing rotor, which is characterized in that a ring is fixed outside the rotor, the ring is composed of at least two materials arranged in sections, and the axial displacement sensor is placed on the The radial direction of the rotor is aligned, and the sensitive element of the axial displacement sensor is aligned with the junction of the two materials, and the interface is used as a measurement reference to measure the axial displacement of the junction with the rotor. In the present invention, the axially placed axial displacement sensor is placed in the radial direction of the rotor, and the method of measuring the axial displacement of the electromagnetic bearing rotor with the radially placed sensor is realized through the displacement of materials at the junction of different materials, which not only simplifies The system structure can be simplified, and the analysis of the system can be simplified, which brings considerable convenience to the detection and control of the electromagnetic bearing rotor. The present invention is particularly suitable for the industrial fields that need to use electromagnetic bearings for high-speed rotation, non-contact, non-lubricating, and friction-free support, such as high-speed machining, turbomachinery and centrifuges, aerospace, vacuum and ultra-clean room technology fields.

Description

A Method for Measuring Axial Displacement of Electromagnetic Bearing Rotor

technical field

The invention relates to a measurement method, in particular to a method for measuring the axial displacement of an electromagnetic bearing rotor.

Background technique

Electromagnetic bearings are also called magnetic suspension bearings. The principle is to use magnetic force to maintain a certain gap between the rotor and the stator, and to suspend the rotor for high-speed rotation. It is a new type of bearing without contact, lubrication, and friction. It is especially suitable for working environments where high-speed rotation and lubricating grease cannot be used, and has broad application prospects in many fields such as high-speed machining, turbomachinery, aerospace, and vacuum technology.

Because passive passive magnetic bearings using permanent magnets generally cannot keep the position of suspended objects stable in all degrees of freedom, and the damping is relatively low; passive magnetic bearings using superconductors are still in the experimental stage, and it is difficult to implement, and High cost. Therefore, active active magnetic bearings (AMBs) are the most widely used in the current industry. The active active electromagnetic bearing utilizes the suction force between the electromagnet and the ferromagnetic material rotor to realize the suspension support.

Due to the active active electromagnetic bearing under the action of constant excitation current, when some external disturbance is received, the center of the rotor will deviate from the original balance position, the gap between the rotor and the electromagnet that is biased to one side will be reduced, and the gap between the rotor and the electromagnet that is deviated will be increased. Large, the further deviation of the rotor will be exacerbated by the magnetic force of this negative stiffness. This is an unstable force-bearing structure similar to an inverted pendulum. It cannot be suspended stably under the action of a constant excitation current. Therefore, the electromagnetic bearing must be adjusted in time by the position deviation signal measured by the rotor position sensor under the action of the controller. The electric current on the iron controls the rotor back to the position of the geometric center, so that it can work normally. Thus, the detection of the axial displacement and radial displacement of the rotor becomes the basis for controlling the entire electromagnetic bearing system.

Traditional electromagnetic bearings (as shown in FIG. 1 ) often use eddy current displacement sensors 11 and 12 to measure their radial displacement and axial displacement. Generally speaking, the axial displacement sensor 11 is placed in the axial direction, and the radial displacement sensor 12 is placed in the radial direction. This will lead to a relatively complicated structure, which will bring inconvenience to the detection and control of the rotor 1 .

Contents of the invention

In view of the above problems, the object of the present invention is to provide a method for measuring the axial displacement of the electromagnetic bearing rotor.

In order to achieve the above object, the present invention adopts the following technical solutions: a method for measuring the axial displacement of an electromagnetic bearing rotor, which is characterized in that a ring is fixed outside the rotor, and the ring is composed of at least two materials arranged in sections , place the axial displacement sensor in the radial direction of the rotor, and align the sensitive element of the axial displacement sensor at the junction of the two materials, and use this interface as a measurement reference to measure the interface With the axial displacement of the rotor.

The axial displacement sensors are arranged in two groups in the axial direction, and two in each group are radially symmetrically arranged. Through processing the output signals of the four sensors, a signal having a linear relationship with the axial displacement of the rotor is finally obtained.

The present invention has the following advantages due to the adoption of the above method: 1. The present invention realizes the use of radially placed transducers through the displacement of materials at the junction of different materials due to the fact that the axial displacement sensor placed generally in the axial direction is placed in the radial direction of the rotor. The method of measuring the axial displacement of the electromagnetic bearing rotor with a unique sensor can not only simplify the system structure, but also simplify the analysis of the system, which brings considerable convenience to the detection and control of the electromagnetic bearing rotor. 2. Since the present invention adopts two pairs of four axial displacement sensors and processes the outputs of these four sensors, it can not only eliminate the influence of radial displacement on the measurement results, but also increase the slope of the output signal. Improve sensitivity. The method of the present invention has simple implementation steps and accurate test results, and is especially suitable for industrial fields that require the application of electromagnetic bearings for high-speed rotation, non-contact, non-lubricating, and friction-free support, such as high-speed machining, turbomachinery and centrifuges, aerospace, vacuum and ultra-clean room technology.

Description of drawings

Figure 1 is a schematic diagram of the sensor setup for traditional electromagnetic bearing rotor measurement

Figure 2 is a schematic diagram of the arrangement of the axial sensor during the measurement of the electromagnetic bearing device of the present invention

Detailed ways

As shown in Figure 2, the method of the present invention is to fix a collar 2 on the outside of the rotor 1, the collar 2 is based on a material 21, and two sections of another material 22 are arranged at intervals on it, and the four shafts The axial displacement sensors 31 , 32 , 33 , 34 are placed in the radial direction of the rotor 1 , and the sensitive elements of the four axial displacement sensors 31 , 32 , 33 , 34 are aligned to the junctions of the two materials 21 , 22 respectively. In this way, the magnetic circuit of the axial displacement sensor 3 is mainly composed of the magnetic circuit of the sensitive element of the sensor, the rotor collar 2 and the air gap. The output of the sensor 3 is affected by factors such as the electrical conductivity and magnetic permeability of the collar 2 material, the excitation frequency of the sensor, and the distance between the sensor and the collar 2. Under the condition of constant excitation frequency and distance, the axial displacement of the rotor 1 affects the magnetic field. The distribution of the road material is equivalent to changing the electrical conductivity and magnetic permeability of the material, thereby affecting the output of the axial displacement sensor 3 .

In the above embodiment, the composition of the two materials of the collar 2 can take various forms, such as welding, inlaying, etc., and the composite materials can also be three or more, but generally two materials can achieve the purpose of the invention.

In the above embodiment, due to the four axial displacement sensors 31, 32, 33, 34 arranged oppositely, the sensors 31, 32 are located on the same vertical plane, and the sensors 33, 34 are located on the same vertical plane; the sensors 31, 33 are located on the same vertical plane. Horizontal plane, the sensors 32, 34 are located on the same horizontal plane. When the rotor deviates from the equilibrium position, the output voltages of the sensors 31, 32, 33, and 34 are: (assuming that the axial and radial displacements of the sensors are z and x respectively)

U ₃₁ =U ₀ +DU(z,x)

U ₃₂ =U ₀ +DU(z,-x)

U ₃₃ =U ₀ +DU(-z,x)

U ₃₄ =U ₀ +DU(-z,-x)

Where U ₀ is the output voltage when the rotor is in the equilibrium position, DU(z, x) is the variation of the output voltage when the rotor deviates from the equilibrium position (it is a function of axial displacement z and radial displacement x)

Within the working range of the sensor, DU(z, x) has a linear relationship with z and x, so two adders are used to add the output signals of sensors 31, 32 and sensors 33, 34 together, and then the two added The sum signal is input to the subtractor, and the final output can be obtained as:

U＝(U ₁ +U ₂ )-(U ₃ +U ₄ )

＝(2U ₀ +K(z))-(2U ₀ +K(-z))

=2K(z)=nz

In this way, an output signal proportional to the rotor axial displacement z is obtained, and n is the characteristic slope. That is to say, the present invention obtains a signal that is linearly related to the axial displacement of the rotor 1 by correspondingly processing the output signals of the sensors 31, 32, 33, and 34. As for how to control the rotor back to the geometric center according to the signal, It belongs to the prior art and will not be repeated here.

Claims (2)

1. A method for measuring the axial displacement of an electromagnetic bearing rotor, characterized in that: a ring is fixed outside the rotor, the ring is composed of at least two materials arranged in sections, and the axial displacement sensor is placed on the The radial direction of the rotor, and the sensitive element of the axial displacement sensor is aligned with the junction of the two materials, and the interface is used as a measurement reference to measure the axial displacement of the interface with the rotor. 2. A method for measuring the axial displacement of an electromagnetic bearing rotor according to claim 1, characterized in that: the axial displacement sensors are two groups arranged in the axial direction, and each group has two radially symmetrical arrangements. The processing of the output signals of the four sensors finally obtains a signal that is linearly related to the axial displacement of the rotor.

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