Eddy current type displacement sensor for magnetic bearing

Abstract

The invention discloses an eddy current type displacement sensor for a magnetic bearing, and relates to the technical field of measurement, and the eddy current type displacement sensor comprises an excitation square wave generation unit which is used for outputting an amplified square wave signal and driving an oscillation unit; the oscillation unit comprises a probe coil and a fixed capacitor which are uniformly distributed on an outer module of the magnetic bearing, and is used for generating a magnetic field and obtaining an oscillation offset signal; the differential amplification filtering unit is used for amplifying the oscillation offset signal and filtering the amplified oscillation offset signal; the sampling unit is used for converting the filtered voltage signal into a digital signal and transmitting the digital signal to the MCU; and the communication unit is used for performing serial port communication transmission on the digital signal and executing a corresponding command according to the upper computer. According to the eddy current displacement sensor, differential processing is carried out on signals of the probe coil, the influence of interference signals is solved, and the measurement precision of the eddy current displacement sensor is improved by collecting temperature data around the probe coil and compensating the collected voltage value.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, in particular to an eddy current displacement sensor for a magnetic bearing. Background Art

[0002] The eddy current displacement sensor is a non-contact measuring device that works based on the principle of electromagnetic induction. This sensor is widely used in industrial automation, precision machinery, aerospace and other fields, especially in application scenarios that require high precision and fast response. When an alternating current is passed through the excitation coil in the eddy current displacement sensor, an alternating magnetic field is generated around it. If there is a conductor (such as a metal part) near this magnetic field, eddy currents will be generated in this conductor. These eddy currents will generate their own magnetic field, which interacts with the original magnetic field, thereby affecting the inductance of the original coil. By detecting the change in this inductance, the position change of the target object can be indirectly measured. .

[0003] Sensors based on the eddy current effect are called eddy current sensors, such as Figure 2 As shown in the figure, the magnetic field H1 generated by the coil and the magnetic field H2 generated by the eddy current of the metal conductor under test affect each other, causing the equivalent inductance of the coil to change. This change is related to the magnetic permeability and electrical conductivity of the metal conductor, the geometric shape and size of the coil, the magnitude and frequency of the current, and the distance between the coil and the metal conductor. When only the distance is an influencing factor, the position change between the coil and the metal conductor can be obtained by judging the equivalent inductance of the coil.

[0004] Magnetic bearings are a technology that uses a magnetic field to support a rotating shaft, enabling frictionless, high-speed operation. In magnetic bearing systems, precise control is key, so the position of the rotor needs to be monitored in real time to maintain its stability and accuracy. Eddy-current displacement sensors are ideal for monitoring the rotor position of magnetic bearing systems due to their non-contact nature. They can provide very high resolution and response speed, which is critical to ensuring the proper operation of magnetic bearings. Although eddy-current displacement sensors have many advantages, there are also some challenges. For example, in some cases, temperature changes may affect the measurement results. Summary of the invention

[0005] The present invention is proposed in view of the problems existing in the above-mentioned eddy current displacement sensor for magnetic bearings.

[0006] Therefore, the problem to be solved by the present invention is how to solve the problem that the magnetic bearing is affected by temperature changes during operation.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: an eddy current displacement sensor for a magnetic bearing, comprising an excitation square wave generating unit, used to output an amplified square wave signal and drive an oscillation unit; the oscillation unit comprises a probe coil and a fixed capacitor evenly distributed on an external module of the magnetic bearing, used to generate a magnetic field and obtain an oscillation offset signal; a differential amplification and filtering unit, used to amplify the oscillation offset signal and filter the amplified oscillation offset signal; a sampling unit, used to convert the filtered voltage signal into a digital signal and transmit it to an MCU; a communication unit, used to transmit the digital signal by serial communication and execute corresponding commands according to a host computer; the excitation square wave generating unit, the oscillation unit, the differential amplification and filtering unit, the sampling unit and the communication unit are all located on a control board.

[0008] As a preferred solution of the eddy current displacement sensor for magnetic bearings described in the present invention, the excitation square wave generating unit includes a square wave generating module and a square wave differential amplification module, the output end of the square wave generating module is connected to the input end of the square wave differential amplification module, and the output end of the square wave differential amplification module is connected to the input end of the oscillation unit.

[0009] As a preferred solution of the eddy current displacement sensor for magnetic bearings described in the present invention, the probe coil and the fixed capacitor form an LC oscillation circuit, and the LC oscillation circuit detects the change in voltage amplitude of the oscillation offset signal by detecting the change in the distance between the probe coil and the magnetic bearing being measured.

[0010] As a preferred solution of the eddy current displacement sensor for magnetic bearings described in the present invention, the differential amplification and filtering unit includes a signal rectification module, a differential amplification module and a filtering module, the input end of the signal rectification module is connected to the output end of the oscillation unit, the output end of the signal rectification module is connected to the input end of the differential amplification module, and the output end of the differential amplification module is connected to the input end of the filtering module.

[0011] As a preferred solution of the eddy current displacement sensor for magnetic bearings described in the present invention, the sampling unit includes a voltage signal offset module and a voltage sampling module, the input end of the voltage signal offset module is connected to the output end of the filtering module, and the voltage sampling module filters the voltage signal again and converts it into a numerical transmission.

[0012] As a preferred solution of the eddy current displacement sensor for the magnetic bearing of the present invention, the probe coil is arranged on the probe coil annular fixing device, and a temperature acquisition module is also fixedly arranged on the probe coil annular fixing device, and the output end of the temperature acquisition module is connected to the MCU for displacement compensation of the measured magnetic bearing, and the probe coil annular fixing device is respectively connected to the output end of the square wave differential amplifier module and the input end of the probe coil.

[0013] As a preferred solution of the eddy current displacement sensor for magnetic bearings described in the present invention, the MCU is used to generate the original square wave signal at the input end of the excitation square wave generating unit, receive the displacement voltage digital signal output by the sampling unit, and receive the command transmitted by the execution communication unit.

[0014] As a preferred solution of the eddy current displacement sensor for magnetic bearings of the present invention, the MCU compensates the temperature data collected by the temperature collection module and outputs it to the communication unit.

[0015] As a preferred solution of the eddy current displacement sensor for magnetic bearings of the present invention, the probe coil is made by etching copper wire on a PCB circuit board.

[0016] As a preferred solution of the eddy current displacement sensor for magnetic bearings of the present invention, it further comprises a power supply unit, which provides the required conversion voltage for the entire system.

[0017] The beneficial effects of the present invention are as follows: by performing differential processing on the signal of the probe coil, the influence of the interference signal in the measurement circuit is resolved; by collecting temperature data around the probe coil and compensating the collected voltage value, the measurement accuracy of the eddy current displacement sensor is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 Block diagram of an eddy-current displacement sensor for magnetic bearings.

[0020] Figure 2 This is the schematic diagram of the eddy current displacement sensor for magnetic bearings.

[0021] Figure 3 This is the block diagram of the excitation square wave generating unit.

[0022] Figure 4 This is the circuit diagram of the excitation square wave generating unit.

[0023] Figure 5 Schematic diagram of the oscillation unit.

[0024] Figure 6 The graph shows the test results when the probe coil is offset by 10 μm in the A+ and A- directions.

[0025] Figure 7 The graph shows the test results when the probe coil is offset by 10 μm in the A+ and A- directions.

[0026] Figure 8 The graph shows the test results when the probe coil is offset by 10 μm in the A+ and A- directions.

[0027] Fig. 9 This is the test result diagram of the probe coil running 100μm from A+ to A-.

[0028] Fig.10 This is the test result diagram of the probe coil running 100μm from A+ to A-.

[0029] Fig.11 This is a block diagram of the differential amplifier and filter unit.

[0030] Fig.12 This is the circuit diagram of the differential amplifier and filter unit.

[0031] Fig.13 A block diagram of the sampling unit.

[0032] Fig.14 This is the circuit diagram of the sampling unit.

[0033] Fig.15 A block diagram of a communication unit.

[0034] Fig.16 Schematic diagram of the two-degree-of-freedom probe coil annular fixture. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0038] Example 1

[0039] Reference Figure 1 , which is the first embodiment of the present invention, and this embodiment provides an eddy current displacement sensor for a magnetic bearing. The eddy current displacement sensor for a magnetic bearing includes an excitation square wave generating unit 100, which is used to output an amplified square wave signal and drive an oscillation unit 200; the oscillation unit 200 includes a probe coil 201 and a fixed capacitor 202 evenly distributed on the outer module of the magnetic bearing, which are used to generate a magnetic field and obtain an oscillation offset signal; a differential amplification and filtering unit 300, which is used to amplify the oscillation offset signal and filter the amplified oscillation offset signal; a sampling unit 400, which is used to convert the filtered voltage signal into a digital signal and transmit it to an MCU 600; a communication unit 500, which is used to transmit the digital signal through serial communication and execute corresponding commands according to the upper computer; the excitation square wave generating unit 100, the oscillation unit 200, the differential amplification and filtering unit 300, the sampling unit 400 and the communication unit 500 are all located on the control board.

[0040] When in use, the oscillation unit 200 is driven by the excitation square wave generating unit 100, and the signal is collected by the sampling unit after filtering by the differential amplification filtering unit 300 and transmitted to the communication unit 500, thereby completing the signal differential processing of the eddy current displacement sensor and solving the influence of interference signals in the measurement circuit.

[0041] Example 2

[0042] Reference Figures 3 to 10 , which is the second embodiment of the present invention, and this embodiment is based on the previous embodiment.

[0043] Specifically, the excitation square wave generating unit 100 includes a square wave generating module 101 and a square wave differential amplifying module 102. The output end of the square wave generating module 101 is connected to the input end of the square wave differential amplifying module 102. The output end of the square wave differential amplifying module 102 is connected to the input end of the oscillating unit 200. Figure 3 As shown, the two original square wave signals are square wave signals with the same amplitude and duty cycle and opposite polarities. The U1 circuit is a square wave amplifier circuit that differentiates and amplifies the two original square wave signals. The U2 circuit converts the square wave logic signal into a driving signal for an external device to improve the current driving capability. The excitation square wave generating unit 100 receives the original square wave generated by the MCU 600. The specific circuit diagram is shown in FIG. Figure 4 shown.

[0044] Preferably, the U1 circuit can amplify the original square wave signal with an amplification factor of [1, 5].

[0045] Preferably, the U2 circuit can increase the driving current of the LC oscillation circuit and improve the detection accuracy of the eddy current sensor.

[0046] Specifically, the probe coil 201 and the fixed capacitor 202 form an LC oscillation circuit 204. The probe coil 201 is located on the surface of the metal object to be measured. When the distance between the probe coil 201 and the metal object to be measured changes, the inductance value of the probe coil 201 will change due to the influence of eddy currents on the surface of the metal object to be measured, causing the amplitude and phase of the signal passing through the LC oscillation circuit 204 to shift.

[0047] The probe coil 201 is made of copper wire etched on a PCB circuit board, with a length and width of 13mm*13mm and a thickness of 1.6mm. The PCB circuit board is a four-layer board, with 10 coils etched on each layer, for a total of 40 turns.

[0048] Preferably, probe coils 201 may be added in multiple directions of the magnetic bearing to monitor the displacement changes in each direction of the magnetic bearing.

[0049] Tests 1 to 3 are the voltage data when using the opposite probe coils A+ and A- for testing. The magnetic bearing is controlled to shift 10μm in the direction of the probe coil A+ or A- each time, and the maximum displacement distance of the single direction is 50μm; Tests 4 to 5 are to control the magnetic bearing to run 100μm from the probe coil A- to the A+ direction. Through multiple tests and calculations, it can be concluded that the sensitivity of the sensor is 11V / mm. Compared with the RS9000XL-8mm eddy current displacement sensor of Shanghai Ruishi, its range is 2mm and its maximum sensitivity is 10V / mm. Compared with it, it has higher sensitivity and smaller range.

[0050] Example 3

[0051] Reference Figures 11 to 16 , which is the third embodiment of the present invention, and is based on the first two embodiments.

[0052] Specifically, the differential amplification and filtering unit 300 includes a signal rectification module 301, a differential amplification module 302 and a filtering module 303. The input end of the signal rectification module 301 is connected to the output end of the oscillation unit 200, the output end of the signal rectification module 301 is connected to the input end of the differential amplification module 302, and the output end of the differential amplification module 302 is connected to the input end of the filtering module 303.

[0053] like Fig.11As shown, U3 is a rectifier circuit, which first rectifies the two groups of oscillation offset signals passing through the LC oscillation module, that is, converts the sinusoidal voltage into a voltage waveform on the positive half axis or the negative half axis. U4 is a differential amplifier circuit, which differentially amplifies the two groups of oscillation offset signals after rectification. The differential voltage value can represent the displacement of the metal object being measured. U5 is a filter circuit, which filters the oscillation offset differential signal to facilitate subsequent collection. The specific circuit is as follows Fig.12 shown.

[0054] Preferably, the U4 differential amplifier circuit can amplify the oscillating offset differential signal, and the amplification factor is [1, 5].

[0055] Preferably, the U5 filter circuit can perform set frequency filtering as needed to filter out unnecessary clutter.

[0056] The sampling unit 400 includes a voltage signal offset module 401 and a voltage sampling module 402. The input end of the voltage signal offset module 401 is connected to the output end of the filtering module 303. The voltage sampling module 402 filters the voltage signal again and converts it into a numerical value for transmission.

[0057] like Fig.13 As shown, U6 is a differential offset circuit, which can subtract the differential filter signal from the reference offset voltage value, so that the midpoint voltage value of the differential filter signal changes from 0V to the set reference offset voltage value, which is convenient for subsequent acquisition. U7 is a filter circuit, which again filters the noise in the displacement voltage signal to increase the sampling accuracy. U8 is a sampling circuit, which converts the displacement voltage value into a digital value, and the digital value can be transmitted. The specific circuit diagram is shown in FIG. Fig.14 shown.

[0058] Preferably, the reference offset voltage in the U6 differential offset circuit can be set differently as needed.

[0059] Preferably, the U7 filter circuit can perform set frequency filtering as needed to filter out unnecessary clutter.

[0060] Preferably, the U8 sampling circuit can select voltage conversion chips with different resolutions and sampling speeds according to needs, and transmit the displacement voltage digital signal through a variety of communication methods.

[0061] The probe coil 201 is arranged on the probe coil annular fixing device 203, and a temperature acquisition module 203a is also fixedly arranged on the probe coil annular fixing device 203. The output end of the temperature acquisition module 203a is connected to the MCU600 for displacement compensation of the magnetic bearing under test. The probe coil annular fixing device 203 is respectively connected to the output end of the square wave differential amplifier module 102 and the input end of the probe coil 201.

[0062] Preferably, two sets of opposite side grooves 203 b are formed on the probe coil annular fixing device 203 , and the probe coil 201 can be vertically placed in the middle groove 203 b .

[0063] MCU600 is used to generate the original square wave signal of the input end of the excitation square wave generating unit 100, receive the displacement voltage digital signal output by the sampling unit 400, and receive and execute the command from the communication unit 500. MCU600 compensates the temperature data collected by the temperature acquisition module 203a and outputs it to the communication unit 500.

[0064] like Fig.15 As shown, U10 is the MCU circuit, U11 is the temperature acquisition circuit, and the temperature value near the probe coil can be obtained by collecting the voltage value of the thermistor on the ring-shaped fixing device of the probe coil. U12 is the communication module, that is, the communication between the eddy current displacement sensor for the magnetic bearing and the control end is established through the set communication method.

[0065] Preferably, the MCU circuit of U10 can generate original square waves of different frequencies, which can be modified according to actual needs.

[0066] Preferably, the MCU circuit of U10 can select a variety of communication methods to receive the digital signal in the voltage conversion chip in the sampling module.

[0067] Preferably, the MCU circuit of U10 can select a variety of communication methods to establish communication with the control end through the communication module to receive commands and send data.

[0068] When in use, the differential amplifier and filter unit 300 rectifies, amplifies, and filters the oscillation offset signal and transmits it to the sampling unit 400. The sampling unit 400 performs offset filtering on the differential filter signal and finally converts it into a digital signal and transmits it to the MCU600. The MCU600 collects the temperature data around the probe coil 201 and compensates the collected voltage value to improve the measurement accuracy of the eddy current displacement sensor.

[0069] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An eddy current displacement sensor for a magnetic bearing, characterized in that: include, An excitation square wave generating unit (100), used for outputting an amplified square wave signal and driving an oscillating unit (200); The oscillation unit (200) comprises a probe coil (201) and a fixed capacitor (202) uniformly distributed on the outer module of the magnetic bearing, and is used to generate a magnetic field and obtain an oscillation offset signal; A differential amplification and filtering unit (300), used for amplifying the oscillation offset signal and performing filtering processing on the amplified oscillation offset signal; A sampling unit (400), used for converting the filtered voltage signal into a digital signal and transmitting the digital signal to the MCU (600); A communication unit (500) is used to transmit digital signals via serial communication and execute corresponding commands according to a host computer; The excitation square wave generating unit (100), the oscillating unit (200), the differential amplifying and filtering unit (300), the sampling unit (400) and the communication unit (500) are all located on a control board.

2. The eddy current displacement sensor for magnetic bearings according to claim 1, characterized in that: The excitation square wave generating unit (100) comprises a square wave generating module (101) and a square wave differential amplifying module (102), wherein the output end of the square wave generating module (101) is connected to the input end of the square wave differential amplifying module (102), and the output end of the square wave differential amplifying module (102) is connected to the input end of the oscillating unit (200).

3. The eddy current displacement sensor for magnetic bearings according to claim 2, characterized in that: The probe coil (201) and the fixed capacitor (202) form an LC oscillation circuit (204), and the LC oscillation circuit (204) detects a change in the voltage amplitude of an oscillation offset signal by detecting a change in the distance between the probe coil (201) and the magnetic bearing to be measured.

4. The eddy current displacement sensor for a magnetic bearing according to claim 3, characterized in that: The differential amplification and filtering unit (300) comprises a signal rectification module (301), a differential amplification module (302) and a filtering module (303); the input end of the signal rectification module (301) is connected to the output end of the oscillation unit (200); the output end of the signal rectification module (301) is connected to the input end of the differential amplification module (302); and the output end of the differential amplification module (302) is connected to the input end of the filtering module (303).

5. The eddy current displacement sensor for magnetic bearings according to claim 4, characterized in that: The sampling unit (400) comprises a voltage signal offset module (401) and a voltage sampling module (402), wherein the input end of the voltage signal offset module (401) is connected to the output end of the filtering module (303), and the voltage sampling module (402) filters the voltage signal again and converts it into a numerical value for transmission.

6. The eddy current displacement sensor for a magnetic bearing according to claim 5, characterized in that: The probe coil (201) is arranged on a probe coil annular fixing device (203), a temperature acquisition module (203a) is also fixedly arranged on the probe coil annular fixing device (203), an output end of the temperature acquisition module (203a) is connected to the MCU (600) for displacement compensation of the magnetic bearing under test, and the probe coil annular fixing device (203) is respectively connected to the output end of the square wave differential amplification module (102) and the input end of the probe coil (201).

7. The eddy current displacement sensor for a magnetic bearing according to claim 6, characterized in that: The MCU (600) is used to generate an original square wave signal at the input end of the excitation square wave generating unit (100), receive a displacement voltage digital signal output by the sampling unit (400), and receive and execute a command transmitted by the communication unit (500).

8. The eddy current displacement sensor for a magnetic bearing according to claim 7, characterized in that: The MCU (600) compensates the temperature data collected by the temperature collection module (203a) and outputs the compensated temperature data to the communication unit (500).

9. The eddy current displacement sensor for a magnetic bearing according to claim 8, characterized in that: The probe coil (201) is made by etching copper wire on a PCB circuit board.

10. The eddy current displacement sensor for a magnetic bearing according to claim 9, characterized in that: The system also comprises a power supply unit (700), wherein the power supply unit (700) provides the required conversion voltage for the entire system.

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