Radial displacement self-detecting device of pure electromagnetic bearing with double-coil structure

Abstract

The application discloses a kind of pure electromagnetic bearing radial displacement self-detection devices of double-coil structure, comprising: digital control system, double-coil magnetic bearing assembly and ripple detection conditioning circuit module;The digital control system is connected with the double-coil magnetic bearing assembly;The double-coil magnetic bearing assembly and the ripple detection conditioning circuit module are connected.This application utilizes the advantage of double-coil structure to solve the nonlinear problem of rotor displacement and PWM switching ripple amplitude, accurately extracts current ripple signal through hardware circuit, and realizes hardware demodulation and signal conditioning, realizes the self-sensing technology of rotor displacement, saves the cost of magnetic bearing control system hardware, is conducive to reducing system volume, realizes more simplified control system.

Description

Technical Field

[0001] The present application belongs to the field of bearing radial detection, and specifically relates to a pure electromagnetic bearing radial displacement self-detection device with a dual-coil structure. Background Art

[0002] Magnetic bearings offer unparalleled advantages over mechanical bearings in terms of improving mechanical efficiency and reducing noise pollution. Compared to traditional mechanical bearings, magnetic bearings require no lubrication, have a wider range of applications, and offer adjustable bearing stiffness and damping, making them more suitable for high-speed environments. However, magnetic bearing systems are unstable in open-loop operation and require constant rotor position information to the controller for stable control. The installation of traditional discrete physical sensors increases the size of the entire electromechanical equipment, affecting the dynamic characteristics of the rotor. They are also expensive and susceptible to uncertainties such as high temperature, aging, short circuits, and open circuits, reducing system reliability. Displacement self-sensing technology can significantly improve system reliability.

[0003] Displacement self-sensing technology uses the current or voltage of the magnetic bearing coils to calculate rotor position information through software algorithms. Active pure electromagnetic bearing displacement self-sensing can be categorized into state estimation, frequency modulation, and amplitude modulation. The state estimation method is sensitive to parameter changes and suffers from poor robustness. The displacement feedback signal estimated by the frequency modulation method suffers from significant phase lag, and the bandwidth of the self-sensing system is low. When high-frequency components are present in the input or feedback signals, the narrow pulses generated by the hysteresis power amplifier can interfere with the drive circuit, easily causing output current distortion and severely impacting the amplifier's efficiency and reliability. The amplitude modulation method can be implemented using high-frequency signal injection or switching ripple detection. However, the choice of high-frequency excitation signal frequency is limited by the amplifier's bandwidth, resulting in poor dynamic characteristics of the self-sensing system. The switching ripple demodulation method introduces nonlinearity due to the PWM duty cycle of the control current, which can easily distort the rotor displacement and cause control system instability. Typically, the PWM drive voltage and current are sampled separately, followed by hardware or software division to eliminate the effects of nonlinearity. However, this system architecture is complex and the hardware cost is high. Summary of the Invention

[0004] This application aims to address the shortcomings of existing technologies by proposing a dual-coil structured, purely electromagnetic bearing radial displacement self-detection device. This device leverages the constant PWM duty cycle of the bias coil in the dual-coil structure to effectively address the nonlinearity of position detection. A bandpass filter is used to precisely extract the switching ripple signal, which is then processed through hardware conditioning and software algorithms to generate a reliable displacement signal for closed-loop control of rotor suspension, providing a feasible solution for self-sensing.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] A pure electromagnetic bearing radial displacement self-detection device with a dual-coil structure, comprising: a digital control system, a dual-coil magnetic bearing assembly, and a ripple detection and conditioning circuit module;

[0007] The digital control system is connected to the dual-coil magnetic bearing assembly;

[0008] The dual-coil magnetic bearing assembly is connected to the ripple detection and conditioning circuit module.

[0009] Preferably, the digital control system includes: a position controller, a current controller, a first switching power amplifier, a second switching power amplifier and a first low-pass filter;

[0010] The position controller is connected to the current controller;

[0011] The current controller is further connected to the first switching power amplifier and the second switching power amplifier respectively, and is used to output a bias PWM signal to the first switching power amplifier, and is also used to output a control PWM signal to the second switching power amplifier;

[0012] The first switching power amplifier and the second switching power amplifier are connected to the dual-coil magnetic bearing assembly, the first switching power amplifier is used to output a first current signal to the dual-coil magnetic bearing assembly based on the bias PWM signal, and the second switching power amplifier is used to output a second current signal to the dual-coil magnetic bearing assembly based on the control PWM signal;

[0013] The second switching power amplifier is further connected to the first low-pass filter;

[0014] The first low-pass filter is also connected to the position controller.

[0015] Preferably, the dual-coil magnetic bearing assembly comprises: a plurality of control coils, a plurality of bias coils and a rotor;

[0016] The control coil is used to generate a differential changing magnetic field to control the suspension of the rotor;

[0017] The bias coil is used to convert the current ripple in the first current signal into a differential signal form to obtain a differential ripple signal.

[0018] Preferably, the ripple detection and conditioning circuit module includes: a bandpass filter circuit, a precision full-wave detection circuit, a differential amplifier and conditioning circuit and a second low-pass filter;

[0019] The bandpass filtering device is used to receive the differential ripple signal and extract the fundamental frequency component of the ripple signal in the differential ripple signal;

[0020] The precise full-wave detection device is used to receive the fundamental frequency component and filter out the high-frequency interference signal in the fundamental frequency component to obtain a detection output signal;

[0021] The differential amplification and conditioning circuit is used to receive the detection output signal and condition the detection output signal into an ADC input signal;

[0022] The second low-pass filter is used to receive the ADC input signal and filter out high-frequency interference in the ADC input signal to obtain a displacement signal.

[0023] Preferably, the bandpass filter circuit is composed of a two-stage infinite gain multi-path feedback bandpass filter, the bandpass center frequency f0 is designed at the first-order ripple frequency point of the bias current, the fundamental frequency component I1 is extracted, and the differential ripple signal is modulated by the rotor displacement signal s(t), and the formula is as follows:

[0024]

[0025] Among them, U s is the bus voltage, α is the bias PWM signal duty cycle, ω s is the switching angular frequency of the PWM signal, μ0 is the vacuum permeability, N is the number of coil turns, A is the magnetic pole area, is the initial phase of the ripple signal.

[0026] Preferably, the precise full-wave detection circuit is composed of a JFET bipolar operational amplifier and a Schottky diode, and can perform absolute value operation on the fundamental frequency component.

[0027] Preferably, the differential amplification and conditioning circuit includes: a gain-adjustable operational amplifier, a gain adjustment resistor, a first operational amplifier, and a second operational amplifier;

[0028] The gain adjustment terminal of the gain adjustable operational amplifier is connected to the gain adjustment resistor.

[0029] The reference pin of the gain-adjustable operational amplifier is connected to a low-impedance point in the circuit through the first operational amplifier;

[0030] The second operational amplifier is used to condition the detection output signal into an ADC input signal, and the formula is as follows:

[0031]

[0032] Among them, R A is the feedback resistor, R i 、R b is the input resistance, k A is the gain constant of the gain-adjustable operational amplifier, Rw is the nominal resistance of the sliding rheostat, R w23 is the resistance between pins 2 and 3 of the sliding rheostat, V ref+ is the positive bias reference voltage, V ref- is the negative bias reference voltage.

[0033] Preferably, the second low-pass filter adopts a voltage-controlled voltage source type second-order low-pass filter, which can filter out high-frequency interference in the ADC input signal to obtain the displacement signal. The final output U of the ripple detection conditioning circuit module is ot The relationship with the displacement signal is:

[0034]

[0035] Among them, U s is the bus voltage, α is the bias PWM signal duty cycle, ω s is the switching angular frequency of the PWM signal, μ0 is the vacuum permeability, N is the number of coil turns, A is the magnetic pole area, is the initial phase of the ripple signal, R A is the feedback resistor, R i 、R b is the input resistance, k A is the gain constant of the gain-adjustable operational amplifier, R w is the nominal resistance of the sliding rheostat, R w23 is the resistance between pins 2 and 3 of the sliding rheostat, V ref+ is the positive bias reference voltage, V ref- is the negative bias reference voltage, K s is the output gain of the current transformer module, K pf is the final output gain of the two-stage bandpass filter.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] This application utilizes the advantages of the dual-coil structure to solve the nonlinear problem of rotor displacement and PWM switch ripple amplitude, accurately extracts the current ripple signal through the hardware circuit, and realizes hardware demodulation and signal conditioning, realizing the self-sensing technology of rotor displacement, saving the hardware cost of the magnetic bearing control system, which is conducive to reducing the system size and realizing a more streamlined control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solution of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0039] Figure 1 This is a structural block diagram of a pure electromagnetic bearing radial displacement self-detection device with a dual-coil structure according to an embodiment of the present application;

[0040] Figure 2 This is a schematic diagram of the wiring method of the dual-coil magnetic bearing assembly according to an embodiment of the present application;

[0041] Figure 3 A circuit diagram of a bandpass filter circuit according to an embodiment of the present application;

[0042] Figure 4 A circuit diagram of a precision full-wave detection circuit according to an embodiment of the present application;

[0043] Figure 5 A circuit diagram of a differential amplifier and conditioning circuit according to an embodiment of the present application;

[0044] Figure 6 A circuit diagram of a low-pass filter according to an embodiment of the present application;

[0045] Figure 7 This is a schematic diagram of the signal processing flow of an embodiment of the present application. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0047] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0048] In this embodiment, if Figure 1 As shown, a pure electromagnetic bearing radial displacement self-detection device with a dual-coil structure includes: a digital control system, a dual-coil magnetic bearing assembly and a ripple detection and conditioning circuit module.

[0049] The digital control system is connected to the dual-coil magnetic bearing assembly. The digital control system includes: a position controller, a current controller, a first switching power amplifier, a second switching power amplifier, and a first low-pass filter; the position controller is connected to the current controller; the current controller is also connected to the first switching power amplifier and the second switching power amplifier, respectively. The current controller is used to output a bias PWM signal to the first switching power amplifier, and the current controller is also used to output a control PWM signal to the second switching power amplifier; the first switching power amplifier and the second switching power amplifier are connected to the dual-coil magnetic bearing assembly, the first switching power amplifier is used to output a first current signal to the dual-coil magnetic bearing assembly based on the bias PWM signal, and the second switching power amplifier is used to output a second current signal to the dual-coil magnetic bearing assembly based on the control PWM signal; the second switching power amplifier is also connected to the first low-pass filter. In this embodiment, the second switching power amplifier can optionally be connected to the first low-pass filter via a current sampling circuit; the first low-pass filter is also connected to the position controller.

[0050] The dual-coil magnetic bearing assembly is connected to the ripple detection and conditioning circuit module. The dual-coil magnetic bearing assembly includes several control coils, several bias coils, and a rotor. The control coils are used to generate a differentially varying magnetic field to control rotor levitation. The bias coils are used to convert the current ripple in the first current signal into a differential signal form, generating a differential ripple signal. In this embodiment, the dual-coil magnetic bearing assembly can optionally be connected to the ripple detection and conditioning circuit module via a current sampling circuit.

[0051] In this embodiment, if Figure 2 As shown, with the geometric center of the octapole radial magnetic bearing assembly as the origin and the middle of any two magnetic poles as the coordinate axis, an OXY rectangular coordinate system is constructed. The bias coils on the two magnetic poles corresponding to the positive X direction are connected in series in opposite directions, and the same is true for the bias coils in the negative X direction. The magnetic properties of the relative magnetic poles in the positive and negative directions are the same, and the current ripples in the two sets of bias coils in the positive and negative directions of X form a differential signal. In addition, the corresponding control coils in the positive X direction are connected in series in opposite directions. The control magnetic field in the positive X direction has the same magnetic pole properties as the bias magnetic field, while the control magnetic field in the negative X direction has opposite magnetic pole properties to the bias magnetic field. The two sets of control coils in the positive and negative X directions are connected in series to generate a differentially changing magnetic field to control the rotor suspension.

[0052] The ripple detection and conditioning circuit module includes: a bandpass filter circuit, a precision full-wave detection circuit, a differential amplifier and conditioning circuit and a second low-pass filter; the bandpass filter device is used to receive the differential ripple signal and extract the fundamental frequency component of the ripple signal in the differential ripple signal; the precision full-wave detection device is used to receive the fundamental frequency component and filter out the high-frequency interference signal in the fundamental frequency component to obtain the detection output signal; the differential amplifier and conditioning circuit is used to receive the detection output signal and condition the detection output signal into an ADC input signal; the second low-pass filter is used to receive the ADC input signal and filter out the high-frequency interference in the ADC input signal to obtain the displacement signal.

[0053] In this embodiment, if Figure 3 As shown in the figure, the bandpass filter circuit consists of a two-stage infinite gain multi-feedback bandpass filter. The bandpass center frequency f0 is designed at the first-order ripple frequency of the bias current. The fundamental frequency component I1 is extracted, and the differential ripple signal is modulated by the rotor displacement signal s(t). The formula is as follows:

[0054]

[0055] Among them, U s is the bus voltage, α is the bias PWM signal duty cycle, ω s is the switching angular frequency of the PWM signal, μ0 is the vacuum permeability, N is the number of coil turns, A is the magnetic pole area, Is the initial phase of the ripple signal. The gain K of the single-stage bandpass filter p , center frequency f0 and quality factor Q are determined by the following formula:

[0056]

[0057] Where R F1 、R F2 、R F3 They are the first, second and third bandpass filter resistors, C F1 、C F2 The first and second bandpass filter capacitors are designed to be the center frequency f0 of the bandpass filter at the first-order ripple frequency of the bias current, and the fundamental frequency component of the current ripple signal is extracted.

[0058] The precision full-wave detection circuit is composed of a JFET bipolar operational amplifier and a Schottky diode, which can perform absolute value operation on the fundamental frequency component. Figure 4 As shown in the figure, the ripple signal is connected to the inverting input terminal of N1 and the non-inverting input terminal of N2 through the input resistors R1 and R3, and the absolute value operation of the current ripple fundamental frequency component is realized. The single sideband amplitude modulation signal extracted from the cathode output of VD2 is connected to the inverting input terminal of N1 and the non-inverting input terminal of N2 through the input resistors R1 and R3. f 、C fAfter forming a low-pass filter, the position information of the rotor is obtained, and the two displacement signals on the opposite sides are differentially generated.

[0059] The differential amplification and conditioning circuit includes: a gain-adjustable operational amplifier, a gain-adjusting resistor, a first operational amplifier, and a second operational amplifier. The gain-adjustable operational amplifier's gain-adjusting terminal is connected to the gain-adjusting resistor. The reference pin of the gain-adjustable operational amplifier is connected to a low-impedance point in the circuit through the first operational amplifier. The second operational amplifier is used to condition the detection output signal into an ADC input signal. The formula is as follows:

[0060]

[0061] Among them, R A is the feedback resistor, R i 、R b is the input resistance, k A is the gain constant of the gain-adjustable operational amplifier, R w is the nominal resistance of the sliding rheostat, R w23 is the resistance between pins 2 and 3 of the sliding rheostat, V ref+ is the positive bias reference voltage, V ref- is the negative bias reference voltage. In this embodiment, Figure 5 As shown, the differential displacement signal is connected to the input terminal of amplifier A1, and the gain adjustment terminal is connected to the gain adjustment resistor R g The reference pin of the first amplifier is connected to a low impedance point in the circuit through a voltage follower formed by a basic operational amplifier A2, and the second amplifier A3 is used to adjust the voltage bias.

[0062] The second low-pass filter adopts a voltage-controlled voltage source type second-order low-pass filter. The second low-pass filter can filter out high-frequency interference in the ADC input signal and obtain the displacement signal. The ripple detection and conditioning circuit module finally outputs U ot The relationship with the displacement signal is:

[0063]

[0064] Among them, K s is the output gain of the current transformer module, K pf is the final output gain of the two-stage bandpass filter. In this embodiment, Figure 6 As shown in the figure, a voltage-controlled voltage source type low-pass filter is designed to filter out the high-frequency noise in the single-sideband signal and obtain a low-frequency rotor displacement signal. The gain K of the low-pass filter is f , cutoff frequency f L0 And the quality factor Q is determined by the following formula:

[0065]

[0066] Among them, R L0 is the feedback resistor, R L is the inverting input resistance, R L1 、R L2 They are the first and second filter resistors, C L1 、C L2 are the first and second filter capacitors.

[0067] like Figure 7 FIG. 1 is a schematic diagram of a signal processing flow chart of an embodiment.

[0068] The embodiments described above are merely descriptions of the preferred embodiments of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements made to the technical solutions of the present application by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present application.

Claims

1. A pure electromagnetic bearing radial displacement self-detection device with a dual-coil structure, characterized in that: The digital control system is connected to the double-coil magnetic bearing assembly; the double-coil magnetic bearing assembly is connected to the ripple detection and conditioning circuit module; The digital control system includes: a position controller connected to a current controller; the current controller is also connected to a first and a second switching power amplifier, respectively, and the current controller is used to output a bias PWM signal and a control PWM signal to the first and the second switching power amplifiers, respectively; the first and the second switching power amplifiers are connected to a dual-coil magnetic bearing assembly, and the first and the second switching power amplifiers are used to output a first and a second current signal to the dual-coil magnetic bearing assembly based on the bias PWM signal and the control PWM signal, respectively; The second switching power amplifier is also connected to the first low-pass filter; The first low-pass filter is also connected to the position controller; The dual-coil magnetic bearing assembly includes: a control coil for generating a differential changing magnetic field to control the rotor suspension; a bias coil for converting the current ripple in the first current signal into a differential signal form to obtain a differential ripple signal; The ripple detection and conditioning circuit module includes: a bandpass filter device for receiving the differential ripple signal and extracting the fundamental frequency component of the ripple signal in the differential ripple signal; a precision full-wave detection device for receiving the fundamental frequency component and filtering out the high-frequency interference signal in the fundamental frequency component to obtain a detection output signal; a differential amplification and conditioning circuit for receiving the detection output signal and conditioning the detection output signal into an ADC input signal; a second low-pass filter, which adopts a voltage-controlled voltage source type second-order low-pass filter, for receiving the ADC input signal and filtering out the high-frequency interference in the ADC input signal to obtain a displacement signal. The final output of the ripple detection and conditioning circuit module The relationship with the displacement signal is: in, is the bus voltage, is the bias PWM signal duty cycle, is the switching angular frequency of the PWM signal, is the vacuum permeability, N is the number of coil turns, A is the magnetic pole area, is the initial phase of the ripple signal, is the feedback resistor, 、 is the input resistance, is the gain constant of the gain-adjustable operational amplifier, is the nominal resistance of the sliding rheostat, is the resistance between pins 2 and 3 of the sliding rheostat. is the positive bias reference voltage, is the negative bias reference voltage, is the output gain of the current transformer module, is the final output gain of the two-stage bandpass filter, R g is the gain adjustment resistor, K f is the gain of the low-pass filter.

2. The dual-coil structured pure electromagnetic bearing radial displacement self-detection device according to claim 1, characterized in that: The bandpass filter circuit is composed of two stages of infinite gain multi-path feedback bandpass filters. The design extracts the fundamental frequency component at the first-order ripple frequency point of the bias current , the differential ripple signal is affected by the rotor displacement signal Modulation, the formula is as follows: in, is the bus voltage, is the bias PWM signal duty cycle, is the switching angular frequency of the PWM signal, is the vacuum permeability, N is the number of coil turns, A is the magnetic pole area, is the initial phase of the ripple signal.

3. The dual-coil structured pure electromagnetic bearing radial displacement self-detection device according to claim 1, characterized in that: The precise full-wave detection circuit is composed of a JFET bipolar operational amplifier and a Schottky diode, and can realize absolute value operation on the fundamental frequency component.

4. The dual-coil structured pure electromagnetic bearing radial displacement self-detection device according to claim 1, characterized in that: The differential amplification and conditioning circuit includes: a gain-adjustable operational amplifier, a gain adjustment resistor, a first operational amplifier, and a second operational amplifier; The gain adjustment terminal of the gain adjustable operational amplifier is connected to the gain adjustment resistor. The reference pin of the gain-adjustable operational amplifier is connected to a low-impedance point in the circuit through the first operational amplifier; The second operational amplifier is used to condition the detection output signal into an ADC input signal, and the formula is as follows: in, is the feedback resistor, 、 is the input resistance, is the gain constant of the gain-adjustable operational amplifier, is the nominal resistance of the sliding rheostat, is the resistance between pins 2 and 3 of the sliding rheostat. is the positive bias reference voltage, is the negative bias reference voltage.

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