A control method for suppressing rotor vibration and a magnetic bearing system

Abstract

This invention relates to the field of magnetic bearing system control technology, and particularly to a control method and magnetic bearing system for suppressing rotor vibration. The control method includes the following steps: acquiring displacement feedback signals of the magnetic bearing rotor in two mutually orthogonal radial directions; acquiring differential displacement signals of the magnetic bearing rotor in the two mutually orthogonal radial directions based on the displacement feedback signals; performing cross-feedback processing on the differential displacement signals of the magnetic bearing rotor in the two mutually orthogonal radial directions, filtering, gain adjustment, and phase compensation of the differential displacement signals through a high-pass filter branch and a low-pass filter branch, respectively, to obtain a cross-feedback output; and superimposing the cross-feedback output onto the original control quantity to obtain a control signal. This invention can significantly improve the open-loop phase margin of the magnetic bearing system at the nutation and precession frequencies, thereby rapidly attenuating nutation and precession at the corresponding speeds, reducing rotor vibration displacement, and enabling the rotor to float stably.

Description

Technical Field

[0001] This invention relates to the field of magnetic bearing system control technology, and in particular to a control method for suppressing rotor vibration and a magnetic bearing system. Background Technology

[0002] In fields such as high-speed rotating machinery, vacuum and cleanroom systems, and turbine machinery, magnetic bearings, compared to traditional mechanical bearings, rely on electromagnetic force to levitate the rotor, achieving contactless operation between the magnetic bearing and the rotor. Therefore, they require no lubrication, have no frictional losses, and require minimal maintenance. Furthermore, magnetic bearings allow the rotor to operate at extremely high speeds, limited only by the rotor material. In addition, magnetic bearings allow for active control of the rotor's inherent mechanical characteristics and external disturbances, ensuring stable rotor operation. Therefore, they have wide applications in the field of high-speed rotating machinery.

[0003] A magnetic bearing system typically includes modules such as a controller, displacement sensor, power amplifier, and magnetic bearing-rotor. When the displacement sensor detects a deviation between the actual rotor displacement and the reference displacement, the controller calculates a control signal based on the displacement deviation. This signal is then amplified by the power amplifier and converted into an actual current, driving the magnetic bearing to generate electromagnetic force that suspends the rotor at the reference position. However, for rotors with a large moment of inertia ratio (axial moment of inertia to radial moment of inertia), as the rotor speed increases, the gyroscopic effect of the rotor gradually intensifies. This causes the rotor to not only rotate around its principal axis of inertia but also to produce nutation (whirling motion in the same direction as the rotational speed) and precession (whirling motion in the opposite direction to the rotational speed). Nutation generally has a high frequency and a rapidly increasing amplitude, which can lead to violent collisions between the rotor and the protective bearing, ultimately causing significant damage to the equipment. Precession has a lower frequency, but its amplitude also continuously increases, eventually causing the rotor to lose stability.

[0004] Therefore, how to suppress the nutation and precession of the rotor is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the problem of nutation and precession in rotors with large moments of inertia at high speeds in existing technologies, this invention provides a control method for suppressing rotor vibration. This method significantly improves the open-loop phase margin of the magnetic bearing system at the nutation and precession frequencies, thereby rapidly attenuating nutation and precession at the corresponding speeds, reducing rotor vibration displacement, enabling stable rotor levitation, and improving the operational stability of the magnetic bearing system. This solves the problem of nutation and precession in rotors with large moments of inertia at high speeds in existing technologies.

[0006] The technical solution adopted by this invention to solve its technical problem is: A control method for suppressing rotor vibration includes the following steps: Obtain the displacement feedback signals of the magnetic bearing rotor in two mutually orthogonal radial directions; The differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions are obtained based on the displacement feedback signal; The differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions are subjected to cross-feedback processing. The differential displacement signals are filtered, gain adjusted and phase compensated by high-pass filter branch and low-pass filter branch respectively to obtain the cross-feedback output. The cross-feedback output is superimposed on the original control quantity to obtain the control signal.

[0007] Optionally, the high-pass filter branch is used to extract the high-frequency eddy component in the differential displacement signal, and after applying high-pass branch gain and high-pass branch phase compensation to the high-frequency eddy component, it outputs a nutation suppression component.

[0008] Optionally, the low-pass filter branch is used to extract the low-frequency eddy component in the differential displacement signal, and after applying low-pass branch gain and low-pass branch phase compensation to the low-frequency eddy component, it outputs a precession suppression component.

[0009] Optionally, the method of obtaining displacement feedback signals of the magnetic bearing rotor in two mutually orthogonal radial directions includes: obtaining a first displacement feedback signal of the magnetic bearing rotor in a first radial direction and a second displacement feedback signal in a second radial direction, wherein the first radial direction and the second radial direction are mutually orthogonal.

[0010] Optionally, the first displacement feedback signal includes an upper radial first displacement feedback signal and a lower radial first displacement feedback signal; the second displacement feedback signal includes an upper radial second displacement feedback signal and a lower radial second displacement feedback signal.

[0011] Optionally, obtaining the differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions based on the displacement feedback signal includes: obtaining the first differential displacement signal of the magnetic bearing rotor in the first radial direction based on the first displacement feedback signal of the magnetic bearing rotor in the first radial direction; and obtaining the second differential displacement signal of the magnetic bearing rotor in the second radial direction based on the second displacement feedback signal of the magnetic bearing rotor in the second radial direction.

[0012] Optionally, the first differential displacement signal is obtained by subtracting the upper radial first direction displacement signal from the lower radial first direction displacement signal; the second differential displacement signal is obtained by subtracting the upper radial second direction displacement signal from the lower radial second direction displacement signal.

[0013] Optionally, the cross-feedback processing of the differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions includes: performing cross-feedback processing on the first differential displacement signal of the magnetic bearing rotor in the first radial direction to obtain a first cross-feedback output; and performing cross-feedback processing on the second differential displacement signal of the magnetic bearing rotor in the second radial direction to obtain a second cross-feedback output.

[0014] Optionally, superimposing the cross-feedback output onto the original control quantity includes: superimposing the first cross-feedback output onto the control channel in the second radial direction; and superimposing the second cross-feedback output onto the control channel in the first radial direction.

[0015] Another object of the present invention is to provide a magnetic bearing system, including a controller; the controller includes a cross-feedback control module; the cross-feedback control module suppresses rotor vibration through the control method for suppressing rotor vibration as described above.

[0016] The beneficial effects of this invention are: The control method for suppressing rotor vibration provided by this invention acquires displacement feedback signals in two mutually orthogonal radial directions and further forms differential displacement signals. This expands the controlled object from ordinary radial displacement deviation to rotor rotation angle, which can characterize changes in rotor attitude, thereby improving the specificity of nutation and precession identification. By processing the differential displacement signals through high-pass and low-pass filter branches respectively, the high-frequency nutation component and the low-frequency precession component can be extracted, their gain adjusted, and their phase compensated separately, avoiding the problem of difficulty in simultaneously addressing high-frequency nutation and low-frequency precession when using a single compensation channel. This control method can significantly improve the open-loop phase margin of the magnetic bearing system at the nutation and precession frequencies, thereby rapidly attenuating nutation and precession at the corresponding speeds, reducing rotor vibration displacement, enabling the rotor to float stably, and improving the operational stability of the magnetic bearing system. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a schematic diagram of the magnetic bearing rotor and its Cardan coordinate system in this invention; Figure 2 This is a control block diagram of the magnetic bearing system in this invention; Figure 3 This is a block diagram of the specific modules of the controller in this invention; Figure 4 This is a block diagram of the principle of the cross-feedback module for suppressing nutation and precession in this invention; Figure 5This is a comparison chart of the open-loop nutation frequency domain characteristics of the magnetic bearing system after applying the cross-feedback control module of this invention; Figure 6 This is a comparison diagram of the open-loop precession frequency domain characteristics of the magnetic bearing system after applying the cross-feedback control module of this invention; Figure 7 This refers to the nutation rotor displacement when the cross-feedback control module of this invention is not applied. Figure 8 This is the frequency domain distribution of the nutated rotor displacement when the cross-feedback control module of this invention is not applied; Figure 9 This refers to the precession rotor displacement when the cross-feedback control module of this invention is not applied. Figure 10 This is the frequency domain distribution of the precessing rotor displacement when the cross-feedback control module of this invention is not applied; Figure 11 It refers to the nutation rotor displacement after applying the cross-feedback control module of this invention; Figure 12 This is the frequency domain distribution of the nutated rotor displacement after applying the cross-feedback control module of this invention; Figure 13 It is the precession rotor displacement after applying the cross-feedback control module of this invention; Figure 14 It is the frequency domain distribution of the precessing rotor displacement after applying the cross-feedback control module of this invention.

[0019] In the diagram: 1-Controller; 11-Dual throw ratio controller module; 12-Integral module; 13-Cross feedback control module; 2-Power amplifier; 3-Magnetic bearing-rotor; 4-Displacement sensor. Detailed Implementation

[0020] The present invention will now be described in further detail. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] The Cardan coordinate system of the rotor in the magnetic bearing system is as follows: Figure 1 As shown, the coordinate system is divided into 6 directions of motion with the rotor's center of mass or geometric center as the origin. x, y, and z represent the rotor's 3 translational motion directions; α, β, and γ represent the rotor's 3 rotational motion directions, and are respectively related to the x, y, and z directions by the right-hand rule. Assume the rotor's mass is m, and the moment of inertia along the axial direction (z direction, which is the rotor's rotational direction) is J.z The radial (x, y) moment of inertia is J. r J z and J r The units are all kg*m 2 The rotational speed is Ω (angular frequency), and the equation of motion for the rotor is as follows: ; Where F x F represents the combined force acting on the rotor in the x-direction. y M represents the combined force exerted on the rotor in the y-direction, expressed in N. x M is the torque in the α direction. y The torque is in the β direction, expressed in N*m; where J z Ωβ (1) and J z Ωα (1) The effect of the gyroscopic torque related to the rotational speed on the rotor's rotational motion is called the gyroscopic effect. When the rotor is running at high speed, this torque component will cause the rotor to nutate and precess.

[0023] To address the issues of nutation and precession that occur in rotors with large moments of inertia under high-speed rotation conditions in existing technologies, this invention provides a control method for suppressing rotor vibration, which includes the following steps: S1: Obtain the displacement feedback signal of the magnetic bearing rotor in two mutually orthogonal radial directions; In this invention, two mutually orthogonal radial directions are preferably defined as the first radial direction and the second radial direction, respectively. The first radial direction can be the x-direction and the second radial direction can be the y-direction. The two are perpendicular to each other in the rotor radial plane.

[0024] S2: Obtain the differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions based on the displacement feedback signal; The differential displacement signal introduced in this invention can reflect the relative offset state of the rotor between the upper and lower radial detection positions. When the rotor undergoes nutation or precession, the rotor mainly exhibits tilting and rotation movements. At this time, the displacement changes of the upper radial detection position and the lower radial detection position are out of phase. By constructing the differential displacement signal, the rotation angles of the rotor corresponding to the rotation axes such as α and β can be indirectly obtained, thereby making the subsequent cross-feedback compensation more targeted.

[0025] Correspondingly, if only the absolute displacement feedback of a single displacement sensor is used for control, it may be difficult to distinguish between ordinary translational deviations and attitude-related eddy deviations caused by gyroscopic effects, thus resulting in limited nutation or precession suppression effects.

[0026] S3: Perform cross-feedback processing on the differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions. Filter, adjust the gain, and compensate the phase of the differential displacement signals through a high-pass filter branch and a low-pass filter branch, respectively, to obtain the cross-feedback output quantity, which is the compensation quantity. In this step, the differential displacement signals of the magnetic bearing rotor in two radial directions are cross-coupled and compensated. The high-pass filter branch and the low-pass filter branch respectively filter, adjust the gain and compensate the phase of the same differential displacement signal, and output nutation suppression component and precession suppression component respectively, thereby improving the phase margin at the key frequency and suppressing the nutation and precession of the high-speed rotor.

[0027] S4: The cross-feedback output is superimposed on the original control input to obtain the control signal.

[0028] In this invention, the original control quantity refers to the control quantity output by the controller before the addition of cross-feedback compensation. Specifically, by superimposing the cross-feedback output quantity as a compensation quantity with the original control quantity, a compensated control quantity is obtained. Based on the compensated control quantity, a magnetic bearing coil current reference command can be generated. The controller further generates a switching drive signal for driving the power amplifier based on the magnetic bearing coil current reference command. The power amplifier drives the magnetic bearing coil to generate current based on the switching drive signal, so that the magnetic bearing generates electromagnetic force to suppress the nutation and precession caused by the gyroscopic effect when the rotor rotates at high speed, and to make the rotor stably levitate.

[0029] The control method for suppressing rotor vibration provided by this invention acquires displacement feedback signals in two mutually orthogonal radial directions and further forms differential displacement signals. This expands the controlled object from ordinary radial displacement deviation to a differential component that can characterize rotor rotation changes and whirl states, thereby improving the specificity of nutation and precession identification. By processing the differential displacement signals through high-pass and low-pass filter branches respectively, the high-frequency nutation component and the low-frequency precession component can be extracted, their gain adjusted, and their phase compensated separately, avoiding the problem of difficulty in simultaneously addressing high-frequency nutation and low-frequency precession when using a single compensation channel. This control method can significantly improve the open-loop phase margin of the magnetic bearing system at the nutation and precession frequencies, thereby rapidly attenuating nutation and precession at the corresponding speeds, reducing rotor vibration displacement, enabling the rotor to float stably, and improving the operational stability of the magnetic bearing system.

[0030] The present invention preferably uses a high-pass filter branch to extract the high-frequency eddy component in the differential displacement signal, and applies high-pass branch gain and high-pass branch phase compensation to the high-frequency eddy component to output the nutation suppression component.

[0031] The high-pass filter branch is used to extract the high-frequency eddy component from the differential displacement signal. This high-frequency eddy component corresponds to the vibration component when the high-speed magnetic bearing rotor nutes. Specifically, the high-pass filter branch may include a high-pass filter, a high-pass branch gain adjustment unit, and a high-pass branch phase compensation unit. The high-pass filter extracts the component above the predetermined cutoff frequency from the differential displacement signal. The high-pass branch gain adjustment unit applies gain to this high-frequency component, and the high-pass branch phase compensation unit applies phase compensation to this high-frequency component to obtain the nutation suppression component. The cutoff frequency of the high-pass filter can be set according to the rotor speed, the nutation frequency range, or the system modal characteristics. As the speed increases, the nutation frequency changes, so the cutoff frequency of the high-pass filter and the high-pass branch gain can be adjusted with the speed. By setting the high-pass branch phase compensation, the applicability range of the high-pass filter branch to different speed ranges can be expanded without frequently switching filter parameters, making the control algorithm more stable and simpler.

[0032] The present invention preferably uses a low-pass filter branch to extract the low-frequency eddy component in the differential displacement signal, and applies low-pass branch gain and low-pass branch phase compensation to the low-frequency eddy component to output the precession suppression component.

[0033] The low-pass filter branch is used to extract the low-frequency eddy component from the differential displacement signal. This low-frequency eddy component corresponds to the vibration component when the high-speed magnetic bearing rotor precesses. Specifically, the low-pass filter branch can include a low-pass filter, a low-pass branch gain adjustment unit, and a low-pass branch phase compensation unit. The low-pass filter extracts the component below a predetermined cutoff frequency from the differential displacement signal. The low-pass branch gain adjustment unit applies gain to this low-frequency component, and the low-pass branch phase compensation unit applies phase compensation to this low-frequency component to obtain the precession suppression component. The cutoff frequency of the low-pass filter can be set according to the precession frequency range. Since the precession frequency is relatively low and changes little with the rotational speed, the cutoff frequency of the low-pass filter branch can remain unchanged or be adjusted only slightly over a wide rotational speed range. Through low-pass branch phase compensation, the phase margin of the magnetic bearing system at the precession frequency can be improved, preventing the low-frequency precession vibration from diverging.

[0034] The present invention preferably obtains displacement feedback signals of the magnetic bearing rotor in two mutually orthogonal radial directions by: obtaining a first displacement feedback signal of the magnetic bearing rotor in a first radial direction and a second displacement feedback signal in a second radial direction, wherein the first radial direction and the second radial direction are mutually orthogonal.

[0035] Furthermore, the present invention preferably includes an upper radial first displacement feedback signal and a lower radial first displacement feedback signal in the first displacement feedback signal; and the second displacement feedback signal includes an upper radial second displacement feedback signal and a lower radial second displacement feedback signal.

[0036] Specifically, a displacement sensor is used to acquire a first displacement feedback signal of the magnetic bearing rotor in the first radial direction and a second displacement feedback signal of the magnetic bearing rotor in the second radial direction. The magnetic bearing rotor is provided with an upper radial detection position and a lower radial detection position along the axial direction to facilitate the acquisition of the upper radial first displacement feedback signal, the lower radial first displacement feedback signal, the upper radial second displacement feedback signal, and the lower radial second displacement feedback signal.

[0037] For example, the upper radial first displacement feedback signal can be denoted as hx, the lower radial first displacement feedback signal as bx, the upper radial second displacement feedback signal as hy, and the lower radial second displacement feedback signal as by. Here, h represents the upper radial detection position, b represents the lower radial detection position, and x and y represent two mutually orthogonal radial directions.

[0038] Specifically, obtaining the differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions based on the displacement feedback signal includes: obtaining the first differential displacement signal of the magnetic bearing rotor in the first radial direction based on the first displacement feedback signal of the magnetic bearing rotor in the first radial direction; and obtaining the second differential displacement signal of the magnetic bearing rotor in the second radial direction based on the second displacement feedback signal of the magnetic bearing rotor in the second radial direction. The first differential displacement signal is obtained by subtracting the upper radial first direction displacement signal from the lower radial first direction displacement signal, as shown in the following formula: Dx = hx - bx; Where Dx represents the first differential displacement signal; The second differential displacement signal is obtained by subtracting the upper radial second direction displacement signal from the lower radial second direction displacement signal, as shown in the following formula: Dy = hy-by; Where Dy represents the second differential displacement signal.

[0039] The present invention preferably performs cross-feedback processing on the differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions, including: performing cross-feedback processing on the first differential displacement signal of the magnetic bearing rotor in the first radial direction to obtain a first cross-feedback output; and performing cross-feedback processing on the second differential displacement signal of the magnetic bearing rotor in the second radial direction to obtain a second cross-feedback output.

[0040] The present invention preferably superimposes the cross-feedback output onto the original control quantity by: superimposing the first cross-feedback output onto the control channel in the second radial direction; and superimposing the second cross-feedback output onto the control channel in the first radial direction.

[0041] Specifically, in this invention, the nutation suppression component output by the high-pass filter branch and the precession suppression component output by the low-pass filter branch can be superimposed to form the corresponding cross-feedback output. For example, after the first differential displacement signal Dx is processed by the high-pass filter branch and the low-pass filter branch, the first nutation suppression component and the first precession suppression component are obtained, and the two are superimposed to obtain the first cross-feedback output U. y-cross The second differential displacement signal Dy is processed by a high-pass filter branch and a low-pass filter branch to obtain the second nutation suppression component and the second precession suppression component. The two components are superimposed to obtain the second cross-feedback output U. x-cross Among them, the first cross-feedback output quantity U y-cross Control channel for the second radial direction, second cross-feedback output U x-cross The control channel is used in the first radial direction; in this invention, the cross-feedback output can be further multiplied by the cross-feedback gain parameter k. dc Cross-feedback gain parameter k dc It can be determined based on the rotor structure.

[0042] The controller superimposes the first cross-feedback output onto the original control value in the second radial direction, and superimposes the second cross-feedback output onto the original control value in the first radial direction, thereby obtaining the final control signal; for example, if the original control value in the first radial direction is U... x0 The original control quantity in the second radial direction is U. y0 Then the final control signal can be expressed as: U x = U x0 + U x-cross ; U y = U y0 + U y-cross ; Among them, U x-cross U is obtained by cross-feedback processing of the second differential displacement signal Dy. y-cross It is obtained by cross-feedback processing of the first differential displacement signal Dx.

[0043] The cross-feedback processing in this invention does not directly feed the first differential displacement signal to the first radial direction, nor does it directly feed the second differential displacement signal to the second radial direction. Instead, it uses the differential displacement signal in the first radial direction to generate a cross-feedback output for the control channel in the second radial direction, and uses the differential displacement signal in the second radial direction to generate a cross-feedback output for the control channel in the first radial direction. This control logic matches the orthogonal directional coupling caused by the high-speed rotor gyro effect. That is, when the rotor's attitude change in the first radial direction causes a coupling response in the second radial direction, processing the first differential displacement signal and applying it to the control channel in the second radial direction can produce a control effect that cancels out the coupling response. Similarly, when the rotor's attitude change in the second radial direction causes a coupling response in the first radial direction, processing the second differential displacement signal and applying it to the control channel in the first radial direction can achieve corresponding compensation.

[0044] This invention uses cross-feedback processing to convert differential displacement information in one radial direction into compensation in another orthogonal radial control channel. This makes the compensation direction compatible with the orthogonal coupling characteristics formed by the coupling of the high-speed rotor gyroscope. This can effectively improve the phase margin of the magnetic bearing system at the nutation and precession frequencies, effectively suppress the nutation and precession of the magnetic bearing rotor at high speed, reduce rotor vibration displacement, and enable the rotor to remain stably suspended at high speeds.

[0045] Another object of the present invention is to provide a magnetic bearing system including a controller; the controller includes a cross-feedback control module; the cross-feedback control module suppresses rotor vibration through the control method for suppressing rotor vibration as described above.

[0046] The magnetic bearing system provided by this invention employs a control method to suppress rotor vibration. By acquiring displacement feedback signals in two mutually orthogonal radial directions and further forming differential displacement signals, the controlled object is expanded from ordinary radial displacement deviation to rotor rotation angle, which can characterize rotor attitude changes and whirl states, thereby improving the specificity of nutation and precession identification. The differential displacement signals are processed by high-pass and low-pass filter branches respectively, so that high-frequency nutation components and low-frequency precession components can be extracted, gain adjusted, and phase compensated separately, avoiding the problem of difficulty in simultaneously addressing high-frequency nutation and low-frequency precession when using a single compensation channel. This control method can significantly improve the open-loop phase margin of the magnetic bearing system at the nutation and precession frequencies, thereby rapidly attenuating nutation and precession at the corresponding speeds, reducing rotor vibration displacement, enabling the rotor to float stably, and improving the operational stability of the magnetic bearing system.

[0047] Existing technologies typically suppress nutation and precession by adding phase lead correction to the controller. However, these methods have limited effect on improving the open-loop phase margin of the system, and the rotor still loses stability under high-speed rotation conditions. In order to suppress nutation and precession caused by gyroscopic effects when the rotor of the magnetic bearing system rotates at high speed, this invention adds a cross-feedback control module to the controller. This can significantly improve the open-loop phase margin of the magnetic bearing system at the nutation and precession frequencies, thereby rapidly attenuating nutation and precession at the corresponding speeds, reducing rotor vibration displacement, enabling the rotor to float stably, and improving the operational stability of the magnetic bearing system.

[0048] Specifically, the preferred magnetic bearing system of the present invention mainly includes: Controller 1: Implemented by a DSP (Digital Signal Processor), it calculates the deviation between the rotor displacement signal detected by displacement sensor 4 and the reference displacement, and outputs the actual control quantity (such as the duty cycle signal of the switching element of power amplifier 2). It drives power amplifier 2 through an internal PWM drive circuit or an external drive circuit, and is the actual implementation unit of the control algorithm. Hardware-wise, it consists of analog circuits including a central processing unit (CPU), memory, and an analog-to-digital / digital-to-analog converter, storing the underlying software and logic programs in memory to drive the various parts to work together. Software logic-wise, it consists of a reference displacement and feedback displacement signal deviation calculation section, a displacement deviation signal calculation section, and a drive output section that converts the calculated value into a switching duty cycle signal. It is the module that executes the control algorithm calculation for the magnetic bearing system. Power Amplifier 2: A switching circuit composed of MOSFETs or IGBTs and power diodes, connected to an external DC power supply, capable of driving the magnetic bearing coil to generate current, thereby controlling the magnitude of the electromagnetic force output of the magnetic bearing. Power Amplifier 2 is an H-type half-bridge circuit, where the switching transistor is a MOSFET. Power Amplifier 2 receives the switching drive signal output from Controller 1 to control the switching of the MOSFET, thereby generating actual current in the magnetic bearing coil. For a 5-DOF electromagnetic magnetic bearing system, a total of 10 such half-bridge circuits are required to drive the magnetic bearing coil to generate current.

[0049] Magnetic bearing-rotor 3: The actuator part of the magnetic bearing system. When current is passed through the magnetic bearing coil, an electromagnetic force is generated on the magnetic bearing rotor. The system calculates and adjusts the output current of the magnetic bearing coil in real time through controller 1. By controlling the current of the magnetic bearing coil, the electromagnetic force of the magnetic bearing is controlled to actively control the rotor, providing adjustable stiffness and damping to the rotor, thereby ensuring the stable suspension of the rotor. Displacement sensor 4: Real-time detection and feedback of the actual rotor displacement signal, inputting the signal to controller 1 to enable closed-loop control of the magnetic bearing rotor displacement; the displacement sensor 4 of the magnetic bearing system is typically an eddy current sensor or an inductive sensor. It has a detection accuracy in the μm range, good linearity, high bandwidth, and can detect rotor displacement in real time and convert it into a voltage signal output to the controller.

[0050] The magnetic bearing control system in this invention is as follows: Figure 2 As shown, its working principle is as follows: Displacement sensor 4 detects rotor displacement in real time and inputs the corresponding voltage signal into controller 1; controller 1 calculates the deviation between the reference displacement and the actual feedback displacement signal of the rotor and outputs a coil current reference command, and converts the current reference command into the duty cycle of the power amplifier switching element; after receiving the switching drive signal output by controller 1, power amplifier 2 drives the magnetic bearing coil to generate current, thereby adjusting the electromagnetic force of the magnetic bearing to make the rotor stably levitate at the reference position.

[0051] In addition, see Figure 3 As shown, in the magnetic bearing system controller 1 of the present invention, in addition to the cross-feedback control module, it may also include a conventional dual-throw ratio controller module (a phase lead controller) and an integral module. The specific details of each module are as follows: Dual-throw ratio controller module 11: Since the magnetic bearing itself is a negative stiffness system, the negative feedback signal provides positive stiffness and damping to the magnetic bearing system through the dual-throw ratio controller, ensuring the stability of the system; the dual-throw ratio controller in the continuous domain is as follows: ; Where, k p ζ is the gain of the dual-throw ratio controller, and ζ is the damping ratio of the dual-throw ratio controller, with a value between 0 and 2; ω z and ω p These correspond to the zero-point frequency and the pole frequency, respectively, where ω z Less than ω p The dual-throw ratio controller functions similarly to a traditional PD (proportional-derivative) controller (but provides greater phase compensation than a PD controller), providing positive stiffness and damping for the magnetic bearing system. Integrator module 12: Eliminates the static difference between the actual rotor displacement and the reference displacement, so that the rotor is suspended at the reference displacement setting position; Cross-feedback control module 13: mainly increases the phase margin of the nutation and precession frequency of the magnetic bearing system by adjusting the cross-feedback parameters, thereby suppressing the nutation and precession caused by the gyroscopic effect when the rotor rotates at high speed.

[0052] The control method for suppressing the nutation and precession of the rotor in the magnetic bearing system in this invention is specifically implemented in the controller as follows: Figure 4As shown, the cross-feedback unit has two inputs: the input is the vertical radial h. x and b x The differential displacements are calculated by the cross-feedback module and the output values ​​are added to h respectively. y and b y The input is the vertical radial direction h. y and b y The differential displacements are calculated by the cross-feedback module and the output values ​​are added to h respectively. x and b x The cross-feedback module takes the following form: ; Where HPF represents a high-pass filter, LPF represents a low-pass filter, and k h k is the gain coefficient corresponding to HPF. l θ is the gain coefficient corresponding to LPF. h To compensate for the HPF phase, θ l To compensate for the LPF phase, the HPF section is used to suppress nutation. The filter's cutoff frequency and gain coefficient vary according to the rotor speed, and θ is added. h After phase compensation, the applicable speed range of the HPF with the same cutoff frequency can be increased, and the number of cutoff frequency switching of the HPF with speed variation can be reduced, making the control algorithm simpler. The LPF part is used to suppress precession. The cutoff frequency and gain coefficient of the filter change little with speed. Adding θ l After phase compensation, the LPF cutoff frequency remains almost unchanged across the entire speed range; k dc Ω is the cross-feedback gain parameter, determined by the rotor structure, and Ω is the angular frequency of the motor speed.

[0053] To verify the technical effect of the present invention, a specific application example is provided.

[0054] After applying this invention, the open-loop amplitude-frequency and phase-frequency characteristics of the magnetic bearing system are compared with those before. Figure 5 , Figure 6 As shown: where Figure 5 The comparison of the open-loop nutation frequency domain characteristics of the magnetic bearing system after applying this invention shows that, after using this invention, the system's open-loop 0dB crossover frequency changed from 196Hz to 183Hz, and the corresponding phase margin increased from 9° to 36°, greatly improving the system's stability; among which... Figure 6 The comparison of the open-loop precession frequency domain characteristics of the magnetic bearing system after applying the present invention shows that after using the present invention, the open-loop 0dB crossover frequency of the system changed from 5.03Hz to 5.45Hz, and the corresponding phase margin increased from 3° (almost lost stability) to 20°, which greatly improved the stability of the system.

[0055] Figure 7Taking the rotor's radial displacement bx in the lower x direction as an example, the rotor displacement when nutation occurs... Figure 8 It is the frequency and corresponding component distribution of the rotor displacement (first 1 second); as shown in the figure, when the rotational speed is 245Hz, nutation occurs on the rotor with a frequency of 140Hz. At this time, the frequency component corresponding to the nutation rapidly increases beyond the same frequency vibration and causes other low-frequency vibrations of the rotor. The rotor amplitude rapidly increases and loses stability.

[0056] Figure 9 Taking the radial displacement bx of the rotor as an example, this describes the rotor displacement when the rotor precesses. Figure 10 The figure shows the frequency and corresponding component distribution of the rotor displacement (first 1 second). As shown in the figure, when the rotational speed is 125Hz, precession occurs on the rotor at a frequency of 4Hz. The amplitude of this low-frequency vibration gradually diverges and increases, causing the rotor to lose stability.

[0057] Figure 11 This describes the control effect of the magnetic bearing system of the present invention on rotor nutation, where bx2 represents the rotor radial displacement at the same speed after applying the present invention. As shown in the figure, the rotor amplitude is within 5μm and does not gradually diverge, maintaining stable suspension; Figure 12 This is a comparison of frequency domain analysis of the displacement of this degree of freedom after applying the present invention. Among them, bx2-fft is the frequency domain analysis result of the rotor displacement after applying the present invention. At the same rotational speed, the nutation vibration with a frequency of 140Hz is almost completely eliminated.

[0058] Figure 13 This describes the control effect of the magnetic bearing system of the present invention on the reverse whirling of the rotor, where bx2 represents the radial displacement of the rotor at the same speed after applying the present invention. As shown in the figure, the rotor amplitude is within 5μm and does not gradually diverge, maintaining stable suspension; Figure 14 This is a comparison of the frequency domain analysis of the displacement of this degree of freedom after applying the present invention. Among them, bx2-fft is the frequency domain analysis result of the rotor displacement after applying the present invention. At the same rotational speed, the precession vibration with a frequency of 4Hz is almost completely eliminated.

[0059] In summary, the advantages of this invention in improving the stability and safety of magnetic bearing systems are mainly reflected in the following aspects: 1. It effectively suppresses the nutation of the magnetic bearing rotor during high-speed rotation, reduces rotor vibration displacement, and enables the rotor to float stably at high speeds; 2. It effectively suppresses the precession of the magnetic bearing rotor when it rotates at high speed, reduces rotor vibration displacement, and enables the rotor to float stably at high speed.

[0060] The control method for suppressing rotor vibration provided by this invention can effectively suppress the nutation and precession of the rotor due to the gyroscopic effect when the rotor rotates at high speed, reduce the vibration amplitude of the rotor, and enable the rotor to operate stably under high speed conditions.

[0061] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A control method for suppressing rotor vibration, characterized in that, Includes the following steps: Obtain the displacement feedback signals of the magnetic bearing rotor in two mutually orthogonal radial directions; The differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions are obtained based on the displacement feedback signal; The differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions are subjected to cross-feedback processing. The differential displacement signals are filtered, gain adjusted and phase compensated by high-pass filter branch and low-pass filter branch respectively to obtain the cross-feedback output. The cross-feedback output is superimposed on the original control quantity to obtain the control signal.

2. The control method for suppressing rotor vibration as described in claim 1, characterized in that, The high-pass filter branch is used to extract the high-frequency eddy component in the differential displacement signal, and after applying high-pass branch gain and high-pass branch phase compensation to the high-frequency eddy component, it outputs the nutation suppression component.

3. The control method for suppressing rotor vibration as described in claim 1, characterized in that, The low-pass filter branch is used to extract the low-frequency eddy component in the differential displacement signal, and after applying low-pass branch gain and low-pass branch phase compensation to the low-frequency eddy component, it outputs the precession suppression component.

4. The control method for suppressing rotor vibration as described in any one of claims 1-3, characterized in that, Obtaining displacement feedback signals of the magnetic bearing rotor in two mutually orthogonal radial directions includes: obtaining a first displacement feedback signal of the magnetic bearing rotor in a first radial direction and a second displacement feedback signal in a second radial direction, wherein the first radial direction and the second radial direction are mutually orthogonal.

5. The control method for suppressing rotor vibration as described in claim 4, characterized in that, The first displacement feedback signal includes an upper radial first displacement feedback signal and a lower radial first displacement feedback signal; the second displacement feedback signal includes an upper radial second displacement feedback signal and a lower radial second displacement feedback signal.

6. The control method for suppressing rotor vibration as described in claim 5, characterized in that, Obtaining the differential displacement signal of the magnetic bearing rotor in two mutually orthogonal radial directions based on the displacement feedback signal includes: obtaining the first differential displacement signal of the magnetic bearing rotor in the first radial direction based on the first displacement feedback signal of the magnetic bearing rotor in the first radial direction; and obtaining the second differential displacement signal of the magnetic bearing rotor in the second radial direction based on the second displacement feedback signal of the magnetic bearing rotor in the second radial direction.

7. The control method for suppressing rotor vibration as described in claim 6, characterized in that, The first differential displacement signal is obtained by subtracting the upper radial first direction displacement signal from the lower radial first direction displacement signal; the second differential displacement signal is obtained by subtracting the upper radial second direction displacement signal from the lower radial second direction displacement signal.

8. The control method for suppressing rotor vibration as described in claim 7, characterized in that, The cross-feedback processing of the differential displacement signals of the magnetic bearing rotor in two mutually orthogonal radial directions includes: performing cross-feedback processing on the first differential displacement signal of the magnetic bearing rotor in the first radial direction to obtain a first cross-feedback output; and performing cross-feedback processing on the second differential displacement signal of the magnetic bearing rotor in the second radial direction to obtain a second cross-feedback output.

9. The control method for suppressing rotor vibration as described in claim 8, characterized in that, Adding the cross-feedback output to the original control quantity includes: adding the first cross-feedback output to the control channel in the second radial direction; and adding the second cross-feedback output to the control channel in the first radial direction.

10. A magnetic bearing system, characterized in that, The system includes a controller; the controller includes a cross-feedback control module; the cross-feedback control module suppresses rotor vibration using the control method for suppressing rotor vibration as described in any one of claims 1-9.

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