A control method and device for a magnetic bearing

Abstract

The application discloses a control method and device of a magnetic suspension bearing, determines the axial offset direction, the axial offset amount and the axial offset speed of a thrust disc relative to a central balance position, sets the proportional coefficient, the integral coefficient and the differential coefficient of a variable parameter PID control algorithm according to the axial displacement actual value and the axial offset speed, combines preset working condition switching rules, calculates a one-way control current instruction according to the axial offset amount, electrifies a stator coil of an axial magnetic bearing on the side opposite to the electromagnetic attractive force direction and the axial offset direction, controls the switch tube in a power amplifier on the other side coil to be in a minimum conduction state, and makes the other side coil pass through standby current less than a preset current threshold or controls the other side coil to be powered off. When the thrust disc is offset relative to the central balance position, only one side of the coil is electrified, the other side coil passes through lower standby current or is directly powered off, so that the thrust disc can return to the central balance position under the condition of reduced loss and heat.

Description

Technical Field

[0001] This invention relates to the field of magnetic levitation bearing control technology, and in particular to a control method and device for magnetic levitation bearings. Background Technology

[0002] Magnetic levitation bearings use electromagnetic force to levitate the rotor within the stator, achieving no mechanical contact between the rotor and the stator. A horizontal five-degree-of-freedom magnetic levitation bearing system typically includes two radial magnetic bearings and one axial magnetic bearing. The axial magnetic bearing is used to constrain the rotor's translational degree of freedom along the axial direction. Its structure generally consists of a thrust disk fixed on the rotor shaft and axial magnetic bearing stator cores and coils symmetrically arranged on both sides of the thrust disk.

[0003] In existing horizontal five-degree-of-freedom magnetic bearing axial control schemes, a differential control strategy is typically employed to maintain the thrust plate at the geometric center of the stator coils of the axial magnetic bearings on both sides. Specifically, this involves the superposition of bias current and feedback control current in the stator coils of the axial magnetic bearings on both sides of the thrust plate based on the axial offset of the thrust plate. That is, the current in the stator coil of one axial magnetic bearing increases to enhance the attraction, while the current in the stator coil of the other axial magnetic bearing decreases to weaken the attraction. The resultant force of the electromagnetic attraction on both sides is used to pull the thrust plate back to the equilibrium position.

[0004] However, in this differential control strategy, the bias current on the stator coils of the axial magnetic bearings on both sides of the thrust disk is usually set to a large constant value. Even when the rotor is suspended at the geometric center of the stator coils of the axial magnetic bearings on both sides, the stator coils of the axial magnetic bearings on both sides still maintain a large bias current. This part of the current is completely converted into Joule heat and dissipated inside the motor cavity, which not only significantly reduces the overall energy efficiency, but also causes the internal temperature of the motor to be too high, affecting the normal operation of the motor. Summary of the Invention

[0005] The purpose of this invention is to provide a control method and device for a magnetic levitation bearing. When the thrust disk deviates from the central balance position, only one side of the coil is energized, while a lower standby current is supplied to the other side of the coil or the power is directly cut off. This allows the thrust disk to return to the central balance position while reducing losses and heat generation.

[0006] To solve the above-mentioned technical problems, the present invention provides a control method for a magnetic levitation bearing, wherein a first axial magnetic bearing stator coil and a second axial magnetic bearing stator coil are symmetrically arranged on both sides of the thrust disk of the rotor in the magnetic levitation bearing, and the method includes: Obtain the actual value of the axial displacement of the thrust disk, and determine the axial offset direction and axial offset amount of the thrust disk relative to the central equilibrium position based on the actual value of the axial displacement and the axial displacement command value. The axial offset velocity of the thrust disk is determined based on the actual value of the axial displacement; Based on the actual value of the axial displacement and the axial offset speed, the proportional coefficient, integral coefficient and derivative coefficient of the variable parameter PID control algorithm are set in combination with the preset working condition switching rules. Based on the axial offset, the variable parameter PID control algorithm is used to calculate the unidirectional control current command; Based on the unidirectional control current command, energize the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk, where the electromagnetic attraction generated in the first and second axial magnetic bearing stator coils is opposite to the electromagnetic attraction generated in the first and second axial magnetic bearing stator coils. Control the switching transistor in the power amplifier supplying power to the other axial magnetic bearing stator coil to be in the minimum conduction state, so as to supply a standby current less than a preset current threshold to the other axial magnetic bearing stator coil, or control the other axial magnetic bearing stator coil to be de-energized.

[0007] Preferably, the preset operating condition switching rules include: If the absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are the same, then the proportional coefficient, integral coefficient, and derivative coefficient of the variable parameter PID control algorithm are set using a first parameter set with high stiffness and high damping characteristics. If the absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are not the same, then the proportional coefficient, integral coefficient and derivative coefficient of the variable parameter PID control algorithm are set using a second parameter set with high stiffness characteristics. If the absolute value of the actual axial displacement is not greater than the preset offset threshold, then the proportional coefficient, integral coefficient, and derivative coefficient of the variable parameter PID control algorithm are set using a third parameter set with high damping characteristics.

[0008] Preferably, the high stiffness characteristic is that the proportional coefficient is the maximum proportional coefficient and the integral coefficient is the maximum integral coefficient; The high damping characteristic is achieved by taking the maximum differential coefficient.

[0009] Preferably, based on the unidirectional control current command, energizing the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk, where the electromagnetic attraction force generated in the first and second axial magnetic bearing stator coils is directed, includes: The unidirectional control current command is input to the power amplifier module so that the power amplifier module supplies the actual power supply current corresponding to the unidirectional control current command to the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk, where the electromagnetic attraction force generated in the first axial magnetic bearing stator coil and the second axial magnetic bearing stator coil is directed.

[0010] Preferably, the power amplifier module includes a first power output channel and a second power output channel that are independent of each other. The first power output channel is connected to the first axial magnetic bearing stator coil, and the second power output channel is connected to the second axial magnetic bearing stator coil. The power amplification module is used to determine a target power output channel from the first power output channel and the second power output channel according to the symbol information carried by the unidirectional control current command or the coil selection signal corresponding to the unidirectional control current command, enable the target power output channel, and control the switching transistor in the other power output channel to be in the minimum conduction state or switch the other power output channel to a high impedance state.

[0011] Preferably, based on the axial offset, the variable parameter PID control algorithm is used to calculate the unidirectional control current command, including: Based on the axial offset, the variable parameter PID control algorithm is used to calculate the initial control current command. When the axial offset direction of the thrust plate is towards the stator coil of the first axial magnetic bearing, the initial control current command is positive; when the axial offset direction of the thrust plate is towards the stator coil of the second axial magnetic bearing, the initial control current command is negative. If the initial control current command is positive, then the absolute value of the initial control current command is determined as the unidirectional control current command of the second axial magnetic bearing stator coil; If the initial control current command is negative, then the absolute value of the initial control current command is determined as the unidirectional control current command of the first axial magnetic bearing stator coil.

[0012] Preferably, determining the absolute value of the initial control current command as the unidirectional control current command of the second axial magnetic bearing stator coil includes: The absolute value of the initial control current command is multiplied by the second preset compensation coefficient of the second axial magnetic bearing stator coil to obtain the unidirectional control current command of the second axial magnetic bearing stator coil. Determining the absolute value of the initial control current command as the unidirectional control current command for the stator coil of the first axial magnetic bearing includes: The absolute value of the initial control current command is multiplied by the first preset compensation coefficient of the first axial magnetic bearing stator coil to obtain the unidirectional control current command of the first axial magnetic bearing stator coil.

[0013] Preferably, it further includes: When the thrust disk is in the central equilibrium position, a preset excitation current is passed into the stator coil of the first axial magnetic bearing, and the actual value of the first test axial displacement after the thrust disk moves toward the stator coil of the first axial magnetic bearing is obtained. When the thrust disk is in the central equilibrium position, the preset excitation current is passed into the stator coil of the second axial magnetic bearing, and the actual value of the second test axial displacement after the thrust disk moves toward the stator coil of the second axial magnetic bearing is obtained. The first preset compensation coefficient and the second preset compensation coefficient are determined based on the ratio between the actual value of the first test axial displacement and the actual value of the second test axial displacement.

[0014] Preferably, before determining the absolute value of the initial control current command as the unidirectional control current command for the second axial magnetic bearing stator coil, the method further includes: When the current amplitude of the initial control current command is not greater than the preset maximum current threshold, the step of determining the absolute value of the initial control current command as the unidirectional control current command of the second axial magnetic bearing stator coil is entered. When the current amplitude of the initial control current command is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the second axial magnetic bearing stator coil. Before determining the absolute value of the initial control current command as the unidirectional control current command for the first axial magnetic bearing stator coil, the method further includes: When the current amplitude of the initial control current command is not greater than the preset maximum current threshold, the step of determining the absolute value of the initial control current command as the unidirectional control current command of the first axial magnetic bearing stator coil is initiated. When the current amplitude of the initial control current command is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the first axial magnetic bearing stator coil.

[0015] To solve the above-mentioned technical problems, the present invention provides a control device for a magnetic levitation bearing, comprising: Memory, used to store computer programs; A processor is used to implement the steps of the control method for magnetic levitation bearings as described above when executing a computer program.

[0016] This application provides a control method and device for a magnetic levitation bearing. The method determines the axial offset direction, axial offset amount, and axial offset velocity of the thrust disc relative to its central equilibrium position. Based on the actual axial displacement and axial offset velocity, and combined with preset operating condition switching rules, the proportional coefficient, integral coefficient, and derivative coefficient of a variable parameter PID control algorithm are set. A unidirectional control current command is calculated based on the axial offset amount, and energizes the stator coil of the axial magnetic bearing on the side opposite to the electromagnetic attraction direction and the axial offset direction. This controls the switching transistor in the power amplifier corresponding to the other coil to be in a minimum conduction state, allowing a standby current less than a preset current threshold to be supplied to the other coil, or de-energizing the other coil. When the thrust disc shifts relative to its central equilibrium position, energizing only one coil and supplying a lower standby current or directly de-energizing the other coil allows the thrust disc to return to its central equilibrium position while reducing losses and heat generation. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating a control method for a magnetic levitation bearing provided in this application; Figure 2 A schematic diagram of the structure of a magnetic levitation bearing provided in this application; Figure 3 A schematic diagram of the control system for a magnetic levitation bearing provided in this application; Figure 4 A schematic diagram of the control device for a magnetic levitation bearing provided in this application; Figure 5 This is a schematic diagram of the structure of a computer-readable storage medium provided in this application. Detailed Implementation

[0019] The core of this invention is to provide a control method and device for a magnetic levitation bearing. When the thrust disk deviates from the central equilibrium position, only one side of the coil is energized, while a lower standby current or direct de-energization is applied to the other side of the coil. This allows the thrust disk to return to the central equilibrium position while reducing losses and heat generation.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating a control method for a magnetic levitation bearing provided in this application. The magnetic levitation bearing has a first axial magnetic bearing stator coil 3 and a second axial magnetic bearing stator coil symmetrically arranged on both sides of the rotor's thrust disk. The method includes: S11: Obtain the actual value of the axial displacement of the thrust disk, and determine the axial offset direction and axial offset amount of the thrust disk relative to the central equilibrium position based on the actual value of the axial displacement and the axial displacement command value. In a magnetic levitation bearing, a first axial magnetic bearing stator coil 3 and a second axial magnetic bearing stator coil are symmetrically arranged on both sides of the rotor's thrust disk 9. The thrust disk 9 is typically a disc-shaped magnetically conductive structure fixed to the rotor shaft, with its end faces forming working air gaps with the end faces of the axial magnetic bearing stator cores on both sides. The first and second axial magnetic bearing stator coils 3 are wound on their respective stator cores. When current flows through the coils, the stator cores generate a magnetic field, producing an axial electromagnetic attraction force on the thrust disk 9. Please refer to... Figure 2 , Figure 2 This is a structural schematic diagram of a magnetic levitation bearing provided in this application. Figure 2 Taking a top view of a horizontal five-degree-of-freedom magnetic bearing as an example, the dashed line represents the axial direction of the horizontal five-degree-of-freedom magnetic bearing. Figure 2 The horizontal five-degree-of-freedom magnetic bearing shown includes a displacement sensor 1, a protective bearing 2, a first axial magnetic bearing stator coil 3, a second axial magnetic bearing stator core 4, the coil on the second axial magnetic bearing stator core 4 being the second axial magnetic bearing stator coil, and also includes a radial magnetic bearing coil 5, a radial magnetic bearing core 6, a motor stator coil 7, a motor rotor 8, and a thrust disk 9 on the motor rotor 8.

[0022] In an ideal suspended state, the thrust disk 9 should be located at the geometric center between the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil, i.e., the central equilibrium position. At this time, the axial air gaps on both sides of the thrust disk 9 are equal, and the axial net force on the thrust disk 9 is zero. However, in actual operation, due to load disturbances, rotor imbalance forces, or external impacts, the thrust disk 9 will shift axially. To monitor the position of the thrust disk 9 in real time, in this embodiment, displacement sensors 1, such as eddy current displacement sensors or inductive displacement sensors, are provided on one or both sides of the thrust disk 9. The displacement sensor detects the distance from its probe end face to the corresponding end face of the thrust disk 9 and outputs a voltage signal or digital signal proportional to the distance. Alternatively, displacement sensors 1 can be provided at the protective bearings 2 on both sides of the entire rotor structure, such as... Figure 2 As shown, displacement sensor 1 detects the distance from its probe end face to the corresponding end face of the protective bearing 2, and outputs a voltage signal or digital signal proportional to the distance. After receiving the sensor signal, processor 42 determines the actual axial displacement value of thrust disk 9, and calculates the current axial offset of thrust disk 9 relative to the central equilibrium position and its axial offset direction by combining it with the pre-calibrated axial displacement command value. For example, if the pre-calibrated axial displacement command value is... It is permissible but not limited to ordering =0, meaning the thrust disk 9 is positioned in the middle of the axial air gap between the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil, which is also the central equilibrium position. Since there is a certain gap between the displacement sensor 1 and the thrust disk 9 or the rotor, meaning the displacement sensor 1 is not in direct contact with the rotor or the thrust disk 9, the axial displacement value output by the displacement sensor 1 when the thrust disk 9 is in the central equilibrium position can be determined as 0, which corresponds to an axial displacement command value of 0. Displacement of the thrust disk 9 relative to the central equilibrium position is not desired. For example, when the thrust disk 9 is in the central equilibrium position, the displacement sensor 1 detects a distance of 'a' between itself and the thrust disk 9 or the rotor, and the actual axial displacement value is 0, consistent with the axial displacement command value of 0. No adjustment of the thrust disk 9's position is required. However, if the position of the thrust disk 9 deviates, such as when the displacement sensor 1 detects a distance of 'ab' between itself and the thrust disk 9 or the rotor, the actual axial displacement value is -b, and then adjustment of the thrust disk 9's position is necessary.

[0023] In this embodiment, the actual axial displacement of the thrust disk 9 is represented by z, then the axial offset e is... Here, it can be set that when the thrust disk 9 is offset towards the direction of the first axial magnetic bearing stator coil 3, the axial offset is positive; when the thrust disk 9 is offset towards the direction of the second axial magnetic bearing stator coil, the axial offset is negative. Of course, this application does not limit this.

[0024] S12: Determine the axial offset speed of the thrust disk based on the actual value of the axial displacement; S13: Based on the actual value of axial displacement and axial offset speed, and combined with preset working condition switching rules, set the proportional coefficient, integral coefficient and derivative coefficient of the variable parameter PID control algorithm; S14: Based on the axial offset, a variable parameter PID control algorithm is used to calculate the unidirectional control current command; After acquiring the axial offset of the thrust disk 9, the processor 42 calculates and generates a unidirectional control current command according to a preset control algorithm. Unlike the pair of current commands with opposite polarities in traditional differential control, the unidirectional control current command has only a single effective output polarity in any control cycle, that is, it is only used to drive the stator coil of the axial magnetic bearing on one side. Specifically, the unidirectional control current command can be calculated based on the axial offset using a PID (Proportional-Integral-Derivative) control algorithm or other feedback control laws. The amplitude of the unidirectional control current command reflects the magnitude of the electromagnetic attraction force required to pull the thrust disk 9 back to the center equilibrium position.

[0025] Specifically, the axial offset velocity dz / dt reflects the rate of change and movement trend of the thrust disk 9 in the axial direction. In practical implementation, the processor 42 can obtain the axial offset velocity dz / dt by performing a first-order numerical differentiation on the actual axial displacement value z. For example, the difference between the actual axial displacement value z(k) at the current sampling moment and the actual axial displacement value z(k-1) at the previous sampling moment can be divided by the sampling period T, i.e., dz / dt = [z(k) - z(k-1)] / T. To suppress the amplification effect of differentiation on high-frequency noise, the actual axial displacement value z can be pre-filtered. Based on this, the processor 42 can not only determine the degree of offset of the thrust disk 9 through the actual axial displacement value, but also determine the speed and direction of the thrust disk 9's movement through the axial offset velocity, thereby accurately determining the offset of the thrust disk 9.

[0026] After obtaining the actual axial displacement z and axial offset velocity dz / dt, the processor 42 uses a variable parameter PID control algorithm to calculate the unidirectional control current command. The basic control law of this variable parameter PID control algorithm can be expressed as: ; Unlike existing technologies, the scaling factor in this embodiment... Integral coefficient and differential coefficients Instead of being a fixed constant, these are variable parameters that are dynamically adjusted according to the current motion condition of the thrust disk 9. Through this variable parameter mechanism, the processor 42 can generate unidirectional control current commands by using control parameter combinations corresponding to the current motion condition under different disturbance intensities and different motion trends. This overcomes the inherent limitation of fixed-parameter PID control algorithms in that they cannot simultaneously achieve both response speed and stability when facing complex disturbances.

[0027] S15: Based on the unidirectional control current command, energize the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk, where the electromagnetic attraction force generated in the first and second axial magnetic bearing stator coils is opposite to the electromagnetic attraction force generated in the second axial magnetic bearing stator coil. Control the switching transistor in the power amplifier that supplies power to the other axial magnetic bearing stator coil to be in the minimum conduction state, so as to supply a standby current less than the preset current threshold to the other axial magnetic bearing stator coil or control the other axial magnetic bearing stator coil to be de-energized.

[0028] Upon receiving a unidirectional control current command, the processor 42 determines the target working coil that should be energized during the current control cycle based on the axial offset direction. Specifically, the processor 42 identifies the current axial offset direction of the thrust disk 9 and selects the axial magnetic bearing stator coil on the side opposite to the axial offset direction as the target working coil. For example, when the thrust disk 9 offsets towards the first axial magnetic bearing stator coil 3, it moves closer to the first axial magnetic bearing stator coil 3 and further away from the second axial magnetic bearing stator coil. In this case, the second axial magnetic bearing stator coil needs to generate an electromagnetic attraction pointing in the direction of the second axial magnetic bearing stator coil to pull the thrust disk 9 back to the central equilibrium position. Therefore, the processor 42 applies a unidirectional control current command to the second axial magnetic bearing stator coil. Conversely, when the thrust disk 9 offsets towards the second axial magnetic bearing stator coil, the processor 42 applies a unidirectional control current command to the first axial magnetic bearing stator coil 3.

[0029] During this process, for the stator coil of the axial magnetic bearing on the other side, which is in the same direction as the axial offset, the processor 42 switches it to an extremely low-power state. Specific implementation methods include, but are not limited to: completely de-energizing the coil on that side, making its current zero; or supplying a standby current with a very small amplitude, such as less than a preset current threshold, to the coil on that side, solely to maintain the minimum conduction state of the switching transistor in the power amplifier supplying the coil, thereby shortening the response delay of the next power-on, without generating an effective electromagnetic attraction force sufficient to affect the position of the thrust disk 9. Since the amplitude of this standby current is typically only in the milliampere range, it is negligible compared to the ampere-level bias current maintained in traditional differential control.

[0030] Based on this, in this embodiment, effective control current is injected into the corresponding single-sided coil only when the thrust plate 9 is axially offset and electromagnetic attraction is required to restore its position. When the thrust plate 9 is near the equilibrium position or only has a small disturbance, both coils can be in a de-energized or micro-current standby state, which eliminates the losses caused by the bias current that exists for a long time to maintain differential linearity, reduces the Joule heat generated during operation, effectively suppresses the temperature rise of the stator coil and surrounding components, and improves the stability and reliability of the magnetic levitation bearing during long-term operation.

[0031] In summary, when the thrust disk 9 shifts relative to the central equilibrium position, energizing only the coil on one side and supplying a lower standby current or de-energizing the coil on the other side can reduce losses and heat generation, allowing the thrust disk to return to the central equilibrium position. As a preferred embodiment, the preset operating condition switching rules include: If the absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are the same, then the proportional coefficient, integral coefficient, and derivative coefficient of the variable parameter PID control algorithm are set using the first parameter set with high stiffness and high damping characteristics. If the absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are not the same, then the proportional coefficient, integral coefficient and derivative coefficient of the variable parameter PID control algorithm are set using a second parameter set with high stiffness characteristics. If the absolute value of the actual axial displacement is not greater than the preset offset threshold, then the proportional coefficient, integral coefficient, and derivative coefficient of the variable parameter PID control algorithm are set using a third parameter set with high damping characteristics.

[0032] In this embodiment, the aforementioned preset operating condition switching rules specifically include the following three types of operating condition discrimination and parameter switching logic: Condition 1: The absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are the same.

[0033] First, a preset offset threshold zth is set to distinguish whether the thrust disk 9 is in a large or small offset state. For example, it can be set to 0.4C, where C is the axial clearance between the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil. Under this condition, the processor 42 first determines that the absolute value of the actual axial displacement of the thrust disk 9, |z|, is greater than the preset offset threshold zth. This indicates that the thrust disk 9 has significantly deviated from its central equilibrium position and is in a large offset state. Further, the processor 42 determines whether the vector direction of the axial offset velocity dz / dt is the same as that of the actual axial displacement value z. Specifically, this can be achieved by determining whether the product of the actual axial displacement value z and the axial offset velocity dz / dt is greater than zero. When this condition is met, it indicates that the instantaneous movement direction of the thrust disk 9 is consistent with its current axial offset direction, and the thrust disk 9 is continuing to move away from the central equilibrium position at a certain speed. This condition, characterized by a large degree of deviation and a continued increase in the degree of deviation, needs to be promptly curbed to prevent the thrust disk 9 from impacting the protective bearing 2 in a short period, leading to suspension failure or even mechanical damage. For this condition, the processor 42 will adjust the proportional coefficient of the variable parameter PID control algorithm. Integral coefficient and differential coefficients All parameters are switched to the first parameter set. The first parameter set has high stiffness and high damping characteristics to generate an electromagnetic attraction force to drive the thrust disk 9 back to resist the further deviation trend of the thrust disk 9, and to generate a damping force opposite to the axial offset velocity, effectively suppressing the inertia of the thrust disk 9 moving outward, avoiding overshoot oscillation that may be caused by stiffness acting alone, thereby curbing the deterioration trend of offset in a short time and pulling the thrust disk 9 back to the central equilibrium position, reducing the risk of hard contact of the protection bearing 2.

[0034] Condition 2: The absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are not the same.

[0035] Under this condition, the processor 42 first confirms that the absolute value of the actual axial displacement of the thrust disk 9, |z|, is greater than the preset offset threshold zth, meaning the thrust disk 9 is still in a state of significant offset. However, unlike condition one, the processor 42 further determines that the vector directions of the axial offset velocity dz / dt and the actual axial displacement value z are not the same, that is, the product of the actual axial displacement value z and the axial offset velocity dz / dt is less than or equal to zero. When this condition is met, it indicates that although the thrust disk 9 is currently far from the central equilibrium position, its instantaneous direction of motion has reversed, meaning that the thrust disk 9 is returning to the central equilibrium position. This condition typically occurs during the return phase after the thrust disk 9 reaches its maximum offset position, or during the return phase after the control system has successfully curbed the outward movement trend. At this time, the direct risk of the thrust disk 9 impacting the protective bearing 2 has been reduced. It is sufficient to pull the thrust disk 9 back to the central equilibrium position as quickly as possible, without applying excessive damping to the return motion to avoid slowing down the return speed. For this condition, the processor 42 will adjust the proportional coefficient of the variable parameter PID control algorithm... Integral coefficient and differential coefficients Switching to the second parameter set with high stiffness characteristics provides a continuous and powerful electromagnetic attraction for regression. Since it does not have high damping characteristics, it avoids providing a large damping force that would hinder the thrust disk 9 from quickly returning to the center equilibrium position. This ensures that the thrust disk 9 can quickly converge from the large offset position to the center equilibrium position, while avoiding unnecessary energy consumption and lag in the regression process, thus improving the dynamic response efficiency and energy utilization efficiency of the system.

[0036] Condition 3: The absolute value of the actual axial displacement is not greater than the preset offset threshold.

[0037] Under this condition, the processor 42 determines that the absolute value of the actual axial displacement of the thrust disk 9, |z|, is less than or equal to the preset offset threshold zth. This indicates that the thrust disk 9 is currently in a small offset region near the central equilibrium position, i.e., in a state of minor offset. Within this region, the risk of the thrust disk 9 impacting the protective bearing 2 is extremely low. Based on this, the processor 42 switches the parameters of the variable parameter PID control algorithm to the third parameter set. The third parameter set has high damping characteristics, effectively absorbing and dissipating the energy of small vibrations, enabling the thrust disk 9 to quickly stabilize at the central equilibrium position and suppress oscillations.

[0038] In a preferred embodiment, the high stiffness characteristic is achieved by taking the maximum proportional coefficient and the maximum integral coefficient. For high damping characteristics, the differential coefficient is taken as the maximum differential coefficient.

[0039] In this embodiment, the high stiffness characteristic specifically refers to the proportional coefficient in the variable parameter PID control algorithm. Set to the preset maximum scaling factor, and simultaneously set the integral factor. Set to the preset maximum integral coefficient. In a magnetic levitation bearing control system, the proportional coefficient... This directly determines the response strength of the control current to the position offset, i.e., the magnitude of the current command corresponding to a unit offset. A larger proportional coefficient indicates a higher system sensitivity to position deviation, a stronger restoring electromagnetic attraction generated by processor 42, and a stronger ability of the thrust disk 9 to resist deviation from the center position. Integral coefficient This determines the response strength of the processor 42 to historical accumulated deviations. Its function is to eliminate steady-state errors and ensure that the thrust disk 9 can accurately return and stabilize at the central equilibrium position when subjected to continuous unidirectional disturbances. Based on this, when the thrust disk 9 is in a large-scale offset state, the large deviation can be eliminated as soon as possible, preventing the thrust disk 9 from further deviating or impacting the protective bearing 2.

[0040] High damping characteristics specifically refer to the differential coefficients in the variable parameter PID control algorithm. The maximum differential coefficient is set to a preset value. In a magnetic levitation bearing control system, the differential coefficient... The response strength of the control current to the axial offset speed is determined. When the thrust disk 9 moves outward rapidly, the larger differential coefficient will immediately generate a current component that hinders its continued acceleration and prevents it from further increasing the degree of offset.

[0041] It should be noted that the proportional, integral, and derivative coefficients of the variable parameter PID control algorithm in Working Condition 1 have high stiffness and high damping characteristics. Therefore, the proportional coefficient in Working Condition 1... The preset maximum proportional coefficient and integral coefficient The maximum integral coefficient and differential coefficient are preset. The maximum derivative coefficient is preset; the proportional coefficient, integral coefficient, and derivative coefficient of the variable parameter PID control algorithm in Working Condition 2 have high stiffness characteristics, so the proportional coefficient in Working Condition 2... The preset maximum proportional coefficient and integral coefficient The maximum integral coefficient and differential coefficient are preset. The preset conventional differential coefficients are sufficient; these conventional differential coefficients are less than the maximum differential coefficient. In operating condition three, the proportional, integral, and derivative coefficients of the variable parameter PID control algorithm exhibit high damping characteristics. Therefore, the proportional coefficient in operating condition three... The preset standard scaling factor is sufficient; if the standard scaling factor is less than the maximum scaling factor, the integral factor will be used. The preset conventional integral coefficients are sufficient; the conventional integral coefficients are less than the maximum integral coefficients, and the differential coefficients are... The maximum differential coefficient is preset.

[0042] It should also be noted that the maximum proportional coefficient, maximum integral coefficient and maximum differential coefficient mentioned above are all design values ​​that are pre-tuned offline and stored in the processor 42 based on the mechanical parameters, electrical parameters and power amplifier capacity of the specific magnetic levitation bearing system. These maximum values ​​are not theoretically infinite, but reasonable upper limits determined through experimental analysis.

[0043] As a preferred embodiment, based on a unidirectional control current command, energizing the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk 9, where the electromagnetic attraction force generated in the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil is directed, includes: The unidirectional control current command is input to the power amplifier module so that the power amplifier module supplies the actual power supply current corresponding to the unidirectional control current command to the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk 9, where the electromagnetic attraction force generated in the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil is directed.

[0044] In a preferred embodiment, the power amplifier module includes a first power output channel and a second power output channel that are independent of each other. The first power output channel is connected to the first axial magnetic bearing stator coil, and the second power output channel is connected to the second axial magnetic bearing stator coil. The power amplifier module is used to determine the target power output channel from the first power output channel and the second power output channel according to the symbol information carried by the unidirectional control current command or the coil selection signal corresponding to the unidirectional control current command, enable the target power output channel, and control the switching transistor in the other power output channel to be in the minimum conduction state or switch the other power output channel to the high impedance state.

[0045] After the processor 42 completes the calculation and generation of the unidirectional control current command, it inputs the unidirectional control current command into the power amplifier module. The power amplifier module is a key interface component connecting the digital signal domain of the processor 42 and the analog power domain of the magnetic bearing coil. Its main function is to convert the low-energy control signal output by the processor 42 into a high-energy actual power supply current capable of driving the axial magnetic bearing stator coil. In this embodiment, the power amplifier module can be a switching power amplifier, such as an H-bridge circuit or a half-bridge circuit based on pulse width modulation technology, or a linear power amplifier. The power amplifier module internally contains at least two independent power output channels, respectively connected to the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil.

[0046] Upon receiving a unidirectional control current command, the power amplifier module determines the target power output channel to be activated based on the coil selection signal provided by the processor 42, or based on the symbol information carried in the unidirectional control current command itself. Specifically, when the unidirectional control current command is determined to correspond to driving the first axial magnetic bearing stator coil 3, the power amplifier module only enables the power output channel connected to the first axial magnetic bearing stator coil 3, injecting an actual supply current corresponding to the amplitude of the unidirectional control current command into that coil; simultaneously, the power output channel connected to the second axial magnetic bearing stator coil is disabled or switched to a high-impedance state, resulting in no effective control current flowing through the second axial magnetic bearing stator coil. Conversely, when the unidirectional control current command corresponds to driving the second axial magnetic bearing stator coil, the power amplifier module only supplies the actual supply current to the second axial magnetic bearing stator coil, while the first axial magnetic bearing stator coil 3 remains de-energized or only receives a very small standby current.

[0047] As a preferred embodiment, based on the axial offset, a variable parameter PID control algorithm is used to calculate the unidirectional control current command, including: Based on the axial offset, a variable parameter PID control algorithm is used to calculate the initial control current command. When the axial offset direction of the thrust disk 9 is towards the first axial magnetic bearing stator coil 3, the initial control current command is positive; when the axial offset direction of the thrust disk 9 is towards the second axial magnetic bearing stator coil, the initial control current command is negative. If the initial control current command is positive, then the absolute value of the initial control current command is determined as the unidirectional control current command of the second axial magnetic bearing stator coil. If the initial control current command is negative, then the absolute value of the initial control current command is determined as the unidirectional control current command of the first axial magnetic bearing stator coil 3.

[0048] In this embodiment, after acquiring the axial offset e of the thrust disk 9 relative to the central equilibrium position, the processor 42 first calculates an initial control current command according to a preset control law. The initial control current command The amplitude reflects the magnitude of the electromagnetic attraction force required to pull the thrust disk 9 back to the center equilibrium position. The larger the amplitude, the stronger the pull-back electromagnetic force that needs to be applied.

[0049] Initial control current command There is a preset and clear mapping relationship between the symbol and the axial offset direction of the thrust disk 9. Specifically, when the axial offset direction of the thrust disk 9 is towards the stator coil 3 of the first axial magnetic bearing, the initial control current command... It is assigned a positive value, that is... When the axial offset direction of the thrust disk 9 is toward the stator coil of the second axial magnetic bearing, the initial control current command is executed. It is assigned a negative value, that is... Of course, this application is not limited to such a convention. This notation convention establishes a unified reference coordinate system at the software level of processor 42, enabling processor 42 to not only respond to initial control current instructions... Determining the required current amplitude information also allows us to determine which side the thrust disk 9 is currently biased to.

[0050] The initial control current command carrying signed information is obtained through calculation. Then, the processor 42 further determines the sign of the instruction and, based on the determination result, sets the initial control current instruction accordingly. The unidirectional control current command is assigned to the stator coil of the corresponding axial magnetic bearing.

[0051] If the initial control current command A positive value indicates that the thrust disk 9 is currently offset towards the first axial magnetic bearing stator coil 3. Since the electromagnetic bearing only generates attraction and not repulsion, to pull the thrust disk 9 back to its central equilibrium position, the electromagnetic attraction generated by the coil currently furthest from the thrust disk 9—the second axial magnetic bearing stator coil—is needed to perform the pull-back action. However, in this embodiment, the symbolic mapping relationship is pre-defined as follows: when the thrust disk 9 is offset towards the first axial magnetic bearing stator coil 3... A positive value indicates that the positive current command corresponds to energizing the coil capable of generating a reverse pull-back force. Since the thrust disk 9 is biased towards the first axial magnetic bearing stator coil 3, the actual force pulling it back comes from the second axial magnetic bearing stator coil on the opposite side; therefore, current needs to be applied to the second axial magnetic bearing stator coil. Accordingly, when the processor 42 recognizes the initial control current command... When it is positive, the initial control current command will be... The absolute value is directly determined as the unidirectional control current command for the stator coil of the second axial magnetic bearing.

[0052] Conversely, if the initial control current command A negative value indicates that the thrust disk 9 is currently deflected towards the second axial magnetic bearing stator coil. Based on the same physical principle, the electromagnetic attraction generated by the first axial magnetic bearing stator coil 3 is needed to pull the thrust disk 9 back. Since the symbol convention corresponds to the thrust disk 9 being biased towards the second axial magnetic bearing stator coil side, and the source of the pull-back force should be the first axial magnetic bearing stator coil 3 on the opposite side, the processor 42 will take the absolute value of the initial control current command with this negative value and determine this absolute value as the unidirectional control current command for the first axial magnetic bearing stator coil 3. In the actual control program implementation, this negative value command can also be directly used as the command input for the first axial magnetic bearing stator coil 3, and the subsequent power amplification module will automatically identify the energizing channel based on the command symbol.

[0053] As a preferred embodiment, determining the absolute value of the initial control current command as the unidirectional control current command of the second axial magnetic bearing stator coil includes: The absolute value of the initial control current command is multiplied by the second preset compensation coefficient of the second axial magnetic bearing stator coil to obtain the unidirectional control current command of the second axial magnetic bearing stator coil. The absolute value of the initial control current command is determined as the unidirectional control current command for the first axial magnetic bearing stator coil 3, including: The absolute value of the initial control current command is multiplied by the first preset compensation coefficient of the first axial magnetic bearing stator coil 3 to obtain the unidirectional control current command of the first axial magnetic bearing stator coil 3.

[0054] In practical magnetic levitation bearing systems, due to factors such as manufacturing tolerances, assembly errors, batch differences in the permeability of the core material, slight deviations in the number of coil turns, and uneven temperature distribution, the actual electromagnetic attraction forces generated on the thrust plate 9 by the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil when the same amplitude current is applied may not be completely equal. Therefore, if the corresponding coil is driven directly with an uncompensated initial control current command, it may cause asymmetry in the recovery electromagnetic attraction force felt by the thrust plate 9 during forward and reverse offsets, thereby leading to a decrease in the accuracy of the thrust plate 9 levitation control.

[0055] Based on this, this embodiment introduces a preset compensation coefficient when generating the unidirectional control current command. Specifically, when the processor 42 determines that the initial control current command is positive and its absolute value needs to be determined as the unidirectional control current command for the second axial magnetic bearing stator coil, it does not directly output the initial control current command as the final command. Instead, it first multiplies the absolute value of the initial control current command by the second preset compensation coefficient corresponding to the second axial magnetic bearing stator coil, and uses the product as the unidirectional control current command applied to the second axial magnetic bearing stator coil. Similarly, when the processor 42 determines that the initial control current command is negative and its absolute value needs to be determined as the unidirectional control current command for the first axial magnetic bearing stator coil 3, it first multiplies the absolute value of the negative value by the first preset compensation coefficient corresponding to the first axial magnetic bearing stator coil 3, and uses the product as the unidirectional control current command applied to the first axial magnetic bearing stator coil 3.

[0056] By introducing a preset compensation coefficient in the command output stage, the problem of asymmetrical output caused by individual differences between the two coils is effectively eliminated. This ensures that no matter which direction the thrust plate 9 deviates or which coil performs the pull-back action, a consistent restoring electromagnetic attraction force can be applied to the thrust plate 9 to ensure that the thrust plate 9 is pulled back to the central equilibrium position.

[0057] As a preferred embodiment, it also includes: When the thrust disk 9 is in the central equilibrium position, a preset excitation current is passed into the first axial magnetic bearing stator coil 3, and the actual value of the first test axial displacement after the thrust disk 9 moves toward the first axial magnetic bearing stator coil 3 is obtained. When the thrust disk 9 is in the central equilibrium position, a preset excitation current is passed into the stator coil of the second axial magnetic bearing, and the actual value of the second test axial displacement after the thrust disk 9 moves toward the stator coil of the second axial magnetic bearing is obtained. The first preset compensation coefficient and the second preset compensation coefficient are determined based on the ratio between the actual value of the first test axial displacement and the actual value of the second test axial displacement.

[0058] In the magnetic levitation bearing system, when the thrust disk 9 is in a free-floating state, if a certain amplitude of excitation current is passed to the stator coil of the axial magnetic bearing on one side, the coil on that side will generate an axial electromagnetic attraction force on the thrust disk 9, causing the thrust disk 9 to move in the direction of the coil on that side. The axial displacement generated by the thrust disk 9 under this excitation reflects the current-force characteristics of the coil on that side. Based on this, the first preset compensation coefficient and the second preset compensation coefficient are determined in this embodiment.

[0059] First, the thrust disk 9 is stably suspended at the central equilibrium position using the levitation control function of the magnetic levitation bearing system itself. At this time, the axial clearance between the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil and the corresponding end face of the thrust disk 9 are both rated clearances, that is, half of the axial clearance between the first axial magnetic bearing stator coil 3 and the second axial magnetic bearing stator coil, and the axial net force on the thrust disk 9 is zero. After confirming that the thrust disk 9 is stable at the central equilibrium position, the processor 42 temporarily switches to the test mode. In the test mode, the processor 42 supplies a preset excitation current with a known amplitude to the first axial magnetic bearing stator coil 3, while keeping the second axial magnetic bearing stator coil in a de-energized or zero-current state. The amplitude of this preset excitation current should be selected to be sufficient to generate an observable axial displacement, but not so that the thrust disk 9 displacement exceeds the safe travel range or impacts the protective bearing 2. After the first axial magnetic bearing stator coil 3 is energized, the thrust disk 9 will move towards the first axial magnetic bearing stator coil 3 under the action of electromagnetic attraction. After the displacement of the thrust disk 9 reaches a new steady-state equilibrium, the processor 42 reads and records the axial position of the thrust disk 9 at this time through the displacement sensor 1, and records the offset of this position relative to the central equilibrium position as the actual value of the first test axial displacement.

[0060] After acquiring the actual value of the first test axial displacement, the processor 42 first de-energizes the first axial magnetic bearing stator coil 3 and restarts the levitation control function to stabilize the thrust disk 9 back in the central equilibrium position, thus eliminating the disturbance to the system state caused by the previous test. Once the thrust disk 9 has stabilized, the processor 42 re-enters the test mode. This time, the processor 42 supplies a preset excitation current with the same amplitude as the previous test to the second axial magnetic bearing stator coil, while keeping the first axial magnetic bearing stator coil 3 de-energized or in a zero-current state. Similarly, the thrust disk 9 will move towards the second axial magnetic bearing stator coil under the action of electromagnetic attraction. After the displacement stabilizes, the processor 42 reads and records the offset of the thrust disk 9 relative to the central equilibrium position, recording it as the actual value of the second test axial displacement.

[0061] After obtaining the actual values ​​of the first and second test axial displacements, the processor 42 calculates the ratio between them and determines the first and second preset compensation coefficients accordingly. Based on this, under the same excitation current amplitude, if the displacement of the thrust disk 9 to one side is larger, it indicates that the actual electromagnetic attraction force generated by the coil on that side under unit current is stronger, that is, the current-force gain of the coil on that side is higher. In order to make the coils on both sides produce symmetrical restoring force effects under the same command current, it is necessary to apply a compensation coefficient less than 1 to the coil on the side with higher gain to weaken its current command, or apply a compensation coefficient greater than 1 to the coil on the side with lower gain to enhance its current command.

[0062] In a specific embodiment, the first axial magnetic bearing stator coil 3 can be set as the reference, i.e., the first preset compensation coefficient = 1. In this case, the second preset compensation coefficient is determined based on the ratio of the two measured displacement values ​​as the actual value of the first test axial displacement / the actual value of the second test axial displacement. That is, if the actual value of the first test axial displacement is greater than the actual value of the second test axial displacement, it indicates that the output capacity of the first axial magnetic bearing stator coil 3 is stronger than that of the second axial magnetic bearing stator coil. To make the second axial magnetic bearing stator coil produce the same output force as the first axial magnetic bearing stator coil 3, the absolute value of the current command input to the second axial magnetic bearing stator coil needs to be multiplied by the second preset compensation coefficient for amplification. In another embodiment, the second axial magnetic bearing stator coil can also be set as the reference, i.e., the second preset compensation coefficient = 1, then the first preset compensation coefficient = the actual value of the second test axial displacement / the actual value of the first test axial displacement.

[0063] As a preferred embodiment, before determining the absolute value of the initial control current command as the unidirectional control current command for the second axial magnetic bearing stator coil, the method further includes: When the current amplitude of the initial control current command is not greater than the preset maximum current threshold, proceed to the step of determining the absolute value of the initial control current command as the unidirectional control current command of the second axial magnetic bearing stator coil. When the current amplitude of the initial control current command is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the second axial magnetic bearing stator coil. Before determining the absolute value of the initial control current command as the unidirectional control current command for the first axial magnetic bearing stator coil 3, the following steps are also included: When the current amplitude of the initial control current command is not greater than the preset maximum current threshold, the step of determining the absolute value of the initial control current command as the unidirectional control current command of the first axial magnetic bearing stator coil 3 is entered. When the current amplitude of the initial control current command is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the first axial magnetic bearing stator coil 3.

[0064] In the actual operation of the magnetic levitation bearing system, both the power amplifier module and the axial magnetic bearing stator coil have their own safe operating ranges. The power amplifier module, limited by the rated current of its internal power switching devices, heat dissipation conditions, and bus voltage, has a maximum allowable continuous output current value. If excessive current is applied to the axial magnetic bearing stator coil for an extended period, it will cause excessive coil temperature rise, accelerating insulation aging and even triggering inter-turn short circuit faults. To ensure system hardware safety and prevent overcurrent damage, current limiting protection is implemented in this embodiment.

[0065] When the processor 42 determines that a unidirectional control current command needs to be output to the second axial magnetic bearing stator coil during the current control cycle, before sending the unidirectional control current command to the power amplifier module, it first compares the calculated current amplitude of the initial control current command with a preset maximum current threshold. The preset maximum current threshold is a safe current upper limit determined based on, but not limited to, the rated output capacity of the power amplifier module and the rated current carrying capacity of the axial magnetic bearing stator coil.

[0066] If the current amplitude of the initial control current command is determined to be no greater than the preset maximum current threshold, it indicates that the unidirectional control current command is within the safe operating range allowed by the system hardware. At this time, the processor 42 normally enters the subsequent process, determines the absolute value of the initial control current command as the unidirectional control current command of the second axial magnetic bearing stator coil, and outputs it to the power amplifier module to drive the corresponding coil.

[0067] However, if the current amplitude of the initial control current command exceeds the preset maximum current threshold, it indicates that the current amplitude corresponding to the initial control current command calculated by the processor 42 has exceeded the range that the system hardware can safely withstand. In this case, if the over-limit command is directly output, it may trigger the overcurrent protection of the power amplifier module, causing a shutdown, or cause the coil to overheat and be damaged. Therefore, the processor 42 determines the preset maximum current threshold as the unidirectional control current command of the second axial magnetic bearing stator coil, that is, within the current control cycle, the target coil is driven with the maximum safe current that the system can provide.

[0068] Alternatively, the absolute value of the initial control current command can be multiplied by a second preset compensation coefficient, and the current amplitude of the resulting product can be compared with a preset maximum current threshold. If the resulting product is not greater than the preset maximum current threshold, the absolute value of the product is determined as the unidirectional control current command of the second axial magnetic bearing stator coil. If the resulting product is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the second axial magnetic bearing stator coil. This application does not limit this.

[0069] Similarly, when the processor 42 determines that a unidirectional control current command needs to be output to the first axial magnetic bearing stator coil 3, it compares the current amplitude of the initial control current command with the same preset maximum current threshold. If the current amplitude is not greater than the preset maximum current threshold, the subsequent process proceeds normally, and the absolute value of the initial control current command is determined as the unidirectional control current command for the first axial magnetic bearing stator coil 3; if the amplitude is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command for the first axial magnetic bearing stator coil 3.

[0070] Alternatively, the initial control current command can be multiplied by a first preset compensation coefficient, and the current amplitude of the resulting product can be compared with a preset maximum current threshold. If the resulting product is not greater than the preset maximum current threshold, the absolute value of the product is determined as the unidirectional control current command of the first axial magnetic bearing stator coil 3. If the resulting product is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the first axial magnetic bearing stator coil 3. This application does not limit this.

[0071] Please refer to Figure 3 , Figure 3 This is a schematic diagram of a control system for a magnetic levitation bearing provided in this application. The magnetic levitation bearing has a first axial magnetic bearing stator coil 3 and a second axial magnetic bearing stator coil symmetrically arranged on both sides of the rotor's thrust disk 9. The system includes: The acquisition unit 31 is used to acquire the actual value of the axial displacement of the thrust disk 9, and to determine the axial offset direction and axial offset amount of the thrust disk 9 relative to the central equilibrium position based on the actual value of the axial displacement and the axial displacement command value. Command generation unit 32 is used to generate unidirectional control current commands based on axial offset. The energizing unit 33 is used to energize the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk 9, based on a unidirectional control current command, and to supply a standby current less than a preset current threshold to the other axial magnetic bearing stator coil or to control the other axial magnetic bearing stator coil to be de-energized.

[0072] For a description of the control system for the magnetic levitation bearing provided by this invention, please refer to the above method embodiments; the invention itself will not be described in detail here.

[0073] Please refer to Figure 4 , Figure 4 This is a schematic diagram of a control device for a magnetic levitation bearing provided in this application. The device includes: Memory 41 is used to store computer programs; The processor 42 is used to implement the steps of the control method for the magnetic levitation bearing described above when executing a computer program.

[0074] For a description of the control device for the magnetic levitation bearing provided by the present invention, please refer to the above method embodiments; the present invention will not be described again here.

[0075] Please refer to Figure 5 , Figure 5This is a schematic diagram of a computer-readable storage medium provided in this application. The computer-readable storage medium 51 stores a computer program 52. When the computer program 52 is executed by the processor 42, it implements the steps of the control method for the magnetic levitation bearing as described above.

[0076] For a description of the computer-readable storage medium provided by the present invention, please refer to the above method embodiments; the present invention will not be described again here.

[0077] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a magnetic levitation bearing, characterized in that, In a magnetic levitation bearing, a first axial magnetic bearing stator coil and a second axial magnetic bearing stator coil are symmetrically arranged on both sides of the thrust disk of the rotor. The method includes: Obtain the actual value of the axial displacement of the thrust disk, and determine the axial offset direction and axial offset amount of the thrust disk relative to the central equilibrium position based on the actual value of the axial displacement and the axial displacement command value. The axial offset velocity of the thrust disk is determined based on the actual value of the axial displacement; Based on the actual value of the axial displacement and the axial offset speed, the proportional coefficient, integral coefficient and derivative coefficient of the variable parameter PID control algorithm are set in combination with the preset working condition switching rules. Based on the axial offset, the variable parameter PID control algorithm is used to calculate the unidirectional control current command; Based on the unidirectional control current command, energize the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk, where the electromagnetic attraction generated in the first and second axial magnetic bearing stator coils is opposite to the electromagnetic attraction generated in the first and second axial magnetic bearing stator coils. Control the switching transistor in the power amplifier supplying power to the other axial magnetic bearing stator coil to be in the minimum conduction state, so as to supply a standby current less than a preset current threshold to the other axial magnetic bearing stator coil, or control the other axial magnetic bearing stator coil to be de-energized.

2. The control method for a magnetic levitation bearing as described in claim 1, characterized in that, The preset operating condition switching rules include: If the absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are the same, then the proportional coefficient, integral coefficient, and derivative coefficient of the variable parameter PID control algorithm are set using a first parameter set with high stiffness and high damping characteristics. If the absolute value of the actual axial displacement is greater than the preset offset threshold, and the vector directions of the axial offset velocity and the actual axial displacement are not the same, then the proportional coefficient, integral coefficient and derivative coefficient of the variable parameter PID control algorithm are set using a second parameter set with high stiffness characteristics. If the absolute value of the actual axial displacement is not greater than the preset offset threshold, then the proportional coefficient, integral coefficient, and derivative coefficient of the variable parameter PID control algorithm are set using a third parameter set with high damping characteristics.

3. The control method for a magnetic levitation bearing as described in claim 2, characterized in that, The high stiffness characteristic is that the proportional coefficient is the maximum proportional coefficient and the integral coefficient is the maximum integral coefficient; The high damping characteristic is achieved by taking the maximum differential coefficient.

4. The control method for a magnetic levitation bearing as described in claim 1, characterized in that, Based on the unidirectional control current command, energizing the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk, where the electromagnetic attraction force generated in the first and second axial magnetic bearing stator coils is directed, includes: The unidirectional control current command is input to the power amplifier module so that the power amplifier module supplies the actual power supply current corresponding to the unidirectional control current command to the axial magnetic bearing stator coil on the side opposite to the axial offset direction of the thrust disk, where the electromagnetic attraction force generated in the first axial magnetic bearing stator coil and the second axial magnetic bearing stator coil is directed.

5. The control method for a magnetic levitation bearing as described in claim 4, characterized in that, The power amplifier module includes a first power output channel and a second power output channel that are independent of each other. The first power output channel is connected to the first axial magnetic bearing stator coil, and the second power output channel is connected to the second axial magnetic bearing stator coil. The power amplification module is used to determine a target power output channel from the first power output channel and the second power output channel according to the symbol information carried by the unidirectional control current command or the coil selection signal corresponding to the unidirectional control current command, enable the target power output channel, and control the switching transistor in the other power output channel to be in the minimum conduction state or switch the other power output channel to a high impedance state.

6. The control method for a magnetic levitation bearing as described in any one of claims 1 to 5, characterized in that, Based on the axial offset, the unidirectional control current command is calculated using the variable parameter PID control algorithm, including: Based on the axial offset, the variable parameter PID control algorithm is used to calculate the initial control current command. When the axial offset direction of the thrust plate is towards the stator coil of the first axial magnetic bearing, the initial control current command is positive; when the axial offset direction of the thrust plate is towards the stator coil of the second axial magnetic bearing, the initial control current command is negative. If the initial control current command is positive, then the absolute value of the initial control current command is determined as the unidirectional control current command of the second axial magnetic bearing stator coil; If the initial control current command is negative, then the absolute value of the initial control current command is determined as the unidirectional control current command of the first axial magnetic bearing stator coil.

7. The control method for a magnetic levitation bearing as described in claim 6, characterized in that, Determining the absolute value of the initial control current command as the unidirectional control current command for the stator coil of the second axial magnetic bearing includes: The absolute value of the initial control current command is multiplied by the second preset compensation coefficient of the second axial magnetic bearing stator coil to obtain the unidirectional control current command of the second axial magnetic bearing stator coil. Determining the absolute value of the initial control current command as the unidirectional control current command for the stator coil of the first axial magnetic bearing includes: The absolute value of the initial control current command is multiplied by the first preset compensation coefficient of the first axial magnetic bearing stator coil to obtain the unidirectional control current command of the first axial magnetic bearing stator coil.

8. The control method for a magnetic levitation bearing as described in claim 7, characterized in that, Also includes: When the thrust disk is in the central equilibrium position, a preset excitation current is passed into the stator coil of the first axial magnetic bearing, and the actual value of the first test axial displacement after the thrust disk moves toward the stator coil of the first axial magnetic bearing is obtained. When the thrust disk is in the central equilibrium position, the preset excitation current is passed into the stator coil of the second axial magnetic bearing, and the actual value of the second test axial displacement after the thrust disk moves toward the stator coil of the second axial magnetic bearing is obtained. The first preset compensation coefficient and the second preset compensation coefficient are determined based on the ratio between the actual value of the first test axial displacement and the actual value of the second test axial displacement.

9. The control method for a magnetic levitation bearing as described in claim 6, characterized in that, Before determining the absolute value of the initial control current command as the unidirectional control current command for the stator coil of the second axial magnetic bearing, the method further includes: When the current amplitude of the initial control current command is not greater than the preset maximum current threshold, the step of determining the absolute value of the initial control current command as the unidirectional control current command of the second axial magnetic bearing stator coil is entered. When the current amplitude of the initial control current command is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the second axial magnetic bearing stator coil. Before determining the absolute value of the initial control current command as the unidirectional control current command for the first axial magnetic bearing stator coil, the method further includes: When the current amplitude of the initial control current command is not greater than the preset maximum current threshold, the step of determining the absolute value of the initial control current command as the unidirectional control current command of the first axial magnetic bearing stator coil is initiated. When the current amplitude of the initial control current command is greater than the preset maximum current threshold, the preset maximum current threshold is determined as the unidirectional control current command of the first axial magnetic bearing stator coil.

10. A control device for a magnetic levitation bearing, characterized in that, include: Memory, used to store computer programs; A processor, configured to, when executing the computer program, implement the steps of the control method for a magnetic levitation bearing as described in any one of claims 1 to 9.

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