A full-magnetic suspension system based on bidirectional active axial force of rotor and a control method thereof

Abstract

The application discloses a full magnetic suspension system based on bidirectional active axial force of a rotor and a control method thereof. The full magnetic suspension system is provided with an axial force winding 3, and a magnetic field rotating synchronously with the rotor generated on the winding can generate stable axial forces in two directions of attraction and repulsion to compensate for axial hydraulic force. The size and direction of the active axial force generated on the rotor can be actively controlled through the current on the axial force winding 3. The active Maxwell force and the Lorentz force in the axial direction are active suspension forces, and together with passive magnetic resistance force, form a composite axial suspension force. The application can effectively improve the axial stiffness by increasing the active axial force. The control method provided by the application can make the axial force of the rotor have good dynamic response speed, and has better anti-interference ability compared with passive suspension. The active axial electromagnetic suspension system greatly improves the stability performance of the magnetic suspension pump in the axial direction.

Description

Technical Field

[0001] This invention relates to a magnetic circuit structure and control method for a magnetic levitation pump, and particularly to a multi-degree-of-freedom electromagnetic levitation system and its control method based on the bidirectional active axial force of the rotor. Background Technology

[0002] Currently, magnetic levitation centrifugal pumps are widely used in semiconductor manufacturing, high-purity chemicals, and biomedicine. Their core suspension drive system can be regarded as a bearingless permanent magnet thin-film motor. As a fluid power source, it can reduce pollution in magnetic levitation centrifugal pumps, and therefore is widely used in high-purity fluid systems.

[0003] Magnetic levitation centrifugal pumps exhibit two degrees of active levitation in the radial direction, two degrees of passive levitation in the inclined direction, active control in the rotational direction, and passive levitation in the axial direction. The residual axial hydraulic force on the impeller of a magnetic levitation pump must be compensated for by a passive axial electromagnetic force. Because magnetic levitation pumps require sealing and liquid transport, the air gap in their magnetic circuit is wider than that of bearingless slab motors, resulting in weaker axial passive stiffness. Therefore, when the impeller is subjected to significant hydrostatic pressure or dynamic reaction force, it may experience axial displacement, even colliding with the pump casing, or vibrating due to axial impact, potentially leading to vibration or even instability in some cases. Therefore, improving axial stiffness and axial controllability is essential.

[0004] At the application level, most magnetic levitation centrifugal pumps on the market currently achieve axial levitation through passive suspension. Some researchers have improved the axial passive stiffness of magnetic levitation electromagnetic systems by altering the magnetic circuit topology, such as using magnetic bearings of the same polarity to increase the bias flux. However, increasing axial passive stiffness weakens some key performance characteristics, such as reducing output torque.

[0005] While increased passive stiffness can compensate for higher hydrostatic pressure, it still cannot resist axial impacts caused by fluid reaction forces. Therefore, active axial control is needed to enhance axial disturbance resistance. However, currently, there is no magnetic circuit structure that meets the requirements of magnetic levitation pumps for active axial control. For example, the presence of an active axial bearing would significantly increase the axial length of the magnetic levitation pump, and existing active axial rotary motors cannot meet the requirements for radial active levitation. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention provides a fully magnetic levitation system and its control method based on the rotor's bidirectional active axial force. This invention embeds the proposed active axial electromagnetic levitation system into the magnetic circuit of a magnetic levitation pump to achieve active axial control. The magnetic field generated on the stator rotates with the rotor, producing stable attractive and repulsive axial forces to compensate for the axial hydraulic force. The axial electromagnetic force consists of active Maxwell force, Lorentz force, and passive magnetic reluctance. By increasing the active axial force, the axial stiffness can be effectively improved, and the proposed control method can give the rotor's axial force excellent damping effect and dynamic response capability, exhibiting better anti-interference capability compared to the original passive levitation.

[0007] The technical solution of the present invention is as follows:

[0008] I. A Full Magnetic Levitation System Based on Bidirectional Active Axial Force of the Rotor

[0009] The full magnetic levitation system includes a rotor, a figure-7 shaped silicon steel assembly, an axial force winding, a suspension winding, a drive winding, and a bottom circular silicon steel assembly;

[0010] The 7-shaped silicon steel assembly is fixedly installed on the bottom circular silicon steel. The rotor is located in the middle of the upper end of the 7-shaped silicon steel assembly. The 7-shaped silicon steel assembly has a drive winding and a suspension winding wound from bottom to top. The axial force winding is fixedly installed in the 7-shaped silicon steel assembly above the suspension winding. The central axis of the axial force winding is perpendicular to the central axis of the rotor. The rotor is located on the side and above the axial force winding.

[0011] The 7-shaped silicon steel assembly comprises multiple 7-shaped silicon steel bars, which are fixedly installed at equal intervals along the circumference on the bottom circular silicon steel bar. Within each 7-shaped silicon steel bar, from bottom to top, a drive winding fixing frame, a suspension winding fixing frame, and an axial force winding fixing frame are sequentially fixedly installed. A drive coil is wound in the drive winding fixing frame, a suspension coil is wound in the suspension winding fixing frame, and a hollow coil is wound in the axial force winding fixing frame. The hollow coil is located inside the axial force winding fixing frame, and its central axis is perpendicular to the central axis of the rotor. The rotor is positioned between the inner surfaces of the upper ends of the multiple 7-shaped silicon steel bars. The drive winding is composed of all the drive coils in the 7-shaped silicon steel assembly, the suspension winding is composed of all the suspension coils in the 7-shaped silicon steel assembly, and the axial force winding is composed of all the hollow coils in the 7-shaped silicon steel assembly.

[0012] The 7-shaped silicon steel group consists of 8 7-shaped silicon steel bars, each of which is equipped with a corresponding hollow coil. Two adjacent hollow coils form a group of axial force coils, and four hollow coils form four groups of axial force coils. The axial force coils of non-adjacent groups are the same phase winding, and the hollow coils of the same phase winding are connected in series.

[0013] The rotor is a pair of parallel radially magnetized poles, and the number of pole pairs of the drive winding and the axial force winding are the same as the number of pole pairs of the rotor.

[0014] The number of phases and pole pairs of the drive winding and the axial force winding are the same.

[0015] The levitation winding is a two-phase, two-pole winding.

[0016] II. A Control Method for a Full Maglev System Based on Bidirectional Active Axial Force of the Rotor

[0017] 1) Collect the actual displacement and actual angle of the rotor along the z-axis, and calculate the actual angular velocity of rotor 1 based on the actual angle;

[0018] 2) Based on the given displacement and actual displacement of the z-axis, the PID controller calculates and outputs the given current signal of the d-axis for controlling the axial force winding;

[0019] 3) Input the desired q-axis current signal, desired d-axis current signal, actual q-axis current signal, actual d-axis current signal, and actual angular velocity of the rotor together into the floating current feedforward decoupling PI controller. The floating current feedforward decoupling PI controller outputs the desired q-axis voltage signal and desired d-axis voltage signal of the axial force winding.

[0020] 4) Calculate the actual voltage U acting on phase a winding in the axial force winding based on the actual rotor angle, the desired q-axis voltage signal of the axial force winding, and the desired d-axis voltage signal. a The actual voltage U on phase b and the winding b This allows us to obtain the actual current i on phase a winding of the axial force winding. a and the actual current i on phase b winding b This causes the axial force winding to generate an active electromagnetic force that acts on the rotor, thereby achieving axial control of the rotor.

[0021] 5) Calculate the actual current signals of the q-axis and d-axis based on the actual angle of the rotor, the actual current signals of the a-phase winding and the actual current signals of the b-phase winding in the axial force winding, and input them into the floating current feedforward decoupling PI controller;

[0022] 6) Repeat steps 1)-5) to continuously control the rotor axially.

[0023] Specifically, 4) refers to:

[0024] Based on the actual rotor angle, the desired voltage signal U of the a-phase winding of the axial force winding is output after performing an inverse Parker transform on the q-axis desired voltage signal and the d-axis given voltage signal of the axial force winding. a The desired voltage signal U of the * and b phase windings b *;

[0025] The desired voltage signal U of the a-phase winding of the axial force winding a The desired voltage signal U of the * and b phase windings b *After passing through a digital-to-analog converter with bipolar output and a DC power amplifier, the actual voltage U on phase a winding of the axial force winding is obtained. a and the actual voltage U on phase b winding b This allows us to obtain the actual current i on phase a winding of the axial force winding. a and the actual current i on phase b winding b This causes the axial force winding to generate electromagnetic force and act on the rotor, thereby achieving axial control of the rotor.

[0026] Specifically, 5) refers to:

[0027] Based on the actual angle of the rotor, the actual current signals on phase a and phase b of the axial force winding are transformed by Parker transformation to obtain the actual current signals on the q-axis and d-axis, which are then input into the floating current feedforward decoupling PI controller.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention, while ensuring the levitation and driving performance of the magnetic levitation pump, proposes an electromagnetic structure that enables the rotor to generate a stable active axial force. An axial force winding is introduced into the original system's magnetic circuit structure. The magnetic flux direction of this winding to generate the axial force is perpendicular to the magnetic flux direction in the original system, allowing for the generation of an independently controllable axial force. Furthermore, this structure does not increase the axial length of the original electromagnetic system. In this invention, the current flowing simultaneously aligns the directions of the active Maxwell force and Lorentz force generated by the rotor, maximizing the efficiency of active electromagnetic force generation. The axial electromagnetic system can provide active electromagnetic force on top of the passive magnetic reluctance experienced by the rotor, thereby significantly improving the system's axial stiffness. Moreover, after active axial control, the axial damping effect of the rotor can be greatly improved, and axial vibration can be suppressed, effectively enhancing the system's anti-interference capability. Attached Figure Description

[0030] Figure 1 This is a partial cross-sectional view of the overall structure of the electromagnetic levitation drive system.

[0031] Figure 2 This is a schematic diagram of the winding method for a two-phase axial force winding.

[0032] Figure 3 This is a diagram illustrating the active axial electromagnetic force and its generation principle.

[0033] Figure 4 This is a diagram illustrating the passive axial magnetic reluctance and its generation principle.

[0034] Figure 5 This is a schematic diagram of the control principle of an active axial electromagnetic levitation system.

[0035] Figure 6 This is a schematic diagram of the winding method of the radial suspension winding of an electromagnetic system.

[0036] Figure 7 This is a schematic diagram of the winding method for an electromagnetic system driving a levitation winding.

[0037] In the diagram: rotor 1, 7-shaped silicon steel 2, axial force winding 3, axial force winding fixing bracket 4a, suspension winding fixing bracket 4b, drive winding fixing bracket 4c, suspension winding 5, drive winding 6, bottom circular silicon steel 7. Detailed Implementation

[0038] The invention will be further described below with reference to the accompanying drawings.

[0039] like Figure 1 As shown, the system includes rotor 1, 7-shaped silicon steel assembly, axial force winding 3, suspension winding 5, drive winding 6, and bottom circular silicon steel 7.

[0040] A 7-shaped silicon steel assembly is fixedly mounted on the bottom circular silicon steel 7. The rotor 1 is located in the middle of the upper part of the 7-shaped silicon steel assembly. From bottom to top, the 7-shaped silicon steel assembly contains a drive winding 6 and a suspension winding 5. The axial force winding 3 is fixedly mounted in the 7-shaped silicon steel assembly above the suspension winding 5. In practice, the central axes of the drive winding 6 and the suspension winding 5 coincide, but the axes of the suspension winding and the drive winding can also be offset, i.e., not coincident. The axial force winding 3 is perpendicular to the central axis of the rotor 1, and the rotor 1 is located to the side and above the axial force winding 3. The drive winding 6 and the axial force winding 3 have the same number of phases and pole pairs. The rotor 1 is a pair of parallel poles radially magnetized, forming a pair-pole magnetic circuit structure. The number of pole pairs in the axial force winding 3 and the drive winding 6 is always consistent with the number of pole pairs in the rotor; it is a two-phase, one-pole winding. The suspension winding 5 is a two-phase, two-pole winding.

[0041] The 7-shaped silicon steel assembly includes multiple 7-shaped silicon steels 2, which are fixedly installed at equal intervals along the circumference on the bottom circular silicon steel 7. In each 7-shaped silicon steel 2, a drive winding fixing frame 4c, a suspension winding fixing frame 4b, and an axial force winding fixing frame 4a are fixedly installed on the outside of the 7-shaped silicon steel 2 from bottom to top. A drive coil is wound in the drive winding fixing frame 4c, and a suspension coil is wound in the suspension winding fixing frame 4b. The central axes of the drive coil and the suspension coil coincide and are parallel to the axial direction of the bottom circular silicon steel 7. A hollow coil is wound in the axial force winding fixing frame 4a. The hollow coil is located inside the axial force winding fixing frame 4a and is installed under the protrusion on the upper part of the 7-shaped silicon steel 2. The central axis of the hollow coil is perpendicular to the central axis of the rotor 1. The central axes of the hollow coils in the multiple 7-shaped silicon steel 2 point to the same center, that is, the central axes of the hollow coils are equally spaced to form a circle. The rotor 1 is located between the inner sides of the upper ends of the multiple 7-shaped silicon steel 2, specifically above and to the side of the hollow coils. The drive winding 6 is composed of all the drive coils in the 7-shaped silicon steel group, the suspension winding 5 is composed of all the suspension coils in the 7-shaped silicon steel group, and the axial force winding 3 is composed of all the hollow coils in the 7-shaped silicon steel group. The axial force winding 3 is a two-phase, two-pole winding. The energized axial force winding 3 can generate an axial suspension force of arbitrary direction and magnitude for the rotor. The 7-shaped silicon steel group can provide the rotor with a passive magnetic resistance opposite to the displacement direction, thereby pulling the rotor 1 back to its initial position and keeping the rotor stable.

[0042] The 7-shaped silicon steel assembly consists of eight 7-shaped silicon steel bars 2. Each of the eight 7-shaped silicon steel bars 2 is equipped with a corresponding hollow coil. Two adjacent hollow coils form a group of axial force coils, and the eight hollow coils form four groups of axial force coils. The axial force coils in non-adjacent groups are the same phase winding, that is, the axial force coils in adjacent groups are different phase windings. The hollow coils of the same phase winding are connected in series. For example Figure 2 As shown, in the axial force winding 3, the four coils of one phase winding are located on one side of I and II, and V and VI of the 7-shaped stator silicon steel 2, respectively. The four coils of the other phase winding are located on one side of III, IV, VII, and VIII. The four coils of the same phase winding are connected in series to form one phase, and the winding direction is as follows. Figure 2 As shown.

[0043] In a full magnetic levitation drive system, there are many possible combinations of stator teeth, pole pairs, and phases, and the selection of stator teeth, pole pairs, and phases for this full magnetic levitation system is not limited to these. In this system, the number of pole pairs and phases of the axial force winding and the drive winding are completely consistent and are represented using the same variables. Therefore, all possible configurations of a bearingless thin-plate motor with a maximum of 12 teeth are summarized, but the summary has the following limitations: the design of the axial force winding, drive winding, and suspension winding is limited to a maximum of three phases, and the configuration of windings of the same type is consistent. After removing combinations that are theoretically feasible but not practical, the combinations of parameters are presented in a table, as shown in the table below.

[0044] Table 1. Configuration of parameters in the full maglev drive system

[0045]

[0046] N: Number of teeth; p i : Extreme logarithm; t i : Winding type (A: Asymmetric winding distribution; S: Symmetric winding distribution); m i :Phase number;

[0047] q i The number of stator slots per pole in each phase, i=1 indicates axial force winding 3 and drive winding 6, i=2 indicates suspension winding 5.

[0048] Figure 3 This is a schematic diagram of the active axial electromagnetic force. Active axial electromagnetic force can be divided into active Maxwell force and active Lorentz force.

[0049] Active Maxwell force is generated through the interaction between the leakage flux of the permanent magnet and the winding flux generated by the axial force winding. This allows the leakage flux density of the permanent magnet to reach its fundamental frequency. The initial phase and the magnetic flux density fundamental wave of the axial force winding in the air gap Keep the initial phase consistent. Let be the spatial position angle of the rotor. Therefore, the expression for the linear analytical model of the Maxwell force in the active axis is:

[0050]

[0051] Among them, F M Let represent the active axial Maxwell force, l be the effective rotor length, r be the rotor radius, k1 be the active Maxwell force model correction coefficient, and μ0 be the free permeability. and These represent the fundamental wave amplitudes of the permanent magnet leakage flux and the axial force winding, respectively. θ M The angle between the active Maxwell force and the magnetic field. F represents the effective magnetic flux generated by the axial force winding, p1 represents the number of pole pairs of the axial force winding, i1 represents the amplitude of the current flowing through the axial force winding, and N1 represents the effective number of series turns per phase of the axial force winding. Therefore, regardless of the rotor's rotational position, F M All of them are linearly related to i1.

[0052] The active Lorentz force is generated by the interaction between the leakage flux of the permanent magnet and the effective side of the axial force winding. This allows the leakage flux density of the permanent magnet to reach its fundamental frequency. The initial phase and the fundamental current density of the axial force winding The initial phase remains consistent. Therefore, the linear analytical model of the active axial Lorentz force can be expressed as follows:

[0053]

[0054] Among them, F L k2 represents the active axial Lorentz force, and k2 represents the active Lorentz force model correction coefficient. θ represents the fundamental amplitude of the current density on the effective side of the axial force winding. L To generate the angle between the active Lorentz force and the magnetic field. Among them, Therefore, no matter what position the rotor rotates to, F L All of them are linearly related to i1.

[0055] In summary, the active axial electromagnetic force F atv =F M +F L It is linearly related to the current amplitude i1 passed through the axial force winding, and the active Maxwell force model correction coefficient k1 and the active Lorentz force model correction coefficient k2 can be determined by experiments or simulations.

[0056] Figure 4 This is a schematic diagram of the passive axial magnetic reluctance principle. Within the linear range, the passive magnetic reluctance acting on the rotor is directly proportional to the rotor's axial displacement. Whenever the rotor experiences axial displacement, it is subjected to a force in the opposite direction and proportional in magnitude, pulling the rotor back to its initial position and thus restoring it to its equilibrium position. Since the rotor is sinusoidally magnetized, the fundamental magnetic flux density at its air gap can be expressed as... Therefore, the linear analytical model expression for the passive axial magnetic reluctance is:

[0057]

[0058] Among them, F psv This represents the passive axial magnetic resistance, where L is the effective length of the rotor. δ represents the fundamental wave amplitude of the permanent magnet's magnetic flux density, δ is the air gap width, Δz is the axial displacement, and k3 represents the passive magnetoresistive model correction coefficient. The passive magnetoresistive model correction coefficient k3 can be determined through simulation or experiment.

[0059] A control method for a fully magnetic levitation system based on bidirectional active axial force of the rotor includes the following steps:

[0060] 1) Collect the actual displacement and actual angle of rotor 1 along the z-axis, and calculate the actual angular velocity of rotor 1 based on the actual angle; In specific implementation, the laser displacement sensor is used to detect the actual displacement of rotor 1 along the z-axis, and the differential orthogonally distributed linear Hall sensor is used to detect and calculate the angle and angular velocity of rotor 1.

[0061] 2) Based on the desired z-axis displacement and the actual z-axis displacement, the PID controller calculates and outputs the desired d-axis current signal for controlling the axial force winding 3;

[0062] 3) The desired q-axis current signal, desired d-axis current signal, actual q-axis current signal, actual d-axis current signal, and actual angular velocity of rotor 1 are input together into the floating current feedforward decoupling PI controller, where the desired q-axis current signal is 0, used to achieve static decoupling of the dq-axis currents. The floating current feedforward decoupling PI controller outputs the desired q-axis voltage signal and the desired d-axis voltage signal of the axial force winding 3.

[0063] 4) Calculate the actual voltage U acting on phase a winding in the axial force winding based on the actual angle of rotor 1, the desired voltage signal along the q-axis of the axial force winding 3, and the desired voltage signal along the d-axis. a The actual voltage U on phase b and the winding b This allows us to obtain the actual current i on phase a winding of axial force winding 3. a and the actual current i on phase b winding b i a and i b This causes the axial force winding 3 to generate electromagnetic force and act on the rotor 1, thereby achieving axial control of the rotor 1;

[0064] 4) Specifically:

[0065] Based on the actual angle of rotor 1, the desired voltage signal U of phase a winding of axial force winding 3 is output after performing Parker inverse transformation on the desired voltage signal of q-axis and the given voltage signal of d-axis. a The desired voltage signal U of the * and b phase windings b *;

[0066] The desired voltage signal U of phase a winding of axial force winding 3 a The desired voltage signal U of the * and b phase windings b*After passing through a bipolar digital-to-analog converter (DAC) with both positive and negative outputs and a DC power amplifier, the actual voltage U on phase a winding of axial force winding 3 is obtained. a and the actual voltage U on phase b winding b The digital-to-analog converter (DAC) outputs two continuously variable analog voltage signals, with the output voltage values ​​corresponding to the desired voltage signal values ​​of the two-phase windings. The DC power amplifier amplifies the voltage values ​​and significantly enhances the current driving capability, which is then used to drive the two-phase axial force windings. This allows the actual current i on phase a of the axial force winding 3 to be obtained. a and the actual current i on phase b winding b i a and i b This causes the axial force winding 3 to generate an active electromagnetic force and act on the rotor 1, thereby achieving axial control of the rotor 1.

[0067] 5) Based on the actual angle of rotor 1 and the actual current signal i on phase a winding of axial force winding 3. a and the actual current signal i on phase b winding b The actual q-axis current signal and the actual d-axis current signal are calculated and input into the floating current feedforward decoupling PI controller;

[0068] 5) Specifically:

[0069] Based on the actual angle of rotor 1, the actual current signal i on phase a winding of axial force winding 3 is... a and the actual current signal i on phase b winding b After performing the Parker transformation, the actual current signals of the q-axis and d-axis are obtained and input into the floating current feedforward decoupling PI controller.

[0070] 6) Repeat steps 1)-5) to continuously control rotor 1 axially.

[0071] like Figure 5As shown, the outer loop of the control block diagram is the position loop, and the inner loop is the current loop. They are used for controlling the z-axis position and the current in the axial force winding, respectively. The deviation of the z-axis displacement is converted into a current control signal after passing through the PID controller. According to the above derivation process, only the d-axis current is needed to control the active axial force, and the q-axis current is 0. The d-axis current signal is controlled by the current loop, which can make the actual current output reach the desired value to complete the control of the axial active electromagnetic levitation system. The controller output of this system is realized through the system's built-in bipolar analog-to-digital converter (DAC). After the output signal is amplified by the DC power amplifier, it can drive the windings of the electromagnetic system. In this system, each phase winding has a current sensor for detecting current, an angle sensing module for detecting the rotor's angular position and speed information, and displacement detection sensors such as laser displacement sensors or eddy current sensors for detecting the rotor's axial position.

[0072] Figure 6 (a) and (b) are respectively the winding methods of the levitation winding in the electromagnetic system of the entire magnetic levitation pump. Figure 7 (a) and (b) show the winding methods of the drive windings in the entire magnetic levitation pump electromagnetic system, respectively. The active axial electromagnetic levitation system proposed in this invention needs to be used in conjunction with this system to achieve stable and controllable axial electromagnetic force output in both levitation and rotation states.

Claims

1. A fully magnetic levitation system based on bidirectional active axial force of a rotor, characterized in that, It includes a rotor (1), a 7-shaped silicon steel assembly, an axial force winding (3), a suspension winding (5), a drive winding (6), and a bottom circular silicon steel assembly (7); The 7-shaped silicon steel assembly is fixedly installed on the bottom circular silicon steel (7). The rotor (1) is located in the middle of the upper end of the 7-shaped silicon steel assembly. The 7-shaped silicon steel assembly is wound with a drive winding (6) and a suspension winding (5) from bottom to top. The axial force winding (3) is fixedly installed in the 7-shaped silicon steel assembly above the suspension winding (5). The central axis of the axial force winding (3) is perpendicular to the central axis of the rotor (1). The rotor (1) is located on the side above the axial force winding (3). The 7-shaped silicon steel assembly includes multiple 7-shaped silicon steel bars (2), which are fixedly installed at equal intervals along the circumference on the bottom circular silicon steel bar (7). Each 7-shaped silicon steel bar (2) has a drive winding fixing frame (4c), a suspension winding fixing frame (4b), and an axial force winding fixing frame (4a) fixedly installed from bottom to top on its exterior. A drive coil is wound in the drive winding fixing frame (4c), a suspension coil is wound in the suspension winding fixing frame (4b), and an axial force winding... A hollow coil is wound in the fixed frame (4a). The hollow coil is located inside the axial force winding fixed frame (4a). The central axis of the hollow coil is perpendicular to the central axis of the rotor (1). The rotor (1) is located between the inner sides of the upper ends of multiple 7-shaped silicon steel (2). The drive winding (6) is composed of all the drive coils in the 7-shaped silicon steel group. The suspension winding (5) is composed of all the suspension coils in the 7-shaped silicon steel group. The axial force winding (3) is composed of all the hollow coils in the 7-shaped silicon steel group.

2. The all-magnetic levitation system based on the bidirectional active axial force of the rotor according to claim 1, characterized in that, The 7-shaped silicon steel group consists of 8 7-shaped silicon steels (2). Each of the 8 7-shaped silicon steels (2) is equipped with a corresponding hollow coil. Two adjacent hollow coils form a group of axial force coils. The 8 hollow coils form four groups of axial force coils. The axial force coils of non-adjacent groups are the same phase winding. The hollow coils of the same phase winding are connected in series.

3. The all-magnetic levitation system based on the bidirectional active axial force of the rotor according to claim 1, characterized in that, The rotor (1) is radially magnetized with a pair of parallel poles, and the number of pole pairs of the drive winding (6) and the axial force winding (3) are the same as the number of pole pairs of the rotor (1).

4. The all-magnetic levitation system based on the bidirectional active axial force of the rotor according to claim 1, characterized in that, The number of phases and pole pairs of the drive winding (6) and the axial force winding (3) are the same.

5. A fully magnetic levitation system based on bidirectional active axial force of a rotor according to claim 1, characterized in that, The suspension winding (5) is a two-phase, two-pole winding.

6. A control method for a fully magnetic levitation system based on bidirectional active axial force of a rotor according to any one of claims 1-5, characterized in that, Includes the following steps: 1) Collect the actual displacement and actual angle of the z-axis of the rotor (1), and calculate the actual angular velocity of the rotor 1 based on the actual angle; 2) Based on the given displacement of the z-axis and the actual displacement of the z-axis, the PID controller calculates and outputs the given current signal of the d-axis for controlling the axial force winding (3); 3) Input the desired q-axis current signal, desired d-axis current signal, actual q-axis current signal, actual d-axis current signal, and actual angular velocity of the rotor (1) together into the floating current feedforward decoupling PI controller. The floating current feedforward decoupling PI controller outputs the desired q-axis voltage signal and desired d-axis voltage signal of the axial force winding (3). 4) Calculate the actual voltage U acting on phase a winding in the axial force winding based on the actual angle of rotor (1), the desired voltage signal of q-axis of axial force winding (3), and the desired voltage signal of d-axis. a The actual voltage U on phase b and the winding b Thus, the actual current i on phase a winding of axial force winding (3) is obtained. a and the actual current i on phase b winding b This causes the axial force winding (3) to generate an active electromagnetic force and act on the rotor (1), thereby achieving axial control of the rotor (1). 5) Calculate the actual current signal of the q-axis and the actual current signal of the d-axis based on the actual angle of the rotor (1), the actual current signal of the a-phase winding and the actual current signal of the b-phase winding in the axial force winding (3), and input them into the floating current feedforward decoupling PI controller; 6) Repeat steps 1)-5) to continuously control the rotor (1) axially.

7. The control method for a fully magnetic levitation system based on bidirectional active axial force of a rotor according to claim 6, characterized in that, Specifically, 4) refers to: Based on the actual angle of the rotor (1), the desired voltage signal U of the a-phase winding of the axial force winding (3) is output after performing the Parker inverse transformation on the q-axis desired voltage signal and the d-axis given voltage signal. a The desired voltage signal U of the * and b phase windings b *; The desired voltage signal U of phase a winding of axial force winding (3) a The desired voltage signal U of the * and b phase windings b After passing through a digital-to-analog converter with bipolar output and a DC power amplifier, the actual voltage U on phase a winding of axial force winding (3) is obtained. a and the actual voltage U on phase b winding b Thus, the actual current i on phase a winding of axial force winding (3) is obtained. a and the actual current i on phase b winding b This causes the axial force winding (3) to generate electromagnetic force and act on the rotor (1), thereby achieving axial control of the rotor (1).

8. The control method for a fully magnetic levitation system based on bidirectional active axial force of a rotor according to claim 6, characterized in that, Specifically, 5) refers to: Based on the actual angle of the rotor (1), the actual current signal on phase a and phase b of the axial force winding (3) is transformed by Parker transformation to obtain the actual current signal on the q-axis and the actual current signal on the d-axis, which are then input into the floating current feedforward decoupling PI controller.

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