Integrated winding based bearingless permanent magnet synchronous axial flow pump and control method thereof

Abstract

The application discloses a bearingless permanent magnet synchronous axial flow pump based on integrated winding and a control method thereof. The claw pole type stator comprises a plurality of claw pole units, each claw pole unit has a stator tooth extending in the axial direction and a claw head extending in the radial direction from the end of the stator tooth, and the inner surfaces of all the claw heads enclose a working air gap opposite to the outer surface of the rotor; the torque winding and the suspension force winding are wound on the stator tooth together, share the same axial winding space, and the electrical phase sequences of the two sets of windings are independent; the suspension force winding is configured to pass through two groups of currents with opposite phase sequences; the pose sensor is arranged in the radial gap between adjacent claw heads; by collecting the position sensor in real time, the magnetic pole state of each claw head is dynamically adjusted by controlling the currents of the torque winding and the suspension force winding, and the driving torque and the controllable radial suspension force are generated simultaneously. The application solves the problems of complex structure and insufficient control precision of the existing magnetic suspension pump, and has the characteristics of compact structure, high control precision and fast dynamic response.

Description

Technical Field

[0001] This invention relates to the field of bearingless magnetic levitation drive technology, and more specifically to a bearingless permanent magnet synchronous axial flow pump based on integrated windings and its control method. Background Technology

[0002] Traditional axial flow pumps mostly use mechanical bearings to support the rotor, which suffers from problems such as frictional loss, the need for lubrication, and limited lifespan. Although magnetic levitation axial flow pumps, which have emerged in recent years, have solved the contact wear problem, most still use independent suspension windings and torque winding structures. This discrete winding layout not only leads to complex system structure, large size, and low power density, but also limits further miniaturization and integration design at the manufacturing level.

[0003] In addition, existing technologies for levitation force control mostly employ open-loop or semi-closed-loop strategies, resulting in slow dynamic response and limited control accuracy, which makes it difficult to meet the needs of modern high-dynamic, high-precision, and miniaturized application scenarios.

[0004] Therefore, how to provide a bearingless permanent magnet synchronous axial flow pump with compact structure, high control precision, and fast dynamic response, and its control method, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed to provide a bearingless permanent magnet synchronous axial flow pump based on integrated winding and a control method thereof that overcomes or at least partially solves the above problems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, embodiments of the present invention provide a bearingless permanent magnet synchronous axial flow pump based on integrated windings, comprising: a claw-pole stator, a rotor, a posture sensor, and a controller; wherein; The claw-pole stator includes multiple claw-pole units, each claw-pole unit having stator teeth extending axially and claw heads extending radially inward from the ends of the stator teeth, the inner surfaces of all the claw heads forming a working air gap opposite to the outer surface of the rotor. The torque winding and the levitation winding are wound together on the stator teeth, sharing the same axial winding space, and the electrical phase sequence of the torque winding and the levitation winding is independent; the levitation winding is configured to carry two sets of currents with opposite phase sequences. The pose sensor is arranged in the radial gap between adjacent claw heads; The controller is electrically connected to the position sensor, the torque winding, and the levitation force winding, respectively, and is used to dynamically adjust the magnetic pole state of each claw by controlling the current of the torque winding and the levitation force winding through real-time acquisition of the position sensor data, so as to simultaneously generate driving torque and controllable radial levitation force.

[0007] Preferably, the posture sensor includes a displacement sensor and an angle sensor; the controller is electrically connected to the displacement sensor and the angle sensor respectively; the displacement sensor is used to detect the radial displacement of the rotor; the angle sensor is used to detect the angular position of the rotor.

[0008] Preferably, the number of permanent magnet pole pairs PM of the rotor and the number of pole pairs PS of the levitation winding satisfy the following levitation force generation condition: PS = PM ± 1.

[0009] Preferably, the number of permanent magnet pole pairs of the rotor is PM=1, the number of pole pairs of the torque winding is PT=1, and the number of pole pairs of the levitation winding is PS=2.

[0010] Preferably, the current flowing through the levitation winding includes two rotating magnetic field current components with equal amplitude, opposite rotation directions, and pole pairs (PM+1) and (PM-1) respectively, and the two rotating magnetic field current components are symmetrically distributed relative to the rotor.

[0011] Secondly, embodiments of the present invention also provide a bearingless permanent magnet synchronous axial flow pump control method for the bearingless permanent magnet synchronous axial flow pump provided in the first aspect, comprising the following steps: Sensor signal acquisition: Real-time acquisition of rotor pose signals detected by the pose sensor; Suspension force closed-loop control command synthesis: The rotor position signal is compared with the preset displacement reference value, and the target suspension force command is obtained by combining the field orientation control principle; Based on the air gap flux observation value, the actual suspension force generated at present is calculated in real time by combining the suspension force mathematical model of Maxwell stress method; The target suspension force command is compared with the actual suspension force, and the suspension force winding current command is generated after calculation. Torque control command synthesis: The rotor position signal is acquired, compared with the preset speed reference value, and the target torque current command is obtained by combining the field-oriented control principle; Execution and Modulation: Based on the levitation force winding current command and the target torque current command, the levitation force winding and the torque winding are driven by space vector pulse width modulation to dynamically control the magnetomotive force of each stator claw head, thereby realizing the levitation closed-loop control of the rotor's radial and axial positions, as well as the continuous adjustable control of the axial flow pump speed.

[0012] Preferably, it further includes: acquiring the rotor radial displacement signal detected by the displacement sensor in real time; comparing the rotor radial displacement signal with a preset displacement reference value, and obtaining the target levitation force command by combining the magnetic field orientation control principle.

[0013] Preferably, it further includes: acquiring rotor angular position and speed signals detected by the angle sensor in real time; comparing the rotor angular position and speed signals with a preset speed reference value, and obtaining a target torque current command by combining the magnetic field orientation control principle.

[0014] Preferably, the real-time calculation of the currently generated actual levitation force is specifically obtained by using the Maxwell tensor method, which is calculated by back-calculation based on the observed air gap flux and levitation winding current.

[0015] Preferably, when using the mathematical model of levitation force based on Maxwell's stress method for calculation, the air gap flux includes: rotor flux, flux generated by torque winding current and flux generated by levitation force winding current.

[0016] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following: This invention achieves a deep physical integration of magnetic levitation and drive functions by integrating the torque winding and levitation force winding into the same tooth of a claw-pole stator in a common-slot concentrated winding configuration. This structure completely eliminates the structural redundancy and volume expansion caused by the spatial separation of the two windings in traditional bearingless motors, providing a foundation for miniaturization and lightweight design.

[0017] This invention employs a dual-closed-loop strategy combining Direct Suspension Force Control (DFC) based on Maxwell's tensor method and Field Oriented Control (FOC) to achieve direct and rapid closed-loop adjustment of the rotor's radial suspension force. Experiments show that this scheme can maintain stable suspension of the rotor under no-load and loaded conditions, with the peak-to-peak value of its radial displacement fluctuation controlled within ±10μm, exhibiting rapid dynamic response and no overshoot.

[0018] At the rated operating point (20W, 3000rpm), the overall system efficiency of this invention exceeds 74%. This is mainly due to the integrated winding structure, which reduces end and copper losses, as well as the optimized pole pair configuration and rotor length-to-diameter ratio, which achieves high electromagnetic torque density and low losses while ensuring sufficient suspension stiffness.

[0019] In summary, the integrated structure and closed-loop control strategy of this invention effectively solve the problems of complex structure and insufficient control precision of existing magnetic levitation pumps, achieving a breakthrough in the field of miniaturized, high-efficiency, and high-precision magnetic levitation power systems. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 The integrated winding arrangement diagram of the bearingless permanent magnet synchronous axial flow pump provided by the present invention; Figure 2 The diagram shows the claw-pole stator structure of the bearingless permanent magnet synchronous axial flow pump provided by this invention. Figure 3 A schematic diagram showing the positional relationship between the rotor and claw-pole stator of the bearingless permanent magnet synchronous axial flow pump provided by the present invention. Figure 4 Axial cross-sectional view of the bearingless permanent magnet synchronous axial flow pump provided by the present invention; Figure 5 This is a schematic diagram of the winding connection provided by the present invention; Figure 6 A schematic diagram of the axial flow pump topology provided by the present invention; Figure 7 This is a schematic diagram of the vector control scheme provided by the present invention; Figure 8 The torque control block diagram provided by the present invention; Figure 9 The levitation force control block diagram provided by the present invention; Figure 10 This is a schematic diagram of the magnetic pull-XY radial displacement characteristics provided by the present invention; Figure 11 This is a schematic diagram of the magnetic pull-Z-axis displacement characteristics provided by the present invention; Figure 12 A schematic diagram of the electromagnetic force-XY radial current characteristics provided by the present invention; Figure 13 A schematic diagram of the electromagnetic force-Z-axis current characteristics provided by the present invention. Detailed Implementation

[0022] 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, and 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.

[0023] This invention is not only applicable to miniaturized, high-efficiency fluid transport propulsion systems, but can also be widely used in high-precision suspension control, contactless transmission and high-performance magnetic levitation power systems, especially suitable for medical and industrial equipment applications with high requirements for dynamic response, positioning accuracy and operational reliability.

[0024] This invention discloses a bearingless permanent magnet synchronous axial flow pump based on integrated windings, comprising: a claw-pole stator 1, a rotor 2, a position sensor 3, and a controller; wherein, like Figures 1-2 As shown, the claw-pole stator 1 includes multiple claw-pole units, each claw-pole unit having stator teeth 11 extending axially and claw heads 12 extending radially inward from the ends of stator teeth 11. The inner surfaces of all claw heads 12 form a working air gap opposite to the outer surface of the rotor 2. The torque winding 4 and the levitation winding 5 are wound together on the stator teeth 11, sharing the same axial winding space, and the torque winding 4 and the levitation winding 5 have independent electrical phase sequences. The levitation winding 5 is configured to carry two sets of currents with opposite phase sequences. like Figures 3-4 As shown, the pose sensor 3 is arranged in the radial gap between adjacent claws 12; The controller is electrically connected to the position sensor, torque winding 4 and levitation winding 5 respectively. It is used to dynamically adjust the magnetic pole state of each claw 12 by controlling the current of torque winding 4 and levitation winding 5 through real-time acquisition of position sensor data, so as to generate driving torque and controllable radial levitation force at the same time.

[0025] The controller is built around a high-speed digital signal processor. Its outputs are connected to two independent three-phase full-bridge power inverters: one inverter's output is connected to the three-phase terminals of torque winding 4; the other inverter's output is connected to the three-phase terminals of levitation winding 5. The controller acquires sensor signals and current feedback in real time through an AD sampling module, and outputs two sets of independent six-channel PWM switching signals through a PWM module.

[0026] In one embodiment, the pose sensor 3 includes a displacement sensor and an angle sensor; the controller is electrically connected to the displacement sensor and the angle sensor respectively; the displacement sensor is used to detect the radial displacement of the rotor 2; the angle sensor is used to detect the angular position of the rotor 2.

[0027] The displacement sensor and angle sensor are integrated inside the stator. The probe of the displacement sensor is installed in the radial gap between adjacent claws 12, and is used for non-contact detection of minute displacements of the rotor 2 in the X, Y, and Z directions. The stator part of the angle sensor is also installed in the gap between the claws 12, and its rotor 2 part is connected to the main shaft, and is used to detect the angular position (electric angle θ) and rotational speed of the rotor 2 in real time.

[0028] In one embodiment, the number of permanent magnet pole pairs PM of rotor 2 and the number of pole pairs PS of levitation winding 5 satisfy the following levitation force generation condition: PS = PM ± 1.

[0029] In one embodiment, the number of permanent magnet pole pairs of rotor 2 is PM=1, the number of pole pairs of torque winding 4 is PT=1, and the number of pole pairs of levitation winding 5 is PS=2.

[0030] In one embodiment, the current flowing through the levitation winding 5 includes two rotating magnetic field current components with equal amplitude, opposite rotation directions, and pole pairs (PM+1) and (PM-1) respectively, and the two rotating magnetic field current components are symmetrically distributed relative to the rotor 2.

[0031] The following is a specific implementation method of the stator structure: The stator adopts a claw-pole structure, coaxially stacked from high-permeability, low-loss 20W250 silicon steel sheets after stamping. The stator includes stator teeth 11 extending axially and claw heads 12 extending radially inward from the ends of the stator teeth 11. In this embodiment, the stator has a total of 8 stator teeth 11 and corresponding 8 claw heads 12, forming an 8-slot structure. The inner surfaces of all claw heads 12 together form a smooth cylindrical surface, creating a working air gap that matches the rotor 2.

[0032] The torque winding 4 and the levitation winding 5 are wound together on the axial section of the same stator tooth 11 in the form of concentrated windings, sharing the same physical winding space, such as... Figure 5 The diagram shows the wiring configuration for the torque coil and the suspension coil. The specific winding parameters are as follows: The torque winding 4 uses enameled copper wire with a diameter of Φ0.6mm, and the number of coil turns on each stator tooth 11 is 68. The three-phase windings (A, B, C) adopt a star connection, and their pole pair number is designed to be PT=1.

[0033] The levitation winding 5 uses enameled copper wire with a diameter of Φ0.35mm, and the number of coil turns on each stator tooth 11 is 154. The three-phase windings are also independently constructed and connected in a star configuration, with a pole pair design of PS=2. The phase sequence of the two windings is designed independently to meet the requirements of the current spatial distribution for each pole pair. The physical co-position of the windings is the physical basis for realizing the electrically independent and controllable magnetic field of the claw 12.

[0034] It should be noted that stable rotation of the axial flow pump can be achieved by adjusting the amplitude and phase of the torque current; stable levitation of the axial flow pump can be achieved by adjusting the amplitude and phase of the levitation force current. The torque winding and levitation force winding are positioned identically in the stator space of the axial flow pump. The difference lies in the current flowing through the two sets of three-phase windings: the torque winding carries current with the same direction of the rotating magnetic field, while the levitation force winding carries current with two sets of current with opposite directions of the rotating magnetic field. Although the torque winding and levitation force winding are positioned identically in the stator space, their phase sequences are inconsistent, resulting in inconsistencies between the phase sequences of the torque current and the levitation force current. By controlling the phase sequence of each current based on the torque and levitation force generation principles, stable rotation and levitation of the axial flow pump are achieved. The integrated winding structure simplifies the structure of the bearingless axial flow pump and is beneficial for improving its power density.

[0035] In the design of permanent magnet axial flow pumps, the magnitude of the electromagnetic load is an extremely important parameter. The electromagnetic load is a collective term for the electrical load A and the magnetic load Bδ. They not only determine the material utilization level of the axial flow pump but also affect its operating temperature, efficiency, and other performance characteristics, and are closely related to various parameters in the axial flow pump design. Considering that the stator of a bearingless axial flow pump has both torque and suspension windings, the electrical load A of this axial flow pump should theoretically be the sum of the electrical loads of the two windings. During the actual operation of the axial flow pump, the rotor is generally stable in the center position, with deviations often on the order of micrometers. Therefore, its suspension current is relatively small. For ease of design calculation, the electrical load of the suspension winding can be ignored here. Thus, the electrical load A of the BPMSM can be expressed as follows:

[0036] In the formula, m represents the number of phases of the torque winding, and D si The values ​​represent the stator inner diameter of the axial flow pump, N1 represents the number of turns in the torque winding, and I1 represents the phase current in the torque winding. After initially determining the electromagnetic load of the BPMSM, its stator inner diameter and armature axial length can be further determined. These dimensions are all related to electromagnetic power. Based on empirical formulas summarized from continuous development in industrial production, the electromagnetic power formula is as follows:

[0037] In the formula, k e This represents the full-load potential coefficient. To achieve better passive levitation performance, the ratio of the axial length to the diameter of the thin-plate rotor is between 1:4 and 1:6, i.e., the value of µ is within the range of 1:4 to 1:6. If the value exceeds this suitable range, the length-to-diameter ratio becomes too large, which reduces the passive levitation stiffness of the BPMSM and decreases the levitation stability. If the length-to-diameter ratio becomes too small, its edge effect will have an unknown impact on the radial force and electromagnetic torque of the axial flow pump, and will also increase the difficulty of processing and manufacturing. The performance of BPMSMS with different combinations of pole pairs p≤3, torque winding pole pairs p1 and levitation winding pole pairs p2 with a difference of 1 was analyzed. It was concluded that the BPMSM with p1=1 and p2=2 has the best overall performance. At the same time, considering the design of small-volume BPMSM, fewer teeth make it easier to process and reserve space for sensors. Therefore, one embodiment of the present invention also adopts an 8-slot torque 1-pole pair and levitation 2-pole pair design.

[0038] The following is a specific implementation method of the rotor structure: The rotor is made of high-performance permanent magnet material, specifically N48 neodymium iron boron permanent magnets, and is formed into a ring structure. Its specific dimensions are: outer diameter Φ18mm, inner diameter Φ12mm, and axial thickness (length) 6mm. The rotor is radially magnetized, and its permanent magnet pole pairs PM=1.

[0039] The rotor is designed as a ring-shaped plate structure with an axial length (6mm) to an outer diameter (18mm) ratio of approximately 1:3. According to the design optimization range (1:4~1:6), this embodiment can precisely control the length-to-diameter ratio within the optimization range of 1:4~1:6 by adjusting the axial thickness of the permanent magnet (for example, changing it to 4.5mm) to improve the passive suspension stiffness.

[0040] Based on the same inventive concept, this invention also discloses a control method for the aforementioned bearingless permanent magnet synchronous axial flow pump, comprising the following steps: Sensor signal acquisition: Real-time acquisition of rotor pose signals detected by the pose sensor; Suspension force closed-loop control command synthesis: The rotor position signal is compared with the preset displacement reference value, and the target suspension force command is obtained by combining the field orientation control principle; Based on the air gap flux observation value, the actual suspension force generated at present is calculated in real time by combining the suspension force mathematical model of Maxwell stress method; The target suspension force command is compared with the actual suspension force, and the suspension force winding current command is generated after calculation. Torque control command synthesis: acquire rotor position signal, compare it with preset speed reference value, and obtain target torque current command by combining field-oriented control principle; Execution and Modulation: Based on the levitation force winding current command and the target torque current command, the levitation force winding and torque winding are driven by space vector pulse width modulation, and the magnetomotive force of each stator claw head is dynamically controlled to realize the levitation closed-loop control of the rotor radial and axial positions, as well as the continuous adjustable control of the axial flow pump speed.

[0041] In one embodiment, the method further includes: acquiring the rotor radial displacement signal detected by the displacement sensor in real time; comparing the rotor radial displacement signal with a preset displacement reference value, and obtaining the target levitation force command by combining the magnetic field orientation control principle.

[0042] In one embodiment, the method further includes: acquiring rotor angular position and speed signals detected by an angle sensor in real time; comparing the rotor angular position and speed signals with a preset speed reference value; and obtaining a target torque current command by combining the magnetic field orientation control principle.

[0043] In one embodiment, the actual levitation force generated at present is calculated in real time, specifically using the Maxwell tensor method, which is calculated by back-calculation based on the observed air gap flux and levitation winding current.

[0044] In one embodiment, when calculating using a mathematical model of levitation force based on Maxwell's stress method, the air gap flux includes: rotor flux, flux generated by torque winding current, and flux generated by levitation force winding current.

[0045] like Figure 6 The diagram shown illustrates the topological relationship between the magnetic field at the claw tip of the claw-type stator and the required controlled torque current and levitation force current, obtained through simulation using the control method of this invention. The control method of this invention is implemented based on... Figures 7-9 The control block diagram shown aims to calculate in real time the three-phase torque current Ic and levitation force current Ir that should be injected into the two independent windings to generate the required composite magnetic field on the claw, and to achieve this through high-precision power drive. The specific steps are as follows: The controller executes the following loop: Read the rotor radial displacement signal (X,Y) and axial displacement signal (Z) output by the displacement sensor.

[0046] Read the rotor electrical angle θ output by the angle sensor and the calculated mechanical speed ω.

[0047] The actual three-phase current of the torque winding and the actual three-phase current of the suspension winding are read by current sensors.

[0048] The three-phase currents of the two windings are transformed using Clarke and Park transformations respectively, from the stationary three-phase coordinate system to the dq coordinate system that rotates synchronously with the rotor magnetic field, to obtain the Id of the torque winding. t 、Iq t and the Id of the suspension winding s 、Iq s .

[0049] Implementation Figure 7 The diagram illustrates an integrated strategy combining direct levitation force and vector control. The core of this strategy lies in using the desired final magnetic field effect of the claw as the control objective, and then inversely calculating the current commands for both sets of windings.

[0050] Outer Displacement Ring: The detected radial displacements X and Y are compared with the reference center position. The deviation is calculated by the PID controller, and the output is the target radial levitation force command Fx to be applied in the X and Y directions. ref and Fy ref .

[0051] Outer speed loop: The detected actual speed ω is compared with the given target speed. The deviation is calculated by the PI controller and output as the target electromagnetic torque command Te. ref .

[0052] The calculation process for the levitation force current command is as follows: The controller has a built-in real-time flux linkage observer that calculates the resultant air gap flux linkage ψ acting on the claw in real time based on motor parameters, namely permanent magnet flux linkage, winding inductance, rotor angle θ, and the measured two sets of winding currents. gap .

[0053] Target levitation force (Fx) ref ,Fy ref ), the observed synthetic air gap flux ψ gap And the rotor angle θ, substituted into the precise mathematical model of levitation force established based on Maxwell's tensor method, are as follows.

[0054] Based on Maxwell's tensor method, a mathematical model of the rotor radial levitation force of the novel integrated winding BPMSM can be derived. Assume the air gap magnetic flux density in the axial flow pump is B. r If the vacuum permeability is μ0, then the force acting on the rotor surface d S Maxwell's force over area is:

[0055] B T B is the air gap magnetic flux density generated by the torque current and the equivalent current of the permanent magnet. c The air gap magnetic flux density B of the axial flow pump is the air gap magnetic flux density generated by the levitation force current. r It is composed of them together.

[0056] Assuming rotor mass m r Taking into account the external disturbance force of rotor F zx F zy (Rotor gravity), eccentric magnetic pull F sx F sy and radial suspension force F x F y The equation of motion for the integrated winding BPMSM is:

[0057] Based on the above formulas, it can be seen that once the winding parameters and other stator and rotor size parameters are determined, the magnitude of the electromagnetic torque is only related to the number of turns per phase of the torque winding and its current, and the relationship is directly proportional.

[0058] This model reveals that, given a magnetic flux ψ gap The nonlinear mapping relationship between levitation force and levitation winding current is established. Through model inverse calculation or table lookup, the current required to generate Fx is calculated in real time. ref ,Fy ref The required levitation force current command in the rotating dq coordinate system.

[0059] The calculated floating current command is compared with the actual feedback (Id). s ,Iq s The error is compared with that of the PI controller, and the output is the voltage command (Vds) required for the levitation winding in the dq coordinate system. ref Vqs ref ).

[0060] The torque current command calculation process is as follows: Under the field-oriented control framework, the target torque Te ref With cross-axis current Iq t Proportional. The torque winding quadrature-axis current command is directly calculated based on the torque equation. The torque winding quadrature-axis current command is then compared with the actual feedback (Idt, Iq). t The torque winding voltage command (Vdt) is obtained after comparison and PI regulation. ref Vqt ref ).

[0061] After calculating the levitation force current command and the torque current command, the voltage command (Vds) of the levitation winding is... ref Vqs ref Through inverse Park transformation, the system is converted to a two-phase stationary α-β coordinate system. Then, through inverse Clarke transformation, a three-phase instantaneous voltage command is finally generated for the levitation winding. The desired three-phase current corresponding to this voltage command is the final current command Ir of the levitation winding. Similarly, the voltage command (Vdt) of the torque winding is... ref Vqt ref By using the inverse Park transform and the inverse Clarke transform, a three-phase instantaneous voltage command is generated to be applied to the torque winding, and the corresponding expected three-phase current is the final current command Ic of the torque winding.

[0062] Two sets of three-phase voltage commands, Ir and Ic, are input to two independent space vector pulse width modulation (SVPWM) modules. The SVPWM modules calculate the optimal switching sequence based on the voltage commands, generating six PWM switching signals to drive inverters R and C. The two three-phase full-bridge inverters precisely inject current Ir into the levitation winding and current Ic into the torque winding according to their respective PWM signals.

[0063] By injecting Ic and Ir into the two co-located windings, the magnetomotive forces generated in the stator teeth are spatially superimposed and transmitted to the claws, jointly determining the instantaneous magnetomotive force and polarity of each claw. Ic (PT=1) mainly generates a strong, synchronously rotating fundamental magnetic field for driving; Ir (PS=2) generates a controllable, spatially modulated magnetic field, which couples with the fundamental magnetic field to generate a controllable radial force. By controlling Icabc and Irabc in real time and with precision, the dynamic regulation of the synthesized magnetic field of the claws can be achieved.

[0064] The controller has an embedded communication module that supports the Modbus-RTU protocol. Users can remotely set the target speed, suspension center position, and other commands via a host computer, and read the axial flow pump's speed, displacement in all directions, winding current, voltage, system status, and fault codes in real time, achieving comprehensive remote monitoring and diagnosis.

[0065] Considering the relationship between electromagnetic force and rotor position, the rotor may deviate radially at any angle in the application. Assuming the rotor's axial position (Z=0) remains stationary, it moves radially along the X direction (-0.5mm, 0.5mm) and similarly along the Y direction (-0.5mm, 0.5mm). Multiple position points are scanned and sampled. With the levitation coil current controlled to be 0, the XY radial magnetic pull of the axial flow pump is calculated. Figure 10 As shown.

[0066] When the rotor of an axial flow pump experiences axial displacement, the rotor magnets and stator core generate axial magnetic pull due to the magnetic circuit characteristics. When the levitation winding current is 0, the axial magnetic pull increases with the further the rotor is displaced. When the axial flow pump is levitation, the rotor needs to overcome its own gravity and fluid impact. To ensure the rotor maintains its axial position, the axial magnetic pull needs to be calculated. Assuming the rotor is radially stationary and moves axially along the Z-direction from (-5mm, 5mm), multiple position points are scanned and sampled. With the levitation coil current controlled at 0, the Z-axis axial magnetic pull of the axial flow pump is calculated as follows: Figure 11 As shown.

[0067] When the rotor of an axial flow pump experiences radial displacement, an asymmetrical magnetic pull is generated on the rotor due to the asymmetry of the air gap magnetic flux. To ensure the rotor remains stably levitated in the center position, the axial flow pump needs to precisely control the radial electromagnetic force by controlling the current in the levitation winding, thereby balancing the magnetic pull generated by the positional displacement. From the perspective of the pump's structural design, assuming the rotor is at position (0, 0, 0), the axial flow pump's levitation winding current varies from (-1.8A, 1.8A), covering all possible operating ranges. The XY radial electromagnetic force is calculated as follows: Figure 12 As shown.

[0068] The axial levitation force of the axial flow pump rotor is mainly provided by the axial magnetic pull generated by the rotor's magnets and the stator core. To test the effect of energizing the levitation winding on the axial levitation force, assuming the rotor is at position (0, 0, 0), the axial flow pump levitation winding current varies from (-2A, 2A) to cover all possible operating ranges. The Z-axis electromagnetic force is calculated as follows: Figure 13 As shown.

[0069] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0070] 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 bearingless permanent magnet synchronous axial flow pump, characterized in that, The bearingless permanent magnet synchronous axial flow pump includes: a claw-pole stator, a rotor, a position sensor, and a controller; wherein... The claw-pole stator includes multiple claw-pole units, each claw-pole unit having stator teeth extending axially and claw heads extending radially inward from the ends of the stator teeth, the inner surfaces of all the claw heads forming a working air gap opposite to the outer surface of the rotor. The torque winding and the levitation winding are wound together on the stator teeth, sharing the same axial winding space, and the electrical phase sequence of the torque winding and the levitation winding is independent; the levitation winding is configured to carry two sets of currents with opposite phase sequences. The pose sensor is arranged in the gap between adjacent claw heads; The controller is electrically connected to the posture sensor, the torque winding and the levitation force winding respectively, and is used to dynamically adjust the magnetic pole state of each claw by controlling the current of the torque winding and the levitation force winding through real-time acquisition of the rotor posture signal detected by the posture sensor, so as to simultaneously generate driving torque and controllable radial levitation force. The control method includes the following steps: Sensor signal acquisition: Real-time acquisition of rotor pose signals detected by the pose sensor; Suspension force closed-loop control command synthesis: The rotor position signal is compared with the preset displacement reference value, and the target suspension force command is obtained by combining the field orientation control principle; Based on the air gap flux observation value, the actual suspension force generated at present is calculated in real time by combining the suspension force mathematical model of Maxwell stress method; The target suspension force command is compared with the actual suspension force, and the suspension force winding current command is generated after calculation. Torque control command synthesis: The rotor position signal is acquired, compared with the preset speed reference value, and the target torque current command is obtained by combining the field-oriented control principle; Execution and Modulation: Based on the levitation force winding current command and the target torque current command, the levitation force winding and the torque winding are driven by space vector pulse width modulation to dynamically control the magnetomotive force of each stator claw, thereby realizing the levitation closed-loop control of the rotor radial position and the continuous adjustable control of the axial flow pump speed.

2. The control method for a bearingless permanent magnet synchronous axial flow pump according to claim 1, characterized in that, The posture sensor includes a displacement sensor and an angle sensor; the controller is electrically connected to the displacement sensor and the angle sensor respectively; the displacement sensor is used to detect the radial displacement of the rotor; the angle sensor is used to detect the angular position of the rotor.

3. The control method for a bearingless permanent magnet synchronous axial flow pump according to claim 1, characterized in that, The number of permanent magnet pole pairs PM of the rotor and the number of pole pairs PS of the levitation winding satisfy the following levitation force generation condition: PS = PM ± 1.

4. The bearingless permanent magnet synchronous axial flow pump control method according to claim 3, characterized in that, The rotor has 1 permanent magnet pole pair, PM = 1, the torque winding has 1 pole pair, and the levitation winding has 2 pole pairs.

5. The control method for a bearingless permanent magnet synchronous axial flow pump according to claim 1, characterized in that, The current flowing through the levitation winding includes two rotating magnetic field current components with equal amplitude, opposite rotation directions, and pole pairs (PM+1) and (PM-1) respectively, and the two rotating magnetic field current components are symmetrically distributed relative to the rotor.

6. The control method for a bearingless permanent magnet synchronous axial flow pump according to claim 2, characterized in that, Also includes: The rotor radial displacement signal detected by the displacement sensor is acquired in real time; the rotor radial displacement signal is compared with the preset displacement reference value, and the target levitation force command is obtained by combining the magnetic field orientation control principle.

7. The control method for a bearingless permanent magnet synchronous axial flow pump according to claim 2, characterized in that, Also includes: The rotor angular position and speed signals detected by the angle sensor are acquired in real time; the speed signals are compared with the preset speed reference value, and the target torque current command is obtained by combining the field-oriented control principle.

8. The control method for a bearingless permanent magnet synchronous axial flow pump according to claim 1, characterized in that, The real-time calculation of the actual levitation force is specifically performed using the Maxwell stress method, which is calculated by back-calculation based on the observed air gap flux and levitation winding current.

9. The control method for a bearingless permanent magnet synchronous axial flow pump according to claim 8, characterized in that, When calculating using the mathematical model of levitation force based on Maxwell's stress method, the air gap flux includes: rotor flux, flux generated by torque winding current, and flux generated by levitation force winding current.

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