A bowl-shaped permanent magnet brushless DC motor, its control method and an artificial heart pump

Abstract

The present invention relates to the technical field of artificial heart pumps, and provides a bowl-shaped permanent magnet brushless DC motor, its control method, and an artificial heart pump, including a bowl-shaped stator core and a plurality of permanent magnets; the bowl-shaped stator core includes a stator yoke portion and a plurality of bent teeth, there is a height difference between the tooth boots of the bent teeth and the plane where the stator yoke portion is located, and the tooth boots of the bent teeth and the permanent magnets are at the same axial height, so that the armature flux path and the permanent magnet excitation flux path are at the same height, thereby realizing the smoothness of the flux path direction, being applicable to artificial heart pumps and capable of operating stably and efficiently, and solving the problem that it is difficult to adapt the artificial heart pump and its permanent magnet brushless DC motor in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial heart pumps, and particularly relates to a bowl-shaped permanent magnet brushless DC motor, its control method, and an artificial heart pump. Background Art

[0002] The statements in this part only provide the background art related to the present invention and do not necessarily constitute the prior art.

[0003] Due to its advantages such as simple structure, high efficiency, high power density, long life, and good mechanical performance, the permanent magnet brushless DC motor is widely used in various power level fields such as medical devices, but it also poses higher requirements for the permanent magnet brushless DC motor.

[0004] The mechanical structure of the artificial heart pump is compact. Due to the limited internal space of the new artificial heart pump, it is required that the stator and rotor of the permanent magnet brushless DC motor are not in the same plane. In the traditional permanent magnet brushless DC motor, the rotor, permanent magnet, stator, and winding are all at the same horizontal height, making it difficult to adapt to the new artificial heart pump, which limits the application and promotion of the artificial heart pump.

[0005] In addition, the permanent magnets of the existing permanent magnet brushless DC motors are mainly tile-shaped, and the torque performance is not optimal for the actual working conditions of the wide air gap of the artificial heart pump. The traditional eccentric permanent magnets are mainly applied to permanent magnet synchronous motors to improve the sinusoidality of the air gap of the permanent magnet synchronous motor, and are not suitable for permanent magnet brushless DC motors. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to design a bowl-shaped permanent magnet brushless DC motor to achieve the optimal torque performance under load conditions.

[0007] To solve the deficiencies of the prior art, the present invention provides a bowl-shaped permanent magnet brushless DC motor, its control method, and an artificial heart pump. The geometric structure is different from that of a conventional motor. The tooth part of the bowl-shaped stator core is bent upward, so that the armature magnetic flux path and the permanent magnet excitation magnetic flux path can be at the same height, thereby realizing the smoothness of the magnetic flux path direction. It is suitable for artificial heart pumps and can operate stably and efficiently, solving the problem that it is difficult to adapt the artificial heart pump and its permanent magnet brushless DC motor in the prior art.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a bowl-shaped permanent magnet brushless DC motor.

[0010] A bowl-shaped permanent magnet brushless DC motor includes a bowl-shaped stator core and a plurality of permanent magnets;

[0011] The bowl-shaped stator core includes a stator yoke and a number of bent teeth. There is a height difference between the tooth shoes of the bent teeth and the plane where the stator yoke is located, and the tooth shoes of the bent teeth and the permanent magnets are at the same axial height, so that the armature flux path and the permanent magnet excitation flux path are at the same height.

[0012] Further, the permanent magnet is a permanent magnet with unequal thickness; the radially outer edge of the permanent magnet with unequal thickness is arc-shaped, and the center of the outer arc is on the rotation axis of the motor; the radially inner edge of the permanent magnet with unequal thickness is also arc-shaped, the center of the inner arc is not on the rotation axis of the motor, and the radius of the inner arc is less than the maximum distance from any point on the inner edge to the center of the outer arc.

[0013] Further, it further includes a rotor core, and the radially outer edge of the rotor core coincides with the radially inner edge of the permanent magnet with unequal thickness to form a plum blossom structure.

[0014] Further, the permanent magnets with unequal thickness are evenly distributed along the circumferential direction of the rotor core, and adjacent permanent magnets with unequal thickness are alternately magnetized inwards and outwards along the radial direction.

[0015] Further, it further includes a stator winding, and the stator winding is wound on the bent teeth.

[0016] The second aspect of the present invention provides a control method for a bowl-shaped permanent magnet brushless DC motor.

[0017] A control method for a bowl-shaped permanent magnet brushless DC motor as described in the first aspect includes the following steps:

[0018] Calculate the control voltage reference value through an active disturbance rejection controller and a hysteresis current controller, and control a bowl-shaped permanent magnet brushless DC motor as described in the first aspect through a three-phase inverter.

[0019] Further, the active disturbance rejection controller obtains the output of the active disturbance rejection controller based on the deviation between the speed set value and the speed observation value.

[0020] Further, the calculation steps of the speed observation value include:

[0021] Obtain the voltage output value and the current output value;

[0022] Based on the voltage output value and the current, obtain the back electromotive force value through back electromotive force detection;

[0023] Based on the back electromotive force value, obtain the speed observation value through speed processing calculation.

[0024] Further, the active disturbance rejection controller uses an extended state observer to estimate the disturbance of the bowl-shaped permanent magnet brushless DC motor.

[0025] The third aspect of the present invention provides an artificial heart pump.

[0026] An artificial heart pump uses a bowl-shaped permanent magnet brushless DC motor as described in the first aspect.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] For the bowl-shaped permanent magnet brushless DC motor described in the present invention, its geometric structure is different from that of a conventional motor. The teeth of the bowl-shaped stator core are bent upward, enabling the armature flux path and the magnetic flux path of the surface-mounted permanent magnet excitation to be at the same height, thereby achieving the smoothness of the magnetic flux path direction. It is suitable for an artificial heart pump and can operate stably and efficiently, solving the problem that it is difficult to match the artificial heart pump and its permanent magnet brushless DC motor in the prior art.

[0029] For the bowl-shaped permanent magnet brushless DC motor described in the present invention, the non-uniform thickness permanent magnet is thin in the middle and thick at both ends, which can reduce the influence caused by the wide air gap and interpolar magnetic leakage of the artificial heart pump and improve the torque performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0031] Figure 1 It is a three-dimensional structure diagram of the bowl-shaped permanent magnet brushless DC motor according to Embodiment 1 of the present invention;

[0032] Figure 2 It is a three-dimensional cross-sectional view of the bowl-shaped permanent magnet brushless DC motor according to Embodiment 1 of the present invention;

[0033] Figure 3 It is a two-dimensional plan view of the rotor of the bowl-shaped permanent magnet brushless DC motor according to Embodiment 1 of the present invention;

[0034] Figure 4 It is a load torque waveform diagram of the bowl-shaped permanent magnet brushless DC motor according to Embodiment 1 of the present invention;

[0035] Figure 5 It is a flowchart of a control method for a bowl-shaped permanent magnet brushless DC motor according to Embodiment 2 of the present invention;

[0036] Figure 6 It is a structure diagram of the active disturbance rejection controller according to Embodiment 2 of the present invention;

[0037] Figure 7 It is a schematic diagram of the artificial heart pump according to Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

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

[0039] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only relational terms determined for the convenience of describing the structural relationship of each component or element of the present invention and do not specifically refer to any component or element of the present invention. It should not be construed as a limitation to the present invention.

[0042] In the present invention, terms such as "fixed connection", "connected", "connected to" should be understood in a broad sense, which may mean a fixed connection, an integral connection or a detachable connection; it may be directly connected or indirectly connected through an intermediate medium. For those skilled in the relevant scientific research or technology in this field, the specific meanings of the above terms in the present invention can be determined according to specific circumstances and should not be construed as a limitation to the present invention.

[0043] Without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0044] Embodiment 1

[0045] Embodiment 1 of the present invention provides a bowl-shaped permanent magnet brushless DC motor, which is applicable to an artificial heart pump, as Figure 1 and Figure 2 shown, including a stator and a rotor, and there is an air gap 4 between the stator and the rotor.

[0046] Among them, the number of slots of the stator is 6, the number of poles of the unequal-thickness permanent magnet 2 is 4, and the stator includes a bowl-shaped stator core 1 and a stator winding 5.

[0047] The bowl-shaped stator core 1 includes a stator yoke 12 and 6 bent teeth 11. In this embodiment, the bent teeth 11 form an angle θ with the stator yoke 12 in space, and the bending angle θ in this embodiment is 30°.

[0048] To ensure smooth magnetic circuits, the bending angles of each bent tooth 11 are the same. Therefore, the upper planes of the tooth boots 13 of the bent teeth 11 are coplanar axially, and the lower planes are coplanar, and are parallel to the plane where the stator yoke 12 is located.

[0049] In other words, the plane where the stator yoke 12 is located is parallel to the horizontal plane. The bent tooth 11 is composed of a ramp-shaped component and a tooth boot 13. The included angle between the ramp-shaped component and the horizontal plane is θ, and the tooth boot 13 is parallel to the plane where the stator yoke 12 is located.

[0050] The stator winding 5 is wound around the bent teeth 11 that are inclined in space to power the bowl-shaped permanent magnet brushless DC motor, thereby driving the artificial heart pump to supply blood.

[0051] The laminations of the bowl-shaped stator core 1 can be formed by secondary stamping and bending on the basis of the existing planar stator core laminations. Due to the limitations of the structure of the artificial heart pump motor, the thickness of the air gap 4 of the bowl-shaped permanent magnet brushless DC motor is greater than half of the axial length of the motor, which will cause a large amount of magnetic flux leakage of the permanent magnet in the circumferential and axial directions.

[0052] The rotor of the bowl-shaped permanent magnet brushless DC motor, as Figure 3 shown, includes a number of permanent magnets 2 with the same shape and size but different thicknesses and a rotor core 3. The outer radial side of each permanent magnet 2 with different thicknesses is arc-shaped, and its center O is on the rotation axis of the motor; the inner radial side of the permanent magnet 2 with different thicknesses is also arc-shaped, and its center O1 is not on the rotation axis of the motor, and its radius is less than the maximum distance from any point on the inner side to point O. The straight line O1O intersects the permanent magnet 2 with different thicknesses at the line segment AB. The length H2 of the line segment AB is the minimum value of the radial thickness of the permanent magnet 2 with different thicknesses, which is less than any radial thickness H1 of the permanent magnet 2 with different thicknesses. The permanent magnet 2 with different thicknesses is thin in the middle and thick at both ends, which can compensate for and reduce the influence caused by the wide air gap and inter-pole magnetic flux leakage of the artificial heart pump, and improve the torque performance. The performance of the motor is as Figure 4 shown, and the average torque value is 0.1546 Nm.

[0053] It should be noted that the arc mentioned in this embodiment is the shape of a part of a circle.

[0054] The permanent magnets 2 with different thicknesses are evenly distributed along the circumferential direction on the rotor, and adjacent permanent magnets 2 with different thicknesses are magnetized alternately inward and outward along the radial direction.

[0055] The outer radial side of the rotor core 3 coincides with the inner radial side of the permanent magnet 2 with different thicknesses to form a plum blossom structure.

[0056] The tooth boot 13 of the bowl-shaped stator core 1 and the non-uniform-thickness permanent magnet 2 are at the same axial height, and there is an axial height difference from the plane where the stator yoke 12 is located, so that the armature flux path and the excitation flux path of the non-uniform-thickness permanent magnet 2 can be at the same height, thereby realizing the smoothness of the flux path direction, making the permanent magnet brushless DC motor applicable to the artificial heart pump and capable of stable and efficient operation, and solving the problem that it is difficult to adapt the artificial heart pump and its permanent magnet brushless DC motor in the prior art.

[0057] Embodiment 2

[0058] This embodiment provides a control method for a bowl-shaped permanent magnet brushless DC motor as described in Embodiment 1, which is a sensorless control method. Sensorless control means realizing the control of the motor without the help of a "position sensor". As Figure 5 shown, it includes the following steps:

[0059] Step 1: Obtain the speed given value ω * , subtract the speed observed value ω from the speed given value ω to obtain the speed deviation ω* - ω; *

[0060] Step 2: Input the speed deviation ω* - ω into the active disturbance rejection controller to obtain the output I * of the compensated active disturbance rejection controller;

[0061] Step 3: Based on the output I * of the active disturbance rejection controller, the current output value I abc , and the output of the commutation logic calculation, control the output (control voltage reference value) of the hysteresis current controller, and further control the bowl-shaped permanent magnet brushless DC motor M as described in Embodiment 1 through a three-phase inverter. Finally, measure the voltage output value U abc of each phase winding of the bowl-shaped permanent magnet brushless DC motor and the current output value I abc ;

[0062] Step 4: Based on the voltage output value U abc and the current output value I abc , obtain the back electromotive force value e abc through back electromotive force detection;

[0063] Step 5: Based on the back electromotive force value e abc , obtain the output of the commutation logic calculation through commutation logic calculation;

[0064] Step 6: Based on the back electromotive force value e abc , obtain the speed observed value ω through speed processing calculation.

[0065] For the active disturbance rejection controller in Step 2, as Figure 6 ​As shown, the active disturbance rejection controller includes a tracking differentiator, a nonlinear state error feedback control law, and an extended state observer. The transition process and the differentiator are implemented in one module. The total disturbance acting on the motor system is estimated using the input, output, and applied control input of the controlled object, and the error and the differential of the error are constructed using the nonlinear state error feedback control law.

[0066] The expression of the nonlinear function fal(x,σ,γ) is given as follows:

[0067]

[0068] where x is the input with error information; σ controls the function to avoid saturation when the x value is large, 0 < σ < 1; γ ensures that the function does not have large values near zero due to small x values.

[0069] In this embodiment, the steps of the active disturbance rejection controller are as follows:

[0070] Step 201: Based on the input speed deviation ω* - ω, through the tracking differentiator, the output value y of the tracking differentiator is obtained * .

[0071] The tracking differentiator is established as:

[0072]

[0073] where x is the input of the tracking differentiator, that is, the input speed deviation ω* - ω; y * is the output of the tracking differentiator, e1 is the error signal of the tracking differentiator, k is the speed tracking coefficient, σ0 and γ0 are the initial values of σ and γ, represents the differential of x.

[0074] Step 202: Based on the compensation factor b0 and the observed speed value ω output by the speed processing calculation module, through the extended state observer, the estimated output z1 and the total disturbance z2 are obtained.

[0075] Since the motor drive system to be controlled is a first-order system, a second-order extended state observer must be constructed for the observer to estimate the overall disturbance and the real-time updated state variables. The disturbances of the bowl-shaped permanent magnet brushless DC motor are all estimated in real time by the extended state observer. The extended state observer can be expressed as:

[0076]

[0077] In the formula, z1 and z2 represent the estimated output and the estimated total disturbance; e2 represents the state error, b0 represents the compensation factor; μ1 and μ2 represent the correction gains of the output error factor; I *That is, the output of the active disturbance rejection controller, where σ1 and γ1 are the initial values of σ and γ in the extended state observer.

[0078] Step 203: The output y of the tracking differentiator * Subtracts the output z1 of the extended state observer to obtain e, that is, e = y * - z1; through the nonlinear state error feedback control law, the output u0 of the nonlinear control law is obtained; the output u0 of the nonlinear control law is then subtracted by the total disturbance Z2 and divided by b0 to obtain the compensated output I of the active disturbance rejection controller * .

[0079] The nonlinear state error feedback control law is responsible for adjusting the compensation of the control quantity and improving the effectiveness of the feedback control. The input of the nonlinear state error feedback control law is the difference between the tracking differentiator and the extended state observer, and its expression is:

[0080]

[0081] where u0 represents the output of the nonlinear control law, mainly depending on the sampling time of the control system, μ3 represents the correction gain of the output error factor, and σ2 and γ2 are the initial values of σ and γ in the nonlinear state error feedback control law.

[0082] Based on the compensated output I of the active disturbance rejection controller * , under the action of the external disturbance d such as the friction force caused by blood flow on the motor, through the motor system, the rotational speed observation value ω is obtained.

[0083] For the back electromotive force detection in step 6, select a non-conducting phase, and the voltage measured across this phase at this time is the back electromotive force.

[0084] For the speed processing calculation in step 6, knowing the back electromotive force value e abc , since the back electromotive force e abc of the bowl-shaped permanent magnet brushless DC motor e and the electrical rotational speed ω

[0085] e abc = K e ω e (5)

[0086] where K e is the back electromotive force constant. The magnitude of the back electromotive force can be estimated according to the amplitude of the line back electromotive force of the observer. Therefore, the estimated speed, that is, the rotational speed observation value ω is:

[0087]

[0088] where p is the number of pole pairs of the motor. The rotor position observation value θ is:

[0089] θ = ∫ωdt + θ0 (7)

[0090] where θ0 is the initial position angle of the rotor.

[0091] A control method for a bowl-shaped permanent magnet brushless DC motor provided in this embodiment has the beneficial effects as follows:

[0092] (1) Strong anti-interference ability: The active disturbance rejection control estimates and compensates for the disturbances in the bowl-shaped permanent magnet brushless DC motor, and has a strong anti-interference ability. For the bowl-shaped permanent magnet brushless DC motor, such as external disturbances like voltage fluctuations and load changes, the active disturbance rejection control can more effectively suppress the influence of these disturbances on the bowl-shaped permanent magnet brushless DC motor, and improve the stability and robustness of the bowl-shaped permanent magnet brushless DC motor.

[0093] (2) Faster response speed: The active disturbance rejection control adopts more advanced control strategies and technologies, and can achieve a faster response speed. In the control of the bowl-shaped permanent magnet brushless DC motor, the desired speed, position or torque control can be achieved faster, and the dynamic performance of the bowl-shaped permanent magnet brushless DC motor can be improved.

[0094] (3) No need for an accurate model: The active disturbance rejection control has a low requirement for the accurate model of the bowl-shaped permanent magnet brushless DC motor. In a complex system like the bowl-shaped permanent magnet brushless DC motor, it is often difficult to accurately establish the system model, so the active disturbance rejection control is more flexible in practical applications.

[0095] (4) Easy to implement and adjust: The control structure of the active disturbance rejection control is relatively simple, and the parameter adjustment is relatively intuitive. In contrast, the proportional-integral control may require more debugging and optimization to achieve the ideal control effect.

[0096] Embodiment III

[0097] This embodiment provides an artificial heart pump using the bowl-shaped permanent magnet brushless DC motor as described in Embodiment I.

[0098] Figure 7 As a schematic diagram of the artificial heart pump, after sampling the voltage of the bowl-shaped permanent magnet brushless DC motor as described in Embodiment I, the signal is input into the single-chip microcomputer (MCU) through an analog-to-digital converter (ADC) to obtain the back electromotive force zero-crossing signal, and then the rotor position observation value θ and the rotational speed observation value ω are calculated. Further, the active disturbance rejection controller and the hysteresis current controller calculate each control voltage reference value, and the reference voltage signal is input into the three-phase inverter bridge, and then fed to each winding through a digital-to-analog converter (DAC) to drive the artificial heart pump to rotate, so that the blood flows in from the inlet and flows out from the outlet.

[0099] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bowl-shaped permanent magnet brushless DC motor, characterized in that: It includes a bowl-shaped stator core, a rotor core, and a number of permanent magnets; The bowl-shaped stator core includes a stator yoke and a number of bent teeth. There is a height difference between the tooth shoes of the bent teeth and the plane where the stator yoke is located, and the tooth shoes of the bent teeth and the permanent magnets are at the same axial height, so that the armature flux path and the permanent magnet excitation flux path are at the same height; The permanent magnets are permanent magnets with unequal thicknesses; the radially outer edge of the permanent magnets with unequal thicknesses is arc-shaped, and the center of the outer arc is on the axis of rotation of the motor; the radially inner edge of the permanent magnets with unequal thicknesses is also arc-shaped, and the center of the inner arc is not on the axis of rotation of the motor, and the radius of the inner arc is less than the maximum distance from any point on the inner edge to the center of the outer arc; The radially outer edge of the rotor core coincides with the radially inner edge of the permanent magnets with unequal thicknesses to form a plum blossom structure; The permanent magnets with unequal thicknesses are evenly distributed along the circumference of the rotor core, and adjacent permanent magnets with unequal thicknesses are magnetized alternately inward and outward along the radial direction.

2. The bowl-shaped permanent magnet brushless DC motor according to claim 1, wherein: It also includes a stator winding, and the stator winding is wound on the bent teeth.

3. A control method for a bowl-shaped permanent magnet brushless DC motor according to any one of claims 1-2, characterized in that: It includes the following steps: Calculate the control voltage reference value through an active disturbance rejection controller and a hysteresis current controller, and control a bowl-shaped permanent magnet brushless DC motor as described in any one of claims 1-2 through a three-phase inverter.

4. The control method of a bowl-shaped permanent magnet brushless DC motor according to claim 3, characterized in that: The active disturbance rejection controller obtains the output of the active disturbance rejection controller based on the deviation between the speed set value and the speed observed value.

5. The control method of a bowl-shaped permanent magnet brushless DC motor according to claim 4, characterized in that: The calculation steps of the speed observed value include: Obtain the voltage output value and the current output value; Based on the voltage output value and the current output value, obtain the back electromotive force value through back electromotive force detection; Based on the back electromotive force value, obtain the speed observed value through speed processing calculation.

6. The control method of a bowl-shaped permanent magnet brushless DC motor according to claim 3, characterized in that: The active disturbance rejection controller uses an extended state observer to estimate the disturbance of the bowl-shaped permanent magnet brushless DC motor.

7. An artificial heart pump, characterized in that: Use a bowl-shaped permanent magnet brushless DC motor as described in any one of claims 1-2.

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