Bowl-shaped permanent magnet brushless direct current motor, control method thereof and artificial heart pump

Abstract

The invention relates to the technical field of artificial heart pumps, and provides a bowl-shaped permanent magnet brushless direct current motor, a control method thereof and an artificial heart pump, the bowl-shaped permanent magnet brushless direct current motor comprises a bowl-shaped stator iron core and a plurality of permanent magnets; the bowl-shaped stator iron core comprises a stator yoke part and a plurality of bent teeth, a height difference exists between tooth boots of the bent teeth and the plane where the stator yoke part is located, and the tooth boots of the bent teeth and the permanent magnets are located at the same height in the axial direction, so that an armature magnetic flux path and a permanent magnet excitation magnetic flux path are located at the same height, and therefore the smoothness of the magnetic flux path trend is achieved; the permanent magnet brushless direct current motor is suitable for an artificial heart pump and can operate stably and efficiently, and the problem that an artificial heart pump and a permanent magnet brushless direct current motor thereof are difficult to adapt in the prior art is solved.

Description

Technical Field

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

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

[0003] Permanent magnet brushless DC motors are widely used in medical devices and other fields with various power levels due to their simple structure, high efficiency, high power density, long life and good mechanical properties. However, higher requirements are also placed on permanent magnet brushless DC motors.

[0004] The mechanical structure of the artificial heart pump is compact. Due to internal space limitations, the new artificial heart pump requires 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, which is difficult to adapt to the new artificial heart pump. This limits the application and promotion of artificial heart pumps.

[0005] In addition, the permanent magnets of existing permanent magnet brushless DC motors are mainly tile-type, and the torque performance is not optimal when facing the actual working conditions of the wide air gap of artificial heart pumps. Traditional eccentric permanent magnets are mainly used in permanent magnet synchronous motors to improve the sinusoidality of the air gap of permanent magnet synchronous motors, but 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 optimal torque performance under load conditions.

[0007] In order to address the deficiencies in the prior art, the present invention provides a bowl-shaped permanent magnet brushless DC motor, a control method thereof, and an artificial heart pump. The geometric structure is different from that of a conventional motor. The teeth of the bowl-shaped stator core are bent upward so that the armature flux path and the permanent magnet excitation flux path can be at the same height, thereby achieving smoothness of the flux path direction. The motor is suitable for an artificial heart pump and can operate stably and efficiently, thereby addressing the problem in the prior art that artificial heart pumps and their permanent magnet brushless DC motors are difficult to adapt.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

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

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

[0011] The bowl-shaped stator core includes a stator yoke and a plurality 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 are at the same axial height as the permanent magnet, so that the armature flux path and the permanent magnet excitation flux path are at the same height.

[0012] Furthermore, the permanent magnets are permanent magnets of unequal thickness; the radial outer edge of the permanent magnets of unequal thickness is an arc, and the center of the outer arc is on the rotation axis of the motor; the radial inner edge of the permanent magnets of unequal thickness is also an arc, and the center of the inner arc is not on the rotation axis of the motor, and the radius of the inner arc is smaller than the maximum distance from any point on the inner edge to the center of the outer arc.

[0013] Furthermore, it also includes a rotor core, wherein the radial outer edge of the rotor core coincides with the radial inner edge of the permanent magnets of unequal thickness to form a plum blossom structure.

[0014] Furthermore, the unequal thickness permanent magnets are evenly distributed along the circumference of the rotor core, and adjacent unequal thickness permanent magnets are magnetized alternately inwardly and outwardly along the radial direction.

[0015] Furthermore, it also includes a stator winding, wherein the stator winding is wound on the bent teeth.

[0016] A 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 comprises the following steps:

[0018] A control voltage reference value is calculated by an anti-disturbance control device and a hysteresis current controller, and a bowl-shaped permanent magnet brushless DC motor as described in the first aspect is controlled by a three-phase inverter.

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

[0020] Furthermore, the calculation step of the rotation speed observation value includes:

[0021] Get voltage output value and current output value;

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

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

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

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

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

[0027] Compared with the prior art, the present invention has the following beneficial effects:

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

[0029] The bowl-shaped permanent magnet brushless DC motor of the present invention has unequal thickness permanent magnets which are thin in the middle and thick in two sections, which can reduce the influence of wide air gap of artificial heart pump and magnetic tape leakage between poles and improve torque performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute improper limitations on the present invention.

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

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

[0033] Figure 3 It is a two-dimensional plane diagram of a bowl-shaped permanent magnet brushless DC motor rotor according to the first embodiment of the present invention;

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

[0035] Figure 5 This is a flow chart of a control method for a bowl-shaped permanent magnet brushless DC motor according to a second embodiment of the present invention;

[0036] Figure 6 is a structural diagram of an active disturbance rejection controller according to a second embodiment of the present invention;

[0037] Figure 7 Schematic diagram of an artificial heart pump according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

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

[0039] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art 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 exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates 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", "back", "vertical", "horizontal", "side", "bottom", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0042] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0043] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0044] Example 1

[0045] Embodiment 1 of the present invention provides a bowl-shaped permanent magnet brushless DC motor suitable for an artificial heart pump, such as Figure 1 and Figure 2 As shown, it includes a stator and a rotor, and an air gap 4 is formed between the stator and the rotor.

[0046] The number of slots of the stator is 6, the number of poles of the unequal thickness permanent magnets 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 comprises a stator yoke 12 and six bent teeth 11. In this embodiment, the bent teeth 11 and the stator yoke 12 form an angle θ in space. In this embodiment, the bending angle θ is 30°.

[0048] In order to make the magnetic circuit smooth, the bending angle of each bent tooth 11 is the same, so the axial upper plane and lower plane of the tooth shoe 13 of the bent tooth 11 are coplanar and 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 slope-shaped component and a tooth shoe 13, the angle between the slope-shaped component and the horizontal plane is θ, and the tooth shoe 13 is parallel to the plane where the stator yoke 12 is located.

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

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

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

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

[0054] The unequal thickness permanent magnets 2 are evenly distributed on the rotor along the circumferential direction, and adjacent unequal thickness permanent magnets 2 are magnetized alternately inwardly and outwardly along the radial direction.

[0055] The radial outer edge of the rotor core 3 coincides with the radial inner edge of the unequal thickness permanent magnets 2 to form a plum blossom structure.

[0056] The tooth shoe 13 of the bowl-shaped stator core 1 is at the same axial height as the unequal thickness permanent magnets 2, and there is an axial height difference with the plane where the stator yoke 12 is located, so that the armature flux path and the excitation flux path of the unequal thickness permanent magnets 2 can be at the same height, thereby achieving the smoothness of the flux path direction, making the permanent magnet brushless DC motor suitable for artificial heart pumps and able to operate stably and efficiently, solving the problem of difficult adaptation of artificial heart pumps and their permanent magnet brushless DC motors in the prior art.

[0057] Example 2

[0058] This embodiment provides a control method for a bowl-shaped permanent magnet brushless DC motor as described in the first embodiment, which is a position sensorless control method. Position sensorless control means controlling the motor without the help of a "position sensor". Figure 5 As shown, the following steps are included:

[0059] Step 1: Get the speed given value ω * , using the speed given value ω * Subtract the speed observation value ω to obtain the speed deviation ω*-ω;

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

[0061] Step 3: Output I based on the ADRC * And the current output value I abc The output of the commutation logic calculation controls the output of the hysteresis current controller (control voltage reference value), and further controls the bowl-shaped permanent magnet brushless DC motor M as described in Example 1 through a three-phase inverter, and finally measures the voltage output value U of each phase winding of the bowl-shaped permanent magnet brushless DC motor through a voltmeter / sensor and an ammeter / sensor. abc 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 , through the back electromotive force detection, the back electromotive force value e is obtained abc ;

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

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

[0065] For the ADRC in step 2, Figure 6As shown in the figure, the ADRC 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] Given the expression of the nonlinear function fal(x,σ,γ):

[0067]

[0068] Among them, 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 will not have a large value 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, obtain the tracking differentiator output value y through the tracking differentiator * .

[0071] The tracking differentiator is built as:

[0072]

[0073] Where x is the tracking differentiator input, 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, 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 rotation speed observation value ω output by the speed processing calculation module, an estimated output z1 and a total disturbance z2 are obtained by extending the state observer.

[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 state variables updated in real time. The disturbance of the bowl-shaped permanent magnet brushless DC motor is estimated in real time by the extended state observer. The extended state observer can be expressed as:

[0076]

[0077] Where 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 gain of the output error factor; I *That is, the output of the ADRC, and σ1 and γ1 are the initial values ​​of σ and γ in the extended state observer.

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

[0079] The nonlinear state error feedback control law is responsible for adjusting the compensation of the control quantity and improving the effectiveness of 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] Among them, u0 represents the output of the nonlinear control law, which mainly depends 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 output of the compensated ADRC controller I * , under the influence of external disturbance d brought to the motor by friction caused by blood flow, the speed observation value ω is obtained through the motor system.

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

[0084] For the speed processing calculation in step 6, knowing the back EMF value e abc , due to the back electromotive force e of the bowl-shaped permanent magnet brushless DC motor abc With electrical speed ω e The relationship is:

[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 based on the amplitude of the line back electromotive force of the observer. Therefore, the estimated speed, that is, the speed observation value ω, is:

[0087]

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

[0089] θ=∫ωdt+θ0 (7)

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

[0091] The present embodiment provides a control method for a bowl-shaped permanent magnet brushless DC motor, which has the following beneficial effects:

[0092] (1) Strong anti-interference ability: The anti-interference control has a strong anti-interference ability by estimating and compensating the disturbances in the bowl-shaped permanent magnet brushless DC motor. For the bowl-shaped permanent magnet brushless DC motor, such as voltage fluctuations, load changes and other external disturbances, the anti-interference 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 anti-disturbance control adopts more advanced control strategies and technologies to achieve faster response speed. In the control of bowl-shaped permanent magnet brushless DC motor, the desired speed, position or torque control can be achieved more quickly, improving the dynamic performance of the bowl-shaped permanent magnet brushless DC motor.

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

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

[0096] Embodiment 3

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

[0098] Figure 7 The schematic diagram of the artificial heart pump is as follows. After sampling the voltage of the bowl-shaped permanent magnet brushless DC motor as described in Example 1, the signal is input into the single-chip microcomputer (MCU) through the analog-to-digital converter (ADC) to obtain the back electromotive force zero-crossing signal, and then the rotor position observation value θ and the speed observation value ω are calculated. Furthermore, the self-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 the digital-to-analog converter (DAC), driving the artificial heart pump to rotate, so that blood flows in from the inlet and flows out from the outlet.

[0099] The above description is only a preferred embodiment of the present invention and is 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 in 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 and a plurality of permanent magnets; The bowl-shaped stator core includes a stator yoke and a plurality 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 are at the same axial height as the permanent magnet, so that the armature flux path and the permanent magnet excitation flux path are at the same height.

2. A bowl-shaped permanent magnet brushless DC motor as claimed in claim 1, characterized in that: The permanent magnets are of unequal thickness; the radial outer edge of the permanent magnets of unequal thickness is an arc, and the center of the outer arc is on the rotation axis of the motor; the radial inner edge of the permanent magnets of unequal thickness is also an arc, and the center of the inner arc is not on the rotation axis of the motor, and the radius of the inner arc is smaller than the maximum distance from any point on the inner edge to the center of the outer arc.

3. A bowl-shaped permanent magnet brushless DC motor as claimed in claim 2, characterized in that: It also includes a rotor core, wherein the radial outer edge of the rotor core overlaps with the radial inner edge of the permanent magnets of unequal thickness to form a plum blossom structure.

4. A bowl-shaped permanent magnet brushless DC motor as claimed in claim 3, characterized in that: The unequal thickness permanent magnets are evenly distributed along the circumference of the rotor core, and adjacent unequal thickness permanent magnets are magnetized alternately inwardly and outwardly along the radial direction.

5. A bowl-shaped permanent magnet brushless DC motor as claimed in claim 1, characterized in that: Also included is a stator winding wound around the bent teeth.

6. A method for controlling a bowl-shaped permanent magnet brushless DC motor according to any one of claims 1 to 5, characterized in that: The steps include: A control voltage reference value is calculated by an anti-disturbance control controller and a hysteresis current controller, and a bowl-shaped permanent magnet brushless DC motor as described in any one of claims 1 to 5 is controlled by a three-phase inverter.

7. A method for controlling a bowl-shaped permanent magnet brushless DC motor as claimed in claim 6, characterized in that: The active disturbance rejection controller obtains an output of the active disturbance rejection controller based on a deviation between a speed set value and a speed observation value.

8. The control method of a bowl-shaped permanent magnet brushless DC motor as claimed in claim 7, characterized in that: The calculation step of the speed observation value comprises: Get voltage output value and current output value; Based on the voltage output value and the current, the back electromotive force value is obtained through back electromotive force detection; Based on the back electromotive force value, the speed observation value is obtained through speed processing calculation.

9. A method for controlling a bowl-shaped permanent magnet brushless DC motor as claimed in claim 6, 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.

10. An artificial heart pump, characterized in that: A bowl-shaped permanent magnet brushless DC motor as described in any one of claims 1 to 5 is used.

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