Three degree of freedom permanent magnet biased magnetic bearing

Abstract

The application discloses a three-degree-of-freedom permanent magnet biased magnetic bearing, which comprises a rotor system, a radial magnetic bearing stator system and an axial magnetic bearing stator system; the rotor system comprises a rotor, a radial magnetized permanent magnet ring and a magnetic conducting ring; the radial magnetic bearing stator system comprises a radial stator core, a magnetic isolation ring and a radial coil winding; the axial magnetic bearing stator system comprises a sheet-shaped circular arc radial magnetized permanent magnet, an axial stator core and an axial coil winding; the three-degree-of-freedom permanent magnet biased magnetic bearing is provided with the axial magnetic bearing stator around the rotor, and the axial magnetic bearing stator is in the same plane with the radial magnetic bearing stator, so that the axial length of the magnetic bearing is reduced, and the structure is compact; the radial two-degree-of-freedom translational control and the axial translational control can be realized; the magnetic isolation ring is arranged between the radial stator cores, so that the decoupling of the magnetic circuit of the two radial channels of the x-axis and the y-axis is realized; the two radial channels are provided with independent permanent magnets for biasing, the decoupling of the biasing magnetic circuit is realized, and the influence of the air gap reluctance change is weakened; the second air gap is arranged, so that the axial control magnetic circuit does not pass through the permanent magnet ring itself, and the power consumption of the magnetic bearing is further reduced.

Description

Technical Field

[0001] This invention relates to the field of magnetic levitation bearings, and more particularly to a three-degree-of-freedom permanent magnet bias bearing. Background Technology

[0002] Magnetic levitation bearings achieve frictionless rotor levitation through the levitation force generated by a magnetic field. They offer advantages such as contactless operation, low loss, high operating speed, and long lifespan, and are widely used in aerospace, artificial hearts, and high-speed blowers. Compared to pure electromagnetic bearings, permanent magnet bias bearings generate a bias magnetic field through permanent magnets, offering advantages such as low power consumption and high load-bearing capacity. Traditional three-degree-of-freedom permanent magnet bias bearings share a permanent magnet and stator core in both radial channels. This results in simultaneous bias magnetic circuit coupling and control magnetic circuit coupling in both radial channels, increasing energy consumption and hindering improvements in levitation accuracy. Furthermore, traditional three-degree-of-freedom permanent magnet bias bearings suffer from large size and long axial dimensions, limiting the rotor's critical speed. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a three-degree-of-freedom permanent magnet bias magnetic bearing. The axial magnetic bearing stator is segmented and installed between the two magnetic poles of the radial magnetic bearing stator, coplanar with the radial magnetic bearing stator, achieving integrated design of radial and axial bearing functions and improving the utilization of structural space. Reducing the axial dimension of the magnetic bearing is beneficial for increasing the rotor's critical speed and enables translational control of both radial and axial degrees of freedom. A magnetic isolation ring is added between the radial stator cores to decouple the control magnetic circuits of the X-axis and Y-axis radial channels. The X-axis and Y-axis radial channels are biased by their respective independent permanent magnets, which weakens the influence of air gap magnetic reluctance changes on the bias flux, achieving decoupling of the bias magnetic circuit, significantly reducing magnetic bearing losses, and improving levitation control accuracy.

[0004] The technical solution of the present invention is as follows:

[0005] A three-degree-of-freedom permanent magnet biased magnetic bearing includes: a rotor system, a radial magnetic bearing stator system, and an axial magnetic bearing stator system;

[0006] The rotor system includes a rotor, a radially magnetized permanent magnet ring, and a magnetic guide ring; the radially magnetized permanent magnet ring is fixed to the radially outer side of the rotor; the magnetic guide ring is located radially outer side of the radially magnetized permanent magnet ring;

[0007] The radial magnetic bearing stator system includes a Y-axis radial stator core, an X-axis radial stator core, a magnetic isolation ring, a +X-axis radial coil winding, a -X-axis radial coil winding, a +Y-axis radial coil winding, and a -Y-axis radial coil winding.

[0008] The Y-axis radial stator core and X-axis radial stator core are located radially outside the left side of the rotor axis; the magnetic isolation ring is located between the Y-axis radial stator core and the X-axis radial stator core. The +X-axis radial coil winding, -X-axis radial coil winding, +Y-axis radial coil winding, and -Y-axis radial coil winding are respectively wound around the four magnetic poles (right, left, top, and bottom) of the radial stator core and fixed with epoxy resin.

[0009] Furthermore, the axial magnetic bearing stator system includes four plate-shaped arc-shaped radially magnetized permanent magnets, four axial stator cores, a left-side axial coil winding of the +Y axis, a right-side axial coil winding of the +Y axis, a left-side axial coil winding of the -Y axis, and a right-side axial coil winding of the -Y axis; the four plate-shaped arc-shaped radially magnetized permanent magnets are respectively located on the yokes of the radial stator cores with the +Y axis deflected counterclockwise by 45°, the +Y axis deflected clockwise by 45°, the -Y axis deflected clockwise by 45°, and the -Y axis deflected counterclockwise by 45°, and are fixed thereto; the four axial stator cores (10) are located inside the four plate-shaped arc-shaped radially magnetized permanent magnets with the +Y axis deflected counterclockwise by 45°, the +Y axis deflected clockwise by 45°, the -Y axis deflected clockwise by 45°, and the -Y axis deflected counterclockwise by 45°, and are fixed thereto.

[0010] The left axial coil winding of the +Y axis, the right axial coil winding of the +Y axis, the left axial coil winding of the -Y axis, and the right axial coil winding of the -Y axis are respectively wound on the annular grooves of the four axial stator cores and fixed with epoxy resin.

[0011] Furthermore, the outer diameter of the radially magnetized permanent magnet ring is smaller than the inner diameter of the outer magnetic pole of the axial stator core; the inner diameter of the radially magnetized permanent magnet ring is larger than the outer diameter of the inner magnetic pole of the axial stator core.

[0012] Furthermore, the rotor, magnetic ring, and axial stator core are made of electrical pure iron DT4C; the magnetic isolation ring is made of non-magnetic material.

[0013] Furthermore, the Y-axis radial stator core and the X-axis radial stator core are pressed from silicon steel sheets with a thickness of 0.3mm, and the X-axis and Y-axis magnetic poles form a radial working air gap of 0.5mm with the outer radial surface of the rotor; the right surface of the axial stator core forms an axial working air gap of 0.5mm with the left surface of the rotor magnetic ring.

[0014] Furthermore, the radially magnetized permanent magnet ring is located between the rotor and the magnetic guide ring, and a second air gap of 0.3 mm is formed between the outer diameter surface of the rotor and the inner diameter surface of the magnetic guide ring.

[0015] Furthermore, the outer diameter of the radially magnetized permanent magnet ring is smaller than the inner diameter of the outer magnetic pole of the axial stator core; the inner diameter of the radially magnetized permanent magnet ring is larger than the outer diameter of the inner magnetic pole of the axial stator core.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] (1) The three-degree-of-freedom permanent magnet biased magnetic bearing of the present invention splits the axial magnetic bearing stator into segments and installs them between the two magnetic poles of the radial magnetic bearing stator, and is on the same plane as the radial magnetic bearing stator, realizing the integrated design of radial and axial bearing functions, improving the utilization rate of structural space, and the magnetic bearing has a small axial dimension and a more compact structure, which is beneficial to improving the critical speed of the rotor.

[0018] (2) In the present invention, the three-degree-of-freedom permanent magnet bias magnetic bearing divides the radial stator core into two layers along the axial direction and adds a magnetic isolation ring. Each layer is an independent radial channel, realizing the decoupling of the control magnetic circuit of the two radial channels of the X-axis and Y-axis.

[0019] (3) In this invention, the three-degree-of-freedom permanent magnet bias magnetic bearing has two radial channels, X-axis and Y-axis, which are biased by their respective independent permanent magnets. This can weaken the influence of air gap magnetic resistance change on bias magnetic flux, realize the decoupling of bias magnetic circuit, greatly reduce magnetic bearing loss, and improve suspension control accuracy. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of the three-degree-of-freedom permanent magnet bias bearing of the present invention;

[0021] Figure 2 This is a schematic diagram of the three-degree-of-freedom permanent magnet biased magnetic bearing rotor system of the present invention;

[0022] Figure 3 This is a schematic diagram of the three-degree-of-freedom permanent magnet biased magnetic bearing stator system of the present invention;

[0023] Figure 4 This is an exploded view of the three-degree-of-freedom permanent magnet biased magnetic bearing stator system of the present invention;

[0024] Figure 5a , Figure 5b This is a three-dimensional and planar schematic diagram of the Y-axis radial control magnetic circuit and the bias magnetic circuit of the three-degree-of-freedom permanent magnet bias magnetic bearing of the present invention;

[0025] Figure 6a , Figure 6b This is a three-dimensional and planar schematic diagram of the X-axis radial control magnetic circuit and the bias magnetic circuit of the three-degree-of-freedom permanent magnet bias magnetic bearing of the present invention;

[0026] Figure 7 This is a schematic diagram of the Z-axis axial control magnetic circuit and bias magnetic circuit of the three-degree-of-freedom permanent magnet biased magnetic bearing of the present invention;

[0027] Figure 8 This invention relates to a PID feedback control scheme for a three-degree-of-freedom permanent magnet biased magnetic bearing.

[0028] Figure label:

[0029] 1. Rotor; 2. Radial magnetized permanent magnet ring; 3. Magnetic guide ring; 4. Y-axis radial stator core; 5. +X-axis radial coil winding; 6. -X-axis radial coil winding; 7. +Y-axis radial coil winding; 8. -Y-axis radial coil winding; 9. Sheet-shaped arc-shaped radial magnetized permanent magnet; 10. Axial stator core; 11. +Y-axis left axial coil winding; 12. +Y-axis right axial coil winding; 13. -Y-axis left axial coil winding; 14. -Y-axis right axial coil winding; 15. Magnetic isolation ring; 16. X-axis radial stator core; 17. X-axis radial control magnetic circuit; 18. Bias magnetic circuit; 19. Y-axis radial control magnetic circuit; 20. Z-axis axial control magnetic circuit. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the following description will be provided in conjunction with the appendix of the present invention. Figure 1-8 The technical solution of the present invention will be clearly and completely described.

[0031] This invention provides a three-degree-of-freedom permanent magnet bias bearing, such as... Figure 1 As shown, it includes: a rotor system, a radial magnetic bearing stator system, and an axial magnetic bearing stator system.

[0032] The rotor system structure is as follows Figure 2 As shown, the rotor system includes a rotor 1, a radially magnetized permanent magnet ring 2, and a magnetically conductive ring 3. The radially magnetized permanent magnet ring 2 is fixed to the radially outer side of the rotor 1; the magnetically conductive ring 3 is located radially outer side of the radially magnetized permanent magnet ring 2.

[0033] The radial magnetic bearing stator system includes a Y-axis radial stator core 4, an X-axis radial stator core 16, a magnetic isolation ring 15, a +X-axis radial coil winding 5, a -X-axis radial coil winding 6, a +Y-axis radial coil winding 7, and a -Y-axis radial coil winding 8.

[0034] The Y-axis radial stator core 4 and the X-axis radial stator core 16 are located radially outside the left side of the rotor 1; the magnetic isolation ring 15 is located between the Y-axis radial stator core 4 and the X-axis radial stator core 16; the +X-axis radial coil winding 5 and the -X-axis radial coil winding 6 are respectively wound around the right and left magnetic poles of the X-axis radial stator core 16 and fixed; the +Y-axis radial coil winding 7 and the -Y-axis radial coil winding 8 are respectively wound around the upper and lower magnetic poles of the Y-axis radial stator core 4 and fixed.

[0035] Furthermore, the axial magnetic bearing stator system includes four plate-shaped arc-shaped radially magnetized permanent magnets 9, four axial stator cores 10, a left-side axial coil winding 11 of the +Y axis, a right-side axial coil winding 12 of the +Y axis, a left-side axial coil winding 13 of the -Y axis, and a right-side axial coil winding 14 of the -Y axis; the four plate-shaped arc-shaped radially magnetized permanent magnets 9 are respectively located on and fixed to the yokes of the radial stator cores with the +Y axis deflected counterclockwise by 45°, the +Y axis deflected clockwise by 45°, the -Y axis deflected clockwise by 45°, and the -Y axis deflected counterclockwise by 45°; the four axial stator cores 10 are located in the following positions: +Y axis deflected counterclockwise by 45°, +Y axis deflected clockwise by 45°, -Y axis deflected clockwise by 45°, and -Y axis deflected counterclockwise by 45°. The four axial stator cores 10 are fixedly connected to the corresponding plate-shaped radially magnetized permanent magnets 9.

[0036] Furthermore, the rotor 1, magnetic ring 3, and axial stator core 10 are made of magnetically conductive materials, such as electrical pure iron DT4C, No. 10 steel, etc.

[0037] Furthermore, the Y-axis radial stator core 4 and the X-axis radial stator core 16 are made of silicon steel sheets with a thickness of 0.3mm, and the X-axis and Y-axis magnetic poles form a radial working air gap of 0.5mm with the outer radial surface of the rotor; the right surface of the axial stator core 10 forms an axial working air gap of 0.5mm with the left surface of the rotor magnetic ring 3.

[0038] Furthermore, the radially magnetized permanent magnet ring 2 is located between the rotor 1 and the magnetic ring 3, and a second air gap of 0.3 mm is formed between the outer diameter surface of the rotor 1 and the inner diameter surface of the magnetic ring 3.

[0039] Furthermore, the outer diameter of the radially magnetized permanent magnet ring 2 is smaller than the inner diameter of the outer magnetic pole of the axial stator core 10; the inner diameter of the radially magnetized permanent magnet ring 2 is larger than the outer diameter of the inner magnetic pole of the axial stator core 10.

[0040] Furthermore, the magnetic isolation ring 15 is made of a non-magnetic material, such as aluminum alloy or non-magnetic stainless steel; the eight protrusions (15a1, 15a2, 15a3, 15a4, 15b1, 15b2, 15b3, 15b4) of the magnetic isolation ring 15 are used for the installation and positioning of the X-axis and Y-axis radial stators, and can prevent mutual interference between the bias magnetic flux and the control magnetic flux of the two channels of the X-axis and Y-axis.

[0041] Furthermore, the four magnetic poles of the radial magnetic bearing stator system are located in the same plane to avoid additional magnetic force in a certain direction caused by the asymmetry of the magnetic bearing structure; the magnetic poles of the Y-axis radial stator core 4 and the X-axis radial stator core 16 are misaligned relative to the yoke, and the four magnetic poles are directly facing the center of the radial magnetic bearing stator system; the cross-sectional area of ​​the magnetic pole is not less than twice the cross-sectional area of ​​the yoke, and to avoid magnetic flux saturation at the corners, the corners between the magnetic poles and the yoke are designed as rounded corners.

[0042] Furthermore, the magnetic isolation ring protrusions 15a1 and 15a3 are located between the upper and lower magnetic poles of the Y-axis and the radial stator core yoke of the X-axis; the magnetic isolation ring protrusions 15a2 and 15a4 are located between the left and right magnetic poles of the X-axis and the radial stator core yoke of the Y-axis; the magnetic isolation ring protrusions 15b1 and 15b3 are located between the radial stator core yoke of the X-axis and the sheet-like arc-shaped radially magnetized permanent magnet; and the magnetic isolation ring protrusions 15b2 and 15b4 are located between the radial stator core yoke of the Y-axis and the sheet-like arc-shaped radially magnetized permanent magnet.

[0043] The three-degree-of-freedom permanent magnet biased magnetic bearing divides the axial magnetic bearing stator into segments, and its structure is as follows: Figure 3 As shown, installing it between the two magnetic poles of the radial magnetic bearing stator, on the same plane as the radial magnetic bearing stator, can reduce the volume of the magnetic bearing and improve the utilization of structural space; as Figure 4 As shown, the radial stator core of the magnetic bearing is divided into two layers along the axial direction, with a magnetic isolation ring installed in between. Each layer forms an independent radial channel, achieving decoupling of the radial control magnetic circuit, which reduces magnetic bearing losses and improves levitation control accuracy. The X-axis and Y-axis radial channels are biased by their respective independent permanent magnets, weakening the influence of air gap magnetic reluctance changes on the bias flux, achieving decoupling of the bias magnetic circuit, and reducing magnetic bearing losses.

[0044] The present invention also provides a method for controlling the above-mentioned three-degree-of-freedom permanent magnet bias bearing, comprising the following steps:

[0045] 1) Four plate-shaped radially magnetized permanent magnets 9 generate bias magnetic flux that passes through the Y-axis and X-axis radial magnetic bearing stators 4 and 16, which are divided into two layers by the magnetic isolation ring. Due to the isolation effect of the protrusions 15b1 and 15b3 of the magnetic isolation ring, the permanent magnets on the upper left and lower right only provide bias to the Y-axis radial channel. The two protrusions 15b2 and 15b4 of the magnetic isolation ring make the permanent magnets on the upper right and lower left only provide bias to the X-axis radial channel. The magnetic lines of force of the X-axis radial channel and the Y-axis radial channel converge at the rotor, flow into the axial magnetic bearing core 10 through the rotor's thrust disk, and finally return to the permanent magnet, forming a closed bias magnetic circuit 18.

[0046] 2) When the magnetic bearing is working normally and there is no external interference, due to the symmetry of the three-degree-of-freedom permanent magnet bias magnetic bearing structure, the radial air gap magnetic flux remains equal. According to the relationship between electromagnetic force and magnetic flux, the electromagnetic net force on the rotor is zero, that is, the rotor remains in balance under the bias magnetic flux.

[0047] When the rotor system is subjected to external disturbance along the positive Y-axis, and the rotor deviates from its equilibrium position, the displacement sensor in the feedback loop detects the rotor displacement and transmits this displacement signal to the controller. The controller converts the displacement signal into a control signal and calculates the control current i. y (t):

[0048]

[0049] Where i0 is the initial current, K u Pe is the amplifier's scaling factor; y (t) represents proportional feedback, and the control parameter is P; It is differential feedback, and the control parameter is D; I∫e y (t)dt represents integral feedback, with control parameters I and L. r and R r These are the radial coil winding inductance and resistance, respectively; e y This represents the rotor's offset displacement along the Y-axis;

[0050] The power amplifier outputs a control current i based on the control signal. y (t) is applied to the +Y axis radial coil winding (7) and the -Y axis radial coil winding (8) to adjust the magnitude and direction of the current, generate an induced electromotive force, and excite the control flux that flows from the -Y axis to the rotor, then to the +Y axis, and back to the -Y axis along the yoke; the control flux and the bias flux are superimposed at the air gap in the negative direction of the Y axis, and the control flux and the bias flux are canceled at the air gap in the positive direction of the Y axis, so that the electromagnetic resultant force generated by the two air gaps is along the negative direction of the Y axis, thereby adjusting the rotor system back to the equilibrium position;

[0051] When the rotor system is subjected to external disturbance along the negative Y-axis, the displacement sensor detects the rotor displacement, the controller converts this displacement signal into a control signal, and the power amplifier converts the control signal into a current i. y (t), and applied to the +Y axis radial coil winding (7) and the -Y axis radial coil winding (8), by adjusting the magnitude and direction of the current, an induced electromotive force is generated, which excites the control flux flowing from the -Y axis to the rotor, then to the +Y axis, and back to the -Y axis along the yoke. At the air gap in the negative direction of the Y axis, the control flux and the bias flux are superimposed; at the air gap in the positive direction of the Y axis, the control flux and the bias flux cancel each other out. The electromagnetic resultant force generated by the two air gaps acts in the negative direction of the Y axis, and finally adjusts the rotor system back to the equilibrium position, thereby realizing the translational control of the magnetic bearing in the Y axis direction;

[0052] 3) The control principle of the magnetic bearing translating along the X-axis is as follows: When the rotor system is subjected to external disturbance along the positive X-axis and the rotor deviates from the equilibrium position, the displacement sensor in the feedback loop detects the rotor displacement and transmits the displacement signal to the controller. The controller converts the displacement signal into a control signal, calculates the control current, and applies a current i of corresponding magnitude and direction to the +X-axis radial coil winding (5) and the -X-axis radial coil winding (6). x (t):

[0053]

[0054] Among them, e x This represents the rotor's offset displacement along the X-axis;

[0055] A control flux is excited in the radial magnetic poles along the X-axis to balance external disturbances and maintain system stability. During this process, the control flux and the bias flux in the air gap are superimposed. When the control flux and the bias flux are in the same direction, the electromagnetic force increases; when the control flux and the bias flux are in opposite directions, the electromagnetic force decreases. The resultant electromagnetic force generated in this process adjusts the rotor system back to the equilibrium position. When the rotor system is subjected to external disturbances along the negative X-axis direction, the current i in the axial coil winding is changed. x The direction and magnitude of (t) enable translational control of the magnetic bearing along the X-axis;

[0056] 4) The axial bias flux is mainly provided by the radially magnetized permanent magnet ring (2), passes through the outer magnetic pole of the axial magnetic bearing core (10), and then returns to the radially magnetized permanent magnet ring (2) through the inner magnetic pole of the axial magnetic bearing core (10). Two of these three-degree-of-freedom permanent magnet bias magnetic bearings are installed on the spindle. When the magnetic bearing system is working normally and there is no external interference, the electromagnetic resultant force of the two magnetic bearings on the spindle is zero, that is, the spindle system remains balanced under the action of the bias flux.

[0057] When the spindle system is subjected to external disturbance along the positive Z-axis and deviates from the equilibrium position, the air gap in the positive Z-axis direction between the left three-degree-of-freedom permanent magnet bias magnetic bearing rotor system and the axial magnetic bearing core (10) decreases, while the air gap in the negative Z-axis direction of the right magnetic bearing increases. Under these circumstances, the magnetic flux in the air gap in the positive Z-axis direction is greater than that in the air gap in the negative Z-axis direction, resulting in the electromagnetic force in the positive Z-axis direction being greater than that in the negative Z-axis direction. The displacement signal detected by the displacement sensor adjusts the current i in the four series-connected axial coil windings (11, 12, 13, 14). z The magnitude and direction of (t) excite the control flux:

[0058]

[0059] Among them, L zand R z e represents the inductance and resistance of the axial coil, respectively. z This represents the rotor's deviation displacement along the Z-axis;

[0060] In the negative Z-axis air gap, the control magnetic flux and the permanent magnet magnetic flux are superimposed; in the positive Z-axis air gap, the control magnetic flux and the permanent magnet magnetic flux cancel each other out. Finally, the electromagnetic resultant force generated by the two air gaps acts along the negative Z-axis, adjusting the rotor system back to the equilibrium position. When the rotor system is subjected to external disturbances along the negative Z-axis, the translational control of the magnetic bearing along the Z-axis is achieved by changing the direction and magnitude of the current in the axial coil winding.

[0061] 5) A second air gap of 0.3mm is formed between the outer diameter surface of the rotor and the inner diameter surface of the magnetic ring, so that the Z-axis axial control magnetic circuit passes through the working air gap and the second air gap without passing through the permanent magnet ring itself, further reducing the power consumption of the magnetic bearing.

[0062] The above control current i x (t), i y (t), i z The derivation of t0 is as follows:

[0063] Based on the working principle of the three-degree-of-freedom permanent magnet bias bearing, a PID feedback control scheme is constructed. Taking the translational control in the X-axis direction as an example, the control framework is shown in the appendix of the instruction manual. Figure 8 As shown.

[0064] First, a reference position input r is set, representing the desired position of the system. The system calculates the difference between the reference input r and the feedback signal x0 (the position measured by the sensor), obtaining the error signal e. The error signal passes through a voltage-controlled PID controller, which converts the voltage signal u... c It can be expressed as a function of displacement, displacement derivative, and displacement integral, as shown in equation (1):

[0065]

[0066] This control system comprises three components: proportional feedback (control parameter P), derivative feedback (control parameter D), and integral feedback (control parameter I). By adjusting these three parameters, precise control of the system can be achieved. The error signal e(t) = r(t) - x0(t) represents the error between the desired value and the measured value, where t is time.

[0067] Because the inductance of the magnetic bearing coil impedes rapid changes in current, the voltage signal needs to be amplified. Control signal u c After amplification, the driving voltage u is obtained, as shown below:

[0068] u=K u u c #(2)

[0069] Among them, K u This is the amplifier's scaling factor.

[0070] Inductance L of the radial coil winding r and resistance R r Under the influence of the coil current i x The relationship with the driving voltage u can be expressed as:

[0071]

[0072] The electromagnetic force F generated by the magnetic bearing system x It can be linearized as follows:

[0073] F x =K ix i x -K sx x#(4)

[0074] Among them, K ix K is the current stiffness coefficient. sx is the displacement stiffness coefficient, and x is the rotor displacement in the X-axis direction.

[0075] Electromagnetic force K ix i x Resilience-K sx x and external disturbance force ΔF e The sum of these forces represents the total force acting on the rotor system. According to Newton's second law, the dynamic equation of the rotor system is:

[0076]

[0077] The total force causes the rotor to accelerate. The displacement x can be obtained by two integrations, and then fed back to the controller through the sensor, thereby achieving precise displacement control under closed-loop control.

[0078] The translational control in the Y and Z axes also adopts the aforementioned PID feedback control scheme. Assuming the initial current is i0, the control current of the three-degree-of-freedom permanent magnet bias bearing can be derived according to equations (1), (2), and (3), as shown in equation (6):

[0079]

[0080] Among them, L z and R z These represent the inductance and resistance of the axial coil, respectively.

[0081] The working principle of the three-degree-of-freedom permanent magnet bias bearing of this invention is as follows:

[0082] Four sheet-like, arc-shaped radially magnetized permanent magnets 9 generate bias magnetic flux that passes through the Y-axis and X-axis radial magnetic bearing stators 4 and 16, which are divided into two layers by a magnetic isolation ring. The upper left and lower right permanent magnets 9 provide bias to the Y-axis radial channel, while the upper right and lower left permanent magnets 9 provide bias to the X-axis radial channel. The flux flows through the rotor 1 thrust disk into the axial magnetic bearing core 10 and finally returns to the permanent magnets, forming a closed bias magnetic circuit 18.

[0083] like Figure 5a , Figure 5b As shown, taking Y-axis translation as an example, when the rotor is in the equilibrium position, the radial air gaps along the Y-axis are equal, the electromagnetic attraction forces are equal, and the electromagnetic resultant force on the magnetic bearing rotor is zero, achieving stable levitation of the rotor. When the rotor system is disturbed and deviates from the equilibrium position along the negative Y-axis, the air gap between the positive Y-axis magnetic poles of the radial magnetic bearing stator system and the rotor system increases, while the air gap in the negative Y-axis direction decreases. The displacement sensor detects the displacement signal and transmits it to the controller amplifier, applying corresponding currents to the +Y-axis radial coil winding 7 and the -Y-axis radial coil winding 8. This causes the induced electromotive force to excite control flux flowing from the +Y-axis to the -Y-axis in the radial magnetic poles of the Y-axis. The control flux and the permanent magnet flux are superimposed in the positive Y-axis air gap and canceled out in the negative Y-axis air gap. The electromagnetic resultant force generated in the air gap is along the positive Y-axis, adjusting the rotor system back to the equilibrium position, thus achieving control of the magnetic bearing's translation along the Y-axis. Similarly, the translational control of the magnetic bearing along the X-axis can be achieved by applying corresponding currents to the +X-axis radial coil winding 5 and the -X-axis radial coil winding 6.

[0084] The X-axis radial control magnetic circuit 17 and bias magnetic circuit 18 are distributed as follows: Figure 6a , Figure 6b As shown. The Z-axis axial control magnetic circuit 20 and the bias magnetic circuit 18 are distributed as follows. Figure 7 As shown, "×" indicates that the coil current direction is perpendicular to the paper and inwards, and "·" indicates that the coil current direction is perpendicular to the paper and outwards.

[0085] At this time, the control magnetic flux and the bias magnetic flux in the axial air gap are superimposed, resulting in a larger electromagnetic force on both surfaces of the air gap. Similarly, when the current is reversed, the control magnetic flux and the bias magnetic flux cancel each other out, resulting in a smaller electromagnetic force. By installing two of these three-degree-of-freedom permanent magnet bias magnetic bearings on the spindle and controlling the resultant force of the axial electromagnetic forces of the two magnetic bearings, the translational control of the magnetic bearings along the Z-axis can be achieved.

[0086] The outer diameter surface of rotor 1 and the inner diameter surface of magnetic ring 3 form a second air gap of 0.3mm, which allows the Z-axis axial control magnetic circuit 20 to pass through the second air gap without passing through the permanent magnet ring 2 itself, further reducing the power consumption of the magnetic bearing.

[0087] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to the embodiments of this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A three-degree-of-freedom permanent magnet bias bearing, characterized in that, This includes the rotor system, the radial magnetic bearing stator system, and the axial magnetic bearing stator system. The rotor system includes a rotor (1), a radially magnetized permanent magnet ring (2), and a magnetic guide ring (3); the radially magnetized permanent magnet ring (2) is located radially outside the rotor (1), and the magnetic guide ring (3) is located radially outside the radially magnetized permanent magnet ring (2); The radial magnetic bearing stator system includes a Y-axis radial stator core (4), an X-axis radial stator core (16), a magnetic isolation ring (15), a +X-axis radial coil winding (5), a -X-axis radial coil winding (6), a +Y-axis radial coil winding (7), and a -Y-axis radial coil winding (8). The Y-axis radial stator core (4) and the X-axis radial stator core (16) are located on the radial outer side of the left side of the rotor (1). The magnetic isolation ring (15) is located between the Y-axis radial stator core (4) and the X-axis radial stator core (16). The +X-axis radial coil winding (5) and the -X-axis radial coil winding (6) are respectively wound around the right and left magnetic poles of the X-axis radial stator core (16) and fixed. The +Y-axis radial coil winding (7) and the -Y-axis radial coil winding (8) are respectively wound around the upper and lower magnetic poles of the Y-axis radial stator core (4) and fixed. The eight protrusions (15a1, 15a2, 15a3, 15a4, 15b1, 15b2, 15b3, 15b4) of the magnetic isolation ring (15) are used for the installation and positioning of the radial stator of the X-axis and Y-axis, and can prevent mutual interference between the bias magnetic flux and the control magnetic flux of the two channels of the X-axis and Y-axis. The axial magnetic bearing stator system includes four plate-shaped arc-shaped radially magnetized permanent magnets (9), four axial stator cores (10), a +Y axis left-side axial coil winding (11), a +Y axis right-side axial coil winding (12), a -Y axis left-side axial coil winding (13), and a -Y axis right-side axial coil winding (14); the four plate-shaped arc-shaped radially magnetized permanent magnets (9) are respectively located on the +Y axis reverse of the Y axis radial stator core. The magnetic yokes are rotated 45° clockwise, 45° clockwise on the +Y axis, 45° clockwise on the -Y axis, and 45° counterclockwise on the -Y axis, and fixed thereto. The four axial stator cores (10) are located at the corresponding positions of the four plate-shaped arc-shaped radially magnetized permanent magnets (9) rotated 45° counterclockwise on the +Y axis, 45° clockwise on the +Y axis, 45° clockwise on the -Y axis, and 45° counterclockwise on the -Y axis, and fixed thereto.

2. The three-degree-of-freedom permanent magnet bias bearing according to claim 1, characterized in that: The rotor (1), magnetic ring (3), and axial stator core (10) are made of electrical pure iron DT4C; the magnetic isolation ring (15) is made of non-magnetic material.

3. The three-degree-of-freedom permanent magnet bias bearing according to claim 1, characterized in that: The Y-axis radial stator core (4) and X-axis radial stator core (16) are made of silicon steel sheets with a thickness of 0.3mm. The X-axis magnetic pole of the X-axis radial stator core (16) and the Y-axis magnetic pole of the Y-axis radial stator core (4) form a radial working air gap of 0.5mm with the outer radial surface of the rotor. The right surface of the axial stator core (10) forms an axial working air gap of 0.5mm with the left surface of the rotor magnetic ring (3).

4. The three-degree-of-freedom permanent magnet bias bearing according to claim 1, characterized in that: A radially magnetized permanent magnet ring (2) is located between the rotor (1) and the magnetic ring (3), and a second air gap of 0.3 mm is formed between the outer diameter surface of the rotor (1) and the inner diameter surface of the magnetic ring (3).

5. The three-degree-of-freedom permanent magnet bias bearing according to claim 1, characterized in that: The outer diameter of the radially magnetized permanent magnet ring (2) is smaller than the inner diameter of the outer magnetic pole of the axial stator core (10); the inner diameter of the radially magnetized permanent magnet ring (2) is larger than the outer diameter of the inner magnetic pole of the axial stator core (10).

6. A method for controlling a three-degree-of-freedom permanent magnet biased magnetic bearing according to any one of claims 1-5, characterized in that: 1) Four plate-shaped radially magnetized permanent magnets (9) generate bias magnetic flux that passes through the Y-axis and X-axis radial magnetic bearing stators (4, 16) which are divided into two layers by the magnetic isolation ring. Due to the isolation effect of the protrusions 15b1 and 15b3 of the magnetic isolation ring, the permanent magnets on the upper left and lower right only provide bias to the Y-axis radial channel. The two protrusions 15b2 and 15b4 of the magnetic isolation ring make the permanent magnets on the upper right and lower left only provide bias to the X-axis radial channel. The magnetic lines of force of the X-axis radial channel and the Y-axis radial channel converge at the rotor, flow into the axial magnetic bearing core (10) through the rotor's thrust disk, and finally return to the permanent magnet, forming a closed bias magnetic circuit (18). 2) When the magnetic bearing is working normally and there is no external interference, due to the symmetry of the three-degree-of-freedom permanent magnet bias magnetic bearing structure, the radial air gap magnetic flux remains equal. According to the relationship between electromagnetic force and magnetic flux, the electromagnetic net force on the rotor is zero, that is, the rotor remains in balance under the bias magnetic flux. When the rotor system is subjected to external disturbances along the positive Y-axis, causing the rotor to deviate from its equilibrium position, the displacement sensor in the feedback loop detects the rotor displacement and transmits this displacement signal to the controller. The controller then converts the displacement signal into a control signal and calculates the control current. : ， in, For the initial current, The amplifier's scaling factor; It is a proportional feedback, and the control parameter is P; It is differential feedback, and the control parameter is D; It is integral feedback, and the control parameter is I; and These are the radial coil winding inductance and resistance, respectively; This represents the rotor's offset displacement along the Y-axis; The power amplifier outputs a control current based on the control signal. The control flux is applied to the +Y axis radial coil winding (7) and the -Y axis radial coil winding (8) to generate an induced electromotive force, which excites the magnetic field lines to flow from the -Y axis to the rotor, then to the +Y axis, and back to the -Y axis along the yoke. The control flux and the bias flux are superimposed in the air gap in the negative direction of the Y axis, and canceled in the air gap in the positive direction of the Y axis, so that the electromagnetic resultant force generated by the two air gaps is along the negative direction of the Y axis, thereby adjusting the rotor system back to the equilibrium position. When the rotor system is subjected to external disturbance along the negative Y-axis, the displacement sensor detects the rotor displacement, the controller converts this displacement signal into a control signal, and the power amplifier converts the control signal into current. The control flux is applied to the +Y axis radial coil winding (7) and the -Y axis radial coil winding (8) to generate an induced electromotive force, which excites the control flux to flow from the -Y axis to the rotor, then to the +Y axis, and back to the -Y axis along the yoke. At the air gap in the negative direction of the Y axis, the control flux and the bias flux are superimposed. At the air gap in the positive direction of the Y axis, the control flux and the bias flux cancel each other out. The electromagnetic resultant force generated by the two air gaps acts in the negative direction of the Y axis, and finally adjusts the rotor system back to the equilibrium position, thereby realizing the translational control of the magnetic bearing in the Y axis direction. 3) The control principle of the magnetic bearing translating along the X-axis is as follows: When the rotor system is subjected to external disturbance along the positive X-axis and the rotor deviates from the equilibrium position, the displacement sensor in the feedback loop detects the rotor displacement and transmits the displacement signal to the controller. The controller converts the displacement signal into a control signal, calculates the control current, and applies current to the +X-axis radial coil winding (5) and the -X-axis radial coil winding (6). : in, This represents the rotor's offset displacement along the X-axis; A control flux is excited in the radial magnetic poles along the X-axis to balance external disturbances and maintain system stability. The control flux and bias flux in the air gap are superimposed. When the control flux and bias flux are in the same direction, the electromagnetic force increases; when they are in opposite directions, the electromagnetic force decreases. The resultant electromagnetic force adjusts the rotor system back to the equilibrium position. When the rotor system is subjected to external disturbances along the negative X-axis direction, the current in the axial coil windings is changed. The direction and size of the magnetic bearing are used to achieve translational control along the X-axis; 4) The axial bias flux is mainly provided by the radially magnetized permanent magnet ring (2), passes through the outer magnetic pole of the axial magnetic bearing core (10), and then returns to the radially magnetized permanent magnet ring (2) through the inner magnetic pole of the axial magnetic bearing core (10). Two of these three-degree-of-freedom permanent magnet bias magnetic bearings are installed on the spindle. When the magnetic bearing system is working normally and there is no external interference, the electromagnetic resultant force of the two magnetic bearings on the spindle is zero, that is, the spindle system remains balanced under the action of the bias flux. When the spindle system is subjected to external disturbance along the positive Z-axis and deviates from the equilibrium position, the air gap in the positive Z-axis direction between the left three-degree-of-freedom permanent magnet bias magnetic bearing rotor system and the axial magnetic bearing core (10) decreases, while the air gap in the negative Z-axis direction of the right magnetic bearing increases. Under these circumstances, the magnetic flux in the air gap in the positive Z-axis direction is greater than that in the air gap in the negative Z-axis direction, resulting in the electromagnetic force in the positive Z-axis direction being greater than that in the negative Z-axis direction. The displacement signal detected by the displacement sensor adjusts the current in the four series-connected axial coil windings (11, 12, 13, 14). Excites the control magnetic flux: in, and These represent the inductance and resistance of the axial coil, respectively. This represents the rotor's deviation displacement along the Z-axis; In the negative Z-axis air gap, the control magnetic flux and the permanent magnet magnetic flux are superimposed; in the positive Z-axis air gap, the control magnetic flux and the permanent magnet magnetic flux cancel each other out. Finally, the electromagnetic resultant force generated by the two air gaps acts along the negative Z-axis, adjusting the rotor system back to the equilibrium position. When the rotor system is subjected to external disturbances along the negative Z-axis, the translational control of the magnetic bearing along the Z-axis is achieved by changing the direction and magnitude of the current in the axial coil winding. 5) A second air gap of 0.3mm is formed between the outer diameter surface of the rotor and the inner diameter surface of the magnetic ring, so that the Z-axis axial control magnetic circuit passes through the working air gap and the second air gap without passing through the permanent magnet ring itself, further reducing the power consumption of the magnetic bearing.

7. An electronic device, characterized in that: It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor runs the computer program, it performs the steps of the method of claim 6.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method of claim 6.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method of claim 6.

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