Three-degree-of-freedom permanent magnet biased magnetic bearing

Abstract

The invention 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 magnetizing permanent magnet ring and a magnetic conducting ring; the radial magnetic bearing stator system comprises a radial stator iron core, a magnetism isolating ring and a radial coil winding; the axial magnetic bearing stator system comprises a sheet-shaped arc-shaped radial magnetizing permanent magnet, an axial stator iron core and an axial coil winding; according to the three-degree-of-freedom permanent magnet biased magnetic bearing, the axial magnetic bearing stator surrounds the periphery of the rotor and 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; radial two-degree-of-freedom translation control and axial translation control can be realized; magnetic isolation rings are additionally arranged among the radial stator iron cores, so that decoupling of a magnetic circuit controlled by two radial channels of an x axis and a y axis is realized; the two radial channels are biased by independent permanent magnets, so that the decoupling of a biased magnetic circuit is realized, and the influence of air gap magnetic resistance change is weakened; and the second air gap is arranged, so that the axial control magnetic circuit does not pass through the permanent magnet ring, and the power consumption of the magnetic bearing is further reduced.

Description

Technical Field

[0001] The invention relates to the field of magnetic suspension bearings, and in particular to a three-degree-of-freedom permanent magnet biased magnetic bearing. Background Art

[0002] Magnetic bearings achieve frictionless suspension of the rotor through the suspension force generated by the magnetic field. They have the advantages of no contact, low loss, high operating speed and long life. They are widely used in aerospace, artificial hearts, high-speed blowers and other fields. Compared with pure electromagnetic magnetic bearings, permanent magnetic biased magnetic bearings generate bias magnetic fields through permanent magnets, which have the advantages of low power consumption and high load-bearing capacity. In traditional three-degree-of-freedom permanent magnetic biased magnetic bearings, the two radial channels share permanent magnets and stator cores, which will cause the two radial channels to have bias magnetic circuit coupling and control magnetic circuit coupling at the same time, which increases energy consumption and is not conducive to improving suspension accuracy. In addition, traditional three-degree-of-freedom permanent magnetic biased magnetic bearings have problems such as large size and long axial size, which limits the critical speed of the rotor. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention provides a three-degree-of-freedom permanent magnet biased magnetic bearing. The axial magnetic bearing stator is divided into petals and installed between the two magnetic poles of the radial magnetic bearing stator, and is in the same plane as the radial magnetic bearing stator, so as to realize the integrated design of radial and axial bearing functions and improve the utilization rate of the structural space. Reducing the axial size of the magnetic bearing is beneficial to improving the critical speed of the rotor, and can realize radial two-degree-of-freedom and axial translational control. A magnetic isolation ring is installed between the radial stator cores to realize the decoupling of the control magnetic circuits of the two radial channels of the X-axis and the Y-axis; the two radial channels of the X-axis and the Y-axis are biased by their own independent permanent magnets, which can weaken the influence of the change of the air gap magnetic resistance on the bias magnetic flux, realize the decoupling of the bias magnetic circuit, and can greatly reduce the loss of the magnetic bearing and improve the accuracy of suspension control.

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

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

[0006] The rotor system comprises a rotor, a radially magnetized permanent magnet ring, and a magnetic conductive ring; the radially magnetized permanent magnet ring is fixed to the radial outer side of the rotor; the magnetic conductive 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 the X-axis radial stator core are located radially outside the axial left side of the rotor; 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 on the four magnetic poles of the radial stator core on the right, left, top and bottom, and fixed with epoxy resin glue;

[0009] Furthermore, the axial magnetic bearing stator system comprises four lamellar arc-shaped radial magnetized permanent magnets, four axial stator cores, a +Y-axis left axial coil winding, a +Y-axis right axial coil winding, a -Y-axis left axial coil winding, and a -Y-axis right axial coil winding; the four lamellar arc-shaped radial magnetized permanent magnets are respectively located on and fixed to the yokes of the radial stator core at 45° counterclockwise deflection of the +Y axis, 45° clockwise deflection of the +Y axis, 45° clockwise deflection of the -Y axis, and 45° counterclockwise deflection of the -Y axis; the four axial stator cores (10) are located inside the four lamellar arc-shaped radial magnetized permanent magnets at 45° counterclockwise deflection of the +Y axis, 45° clockwise deflection of the +Y axis, 45° clockwise deflection of the -Y axis, and 45° counterclockwise deflection of the -Y axis, and are fixed thereto.

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

[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 conductive ring and axial stator core are made of electrical pure iron DT4C; and the magnetic isolation ring is made of non-magnetic conductive 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 0.3 mm, and the X-axis and Y-axis magnetic poles and the radial outer surface of the rotor form a radial working air gap of 0.5 mm; the right surface of the axial stator core and the left surface of the rotor magnetic ring form an axial working air gap of 0.5 mm.

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

[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 present invention has the following beneficial effects:

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

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

[0019] (3) In the three-degree-of-freedom permanent magnet bias magnetic bearing of the present invention, the two radial channels of the X-axis and the Y-axis are biased by independent permanent magnets, which can weaken the influence of the change of the air gap magnetic resistance on the bias flux, realize the decoupling of the bias magnetic circuit, greatly reduce the loss of the magnetic bearing, and improve the suspension control accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0023] Figure 4 An exploded diagram of a three-degree-of-freedom permanent magnetic biased magnetic bearing stator system of the present invention;

[0024] Figure 5a , Figure 5b It 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 magnetic bias magnetic bearing of the present invention;

[0025] Figure 6a , Figure 6b It 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 magnetic bias magnetic bearing of the present invention;

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

[0027] Figure 8 This is the PID feedback control scheme for the three-degree-of-freedom permanent magnet biased magnetic bearing of the present invention.

[0028] Reference numerals:

[0029] 1. Rotor; 2. Radial magnetized permanent magnet ring; 3. Magnetic conductive 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 circular arc 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 DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following will be combined with the appended claims of the present invention. Figure 1-8 The technical solution of the present invention is described clearly and completely.

[0031] The present invention provides a three-degree-of-freedom permanent magnetic bias magnetic 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 magnetic conductive ring 3. The radially magnetized permanent magnet ring 2 is fixed to the radial outer side of the rotor 1; the magnetic conductive ring 3 is located at the radial 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 axial 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 on the right and left magnetic poles of the X-axis radial stator core 16 and fixed, and the +Y-axis radial coil winding 7 and the -Y-axis radial coil winding 8 are respectively wound on 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 lamellar arc-shaped radial magnetized permanent magnets 9, four axial stator cores 10, an axial coil winding 11 on the left side of the +Y axis, an axial coil winding 12 on the right side of the +Y axis, an axial coil winding 13 on the left side of the -Y axis, and an axial coil winding 14 on the right side of the -Y axis; the four lamellar arc-shaped radial magnetized permanent magnets 9 are respectively located and fixed on the yokes of the radial stator core at a deflection of 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; the four axial stator cores 10 are located at the following positions: a deflection of 45° counterclockwise on the +Y axis, a deflection of 45° clockwise on the +Y axis, a deflection of 45° clockwise on the -Y axis, and a deflection of 45° counterclockwise on the -Y axis. The four axial stator cores 10 are fixedly connected to the sheet-like circular arc-shaped radially magnetized permanent magnets 9 at corresponding positions.

[0036] Furthermore, the rotor 1, the magnetic ring 3, and the axial stator core 10 are made of magnetic 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 pressed from silicon steel sheets with a thickness of 0.3 mm, and the X-axis and Y-axis magnetic poles and the radial outer surface of the rotor form a radial working air gap of 0.5 mm; the right surface of the axial stator core 10 and the left surface of the rotor magnetic ring 3 form an axial working air gap of 0.5 mm.

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

[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 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 installation and positioning of the X-axis and Y-axis radial stators, and can prevent mutual interference between the bias flux and the control flux of the X-axis and Y-axis channels.

[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 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 in order to avoid magnetic flux saturation at the corners, the corners between the magnetic pole and the yoke are designed to be rounded.

[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 circular arc-shaped radial magnetized permanent magnet; the magnetic isolation ring protrusions 15b2 and 15b4 are located between the radial stator core yoke of the Y-axis and the sheet-like circular arc-shaped radial magnetized permanent magnet.

[0043] The three-degree-of-freedom permanent magnetic bias magnetic bearing divides the axial magnetic bearing stator into petals, and its structure is as follows Figure 3 As shown, it is installed between the two magnetic poles of the radial magnetic bearing stator and in the same plane as the radial magnetic bearing stator, which can reduce the volume of the magnetic bearing and improve the utilization of the structural space; Figure 4 As shown in the figure, the radial stator core in the magnetic bearing is divided into two layers along the axial direction, and a magnetic isolation ring is installed in the middle. Each layer forms an independent radial channel to achieve decoupling of the radial control magnetic circuit, which can reduce the loss of the magnetic bearing and improve the suspension control accuracy. The two radial channels of the X-axis and Y-axis are biased by independent permanent magnets, which weakens the influence of the change of air gap magnetic resistance on the bias flux, realizes decoupling of the bias magnetic circuit, and reduces the loss of the magnetic bearing.

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

[0045] 1) Four pieces of sheet-shaped arc-shaped radial magnetized permanent magnets 9 generate bias magnetic fluxes that pass through the Y-axis and X-axis radial magnetic bearing stators 4 and 16 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 upper left and lower right permanent magnets only provide bias for the Y-axis radial channel; the two protrusions 15b2 and 15b4 of the magnetic isolation ring make the upper right and lower left permanent magnets only provide bias for 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 thrust plate of the rotor, and finally return to the permanent magnet to form a closed bias magnetic circuit 18;

[0046] 2) When the magnetic bearing works 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. From the relationship between the electromagnetic force and the magnetic flux, it can be seen that the electromagnetic force on the rotor is zero, that is, the rotor remains balanced under the bias magnetic flux;

[0047] When the rotor system is disturbed by external factors along the positive direction of the Y 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 and calculates the control current i y (t):

[0048]

[0049] Where i0 is the initial current, K u is the proportional coefficient of the amplifier; Pe y (t) is proportional feedback, and the control parameter is P; is differential feedback, the control parameter is D; I∫e y (t)dt is integral feedback, and the control parameter is I; L r and R r are the inductance and resistance of radial coil winding respectively; e y is the deviation displacement of the rotor on the Y axis;

[0050] The power amplifier outputs a control current i according to the control signal y (t), 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 stimulate a control magnetic flux that flows from the -Y axis to the rotor, then to the +Y axis, and returns to the -Y axis along the magnetic yoke; the control magnetic flux and the bias magnetic flux are superimposed at the air gap in the negative direction of the Y axis, and the control magnetic flux and the bias magnetic flux are offset at the air gap in the positive direction of the Y axis, so that the electromagnetic force generated by the two air gaps is along the negative direction of the Y axis, thereby adjusting the rotor system back to a balanced position;

[0051] When the rotor system is disturbed by external factors along the negative direction of the Y axis, the displacement sensor detects the rotor displacement, the controller converts the 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 current size and direction, an induced electromotive force is generated, which stimulates the control flux to flow from the -Y axis to the rotor, then to the +Y axis, and return to the -Y axis along the magnetic 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 are offset, and the electromagnetic 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 translation of the magnetic bearing along the X-axis is as follows: when the rotor system is disturbed by the outside world along the positive direction of the 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 is the deviation displacement of the rotor on the X axis;

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

[0056] 4) The axial bias magnetic 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) from the inner magnetic pole of the axial magnetic bearing core (10). Two three-degree-of-freedom permanent magnetic bias magnetic bearings are installed on the main shaft. When the magnetic bearing system works normally and there is no external interference, the electromagnetic force of the two magnetic bearings on the main shaft is zero, that is, the main shaft system maintains balance under the action of the bias magnetic flux.

[0057] When the spindle system is disturbed by the outside world along the positive direction of the Z axis and deviates from the equilibrium position, the air gap in the positive direction of the Z axis between the left three-degree-of-freedom permanent magnet bias magnetic bearing rotor system and the axial magnetic bearing core (10) becomes smaller, and the air gap in the negative direction of the Z axis of the right magnetic bearing becomes larger. In this case, the magnetic flux in the air gap in the positive direction of the Z axis is greater than the magnetic flux in the air gap in the negative direction of the Z axis, resulting in the electromagnetic force in the positive direction of the Z axis being greater than the electromagnetic force in the negative direction of the Z axis. The displacement signal detected by the displacement sensor is used to adjust 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 They represent the inductance and resistance of the axial coil, respectively, and e z is the deviation displacement of the rotor on the Z axis;

[0060] At the air gap in the negative direction of the Z axis, the control magnetic flux is superimposed on the permanent magnetic flux; at the air gap in the positive direction of the Z axis, the control magnetic flux and the permanent magnetic flux are offset. Finally, the electromagnetic force generated by the two air gaps acts in the negative direction of the Z axis to adjust the rotor system back to the equilibrium position; when the rotor system is disturbed by the outside world in the negative direction of the Z axis, the translational control of the magnetic bearing along the Z axis is achieved by changing the current direction and magnitude of the axial coil winding.

[0061] 5) 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 conductive ring, so that the Z-axis axial control magnetic circuit passes through the working air gap and the second air gap instead of 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 process of t0 is as follows:

[0063] Based on the working principle of the three-degree-of-freedom permanent magnet biased magnetic bearing, a PID feedback control scheme is constructed. Taking the translation control in the X-axis direction as an example, its control framework is shown in the attached manual. Figure 8 shown.

[0064] First, the reference position input r is set to represent 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) to obtain the error signal e. The error signal is passed through a voltage-based PID controller to convert the voltage signal u c It is expressed as a function of displacement, displacement derivative and displacement integral, as shown in formula (1):

[0065]

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

[0067] Since the inductance of the magnetic bearing coil will hinder the rapid change of current, the voltage signal needs to be amplified. c After passing through the amplifier, the driving voltage u is obtained as follows:

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

[0069] Among them, K u is the proportionality factor of the amplifier.

[0070] The radial coil winding inductance L r and resistor R r Under the influence of 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:

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

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

[0075] Electromagnetic force K ix i x , Resilience-K sx x and the external disturbance force ΔF e The sum is 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 through two integrations and fed back to the controller through the sensor, thus achieving precise displacement control under closed-loop control.

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

[0079]

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

[0081] The working principle of the three-degree-of-freedom permanent magnetic bias magnetic bearing of the present invention is:

[0082] Four pieces of circular arc-shaped radial magnetized permanent magnets 9 generate bias magnetic fluxes that pass 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. The upper left and lower right permanent magnets 9 provide bias for the Y-axis radial channel, and the upper right and lower left permanent magnets 9 provide bias for the X-axis radial channel, and flow into the axial magnetic bearing core 10 through the thrust plate of the rotor 1, and finally return to the permanent magnets to form a closed bias magnetic circuit 18.

[0083] like Figure 5a , Figure 5b As shown, taking the Y-axis translation as an example, when the rotor is in the equilibrium position, the Y-axis radial air gap is equal, the electromagnetic attraction is equal, the electromagnetic force on the magnetic bearing rotor is zero, and the magnetic bearing realizes the stable suspension of the rotor. When the rotor system is disturbed and deviates from the equilibrium position along the negative direction of the Y-axis, the air gap between the positive magnetic pole of the Y-axis of the radial magnetic bearing stator system and the rotor system becomes larger, and the air gap in the negative direction of the Y-axis becomes smaller. The displacement sensor recognizes the displacement signal and transmits it to the controller amplifier, and applies corresponding current to the +Y-axis radial coil winding 7 and the -Y-axis radial coil winding 8, so that the induced electromotive force excites the control magnetic flux from the +Y-axis to the -Y-axis in the Y-axis radial magnetic pole. The control magnetic flux is superimposed with the permanent magnetic flux at the air gap in the positive direction of the Y-axis, and is offset with the permanent magnetic flux at the air gap in the negative direction of the Y-axis. The electromagnetic force generated at the air gap is along the positive direction of the Y-axis, adjusting the rotor system back to the equilibrium position, and realizing the control of the translation of the magnetic bearing along the Y-axis. Similarly, the translation 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 the bias magnetic circuit 18 are distributed as follows: Figure 6a , Figure 6b The Z-axis axial control magnetic circuit 20 and the bias magnetic circuit 18 are distributed as shown in FIG. Figure 7 As shown, “×” indicates that the direction of the coil current is perpendicular to the paper surface and inwards, and “·” indicates that the direction of the coil current is perpendicular to the paper surface and outwards.

[0085] At this time, the control magnetic flux and the bias magnetic flux in the axial air gap are superimposed, so that a greater electromagnetic force is generated on the two surfaces of the air gap. Similarly, when the current is reversed, the control magnetic flux and the bias magnetic flux cancel each other out, so that the electromagnetic force becomes smaller. Two three-degree-of-freedom permanent magnet biased magnetic bearings are installed on the main shaft. By controlling the combined axial electromagnetic force 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 the rotor 1 and the inner diameter surface of the magnetic conductive ring 3 form a second air gap of 0.3 mm, so that the Z-axis axial control magnetic circuit 20 passes through the second air gap instead of the permanent magnet ring 2 itself, further reducing the power consumption of the magnetic bearing.

[0087] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the embodiments of the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A three-degree-of-freedom permanent magnet biased magnetic bearing, characterized in that: It includes a rotor system, a radial magnetic bearing stator system, and an axial magnetic bearing stator system; The rotor system comprises a rotor (1), a radially magnetized permanent magnet ring (2), and a magnetic conductive ring (3); the radially magnetized permanent magnet ring (2) is located radially outside the rotor (1), and the magnetic conductive ring (3) is located radially outside the radially magnetized permanent magnet ring (2); The radial magnetic bearing stator system comprises 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 radially outside the axial 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.

2. The three-degree-of-freedom permanent magnet biased magnetic bearing according to claim 1, characterized in that: The axial magnetic bearing stator system comprises four sheet-shaped circular arc-shaped radial magnetized permanent magnets (9), four axial stator iron cores (10), a +Y-axis left axial coil winding (11), a +Y-axis right axial coil winding (12), a -Y-axis left axial coil winding (13), and a -Y-axis right axial coil winding (14); the four sheet-shaped circular arc-shaped radial magnetized permanent magnets (9) are respectively located on the +Y-axis counterclockwise direction of the Y-axis radial stator iron core. The four axial stator cores (10) are located at positions corresponding to the four sheet-shaped circular arc radial magnetized permanent magnets (9) with a clockwise deflection of 45°, a clockwise deflection of 45° on the +Y axis, a clockwise deflection of 45° on the -Y axis, and a counterclockwise deflection of 45° on the -Y axis, and are fixed thereto.

3. The three-degree-of-freedom permanent magnet biased magnetic bearing according to claim 1, characterized in that: The materials of the rotor (1), magnetic conductive ring (3) and axial stator core (10) are electrical pure iron DT4C; the magnetic isolation ring (14) is made of non-magnetic conductive material.

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

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

6. The three-degree-of-freedom permanent magnet biased magnetic 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); and 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).

7. A method for controlling a three-degree-of-freedom permanent magnetic bias magnetic bearing according to any one of claims 1 to 6, characterized in that: 1) Four pieces of circular arc-shaped radial magnetized permanent magnets (9) generate bias magnetic fluxes that pass through the Y-axis and X-axis radial magnetic bearing stators (4, 16) 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 upper left and lower right permanent magnets only provide bias for the Y-axis radial channel; the two protrusions 15b2 and 15b4 of the magnetic isolation ring enable the upper right and lower left permanent magnets to only provide bias for the X-axis radial channel. The magnetic lines of force of the X-axis radial channel and the Y-axis radial channel merge at the rotor, flow into the axial magnetic bearing core (10) through the thrust plate of the rotor, and finally return to the permanent magnets to form a closed bias magnetic circuit 18; 2) When the magnetic bearing works 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. From the relationship between the electromagnetic force and the magnetic flux, it can be seen that the electromagnetic force on the rotor is zero, that is, the rotor remains balanced under the bias magnetic flux; When the rotor system is disturbed by external factors along the positive direction of the Y 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 and calculates the control current i y (t): Where i0 is the initial current, K u is the proportional coefficient of the amplifier; Pe y (t) is proportional feedback, and the control parameter is P; is differential feedback, the control parameter is D; I∫e y (t)dt is integral feedback, and the control parameter is I; L r and R r are the inductance and resistance of radial coil winding respectively; e y is the deviation displacement of the rotor on the Y axis; The power amplifier outputs a control current i according to the control signal y (t), applied to the +Y-axis radial coil winding (7) and the -Y-axis radial coil winding (8), generates an induced electromotive force, excites the magnetic lines of force to flow from the -Y-axis to the rotor, then to the +Y-axis, and returns to the -Y-axis along the magnetic yoke to control the magnetic flux, superimposes the control magnetic flux and the bias magnetic flux at the air gap in the negative direction of the Y-axis, and cancels the control magnetic flux and the bias magnetic flux at the air gap in the positive direction of the Y-axis, so that the electromagnetic force generated by the two air gaps is along the negative direction of the Y-axis, thereby adjusting the rotor system to return to the equilibrium position; When the rotor system is disturbed by external factors along the negative direction of the Y axis, the displacement sensor detects the rotor displacement, the controller converts the 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), generating an induced electromotive force, exciting a control magnetic flux that flows from the -Y-axis to the rotor, then to the +Y-axis, and returns to the -Y-axis along the magnetic yoke; at the air gap in the negative direction of the Y-axis, the control magnetic flux and the bias magnetic flux are superimposed, and at the air gap in the positive direction of the Y-axis, the control magnetic flux and the bias magnetic flux are offset, and the electromagnetic 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 translation of the magnetic bearing along the X-axis is as follows: when the rotor system is disturbed by the external environment along the positive direction of the 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 to the +X-axis radial coil winding (5) and the -X-axis radial coil winding (6). x (t): Among them, e x is the deviation displacement of the rotor on the X axis; The control magnetic flux is excited in the radial magnetic pole of the X-axis to balance the external interference and maintain the stability of the system. In this process, the control magnetic flux in the air gap is superimposed with the bias magnetic flux. When the control magnetic flux and the bias magnetic flux are in the same direction, the electromagnetic force increases; when the control magnetic flux and the bias magnetic flux are in opposite directions, the electromagnetic force decreases. In this process, the electromagnetic force generated by the combined force adjusts the rotor system back to the equilibrium position; when the rotor system is disturbed by the external environment along the negative direction of the X-axis, the current i of the axial coil winding is changed. x (t) direction and magnitude, to achieve translational control of the magnetic bearing along the X-axis; 4) The axial bias magnetic 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) from the inner magnetic pole of the axial magnetic bearing core (10). Two three-degree-of-freedom permanent magnetic bias magnetic bearings are installed on the main shaft. When the magnetic bearing system works normally and there is no external interference, the electromagnetic force of the two magnetic bearings on the main shaft is zero, that is, the main shaft system maintains balance under the action of the bias magnetic flux; When the spindle system is disturbed by the outside world along the positive direction of the Z axis and deviates from the equilibrium position, the air gap in the positive direction of the Z axis between the left three-degree-of-freedom permanent magnet bias magnetic bearing rotor system and the axial magnetic bearing core (10) becomes smaller, and the air gap in the negative direction of the Z axis of the right magnetic bearing becomes larger. In this case, the magnetic flux in the air gap in the positive direction of the Z axis is greater than the magnetic flux in the air gap in the negative direction of the Z axis, resulting in the electromagnetic force in the positive direction of the Z axis being greater than the electromagnetic force in the negative direction of the Z axis. The displacement signal detected by the displacement sensor is used to adjust the current i in the four series-connected axial coil windings (11, 12, 13, 14). z (t), stimulates the control flux: Among them, L z and R z They represent the inductance and resistance of the axial coil, respectively, and e z is the deviation displacement of the rotor on the Z axis; At the air gap in the negative direction of the Z axis, the control magnetic flux is superimposed on the permanent magnetic flux; at the air gap in the positive direction of the Z axis, the control magnetic flux and the permanent magnetic flux are offset. Finally, the electromagnetic force generated by the two air gaps acts in the negative direction of the Z axis to adjust the rotor system back to the equilibrium position; when the rotor system is disturbed by the outside world in the negative direction of the Z axis, the translational control of the magnetic bearing along the Z axis is achieved by changing the current direction and magnitude of the axial coil winding. 5) 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 conductive ring, so that the Z-axis axial control magnetic circuit passes through the working air gap and the second air gap instead of the permanent magnet ring itself, further reducing the power consumption of the magnetic bearing.

8. An electronic device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the steps of the method according to claim 7 are executed when the processor executes the computer program.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to claim 7 are implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to claim 7 are implemented.

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