A five-degree-of-freedom active magnetic levitation motor

Abstract

This application relates to the field of motor equipment technology and discloses a five-degree-of-freedom active magnetic levitation motor comprising: a housing, a main shaft, two radial magnetic bearings, and an axial magnetic bearing; the housing has a mounting cavity; the main shaft is rotatably connected within the mounting cavity; the main shaft includes a first shaft segment, a second shaft segment, and a connecting plate; both the first and second shaft segments are fixedly connected to the connecting plate; the axis of the first shaft segment and the axis of the second shaft segment coincide; the two radial magnetic bearings are respectively fitted onto the first and second shaft segments; the axial magnetic bearing is fitted outside the connecting plate; both the radial and axial magnetic bearings are fixedly connected within the mounting cavity. This eliminates a major source of vibration excitation, enabling the rotor to maintain extremely high rotational accuracy and dynamic stability even under long-term high-speed operation, significantly improving the reliability and lifespan of the entire motor system.

Description

Technical Field

[0001] This application relates to the field of motor equipment technology, and specifically to a five-degree-of-freedom active magnetic levitation motor. Background Technology

[0002] Magnetic levitation motors, as highly efficient power devices that levitate rotors in the air using electromagnetic force to achieve contactless transmission, are increasingly widely used in high-end manufacturing, energy and chemical industries, and aerospace due to their significant advantages such as frictionless operation, high speed, and no need for lubrication. A five-degree-of-freedom active magnetic levitation motor achieves stable, fully levitated control of the rotor across all five degrees of freedom by coordinating the control of two radial magnetic bearings and one axial magnetic bearing. This control encompasses three translational degrees of freedom along the X, Y, and Z axes (vertical, left-right, and forward / backward motion) and two rotational degrees of freedom (pitch and yaw motion) about the X, Y, and Z axes.

[0003] Currently, the rotors of this type of motor mostly adopt a one-piece long spindle structure. This spindle is machined from a single material and supported at both ends by radial magnetic bearings. Axial magnetic bearings are usually arranged at one or both ends of the spindle to bear axial forces. Although this one-piece long spindle structure has the advantages of simple structure and good overall rigidity, it exposes a difficult-to-overcome technical defect during actual high-speed operation: the problem of thermal stress bending deformation.

[0004] When a motor operates at high speed, the rotor generates a large amount of heat due to electromagnetic losses and windage losses, causing the spindle temperature to rise. Due to the thermal expansion and contraction of the materials themselves, the spindle will expand axially. More problematic is the uneven temperature distribution along the radial cross-section of the spindle, often caused by factors such as cooling conditions, uneven heat dissipation, and winding heating—one side of the spindle will be slightly hotter than the other. For a long, integrated spindle, its overall rigidity is extremely high, with strong mutual constraints between the materials. This uneven radial thermal expansion is suppressed by the overall structure, resulting in enormous thermal stress within the spindle, ultimately manifesting as thermal bowing of the rotor.

[0005] This thermal bending can lead to a series of serious consequences: First, it disrupts the rotor's mass balance, introduces unpredictable vibration sources, seriously challenges the stability and accuracy of the magnetic bearing control system, and may even lead to runaway; second, it changes the air gap distribution of the magnetic bearing, making the side with the smaller air gap susceptible to friction or even collision with the protective bearing; finally, in order to suppress this vibration, the control system has to increase the control current, thereby increasing system energy consumption and potentially causing additional heat generation, forming a vicious cycle. Summary of the Invention

[0006] This application provides a five-degree-of-freedom active magnetic levitation motor to solve the above-mentioned problems.

[0007] One solution provides a five-degree-of-freedom active magnetic levitation motor, comprising:

[0008] Housing, the housing having a mounting cavity;

[0009] A main shaft is rotatably connected within the mounting cavity; the main shaft includes a first shaft segment, a second shaft segment, and a connecting plate; both the first shaft segment and the second shaft segment are fixedly connected to the connecting plate; the axis of the first shaft segment and the axis of the second shaft segment coincide.

[0010] Two radial magnetic bearings are respectively fitted onto the first shaft segment and the second shaft segment in a one-to-one correspondence;

[0011] An axial magnetic bearing is sleeved outside the connecting disc; both the radial magnetic bearing and the axial magnetic bearing are fixedly connected inside the mounting cavity.

[0012] Both the radial magnetic bearing and the axial magnetic bearing are rotatably connected to the main shaft.

[0013] In one embodiment, both the first shaft segment and the second shaft segment are fixedly connected to rotors; a stator corresponding to each rotor is fixedly installed in the mounting cavity.

[0014] In one embodiment, both the first shaft segment and the second shaft segment are fitted with a radial displacement sensor and an axial displacement sensor; the radial displacement sensor is positioned close to the radial magnetic bearing; and the axial displacement sensor is positioned close to the axial magnetic bearing.

[0015] Specifically, eddy current displacement sensors are used. Two radial displacement sensors are used, one for each of them, located near the radial magnetic bearing.

[0016] In one embodiment, protective bearings are fitted onto both the first and second shaft segments, and the protective bearings are fixedly connected to the mounting cavity.

[0017] In one embodiment, the radial magnetic bearing includes a first fixed frame, a first core frame having multiple first magnetic poles, a first coil winding, core laminations, and a first permanent magnet; the first fixed frame is fixedly connected to the mounting cavity; the first core frame is fixedly connected to the fixed frame; the multiple first magnetic poles are circumferentially equidistantly distributed around the main shaft; the first coil winding is wound around each of the first magnetic poles; the core laminations are fixedly connected to the main shaft, and the core laminations are located in the extending direction of the first magnetic poles; each first magnetic pole is spaced apart from the core laminations; the first permanent magnet is fixedly connected to the first core frame, and the first permanent magnet is located directly above the core laminations.

[0018] Specifically, both the first and second shaft sections are fixedly connected with iron core laminations.

[0019] In one embodiment, the axial magnetic bearing includes a second fixed frame, a second core frame having multiple second magnetic poles, a second coil winding, and a second permanent magnet; the second fixed frame is fixedly connected to the mounting cavity; the second core frame is fixedly connected to the second fixed frame; multiple second magnetic poles are equidistantly distributed around the connecting disk in a circumferential direction; the second coil winding is wound around each of the second magnetic poles; the connecting disk is located in the extending direction of the second magnetic poles; each second magnetic pole is spaced apart from the connecting disk; the second permanent magnet is fixedly connected to the second core frame, and the second permanent magnet is located directly above the connecting disk;

[0020] The number of the second core frame and the second coil winding are both two in a one-to-one correspondence; the two second core frames are symmetrically distributed on both sides of the connecting plate.

[0021] In one embodiment, the connecting disc includes a first disc body and a second disc body; the first disc body and the second disc body each have through holes for interference fit of the first shaft segment and the second shaft segment; the first disc body and the second disc body are bolted together.

[0022] Specifically, the inner wall of the through hole is provided with a slot for the protrusion on the first shaft segment or the second shaft segment to be engaged.

[0023] In one embodiment, the first disk and the second disk correspond one-to-one with each other, and the end faces of the two second iron core frames are both smooth conical inclined surfaces; the tangent of the end face of the second magnetic pole is parallel to the tangent of the conical inclined surface.

[0024] Specifically, the conical inclined surface is the surface formed by the generatrix of the cone around the axis of rotation of the cone. Both the first and second discs have threaded holes on their conical inclined surfaces for bolts to pass through. After the bolts are connected, filler blocks are inserted into the threaded holes to fill them completely, ensuring that the conical inclined surfaces of the first and second discs are smooth curved surfaces.

[0025] In one embodiment, the extension direction of the second magnetic pole intersects the axis of the first shaft segment at a 45-degree angle.

[0026] Specifically, the extension direction of the second magnetic pole intersects the tangent of the conical inclined plane at a 90-degree angle.

[0027] In one embodiment, a processor is installed within the mounting cavity; the radial displacement sensor, the axial displacement sensor, the radial magnetic bearing, and the axial magnetic bearing are all electrically connected to the processor.

[0028] The beneficial effects of this application are:

[0029] The traditional one-piece long spindle is divided into a segmented structure, consisting of a first shaft segment and a second shaft segment connected by a connecting plate. This design allows each shaft segment to expand thermally to a certain extent independently, greatly releasing internal thermal stress caused by radial temperature unevenness. Compared to the one-piece long spindle, the segmented structure significantly reduces the risk of rotor bending deformation under thermal loads, eliminating a major source of vibration excitation at its source. This allows the rotor to maintain extremely high rotational accuracy and dynamic stability even under long-term high-speed operation, greatly improving the reliability and lifespan of the entire motor system.

[0030] Because rotor thermal bending deformation is effectively suppressed and mass imbalance is reduced, the magnetic bearing control system no longer needs to output additional control force to compensate for the severe vibration caused by thermal bending. This not only reduces the stringent requirements on the control algorithm, making control smoother and more efficient, but also reduces the system's operating energy consumption and avoids the additional heat generation problem caused by over-control. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the magnetic levitation motor structure in one embodiment of this application;

[0033] Figure 2 yes Figure 1 A schematic diagram of the cross-sectional structure at point A in the diagram;

[0034] Figure 3 yes Figure 1 Schematic diagram of the cross-sectional structure at point B in the diagram;

[0035] Labels for each item in the figure:

[0036] 1. Housing; 11. Mounting cavity; 2. Main shaft; 21. First shaft section; 22. Second shaft section; 23. Connecting disc; 231. First disc body; 232. Second disc body; 233. Protrusion; 234. Slot; 24. Rotor; 25. Radial displacement sensor; 26. Axial displacement sensor; 3. Radial magnetic bearing; 31. First fixing frame; 32. First magnetic pole; 33. First iron core frame; 34. First coil winding; 35. Iron core lamination; 36. First permanent magnet; 4. Axial magnetic bearing; 41. Second fixing frame; 42. Second magnetic pole; 43. Second iron core frame; 44. Second coil winding; 45. Second permanent magnet; 5. Protective bearing. Detailed Implementation

[0037] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application. Similarly, the following examples are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0042] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0043] This application proposes improvements and innovations, and presents the following embodiments.

[0044] In some implementations, please refer to Figures 1 to 3 A five-degree-of-freedom active magnetic levitation motor is provided, comprising:

[0045] Housing 1, housing 1 has mounting cavity 11;

[0046] The main shaft 2 is rotatably connected within the mounting cavity 11; the main shaft 2 includes a first shaft segment 21, a second shaft segment 22, and a connecting plate 23; both the first shaft segment 21 and the second shaft segment 22 are fixedly connected to the connecting plate 23; the axis of the first shaft segment 21 and the axis of the second shaft segment 22 coincide.

[0047] Two radial magnetic bearings 3 are respectively fitted onto the first shaft segment 21 and the second shaft segment 22 in a one-to-one correspondence.

[0048] Axial magnetic bearing 4 is sleeved outside the connecting plate 23; radial magnetic bearing 3 and axial magnetic bearing 4 are both fixedly connected in the mounting cavity 11.

[0049] Although both the first shaft segment 21 and the second shaft segment 22 are fixedly connected to the connecting plate 23, the first shaft segment 21 and the second shaft segment 22 can extend into the connecting plate 23 when heated.

[0050] Both the radial magnetic bearing 3 and the axial magnetic bearing 4 are rotatably connected to the main shaft 2. A cooling device is installed inside the mounting cavity 11.

[0051] Specifically, an exhaust vent is provided inside the mounting cavity 11 to connect with the outside, and a cooling fan is fixedly installed in the exhaust vent to achieve forced convection cooling of the radial magnetic bearing 3 and the axial magnetic bearing 4.

[0052] Alternatively, cooling water pipes can be wound around the radial magnetic bearing 3 and the axial magnetic bearing 4; water cooling is used to reduce the bending deformation of the spindle 2 due to heat.

[0053] The traditional one-piece long spindle 2 is divided into a segmented structure consisting of a first shaft segment 21 and a second shaft segment 22 connected by a connecting plate 23. This design allows each shaft segment to expand thermally to a certain extent independently, greatly releasing the internal thermal stress caused by radial temperature unevenness. Compared with the one-piece long shaft, the segmented structure significantly reduces the risk of bending deformation of the rotor 24 under thermal load, eliminating a major source of vibration excitation at the source. This allows the rotor 24 to maintain extremely high rotational accuracy and dynamic stability even under long-term high-speed operation, greatly improving the reliability and lifespan of the entire motor system.

[0054] Because the thermal bending deformation of rotor 24 is effectively suppressed, the mass imbalance is reduced, and the magnetic bearing control system no longer needs to output additional control force to compensate for the severe vibration caused by thermal bending. This not only reduces the stringent requirements on the control algorithm, making the control smoother and more efficient, but also reduces the system's operating energy consumption and avoids the additional heat generation problem caused by over-control.

[0055] In one embodiment, the first shaft segment 21 and the second shaft segment 22 are both fixedly connected to rotors 24; a stator corresponding to each rotor 24 is fixedly installed in the mounting cavity 11.

[0056] Rotors 24 and stators are fixedly connected to both the first shaft segment 21 and the second shaft segment 22, forming a distributed drive dual-rotor 24 motor system. This structure not only provides greater drive power and torque, but also further shortens the span of each rotor segment 24 and reduces the deflection of a single rotor 24.

[0057] In one embodiment, both the first shaft segment 21 and the second shaft segment 22 are fitted with a radial displacement sensor 25 and an axial displacement sensor 26; the radial displacement sensor 25 is disposed near the radial magnetic bearing 3; and the axial displacement sensor 26 is disposed near the axial magnetic bearing 4.

[0058] Each shaft segment and connecting disc 23 is equipped with independent radial and axial displacement sensors 26 (such as eddy current sensors), establishing a comprehensive and high-precision state sensing network. This provides the controller with the most comprehensive and accurate rotor 24 position information, providing a solid data foundation for achieving multivariable decoupled control and is a prerequisite for achieving high-precision suspension.

[0059] Specifically, eddy current displacement sensors are used. There are two radial displacement sensors 25, one for each of them, located near the radial magnetic bearing 3.

[0060] In one embodiment, a protective bearing 5 is fitted on both the first shaft segment 21 and the second shaft segment 22, and the protective bearing 5 is fixedly connected to the mounting cavity 11.

[0061] Protective bearings 5 ​​are installed on each shaft segment, providing double safety protection for the motor. In extreme fault conditions (such as power failure or control system failure), they can reliably support the segmented rotor 24, avoiding catastrophic damage caused by the rotor 24 colliding with the stator, thus improving the system's fault tolerance and safety.

[0062] In one embodiment, the radial magnetic bearing 3 includes a first fixed frame 31, a first core frame 33 having a plurality of first magnetic poles 32, a first coil winding 34, a core lamination 35, and a first permanent magnet 36; the first fixed frame 31 is fixedly connected to the mounting cavity 11; the first core frame 33 is fixedly connected to the fixed frame; the plurality of first magnetic poles 32 are equidistantly distributed around the main shaft 2 in the circumferential direction; the first coil winding 34 is wound around each of the first magnetic poles 32; the core lamination 35 is fixedly connected to the main shaft 2, and the core lamination 35 is located in the extension direction of the first magnetic poles 32; each first magnetic pole 32 is spaced apart from the core lamination 35; the first permanent magnet 36 is fixedly connected to the first core frame 33, and the first permanent magnet 36 is located directly above the core lamination 35.

[0063] Specifically, both the first shaft segment 21 and the second shaft segment 22 are fixedly connected with iron core laminations 35.

[0064] A hybrid magnetic bearing structure, employing permanent magnets to provide the bias magnetic field and electromagnetic coils only for providing the control magnetic field, significantly reduces coil power consumption and heat generation. The iron core laminations 35 are fixed to the main shaft 2, forming a closed magnetic circuit with the magnetic poles, improving magnetic field utilization and electromagnetic efficiency, enabling the bearing to achieve greater load-bearing capacity while being more energy-efficient.

[0065] In one embodiment, the axial magnetic bearing 4 includes a second fixed frame 41, a second core frame 43 having a plurality of second magnetic poles 42, a second coil winding 44, and a second permanent magnet 45; the second fixed frame 41 is fixedly connected to the mounting cavity 11; the second core frame 43 is fixedly connected to the second fixed frame; the plurality of second magnetic poles 42 are equidistantly distributed around the connecting disk 23 in the circumferential direction; the second coil winding 44 is wound around each of the second magnetic poles 42; the connecting disk 23 is located in the extending direction of the second magnetic poles 42; each of the second magnetic poles 42 is spaced apart from the connecting disk 23; the second permanent magnet 45 is fixedly connected to the second core frame 43, and the second permanent magnet 45 is located directly above the connecting disk 23;

[0066] The number of the second core frame 43 and the second coil winding 44 are both one-to-one; the two second core frames 43 are symmetrically distributed on both sides of the connecting plate 23.

[0067] Two second iron core frames 43 are symmetrically arranged on both sides of the connecting plate 23, realizing bidirectional control of axial force. This layout has a short force flow path, compact structure, good rigidity, fast response speed, and can effectively resist axial disturbances from two directions.

[0068] In one embodiment, the connecting disc 23 includes a first disc body 231 and a second disc body 232; the first disc body 231 and the second disc body 232 respectively have through holes for interference fit of the first shaft segment 21 and the second shaft segment 22; the first disc body 231 and the second disc body 232 are bolted together.

[0069] Specifically, the inner wall of the through hole is provided with a slot 234 for the protrusion 233 on the first shaft segment 21 or the second shaft segment 22 to be engaged.

[0070] The connecting plate 23 adopts a split design and is connected by bolts. The inner wall of the through hole is provided with a groove 234 that cooperates with the shaft section protrusion 233. While ensuring the transmission of torque and connection rigidity, it provides axial "sliding" space for the thermal expansion of the shaft section. This design cleverly guides thermal expansion into a controllable displacement inside the connecting plate 23, rather than harmful bending of the rotor 24, completely avoiding huge axial compressive stress and protecting all connecting parts and bearings.

[0071] The first shaft segment 21 and the second shaft segment 22 are partially spaced apart in the through hole. Although the first shaft segment 21 and the second shaft segment 22 are interference-fitted with the through hole, they can still extend in the through hole when the first shaft segment 21 and the second shaft segment 22 expand and contract with heat.

[0072] The axial expansion of the spindle 2 after being heated can be naturally manifested in the extension of the first shaft segment 21 and the second shaft segment 22 towards both ends of the connecting plate 23, without generating huge axial compressive stress due to the fixed constraints at both ends as in a one-piece long shaft. This design provides a reasonable release channel for thermal expansion, protects the spindle 2, connecting components, and magnetic bearings from harmful internal stresses, and further ensures the mechanical integrity of long-term operation.

[0073] In one embodiment, the first disk 231 and the second disk 232 correspond one-to-one with the end faces of the two second iron core frames 43, both of which are smooth conical inclined surfaces; the tangent of the end face of the second magnetic pole 42 is parallel to the tangent of the conical inclined surface.

[0074] Specifically, the conical inclined surface is the surface formed by the generatrix of the cone around the axis of rotation of the cone. Threaded holes for bolts to pass through are provided on the conical inclined surfaces of both the first disc 231 and the second disc 232. After the bolts are connected, filler blocks are inserted into the threaded holes to fill them completely, ensuring that the conical inclined surfaces of the first disc 231 and the second disc 232 are smooth curved surfaces.

[0075] The end face of the connecting plate 23 is designed as a smooth conical slope, parallel to the end face of the second magnetic pole 42, laying the foundation for the use of a conical magnetic pole. Filler blocks are used to fill the threaded holes to ensure the smoothness and continuity of the curved surface, ensuring a uniform distribution of the air gap magnetic field, avoiding local magnetic field distortion, thereby reducing force fluctuations and noise, and improving control accuracy.

[0076] In one embodiment, a processor is installed in the mounting cavity 11; the radial displacement sensor 25, the axial displacement sensor 26, the radial magnetic bearing 3, and the axial magnetic bearing 4 are all electrically connected to the processor.

[0077] One or more axial displacement sensors 26 and radial displacement sensors 25 (typically eddy current sensors) are installed inside the housing 1 to measure the actual gap between the connecting plate 23 and the second magnetic pole 42, and the actual gap between the first shaft segment 21 and the second shaft segment 22 and the first magnetic pole 32 in real time and with high precision.

[0078] The axial displacement sensor 26 and the radial displacement sensor 25 convert the position signals into electrical signals and send them to the controller. The controller (usually a digital processor, such as a DSP) compares the actual position values ​​from the sensors with the preset ideal target position value (center position) and calculates the position deviation.

[0079] Then, based on the control algorithm (such as PID control), it is calculated how much axial or radial force needs to be applied to eliminate the deviation, and this "force command" is converted into a corresponding "current command".

[0080] The power amplifier receives a current command from the controller and drives two second coil windings 44 symmetrically distributed on both sides of the connecting plate 23. This generates a corresponding net electromagnetic force to pull the first shaft segment 21, the second shaft segment 22, and the connecting plate 23 back to their predetermined positions.

[0081] In one embodiment, both the second core frame 43 and the first core frame 33 are made of stacked silicon steel sheets to reduce eddy current losses. The coils on the first magnetic pole 32 and the second magnetic pole 42 can be connected in series or in parallel.

[0082] Each first magnetic pole 32 is wound with a copper wire coil. The first magnetic poles 32 are arranged in pairs, with the two first magnetic poles 32 in each pair symmetrically distributed on both sides of the main shaft 2 (180° symmetrical distribution); the coils on the two pairs of magnetic poles are connected in series to form a control channel (e.g., +X and -X are a pair, +Y and -Y are a pair; X is the X-axis on the radial plane of the main shaft 2, and Y is the Y-axis on the radial plane of the main shaft 2); there are eight pairs of magnetic poles on the first core frame 33, with adjacent pairs of magnetic poles spaced 45° apart. The surface of the core laminations 35 is a smooth surface.

[0083] Specifically, to generate a force in the +X direction, the current in the +X direction magnetic pole coil is increased, while the current in the -X direction magnetic pole coil is decreased. This strengthens the air gap magnetic field in the +X direction, increasing the attractive force; conversely, it weakens the air gap magnetic field in the -X direction, decreasing the attractive force. The difference between these two forces is the net restoring force in the +X direction.

[0084] By controlling the current in the four quadrants (X+, X-, Y+, Y-), radial forces in any direction can be synthesized.

[0085] Magnetic poles are typically arranged symmetrically at 90° intervals (4 pairs of poles / 8 poles), or more densely at 45° intervals (8 pairs of poles / 16 poles) to provide a smoother force.

[0086] The working process of radial magnetic bearing 3 is as follows:

[0087] Two radial displacement sensors 25 continuously measure the positions of the first shaft segment 21 and the second shaft segment 22, respectively, and send the signals to the controller.

[0088] The controller compares the measured position with the set target position, calculates the required correction force, and converts it into a corresponding current command.

[0089] The power amplifier amplifies the current command and inputs it into the first coil winding 34. Current flows through the coil, generating a magnetic field in the first magnetic pole 32. According to the differential control principle, by applying different currents to the paired first coil windings 34, a net radial force is generated acting on the first shaft segment 21 and the second shaft segment 22. This force pushes or pulls the rotor 24 back to the target center position, forming a closed-loop control.

[0090] Specifically, all the coils on the multiple second magnetic poles 42 of the axial magnetic bearing 4 together generate a resultant force in the axial direction (Z-axis) of the main shaft 2.

[0091] To generate a force to the left (+Z), increase the current in the second coil winding 44 located on the left side of the connecting plate 23, while decreasing the current in the second coil winding 44 located on the right side of the connecting plate 23.

[0092] In this way, the attraction on the left increases and the attraction on the right decreases, and the resulting net force pushes the connecting plate 23 to the left.

[0093] By controlling the current difference between the two coils, the magnitude and direction of the axial force can be precisely controlled.

[0094] Specifically, the connecting disc 23 is made of high-strength soft magnetic material (such as low-carbon steel, 34CrMo1, 17-4PH stainless steel), which can provide a low magnetic resistance path for the magnetic flux and withstand the huge centrifugal stress generated by high-speed rotation. There is a uniform gap between the connecting disc 23 and the second magnetic pole 42, with a gap size of 0.3 mm to 1.0 mm.

[0095] In one embodiment, the extension direction of the second magnetic pole 42 intersects the axis of the first shaft segment 21 at a 45-degree angle.

[0096] In one embodiment, the extension direction of the second magnetic pole 42 intersects the axis of the first shaft segment 21 at a 45-degree angle, and the second magnetic pole 42 is arranged in a circle (e.g., 8 poles), but the end face of each magnetic pole intersects the axis of the first shaft segment 21 at a 45-degree angle.

[0097] The second core frame 43 is made of stacked silicon steel sheets to reduce eddy current losses.

[0098] Its working process is based on the above-mentioned principle of force decomposition, and its mode can be switched through control strategies:

[0099] Pure axial control mode:

[0100] When the system only needs to control axial displacement, the controller sends the same control current command to all second coil windings 44. The control current is amplified and then input to the second coil windings 44, causing a magnetic field to be generated on the second magnetic poles 42.

[0101] Each second magnetic pole 42 generates an electromagnetic force perpendicular to the inclined plane of the cone.

[0102] Based on the above decomposition, each electromagnetic force is decomposed into axial and radial components.

[0103] Since the second magnetic pole 42 is circumferentially symmetrical, the radial components generated by all magnetic poles will cancel each other out, and finally synthesize into a pure and powerful axial force to control the axial position of the rotor 24.

[0104] In one embodiment, when it is necessary to control both axial and radial displacements simultaneously (the axial magnetic bearing 4 is used to provide partial radial stiffness at the same time), the following mode is adopted.

[0105] The controller also assigns control commands for the radial bearing to the axial magnetic bearing 4.

[0106] At this point, the coils no longer carry the same current. For example, to generate a radial force in the +X direction, the current in the +X region of the coil is increased, and the current in the -X region of the coil is decreased.

[0107] This not only generates a net radial force, but also an additional axial force due to the change in current.

[0108] The following control algorithm is used to calculate in real time and compensate the current of the second coil winding 44 of the other second magnetic poles 42 to ensure that the final synthesized axial force and radial force fully meet the control requirements.

[0109] Specifically, for the second magnetic pole 42, whose extension direction forms an angle θ = 45° with the axis of the first shaft segment 21, the electromagnetic force F1 generated by it is decomposed into an axial component Fz and a radial component Fr in a fixed ratio: Fz = F1 × cos(45°) = F1 × Fr = F1×sin(45°) = F1× That is, the axial force and the radial force are equal in magnitude: Fz = Fr.

[0110] This means that the force generated by the current on any magnetic pole contributes equally to both the axial and radial directions. A single magnetic pole cannot independently control a direction.

[0111] The system modeling and force transformation matrix are shown below:

[0112] Suppose there are N magnetic poles (e.g., N=8) evenly distributed along the circumference.

[0113] 1. Define target control force

[0114] Based on the displacement error, the controller calculates the total axial and radial forces that need to be applied.

[0115] Fz: The total axial force (Z direction) required to be generated.

[0116] Fx: The total radial force (X direction) required to be generated.

[0117] Fy: The total radial force (Y direction) required to be generated.

[0118] 2. Define the contribution of a single magnetic pole.

[0119] For the i-th magnetic pole (with azimuth angle φi):

[0120] The total electromagnetic force it generates is Fi, and its direction is perpendicular to the inclined plane of the cone.

[0121] This force Fi can be decomposed into:

[0122] Axial force: Fzi = Fi×cos(45°) = k×Ii (where k is the force-current coefficient and Ii is the coil current); the factors affecting the value of k are:

[0123] Air gap size (g): k is inversely proportional to the square of the air gap (k ∝ 1 / g) 2 This is the most significant influencing factor. A reduction of half the air gap increases the k value to approximately four times.

[0124] Magnetic pole area (A): k is directly proportional to the magnetic pole area (k ∝ A). Larger magnetic poles can generate stronger magnetic fields and forces.

[0125] Number of coil turns (N): k is proportional to the square of the number of coil turns (k ∝ N) 2 Increasing the number of turns can significantly improve efficiency, but it also increases inductance and resistance.

[0126] Materials and Magnetic Circuit Design: The permeability of the iron core and the saturation characteristics of the magnetic circuit affect k. Under high current, core saturation causes the value of k to decrease (nonlinear).

[0127] Bias magnetic field: For permanent magnet bias magnetic bearings, k is also related to the strength of the bias magnetic field provided by the permanent magnet.

[0128] In this invention, the value of k is taken as 50 ~ 200 N / A.

[0129] Radial force: can be further decomposed into X and Y directions.

[0130] Fxi = Fi×sin(45°)×cos(φi) = k×Ii×cos(φi).

[0131] Fyi = Fi×sin(45°)×sin(φi) = k×Ii×sin(φi).

[0132] 3. Establish the global force equations

[0133] The total control force is the sum of the components of the force generated by all magnetic poles in their respective directions: Fz = ΣFzi = k×ΣIi; Fx = ΣFxi = k×Σ(Ii×cos(φi)); Fy = ΣFyi = k×Σ(Ii×sin(φi));

[0134] Representing this in matrix form: [Fz] [1, 1, ..., 1 ][I1]; [Fx] = k × [cosφ1, cosφ2, ..., cosφN] × [I2]; [Fy] [sinφ1, sinφ2, ..., sinφN][..]; [IN];

[0135] Simplified to: F = k × T × I; where:

[0136] F = [Fz, Fx, Fy]^T is the target force vector of 3x1.

[0137] k is the force-current coefficient (assuming all magnetic poles are the same).

[0138] T is a 3xN transformation matrix, determined by the geometric position of the magnetic poles.

[0139] I = [I1, I2, ..., IN]^T is the current vector to be determined for Nx1.

[0140] III. Current Distribution Algorithm: Pseudocode Implementation;

[0141] Our goal is to solve for I in the above equation. This is an underdetermined equation (3 equations, N>3 unknowns) with infinitely many solutions. We need to find an optimal solution.

[0142] Step 1: Initialization and parameter settings;

[0143] The Python code for solving the problem is provided, but the detailed solution process is not.

[0144] # Assume there are 8 magnetic poles and a cone angle of 45 degrees;

[0145] N = 8

[0146] phi = np.array([0, 45, 90, 135, 180, 225, 270, 315]) x np.pi / 180 # Convert azimuth to radians

[0147] # Define the transformation matrix T (3xN);

[0148] T = np.array([

[0149] np.ones(N), # The first line contains all 1s, corresponding to axial force;

[0150] np.cos(phi), # The second line, cosφ_i, corresponds to the radial force in the X direction;

[0151] np.sin(phi) # Third line, sinφ_i, corresponding to radial force in the Y direction; force-current coefficient k (needs to be calibrated through electromagnetic simulation or experiment);

[0152] k = 100.0 # Example value, unit: N / A;

[0153] # Define the target force vector F_cmd (3x1), provided by the upper-level controller;

[0154] F_cmd = np.array([fz_cmd, fx_cmd, fy_cmd])

[0155] Step 2: Solve for the current command (core);

[0156] The least squares method is used to find a set of currents I that can satisfy the force command F_cmd and minimize the sum of squares of the total current (i.e., minimize power consumption).

[0157] Provide the Python code involved in the solution;

[0158] # Calculate the generalized inverse matrix (Moore-Penrose Pseudoinverse);

[0159] T_plus = np.linalg.pinv(T) # This is an Nx3 matrix;

[0160] # Calculate the required current vector I_required# Formula: I = (1 / k) x T_plus x F_cmd;

[0161] I_required = (1 / k) x np.dot(T_plus, F_cmd)

[0162] The generalized inverse matrix of T was calculated using pinv(T).

[0163] The solution I = T_plus x F_cmd is the minimum norm solution of the equation F_cmd = T x I, that is, among all solutions that satisfy the condition, I1 2 + I2 2 + ... + IN 2 The smallest one, which is equivalent to having the minimum total power consumption.

[0164] Step 3: Apply bias current

[0165] The calculated I_required may include negative current. However, power amplifiers typically only output unidirectional current (e.g., 0~±10A). Therefore, we introduce a common bias current I_bias to "boost" all currents to positive.

[0166] Provide the Python code involved in the solution;

[0167] # Calculate the minimum current required, ensuring all currents are non-negative;

[0168] min_current = np.min(I_required);

[0169] I_bias = -min_current if min_current<0 else 0.0;

[0170] # Generate the final current command;

[0171] I_final = I_required + I_bias;

[0172] Step 4: Output and saturation processing;

[0173] Check if the final current exceeds the amplifier's maximum allowable current I_max, and then limit it.

[0174] Provide the Python code involved in the solution;

[0175] I_max = 10.0 # Maximum output current of the power amplifier, for example, 10A;

[0176] I_final = np.clip(I_final, 0, I_max) # Limit all currents to the range [0, I_max];

[0177] # Output I_final to the corresponding power amplifier channel for i in range(N):

[0178] set_current_to_amplifier_channel(i, I_final[i])

[0179] The core of the algorithm relies on a known, precise transformation matrix T. T is uniquely determined by the geometric layout of the second magnetic pole (azimuth angle φi and cone angle θ). The 45-degree cone angle makes sinθ = cosθ, simplifying the calculation.

[0180] By using the least squares method to find the generalized inverse, we directly obtained the current distribution scheme that satisfies the force requirement and minimizes the total power consumption.

[0181] Real-time performance: Once the matrix T_plus is pre-calculated, the amount of online computation is very small, involving only a multiplication of a 3xN matrix and a 3x1 vector and a scalar multiplication. The computation speed is extremely fast and it is easy to implement in real time on DSP or FPGA.

[0182] Decoupling: This algorithm is essentially a feedforward decoupler. It dynamically and optimally maps the three-dimensional force commands (Fz, Fx, Fy) output by the upper controller to the eight second-pole 42 coils, thereby achieving decoupled force control.

[0183] This algorithm enables the 45-degree tapered magnetic bearing to simultaneously and independently control the axial and radial positions of the rotor 24, fully leveraging its integrated advantages.

[0184] By establishing a force-current transformation matrix and solving for the generalized inverse using the least squares method, precise and decoupled control of axial and radial forces is achieved. This algorithm can calculate the optimal current distribution scheme for each coil with minimal total power consumption and can handle the unidirectional current constraints and saturation limits of the power amplifier in real time.

[0185] Specifically, the extension direction of the second magnetic pole 42 intersects the tangent of the conical inclined plane at a 90-degree angle.

[0186] In one embodiment, the expansion of the shaft due to thermal expansion poses a challenge to the control system of the axial magnetic bearing 4. Multiple axial displacement sensors 26 and a controller are used to achieve this adjustment.

[0187] Using a "primary-secondary" sensor layout:

[0188] Main sensor: directly measures the air gap between the connecting plate 23 and the second magnetic pole 42.

[0189] Auxiliary sensor: measures the relative position between the upper end of the first shaft segment 21 or the second shaft segment 22 and the housing 1.

[0190] The controller no longer uses the absolute physical position of the connection plate 23 as the control target.

[0191] The controller's setpoint is dynamically and in real-time adjusted based on the expansion amount ΔL detected by the auxiliary sensor.

[0192] For example, if spindle 2 expands by 10 μm, the controller will change the target position of the axial center from 0 μm to +10 μm. In this way, the axial magnetic bearing 4 will "allow" the connecting plate 23 to move forward by 10 μm and re-establish balance at this new position.

[0193] The system no longer chases a fixed physical point, but a "floating zero point" that changes with temperature. This ensures that rotor 24 is always at its current mechanical center.

[0194] A temperature-expansion model is established. Temperature sensors mounted on the spindle 2 or axial and radial magnetic bearings 3 are used to predict the trend of thermal expansion in advance.

[0195] The temperature-expansion model uses existing models available on the market.

[0196] Before the expansion actually occurs and is detected by the displacement sensor, the controller fine-tunes the current output to the axial bearing in advance, thereby suppressing disturbances caused by the expansion and making the process smoother.

[0197] The controller can automatically adjust its control parameters (such as PID gain) to adapt to the slow changes in the system's dynamic characteristics caused by thermal expansion, and always maintain optimal control performance.

[0198] In response to the thermal expansion of the shaft, multiple axial displacement sensors 26 provide redundant position information, enabling the control system to distinguish between genuine external force interference and slow thermal expansion.

[0199] Based on the trend of thermal expansion, the target position of axial control is intelligently redefined (zero-point migration).

[0200] Through feedforward compensation and adaptive adjustment, the rotor 24 is smoothly stabilized at a new mechanical center that conforms to the current thermal state.

[0201] Employing a "primary-secondary" sensor layout and intelligent algorithms, the system can intelligently distinguish between external force disturbances and thermal expansion. Through dynamic adjustment of control targets (zero-point migration), feedforward compensation, and adaptive control, it allows rotor 24 to operate stably at a new equilibrium position after thermal expansion. This ensures that the system can automatically maintain the optimal mechanical center under various operating conditions, representing the most intelligent and thorough solution to thermal problems.

[0202] The above are merely optional embodiments of this application and are not intended to limit this application. 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. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A five degree of freedom active magnetic levitation motor, characterized by, The utility model relates to a kind of magnetic bearing, including: Casing, the casing has installation cavity; Main shaft, the main shaft is rotatably connected in the installation cavity;The main shaft includes first shaft section, second shaft section, connecting disc;The first shaft section and the second shaft section are fixedly connected with the connecting disc;The axis of the first shaft section and the axis of the second shaft section coincide; Two radial magnetic bearings, two the radial magnetic bearings are respectively one-to-one corresponding and set on the first shaft section and the second shaft section; Axial magnetic bearing, the axial magnetic bearing is set outside the connecting disc;The radial magnetic bearing and the axial magnetic bearing are fixedly connected in the installation cavity; The axial magnetic bearing includes second fixed frame, second core frame with multiple second magnetic poles, second coil winding, second permanent magnet;The second fixed frame is fixedly connected with the installation cavity;The second core frame is fixedly connected with the second fixed frame;Multiple the second magnetic poles are equidistantly distributed around the circumference of the connecting disc;The second coil winding is wound on each second magnetic pole;The connecting disc is located in the extension direction of the second magnetic pole;Each second magnetic pole is spaced apart from the connecting disc; The second permanent magnet is fixedly connected with the second core frame, and the second permanent magnet is located directly above the connecting disc; The number of the second core frame and second coil winding is one-to-one corresponding two;Two the second core frames are symmetrically distributed on the two sides of the connecting disc; The connecting disc includes first disc body and second disc body;The first disc body and the second disc body are respectively provided with through hole for interference fit of the first shaft section and the second shaft section;The first disc body and the second disc body are bolted; The end face of the first disc body and the second disc body one-to-one corresponding close to two the second core frames is smooth conical inclined surface;The tangent of the end face of the second magnetic pole is parallel to the tangent of the conical inclined surface;The extension direction of the second magnetic pole and the axis of the first shaft section are 45 degrees intersection.

2. The magnetic levitation motor of claim 1, wherein, The first shaft section and the second shaft section are fixedly connected with rotor;The installation cavity is fixedly installed with stator corresponding to each rotor.

3. The magnetic levitation motor of claim 1, wherein, The first shaft section and the second shaft section are set with radial displacement sensor and axial displacement sensor;The radial displacement sensor is close to the radial magnetic bearing arrangement;The axial displacement sensor is close to the axial magnetic bearing arrangement.

4. The magnetic levitation motor of claim 1, wherein, The first shaft section and the second shaft section are set with protection bearing, and the protection bearing is fixedly connected with the installation cavity.

5. The magnetic levitation motor of claim 3, wherein, The radial magnetic bearing comprises a first fixed frame, a first iron core frame with a plurality of first magnetic poles, a first coil winding, an iron core lamination, and a first permanent magnet; the first fixed frame is fixedly connected with the mounting cavity; the first iron core frame is fixedly connected with the fixed frame; the plurality of first magnetic poles are equidistantly distributed around the circumference of the main shaft; the first coil winding is wound on each first magnetic pole; the iron core lamination is fixedly connected on the main shaft, and the iron core lamination is located in the extension direction of the first magnetic pole; each first magnetic pole is spaced apart from the iron core lamination; the first permanent magnet is fixedly connected with the first iron core frame, and the first permanent magnet is located directly above the iron core lamination.

6. The magnetic levitation motor of claim 3, wherein, A processor is mounted in the mounting cavity; the radial displacement sensor, the axial displacement sensor, the radial magnetic bearing, and the axial magnetic bearing are electrically connected with the processor.

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