Ring axial flux motor

Abstract

An annular axial flux motor includes a rotor mounted on an annular segment of a rotatable cam ring and a stator mounted on an annular segment of a bracket. The rotor includes two Halbach permanent magnet arrays spaced apart from each other along the axial direction on the cam ring. The stator includes a multi-phase electrical winding printed on multiple layers of a printed circuit board (PCB) stacked along the axial direction. The multiple layers are located between the Halbach arrays, wherein the active sides of the Halbach arrays face opposite sides of the multiple layers. The Halbach arrays are configured to generate a symmetrical magnetic field, and the multi-phase electrical windings are configured to have the same rotor-related torque constant so that the stator can generate a constant torque to rotate the rotor and the cam ring within a limited range of travel.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 62 / 852,940, filed on May 24, 2019, entitled “VARIABLE FOCUS ASSEMBLIES,” the entire contents of which are hereby incorporated by reference. Technical Field

[0003] The present disclosure relates generally to electric machines and, more particularly, to toroidal axial flux electric machines. Background Art

[0004] It is desirable for mixed reality (MR) or augmented reality (AR), near-eye displays to be lightweight, low cost, small form factor, have a wide virtual image field of view, and be as transparent as possible. In addition, it is desirable to have a configuration that presents virtual image information in multiple focal planes to suit a variety of use cases without exceeding acceptable tolerances for vergence-accommodation mismatch.

[0005] Components of the display can be driven by an actuator. In some cases, in order to obtain an actuator that can provide the required range of travel, form factor, service life and peak torque / force required to drive the liquid lens, a heavy magnetic motor is integrated into a mechanical actuator, which may be undesirable for a lightweight display. In some other cases, a micromotor is used in a mechanical actuator to meet the weight requirements of the display. The mechanical actuator may include a cam ring with an axial cutout. The cutout is inclined at a certain angle, and a guide pin is connected to another ring (e.g., a forming ring) located inside the cam ring. When the cam ring is rotated, the inner ring moves axially and actuates the liquid lens axially located inside the cam ring. The pin extending axially from the cam ring can be driven by a connecting rod connected to the micromotor. However, the micromotor may not meet the required output torque and power specifications. Summary of the invention

[0006] One aspect of the present disclosure features an annular axial flux motor, the annular axial flux motor comprising a rotor, comprising a permanent magnet array mounted on a first annular segment of a rotatable structure, the permanent magnet array extending along the circumferential direction (or tangential direction) of the first annular segment and configured to have a stronger magnetic field on an active side of the array relative to the axial direction of the first annular segment than on an opposite inactive side of the array; and a stator, comprising a multilayer printed electrical winding on a printed circuit board (PCB), the printed circuit board being mounted on a second annular segment of a carrier corresponding to the first annular segment, the electrical winding extending along the circumferential direction, the multilayers of the PCB being stacked along the axial direction, the active side of the permanent magnet array facing one side of the multilayers of the PCB and separated by a nominal gap. The stator is configured to be excited to generate a torque (e.g., a constant torque) to drive the rotor to rotate relative to the carrier within a limited range of travel together with the rotatable structure.

[0007] In some embodiments, the permanent magnet array is a Halbach array. The Halbach array may include periodic units of permanent magnets arranged on the first annular segment along the circumference, each of the periodic units including a plurality of rows of magnetic pole pairs.

[0008] In some examples, each of the periodic units includes four rows of magnetic pole pairs, adjacent rows are separated from each other by a magnetic interval along the circumferential direction, and each magnetic pole pair includes an N pole and an S pole. The four rows include: a first row having N poles and S poles stacked in sequence vertically along the axial direction, a second row having S poles and N poles stacked in sequence horizontally along the circumferential direction, a third row having S poles and N poles stacked in sequence vertically along the axial direction, and a fourth row having N poles and S poles stacked in sequence horizontally along the circumferential direction.

[0009] In some embodiments, the rotor includes two permanent magnet arrays mounted on the first annular segment and separated from each other along the axial direction, the multilayer printed electrical winding on the PCB is arranged between the two permanent magnet arrays, the active sides of the two arrays face the opposite sides of the multilayer relative to the axial direction, and the nominal gap between the active side of each Halbach array and the opposite side of the multilayer has the same width along the axial direction.

[0010] The two permanent magnet arrays can be configured to generate a magnetic field that is symmetrical relative to the center of the multiple layers of the PCB, and the axial component of the symmetrical magnetic field along the axial direction can be much larger than the tangential component of the symmetrical magnetic field along the tangential direction of the first annular segment. In some examples, each of the two permanent magnet arrays is a corresponding Halbach array, and each Halbach array has a different magnetic pole arrangement and is configured to have an active side opposite to the two sides of the multi-layer printed electrical winding. In some examples, the stator includes a multi-phase electrical winding, and each phase of the multi-phase electrical winding of the stator is configured to have the same rotor-related torque constant so that the stator is configured to generate a constant torque to drive the rotor.

[0011] The electric winding may have a height along the radial direction of the structure, the height being substantially the same as a height of the permanent magnet array along the radial direction. The electric winding may be configured such that a winding period of the electric winding corresponds to a magnetic period of the magnetic field of the rotor.

[0012] In some embodiments, the stator includes two-phase electrical windings configured to be driven with a sinusoidal drive current having a phase difference of π / 2. Each of the multiple layers may correspond to a corresponding phase electrical winding, and respective phase electrical windings having different phases may alternate in the multiple layers. The two-phase electrical windings may have the same winding pattern and be offset by a quarter winding period.

[0013] The multilayer printed electrical winding may include a first layer, a second layer, a third layer and a fourth layer stacked together in sequence along the axial direction, and the printed electrical windings on the first layer and the third layer may be formed by a first continuous line to serve as a first phase electrical winding, and the printed electrical windings on the second layer and the fourth layer may be formed by a second continuous line to serve as a second phase electrical winding.

[0014] In some examples, the first wire is printed from the input port of the first layer, extends along a first path on the first layer to a first through-hole, the first wire passes through the first through-hole to the third layer and extends along a second path on the third layer to a second through-hole, the first wire passes through the second through-hole back to the first layer and extends along a third path on the first layer to a third through-hole, the first wire passes through the third through-hole to the third layer and extends along a fourth path on the third layer to a fourth through-hole, the first wire passes through the fourth through-hole to the first layer and extends along a fifth path on the first layer to a fifth through-hole, the first wire passes through the fifth through-hole to the third layer and extends along a sixth path on the third layer to an output port of the third layer. The first wire extending along the first path, the third path, and the fifth path forms a first electrical winding on the first layer, the first wire extending along the second path, the fourth path, and the sixth path forms a second electrical winding on the third layer, and the first electrical winding and the second electrical winding form a first phase electrical winding. The first electrical winding and the second electrical winding have the same winding pattern offset by a quarter winding period, and wherein the first through-hole, the third through-hole, and the fifth through-hole are adjacent to each other, and the second through-hole and the fourth through-hole are adjacent to each other.

[0015] In some examples, the electrical winding has a rectangular winding pattern.

[0016] In some examples, the electrical winding has a triangular winding pattern. The triangular winding pattern may have a winding angle of 45 degrees.

[0017] The rotor is configured to generate a magnetic field having a sinusoidal shape corresponding to positions of magnetic pole pairs of the rotor, and the stator may be configured to be driven by a sinusoidal current that varies corresponding to the positions of the magnetic pole pairs of the rotor.

[0018] In some embodiments, the stator includes three-phase electrical windings configured to be driven with sinusoidal drive currents having a phase difference of 2π / 3 with respect to each other.

[0019] Another aspect of the present disclosure includes a system, the system including a carrier; a cam ring, which is located inside the carrier and is configured to be rotatable about an axis relative to the carrier in an axial direction; and an annular axial flux motor, the annular axial flux motor including a rotor, which includes a permanent magnet array mounted on a first annular segment of the cam ring, the permanent magnet array extending along the circumference of the first annular segment and configured to have a stronger magnetic field on an active side of the array relative to the axial direction than on an opposite inactive side of the array; and a stator, which includes a multi-layer printed electrical winding printed on a circuit board (PCB), the printed circuit board being mounted on a second annular segment of the carrier corresponding to the first annular segment, the printed electrical winding extending along the circumference, the multi-layers of the PCB being stacked on each other in the axial direction, the active side of the permanent magnet array facing one side of the multi-layers of the PCB and separated by a nominal gap. The stator is configured to be energized to generate a torque (e.g., a constant torque) to drive the rotor to rotate with the cam ring relative to the carrier within a limited range of travel.

[0020] In some embodiments, the system further comprises a shaping ring positioned inside the cam ring and configured to be connected to the cam ring so that rotational movement of the cam ring relative to the bracket causes axial movement of the shaping ring relative to the cam ring along the axial direction. The system further comprises a flexible lens membrane configured to be coupled to the shaping ring so that the axial movement of the shaping ring causes a change in curvature of the flexible lens membrane. In some embodiments, the system further comprises a liquid lens assembly comprising an incompressible fluid encapsulated between the shaping ring, the flexible lens membrane, a refractive component, and a flexible annular membrane. The incompressible fluid is configured to be pushed toward the flexible lens membrane to cause the change in curvature when the shaping ring moves toward the refractive component with the axial movement.

[0021] In some implementations, the rotor includes two Halbach permanent magnet arrays mounted on the first annular segment and separated from each other along the axial direction, the multi-layer printed electrical winding on the PCB is arranged between the two Halbach arrays, and the active sides of the two Halbach arrays face the opposite sides of the multi-layer relative to the axial direction. The two Halbach arrays can be configured to generate a magnetic field that is symmetrical relative to the center of the multi-layer, and the axial component of the magnetic field along the axial direction is much larger than the tangential component of the magnetic field along the tangential direction of the first annular segment. The two Halbach arrays can have different magnetic pole arrangements and be configured to have active sides facing the opposite sides of the multi-layer printed electrical winding.

[0022] In some embodiments, the stator includes two-phase electrical windings configured to be driven by a sinusoidal current with a phase difference of π / 2. Each phase electrical winding of the stator can be configured to have the same rotor-related torque constant so that the stator is configured to generate a constant torque to drive the rotor. The two-phase electrical windings can have the same winding pattern and be offset by a quarter winding period. The winding pattern can be rectangular or triangular.

[0023] In some examples, the multilayer printed electrical winding includes a first layer, a second layer, a third layer, and a fourth layer stacked in sequence along the axial direction, and the printed electrical windings on the first layer and the third layer are formed by a first continuous line to serve as a first phase electrical winding, and the printed electrical windings on the second layer and the fourth layer are formed by a second continuous line to serve as a second phase electrical winding.

[0024] The rotor may be configured to generate a magnetic field having a sinusoidal shape corresponding to the position of the magnetic pole pairs of the rotor, and the stator may be configured to be driven by a sinusoidal current that varies corresponding to the position of the magnetic pole pairs of the rotor. The cam ring may be made of a non-ferromagnetic material.

[0025] Another aspect of the present disclosure features a method, the method comprising inputting respective drive currents into different phase electrical windings of a stator of an annular axial flux motor, the respective drive currents having a phase difference of a predetermined degree from each other, the different phase electrical windings being printed in multiple layers of a printed circuit board (PCB) mounted on a first annular segment of a bracket, the printed electrical windings extending along a circumferential direction of the first annular segment, the multiple layers being stacked one on another along an axial direction of the first annular segment; and driving a rotor of the motor mounted on a second annular segment of a cam ring to rotate around an axis of the cam ring within a limited range of travel, the second annular segment corresponding to the first annular segment, the rotor comprising two Halbach permanent magnet arrays spaced from each other along the axial direction and extending along the circumferential direction, each of the Halbach arrays being configured to generate a stronger magnetic field on an active side of the Halbach array relative to the axial direction than on an inactive side of the Halbach array. The multiple layers of the PCB are positioned between the two Halbach arrays of the rotor along the axial direction, wherein the two active sides of the Halbach arrays face opposite sides of the multiple layers of the PCB. The two Halbach arrays are configured to generate a magnetic field that is symmetrical with respect to the center of the multiple layers of the PCB along the axial direction. Each phase electrical winding of the stator is configured to have the same rotor-related torque constant so that the stator is excited by the drive current to generate a constant torque to drive the rotor and the cam ring relative to the bracket.

[0026] The method also includes moving a shaping ring mechanically coupled to the cam ring in an axial motion along the circumferential direction by the rotational motion of the cam ring due to the rotation of the rotor mounted on the cam ring, and also includes changing the curvature of a flexible lens film coupled to the shaping ring by the axial motion of the shaping ring.

[0027] In some embodiments, the stator includes a two-phase electrical winding, and the corresponding driving currents for the two-phase electrical windings are sinusoidal currents with a phase difference of π / 2. In some examples, the multi-layer printed electrical winding includes a first layer, a second layer, a third layer, and a fourth layer stacked sequentially along the axial direction, and the printed electrical windings on the first layer and the third layer are formed by a first continuous wire as a first-phase electrical winding, and the printed electrical windings on the second layer and the fourth layer are formed by a second continuous wire as a second-phase electrical winding.

[0028] In some embodiments, the stator includes three-phase electrical windings, and the corresponding drive currents for the three-phase electrical windings are sinusoidal currents with a phase difference of 2π / 3.

[0029] The rotor is configured to generate a sinusoidal-shaped magnetic field corresponding to positions of magnetic pole pairs of the rotor, and the respective drive currents are sinusoidal currents that vary corresponding to the positions of the magnetic pole pairs of the rotor.

[0030] The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of an example of an augmented reality system.

[0032] Figure 2 is a partial cross-sectional view of an optical element including a pair of variable focus components.

[0033] Figure 3A and Figure 3B An example of a liquid lens assembly in a variable focus assembly is shown.

[0034] Figure 4 is an exploded view of an example of a variable focus assembly.

[0035] Figure 5A and Figure 5B is a schematic diagram showing an example of mechanical features for engaging a forming ring and a cam ring in a variable focus assembly.

[0036] Fig. 6A is a schematic diagram of an example of a toroidal axial flux motor actuation system.

[0037] Figure 6B and Figure 6C Shows Fig. 6A The actuation system is in the operating state ( Figure 6B ) and the released state ( Figure 6C ) below.

[0038] Figure 7 is a schematic diagram of an example of an actuator including an annular axial flux motor.

[0039] Figure 8 is a schematic diagram of an example of a toroidal axial flux machine including a Halbach array and a multi-layer PCB.

[0040] Fig. 9 An example of the magnetic field of a Halbach array is shown.

[0041] Fig.10 Shows Figure 8 Simulated magnetic field of a Halbach array.

[0042] Fig.11A and Fig. 11B Shows Fig.10 The simulated magnetic field component of .

[0043] Fig.12 is a schematic diagram of an example of a two-phase electrical winding having a rectangular pattern.

[0044] Fig.13A is a schematic diagram of another example of a toroidal axial flux machine including a multilayer PCB located between two Halbach arrays.

[0045] Fig. 13B yes Fig.13A Schematic diagram of an example arrangement of an electric machine.

[0046] Fig.14 Shows Fig.13A Simulated magnetic fields of two Halbach arrays.

[0047] Fig.15A -C shows the difference between the two Halbach arrays at different positions Fig.14 The simulated magnetic field component of .

[0048] Fig.16A is a schematic diagram of an example printed electrical winding having a rectangular winding pattern.

[0049] Fig. 16B is a schematic diagram of an example printed electrical winding having a triangular winding pattern.

[0050] Fig.17A The corresponding relationship between the winding period λ of the rectangular winding and the effective length of each pole pair and between the winding period λ and the effective ratio is shown.

[0051] Fig. 17B The corresponding relationship between the winding angle β of the triangle winding and the effective length of each pole pair and between the winding angle β and the effective ratio is shown.

[0052] Fig.18 is a schematic diagram of an example wiring scheme for a single-phase electrical winding on two layers.

[0053] Fig.19 is a flow chart illustrating an example of a process for operating an optical system using an annular axial flux motor as an actuator.

[0054] The same reference numbers and designations in different drawings indicate the same elements. DETAILED DESCRIPTION

[0055] The implementation of the present disclosure provides a compact coreless annular axial flux motor that can operate in, for example, a high torque low speed regime rather than a low torque high speed regime. The compact high torque motor can be used in an actuation system based on a mechanical cam ring to drive a liquid lens assembly within a limited range of travel in an optical system (such as an MR or AR display). Specifically, by embedding one or more permanent magnet arrays, such as a Halbach array, on the cam ring, the cam ring can be converted into a rotor for the motor. The stator of the motor can be implemented by a printed electrical winding of a printed circuit board (PCB) mounted on a bracket of the liquid lens assembly. The cam ring can rotate relative to the bracket. The stator can be implemented using two-phase or three-phase, or even more-phase electrical windings. The windings can be printed in multiple layers of the PCB.

[0056] In some embodiments, an array of permanent magnets embedded in the cam ring can be placed along the entire circumference or annular segments (or arcs) of the cam ring. In some cases, considering the form factor of the MR or AR display, the permanent magnets can be placed within the arc of the cam ring, which is limited to a certain degree, such as less than 120 degrees. That is, instead of forming a complete circle, the motor has a limited or restricted arc length, which causes the cam ring to rotate back and forth within a limited angle rather than continuously. In some embodiments, the windings of the motor are implemented as traces on a curved PCB. By adding layers to the PCB, multiple winding phases and a high number of winding turns can be achieved.

[0057] The permanent magnets can be arranged in a Halbach array in a special arrangement so that the magnetic field generated on one side of the Halbach array (e.g., the active side) is stronger than the other opposite side (e.g., the inactive side). The side with the stronger magnetic field can be arranged to face the electrical winding on the PCB. The permanent magnet array can produce a magnetic flux density that varies sinusoidally along the circumference of the cam ring. When the electrical winding moves in and out along the axial direction and the current varies sinusoidally along the circumference, the magnetic field component oriented along the axial direction can provide a constant torque along the circumference. The torque can drive the permanent magnet and the cam ring to rotate. The pattern of the electrical winding can be arranged according to the sinusoidal magnetic flux density of the permanent magnet. The cam ring can be made of a non-ferromagnetic material (such as plastic).

[0058] Different motor architectures can be implemented. For example, a first motor architecture can include a single permanent magnet array (e.g., a Halbach array) and a multi-layer PCB, which can minimize the total axial width and utilize fewer magnets. The second motor architecture can include two permanent magnet arrays (e.g., two Halbach arrays) and a multi-layer PCB located therebetween. Since the multi-layer PCB is located at the center between the two permanent magnet arrays, the magnetic field components can be axially symmetrical around the center of the multi-layer PCB, which allows each phase winding to have exactly the same rotor-related torque constant, thereby producing a constant torque output through an appropriate drive scheme. In addition, since the total magnetic flux density in the PCB is greater than the total magnetic flux density in the first motor architecture, the torque constant of the motor in the second motor architecture can be larger.

[0059] The technology implemented in the present disclosure can use a coreless Halbach array, which can avoid the use of low reluctance (e.g., iron) components to complete the permanent magnet flux path and avoid losses due to eddy currents. The axial design can also allow the winding to be implemented on a multi-layer PCB that is easy to manufacture. In addition, the 2D layered motor design can achieve a compact motor and related actuation system.

[0060] The technologies can get rid of brushes, axial cam pins, connecting rods, and micromotors in existing mechanical actuation systems. For example, these technologies can eliminate worm gear connecting rods and brushes and bypass the associated mechanical power inefficiencies or failures. Actuation systems with fewer mechanical parts can also have longer service lives. Moreover, these technologies can solve serious noise problems by allowing motors to run at low speeds and generate little or no noise.

[0061] Devices or systems based on coreless annular axial flux motors implemented in the present disclosure can be widely used in various applications, including compact actuation systems, portable electronic and communication devices such as wearable devices (e.g., glasses), virtual reality (VR) / augmented reality (AR) displays, or any other application requiring an axial motor.

[0062] Exemplary Systems and Optical Elements

[0063] Figure 1 1 is a schematic diagram of an example augmented reality system 100, featuring a head-mounted viewing component 102, a handheld controller component 104, and an optional interconnected auxiliary computing or controller component 106, which optional component can be configured to be worn on a user as a waist pack or the like. Each of the components 102, 104, 106 can be operably coupled via connections 110, 112, 114, 116, 117, 118 to communicate with each other and other connected resources 108 (such as cloud computing or cloud storage resources) via wired or wireless communication configurations such as specified by IEEE 802.11, Bluetooth (RTM), and other connection standards and configurations. In various embodiments, the optical element 120 shown can be operated to enable a user wearing the viewing component 102 to view the world around the user and the visual components that can be generated by the associated system components to achieve an augmented reality experience. These systems and experiences have been described in U.S. patent applications serial numbers 14 / 555,585, 14 / 690,401, 14 / 331,218, 15 / 481,255, and 62 / 518,539, the entire contents of which are incorporated herein by reference.

[0064] A variable focus component may be used as a component of the optical element 120 to provide any suitable number of focal planes. In some embodiments, the optical element 120 may include an assembly of one or more variable focus components (or variable focus assemblies) to provide a spectrum of focal planes that can be selected or tuned by an integrated control system. For example, a pair of variable focus assemblies (such as an inner lens assembly (ILA) and an outer lens assembly (OLA)) may be used in the optical element 120 to impart one of a range of focal depths to virtual content using the ILA while using the OLA to correct or compensate for distorted ambient light.

[0065] Figure 2 is a partial cross-sectional view of an optical element 200 including a pair of variable focus components with an augmented reality (AR) eyepiece between the variable focus components. The optical element 200 may be Figure 1 The optical element 200 includes an eyepiece 230 and an ILA 210 and an OLA 220 disposed on either side of the eyepiece 230, respectively. A virtual image from the eyepiece 230 may be projected toward the ILA 210 and shaped by the ILA 210. Light from the surrounding environment may be shaped a first time by the OLA 220 and then a second time by the ILA 210 such that after the two shaping events, the net change in focus of the ambient light is zero. In some embodiments, the diameter of the OLA 220 is greater than the diameter of the ILA 210.

[0066] In some embodiments, Figure 3A-3B and Figure 4 As discussed in further detail in , each of the ILA 210 and OLA 220 may include a cam ring and a shaping ring axially located inwardly of the cam ring. The shaping ring may be actuated using an actuation system to move axially within a limited range of travel. The actuation system may be Fig. 6A A rotary actuation system 600 includes a rotary actuator and a radial force latch. The rotary actuator may be composed of Figure 7 Motor 700, Figure 8 Motor 800, or Fig.13A The motor 1300 is implemented. The rotary actuator can rotate the cam ring with a limited rotational motion, which can cause the forming ring (or load) to move with an axial motion.

[0067] In a particular embodiment, the ILA 210 can include one or more of the following specifications: a travel range of approximately 721 μm, where the travel range can be a combination of the alignment offset and the actual motion requirements of the system; a maximum load spring force of approximately 2.24±0.3N and a minimum load spring force of approximately 0.70±0.3N; a mass of the forming ring of approximately 0.72 grams; a load stiffness of approximately 3.31 N / mm; a lens damping of approximately ~1.0; a system natural frequency of approximately 100 Hz; a refractive decentering to the forming ring (reference) of approximately ±0.05 mm; a power error (combination of ILA and OLA) of less than 0.1 diopters; a power error (for a virtual system) of less than 0.1 diopters; a flatness of the forming ring attached to the membrane of less than 10 μm; and a tilt / tilt of the forming ring attached to the membrane of less than 3 arc minutes.

[0068] In a particular implementation, the OLA 220 may include one or more of the following specifications: a travel range of approximately 760 μm, where the travel range may be a combination of the alignment offset and the actual motion requirements of the system; a maximum load spring force of approximately 3.21 ± 0.3 N and a minimum load spring force of approximately 1.35 ± 0.3 N; a forming ring mass of approximately 0.72 grams; a load stiffness of approximately 3.31 N / mm; a lens damping of approximately ~1.0; a system natural frequency of approximately 100 Hz; a refractive decentering to the forming ring (reference) of approximately ±0.05 mm; a power error (combination of ILA and OLA) of less than 0.1 diopters; a power error (for a virtual system) of less than 0.1 diopters; a flatness of the forming ring attached to the membrane of less than 10 μm; and a tilt / tilt of the forming ring attached to the membrane of less than 3 arc minutes.

[0069] Exemplary Variable Focus Assembly

[0070] Figure 3A and Figure 3B A method for using a variable focus assembly (e.g., Figure 2ILA 210 or OLA 220 or Figure 1 1. An example of a liquid lens assembly 300 in a variable focus assembly in an optical element 120 of the embodiment of the present invention. The variable focus assembly is operable to adjust the curved shape of the fluid volume within the liquid lens assembly 300. Light propagating through the fluid encapsulated in the volume has a wavefront that can be changed when the light encounters the curved surface of the encapsulating fluid. The change in the light wavefront corresponds to a change in the focus of the light.

[0071] In some embodiments, the liquid lens assembly 300 includes a refractive component 302 and a shaping ring 304. The refractive component 302 can be a rigid, optically transparent material (such as plastic or glass) and can have a flat surface, a curved surface, or one flat surface and one curved surface (such as surfaces 306, 308, respectively). The shaping ring 304 can be made of a rigid material, such as a metal (aluminum, steel, or titanium), a plastic, or other suitable lightweight rigid material. A flexible lens film 310 can cover the entire shaping ring 304 so that the flexible lens film 310 is attached along the entire circumference of the shaping ring 304 to form a seal. A constant volume of substantially incompressible fluid 312 can be encapsulated between the flexible lens film 310, the shaping ring 304, the refractive component 302, and the annular film 314. The annular film 314 is flexible to allow axial movement of the shaping ring 304 relative to the refractive component 302 (along the axis of the shaping ring 304) while maintaining the fluid seal within the liquid lens assembly 300.

[0072] Figure 3A The shaping ring 304 is shown to be at a greater distance from the refractive component 302, while Figure 3B FIG. 3 shows that the shaping ring 304 moves to shorten the distance to the refractive component 302. When the shaping ring 304 moves axially toward the refractive component 302 to cause a shorter distance, the surface of the flexible lens film 310 is Figure 3B The curvature in Figure 3A The curvature is greater, wherein the incompressible fluid 312 is pushed toward the flexible lens membrane 310.

[0073] Figure 4 A variable focus assembly 400 (eg, Figure 2 ILA 210 or OLA 220, or Figure 1 The variable focus assembly 400 includes a liquid lens assembly 402, such as Figure 3A-3BLiquid lens assembly 300. Liquid lens assembly 402 includes shaping ring 404, lens core 406, and other parts of the liquid lens assembly (not shown separately). In some embodiments, liquid lens assembly 402 including shaping ring 404 is nested within cam ring 416. Mechanical features on shaping ring 404 can engage mechanical features of cam ring 416 so that rotational movement of cam ring 416 causes axial movement of shaping ring 404 and, therefore, causes a flexible lens membrane (e.g., Figure 3A-3B The shape of the flexible lens film 310) changes.

[0074] The cam ring 416 and the liquid lens assembly 402 can be nested within the bracket 418. The cam ring 416 can rotate relative to both the bracket 418 and the shaping ring 404. The shaping ring 404 can move axially relative to both the cam ring 416 and the bracket 418. The cap 420 can be fixed to the bracket 418 to fix the position of the components such as the cam ring 416 that are contained in the bracket 418 or mounted to the bracket 418. In some embodiments, the actuation system for adjusting the curvature of the flexible lens membrane uses relative rotational movement between the cam ring 416 and both the bracket 418 and the shaping ring 404 to move the shaping ring 404 axially, and thus the flexible lens membrane axially. During actuation, the bracket 418 can be stationary, the cam ring 416 can perform rotational movement, and the shaping ring 404 can perform axial movement.

[0075] Figure 5A and Figure 5B Examples of mechanical features for engaging the forming ring 404 and the cam ring 416 are shown. Figure 5A , a specific surface geometry is shown at the interface 502 between the forming ring 404 and the cam ring 416. A lug 504 is shown on the forming ring 404, which extends axially and engages a helical spline feature on the cam ring 416 to allow the forming ring 404 to move axially as the cam ring 416 rotates. Other geometric shapes such as ramps, steps, guide pins, and other mechanical features may be used to guide the axial movement of the forming ring 404 relative to the cam ring 416, and in particular, suitable geometric shapes are used to convert the relative rotation of the cam ring 416 relative to the forming ring 404 into axial movement of the forming ring 404 relative to the cam ring 416.

[0076] Exemplary Rotary Actuation System

[0077] Fig. 6A An example of an actuation system 600 based on an annular axial flux motor is shown. The system 600 includes a rotary actuator 602 configured to actuate a rotary cam element 610. The cam element 610 may be Figure 4416 of the cam ring. In some cases, the cam element 610 can be a ring segment of the cam ring, such as half of the cam ring. The cam element 610 can have a limited (or restricted) actuation range, such as ±4 degrees. Figure 7 , Figure 8 and Fig.13A As described in further detail in , a limited actuation range may be achieved by implementing the rotary actuator 602 to correspond to annular segments of the cam element 610 .

[0078] The system 600 may include a position sensor 604 configured to detect the position of the cam element 610. For example, when the cam element is in an original position, the position sensor 604 may be calibrated to zero. When the rotary actuator actuates the cam element 610 to rotate, the position sensor 604 may detect the degree to which the cam element 610 has rotated, and then determine the current position of the cam element 610 based on the detection result.

[0079] In some embodiments, the cam element 610 has sufficient friction to self-lock in the absence of actuation from the rotary actuator 602. In some embodiments, the system 600 includes a radial force latch 606 configured to prevent movement of the cam element 610. When the radial force latch 606 is released, the rotary actuator actuates the cam element 610.

[0080] Figure 6B and Figure 6C Shown in operation state ( Figure 6B ) and the released state ( Figure 6C ) is an example of a radial force latch 606. The radial force latch 606 may include a drive spring 620 loaded with a spring 622 and radially entering the cam element 610. The drive spring 620 may be made of a ferromagnetic metal and may be released via a radially oriented solenoid 630. Solenoid power is consumed only during actuation. In an operating state, as Figure 6B As shown, the solenoid electromagnet is not energized. The spring 622 pushes the drive lock spring 620 toward the cam element 610 to prevent the cam element 610 from moving. In the released state, as shown Figure 6C As shown, the solenoid electromagnet is energized and drives the lock spring 620 to retract toward the spring 622 (as shown by the arrow) and the cam element 610 is free to move.

[0081] In some embodiments, the circuit for actuating the solenoid 630 may include a low-side drive switch for unidirectional actuation. If the solenoid 630 needs to be actuated slowly, a buffer may be connected in parallel to the load. If the current driving the solenoid 630 needs to be gradually varied, open-loop current control may be achieved by replacing a metal oxide semiconductor field effect transistor (MOSFET) with a bipolar junction transistor (BJT) or a BJT Darlington compound transistor and using a digital-to-analog converter circuit (DAC) of a microcontroller unit (MCU) to gradually vary the base current of the BJT.

[0082] In certain embodiments, the actuator 602 may have one or more of the following specifications: mass less than 7.9 grams; thrust and actuation thrust of ±1 N to ±4 N; speed of approximately 50 mm / second; travel in the range of 0.8 to 3.5 mm; dynamics of the motion system (transfer functions: stiffness (k), mass damping (m), natural frequency (fn), and damping ratio (β)): meff less than 5 grams, k greater than a value in the range of 2.0 N / mm-4 N / mm or 4.0 N / mm-8 N / mm, fn between 30-200 Hz, β between 0.5-3.0; positioning accuracy (allowable error motion of the motor in six degrees of freedom) ±0.2 mm; smallest possible motion step size less than 1 μm; orientation (tilt / inclination) uncertainty less than 120 arc minutes; distributed load characteristics of approximately Φ40 mm; duty cycle of approximately 1200 million switches at a frequency of 0.3 Hz; form factor of the motor: size <33 mm x 16 mm x 9.2mm; the form factor of the actuator: Ф40mm, with distributed load; the allowable deformation of mechanical parts and installation positions is less than 0.020-0.300mm; the self-locking holding force is greater than 1.2 times the driving force; power consumption: the average value is less than 0.5 watts, the maximum value is less than 1.0 watts; the driving sound (allowable noise) is less than 25-32dbA at 25mm; the thermal value is less than 1 watt; the temperature during driving is lower than 60℃; the service life is about 10,000 hours; operating environment (operating temperature, operating humidity): the ambient temperature is in the range of -10℃ to +55℃, and the non-condensing humidity is in the range of 5-95%; and the shock resistance can withstand a drop of 1 meter in 3 directions without damage.

[0083] Exemplary Annular Axial Flux Machine

[0084] Figure 7 An example of a toroidal flux permanent magnet axial motor 700 is shown. The motor 700 may be implemented as a variable focus assembly (e.g., Figure 2 ILA 210 or OLA 220, Figure 4 Variable focus assembly 400) or a liquid crystal lens assembly (e.g., Figure 3A-3B The liquid crystal lens assembly 300 or Figure 4The actuator (e.g., Figure 6A-6C Actuator 602).

[0085] The motor 700 is configured to move the variable focus assembly, for example, by moving a cam ring 702 of a liquid lens assembly in the variable focus assembly. The cam ring 702 may be Figure 4 The cam ring 416 of the embodiment of the present invention. The variable focus assembly may include a shaped ring nested within the cam ring 702, such as Figure 4 Forming ring 404 or Figure 3A-3B The cam ring 702 may be nested in a bracket (not shown), such as Figure 4 The bracket 418. The cam ring 702 can rotate relative to the bracket. The shaping ring can move axially relative to both the cam ring 702 and the bracket. The axial movement of the shaping ring can cause a change in the curvature of the flexible lens film coupled to the shaping ring.

[0086] The motor 700 can rotate the cam ring 702 within a limited (or restricted) range of travel, such as within a limited angular range, but not continuously in a full circle. The cam ring 702 can be rotated forward and / or backward within a limited range of travel.

[0087] In some embodiments, the motor 700 includes a rotor 710 formed by placing a permanent magnet array (or multiple permanent magnet arrays) having a specific arrangement around at least a portion of the annular opening of the cam ring 702. Figure 7 As shown, the permanent magnet array can be arranged on an annular segment (e.g., an arc within an angle θ) of the cam ring 702. The permanent magnets are arranged along the circumference of the cam ring 702. The permanent magnet array can include alternating pairs of opposite magnetic poles (N and S). The cam ring 702 can be made of a non-ferromagnetic material (such as plastic).

[0088] The motor 700 also includes a stator 720, which is formed by placing an electric winding around at least a portion of the annular opening of the bracket so that the permanent magnet and the electric winding are mounted to separate components and correspond to each other. The electric winding can be made of copper using a conductive material (such as copper) printed on a printed circuit board (PCB). The PCB can then be cut to a certain size or bent and mounted on the bracket. In some embodiments, multi-layer printed electric windings can be stacked on top of each other on the PCB, thereby increasing the density of the windings. A higher density winding can provide a higher torque output. The stator 720 can be implemented in two-phase, three-phase, or even more phase windings.

[0089] When current passes through the PCB winding, a time-varying magnetic field is generated, which interacts with the permanent magnet array of the rotor 710 to cause relative rotation between the rotor 710 and the cam ring 702 and the bracket. Coordinate axes x, y, and z represent the tangential direction, axial direction, and radial direction, respectively. The permanent magnet array and the electrical winding can be configured so that the changing magnetic field of the PCB winding interacts with the axial component of the magnetic field along the rotor 710 along the axial direction (i.e., the y direction) to provide a constant torque to generate a force along the tangential direction (i.e., the x direction), thereby rotating the permanent magnets of the rotor 710 and the cam ring 702.

[0090] In some other embodiments, the permanent magnet array of the rotor 710 may be formed on a bracket, and the electrical windings on the PCB of the stator 720 may be formed on the cam ring 702, so that the electrical windings and the permanent magnet array may be formed on separate components and may have relative movement.

[0091] Figure 8 An example of a toroidal flux permanent magnet axial motor 800 is shown. The motor 800 may be Figure 7 The motor 700 includes a rotor 810 (eg, Figure 7 The rotor 710) and the stator 820 ( Figure 7 The rotor 810 may include a stator 720 mounted on a rotatable cam ring (e.g., Figure 7 The stator 820 may be mounted on a bracket that carries a rotatable cam ring, such as Figure 4 On bracket 418. Figure 8 An expanded side (radial) view of electric machine 800 is shown.

[0092] In some embodiments, the rotor 810 includes a Halbach array, which has a special arrangement of permanent magnets that increases the magnetic field on one side of the array (e.g., the active side) while nulling the magnetic field on the other side (e.g., the inactive side). The Halbach array has a magnetization pattern that rotates in space. The rotating pattern of permanent magnets (on the front; on the left, top, right, bottom) can continue indefinitely and have the same effect. The effect of this arrangement is similar to that of horseshoe magnets placed next to each other with many similar poles touching.

[0093] Fig. 9An example of a magnetic field 910 of a Halbach array 900 is shown. The Halbach array 900 includes a linear array of permanent magnets extending in a horizontal direction (i.e., an x-direction). The magnetic field 910 has a horizontal component (e.g., an x-direction) and a vertical component (or an axial direction, e.g., a y-direction). Arrows 912 show the field direction in each magnetic pole of the Halbach array 900. Due to the special arrangement of the Halbach array 900, the magnetic field 910 on one side of the Halbach array 900 (the bottom side of the Halbach array 900 as shown) is stronger than the magnetic field on the other side of the Halbach array 900 (the top side of the Halbach array 900 as shown).

[0094] The magnetic field 910 of the Halbach array 900 on the stronger side (or active side) can be expressed by the following formula:

[0095] B(x,y)=B x +jB y =B0e jkx e -ky =B0cos(kx)e -ky +jB0sin(kx)e -ky (1)

[0096] Among them, B0 represents the magnitude of the magnetic field, B x represents the magnetic field vector along the x direction, B y represents the magnetic field vector along the y direction, and k represents the wave vector.

[0097] When current flows through the electrical winding, a time-varying magnetic field is generated, which interacts with the magnetic field 910 of the Halbach array 900 to generate a Lorentz force F. The Lorentz force F can be expressed by the following expression:

[0098] F=(N*i)L×B (2),

[0099] Wherein, N represents the number of turns of the electrical winding, i represents the magnitude of the current passing through the electrical winding, L represents the winding length vector, and B represents the magnetic field vector from the Halbach array 900 .

[0100] As mentioned above, in order to rotate the rotor arranged on the cam ring, a force along the tangent direction of the cam ring (i.e., the x-direction) is required. If the electrical winding moves in and out along the z-direction, only the y-component B of the magnetic field of the Halbach array 900 y For the Lorentz force F x The x component contributes to the magnetic field B x The x component of the force produces a y force, which is converted into an axial force F y Therefore, the magnetic field component B y can be maximized to increase the tangential force F x , and the magnetic field component Bx can be minimized to reduce the axial force F y .

[0101] Return to reference Figure 8 , the active side of the Halbach array of the rotor 810 is configured to face the multi-layer PCB of the stator 820. In some embodiments, the Halbach array is a linear array extending along the tangent direction (x direction) of the cam ring or along the circumference. The Halbach array includes periodic units of permanent magnets. Each unit may include multiple rows of magnetic pole pairs N and S. Figure 8 As shown, an example magnetic unit includes 4 rows of magnetic pole pairs ordered along the tangential direction: vertical N poles and vertical S poles along the axial direction on the first row, horizontal S poles and horizontal N poles along the axial direction on the second row, vertical S poles and vertical N poles along the axial direction on the third row, and horizontal N poles and horizontal S poles along the axial direction on the fourth row. Other sequences can also be implemented in the rotor 810, which can form a stronger field on one side of the permanent magnet than the other side. Adjacent rows can have magnetic gaps, which can be air cavities filled with a material with lower rigidity than the permanent magnets.

[0102] Fig.10 Shows Figure 8 Figure 1000 shows a simulated magnetic field of a Halbach array. The magnetic field of a Halbach array can be simulated by a software tool for performing finite element simulations of magnetic fields, such as FEMM (Finite Element Method Magnetism). In the simulation, each magnetic pole is configured to have a width of 1 mm, a height of 1 mm, and a magnetic spacing of 0.1 mm. The magnet grade is N42H. The simulated field 1000 shows that the field generated by the Halbach array on the active side of the array is stronger than the other inactive side of the array, similar to Fig. 9 Magnetic field 910 is shown.

[0103] Fig.11A and Fig. 11B 1000 along the horizontal direction (ie, the x-direction) of the Halbach array. Curves 1102 and 1112 show the y-component B of the magnetic field. y , while curves 1104 and 1114 represent the x-component B of the magnetic field x . Fig.11A shows the magnetic field at a distance of 0.25 mm from the active side of the Halbach array, while Fig. 11B The magnetic field at a distance of 0.50 mm from the active side of the Halbach array is shown. These curves show the magnetic field component B x and B y It is a sine curve with a phase difference of 90 degrees. The closer to the Halbach array, the stronger the magnetic field B.

[0104] Return to reference Figure 8 , if the stator 820 has a single-phase electrical winding, the Lorentz force Fx The x component of can be expressed by the following expression:

[0105] Fx=iL z (x)B y (x)cos(kx+π / 2)=iL z (x)B0(y)│sin(kx)│ (3),

[0106] Among them, L z (x) represents the winding length of the square wave that changes with x. The winding direction changes every π electrical radians, thus ensuring that L z With B y The product of is positive, F x The polarity of F is determined by the polarity of current i. Expression (3) shows that the force F x is a constant and varies with x.

[0107] In order to generate a constant torque for the rotor 810, the stator 820 can be configured to have at least 2-phase electrical windings. For example, for a stator 820 having 2-phase (phase A and phase B) electrical windings with a sinusoidal drive current with a phase difference of π / 2rad, the force Fx can be expressed by the following expression:

[0108] F x =i A (x)L z-A (x)B y (x)+i B (x)L z-B (x)B y (x)

[0109] =2i│L z │B0(y)(sin 2 (kx)+(sin 2 (kx+π / 2))=B0(y)2iL z │ (4).

[0110] The above expression shows that when the current i passing through the two-phase winding A and i B When x varies sinusoidally, for example, by field orientation control (FOC), F x Does not change with x.

[0111] The stator 820 may also be configured to have 3-phase electrical windings having sinusoidal drive currents with a phase difference of 2π / 3 rad (ie, 120 degrees) relative to each other, and the force F x can remain unchanged as in expression (4). For illustration purposes only, Figure 8The stator 820 is shown to have 2-phase electrical windings. The stator 820 may be a multi-layer PCB, with each layer representing each phase winding. The stator 820 may include 2-phase windings, wherein the phase difference of the current passing through the two-phase windings is π / 2. The stator 820 may include one or more pairs of phase A windings and phase B windings. For example, Figure 8 Stator 820 is shown to include a 2-phase winding having 2 pairs of phase A and phase B windings.

[0112] Fig.12 An example of phase A and phase B electrical windings having rectangular patterns is shown. Rectangular winding 1200 represents a phase A electrical winding on a first PCB layer, while rectangular winding 1210 represents a phase B electrical winding on a second PCB layer. Phase A rectangular winding 1200 and phase B rectangular winding 1210 are configured to be offset by a quarter winding period, corresponding to a π / 2 phase difference. Rectangular winding 1200 has a nominal gap (e.g., air gap) 1202 between windings on the first PCB layer, and rectangular winding 1210 has a nominal gap (e.g., air gap) 1212 between windings on the second PCB layer. Gap 1202 and gap 1212 can have the same width or different widths.

[0113] The dashed boxes 1204 and 1214 represent the regions that contribute to the useful current, and the height of the dashed boxes along the radial direction (z direction) is related to the rotor (eg, Figure 8 The height of the permanent magnets in the rotor 810 along the radial direction (z direction). The ratio of magnet height to electrical winding period can be configured to be "high" so that the heat generated due to the resistance of the winding coil can be minimized. The nominal gaps 1202 and 1212 can be kept small to maximize the torque constant K T The total resistance of the winding (Ra) and the torque constant (K T ) square ratio (Ra / K T 2 ) can be minimized to reduce energy losses due to the coil material (e.g., copper) and maximize the motor (e.g., Figure 8 The working efficiency of the motor 800).

[0114] Fig.13A Another example of a toroidal flux permanent magnet axial motor 1300 is shown. The motor 1300 may be implemented as Figure 6A-6C Actuator 602. With Figure 8Compared to the motor 800, the motor 1300 includes two permanent magnet arrays 1310a and 1310b as rotors and an electrical winding 1320 of a multilayer PCB as a stator, which is located between the two permanent magnet arrays 1310a and 1310b along the axial direction (e.g., the y direction). The multilayer PCB 1320 can be implemented as a two-phase winding scheme and includes alternating pairs of phase B and phase A electrical winding layers. The number of layers is evenly divided into two groups of windings with a phase difference of 90 degrees. Given a drive scheme that implements magnetic field orientation control, the scheme implements a drive current that varies sinusoidally with the rotor position, and a flat torque output can be obtained. The multilayer PCB 1320 can also be configured as a 3-phase winding scheme, in which the number of layers in the PCB is an integer multiple of 3 (or 6), and different windings are wired 120 degrees out of phase with each other.

[0115] Since the multilayer PCB 1320 is located between the two groups of permanent magnets 1310a and 1310b, the magnetic field components of the magnetic fields of the two groups 1310a and 1310b can be symmetrical along the axial direction (i.e., the y direction) around the center of the PCB 1320, which allows each winding phase to have exactly the same rotor-related torque constant so as to produce a constant torque output through a suitable drive scheme. In addition, a stronger and more uniform magnetic flux density can be achieved in the motor 1300. Therefore, the torque constant of the motor 1300 can be increased.

[0116] In some embodiments, the first permanent magnet array 1310a includes a Halbach array, for example Figure 8 The first array 1310a has a special permanent magnet arrangement that enhances the magnetic field on one side of the array while eliminating the magnetic field to near zero on the other side. The first array 1310a is configured so that the stronger side faces one side of the multilayer PCB 1320, such as the first layer of the multilayer PCB 1320. In some embodiments, the first array 1310a is a linear Halbach array, including periodic magnet units extending along the tangential direction. Each magnet unit may include four rows of magnetic pole pairs arranged in an orderly manner along the tangential direction: vertical N poles and vertical S poles stacked in sequence along the axial direction on the first row, horizontal S poles and horizontal N poles stacked in sequence along the tangential direction on the second row, vertical S poles and vertical N poles stacked in sequence along the axial direction on the third row, and horizontal N poles and horizontal S poles stacked in sequence along the tangential direction on the fourth row. Adjacent rows have magnetic spacing.

[0117] In some embodiments, the second permanent magnet array 1310b may also be a Halbach array, which has a special permanent magnet arrangement that enhances the magnetic field on one side of the array while eliminating the magnetic field to near zero on the other side. The second array 1310b is configured so that the stronger side of the magnetic field faces the other side of the multilayer PCB 1320, for example, the last layer of the multilayer PCB 1320. In some embodiments, the second array 1310b is a linear Halbach array, including periodic magnet units extending along the tangential direction. Each magnet unit may include four rows of magnetic pole pairs arranged in an orderly manner along the tangential direction: vertical N poles and vertical S poles stacked in sequence along the axial direction on the first row, horizontal N poles and horizontal S poles stacked in sequence along the tangential direction on the second row, vertical S poles and vertical N poles stacked in sequence along the axial direction on the third row, and horizontal S poles and horizontal N poles stacked in sequence along the tangential direction on the fourth row. Adjacent rows have magnetic spacing.

[0118] like Fig.13A As shown, the second array 1310b has a different arrangement than the first array 1310a, wherein the second row and the fourth row have opposite magnetic polarities so that the stronger side of the second array 1310b is on the left side of the Halbach array of the second array 1310b, and the stronger side of the first array 1310a is on the right side of the Halbach array of the first array 1310a.

[0119] Fig. 13B Shows Fig.13A Schematic diagram of the arrangement of the motor 1300. Two permanent magnet arrays 1310a and 1310b may be mounted on the cam ring 1302. The cam ring 1302 may include a groove and a multilayer PCB 1320, with two groups of permanent magnets 1310a and 1310b on both sides of the groove, and the multilayer PCB 1320 may be inserted into the groove and mounted on a bracket 1304 outside the cam ring 1302. In some embodiments, the cam ring 1302 has no groove, and a gap may be formed between the two groups of permanent magnets 1310a and 1310 mounted on the circumference of the cam ring 1302, and in addition, the multilayer PCB 1320 mounted on the bracket 1304 may be inserted into the gap. The multilayer PCB 1320 may have substantially the same height (along the radial direction) as the permanent magnet arrays 1310a and 1310b along the radial direction.

[0120] In a specific embodiment, if Fig.13AAs shown, each magnetic pole N or S has a length of 1.0 mm along the x direction and a width of 0.5 mm along the y direction. Therefore, each permanent magnet array has a width of 1 mm along the y direction. The multilayer PCB 1320 has a total width of 1.6 mm along the y direction. PCB 1320 may include two pairs of alternating phase A and phase B printed electrical winding layers. The nominal gap between the multilayer PCB 1320 and each permanent magnet array 1310a, 1310b is approximately 0.2 mm along the y direction. The thickness of the cam ring 1302 may be not less than 4 mm. The magnetic spacing between adjacent rows in the permanent magnet array may be 0.25 mm. The magnet grade is N42H.

[0121] Fig.14 Shown with Fig.13A Simulated magnetic field 1400 of two identical sets of permanent magnets 1310a and 1310b separated from each other. Magnetic field 1400 can be simulated by a software tool for performing finite element simulation of magnetic fields, such as FEMM (Finite Element Method Magnetism). In the simulation, as described in a specific embodiment, each set of permanent magnets has a length of 1.0 mm and a width of 1.0 mm. The magnetic spacing is 0.25 mm. The magnet grade is N42H. The simulated field 1400 shows that the two Halbach arrays generate a stronger field in the active side (inside) of the Halbach array, and a much weaker field on the other inactive side (outside) of the Halbach array.

[0122] Fig.15A -C shows the components of the simulated magnetic field 1400 along the horizontal direction (ie, x direction) of the two Halbach arrays at different distances along the vertical (axial) direction (ie, y direction). Curves 1502, 1512, and 1522 show the y component B of the magnetic field 1400. y , while curves 1504, 1514 and 1524 represent the x-component B of the magnetic field 1400 x . Fig.15A The magnetic field at a distance of 0.2 mm from the first permanent magnet array 1310a, ie, the magnetic field on the edge of the first side of the PCB 1320, is shown. Fig. 15B The magnetic field is shown at a distance of 1.80 mm from the first array 1310 a or 0.2 mm from the second array 1310 b in the axial direction, ie, the magnetic field on the edge of the second side of the PCB 1320 . Fig. 15C 1310a, i.e., the magnetic field at the center of the PCB 1320. These curves show that these magnetic field components B x and B y is a sinusoidal curve with a phase difference of 90 degrees. The magnetic field 1400 is symmetrical around the center of the PCB 1320. When the magnetic field is closer to the center of the PCB 1320, the field component Bx The decay is significantly faster than field component B y Therefore, the y component of the total accumulated magnetic field, B y Ratio x component B x As mentioned above, the magnetic field component B y The Lorentz force F that can rotate the cam ring x Have contributed.

[0123] Fig.16A and Fig. 16B Shown in Fig.13A An example of a winding pattern for a printed electrical winding on a multilayer PCB 1320. A rectangular pattern ( Fig.16A ) or a triangle pattern ( Fig. 16B ) to design the windings. Note that only the routing components along the radial direction (z direction) can produce useful torque. The routing components along the circumferential direction (x direction) do not contribute useful torque and will increase winding resistance, dissipate heat, and reduce the efficiency of the motor 1300. Mathematical models and simulations can be developed to optimize the two types of windings ( Fig.16A The rectangular winding and Fig. 16B The winding design of the triangular winding in the motor involves multiple design variables, including: magnetic spacing, magnet width (circumferential), magnet height (radial) and triangular winding angle (β).

[0124] For example, in Fig.16A In the case of rectangular windings, the following characteristics can be achieved:

[0125] N turn =floor[(λ / 2) / (W trace +S trace )] (5),

[0126] Lz=2N turn (H PCB -λ / 2) (6), and

[0127] L total =λN turn (7)

[0128] Where λ represents the winding period, N turn Indicates the number of turns of the electrical winding in the winding cycle, L z represents the winding length along the z direction (or effective length per winding cycle or per pole pair), W trace Indicates the width of the winding line, S trace Indicates the spacing between the winding lines, H PCB Indicates the height of the PCB along the z direction.

[0129] For example, in Fig. 16BIn the case of a delta winding, the following characteristics can be achieved:

[0130] N turn =floor[(H PCB -λ / 2*tan(β)) / (W trace +S trace )] (8),

[0131] Lz=2N turn (λ / 2)*tan(β) (9), and

[0132] L total =2N turn (λ / 2) / cos(β) (10),

[0133] Where β represents the triangle winding angle.

[0134] Effective ratio L z / L total It can be determined based on the above expression. The higher the effective ratio, the higher the electrical efficiency of the winding. Fig. 16B The effective ratio L of the delta winding configured in z / L total Can be compared Fig.16A The effective ratio L of the rectangular winding configured in z / L total In addition, as shown in expression (4), the Lorentz force F x and effective winding length L z Proportional to the effective winding length L z The larger the force F x Therefore, when designing the electrical winding, the effective ratio L can be considered. z / L total and effective winding length L z .

[0135] Fig.17A The relationship between the winding period λ and the effective length Lz of each pole pair of the rectangular winding 1600 and the winding period λ and the effective ratio Lz are shown. z / L total Curve 1702 shows the relationship between the winding period and the effective length of each pole pair. This shows that when the winding period is about 5 mm, the maximum effective length of each pole pair can reach about 60 mm. Curve 1704 shows that the effective ratio is inversely proportional to the winding period. When the winding period is about 5 mm, the effective ratio is about 0.5.

[0136] Fig. 17B The relationship between the winding angle β of the triangle winding 1610 and the effective length of each pole pair and the winding angle β and the effective ratio L are shown when the winding period λ is 5 mm. z / L total . Curve 1712 shows the relationship between the winding angle and the effective length of each pole pair. This shows that when the winding angle is 45°, the maximum effective length of each pole pair can reach about 55 mm. Curve 1714 shows that the effective ratio increases with the winding angle. When the winding angle is 45°, the effective ratio is about 0.7. Therefore, compared with the rectangular winding 1600, the triangular winding 1610 can have a slightly smaller effective length but a higher effective ratio. Considering the form factor of the motor, the PCB height H PCB There may be limitations so that the triangular winding 1610 can have overall better performance than the rectangular winding 1600.

[0137] Routing multiple windings in a full-circle stator can be straightforward. However, routing multiple windings along a finite arc length can be challenging. Fig.18 A wiring scheme 1800 is shown which involves combining two layers into a single layer to form an electrical winding having one phase, e.g. Fig.13A The wiring scheme 1800 can form a winding on a limited arc length.

[0138] like Fig.18 As shown, a wire 1810 made of, for example, copper material starts from an input port 1801 on the first layer and extends to a first through hole 1802 along a first path on the first layer. Passing through the first through hole 1802, the wire 1810 reaches the second layer and extends to a second through hole 1803 along a second path on the second layer. The first layer and the second layer may be separated by an additional layer. The second path and the first path may be offset by a quarter of a winding cycle. Passing through the second through hole 1803, the wire 1810 returns to the first layer and extends to a third through hole 1804 along a third path on the first layer. Passing through the third through hole 1804, the wire 1810 reaches the second layer and extends to a fourth through hole 1805 along a fourth path on the second layer. Passing through the fourth through hole 1805, the wire 1810 reaches the first layer and extends to a fifth through hole 1806 along a fifth path on the first layer. Passing through the fifth through hole 1806, the wire 1810 reaches the second layer and extends to an output port 1807 on the second layer along a sixth path on the second layer. The first path, the third path, and the fifth path have similar shapes and the line 1810 extending along the first, third, and fifth paths forms a first winding 1820A on the first layer. The second path, the fourth path, and the sixth path have similar shapes and the line 1810 extending along the second, fourth, and sixth paths forms a second winding 1820B on the second layer. Each of the first winding 1820A and the second winding 1820B can be configured as a rectangular winding (e.g., Fig.16A A rectangular winding 1600) or a triangular winding (e.g., Fig. 16B The delta winding 1610 in FIG. 1 is for illustration purposes only. Fig.18 Each of the first winding 1820A and the second winding 1820B is shown to be a rectangular winding.

[0139] The driving current may flow from the input port 1801 on the first layer into the line 1810 and out of the output port 1807 on the second layer. The first winding 1820A and the second winding 1820B form a single-phase winding 1820, for example Fig.13A In the embodiment of the present invention, the first winding 1820A can be located on the first layer of the PCB, the second winding 1820B can be located on the third layer of the PCB, and the first winding 1820A and the second winding 1820B can form a phase B winding. Similarly, the winding on the second layer of the PCB and the winding on the fourth layer of the PCB can form a phase A winding. The driving current of the phase A and phase B electrical windings can be a sinusoidal current with a phase difference of π / 2rad, so that the stator can interact with the rotor to generate a constant force along the x-direction.

[0140] Each of the first winding 1820A and the second winding 1820B may be arranged to be aligned with a rotor (eg, Fig.13A The magnetic field B in the x direction of the rotor including two permanent magnet arrays 1310a and 1310b y The distribution 1850 corresponds to the distribution 1850. The distribution 1850 is a sine curve whose magnetic period is the same as the winding period of each of the first winding 1820A and the second winding 1820B. Fig.18 As shown, the magnetic cycles correspond to positive magnetic fields (N) and negative magnetic fields (S).

[0141] In some embodiments, the stator 1320 can be designed as a 2-phase system stator with the following parameters: the total arc angle used on the cam ring 1302 is 180 degrees; the number of PCB layers is 16; the PCB annular / radial height is 5mm; the winding trace width and spacing are 100μm and 100μm respectively; the trace thickness is 2oz copper (2.8mil); the magnet width along the circumferential direction (x direction) is 1mm; the magnetic spacing is 0.25mm; the magnet grade is NdFeB N42H; the average sinusoidal axial flux density amplitude is 0.5T; the winding type is triangular, and the winding angle is 45 degrees.

[0142] The magnetic flux density can be simulated, for example in FEMM, and the performance of the motor can be derived in numerical simulations. The torque constant shape can match the expected results, and the performance of the motor can be calculated for each phase. For example, the torque constant K TIt can be 80mNm / A, the pole pair number of the Halbach array can be 12, the electrical speed can be 12 times the mechanical speed, and the trace resistance per phase can be 32.6Ohm. Given the torque load and actuation speed, the average efficiency of the motor is about 5.9%. In order to maximize efficiency, the gear ratio of the motor and the torque constant of the motor can be maximized.

[0143] The drive source can have the following characteristics:

[0144] I max =T max / K T (11)

[0145] V max =W electrical-max (K v )+I max R phase (12)

[0146] Among them, the torque constant K of the permanent magnet rotor T and the rate constant K v Same, T max Indicates the maximum torque, W electrical-max represents the maximum angular velocity, R phase Represents the resistance of each phase line. According to the above parameters, I max Can be 250mA, V max It can be 9 V. In addition, the weight of the permanent magnet array of the rotor is about 3.6 g, the number of poles is 96, and the density of the magnet material is 7.5 mg / mm 3 .

[0147] There are three methods to derive the torque constant. In the first method, the Lorentz magnetic force of each wire is calculated and summed, and then the rotor angle is changed between 0 and 2π to obtain the change. In the second method, the induced voltage in the winding is calculated by moving the rotor at a fixed speed via Faraday's law. The torque constant K T and the rate constant K v are the same, so the rate constant K v Can be used to derive the torque constant K T In the third method, the flux linkage per turn relative to the rotor angle (integrating the flux density over the turn area) is calculated and summed, and then the torque constant can be obtained by taking the derivative of the flux linkage with respect to the rotor angle. The third method can be equivalent to the second method.

[0148] Example Process

[0149] Fig.19A flow chart showing an example of a process 1900 for operating a system using an annular axial flux motor as an actuator. The system may be a liquid lens assembly, such as Figure 3A-3B Liquid lens assembly 300 or Figure 4 Liquid lens assembly 402; variable focus assembly, such as Figure 2 ILA 210 or OLA 220, Figure 1 The optical element 120 may be a variable focus assembly, or Figure 4 The variable focus assembly 400. The annular axial flux motor may be Figure 13A-13B Motor 1300.

[0150] In some embodiments, an annular axial flux motor includes a stator mounted on a first annular segment of a bracket and a rotor mounted on a second annular segment of a cam ring inside the bracket. The first annular segment of the bracket corresponds to the second annular segment so that the stator can interact with the rotor. The cam ring can rotate relative to the bracket. The cam ring can be made of a non-ferromagnetic material.

[0151] The stator includes a multi-phase (2-phase, 3-phase or more phase) electrical winding printed on multiple layers of a printed circuit board (PCB). The printed electrical winding extends along the circumference of the first annular segment. The multiple layers are stacked on each other along the axial direction of the first annular segment. Each phase electrical winding of the stator can be configured to have the same rotor-related torque constant so that the stator is configured to generate a constant torque to drive the rotor.

[0152] In some embodiments, the stator includes 2-phase electrical windings. The two-phase electrical windings may have the same winding pattern and be offset by a quarter winding period. The winding pattern may be a rectangular pattern or a triangular pattern (eg, a triangular winding angle of 45 degrees).

[0153] In some embodiments, each of the multiple layers corresponds to a respective phase electrical winding, and respective phase electrical windings having different phases alternate among the multiple layers.

[0154] In some embodiments, the multilayer printed electrical winding includes a first layer, a second layer, a third layer, and a fourth layer stacked together in sequence along the axial direction, and the printed electrical windings on the first layer and the third layer are formed by a first continuous line as a first phase electrical winding, and the printed electrical windings on the second layer and the fourth layer are formed by a second continuous line as a second phase electrical winding.

[0155] In a specific embodiment, the first wire is printed in the following manner: starting from an input port of the first layer, extending along a first path on the first layer to a first through-hole, the first wire passes through the first through-hole to the third layer and extends along a second path on the third layer to a second through-hole, the first wire passes through the second through-hole back to the first layer and extends along a third path on the first layer to a third through-hole, the first wire passes through the third through-hole to the third layer and extends along a fourth path on the third layer to a fourth through-hole, the first wire passes through the fourth through-hole to the first layer and extends along a fifth path on the first layer to a fifth through-hole, the first wire passes through the fifth through-hole to the third layer and extends along a sixth path on the third layer to an output port of the third layer. The first wire extending along the first path, the third path, and the fifth path forms a first electrical winding on the first layer, the first wire extending along the second path, the fourth path, and the sixth path forms a second electrical winding on the third layer, and the first electrical winding and the second electrical winding form a first phase electrical winding. The first electrical winding and the second electrical winding have the same winding pattern shifted by a quarter winding period, and the first through-hole, the third through-hole, and the fifth through-hole are adjacent to each other, and the second through-hole and the fourth through-hole are adjacent to each other.

[0156] The rotor may include a permanent magnet array mounted on the second annular segment of the cam ring. In some embodiments, the rotor includes two Halbach arrays mounted on the second annular segment and spaced apart from each other along the axial direction of the second annular segment. Each Halbach array is configured so that the magnetic field on the active side of the Halbach array is stronger than the magnetic field on the opposite inactive side of the Halbach array with respect to the axial direction. The magnetic field on the inactive side of the Halbach array is almost equal to zero.

[0157] In some embodiments, a multi-layer printed electrical winding is inserted axially between two Halbach arrays of the rotor, with the active sides of the Halbach arrays facing opposite sides of the multi-layers and separated by a nominal gap.

[0158] The nominal gap may have the same width along the axial direction. The two Halbach arrays are configured to generate a magnetic field that is symmetrical along the axial direction relative to the center of the multiple layers of the PCB, and the axial component of the magnetic field along the axial direction is much larger than the tangential component of the magnetic field along the tangential direction of the second annular segment.

[0159] The two Halbach arrays may have different magnetic pole arrangements and be configured to have active sides facing opposite sides of the multilayer printed electrical winding. Each Halbach array may include periodic units of permanent magnets arranged circumferentially on a second annular segment. Each periodic unit may include multiple rows of magnetic pole pairs. Adjacent rows may be separated from each other by a magnetic interval along the circumference, and each magnetic pole pair may include an N pole and an S pole.

[0160] In some embodiments, in a first Halbach array, each periodic unit includes four rows of magnetic pole pairs, including: a first row having N poles and S poles stacked in sequence vertically along an axial direction, a second row having S poles and N poles stacked in sequence horizontally along a circumferential direction, a third row having S poles and N poles stacked in sequence vertically along an axial direction, and a fourth row having N poles and S poles stacked in sequence horizontally along a circumferential direction.

[0161] The second Halbach array has a different arrangement from the first Halbach array. Each periodic unit in the second Halbach array may include four rows of magnetic pole pairs, including: a first row having vertical N poles and vertical S poles stacked in sequence along the axial direction, a second row having horizontal N poles and horizontal S poles stacked in sequence along the tangential direction, a third row having vertical S poles and vertical N poles stacked in sequence along the axial direction, and a fourth row having horizontal S poles and horizontal N poles stacked in sequence along the tangential direction.

[0162] The height of the stator's electrical winding along the radial direction of the structure is substantially the same as the height of the permanent magnet Halbach array along the radial direction. The electrical winding may be configured such that a winding period of the electrical winding corresponds to a magnetic period of the rotor magnetic field.

[0163] At 1902, respective drive currents are input into different phase electrical windings of the stator. The respective drive currents have a phase difference of a predetermined degree with respect to each other. For example, for a two-phase electrical winding, the drive currents are sinusoidal currents with a phase difference of π / 2; for a three-phase electrical winding, the drive currents are sinusoidal currents with a phase difference of 2π / 3.

[0164] In some embodiments, the rotor generates a magnetic field having a sinusoidal shape corresponding to the position of the rotor's magnetic pole pairs, and the stator is driven by a sinusoidal current that varies corresponding to the position of the rotor's magnetic pole pairs.

[0165] At 1904, a rotor mounted on the second annular segment of the cam ring is driven to rotate about the axis of the cam ring within a limited range of travel. The electrical windings input with the drive current may generate a time-varying magnetic field, which may interact with the magnetic field of the rotor to generate a Lorentz force. In particular, an axial component of the magnetic field along the axial direction of the second annular segment may contribute to a Lorentz force along the tangential direction of the second annular segment, which may cause the rotor to rotate together with the cam ring.

[0166] At 1906, a shaping ring coupled to the cam ring moves with axial movement along the axial direction by the rotational movement of the camshaft. The shaping ring can be located inside the cam ring. The mechanical features of the shaping ring can engage with the mechanical features of the cam ring so that the rotational movement of the cam ring causes the axial movement of the shaping ring.

[0167] At 1908, the curvature of the flexible lens membrane coupled to the shaping ring is changed by axial movement of the shaping ring. The flexible lens membrane and the shaping ring can be included in a liquid lens assembly. The liquid lens assembly can include an incompressible fluid encapsulated between the shaping ring, the flexible lens membrane, the refractive component, and the flexible annular membrane. When the shaping ring moves toward the refractive component with the axial movement, the incompressible fluid is pushed toward the flexible lens membrane to cause the curvature change.

[0168] Various example embodiments of the present disclosure are described herein, and reference is made to these examples in a non-limiting manner. They are provided to illustrate the more widely applicable aspects of the present disclosure. Without departing from the true spirit and scope of the present disclosure, various changes can be made to the described present disclosure and can be replaced with equivalents. In addition, many modifications can be made to adapt specific situations, materials, material compositions, processes, one or more process actions or one or more steps to one or more purposes, spirit or scope of the present disclosure. In addition, as will be appreciated by those skilled in the art, each of the various variants described and illustrated herein has discrete components and features, which can be easily separated or combined with the features of any one of the other several embodiments without departing from the scope or spirit of the present disclosure. All of these modifications are intended to fall within the scope of the claims associated with the present disclosure.

[0169] The present disclosure includes methods that can be performed using subject equipment. The method may include an action of providing such suitable equipment. Such provision may be performed by an end user. In other words, the "providing" action may include one or more steps in which the end user may obtain, access, approach, locate, set, activate, power on, or otherwise act to provide the necessary equipment in the subject method. The methods described herein may be performed in any order of the listed events that is logically possible and in the listed order of events.

[0170] Exemplary aspects of the present disclosure and details on material selection and manufacturing have been set forth above. As for other details of the present disclosure, these can be understood in conjunction with the patents and publications cited above and what is generally known or understood by those skilled in the art. This also applies to the method-based aspects of the present disclosure in terms of additional actions that are generally or logically employed.

[0171] In addition, although the present disclosure has been described with reference to several examples that optionally include various features, the present disclosure is not limited to the contents of the description or indication conceived with respect to each variant of the present disclosure. Various changes may be made to the described disclosure and may be replaced with equivalents (whether referenced herein or not included for the sake of brevity) without departing from the true spirit and scope of the present disclosure. In addition, where a range of values ​​is provided, it is understood that each intermediate value between the upper and lower limits of the range, as well as any other stated value or intermediate value within the stated range, is included in the present disclosure.

[0172] In addition, it is contemplated that any optional features of the described invention variants may be proposed and claimed independently or in combination with any one or more features described herein. References to singular items include the possibility of the presence of multiple identical items. More specifically, as used herein and in the claims associated therewith, the singular forms "a", "an", "said" and "the" include plural referents unless otherwise specifically stated. In other words, the use of the article allows "at least one" of the subject items in the above description and claims associated with the present disclosure. It should also be noted that such claims can be drafted to exclude any optional elements. Therefore, this statement is intended to serve as a prior basis for the use of exclusive terms such as "only", "only" and the like in conjunction with the recitation of claim elements, or the use of "negative" limitations. Without the use of these exclusive terms, the term "comprising" in the claims associated with the present disclosure should allow the inclusion of any additional elements, regardless of whether a given number of elements are listed in these claims, or the addition of features can be considered to be changing the nature of the elements set forth in such claims. Unless explicitly defined herein, all technical and scientific terms used herein should have as much commonly understood meaning as possible while maintaining the validity of the claims.

[0173] The breadth of the present disclosure is not limited to the examples and / or subject description provided, but is limited only by the scope of the claim language associated with the present disclosure.

Claims

1. A ring-shaped axial flux motor, comprising: a rotor comprising an array of permanent magnets mounted on a first annular segment of a rotatable structure, the first annular segment of the rotatable structure being formed with a finite arc length less than a full circle, the array of permanent magnets extending along a circumference of the first annular segment and configured such that a magnetic field on an active side of the array relative to an axial direction of the first annular segment is stronger than a magnetic field on an opposite, inactive side of the array; as well as a stator comprising a multi-layer printed electric winding on a printed circuit board, the printed circuit board being mounted on a second annular segment of a carrier corresponding to the first annular segment, the electric winding extending along the circumferential direction, the multi-layer printed electric winding of the printed circuit board being stacked along the axial direction, the active side of the permanent magnet array facing one side of the multi-layer printed electric winding of the printed circuit board and separated by a nominal gap; wherein the stator is configured to be excited to generate torque to drive the rotor to rotate forward or backward together with the rotatable structure relative to the carrier within a limited angular range less than a full circle; and The electric winding has a height along the radial direction of the structure, and the height is substantially the same as the height of the permanent magnet array along the radial direction.

2. The annular axial flux motor according to claim 1, wherein: The permanent magnet array is a Halbach array.

3. The annular axial flux motor according to claim 2, wherein: The Halbach array includes periodic units of permanent magnets arranged on the first annular segment along the circumferential direction, each of the periodic units including a plurality of rows of magnetic pole pairs.

4. The annular axial flux motor according to claim 3, wherein: Each of the periodic units includes four rows of magnetic pole pairs, adjacent rows are separated from each other by a magnetic interval along the circumferential direction, each magnetic pole pair includes an N pole and an S pole, and Wherein, the four rows of magnetic pole pairs include: A first row having N poles and S poles stacked vertically in sequence along the axial direction; a second row having S poles and N poles stacked in sequence horizontally along the circumferential direction; a third row having S poles and N poles vertically stacked in sequence along the axial direction; and A fourth row has N poles and S poles stacked in sequence horizontally along the circumferential direction.

5. An annular axial flux motor according to any one of claims 1 to 4, wherein: The rotor comprises two permanent magnet arrays mounted on the first annular segment and spaced apart from each other along the axial direction; wherein the multilayer printed electrical winding on the printed circuit board is arranged between the two permanent magnet arrays, active sides of the two arrays facing opposite sides of the multilayer printed electrical winding relative to the axial direction; and Wherein, the nominal gap between the active side of each Halbach array and the opposite side of the multi-layer printed electrical winding has the same width along the axial direction.

6. The annular axial flux electric machine according to claim 5, wherein: The two permanent magnet arrays are configured to generate a magnetic field that is symmetrical with respect to the center of the multilayer printed electrical winding of the printed circuit board, The axial component of the symmetrical magnetic field along the axial direction is much larger than the tangential component of the symmetrical magnetic field along the tangential direction of the first annular segment.

7. The annular axial flux motor according to claim 5, wherein: Each of the two permanent magnet arrays is a respective Halbach array; Each Halbach array has a different magnetic pole arrangement and is configured to have an active side opposite to two sides of the multi-layer printed electrical winding.

8. The annular axial flux electric machine according to claim 5, wherein: The stator comprises a multi-phase electrical winding; and Wherein each phase of the multi-phase electrical winding of the stator is configured to have the same rotor-related torque constant such that the stator is configured to generate a constant torque to drive the rotor.

9. The annular axial flux electric machine according to claim 1, wherein: The electrical winding is configured such that a winding period of the electrical winding corresponds to a magnetic period of a magnetic field of the rotor.

10. The annular axial flux electric machine according to claim 1, wherein: The stator includes two-phase electrical windings configured to be driven with sinusoidal drive currents having a phase difference of π / 2.

11. The annular axial flux electric machine according to claim 10, wherein: Each layer of the printed electrical winding in the multi-layer printed electrical winding corresponds to a corresponding phase electrical winding, and the respective phase electrical windings with different phases are alternated in the multi-layer printed electrical winding.

12. An annular axial flux electric machine according to claim 10 or 11, wherein: The multi-layer printed electrical winding comprises a first layer, a second layer, a third layer, and a fourth layer stacked in sequence along the axial direction; as well as The printed electrical windings on the first and third layers are formed by first continuous wires as first-phase electrical windings, and the printed electrical windings on the second and fourth layers are formed by second continuous wires as second-phase electrical windings.

13. An annular axial flux electric machine according to claim 12, wherein: The first continuous line is printed starting from the input port of the first layer, extending along a first path on the first layer to a first through-hole, the first continuous line passes through the first through-hole to the third layer and extends along a second path on the third layer to a second through-hole, the first continuous line passes through the second through-hole back to the first layer and extends along a third path on the first layer to a third through-hole, the first continuous line passes through the third through-hole to the third layer and extends along a fourth path on the third layer to a fourth through-hole, the first continuous line passes through the fourth through-hole to the first layer and extends along a fifth path on the first layer to a fifth through-hole, the first continuous line passes through the fifth through-hole to the third layer and extends along a sixth path on the third layer to an output port of the third layer; wherein a first continuous line extending along the first path, the third path, and the fifth path forms a first electrical winding on the first layer, the first continuous line extending along the second path, the fourth path, and the sixth path forms a second electrical winding on the third layer, and the first electrical winding and the second electrical winding form a first-phase electrical winding; wherein the first electrical winding and the second electrical winding have the same winding pattern offset by a quarter of a winding period; and The first through hole, the third through hole, and the fifth through hole are adjacent to each other, and the second through hole and the fourth through hole are adjacent to each other.

14. The annular axial flux electric machine according to claim 10, wherein: The two-phase electrical windings have the same winding pattern and are offset by a quarter of a winding period.

15. The annular axial flux electric machine according to claim 1, wherein: The stator includes three-phase electrical windings configured to be driven with sinusoidal drive currents having a 2π / 3 phase difference with respect to each other.

16. The annular axial flux electric machine according to claim 1, wherein: The electrical winding has a rectangular winding pattern.

17. The annular axial flux electric machine according to claim 1, wherein: The electrical winding has a triangular winding pattern.

18. An annular axial flux electric machine according to claim 17, wherein: The triangular winding pattern has a winding angle of 45 degrees.

19. The annular axial flux electric machine according to claim 1, wherein: The rotor is configured to generate a magnetic field having a sinusoidal shape corresponding to the positions of the magnetic pole pairs of the rotor; as well as The stator is configured to be driven by a sinusoidal current that changes correspondingly to the position of the magnetic pole pairs of the rotor.

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