Transverse flux machine

Abstract

A transverse flux machine (TFM) includes: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets in which flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets, each pair of permanent magnets being arranged to generate a magnetic flux entering the flux concentrating core in a circumferential direction and away from the flux diverging core; and a stator including a transverse flux core configured to direct magnetic flux in each of a radial direction and an axial direction. The rotor further comprises a non-magnetic material located between the permanent magnets of each pair, adjacent to the flux concentrating core and opposite the stator, the non-magnetic material having a thickness (TH) in a radial direction. A steer-by-wire system for a vehicle includes a steering wheel actuator including a TFM coupled to a steered wheel.

Description

Related Applications

[0001] This patent application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 525,064, filed on July 5, 2023, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] The present disclosure relates to a transverse flux machine. The present disclosure also relates to the use of such a transverse flux machine in a steering wheel actuator of a steering system of a vehicle. Background Art

[0003] Vehicles such as automobiles, trucks, sport utility vehicles, crossovers, minivans, boats, airplanes, all-terrain vehicles, recreational vehicles, or other suitable forms of transportation typically include a steering system, such as an electric power steering (EPS) system, a steer-by-wire (SbW) steering system, a hydraulic steering system, or other suitable steering system. The steering system of such a vehicle typically controls various aspects of the vehicle's steering, including providing steering assistance to the operator of the vehicle, controlling the vehicle's steerable wheels, etc.

[0004] Steer-by-wire (SbW) is a direct evolution of the EPS system where there is no mechanical connection between the steering wheel and the steering rack. An EPS system may include a single actuator whose sole purpose is to provide assistance to the driver during steering maneuvers. However, on an SbW system, there can be two electric actuators / motors with different functionalities. The electric actuator attached to the rack in an SbW system is called a road wheel actuator (RWA), while the actuator on the driver's side is called a steering wheel actuator (HWA). The RWA has the same assistance-providing function as the EPS system actuator. The HWA, on the other hand, acts more as a feedback motor rather than providing assistance to the driver. In the absence of the HWA, the steering wheel on an SbW system can turn freely since there is no mechanical connection / friction. The functionality of the HWA opens up a wide array of design-related opportunities for the HWA.

[0005] Based on their functions, the torque-speed curves of different actuators used in steering systems may also be different. The distinct operating domains of EPS / RWA and HWA drive the design exploration of HWA technology. Summary of the invention

[0006] The present disclosure relates generally to transverse flux machines.

[0007] One aspect of the disclosed embodiment includes a transverse flux machine (TFM). The TFM includes: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between permanent magnets of each pair of permanent magnets, and each pair of permanent magnets is arranged to generate a magnetic flux that enters the flux concentrating core and moves away from the flux diverging core in a circumferential direction. The TFM also includes a stator, the stator including a transverse flux core, the transverse flux core configured to guide the magnetic flux in each of a radial direction and an axial direction. The rotor also includes a non-magnetic material, the non-magnetic material being located between the permanent magnets of each pair of permanent magnets, adjacent to the flux concentrating core and opposite to the stator, the non-magnetic material having a thickness (TH) in the radial direction.

[0008] Another aspect of the disclosed embodiment includes a dual-winding transverse flux machine (TFM). The dual-winding TFM includes a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets of each pair of permanent magnets, and each pair of permanent magnets is arranged to generate a magnetic flux that enters the flux concentrating core and moves away from the flux diverging core in a circumferential direction. The dual-winding TFM also includes a stator including a plurality of transverse flux cores, each transverse flux core configured to guide magnetic flux in each of a radial direction and an axial direction; and a first annular winding and a second annular winding, each annular winding being disposed in a shared transverse flux core of the plurality of transverse flux cores, and each annular winding being configured to conduct a corresponding current.

[0009] Another aspect of the disclosed embodiment includes a steer-by-wire system for a vehicle. The steer-by-wire system includes a steering wheel actuator that is coupled (to a steering wheel) to apply torque to the steering wheel. The steering wheel actuator includes a transverse flux machine (TFM). The TFM includes: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets of each pair of permanent magnets, and each pair of permanent magnets is arranged to generate a magnetic flux that enters the flux concentrating core and moves away from the flux diverging core in a circumferential direction; and a stator including a transverse flux core that is configured to guide magnetic flux in each of a radial direction and an axial direction.

[0010] These and other aspects of the present disclosure are disclosed in the following detailed description of the embodiments, the appended claims and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, according to common practice, the various features of the drawings are not drawn to scale. Instead, the sizes of the various features are arbitrarily enlarged or reduced for clarity.

[0012] Figure 1 is a schematic diagram of an electric power steering (EPS) system in accordance with the principles of the present disclosure.

[0013] Figure 2 An EPS system in accordance with the principles of the present disclosure is generally shown.

[0014] Figure 3 A steer-by-wire (SbW) steering system in accordance with the principles of the present disclosure is generally shown.

[0015] Figure 4 is a schematic diagram of a dual-winding motor drive system according to the principles of the present disclosure.

[0016] Figure 5 Shown is a graph illustrating a torque-speed curve for a steering system actuator according to the principles of the present disclosure.

[0017] Figure 6 A graph illustrating a torque-speed curve for a direct-drive steering wheel actuator in a SbW steering system is shown.

[0018] Figure 7 A cross-sectional view of a radial flux machine (RFM) is shown in accordance with the principles of the present disclosure.

[0019] Figure 8 A cross-sectional view of an axial flux machine (AFM) is shown in accordance with the principles of the present disclosure.

[0020] Fig. 9 A cross-sectional view of a transverse flux machine (TFM) is shown in accordance with the principles of the present disclosure.

[0021] Fig.10 A partial perspective view of a U-core TFM according to the principles of the present disclosure is shown.

[0022] Fig.11 A partial perspective view of a U-core TFM with an iron bridge is shown in accordance with the principles of the present disclosure.

[0023] Fig.12 A partial perspective view of a hook-shaped TFM according to the principles of the present disclosure is shown.

[0024] Fig.13 A partial perspective view of a U-core TFM with a flux concentrating inner rotor is shown in accordance with the principles of the present disclosure.

[0025] Fig.14 A partial perspective view of a TFM having a claw-pole configuration according to the principles of the present disclosure is shown.

[0026] Fig.15 A partial perspective view of a TFM having a flux concentrating outer rotor and a single-piece stator in accordance with the principles of the present disclosure is shown.

[0027] Fig.16 A perspective view of a stator in an outer rotor TFM is shown according to the principles of the present disclosure.

[0028] Fig.17 A perspective view of a stator in an inner rotor TFM is shown according to the principles of the present disclosure.

[0029] Fig.18 A partial perspective view illustrating flux leakage in an inner rotor TFM at an axial end and opposite the stator is shown in accordance with the principles of the present disclosure.

[0030] Fig.19 A cross-sectional view illustrating flux leakage between stators of different phases in an inner rotor TFM is shown in accordance with the principles of the present disclosure.

[0031] Fig. 20 A partial perspective view illustrating flux leakage in an outer rotor TFM at an axial end and opposite the stator is shown in accordance with the principles of the present disclosure.

[0032] Fig.21 A partial cross-sectional view of an inner rotor TFM is shown in accordance with the principles of the present disclosure.

[0033] Fig. 22 A partial cross-sectional view of an outer rotor TFM according to the principles of the present disclosure is shown.

[0034] Fig.23A A partial cutaway view of a first inner rotor TFM of the present disclosure is shown, showing flux leakage relative to the stator.

[0035] Fig. 23B Show Fig.23A A partial perspective view of the first inner rotor TFM.

[0036] Fig.24A A partial cutaway view of a second inner rotor TFM of the present disclosure is shown, showing flux leakage relative to the stator.

[0037] Fig. 24B Show Fig.24A A partial perspective view of the second inner rotor TFM.

[0038] Fig.25 A graph showing average torque (Nm) of the inner rotor TFM versus BetaCc (degrees) for various thicknesses of non-magnetic material (TH).

[0039] Fig.26 A graph of torque ripple (%) versus BetaCc (degrees) for the inner rotor TFM is shown for various thicknesses of non-magnetic material (TH).

[0040] Fig. 27 Graphs showing average torque (Nm) and torque ripple (%) versus thickness (mm) of non-magnetic material (TH) for the inner rotor TFM of the present disclosure.

[0041] Fig.28 A partial perspective view of an inner rotor TFM of the present disclosure is shown, having a non-magnetic material (TH) with a thickness of TH=0, showing leakage flux relative to the stator.

[0042] Fig.29 A partial perspective view of an inner rotor TFM of the present disclosure is shown, having a non-magnetic material (TH) with a thickness of TH=1.5 mm, showing the leakage flux relative to the stator.

[0043] Fig.30 A graph of average torque (Nm) versus BetaDc (degrees) for the inner rotor TFM of the present disclosure is shown for various BetaCc values ​​(2 degrees, 3 degrees, and 4 degrees).

[0044] Fig.31 A graph of torque ripple (%) versus BetaDc (degrees) is shown for the inner rotor TFM of the present disclosure for various BetaCc values ​​(2 degrees, 3 degrees, and 4 degrees).

[0045] Fig.32 Shown is a cross-sectional view of a permanent magnet synchronous machine (PMSM) having a 3-phase group in a 9s / 6p configuration, coupled to three different electronic control units (ECUs).

[0046] Fig.33 Shown is a cross-sectional view of a permanent magnet synchronous machine (PMSM) having a 4-phase group in a 12s / 8p configuration, coupled to two different electronic control units (ECUs).

[0047] Fig.34 A perspective view of a stator in an external rotor TFM is shown, the stator having a dual winding configuration and having three rings that are axially stacked and circumferentially offset relative to each other.

[0048] Fig.35 A perspective view of a single stator ring of an outer rotor TFM with a dual winding configuration is shown.

[0049] Fig.36 A partial perspective view of a single stator within a single-winding TFM according to the present disclosure is shown, the single stator having a wire winding of circular cross-section.

[0050] Fig.37A partial perspective view of a single stator within a dual-winding TFM according to the present disclosure is shown, the single stator having wire windings of rectangular cross-section. DETAILED DESCRIPTION

[0051] The following discussion is directed to various embodiments of the present disclosure. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted or otherwise used as limiting the scope of the present disclosure, including the claims. In addition, it will be understood by those skilled in the art that the following description has a wide range of applications, and any discussion of an embodiment is intended only as an example of that embodiment, and is not intended to imply that the scope of the present disclosure, including the claims, is limited to that embodiment.

[0052] As described above, vehicles such as automobiles, trucks, sport utility vehicles, crossovers, minivans, boats, airplanes, all-terrain vehicles, recreational vehicles, or other suitable forms of transportation typically include a steering system, such as an electric power steering system (EPS) system, a SbW steering system, a hydraulic steering system, or other suitable steering system. The steering system of such a vehicle typically controls various aspects of the vehicle's steering, including providing steering assistance to the operator of the vehicle, controlling the vehicle's steerable wheels, etc.

[0053] Figure 1 is a schematic diagram of an EPS system 40 suitable for implementing the disclosed technology. The EPS system 40 includes a steering mechanism 36, which includes a rack and pinion type mechanism having a rack (not shown) located within a housing 50 and a pinion (also not shown) located below the gear housing 52. With operator input, hereinafter represented by turning the steering wheel 26 (e.g., a steering wheel, etc.), the upper steering shaft 29 is rotated, and the lower steering shaft 51 connected to the upper steering shaft 29 by a universal joint 34 causes the pinion to rotate. The rotation of the pinion causes the rack to move, which moves the tie rods 38 (only one shown), which in turn moves the steering knuckle 39 (only one shown), thereby rotating the steerable wheel(s) 44 (only one shown).

[0054] The electric power steering assistance is provided by a steering motion control system generally designated by reference numeral 24 and includes a controller 16 and an electric machine, which may be a permanent magnet synchronous motor and is hereinafter indicated as motor 19. The controller 16 is powered by a vehicle power supply 10 via power supply conductors 12. The controller 16 receives a vehicle speed signal 14 representing the vehicle speed from a vehicle speed sensor 17. The steering angle is measured by a position sensor 32, which may be an optically encoded type sensor, a variable resistance type sensor, or any other suitable type of position sensor, and supplies a position signal 20 to the controller 16. The motor speed may be measured with a tachometer or any other device and transmitted to the controller 16 as a speed signal 21. The speed signal 21 may be measured, calculated, or measured and calculated as indicated by ω. m For example, the motor speed ω m can be calculated as the change in motor position measured by the position sensor 32 over a specified time interval. For example, the motor speed ω m can be determined as the motor position θ m Derivative with respect to time. It will be appreciated that there are many well-known methods for performing the derivative function.

[0055] When the steering wheel 26 is turned, the torque sensor 28 senses the torque applied to the steering wheel 26 by the vehicle operator. The torque sensor 28 may include a torsion bar (not shown) and a variable resistor type sensor (also not shown) that outputs a torque signal 18 related to the amount of twist on the torsion bar to the controller 16. Although this is one type of torque sensor, any other suitable torque sensing device used with known signal processing techniques will suffice. In response to various inputs, the controller sends a command 22 to the motor 19, which provides torque assistance to the steering system through the worm 47 and worm gear 48 to provide torque assistance for vehicle steering.

[0056] It should be noted that although the disclosed embodiments are described with reference to motor control for electric steering applications, it should be understood that such reference is exemplary only and the disclosed embodiments may be applied to any motor control application using an electric motor, such as steering, valve control, etc. In addition, the references and descriptions herein may be applicable to many forms of parameter sensors, including but not limited to torque, position, speed, etc. It should also be noted that the motors mentioned herein include but are not limited to motors, and for the sake of brevity and simplicity, only motors will be mentioned below without limitation to motors.

[0057] In the described steering motion control system 24, the controller 16 uses torque, position, speed, etc. to calculate (one or more) commands to deliver the desired output power. The controller 16 is configured to communicate with various systems and sensors of the motor control system. The controller 16 receives signals from each system sensor, quantifies the received information, and provides (one or more) output command signals in response to the received information (in this example, for example, to the motor 19). The controller 16 is configured to generate corresponding (one or more) voltages from an inverter (not shown), which can be optionally combined with the controller 16 and will be referred to as the controller 16 in this article, so that when applied to the motor 19, the desired torque or position is generated. In one or more examples, the controller 16 operates as a current regulator in a feedback control mode to generate the command 22. Alternatively, in one or more examples, the controller 16 operates in a feedforward control mode to generate the command 22. Because these voltages are related to the position and speed of the motor 19 and the desired torque, the position and / or speed of the rotor and the torque applied by the operator are determined. The position encoder is connected to the steering shaft 51 to detect the angular position θ. The encoder can sense the rotational position based on optical detection, magnetic field changes or other methods. Typical position sensors include potentiometers, rotary transformers, synchronizers, encoders, etc., and combinations including at least one of the above. The position encoder outputs a position signal 20, which indicates the angular position of the steering shaft 51, thereby indicating the angular position of the motor 19.

[0058] The desired torque may be determined by one or more torque sensors 28 that transmit a torque signal 18 indicative of the applied torque. The torque sensors 28 and the torque signal 18 therefrom may be responsive to a compatible torsion bar, spring, or similar device (not shown) configured to provide a response indicative of the applied torque.

[0059] In one or more examples, the temperature sensor 23 is located at the motor 19. Preferably, the temperature sensor 23 is configured to directly measure the temperature of the sensing portion of the motor 19. The temperature sensor 23 transmits a temperature signal 25 to the controller 16 for processing and compensation as specified herein. Typical temperature sensors include thermocouples, thermistors, thermostats, etc., and combinations including at least one of the above sensors, which, when properly placed, provide calibratable signals that are proportional to a specific temperature.

[0060] Position signal 20, speed signal 21, torque signal 18, etc. are applied to controller 16. Controller 16 processes all input signals to generate values ​​corresponding to each signal, thereby generating rotor position values, motor speed values, and torque values ​​that can be used for processing in the algorithm specified in this article. The measurement signals as described above are usually linearized, compensated, and filtered as needed to enhance the characteristics of the collected signals or eliminate undesirable characteristics. For example, the signal can be linearized to increase the processing speed or to solve the large dynamic range of the signal. In addition, frequency or time-based compensation and filtering can be used to eliminate noise or avoid undesirable spectral characteristics.

[0061] In order to perform the specified functions and perform the desired processing, and thereby perform calculations (e.g., identification of motor parameters, (one or more) control algorithms, etc.), the controller 16 may include, but is not limited to, (one or more) processors, (one or more) computers, (one or more) DSPs, memories, storage devices, (one or more) registers, timers, (one or more) circuit breakers, (one or more) communication interfaces and input / output signal interfaces, etc., and combinations including at least one of the above. For example, the controller 16 may include input signal processing and filtering to achieve accurate sampling and conversion or acquisition of such signals from the communication interface.

[0062] Figure 2 The EPS system is generally shown. Figure 3 A steer-by-wire (SbW) steering system is generally shown. Figure 2 The EPS system can be used with Figure 1 The EPS system 40 is similar or identical, except that the motor 19 is mounted directly to the steering mechanism 36 . Figure 3 The SbW system can be used with Figure 1 The EPS system 40 of FIG. 1 is similar or identical to the EPS system 40 of FIG. 1 except that there is no physical connection between the steerable wheel 26 and the steerable wheel 44 and there are two separate and independent motors 19a, 19b. As shown, the SbW system includes a first motor 19a, also known as a road wheel actuator (RWA), and a second motor 19b, also known as a steering wheel actuator (HWA). The HWA 19b is configured to provide torque to the steerable wheel 26 for providing tactile feedback to the driver.

[0063] The SbW is a direct evolution of the EPS system, where there is no mechanical connection between the steering wheel 26 and the steering rack. Figure 2As shown, an EPS system may include a single actuator 19 whose sole purpose is to provide assistance to the driver during steering maneuvers. However, in an SbW system, there are two electric actuators / motors with different functions. The electric actuator attached to the steering mechanism 36 in the SbW system is called the road wheel actuator (RWA) 19a, while the actuator on the driver's side is called the steering wheel actuator (HWA) 19b. The RWA 19a can provide the same assistance functions as the actuator 19 in the EPS system. On the other hand, the HWA 19b acts more as a feedback motor rather than providing assistance to the driver. In the absence of the HWA 19b, the steering wheel on the SbW system can turn freely since there is no mechanical connection / friction. Because of the functionality of the HWA 19b, it opens up a series of design-related opportunities.

[0064] As used herein, variables with a tilde (~) above the variable symbol represent approximate values ​​that can be determined by mathematical calculations, lookup tables, etc. Variables with a bar above the variable symbol represent vector quantities. Variables with a superscript asterisk (*) represent commanded or desired set point values.

[0065] Figure 4 An electric motor drive system 100 is shown having a dual-winding permanent magnet synchronous motor (DW-PMSM), also known as a dual-winding synchronous machine (DWSM) or dual-winding motor 60, power converters 66a and 66b (each including a gate driver and a corresponding inverter), and a motor controller 70 (also known as a controller). The dual-winding motor 60 can be used in many applications, such as for Figure 1 The motor 19 in the steering motion control system 24 is shown. The power converters 66a and 66b may include a number of switching devices, such as field effect transistors (FETs) for switching high current loads and gate driver circuits for operating the switching devices. The motor controller 70 receives motor torque commands from a motion controller 80 (such as, for example, a power steering controller).

[0066] The motor controller 70 can be based on the motor torque command from the motion controller 80 and use any feed-forward control technique to generate the voltage command For example, the motor controller 70 may include a voltage command generator (not shown) to generate a voltage command using one or more optimizations. and / or causing the electric motor drive system to satisfy one or more operating constraints, such as constraints on voltage and / or current generated by or supplied to the electric motor drive system. Feedforward voltage control techniques may include techniques provided in the present disclosure, however other feedforward control techniques may also be used.

[0067] The dual-winding motor 60 includes a first winding combination 62a and a second winding combination 62b electrically independent of the first winding combination 62a. The dual-winding motor 60 is capable of generating electromagnetic torque by energizing one or two of the winding combinations 62a, 62b. The two winding combinations 62a and 62b can each include three phases, and therefore, each of the two winding combinations 62a, 62b can include a three-phase winding. Optionally, each winding combination 62a, 62b can include any number of winding phases, such as five or seven phases. In some embodiments, the dual-winding motor 60 is a multi-phase permanent magnet synchronous machine (PMSM). Each of the winding combinations 62a, 62b can operate separately, and the dual-winding motor 60 can operate by energizing one or two of the winding combinations 62a, 62b.

[0068] Power converters 66a and 66b are configured to supply alternating current (AC) voltage to winding combinations 62a and 62b, respectively. Winding combinations 62a, 62b are connected to their respective power converters 66a, 66b via phase leads 68a and 68b. This configuration can provide redundancy, allowing the dual-winding motor 60 to continue to operate even in the event of a complete failure or malfunction of one of the winding combinations 62a, 62b, one of the motor leads 68a, 68b, and / or one of the power converters 66a, 66b. Additional redundancy can be achieved with electrical isolation of the power converters 66a, 66b.

[0069] The dual winding motor 60 includes a first winding combination 62a and a second winding combination 62b electrically independent of the first winding combination 62a. The dual winding motor 60 is capable of generating electromagnetic torque by energizing one or both of the winding combinations 62a and 62b. The two winding combinations 62a and 62b can each include three phases, so each of the two winding combinations 62a and 62b can include a three-phase winding. Optionally, each winding combination 62a, 62b can include any number of winding phases, such as five or seven phases. In some embodiments, the dual winding motor 60 is a multi-phase PMSM. However, the dual winding motor 60 can be any type of synchronous machine, such as a poly-phase wound-field synchronous machine. In addition, the dual winding motor 60 can have a salient pole configuration or a non-salient pole configuration, depending on the position of the permanent magnet or field winding on the rotor. Each of the winding combinations 62a, 62b can function individually, and the dual winding motor 60 can be operated by energizing one or both of the winding combinations 62a, 62b.

[0070] The power converters 66a and 66b are configured to supply an alternating current (AC) voltage to the winding combinations 62a and 62b, respectively. The winding combinations 62a, 62b are connected to their respective power converters 66a, 66b via phase leads 68a and 68b. This configuration can provide redundancy, allowing the dual-winding motor 60 to continue to operate even if one of the winding combinations 62a, 62b, one of the motor leads 68a, 68b, and / or one of the power converters 66a, 66b completely fails or fails. The power converters 66a, 66b can achieve additional redundancy through electrical isolation.

[0071] In some embodiments, electric motor drive system 100 may include a motor controller, such as controller 150. Figure 4 The controller 150 generates a voltage command The voltage command Can include d-axis components separately and q-axis components For example, the controller 150 may be based on the motor torque command Generate voltage command Each of the power converters 66a, 66b is based on a voltage command An output voltage is applied to a corresponding one of the winding combinations 62a, 62b.

[0072] Controller 150 may include any suitable controller. Controller 150 may be configured to control various functions of the vehicle system, such as those described herein. Controller 150 may include processor 152 and memory 154. Processor 152 may include any suitable processor, such as those described herein. Additionally or alternatively, in addition to or different from processor 152, controller 150 may include any suitable number of processors. Memory 154 may include a single disk or multiple disks (e.g., a hard disk drive), and include a storage management module that manages one or more partitions within memory 154. In some embodiments, memory 154 may include flash memory, semiconductor (solid-state) memory, etc. Memory 154 may include random access memory (RAM), read-only memory (ROM), or a combination thereof. Memory 154 may include instructions that, when executed by processor 152, cause processor 152 to at least control various functions of the steering system and / or any other suitable functions, including the functions of the systems and methods described herein.

[0073] Figure 5A graph illustrating torque-speed curves of steering system actuators 19, 19a and 19b is shown. Different steering system actuators 19, 19a, 19b have different speed curves based on their functions. Figure 5 As shown by the dashed lines in , both the EPS actuator 19 and the RWA 19a in the SbW operate in the first quadrant (Q1) of the torque-speed curve. In Q1, the positive direction of velocity indicates that the actuator is acting in the same direction as the driver's steering wheel movement and providing assistance. However, as shown by the solid lines, the HWA 19b of the SbW system operates primarily in the second quadrant (Q2) of the torque-speed curve. The HWA 19b moves in the opposite direction of the driver's steering wheel movement (speed -ve) and provides feedback to the driver. This feedback may be necessary to provide the driver with general steering feel and road condition feedback. In addition, as shown in FIG. Figure 5 As shown, some low speed assistance from HWA 19b may also be required (Q1 operation).

[0074] The HWA 19b can include a coupled electric motor that applies torque to the steering wheel 26 configuration, such as a worm drive, belt drive, and / or direct drive. For the case of worm drive and belt drive, low torques of about 3 Newton meters (Nm) and high speeds of about 3000 revolutions per minute (RPM) are possible. PMSMs can be used as actuators. Both surface mounted PMSM (SPMSM) and interior PMSM (IPMSM) topologies can be used for this HWA architecture. In addition, due to their similarities (in terms of torque-speed range), a large number of components can be directly transferred from a column EPS (CEPS) system to a worm drive or belt drive SbW steering wheel system.

[0075] The torque-speed curves of the different actuators used in the steering system also vary based on their function. Figure 5 As shown, the EPS actuator and RWA in the SbW system each operate in the first quadrant (Q1) of the torque-speed curve. In Q1, the positive direction of velocity indicates that the actuator acts in the same direction as the driver's steering wheel movement and provides assistance. However, the SbW HWA operates primarily in the second quadrant (Q2) of the torque-speed curve. The HWA moves in the opposite direction of the driver's steering wheel movement (velocity -ve) and provides feedback to the driver. This feedback is necessary to provide the driver with general steering feel and road condition feedback. In addition, as Figure 5 As shown, some low-speed assistance from HWA may also be required (Q1 operation). The distinct operating domains of EPS / RWA and HWA drive the design exploration of HWA technology.

[0076] The HWA 19b may include a coupled electric motor that applies torque to the steering wheel 26 configuration, such as a worm drive, belt drive, and / or direct drive. For the worm drive and belt drive cases, a low torque (approximately 3Nm) and high speed (approximately 3000rpm) PMSM can be used as an actuator. Both surface mounted PMSM (SPMSM) and internal PMSM (IPMSM) topologies can be used for this HWA architecture. In addition, due to their similarities (in terms of torque-speed range), a large number of components can be directly transferred from a column EPS (CEPS) system to a worm drive or belt drive SbW steering wheel system. For the direct drive case, a high torque (approximately 30Nm at the outlet / inlet) and low speed (approximately 200-300rpm) actuator is required. For a direct drive architecture, the number of mechanical components is reduced, which in turn has the potential to reduce cost and weight. In addition, the reduction in weight is directly related to range efficiency or mileage (miles per gallon) increments. However, conventional PMSMs need to be redesigned to meet the high torque and low speed output requirements of a direct drive architecture.

[0077] Figure 6 A graph showing the torque-speed curve of the HWA 19b in the illustrated SbW steering system, having a direct drive configuration (1:1 gear ratio). As shown, the HWA 19b typically operates at a speed of -200 to +80 revolutions per minute (RPM) and produces a torque of 0 to about 30 Newton meters (Nm). Transverse flux machines have the potential to play a role in such low speed, high torque direct drive applications.

[0078] Figure 7 A cross-sectional view of a radial flux machine (RFM) is shown. Figure 8 A cross-sectional view of an axial flux machine (AFM) is shown. Fig. 9 A cross-sectional view of a transverse flux machine (TFM) is shown. Each of the RFM, AFM, and TFM devices includes a shaft configured to rotate about an axis A. Classification between RFM, AFM, and TFM configurations can be made based on the direction of the magnetic flux.

[0079] Figure 7 The RFM includes a first rotor 110a having a first rotor core 112a attached to rotate with a first shaft 114a about an axis A. The first rotor 110a is located within a first housing 115a, and the first shaft 114a extends through and out of the first housing 115a and is supported by a pair of first bearings 116a. A set of first permanent magnets 118a is attached to the first rotor core 112a and generates magnetic flux extending radially outward. Figure 7The RFM also includes a first stator 120a having a first stator core 122a through which a set of first windings 124a extend and carry current in an axial direction parallel to the axis A and perpendicular to the magnetic flux.

[0080] Figure 8 The AFM includes a second rotor 110b having a second rotor core 112b, the second rotor core 112b being attached to rotate with a second shaft 114b about an axis A. The second rotor 110b is located within a second housing 115b, the second shaft 114b extends through and out of the second housing 115b, and is supported by a pair of second bearings 116b. A set of second permanent magnets 118b is attached to the second rotor core 112b and generates a magnetic flux extending in an axial direction parallel to the axis A. Figure 8 The AFM also includes a second stator 120b having a second stator core 122b through which a set of second windings 124b extend and carry current in a radial direction perpendicular to the axis A and perpendicular to the magnetic flux.

[0081] Fig. 9 The TFM includes a third rotor 110c having a third rotor core 112c attached to rotate with a third shaft 114c about an axis A. The third rotor 110c is located within a third housing 115c, the third shaft 114c extends through and out of the third housing 115c, and is supported by a pair of third bearings 116c. A set of third permanent magnets 118c are attached to the third rotor core 112c and generate a magnetic flux that extends radially inward at a first location, axially through the third rotor core 112c, and radially outward at a second location axially spaced from the first location. Fig. 9 The TFM also includes a third stator 120c having a third stator core 122c, a set of third windings 124c extending through the third stator core 122c and carrying current in a circumferential direction perpendicular to the axis A and the magnetic flux. As shown, the third stator core 122c defines a U-shape, with an open end aligned with the third permanent magnet 118c in a first position and a second position for providing a closed rectangular magnetic flux path with the third rotor core 112c.

[0082] Figure 7-Figure 9 Figure 2 shows the flux direction in the three machine topologies. For the RFM, the flux moves radially in the air gap, while for the AFM, the flux moves axially from the stator to the rotor and vice versa. Fig. 9As shown, for the TFM, the flux moves in both the radial and axial directions. Although several topologies of TFM can be identified from the literature, the 3D (radial and axial) flux path is a common feature across the different topologies. TFMs are known for their higher volumetric and gravimetric power densities compared to radial flux machines. AFMs and TFMs are known to have comparable power densities. However, the simplicity of the toroidal winding in the TFM has the potential to simplify the manufacturing process and save costs.

[0083] like Figure 6 As shown, the magnetic flux in the RFM extends mainly in the radial direction perpendicular to the axis A. Figure 7 As shown, the magnetic flux in the AFM extends primarily in the axial direction parallel to the axis A. Figure 8 As shown, the magnetic flux in the TFM defines a closed loop path, a portion of which extends in a radial direction perpendicular to the axis A, and the other portion extends in an axial direction parallel to the axis A. AFM, AFM, and TFM configurations may each provide different volumetric and gravimetric power densities. TFM configurations may be particularly suitable for low speed and high torque operation.

[0084] The present disclosure provides a transverse flux machine (TFM) topology for a direct drive SbW HWA architecture. In the low speed, high torque operating region of a direct drive SbW HWA, transverse flux machines have the potential to provide significant power density advantages over conventional radial flux machines. A general design guide for TFMs is given below. Conventional RFMs can be stacked in the radial XY plane to accommodate their 2D access paths and reduce eddy current losses at high frequency operation. AFMs can also be stacked in the axial XZ plane to facilitate axial travel of flux from stator to rotor and vice versa. However, as Fig. 9 As shown, for a TFM, the flux moves in both radial and axial directions. If the TFM is to be stacked (laminated), it is necessary to have stacking in XY and XZ directions, depending on the core position and the expected direction of flux travel. This will seriously complicate the manufacturing process of the TFM. In order to avoid complexity and ensure 3D flux travel in the TFM core, a soft magnetic core (SMC) material is chosen here. SMC is insulating iron particles that are compacted into the shape of the core. The electrical insulation between the iron particles of the compacted SMC core significantly reduces eddy current losses at higher operating frequencies. The conclusions drawn in this paper are also applicable to TFMs made of laminated steel.

[0085] Several TFM topologies are available, with different performance areas where each excels. TFM designs generally indicate a trend toward increasing volumetric torque density. However, for steering applications, the actuator may be subject to tighter constraints on torque ripple, cogging torque, friction losses, etc. In addition, ease of manufacturing may be an important criterion.

[0086] Figure 10-15 Various different topologies of TFM are shown. Fig.10 A partial perspective view of a U-core TFM is shown. Fig.11 A partial perspective view of a U-core TFM with an iron bridge is shown. Fig.12 A partial perspective view of a hook-shaped TFM is shown. Fig.13 A partial perspective view of a U-core TFM with a flux concentrating inner rotor is shown. Fig.14 A partial perspective view of a TFM having a claw-pole structure is shown. Fig.15 A partial perspective view of a TFM with a flux concentrating outer rotor and a one-piece stator is shown.

[0087] Reducing the number of parts in a TFM can simplify the manufacturing process. In addition, the flux-concentrated rotor structure shows higher power density and lighter magnet weight compared to other rotor topologies. In addition, the toroidal winding structure of TFMs simplifies the winding process compared to needle-wound radial flux machines. Fig.15 The TFM design shown may be advantageous for the ease of manufacturing provided by the topology. It can be stacked axially and spaced circumferentially to form a multi-phase machine.

[0088] As shown in the figure, Fig.15 A first TFM 200 is presented having an outer rotor configuration, wherein a first rotor 210 is configured to rotate about an axis, the rotor extending annularly around an inner stator assembly 220 . Fig.15 A 45 degree section of the first TFM 200 is shown, with markings indicating magnetic flux. However, the complete first TFM 200 will include eight such sections. The first rotor 210 includes a plurality of pairs of first permanent magnets 212a, 212b, which are arranged at regular angular intervals and are configured to generate a magnetic flux in a circumferential direction therebetween. The first rotor 210 also includes a plurality of first flux concentrating cores 214, which are located between the first permanent magnets 212a, 212b of each pair of first permanent magnets 212a, 212b and are configured to conduct magnetic flux therebetween. The first rotor 210 also includes a plurality of first flux diverging cores 216, each core being located between adjacent pairs of first permanent magnets 212a, 212b. The first rotor 210 has a tubular shape and extends between a first axial end 218a and a second axial end 218b.

[0089] Also like Fig.15As shown, the inner stator assembly 220 includes an inner stator core 222 having a U-shaped cross-section, the inner stator core 222 having an inner cylindrical portion 224 and a pair of arms 226 extending radially outward from each end of the inner cylindrical portion 224 toward the first rotor 210. The winding 228 extends through the center of the U-shaped cross-section of the inner stator core 222 in the circumferential direction and conducts current in the circumferential direction.

[0090] As shown, each arm 226 of the inner stator core 222 includes an arcuate groove 230 to define two radially extending protrusions 232 that are angularly spaced apart to align with adjacent cores in the first flux concentrating core 214 and the first flux diverging core 216. In this way, magnetic flux is conducted from each first flux concentrating core 214 adjacent to the first axial end 218, through the air gap and into the radially extending protrusion 232 of the adjacent inner stator core 222. The magnetic flux is directed into the inner cylindrical portion 224 of the inner stator core 222, where the magnetic flux continues in the axial direction. The magnetic flux is also directed out of the inner cylindrical portion 224 of the inner stator core 222 and radially outward through the arm 226 of the inner stator core 222 adjacent to the second axial end 218b, where the magnetic flux passes through the air gap and enters the corresponding first flux diverging core 216. The magnetic flux continues through the respective first permanent magnets 212a, 212b and then returns to the first flux concentrating core 214, thereby completing a closed path.

[0091] TFMs may be particularly well suited for direct drive low speed operation. TFMs may include a modular, spatially displaced, three-phase stator architecture. TFMs may include a simple toroidal winding with an inner stator topology. TFMs may provide relatively low phase resistance, independent of the number of rotor poles and stator slots. TFMs may include an outer rotor structure with high volumetric and weight torque density. TFMs may be relatively easy and efficient to manufacture, and may provide suitable performance for a variety of applications in EPS and / or SbW systems.

[0092] The phase resistance and coil cross-section in a toroidal winding TFM are independent of the number of poles, which allows the TFM to have a higher torque density than the RFM. In addition, for some applications, such as direct drive HWA in SbW systems, the operating speed is relatively low. This suggests that even if a higher pole number TFM is selected, the fundamental electrical frequency of operation will be within a reasonable range. For example, for a 12-slot 8-pole SbW HWA with a gear ratio of 11:1, the fundamental frequency is 166.67 Hz at a motor rpm (revolutions per minute) of 2500. On the other hand, for a TFM with 100 poles and a direct drive structure, the fundamental frequency is 189.39 Hz at a motor rpm of 227.27. The limiting pole number (P) of a TFM max ) can be calculated using equation (1): Where n limit is the maximum motor speed in rpm, f e,max It is the maximum fundamental electrical frequency that the motor drive can handle.

[0093] Furthermore, despite the higher number of poles in the TFM, the phase resistance does not increase, which reduces copper losses, thereby improving efficiency and thermal performance. Inside rotor / outside rotor topology

[0094] The general size equation of TFM can be written as equation (2): Where P R is the rated output power, K phi is the ratio of the electrical load on the rotor and stator (K phi can be equal to zero), m is the number of phases, K e is the BEMF coefficient, which divides the winding distribution coefficient K w Combined with the per-unit fraction of the total air gap area spanned by the machine's salient poles (if any), K i is the current waveform factor, K p is the electric power waveform factor, K L is the stack length L e Diameter D of the air gap surface g ratio, n is the machine efficiency, B g is the air gap flux density, A is the total electrical load, f is the drive frequency, p is the number of pole pairs, D o is the outer diameter of the machine, λ o Yes D g and D o The ratio between .

[0095] As shown in equation (2), the rated power and resulting torque output of the TFM are related to the machine's outer diameter D o Proportional to the square of. g / D o Replace λ o From (2), we can see that the output power is related to D g The square of the air gap is directly related to the diameter of the air gap surface. From the inner rotor TFM to the outer rotor TFM, the diameter of the air gap surface can be increased with better space utilization. This results in a higher volumetric torque density in the outer rotor TFMs. In addition, in the outer rotor TFMs, the winding process is relatively simple. According to the present disclosure, both the outer rotor TFM and the inner rotor TFM are systematically optimized.

[0096] Fig.16A perspective view of an inner stator assembly 220 for an external rotor TFM is shown, the inner stator assembly 220 being configured to have a rotor (not shown) disposed annularly therearound. The inner stator assembly 220 includes three inner stator cores 222a, 222b, 222c, including an A-phase inner stator core 222a, a B-phase inner stator core 222b, and a C-phase inner stator core 222c. The three inner stator cores 222a, 222b, 222c each have a similar or identical annular shape that is axially stacked and circumferentially offset relative to each other. Each of the three inner stator cores 222a, 222b, 222c of the inner stator assembly 220 includes a corresponding winding 224a, 224b, 224c of a corresponding phase, and the corresponding winding extends circumferentially through the inner stator core. Each of the three inner stator cores 222a, 222b, 222c of the inner stator assembly 220 also defines a plurality of radially extending protrusions at regular angular intervals and extending radially outward.

[0097] The stacked assembly of the TFM stator leads to inherent asymmetry issues. Fig.16 As shown, in the three-phase TFM, the B-phase inner stator core 222b is stacked between the A-phase inner stator core 222a and the C-phase inner stator core 222c. The A-phase inner stator core 222a and the C-phase inner stator core 222c can each be referred to as an outer core because their positions are adjacent to the axial ends of the stator assembly. The B-phase inner stator core 222b can be referred to as an inner stator core because its position is spaced apart from the axial ends of the stator assembly.

[0098] Fig.17 A perspective view of an external stator assembly 320 for an internal rotor TFM is shown, the external stator assembly 320 being configured to be arranged annularly around a rotor (not shown). The external stator assembly 320 includes three external stator cores 322a, 322b, 322c, including an A-phase external stator core 322a, a B-phase external stator core 322b, and a C-phase external stator core 322c. The three external stator cores 322a, 322b, 322c each have a similar or identical annular shape, which are axially stacked and circumferentially offset relative to each other. Each of the three external stator cores 322a, 322b, 322c of the external stator assembly 320 can contain a corresponding winding ( Fig.17 322a, 322b, 322c of the outer stator assembly 320 also defines a plurality of radially extending projections extending radially inwardly at regular angular intervals.

[0099] Several different factors may influence the design of a TFM. Such design factors may include: topology selection and manufacturing challenges; material selection; number of poles; inner / outer rotor (i.e., inner rotor or outer rotor configuration); multiphysics capabilities; and three-dimensional (3D) simulations, which can be computationally expensive. Flux leakage

[0100] Although TFM has some advantages, it suffers from flux leakage due to the complex 3D nature of its flux path. The amount of flux leakage varies from topology to topology. In addition, flux leakage is highly dependent on the number of poles in the TFM. Figure 18-Figure 19 An example of leakage occurring in a TFM rotor and stacked stator structure is shown. If not addressed, these leakages will increase the weight of the magnet material in the optimized machine, thereby increasing cost. A method of reducing rotor flux leakage is proposed in this ROI.

[0101] Due to the 3D nature of the flux path, transverse flux machines have inherent leakage problems. Fig.18 As shown, the rotor leakage occurs on the flux concentration core opposite to the air gap (i.e. opposite to the stator). Fig.19 As shown, stator-to-stator leakage may occur in a modular stator architecture. A modular stator structure with annular windings may result in asymmetric electromagnetic behavior between stators of a multi-phase motor, such as a three-phase motor. Flux leakage reduction

[0102] Fig.18 and Fig. 20 The rotor flux leakage is shown for the inner rotor and outer rotor topologies respectively. Fig.18 The inner rotor TFM in the Fig. 20 The outer rotor TFM in has a 60-pole structure. Regardless of the topology (inner / outer rotor) and number of poles, rotor leakage appears in the TFM on the opposite side of the air gap.

[0103] The present disclosure provides TFMs 300 , 400 having design features configured to reduce rotor flux leakage.

[0104] Fig.21 A partial cross-sectional view of a second TFM 300 having an inner rotor configuration is shown. The second TFM 300 includes an outer stator assembly 320 and a second rotor 310. The second rotor 310 may be similar or identical to the first rotor 210 except for the differences described herein.

[0105] The second rotor 310 includes a plurality of pairs of second permanent magnets 312a, 312b, which are arranged at regular angular intervals and are configured to generate a magnetic flux in a circumferential direction therebetween. The second rotor 310 also includes a plurality of second flux concentrating cores 314, which are located between the second permanent magnets 312a, 312b of each pair of second permanent magnets 312a, 312b and are configured to conduct magnetic flux therebetween. As shown in the figure, the magnetization of the second permanent magnets 312a, 312b is directed inwardly into a corresponding second flux concentrating core 314. The second rotor 310 also includes a plurality of second flux diverging cores 316, each of which is located between adjacent pairs of second permanent magnets 312a, 312b.

[0106] The second flux concentrating cores 314 each define a first angular spread BetaCc, and the second flux diverging cores 316 each define a second angular spread BetaDc. In some embodiments, the first angular spread BetaCc of the second flux concentrating cores 314 may not be equal to the second angular spread BetaDc of the second flux diverging cores 316. For example, the first angular spread BetaCc of the second flux concentrating cores 314 may be greater than the second angular spread BetaDc of the second flux diverging cores 316.

[0107] The second rotor 310 also includes a first non-magnetic portion 318 of non-magnetic material, which is located between the second permanent magnets 312a, 312b of each pair of second permanent magnets 312a, 312b and adjacent to each second flux concentration core 314. The first non-magnetic portion 318 may include a non-magnetic solid material, such as aluminum or epoxy resin. Alternatively or additionally, the first non-magnetic portion 318 may include a space filled with ambient air. The first non-magnetic portions 318 are respectively positioned relative to the outer stator assembly 320, and a corresponding second flux concentration core 314 is disposed between each first non-magnetic portion 318 and the outer stator assembly 320. The non-magnetic material of the first non-magnetic portion 318 defines a thickness (TH) in the radial direction. In some embodiments, the thickness (TH) may be at least about 1.5 mm. However, the thickness (TH) may have different values, depending on design requirements.

[0108] The second rotor 310 may further include a first rotor housing 319 ( Fig.21310 ), wherein the second permanent magnets 312a, 312b, the second flux concentrating core 314, and the second flux diverging core 316 are attached to the outer surface of the first rotor housing 319. The housing of the first rotor housing 319 may have a generally cylindrical or tubular shape attached to the motor shaft. In some embodiments, the first rotor housing 319 may protrude radially outward to define a first non-magnetic portion 318. In addition to minimizing flux leakage, the first non-magnetic portion 318 may be helpful during assembly of the second rotor 310. For example, the protrusion defining the first non-magnetic portion 318 may facilitate the correct placement of the second permanent magnets 312a, 312b, the second flux concentrating core 314, and the second flux diverging core 316 during assembly.

[0109] Fig. 22 A partial cross-sectional view of a third TFM 400 having an outer rotor configuration is shown. The third TFM 400 includes the inner stator assembly 220 and a third rotor 410. The third rotor 410 may be similar or identical to the third rotor 410 except for the differences described herein.

[0110] The third rotor 410 includes a plurality of pairs of third permanent magnets 412a, 412b, which are arranged at regular angular intervals and are configured to generate a magnetic flux in a circumferential direction therebetween. The third rotor 410 also includes a plurality of third flux concentrating cores 414, which are located between the third permanent magnets 412a, 412b of each pair of third permanent magnets 412a, 412b and are configured to conduct magnetic flux therebetween. As shown in the figure, the magnetization of the third permanent magnets 412a, 412b is directed inwardly into a corresponding third flux concentrating core 414. The third rotor 410 also includes a plurality of third flux diverging cores 416, each of which is located between adjacent pairs of third permanent magnets 412a, 412b.

[0111] The third flux concentrating cores 414 each define a first angular spread BetaCc, and the third flux diverging cores 416 each define a second angular spread BetaDc. In some embodiments, the first angular spread BetaCc of the third flux concentrating cores 414 may not be equal to the second angular spread BetaDc of the third flux diverging cores 416. For example, the first angular spread BetaCc of the third flux concentrating cores 414 may be greater than the second angular spread BetaDc of the third flux diverging cores 416.

[0112] The third rotor 410 also includes a second non-magnetic portion 418 of non-magnetic material, which is located between the third permanent magnets 412a, 412b of each pair of third permanent magnets 412a, 412b and adjacent to each third flux concentration core 414. The second non-magnetic portion 418 may include a non-magnetic solid material, such as aluminum or epoxy resin. Alternatively or additionally, the second non-magnetic portion 418 may include a space filled with ambient air. The second non-magnetic portions 418 are respectively positioned relative to the inner stator assembly 220, and a corresponding third flux concentration core 414 is disposed between each second non-magnetic portion 418 and the inner stator assembly 220. The non-magnetic material of the second non-magnetic portion 418 defines a thickness (TH) in the radial direction. In some embodiments, the thickness (TH) may be at least about 1.5 mm. However, the thickness (TH) may have different values, depending on design requirements.

[0113] The third rotor 410 may further include a second rotor housing ( Fig. 22 410 ). The third permanent magnets 412a, 412b, the third flux concentrating core 414, and the third flux diverging core 416 are attached to the inner surface of the second rotor housing. The second rotor housing may have a generally tubular shape attached to the motor shaft. In some embodiments, the second rotor housing may protrude radially inward to define a second non-magnetic portion 418. In addition to minimizing flux leakage, the second non-magnetic portion 418 may be helpful during assembly of the third rotor 410. For example, the protrusion defining the second non-magnetic portion 418 may help to properly place the third permanent magnets 412a, 412b, the third flux concentrating core 414, and the third flux diverging core 416 during assembly.

[0114] Fig.23A – Fig. 23B The inner rotor TFM is shown, showing flux leakage relative to the stator. Figure 23A-23B The inner rotor TFM shown in FIG. 3 is a specific example of a second TFM 300 having a thickness (TH) = 3.0 mm. Figure 24A-24B The inner rotor TFM is shown, showing flux leakage relative to the stator. Figure 24A-24B The inner rotor TFM shown in is a specific example of the second TFM 300 with a thickness (TH) = 5.0 mm. Figure 23A-23B and Figure 24A-24B In the magnet magnetization, the values ​​of BetaCc and BetaDc are different. BetaCc is greater than BetaDc. By making the concentrating core wider than the diverging core, the flux leakage can be reduced. In addition, increasing BetaCc can also reduce the weight of the magnet.

[0115] Fig.25A graph of average torque (Nm) versus BetaCc (degrees) of the second TFM 300 is shown for different thicknesses of non-magnetic material (TH). Fig.25 A first dot plot 502 includes a first non-magnetic portion 318 having a thickness (TH) = 0.1 mm. Fig.25 Also included is a second plot 504 of the first nonmagnetic portion 318 having a thickness (TH) = 1.0 mm. Fig.25 Also included is a third plot 506 of the first nonmagnetic portion 318 having a thickness (TH) = 3.0 mm. Fig.25 Also included is a fourth plot 508 of the first nonmagnetic portion 318 having a thickness (TH) = 5.0 mm. Fig.25 Also included is a fifth plot 510 of the first nonmagnetic portion 318 having a thickness (TH) = 7.0 mm. As shown, the first nonmagnetic portion 318 having a thickness (TH) = 3.0 mm provides the highest average torque over the entire range of angular spread (BetaCc).

[0116] Fig.26 A graph of torque ripple (%) versus BetaCc (degrees) of the second inner rotor TFM is shown for different thicknesses of non-magnetic material (TH). Fig.26 A first dot plot 522 includes a first non-magnetic portion 318 having a thickness (TH) = 0.1 mm. Fig.26 Also included is a second plot 524 of the first nonmagnetic portion 318 having a thickness (TH) = 1.0 mm. Fig.26 Also included is a third plot 526 of the first nonmagnetic portion 318 having a thickness (TH) = 3.0 mm. Fig.26 Also included is a fourth plot 528 of the first nonmagnetic portion 318 having a thickness (TH) = 5.0 mm. Fig.26 Also included is a fifth plot 530 of the first nonmagnetic portion 318 having a thickness (TH) = 7.0 mm. As shown, the first nonmagnetic portion 318 having a thickness (TH) = 5.0 mm provides the lowest torque ripple over the entire range of angular spread (BetaCc).

[0117] Figure 23A-23B A specific example of the second TFM 300 shown in FIG. Fig.25 The design with the highest average torque among Figure 24A-24B A specific example of the second TFM 300 shown in FIG. Fig.26 Design with lowest torque ripple. Figure 23A-23B , Figure 24A-24B and Figure 25-26As shown in Figure 1, the effect of TH on the average torque is low compared to the effect of BetaCc changes. As the TH value increases, the average torque increases, reaches a peak, and then decreases significantly with further increase. For torque fluctuations, the effect of BetaCc is more prominent.

[0118] An external rotor, 60-pole TFM is used to demonstrate the general applicability of the proposed method. First, TH is varied. Fig. 27 A first plot 540 of average torque (Nm) is shown, and a second plot 542 of torque ripple (%) versus thickness (TH) of the non-magnetic material of the inner rotor TFM. Fig.28 A partial perspective view of an inner rotor TFM of the present disclosure is shown, and having a non-magnetic material thickness (TH) of thickness TH=0 mm, showing leakage flux relative to the stator; and Fig.29 A partial perspective view of an inner rotor TFM of the present disclosure is shown, and has a non-magnetic material (TH) with a thickness of TH=1.5 mm, showing the leakage flux relative to the stator. Fig. 27 It is shown that as TH increases, the average torque reaches a peak and then begins to decrease with further increase. Fig. 27 As shown, the torque ripple increases with TH. Therefore, a careful combination of the three parameters (TH, BetaCc, BetaDc) can be considered to ensure better torque production. Fig.29 The reduction in leakage flux is shown when TH = 1.5 mm.

[0119] The TH value is fixed at 1.5 mm, and BetaCc and BetaDc are varied within a certain range to observe the effects on the average torque and torque fluctuation, such as Figure 30-Figure 31 The effects of BetaCc and BetaDc on the mean torque follow the same trend.

[0120] Fig.30 The average torque (Nm) of the inner rotor TFM of the present disclosure is shown relative to BetaDc , and illustrates the effect of varying the second angular spread BetaDc of the second flux diverging core 316 between 2.0 degrees and 4.0 degrees. Fig.30 A first plot 552 is included that illustrates the effect of varying BetaDc, where BetaCc = 2.0 degrees. Fig.30 Also included is a second plot 554 showing the effect of varying BetaDc, where BetaCc = 3.0 degrees. Fig.30 Also included is a third plot 556 showing the effect of varying BetaDc, where BetaCc = 4.0 degrees.

[0121] Fig.31The torque ripple (%) of the inner rotor TFM of the present disclosure is shown relative to BetaDc , and illustrates the effect of varying the second angular spread BetaDc of the second flux diverging core 316 between 2.0 degrees and 4.0 degrees. Fig.31 A first plot 562 is included that illustrates the effect of varying BetaDc, where BetaCc = 2.0 degrees. Fig.31 Also included is a second plot 564 showing the effect of varying BetaDc, where BetaCc = 3.0 degrees. Fig.31 Also included is a third plot 566 showing the effect of varying BetaDc, where BetaCc = 4.0 degrees.

[0122] As BetaCc or BetaDc increases, the average torque reaches a peak and then decreases. For low BetaCc values, as BetaDc increases, the torque fluctuation increases. However, as the BetaCc value increases, the torque fluctuation decreases as the BetaDc value increases. From the perspective of average torque, a value of BetaCc=BetaDc=3 degrees (deg.) is more desirable. However, this combination does not produce the best torque fluctuation performance. BetaCc=BetaDc=4deg. produces the best torque fluctuation performance, and its average torque is poor. Unequal values ​​of BetaCc=4deg., BetaDc=3deg. produce torque fluctuation performance similar to the case of BetaCc=BetaDc=4deg.

[0123] The analysis presented in this paper shows that each of the three design parameters TH, BetaCc, and BetaDc has the ability to increase the average torque production and reduce torque fluctuations in the TFM, regardless of the configuration (external rotor or internal rotor) and the number of poles. In addition, any TH value above 0 makes the rotor lighter. The empty space in the rotor created by the introduction of TH can be filled with non-magnetic materials such as aluminum (such as the sleeve around the rotor) that are much lighter than SMC. This significantly improves the weight power density of the TFM. For example, for the optimized design with BetaCc=4.1deg, BetaDc=3.9deg and TH=2mm, the weight of the SMC in the rotor core is reduced by 14.26% due to the introduction of TH. Fault-Tolerant TFM

[0124] Steering is a safety critical application. To ensure safety in case of power failure, redundancy of the actuator system is a popular solution. Dual-winding PMSMs have been used in EPS systems for a long time. Dual-winding TFMs are able to provide redundancy and safety in case of power failure. Dual-winding TFMs can be designed with a selected TFM topology. Here an optimized version of the outer rotor TFM is chosen to demonstrate the dual-winding process.

[0125] Fig.32 A cross-sectional view of a dual-winding PMSM having a 3-phase group in a 9s / 6p configuration coupled to three different electronic control units (ECUs) labeled ECU1 , ECU2 and ECU3 is shown. Fig.33 A cross-sectional view of a PMSM with a 4-phase group in a 12s / 8p configuration coupled to two different ECUs is shown. Fig.32 – Fig.33 Examples of popular 9-slot / 6-pole and 12-slot / 8-pole PMSMs are shown, where the windings on the stator can be divided into phase groups. For the 9s / 6p PMSM, three equivalent phase groups are seen, while for the 12s / 8p, four phase groups are determined. Depending on the required level of redundancy, these phase groups can be sent to a single / multiple electronic control units (ECUs) / inverters.

[0126] Figure 34-Figure 35 A dual-winding TFM stator 620 is shown having an outer rotor configuration. The dual-winding TFM stator 620 may be similar or identical to the inner stator assembly 220 of the first TFM 200 except for the differences described herein.

[0127] The dual-winding TFM stator 620 includes three inner stator cores 622a, 622b, 622c, including an A-phase inner stator core 622a, a B-phase inner stator core 622b, and a C-phase inner stator core 622c. The three inner stator cores 622a, 622b, 622c each have a similar or identical annular shape, which are axially stacked and circumferentially offset relative to each other. Each of the three inner stator cores 622a, 622b, 622c of the dual-winding TFM stator 620 includes two corresponding annular windings 624a, 624b, 624c, 626a, 626b, 626c of the corresponding phase, and the corresponding annular windings extend circumferentially through the inner stator core. In other words, each of the three internal stator cores 622a, 622b, 622c is a shared stator core that holds two of the annular windings 624a, 624b, 624c, 626a, 626b, 626c. For example, the first A-phase annular winding 624a and the second A-phase annular winding 626a may both be disposed within the A-phase internal stator core 622a. The first A-phase annular winding 624a and the second A-phase annular winding 626a may each be connected to a different corresponding ECU, and either or both of the first A-phase annular winding 624a and / or the second A-phase annular winding 626a may be energized to generate magnetic flux in the A-phase internal stator core 622a.

[0128] To clarify the placement of the windings, Fig.35A closer view of the A-phase inner stator core 622a is shown, with corresponding A-phase annular windings 624a, 626a. The first A-phase annular winding 624a and the second A-phase annular winding 626a are axially displaced, rather than radially displaced (ie, have the same radial size and position), which can prevent resistance imbalance.

[0129] Fig.36 – Fig.37 The effect of wire type and size on the TFM winding process is shown. The outer rotor TFM in each stator has 16 turns. Both round magnet wire and rectangular magnet wire can be used for the winding process. Fig.36 As shown, 12AWG round magnet wire was found to fit into the available slot area for 16 turns. A readily available rectangular wire of 3.2544mm x 1.4478mm was found to fit into the available slot area for 16 turns. Fig.37 The 16 turns shown are optimized for TFM matching. Fig.36 As shown in , the turns of round wire cannot be easily and symmetrically divided into two axial segments, so round wire is difficult to configure with a double winding TFM. Therefore, round wire may be more suitable for a single winding TFM configuration. However, as Fig.37 As shown, a dual winding TFM may include 8 turns of rectangular wire per segment. Fig.37 The top and bottom wires in the TFM in FIG. 1 have 8 turns each and can be sent to two identical inverters, such as ECU1, ECU2. A double winding configuration can also be achieved with round wires by using a thicker wire cross section. The double winding configuration can be applied to any TFM with a toroidal winding on the stator.

[0130] The present disclosure provides a transverse flux machine (TFM) for a steer-by-wire steering wheel actuator system. The proposed TFM has high volumetric and gravimetric power density with a simple toroidal wound single piece stator and flux concentrated rotor per phase. The present disclosure also provides a method for reducing flux leakage, which reduces magnet weight and cost, improves average torque and reduces torque ripple in the TFM. The present disclosure also provides a dual winding TFM structure to provide redundancy in the event of a steering system power failure.

[0131] One aspect of the disclosed embodiment includes a transverse flux machine (TFM). The TFM includes: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets of each pair of permanent magnets, and each pair of permanent magnets is arranged to generate a magnetic flux that enters the flux concentrating core and moves away from the flux diverging core in a circumferential direction; and a stator including a transverse flux core configured to guide the magnetic flux in each of a radial direction and an axial direction. The rotor also includes a non-magnetic material located between the permanent magnets of each pair of permanent magnets, adjacent to the flux concentrating core and opposite to the stator, the non-magnetic material having a thickness (TH) in the radial direction.

[0132] In some embodiments, the TFM has an inside rotor configuration in which the stator extends annularly around the rotor.

[0133] In some embodiments, the TFM has an external rotor configuration in which the rotor extends annularly around the stator.

[0134] In some embodiments, the rotor further comprises a rotor housing, wherein each of the plurality of pairs of permanent magnets, the flux concentrating core and the flux diverging core is attached to the rotor housing, and the rotor housing protrudes radially to define a non-magnetic material located between the permanent magnets of each pair of permanent magnets.

[0135] In some embodiments, the TFM is a multi-phase electric machine, the transverse flux core is one of a plurality of stator cores, each stator core having an annular shape, and the plurality of stator cores are axially stacked and circumferentially offset relative to each other.

[0136] In some embodiments, the TFM further includes a first toroidal winding and a second toroidal winding, each of which is disposed in a shared stator core of the plurality of stator cores and each configured to conduct a respective current.

[0137] In some embodiments, the thickness (TH) of the non-magnetic material is at least about 1.5 mm.

[0138] In some embodiments, the flux concentrating core defines a first angular spread (BetaCc); the rotor further comprises a flux diverging core located between adjacent pairs of permanent magnets and defining a second angular spread (BetaDc); and the first angular spread (BetaCc) is not equal to the second angular spread (BetaDc).

[0139] In some embodiments, the first angular spread (BetaCc) is greater than the second angular spread (BetaDc).

[0140] One aspect of the disclosed embodiment includes a dual-winding transverse flux machine (TFM). The dual-winding TFM includes: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets of each pair of permanent magnets, and each pair of permanent magnets is arranged to generate a magnetic flux that enters the flux concentrating core and moves away from the flux diverging core in a circumferential direction; a stator including a plurality of transverse flux cores, each transverse flux core configured to guide magnetic flux in each of a radial direction and an axial direction; and a first annular winding and a second annular winding, each disposed in a shared transverse flux core of the plurality of transverse flux cores, and each configured to conduct a corresponding current.

[0141] In some embodiments, the first toroidal winding and the second toroidal winding each include a wire having a rectangular cross-section.

[0142] In some embodiments, the TFM has an inside rotor configuration in which the stator extends annularly around the rotor.

[0143] In some embodiments, the TFM has an external rotor configuration in which the rotor extends annularly around the stator.

[0144] In some embodiments, the TFM is a multi-phase machine, each of the plurality of transverse flux cores has an annular shape, and the plurality of transverse flux cores are axially stacked and circumferentially offset relative to each other.

[0145] One aspect of the disclosed embodiment includes a steer-by-wire system for a vehicle. The steer-by-wire system includes a steering wheel actuator coupled (to a steering wheel) to apply torque to the steering wheel. The steering wheel actuator includes a transverse flux machine (TFM). The TFM includes a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein a flux concentrating core is located between the permanent magnets of each pair of permanent magnets; and a stator including a transverse flux core configured to direct magnetic flux in each of a radial direction and an axial direction.

[0146] In some embodiments, the steering wheel actuator is coupled to the steering wheel via a direct drive mechanism.

[0147] In some embodiments, the transverse flux core is one of a plurality of transverse flux cores, each transverse flux core having a toroidal shape, and

[0148] Therein a plurality of transverse flux cores are stacked axially and circumferentially offset relative to one another.

[0149] In some embodiments, the TFM further includes: a first toroidal winding and a second toroidal winding, each disposed in a shared transverse flux core of the plurality of transverse flux cores, and each configured to conduct a respective current.

[0150] In some embodiments, the rotor further includes a non-magnetic material located between the permanent magnets of each pair of permanent magnets, adjacent to the flux concentrating core and opposite to the stator, the non-magnetic material having a thickness (TH) in a radial direction.

[0151] In some embodiments, the flux concentrating core defines a first angular spread (BetaCc); the rotor further comprises a flux diverging core located between adjacent pairs of permanent magnets and defining a second angular spread (BetaDc); and the first angular spread (BetaCc) is not equal to the second angular spread (BetaDc).

[0152] The above discussion is intended to illustrate the principles and various embodiments of the present disclosure. Once the above disclosure is fully understood, many changes and modifications will become apparent to those skilled in the art. The following claims are intended to be interpreted as involving all such changes and modifications.

[0153] The word "example" is used herein to mean used as an example, instance or illustration. Any aspect or design described as an "example" herein is not necessarily to be interpreted as being more preferred or advantageous than other aspects or designs. Instead, the use of the word "example" is intended to present the concept in a specific way. As used in this application, the term "or" is intended to represent an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clearly seen from the context, "X includes A or B" is intended to represent any common inclusive arrangement. That is, if X includes A; X includes B; or X includes both A and B, then "X includes A or B" is satisfied in any of the foregoing cases. In addition, the articles "one" and "an" used in this application and the appended claims should generally be interpreted as meaning "one or more", unless otherwise specified or clearly pointed to the singular form from the context. In addition, unless so described, the use of the term "embodiment" or "one embodiment" throughout the text is not intended to represent the same embodiment or embodiment.

[0154] Implementations of the systems, algorithms, methods, instructions, etc. described herein can be implemented in hardware, software, or any combination thereof. Hardware can include, for example, a computer, an intellectual property (IP) core, an application specific integrated circuit (ASIC), a programmable logic array, an optical processor, a programmable logic controller, microcode, a microcontroller, a server, a microprocessor, a digital signal processor, or any other suitable circuit. In the claims, the term "processor" should be understood to include any of the foregoing hardware, alone or in combination. The terms "signal" and "data" can be used interchangeably.

[0155] As used herein, the term module can include a packaged functional hardware unit designed to be used with other components, an instruction set that can be executed by a controller (e.g., a processor that executes software or firmware), a processing circuit configured to perform a specific function, and a self-contained hardware or software component that interfaces with a larger system. For example, a module can include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a circuit, a digital logic circuit, an analog circuit, a combination of discrete circuits, gate circuits, and other types of hardware, or a combination thereof. In other embodiments, a module can include a memory that stores instructions that can be executed by a controller to implement the features of the module.

[0156] Furthermore, in one aspect, for example, the systems described herein can be implemented using a general purpose computer or general purpose processor with a computer program that, when executed, performs any corresponding method, algorithm and / or instruction described herein. Additionally or alternatively, for example, a special purpose computer / processor can be utilized that can include other hardware for executing any method, algorithm or instruction described herein.

[0157] In addition, all or part of the implementation of the present disclosure can take the form of a computer program product accessible from, for example, a computer usable or computer readable medium. A computer usable or computer readable medium can be any device that can, for example, tangibly contain, store, communicate, or transmit a program for use by or in conjunction with any processor. The medium can be, for example, an electrical, magnetic, optical, electromagnetic device, or a semiconductor device. Other suitable media may also be used.

[0158] The above embodiments, implementations and aspects have been described to allow easy understanding of the present disclosure and are not intended to limit the present disclosure. On the contrary, the present disclosure is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope should be given the broadest interpretation to cover all such modifications and equivalent structures permitted by law.

Claims

1. A transverse flux machine TFM, comprising: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets of each of the plurality of pairs of permanent magnets, each of the plurality of pairs of permanent magnets being arranged to generate a magnetic flux that enters the flux concentrating cores and moves away from the flux diverging cores in a circumferential direction; as well as a stator comprising a transverse flux core configured to direct the magnetic flux in each of a radial direction and an axial direction, The rotor further includes a non-magnetic material located between the permanent magnets of each of the plurality of pairs of permanent magnets, adjacent to the flux concentrating core and opposite to the stator, the non-magnetic material having a thickness TH in a radial direction.

2. A transverse flux machine according to claim 1, wherein: The TFM has an inner rotor configuration in which the stator extends annularly around the rotor.

3. The transverse flux machine of claim 1 , wherein: The TFM has an external rotor configuration in which the rotor extends annularly around the stator.

4. The transverse flux machine of claim 1, wherein: The rotor further comprises a rotor housing, wherein each of the plurality of pairs of permanent magnets, the flux concentrating core, and the flux diverging core is attached to the rotor housing, and The rotor housing protrudes in a radial direction to define the non-magnetic material between the permanent magnets of each of the plurality of pairs of permanent magnets.

5. The transverse flux machine of claim 1, wherein: The TFM is a multi-phase machine, wherein the transverse flux core is one of a plurality of stator cores, each stator core having a toroidal shape, and The plurality of stator cores are axially stacked and circumferentially offset relative to each other.

6. The transverse flux machine of claim 5, further comprising: A first annular winding and a second annular winding, the first annular winding and the second annular winding are both disposed in a shared stator core of the plurality of stator cores, and the first annular winding and the second annular winding are both configured to conduct corresponding currents.

7. The transverse flux machine of claim 1, wherein: The thickness TH of the non-magnetic material is at least about 1.5 mm.

8. The transverse flux machine of claim 1, wherein: The flux concentrating core defines a first angular spread BetaCc; wherein the rotor further comprises a flux diverging core located between adjacent pairs of permanent magnets and defining a second angular spread BetaDc; and The first angular spread BetaCc is not equal to the second angular spread BetaDc.

9. A transverse flux machine according to claim 8, wherein: The first angular spread BetaCc is greater than the second angular spread BetaDc.

10. A dual-winding transverse flux machine (TFM), comprising: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets of each of the plurality of pairs of permanent magnets, each of the plurality of pairs of permanent magnets being arranged to generate a magnetic flux that enters the flux concentrating cores and moves away from the flux diverging cores in a circumferential direction; a stator comprising a plurality of transverse flux cores, each transverse flux core configured to direct the magnetic flux in each of a radial direction and an axial direction; as well as A first toroidal winding and a second toroidal winding, wherein the first toroidal winding and the second toroidal winding are both disposed in a shared transverse flux core of the plurality of transverse flux cores, and the first toroidal winding and the second toroidal winding are both configured to conduct corresponding currents.

11. A two-winding transverse flux machine according to claim 10, wherein: The first toroidal winding and the second toroidal winding each include a wire having a rectangular cross-section.

12. The dual-winding transverse flux machine of claim 10, wherein: The TFM has an inner rotor configuration in which the stator extends annularly around the rotor.

13. The dual winding transverse flux machine of claim 10, wherein: The TFM has an external rotor configuration in which the rotor extends annularly around the stator.

14. The dual-winding transverse flux machine of claim 10, wherein: The TFM is a multi-phase machine, wherein each transverse flux core of the plurality of transverse flux cores has a toroidal shape, and Wherein the plurality of transverse flux cores are axially stacked and circumferentially offset relative to each other.

15. A steer-by-wire system for a vehicle, comprising: a steering wheel actuator coupled to apply torque to the steering wheel; The steering wheel actuator comprises a transverse flux machine TFM, comprising: a rotor configured to rotate about an axis and having a plurality of pairs of permanent magnets, wherein flux concentrating cores and flux diverging cores are alternately placed between the permanent magnets of each of the plurality of pairs of permanent magnets, each of the plurality of pairs of permanent magnets being arranged to generate a magnetic flux that enters the flux concentrating cores and moves away from the flux diverging cores in a circumferential direction; as well as A stator includes a transverse flux core configured to direct the magnetic flux in each of a radial direction and an axial direction.

16. The steer-by-wire system according to claim 15, wherein: The steering wheel actuator is coupled to the steering wheel via a direct drive mechanism.

17. The steer-by-wire system according to claim 15, wherein: The transverse flux core is one of a plurality of transverse flux cores, each transverse flux core having a toroidal shape, and Wherein the plurality of transverse flux cores are axially stacked and circumferentially offset relative to each other.

18. The steer-by-wire system according to claim 17, further comprising: A first toroidal winding and a second toroidal winding, the first toroidal winding and the second toroidal winding are both disposed in a shared transverse flux core of the plurality of transverse flux cores, and the first toroidal winding and the second toroidal winding are both configured to conduct corresponding currents.

19. The steer-by-wire system according to claim 15, wherein: The rotor further includes a non-magnetic material located between the permanent magnets of each of the plurality of pairs of permanent magnets, adjacent to the flux concentrating core and opposite to the stator, the non-magnetic material having a thickness TH in a radial direction.

20. The steer-by-wire system according to claim 15, wherein: The flux concentrating core defines a first angular spread BetaCc; wherein the rotor further comprises a flux diverging core located between adjacent pairs of permanent magnets and defining a second angular spread BetaDc; and The first angular spread BetaCc is not equal to the second angular spread BetaDc.

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