Analysis of secondary torque harmonics reduction in pmsm drives

Abstract

A method for operating a multiphase permanent magnet synchronous motor (PMSM) includes: determining the values ​​of one or more back electromotive force (BEMF) constants of the multiphase PMSM; determining an initial fundamental current command to cause the multiphase PMSM to generate output torque according to a torque command; determining a final current command based on the initial fundamental current command and the values ​​of one or more BEMF constants; and instructing an inverter to apply an output voltage to the multiphase PMSM based on the final current command, thereby generating an output current in the windings according to the final current command.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to U.S. Provisional Patent Application No. 63 / 778,750, filed March 27, 2025, and U.S. Patent Application No. 19 / 555,102, filed March 3, 2026, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a transverse flux motor. It also relates to the application of such a transverse flux motor in a handwheel actuator of a vehicle steering system. Background Technology

[0004] Vehicles (such as cars, trucks, SUVs, crossovers, minivans, boats, aircraft, 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) system, a hydraulic steering system, or other suitable steering system. The steering system of such vehicles typically controls various aspects of the vehicle's steering, including providing steering assistance to the vehicle operator and controlling the steerable wheels of the vehicle.

[0005] Steering-by-wire (SbW) is a direct upgrade to the EPS system, where there is no mechanical coupling between the handwheel 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, in an SbW system, there can be two electric actuators / motors with different functions. The electric actuator attached to the rack in an SbW system is called the wheel actuator (RWA), while the actuator on the driver's side is called the handwheel actuator (HWA). The RWA has the same assistance-providing function as the EPS system actuator. The HWA, on the other hand, functions more as a feedback motor than to provide driver assistance. Without the HWA, the handwheel in an SbW system could simply spin freely due to the lack of any mechanical coupling / friction. The HWA opens up a range of design-related opportunities due to its functionality.

[0006] Several different motor architectures are known, each with advantageous characteristics for a given application. Transverse flux motors (TFMs) may be particularly well-suited for use as the power wave motor (HWA) in EPS systems. However, TFMs can produce torque ripple when powered with conventional symmetrical alternating current (AC).

[0007] Using a lookup table to modify the current supplied to the motor can suppress torque ripple. However, this lookup table-based method may require torque measurements synchronized with the offline position, which may only be feasible for a single six-sigma part in each production design. Therefore, any deviation from the specifications of each part will result in suboptimal torque performance. Summary of the Invention

[0008] One aspect of the disclosed embodiments includes a method for operating a multiphase permanent magnet synchronous motor (PMSM). The method includes: determining values ​​of one or more back electromotive force (BEMF) constants of the multiphase PMSM; determining an initial fundamental current command to cause the multiphase PMSM to generate output torque according to a torque command; determining a final current command based on the initial fundamental current command and the values ​​of one or more BEMF constants; and instructing an inverter to apply an output voltage to the multiphase PMSM based on the final current command, thereby generating an output current concentrated in the windings according to the final current command.

[0009] Another aspect of the disclosed embodiments includes a motor control system. The motor control system includes: a multiphase permanent magnet synchronous motor (PMSM); an inverter configured to provide alternating current (AC) power to the multiphase PMSM; and a controller. The controller is configured to: determine an initial fundamental current command to cause the multiphase PMSM to generate output torque according to a torque command; load values ​​of a plurality of back electromotive force (BEMF) constants of the multiphase PMSM from a machine-readable storage memory; determine a final current command based on the initial fundamental current command and the values ​​of one or more BEMF constants; and instruct the inverter to apply an output voltage to the multiphase PMSM based on the final current command, thereby generating an output current in the windings according to the final current command.

[0010] These and other aspects of the invention are disclosed in the following detailed description of the embodiments, the appended claims and the accompanying drawings. Attached Figure Description

[0011] The invention is best understood from the following detailed description, which is read in conjunction with the accompanying drawings. It should be emphasized that, by convention, the various features in the drawings are not to scale. Rather, for clarity, the dimensions of the various features have been arbitrarily enlarged or reduced.

[0012] Figure 1 This is a schematic diagram of an electric power steering (EPS) system based on the principles of the present invention.

[0013] Figure 2 An EPS system based on the principles of the present invention is shown in general.

[0014] Figure 3 The steer-by-wire (SbW) system according to the principles of the present invention is shown in general.

[0015] Figure 4 This is a schematic diagram of a motor control system based on the principles of the present invention.

[0016] Figure 5 This is a schematic diagram of a motor controller based on the principles of the present invention.

[0017] Figure 6 A cross-sectional view of a radial flux motor (RFM) according to the principles of the present invention is shown.

[0018] Figure 7 A cross-sectional view of an axial flux motor (AFM) according to the principles of the present invention is shown.

[0019] Figure 8 A cross-sectional view of a transverse flux motor (TFM) according to the principles of the present invention is shown.

[0020] Figure 9 A partial perspective view of a TFM having a magnetically focused outer rotor and an integral stator according to the principles of the present invention is shown.

[0021] Figure 10 A perspective view of the stator in an external rotor TFM according to the principle of the present invention is shown.

[0022] Figure 11 A perspective view of the stator in an internal rotor TFM according to the principle of the present invention is shown.

[0023] Figure 12 A partial perspective view according to the principle of the invention is shown, which illustrates the leakage flux in the inner rotor TFM at the axial end and opposite to the stator.

[0024] Figure 13 A cross-sectional view according to the principle of the invention is shown, which illustrates the leakage flux between different phases of the stator in the inner rotor TFM.

[0025] Figure 14 A graph illustrating the flux linkage imbalance between the phases of a three-phase TFM is shown.

[0026] Figure 15 A graph illustrating the first harmonic of the unloaded flux linkage for each phase of a three-phase TFM is shown.

[0027] Figure 16 A graph illustrating the back electromotive force waveform of each phase of a three-phase TFM is shown.

[0028] Figure 17 A graph illustrating the BEMF constant for each phase of a three-phase TFM is shown.

[0029] Figure 18A graph illustrating the BEMF constant for each of the three line-to-line voltages of a three-phase TFM is shown.

[0030] Figure 19 A flowchart illustrating a method for operating a multiphase PMSM according to the principles of the present invention is shown. Detailed Implementation

[0031] The following discussion relates to various embodiments of the invention. While one or more of these embodiments may be preferred, the disclosed embodiments should not be construed as or otherwise used to limit the scope of the invention (including the claims). Furthermore, those skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is merely illustrative and not intended to imply that the scope of the invention (including the claims) is limited to that embodiment.

[0032] As mentioned above, vehicles (such as automobiles, trucks, sport utility vehicles, crossovers, minivans, boats, aircraft, 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 sbW steering system, a hydraulic steering system, or other suitable steering system. The steering system of such vehicles typically controls various aspects of the vehicle, including providing steering assistance to the operator and controlling the steerable wheels.

[0033] Figure 1 This is a schematic diagram of an EPS system 40 applicable to implementing the disclosed technology. The EPS system 40 includes a steering mechanism 36 comprising a rack and pinion mechanism having a rack (not shown) located within a housing 50 and a pinion (also not shown) located below a gearbox 52. When an operator inputs (hereinafter referred to as rotation of the steering wheel 26 (e.g., a handwheel),), the upper steering shaft 29 rotates, and the lower steering shaft 51, connected to the upper steering shaft 29 via a universal joint 34, rotates the pinion. The rotation of the pinion moves the rack, which in turn moves a lever 38 (only one shown), which in turn moves a steering knuckle 39 (only one shown), which in turn rotates a steerable wheel 44 (only one shown).

[0034] Electric power steering is provided via a steering motion control system, generally indicated by reference numeral 24, which includes a controller 16 and a motor, which may be a permanent magnet synchronous motor and is referred to hereinafter as motor 19. The controller 16 is powered by the vehicle power supply 10 via power supply wire 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 coded sensor, a variable resistance sensor, or any other suitable type of position sensor, and provides a position signal 20 to the controller 16. The motor speed can be measured using a tachometer or any other device and transmitted to the controller 16 as a speed signal 21. The indicated motor speed... It can be measured, calculated, or a combination thereof. For example, motor speed. This can be calculated as the change in motor position measured by position sensor 32 over a specified time interval. For example, motor speed. The position of the motor can be determined. The derivative with respect to time. It should be understood that there are many well-known methods to perform differentiation operations.

[0035] When the steering wheel 26 rotates, 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 resistance sensor (also not shown), which outputs a torque signal 18 to the controller 16 related to the amount of torsion applied to the torsion bar. Although this is one type of torque sensor, any other suitable torque sensing device used with known signal processing techniques may be applicable. In response to various inputs, the controller sends a command 22 to the motor 19, which provides torque assistance to the steering system via the worm gear 47 and worm wheel 48, thereby providing torque assistance for steering the vehicle.

[0036] It should be noted that although the disclosed embodiments are described with reference to motor control for electric steering applications, this reference is merely illustrative, and the disclosed embodiments can be applied to any motor control application employing an electric motor, such as steering, valve control, etc. Furthermore, the references and descriptions herein are applicable to many forms of parameter sensors, including but not limited to torque, position, and speed. It should also be noted that the motors mentioned herein include, but are not limited to, electric motors; for the sake of brevity and simplicity, electric motors will be referred to only without limitation.

[0037] In the illustrated steering motion control system 24, controller 16 uses torque, position, and speed, among other factors, to calculate the command to deliver the required output power. Controller 16 is configured to communicate with various systems and sensors of the motor control system. Controller 16 receives signals from each system sensor, quantifies the received information, and in response provides an output command signal, in this case, for example, to motor 19. Controller 16 is configured to generate a corresponding voltage from an inverter (not shown), which may optionally be combined with controller 16 and will be referred to herein as controller 16, such that when applied to motor 19, the desired torque or position is produced. In one or more examples, controller 16 operates as a current regulator in feedback control mode to generate command 22. Alternatively, in one or more examples, controller 16 operates in feedforward control mode to generate command 22. Because these voltages are related to the position and speed of motor 19 and the desired torque, the rotor position and / or speed, as well as the torque applied by the operator, are determined. Steering shaft 51 is connected to a position encoder to detect angular position θ. The encoder may sense rotational position based on optical detection, magnetic field changes, or other methods. Typical position sensors include potentiometers, resolvers, synchronizers, encoders, and combinations thereof. 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.

[0038] The desired torque can be determined by one or more torque sensors 28, which transmit torque signals 18 indicating the applied torque. Such torque sensors 28 and the torque signals 18 from them can be responsive to a flexible torsion bar, spring, or similar device (not shown) configured to provide a response indicating the applied torque.

[0039] In one or more examples, a 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 described herein. Typical temperature sensors include thermocouples, thermistors, thermostats, etc., as well as combinations including at least one of the aforementioned sensors, which, when properly positioned, provide a calibrable signal proportional to a specific temperature.

[0040] Position signal 20, speed signal 21, and torque signal 18, etc., are applied to controller 16. Controller 16 processes all input signals to generate a value corresponding to each signal, resulting in rotor position values, motor speed values, and torque values ​​that can be used for processing in the algorithm described herein. The measured signals, as described above, are also typically linearized, compensated, and filtered as needed to enhance the characteristics of the acquired signals or eliminate undesirable characteristics. For example, signals can be linearized to improve processing speed or to address a large dynamic range of the signal. Furthermore, frequency- or time-based compensation and filtering can be employed to eliminate noise or avoid undesirable spectral characteristics.

[0041] In order to perform the prescribed functions and desired processing and therefore calculations (e.g., identifying motor parameters, control algorithms, etc.), controller 16 may include, but is not limited to, processors, computers, DSPs, memories, storage devices, registers, timing devices, interrupt devices, communication interfaces, and input / output signal interfaces, as well as combinations including at least one of the foregoing. For example, controller 16 may include input signal processing and filtering to achieve accurate sampling, conversion, or acquisition of such signals from the communication interface.

[0042] Figure 2 The EPS system is roughly shown, and Figure 3 The steer-by-wire (SbW) system is roughly shown. Figure 2 The EPS system can be integrated with Figure 1 The EPS system 40 is similar or identical to the EPS system 40, except that the motor 19 is directly mounted to the steering mechanism 36. Figure 3 The SbW system can be with Figure 1 The EPS system 40 is similar to or identical to the one described above, except that there is no physical connection between the steering wheel 26 and the steerable wheel 44, and that it has two separate and independent motors 19a and 19b. As shown, the SbW system includes a first motor 19a (also known as the handwheel actuator (HWA)) and a second motor 19b (also known as the wheel actuator (RWA)). The HWA 19a is configured to provide torque to the steering wheel 26 for providing tactile feedback to the driver.

[0043] SbW is a direct upgrade of the EPS system, in which there is no mechanical coupling between the steering wheel 26 and the steering rack. For example... 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 referred to as the wheel actuator (RWA) 19b, while the actuator on the driver's side is referred to as the handwheel actuator (HWA) 19a. The RWA 19b can provide the same assistance function as actuator 19 in the EPS system. On the other hand, the HWA 19a acts more as a feedback motor than to provide assistance to the driver. Without the HWA 19a, the handwheel on the SbW system would simply spin freely due to the lack of any mechanical coupling / friction. The HWA 19a offers ample design-related expansion possibilities due to its functionality.

[0044] As used in this article, variables marked with a wavy line (~) above their variable symbols represent estimated values, which can be determined through mathematical calculations, table lookups, etc. Variables marked with a horizontal line above their variable symbols represent vectors. Variables marked with an asterisk (~) The variable represents the instruction or the required setting value.

[0045] Figure 4 An electric motor control system 80 is shown, which includes a multiphase permanent magnet synchronous motor (PMSM) 60, a power converter 66 (including a gate driver and a corresponding inverter), and a controller 70, which may also be referred to as an electronic control unit (ECU). The multiphase PMSM 60 can be a transverse flux motor (TFM). However, the multiphase PMSM 60 can have different configurations, such as radial flux motor (RFM) or axial flux motor (AFM) topologies. The PMSM 60 can be used in many applications, such as for... Figure 1 The motor 19 is shown in the steering motion control system 24. The power converter 66 may include several switching devices, such as field-effect transistors (FETs) for switching high-current loads and gate driver circuitry for operating the switching devices. The controller 70 may receive motor torque command T from an external source, such as a power steering controller. Alternatively, controller 70 may include hardware and / or software to calculate motor torque command T. This enables the multiphase PMSM 60 to generate corresponding torque to perform certain given tasks (such as initiating steering).

[0046] The multiphase PMSM 60 includes a winding set 62. The multiphase PMSM 60 is capable of generating electromagnetic torque by exciting the winding set 62. The winding set 62 may include three phases, and therefore may include three-phase windings. Alternatively, the winding set 62 may include any number of winding phases, such as five-phase or seven-phase. A power converter 66 is configured to provide an alternating current (AC) voltage to the winding set 62. The winding set 62 is connected to the power converter 66 via phase lines 68.

[0047] Controller 70 is based on motor torque command T Generate voltage command The voltage command can include d-axis components separately. and q-axis components Controller 70 may include any suitable controller. Controller 70 may be configured to control various functions of, for example, the transportation system described herein. Controller 70 may include processor 72 and memory 74. Processor 72 may include any suitable processor, such as those described herein. Additionally or alternatively, in addition to processor 72, controller 70 may include any suitable number of processors. Memory 74 may include a single disk or multiple disks (e.g., a hard disk drive) and includes a storage management module that manages one or more partitions within memory 74. In some embodiments, memory 74 may include flash memory, semiconductor (solid-state) memory, etc. Memory 74 may include random access memory (RAM), read-only memory (ROM), or a combination of both. Memory 74 may include instructions that, when executed by processor 72, cause processor 72 to control at least various functions of the steering system and / or any other suitable functions, including those of the systems and methods described herein.

[0048] Figure 5 This is a schematic diagram of a motor controller 100, which is configured to operate based on a motor torque command T. To generate instructions The motor controller 100 can be implemented using hardware and / or software. In some embodiments, the motor controller 100 can be implemented using software instructions running on the processor 72. The motor controller 100 includes a current command generator 102, which is based on the motor torque command T. To calculate or otherwise generate the initial fundamental current command. The current command generator 102 can use any technique, such as conventional functions utilizing the maximum torque per ampere method and / or maximum torque per voltage method, to generate the initial fundamental current command. This allows the multiphase PMSM 60 to operate according to the motor torque command T. Generate output torque.

[0049] The motor controller 100 also includes a current command booster 104, which is based on an initial fundamental current command. And based on one or more BEMF constants The value is used to calculate or otherwise generate the final current command. According to the final current command The operation can bring favorable results to the multiphase PMSM 60 (e.g., reduced torque ripple), which could otherwise be caused by the asymmetry of the flux linkage in the multiphase PMSM 60.

[0050] The motor controller 100 also includes a voltage command generator 106, which is based on the final current command. Calculate or otherwise generate voltage commands The voltage command generator 106 can use a feedforward technique, which is based solely on the final current command. Determine the voltage command Alternatively or additionally, the voltage command generator 106 may use a feedback technique based on the final current command. And based on the measured current signal from one or more current sensors 108 Determine voltage command .

[0051] Figure 6 A cross-sectional view of a radial flux motor (RFM) is shown. Figure 7 A cross-sectional view of an axial flux motor (AFM) is shown. Figure 8 A cross-sectional view of a transverse flux motor (TFM) is shown. RFM, AFM, and TFM devices all include a shaft configured to rotate about axis A. The classification between RFM, AFM, and TFM configurations can be based on the direction of the magnetic flux.

[0052] Figure 6 The RFM includes a first rotor 110a having a first rotor core 112a attached to rotate about axis A together with a first shaft 114a. The first rotor 110a is located within a first housing 115a, the first shaft 114a extending through and out of the first housing 115a and supported by a pair of first bearings 116a. A set of first permanent magnets 118a are attached to the first rotor core 112a and generate radially outward magnetic flux. Figure 6 The RFM also includes a first stator 120a having a first stator core 122a having a set of first windings 124a extending therethrough and conducting current in an axial direction parallel to axis A and perpendicular to magnetic flux.

[0053] Figure 7The AFM includes a second rotor 110b having a second rotor core 112b attached to rotate about axis A together with a second shaft 114b. The second rotor 110b is located within a second housing 115b, through which the second shaft 114b extends 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 magnetic flux in an axial direction parallel to axis A. Figure 7 The AFM also includes a second stator 120b having a second stator core 122b, wherein a set of second windings 124b extends through the second stator core 122b and conducts current in a radial direction perpendicular to axis A and perpendicular to the magnetic flux.

[0054] Figure 8 The TFM includes a third rotor 110c having a third rotor core 112c, the third rotor core 112c being attached to rotate about axis A together with a third shaft 114c. The third rotor 110c is located within a third housing 115c, and 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 is attached to the third rotor core 112c and generates magnetic flux that extends radially inward in a first position, axially through the third rotor core 112c, and radially outward in a second position axially spaced from the first position. Figure 8 The TFM also includes a third stator 120c having a third stator core 122c, wherein a set of third windings 124c extends through the third stator core 122c and conducts current in a circumferential direction perpendicular to axis A and perpendicular to the magnetic flux. As shown, the third stator core 122c defines a U-shape with its open ends aligned with the third permanent magnet 118c at first and second positions to provide a closed rectangular magnetic flux path together with the third rotor core 112c.

[0055] Figures 6-8 The flux directions in three motor topologies are shown. For RFM, the flux moves radially in the air gap, while for AFM, the flux moves axially from the stator to the rotor and from the rotor to the stator. However, as... Figure 8 As shown in the diagram for TFM, the magnetic flux moves in both the radial and axial directions. Although several topologies of TFM can be identified from the literature, a 3D (radial and axial) flux path is a common feature across different topologies. Compared to radial flux motors, TFM is known for its higher volumetric power density and gravimetric power density. AFM and TFM are known to have roughly equivalent power densities. However, the simplicity of the toroidal winding in TFM has the potential to simplify the manufacturing process and reduce costs.

[0056] like Figure 6As shown, the magnetic flux in the RFM extends primarily in the radial direction perpendicular to axis A. For example... Figure 7 As shown, the magnetic flux in the AFM extends primarily in the axial direction parallel to axis A. For example... Figure 8 As shown, the flux in the TFM defines a closed-loop path, with some portions extending in a radial direction perpendicular to axis A, and others extending in an axial direction parallel to axis A. RFM, AFM, and TFM configurations can each offer different volumetric and weight-based power densities. The TFM configuration may be particularly well-suited for low-speed and high-torque operation.

[0057] This invention provides a transverse flux motor (TFM) topology for direct-drive SbW HWA architectures. In the low-speed, high-torque operating region of direct-drive SbW HWAs, transverse flux motors have the potential to provide a significant power density advantage over conventional radial flux motors. Conventional RFMs can be stacked in the radial XY plane to accommodate their 2D flux paths and reduce eddy current losses during high-frequency operation. AFMs can also be stacked in the axial XZ plane to facilitate axial flux transfer from the stator to the rotor and from the rotor to the stator. However, as... Figure 8 As shown, for TFM, the magnetic flux moves in both the radial and axial directions. If TFM is to be laminated, lamination in both the XY and XZ directions is required depending on the core position and the expected direction of flux transmission. This would significantly complicate the manufacturing process of TFM. To avoid this complexity and ensure 3D flux transmission in the TFM core, this approach uses soft magnetic core (SMC) material. SMC consists of insulating iron particles pressed into a core shape. The electrical insulation between the iron particles in the pressed SMC core significantly reduces eddy current losses at higher operating frequencies. The conclusions drawn in this paper also apply to TFMs made from laminated steel sheets.

[0058] As shown in the figure Figure 9 A first TFM 200 with an outer rotor configuration is presented, wherein a first rotor 210 is configured to rotate about an axis and the rotor extends annularly about an inner stator assembly 220. Figure 9A 45° segment of the first TFM 200 is shown, with labels indicating magnetic flux. However, the complete first TFM 200 will include eight such segments. The first rotor 210 includes multiple pairs of first permanent magnets 212a, 212b, arranged at regular angular intervals and configured to generate magnetic flux circumferentially therebetween. The first rotor 210 also includes multiple first magnetic cores 214 located between the first permanent magnets 212a, 212b of each pair of first permanent magnets 212a, 212b and configured to conduct magnetic flux therebetween. The first rotor 210 also includes multiple first flux-diverging cores 216, each located between adjacent pairs of first permanent magnets 212a, 212b. The first rotor 210 is tubular and extends between a first axial end 218a and a second axial end 218b.

[0059] For example Figure 9 As shown, the inner stator assembly 220 includes an inner stator core 222 with a U-shaped cross-section. The inner stator core 222 has an inner cylindrical portion 224 and a pair of arms 226, which extend radially outward from each end of the inner cylindrical portion 224 toward the first rotor 210. A winding 228 extends circumferentially through the center of the U-shaped cross-section of the inner stator core 222 and conducts current circumferentially.

[0060] As shown, each arm 226 of the inner stator core 222 includes an arcuate groove 230 to define two radially extending protrusions 232, which are angularly spaced to align with adjacent members of the first concentrating magnet core 214 and the first flux-diverging core 216. Thus, magnetic flux is conducted from each of the first concentrating magnet cores 214 adjacent to the first axial end 218, across the air gap, and into the radially extending protrusions 232 of the adjacent inner stator core 222. The magnetic flux is guided into the inner cylindrical portion 224 of the inner stator core 222, where it continues axially. Magnetic flux is also guided 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 it crosses the air gap and enters the corresponding member of the first flux-diverging core 216. The magnetic flux continues to pass through one of the corresponding first permanent magnets 212a and 212b, and then returns to the first magnetic core 214, thus completing a closed path.

[0061] TFM may be particularly well-suited for direct drive at low speeds. TFM can include modular, spatially shifted three-phase stator architectures. TFM can include simple toroidal windings with an inner stator topology. TFM can provide relatively low phase resistance, independent of the number of stator slots and rotor poles. TFM can include outer rotor structures with high volumetric torque density and weight torque density. TFM can be manufactured relatively easily and efficiently, and can provide suitable performance for a variety of applications in EPS and / or SbW systems.

[0062] 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. Furthermore, for some applications, such as direct-drive HWA in an SbW system, the operating speed is relatively low. This indicates that even with a higher pole number TFM, the operating fundamental frequency will remain within a reasonable range. For example, for a 12-slot, 8-pole SbW HWA with a transmission ratio of 11:1, the fundamental frequency is 166.67 Hz at a motor speed of 2500 rpm. 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 speed of 227.27 rpm. Regarding the maximum number of poles for a TFM (… P max The following can be calculated using equation (1):

[0063] in, It is the maximum motor speed in rpm (revolutions per minute). It is the maximum fundamental frequency that the motor drive can handle.

[0064] Furthermore, despite having more poles in TFM, the phase resistance does not increase, which can provide reduced copper losses, thereby improving efficiency and thermal performance.

[0065] Inner rotor / outer rotor topology

[0066] The general dimensional equation for TFM can be written as equation (2):

[0067] Among them, P R It is the rated output power, K phi It is the ratio of the electrical load on the rotor to that on the stator (K). phi (can be equal to 0), m is the number of phases, K e It incorporates the salient poles (if any) of the motor across the total air gap region for each unit portion and the winding distribution factor K. w BEMF factor, K i It is the current waveform factor, K pIt is the electrical power waveform factor, K L It is the stack length L e Compare the diameter D of the air gap surface g The ratio, where n is the motor efficiency and B is the ratio. g λ0 is the air gap flux density, A is the total electrical load, f is the driver frequency, p is the number of pole pairs, D0 is the outer diameter of the motor, and λ0 is the value of D. g The ratio between D0 and D0.

[0068] As can be seen from equation (2), the rated power and therefore the torque output of the TFM are directly proportional to the square of the motor's outer diameter D0. This can be achieved by using D... g Replacing λ0 with / D0, we can see from equation (2) that the output power is related to D g The square of the value is directly related. From the inner rotor TFM to the outer rotor TFM, the diameter of the air gap surface can be increased due to better space utilization. This results in a higher volumetric torque density in the outer rotor TFM. Furthermore, the winding process is relatively simpler in the outer rotor TFM. According to the present invention, the outer rotor TFM and the inner rotor TFM are symmetrically optimized.

[0069] Figure 10 A 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) arranged annularly around it. The inner stator assembly 220 includes three inner stator cores 222a, 222b, and 222c, comprising an A-phase inner stator core 222a, a B-phase inner stator core 222b, and a C-phase inner stator core 222c. Each of the three inner stator cores 222a, 222b, and 222c is in a similar or identical annular shape, these annularities being axially stacked and circumferentially offset from each other. Each of the three inner stator cores 222a, 222b, and 222c of the inner stator assembly 220 includes corresponding windings 224a, 224b, and 224c for the corresponding phase, and extends circumferentially through them. The three inner stator cores 222a, 222b, and 222c of the inner stator assembly 220 also define multiple radially extending protrusions that are regularly angularly spaced and extend radially outward.

[0070] The stacked components of the TFM stator cause inherent asymmetry problems. For example... Figure 10 As shown, in a 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 outer cores because they are located near 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 location is spaced apart from the axial ends of the stator assembly.

[0071] Figure 11A perspective view of an outer stator assembly 320 for an inner rotor TFM is shown. The outer stator assembly 320 is configured to be arranged in a ring around a rotor (not shown). The outer stator assembly 320 includes three outer stator cores 322a, 322b, and 322c, including an A-phase outer stator core 322a, a B-phase outer stator core 322b, and a C-phase outer stator core 322c. Each of the three outer stator cores 322a, 322b, and 322c is in a similar or identical ring shape, these rings are axially stacked and circumferentially offset from each other. Each of the three outer stator cores 322a, 322b, and 322c of the outer stator assembly 320 may contain a corresponding winding for the corresponding phase. Figure 11 (not shown in the figure), and extends circumferentially through it. The three outer stator cores 322a, 322b, and 322c of the outer stator assembly 320 also define a plurality of radially extending protrusions that extend radially inward at regular angular intervals.

[0072] Several different factors can influence the design of a TFM. These design factors may include: topology selection and manufacturing challenges; material selection; number of poles; inner / outer rotor (i.e., inner or outer rotor configuration); multiphysics performance; and three-dimensional (3D) simulation, which can be computationally expensive.

[0073] Magnetic leakage

[0074] Despite its several advantages, TFM suffers from magnetic flux leakage due to the complex 3D nature of its flux path. The amount of leakage can vary depending on the topology. Furthermore, leakage is highly dependent on the number of poles in the TFM. Figures 12-13 An example of leakage flux occurring in the TFM rotor and stacked stator structure is shown. If left untreated, this leakage flux will increase the weight of the magnet material in the optimized machine, thus increasing costs.

[0075] Due to the 3D nature of the magnetic flux path, transverse flux motors inherently suffer from magnetic leakage. Rotor leakage occurs in the magnetic core opposite the air gap (i.e., opposite the stator), such as... Figure 12 As shown. Figure 13 As shown, inter-stator leakage flux may exist in modular stator architectures. Modular stator structures with toroidal windings may lead to asymmetrical electromagnetic characteristics between the stators of multiphase motors (e.g., three-phase motors).

[0076] Continue to refer to Figure 13 Phase B lies between phases A and C. However, for phases A and C, one side of the stator is air instead of ferromagnetic material. As a result, magnetic flux leaks through the air instead of entering the interior of the ferromagnetic material, such as... Figure 12 As shown.

[0077] like Figure 14As shown, the peak value of the unloaded flux linkage is different for different phases. The flux linkage of phase B is higher than that of phases A and C. As shown in the figure, the flux linkage values ​​of phase A and phase C are similar, while the flux linkage of phase B is higher than that of phases A and C by the leakage flux difference ΔΛ. Furthermore, as... Figure 15 As shown, the first harmonics of the unloaded flux linkage are also unequal. This asymmetry in the flux linkage generates second-order torque pulsating harmonics in the motor.

[0078] Due to the unbalanced unloaded flux linkages in each phase, the BEMF waveforms in each phase are also unbalanced, which makes the BEMF constant... for Figure 17 The phases shown are not equal. For example... Figure 16 As shown, phases A and C each have similar BEMF peak values, while the peak BEMF of phase B is higher than the BEMF values ​​of phases A and C by a voltage difference ΔV. BEMF constants for different phases are also shown. Values ​​such as Figure 17 As shown, the BEMF constant is observed. The imbalance. Similarly, the inter-line BEMF constant. The imbalance is also like Figure 18 As shown.

[0079] Using a lookup table to change the current supplied to the motor can suppress torque ripple. However, this lookup table method may require torque measurements synchronized with the offline position, which may only be feasible for one qualified part per production design. Therefore, any deviation from the specifications of each part can lead to suboptimal torque performance. However, back electromotive force (BEMF) open-circuit testing is likely a standard test for every part leaving the assembly line. For TFM designs, Figures 15-17 The BEMF constant shown Differences in the BEMF test can be quantified. This invention provides a method for torque ripple elimination that utilizes information from the BEMF to not only provide effective and targeted ripple suppression, but also makes it easy to implement.

[0080] Equations (3) to (5) describe the fundamental magnetic flux generated by the permanent magnet in the motor winding.

[0081]

[0082] in It is the flux linkage amplitude. It refers to the position of the motor rotor. and It considers any phase shift term in the flux linkage that is asymmetrical. Unlike conventional PMSM, in TFM, the flux linkage amplitudes are not equal ( Sometimes the phase shift offset is not zero. Considering these conditions, the flux linkages in equations (3)-(5) are transformed into dq synchronous reference frame variables through the Park transformation and Clark transformation, as shown in the following equation (6):

[0083] Using trigonometric identities, equation (6) can be decomposed into the following two components:

[0084] The expressions in equations (7)-(8) are divided into constants ( ) and second harmonic term ( This helps to distinguish their contributions to the output electromagnetic torque. (With) The electromagnetic torque of the PMSM of each magnetic pole ( Equations and the total magnetic flux of the synchronous reference system ( The equations are described in equations (9) to (10), while equations (7) to (8) are substituted to derive the contributions of the fundamental and second harmonic torques:

[0085] In order to design a q-axis current command component with second harmonic ( The control law compensates for and thereby eliminates the second harmonic electromagnetic torque.

[0086] in, It is the fundamental value of the q-axis current command. It is the fundamental value of the d-axis current command. This is the final q-axis current command. This is the final d-axis current command. It is the position of the electric angle. It is the second harmonic q-axis current command component. The phase shift angle, and It is the synchronous inductance of the electric motor.

[0087] Substitute equations (11) to (12) into equations (9) to (10) and solve for... ,available:

[0088] in, It is a torque command. It is the number of poles of the motor. It is the d-axis flux linkage constant. It is the q-axis flux linkage constant. It is the second harmonic d-axis flux linkage. It is the second harmonic q-axis flux linkage. It is a zero-frequency (0th harmonic) torque command. It is a second harmonic torque command. It is a fourth harmonic torque command, and These are the synchronous inductors for the d-axis and q-axis motors, respectively.

[0089] Including the fundamental values ​​of d-axis and q-axis current commands Initial fundamental current command This can be calculated using any technique, such as conventional functions employing the maximum torque per ampere method and / or the maximum torque per voltage method. Initial fundamental current command. Then it can be compared with magnetic flux. , Together, they are used to calculate the second harmonic q-axis current command. Therefore, after reordering some variables, the final q-axis motor current command is derived as follows:

[0090] By calculating the BEMF constant for each line and synchronous inductor The final q-axis current command can be calculated using equation (15) from the standard open-circuit voltage test and short-circuit current test. All required calibration data. It should be noted that the BEMF constant... Indicates the magnitude of magnetic flux in the motor And the number of magnetic pole pairs. Therefore, in the proposed method, equations (3) to (15) can be used instead of line-to-line. Derived from measurements. A -30° phase lead can be introduced from the line-to-phase vector conversion. Furthermore, any phase asymmetry ( It can also be quantified according to the BEMF test procedure and incorporated into the calibration to achieve the maximum torque ripple elimination effect.

[0091] This invention provides a novel system and method for operating a TFM (Torque Fluctuation Mitigation) with torque ripple compensation. More specifically, this invention provides an extended mathematical expression for flux linkage that takes into account the unique characteristics of TFM-type PMSMs, which result in an asymmetric distribution of flux linkage in the synchronous reference frame. This invention also provides an innovative analytical method for calculating the optimal commutation current command for TFM-type PMSMs and other motors with asymmetric flux distribution in the windings.

[0092] The system and method of this invention offer significant advantages over alternative, lookup-based methods because it can be calibrated using a simple open-circuit BEMF test, which can be performed on every part in production and as part of existing quality control testing, rather than being performed only once per design; thus providing better performance for the parts. The system and method of this invention also require less calibration process time than lookup-based methods.

[0093] Figure 19 A flowchart is shown illustrating a method 400 for operating a multiphase permanent magnet synchronous motor (PMSM) according to the principles of the invention. Method 400 has shown advantages in suppressing second-harmonic electromagnetic torque ripple in transverse flux motor (TFM) type multiphase PMSMs. Method 400 can provide similar advantageous results with other types of PMSMs, such as radial flux motor (RFM) or axial flux motor (AFM) topologies. According to some embodiments of the invention, one or more steps of method 400 can be executed by controller 70. It will be understood according to the invention that the order of operations in this method is not limited to... Figure 19 The order shown may be executed, but it can be executed in one or more different orders (if applicable) according to the present invention.

[0094] Method 400 includes determining the values ​​of one or more back electromotive force (BEMF) constants for a multiphase TFM in step 402. For example, the BEMF constant for a given TFM can be determined by testing the TFM using an open-circuit test, which can be performed as part of the manufacturing process during off-line testing. Optionally, the BEMF constant can be determined based on the standardized design of the TFM or at a later time, such as after the TFM is integrated into a larger component, for example during testing of an assembled drive unit or an assembled vehicle. One or more BEMF constants can include the BEMF constant for each phase of the multiphase TFM. Optionally, one or more BEMF constants can include the BEMF constant for all phases of a multiphase TFM, for example, in a multiphase TFM with... Figure 10 The BEMF constant of phase B, which is located at the center, in the multiphase TFM of the inner stator assembly 220 or the TFM with the outer stator assembly 320 shown.

[0095] In some embodiments, for each of a plurality of instances of a multiphase TFM, the values ​​of one or more BEMF constants may be determined on an item-by-item basis. In some embodiments, step 402 may include determining the values ​​of one or more BEMF constants by performing a BEMF open-circuit test on the multiphase TFM. In some embodiments, step 402 may include performing the determination of the values ​​of one or more BEMF constants during off-line testing during the manufacture of the multiphase TFM or a component including a multiphase TFM.

[0096] In some embodiments, each of the one or more BEMF constants can represent a corresponding phase of a multiphase TFM. For example, BEMF constants can be determined for each of the A, B, and C phases of the TFM. For reference Figure 16 As shown and described. Optionally, each of the one or more BEMF constants can represent the corresponding line-to-line wiring arrangement of a multiphase TFM. For example, a BEMF constant can be determined for each of the AB connection, BC connection, and CA connection (each representing the wiring arrangement between two phase lines 68). , as reference Figure 17 As shown and described.

[0097] Method 400 further includes determining an initial fundamental current command in step 404 to cause the multiphase TFM to generate output torque according to the torque command. For example, processor 72 may execute instructions to utilize the maximum torque per ampere and / or maximum torque per voltage method based on the torque command. To calculate the initial fundamental current command .

[0098] Method 400 further includes determining a final current command in step 406 based on the initial fundamental current command and the values ​​of one or more BEMF constants. For example, processor 72 may execute instructions to implement current command enhancer 104 to determine the final current command based on the initial fundamental current command. And based on the BEMF constant The value is used to calculate or otherwise determine the final current command. .

[0099] Method 400 further includes instructing the inverter to apply an output voltage to the multiphase TFM based on a final current command in step 408, thereby generating an output current in the winding cluster according to the final current command. For example, processor 72 may execute instructions to implement voltage command generator 106 to generate an output current based on the final current command. To calculate or otherwise determine voltage commands Step 408 may also include setting a voltage command. The voltage is transmitted from controller 70 to power converter 66, causing the inverter of power converter 66 to apply an output voltage to multiphase TFM 60. This, in turn, generates an output current in the winding set 62. .

[0100] This invention provides a method for operating a multiphase permanent magnet synchronous motor (PMSM). The method includes: determining the values ​​of one or more back electromotive force (BEMF) constants of the multiphase PMSM; determining an initial fundamental current command to cause the multiphase PMSM to generate output torque according to a torque command; determining a final current command based on the initial fundamental current command and the values ​​of one or more BEMF constants; and, based on the final current command, instructing an inverter to apply an output voltage to the multiphase PMSM, thereby causing an output current to be generated in the windings according to the final current command.

[0101] In some embodiments, each of the one or more BEMF constants represents the corresponding phase of a multiphase PMSM.

[0102] In some embodiments, each of the one or more BEMF constants represents the corresponding line-to-line wiring arrangement of a multiphase PMSM.

[0103] In some embodiments, for each of a plurality of instances of a multiphase PMSM, the value of one or more BEMF constants is determined on an instance-by-instance basis.

[0104] In some embodiments, determining the value of one or more BEMF constants includes performing a BEMF open-circuit test on a multiphase PMSM.

[0105] In some embodiments, the determination of the value of one or more BEMF constants is performed during off-line testing during the manufacturing of a multiphase PMSM or a component including a multiphase PMSM.

[0106] In some embodiments, the final current command includes a final q-axis current command, and determining the final current command further includes calculating the final q-axis current command to compensate for second harmonic electromagnetic torque pulsations caused by flux linkage differences between two or more phases of a multiphase PMSM.

[0107] In some embodiments, calculating the final q-axis current command includes calculating the final q-axis current command according to the following equation ( ):

[0108] in, It is the d-axis flux linkage constant. It is the second harmonic d-axis flux linkage. It is the q-axis component of the initial fundamental current command. It is the second harmonic q-axis flux linkage. It is the d-axis component of the initial fundamental current command. It is the synchronous inductance of the motor.

[0109] In some embodiments, the multiphase PMSM includes a plurality of stator cores, each stator core being annular, and the plurality of stator cores being axially stacked and circumferentially offset from each other.

[0110] In some embodiments, the multiphase PMSM has an inner rotor configuration in which the stator extends annularly around the rotor.

[0111] In some embodiments, the multiphase PMSM has an outer rotor configuration in which the rotor extends annularly around the stator.

[0112] The present invention also provides a motor control system. The motor control system includes: a multiphase permanent magnet synchronous motor (PMSM); an inverter configured to provide alternating current (AC) power to the multiphase PMSM; and a controller. The controller is configured to: determine an initial fundamental current command to cause the multiphase PMSM to generate output torque according to a torque command; load values ​​of a plurality of back electromotive force (BEMF) constants of the multiphase PMSM from a machine-readable storage memory; determine a final current command based on the initial fundamental current command and the values ​​of one or more BEMF constants; and instruct the inverter to apply an output voltage to the multiphase PMSM based on the final current command, thereby generating an output current in the windings according to the final current command.

[0113] In some embodiments, each of the one or more BEMF constants represents the corresponding phase of a multiphase PMSM.

[0114] In some embodiments, each of the one or more BEMF constants represents the corresponding line-to-line wiring arrangement of a multiphase PMSM.

[0115] In some embodiments, for each of a plurality of instances of a multiphase PMSM, the determination of the value of one or more BEMF constants is performed on an instance-by-instance basis.

[0116] In some embodiments, determining the value of one or more BEMF constants includes performing a BEMF open-circuit test on a multiphase PMSM.

[0117] In some embodiments, the determination of the value of one or more BEMF constants is performed during off-line testing during the manufacturing of a multiphase PMSM or a component including a multiphase PMSM.

[0118] In some embodiments, the final current command includes a final q-axis current command, and determining the final current command further includes calculating the final q-axis current command to compensate for second harmonic electromagnetic torque pulsations caused by flux linkage differences between two or more phases of a multiphase PMSM.

[0119] In some embodiments, the controller is configured to calculate the final q-axis current command according to the following equation ( ):

[0120] in, It is the d-axis flux linkage constant. It is the second harmonic d-axis flux linkage. It is the q-axis component of the initial fundamental current command. It is the second harmonic q-axis flux linkage. It is the d-axis component of the initial fundamental current command. It is the synchronous inductance of the motor.

[0121] In some embodiments, the multiphase PMSM includes a plurality of stator cores, each stator core being annular, and the plurality of stator cores being axially stacked and circumferentially offset from each other.

[0122] The foregoing discussion is intended to illustrate the principles and various embodiments of the invention. Once the foregoing disclosure is fully understood, many variations and modifications will become apparent to those skilled in the art. The following claims are intended to be construed as covering all such variations and modifications.

[0123] The term “example” as used herein is intended to serve as an example, instance, or illustration. Any aspect or design described herein as an “example” is not necessarily to be construed as preferred or superior to other aspects or designs. Rather, the term “example” is used to present concepts in a specific manner. As used herein, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless otherwise stated or explicitly stated from the context, “X comprises A or B” is intended to mean any natural inclusive arrangement. That is, if X comprises A; X comprises B; or X comprises A and B, then “X comprises A or B” is satisfied in any of the foregoing cases. Furthermore, the articles “a” and “an” used in this application and the appended claims should generally be interpreted as meaning “one or more” unless otherwise stated or explicitly stated from the context to refer to the singular form. Additionally, the use of the terms “implementation” or “an implementation” throughout does not imply the same embodiment or implementation unless described as such.

[0124] The implementations of the systems, algorithms, methods, instructions, etc., described herein can be implemented in hardware, software, or any combination thereof. Hardware may include, for example, a computer, intellectual property (IP) core, application-specific integrated circuit (ASIC), programmable logic array, optical processor, programmable logic controller, microcode, microcontroller, server, microprocessor, digital signal processor, or any other suitable circuit. In the claims, the term "processor" should be understood to include any of the foregoing hardware, whether alone or in combination. The terms "signal" and "data" are used interchangeably.

[0125] As used herein, the term "module" can include packaged functional hardware units designed for use with other components, a set of instructions executable by a controller (e.g., a processor executing software or firmware), processing circuitry configured to perform a specific function, and stand-alone hardware or software components that interface with a larger system. For example, a module can include application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), circuits, digital logic circuits, analog circuits, combinations of discrete circuits, gates, and other types of hardware or combinations thereof. In other embodiments, a module can include memory storing instructions executable by a controller to implement the module's features.

[0126] 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 of the corresponding methods, algorithms, and / or instructions described herein. Additionally or alternatively, for example, a dedicated computer / processor may be utilized, which may contain additional hardware for performing any of the methods, algorithms, or instructions described herein.

[0127] Furthermore, all or part of the embodiments of the present invention may be in the form of a computer program product, which may be obtained from, for example, a computer-usable or computer-readable medium. A computer-usable or computer-readable medium may be any device capable of, for example, tangibly containing, storing, transmitting, or transporting a program used by or in conjunction with any processor. This medium may be, for example, an electronic, magnetic, optical, electromagnetic, or semiconductor device. Other suitable media are also available.

[0128] To facilitate understanding of the invention, the embodiments, implementation methods, and aspects described above have been presented, but these descriptions are not intended to limit the invention. Rather, the invention is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which should be interpreted in the broadest possible sense to encompass all such modifications and equivalent structures permitted by law.

Claims

1. A method for operating a multiphase permanent magnet synchronous motor (PMSM), comprising: Determine the values ​​of one or more back electromotive force (BEMF) constants of the multiphase PMSM; Determine the initial fundamental current command so that the multiphase PMSM generates output torque according to the torque command; Based on the initial fundamental current command and the values ​​of the one or more BEMF constants, the final current command is determined; and Based on the final current command, the inverter is instructed to apply an output voltage to the multiphase PMSM, thereby generating an output current in the windings according to the final current command.

2. The method according to claim 1, wherein, Each of the one or more BEMF constants represents the corresponding phase of the multiphase PMSM.

3. The method according to claim 1, wherein, Each of the one or more BEMF constants represents the corresponding line-to-line wiring arrangement of the multiphase PMSM.

4. The method according to claim 1, wherein, For each of the multiple instances of the multiphase PMSM, the value of one or more BEMF constants is determined piece by piece.

5. The method according to claim 1, wherein, Determining the value of the one or more BEMF constants includes performing an open-circuit BEMF test on the multiphase PMSM.

6. The method according to claim 1, wherein, The determination of the values ​​of the one or more BEMF constants is performed during off-line testing during the manufacturing of the multiphase PMSM or a component including the multiphase PMSM.

7. The method according to claim 1, wherein, The final current command includes the final q-axis current command, and The determination of the final current command also includes calculating the final q-axis current command to compensate for the second harmonic electromagnetic torque pulsation caused by the flux linkage difference between two or more phases of the multiphase PMSM.

8. The method according to claim 7, wherein, Calculating the final q-axis current command includes calculating the final q-axis current command according to the following equation ( ): in, It is the d-axis flux linkage constant. It is the second harmonic d-axis flux linkage. It is the q-axis component of the initial fundamental current command. It is the second harmonic q-axis flux linkage. It is the d-axis component of the initial fundamental current command, and It is the synchronous inductance of the motor.

9. The method according to claim 1, wherein, The multiphase PMSM includes multiple stator cores, each stator core being annular, wherein the multiple stator cores are axially stacked and circumferentially offset from each other.

10. The method according to claim 1, wherein, The multiphase PMSM has an inner rotor configuration in which the stator extends in a ring around the rotor.

11. The method according to claim 1, wherein, The multiphase PMSM has an outer rotor configuration, wherein the rotor extends in a ring around the stator.

12. A motor control system, comprising: Multiphase permanent magnet synchronous motor (PMSM); The inverter is configured to provide AC power to the multiphase PMSM; as well as The controller is configured as follows: Determine the initial fundamental current command so that the multiphase PMSM generates output torque according to the torque command; The values ​​of the multiple back electromotive force (BEMF) constants of the multiphase PMSM are loaded from the machine-readable storage memory; The final current command is determined based on the initial fundamental current command and the values ​​of one or more BEMF constants; and Based on the final current command, the inverter is instructed to apply an output voltage to the multiphase PMSM, thereby generating an output current in the windings according to the final current command.

13. The motor control system according to claim 12, wherein, Each of the one or more BEMF constants represents the corresponding phase of the multiphase PMSM.

14. The motor control system according to claim 12, wherein, Each of the one or more BEMF constants represents the corresponding line-to-line wiring arrangement of the multiphase PMSM.

15. The motor control system according to claim 12, wherein, For each of the multiple instances of the multiphase PMSM, the value of one or more BEMF constants is determined piece by piece.

16. The motor control system according to claim 12, wherein, Determining the value of the one or more BEMF constants includes performing an open-circuit BEMF test on the multiphase PMSM.

17. The motor control system according to claim 12, wherein, The determination of the values ​​of the one or more BEMF constants is performed during off-line testing during the manufacturing of the multiphase PMSM or a component including the multiphase PMSM.

18. The motor control system according to claim 12, wherein, The final current command includes a final q-axis current command, and determining the final current command further includes calculating the final q-axis current command to compensate for second harmonic electromagnetic torque pulsations caused by flux linkage differences between two or more phases of the multiphase PMSM.

19. The motor control system according to claim 18, wherein, The controller is configured to calculate the final q-axis current command according to the following equation ( ): in, It is the d-axis flux linkage constant. It is the second harmonic d-axis flux linkage. It is the q-axis component of the initial fundamental current command. It is the second harmonic q-axis flux linkage. It is the d-axis component of the initial fundamental current command, and It is the synchronous inductance of the motor.

20. The motor control system according to claim 12, wherein, The multiphase PMSM includes multiple stator cores, each stator core being annular, wherein the multiple stator cores are axially stacked and circumferentially offset from each other.

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