Asymmetric six-phase wheel hub axial flux motor, control strategy and reducer architecture

Abstract

The application discloses an asymmetric six-phase wheel hub axial flux motor, a control strategy and a speed reducer architecture. The asymmetric six-phase wheel hub axial flux motor adopts a single-stator single-rotor topology. The single stator is composed of two sets of star-type connection windings. The two sets of windings are a spatial double-Y shift 30-degree asymmetric topology, and the midpoints of the two sets of windings are isolated from each other. The first set of windings is Um-Vm-Wm, the second set of windings is Us-Vs-Ws, the electrical angle phase difference between the two sets of adjacent windings is 30 degrees, the two sets of windings are matched with two-level controllers, and the six-phase motor coordinate system is mapped onto three orthogonal coordinate spaces. The asymmetric six-phase wheel hub axial flux motor, the control strategy and the speed reducer architecture disclosed by the application overcome the problems in the prior art that the non-uniform air gap magnetic field of the axial flux motor leads to torque pulsation, the fault tolerance of the traditional three-phase motor is poor, and the powertrain system is difficult to balance the low-speed climbing degree and the highest vehicle speed.

Description

Technical Field

[0001] This invention belongs to the field of new energy vehicle power system technology, specifically involving an asymmetric six-phase hub axial flux motor, control strategy, and two-speed coaxial reducer architecture. Background Technology

[0002] Currently, the powertrain motors used in new energy vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs / PHEVs), range-extended electric vehicles (REEVs), and fuel cell electric vehicles (FCEVs), mostly employ three-phase permanent magnet synchronous motors (IPMSMs). IPMSMs offer advantages such as small size, lightweight design, and high efficiency, leading to their widespread application. Permanent magnet synchronous motors can be categorized into two types based on their flux path: radial flux permanent magnet synchronous motors (RFPMSMs) and axial flux permanent magnet synchronous motors (AFPMSMs).

[0003] Radial flux permanent magnet motors (AFPMs) have a ring-shaped stator and rotor structure with radially distributed air gap flux, resulting in poor heat dissipation and low core magnetic field utilization. Axial flux permanent magnet motors differ significantly from traditional radial flux permanent magnet motors in structure. Their stator and rotor are arranged in parallel, with axially distributed air gap flux, offering advantages such as small size, light weight, high torque density, and high efficiency. Based on the stator and rotor arrangement, typical AFPM topologies can generally be classified into four types: single-stator single-rotor structure, double-stator single-rotor structure, double-rotor single-stator structure, and multi-disc structure.

[0004] However, AFPM has its drawbacks: Radial flux motors have a cylindrical air gap, with the rotor rotating inside the stator. The air gap length remains constant radially along the motor's axial length, meaning the air gap magnetic field is uniformly distributed circumferentially. In contrast, axial flux motors have a planar air gap, with the rotor and stator discs placed parallel to each other. The rotor discs rotate, and their linear velocities differ at different radii: the outer edge has a larger radius and higher linear velocity, resulting in faster magnet sweep across the stator; the inner edge has a smaller radius and lower linear velocity, resulting in slower magnet sweep across the stator. This difference in linear velocity directly leads to an uneven radial distribution of the air gap magnetic field, with a higher flux change rate and stronger induced electromotive force at the outer edge, and a weaker magnetic field at the inner edge. This increases eddy current and hysteresis losses in the stator core, making it difficult to further improve efficiency at high speeds. It also causes torque pulsation, resulting in motor vibration and noise, affecting driving comfort.

[0005] In addition, traditional three-phase motors can only stop when the drive motor is disconnected, which has poor fault tolerance and cannot guarantee the functional safety of the whole vehicle; and the existing powertrain system is still insufficient in improving the low-speed climbing ability and maximum speed of the whole vehicle. Summary of the Invention

[0006] The main objective of this invention is to provide an asymmetric six-phase hub axial flux motor, control strategy, and reducer architecture, overcoming the problems of torque pulsation caused by uneven air gap magnetic field in existing axial flux motors, poor fault tolerance of traditional three-phase motors, and difficulty in powertrain systems to balance low-speed climbing ability and maximum vehicle speed.

[0007] To achieve the above objectives, this invention provides an asymmetric six-phase hub axial flux motor, employing a single stator and single rotor topology, wherein: The single stator consists of two sets of star-connected windings. The two sets of windings are spatial double Y-shifted 30-degree asymmetric topology, and the midpoints of the two sets of windings are isolated from each other. The first set of windings is Um-Vm-Wm, and the second set of windings is Us-Vs-Ws. The electrical angular phase difference between the two sets of adjacent windings is 30 degrees. The two sets of windings are matched with a two-level controller (the controller has 2...). 6 =64 switching states), the six-phase motor coordinate system is mapped to three orthogonal coordinate spaces: α-β space, xy space, and zero-sequence n1-n2 space; the coordinate system corresponding to α-β space is used to control the fundamental current and torque output; the coordinate system corresponding to xy space is used to control the current harmonics; the coordinate space corresponding to zero-sequence n1-n2 space is the zero-sequence space and does not participate in energy conversion; (α-β space, xy space, and zero-sequence n1-n2 space belong to the stationary coordinate system; in order to solve the complex, time-varying, and coupled AC control problems under the stationary coordinate system, it can be transformed into DC control under the easier rotating coordinate system) The α-β coordinate system is transformed from the stationary coordinate system to the dq rotating coordinate system, and the AC quantity is transformed into the DC quantity to achieve decoupling control, while the xy space and zero-sequence n1-n2 space are processed in the stationary coordinate system.

[0008] To achieve the above objectives, this invention provides a control strategy for an asymmetric six-phase hub axial flux motor, specifically implemented through the following steps: Step S1: Set the wheel hub drive torque (the wheel hub drive torque command is issued by the vehicle controller VCU, and the asymmetric six-phase wheel hub axial flux motor is converted into command current to control the motor in order to meet the command torque requirement). The electromagnetic torque of the asymmetric six-phase wheel hub axial flux motor is calculated by the following formula: ; in, The number of rotor pole pairs, The magnetic flux of the air gap magnetic field generated by the rotor magnet (which is the magnetic field generated by the magnet itself). For the d-axis motor inductance, For the q-axis motor inductance, , These represent the commanded d-axis current and q-axis current in the dq coordinate system, respectively. Step S2: Calculate the six actual currents in the dq coordinate system, xy coordinate system, and zero-sequence n1-n2 coordinate system. The six-phase winding phase currents Ium, Ivm, Iwm and Ius, Ivs, Iws in the single stator of the asymmetric six-phase axial flux permanent magnet motor are transformed into six currents in the dq, xy, and n1-n2 coordinate systems by the following formula: ; The angle of the motor rotor; Ium, Ivm, and Iwm are the three-phase currents of the first winding; Ius, Ivs, and Iws are the three-phase currents of the second set of windings; and Let be the d-axis and q-axis currents in the dq rotating coordinate system; and For the x-axis and y-axis currents in the xy coordinate system; and For the n1-n2 axis currents in the zero-sequence n1-n2 coordinate system; Step S3: Calculate the d-axis and q-axis voltages in the dq rotating coordinate system. The voltage equations for the asymmetric six-phase axial flux permanent magnet motor in the dq rotating coordinate system are as follows: ; in, , These are the actual currents along the d-axis and q-axis, and the commanded currents in step S1. , PI feedback control is obtained; The magnetic flux of the air gap magnetic field generated by the rotor magnet; This refers to the voltage of the d-axis motor. This refers to the voltage of the q-axis motor. For the d-axis motor inductance, The inductance of the q-axis motor; This refers to the rotor magnetic pole deviation angle of the motor. The phase resistance of the motor; The electrical angle of the motor rotor; Step S4: The voltage equation of the asymmetric six-phase axial flux permanent magnet motor based on the xy coordinate system is: ; in, The motor voltage along the x-axis in the xy coordinate space; The voltage of the motor along the y-axis in the xy coordinate space; The motor current along the x-axis in the xy coordinate space; The motor current along the y-axis in the xy coordinate space; Leakage inductance; The xy coordinate system is used to control current harmonics; the current command value in the xy coordinate space... , Set to 0, via instruction value , and actual current , The PI feedback control achieves zero actual current harmonic content in the asymmetric six-phase axial flux permanent magnet motor. Step S5: Setting the current command value in the xy coordinate space. ; Step S6: Four-vector voltage SVPWM (Space Vector Pulse Width Modulation) control. The two-level controller has 64 switching states. The vectors corresponding to the 64 switching states in the α-β and xy spaces are represented by the following formula: ; ; in, and Let S represent the voltage composite vectors corresponding to the α-β and xy spaces, respectively, and let S represent the switching states of all bridge arms. This represents the switching state of the first set of windings. This represents the switching state of the second set of windings. 1 indicates the upper bridge arm is on and the lower bridge arm is off, and 0 indicates the upper bridge arm is off and the lower bridge arm is on. The vector sequence number uses binary numbers to represent the switching state. , Convert to octal representation (e.g.: =1, =1, =0, =1, =0, =0; the corresponding binary number is 110100, which is 64 in octal. To improve voltage utilization, a 360-degree electrical cycle is divided into 12 sectors, Section 1 to Section 12, each with a 30-degree control area. Within each sector, the synthesized voltage vector in the α-β and xy coordinate systems is... and Voltage synthesis is performed using four maximum voltage vectors; In sector 1 (taking sector 1 as an example). , , , The four maximum vectors are synthesized, and according to the volt-second balance principle, the following is obtained: ; ; The voltage composite value in the α-β coordinate system. The voltage composite value in the x-y coordinate system is obtained by transforming the dq coordinate system to the α-β coordinate system. The time values ​​of each voltage vector in the α-β and xy coordinate systems within one PWM control cycle Ts are expressed by the following formula: ; The operating times T1, T2, T3, and T4 in the above formula represent the duty cycles of the six power devices within one PWM cycle, ultimately ensuring that the actual torque of the asymmetric six-phase hub axial flux motor is equal to the command torque issued by the VCU.

[0009] To achieve the above objectives, the present invention also provides a reducer architecture equipped with an asymmetric six-phase hub axial flux motor, which is used in conjunction with the asymmetric six-phase hub axial flux motor. The reducer architecture includes a two-speed coaxial planetary gear set and wet friction brake pad mechanisms B1 and B2. The output end of the asymmetric six-phase hub axial flux motor is connected to the input end of the two-speed coaxial planetary gear set. Through the planet carrier of the two-speed planetary gear set mechanism, power is output to the wheels (the two-speed architecture can significantly improve low-speed climbing ability and the maximum speed of the vehicle).

[0010] As a further preferred technical solution to the above technical solution, when in 1st gear, the wet friction brake pad mechanism B2 is disengaged, and the wet friction brake pad mechanism B1 is engaged (equivalent to the planetary gear ring speed nR=0); the motor TM receives power through the coaxial planetary gear sun gear S1, then transmits power through the planetary gear P1, and finally the power is directly output to the wheels by the planet carrier C for driving; the 1st gear reduction ratio is calculated by the following formula: ; in, The reduction ratio for the first gear of the planetary gear set is... This refers to the number of teeth on the planetary gear ring. Let nR be the number of teeth on the first sun gear of the planetary gear set, at which point the rotational speed of the planetary gear set ring gear is nR = 0.

[0011] As a further preferred technical solution to the above technical solution, when in 2nd gear, the wet friction brake pad mechanism B1 is disengaged, and the wet friction brake pad mechanism B2 is engaged; the motor TM receives power through the coaxial planetary gear sun gear S1, then through planet gears P1 and P2, and finally the power is directly output to the wheels by the planet carrier C for driving; the 2nd gear reduction ratio is calculated by the following formula: ; in, It is a planetary gear set with a 2nd gear reduction ratio. The number of teeth on the first solar wheel of the planets. Let nS2 be the number of teeth on the second sun gear of the planetary array. At this time, the rotational speed of the second sun gear of the planetary array is nS2=0.

[0012] The beneficial effects of this invention are as follows: 1. Within the limited space of the wheel hub, the power density of the drive motor is further increased by inventing an asymmetric six-phase axial flux permanent magnet motor (ASPAFPMSM) electric drive system and control method. At the same time, the fault tolerance of the motor is improved. In the event of a drive motor disconnection, a traditional three-phase motor can only stop, while a six-phase motor can reduce its output power and continue to run, greatly improving the functional safety of the entire vehicle.

[0013] 2. The new control algorithm for the asymmetric six-phase axial flux permanent magnet motor can effectively suppress torque pulsation caused by the non-uniformity of the air gap magnetic field by directly controlling the harmonic current.

[0014] 3. The asymmetric six-phase axial flux permanent magnet motor is deeply integrated with the two gearbox, further improving the vehicle's low-speed climbing ability and maximum speed.

[0015] 3. Based on the asymmetric six-phase axial flux permanent magnet motor ASPFPMSM and a two-speed coaxial planetary gear reducer, it can be installed in the rear-wheel drive and two-wheel drive wheel hubs of new energy vehicles, including electric vehicles (EVs), hybrid vehicles (HEVs / PHEVs), range-extended electric vehicles (REEVs), and fuel cell vehicles (FCEVs), as well as in the drive wheel hubs of two-wheeled motorcycles and three-wheeled vehicles, with a wide range of applications. Attached Figure Description

[0016] Figure 1 This is a block diagram of the electric drive system of the present invention equipped with a dual Y-shift 30-degree asymmetric six-phase axial flux permanent magnet motor ASPAFPMSM.

[0017] Figure 2This is a control block diagram of the electric drive system of the ASPAFPMSM dual Y-shift 30-degree asymmetric six-phase axial flux permanent magnet motor of the present invention.

[0018] Figure 3 This is a diagram of the two-speed hub power drive system based on an asymmetric six-phase hub axial flux motor and a two-speed coaxial planetary gear set, according to the present invention. Detailed Implementation

[0019] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0020] In the preferred embodiments of the present invention, those skilled in the art should note that AFPM and the like involved in the present invention can be considered as prior art.

[0021] Preferred embodiment.

[0022] like Figure 1-3 As shown, this invention discloses an asymmetric six-phase hub axial flux motor, employing a single stator and single rotor topology, wherein: The single stator consists of two sets of star-connected windings. The two sets of windings are spatial double Y-shifted 30-degree asymmetric topology, and the midpoints of the two sets of windings are isolated from each other. The first set of windings is Um-Vm-Wm, and the second set of windings is Us-Vs-Ws. The electrical angular phase difference between the two sets of adjacent windings is 30 degrees. The two sets of windings are matched with a two-level controller (the controller has 2...). 6 =64 switching states), the six-phase motor coordinate system is mapped to three orthogonal coordinate spaces: α-β space, xy space, and zero-sequence n1-n2 space; the coordinate system corresponding to α-β space is used to control the fundamental current and torque output; the coordinate system corresponding to xy space is used to control the current harmonics; the coordinate space corresponding to zero-sequence n1-n2 space is the zero-sequence space and does not participate in energy conversion; (α-β space, xy space, and zero-sequence n1-n2 space belong to the stationary coordinate system; in order to solve the complex, time-varying, and coupled AC control problems under the stationary coordinate system, it can be transformed into DC control under the easier rotating coordinate system) The α-β coordinate system is transformed from the stationary coordinate system to the dq rotating coordinate system, and the AC quantity is transformed into the DC quantity to achieve decoupling control, while the xy space and zero-sequence n1-n2 space are processed in the stationary coordinate system.

[0023] like Figure 1As shown, the controller uses a six-phase two-level controller. The stator winding consists of two sets of star-connected three-phase symmetrical windings, with the midpoints of the two sets isolated from each other. The first set of windings is the main winding Um-Vm-Wm; the second set is the auxiliary winding Us-Vs-Ws. These are connected to two three-phase PWM controllers, the left being the main controller and the right being the auxiliary controller. Both controllers are powered by the vehicle battery. The main motor controller's stator winding control is composed of six IGBTs or MOSFETs and six freewheeling diodes (FWD) power modules, thin-film capacitors, and control circuitry, performing real-time control of the stator three-phase current. The auxiliary controller has the same structure, with a total of 12 power modules, requiring 12 PWM signals for drive control. The three-phase currents Ium, Ivm, and Iwm of the main controller and the three-phase currents Ius, Ivs, and Iws of the auxiliary controller are obtained from current sensors. The rotor angle signal is obtained from a resolver. Vdc is the vehicle battery voltage. The electrical angular phase difference between two sets of adjacent windings is 30 degrees, hence the name "double Y-shift 30-degree six-phase axial flux permanent magnet motor". The two-level controller has two... 6 =64 switch states.

[0024] This invention also discloses a control strategy for an asymmetric six-phase hub axial flux motor, applied to an asymmetric six-phase hub axial flux motor, specifically implemented through the following steps: Step S1: Set the wheel hub drive torque (the wheel hub drive torque command is issued by the vehicle controller VCU, and the asymmetric six-phase wheel hub axial flux motor is converted into command current to control the motor in order to meet the command torque requirement). The electromagnetic torque of the asymmetric six-phase wheel hub axial flux motor is calculated by the following formula: ; in, The number of rotor pole pairs, The magnetic flux of the air gap magnetic field generated by the rotor magnet (which is the magnetic field generated by the magnet itself). For the d-axis motor inductance, For the q-axis motor inductance, , These represent the commanded d-axis current and q-axis current in the dq coordinate system, respectively. Step S2: Calculate the six actual currents in the dq coordinate system, xy coordinate system, and zero-sequence n1-n2 coordinate system. The six-phase winding phase currents Ium, Ivm, Iwm and Ius, Ivs, Iws in the single stator of the asymmetric six-phase axial flux permanent magnet motor are transformed into six currents in the dq, xy, and n1-n2 coordinate systems by the following formula: ; The angle of the motor rotor; Ium, Ivm, and Iwm are the three-phase currents of the first winding; Ius, Ivs, and Iws are the three-phase currents of the second set of windings; and Let be the d-axis and q-axis currents in the dq rotating coordinate system; and For the x-axis and y-axis currents in the xy coordinate system; and For the n1-n2 axis currents in the zero-sequence n1-n2 coordinate system; Step S3: Calculate the d-axis and q-axis voltages in the dq rotating coordinate system. The voltage equations for the asymmetric six-phase axial flux permanent magnet motor in the dq rotating coordinate system are as follows: ; in, , These are the actual currents along the d-axis and q-axis, and the commanded currents in step S1. , PI feedback control is obtained; The magnetic flux of the air gap magnetic field generated by the rotor magnet; This refers to the voltage of the d-axis motor. This refers to the voltage of the q-axis motor. For the d-axis motor inductance, The inductance of the q-axis motor; This is the rotor pole deviation angle of the motor. ; The phase resistance of the motor; The electrical angle of the motor rotor; Step S4: The voltage equation of the asymmetric six-phase axial flux permanent magnet motor based on the xy coordinate system is: ; in, The motor voltage along the x-axis in the xy coordinate space; The voltage of the motor along the y-axis in the xy coordinate space; The motor current along the x-axis in the xy coordinate space; The motor current along the y-axis in the xy coordinate space; Leakage inductance; The xy coordinate system is used to control current harmonics; the current command value in the xy coordinate space... , Set to 0, via instruction value , and actual current , The PI feedback control achieves zero harmonic content in the actual current of the asymmetric six-phase axial flux permanent magnet motor, such as... Figure 2 As shown, the six-phase asymmetrical winding consists of two sets of three-phase windings. The dq rotating coordinate system is used to control the fundamental current and torque output; the xy coordinate system is used to control the current harmonics. Spatial four-vector control is employed to minimize harmonic content and expand the maximum speed and output power.

[0025] Step S5: Setting the current command value in the xy coordinate space. ; Step S6: Four-vector voltage SVPWM (Space Vector Pulse Width Modulation) control. The two-level controller has 64 switching states. The vectors corresponding to the 64 switching states in the α-β and xy spaces are represented by the following formula: ; ; in, and Let S represent the voltage composite vectors corresponding to the α-β and xy spaces, respectively, and let S represent the switching states of all bridge arms. This represents the switching state of the first set of windings. This represents the switching state of the second set of windings. 1 indicates the upper bridge arm is on and the lower bridge arm is off, and 0 indicates the upper bridge arm is off and the lower bridge arm is on. The vector sequence number uses binary numbers to represent the switching state. , Convert to octal representation (e.g.: =1, =1, =0, =1, =0, =0; the corresponding binary number is 110100, which is 64 in octal. To improve voltage utilization, a 360-degree electrical cycle is divided into 12 sectors, Section 1 to Section 12, each with a 30-degree control area. Within each sector, the synthesized voltage vector in the α-β and xy coordinate systems is... and Voltage synthesis is performed using four maximum voltage vectors; In sector 1 (taking sector 1 as an example). , , , The four maximum vectors are synthesized, and according to the volt-second balance principle, the following is obtained: ; ; The voltage composite value in the α-β coordinate system. The voltage composite value in the x-y coordinate system is obtained by transforming the dq coordinate system to the α-β coordinate system. The time values ​​of each voltage vector in the α-β and xy coordinate systems within one PWM control cycle Ts are expressed by the following formula: ; The operating times T1, T2, T3, and T4 in the above formula represent the duty cycles of the six power devices within one PWM cycle, ultimately ensuring that the actual torque of the asymmetric six-phase hub axial flux motor is equal to the command torque issued by the VCU.

[0026] like Figure 3 As shown, the present invention also discloses a reducer architecture equipped with an asymmetric six-phase hub axial flux motor, which is used in conjunction with the asymmetric six-phase hub axial flux motor. The reducer architecture includes a two-speed coaxial planetary gear set and wet friction brake pad mechanisms B1 and B2. The output end of the asymmetric six-phase hub axial flux motor is connected to the input end of the two-speed coaxial planetary gear set. Through the planet carrier of the two-speed planetary gear set mechanism, the power is output to the wheels (the two-speed architecture can greatly improve the low-speed climbing ability and the maximum speed of the vehicle).

[0027] Specifically, when in first gear, wet friction brake pad mechanism B2 is disengaged, and wet friction brake pad mechanism B1 is engaged (equivalent to planetary gear ring speed nR=0); the motor TM receives power through the coaxial planetary gear sun gear S1, then transmits power through planetary gears P1, and finally the power is directly output to the wheels by the planet carrier C for driving; the first gear reduction ratio is calculated using the following formula: ; in, The reduction ratio for the first gear of the planetary gear set is... This refers to the number of teeth on the planetary gear ring. Let nR be the number of teeth on the first sun gear of the planetary gear set, at which point the rotational speed of the planetary gear set ring gear is nR = 0.

[0028] More specifically, when in 2nd gear, wet friction brake pad mechanism B1 is disengaged, and wet friction brake pad mechanism B2 is engaged; the motor TM receives power through the coaxial planetary gear set sun gear S1, then through planet gears P1 and P2, and finally the power is directly output to the wheels by the planet carrier C for driving; the 2nd gear reduction ratio is calculated using the following formula: ; in, It is a planetary gear set with a 2nd gear reduction ratio. The number of teeth on the first solar wheel of the planets. Let nS2 be the number of teeth on the second sun gear of the planetary array. At this time, the rotational speed of the second sun gear of the planetary array is nS2=0.

[0029] It is worth mentioning that the technical features such as AFPM involved in this patent application should be regarded as prior art. The specific structure, working principle and possible control methods and spatial arrangement of these technical features can be adopted by conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0030] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. An asymmetric six-phase hub axial flux motor, characterized in that, It adopts a single-stator single-rotor permanent magnet topology that is adapted to be installed inside the wheel hub. The rotor only has permanent magnets embedded in it and no rotor excitation winding. The single stator consists of two sets of star-connected windings. The two sets of windings are spatial double Y-shifted 30-degree asymmetric topology. The midpoints of the two sets of windings are isolated from each other. The first set of windings is Um-Vm-Wm, and the second set of windings is Us-Vs-Wm. The electrical phase difference between the two sets of adjacent windings is 30 degrees. Two sets of star windings are respectively matched with two fully electrically isolated six-phase two-level independent drive branches, corresponding to the INV_M main inverter and the INV_S auxiliary inverter, respectively. A total of 12 power devices are powered by two independent buses. The six-phase motor coordinate system is mapped to three orthogonal coordinate spaces: α-β, xy, and zero-sequence n1-n2. The α-β coordinate system is converted into the dq rotating coordinate system to complete the fundamental torque decoupling control. The xy and n1-n2 spaces remain as stationary coordinate systems to handle harmonics and zero-sequence components. The motor stator disk is rigidly limited and fitted to the hub housing. Through the axial plane air gap and the double Y-shift 30-degree winding structure, combined with the six-phase coordinate transformation matrix adapted to the axial flux radial gradient air gap working condition, the air gap harmonics and torque pulsation caused by the difference in linear velocity between the inner and outer diameters of the axial flux motor are suppressed. The working process of the asymmetric six-phase hub axial flux motor is as follows: Step S1: Receive the wheel hub drive torque command issued by the vehicle VCU, and calculate the target electromagnetic torque based on the model containing only a single magnetic flux component of permanent magnets and eliminating the excitation superposition term; Step S2: Using a six-phase coordinate transformation matrix adapted to the radial gradient air gap of the axial flux motor and targeting the harmonics of the inner and outer diameter linear velocity difference, the six-phase winding phase currents Ium, Ivm, Iwm and Ius, Ivs, Iws are transformed into six currents in the dq, xy, n1-n2 coordinate system. Step S3: Construct the dq axis voltage equations adapted to a pure permanent magnet axial flux motor without excitation flux superposition terms, and perform PI closed-loop control based on the command current and actual current of the d and q axes; Step S4: Construct the voltage equation of the xy coordinate system, bind the xy zero current PI closed loop with the axial gradient air gap unique subharmonic suppression, fix the xy space current command value to 0, and use the PI closed loop control of the command value and the actual current to specifically cancel the gradient harmonics generated by the difference between the inner and outer diameters of the axial flux motor. Step S5: Setting the current command value in the xy coordinate space; Step S6: A four-vector voltage SVPWM control is adopted to adapt to the full speed range of the hub motor and to establish dynamic torque feedforward matching with the two-speed coaxial planetary reducer; the two-level controller has a total of 64 switching states.

2. A control strategy for an asymmetric six-phase hub axial flux motor, characterized in that, Applied to the asymmetric six-phase hub axial flux motor of claim 1, the overall control process does not include rotor excitation current and excitation flux adjustment calculation modules. The specific implementation includes the following steps: The formula for calculating the electromagnetic torque in step S1 is: ； in, The number of rotor pole pairs, This refers to the magnetic flux of the air gap magnetic field generated by the rotor magnets, without any additional magnetic flux component from the rotor excitation winding. For the d-axis motor inductance, For the q-axis motor inductance, , These represent the commanded d-axis current and q-axis current in the dq coordinate system, respectively. In step S2, the phase currents Ium, Ivm, Iwm and Ius, Ivs, Iws of the six-phase winding are transformed into six currents in the dq, xy, n1-n2 coordinate system using the following formula: ； The angle of the motor rotor; Ium, Ivm, and Iwm are the three-phase currents of the first winding; Ius, Ivs, and Iws are the three-phase currents of the second set of windings; and Let be the d-axis and q-axis currents in the dq rotating coordinate system; and For the x-axis and y-axis currents in the xy coordinate system; and For the n1-n2 axis currents in the zero-sequence n1-n2 coordinate system; The equation in step S3 is: ； in, , These are the actual currents of the d-axis and q-axis, and the commanded currents in step S1. , PI feedback control is obtained; The magnetic flux of the air gap magnetic field generated by the rotor magnet; This refers to the voltage of the d-axis motor. This refers to the voltage of the q-axis motor. For the d-axis motor inductance, The inductance of the q-axis motor; This refers to the rotor magnetic pole deviation angle of the motor. The phase resistance of the motor; The electrical angle of the motor rotor; The xy voltage equation in step S4 is as follows: ； in, The motor voltage along the x-axis in the xy coordinate space; The voltage of the motor along the y-axis in the xy coordinate space; The motor current along the x-axis in the xy coordinate space; The motor current along the y-axis in the xy coordinate space; Leakage inductance; The xy coordinate system is used to control current harmonics; the current command value in the xy coordinate space... , Set to 0, via instruction value , and actual current , The PI feedback control achieves zero actual current harmonic content in the asymmetric six-phase axial flux permanent magnet motor. The current command value is set to the value in step S5. ; Step S6: The vectors corresponding to the 64 switching states in the α-β and xy spaces are represented by the following formula: ； ； in, and Let S represent the voltage composite vectors corresponding to the α-β and xy spaces, respectively, and let S represent the switching states of all bridge arms. This represents the switching state of the first set of windings. This represents the switching state of the second set of windings. 1 indicates the upper bridge arm is on and the lower bridge arm is off, and 0 indicates the upper bridge arm is off and the lower bridge arm is on. The vector sequence number uses binary numbers to represent the switching state. , Convert to octal representation; Within a 360-degree electrical cycle, the control area is divided into 12 sectors, Section 1 to Section 12, each with a 30-degree control zone. In each sector, the synthesized voltage vector in the α-β and xy coordinate systems is... and Voltage synthesis is performed using four maximum voltage vectors; In sector 1, , , , The four maximum vectors are synthesized, and according to the volt-second balance principle, the following is obtained: ； ； The voltage composite value in the α-β coordinate system. The voltage composite value in the x-y coordinate system is obtained by transforming the dq coordinate system to the α-β coordinate system. The time values ​​of each voltage vector in the α-β and xy coordinate systems within one PWM control cycle Ts are expressed by the following formula: ； The operating times T1, T2, T3, and T4 in the above formula represent the duty cycles of the six power devices within one PWM cycle, ultimately ensuring that the actual torque of the asymmetric six-phase hub axial flux motor is equal to the command torque issued by the VCU.

3. A reducer architecture equipped with an asymmetric six-phase hub axial flux motor, characterized in that, When used in conjunction with the asymmetric six-phase hub axial flux motor as described in claim 1, the reducer architecture includes a two-speed coaxial planetary gear set and wet friction brake pad mechanisms B1 and B2; the output end of the asymmetric six-phase hub axial flux motor is connected to the input end of the two-speed coaxial planetary gear set, and the power is output to the wheel through the planet carrier of the two-speed planetary gear set mechanism. When in 1st gear, wet friction brake pad mechanism B2 is disengaged and wet friction brake pad mechanism B1 is engaged. The motor TM receives power through the coaxial planetary set sun gear S1, then transmits power through the planetary gear P1, and finally the power is directly output to the wheels by the planetary carrier C to drive them. The reduction ratio of first gear is calculated using the following formula: ； in, The reduction ratio for the first gear of the planetary gear set is... This refers to the number of teeth on the planetary gear ring. This is the number of teeth on the first sun gear of the planetary gear set, at which point the rotational speed of the planetary gear set ring gear is nR=0; When in 2nd gear, wet friction brake pad mechanism B1 is disengaged, and wet friction brake pad mechanism B2 is engaged; the motor TM receives power through the coaxial planetary gear set sun gear S1, then through planet gears P1 and P2, and finally the power is directly output to the wheels via the planet carrier C for driving; the 2nd gear reduction ratio is calculated using the following formula: ； in, It is a planetary gear set with a 2nd gear reduction ratio. The number of teeth on the first solar wheel of the planets. Let nS2 be the number of teeth on the second sun gear of the planetary array. At this time, the rotational speed of the second sun gear of the planetary array is nS2=0.

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