GEARLESS WHEEL MOTOR DRIVE SYSTEM

• US 20090295316A1
• Filed: 08/14/2009
• Published: 12/03/2009
• Est. Priority Date: 07/29/2004
• Status: Abandoned Application

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: PATEL, NITINKUMAR R., HITI, SILVA, RAHMAN, KHWAJA M.
• Application Number:
  US12/541,409
• Publication Number:
  US 20090295316A1
• Time in Patent Office: Days
• US Class Current: 318/400.02
• CPC Class Codes: B60K 2007/0038 the motor moving together with the wheel axle
• CPC Class Codes: B60K 2007/0092 the motor axle being coaxial to the wheel axle
• CPC Class Codes: B60K 6/26 characterised by the motors or the generators
• CPC Class Codes: B60K 7/0007 the motor being electric
• CPC Class Codes: B60L 1/02 to electric heating circuits
• CPC Class Codes: B60L 15/025 using field orientation; Vector control; Direct Torque Control [DTC]
• CPC Class Codes: B60L 15/06 using substantially sinusoidal ac
• CPC Class Codes: B60L 15/08 using pulses
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2210/40 DC to AC converters
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 2220/16 DC brushless machines
• CPC Class Codes: B60L 2220/44 Wheel Hub motors, i.e. integrated in the wheel hub
• CPC Class Codes: B60L 2220/50 Structural details of electrical machines
• CPC Class Codes: B60L 2240/36 Temperature of vehicle components or parts
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/425 Temperature
• CPC Class Codes: B60L 2240/427 Voltage
• CPC Class Codes: B60L 2240/429 : Current
• CPC Class Codes: B60L 2240/526 : Operating parameters
• CPC Class Codes: B60L 2240/527 : Voltage
• CPC Class Codes: B60L 2240/529 : Current
• CPC Class Codes: B60L 2240/547 : Voltage
• CPC Class Codes: B60L 2250/26 : by pedal actuation
• CPC Class Codes: B60L 2270/145 : Structure borne vibrations
• CPC Class Codes: B60L 3/003 : relating to inverters
• CPC Class Codes: B60L 3/0046 : relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/0061 : relating to electrical machines
• CPC Class Codes: B60L 50/51 : characterised by AC-motors
• CPC Class Codes: B60L 58/30 : for monitoring or controlling fuel cells
• CPC Class Codes: B60L 7/14 : for vehicles propelled by ac motors
• CPC Class Codes: H02K 1/2798 : where both axial sides of the stator face a rotor
• CPC Class Codes: H02K 21/24 : with magnets axially facing the armatures, e.g. hub-type cycle dynamos
• CPC Class Codes: H02K 29/03 : with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
• CPC Class Codes: H02K 7/14 : Structural association with mechanical loads, e.g. with hand-held machine tools or fans with fan or impeller for cooling the machine H02K9/06
• CPC Class Codes: H02P 21/06 : Rotor flux based control involving the use of rotor position or rotor speed sensors
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y02T 90/40 : Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

Methods and apparatus are provided for an electric vehicle embodying an axial flux traction motor directly coupled to a wheel thereof. The traction motor comprises a stator having coils for producing a magnetic field, an annular rotor magnetically coupled to the stator and mechanically to an output shaft. Permanent magnets of alternating polarity are mounted on the annular rotor. Magnetic shunts bridge a portion of the stator slots above the coils. The magnets are arranged in groups with group-to-group spacing exceeding magnet-to-magnet spacing. Adjacent edges of the magnets diverge. The method comprises, looking up d- and q-axis currents to provide the requested torque and motor speed for the available DC voltage, combining at least one of the d- and q-axis currents with a field weakening correction term, converting the result from synchronous to stationary frame and operating an inverter therewith to provide current to the coils of the motor.

Claims

1. A method of operating a permanent magnet axial flux motor, comprising:

receiving a requested torque and motor speed;

determining commanded d- and q-axis currents corresponding to the requested torque and motor speed;

combining at least one of the commanded d-axis current or the commanded q-axis current with a field weakening correction to provide a corrected output;

converting the corrected output to a stationary current frame of reference output; and

operating an inverter based on the stationary frame of reference output to provide current to coils of the motor, thereby causing the motor to operate substantially at the requested torque and motor speed.

2. The method of claim 1, wherein the combining step comprises:

for M*_index<

M_low, omitting the field weakening correction;

for M_low<

M*_index<

M_high, setting M_ref=M*_index; and

for M*_index>

M_high, setting M_ref=M_high.

3. The method of claim 1, wherein the determining step includes determining the commanded d- and q-axis currents from an optimized current command table.

4. The method of claim 3, wherein the combining step comprises:

adding or subtracting an incremental d-axis current to accommodate differences between data stored in the optimized current command table and actual behavior of the motor.

5. The method of claim 3 further comprising, prior to the obtaining step,

measuring operating parameters of the motor under different combinations of torque and speed;

and

determining, based on the operating parameters, the commanded d- and q- axis current expected to produce the requested torque and speed for a given DC supply voltage at optimum operating efficiency, then storing these values in the optimized current command table.

6. A method of controlling an electric motor, comprising:

receiving a requested torque and speed associated with the electric motor;

determining commanded currents corresponding to the requested torque and speed;

adjusting at least one of the commanded currents with a field weakening correction to provide a corrected output; and

operating an inverter associated with the electric motor based on the corrected output, thereby causing the electric motor to operate substantially at the requested torque and speed.

7. The method of claim 6, wherein the determining step includes determining commanded d- and q-axis currents.

8. The method of claim 7, further comprising determining a commanded modulation index (M*_index), and wherein the adjusting step includes adjusting the at least one of the commanded currents with the field weakening correction based on the M*_index.

9. The method of claim 8, wherein the adjusting step comprises:

for M*_index<

M_low, omitting the field weakening correction;

for M_low<

M*_index<

M_high, setting M_ref=M*_index; and

for M*_index>

M_high, setting M_ref=M_high.

10. The method of claim 7, wherein the determining step includes determining the commanded d- and q-axis currents from an optimized current command table.

11. The method of claim 10, wherein the combining step comprises:

adding or subtracting an incremental d-axis current to accommodate differences between data stored in the optimized current command table and actual behavior of the motor.

12. The method of claim 10 further comprising, prior to the obtaining step,

measuring operating parameters of the motor under different combinations of torque and speed;

and

determining, based on the operating parameters, the commanded d- and q-axis current expected to produce the requested torque and speed for a given DC supply voltage at optimum operating efficiency, then storing these values in the optimized current command table.