Control system for electric vehicles

Patent metadata

Field	Value
Publication number	US-10293243-B1
Application number	US-201816208485-A
Country	US
Kind code	B1
Filing date	Dec 3, 2018
Priority date	Dec 1, 2017
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

When an electric vehicle is traveling downhill, experiencing regenerative braking, or otherwise forcing the vehicle motor to turn faster than the commanded motor torque, the vehicle motor produces electrical energy that can be used to recharge a vehicle battery. However, if the vehicle battery is already nearly or fully charged, the excess electrical energy produced may damage the battery. Control systems described herein may reduce and/or dispose of the excess energy by manipulating the motor flux (i.e., direct) current and quadrature current independently.

First claim

What is claimed is:

1. A control system for an electric vehicle, the control system comprising:
a power supply;
an electric motor coupled to the power supply; and
a motor controller having a field-oriented control (FOC) scheme configured to control the electric motor by manipulating a direct current aligned with a rotating rotor flux angle and a quadrature current defined at ninety degrees from the rotating rotor flux angle, wherein manipulation of the direct current is independent of manipulation of the quadrature current, and the motor controller includes processing logic configured to:
determine whether a counter electromotive force (CEMF) of the electric motor exceeds a voltage of the power supply by comparing a bus voltage of the power supply to a voltage threshold; and
in response to the bus voltage being greater than the voltage threshold, weakening a motor flux of the electric motor and reducing the CEMF by automatically increasing the direct current.

2. The control system of claim 1 , wherein the processing logic of the motor controller is further configured to:
while the bus voltage is greater than the voltage threshold, automatically continue to increase the direct current of the motor; and
in response to the direct current reaching a direct current threshold, automatically stop increasing the direct current.

3. The control system of claim 1 , wherein automatically increasing the direct current comprises:
increasing a flux setpoint of the motor controller by a selected amount;
comparing an existing flux command to the flux setpoint; and
adjusting direct current to a higher of the existing flux command and the flux setpoint.

4. The control system of claim 1 , wherein the processing logic of the motor controller is further configured to:
in response to the bus voltage being less than the voltage threshold and the direct current being greater than zero, reducing inefficiency of the motor by automatically reducing the direct current.

5. The control system of claim 4 , wherein automatically reducing the direct current comprises:
decreasing a flux setpoint of the motor controller by a selected amount;
comparing an existing flux command to the flux setpoint; and
adjusting direct current to a higher of the existing flux command and the flux setpoint.

6. The control system of claim 1 , wherein the power supply comprises a lithium ion battery.

7. The control system of claim 1 , wherein the electric motor comprises a hub motor configured to rotate a wheel of a vehicle.

8. An electric vehicle comprising:
one or more wheels;
an electric hub motor coupled to a power supply and configured to drive the one or more wheels;
a motor controller having a field-oriented control (FOC) scheme configured to control the electric hub motor by manipulating a direct current aligned with a rotating rotor flux angle and a quadrature current defined at ninety degrees from the rotating rotor flux angle, wherein manipulation of the direct current is independent of manipulation of the quadrature current, and the motor controller includes processing logic configured to:
determine whether a counter electromotive force (CEMF) of the electric motor exceeds a voltage of the power supply by comparing a bus voltage of the power supply to a voltage threshold; and
in response to the bus voltage being greater than the voltage threshold, weakening a motor flux of the electric motor and reducing the CEMF by automatically increasing the direct current.

9. The vehicle of claim 8 , wherein the vehicle has exactly one wheel.

10. The vehicle of claim 9 , wherein the vehicle comprises a self-balancing electric skateboard, the skateboard comprising:
a board including first and second deck portions each configured to receive a left or right foot of a rider oriented generally perpendicular to a direction of travel of the board;
a wheel assembly including the exactly one wheel disposed between and extending above the first and second deck portions, wherein the electric hub motor is configured to rotate the wheel around an axle to propel the skateboard; and
at least one sensor configured to measure orientation information of the board;
wherein the motor controller is further configured to receive orientation information measured by the sensor and to cause the hub motor to propel the skateboard based on the orientation information.

11. The vehicle of claim 8 , wherein the processing logic of the motor controller is further configured to:
while the bus voltage is greater than the voltage threshold, automatically continue to increase the direct current of the motor; and
in response to the direct current reaching a direct current threshold, automatically stop increasing the direct current.

12. The vehicle of claim 8 , wherein automatically increasing the direct current comprises:
increasing a flux setpoint of the motor controller by a selected amount;
comparing an existing flux command to the flux setpoint; and
adjusting direct current to the higher of the existing flux command and the flux setpoint.

13. The vehicle of claim 8 , wherein the processing logic of the motor controller is further configured to:
in response to the bus voltage being less than the voltage threshold and the direct current being greater than zero, reducing inefficiency of the motor by automatically reducing the direct current.

14. The vehicle of claim 13 , wherein automatically reducing the direct current comprises:
decreasing a flux setpoint of the motor controller by a selected amount;
comparing an existing flux command to the flux setpoint; and
adjusting direct current to a higher of the existing flux command and the flux setpoint.

15. A method for preventing damage to a power supply of an electric vehicle during regenerative braking, the method comprising:
controlling an electric motor using a motor controller having a field-oriented control (FOC) scheme configured to control the electric motor by manipulating a direct current aligned with a rotating rotor flux angle and a quadrature current defined at ninety degrees from the rotating rotor flux angle, wherein manipulation of the direct current is independent of manipulation of the quadrature current;
using processing logic of the motor controller to determine whether a counter electromotive force (CEMF) of the electric motor exceeds a voltage of the power supply; and
in response to the CEMF of the electric motor exceeding the voltage of the power supply, weakening a motor flux of the electric motor and reducing the CEMF by automatically increasing the direct current.

16. The method of claim 15 , wherein determining whether the CEMF of the electric motor exceeds the voltage of the power supply comprises comparing a bus voltage of the power supply to a voltage threshold.

17. The method of claim 15 , further comprising:
while the CEMF of the electric motor exceeds the voltage of the power supply, automatically continuing to increase the direct current of the motor until the direct current reaches a direct current threshold.

18. The method of claim 15 , wherein automatically increasing the direct current comprises:
increasing a flux setpoint of the motor controller by a selected amount;
comparing an existing flux command to the flux setpoint; and
adjusting direct current to a higher of the existing flux command and the flux setpoint.

19. The method of claim 15 , further comprising:
in response to the CEMF of the electric motor being below the voltage of the power supply and the direct current being

Assignees

• Future Motion Inc

Inventors

• Doerksen Kyle Jonathan
• Wood Daniel J
• De La Rua Julian

Classifications

• B60L15/2018

  for braking on a slope · CPC title

• B60L2220/44

  Wheel Hub motors, i.e. integrated in the wheel hub · CPC title

• B60L2240/22

  Yaw angle · CPC title

• B60L2220/46

  Wheel motors, i.e. motor connected to only one wheel · CPC title

• B60L2240/12

  Speed · CPC title