ELECTRIC VEHICLE TRACTION CONTROL SYSTEM AND METHOD

• US 20150005988A1
• Filed: 12/06/2012
• Published: 01/01/2015
• Est. Priority Date: 12/09/2011
• Status: Active Grant

• Current Assignee: Borealis Technical Limited (Borealis Exploration Ltd.)
• Original Assignee: Borealis Technical Limited (Borealis Exploration Ltd.)
• Inventors: Cox, Isaiah W.
• Granted Patent: US 9,205,758 B2
• Time in Patent Office: Days
• US Class Current: 701/3
• 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 2200/10 Air crafts
• CPC Class Codes: B60L 2220/12 Induction machines
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 2220/16 DC brushless machines
• CPC Class Codes: B60L 2220/18 Reluctance machines
• CPC Class Codes: B60L 2240/12 Speed
• 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 2240/461 Speed
• CPC Class Codes: B60L 3/106 for maintaining or recovering the adhesion of the drive wheels
• CPC Class Codes: B60L 3/108 whilst braking, i.e. ABS
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: B60L 50/66 Arrangements of batteries
• CPC Class Codes: B60L 7/006 Dynamic electric braking by reversing current, i.e. plugging
• CPC Class Codes: B60L 7/18 Controlling the braking effect B60L7/12, B60L7/14, B60L7/16 take precedence
• CPC Class Codes: B64C 25/405 Powered wheels, e.g. for taxing
• 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 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility

Abstract

A traction control system and method are provided for electric vehicles with at least one drive wheel powered by an electric drive motor to maintain optimum maximum traction while the vehicle is driven on the ground. The traction control system includes drive means capable of transmitting torque through a vehicle drive wheel and controllable to move the vehicle over a ground surface. A preferred drive means is an electric motor designed to move the vehicle at desired ground speeds in response to operator input. Operator input requests a desired speed, and the system determines drive wheel torque required to produce the desired speed and provides maximum current to produce maximum torque to drive the vehicle with optimum traction at the desired speed. The system uses constant feedback to find maximum current corresponding to torque required for an inputted speed request to automatically control traction in any electric powered vehicle.

Claims

1. A system for controlling and maintaining optimum traction between wheels of a vehicle and a surface on which said vehicle is driven, wherein said vehicle is equipped with at least one drive wheel electrically powered to drive said vehicle, said system comprising:

(a) electric drive means designed to translate torque through said drive wheel to drive said vehicle on said surface;

(b) vehicle operator input means actuatable to input a desired vehicle speed into said system;

(c) processor means for receiving the desired vehicle speed and automatically determining a maximum electric current to be supplied to said electric drive means to translate the torque required to drive the vehicle at the desired speed and optimum traction to said drive wheel; and

(d) controller means for automatically controlling, in response to said processor means maximum electric current determination, a supply of electric current to said electric drive means corresponding to said maximum electric current and maintaining said supply of electric current to drive said vehicle at said desired speed and optimum traction until said vehicle operator input means is actuated to input a different desired speed into said system.

2. The traction control system of claim 1, wherein said vehicle is an electric powered vehicle selected from the group comprising automobiles, trucks, construction vehicles, military vehicles, aircraft, and trains.

3. The traction control system of claim 1, wherein said electric drive means is an electric motor selected from the group comprising toroidally-wound motors, axial flux motors, permanent magnet brushless motors, synchronous motors, asynchronous motors, pancake motors, switched reluctance motors, and electric induction motors.

4. The traction control system of claim 1, wherein said processor includes software means for automatically intelligently determining a torque/speed curve controlled by electrical operating parameters for said electric drive means and the torque translated to said drive wheels depends on the desired vehicle speed inputted into said system.

5. The traction control system of claim 2, wherein said vehicle is an automobile.

6. The traction control system of claim 2, wherein said vehicle is an aircraft.

7. The traction control system of claim 1, further comprising traction maintenance means for automatically continuously maintaining a maximum supply of power to said drive wheel in response to inputted desired vehicle speed to produce a torque required to maintain optimum traction for ground surface and travel conditions.

8. The traction control system of claim 1, wherein said system further comprises automatically or manually controllable deicing mode means for generating sufficient heat and pressure between said drive wheel and said surface to melt ice on said surface, thereby improving traction, when said controller means determines that less than a maximum supply of power indicates a loss of traction and said ground surface is ice covered.

9. A method comprising maintaining control of traction between at least one vehicle drive wheel and a ground travel surface in a vehicle equipped with an electric drive control system and electric drive means for translating torque through the drive wheel to drive the vehicle on the ground surface, said method further comprising:

(a) providing vehicle operator speed input means whereby a desired vehicle speed can be input into said electric drive control system and inputting a desired speed;

(b) providing a source of electric power to power the electric drive means;

(c) providing an electric drive control system controller capable of converting the desired speed into a torque required to drive the vehicle at the desired speed and determining the maximum current required for the electric drive means to translate the torque required to drive the vehicle at the desired speed;

(d) determining maximum current required to drive the vehicle at the desired speed and directing electric power from the power source to apply said maximum current to said electric drive means to drive the vehicle on the ground at the desired speed; and

(e) maintaining a supply of maximum current to said electric drive means and said drive wheel corresponding to the desired speed to produce optimum traction between the drive wheel and the ground surface.

10. The method of claim 9, further comprising continuously monitoring the inputted desired speed during vehicle ground travel, automatically finding maximum electric current draw for the desired speed, and applying the maximum electric current to the drive wheel to produce optimum torque.

11. The method of claim 9, further comprising measuring current consumed by the drive means, wherein a decrease in current consumed indicates that the drive wheel is slipping and traction is not optimum.

12. The method of claim 11, further comprising restoring traction to optimum by intermittently supplying pulses of current to said drive wheel.

13. The method of claim 9, wherein a supply of current below 100% of maximum current is maintained to said drive wheel, thereby reducing wear on a tire mounted on said wheel.

14. The method of claim 13, wherein current is maintained in the range of about 95% to 98% of maximum.

15. The method of claim 9, further comprising, when the ground surface is icy and traction between at least one drive wheel and the ground surface is lost, maximizing the current applied to the electric drive means to melt ice under the at least one drive wheel with heat generated by said drive means.

16. The method of claim 10, wherein traction is controlled in an electric powered vehicle selected from the group comprising automobiles, trucks, construction vehicles, military vehicles, aircraft, and trains.

17. The method of claim 16, wherein traction is controlled in an automobile.

18. The method of claim 16, wherein traction is controlled in an aircraft.

19. A method comprising controlling traction in an electric vehicle by continuously locating a maximum power consumption case within a range for an electric drive means powering the vehicle and automatically continuously applying the maximum power to the electric drive means to drive the vehicle with optimum traction.

20. A method for detecting a loss of traction in a vehicle driven at a desired speed by electric drive means, comprising providing a torque/speed curve for electric drive means driving a vehicle at a desired speed, using the torque/speed curve to detect a change in vehicle wheel torque from a torque corresponding to the desired speed, identifying a present acceleration of the vehicle wheel and an acceleration required to drive the vehicle, and detecting a loss of traction when the present acceleration of the vehicle wheel is substantially greater than the acceleration required to drive the vehicle.

21. The method of claim 20, further comprising, when loss of traction is detected, restoring traction to optimum by modulating torque provided to the vehicle wheel until a target torque corresponding to optimum traction is reached and traction is restored.

22. The method of claim 20, wherein said method is performed automatically.

23. A method comprising controlling traction in an electric vehicle powered by an induction motor, wherein open loop torque control that uses vehicle operator inputs adjusted by limit laws to set a motor commanded torque value based on a selected motor model to maximize traction is applied.

24. The method of claim 23, wherein the vehicle operator inputs comprise inputs selected from the list comprising motor commanded torque from vehicle desired speed, rotor speed, motor stator temperature, and available inverter voltage.

25. The method of claim 23, further comprising detecting changed vehicle speed, comparing changed speed to the motor model, and calculating a new synchronous speed to produce a desired torque.

26. The method of claim 23, further comprising detecting sudden acceleration of a vehicle wheel indicating slip, measuring wheel slip, and using the motor model to adjust torque to control acceleration of the slipping wheel and maximize traction.

27. The method of claim 26, wherein when sudden acceleration of the wheel is detected, controlling the motor by directly controlling synchronous speed and selecting a torque/speed curve that produces optimal efficiency to produce optimal torque at a target wheel speed.

28. A method comprising using an electric motor in a vehicle powered by the electric motor to measure available traction, further comprising calculating motor output torque when rotor speed is known based on a fixed torque/speed curve by reversing motor model calculations for an open loop torque control to measure wheel slipping traction.

29. A method comprising using an electric motor in a vehicle powered by the electric motor to measure available traction, further comprising adjusting drive frequency and drive voltage to command different torque/speed curves that share a target operating point, determining whether a vehicle wheel is operating at the target operating point or slipping, and modulating a selected torque/speed curve to modulate wheel speed and prevent slipping.

30. A method comprising controlling traction in an electric vehicle by continuously locating a maximum power consumption case within a range for an electric drive means powering the vehicle and automatically continuously applying the maximum power to the electric drive means to drive the vehicle with optimum traction, wherein said method is applied in combination with known traction control methods to control vehicle traction.