Method and apparatus for braking and stopping vehicles having an electric drive

• US 20070124052A1
• Filed: 01/29/2007
• Published: 05/31/2007
• Est. Priority Date: 08/25/2004
• Status: Active Grant

• Current Assignee: Ford Motor Company
• Original Assignee: Ford Motor Company
• Inventors: Prakash, Raj, Crombez, Dale, Worrel, Peter, Garg, Vijay
• Granted Patent: US 7,698,044 B2
• Time in Patent Office: Days
• US Class Current: 701/70
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: B60L 7/18 Controlling the braking effect B60L7/12, B60L7/14, B60L7/16 take precedence
• CPC Class Codes: B60T 13/586 the retarders being of the electric type
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60W 30/18127 Regenerative braking
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y10S 903/947 Characterized by control of braking, e.g. blending of regeneration, friction braking

Abstract

A method and apparatus are provided for braking and stopping a vehicle whose powertrain includes an electric drive. The electric drive is used to generate braking torque which is used to decelerate the vehicle down to a full stop. The braking torque is achieved using any of several closed loop speed control systems. The system can be used as a substitute for or as a supplement to conventional friction bakes.

Claims

1. A method of braking and stopping a vehicle having at least one traction wheel driven by an electric motor, comprising the steps of:

sensing a speed parameter related to the speed of the vehicle;

sensing a commanded braking rate;

generating a motor control signal to achieve a desired braking action;

producing a negative torque using the electric motor;

applying a braking force to the traction wheel using the negative torque produced by the electric motor; and

,

controlling the amount of negative torque produced by the electric motor using the motor control signal to achieve the commanded braking rate.

2. The method of claim 1, wherein the motor control signal is a torque command signal.

3. The method of claim 1, wherein, the motor control signal is a speed command signal.

4. The method of claim 1, wherein, the motor control signal is a power command signal.

5. The method of claim 1, wherein, the motor control signal is a force command signal.

6. The method of claim 1, wherein the motor control signal is generated using the sensed speed parameter and the commanded braking rate.

7. The method of claim 1, wherein the step of applying braking force is continued until the vehicle is stopped.

8. The method of claim 1, wherein the step of generating the motor control signal comprises:

producing a torque command signal used to control the motor until the vehicle decelerates to a preselected speed, and

producing a speed control signal used to control the motor after the vehicle has decelerated to the preselected speed.

9. The method of claim 1, wherein the step of applying braking force is continued until the vehicle decelerates to a stop.

10. The method of claim 1, wherein the step of generating the motor control signal comprises producing a torque control signal based on the positions of the vehicle'"'"'s brake and accelerator pedals.

11. The method of claim 1, wherein the step of generating the motor control signal comprises:

generating a negative torque control signal used to control the amount of negative torque produced by the electric motor until the sensed speed parameter reaches a preselected value, and

then, generating a speed control signal used to control the speed of the electric motor after the sensed speed reaches the preselected value.

12. The method of claim 1, wherein the step of

sensing the speed parameter comprises:

sensing the speed of the motor, and sensing the speed of at least one wheel of the vehicle.

13. The method of claim 1, wherein the step of sensing the commanded braking rate comprises sensing a parameter related to the operation of the brake pedal.

14. The method of claim 1, wherein the step of generating the motor control signal comprises:

generating a torque command signal,

generating a speed command signal,

modifying the speed command signal using the torque command signal.

15. The method of claim 14, wherein;

the step of sensing the speed parameter comprises generating a motor speed signal representing the speed of the electric motor, and

the step of generating the motor control signal comprises feeding back the motor speed signal in a motor control feedback loop, and controlling the motor using the feedback signal and the modified speed command signal.

16. A method of braking and stopping a vehicle powered by an electric motor driving at least one traction wheel, comprising the steps of:

sensing a speed parameter related to the speed of the vehicle;

sensing a commanded braking rate;

generating a commanded motor speed signal;

generating a torque limiting signal using the commanded braking rate;

generating a torque command signal using the commanded motor speed signal and torque limiting signal;

controlling the motor using the torque command signal to produce negative torque; and

,

applying a braking force to the traction wheel using the negative torque.

17. The method of claim 16, wherein the step of sensing the speed parameter comprises sensing the speed of the motor.

18. A method of claim 16, wherein the step of sensing the speed parameter comprises sensing the speed of at least one wheel of the vehicle.

19. The method of claim 16, wherein the step of sensing the commanded braking rate comprises sensing a parameter related to the operation of a brake pedal on the vehicle.

20. The method of claim 16, wherein the step of generating the torque command signal comprises using the sensed speed parameter as a feedback signal in a closed feedback loop, and performing dynamic compensation of the torque command signal using the feedback signal.

21. The method of claim 16, wherein the step of generating the torque command signal comprises modifying the torque command signal using the torque limiting signal.

22. The method of claim 16, wherein the torque limiting signal is determined by at least one of the brake pedal or accelerator pedal inputs.

23. The method of claim 16, further comprising the steps of:

controlling the motor using the torque command signal to produce positive torque; and

,

applying a braking force to the traction wheel using the positive torque.

24. A system for braking and stopping a vehicle powered by an electric motor driving at least one traction wheel, comprising:

a torque command signal generator for generating a torque command signal used to drive the motor and produce negative torque for braking the traction wheel; and

,

a torque limiting signal generator for converting brake pedal and accelerator pedal position values into torque limiting signals used to modify the torque command signal.

25. The system of claim 24, wherein the torque command signal generator comprises a dynamic compensator for compensating for the effects of changes in motor speed.

26. The system of claim 24, wherein the torque command signal generator comprises a closed speed control loop.

27. The system of claim 26, wherein the torque limiting signal generator includes a bipolar signal generator.