Adaptive controller for regenerative and friction braking system

• US 4,962,969 A
• Filed: 09/30/1988
• Issued: 10/16/1990
• Est. Priority Date: 09/30/1988
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Motor Company
• Inventors: Davis, Roy I.
• Primary Examiner(s): Reger, Duane A.
• Application Number:
  US07/251,421
• Time in Patent Office: 746 Days
• Field of Search: 303/3, 303/6.01, 303/9.76, 303/97, 303/99, 303/100, 303/111, 303/101, 303/103, 303/112, 188/156, 188/159, 188/160, 188/181 A, 188/181 C, 188/181 T, 180/165, 318/139, 318/369, 318/371, 364/426.02
• US Class Current: 303/3
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/461 Speed
• CPC Class Codes: B60L 2250/26 by pedal actuation
• CPC Class Codes: B60L 50/66 Arrangements of batteries
• CPC Class Codes: B60L 7/12 for vehicles propelled by dc motors
• CPC Class Codes: B60L 7/26 Controlling the braking effect
• CPC Class Codes: B60T 13/586 the retarders being of the electric type
• CPC Class Codes: B60T 13/662 characterised by specified functions of the control system components
• CPC Class Codes: B60T 2270/602 ABS features related thereto
• CPC Class Codes: B60T 8/00 Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force by changing number of effective brake cylinders in power brake systems B60T17/10
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 30/18127 Regenerative braking
• 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

Abstract

A regenerative and friction braking system for a vehicle having one or more roadwheels driven by an electric traction motor includes a driver responsive device for producing a brake demand signal having a magnitude corresponding to the level of braking force selected by the driver and friction and regenerative brakes operatively connected with the roadwheels of the vehicle. A system according to this invention further includes control means for operating the friction and regenerative braking subsystems so that maximum brake torques sustainable by the roadwheels of the vehicle without skidding or slipping will not be exceeded.

Claims

1. A regenerative and friction braking system for a vehicle having one or more roadwheels driven by an electric traction motor, comprising:

driver responsive means for producing a brake demand signal having a magnitude corresponding to the level of braking force selected by the driver;

friction braking means operatively connected with one or more roadwheels of said vehicle;

regenerative braking means operatively connected with said electric traction motor; and

control means for operating said friction braking means and said regenerative braking means, with said control means comprising;

means for periodically determining the maximum brake torques which may be developed by both of said braking means without causing skidding or slipping of said roadwheels, said means including means for determining the coefficient of friction between at least one of said roadwheels and the surface upon which said vehicle is being operated; and

means for calculating brake commands for said friction and regenerative braking means based upon said brake demand signal and upon said determining maximum brake torques, such that said determined maximum brake torques will not be exceeded.

2. A regenerative and friction braking system for a vehicle according to claim 1, wherein said means for determining the maximum brake torques which may be developed by said braking means without causing skidding or slipping of said roadwheels comprises means for determining the loading applied to each of said roadwheels.

3. A regenerative and friction braking system for a vehicle according to claim 2, wherein said means for determining the coefficient of friction between said roadwheels and the surface upon which said vehicle is being operated determines a separate coefficient of friction for each of said roadwheels.

4. A regenerative and friction braking system for a vehicle according to claim 2, wherein said means for determining the coefficient of friction between said roadwheels and the surface upon which said vehicle is being operated determines a separate coefficient of friction for at least one of said roadwheels operatively connected with said friction braking means and at least one roadwheel operatively connected with said regenerative braking means.

5. A regenerative and friction braking system for a vehicle according to claim 2, wherein said means for determining the coefficient of friction between said roadwheels and the surface upon which said vehicle is being operated comprises means for causing said braking means to apply a braking torque to at least one of said roadwheels and means for observing the rotational deceleration of said roadwheel in response to said brake application.

6. A regenerative and friction braking system for a vehicle according to claim 1, wherein said means for calculating brake commands for said friction and regenerative braking means based upon said brake demand signal and upon said determined maximum brake torques calculates said commands so that the brake torque produced by each of said braking means will be less than the maximum torque value determined for such means by an equivalent amount.

7. A regenerative and friction braking system for a vehicle according to claim 1, wherein said means for calculating brake commands for said friction and regenerative braking means based upon said brake demand signal and upon said determined maximum brake torques calculates said commands so that said regenerative braking subsystem will be commanded to produce the entirety of the desired braking torque corresponding to the brake demand signal in the event that such torque may be developed without exceeding the determined maximum torque for said regenerative subsystem, but that in the event that said regenerative subsystem is incapable of supplying all of the desired braking torque, each of said braking means will be given commands such that the brake torque produced by each of said braking means will be less than the maximum torque value determined for each such means by an equivalent amount.

8. A method for operating regenerative and friction braking subsystems for a vehicle having one or more roadwheels driven by an electric traction motor, with said vehicle having one or more dual-braked roadwheels braked by said regenerative and said friction braking subsystems and one or more friction-braked wheels braked only by said friction subsystem, comprising:

producing a brake demand signal having a magnitude corresponding to the level of braking force selected by the driver;

determining the coefficient of friction between at least one of said roadwheels and the surface upon which the vehicle is being operated;

determining the maximum brake torques which may be developed by said braking systems without causing skidding or slipping of said roadwheels; and

calculating brake commands for said friction and regenerative braking systems based upon the magnitude of said brake demand signal and upon said determined maximum brake torques.

9. A method for operating regenerative and friction braking subsystems according to claim 8, wherein said brake commands are calculated according to the steps of:

computing a desired braking torque from said brake demand signal;

comparing said desired braking torque to said maximum brake torques determined for said roadwheels; and

in the event that said desired braking torque and the maximum brake torque which said regenerative subsystem is capable of developing exceed the maximum brake torque determined for said dual-braked wheel, commanding said regenerative means to develop a braking torque which is equal to the maximum torque determined for said dual-braked roadwheel, while commanding said friction-brake subsystem to develop the remaining portion of said desired braking torque with said friction-braked wheel without exceeding the maximum torque determined for said friction-braked wheel;

in the event that said desired braking torque is less than both the maximum brake torque which said regenerative subsystem is capable of developing and the maximum brake torque determined for said dual-braked wheel, commanding said regenerative means to develop a braking torque which equals the desired braking torque;

in the event that said desired braking torque and the maximum brake torque determined for said dual-braked wheel exceed the maximum brake torque which said regenerative subsystem is capable of developing, commanding said regenerative means to develop maximum regenerative braking torque, while commanding said friction-brake subsystem to develop the remaining portion of said desired braking torque with said dual and said friction-braked roadwheels without exceeding the maximum sustainable torques determined for each of said wheels.

10. A method for operating regenerative and friction braking subsystems according to claim 9, wherein in the event that said desired braking torque and the maximum brake torque determined for said dual-braked wheel exceed the maximum brake torque which said regenerative subsystem is capable of developing, with the result that said regenerative means is commanded to develop maximum braking torque, and said friction-brake subsystem is commanded to develop the remaining portion of said desired braking torque with said dual and said friction-braked roadwheels without exceeding the maximum torques determined for each of said wheels, said method will determine said brake torque commands for said regenerative and said friction braking subsystems such that each of said subsystems will develop a brake torque at each roadwheel which is less than the predetermined maximum torque for each roadwheel by an equivalent amount.

11. A regenerative and friction braking system for a vehicle having one or more powered roadwheels driven by an electric traction motor and one or more unpowered roadwheels, comprising:

driver responsive means for producing a brake demand signal having a magnitude corresponding to the level of braking force selected by the driver;

friction braking means operatively connected with one or more of said unpowered roadwheels and with one or more powered roadwheels of said vehicle;

regenerative braking means operatively connected with said electric traction motor; and

control means for operating said friction braking means and said regenerative braking means, with said control means comprising;

means for determining the maximum brake torques which may be sustained by said roadwheels without causing skidding or slipping of said roadwheels, said means including means for determining the coefficient of friction between at least one of said roadwheels and the surface upon which said vehicle is being operated; and

means for calculating brake commands for said friction and regenerative braking means based upon said brake demand signal and upon said determined maximum brake torques, such that said determined maximum brake torques will not be exceeded.

12. A regenerative and friction braking system according to claim 11, wherein said means for determining the maximum brake torques which may be sustained by said roadwheels without causing skidding or slipping of said roadwheels comprises means for determining the brake torque at which each of said roadwheels will decelerate rotationally at a rate which exceeds a periodically computed deceleration threshold.

13. A regenerative and friction braking system according to claim 12, wherein said deceleration threshold is determined by calculating a deceleration rate corresponding to the total brake torque being applied by said friction and regenerative braking means.

14. A regenerative and friction braking system according to claim 13, wherein said maximum sustainable brake torques are determined by adjusting the brake torques produced by said friction and regenerative braking means until said threshold deceleration rate is not exceeded.

15. A regenerative and friction braking system according to claim 14, wherein said roadwheel deceleration rate is determined by sensing the rotational velocity of said roadwheel and by taking the time derivative of the sensed velocity.

16. A regenerative and friction braking system according to claim 11, wherein said means for calculating brake commands for said friction and regenerative braking means based upon said brake demand signal and upon said determined maximum brake torques is programmed to balance the brake torques produced by said roadwheels.

17. A regenerative and friction braking system according to claim 16, wherein said brake torques are balanced so that each of said roadwheels is commanded to produce an individualized brake torque which is less than the maximum no-skid brake torque for that particular wheel by an amount which is the same for every roadwheel.

18. A regenerative and friction braking system according to claim 11, wherein said friction braking means comprises:

a master cylinder;

a control valve operatively connected with said control means and said master cylinder; and

a wheel brake assembly operatively connected with said control valve.

19. A regenerative and friction braking system according to claim 18, wherein said friction braking means further comprises a brake fluid accumulator operatively connected with said wheel brake assembly.