Extended braking compensation in hybrid braking systems

• US 20060089777A1
• Filed: 10/22/2004
• Published: 04/27/2006
• Est. Priority Date: 10/22/2004
• Status: Active Grant

• Current Assignee: BWI Company Limited SA (Shougang Corporation)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Pfeil, Michael C., Thomas, Richard J., Riddiford, Bryan P.
• Granted Patent: US 7,499,785 B2
• Time in Patent Office: Days
• US Class Current: 701/70
• CPC Class Codes: B60T 13/586 the retarders being of the electric type

Abstract

A method for balancing brake force is disclosed. The method includes determining whether a deceleration value reaches a first deceleration threshold in response to a braking event and determining brake condition and vehicle motion. Based on brake condition and vehicle motion determination and the first deceleration threshold determination, the method determines whether the deceleration value reaches a second deceleration threshold, and applies threshold balancing when the second deceleration threshold is reached.

Claims

1. A method for balancing brake force, the method comprising:

Determining an extended braking state including whether a deceleration value reaches a first deceleration threshold in response to a braking event;

Determining brake condition and vehicle motion;

Determining whether the deceleration value reaches a second deceleration threshold based on the brake condition and vehicle motion determination and the first deceleration threshold determination; and

Applying threshold balancing when the second deceleration threshold is reached.

2. The method of claim 1 wherein the first deceleration threshold is a low deceleration threshold and the second deceleration threshold is a very low deceleration threshold.

3. The method of claim 1 wherein determining brake condition comprises determining pedal displacement.

4. The method of claim 1 wherein applying threshold balancing comprises:

determining a front brake force and a rear brake force in response to the extended braking state and low deceleration, wherein the rear brake force is calculated using a weighted sum of the pedal displacement and master cylinder pressure and the front brake force is calculated using master cylinder pressure.

5. The method of claim 4 wherein the rear brake force is calculated according to the formula F_cmd=w*K_pressure—

_gain*P+(1−

w)*N, wherein F_cmd represents the rear brake force, K<sub>pressure—

gain</sub> represents a predetermined constant, P represents master cylinder pressure, N represents the normal brake force and w is a dynamically determined weighting factor such that 0≦

w≦

1.

6. The method of claim 5 wherein w is calculated according to the formula w(k)=MIN {k_w—

_max, w(k−

1)+k<sub>enter—

gain</sub>}, and wherein k<sub>w—

max</sub> is a predetermined constant such that 0≦

k<sub>w—

max</sub>≦

1 and k<sub>enter—

gain</sub> is a predetermined constant.

7. The method of claim 5 wherein w is calculated according to the formula w(k)=MAX{0, w(k−

1)−

k<sub>exit—

hi—

gain—

decel</sub>²+k<sub>exit—

hi—

offset</sub>}, and wherein k<sub>exit—

hi—

gain—

decel</sub> and k<sub>exit—

hi—

offset</sub> are predetermined constants.

8. The method of claim 5 wherein w is calculated according to the formula w(k)=MAX {0, w(k−

1)−

k<sub>exit—

off—

gain</sub>}, and wherein k<sub>exit—

off—

gain</sub> is a predetermined constant.

9. The method of claim 1 wherein determining an extended braking state includes determining a lapse time.

10. A computer readable medium comprising computer readable code for balancing brake force including:

computer readable code for determining whether a deceleration value reaches a first deceleration threshold in response to a braking event;

computer readable code for determining brake condition and vehicle motion;

computer readable code for determining whether the deceleration value reaches a second deceleration threshold based on the brake condition and vehicle motion determination and the first deceleration threshold determination; and

computer readable code for applying threshold balancing when the second deceleration threshold is reached.

11. The medium of claim 10 wherein the first deceleration threshold is a low deceleration threshold and the second deceleration threshold is a very low deceleration threshold.

12. The medium of claim 10 wherein computer readable code for determining brake condition comprises computer readable code for determining pedal displacement.

13. The medium of claim 10 wherein computer readable code for applying threshold balancing comprises computer readable code for determining a front brake force and a rear brake force in response to the extended braking state and low deceleration, wherein the rear brake force is calculated using a weighted sum of the pedal displacement and master cylinder pressure and the front brake force is calculated using master cylinder pressure.

14. The medium of claim 13 wherein the rear brake force is calculated according to the formula F_cmd=w*K_pressure—

_gain*P+(1−

w)*N, wherein F_cmd represents the rear brake force, K<sub>pressure—

gain</sub> represents a predetermined constant, P represents master cylinder pressure, N represents the normal brake force and w is a dynamically determined weighting factor such that 0<

=w<

=1.

15. The medium of claim 14 wherein w is calculated according to the formula w(k)=MIN{k_w—

_max, w(k−

1)+k<sub>enter—

gain</sub>}, and wherein k<sub>w—

max</sub> is a predetermined constant such that 0<

=k<sub>w—

max</sub><

=1 and k<sub>enter—

gain</sub> is a predetermined constant.

16. The medium of claim 14 wherein w is calculated according to the formula w(k)=MAX{0, w(k−

1)−

k<sub>exit—

hi—

gain—

decel</sub>²+k<sub>exit—

hi—

offset</sub>}, and wherein k<sub>exit—

hi—

gain—

decel</sub> and k<sub>exit—

hi—

offset</sub> are predetermined constants.

17. The medium of claim 14 wherein w is calculated according to the formula w(k)=MAX{0, w(k−

1)−

k<sub>exit—

off—

gain</sub>}, and wherein k<sub>exit—

off—

gain</sub> is a predetermined constant.

18. The medium of claim 10 wherein computer readable code for determining an extended braking state includes computer readable code for determining a lapse time.

19. A system for balancing brake force, the method comprising:

means for determining whether a deceleration value reaches a first deceleration threshold in response to a braking event;

means for determining brake condition and vehicle motion;

means for determining whether the deceleration value reaches a second deceleration threshold based on the brake condition and vehicle motion determination and the first deceleration threshold determination; and

means for applying threshold balancing when the second deceleration threshold is reached.

20. The system of claim 19 wherein applying threshold balancing comprises determining a front brake force and a rear brake force in response to the extended braking state and low deceleration, wherein the rear brake force is calculated using a weighted sum of the pedal displacement and master cylinder pressure and the front brake force is calculated using master cylinder pressure.