Hill hold decay
View Patent ↗A hill hold decay (HDD) system of a vehicle. The system includes a longitudinal acceleration sensor, a wheel speed sensor, a brake pedal detector, a gas pedal detector, a gear sensor, and a controller. The controller is configured to determine the vehicle has come to a standstill, determine a slope of the ground the vehicle is on, determine a direction of travel of the vehicle is downhill, detect a release of a brake release a brake force applied to a plurality of wheels of the vehicle at a constant first rate, determine a speed of the vehicle has reached a minimum threshold, release the brake force at a second rate as long as the speed of the vehicle is increasing, determine the speed of the vehicle has reached a maximum threshold, and release the brake force.
1. A hill hold decay (HDD) system of a vehicle, the system comprising:
a longitudinal acceleration sensor configured to detect the longitudinal acceleration of the vehicle;
a wheel speed sensor configured to detect the speed of the vehicle;
a brake pedal detector configured to detect a pressure applied to a brake pedal;
a gas pedal detector configured to detect a pressure applied to a gas pedal;
a gear sensor configured to sense a gear the vehicle is in; and
a controller configured to receive an indication of the longitudinal acceleration of the vehicle from the longitudinal acceleration sensor, an indication of the speed of the vehicle from the wheel speed sensor, an indication of the pressure on the brake pedal from the brake pedal detector, an indication of the pressure on the gas pedal from the gas pedal sensor, and an indication of the gear the vehicle is in from the gear sensor, the controller further configured to
determine the vehicle has come to a standstill;
after determining the vehicle has come to a standstill
determine a slope of the ground the vehicle is on;
determine a direction of travel of the vehicle is downhill;
detect a release of the brake pedal;
release a brake force applied to a plurality of wheels of the vehicle at a constant first rate;
determine a speed of the vehicle has reached a minimum threshold;
after determining the speed of the vehicle has reached the minimum threshold;
release the brake force at a second rate as long as the speed of the vehicle is increasing;
determine the speed of the vehicle has reached a maximum threshold; and
after determining the speed of the vehicle has reached the maximum threshold, release the brake force.
2. The HDD system of claim 1 , further comprising detecting a drive off condition and releasing the brake force immediately.
3. The HDD system of claim 2 , wherein the drive off condition is detected when a gas pedal is pressed.
4. The HDD system of claim 1 , wherein the method is not executed if the slope of the ground is less than a predetermined slope threshold.
5. The HDD system of claim 1 , wherein the brake force is reduced after the speed of the vehicle has reached the minimum if the vehicle slows down.
6. The HDD system of claim 1 , wherein the slope is determined using the formula
Slope
{
AxSensor
-
a
x
;
if
J
x
≤
Value
Jx
⋂
Jounce
x
≤
Value
Jounce
x
is
met
over
a
defined
period
of
time
Slope
t
-
1
;
In
any
other
case
where
J
x
=
ⅆ
ⅆ
t
Slope
Jounce
=
ⅆ
ⅆ
t
J
x
.
7. The HDD system of claim 1 , wherein the first rate of brake force release is determined based on the determined slope.
8. The HDD method of claim 1 , wherein the second rate is zero, holding the brake force steady.
9. A HHD method for controlled acceleration of a vehicle, the method comprising:
determining the vehicle has come to a standstill;
after determining the vehicle has come to a standstill
determining a slope of the ground the vehicle is on;
determining a direction of travel of the vehicle is downhill;
detecting a release of a brake;
releasing a brake force applied to a plurality of wheels of the vehicle at a constant first rate;
determining a speed of the vehicle has reached a minimum threshold;
after determining the speed of the vehicle has reached the minimum threshold;
releasing the brake force at a second rate as long as the speed of the vehicle is increasing;
determining the speed of the vehicle has reached a maximum threshold; and
after determining the speed of the vehicle has reached the maximum threshold, releasing the brake force.
10. The HDD method of claim 9 , further comprising detecting a drive off condition and releasing the brake force immediately.
11. The HDD method of claim 10 , wherein the drive off condition is detected when a gas pedal is pressed.
12. The HDD method of claim 9 , wherein the method is not executed if the slope of the ground is less than a predetermined slope threshold.
13. The HDD method of claim 9 , wherein the brake force is reduced after the speed of the vehicle has reached the minimum if the vehicle slows down.
14. The HDD method of claim 9 , wherein the release of the brake is a release of a brake pedal.
15. The HDD method of claim 9 , wherein the direction of travel of the vehicle is determined by a selected gear of the vehicle.
16. The HDD method of claim 9 , wherein the slope is determined using the formula
Slope
{
AxSensor
-
a
x
;
if
J
x
≤
Value
Jx
⋂
Jounce
x
≤
Value
Jounce
x
is
met
over
a
defined
period
of
time
Slope
t
-
1
;
In
any
other
case
where
J
x
=
ⅆ
ⅆ
t
Slope
Jounce
=
ⅆ
ⅆ
t
J
x
.
17. The HDD method of claim 9 , wherein the first rate of brake force release is determined based on the determined slope.
18. The HDD method of claim 9 , wherein the second rate is zero, holding the brake force steady.