Collision avoidance system in a vehicle
View Patent ↗A method for determining the time to collision between a host vehicle and an oncoming target vehicle, and for determining the necessary host vehicle deceleration for bringing the host vehicle to a standstill at the moment of collision. The method furthermore comprises the steps: determining the position (p H ) of the host vehicle as a function of time; determining the position (p T ) of the target vehicle as a function of time; for the moment of collision, as a first condition, setting the position (p H ) of the host vehicle equal to the position (p T ) of the target vehicle, and, as a second condition, setting the velocity (v H ) of the host vehicle to zero; using the positions and the conditions above to solve for the time to collision and the necessary host vehicle deceleration; and choosing the solution for time to collision that is positive and has the largest value.
1. A method for vehicle collision mitigation comprising the steps of:
determining a position of a host vehicle as a function of time;
determining a position of a target vehicle as a function of time;
determining whether the target vehicle is travelling toward the host vehicle or away from the host vehicle;
as a first condition, setting the host vehicle position equal to the target vehicle position;
as a second condition, setting a velocity of the host vehicle equal to zero if the target vehicle is travelling toward the host vehicle and setting the velocity of the host vehicle equal to a velocity of the target vehicle if the target vehicle is travelling away from the host vehicle;
using the positions and the conditions above, solving for a time to collision and a required host vehicle acceleration to be applied over the time to collision in order to avoid collision; and
based upon the time to collision, activating a host vehicle braking system to achieve the required host vehicle acceleration.
2. A method according to claim 1 , wherein the host vehicle position as a function of time is given by the expression
p
H
(
t
)
=
v
H
(
t
0
)
(
t
-
t
0
)
+
1
2
a
H
(
t
-
t
0
)
2
and the target vehicle position as a function of time is given by the expression
p
T
(
t
)
-
p
T
(
t
0
)
+
v
T
(
t
0
)
(
t
-
t
0
)
+
1
2
a
T
(
t
-
t
0
)
2
,
where p H is host vehicle position as a function of time, p T is target vehicle position as a function of time, v H is host vehicle velocity as a function of time, v T is target vehicle velocity as a function of time, a H is host vehicle acceleration as a function of time, a T is target vehicle acceleration as a function of time, and t 0 is an initial time value.
3. A method according to claim 2 , wherein if the target vehicle is travelling toward the host vehicle the time to collision is calculated as
t
-
t
0
-
4
p
T
(
t
0
)
2
v
T
(
t
0
)
-
v
H
(
t
0
)
±
(
v
H
(
t
0
)
-
2
v
t
(
t
0
)
)
2
-
8
p
T
(
t
0
)
a
T
(
t
0
)
and the required host vehicle acceleration is calculated as
a
H
1
,
2
(
t
)
=
v
H
(
t
0
)
4
p
T
(
t
0
)
(
2
v
T
(
t
0
)
-
v
H
(
t
0
)
±
(
v
H
(
t
0
)
-
2
v
t
(
t
0
)
)
2
-
8
p
T
(
t
0
)
a
T
(
t
0
)
)
.
4. A method according to claim 2 , wherein the host vehicle position as a function of time is given by the expression
p
H
(
t
)
-
v
H
(
t
0
)
(
t
-
t
0
)
+
1
2
a
H
(
t
-
t
0
)
2
and the target vehicle position as a function of time is given by the expression
p
T
(
t
)
=
p
T
(
t
0
)
-
(
v
T
(
t
0
)
2
2
a
T
(
t
0
)
)
,
where p H is the host vehicle position as a function of time, p T is the target vehicle position as a function of time, v H is the host vehicle velocity as a function of time, v T is a target vehicle velocity as a function of time, a H is a host vehicle acceleration as a function of time, a T is a target vehicle acceleration as a function of time, and t 0 is an initial time value.
5. A method according to claim 2 , wherein the required host vehicle acceleration needed such that at the time of collision the host vehicle is at a standstill, is
a
H
(
t
)
=
-
v
H
(
t
0
)
2
2
(
p
T
(
t
0
)
-
v
T
(
t
0
)
2
2
a
T
(
t
0
)
)
and a time needed for the host vehicle to stop, t HStop is:
t
HStop
=
t
0
+
2
p
T
(
t
0
)
a
T
(
t
0
)
-
v
T
(
t
0
)
2
v
H
(
t
0
)
a
T
(
t
0
)
,
which time t HStop greater than a time to stop of the target vehicle, t Tstop , which is
t
TStop
=
t
0
-
v
T
(
t
0
)
a
T
(
t
0
)
,
if and only if
2 p T ( t 0 ) a T ( t 0 )− v T ( t 0 ) 2 +v H ( t 0 ) v T ( t 0 )>0.
6. A method of operating a vehicle collision mitigation system comprising the steps of:
determining a host vehicle position (p H ) as a function of time, a host vehicle velocity (v H ) as a function of time, and a host vehicle acceleration (a H ) as a function of time;
determining a target vehicle position (p T ) as a function of time, a target vehicle velocity (v T ) as a function of time, and a target vehicle acceleration (a T ) as a function of time;
determining whether the target vehicle is travelling toward the host vehicle or away from the host vehicle;
as a first condition, setting the host vehicle position equal to the target vehicle position;
as a second condition, setting a velocity of the host vehicle equal to zero if the target vehicle is travelling toward the host vehicle and setting the velocity of the host vehicle equal to a velocity of the target vehicle if the target vehicle is travelling away from the host vehicle;
using the positions and the conditions above, solving for a time to collision and a required host vehicle acceleration to be applied during the time to collision in order to avoid or mitigate a collision between the host vehicle and the target vehicle; and
based upon the time to collision, activating a host vehicle braking system to achieve the required host vehicle acceleration.
7. A method according to claim 6 , wherein the target vehicle is initially travelling away from the host vehicle and the braking system is activated to slow the host vehicle such that the host vehicle velocity is equal to the target vehicle velocity at the time to collision.
8. A method according to claim 6 , wherein the target vehicle is initially travelling toward the host vehicle and the braking system is activated to slow the host vehicle such that the host vehicle is at a standstill at the time to collision.
9. A method according to claim 6 , wherein the required acceleration is calculated based at least in part on predetermined vehicle performance factors.