Lane keeping assist system and method
The present disclosure relates to a lane keeping assist system for controlling a vehicle on the basis of traveling information and road information of the vehicle when the vehicle begins to leave its lane in order to prevent the vehicle from deviating from its lane, which is a system for assisting the vehicle in keeping the lane by generating multiple target routes each being a path for the vehicle to travel without deviating from the lane, calculating a target yaw rate for each target route, and controls the vehicle according to a target steering angle calculated using the target yaw rate.
1. A lane keeping assist system, comprising:
a receiver outputting information about an vehicle and information about a road where the vehicle are traveling on the basis of information received from an image sensor and a vehicle sensor;
a target route generator receiving the information output by the receiver and generating a target route of the vehicle;
a target yaw rate calculator receiving the target route from the target route generator and calculating a target yaw rate of the vehicle; and
a controller determining a time point for starting lane keeping assist control of the vehicle on the basis of the information output by the receiver, calculating a target steering angle using the target yaw rate received from the target yaw rate calculator, and controlling a steering device according to the target steering angle,
wherein the target yaw rate calculator calculates a radius of curvature of the target route received from the target route generator and calculates the target yaw rate using the radius of curvature,
wherein the target yaw rate calculator calculates the radius of curvature using a distance to any target position of the vehicle and a deviation angle between the vehicle and the road, and,
wherein the target yaw rate calculator calculates the radius of curvature of the target route using the following equation:
R ·cos(φ+α)= L/ 2
where R is a radius of curvature, φ is a deviation angle, α is an angle between a straight line to a target position and a straight line to a center of a circle having a road as an arc, and L is a distance to the target position;
wherein the target route generator calculates the target route using a distance to any target position of the vehicle, the road curvature to the target position, and a lateral offset of the vehicle, and,
wherein the target route generator calculates coordinate (x i , y i ) on the target route for the vehicle to travel without deviating from the road to any target position, by the following equation:
x
i
=
L
2
-
y
i
2
,
y
i
=
ρ
i
(
L
2
-
ɛ
1
2
)
2
(
1
-
ρ
i
ɛ
i
)
-
ɛ
i
where L is any target distance, ρ i is a road curvature, and e is a lateral offset of a vehicle.
2. The lane keeping assist system of claim 1 , wherein the target yaw rate calculator calculates the target yaw rate by multiplying the curvature of the target route and a speed of the vehicle.
3. The lane keeping assist system of claim 1 , wherein the target yaw rate calculator updates the target yaw rate in real time during traveling of the vehicle.
4. The lane keeping assist system of claim 1 , wherein the controller calculates the target steering angle using the target yaw rate, the steering angle in a steady state of the vehicle, and a yaw rate in a steady state of the vehicle.
5. The lane keeping assist system of claim 4 , wherein the controller calculates the target steering angle by the following equation:
δ
cmd
=
k
p
·
δ
ss
·
YR
d
YR
SS
where δ cmd is a target steering angle, k p is a proportional gain that is a control gain, δ ss is a steering angle in a steady state, YR SS is a yaw rate in a steady state, and YR d is a target yaw rate.
6. The lane keeping assist system of claim 1 , wherein the target route generator generates at least one of traveling paths to deviate from a boundary of the road, as the target route.
7. The lane keeping assist system of claim 1 , wherein the target route generator generates multiple target routes for at least one of travelling paths for the vehicle to travel without deviating from the road up to any target and a path for the vehicle to travel without deviating from a given offset distance from the boundary of the road.
8. The lane keeping assist system of claim 1 , wherein the target yaw rate calculator receives a plurality of target routes from the target route generator and calculates the target yaw rate for each target route.
9. A lane keeping assist method, comprising:
receiving at least one of an image sensing signal and a vehicle sensing signal of a vehicle and outputting traveling information about the vehicle;
generating a target route of the vehicle on the basis of the traveling information;
calculating a target yaw rate, a target behavior of the vehicle, on the basis of the target route;
determining a time point for starting lane keeping assist control on the basis of the traveling information and calculating a target steering angle using the target yaw rate; and
controlling a steering device of the vehicle according to the target steering angle,
wherein generating the target route of the vehicle comprises generating multiple target routes for at least one of travelling paths for the vehicle to travel without deviating from the road up to any target,
wherein calculating a target yaw rate comprises receiving a plurality of target routes from the target route generator and calculates the target yaw rate for each target route,
wherein calculating a target steering angle comprises selecting a target yaw rate appropriate for a traveling condition rate from among the target yaw rates for each target route and calculating the target steering angle using the selected target yaw rate,
wherein the calculating a target yaw rate comprises calculating a radius of curvature of the target route received from the target route generator and calculates the target yaw rate using the radius of curvature,
wherein the calculating a target yaw rate comprises calculating the radius of curvature using a distance to any target position of the vehicle and a deviation angle between the vehicle and the road,
wherein the calculating the target yaw rate calculator comprises calculating a radius of curvature of the target route; and calculating the target yaw rate using the radius of curvature and a speed of the vehicle,
wherein the calculating the target yaw rate comprises calculating the radius of curvature of the target route using the following equation:
R ·cos(φ+α)= L/ 2
where R is a radius of curvature, φ is a deviation angle, α is an angle between a straight line to a target position and a straight line to a center of a circle having a road as an arc, and L is a distance to the target position,
wherein the generating target route comprises calculating coordinate (x i , y i ) on the target route for the vehicle to travel without deviating from the road to any target position, by the following equation:
x
i
=
L
2
-
y
i
2
,
y
i
=
ρ
i
(
L
2
-
ɛ
1
2
)
2
(
1
-
ρ
i
ɛ
i
)
-
ɛ
i
where L is any target distance, ρ i is a road curvature, and ε i is a lateral offset of a vehicle.
10. The lane keeping assist method of claim 9 , wherein the calculating a target steering angle comprises calculating the target steering angle by the following equation:
δ
c
m
d
=
k
p
·
δ
s
s
·
Y
R
d
Y
R
S
S
where δ cmd is a target steering angle, k p is a proportional gain that is a control gain, δ ss is a steering angle in a steady state, YR SS is a yaw rate in a steady state, and YR d is a target yaw rate.