Lane departure prevention system of vehicle

1. A lane departure prevention system of a vehicle, comprising:

a detection sensor configured to detect a positional relationship of the vehicle relative to a lane;

an actuator; and

at least one electronic control unit configured to control a braking force of vehicle wheels by driving the actuator such that a lane departure prevention yaw moment in a direction in which departure from the lane is prevented is applied to the vehicle when it is determined that there is a likelihood that the vehicle departs from the lane based on a detection result of the detection sensor, the at least one electronic control unit being configured to

determine whether there is a likelihood that the vehicle enters a spinning state based on at least one of a difference between an actual turning state quantity and a normative turning state quantity of the vehicle and a degree of braking slip of a turning inside wheel when the lane departure prevention yaw moment is a yaw moment for preventing departure of the vehicle from the lane and a braking force is applied to the turning inside wheel, the normative turning state quantity being calculated based on a steering angle, a vehicle speed, and the lane departure prevention yaw moment,

apply a spin prevention yaw moment, instead of the lane departure prevention yaw moment, to the vehicle by applying a braking force to a turning outside wheel until a predetermined end condition is satisfied when it is determined that there is the likelihood that the vehicle enters the spinning state,

calculate a target lane departure prevention yaw moment for preventing the vehicle from departing from the lane to a turning outside when it is determined that there is the likelihood that the vehicle departs from the lane to the turning outside,

calculate a target spin prevention yaw moment for preventing the vehicle from entering the spinning state when it is determined that there is the likelihood that the vehicle enters the spinning state, and

control the spin prevention yaw moment based on the target spin prevention yaw moment without determining which magnitude of the target lane departure prevention yaw moment and the target spin prevention yaw moment is greater.

2. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to determine a magnitude of the target spin prevention yaw moment based on the magnitude of the target lane departure prevention yaw moment at a time point at which a determination result that there is no likelihood that the vehicle enters the spinning state is changed to a determination result that there is the likelihood that the vehicle enters the spinning state.

3. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to:

calculate a target yaw rate of the vehicle based on the steering angle and the vehicle speed; and

calculate the target spin prevention yaw moment based on a difference between the target yaw rate and an actual yaw rate detected by a yaw rate sensor mounted in the vehicle.

4. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to:

calculate a target lateral acceleration of the vehicle based on the steering angle and the vehicle speed; and

calculate the target spin prevention yaw moment based on a difference between the target lateral acceleration and an actual lateral acceleration detected by a lateral acceleration sensor mounted in the vehicle.

5. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to:

calculate a target yaw rate of the vehicle based on the steering angle and the vehicle speed; and

determine that the predetermined end condition is satisfied when a magnitude of an actual yaw rate detected by a yaw rate sensor mounted in the vehicle is equal to or less than the magnitude of the target yaw rate.

6. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to:

calculate a target lateral acceleration of the vehicle based on the steering angle and the vehicle speed; and

determine that the predetermined end condition is satisfied when a magnitude of an actual lateral acceleration detected by a lateral acceleration sensor mounted in the vehicle is equal to or less than the magnitude of the target lateral acceleration.

7. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to:

calculate a target yaw rate of the vehicle based on the steering angle and the vehicle speed;

set the target yaw rate at a time point at which a determination result that there is no likelihood that the vehicle enters the spinning state is changed to a determination result that there is the likelihood that the vehicle enters the spinning state as a reference value of a yaw rate; and

determine that the predetermined end condition is satisfied when a difference between a magnitude of the reference value of the yaw rate and a magnitude of an actual yaw rate detected by a yaw rate sensor mounted in the vehicle is equal to or greater than an end reference value of the target yaw rate.

8. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to:

calculate a target lateral acceleration of the vehicle based on the steering angle and the vehicle speed;

set the target lateral acceleration at a time point at which a determination result that there is no likelihood that the vehicle enters the spinning state is changed to a determination result that there is the likelihood that the vehicle enters the spinning state as a reference value of a lateral acceleration; and

determine that the predetermined end condition is satisfied when a difference between a magnitude of the reference value of the lateral acceleration and a magnitude of an actual lateral acceleration detected by a lateral acceleration sensor mounted in the vehicle is equal to or greater than an end reference value of the lateral acceleration.

9. The lane departure prevention system according to claim 1 , wherein

the at least one electronic control unit is configured to use a phase-compensated normative turning state quantity as the normative turning state quantity of the vehicle.