Lane keeping assist method and system

1. A lane keeping assist method, comprising steps of:

determining whether a turn signal is applied;

determining a state of a lane change in which a timing of a driver's driving control of a vehicle is reflected when the turn signal is applied;

adjusting a criterion for driver override depending on an error between a driving path of the vehicle and a target path; and

comparing a steering torque of the driver with the adjusted criterion to determine the driver override, wherein the steering toque of the driver is obtained by a torque sensor,

wherein the driver override is a state that the driver has driving control of the vehicle in autonomous driving of the vehicle, and

wherein the adjusting the criterion for the driver override includes:

setting the criterion for the driver override to a second value greater than a first value when the error is less than a threshold; and

determining cancellation of the driver override when the steering torque of the driver is less than the second value, wherein the first value is set to the criterion for the driver override when the error is greater that the threshold.

2. The lane keeping assist method according to claim 1 , wherein the adjusting the criterion for the driver override further includes:

determining activation of the driver override when the steering torque of the driver is greater than the first value.

3. The lane keeping assist method according to claim 1 , wherein the determining the state of the lane change includes dividing a driving state of the vehicle into a lane keeping state, a ready state for direct lane change, a direct lane change state, and a ready state for lane keeping, according to the state of the lane change.

4. The lane keeping assist method according to claim 3 , wherein the lane keeping state refers to a state in which the turn signal is not applied and a lane change completion rate is 0.

5. The lane keeping assist method according to claim 4 , wherein the lane change completion rate refers to a degree of completion of lane change, which is determined by comparing a lateral movement amount of the vehicle.

6. The lane keeping assist method according to claim 3 , wherein the ready state for direct lane change refers to a state in which the driving state of the vehicle is the lane keeping state when the turn signal is applied, and refers to a state after the turn signal is applied and before a lateral position error is greater than a first threshold or a heading error is greater than a second threshold.

7. The lane keeping assist method according to claim 3 , wherein the direct lane change state refers to a state in which a lateral position error is greater than a first threshold or a heading error is greater than a second threshold, and refers to a state after the ready state for direct lane change and before a lane change completion condition is satisfied.

8. The lane keeping assist method according to claim 7 , wherein the lane change completion condition includes:

the lateral position error is less than a third threshold;

the heading error is less than a fourth threshold; and

a lane change completion rate is greater than a fifth threshold.

9. The lane keeping assist method according to claim 3 , wherein the ready state for lane keeping refers to a state in which a lateral position error is less than a third threshold, a heading error is less than a fourth threshold, and a lane change completion rate is greater than a fifth threshold, or a state in which the lane change completion rate is greater than or equal to a sixth threshold when the turn signal is applied.

10. The lane keeping assist method according to claim 3 , wherein the criterion for driver override varies according to the lane keeping state, the ready state for direct lane change, the direct lane change state, and the ready state for lane keeping.

11. The lane keeping assist method according to claim 1 , wherein the adjusting the criterion for the driver override includes setting the first value and the second value with a hysteresis to allow each of the first value and the second value to have a predetermined range to prevent an activation of the driver override and the cancellation of the driver override from being repeatedly switched around the first value and the second value.

12. The lane keeping assist method according to claim 1 , wherein a case in which the error is greater than the threshold in the adjusting the criterion for the driver override depending on the error between the driving path of the vehicle and the target path, includes any one of a case in which a timing of the driver's driving control of the vehicle is slower than changing a lane to the target path and a case in which the timing of the driver's driving control of the vehicle is faster than changing the lane to the target path.

13. A lane keeping assist system, comprising:

a lane change state determination device determining a state of a lane change of a vehicle after a turn signal is applied;

a threshold adjustment device receiving a result of the state of the lane change from the lane change state determination device and adjusting a criterion for driver override depending on an error between a driving path of the vehicle and a target path according to the state of the lane change; and

an override determination device comparing a steering torque of a driver with the adjusted criterion to determine the driver override, wherein the steering torque of the driver is obtained by a torque sensor,

wherein the driver override is a state that the driver has driving control of the vehicle in autonomous driving of the vehicle, and

wherein the threshold adjustment device adjusts the criterion for the driver override to a first value when the error is greater than a threshold, and adjusts the criterion for the driver override to a second value greater than the first value when the error is less than the threshold.

14. The lane keeping assist system according to claim 13 , wherein the lane change state determination device is configured to determine a driving state of the vehicle as one of a lane keeping state, a ready state for direct lane change, a direct lane change state, and a ready state for lane keeping, according to the state of the lane change.

15. The lane keeping assist system according to claim 14 , wherein the threshold adjustment device adjusts the criterion for the driver override to vary according to the lane keeping state, the ready state for direct lane change, the direct lane change state, and the ready state for lane keeping.

16. The lane keeping assist system according to claim 14 , wherein the threshold adjustment device adjusts the criterion for the driver override to the first value in the direct lane change state, and adjusts the criterion for the driver override to the second value greater than the first value in the ready state for lane keeping.

17. The lane keeping assist system according to claim 14 , wherein the lane change state determination device is configured to determine the driving state of the vehicle as the direct lane change state when a timing of the driver's driving control of the vehicle is slower than changing a lane to the target path or when the timing of the driver's driving control of the vehicle is faster than changing the lane to the target path.

18. The lane keeping assist system according to claim 13 , wherein the override determination device is configured to determine activation of the driver override when the steering torque of the driver is greater than the first value, and is configured to determine cancellation of the driver override when the steering torque of the driver is less than the second value.