LANE KEEPING ASSIST DEVICE AND LANE KEEPING ASSIST METHOD

• US 20110015850A1
• Filed: 12/10/2008
• Published: 01/20/2011
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kimura, Takeshi, Takeda, Yuya, Tange, Satoshi, Nishida, Yukinori
• Granted Patent: US 8,457,868 B2
• Time in Patent Office: Days
• US Class Current: 701/116
• CPC Class Codes: B60T 8/17557 specially adapted for lane departure prevention road vehicle drive control systems for lane keeping otherwise than by controlling a particular sub-unit B60W30/12
• CPC Class Codes: B60W 30/12 Lane keeping
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence

Abstract

Lateral displacement reference positions LXL, LXR are set on left and right from a center in a width direction of a traffic lane L where a vehicle travels. Then, at least in a case where the vehicle is positioned on an inner side of the left and right lateral displacement reference position LXL, LXR, the vehicle is feedback-controlled so as to decrease a yaw angle deviation. Further, in a case where the vehicle is positioned at an outer side of the left and right lateral displacement reference position LXL, LXR with respect to the traffic lane center, the feedback control is performed so as to decrease the angle deviation and a lateral displacement deviation.

Claims

1. A lane keeping assist device comprising:

a lateral direction displacement obtaining means which obtains information concerning a lateral direction displacement of a vehicle with respect to a traffic lane;

a lateral direction displacement threshold value setting means which sets a lateral direction displacement threshold value on the traffic lane where the vehicle travels;

a first control amount calculating means which calculates a first control amount that decreases a lateral displacement deviation of the vehicle from the lateral direction displacement threshold value;

a second control amount calculating means which calculates a second control amount that decreases an angle deviation of a travelling direction of the vehicle with respect to the traffic lane; and

a travelling direction controlling means which, when the vehicle passes across the lateral direction displacement threshold value from a center side of a width direction of the traffic lane, controls a turning angle or a turning torque or a braking/driving amount or a braking/driving force of a road wheel, on the basis of the second control amount at the traffic lane center side with respect to the lateral direction displacement threshold value and on the basis of at least the first control amount at an outer side of the width direction of the traffic lane with respect to the lateral direction displacement threshold value.

2. The lane keeping assist device as claimed in claim 1, wherein the second control amount is calculated as a control amount of a preliminary control for reducing the first control amount, before the vehicle reaches either one of the lateral direction displacement threshold values from the lane center side.

3. The lane keeping assist device as claimed in claim 1, wherein

in at least a part of an area in a range of a lane edge side with respect to the lateral direction displacement threshold value, the travelling direction controlling means performs the control on the basis of both control amounts of the first control amount and the second control amount.

4. The lane keeping assist device as claimed in claim 3, wherein

in a case where the vehicle travels in a direction moving away from the lateral direction displacement threshold value, directions of displacement of the vehicle by the first control amount and by the second control amount, with respect to the lateral direction displacement threshold value, become the same direction, and

in a case where the vehicle travels in a direction toward the lateral direction displacement threshold value, the directions of displacement of the vehicle by the first control amount and by the second control amount, with respect to the lateral direction displacement threshold value, become opposite directions.

5. The lane keeping assist device as claimed in claim 1, wherein

the first control amount calculating means calculates a first target imaginary repulsion that is imaginarily applied to the vehicle from the lane edge side toward the lane center side to decrease the lateral displacement deviation, and calculates the first control amount on the basis of the first target imaginary repulsion, and

the second control amount calculating means calculates a second target imaginary repulsion that is imaginarily applied to the vehicle from the left and right width directions of the traffic lane to decrease the angle deviation, and calculates the second control amount on the basis of the second target imaginary repulsion.

6. The lane keeping assist device as claimed in claim 1, wherein

left and right lateral displacement reference positions are set on inner sides of the left and right lateral direction displacement threshold values respectively, which are two positions that are each offset to left and right from the center of the width direction of the traffic lane,

the control amount calculating means calculates the first control amount using the lateral displacement deviation from the lateral displacement reference position which is situated near the vehicle of the left and right lateral displacement reference positions, and

in a case where it is judged that the vehicle is positioned between the left and right lateral direction displacement threshold values, the lateral displacement deviation is considered to be zero, or a control gain for the lateral displacement deviation is set to be small.

7. The lane keeping assist device as claimed in claim 1, wherein

the travelling direction controlling means calculates a final control amount from the sum of a value obtained by multiplying the first control amount by a first weighting factor and a value obtained by multiplying the second control amount by a second weighting factor, and

the first weighting factor and the second weighting factor are changed according to the lateral displacement deviation, and are set so that the larger the lateral displacement deviation is, the larger the first weighting factor is as compared with the second weighting factor.

8. The lane keeping assist device as claimed in claim 1, wherein

the travelling direction controlling means compares values of the first control amount and the second control amount and sets the greater value as a final control amount.

9. The lane keeping assist device as claimed in claim 7, wherein

the first control amount is corrected by a lateral displacement velocity of the vehicle.

10. The lane keeping assist device as claimed in claim 7, wherein

a control gain of the second control amount is corrected by a distance of the vehicle to the traffic lane edge side which is located at a travelling direction side of the vehicle of the left and right traffic lane edge sides, and

the control gain is corrected so that the shorter the distance of the vehicle to the traffic lane edge side is, the larger the control gain is.

11. The lane keeping assist device as claimed in claim 1, further comprising:

a curve road correcting means which, when a curvature of the traffic lane is a certain value or more, corrects a control gain for the control amount calculated by the control amount calculating means, on the basis of a position of the vehicle with respect to the center of the traffic lane and the curvature of the traffic lane, and wherein

in a case where the vehicle is positioned at a curve inside of the traffic lane with respect to the width direction center of the traffic lane, when the curvature is large, the control gain is corrected and set to be small, as compared with small curvature, and

in the case where the vehicle is positioned at a curve outside of the traffic lane with respect to the width direction center of the traffic lane, when the curvature is large,

the control gain is corrected and set to be large, as compared with the small curvature.

12. The lane keeping assist device as claimed in claim 1, wherein

a zone between a position that is offset to the lane center side from the lateral direction displacement threshold value and this lateral direction displacement threshold value is set as a departure side transition area, and

in an area on the lane center side with respect to the departure side transition area, the second control amount is set to zero.

13. A vehicle travelling direction control device comprising:

a lateral direction position information obtaining means which obtains information concerning a lateral direction position of a target vehicle with respect to a traffic lane;

a lateral direction displacement threshold value setting means which sets a first lateral direction displacement threshold value and a second lateral direction displacement threshold value on the traffic lane where the target vehicle travels;

a first control amount calculating means which calculates a first control amount that decreases a lateral displacement deviation of the target vehicle from the first or second lateral direction displacement threshold value;

a second control amount calculating means which calculates a second control amount that decreases an angle deviation of a travelling direction of the target vehicle with respect to the traffic lane; and

a lateral direction displacement threshold value passing judging means which judges whether or not the lateral direction position exceeds either of the lateral direction displacement threshold values across a range of the first and second lateral direction displacement threshold values, and

in a case where it is judged that the lateral direction position does not exceed the lateral direction displacement threshold value, a command signal of a second control that controls the angle deviation being outputted, and

in a case where it is judged that the lateral direction position exceeds the lateral direction displacement threshold value, at least a command signal of a first control that controls the lateral direction position being outputted.

14. The vehicle travelling direction control device as claimed in claim 13, wherein

in a part of an area where the lateral direction position exceeds the lateral direction displacement threshold value, both command signals of the first control and the second control are outputted.

15. The vehicle travelling direction control device as claimed in claim 14, wherein

weights of the control amount of the first control and the control amount of the second control are changed according to the lateral direction position out of the lateral direction displacement threshold value.

16. The vehicle travelling direction control device as claimed in claim 15, wherein

the weights are set so that the farther the lateral direction position is positioned away from the lateral direction displacement threshold value, the larger the weight of the control amount of the first control as compared with the weight of the control amount of the second control.

17. The vehicle travelling direction control device as claimed in claim 14, wherein

in a case where the lateral direction position is positioned in a direction moving away from the lateral direction displacement threshold value, directions of both control amounts of the first control and the second control become the same direction, and

in a case where the lateral direction position is positioned in a direction toward the lateral direction displacement threshold value, the directions of the control amounts of the first control and the second control become opposite directions.

18. A lane keeping assist method comprising:

obtaining information concerning a lateral direction displacement of a vehicle with respect to a traffic lane, and setting a lateral direction displacement threshold value on the traffic lane where the vehicle travels, and

when the vehicle passes across the lateral direction displacement threshold value from a center side of a width direction of the traffic lane,

at the traffic lane center side with respect to the lateral direction displacement threshold value, controlling a travelling direction of the vehicle so as to decrease an angle deviation of the travelling direction of the vehicle with respect to the traffic lane, and

at an outer side of the width direction of the traffic lane with respect to the lateral direction displacement threshold value, controlling the travelling direction of the vehicle so as to decrease at least a lateral displacement deviation of the vehicle from the lateral direction displacement threshold value.