Speed control system for vehicles

• US 20090093938A1
• Filed: 09/25/2008
• Published: 04/09/2009
• Est. Priority Date: 10/09/2007
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Isaji, Kazuyoshi, Tsuru, Naohiko
• Granted Patent: US 8,078,383 B2
• Time in Patent Office: Days
• US Class Current: 701/96
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2552/00 Input parameters relating to infrastructure
• CPC Class Codes: B60W 2552/20 Road profile, i.e. the change in elevation or curvature of a plurality of continuous road segments
• CPC Class Codes: B60W 2552/30 Road curve radius
• CPC Class Codes: B60W 2552/40 Coefficient of friction
• CPC Class Codes: B60W 2554/4041 Position
• CPC Class Codes: B60W 2555/20 Ambient conditions, e.g. wind or rain
• CPC Class Codes: B60W 2556/50 of positioning data, e.g. GPS [Global Positioning System] data
• CPC Class Codes: B60W 2720/106 Longitudinal acceleration
• CPC Class Codes: B60W 30/16 Control of distance between vehicles, e.g. keeping a distance to preceding vehicle

Abstract

In a vehicle speed control system, a preset offset distance is taken as a zero value of an inter-vehicle distance in a brake discriminant. When the current value of a corrected distance condition evaluation index is higher than the brake discriminant, a value on the brake discriminant is set as a target value of the corrected distance condition evaluation index. Deceleration control is started to decelerate the subject vehicle so that the deceleration of the subject vehicle becomes equal to the target deceleration of the subject vehicle computed based on the target relative speed corresponding to the set target value and the actual relative speed.

Claims

1. A speed control system for vehicles comprising:

a distance detecting means that detects a distance to a preceding vehicle;

a relative speed detecting means that detects a relative speed between a subject vehicle and the preceding vehicle;

an evaluation index computing means that computes a corrected distance condition evaluation index which is increased with increase in the relative speed when approaching the preceding vehicle and whose increase gradient becomes greater as the distance to the preceding vehicle becomes shorter at each relative speed as an index indicating the condition of approaching or separating from the preceding vehicle by taking into consideration of a speed of the preceding vehicle;

an evaluation index threshold value computing means that sets a threshold value of the corrected distance condition evaluation index and takes an offset amount preset with respect to distance as zero value of distance at the threshold value of the corrected distance condition evaluation index;

a deceleration target checking means that checks whether the corrected distance condition evaluation index is higher than the threshold value of the corrected distance condition evaluation index;

a target value setting means that, when the corrected distance condition evaluation index is higher than the threshold value of the corrected distance condition evaluation index, sets the threshold value of the corrected distance condition evaluation index as a target value of the corrected distance condition evaluation index;

a target deceleration computing means that computes the target deceleration of the subject vehicle based on a target relative speed corresponding to the target value set by the target value setting means and an actual relative speed; and

a controlling means that starts deceleration control to decelerate the subject vehicle so that deceleration of the subject vehicle becomes equal to the target deceleration.

5. The speed control system for vehicles of claim 1,

wherein the controlling means maintains the target deceleration of the subject vehicle when the actual distance is equal to the offset amount and continues the execution of deceleration control, when the actual distance is shorter than the offset amount.

6. The speed control system for vehicles of claim 1,

wherein the controlling means takes a deceleration obtained by dividing the relative speed by a predetermined time as the target deceleration of the subject vehicle and continues execution of deceleration control, when the actual distance is shorter than the offset amount.

7. The speed control system for vehicles of claim 1, wherein:

the evaluation index threshold value computing means also computes the threshold value of a corrected distance condition evaluation index in which the zero value of the actual distance is taken as the zero value of distance at the threshold value of the corrected distance condition evaluation index; and

the deceleration target determining means carries out determination using the threshold value of the corrected distance condition evaluation index in which the zero value of the actual distance to the preceding vehicle is taken as the zero value of distance at the threshold value of the corrected distance condition evaluation index, when the actual distance is shorter than the offset amount.

8. The speed control system for vehicles of claim 1,

wherein the offset amount is set based on speed control setting information of the subject vehicle.

9. The speed control system for vehicles of claim 8,

wherein, when the speed control setting information indicates that control to carry out speed control so that the relative speed between the subject vehicle and the preceding vehicle becomes zero at a constant distance to the preceding vehicle is active, the offset amount is set using the following formula for computation of offset distance

10. The speed control system for vehicles of claim 1,

wherein the offset amount is set based on information acquired by wireless communication with an external source, the information being on external environment having influence on traveling speed of the subject vehicle.

2. A speed control system for vehicles comprising:

a distance detecting means that detects a distance to an object ahead;

a relative speed detecting means that detects a relative speed between a subject vehicle and the object ahead;

a storing means that stores a correction formula for computation of a corrected target relative speed obtained by correcting a formula for computation of a target relative speed with an offset amount indicating the target relative speed when the distance is zero,

wherein the formula for computation of target relative speed is determined from a distance condition evaluation index relational expression and a tangential expression so that a target relative speed is determined based on the distance,

wherein, the distance condition evaluation index relational expression indicates a relation among the distance condition evaluation index indicating condition of distance to the object ahead, a distance to the object ahead and the relative speed, so that the distance condition evaluation index is increased with increase in the relative speed when approaching the object ahead and an increase gradient of the distance condition evaluation index becomes greater as the distance to the object ahead becomes shorter at identical relative speed, and

wherein the tangential expression indicates a tangent of a curve represented by the distance condition evaluation index relational expression, and is determined by differentiating the distance condition evaluation index relational expression by the distance, thereby indicating a relation between the distance condition evaluation index and the distance;

a target relative speed computing means that computes a target relative speed from the correction formula for computation of target relative speed and a distance actually detected by the distance detecting means;

a target deceleration computing means that computes a target deceleration from a target relative speed computed by the target relative speed computing means and a relative speed actually detected by the relative speed detecting means; and

a controlling means that performs deceleration control on the subject vehicle based on the target deceleration.

13. The speed control system for vehicles of claim 2,

wherein the offset amount is set based on speed control setting information of the subject vehicle.

14. The speed control system for vehicles of claim 13,

wherein, when the speed control setting information indicates that control to carry out speed control so that the relative speed between the subject vehicle and the preceding vehicle becomes zero at a constant distance to the preceding vehicle is active, the offset amount is set using the following formula for computation of offset distance

17. The speed control system for vehicles of claim 2,

wherein the offset amount is set based on information acquired by wireless communication with an external source, the information being on external environment having influence on traveling speed of the subject vehicle.

3. A speed control system for vehicles comprising:

a distance detecting means that detects a distance to an object ahead;

a relative speed detecting means that detects a relative speed between a subject vehicle and the object ahead;

a storing means that stores a correction formula for computation of a corrected target relative speed obtained by correcting a formula for computation of a target relative speed with an offset amount indicating the distance when the relative speed is zero,

wherein the formula for computation of target relative speed is determined from a distance condition evaluation index relational expression and a tangential expression so that a target relative speed is determined based on the distance,

wherein, the distance condition evaluation index relational expression indicates a relation among the distance condition evaluation index indicating condition of distance to the object ahead, a distance to the object ahead and the relative speed, so that the distance condition evaluation index is increased with increase in the relative speed when approaching the object ahead and an increase gradient of the distance condition evaluation index becomes greater as the distance to the object ahead becomes shorter at identical relative speed, and

wherein the tangential expression indicates a tangent of a curve represented by the distance condition evaluation index relational expression, and is determined by differentiating the distance condition evaluation index relational expression by the distance, thereby indicating a relation between the distance condition evaluation index and the distance;

a target relative speed computing means that computes a target relative speed from the correction formula for computation of target relative speed and a distance actually detected by the distance detecting means;

a target deceleration computing means that computes a target deceleration from a target relative speed computed by the target relative speed computing means and a relative speed actually detected by the relative speed detecting means; and

a controlling means that performs deceleration control on the subject vehicle based on the target deceleration.

4. The speed control system for vehicles of claim 3, wherein:

the distance condition evaluation index is computed as a corrected distance condition evaluation index from the relative speed between the subject vehicle and the preceding vehicle, the speed of the preceding vehicle and the distance to the preceding vehicle, so that the distance condition to the preceding vehicle in consideration of the speed of the preceing vehicle is indicated, the corrected distance condition evaluation index being increased with increase in the relative speed when approaching the preceding vehicle, and an increase gradient becoming greater as the distance to the preceding vehicle becomes shorter at each relative speed;

the offset amount in the formula for computation of corrected target relative speed uses the distance to the preceding vehicle computed by taking the speed of the preceding vehicle as actual detection value in a formula for computation of offset distance, which indicates a relation between the distance to the preceding vehicle and the speed of the preceding vehicle, and which is obtained from a formula for computing the corrected evaluation index and a deceleration start discriminant by zeroing the relative speed, the deceleration start discriminant indicating a relation between the corrected distance condition evaluation index and the distance to the preceding vehicle when deceleration of the subject vehicle is started.

11. The speed control system for vehicles of claim 3,

wherein the controlling means maintains the target deceleration of the subject vehicle when the actual distance is equal to the offset amount and continues the execution of deceleration control, when the actual distance is shorter than the offset amount.

12. The speed control system for vehicles of claim 3,

wherein the controlling means takes a deceleration obtained by dividing the relative speed by a predetermined time as the target deceleration of the subject vehicle and continues execution of deceleration control, when the actual distance is shorter than the offset amount.

15. The speed control system for vehicles of claim 3,

wherein the offset amount is set based on speed control setting information of the subject vehicle.

16. The speed control system for vehicles of claim 15,

wherein, when the speed control setting information indicates that control to carry out speed control so that the relative speed between the subject vehicle and the preceding vehicle becomes zero at a constant distance to the preceding vehicle is active, the offset amount is set using the following formula for computation of offset distance

18. The speed control system for vehicles of claim 3,

wherein the offset amount is set based on information acquired by wireless communication with an external source, the information being on external environment having influence on traveling speed of the subject vehicle.