Speed control system for vehicles
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.
1. A speed control system for vehicles comprising:
means for detecting a distance to a preceding vehicle;
means for detecting a relative speed between a subject vehicle and the preceding vehicle;
means for computing 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;
first means for setting a threshold value of the corrected distance condition evaluation index and taking an offset amount preset with respect to distance as zero value of distance at the threshold value of the corrected distance condition evaluation index;
means for checking whether the corrected distance condition evaluation index is higher than the threshold value of the corrected distance condition evaluation index;
second means for setting the threshold value of the corrected distance condition evaluation index as a target value of the corrected distance condition evaluation index when the corrected distance condition evaluation index is higher than the threshold value of the corrected distance;
means for computing the target deceleration of the subject vehicle based on a target relative speed corresponding to the target value set by the means for setting the threshold value as the target value and an actual relative speed; and
means for starting deceleration control to decelerate the subject vehicle so that deceleration of the subject vehicle becomes equal to the target deceleration.
2. The speed control system for vehicles of claim 1 ,
wherein the starting 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.
3. The speed control system for vehicles of claim 1 ,
wherein the starting 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.
4. The speed control system for vehicles of claim 1 , wherein:
the first setting 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 checking 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.
5. 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.
6. The speed control system for vehicles of claim 5 ,
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
Doffset
=
10
80
+
10
log
10
α
2.5
+
10
log
10
Vb
-
γ
β
+
30
where, α, β and γ are constants determined based on experiment and Vb is the speed of the preceding vehicle.
7. 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.
8. A speed control system for vehicles comprising:
means for detecting a distance to an object ahead;
means for detecting a relative speed between a subject vehicle and the object ahead;
means for storing 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;
means for computing a target relative speed from the correction formula for computation of target relative speed and a distance actually detected by the means for detecting the distance;
means for computing a target deceleration from a target relative speed computed by the means for computing a target relative speed and a relative speed actually detected by the means for detecting the relative speed; and
means for performing deceleration control on the subject vehicle based on the target deceleration.
9. The speed control system for vehicles of claim 8 ,
wherein the offset amount is set based on speed control setting information of the subject vehicle.
10. The speed control system for vehicles of claim 9 ,
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
Doffset
=
10
80
+
10
log
10
α
2.5
+
10
log
10
Vb
-
γ
β
+
30
where, α, β and γ are constants determined based on experiment and Vb is the speed of the preceding vehicle.
11. The speed control system for vehicles of claim 8 ,
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.
12. A speed control system for vehicles comprising:
means for detecting a distance to an object ahead;
means for detecting a relative speed between a subject vehicle and the object ahead;
means for storing 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;
means for computing a target relative speed from the correction formula for computation of target relative speed and a distance actually detected by the means for detecting the distance;
means for computing a target deceleration from a target relative speed computed by the means for computing a target relative speed and a relative speed actually detected by the means for detecting the relative speed; and
means for performing deceleration control on the subject vehicle based on the target deceleration.
13. The speed control system for vehicles of claim 12 , 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 preceding 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.
14. The speed control system for vehicles of claim 12 ,
wherein the starting 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.
15. The speed control system for vehicles of claim 12 ,
wherein the starting 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.
16. The speed control system for vehicles of claim 12 ,
wherein the offset amount is set based on speed control setting information of the subject vehicle.
17. The speed control system for vehicles of claim 16 ,
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
Doffset
=
10
80
+
10
log
10
α
2.5
+
10
log
10
Vb
-
γ
β
+
30
where, α, β and γ are constants determined based on experiment and Vb is the speed of the preceding vehicle.
18. The speed control system for vehicles of claim 12 ,
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.