Vehicle travel assist apparatus

• US 9,365,215 B2
• Filed: 06/13/2013
• Issued: 06/14/2016
• Est. Priority Date: 06/13/2012
• Status: Active Grant

• Current Assignee: Advics Company Limited (Aisin Corp.)
• Original Assignee: Advics Company Limited (Aisin Corp.)
• Inventors: Ohmori, Yosuke, Shiota, Masaki, Takeda, Masayoshi, Mori, Yukio
• Primary Examiner(s): Black, Thomas G
• Assistant Examiner(s): PAIGE, TYLER D
• Application Number:
  US14/405,652
• Publication Number:
  US 20150314784A1
• Time in Patent Office: 1,097 Days
• Field of Search: 701/70, 342/70
• US Class Current: 1/1
• CPC Class Codes: B60T 2201/022 Collision avoidance systems
• CPC Class Codes: B60T 7/22 initiated by contact of vehicle, e.g. bumper, with an external object, e.g. another vehicle , or by means of contactless obstacle detectors mounted on the vehicle
• CPC Class Codes: B60W 2520/00 Input parameters relating to overall vehicle dynamics
• CPC Class Codes: B60W 2554/00 Input parameters relating to objects
• CPC Class Codes: B60W 2720/106 Longitudinal acceleration
• CPC Class Codes: B60W 30/09 Taking automatic action to avoid collision, e.g. braking and steering
• CPC Class Codes: B60W 30/14 Adaptive cruise control
• CPC Class Codes: B60W 30/143 Speed control B60W30/16 takes precedence
• CPC Class Codes: B60W 30/16 Control of distance between vehicles, e.g. keeping a distance to preceding vehicle
• CPC Class Codes: G08G 1/16 Anti-collision systems road vehicle drive control systems for predicting or avoiding probable or impending collision otherwise than by control of a particular sub-unit B60W30/08

Abstract

A collision avoidance ECU sets a model deceleration change amount to smaller value in a state in which it is difficult to reduce the speed of a host vehicle than in a state in which it is easy to reduce the speed of the host vehicle. The collision avoidance ECU calculates a first target value by multiplying the model deceleration change amount by the elapsed time. The collision avoidance ECU obtains a subtraction value by subtracting the current reference relative deceleration from the first target value. Then, the collision avoidance ECU determines a target relative deceleration to be a greater value when the subtraction value is large than when the subtraction value is small, and carries out brake control so that the reference relative deceleration approaches the target relative deceleration.

Claims

1. A vehicle travel assist apparatus, adapted to a vehicle control system which performs speed-reduction control in which a relative deceleration of a host vehicle with respect to an object present ahead of the host vehicle in a traveling direction approaches a target relative deceleration, the vehicle travel assist apparatus comprising:

an electronic control unit configured to determine the target relative deceleration such that a relative speed of the host vehicle with reference to the object becomes less than or equal to a specified speed at a target position set behind the object and ahead of the host vehicle, wherein the electronic control unit is configured such that

under a condition that the host vehicle is decelerating due to performing the speed-reduction control by the vehicle control system,

a reference relative deceleration is defined as a value that is obtained by subtracting a relative deceleration of the host vehicle from a current relative deceleration, when a starting condition of the speed-reduction control has been met,

a model deceleration change amount is defined as a value which is indicative of a change amount of the relative deceleration, and also as a value which corresponds to a reference relative deceleration at a time point in which the host vehicle is in constant deceleration gradient,

when the reference relative deceleration reaches a specified relative deceleration, the model deceleration change amount is set to be a smaller value in a state in which it is relatively more difficult to reduce the speed of the vehicle than in a state in which it is relatively easy to reduce the speed of the vehicle,

a subtraction value is obtained by subtracting the current relative deceleration from a target value, which corresponds to a result obtained by multiplying the model deceleration change amount by an elapsed time from a time point at which the reference relative deceleration reaches the specified relative deceleration, and

the target relative deceleration is determined to be a greater value when the subtraction value is great than when the subtraction value is small.

2. The vehicle travel assist apparatus according to claim 1, wherein the electronic control unit is further configured such that

the target value that corresponds to the result obtained by multiplying the model deceleration change amount by the elapsed time is set as a first target value,

based on the current relative speed and a distance between a current position of the vehicle and the target position, a target relative deceleration with which the relative speed becomes equal to or less than the specified speed at the target position is calculated as a second target value,

a subtraction value is obtained by subtracting the current relative deceleration from a smaller target value of the first and the second target values, and

the target relative deceleration is determined to be a greater value when the subtraction value is great than when the subtraction value is small.

3. The vehicle travel assist apparatus according to claim 2, wherein the electronic control unit is further configured such that;

under the condition that the host vehicle is decelerating due to performing the speed-reduction control by the vehicle control system,

when the reference relative deceleration reaches the specified relative deceleration, the model deceleration change amount is set to be a smaller value when a deceleration change amount, which is an amount of change of a reference relative deceleration at the time point, is small than when the deceleration change amount is great.

4. The vehicle travel assist apparatus according to claim 3, wherein the electronic control unit is further configured such that

when the reference relative deceleration is less than the specified relative deceleration, the target relative deceleration is kept at a target relative deceleration reference value, and

in a case in which the reference relative deceleration becomes equal to or more than the specified relative deceleration, the target relative deceleration is determined to be a greater value when a subtraction value obtained by subtracting the current relative deceleration from a smaller target value of the first and the second target values is great than when the subtraction value is small.

5. The vehicle travel assist apparatus according to claim 4, wherein the electronic control unit is further configured such that, when the reference relative deceleration becomes equal to or more than the specified relative deceleration,

with the deceleration of the vehicle maintained at the smaller target value of the first and the second target values, an estimated value of the distance traveled by the vehicle from the present time to a time point at which the relative speed becomes equal to or less than the specified speed is calculated as a target distance, and

with the deceleration of the vehicle maintained at a current deceleration of the vehicle, an estimated value of the distance traveled by the vehicle from the present time to a time point at which the relative speed becomes equal to or less than the specified speed is calculated as a speed reduction distance, and the target relative deceleration is set to be a greater value when a subtraction value obtained by subtracting the target distance from the speed reduction distance is great than when the subtraction value is small.

6. The vehicle travel assist apparatus according to claim 3, wherein the electronic control unit is further configured such that

when the reference relative deceleration is less than the specified relative deceleration, the target relative deceleration is kept at the target relative deceleration reference value, and

when the reference relative deceleration becomes equal to or more than the specified relative deceleration,

with the deceleration of the vehicle maintained at the smaller target value of the first and the second target values, an estimated value of the distance traveled by the vehicle from the present time to a time point at which the relative speed becomes equal to or less than the specified speed as the target distance, and

the target relative deceleration is set to be a greater value when a subtraction value obtained by subtracting the distance between the current position of the vehicle and the target position from the target distance is great than when the subtraction value is small.