Vehicle steering apparatus and vehicle steering method

• US 7,416,264 B2
• Filed: 06/09/2005
• Issued: 08/26/2008
• Est. Priority Date: 06/14/2004
• Status: Expired due to Fees

• Current Assignee: Subaru Corp.
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Tsukasaki, Yuichiro
• Primary Examiner(s): Siconolfi; Robert A.
• Assistant Examiner(s): SY, MARIANO ONG
• Application Number:
  US11/148,334
• Publication Number:
  US 20050275283A1
• Time in Patent Office: 1,174 Days
• Field of Search: 303/155, 303/189, 303/191, 180/402, 180/410, 701/41, 280/5.52, 280/5.522, 280/86.758
• US Class Current: 303/189
• CPC Class Codes: B60T 11/21 with two pedals operating on respective circuits, pressures therein being equalised when both pedals are operated together, e.g. for steering steering non-deflectable wheels or endless tracks by differentially driving ground-engaging elements on opposite vehicle sides using brakes as main steering effecting means B62D11/08
• CPC Class Codes: B60T 2260/02 Active Steering, Steer-by-Wire
• CPC Class Codes: B60T 7/10 Disposition of hand control
• CPC Class Codes: B60T 8/00 Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force by changing number of effective brake cylinders in power brake systems B60T17/10
• CPC Class Codes: B60T 8/1766 Proportioning of brake forces according to vehicle axle loads, e.g. front to rear of vehicle
• CPC Class Codes: B60W 10/119 including control of all-wheel-driveline means, e.g. transfer gears or clutches for dividing torque between front and rear axle B60W10/14 takes precedence
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 10/20 including control of steering systems
• CPC Class Codes: B60W 2510/20 Steering systems
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 40/10 related to vehicle motion
• CPC Class Codes: B62D 9/007 Emergency systems using the steering system for braking

Abstract

A wheel adjusting device can adjust separately the wheel angles of left and right wheels. A judgment portion which determines whether vehicle braking is to be permitted or not based on the driving state of the vehicle. A control portion controls the wheel adjusting device. More specifically, under conditions where the vehicle braking is permitted by the judgment portion, the control portion defines the wheel angles of the left and right wheels to be in opposite phase and adjusts the wheel angles in accordance with the braking force to be applied to the left and right wheels.

Claims

1. A vehicle steering apparatus comprising:

a driving state detecting device for detecting a driving state of the vehicle;

a wheel adjusting device for adjusting separately the wheel angles of left and right wheels;

a braking force estimating device for estimating braking force to be applied to the left and right wheels periodically;

a judgment portion for determining whether vehicle braking is to be permitted or not based on the driving state of the vehicle; and

a control portion controlling the wheel adjusting device,

wherein, in the case that vehicle braking is permitted by the judgment portion, the control portion sets the wheel angles of the left and right wheels to be in opposite phase and adjusts the wheel angles in accordance with the braking force to be applied to the left and right wheels, and

said control portion sets

first target wheel angles of the left and right wheels to be the sum of a predetermined step value and current wheel angles when a current braking force is larger than a previous braking force or

second target wheel angles of the left and right wheels to be the subtraction of a predetermined step value from the current wheel angles when the current braking force is smaller than the previous braking force.

2. The vehicle steering apparatus according to claim 1,

wherein the control portion sets the wheel angles to be larger than the current value if the current braking force to be applied is larger than the previous braking force, and sets the wheel angles to be smaller than the current value if the current braking force to be applied is smaller than the previous braking force.

3. The vehicle steering apparatus according to claim 1, further comprising:

a detecting portion which detects the deceleration of the vehicle, wherein the control portion estimates the braking force based on the deceleration of the vehicle.

4. The vehicle steering apparatus according to claim 1, further comprising:

a detecting portion which directly detects the longitudinal force and lateral force acting on the wheels, wherein the control portion estimates the braking force based on the size of the circle of friction of the wheels calculated from the longitudinal force and lateral force.

5. The vehicle steering apparatus according to claim 1, further comprising:

a detecting portion which directly detects the longitudinal force and lateral force acting on the wheels, wherein the control portion estimates the braking force based on the longitudinal force, lateral force and angle of wheels.

6. The vehicle steering apparatus according to claim 1,

wherein the control portion defines the angle of wheels so that the left and right wheels are in a toe-in orientation.

7. The vehicle steering apparatus according to claim 1,

wherein the driving state detecting device detects an operation state of an anti-lock brake system and the judgment portion determines whether vehicle braking is to be permitted or not based on the operation state of the anti-lock braking system.

8. The vehicle steering apparatus according to claim 7,

wherein the judgment portion permits the vehicle braking when the anti-lock brake system operates.

9. The vehicle apparatus according to claim 1,

wherein the control portion sets target wheel angles based on whether the braking force is increasing or decreasing.

10. The vehicle apparatus according to claim 1,

wherein the braking force estimating device estimates braking force to be applied to the left and right wheels periodically and

the control portion sets target wheel angles based on a comparison a current braking force with a previous braking force.

11. The vehicle apparatus according to claim 1,

wherein the control portion makes a determination during vehicle braking is permitted by the judgment portion that a current braking force value is equal, higher or lower than a previous braking force value and

sets target wheel angles of the left and right wheels based on the determination.

12. The vehicle apparatus according to claim 1,

wherein said control portion sets

the first target wheel angles of the left and right wheels to be the sum of the predetermined step value and the current wheel angles when the current braking force is equal or larger than the previous braking force.

13. The vehicle steering apparatus according to claim 1, further comprising a detecting portion which detects friction forces acting on the wheels and said braking force estimating device estimates braking force periodically based on detected friction forces during a vehicle braking action.

14. A vehicle steering method comprising:

a first step of determining whether vehicle braking is to be permitted or not based on a driving state of the vehicle;

a second step of estimating braking force to be applied to left and right wheels periodically; and

a third step of controlling the wheel angles of the left and right wheels, wherein, in the case that the vehicle braking is permitted, the third step sets the wheel angles of the left and right wheels to be in opposite phase and adjusts the wheel angles in accordance with the braking force to be applied to the left and right wheels, and

said third step sets

first target wheel angles of the left and right wheels to be the sum of a predetermined step value and current wheel angles when a current braking force is larger than a previous braking force or

second target wheel angles of the left and right wheels to be the subtraction of a predetermined step value from the current wheel angles when the current braking force is smaller than the previous braking force.

15. The vehicle steering method according to claim 14,

wherein the third step sets the wheel angles to be larger than the current angles if the current braking force to be applied is equal to or larger than the previous braking force and sets the wheel angles to be smaller than the current value if the current braking force to be applied is smaller than the previous braking force.

16. The vehicle steering method according to claim 14,

wherein the braking force is estimated based on the deceleration of the vehicle.

17. The vehicle steering method according to claim 14,

wherein the braking force is estimated based on the size of the circle of friction of the wheels calculated from a longitudinal force and lateral force acting on the wheels.

18. The vehicle steering method according to claim 14, further comprising:

wherein the braking force is estimated based on a longitudinal force acting on the wheels, lateral force acting on the wheels and angle of wheels.

19. The vehicle steering method according to claim 14,

wherein the angle of wheels is set in the third step as that the left and right wheels are in a toe-in orientation.

20. The vehicle method according to claim 14,

wherein the first step determines whether vehicle braking is to be permitted or not based on a operation state of an anti-lock braking system.

21. The vehicle method according to claim 20,

wherein the first step permits vehicle braking when the anti-lock braking system operates.