Steering assist apparatus and method for vehicle

• US 20050273234A1
• Filed: 05/27/2005
• Published: 12/08/2005
• Est. Priority Date: 06/02/2004
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Kataoka, Hiroaki, Iwazaki, Katsuhiko, Rattapon, Chumsamutr, Niwa, Satoru, Kawakami, Seiji
• Granted Patent: US 7,373,230 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 1/28 non-mechanical , e.g. following a line or other known markers
• CPC Class Codes: B62D 6/00 Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits means for initiating a change in direction B62D1/00; steering valves B62D5/06; combined with means for inclining the vehicle body or wheels on bends B62D9/00
• CPC Class Codes: B62D 6/001 the torque NOT being among the input parameters
• CPC Class Codes: B62D 6/04 responsive only to forces disturbing the intended course of the vehicle, e.g. forces acting transversely to the direction of vehicle travel

Abstract

Characteristic lines A to D of lateral acceleration G-required torque T in determination of required torque T are used as switched according to increase/decrease of the absolute value of the lateral acceleration, and the direction thereof. The lines A, C used in increase of the absolute value of the lateral acceleration G are so set that the absolute value of required torque T becomes larger at the same lateral acceleration G (G≠0) than that with the lines B, D used in decrease of the absolute value of the lateral acceleration G. The difference between line A and line B (the difference between line C and line D as well) at the same lateral acceleration G is so set that the difference near the lateral acceleration of 0 is smaller than that in the other regions. Particularly, it is preferable to set the required torque T to 0 at the lateral acceleration G of 0.

Claims

1. A steering assist apparatus for a vehicle to apply an assist steering force for assisting a driver'"'"'s steering force in response to a target lateral acceleration for the vehicle,

wherein an assist torque to be applied at an arbitrary target lateral acceleration is so set that the assist torque in an increasing state of the target lateral acceleration is larger than the assist torque in a decreasing state of the target lateral acceleration, and wherein a difference between the assist torque applied in the decreasing state of the target lateral acceleration and the assist torque applied in the increasing state of the target lateral acceleration in a region near the target lateral acceleration of 0 is set smaller than in the other case.

2. The steering assist apparatus according to claim 1, wherein at the target lateral acceleration of 0, the difference between the assist torque applied in the decreasing state of the target lateral acceleration and the assist torque applied in the increasing state of the target lateral acceleration is set to 0.

3. The steering assist apparatus according to claim 1, wherein on the basis of a transition of time change of the target lateral acceleration, it is determined that a switch of an increase/decrease direction was made, if an identical tendency further continues after a switch from decrease to increase or from increase to decrease of the target lateral acceleration.

4. The steering assist apparatus according to claim 1, wherein a device for applying the assist steering force is an electric motor for driving a steering system, and wherein a drive torque of the electric motor is controlled.

5. The steering assist apparatus according to claim 1, further comprising means for recognizing a future course of the host vehicle and a driving lane and for calculating a lateral acceleration necessary for keeping the vehicle running on the driving lane, wherein steering assist is performed according to the lateral acceleration calculated.

6. A steering assist method for a vehicle comprising the step of determining the target lateral acceleration for a steering assist operation, and applying an assist steering force for assisting a driver'"'"'s steering force in response to the target lateral acceleration,

wherein an assist torque to be applied at an arbitrary target lateral acceleration is so set that the assist torque in an increasing state of the target lateral acceleration is larger than the assist torque in a decreasing state of the target lateral acceleration, and wherein a difference between the assist torque applied in the decreasing state of the target lateral acceleration and the assist torque applied in the increasing state of the target lateral acceleration in a region near the target lateral acceleration of 0 is set smaller than in the other case.

7. The steering assist method according to claim 6, wherein at the target lateral acceleration of 0, the difference between the assist torque applied in the decreasing state of the target lateral acceleration and the assist torque applied in the increasing state of the target lateral acceleration is set to 0.

8. The steering assist method according to claim 6, wherein on the basis of a transition of time change of the target lateral acceleration, it is determined that a switch of an increase/decrease direction was made, if an identical tendency further continues after a switch from decrease to increase or from increase to decrease of the target lateral acceleration.

9. The steering assist method according to claim 6, further comprising a step of recognizing a future course of the host vehicle and a driving lane and calculating a lateral acceleration necessary for keeping the vehicle traveling on the driving lane, wherein steering assist is performed according to the lateral acceleration calculated.