Vehicle motion control system

• US 5,816,669 A
• Filed: 10/18/1996
• Issued: 10/06/1998
• Est. Priority Date: 10/19/1995
• Status: Expired due to Fees

• Current Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Takahashi, Akira, Matsuura, Munenori, Matsuno, Koji, Hiwatashi, Yutaka
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US08/733,582
• Time in Patent Office: 718 Days
• Field of Search: 303/146, 303/147, 303/148, 303/140, 303/122, 303/122.04, 303/122.05, 364/426.016, 364/424.051, 180/197, 188/181 C, 701/41, 701/42, 701/72, 701/43, 701/76, 701/92, 701/48
• US Class Current: 303/140
• CPC Class Codes: B60T 2260/022 Rear-wheel steering; Four-wheel steering
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

In a vehicle motion control system, a target rear-wheel steering-angle calculating section calculates a target rear-wheel steering angle, a rear-wheel steering-quantity setting section sets a rear-wheel steering quantity, and a rear-wheel steering signal output section outputs a rear-wheel steering quantity to a motor driving section to perform a steering angle control. In addition, a front-and-rear wheel steering response-parameter calculating section calculates a response parameter, and a front-and-rear wheel steering target yaw-rate calculating section calculates a target yaw rate. A yaw-rate difference calculating section calculates a yaw-rate difference, a target braking-force calculating section calculates a target braking force, and a braked-wheel discriminating section selects a wheel to be braked. When an output discriminating section determines that there is within a controllable region, a braking signal output section outputs a signal to a brake driving section so as to add the target braking force to the selected wheel.

Claims

1. A vehicle motion control system having vehicle-speed detecting means, responsive to signals from each left and right front wheel speed sensors and each left and right rear wheel speed sensors mounted on a vehicle, for detecting a running speed of the vehicle and for producing a vehicle speed signal indicative thereof, front-wheel steering-angel detecting means, provided near a steering wheel, for detecting a steering angle of a front wheel of the vehicle and for generating a front-wheel-steering-angle signal indicative thereof, rear-wheel steering-angle detecting means, provided near rear wheels, for detecting a rear-wheel steering angle of the vehicle and for producing a detected rear-wheel-steering-angle signal indicative thereof, and actual yaw-rate detecting means for detecting an actual yaw rate of the vehicle and for producing an actual yaw-rate signal indicative thereof, comprising:

target rear-wheel steering-angle calculating means, responsive to said actual yaw-rate signal and said vehicle speed signal, for calculating a target rear-wheel steering angle and for producing a target rear-wheel-steering-angle signal indicative thereof;

rear-wheel steering quantity signal output means, responsive to said detected rear-wheel-steering-angle signal and said target rear-wheel-steering-angle signal, for outputting the steering quantity of rear wheels;

front-and-rear wheel steering response-parameter calculating means, responsive to said vehicle speed signal, for calculating a front-and-rear wheel steering response parameter in accordance with a front-and-rear wheel steering vehicle model on the basis of the running speed of the vehicle and for generating a parameter signal indicative thereof;

front-and-rear wheel steering target yaw-rate calculating means, responsive to said parameter signal and said front-wheel-steering-angle signal, for calculating a front-and-rear wheel steering target yaw rate on the basis of the parameter signal and the front-wheel-steering-angle signal and for producing a target yaw-rate signal indicative thereof;

yaw-rate difference calculating means, responsive to said target yaw-rate signal and said actual yaw-rate signal, for calculating a yaw rate difference between the front-and-rear wheel steering target yaw rate and the actual yaw rate, and for generating a difference signal indicative thereof;

target braking-force calculating means, responsive to said difference signal, said front-wheel-steering-angle signal, said actual yaw-rate signal, said parameter signal and said vehicle speed signal, for calculating a target braking force of said vehicle on the basis of an operating condition of vehicle motion, and for producing a target braking-force signal indicative thereof;

braked-wheel discriminating means, responsive to said actual yaw-rate signal and said difference signal, for selecting either one of a rear-inside wheel or a front-outside wheel to be braked in accordance with said actual yaw rate signal, and for producing a brake signal indicative thereof;

output discriminating means, responsive to said actual yaw-rate signal and said difference signal, for judging whether or not the vehicle is operating within a braking controllable region, and for producing a judgement signal indicative thereof; and

braking-signal output means, responsive to said judgement signal, said brake signal, and said target braking force signal, for controlling a braking force to each wheel selected by the braked-wheel discriminating means in accordance with said target braking force when said output discriminating means determines that said vehicle is operating within the braking controllable region.

2. A vehicle motion control system having vehicle-speed detecting means, responsive to signals from each left and right front wheel speed sensors and each left and right rear wheel speed sensors mounted on a vehicle, for detecting a running speed of the vehicle and for producing a vehicle speed signal indicative thereof, front-wheel steering-angle detecting means, provided near a steering wheel, for detecting a steering angle of a front wheel of the vehicle and for generating a front-wheel-steering-angle signal indicative thereof, rear-wheel steering-angle detecting means, provided near rear wheels, for detecting a rear-wheel steering angle of the vehicle and for producing a detected rear-wheel-steering-angle signal indicative thereof, and actual yaw-rate detecting means for detecting an actual yaw rate of the vehicle and for producing an actual yaw-rate signal indicative thereof, comprising:

target rear-wheel steering-angle calculating means, responsive to said actual yaw-rate signal and said vehicle speed signal, for calculating a target rear-wheel steering angle and for producing a target rear-wheel-steering-angle signal indicative thereof;

rear-wheel steering quantity signal output means, responsive to said detected rear-wheel-steering-angle signal and said target rear-wheel-steering-angle signal, for outputting the steering quantity of rear wheels;

front-and-rear wheel steering response-parameter calculating means, responsive to said vehicle speed signal, for calculating a front-and-rear wheel steering response parameter in accordance with a front-and-rear wheel steering vehicle model on the basis of the running speed of the vehicle and for generating a first parameter signal indicative thereof;

front-wheel steering response-parameter calculating means, responsive to said vehicle speed signal, for calculating a front-wheel steering response parameter in accordance with a front-wheel steering vehicle model on the basis of the running speed of the vehicle and for generating a second parameter signal;

front-and-rear wheel steering target yaw-rate calculating means, responsive to said first parameter signal and said front-wheel-steering-angle signal, for calculating a front-and-rear wheel steering target yaw rate on the basis of the first parameter signal and the front-wheel-steering-angle signal and for producing a first target yaw-rate signal indicative thereof;

front-wheel steering target yaw-rate calculating means, responsive to said second parameter signal and said front-wheel-steering-angle signal, for calculating a front-wheel steering target yaw-rate on the basis of the second parameter signal and the front-wheel-steering-angle signal and for producing a second target yaw-rate signal;

steering-angle control failure diagnosing means for detecting abnormality in a steering angle control;

steering characteristic switching means for outputting the front-and-rear wheel steering response parameter as a response parameter and the first target yaw-rate signal as an outputted target yaw rate signal in a usual condition, and for outputting the front-wheel steering response parameter and the second target yaw-rate signal as the outputted target yaw rate signal when the steering-angle control failure diagnosing means detects abnormality in the steering angle control;

yaw-rate difference calculating means, responsive to said outputted target yaw-rate signal and said actual yaw-rate signal, for calculating a yaw rate difference between the outputted target yaw rate and the actual yaw rate, and for generating a difference signal indicative thereof;

target braking-force calculating means, responsive to said difference signal, said front-wheel-steering-angle signal, said actual yaw-rate signal, said parameter signal and said vehicle speed signal, for calculating a target braking force of said vehicle on the basis of an operating condition of vehicle motion, and for producing a target braking-force signal indicative thereof;

braked-wheel discriminating means, responsive to said actual yaw-rate signal and said difference signal, for selecting either one of a rear-inside wheel or a front-outside wheel to be braked in accordance with said actual yaw rate signal, and for producing a brake signal indicative thereof;

output discriminating means, responsive to said actual yaw-rate signal and said difference signal, for judging whether or not the vehicle is operating within a braking controllable region and for producing a judgement signal indicative thereof; and

braking-signal output means, responsive to said judgement signal, said brake signal, and said target braking-force signal, for controlling a braking force to each wheel selected by the braked-wheel discriminating means in accordance with said target braking force when said output discriminating means determines that said vehicle is operating within the braking controllable region.

3. A vehicle motion control system as set forth in claim 2, wherein said steering characteristic switching means outputs the front-wheel steering response parameter as the response parameter and the second target yaw rate signal as the outputted target yaw rate signal in a predetermined response characteristic, when the outputs of the response parameter and the outputted target yaw rate are changed to those of the front-wheel steering response parameter and the front-wheel steering target yaw rate.