Vehicle rear wheel steer angle control system

• US 5,150,764 A
• Filed: 10/01/1990
• Issued: 09/29/1992
• Est. Priority Date: 12/28/1987
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Sakita, Yuzo, Eguchi, Takaaki
• Primary Examiner(s): Kashnikow, Andres
• Assistant Examiner(s): CAMBY, RICHARD M
• Application Number:
  US07/593,269
• Time in Patent Office: 729 Days
• Field of Search: 180/140, 180/141, 180/142, 180/143, 180/79.1, 180/79, 280/91, 364/424.01, 364/424.05, 74/388 PS, 60/385, 60/386, 91/536, 91/386, 92/7, 92/131, 92/117 R
• US Class Current: 180/415
• CPC Class Codes: B62D 7/1572 provided with electro-hydraulic control means
• 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

A vehicle rear wheel steering control system includes a steering actuator for varying an actual rear wheel steer angle in accordance with a control signal, a steering input sensor, and a controller for producing the control signal in accordance with the steering input. The controller has a first functional section for determining a first desired rear wheel steer angle so as to obtain a flat characteristic of a yaw rate gain with respect to a steering frequency, a second functional section for determining a second desired rear wheel steer angle in accordance with a steering acceleration, and a third functional section for adding the second desired rear wheel steer angle to the first desired rear wheel steer angle.

Claims

1. A rear wheel control steering system for a vehicle, comprising:

a steering actuator for varying an actual rear wheel steering angle of said vehicle in response to a control signal; and

a controller for producing said control signal said controller having first operational means for determining a first desired rear wheel steer angle so as to hold a yaw rate gain of said vehicle substantially constant in relation to a steering frequency, second operational means for determining a second desired rear wheel steer angle in accordance with steering acceleration proportional to a time rate of change of a steering speed which is a time rate of change of a front wheel steer angle, a third operational means for adding said second desired rear wheel steer angle to said first desired rear wheel steer angle,

a steering input sensor for sensing a steering input of said vehicle, said controller being connected with said steering input sensor, and

first differentiating means for determining a steering speed which is substantially equal to a first derivative of said steering input with respect to time, second differentiating means for determining said steering acceleration which is substantially equal to a second derivative of said steering input with respect to time, and wherein said first operational means is connected with said first differentiating means and determines said first desired rear wheel steer angle in accordance with said steering input and said steering speed, and said second operational means is connected with said second differentiating means.

2. A control system according to claim 1 wherein said first operational means has such a characteristic that said first desired rear wheel steer angle is proportional to a linear combination of said steering input and said steering speed, and said second operational means has such a characteristic that said second desired rear wheel steer angle is proportional to said steering acceleration.

3. A control system according to claim 2 wherein said second desired rear wheel steer angle is equal to a product obtained by multiplying said steering acceleration by a second derivative constant which is negative.

4. A control system according to claim 3 wherein said control system further comprises a vehicle speed sensor for sensing a vehicle speed of said vehicle, said vehicle speed sensor being connected with said controller, and wherein said controller further comprises means for determining a proportional constant in accordance with said vehicle speed, means for determining a first derivative constant in accordance with said vehicle speed, and means for determining said second derivative constant in accordance with said vehicle speed, and said first operational means determines said first desired rear wheel steer angle by adding said steering input multiplied by said proportional constant and said steering speed multiplied by said first derivative constant.

5. A control system according to claim 4 wherein said steering input sensor is a sensor for sensing a steering wheel angle of said vehicle.

6. A rear wheel steering control system of an automobile, comprising:

a steering actuator for varying an actual rear wheel steer angle of said vehicle in response to a control signal;

a steering input sensor for sensing a steering input of said vehicle; and

a controller for producing said control signal, said controller being connected with said steering input sensor, said controller comprising;

first operational means for determining a first desired rear wheel steer angle so as to hold a yaw rate gain of said vehicle substantially constant;

second operational means for determining a second desired rear wheel steer angle in accordance with a steering acceleration;

third operational means for adding said second desired rear wheel steer angle to said first desired rear wheel steering angle;

first differentiating means for determing a steering speed which is substantially equal to a first derivative of said steering input with respect to time; and

second differentiating means for determining said steering acceleration which is substantially equal to a second derivative of said steering input with respect to time, and wherein said first operational means is connected with said first differentiating means and determines said first rear wheel steer angle in accordance with said steering input and said steering speed, and said second operational means is connected with said second differentiating means.

7. A control system according to claim 6, wherein said first operational means has such a characteristic that said first desired rear wheel steer angle is proportional to a linear combination of said steering input and said steering speed, and said second operation means has such a characteristic that said second desired rear wheel steer angle is proportional to said steering acceleration.

8. A control system according to claim 7, wherein said second desired rear wheel steer angle is equal to a product obtained by multiplying said steering acceleration by a negative second derivative constant.

9. A control system according to claim 8, wherein said control system further comprises a vehicle speed sensor for sensing the speed of said vehicle, said vehicle speed sensor being connected with said controller, and wherein said controller further comprises means for determining a proportional constant in accordance with said vehicle speed, means for determining a first derivative constant in accordance with said vehicle speed, and means for determining said second derivative constant in accordance with said vehicle, said first operational means determining said first desired rear wheel steering angle by adding said steering input multiplied by said proportional constant and said steering speed multiplied by said first derivative constant.

10. A control system according to claim 9, wherein said steering input sensor senses the steering wheel angle of said vehicle.

11. A rear wheel steering control system for a vehicle, comprising:

a steering actuator for steering the rear wheel of a vehicle in response to a control signal representing a desired rear wheel steer angle;

a steering input sensor for sensing a steering input of said vehicle; and

a controller which is connected with said steering input sensor, and which produces said control signal representing said desired rear wheel steering angle which is equal to the sum of a first term determined in accordance with said steering input, and a second term substantially proportional to a second derivative of said steering input with respect to time.

12. A control system according to claim 11, wherein said controller comprises a means for determining said second term which is substantially equal to the product obtained by multiplying said second derivative of said steering input by a negative second derivative constant.

13. A control system according to claim 11, wherein said control system further comprises a vehicle speed sensor for sensing the vehicle speed of said vehicle, said vehicle speed sensor being connected to said controller, and wherein said controller further comprises a means, connected with said vehicle speed sensor, for determining a second derivative constant in accordance with said vehicle speed, and a means for determining said second term which is substantially equal to a product obtained by multiplying said second derivative of said steering input by said second derivative constant.

14. A rear wheel steering control system for a vehicle, comprising:

a steering actuator for steering the rear wheels of said vehicle in response to a control signal representing a desired rear wheel steer angle;

a steering input sensor for sensing a steering input of said vehicle, and a controller which is connected with said steering input sensor, and which produces said control signal representing said desired rear wheel steer angle which is equal to a sum of a first term determined in accordance with said steering input, said first term being equal to a sum of a first product obtained by multiplying said steering input by a proportional constant, and a second product obtained by multiplying a steering speed which is substantially equal to a time rate of change of said steering input by a first derivative constant, and said second term is equal to a third product obtained by multiplying a steering acceleration which is substantially equal to a time rate of change of said steering speed by a second derivative constant, a second term substantially proportional to a second derivative of said steering input with respect to time, wherein said control system further includes a vehicle speed sensor being connected with said controller, each of said proportional first derivative and second derivative constants being a function of said vehicle speed.