Vehicle motion control system

• US 5,931,546 A
• Filed: 10/24/1997
• Issued: 08/03/1999
• Est. Priority Date: 10/25/1996
• Status: Expired due to Term

• Current Assignee: Advics Company Limited (Aisin Corp.)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Inventors: Mihara, Jun, Nakashima, Hiroshi, Hamada, Toshiaki
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US08/957,461
• Time in Patent Office: 648 Days
• Field of Search: 303/122.03, 303/122.05, 303/122.04, 303/122.06, 303/122.07, 303/140, 303/147, 303/146, 701/76, 701/92, 701/43, 701/72
• US Class Current: 303/146
• CPC Class Codes: B60T 2210/22 Banked curves
• CPC Class Codes: B60T 2270/402 Back-up
• CPC Class Codes: B60T 2270/413 Plausibility monitoring, cross check, redundancy
• 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: B60T 8/4827 in hydraulic brake systems
• CPC Class Codes: B60T 8/885 using electrical circuitry

Abstract

A vehicle motion control system for a vehicle for maintaining stability of a vehicle when the vehicle is in motion includes braking device for applying a braking force to each wheel of the vehicle. The system includes a lateral acceleration sensor for sensing a lateral acceleration of the vehicle and a yaw rate sensor for sensing a yaw rate of the vehicle. A vehicle slip angular velocity is calculated on the basis of output signals of the lateral acceleration sensor and the yaw rate sensor and then a vehicle motion condition is determined on the basis of the vehicle slip angular velocity. The braking device is actuated to apply a braking force to at least one of the wheels on the basis of the vehicle motion condition and irrespective of depression of the brake pedal in order to maintain the stability of the vehicle in motion. An abnormal condition of at least one of the lateral acceleration sensor and the yaw rate sensor is determined on the basis of the vehicle slip angular velocity.

Claims

1. A vehicle motion control system for maintaining stability of a vehicle having a plurality of wheels when the vehicle is in motion, comprising:

braking means for applying a braking force to each wheel of the vehicle;

a lateral acceleration sensor for sensing a lateral acceleration of the vehicle;

a yaw rate sensor for sensing a yaw rate of the vehicle;

slip angular velocity calculation means for calculating a vehicle slip angular velocity on the basis of output signals of the lateral acceleration sensor and the yaw rate sensor;

vehicle motion determination means for determining vehicle motion on the basis of the vehicle slip angular velocity calculated by the slip angular velocity calculation means;

motion control means for actuating the braking means to apply a braking force to at least one of the wheels on the basis of an output of the vehicle motion determination means and irrespective of depression of a brake pedal in order to maintain stability of the vehicle in motion; and

sensor condition determination means for determining if at least one of the lateral acceleration sensor and the yaw rate sensor is in an abnormal condition on the basis of the vehicle slip angular velocity calculated by the slip angular velocity calculation means.

2. A vehicle motion control system according to claim 1, wherein the sensor condition determination means determines that said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition when the vehicle slip angular velocity calculated by the slip angular velocity calculation means is greater than a first predetermined upper limit value.

3. A vehicle motion control system according to claim 2, wherein the sensor condition determination means determines that said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition when the vehicle slip angular velocity calculated by the slip angular velocity calculation means is greater than the first predetermined upper limit value and when a first predetermined time period has elapsed.

4. A vehicle motion control system according to claim 1, further including slip angular acceleration calculation means for calculating a vehicle slip angular acceleration on the basis of the vehicle slip angular velocity calculated by the slip angular velocity calculation means, the sensor condition determination means determining that said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition when the vehicle slip angular acceleration calculated by the slip angular acceleration calculation means is greater than a second predetermined upper limit value.

5. A vehicle motion control system according to claim 4, wherein the sensor condition determination means determines said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition when the vehicle slip angular acceleration calculated by the slip angular acceleration calculation means is greater than the second predetermined upper limit value and when a second predetermined time period has elapsed.

6. A vehicle motion control system according to claim 1, further including vehicle speed detecting means for detecting a vehicle speed and fail-control means for holding the braking force applied to said at least one of the wheels until the vehicle speed detected by the vehicle speed detecting means is less than the predetermined value, when the sensor condition determination means determines that said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition.

7. A vehicle motion control system according to claim 6, wherein the fail-control means decreases the braking force applied to said at least one of the wheels after the vehicle speed detected by the vehicle speed detecting means is less than the predetermined value.

8. A vehicle motion control system according to claim 1, wherein the vehicle motion determination means determines if an excessive oversteer occurs on the basis of the vehicle slip angular velocity calculated by the slip angular velocity calculation means.

9. A vehicle motion control system according to claim 1, wherein the motion control means includes:

desired slip rate setting means for setting a desired slip rate for said at least one of the wheels in accordance with the vehicle motion determined by vehicle motion determination means;

actual slip rate measuring means for measuring an actual slip rate of said at least one of the wheels;

slip rate deviation calculation means for calculating a deviation between the desired slip rate and the actual slip rate; and

control means for controlling the braking means to apply a braking force to said at least one of the wheels on the basis of the deviation calculated by the slip rate deviation calculation means.

10. A vehicle motion control system according to claim 1, wherein the braking means includes:

wheel brake cylinders operatively connected to respective wheels for applying a braking force;

a braking pressure generator for supplying a braking pressure to the wheel brake cylinders; and

actuating means disposed between the braking pressure generator and the wheel brake cylinders for controlling the braking pressure in the wheel brake cylinders.

11. A vehicle motion control system according to claim 10, wherein the braking pressure generator includes a master cylinder for generating the braking pressure in response to depression of the brake pedal, and an auxiliary pressure source for generating the braking pressure irrespective of depression of the brake pedal.

12. A vehicle motion control system for maintaining stability of a vehicle having a plurality of wheels when the vehicle is in motion, comprising:

braking means for applying a braking force to each wheel of the vehicle;

a lateral acceleration sensor for sensing a lateral acceleration of the vehicle;

a yaw rate sensor for sensing a yaw rate of the vehicle;

slip angular velocity calculation means for calculating a vehicle slip angular velocity on the basis of output signals of the lateral acceleration sensor and the yaw rate sensor;

slip angular acceleration calculation means for calculating a vehicle slip angular acceleration on the basis of the vehicle slip angular velocity calculated by the slip angular velocity calculation means;

vehicle motion determination means for determining vehicle motion on the basis of the vehicle slip angular velocity calculated by the slip angular velocity calculation means;

motion control means for actuating the braking means to apply a braking force to at least one of the wheels on the basis of an output of the vehicle motion determination means and irrespective of depression of a brake pedal in order to maintain stability of the vehicle in motion; and

sensor condition determination means for determining if at least one of the lateral acceleration sensor and the yaw rate sensor is in an abnormal condition on the basis of the vehicle slip angular acceleration calculated by the slip angular acceleration calculation means.

13. A vehicle motion control system according to claim 12, wherein the sensor condition determination means determines that said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition when the vehicle slip angular acceleration calculated by the slip angular acceleration calculation means is greater than a first predetermined upper limit value.

14. A vehicle motion control system according to claim 12, wherein the sensor condition determination means determines that said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition when the vehicle slip angular acceleration calculated by the slip angular acceleration calculation means is greater than a first predetermined upper limit value and when a first predetermined time period has elapsed.

15. A vehicle motion control system according to claim 12, further including vehicle speed detecting means for detecting a vehicle speed and fail-control means for holding the braking force applied to said at least one of the wheels until the vehicle speed detected by the vehicle speed detecting means is less than the predetermined value, when the sensor condition determination means determines that said at least one of the lateral acceleration sensor and the yaw rate sensor is in the abnormal condition.

16. A vehicle motion control system according to claim 12, wherein the motion control means includes:

desired slip rate setting means for setting a desired slip rate for said at least one of the wheels in accordance with the vehicle motion determined by vehicle motion determination means;

actual slip rate measuring means for measuring an actual slip rate of said at least one of the wheels;

slip rate deviation calculation means for calculating a deviation between the desired slip rate and the actual slip rate; and

control means for controlling the braking means to apply a braking force to said at least one of the wheels on the basis of the deviation calculated by the slip rate deviation calculation means.