Vehicle active brake control with bank angle compensation

• US 6,195,606 B1
• Filed: 12/07/1998
• Issued: 02/27/2001
• Est. Priority Date: 12/07/1998
• Status: Expired due to Fees

• Current Assignee: BWI Company Limited SA (Shougang Corporation)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Barta, David John, Hac, Aleksander Boguslaw
• Primary Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US09/207,012
• Time in Patent Office: 813 Days
• Field of Search: 701/70, 701/71, 701/72, 701/76, 701/82, 701/74, 701/36, 701/37, 701/73, 701/90, 701/91, 701/80, 303/140, 303/146, 303/148, 303/116.2, 180/422, 180/197, 180/421
• US Class Current: 701/70
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 2210/22 Banked curves
• CPC Class Codes: B60T 2230/02 Side slip angle, attitude angle, floating angle, drift angle
• CPC Class Codes: B60T 8/17552 responsive to the tire sideslip angle or the vehicle body slip angle

Abstract

An improved active brake control method which compensates for the effects of a banked road surface under both steady state and transient operating conditions of the vehicle. The control includes an observer for estimating the lateral velocity of the vehicle as a means of determining vehicle slip angle, and a time derivative of the estimated lateral velocity is used along with measured values of lateral acceleration, vehicle speed and yaw rate to compute the lateral acceleration component due to the banked road surface, referred to as the bank acceleration. The bank acceleration, in turn, is then used to correct the values of measured steering angle and the measured lateral acceleration used (1) to develop the desired yaw rate, slip angle and lateral acceleration, and (2) to estimate the surface coefficient of adhesion and slip angle. Partial compensation can be achieved by applying suitable gain factors to the computed bank acceleration, if desired.

Claims

1. An active brake control method utilizing differential braking of vehicle wheels to impart a desired yaw moment on the vehicle, the method comprising the steps of:

measuring longitudinal speed, yaw rate, lateral acceleration and steering angle of the vehicle;

estimating a time rate of change of lateral velocity of the vehicle based on the measured yaw rate, lateral acceleration and steering angle, and an initial estimation of lateral bank acceleration due to banking of a road surface;

updating the estimated bank acceleration based on the time rate of change of lateral velocity and the measured longitudinal speed, yaw rate and lateral acceleration;

compensating the measured lateral acceleration and steering angle based on the updated estimated lateral bank acceleration to form lateral acceleration and steering angle values that are compensated for the effects of the banking of the road surface;

determining a desired yaw rate for the vehicle based on the compensated lateral acceleration and steering angle values and the measured longitudinal speed using a reference model of the vehicle; and

computing the desired yaw moment based on a deviation of said measured yaw rate from said desired yaw rate.

2. The active brake control method of claim 1, wherein the step of estimating a time rate of change of lateral velocity includes the steps of:

estimating the lateral velocity based on the measured yaw rate, lateral acceleration and steering angle, and the estimate of lateral bank acceleration, using a nonlinear dynamic observer; and

high pass filtering the estimated lateral velocity to estimate the time rate of change of the estimated lateral velocity.

3. The active brake control method of claim 2, wherein the nonlinear dynamic observer is also used to estimate a slip angle of the vehicle, the reference model is also used to determine a desired slip angle of the vehicle and the desired lateral acceleration, and the desired yaw moment is based in part on a deviation of the estimated slip angle from the desired slip angle.

4. The active brake control method of claim 3, including the steps of:

estimating a lateral surface coefficient of adhesion of the vehicle based on the measured yaw rate and longitudinal speed and the compensated lateral acceleration; and

limiting the desired slip angle based on the estimated lateral surface coefficient of adhesion.

5. The active brake control method of claim 1, wherein the desired yaw moment is additionally based on an estimate of a lateral surface coefficient of adhesion of the vehicle, the control method including the additional step of:

estimating the lateral surface coefficient of adhesion of the vehicle based on the measured yaw rate and longitudinal speed and the compensated lateral acceleration.

6. The active brake control method of claim 1, wherein the initial estimated lateral bank acceleration is updated according to the sum of the estimated time rate of change of lateral velocity and a product of the measured vehicle speed and yaw rate, less the measured lateral acceleration.

7. The active brake control method of claim 6, including the steps of:

determining if the vehicle is in a transient condition or a steady state condition;

low pass filtering the updated estimate of lateral bank acceleration with a first gain when it is determined that the vehicle is in a steady state condition; and

low pass filtering the updated estimate of lateral bank acceleration with a second gain which is lower than said first gain when it is determined that the vehicle is in a transient condition.

8. The active brake control method of claim 7, wherein the transient condition is detected when a magnitude of said deviation between measured and desired yaw rates or a magnitude of a time rate of change of a desired lateral acceleration exceed respective thresholds.

9. The active brake control method of claim 1, wherein the measured lateral acceleration is compensated for the effects of the banking of the road surface by increasing the measured lateral acceleration by the estimated lateral bank acceleration.

10. The active brake control method of claim 1, wherein the measured steering angle is compensated for the effects of the banking of the road surface by decreasing the measured steering angle by a product of the estimated lateral bank acceleration and a desired understeer factor.