Integration of rear wheel steering with vehicle stability enhancement system
First Claim
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1. A method for integrating a vehicle stability enhancement system and rear wheel steering, the method comprising the steps of:
- a) inputting a vehicle speed;
b) inputting a measured vehicle yaw rate;
c) determining a front wheel steer angle;
d) determining a rear wheel steer angle;
e) calculating a desired yaw rate;
f) comparing the measured yaw rate with the desired yaw rate to determine a yaw error term; and
g) applying a braking force to a wheel of the vehicle to impart a yaw moment based upon the magnitude of the error term calculated wherein the rear wheel steering angle is taken into account in calculating the desired yaw rate.
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Abstract
There is disclosed a method for integrating a vehicle stability enhancement system and rear wheel steering. The method includes inputting a vehicle speed and measured vehicle yaw rates. Determining a front and rear wheel steer angle. Calculating a desired yaw rate. Comparing the measured yaw rate with the desired yaw rate to determine a yaw error term. Applying a braking force to a wheel of a vehicle imparting a yaw moment based upon the magnitude of the error term calculated. The rear wheel steer angle is taken into account in calculating a desired yaw rate.
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Citations
21 Claims
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1. A method for integrating a vehicle stability enhancement system and rear wheel steering, the method comprising the steps of:
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a) inputting a vehicle speed;
b) inputting a measured vehicle yaw rate;
c) determining a front wheel steer angle;
d) determining a rear wheel steer angle;
e) calculating a desired yaw rate;
f) comparing the measured yaw rate with the desired yaw rate to determine a yaw error term; and
g) applying a braking force to a wheel of the vehicle to impart a yaw moment based upon the magnitude of the error term calculated wherein the rear wheel steering angle is taken into account in calculating the desired yaw rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
a) inputting a vehicle speed;
b) inputting a measured vehicle yaw rate;
c) inputting a vehicle lateral acceleration;
d) inputting a rear wheel steer angle;
e) determining an estimated hand wheel position;
f) determining if the vehicle is undergoing a severe maneuver;
g) assigning the estimated hand wheel position as the true hand wheel position;
h) calculating a front wheel steer angle according to the equation;
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4. The method for integrating a vehicle stability enhancement system and rear wheel steering of claim 3 wherein the step of calculating the front wheel steer angle utilizes a rear wheel steer gain such that the rear wheel steer angle does not need to be measured directly.
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5. The method for integrating a vehicle stability enhancement system and rear wheel steering of claim 4 wherein the step of calculating the front wheel steer angle is according to the equation:
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δ
f*=(r/V)+Kuay/(1+Gr/f)wherein δ
f* is the front wheel steer angle;
r is the measured vehicle yaw rate;
V is the vehicle speed;
Ku is the under steer coefficient;
ay is the lateral acceleration; and
Gr/f is the rear wheel steer gain.
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6. The method for integrating a vehicle stability enhancement system and rear wheel steering of claim 1 wherein the step of determining a rear wheel steer angle comprises:
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a) inputting a vehicle speed;
b) inputting a front steering angle;
c) determining a rear steering gain corresponding to the inputted vehicle speed;
d) determining if the vehicle is in an oversteer or an understeer condition;
e) adjusting the value of the rear steering gain based upon the determination of the oversteer or understeer condition and the value of the gain;
f) calculating the rear wheel steer angle according to the equation;
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7. The method for integrating a vehicle stability enhancement system and rear wheel steering of claim 1 wherein the desired steady state yaw rate is determined according to the equation:
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8. The method for integrating a vehicle stability enhancement system and rear wheel steering of claim 1 wherein the desired dynamic yaw rate is determined according to the equation:
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9. The method for integrating a vehicle stability enhancement system and rear wheel steering of claim 8 wherein the step of calculating the desired vehicle yaw rate utilizes a rear wheel steer gain such that the rear wheel steer angle does not need to be measured directly.
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10. The method for integrating a vehicle stability enhancement system and rear wheel steering of claim 9 wherein the desired dynamic yaw rate is determined according to the equation:
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11. A method of operation for an active brake control, the method providing an integration of rear wheel steering and active brake control such that a desired yaw rate term is calculated utilizing a formula including variables to account for rear wheel steering, the method including the steps of:
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a) inputting a vehicle speed;
b) inputting a measured vehicle yaw rate;
c) determining a front wheel steer angle;
d) determining a rear wheel steer angle;
e) calculating a desired yaw rate;
f) comparing the measured yaw rate with the desired yaw rate to determine a yaw error term; and
g) applying a braking force to a wheel of the vehicle to impart a yaw moment based upon the magnitude of the error term calculated wherein the rear wheel steering angle is taken into account in calculating the desired yaw rate. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
a) inputting a vehicle speed;
b) inputting a measured vehicle yaw rate;
c) inputting a vehicle lateral acceleration;
d) inputting a rear wheel steer angle;
e) determining an estimated hand wheel position;
f) determining if the vehicle is undergoing a severe maneuver;
g) assigning the estimated hand wheel position as the true hand wheel position;
h) calculating a front wheel steer angle according to the equation;
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14. The method of operation for an active brake control on a vehicle of claim 13 wherein the step of calculating the front wheel steer angle utilizes a rear wheel steer gain such that the rear wheel steer angle does not need to be measured directly.
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15. The method of operation for an active brake control on a vehicle of claim 14 wherein the step of calculating the front wheel steer angle is according to the equation:
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16. The method of operation for an active brake control on a vehicle of claim 11 wherein the step of determining a rear wheel steer angle comprises:
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a) inputting a vehicle speed;
b) inputting a front steering angle;
c) determining a rear steering gain corresponding to the inputted vehicle speed;
d) determining if the vehicle.is in an oversteer or an understeer condition;
e) adjusting the value of the rear steering gain based upon the determination of the oversteer or understeer condition and the value of the gain;
f) calculating the rear wheel steer angle according to the equation;
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17. The method of operation for an active brake control on a vehicle of claim 11 wherein the desired yaw rate is determined according to the equation:
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18. The method of operation for an active brake control on a vehicle of claim 11 wherein the desired dynamic yaw rate is determined according to the equation:
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19. The method of operation for an active brake control on a vehicle of claim 18 wherein the step of calculating the desired vehicle yaw rate utilizes a rear wheel steer gain such that the rear wheel steer angle does not need to be measured directly.
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20. The method of operation for an active brake control on a vehicle of claim 19 wherein the desired dynamic yaw rate is determined according to the equation:
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21. A method for integrating a vehicle stability enhancement system and rear wheel steering, the method comprising the steps of:
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a) inputting a vehicle speed;
b) inputting a measured vehicle yaw rate;
c) determining a front wheel steer angle;
d) determining a rear wheel steer angle;
e) calculating a desired yaw rate according to the equation;
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Specification