Vehicle yaw control based on yaw rate estimate

• US 6,205,391 B1
• Filed: 05/18/1998
• Issued: 03/20/2001
• Est. Priority Date: 05/18/1998
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated), General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Lin, William Chin-Woei, Ghoneim, Youssef Ahmed, Sidlosky, David Michael
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): MANCHO, RONNIE M
• Application Number:
  US09/080,372
• Time in Patent Office: 1,037 Days
• Field of Search: 701/70, 701/36, 701/73, 701/79, 701/89, 180/167, 180/170, 303/146, 303/147, 303/155, 303/140, 342/70
• US Class Current: 701/70
• CPC Class Codes: B60T 2250/03 Vehicle yaw rate
• CPC Class Codes: B60T 2270/313 with less than three sensors (yaw rate, steering angle, lateral acceleration)
• 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

Abstract

An improved vehicle yaw control that does not require a yaw sensor, wherein the validity of an estimate of vehicle yaw is determined and used to select an appropriate control methodology. The vehicle yaw is estimated based on the measured speeds of the un-driven wheels of the vehicle, and various other conditions are utilized to determine if the estimated yaw rate is valid for control purposes. When it is determined that the estimated yaw rate is valid, a closed-loop yaw rate feedback control strategy is employed, whereas in conditions under which it is determined that the estimated yaw rate is not valid, a different control strategy, such as an open-loop feed-forward control of vehicle yaw, is employed. The validity of the estimated yaw rate is judged based on a logical analysis of the measured wheel speed information, braking information, and steering wheel angle. The measured speeds of the un-driven wheels are used to compute an average un-driven wheel speed and an average un-driven wheel acceleration. The operator steering angle and the vehicle velocity are used to determine a desired yaw rate, which is compared to the yaw estimate to find a yaw rate error. Based on these variables, the control reliably determines whether the estimated yaw rate is valid, and selects an appropriate control methodology in accordance with the determination.

Claims

1. A yaw control method utilizing differential braking of the vehicle wheels to impart a desired yaw moment on the vehicle, the vehicle having a pair of un-driven wheels, the method comprising the steps of:

measuring speeds of the un-driven wheels of the vehicle;

estimating a yaw rate of the vehicle based on a difference between the measured speeds;

analyzing known vehicle parameters including the measured wheel speeds, a yaw error based on deviation of the estimated yaw rate from a desired yaw rate, vehicle steering angle, and presence of driver braking to determine when the estimated yaw rate is valid and when the estimated yaw rate is invalid;

differentially braking the vehicle wheels to impart a yaw moment based on the deviation of the estimated yaw rate from the desired yaw rate when the estimated yaw rate is determined to be valid;

differentially braking the vehicle wheels to impart a yaw moment based on the desired yaw rate without regard to the estimated yaw rate when the estimated yaw rate is determined to be invalid; and

wherein the step of analyzing known vehicle parameters to determine when the estimated yaw rate is valid and when the estimated yaw rate is invalid includes the step of determining that the estimated yaw rate is invalid in response to an indication that the vehicle has a tendency to be unstable.

2. The yaw control method according to claim 1, wherein the desired yaw rate is determined based on the vehicle steering angle, the vehicle velocity, and a desired understeer of the vehicle.

3. The yaw control method according to claim 1, wherein the step of analyzing known vehicle parameters to determine when the estimated yaw rate is valid and when the estimated yaw rate is invalid includes the step of:

determining that the estimated yaw rate is invalid in response to an indication that the vehicle is in a spin-out condition.

4. The yaw control method according to claim 3, including the steps of:

computing an average of the measured wheel speeds,

computing an average acceleration of the un-driven wheels based on the computed average of the measured wheel speeds;

generating the indication that the vehicle is in a spin-out condition when the computed average of the measured wheel speeds is less than a predefined speed threshold and the computed average acceleration is greater than a predefined acceleration threshold.

5. The yaw control method according to claim 4, wherein after the indication that the vehicle is in a spin-out condition has been generated, it is maintained even though the computed average of the measured wheel speeds is greater than the predefined speed threshold and the computed average acceleration is less than the predefined acceleration threshold if the steering angle or yaw error fail to fall within predefined thresholds for a predefined period of time.

6. The yaw control method according to claim 1, including the steps of:

computing an average of the measured wheel speeds,

computing an average acceleration of the un-driven wheels based on the computed average of the measured wheel speeds;

generating the indication that the vehicle has a tendency to be unstable when the computed average acceleration is greater than a predefined acceleration threshold for at least a predefined period of time.

7. The yaw control method according to claim 6, wherein the indication that the vehicle has a tendency to be unstable is terminated when the computed average acceleration is falls below the predefined acceleration threshold.

8. A yaw control method utilizing differential braking of the vehicle wheels to impart a desired yaw moment on the vehicle, the vehicle having a pair of undriven wheels, the method comprising the steps of:

measuring speeds of the undriven wheels of the vehicle;

estimating a yaw rate of the vehicle based on a difference between the measured speeds;

analyzing known vehicle parameters including the measured wheel speeds, a yaw error based on deviation of the estimated yaw rate from a desired yaw rate, the vehicle steering angle, and presence of driver braking to determine when the estimated yaw rate is valid and when the estimated yaw rate is invalid;

differentially braking the vehicle wheels to impart a yaw moment based on the deviation of the estimated yaw rate from the desired yaw rate when the estimated yaw rate is determined to be valid;

differentially braking the vehicle wheels to impart a yaw moment based on the desired yaw rate without regard to the estimated yaw rate when the estimated yaw rate is determined to be invalid;

wherein the step of analyzing known vehicle parameters to determine when the estimated yaw rate is valid and when the estimated yaw rate is invalid includes the step of determining that the estimated yaw rate is invalid in response to an indication that driver braking is present; and

wherein the indication that driver braking is present is maintained for a predefined period of time after driver braking is no longer present.

9. A yaw control method utilizing differential braking of the vehicle wheels to impart a desired yaw moment on the vehicle, the vehicle having a pair of undriven wheels, the method comprising the steps of:

measuring speeds of the undriven wheels of the vehicle;

estimating a yaw rate of the vehicle based on a difference between the measured speeds;

analyzing known vehicle parameters including the measured wheel speeds, a yaw error based on deviation of the estimated yaw rate from a desired yaw rate, the vehicle steering angle, and presence of driver braking to determine when the estimated yaw rate is valid and when the estimated yaw rate is invalid;

differentially braking the vehicle wheels to impart a yaw moment based on the deviation of the estimated yaw rate from the desired yaw rate when the estimated yaw rate is determined to be valid;

differentially braking the vehicle wheels to impart a yaw moment based on the desired yaw rate without regard to the estimated yaw rate when the estimated yaw rate is determined to be invalid; and

wherein the step of analyzing known vehicle parameters to determine when the estimated yaw rate is valid and when the estimated yaw rate is invalid includes the step of determining that the estimated yaw rate is invalid in response to an indication that the vehicle is in a spin-out condition.