Control algorithm for a yaw stability management system

• US 20040225427A1
• Filed: 04/24/2003
• Published: 11/11/2004
• Est. Priority Date: 04/24/2003
• Status: Active Grant

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Anwar, Sohel
• Granted Patent: US 6,885,931 B2
• Time in Patent Office: Days
• US Class Current: 701/38
• CPC Class Codes: B60G 17/0162 mainly during a motion involving steering operation, e.g. cornering, overtaking B60G17/0164 takes precedence
• CPC Class Codes: B60G 2400/0523 Yaw rate
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/41 Steering angle
• CPC Class Codes: B60G 2400/64 Wheel forces, e.g. on hub, spindle or bearing
• CPC Class Codes: B60G 2600/1873 Model Following
• CPC Class Codes: B60G 2800/016 Yawing condition
• CPC Class Codes: B60G 2800/215 by applying a braking action on each wheel individually
• CPC Class Codes: B60G 2800/244 Oversteer
• CPC Class Codes: B60T 2230/02 Side slip angle, attitude angle, floating angle, drift angle
• CPC Class Codes: B60T 2270/86 Optimizing braking by using ESP vehicle or tire model
• CPC Class Codes: B60T 8/17555 specially adapted for enhancing driver or passenger comfort, e.g. soft intervention or pre-actuation strategies

Abstract

A yaw stability control system is based on a linearized vehicle model and a predictive control algorithm. The control algorithm compares the vehicle yaw rate, from, for example, a production grade yaw rate sensor, with a desired yaw rate, which may be computed based on the vehicle speed and the steering wheel angle. If the yaw rate error, defined as the difference between the desired and measured yaw rates, exceeds a certain threshold, a controlling yaw moment is calculated based on the predictive control algorithm. This controlling yaw moment, or yaw torque, command is then translated into one or more actuator commands. For example, the control yaw moment may be produced by braking one or more of the vehicle'"'"'s wheels.

Claims

1. A method for controlling the yaw stability of a vehicle, comprising:

measuring a yaw rate of the vehicle with a sensor;

calculating a desired yaw rate based on the vehicle'"'"'s speed and steering wheel angle;

calculating a yaw rate error as the difference between the desired yaw rate and the measured yaw rate;

comparing the yaw rate error to a threshold;

if the yaw rate error exceeds the threshold, calculating a controlling yaw moment based on a predictive control algorithm.

2. The method of claim 1, wherein the control algorithm is represented by linearized state equations for the rate of change of the vehicle yaw rate and rate of change for the body side slip angle.

3. The method of claim 1, wherein the predictive control algorithm tracks a desired yaw rate by minimizing the sum of future yaw rate errors according to the expression

Δ

M_z(t)=Δ

M_z(t−

1)+g^T(R_Des−

ƒ

)

where M_z is the control yaw moment, g^T is the first row of [G^TG]<sup>−

1</sup>G^T, t is time, R_Des is the component of an objective function of the desired yaw rate, and f is a vector of terms predicting vehicle yaw dynamics in the future.

4. The method of claim 3, wherein a transfer function of the state equations is discretized to obtain a discrete time transfer function.

5. The method of claim 4, wherein the predictive control algorithm utilizes Diophantine type discrete mathematical identities.

6. The method of claim 1, further comprising applying a control yaw moment by braking a rear wheel on a inner side of the vehicle when the vehicle is in an under-steer condition as it turns.

7. The method of claim 6, wherein the applying a control yaw moment includes braking both the front and rear wheels on the inner side of the vehicle.

8. The method of claim 1, further comprising applying a control yaw moment by braking a front wheel on the outer side of the vehicle when the vehicle is in an over-steer condition as it turns.

9. The method of claim 8, wherein the applying a control yaw moment includes braking both front and rear wheels on the outer side of the vehicle.