Method and apparatus for determining the dynamic stability of an automotive vehicle

• US 6,122,568 A
• Filed: 12/22/1998
• Issued: 09/19/2000
• Est. Priority Date: 12/22/1998
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Madau, Dinu Petre, Tseng, Hongtei Eric, Ashrafi, Behrouz
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/218,284
• Time in Patent Office: 637 Days
• Field of Search: 701/1, 701/70, 701/72, 701/74, 701/79, 701/82, 303/140, 303/146, 303/147, 180/197
• US Class Current: 701/1
• CPC Class Codes: B60G 17/019 characterised by the type of sensor or the arrangement thereof B60G17/01941 takes precedence
• CPC Class Codes: B60G 17/0195 characterised by the regulation being combined with other vehicle control systems conjoint control of vehicle sub-units including control of suspension systems B60W10/22
• CPC Class Codes: B60G 2400/0523 Yaw rate
• CPC Class Codes: B60G 2400/104 lateral or transversal with regard to vehicle
• CPC Class Codes: B60G 2400/412 of steering wheel or column
• CPC Class Codes: B60G 2800/24 Steering, cornering
• CPC Class Codes: B60G 2800/70 Estimating or calculating vehicle parameters or state variables
• CPC Class Codes: B60G 2800/91 Suspension Control
• CPC Class Codes: B60G 2800/92 ABS - Brake Control
• CPC Class Codes: B60G 2800/94 Electronic Stability Program (ESP, i.e. ABS+ASC+EMS)
• CPC Class Codes: B60G 2800/96 ASC - Assisted or power Steering control
• CPC Class Codes: B60T 8/17551 determining control parameters related to vehicle stability used in the regulation, e.g. by calculations involving measured or detected parameters
• CPC Class Codes: B60W 2510/20 Steering systems
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2710/18 Braking system
• CPC Class Codes: B60W 2710/20 Steering systems
• CPC Class Codes: B60W 2710/22 Suspension systems
• CPC Class Codes: B60W 2720/14 Yaw
• CPC Class Codes: B60W 30/02 : Control of vehicle driving stability

Abstract

A method and apparatus for determining the stability of an automotive vehicle includes a steering wheel sensor generating a steering wheel signal, a yaw rate sensor generating a yaw rate signal and a lateral acceleration sensor for generating a lateral acceleration signal. A controller is coupled to the steering wheel sensor, the yaw rate sensor, and the accelerometer. The controller determines a first steering wheel angle from the yaw rate signal, a second steering wheel angle from the lateral acceleration signal, and a third steering angle from a steering wheel signal. The controller generates a vehicle stability indicator in response to the first steering wheel angle, the second steering wheel angle and the third steering wheel angle.

Claims

1. A method for determining the dynamic stability of an automotive vehicle comprising the steps of:

measuring a yaw rate from a yaw rate sensor;

determining a first steering wheel angle from the yaw rate;

measuring a lateral acceleration from lateral acceleration sensor;

determining a second steering wheel angle from the lateral acceleration;

calculating a first difference between the first steering wheel angle and the second steering wheel angle;

determining if the first difference is less than a first predetermined limit;

determining a third steering angle from a steering wheel sensor;

calculating a second difference between the first steering wheel angle and the third steering wheel angle; and

generating a vehicle stability indicator if the first difference is less than a first predetermined limit and if the second difference is less than a second predetermined limit.

2. A method as recited in claim 1 wherein the step of determining a third steering wheel angle from a steering wheel sensor comprises the step of calculating a relative steering wheel angle by calculating a third difference between a measured steering wheel angle and an estimated center steering wheel position.

3. A method as recited in claim 1 further comprising the step of determining the vehicle velocity and determining a highest wheel velocity from each vehicle wheel.

4. A method as recited in claim 1 wherein said step of generating a vehicle stability indicator comprises generating an indicator if the highest wheel vehicle velocity is not within a predetermined velocity from the vehicle velocity.

5. A method as recited in claim 1 wherein the step of generating a vehicle stability indicator further comprises the step of setting a software flag.

6. A method as recited in claim 1 wherein the step of determining a third steering angle comprises the steps of measuring a third steering wheel angle from a steering wheel sensor.

7. A method as recited in claim 1 wherein determining a first steering wheel angle from the yaw comprises the step of evaluating the following relationship:

##EQU3##

space="preserve" listing-type="equation">SWA.sub.1= δ

.sub.f *K.sub.st 57.295

where δ

_f is an average of the front tire steering angles, L is a vehicle'"'"'s wheel base, g is gravity, r is a vehicle'"'"'s yaw rate, u is a vehicle'"'"'s longitudinal velocity, K_us is a vehicle'"'"'s understeer coefficient;

K_st is the steering ratio, and 57.295 is a conversion factor from radians to degrees.

8. A method as recited in claim 1 wherein the step of determining a second steering wheel angle from the lateral acceleration comprises the step of evaluating the following relationship:

##EQU4##

space="preserve" listing-type="equation">SWA.sub.2= δ

.sub.f *K.sub.st 57.295

where A_y is the vehicle'"'"'s lateral acceleration, δ

_f is an average of the front tire steering angles, L is a vehicle'"'"'s wheel base, g is gravity, u is a vehicle'"'"'s longitudinal velocity, K_us is a vehicle'"'"'s understeer coefficient;

K_st is the steering ratio, and 57.295 is a conversion factor from radians to degrees and SWA₂ is said second steering wheel angle.

9. A method as recited in claim 1 further comprising the step of determining if the vehicle is under the control of a control device, and wherein the step of generating a vehicle stability indicator comprises the step of generating a vehicle indicator if the vehicle is not under the control of said control device.

10. A method as recited in claim 1 further comprising the step of repeating the step of determining a first steering wheel for a first predetermined time.

11. A method as recited in claim 1 further comprising the step of repeating the step of determining a second steering wheel angle for a second predetermined time.