Tire imbalance detection system and method using anti-lock brake wheel speed sensors

• US 20040172181A1
• Filed: 02/27/2003
• Published: 09/02/2004
• Est. Priority Date: 02/27/2003
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Lu, Jianbo, Rhode, Douglas Scott
• Granted Patent: US 6,834,222 B2
• Time in Patent Office: Days
• US Class Current: 701/36
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00
• CPC Class Codes: B60C 23/062 Frequency spectrum analysis of wheel speed signals, e.g. using Fourier transformation
• CPC Class Codes: B60T 2240/06 Wheel load; Wheel lift
• CPC Class Codes: B60T 2240/07 Tire tolerance compensation

Abstract

A system and method for developing signals to activate vehicle stability controllers wherein wheel speed sensors for the wheels of the vehicle are used as input variables. The wheel speed values are used in a wheel rolling radius determination. Dynamic imbalance strength estimation and dynamic imbalance strength magnitude use the computed wheel rolling radius information in a tire imbalance logic unit to develop signals to activate the vehicle stability controllers.

Claims

1. A method for detecting dynamic imbalance of road tires for wheels of a wheeled vehicle comprising the steps of:

monitoring and measuring wheel speeds for each of the wheels;

computing an instantaneous dynamic rolling radius estimation for each wheel as a function of wheel speeds;

determining dynamic imbalance strength estimation as a function of instantaneous dynamic rolling radii;

computing dynamic imbalance strength magnitude as a function of dynamic imbalance strength estimation;

computing wheel imbalance as a function of dynamic imbalance strength magnitude for each wheel; and

developing a control signal based upon the magnitude of the computed dynamic imbalance.

2. The method set forth in claim 1 wherein the step of computing rolling radii for a front wheel comprises solving a functional relationship of yaw angular rate, vehicle reference velocity, steering angle for the front wheel, half track distances from a vehicle centerline to a front wheel, front wheel speed, and distances between the center of gravity of the vehicle and the front wheels.

3. The method set forth in claim 1 wherein the step of computing an instantaneous dynamic rolling radius for a rear wheel comprises solving a functional relationship of vehicle reference velocity, yaw angular rate, half track distances from a vehicle centerline to a rear wheel, and rear wheel speed.

4. The method set forth in claim 1 wherein the step of computing the dynamic imbalance strength estimation for a wheel comprises solving a functional relationship of the mass of the wheel, wheel speed, tire damping rate in the vertical direction, tire spring rate in the vertical direction, mass distribution and tire rolling radius.

5. The method set forth in claim 1 wherein the step of computing the dynamic imbalance strength magnitude of a wheel comprises solving a functional relationship of wheel speed and filtered dynamic imbalance strength.

6. The method set forth in claim 1 wherein the step of developing a control signal comprises solving a functional relationship of wheel speed and filtered dynamic imbalance strength and developing the control signal when a threshold value for the dynamic imbalance strength is exceeded.

7. The method set forth in claim 1 wherein wheel imbalance is characterized as a sinusoidal function, the method involving computing characteristic parameters for computed magnitude and phase of a sinusoidal function representing actual imbalance of a sinusoidal function for computed imbalance and minimizing the differences in the amplitude and phase for the sinusoidal functions by changing characteristic parameters.

8. A control system for detecting dynamic imbalance of vehicle wheels, the control system comprising:

means for monitoring and measuring wheel speeds;

means for computing an instantaneous dynamic rolling radius estimation for each wheel as a function of wheel speeds;

means for determining dynamic imbalance strength estimation as a function of instantaneous dynamic rolling radius;

means for computing dynamic imbalance strength magnitude as a function of dynamic imbalance strength estimation;

means for computing wheel imbalance as a function of dynamic imbalance strength magnitude for each wheel; and

means for developing a control signal based upon the magnitude of the computed dynamic imbalance.

9. A method for detecting dynamic imbalance of road tires for wheels of a wheeled vehicle equipped with a vehicle dynamic control including at least one stability controller comprising the steps of:

monitoring and measuring wheel speeds for each of the wheels;

computing an instantaneous dynamic rolling radius estimation for each wheel as a function of wheel speeds;

determining dynamic imbalance strength estimation as a function of instantaneous dynamic rolling radii;

computing dynamic imbalance strength magnitude as a function of dynamic imbalance strength estimation;

computing wheel imbalance as a function of dynamic imbalance strength magnitude for each wheel; and

developing a control signal input for the stability controller based upon the magnitude of the computed dynamic imbalance.

10. The method set forth in claim 9 wherein the step of computing rolling radii for a front wheel comprises solving a functional relationship of yaw angular rate, vehicle reference velocity, steering angle for the front wheel, half track distances from a vehicle centerline to a front wheel, front wheel speed, and distances between the center of gravity of the vehicle and the front wheels.

11. The method set forth in claim 9 wherein the step of computing an instantaneous dynamic rolling radius for a rear wheel comprises solving a functional relationship of vehicle reference velocity, yaw angular rate, half track distances from a vehicle centerline to a rear wheel, and rear wheel speed.

12. The method set forth in claim 9 wherein the step of computing the dynamic imbalance strength estimation for a wheel comprises solving a functional relationship of the mass of the wheel, wheel speed, tire damping rate in the vertical direction, tire spring rate in the vertical direction, mass distribution and tire rolling radius.

13. The method set forth in claim 9 wherein the step of computing the dynamic imbalance strength magnitude of a wheel comprises solving a functional relationship of wheel speed and filtered dynamic imbalance strength.

14. The method set forth in claim 9 wherein the step of developing a control signal comprises solving a functional relationship of wheel speed and filtered dynamic imbalance strength and developing the control signal when a threshold value for the dynamic imbalance strength is exceeded.

15. The method set forth in claim 9 wherein wheel imbalance is characterized as a sinusoidal function, the method involving computing characteristic parameters for computed magnitude and phase of a sinusoidal function representing actual imbalance of a sinusoidal function for computed imbalance and minimizing the differences in the amplitude and phase for the sinusoidal functions by changing characteristic parameters.

16. A control system for detecting dynamic imbalance of vehicle wheels, the control system comprising:

means for monitoring and measuring wheel speeds;

means for computing an instantaneous dynamic rolling radius estimation for each wheel as a function of wheel speeds;

means for determining dynamic imbalance strength estimation as a function of instantaneous dynamic rolling radius;

means for computing dynamic imbalance strength magnitude as a function of dynamic imbalance strength estimation;

means for computing wheel imbalance as a function of dynamic imbalance strength magnitude for each wheel; and

means for developing a control signal based upon the magnitude of the computed dynamic imbalance.

17. The control system set forth in claim 16 wherein the vehicle dynamics control includes anti-lock brake wheel speed sensors and vehicle yaw and vehicle roll sensors, the wheel speed sensors developing input speed variables for the control system.