Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
1998-12-22
2001-03-13
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C180S197000, C180S199000, C303S122000, C303S122050
Reexamination Certificate
active
06202009
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a fault detection for vehicle motion sensors. More particularly, the present invention relates to an active brake control system with the capability to detect a fault in a vehicle motion sensor.
BACKGROUND OF THE INVENTION
Disclosure Information
Automotive vehicles having vehicle control systems typically include vehicle motion sensors which serve to trigger the actuation of the active brake control system when a fault signal or condition is detected. Further, a vehicle motion sensor fault may often invalidate the wheel speed information by triggering the actuation of the active brake control system, thereby resulting in undesired vehicle braking. Moreover, speed differences across wheel speed sensors are sensitive to the braking control system actuation and are thus poor sources for the reproduction of vehicle motion signal in the even of a sensor fault. Therefore, it is desirable to detect a motion sensor fault which is insensitive to wheel braking actuation, and which is also independent of the differences across wheel speed sensors, left versus right.
While U.S. Pat. No. 5,707,117 addresses the issue of a fault detection for an active brake control diagnostic, it is based on wheel speed differences between left and right wheels, which has the aforementioned disadvantages.
Therefore, it would be desirable to provide a method for detecting fault in a vehicle control system that is insensitive to wheel braking actuation, and independent of wheel speed differences. The method should also be able to detect fault independent of the specific fault type and also detect fault that is otherwise not detectable by checking electrical specifications.
SUMMARY OF THE INVENTION
There is disclosed herein a method for detecting fault of vehicle motion sensors, and particularly the yaw rate sensor and the lateral acceleration sensor. According to the present invention, in order to detect fault in these sensors, correlations are made based on the vehicle model, between steering wheel angle and yaw rate, and also between steering wheel angle and lateral acceleration. The aforementioned correlations between steering wheel angle and yaw rate, and between steering wheel angle and lateral acceleration, have a physical sense which is defined as the road bank angle estimate. The present invention also uses signals insensitive to differences between wheel speed sensors and wheel braking actuation. In a preferred embodiment, an additional vehicle stability verification is made of the lateral accelerometer fault detection method to provide for a more robust fault detection system.
The method for detecting fault in vehicle motion sensors for a motor vehicle includes providing a measured lateral acceleration signal and calculating a first estimated value, corresponding to an estimated first road bank angle, and which is based on the lateral acceleration signal. The method also includes providing a measured yaw rate signal and calculating a second estimated value, corresponding to an estimated second road bank angle, based on the yaw rate signal. Further, the method includes determining a first maximum road bank angle based on the first road bank angle, and determining a second maximum road bank angle based on the second road bank angle. The method further includes calculating a first threshold based on the first maximum road bank angle and calculating a second threshold based on the second maximum road bank angle.
Moreover, the present method includes comparing whether the first road bank angle estimate exceeds the second threshold, and if so, indicating a lateral acceleration signal fault. The method also includes comparing whether the second road bank angle estimate exceeds the first threshold, and if so, indicating a yaw rate signal fault.
In one preferred embodiment according to the present invention, the step of determining the maximum first road bank angle includes calculating a rolling maximum first road bank angle which is continuously updated in a predetermined time period; and also the step of determining the maximum second road bank angle includes calculating a rolling maximum second road bank angle which is continuously updated in a predetermined time period. In yet another preferred embodiment of the disclosed method, included is providing a steering wheel angle signal, and calculating the first and second bank angles using the steering wheel angle signal.
In a most preferred embodiment of the method disclosed herein, the lateral acceleration check includes determining whether the vehicle is stable by a function which may be characterized as product of (a) the difference between a front slip angle and a rear slip angle and (b) its time rate of change, wherein the vehicle is determined to be stable when the product is less than a calibrated threshold.
And still in yet another preferred embodiment of this method according to this application, the step of comparing whether the first road bank angle exceeds the second threshold includes generating a first counter increment when the first bank angle exceeds the second threshold, and indicating a lateral acceleration signal fault when the first counter exceeds a predetermined first counter threshold. Similarly, the step of comparing whether the second road bank angle exceeds the first threshold includes generating a second counter increment when the second bank angle exceeds the first threshold, and indicating a yaw rate signal fault when the second counter exceeds a predetermined second counter threshold.
The above objects and other objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.
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Beaulieu Yonel
Brown Gregory P.
Cuchlinski Jr. William A.
Ford Global Technologies Inc.
May Roger L.
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