Method and apparatus for determining a vehicle pitch-over condition

1. An apparatus for determining a pitch-over condition of a vehicle, said apparatus comprising:

a first accelerometer for sensing acceleration in a Z-axis direction substantially perpendicular to both a front-to-rear axis of the vehicle and a side-to-side axis of the vehicle and for providing a first acceleration signal indicative thereof;

a second accelerometer for sensing acceleration in an X-axis direction substantially parallel to said front-to-rear axis of the vehicle and for providing a second acceleration signal indicative thereof; and

a controller for determining a Z-axis velocity value from the first acceleration signal and determining a pitch-over condition of the vehicle in response to both the determined Z-axis velocity value and the second acceleration signal, wherein said controller determines an X-axis acceleration value from said second acceleration signal as a function of displacement in said Z-axis direction.

2. The apparatus of claim 1 wherein said controller also provides an actuation signal for actuating an actuatable safety device of the vehicle in response to determining a pitch-over condition of the vehicle.

3. The apparatus of claim 1 wherein said controller determines said Z-axis velocity value as a function of displacement in said Z-axis direction.

4. The apparatus of claim 1 wherein said controller determines said Z-axis velocity value as a function of displacement in said Z-axis direction.

5. The apparatus of claim 4 wherein said controller determines said X-axis acceleration value as a first moving average of acceleration in said X-axis direction as a function of displacement in said Z-axis direction.

6. The apparatus of claim 4 wherein said controller provides an actuation signal for actuating an actuatable safety device of the vehicle when both said Z-axis velocity value exceeds a first threshold and said X-axis acceleration value exceeds a second threshold.

7. The apparatus of claim 6 wherein at least one of said first and second thresholds is a variable threshold.

8. The apparatus of claim 6 wherein at least one of said first and second thresholds is a fixed threshold.

9. The apparatus of claim 1 wherein at least one of said first and second accelerometers is located at a substantially central vehicle location.

10. An apparatus for controlling actuation of an actuatable occupant restraint device of a vehicle, said apparatus comprising:

an actuatable occupant restraint device;

a first accelerometer for sensing acceleration in a Z-axis direction substantially perpendicular to both a front-to-rear axis of the vehicle and a side-to-side axis of the vehicle and for providing a first acceleration signal indicative thereof;

a second accelerometer for sensing acceleration in an X-axis direction substantially parallel to said front-to-rear axis of the vehicle and for providing a second acceleration signal indicative thereof; and

a controller for determining a Z-axis velocity value from the first acceleration signal and providing an actuation signal for actuating the actuatable occupant restraint device of the vehicle in response to both the determined Z-axis velocity value and the second acceleration signal, wherein said controller determines an X-axis acceleration value from said second acceleration signal as a function of displacement in said Z-axis direction.

11. The apparatus of claim 10 wherein said controller determines said Z-axis velocity value as velocity in said Z-axis direction as a function of displacement in said Z-axis direction.

12. The apparatus of claim 10 wherein said controller determines said Z-axis velocity value as a function of displacement in said Z-axis direction.

13. The apparatus of claim 12 wherein said controller determines said X-axis acceleration value as a first moving average of acceleration in said X-axis direction as a function of displacement in said Z-axis direction.

14. The apparatus of claim 12 wherein said controller provides an actuation signal for actuating the actuatable occupant restraint device when both said Z-axis velocity value exceeds a first threshold and said X-axis acceleration value exceeds a second threshold.

15. The apparatus of claim 14 wherein at least one of said first and second thresholds is a variable threshold.

16. The apparatus of claim 14 wherein at least one of said first and second thresholds is a fixed threshold.

17. The apparatus of claim 10 wherein at least one of said first and second accelerometers is located at a substantially central vehicle location.

18. An apparatus for controlling actuation of an actuatable occupant restraint device of a vehicle, said apparatus comprising:

a first accelerometer for sensing acceleration in a Z-axis direction substantially perpendicular to both a front-to-rear axis of the vehicle and a side-to-side axis of the vehicle and for providing a first acceleration signal indicative thereof;

a second accelerometer for sensing acceleration in an X-axis direction substantially parallel to said front-to-rear axis of the vehicle and for providing a second acceleration signal indicative thereof; and

a controller for determining Z-axis velocity and Z-axis displacement from the first acceleration signal, determining X-axis acceleration from the second acceleration signal, and providing an actuation signal for actuating the actuatable occupant restraint device of the vehicle in response to both the determined Z-axis velocity as a function of the determined Z-axis displacement and the determined X-axis acceleration as a function of the determined Z-axis displacement.

19. A method for determining a pitch-over condition of a vehicle, the method comprising the steps of:

sensing acceleration using an accelerometer in a Z-axis direction substantially perpendicular to both a front-to-rear axis of the vehicle and a side-to-side axis of the vehicle and providing a first acceleration signal indicative thereof;

sensing acceleration using an accelerometer in an X-axis direction substantially parallel to said front-to-rear axis of the vehicle and providing a second acceleration signal indicative thereof;

determining a Z-axis velocity value from the first acceleration signal;

determining an X-axis acceleration value from said second acceleration signal, said step of determining an X-axis acceleration value comprising determining acceleration in said X-axis direction as a function of displacement in said Z-axis direction; and

determining a pitch-over condition of the vehicle in response to both the determined Z-axis velocity value and the second acceleration signal.

20. The method of claim 19 further comprising the step of providing an actuation signal for actuating an actuatable safety device of the vehicle in response to determining a pitch-over condition of the vehicle.

21. The method of claim 19 wherein said step of determining a Z-axis velocity value comprises determining velocity in said Z-axis direction as a function of displacement in said Z-axis direction.

22. The method of claim 19 wherein said step of determining a Z-axis velocity value comprises determining velocity in said Z-axis direction as a function of displacement in said Z-axis direction.

23. The method of claim 22 wherein said step of determining the X-axis acceleration value comprises determining a first moving average of acceleration in said X-axis direction as a function of displacement in said Z-axis direction.

24. The method of claim 22 further comprising the step of actuating an actuatable safety device of the vehicle when both said Z-axis velocity value exceeds a first threshold and said X-axis acceleration value exceeds a second threshold.