Method for operating a pre-crash sensing system to deploy airbags using inflation control

1. A method of operating a restraint system comprising:

deploying an airbag prior to a collision in pre-collision mode in response to a pre-crash sensing system output signal including a predicted time to impact;

activating active vents based on the predicted time to impact;

confirming a collision using vehicle acceleration signals, wherein the collision is confirmed at an elapsed time that differs from the predicted time to impact;

adjusting the predicted time to impact based on the vehicle acceleration signals; and

controlling the active vents according to the adjusted predicted time to impact.

2. A method as recited in claim 1 wherein controlling the active vents comprises controlling the timing of an airbag vent.

3. A method as recited in claim 2 wherein the timing of the vent is determined in response to an occupant characteristic.

4. A method as recited in claim 2 wherein the timing of the vent is determined in response to a seat position.

5. A method as recited in claim 1 wherein the airbag comprises a dual stage airbag comprising the first stage and the second stage with a means to control time delay between the two stages.

6. A method as recited in claim 1 further comprising monitoring a seatbelt status and wherein controlling the active vent comprises controlling the inflation also in response to the seatbelt status.

7. A method as recited in claim 1 further comprising determining an occupant characteristic and wherein controlling the active vents comprises controlling the active vents also in response to the occupant characteristics.

8. A method as recited in claim 1 further comprising classifying a collision into a collision classification in response to a pre-crash sensing system.

9. A method as recited in claim 8 wherein the block of classifying comprises scanning a frontal zone with a pre-crash sensing system.

10. A method as recited in claim 8 wherein the block of classifying comprises determining a relative velocity of a threat.

11. A method as recited in claim 1 further comprising determining a confidence factor threshold and a pre-crash collision confidence factor and wherein deploying comprises deploying in response to comparing the confidence factor and the confidence factor threshold.

12. A method as recited in claim 11 wherein if the confidence factor is not above a threshold, determining a collision in response to a vehicle accelerometer and wherein controlling the restraint system in response to the vehicle accelerometer in a post-collision mode.

13. A method of operating an airbag having a controllable vent comprising:

deploying an airbag prior to a crash in response to a pre-crash sensing system output including a predicted time to impact;

operating an airbag vent to control a rate of inflation;

determining a crash severity;

determining occupant information;

confirming a crash using vehicle acceleration signals wherein the crash is confirmed at a point in time other than the predicted time to impact;

adjusting a predicted time to impact based on the vehicle acceleration signals; and

operating the airbag vent in response to confirmation of the crash, the crash severity, the occupant information, and the adjusted predicted time to impact.

14. A method as recited in claim 13 wherein determining occupant information comprises determining belted or unbelted status.

15. A method as recited in claim 13 wherein determining occupant information comprises determining a weight range.