System and method for safing and monitoring a plurality of vehicle sensors
A system and method for safing vehicle sensors includes two safety systems, each with a primary sensor for monitoring vehicle motion and activating its corresponding safety system in response to certain vehicle motions. Each sensor may act as a safing sensor for the other in the event that activation of a safety system is indicated by the primary sensor. Each sensor may also monitor the other prior to such an event, to detect a sensor malfunction before that sensor is needed to active a safety system.
1. A method of operating a plurality of safety systems in a vehicle, the method comprising:
providing a first safety system comprising:
a first airbag, and characterized by a first airbag deployment threshold and a first plausibility threshold; and
a high-G accelerometer configured to provide a high-G output and specified to measure at least about 20 Gs of acceleration and configured to act as a first-system primary sensor for the first safety system;
providing a second safety system comprising:
a second safety device selected from a group comprising a second airbag, a braking system, and a vehicle stability control system, the second safety device being characterized by a second deployment threshold; and
a low-G accelerometer configured to provide a low-G output, and specified to measure not more than about 20 Gs and configured to act as a second-system primary sensor for the second safety system and as a safing sensor for the first safety system;
monitoring a motion of the vehicle with the high-G accelerometer to determine whether the high-G output exceeds the airbag deployment threshold;
monitoring the same motion of the vehicle with the low-G accelerometer to determine whether the low-G output exceeds the first plausibility threshold; and
deploying the first airbag if the high-G output exceeds the first airbag deployment threshold and the low-G output exceeds the first plausibility threshold.
2. A method of operating a plurality of safety systems in a vehicle according to claim 1 , wherein:
the second safety system is characterized by a second plausibility threshold, and the method further comprises:
determining whether the low-G accelerometer's measurement exceeds the second deployment threshold;
determining whether the high-G accelerometer's measurement exceeds the second plausibility threshold; and
deploying the second safety system if low-G accelerometer's measurement exceeds the second deployment threshold and the high-G accelerometer's measurement exceeds the second plausibility threshold such that the high-G accelerometer is configured as a safing sensor for the second safety system.
3. A method of operating a plurality of safety systems in a vehicle according to claim 1 , wherein the second safety system is a vehicle stability control system.
4. A method of operating a plurality of safety systems in a vehicle according to claim 1 , wherein the second safety system is a braking system.
5. A computer program product for use with a computer processor for operating an airbag safety system and a second safety system on a vehicle, the airbag safety system characterized by an airbag deployment threshold and an airbag plausibility threshold, and comprising an airbag and a high-G accelerometer associated with the airbag deployment threshold, the high-G accelerometer specified to measure at least about 20 Gs of acceleration, the second safety system being characterized by a second deployment threshold and a second plausibility threshold, and comprising a low-G accelerometer associated with a second deployment threshold, the low-G accelerometer specified to measure not more than about 20 Gs and configured to act as a safing sensor for the airbag safety system, the computer program product comprising a tangible medium having a non-transient computer readable program code thereon, the computer readable program code including:
computer code for monitoring an output of the high-G accelerometer in response to a vehicle motion event to determine whether the output of the high-G accelerometer exceeds the airbag deployment threshold;
computer code for monitoring an output of the low-G accelerometer in response to the same vehicle motion event to determine whether the output of the low-G accelerometer exceeds the airbag plausibility threshold such that the low-G accelerometer is a safing sensor for the high-G accelerometer; and
computer code for deploying the airbag if the output of the high-G accelerometer exceeds the airbag threshold and the output of the low-G accelerometer exceeds the airbag plausibility threshold.
6. The computer program product according to claim 5 , further comprising:
computer code for monitoring the output of the low-G accelerometer in response to a vehicle motion event to determine whether the output of the low-G accelerometer exceeds the second deployment threshold;
computer code for monitoring the output of the high-G accelerometer to determine whether the output of the high-G accelerometer exceeds the second plausibility threshold such that the high-G accelerometer is a safin sensor for the low-G accelerometer; and
computer code for deploying the second safety system if the output of the low-G accelerometer exceeds the second deployment threshold and the output of the high-G accelerometer exceeds the second plausibility threshold.
7. The computer program product according to claim 5 , wherein the second safety system is a vehicle stability control system.
8. The computer program product according to claim 5 , wherein the second safety system is a braking system.
9. The computer program product according to claim 5 wherein the code determines whether the output of the low-G accelerometer exceeds the airbag plausibility threshold after the code determines whether the output of the high-G accelerometer exceeds the airbag deployment threshold.
10. A vehicle safety apparatus comprising:
a first safety system comprising:
a first airbag, and characterized by a first airbag deployment threshold and a first plausibility threshold; and
a high-G accelerometer having a high-G output, the high-G accelerometer specified to measure at least about 20 Gs of acceleration and configured to act as a first-system primary sensor for the first safety system;
a second safety system comprising:
a second safety device selected from a group comprising a second airbag, a braking system, and a vehicle stability control system, the second safety device being characterized by a second deployment threshold; and
a low-G accelerometer having a low-G output, the low-G accelerometer specified to measure not more than about 20 Gs and configured to act as a second-system primary sensor for the second safety system and as a safing sensor for the first safety system;
a comparison circuit, the comparison circuit configured:
to determine whether the high-G output exceeds the airbag deployment threshold, and to determine whether the low-G output exceeds the airbag plausibility threshold, the comparison circuit producing a comparison signal including information relating to the determinations; and
a deployment module operably coupled with the comparison circuit and configured to deploy the airbag system if the comparison signal indicates that the high-G output exceeds the airbag deployment threshold and the low-G output exceeds the airbag plausibility threshold.
11. The apparatus according to claim 10 wherein the second safety system is characterized by a second plausibility threshold, and the comparison circuit is further configured to
determine whether the low-G output exceeds the second deployment threshold; and
determine whether the high-G output exceeds the second plausibility threshold; and the deployment module is configured to deploy the second safety system if the low-G output exceeds the second deployment threshold and the high-G output exceeds the second plausibility threshold
such that the high-G accelerometer is configured as a safing sensor for the second safety system.
12. The apparatus according to claim 10 wherein the first safety systems is a passenger restraint system and the second safety system is a vehicle braking system.
13. A method of operating a plurality of safety systems in a vehicle, the method comprising:
providing a first safety system comprising:
a first airbag, and characterized by a first airbag deployment threshold and a first plausibility threshold; and
a high-G accelerometer configured to provide a high-G output and specified to measure at least about 20 Gs of acceleration and configured to act as a first-system primary sensor for the first safety system;
providing a second safety system comprising:
a second safety device selected from a group comprising a second airbag, a braking system, and a vehicle stability control system, the second safety device being characterized by a second deployment threshold; and
a gyroscope configured to provide a gyro output, and configured to act as a second-system primary sensor for the second safety system and as a safing sensor for the first safety system;
monitoring a motion of the vehicle with the high-G accelerometer to determine whether the high-G output exceeds the airbag deployment threshold;
monitoring the same motion of the vehicle with the gyrosocope to determine whether the gyro output exceeds the first plausibility threshold; and
deploying the first airbag if the high-G output exceeds the first airbag deployment threshold and the gyro output exceeds the first plausibility threshold, such that the gyroscope is configured to act as a safing sensor for the first safety system.
14. The method of operating a plurality of safety systems in a vehicle according to claim 13 , wherein the second safety system is a vehicle stability control system.
15. The method of operating a plurality of safety systems in a vehicle according to claim 13 , wherein the second safety system is a braking system.