Dual stage occupant restraint deployment control for motor vehicle

A method for controlling the deployment of an occupant restraint in a motor vehicle comprising the steps:

• sensing a possible crash event;
• sensing a vehicle acceleration and deriving therefrom an acceleration signal;
• deriving a velocity signal from the acceleration signal;
• deriving a crash severity measure as the scaled sum of (1) an oscillation value derived from the time integral of the absolute value of the time derivative of the acceleration and (2) the value of the velocity signal.

Apparatus for controlling the deployment of a dual stage occupant restraint in a motor vehicle comprising:

• means for sensing a possible crash event;
• means for deriving a vehicle acceleration signal;
• means for deriving a velocity signal from the vehicle acceleration signal;
• means for deriving one or more immunity measures for indicating non-crash events;
• means for generating a first stage activation signal if the velocity value and all derived immunity measures meet predetermined criteria during the sensed possible crash event;
• means for deriving a crash severity measure from the acceleration signal, the crash severity measure not being immune from accelerations due to non-crash events;
• and
• means for generating a second stage activation signal in response to the crash severity measure meeting predetermined criteria if the first stage activation signal has been generated.