Method and apparatus for sensing a vehicle crash in the frequency domain

An apparatus for providing an actuation signal for a passenger restraint system in a vehicle upon an occurrence of a predetermined type of vehicle crash condition, said apparatus comprising:

• sensing means securable to the vehicle for providing a vibratory electric signal having various frequency components upon the occurrence of a vehicle crash condition;
• first filter means connected to said sensing means for passing an electric signal from said sensing means when the signal from said sensing means has particular frequency components indicative of the vehicle being in said predetermined type of crash condition;
• first envelope detector means connected to said first filter means for providing a voltage value responsive to the value of the signal from said first filter means;
• second filter means connected to said sensing means for passing an electric signal from said sensing means when the signal from said sensing means has particular frequency components indicative of the vehicle not being in said predetermined type of crash condition;
• second envelope detector means connected to said second filter means for providing a voltage value responsive to the value of the signal from said second filter means;
• summing circuit means connected to said first envelope detector means and to said second envelope detector means for providing a signal having a value indicative of the sum of output signals from said first and second envelope detector means;
• and
• comparative means connected to the summing circuit means and to a voltage reference signal for providing said actuation signal when the value of the signal from said summing circuit means is greater than the value of the reference signal.

An apparatus for providing an actuation signal for a passenger restraint system in a vehicle upon an occurrence of a plurality of possible predetermined types of vehicle crash conditions, said apparatus comprising:

• sensing means securable to the vehicle for providing vibratory electric signals having various frequency components indicative of particular types of crash conditions to which the vehicle is subjected;
• a plurality of first filter means connected to said sensing means, each said first filter means passing an electric signal from said sensing means when the signal from said sensing means has a particular frequency component indicative of the vehicle being in an associated one of said predetermined types of vehicle crash conditions;
• a plurality of first envelope detector means, each said first envelope detector means connected to an associated one of said first filter means for providing a voltage value responsive to the value of the signal passed from its associated first filter means;
• a plurality of second filter means connected to said sensing means, each said second filter means passing an electric signal from said sensing means when the signal from said sensing means has a particular frequency component indicative of the vehicle not being in one of said predetermined types of vehicle crash conditions;
• a plurality of second envelope detector means, each said second envelope detector means connected to an associated one of said second filter means for providing a voltage value responsive to the value of the signal passed from its associated second filter means;
• summing circuit means connected to said plurality of first envelope detector means and to said plurality of second envelope detector means for providing a signal having a value indicative of the sum of output signals from said plurality of first and second envelope detector means;
• and
• comparator means connected to the summing circuit means and to a voltage reference signal for providing said actuator signal when the value of the signal from said summing circuit means is greater than the value of the reference signal.

A method for providing an actuation system for a passenger restraint system in a vehicle upon an occurrence of one of a plurality of predetermined types of vehicle crash conditions, said method comprising the steps of:

• providing a vibratory electric signal having particular frequency components upon the occurrence of said predetermined type of crash condition, each of the predetermined types of crash conditions having an identifiable frequency component which, for that type of vehicle, has been empirically determined to be indicative of that type of vehicle crash condition, each of said identifiable frequency components having a value less than 3000 hertz;
• filtering said vibratory signal to pass said identifiable frequency components;
• and
• providing said actuation signal when said filtering step passes one of said identifiable frequency components indicative of the vehicle being in one of said predetermined types of vehicle crash conditions.