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Accident data recorder

  • US 4,638,289 A
  • Filed: 10/23/1984
  • Issued: 01/20/1987
  • Est. Priority Date: 02/26/1983
  • Status: Expired due to Term
First Claim
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1. A method of recording and storing vehicle data representing events and conditions relating to an accident of a motor vehicle having wheels that normally revolve with longitudinal travel of the vehicle and which is subjected to at least one of longitudinal, transverse and rotational acceleration during an accident, comprising:

  • generating a wheel revolution signal corresponding to revolutions of a wheel of the vehicle;

    providing an acceleration sensor having at least three cantilever mounted tongues each acting as a movable plate of a capacitor, and a fixed capacitor plate for each tongue which is fixed with respect to the vehicle, two of said tongues lying in a common plane transverse to the direction of longitudinal travel of the vehicle, and the remaining tongue lying in a plane extending in the direction of longitudinal travel, said movable plates being movable toward and away from said fixed plates when the vehicle is subjected to longitudinal, transverse and rotational accelerations to change capacitance between said fixed and movable plates, said sensor including an oscillator circuit for each set of fixed and movable plates which produces frequency variation with a capacitance for each set of fixed and movable plates, said frequency variations comprising acceleration signals which are indicative of longitudinal, transverse and rotational accelerations of the vehicle;

    generating a plurality of additional data signals corresponding to additional conditions of the vehicle;

    continuously generating central timing pulses indicative of the absolute passage of time;

    subjecting said revolution signal and said acceleration signals to an analog-to-digital conversion to form digital revolution data and digital acceleration data corresponding to the revolution and acceleration signals;

    writing the digital revolution data, the acceleration data and the additional data signals into a sequence of data storing locations of a fixed storage at intervals timed by the central timing pulses, the locations being disposed in a primary storage loop having a beginning and an end, with the data being stored in sequential locations from the beginning to the end of the primary loop and then back into the beginning of the primary loop;

    generating a trigger event when an accident occurs; and

    after the occurrence of the trigger event, writing additional revolution data, acceleration data and data signals which occur after the trigger event, into a secondary loop of storage locations having a new starting address in the fixed storage so that data remains stored in the primary loop and additional data after the trigger event becomes stored in the secondary loop.

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