Accelerometer-based differential free fall detection system, apparatus, and method and disk drive protection mechanism employing same

Apparatus comprising:

• an accelerometer arrangement providing acceleration outputs for each of a plurality of axes;
• a free fall detector in communication with the acceleration outputs, wherein the free fall detector is configured to measure acceleration for each of the plurality of axes in each of a plurality of successive sample periods based on the acceleration outputs;
• compute an acceleration delta for each axis for each of the plurality of successive sample periods, wherein each acceleration delta represents a change in acceleration between two successive sample periods;
• compute, for each of the plurality of successive sample periods, a sum of the squares of the acceleration deltas from that sample period;
• and signal a free fall condition if the sum falls within a first predetermined range for each of a first predetermined number of consecutive sample periods.

Apparatus comprising a computer readable medium having embodied therein a computer program for detecting a free fall condition, the computer program comprising:

• first program code for measuring acceleration for each of a plurality of axes in each of a plurality of successive sample periods;
• second program code for computing an acceleration delta for each axis for each of the plurality of successive sample periods, wherein each acceleration delta represents a change in acceleration between two successive sample periods;
• third program code for computing, for each of the plurality of successive sample periods, a sum of the squares of the acceleration deltas from that sample period;
• and
• fourth program code for signaling a free fall condition, if the sum falls within a first predetermined range for each of a first predetermined number of consecutive sample periods.