Accelerometer-based differential free fall detection system, apparatus, and method and disk drive protection mechanism employing same
First Claim
1. A method for signaling a free fall condition, the method comprising:
- measuring acceleration for each of a plurality of axes in each of a plurality of successive sample periods;
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;
computing, for each of the plurality of successive sample periods, a sum of the squares of the acceleration deltas from that sample period; and
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.
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Abstract
Embodiments of the present invention employ differential acceleration computations for detecting free fall conditions. The differential acceleration computations can be based on two-axis or three-axis acceleration measurements, and therefore can be implemented using a two-axis accelerometer or a three-axis accelerometer (or combinations of accelerometers that enable acceleration measurements in two or three axes). When a free fall condition is detected, an appropriate signal can be generated, for example, to place a HDD in a protected state before damage is likely to occur. Differential acceleration measurements can also be used to detect a “safe” condition following a free fall condition.
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Citations
23 Claims
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1. A method for signaling a free fall condition, the method comprising:
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measuring acceleration for each of a plurality of axes in each of a plurality of successive sample periods;
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;
computing, for each of the plurality of successive sample periods, a sum of the squares of the acceleration deltas from that sample period; and
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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Apparatus comprising:
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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. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. Apparatus comprising a computer readable medium having embodied therein a computer program for detecting a free fall condition, the computer program comprising:
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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. - View Dependent Claims (22, 23)
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Specification