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Directional tap detection algorithm using an accelerometer

  • US 8,442,797 B2
  • Filed: 03/30/2010
  • Issued: 05/14/2013
  • Est. Priority Date: 03/30/2009
  • Status: Active Grant
First Claim
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1. A processor-implemented method for detecting tap inputs on a device based on first, second and third axis outputs from a three axis accelerometer attached to said device, said processor being programmed to carry out the steps of:

  • detecting acceleration signals generated by said first, second and third axis outputs of said three-axis accelerometer caused by movement of said device;

    for each of said as outputs, calculating the derivative of each acceleration signal as a function of time;

    determining whether said movement of the device is caused by a tap input on a housing of said device by calculating the sum of the absolute values of said acceleration derivatives along each axis of said three axis accelerometer resulting from said movement and determining that said movement is a tap input if the sum of said absolute values exceeds a threshold value for a predetermined amount of time;

    determining the axis of said tap by determining which output of said three axis accelerometer generated the acceleration derivative with the largest magnitude;

    determining the direction of the tap by determining the sign of the acceleration derivative with the largest magnitude; and

    employing the determined tap axis and direction to generate an input command to control operation of said device.

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