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ROTATION SPEED MEASURING SYSTEM

  • US 20170023602A1
  • Filed: 07/14/2016
  • Published: 01/26/2017
  • Est. Priority Date: 07/21/2015
  • Status: Active Grant
First Claim
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1. A rotation speed measuring system that measures a rotation speed of a ball moving in midair, the rotation speed measuring system comprising:

  • a magnetic sensor that is provided in the ball and measures earth magnetism at least in one axis direction;

    an acceleration sensor that is provided in the ball and measures acceleration at least in one axis direction;

    an end detecting unit that detects, as an end time point at which midair movement of the ball is considered to end, a time point of a switch at which an acceleration variation obtained as an absolute value of a variation in the acceleration measured by the acceleration sensor in a predetermined small time unit is switched to a large-variation state after a small-variation state, wherein the small-variation state corresponds to a state in which the acceleration variation is equal to or below a predetermined first threshold value and the large-variation state corresponds to a state in which the acceleration variation is equal to or above a predetermined second threshold value; and

    a calculating unit that calculates the rotation speed of the ball moving in midair by analyzing a frequency of measurement data on the earth magnetism acquired by the magnetic sensor until the end time point.

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