ROTATION SPEED MEASURING SYSTEM
First Claim
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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Accused Products
Abstract
A rotation speed measuring system includes a magnetic sensor, an acceleration sensor, an end detecting unit, and a calculating unit. The magnetic sensor measures earth magnetism in at least one axis direction. The acceleration sensor measures acceleration in at least one axis direction. The end detecting unit detects a time point of a switch at which an acceleration variation 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. The calculating unit 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.
5 Citations
14 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification