Free fall detection device

• US 20060236761A1
• Filed: 02/17/2006
• Published: 10/26/2006
• Est. Priority Date: 04/22/2005
• Status: Active Grant

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Metals (Thailand) Ltd.
• Inventors: Abe, Yasunori, Saitoh, Masakatsu, Unuma, Munetoshi, Inoue, Hideki
• Granted Patent: US 7,549,335 B2
• Time in Patent Office: Days
• US Class Current: 73/510
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: G01P 3/22 transferred to the indicator by electric or magnetic means
• CPC Class Codes: G11B 19/04 Arrangements for preventing, inhibiting, or warning against double recording on the same blank or against other recording or reproducing malfunctions
• CPC Class Codes: H04M 2250/12 including a sensor for measuring a physical value, e.g. temperature or motion

Abstract

A free fall detection device capable of detecting a fall accompanied by rotation is provided. A fall accompanied by rotation is detected based on a waveform of an acceleration signal output from the acceleration detection unit and an angular velocity signal output from the angular velocity detection unit. A gravity center acceleration of the device to be protected is calculated from the acceleration detected by the acceleration detection unit and from the angular velocity detected by the angular velocity detection unit. Even when the device being protected rotates as it falls, the fall of the device can be detected from the detected acceleration or angular velocity. Further, by calculating the gravity center acceleration not affected by the rotation, it is possible to detect a fall of the device with high precision even if the device rotates as it falls.

Claims

1. A free fall detection device comprising:

an acceleration detection unit installed in the device to detect an acceleration of the device; and

a rotation decision unit to detect a fall accompanied by a rotation of the device from a waveform of the acceleration detected by the acceleration detection unit.

2. A free fall detection device according to claim 1, wherein the waveform is a smooth, self-repeating waveform.

3. A free fall detection device according to claim 1, wherein the waveform is almost sinusoidal.

4. A free fall detection device according to claim 1, wherein the acceleration detection unit detects accelerations of the device in a plurality of axial directions,

wherein the rotation decision unit detects a fall of the device accompanied by its rotation, based on a waveform of the acceleration in at least one axial direction, the acceleration in one axial direction being one of the accelerations in the plurality of axial directions detected by the acceleration detection unit.

5. A free fall detection device according to claim 4, wherein the one axial direction is one of the plurality of axial directions which has a moment of inertia of an intermediate value.

6. A free fall detection device according to claim 4, further including a fall decision unit that detects a fall of the device when all of the accelerations in the plurality of axial directions are almost zero.

7. A free fall detection device according to claim 6, wherein the fall decision unit detects a fall of the device when all of the accelerations in the plurality of axial directions are smaller than a predetermined threshold.

11. A free fall detection device according to claim 2, wherein the waveform is almost sinusoidal.

12. A free fall detection device according to claim 2, wherein the acceleration detection unit detects accelerations of the device in a plurality of axial directions,

wherein the rotation decision unit detects a fall of the device accompanied by its rotation, based on a waveform of the acceleration in at least one axial direction, the acceleration in one axial direction being one of the accelerations in the plurality of axial directions detected by the acceleration detection unit.

13. A free fall detection device according to claim 3, wherein the acceleration detection unit detects accelerations of the device in a plurality of axial directions,

wherein the rotation decision unit detects a fall of the device accompanied by its rotation, based on a waveform of the acceleration in at least one axial direction, the acceleration in one axial direction being one of the accelerations in the plurality of axial directions detected by the acceleration detection unit.

14. A free fall detection device according to claim 5, further including a fall decision unit that detects a fall of the device when all of the accelerations in the plurality of axial directions are almost zero.

8. A free fall detection device comprising:

an acceleration detection unit installed in the device to detect accelerations of the device in a plurality of axial directions;

a fall decision unit to detect a fall of the device when all of the accelerations in the plurality of axial directions are almost zero;

an angular velocity detection unit to detect an angular velocity in at least one axial direction; and

a rotation decision unit to detect a fall of the device accompanied by its rotation, based on the angular velocity detected by the angular velocity detection unit.

9. A free fall detection device comprising:

an acceleration detection unit to detect accelerations of the device in a plurality of axial directions;

a fall decision unit to detect a fall of the device when all of the accelerations in the plurality of axial directions are almost zero; and

a terminal to connect an output of the acceleration detection unit to a rotation decision unit for detecting a fall accompanied by rotation.

10. A free fall detection device comprising:

an acceleration detection unit installed in the device to detect accelerations of the device in a plurality of axial directions;

an angular velocity detection unit installed in the device to detect an angular velocity in at least one of the plurality of axial direction; and

a gravity center acceleration calculation unit to calculate a gravity center acceleration of the device from the accelerations detected by the acceleration detection unit and from the angular velocity detected by the angular velocity detection unit.