Capsize risk level calculation system

• US 9,797,724 B2
• Filed: 05/16/2013
• Issued: 10/24/2017
• Est. Priority Date: 05/17/2012
• Status: Active Grant

• Current Assignee: Tokyo University of Marine Science and Technology
• Original Assignee: Tokyo University of Marine Science and Technology
• Inventors: Watanabe, Yutaka
• Primary Examiner(s): Nguyen, Lam
• Application Number:
  US14/401,471
• Publication Number:
  US 20150134293A1
• Time in Patent Office: 1,622 Days
• Field of Search: 701124, 701 45, 701 70, 114124
• CPC Class Codes: B63B 39/14 for indicating inclination or duration of roll
• CPC Class Codes: G01B 21/00 Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant

Abstract

Provided is a capsize risk level calculation system which can calculate a capsize risk level providing an index of the capsize risk on an oscillation of hull without using hull information. This system includes an acceleration sensor detecting a reciprocating motion in an up-down direction of a vessel as an oscillation in an up-down direction of a virtual oscillation center axis; an angular velocity sensor detecting a simple pendulum motion in a rolling direction around the vessel center axis as a simple pendulum motion of the vessel COG around the oscillation center axis; and an arithmetic part calculating a capsize risk level from an oscillation radius connecting between the oscillation center axis and the vessel COG, and a capsize limit oscillation radius connecting between the oscillation center axis and the vessel metacenter, which are obtained on the results of detection by the acceleration sensor and the angular velocity sensor.

Claims

1. A capsize risk level calculation system comprising:

an up-down direction detection means for detecting a reciprocating motion in an up-down direction of a vessel as an oscillation in an up-down direction of a virtual oscillation center axis,

a rolling direction detection means for detecting a simple pendulum motion in a rolling direction around the center axis of said vessel as a simple pendulum motion of the center of gravity of said vessel around said oscillation center axis, and

a calculation means for calculating a capsize risk level on the basis of the results of detection by said up-down direction detection means and said rolling direction detection means, said calculation means calculating,

a simple harmonic motion frequency of the reciprocating motion on the basis of the results of detection by said up-down direction detection means,

calculating a rolling frequency of the simple pendulum motion on the basis of the results of detection by said rolling direction detection means, and

calculating an oscillation radius connecting between said oscillation center axis and the center of gravity of said vessel, and a capsize limit oscillation radius connecting between said oscillation center axis and the metacenter of said vessel as said capsize risk level on the basis of the simple harmonic motion frequency and the rolling frequency, wherein

said oscillation center axis is the lower center of said vessel, being set as a point around which a vertical oscillation and a horizontal oscillation of said vessel floating on the surface of the water are generated.

2. The capsize risk level calculation system according to claim 1, wherein said calculation means calculates a capsize limit inclination angle on the basis of said oscillation radius and said capsize limit oscillation radius as said capsize risk level.

3. The capsize risk level calculation system according to claim 1, wherein said metacenter is the upper center of said vessel, being the intersection point between the perpendicular line passing through the buoyancy center and the perpendicular line passing through the center of gravity when said vessel is not inclined.