EP1749739A2 - Procede d'obtention de parametres de stabilite de navires - Google Patents

Procede d'obtention de parametres de stabilite de navires Download PDF

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Publication number
EP1749739A2
EP1749739A2 EP05735897A EP05735897A EP1749739A2 EP 1749739 A2 EP1749739 A2 EP 1749739A2 EP 05735897 A EP05735897 A EP 05735897A EP 05735897 A EP05735897 A EP 05735897A EP 1749739 A2 EP1749739 A2 EP 1749739A2
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EP
European Patent Office
Prior art keywords
inclinometer
inclinometers
ships
roll
ship
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05735897A
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German (de)
English (en)
Inventor
Mª del Rosario BRAVO RAMOS
Ricardo Abad Arroyo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BRAVO RAMOS, M?? DEL ROSARIO
Original Assignee
Universidad Politecnica de Madrid
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Filing date
Publication date
Application filed by Universidad Politecnica de Madrid filed Critical Universidad Politecnica de Madrid
Publication of EP1749739A2 publication Critical patent/EP1749739A2/fr
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B79/00—Monitoring properties or operating parameters of vessels in operation
    • B63B79/20—Monitoring properties or operating parameters of vessels in operation using models or simulation, e.g. statistical models or stochastic models
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/14—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude for indicating inclination or duration of roll
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B79/00—Monitoring properties or operating parameters of vessels in operation
    • B63B79/10—Monitoring properties or operating parameters of vessels in operation using sensors, e.g. pressure sensors, strain gauges or accelerometers

Definitions

  • ship includes all: ships, vessels, yachts, floating artefacts, semi submergible vehicles, etc.
  • the invention is related to the ship building field, more specifically with the inclining experiment carried out on ships, necessary to determine the parameters regarding its stability, specifically the initial metacentric height (GM) and the centre of gravity.
  • GM initial metacentric height
  • the inclining experiment is a test required by the Maritime authorities with newly built ships (before leaving the ship yard) and with all those ships that have been subjected to any structural alteration.
  • the test is definitive to know all the parameter indicators of the characteristics of the stability of a ship, therefore its importance and is compulsory to carry out.
  • the inclining experiment basically consists in subjecting the ship to different known roll torques, generally by moving weights from side to side of the ship, and measuring, for each roll torque, the roll angle adopted by the ship, in each one of the static equilibrium conditions. Also with the test other data is taken (draught marks of the ship when it straitens to obtain, by means of the hydrostatic curves, the displacement and the position of the metacentre, a series of weighs of the ship (magnitude and position), its own, including those that do not form part of its light ship weight, and others; free surfaces etc.). With the information obtained and applying basic hydrostatic laws are obtained the parameters wanted: transversal metacentric height and vertical position of the centre of gravity.
  • the dynamic point of view of the process of each equilibrium condition of the ship in which the measurements are carried out is a combination of two dynamic systems: the ship being one and the pendulum the other.
  • the traditional methodology recommends that the pendulums used be as long as possible with the purpose of obtaining the greatest precision possible in reading the roll angle. This presents problems, in occasions, to find the adequate place for the pendulums on the ship and in the comfort of the observer (an essential factor in the measurement) to take the readings.
  • the readings of the pendulum in the dynamic case differ notably from the case when dealing with a static process.
  • the pendulum remains in a fixed position and the observer has all the time he needs to carry out the reading.
  • the pendulum is continuously moving, therefore there will be errors associated with the observer.
  • the inclinometer can be classified in two big groups:
  • the difficulty which we referred to previously, in the use of gravitational inclinometers in the measurement of the roll angle is when the ship is oscillating around the equilibrium position, the reading of the inclinometer is affected by the acceleration induced by the roll motion.
  • the present invention incorporates an algorithm, understood as an ordered and finite set of operations that permit find the solution of a problem, in which, from the register of the gravitational inclinometer, is obtained the component due to the roll angle that the ship adopts in each instant.
  • the invention also analyses the temporized evolution of the roll angle and establishes quality indexes of the measurement.
  • the system is susceptible to be implemented with the connections of an anemometer and a weather vane with the purpose of recording simultaneously with the roll angle, the direction and velocity of the wind, which will allow increase the features of the system, being able to carry out the inclining experiment in weather conditions which, with the traditional methodology, is not done.
  • the present invention refers to a procedure to obtain the parameters of the stability of ships, specially the initial metacentric height (GM) and the position of the centre of gravity, by means of measurements with inclinometers and is carried out in three modes of execution.
  • GM initial metacentric height
  • GM position of the centre of gravity
  • the procedure to carry out the inclining experiment on ships by means of equipment based on the use of inclinometers has its fundament in an algorithm developed to be able to use gravitational inclinometers on ships discriminating the component of the signal due to the roll angle, even though the ship is rolling, and it is a methodology that has its fundament in considering the equilibrium conditions from a dynamic point of view taking into account the perturbations of the roll torque.
  • the procedure is materialized in equipment that has an original system to calibrate the inclinometer and another system that allows to register the evolution in time of the measurement, analyse it and to establish reliability indexes.
  • the developed algorithm also allows determining the centre of gravity of a ship by means of a system independent of the inclining experiment.
  • the first method consists in obtaining the stability parameters by carrying out the inclining experiment based on the measurement and register, by means of inclinometers, of the roll angle of the ship in different equilibrium conditions in which are based the inclining experiment, and also in the analysis of the register of the roll angle, which allows to consider the dynamic effects, that are produced in the equilibrium conditions mentioned, due to uncontrolled torques (mainly gusts of wind and waves) and evaluate zones of the register where the reliability of the measurement of the roll angle is greater.
  • This mode of execution is applicable to inertial inclinometers as to gravitational inclinometers since in the case gravitational inclinometers are used an algorithm has been developed which allows to filter the component of the signal from the inclinometer due to the roll angle, eliminating the component due to the rolling motion of the ship.
  • the second mode consists in determining the centre of gravity of the ship by means of the analysis of the registers of two gravitational inclinometers situated on the centre line, on the same vertical and at different heights above the base line of the ship.
  • the procedure to obtain the stability parameters by means of the invention consists in doing the inclining experiment, but using an inclinometer instead of a pendulum for the measurement of the roll angle.
  • the stages of this execution mode are the following: 1°) Checking / calibrating and setting to zero of the inclinometer. Its done on dry land before starting the inclining experiment. For this you place the levelling platform (figure 2) on a stable table and, with the help of a two dimensional spirit level, you level. Afterwards the inclinometer is used, which is place in the coupling piece as is shown in figure 1, as precision level, placing the levelling platform in the direction parallel to the levelling screws (H and I of figure 2), taking readings of the inclinometers signal.
  • the inclinometer 180° and again reading is taken. If the readings are not the same, the levelling screws are adjusted until the two reading converge. At this moment the inclinometer is in a horizontal position with a precision of a hundredth of a degree and in this position the reading should be "0.00°". If this were not the case, the assigned inclinometer would take that value as "zero”.
  • the inclinometer (E) is placed in its coupling piece (A), with the different angle supplied by the calibrated angle generators (N), which, at the same time, are on the levelling platform (K), and the calibration of the inclinometer is checked. In the case it should be necessary, and with the help of these pieces, the inclinometer would be newly calibrated.
  • the algorithm developed to "filter" the component of the roll angle for the signals produced by the gravitational inclinometers can have a second application and that is to determine directly the centre of gravity of a ship.
  • 3 rd Mode to execute the invention Determining the metacentric height of a ship by means of the calculation of the natural period of the roll obtained from the register of an inclinometer.
  • the procedure consists of the following phases: 1°) Checking / calibrating and setting to zero of the inclinometer. On dry land a checking of the signal of the inclinometer will be carried out and, if necessary, a calibration and a setting to zero of it. 2°) Preliminary trials with the ship. Once calibrated, the inclinometer is placed anywhere on the ship, the only condition is that it be on the centre line.
  • a procedure of statistical spectral analysis consisting in the following: 1) Denominating LP the time a register lasts. If, for example, the natural period of the ships roll is of the order of 10 seconds, it will be presumed that LP is 1000 seconds. 2) Dividing the main register in samples of size LM and given a time dM. LM and dM will depend on the type of ship and, without any loss of generality, supposing that dM is equal to 20 seconds and LM equal to 300 seconds.
  • the first sample will start in the instant zero and will finish in the instant (300)
  • the second sample will start in the instant dM (20) and will finish in LM+dM (320), and like that successively until reaching the sample that starts in LP (1000) and finishes in LP + LM (1300).
  • the first LM (300) seconds have been added to the main register.
  • the Fourier transform in the following way: A wide rang of periods is defined that contain the possible natural periods of the ships roll defined by Pinit (Lowest period), Pend (highest period) and Pdelta (period increments).
  • Pend (A m1 +A m2 +....+A mn )/n Normalized spectrum Pinit (A 11 /M 1 +A 12 /M 2 +....+A 1n /M n )/n Pinit + Pdelta (A 21 /M 1 +A 22 /M 2 +....+A 2n /M n )/n .......... .......... Pend (A m1 /M 1 +A m2 /M 2 +....+A mn /M n )/n In the normalized spectrum all the samples have the same weight, Independently of the magnitude of the roll motion of the sample. 4) From the study of both spectrums is determined the natural period of the ships roll (T ⁇ ) and the GM is obtained by the formula: GM K ⁇ B / T ⁇ 2 Being K the coefficient obtained in the ships trials and B its breadth.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Probability & Statistics with Applications (AREA)
  • Navigation (AREA)
  • Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)
  • Testing Of Balance (AREA)
EP05735897A 2004-04-22 2005-04-19 Procede d'obtention de parametres de stabilite de navires Withdrawn EP1749739A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ES200400975A ES2242533B2 (es) 2004-04-22 2004-04-22 Procedimiento para la obtencion de los parametros de estabilidad de barcos mediante medidas con clinometros.
PCT/ES2005/000200 WO2005101953A2 (fr) 2004-04-22 2005-04-19 Procede d'obtention de parametres de stabilite de navires

Publications (1)

Publication Number Publication Date
EP1749739A2 true EP1749739A2 (fr) 2007-02-07

Family

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EP05735897A Withdrawn EP1749739A2 (fr) 2004-04-22 2005-04-19 Procede d'obtention de parametres de stabilite de navires

Country Status (3)

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EP (1) EP1749739A2 (fr)
ES (1) ES2242533B2 (fr)
WO (1) WO2005101953A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109178203A (zh) * 2018-08-15 2019-01-11 上海交通大学 一种浮托安装实测的船体姿态校准方法

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57149935A (en) * 1981-03-11 1982-09-16 Utsuki Keiki:Kk Gm measuring device
US4647928A (en) * 1984-02-06 1987-03-03 Marine Partners Stability indicator for marine vessel
GB8521702D0 (en) * 1985-08-31 1985-10-02 British Petroleum Co Plc Determination of stability of floating structures
WO1987003855A1 (fr) * 1985-12-18 1987-07-02 University Of Southampton Stabilimetre pour objets flottants
GB0214851D0 (en) * 2002-06-27 2002-08-07 Kranskan Ltd Safety monitor apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2005101953A2 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109178203A (zh) * 2018-08-15 2019-01-11 上海交通大学 一种浮托安装实测的船体姿态校准方法
CN109178203B (zh) * 2018-08-15 2020-05-05 上海交通大学 一种浮托安装实测的船体姿态校准方法

Also Published As

Publication number Publication date
WO2005101953A3 (fr) 2007-03-22
ES2242533A1 (es) 2005-11-01
ES2242533B2 (es) 2007-10-01
WO2005101953A2 (fr) 2005-11-03

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