RU2405712C1 - Method to control ship stability - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to control over ship stability during heaving. Method comprises additional measurement of the ship bow and stern draft, relative bearing and speed in irregular heaving, wind speed, ship location coordinates and distance to nearest shelter port. In estimating ship stability at current load, water layer depth in deck shaft is measured for ship straight position to define the arm of heeling moment caused by water running onto deck. Measured angle at which bulwark edge enters the water, heel angle, bow and stern drafts are used to calculate ship displacement and current heel moment. The latter magnitude is represented in the form of graphic dependence on heel angle to be compared with marginal critical diagram of ship stability on wave top calculated with due allowance for normalised parametres of heaving. Note here that stability estimation is performed by criterion based on calculation of actual transverse metacentric height of ship center of gravity for current diagram of stability on wave top the magnitude of which may not exceed critical transverse metacentric height of ship center of gravity for marginal diagram.

EFFECT: higher validity of stability estimation.

2 dwg

Description

The invention relates to shipbuilding, in particular to methods for monitoring the stability of a vessel under operating conditions, and can be used to create navigation expert systems.

The purpose of the invention is to increase the safety of navigation of the vessel by assessing the stability of the vessel in the conditions of flooding of the deck with passing waves.

The closest technical solutions for operational stability control in operating conditions are the "Method of stability control" according to A.S. No. 16667334 dated 04/01/91 and “A method for monitoring the stability of a ship” according to patent No. 2091269 dated September 27, 1997 Both of these inventions are based on the development of the stability control method described in the monograph by Sebastyanov NB Stability of fishing vessels. - L .: Shipbuilding, 1979, p.187-190.

As a prototype, patent No. 2057678 of 04/10/96 was used, containing a technical solution requiring the use of expert systems technology. The disadvantage of this method is the inability to take into account the effect of water on the deck due to flooding when the vessel is moving along waves, which generally reduces the reliability of the stability assessment.

The technical result is achieved by the fact that they additionally measure the water level in the deck well for the direct position of the vessel and the angle of entry of the edge of the bulwark into the water.

The drawing (figure 1) shows a generalized structural diagram of a device that implements the proposed method.

The rolling period, bow and bow draft, heading angle, ship speed on irregular waves, wind speed, ship position and distance to the nearest port of refuge, the water level in the deck well for the ship’s direct position, the angle of the edge of the bulwark into the water are measured .

According to measurements establish the following.

- Leverage of heeling moment from water on deck

where α _to - the relative coefficient of the deck well; B / T is the ratio of breadth to draft; χ is the reduction coefficient; f ₀ is the measured water level in the deck well.

- The heeling moment from the water on the deck of the ship

- измеренный угол входа кромки фальшборта в воду.where D = f (T _H , T _K ) is the displacement of the vessel; T _H and T _K - measured draft of the vessel by bow and stern; ϑ = (θ-α) is the current value of the relative roll angle; θ is the absolute value of the angle of heel; α is the angle of the wave slope;

- the measured angle of entry of the edge of the bulwark into the water.

- Minimum allowable initial metacentric height:

where h _f - the initial transverse metacentric height; d is the freeboard height on the midship of the vessel; θ _f - the angle of entry of the edge of the bulwark into the water.

- Parameters of running waves:

medium wavelength

m ₀₀ and m _{2 max} are the moments of the wave spectrum S (σ) calculated according to well-known formulas [Handbook of ship theory. 4.1. - L .: Shipbuilding, 1985, p.124-125];

wavelength of 3% security h _w

Where

measured wave height of 3% coverage; D _ζ is the dispersion of the wave process calculated from the spectral density S (σ).

- Charts of static stability of the vessel in still water l _θ and at the top of the wave l _r . The initial diagram of static stability l _θ = f (θ) is constructed for the current case of load from the measured draft of the vessel by the bow and stern using the ship’s static methods. Accounting for add-ons and logging, as well as possible related trim. The calculation of the static stability diagram at the top of a passing wave is carried out by calculating the corrections for the influence of passing waves for a given wave steepness h _W / λ, calculated by formulas (4) and (6) and the methodology described in [Ship theory reference book. Part 2, L .: Shipbuilding. 1985, p. 78-82].

- The diagram of the shoulders of the heeling moment from the water in the deck well l _w is determined by calculation according to the theoretical drawing, taking into account the general arrangement of the vessel.

- Actual application of the center of gravity Z _G corresponding to the calculated stability diagram at the top of the wave.

- The critical application of the center of gravity (Z _G ) _CR corresponding to the limiting diagram of static stability is determined from the condition of equality of the areas “a” and “c” in figure 2 (the condition for equality of work of the recovery moment of the vessel corresponding to the calculated diagram of static stability and heeling moment from water on the deck of the ship). Equality of areas is achieved by the method of successive approximations.

When calculating the critical center of gravity (Z _G ) _CR vessel applicates, the initial wave parameters are checked. If λ <L, then the wavelength equal to the length of the vessel L is taken as the calculated one, and the steepness of the wave (the ratio of wave height to its length) h _W / λ for ships up to 45 m in length must be at least the data indicated in the table:

λ, m twenty 25 thirty 35 40 45

0.108 0.100 0.093 0.089 0.084 0.081

- The condition of sufficient stability

The device for implementing the method includes a measuring unit 1, including a sensor for angular displacements during rolling 2, sensors 3 and 4 for measuring the draft of the vessel with bow and stern, a sensor 5 that registers the speed of the vessel on irregular waves, sensor 6 of the wind speed, sensor 7, measuring level water in the deck well for the direct position of the vessel, a sensor 8 of the angle of entry of the edge of the bulwark into the water, the output of which is connected to the module for converting measurement information 9, including a switch 10, an analog-to-digital converter (ADC) 11 and the standard interface 12 is received for further processing in a computer 13, where operations are carried out to analyze the initial information, mathematical modeling and forecast the stability and speed of the vessel in an increasing storm, based on which, with the help of an expert system 14, including a database 15, the knowledge base 16 , the output mechanism 17 and the user interface 18, an assessment of the danger of the situation is made and practical recommendations are developed to ensure the stability of the vessel with water on the deck, which together with annymi modeling and algorithm information transformation 1-7 are shown on the screen color graphic station 19 and are printed by a printer 20. The data on the coordinates of the ship's position 21 and the distance to the nearest port of refuge 22 entered by the user via the computer keyboard.

Claims (1)

A method of monitoring the stability of a ship, based on measuring the rolling period and determining the calculation of metacentric height, when calculating which additionally measure the draft of the ship's bow and stern, heading angle and speed of the ship at irregular waves, wind speed, the coordinates of the ship and the distance to the nearest port of refuge characterized in that when assessing the stability of the vessel under the current load condition, the thickness of the water layer in the deck well is additionally measured for the direct position of the vessel, on the basis of which dividing the shoulder of the heeling moment from the water that poured onto the deck, and from the measured values of the angle of entry of the edge of the bulwark into the water, the angle of heel, draft and bow, calculate the displacement of the vessel and the effective heeling moment, the value of which is presented as a graphical dependence on the angle of heel for comparison with the limit , a critical diagram of the stability of the vessel at the top of the wave, calculated taking into account the normalized parameters of the waves, and the stability assessment is performed according to a criterion based on the calculation of the actual application Ata center of gravity of the vessel to the current stability curves on top of the wave, the value of which should not exceed the critical z-vessel's center of gravity to the limit of the diagram.

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