The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform

C.b. Barrass - One of the best experts on this subject based on the ideXlab platform.

  • IMO Grain Rules for the safe carriage of grain in bulk
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    This chapter discussesthe grain rules proposed by international maritime organization (IMO) for the safe carriage of grain in bulk. The intact stability characteristics of any ship carrying bulk grain must be shown to meet, throughout the voyage, three criteria relating to the moments due to grain shift: (1) the angle of heel due to the shift of grain shall not be greater than 12° or—in the case of ships constructed on or after 1 January 1994—the angle at which the deck edge is immersed, whichever is the lesser; (2) in the statical stability diagram, the net or residual area between the heeling arm curve and the righting arm curve up to the angle of heel of maximum difference between the ordinates of the two curves, or 40° or the angle of flooding, whichever is the least, shall be not less than 0.075 metre-radians in all conditions of loading; and (3) the Initial Metacentric Height, after correction for free surface effects of liquids in tanks, shall not be less than 0.30 m. Before loading bulk grain, the master shall, if so required by the contracting government of the country of the port of loading, demonstrate the ability of the ship at all stages of any voyage to comply with the required stability criteria. After loading, the master shall ensure that the ship is upright before proceeding to sea.

  • Rolling, pitching and heaving motions
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    This chapter deals with rolling, pitching, and heaving motions of the ship. When a ship rolls, the axis about which the oscillation takes place cannot be accurately determined, but it would appear to be near to the longitudinal axis through the ship's centre of gravity (G). Hence, the ship rotates or rolls about its G. It is assumed that the amplitude of the roll is small and that the ship has positive Initial Metacentric Height. Under these conditions, rolling is considered to be simple harmonic motion. The time period of roll is completely independent of the actual amplitude of the roll so long as it is a small angle. It varies directly as the radius of gyration, and inversely as the square root of the Initial Metacentric Height. It changes when weights are loaded, discharged or shifted within a ship. Pitching is the movement of the ship's bow, from the lowest position to the highest position and back down to its lowest position. Heaving motion is the vertical upward or downward movement in the water of the ship's G.

  • Angle of loll
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    When a ship with negative Initial Metacentric Height is inclined to a small angle, the righting lever is negative, resulting in a capsizing moment. This effect makes the ship heel still further. At a large angle of heel, the centre of buoyancy moves further out the low side and the force of buoyancy does not act vertically upwards. If, by heeling still further, the centre of buoyancy can move out far enough to lie vertically under the centre of gravity (G), the righting lever and thus the righting moment, will be zero. The angle of heel at which this occurs is referred to as the angle of loll and may be defined as the angle to which a ship with negative Initial Metacentric Height lies at rest in still water. If the ship is inclined to an angle greater than the angle of loll, the righting lever will be positive, giving a moment to return the ship to the angle of loll. The ship will oscillate about the angle of loll instead of the upright. At angles of heel less than the angle of loll, the righting levers are negative.

  • Transverse statical stability
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    This chapter provides an overview of equilibrium states of a ship. A ship is said to be in stable equilibrium if, when inclined, it tends to return to the Initial position. For this to occur the center of gravity must be below the metacenter, that is, the ship must have positive Initial Metacentric Height. The position of center of gravity, G , remains unaffected by the heel and the force of gravity is considered to act vertically downwards through this point. When a ship which is inclined to a small angle tends to heel over still further, it is said to be in unstable equilibrium. When G coincides with Initial metacenter, M , the ship is said to be in neutral equilibrium, and if inclined to a small angle it tends to remain at that angle of heel until another external force is applied. Several measures that should be taken for correcting unstable and neutral equilibrium are discussed in the chapter. When a ship in unstable or neutral equilibrium is to be made stable, the effective center of gravity of the ship should be lowered. To do this several methods may be employed such as weights already in the ship may be lowered, weights may be loaded below the center of gravity of the ship, and weights may be discharged from positions above the center of gravity.

  • list with zero Metacentric Height
    Ship Stability for Masters and Mates (Sixth Edition), 2006
    Co-Authors: C.b. Barrass, Captain D R Derrett
    Abstract:

    This chapter discusses how to find list with zero Metacentric Height. When a weight is shifted transversely in a ship with zero Initial Metacentric Height, the resulting list can be found using the wall-sided formula. The chapter discusses wall-sided formula, and calculates the list.

D.r. Derrett - One of the best experts on this subject based on the ideXlab platform.

  • IMO Grain Rules for the safe carriage of grain in bulk
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    This chapter discussesthe grain rules proposed by international maritime organization (IMO) for the safe carriage of grain in bulk. The intact stability characteristics of any ship carrying bulk grain must be shown to meet, throughout the voyage, three criteria relating to the moments due to grain shift: (1) the angle of heel due to the shift of grain shall not be greater than 12° or—in the case of ships constructed on or after 1 January 1994—the angle at which the deck edge is immersed, whichever is the lesser; (2) in the statical stability diagram, the net or residual area between the heeling arm curve and the righting arm curve up to the angle of heel of maximum difference between the ordinates of the two curves, or 40° or the angle of flooding, whichever is the least, shall be not less than 0.075 metre-radians in all conditions of loading; and (3) the Initial Metacentric Height, after correction for free surface effects of liquids in tanks, shall not be less than 0.30 m. Before loading bulk grain, the master shall, if so required by the contracting government of the country of the port of loading, demonstrate the ability of the ship at all stages of any voyage to comply with the required stability criteria. After loading, the master shall ensure that the ship is upright before proceeding to sea.

  • Rolling, pitching and heaving motions
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    This chapter deals with rolling, pitching, and heaving motions of the ship. When a ship rolls, the axis about which the oscillation takes place cannot be accurately determined, but it would appear to be near to the longitudinal axis through the ship's centre of gravity (G). Hence, the ship rotates or rolls about its G. It is assumed that the amplitude of the roll is small and that the ship has positive Initial Metacentric Height. Under these conditions, rolling is considered to be simple harmonic motion. The time period of roll is completely independent of the actual amplitude of the roll so long as it is a small angle. It varies directly as the radius of gyration, and inversely as the square root of the Initial Metacentric Height. It changes when weights are loaded, discharged or shifted within a ship. Pitching is the movement of the ship's bow, from the lowest position to the highest position and back down to its lowest position. Heaving motion is the vertical upward or downward movement in the water of the ship's G.

  • Angle of loll
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    When a ship with negative Initial Metacentric Height is inclined to a small angle, the righting lever is negative, resulting in a capsizing moment. This effect makes the ship heel still further. At a large angle of heel, the centre of buoyancy moves further out the low side and the force of buoyancy does not act vertically upwards. If, by heeling still further, the centre of buoyancy can move out far enough to lie vertically under the centre of gravity (G), the righting lever and thus the righting moment, will be zero. The angle of heel at which this occurs is referred to as the angle of loll and may be defined as the angle to which a ship with negative Initial Metacentric Height lies at rest in still water. If the ship is inclined to an angle greater than the angle of loll, the righting lever will be positive, giving a moment to return the ship to the angle of loll. The ship will oscillate about the angle of loll instead of the upright. At angles of heel less than the angle of loll, the righting levers are negative.

  • Transverse statical stability
    Ship Stability for Masters and Mates, 2012
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    This chapter provides an overview of equilibrium states of a ship. A ship is said to be in stable equilibrium if, when inclined, it tends to return to the Initial position. For this to occur the center of gravity must be below the metacenter, that is, the ship must have positive Initial Metacentric Height. The position of center of gravity, G , remains unaffected by the heel and the force of gravity is considered to act vertically downwards through this point. When a ship which is inclined to a small angle tends to heel over still further, it is said to be in unstable equilibrium. When G coincides with Initial metacenter, M , the ship is said to be in neutral equilibrium, and if inclined to a small angle it tends to remain at that angle of heel until another external force is applied. Several measures that should be taken for correcting unstable and neutral equilibrium are discussed in the chapter. When a ship in unstable or neutral equilibrium is to be made stable, the effective center of gravity of the ship should be lowered. To do this several methods may be employed such as weights already in the ship may be lowered, weights may be loaded below the center of gravity of the ship, and weights may be discharged from positions above the center of gravity.

  • Effect of free surface of liquids on stability
    Ship Stability for Masters and Mates, 2006
    Co-Authors: C.b. Barrass, D.r. Derrett
    Abstract:

    When a tank in a ship is completely filled with liquid, the liquid cannot move within the tank when the ship heels. For this reason, as far as stability is concerned, the liquid may be considered as a static weight having its center of gravity at the center of gravity of the liquid within the tank. If free surface be created in a ship with a small Initial Metacentric Height (GM), the virtual loss of Metacentric Height due to the free surface may result in a negative Metacentric Height. This causes the ship to take up an angle of loll which may be dangerous and in any case is undesirable. When a ship takes up an angle of loll due to a very small negative GM it should be corrected as soon as possible. The ship cannot roll suddenly over to the other side as there is more water in the low side than in the high side. If sufficient weight of water is loaded to bring center of gravity, G , on the center line below Initial metacenter, M , the ship should complete the operation upright.

Weijie Zhou - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear robust stabilization of ship roll by convex optimization
    IEEE CAA Journal of Automatica Sinica, 1
    Co-Authors: Jiafeng Yu, Qinsheng Li, Weijie Zhou
    Abstract:

    For ship roll stabilization, this paper presents a nonlinear robust controller design method using the sum of squares (SOS) technique combined with the dual of Lyapunov's stability theorem. Varying ship speed and Initial Metacentric Height are seen as uncertainties, sea waves are regarded as external disturbance, and then the robust nonlinear controller is also designed based on the suggested method. Simulations are performed by taking container ship model as an example. It is shown that the designed system guarantees robust performance with respect to the uncertainties and disturbance.

Jiafeng Yu - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear robust stabilization of ship roll by convex optimization
    IEEE CAA Journal of Automatica Sinica, 1
    Co-Authors: Jiafeng Yu, Qinsheng Li, Weijie Zhou
    Abstract:

    For ship roll stabilization, this paper presents a nonlinear robust controller design method using the sum of squares (SOS) technique combined with the dual of Lyapunov's stability theorem. Varying ship speed and Initial Metacentric Height are seen as uncertainties, sea waves are regarded as external disturbance, and then the robust nonlinear controller is also designed based on the suggested method. Simulations are performed by taking container ship model as an example. It is shown that the designed system guarantees robust performance with respect to the uncertainties and disturbance.

Qinsheng Li - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear robust stabilization of ship roll by convex optimization
    IEEE CAA Journal of Automatica Sinica, 1
    Co-Authors: Jiafeng Yu, Qinsheng Li, Weijie Zhou
    Abstract:

    For ship roll stabilization, this paper presents a nonlinear robust controller design method using the sum of squares (SOS) technique combined with the dual of Lyapunov's stability theorem. Varying ship speed and Initial Metacentric Height are seen as uncertainties, sea waves are regarded as external disturbance, and then the robust nonlinear controller is also designed based on the suggested method. Simulations are performed by taking container ship model as an example. It is shown that the designed system guarantees robust performance with respect to the uncertainties and disturbance.