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The ship
Published in Alan E. Branch, Michael Robarts, Branch's Elements of Shipping, 2014
Alan E. Branch, Michael Robarts
Manoeuvrability is a basic safety requirement for all vessels, as well as being an intrinsic element of the operational capability in some applications. The thruster system enables a more dynamic positioning of the vessel and is widely used in ro/ro ships, cruise ships and types of offshore support ships. Three types of thrusters exist. The azimuth thruster provides the main or auxiliary inboard or outboard propulsion and manoeuvring with 360° turn, using controllable or fixed pitch propeller. The bow and stern thrusters are conventional turned thrusters, both having either controllable or fixed pitch propellers.
Basics of Electrical Propulsion and Thruster Types
Published in Surender Kumar, Dynamic Positioning for Engineers, 2020
Azimuth thrusters are special type of thruster which have a rotatable device for production of thrust in any direction. The main drive motor for these types of thrusters may be mounted vertically and drive a shaft gear arrangement suitably designed to meet a vessel’s thrust requirements. Sometimes an L shaped or Z shaped installation with a suitable RPM control system, such as variable frequency drives, help in reducing losses.
Energy-efficient control of a thruster-assisted position mooring system using neural Q-learning techniques
Published in Ships and Offshore Structures, 2021
Huacheng He, Lei Wang, Xuefeng Wang, Bo Li, Shengwen Xu
The reward r is determined by the mean power consumption of the thrusters over the time horizon H, because of the discretization of the state variable and the stochastic nature of irregular waves. Given N azimuth thrusters, the average power consumption level of the PM system is determined by: where represents the thrust (unit: kN) of the kth azimuth thruster. Numerical simulations with only the plant control level are conducted under the environmental condition given by Table 4, for a series of fixed radius setpoints. The simulator is developed with C++. For each three-hour simulation, the mean power consumption levels in each time horizon (H = 5 min) are calculated. The mean value of all the time-averaged power consumption levels are plotted against the radius setpoints in Figure 7. The average power consumption reaches its minimum when , which is roughly the equilibrium position of the mooring system under the given environmental condition.
Application of novel all-direction thruster for dynamic positioning of sandglass-type FDPSO
Published in Ships and Offshore Structures, 2020
Lin-lin Wang, Wen-hua Wang, Yong-jie Wang, Ya-zhen Du, Yi Huang
For the purpose of the average position of pitch motion analysis, making the dynamic time-varying acceleration and velocity items , , and of surge and pitch motions equal zero. Thus the static equations simplified from Equation (5) can be expressed as,By solving the simultaneous equations, x5 can be shown in Equation (7)Through Equation (7), it can be seen that the mean pitch angle relates to the wind moment in the pitch direction, and it cannot be resisted by the control force . Apparently, because of the wind force acting above the waterline and the traditional azimuth thrusters located on the bottom of the floating body, a constant moment exists inevitably. Thus, it is necessary to deal with the mean pitch angle problem with some special thrusters instead of traditional azimuth thruster.
Virtual prototyping: a case study of positioning systems for drilling operations in the Barents Sea
Published in Ships and Offshore Structures, 2019
Pierre Major, Robert Skulstad, Guoyuan Li, Houxiang Zhang
The Island Innovator (Island Drilling 2018) depicted in Figure 1, has been used as a MODU model with high resolution 3D model consisting of tri-meshes for high fidelity aero- and hydrodynamics (drag coefficients) computation in the physics engine. Wind, current, and waves affect the MODU. The tensioners compensating the platform heave for the drill string connecting the MODU to wellhead via the BOP are modelled as a winch holding a constant tension. Four mooring winches, controllable by a positioning algorithm developed for the purpose of the study, are each connected to a suction anchor (N355m, E355m) (N355m, E-355m) (N-355m, E355m) (N-355m, E-355m) by a 76 mm nominal diameter, 12 × 3 strand HMPE rope, made from the Dyneema® fibre type DM20 XBO. For the sake of simplicity, due to time and resource shortage, a single azimuth thruster is mounted at the barycentric position of the real thrusters.