12,833 research outputs found
A reclaimer scheduling problem arising in coal stockyard management
We study a number of variants of an abstract scheduling problem inspired by
the scheduling of reclaimers in the stockyard of a coal export terminal. We
analyze the complexity of each of the variants, providing complexity proofs for
some and polynomial algorithms for others. For one, especially interesting
variant, we also develop a constant factor approximation algorithm.Comment: 26 page
Review of dynamic positioning control in maritime microgrid systems
For many offshore activities, including offshore oil and gas exploration and offshore wind farm construction, it is essential to keep the position and heading of the vessel stable. The dynamic positioning system is a progressive technology, which is extensively used in shipping and other maritime structures. To maintain the vessels or platforms from displacement, its thrusters are used automatically to control and stabilize the position and heading of vessels in sea state disturbances. The theory of dynamic positioning has been studied and developed in terms of control techniques to achieve greater accuracy and reduce ship movement caused by environmental disturbance for more than 30 years. This paper reviews the control strategies and architecture of the DPS in marine vessels. In addition, it suggests possible control principles and makes a comparison between the advantages and disadvantages of existing literature. Some details for future research on DP control challenges are discussed in this paper
A path planning control for a vessel dynamic positioning system based on robust adaptive fuzzy strategy
The thrusters and propulsion propellers systems, as well as the operating situations, are all well-known nonlinearities which are caused less accuracy of the dynamic positioning system (DPS) of vessels in the path planning control process. In this study, to enhance the robust performance of the DPS, we proposed a robust adaptive fuzzy control model to reduce the effect of uncertainty problems and disturbances on the DPS. Firstly, the adaptive fuzzy controller with adaptive law is designed to adjust the membership function of the fuzzy controller to minimize the error in path planning control of the vessel. Secondly, the H∞ performance of robust tracking is proved by the Lyapunov theory. Moreover, compared to the other controller, a simulation experiment comprising two case studies confirmed the efficiency of the approach. Finally, the results showed that the proposed controller reaches control quality, performance and stability
Optimal Universal Controllers for Roll Stabilization
Roll stabilization is an important problem of ship motion control. This
problem becomes especially difficult if the same set of actuators (e.g. a
single rudder) has to be used for roll stabilization and heading control of the
vessel, so that the roll stabilizing system interferes with the ship autopilot.
Finding the "trade-off" between the concurrent goals of accurate vessel
steering and roll stabilization usually reduces to an optimization problem,
which has to be solved in presence of an unknown wave disturbance. Standard
approaches to this problem (loop-shaping, LQG, -control etc.)
require to know the spectral density of the disturbance, considered to be a
\colored noise". In this paper, we propose a novel approach to optimal roll
stabilization, approximating the disturbance by a polyharmonic signal with
known frequencies yet uncertain amplitudes and phase shifts. Linear quadratic
optimization problems in presence of polyharmonic disturbances can be solved by
means of the theory of universal controllers developed by V.A. Yakubovich. An
optimal universal controller delivers the optimal solution for any uncertain
amplitudes and phases. Using Marine Systems Simulator (MSS) Toolbox that
provides a realistic vessel's model, we compare our design method with
classical approaches to optimal roll stabilization. Among three controllers
providing the same quality of yaw steering, OUC stabilizes the roll motion most
efficiently
Supervisory Control of Line Breakage for Thruster-Assisted Position Mooring System
Thruster-assisted position mooring (TAPM) is an energy-efficient and reliable stationkeeping method for deep water structures. Mooring line breakage can significantly
influence the control system, and ultimately reduce the reliability and safety during operation and production. Therefore, line break detection is a crucial issue for TAPM systems. Tension measurement units are useful tools to detect line failures. However, these units increase the building cost of the system, and in a large portion of existing units in operation line tension sensors are not installed. This paper presents a fault-tolerant control scheme based on estimator-based supervisory control methodology to detect and isolate a line failure with only position measurements. After detecting a line break, a supervisor switches automatically a new controller into the feedback loop to keep the vessel within the safety region. Numerical simulations are conducted to verify the performance of the proposed technique, for a turret-based mooring system.© 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. This is the authors’ accepted and refereed manuscript to the articl
Modeling and Real-Time Scheduling of DC Platform Supply Vessel for Fuel Efficient Operation
DC marine architecture integrated with variable speed diesel generators (DGs)
has garnered the attention of the researchers primarily because of its ability
to deliver fuel efficient operation. This paper aims in modeling and to
autonomously perform real-time load scheduling of dc platform supply vessel
(PSV) with an objective to minimize specific fuel oil consumption (SFOC) for
better fuel efficiency. Focus has been on the modeling of various components
and control routines, which are envisaged to be an integral part of dc PSVs.
Integration with photovoltaic-based energy storage system (ESS) has been
considered as an option to cater for the short time load transients. In this
context, this paper proposes a real-time transient simulation scheme, which
comprises of optimized generation scheduling of generators and ESS using dc
optimal power flow algorithm. This framework considers real dynamics of dc PSV
during various marine operations with possible contingency scenarios, such as
outage of generation systems, abrupt load changes, and unavailability of ESS.
The proposed modeling and control routines with real-time transient simulation
scheme have been validated utilizing the real-time marine simulation platform.
The results indicate that the coordinated treatment of renewable based ESS with
DGs operating with optimized speed yields better fuel savings. This has been
observed in improved SFOC operating trajectory for critical marine missions.
Furthermore, SFOC minimization at multiple suboptimal points with its treatment
in the real-time marine system is also highlighted
Autonomous docking using direct optimal control
We propose a method for performing autonomous docking of marine vessels using
numerical optimal control. The task is framed as a dynamic positioning problem,
with the addition of spatial constraints that ensure collision avoidance. The
proposed method is an all-encompassing procedure for performing both docking,
maneuvering, dynamic positioning and control allocation. In addition, we show
that the method can be implemented as a real-time MPC-based algorithm on
simulation results of a supply vessel.Comment: 12th IFAC Conference on Control Applications in Marine Systems,
Robotics, and Vehicles (CAMS 2019). IFAC; Daejeon. 2019-09-18 - 2019-09-2
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