LQR-based Ship Roll Reduction Control Using Fin Stabilizer

An experiment was performed to examine and characterize physical phenomena which occur during the process of large amplitude ship roll motions. These phenomena result in distinctly different behavior compared to the small amplitude roll motion regime. Because these processes are highly nonlinear, it is important to consider them when modeling ship motions in heavy seas. An understanding of the relevant physics for large amplitude ship roll motions and the characterization of the phenomena from this investigation are intended to provide additional understanding of the processes which should be modeled, to enable more accurate predictions of ship roll motion. The results from this experiment provide useful insight in the physical phenomena which occur during large amplitude roll motion and will help with the formulation of a new model for large amplitude ship roll motion, including ship roll damping and forces on the bilge keel.

A backstepping control design procedure for nonlinear fin roll control of a trawler is presented in this paper. A roll equation consisting of linear and nonlinear damping and restoring moment on the roll response is expressed. Flow analyses are carried out for a scaled model of trawler type fishing vessel including fin stabilizers on both sides of the hull. The fin stabilizer geometry is chosen as NACA 0015 foil section which is widely used in the literature. The flow analyses are performed by using a commercial computational fluid dynamics (CFD) software based on finite volume method. The flow problem is modeled in a 3-dimensional manner while the flow is considered as steady, incompressible and fully turbulent. The numerical model consists of the ship wetted surface and the fin stabilizer in order to investigate the hull-fin interaction. Non dimensional lift coefficients of the fin stabilizer for different angles of attack are gained. Both controlled and uncontrolled roll motions are examined and simulated in time domain for the maximum lift coefficient. Backstepping controller for roll motion has given a rapid and precise result.

Magnus rotor wing is a novel roll reduction device that it generates anti-rolling force through the rotation of the rotor wing installed at the bilge of ship hull to reduce ship's roll motion. It is effective at medium/low speed and at zero speed, which is different from fin stabilizer. This paper focuses on the situation that the rotor wing is perpendicular to ship hull. The lift generating and anti-rolling mechanism of Magnus rotor wing are analyzed based on Kutta-Joukowski theorem. The hydrodynamic characteristics of Magnus rotor wing at medium/low speed is achieved using CFD software Fluent. The relationship between the lift/drag of the rotor wing and its rotation speed at a certain sailing speed is analyzed and discussed in details. The numerical simulation results have a good correspondence with theory analysis results. Finally, The conclusion that Magnus rotor wing is more suitable for ship roll stabilization at medium/low speed is achieved.

By making use of the λ 21-cm line survey of the galactic plane by Westerhout (1966), a rolling motion of neutral hydrogen gas has been found along the nearest, Perseus, and distant arms in the galactic longitude range l = 50° — 195° at |b| ≤1°. The sense of the rolling motion around an arm changes from place to place with a typical scale of 300pc or more along the identical arm. The velocity of the observed rolling motion takes a value of several km/sec near the arm surface, compatible with an early theoretical study. Some large rolling motions have been found locally at l = 110° — 119° and l = 160° —170° in the nearest arm, l = 50°—60° and l = 95° —110° in the Perseus arm, and l = 130°—150° in the distant arm. The kinetic energy of the local large rolling motion is about 1051–52 ergs, which amounts to, if we compare it with other known energy release, a total kinetic energy of one Type II supernova explosion.

Broaching, surf-riding, and capsizing of ships and offshore structures are transient wave-structure interactions which imply high risks for crew, vessel and cargo. As nonlinear effects are of great importance, time-domain investigations are indispensable. For unveiling the associated driving mechanism of these critical motions, it is desirable to analyze the cause-reaction chains in detail: Depending on the transient wave elevation, we obtain an instationary pressure distribution on the wetted surface of the cruising vessel. Resulting forces and moments excite vessel motions in six degrees of freedom. Based on the linear panel-method program for transient wave-body interactions, TiMIT [Korsmeyer et al. (1999)], this paper investigates seakeeping characteristics of offshore structures with forward speed. Results are presented in frequency and time domain. The procedure allows to identify critical seaways, and to analyze cause-reaction chains in deterministic wave sequences where critical and steep wave packets are embedded in random seas. The detailed evaluation reveals that large roll and pitch motions are easily reduced by variation of course and speed. For investigating the mechanism of wave/structure interactions, this paper introduces the relevant time-domain methodology, and indicates how nonlinear wave characteristics can be introduced in the time-stepping analysis. In subsequent steps nonlinear wave/structure interactions will also be considered.

Numerical study on damaged ship rolling and capsizing in irregular beam waves during quasi-steady flooding

It is different from conventional ship fin stabilizer that the lift of fin stabilizer is produced by initiative swing of movement mode of pitching and heaving at zero speed. For the fin stabilizer is belong to bigger inertia load, the reverse lift could be generated with the shorter braking time and the ship rolling would be acute and getting worse. So the lift limit element should be improved and lift limit is introduced. It is undoubtedly another development to introduce lift control to ship roll stabilization at zero forward speed. The simulation of anti rolling effect is researched at the different sea wave condition. And the anti rolling effects achieved over 55% respectively. It is proved that the designed system could be satisfied with the need of anti rolling ship at zero speed. This research is supported by the science and technology research project of Education Department of Heilongjiang Province (11544044).

Potential and viscous hybrid calculation method for ship motion prediction considering the change of ship motion attitude

Applying the PD controller on the roll reduction and track keeping for the ship advancing in waves

Parametric roll is a phenomenon in which there is a large rolling motion of a ship even when the ship is moving into head seas with no direct excitation. It is a nonlinear dynamic phenomenon of a ship rolling system with nonlinearities in the stiffness as well as the damping terms. Parametric roll of container ships in head seas is a relatively new problem, which has gained lot of importance after the catastrophic incidence of APL China in 1998. Analysis of parametric roll of container ships in regular head waves has been studied extensively. However, the ships do not encounter regular waves in the ocean. So, it is necessary to study how important parametric roll is in irregular seas. To study this, it is first important to model the variation of metacentric height in irregular waves, which is nonlinear as a result of the influence of underwater geometry and the motions of the ship in a seaway. In this work, the change of metacentric height (GM) in irregular waves has been modeled using a Volterra series approach. This transfer function for metacentric height (GM) is used to study parametric rolling of ships in irregular waves. Based on this study, roll motion sensitivity to the spectral peak period and significant wave height has been carried out.

This study focuses on mitigating ship roll, which significantly impacts navigation. The research investigates a design method for a rudder and fin joint roll reduction controller based on non-linear feedback. A comprehensive 4-DOF motion model of the ship is developed. The controller aims to enhance roll stability by effectively regulating the anti-rolling forces generated by the rudder and fin. Employing a PID controller with time-varying gains enhances the system’s dynamic response and enables it to withstand diverse wave conditions. Non-linear feedback techniques are implemented to minimise control variable outputs, thereby preventing excessive roll reduction forces that might lead to reverse roll. Simulation experiments are conducted to evaluate the roll suppression capability of the proposed controller. The obtained results demonstrate that the non-linear feedback-based roll reduction controller achieves outstanding roll stabilisation efficiency, reduced fin angle and rudder angle outputs, and improved heading stability when compared to conventional PID controllers.

This paper describes some recently completed research at the University of New Orleans into the nonlinear and coupled aspects of large amplitude ship rolling motion, including capsizing, at all heading angles. The study analyzes the roll motion of a vessel which experienced large amplitude motions. By studying the nonlinear and coupled aspects of the critical roll motion, insight into the important parameters affecting the roll was obtained. The roll was found to be multivalued and highly coupled to the sway and the yaw motion. Additional work has been completed and more work is in progress to investigate additional aspects of the subject vessel's motion.

A data driven method for multi-step prediction of ship roll motion in high sea states

The violent ship roll directly affects the safety of sea navigation and the ability to perform tasks, which makes ship anti-rolling become a research focus. Fin stabilizer is the most widely used and effective active anti-rolling device for ships. However, in the available literature, there is no real-time hardware-in-the-loop (HIL) platform to help researchers and engineers design fin stabilizer control systems. Accurate ship motion control platform is of great importance. It solves problems that are difficult to solve with digital simulation by providing motion attitude monitoring and more realistic simulation environment. In order to solve the problem, this paper develops a real-time visual hardware-in-the-loop simulation platform (RTV-HILSP) for ship roll control system design, which makes it easier to find the defects in the actual system. In this paper, the design scheme and the working principle of the platform are introduced in detail, and the roll mathematical model of a research ship is established. In order to test the performance of the new platform, a series of simulations is carried out. The results show that the RTV-HILSP meets the requirements of industry standards and can be used in the design and verification phase of the controller, which has proved to be a good research platform.

The lift is not be generated on the wings when the water velocity is zero. So the conventional theory is not adapted to the anti rolling ship research at zero speed. And the technology of anti rolling ship at zero forward speed is a kind of new theory. In order to study the process of lift generation of fin stabilizer at zero speed, the model of lift generation of variable chord fin stabilizer is built based on Weis-Fogh mechanism by the conformal representation. And 2 dimensional lift generation model of zero ship fin stabilizer with variable chord is studied by simulation with different motion law. The results show that the different lift characteristics could be provided for ship according to different wave periods by changing chord length dynamically at stated fling law. So the proposed model of zero ship fin stabilizer with variable chord could be able to reflect the lift characteristic in still flow field. This paper is supported by the science and technology research of Education Department of Heilongjiang Province (11544044).