Rudder Action Research Articles

Supertwisting and terminal sliding mode control of course keeping for ships by using particle swarm optimization

Ships are highly vulnerable to external disturbances like sea waves and sea winds; its course keeping is a core problem of ship motion control. In order to solve the problems of ship heading control a better rudder action is needed to control the ship motion. In this research study, variable structure based nonlinear control algorithms namely integral sliding mode, double integral sliding mode, terminal sliding mode and supertwisting sliding mode controllers have been proposed to provide the robust solution against external disturbances. Lyapunov stability theory has been considered to check the asymptotic stability of the system. Smoothness, energy consumption and output response performances have also been calculated to further validate the performance of suggested controllers. Robustness of all the suggested controllers have been validated by adding the disturbance effect into system model. Particle swarm optimization approach has been used to get the optimal performance of better performing controller by tuning its gains. Furthermore, suggested nonlinear controllers have been simulated in MATLAB/Simulink and their comparative analysis has been showed with each other and with the literature’s developed nonlinear controllers. To further ensure the superiority of best performing proposed controller, a real-time controller hardware in the loop experimental test has also been presented.

Robust integral backstepping and terminal synergetic control of course keeping for ships

Course keeping control of ships deals with the automation of their trajectories for which a better rudder action is required to control the ship heading to continuously remain at the desired reference despite of environmental disturbances like sea winds and sea waves. For this purpose, this paper proposes Robust Integral Backstepping, Synergetic, and Terminal Synergetic controllers for good course keeping performance and reducing the energy consumption in course keeping control for ships. Output response of system, energy consumption and smoothness performances have been computed to check the efficiency of these proposed controllers. Lyapunov stability theory has been used for the proposed nonlinear controllers to ensure the global asymptotic stability of the system. Proposed controllers have been simulated on MATLAB/Simulink, where a comparative analysis of the proposed nonlinear controllers has been presented with each other, with conventional PID controller and with recently proposed nonlinear controllers for the course keeping control of ships.

Full-scale measurements of vertical motions on ultra large container vessels in Scheldt estuary

From September 2017 to July 2018 the Flemish Pilotage executed nine ship measurements on container ships to and from Antwerp. The measurement results were processed by Flanders Hydraulics Research and Ghent University providing 6 DoF motions of the vessels. Furthermore environmental data regarding tide, currents, waves, bathymetry and AIS were processed in order to assess the influence of environmental conditions on the vertical motions of container ships.The paper presents the vertical ship motions separately for steady and unsteady sinkages in different DoF. As such the relation with ship squat, hydrostatics, sea keeping, turning, steering and ship-to-ship interaction could be assessed and related to the driving parameters such as ship speed, rate of turn, under keel clearance, water density, waves, rudder action and ship meetings.

Exploration of a systems and control approach to reduce propeller cavitation in a seaway

Dramatic increases in the underwater acoustic signature of ships have been observed during full scale trials in a seaway, compared to calm water conditions. The observed behaviour can be explained by the interaction of waves, wake field and ship propulsion system dynamics in combination with rudder action and ship motions. This paper explores whether a propulsion control system can increase the cavitation free time when sailing a straight course in a seaway. While in the past non-linear simulation tools have been used to analyse propeller cavitation in a seaway, the original contribution of this paper is that it considers the problem from a systems and control point of view. It is shown that the objective of significantly increasing the cavitation free time while simultaneously preventing thermal overloading of the diesel engine cannot simply be met by adjusting engine speed governor settings. It is however concluded that the developed plant and disturbance model are promising tools for advanced controller development and tuning aiming to reduce underwater acoustic signature.

조타장치 제어에 의한 횡동요 감소 효과

Reduction of ship ′s rolling is the most important performance requirement for improving the safety of thecrew on board and preventing damage to cargo as well as improving the comfort of the ride . It is acommonexperience for mariners , to see that steering with a rudder generally induces rolling of the ship , though theoriginal aim of the rudder is to keep the ship ′s heading to the required course . At the first stage , when arudder is steered , usually aship heels in an inward direction , due to the roll moment acting on the rudder . Atthe next stage in steering , the main heel may change to an outward . This coupling between rudder and rollmotion has become an attractive problem from the point of view of roll stabilization using the rudder ,because it is a natural in sight that if the rudder action is skillfully related to the change of roll as well as tothe course deviation , the roll can be reduced to acertain degree . The main aim of this paper is to discuss theresults of the actual full-scale sea trials carried out on steer gear No .1 and No .1 ·2, the individual quarter -master and to make clear their statistical properties , using the actual data which included measurement ofroll angle , roll rate and the comparative tests were carried out immediately after each other , in order tominimize any statistical variation in sea conditions . It can be concluded that the steer gear No . 1 ·2 reducedthe roll motion on average by about 21% in comparison with the No .1 and confirmed the some difference asper aability of quarter -master ′smaneuver .Keywords: Roll stabilization reduction , Steering gear , Rudder , Roll angle , quarter -master ′smaneuver

Course Stability of a Ship Towing System

This paper proposes a numerical model for course stability of a towed ship coupled to tow ship through towline using both nonlinear and linear approaches. Captive model tests were conducted at the towing tank to obtain hydrodynamic derivatives of both tow and towed ships. Effects of unstable towed ship (2B) and stable towed ship (2Bs), towline, tow points and rudder autopilot parameters at tow ship were treated in the numerical analysis. The simulation results demonstrated better course stability of 2Bs compared to 2B. A longer towline and shifting the tow point towards the bow both for 2B and 2Bs made the towing system more course stable, which is indicated through attenuation in slewing motion. Lateral motion of the tow ship increased gradually with shifting the tow point forward of the ship’s centre of gravity. This degrades the course stability of the towing system. The rudder action enforced by the autopilot improved the course stability. In general, the increase of the tow ship’s dimension was still insufficient to improve the course stability of the ship towing system.

Fin and rudder hybrid stabilization system

Modern roll stabilization system, namely fin, anti-roll tank and rudder action are used respectively or in combination on most passengers and naval ships. This paper proposes the advanced rudder roll stabilization control system with fin control. Fin and rudder multivariate hybrid control system were designed using multivariate autoregressive model with multi-input (yaw and roll motion) and multi-output (rudder and fin angle), named MAFRCS (Multivariate Autoregressive Fin and Rudder hybrid Control System). This paper presents the results of studies which led to the development of performing mode of operation for this hybrid control system which system has full control of rudder while fin automatically reduce the roll motion and keep the yaw motion. The results of full scale experiments and simulations studies were given to illustrate the system performances.

Small Marine Vessel Application of a Fuzzy PID Autopilot

A fuzzy logic PID controller is developed for a small maritime vessel. Responses in the course-keeping mode are investigated and compared to a classical PID autopilot over a typical range of weather conditions with RMS yaw error and rudder action being utilised to quantify the quality of results obtained.

Analysis of Apparent Spontaneous Yawing for a Ship Under Way

In this paper a mathematical model is presented to explain the phenomenon of yawing oscillations of a ship, when sailing in a mean straight course with a constant mean speed. With this model, periodic yawing can be simulated as a result of simultaneous periodic rolling and pitching, emphatically without the input of any rudder action. Additionally, the study throws a new light on the old question of whether the Cardan suspension of the compass bowl should be with the outer gimbal axes fore and aft or athwartships.

Prediction of Wave Forces on a Ship Running in Following Waves with Very Low Encounter Frequency

A theoretical method is proposed for computing the wave forces on a ship running in the following oblique waves with very low encounter frequency. It incorporates, in addition to the Froude-Krylov forces, all the terms up to the lowest order of magnitude with respect to the disturbance of the incident waves. They include the interaction effect between the stationary waves generated when the ship running on a calm water and the disturbed incident waves.Several examples of numerical results by the method are presented to test its validity, for example, for predicting the wave yaw moment which was found by Motora et al. to bring about broaching-to phenomenon when it exceeds the course keeping ability of the ship given by the rudder action. The results show that the method proposed is better than the Froude-Krylov assumption for describing the relation between the wave force magnitude and the location of the incident waves relative to the hull.

Safety Criterion of a Ship considered from the Stability

When a ship, which is rolling among waves around the steady heel due to wind, is attacked by a sudden gust, sometimes accompanied by the rudder action, if the work done by the gust and rudder action be greater than the reserve of her stability, she capsi es. The condition, that the capsize may not occur, can be expressed by the following relations:C'=Sd/CwDw(θr+2θ0) 2D0θ0+1/2mθ02>1......(A)where Sd: dynamical stability arm, i. e. the area of t e stability curve divided by the weight of the ship, Dw: heeling moment arm (the speed of the gust assumed to be 1.4 time of the mean wind speed), θr: range of the stability curve, Cw: reduction coefficient determined from the fact of the reduction of wind speed near the sea level, θ0: rolling angle. D0: heeling moment arm due to the rudder action, m: metacentric eight.Being given the speed and the rolling period of a ship, the waves (length and height) and wind speed, which cause the severest conditions to her heel, are to be found from the curves given in the paper. C' in (A) should be at least greater than unity, but, considering the other conditions which are not taken into account in the deduction of (A), the permissible lowest value of C' must be taken much greater than unity. C' is called in this paper the safety criterion, and can be considered as like the factor of safety in the strength of materials, and its permissible lowest value should be determined from the experiences of actual ships. Values of C' are calculated with several small-typed vessels, and given in the Table.