Rudder Effectiveness Research Articles

Real-time simulation of ship overtake maneuvering at different water depths with a ship motion controller

This study aimed to predict ship trajectories in deep and shallow waters in real-time by properly accounting for the effects of hydrodynamic interactions on ship maneuvering. Ship maneuverability and motion control were investigated under hydrodynamic interactions arising from the effects of water depth, ship speed, and lateral distance between interacting ships on parallel courses. The Maneuvering Modeling Group (MMG) model was used, and the hydrodynamic interaction effect was estimated using an efficient three-dimensional potential-flow code that can run in real time. The influence of water depth on ship maneuverability was analyzed. The ship velocity response to the hydrodynamic interactions and maneuvering motion was simulated during the overtaking process of two ships at a range of water depths, lateral distances, and speeds. The findings suggest that, in shallow waters, changing the heading of the ship becomes more difficult, and the course deviation associated with the overtaking maneuver of two ships also increases. A conventional proportional-integral-derivative (PID) controller was employed for course-keeping. When the ratio of the water depth to ship draft was less than 2.0, the PID controller continued to perform effectively for the overtaking ship. For the overtaken ship, the effectiveness of the controller was diminished owing to the relatively low rudder effect at slow speeds.

Estimation of steady wave forces and moment acting on an obliquely moving ship in short waves, and its application in a manoeuvring simulation

In this study, we propose a prediction method for steady wave forces acting on an obliquely moving ship in short waves. Particularly, we enhance an existing method that focuses on refraction of flow and waves in the vicinity of ship's waterline, in terms of the wave amplitude in the near region of the ship and the flow velocity. The former is theoretically modified by deriving an advection equation for wave energy on a ship-fixed frame, and the latter is improved by reflecting the results of computational fluid dynamics that automatically includes viscous effects. A comparison between the prediction and published captive model test results shows that the present method can more adequately capture the variation of the steady wave forces owing to the ship advancing speed and lateral drift than the original method, although the prediction accuracy is not necessarily improved under all conditions. To confirm the applicability of the present method for steady wave forces to ship manoeuvring problems, we predict course-keeping manoeuvres of a ship in regular short waves through a numerical simulation that considers only the steady wave forces in the equation of motion in calm water. The manoeuvring simulation results are validated using previously published free-running model test results, involving various rudder effectiveness conditions for the ship model and full-scale ships, both with and without engine limits. The comparison shows that the present method for steady wave forces is effective in predicting the course-keeping manoeuvres under rudder effectiveness conditions for a ship model in regular short waves. Nonetheless, the present method is insufficiently practical in terms of the manoeuvring simulation under rudder effectiveness conditions for a full-scale ship that is relatively more susceptible to waves. We confirm that an empirical correction for the computed steady wave surge forces based on the discrepancy between the measured and computed values under the ship resting enables the approximate prediction of the course-keeping manoeuvres even under the rudder effectiveness conditions for the full-scale ship.

Reconfiguration control allocation of actuator faults for tailless aircraft with low aspect ratio

The triaxial attitude control of the tailless aircraft depends heavily on the effectiveness of the actuators. Still, the actuators have redundancy characteristics, cross-coupling of rudder effect, and so on. Therefore, the reconfigurable control allocation of the tailless aircraft under typical actuator faults is deeply studied in this paper. The effectiveness and rationality of the incremental control allocation method based on quadratic programming are thoroughly verified for application to maximize the residual control ability of the aircraft, ensure that the aircraft can still complete the flight mission typically, and guarantee flight safety. According to the research principle of surface failures from slight to severe, three typical rudder surface faults are designed successively: Efficiency loss of single actuator, single actuator stuckness, and double actuators combined stuckness. On this basis, the mechanism of reconfiguration allocation after actuator failures is studied, and the residual control ability of the actuator after loss is fully explored. What’s more, the range of allowable reduction of efficiency of each actuator and the acceptable stuck angle range of each actuator are explored, and the most severe failure in the combination of double actuators stuck is obtained. The attitude controller is designed with incremental backstepping (IBKS). The reconstruction allocation adopts a quadratic programming allocation method based on an effective set solver, which can be seamlessly connected with the IBKS method to improve the control accuracy and disturbance immunity effectively.

선박의 종경사와 횡경사 변화에 따른 조종특성

This study was conducted to analyse the changes in trim and heeling using Zig-zag test, at T/S SAE DONG BACK was used to examine the manoeuvrability according to the trim and heeling changes of the vessels. Regarding the Zig-zag test to observe the trim changes at the port and with starboard rudder angles of 10° and 20° at 0.30m, and 0.52m, the overshoot angle of starboard was 18% bigger than that of the port at the rudder angle of 10°, and the course changing ability was better than the turning ability at the rudder angle of 10°. The size of the turning circle, final diameter was 4-5% and the required time was 2-7% larger than the port at the trim of 0.52m and 0.30m. External forces and superstructures that are larger than those of general ships showed characteristics that affect turning performance. When the Zig-zag test was used to compare the heeling changes, the overshoot angle of the starboard was 12°-14° larger than that of the port at 0° with no heeling compared to the 3° heeling. As a result, the Turning ability of the vessel was satisfactory. Furthermore, the second overshoot angle at 3° heeling was 6° larger; thus, the port veering showed a better rudder effect than the starboard veering. Hence, the turning ability decreased and the course-changing ability increased as the trim change in the vessel increased. Regarding the values of the turning ability index, K′, and the course changing ability, T′, according to the Trim increased when the rudder angle was used on The larger the trim, the lower the turning ability and the higher the course change ability, and when the burp is low, the turning ability is good, but the course change ability is somewhat decreased.

Effects of steady wave forces on course-keeping manoeuvres of full- and model-scale ships moving obliquely in short waves

ABSTRACT We investigated the effects of the steady wave force variations generated by oblique motions upon ship manoeuvre estimations, using a numerical simulation that incorporated only steady wave forces into a three-degrees-of-freedom conventional modular mathematical model in calm water. The investigation was conducted for a very large crude carrier undergoing course-keeping manoeuvres in regular short waves. The steady wave forces in the simulation were provided via two methods, depending on the experimental data and the presence or absence of a ship drift angle. The simulation was validated via a free-running model test; this involved various rudder effectiveness conditions for the ship model and full-scale ships, both with and without engine limits. Through this validation, we showed that the steady wave force variations generated by oblique motions are non-negligible when accurately estimating the manoeuvres of full-scale ships in short waves, although they are negligible for ship models.

Bioinspired Drone Actuated Using Wing and Aileron Motion for Extended Flight Capabilities

Since the advent of flying machines, engineers have strived to develop aircraft that can fly as flexibly as birds. From the original traditional control surface to the controllable morphing wing design, they all aim to improve the flight performance of drones, including the load capacity, maneuverability and stability. We believe that a single control method has certain limitations. For example, for roll control, the aileron rudder effect will be significantly reduced when flying at a high angle of attack (AOA), and the asymmetric deformation control of a wing is almost useless under the conditions of low-speed and small AOA. Until now, solutions to the above problems have remained largely unexplored. Therefore, the combination of wing deformation and ailerons is proposed to improve the roll control ability of drones. In this research, a new bionic deformable wing drone is designed, which demonstrates the advantages of the combination of ailerons and wing morphing in roll control and verifies that the symmetrical folding of a wing can change the flight envelope. The aerodynamic characteristics of the drone were tested in a numerical simulation, and its flight capabilities for different configurations were characterized in flight experiments.

Study on tolerance control of flying-wing layout vectored thrust UAV

The flying-wing layout vectored thrust UAV often uses multiple sets of aerodynamic rudder surfaces and vector nozzles to jointly generate the required control force and torque, which belongs to a typical overdrive system. Multiple sets of rudder surfaces give UAV a higher redundancy configuration, but also result in multiplying the rudder surface failure rate. Especially for the statically unstable flying-wing UAV in lateral direction, the moment imbalance caused by the failure of the executive rudder will seriously affect the flight safety. Therefore, this paper takes the failure of elevator and rudder damage as an example, and proposes a kind of control distribution method of aerodynamic-based control and vectored thrust as auxiliary. The binary vector deflection mechanism is used to generate vector thrust, compensate damaged actuator mechanism rudder effect, release the control margin of the rudder actuator, and restore the maneuverability of the aircraft. Under the failure of the aerodynamic rudder actuator damage, the stable control UAV is realized.

Under-actuated USV path following control under multiple constraints

The path following control of an under-actuated unmanned surface vehicle (USV) under the constraints of rudder angle, rudder velocity, and rudder response time in the disturbing environment is studied, and a cascaded path following control system based on guidance law and heading control law is designed. First, the guidance law is designed on the basis of integral line-of-sight, while the tracking error state is introduced to design a variable gain disturbance observer, which not only ensures the stability of the convergence section but also takes into account the tracking accuracy of the stable section. The stability of the system is analyzed. Subsequently, the rudder maneuverability constraint and rudder effect delay are further imposed after fully considering the limited range of rudder angle, rudder velocity, and rudder response time in the process of path following. In addition, the heading control law is, therefore, designed on the basis of the rolling optimization strategy, which effectively reduces the oscillation while ensuring the convergence speed. The stability of the control law is further proved. Thereafter, a simulation experiment proves the effectiveness and advancement of the algorithm designed in this paper. In the end, based on the software and hardware design of the control system, “Sea Sturgeon” USV is used for the lake test of the proposed control algorithm to verify its feasibility in practical engineering applications.

Aspects of yaw control design of an aircraft with distributed electric propulsion

Distributed electric propulsion (DEP) offers new options in aircraft design. Besides the optimization of the wing, another area of optimization is the vertical tail plane (VTP) and yaw control. The large number of engines significantly relaxes the one-engine-inoperative (OEI) case during take-off, which is mostly the sizing case for the VTP. This offers the possibility to reduce the VTP and rudder size to a certain amount. Also, the dynamics of electric motors offer the possibility to use differential thrust for yaw control. This can compensate at least some of the reduced rudder effectiveness coming from the smaller VTP size. In the framework of the German nationally funded project SynergIE, different aircraft designs of a hybrid-electric regional aircraft were investigated. Three aircraft concepts with 2, 6 and 12 propellers were designed in the project, for which reasonable minimum VTP sizes were investigated. For the 12-propeller aircraft, the investigations showed that the VTP could be reduced by 50%, still allowing the compensation of OEI during take-off and the generation of sideslip angle during crosswind operations. This reduction in VTP size results in a reduction of the block fuel by about 4%. For the 12-engine aircraft, a 6-degrees-of-freedom simulation model was developed including flight control laws for yaw control using the rudder and differential thrust. Virtual flight tests were performed in a full-flight simulator. The tests generally showed a good agreement with the theoretical results from the handling quality analysis but also outlined deficiencies in aircraft handling at low speed with full flaps. The use of a flight simulator at this early stage of aircraft design has proven to be a useful tool to investigate such unconventional designs.

Effects of Rudder and Blade Pitch on Hydrodynamic Performance of Marine Propeller Using CFD

Abstract The use of computational fluid dynamics (CFD) to predict internal and external flows has risen dramatically in the past decade. This research aims to use the commercial software, ANSYS Fluent V.14.5, to illustrate the effects of the rudder and blade pitch on the hydrodynamic performance of the marine propeller by experimenting with propellers and rudders of the M/V Tan Cang Foundation ship, which has designed conditions as follows: diameter of 3.65 m; speed of 200 rpm; average pitch of 2.459 m; boss ratio of 0.1730. Using CFD, the characteristic curves of the marine propeller and some important results showed that the maximum efficiency of the propeller is 0.66 with the open water propeller and 0.689 with the rudder‒propeller system at the advance ratio of 0.6. The obtained outcomes of this research are a significant foundation to calculate and design an innovative kind of propulsion for ships with high performance.

Hydrodynamic characteristic investigations of a collaborative spoiled rudder under open water conditions

This study presents the hydrodynamic performance estimation of a collaborative spoiled rudder (CSR) - a new concept of ship rudder under open water conditions. The grid sensitivity study is carried out and the numerical method used in this work is validated by comparing with experimental data. The hydrodynamic performances of different CSR configurations at various rudder angles are simulated. The result shows that the existence of the spoiler has positive effect on the rudder lift and the effect gets more obvious with the increase of spoiler open angle. The spoiler can be controlled easily owing to the small spoiler stock torque. The optimal matching results show that, under the optimal matching conditions, the lift to drag ratios of the CSR are generally higher than those of the CR for the same target lift, and the improvement of the CSR in the rudder effectiveness gets more obvious with the increase of target lift. Furthermore, the CSR having the optimal matching rudder angle and spoiler open angle is much easier to steer compared with the CR with the same lift being generated. Overall, properly adjusting the rudder angle and the spoiler open angle of the CSR can significantly improve the rudder effectiveness.

Study on the design procedure of rudder attached thrust fin for merchant ship based on computational fluid dynamics

Rudder added thrust fins have gained popularity as an energy saving device (ESD) by virtue of; simple design, easy installation and its effectiveness. The current work seeks to investigate the influence of geometric parameters and mounting orientation on the energy saving effect of rudder attached thrust fins based on numerical analysis. Open water, bare hull resistance and self-propulsion simulations were carried out by solving the Reynolds-Averaged-Navier-Stokes Equations (RANSE) using a Computational fluid Dynamics (CFD) code. In the case of geometrical parameters, hydrofoil camber and fin span were varied. The fin orientation was then studied by varying the mounting direction in relation to the angle of attack and the location of pressure and suction sides. A validation study carried out showed good agreement between CFD and model tests. It was noted that the rudder thrust fin is sensitive to the hydrofoil orientation. Also, with the right hydrofoil orientation, the fin performance is optimum at an angle of attack of about 2°. This study presents a design guideline for rudder thrust fins to ensure optimum energy gains.

Bow and Stern Control Surface’s Effectiveness and Influence on Supercavity

The numerical model of supercavitating flow field was established based on multiphase model, cavitation model, and turbulence model. The model was employed to simulate the supercavitation flow for the supercavitating vehicle with two types of control surfaces: bow rudder and stern rudder. The influence of both control surfaces on the supercavity shape and rudder effectiveness is compared under the different rudder angles (0‐12°), and the effectiveness and the influences on supercavities of bow rudder and stern rudder were explored according to the numerical research results. From the research results, the following conclusions can be drawn: (1) the bow rudders have stable rudder effectiveness and available rudder angle, and the bow rudders also have significant influence on supercavities’ shape. (2) By contrast with the bow rudder, stern rudders’ effectiveness is difficult to predict accurately, and the phenomenon of stalling will occur when stern rudders’ rudder angle exceeds 6°; however, there is almost no influence of stern rudders on supercavities. (3) The bow and stern rudders joint control mode must take the influence on supercavities’ shape and the accuracy of control force’s forecasting into account at the same time. The research is helpful to the optimizing of superhigh‐speed vehicles and the design of control modes.

Prediction of a research vessel manoeuvring using numericalPMM and free running tests

International Maritime Organisation (IMO) regulations insist on reduced emission of CO2, noxious and other environmentally dangerous gases from ship, which are usually let out while burning fossil fuel for running its propulsive machinery. Contrallability of ship during sailing has a direct implication on its course keeping and changing ability, and tries to have an optimised routing. Bad coursekeeping ability of a ship may lead to frequent use of rudder and resulting changes in the ship\'s drift angle. Consequently, it increases vessels resistance and also may lead to longer path for its journey due to zigzag movements. These adverse effects on the ship journey obviously lead to the increase in fuel consumption and higher emission. Hence, IMO has made it mandatory to evaluate the manoeuvring qualities of a ship at the designed stage itself. In this paper a numerical horizontal planar motion mechanism is simulated in CFD environment and from the force history, the hydrodynamic derivatives appearing in the manoeuvring equation of motion of a ship are estimated. These derivatives along with propeller thrust and rudder effects are used to simulate different standard manoeuvres of the vessel and check its parameters against the IMO requirements. The present study also simulates these manoeuvres by using numerical free running model for the same ship. The results obtained from both these studies are presented and discussed here.

Estimation of full-scale ship manoeuvrability in adverse weather using free-running model test

The ship manoeuvrability in actual seas with both wind and waves, especially in adverse weather conditions, for a full-scale tanker with different maximum available power of the engine is studied. It is directly evaluated based on the result of a free-running model test (FRMT) under a course-keeping manoeuvre in long-crested and short-crested irregular waves of Beaufort scale force (BF) 7–10. The FRMT combines rudder effectiveness and speed correction considering the operational limit of an engine, and a wind load simulator, both of which were previously proposed by the authors. Therefore, not only the effect of waves but also effect of wind, rudder effectiveness of the full-scale ship, and the engine limit for continuous operation are considered in the FRMT. To validate the reliability of the direct evaluation method in FRMT and the measured data in irregular waves of large amplitude, the time-averaged manoeuvring motion of the FRMT at BF 9 is compared with ship manoeuvring motion under steady equilibrium conditions estimated using numerical simulation based on a modular mathematical model. The wave drift forces and moment in the simulation are determined on the basis of the results of the captive model test in regular waves, which is carried out using the same tanker model before the FRMT, so that we can eliminate the estimation errors in the manoeuvring motion caused by the imprecision in the wave drift forces as much as possible. The comparison shows the FRMT results acceptably agree with the simulation results, although a discrepancy is observed in the rudder angle in beam seas for the tanker with a low engine output. Further, FRMT data themselves show that full-scale rudder effectiveness, operational limit of an engine, and the engine with lower power cause the ship speed to decrease and the drift angle and the rudder angle to increase in head, bow, or beam seas because of the difference in the propeller rotational speed in each model control condition. In addition, it was clarified that operational limit of an engine also affects the significant single amplitudes of the fluctuating components of them and the oscillatory ship motion. Next, the authors assess the manoeuvring limit in adverse weather by comparing the FRMT data of the time-averaged values of the longitudinal ship speed, as well as the drift and rudder angles in short-crested irregular waves at BF 7–10 with their thresholds. The assessment clarifies that the tanker becomes unmanoeuvrable at BF 9–10 and in head, bow, or beam seas owing to a lack of sufficient advancing speed. However, the limit is not attributable to the drift or rudder angle, although the lower-power engine worsens the course-keeping ability owing to the decrease in the ship speed and the increase in the drift and rudder angles. Furthermore, the tanker is manoeuvrable in any wind and waves directions at BF 8, which is defined as adverse weather conditions for this subject ship in the interim guideline (IMO, 2013). It indicates that the tanker has sufficient margin of the engine power to keep manoeuvrability in adverse weather conditions. In summary, these findings reflect the possibility that FRMT can replace numerical simulation as a direct evaluation method of full-scale ship manoeuvring motion and limits in adverse weather.

A Fault-Tolerant Steering Prototype for X-Rudder Underwater Vehicles.

The X-rudder concept has been applied to more and more autonomous underwater vehicles (AUVs) in recent years, since it shows better maneuverability and robustness against rudder failure compared to the traditional cruciform rudder. Aiming at the fault-tolerant control of the X-rudder AUV (hereinafter abbreviated as xAUV), a fault-tolerant steering prototype system which can realize dynamics control, autonomous rudder fault detection and fault-tolerant control is presented in this paper. The steering prototype system is deployed on a verification platform, an xAUV, in which the monitor software is developed based on the factory method and the onboard software is developed based on the finite state machine (FSM). Dual-loop increment feedback control (DIFC) is first introduced to obtain smooth virtual rudder commands considering actuator’s limitations. Then the virtual rudder commands are transformed into X-rudder commands based on the mapping theory. In rudder fault diagnosis, an optimized particle filter is proposed for estimating rudder effect deduction, with proposal distribution derived from unscented Kalman filter (UKF). Then the fault type can be determined by analyzing indicators related to the deduction. Fault-tolerant control is addressed by dealing with nonlinear programming (NLP) problem, where minimization of allocation errors and control efforts are set as the optimization objectives, and rudder failure, saturation and actuators limitations are considered as constraints. The fixed-point iteration method is utilized to solve this optimization problem. Many field tests have been conducted in towing tank. The experimental results demonstrate that the proposed steering prototype system is able to detect rudder faults and is robust against rudder failure.

Towed underwater PIV measurement of propeller wake in self-propelled condition

A series of particle image velocimetry measurements was conducted in a towing tank to analyze the propeller wake dynamics of a fully appended very large crude oil carrier model. The Froude number and the Reynolds number of the test condition based on the model length and towing speed were 0.142 and 2.32 × 106, respectively. The propeller wake dynamics was investigated in terms of vortical structure and wake acceleration. It was found that the propeller loading on the starboard side was larger than that on the port side, as upward component of the propeller inflow resulted in a higher inflow speed on that side. The different propeller loading deformed the wake structure and bent it towards the port side. Between neighboring tip vortices, the local maxima of the turbulence kinetic energy and corresponding local turbulence structure were found. The rudder effects on the propeller wake were also investigated, proving that the rudder blocked the progress of the hub vortex and straightened the propeller wake.

Manoeuvring prediction of a container ship using the numerical PMM test and experimental validation using the free running model test

ABSTRACT Accurate determination of hydrodynamic derivatives, appearing in the equations of motion of a marine vehicle, is essential for the correct prediction of its manoeuvring performance. Solution of these equations leads to the simulation of the ship motions in the horizontal plane for a surface ship and thus helps in understanding its course stability, turning ability, rudder effectiveness and ship responsiveness. This paper presents the numerical simulation of the Planar Motion Mechanism test using RANS-based equation to obtain the hydrodynamic derivatives appearing in the equations of motion and to assess the manoeuvrability of a container ship using standard definitive manoeuvers. Experimental validation of the numerical test is carried out by conducting free running model tests in a manoeuvring basin.

CFD results on hydrodynamic performances of a marine propeller

In this work, the commercial Computational Fluid Dynamics (CFD), ANSYS-Fluent V.14.5 has been used to illustrate the effects of rudder and blade pitch on hydrodynamic performances of a propeller. At first, the characteristic curves of a container ship propeller are computed. Then, effects of rudder on hydrodynamic performances of the propeller in the both cases of the propeller with and without rudder have been investigated. The relationships between the blade pitch angle and the hydrodynamic performances of the selected referent propeller in this work having designed conditions as diameter of 3.65 m; speed of 200 rpm; average pitch of 2.459 m and the boss ratio of 0.1730. Using CFD, the characteristic curves of the marine propeller, pressure distribution, velocity distribution around propeller and the efficiency of the propeller have been shown. From the obtained results, the effects of rudder and blade pitch angle on hydrodynamic performances of the propeller have been evaluated.

Full-scale ship propeller torque in wind and waves estimated by free-running model test

A free-running model test in which a ship model controlled by the rudder effectiveness and speed correction using the auxiliary thruster was carried out. The model runs in long-crested irregular waves and under wind loads simulated by the wind loads simulator. The authors’ procedure to analyze the data of the controlled ship model estimated the full-scale propeller torque in wind and waves and revealed how the scale effects appeared in the propeller torque. The numerical simulation for the model and the full-scale ship confirmed that the ship model control ensured the similarity of ship motion in external forces.