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Kensaku Nomoto

Bio: Kensaku Nomoto is an academic researcher. The author has contributed to research in topics: Rudder & Directional stability. The author has an hindex of 3, co-authored 9 publications receiving 170 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the yaw-sway-roll-rudder coupling can be a cause of anomalous rolling which is frequently observed at automatically steered, high speed operations in seaways.
Abstract: Digital simulation of maneuvering motions and numerical calculation of directional stability indices are carried out on the basis of captive model test of a typical container ship. An emphasis is laid upon yaw-sway-roll-rudder coupled motion. The smaller metacenteric height proved to introduce the better turning performance and the poorer course-keeping characteristics.The yaw-sway-roll-rudder coupling can be a cause of anomalous rolling which is frequently observed at automatically steered, high speed operations in seaways. We introduce a perturbation stability analysis on the problem. It reveals the possibility of an unstable yaw-roll behavior due to roll-induced yaw moment, small GM and inadequate control parameters of autopilot steering system.

133 citations

Journal ArticleDOI
TL;DR: In this article, the authors reduced the well-known coupled equations of forward, sway and yaw motion of a ship, Eq. (2. 1), into a simple mathematical model of ship response in such manoeuvres.
Abstract: Frequent use of the engine telegraph is not unusual when manoeuvring in and out of harbours, or navigating through a narrow waterway. The captain may let the ship proceed by herself with the propeller idling, brake her by reversing the propeller, or actuate the engine shortly with the helm hard-over to correct the heading.Naturally, these operations cause a significant headway change, and at the same time introduce quite an extensive variation in propeller slip, which considerably affects the rudder effectiveness. We reduced the well-known coupled equations of forward, sway and yaw motion of a ship, Eq. (2. 1), into a simple mathematical model of ship response in such manoeuvres. Those are Eqs. (2. 10), (2. 20) and (2. 25).We make use of the existing knowledge on the rudder-to-yaw response in steady steaming as well as of a somewhat modified self-propulsion tank test to determine the propeller performance. The effect of propeller slip on the rudder effectiveness and the hydrodynamic force exerted by a reversing propeller are also investigated.According to the free-sailing model experiments, two VLCCs and one container ship model, the present simple mathematical model of ship response proved successful.

49 citations

Journal ArticleDOI
Abstract: In this paper, the emphasis is laid upon yaw-sway-roll-rudder coupled motion of a container ship in following seasWe take the case that the component of ship speed in the direction of wave propagation is equal to the wave celerity, i e, the encounter frequency is nil The linearized equations of sway, yaw and roll coupled motion in still water are generalized to use by adding the terms of wave exciting forcesThe hydrodynamic force coefficients varying with ship's relative position to wave system, are obtained by captive model tests in regular following waves generated by means of a wave making board Using the experimental results, dynamic stability of a ship in following seas is discussedIt reveals the possibility and physical mechanism of an unstable yaw-roll behavior due to the fact that :1) the wave exciting yaw moment acts as a negative restoring moment ;2) hydrodynamic forces acting upon a ship in following seas give less damping compared with in still water ;3) small metacentric height encourages a heavy yaw-roll couplingHowever, such unstable behavior in following seas can be stabilized by adding an adequate control parameters of autopilot steering system

9 citations

Journal ArticleDOI
TL;DR: In this paper, a new approach was proposed to estimate the yaw-acceleration of a ship from a zig-zag test record using a cubic nonlinear model of the rudder-to-yaw response.
Abstract: There are a number of procedures of analysing the zig-zag test to obtain the steering quality parameters of a relevant ship, ranging from the simple method with the first-order (K and T) equation to the phase-plane analysis taking the higher-order time constants and non-linearity into account.Growing importance of closed-loop studies of steering control and increasing number of less course-stable ships (e. g. very large tankers) call for the latter type of comprehensive mathematical model of steering response. However, it is not an easy task, unlike the simple K-T analysis, to define all the parameters involved in such mathematical model from a zig-zag test record. The more numbers of parameters to be defined, the harder to keep the numerical accuracy and to assure the feasibility of such analysis.The present paper relates to a new approach to this task which proved promising. That is, (1) to adopt numerical filtering to minimize the noise involved in the yaw-rate record and at the same time to obtain a reasonably noise-free yaw-acceleration ; the result gives us a measured yaw-acceleration to yaw-rate phase-plane trajectory of a relevant zig-zag test.(2) to adjust the parameters of the mathematical model built in an analogue computer by turning a number of knobs, keeping one eye to the phase-plane trajectory displayed on a cathode-ray oscilloscope, so that the displayed trajectory coincide with the measured one.The mathematical model employed is the rudder-to-yaw response equation with a cubic-type non-linear term, i. e.T1T2ψ+ (T1+T2) ψ+ψ+αψ3=Kδ+KT3δ

3 citations


Cited by
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BookDOI
08 Apr 2011
TL;DR: In this article, the authors present a survey of the latest tools for analysis and design of advanced guidance, navigation and control systems and present new material on underwater vehicles and surface vessels.
Abstract: The technology of hydrodynamic modeling and marine craft motion control systems has progressed greatly in recent years. This timely survey includes the latest tools for analysis and design of advanced guidance, navigation and control systems and presents new material on underwater vehicles and surface vessels. Each section presents numerous case studies and applications, providing a practical understanding of how model-based motion control systems are designed.

1,389 citations

Journal ArticleDOI
TL;DR: The paper describes the development, analysis, and experimental implementation of two trajectory tracking control algorithms: a cascade of proportional-derivative controllers and a nonlinear controller obtained through backstepping that is much more effective at tracking trajectories with highly variable speed and course angle.
Abstract: This paper describes planar motion modeling for an unmanned surface vehicle (USV), including a comparative evaluation of several experimentally identified models over a wide range of speeds and planing conditions. The modeling and identification objective is to determine a model that is sufficiently rich to enable effective model-based control design and trajectory optimization, sufficiently simple to allow parameter identification, and sufficiently general to describe a variety of hullforms and actuator configurations. We focus, however, on a specific platform: a modified rigid hull inflatable boat with automated throttle and steering. Analysis of experimental results for this vessel indicates that Nomoto's first-order steering model provides the best compromise between simplicity and fidelity at higher speeds. At low speeds, it is helpful to include a first-order lag model for sideslip. Accordingly, we adopt a multiple model approach in which the model structure and parameter values are scheduled based on the nominal forward speed. The speed-scheduled planar motion model may be used to generate dynamically feasible trajectories and to develop trajectory tracking control laws. The paper describes the development, analysis, and experimental implementation of two trajectory tracking control algorithms: a cascade of proportional-derivative controllers and a nonlinear controller obtained through backstepping. Experimental results indicate that the backstepping controller is much more effective at tracking trajectories with highly variable speed and course angle. © 2013 Wiley Periodicals, Inc.

144 citations

Journal ArticleDOI
TL;DR: In this article, a two-dimensional channel was used to investigate the influence of micro-bubbles on frictional resistance reduction by micro-bubbles in the presence of a wall.
Abstract: Investigations into frictional resistance reduction by microbubbles were carried out using a two-dimensional channel. The flow velocity and the amount of air injected were varied, and the frictional resistance reduction was measured. The frictional resistance reduction increased with increasing mean void ratio. When the bubble diameter was changed, the influence on frictional resistance reduction was negligible. The influence of bubble distribution near a wall was also investigated. Although it is thought that the influence of microbubbles near a wall is large, further investigations are required.

122 citations

Journal ArticleDOI
TL;DR: A mathematical model including seakeeping and maneuvering characteristics to analyze the roll reduction for a ship traveling with the stabilizer fin in random waves and shows that the present developed self-tuning PID control scheme based on the neural network theory is indeed quite practical and sufficient for the ship roll reduction in the realistic sea.

108 citations

Journal ArticleDOI
TL;DR: In this paper, a ship maneuverability based collision avoidance dynamic support system in close-quarters situation is presented, where the dynamic calculation model of collision avoidance parameter is employed to calculate the dynamic DCPA and TCPA in real-time when ship is maneuvering.

76 citations