Auxiliary Thruster Research Articles

2016S-GS2-15 補助推力装置付き自走模型船を使った停止試験の方法

2016S-GS2-15 補助推力装置付き自走模型船を使った停止試験の方法

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.

Estimation of full-scale ship manoeuvring motions from free-running model test with consideration of the operational limit of an engine

Rudder effectiveness and speed correction (RSC), previously proposed by the authors, is a free-running model test method for making the manoeuvring motions of a model ship using an auxiliary thruster similar to those of a full-scale ship. In this paper, the authors propose a method for estimating full-scale ship manoeuvring motions with consideration of the operational limit of an engine (OLE), the so-called torque limit, by means of a free-running model test involving application of RSC. In this method, the control variables in RSC, namely, the auxiliary thrust and model-scale propeller rotational speed, are determined considering the change in rudder effectiveness and ship speed response caused by continuous operation at the torque limit in full scale. Numerical simulations of manoeuvring motions using the modular mathematical model in model scale with the proposed method were carried out to investigate the similarity to the corresponding full-scale ship operation at the OLE. Moreover, the authors applied the proposed method to tank tests that consist of turning manoeuvres in calm water and course-keeping manoeuvres in regular waves. The simulation results and the tank test data confirm that the proposed method can explain the effect of OLE on the variation in full-scale ship manoeuvring motions.

High Accuracy Positioning using Jet Thrusters for Quadcopter

A quadcopter is equipped with four additional jet thrusters on its horizontal plane and vertical to each other in order to improve the maneuverability and positioning accuracy of quadcopter. A dynamic model of the quadcopter with jet thrusters is derived and two controllers are implemented in simulation, one is a dual loop state feedback controller for pose control and another is an auxiliary jet thruster controller for accurate positioning. Step response simulations showed that the jet thruster can control the quadcopter with less overshoot compared to the conventional one. Over 10s loiter simulation with disturbance, the quadcopter with jet thruster decrease 85% of RMS error of horizontal disturbance compared to a conventional quadcopter with only a dual loop state feedback controller. The jet thruster controller shows the possibility for further accurate in the field of quadcopter positioning.

Model Ship Control and Estimation of Full-scale Propeller Torque in Wind and Waves

This paper presents free-running model ship test data estimating full-scale propeller torque fluctuating in wind and waves. The model ship control using the auxiliary thruster ensures the similarity of model ship motion to full scale that leads the similar propeller situation The wind load simulator controls six duct fans on the model ship for simulating the wind loads. The estimation algorithm converts the measured model propeller torque to full scale assuming no scale effect on the wave component in the effective inflow velocity to propeller. The analysis reveals the differences of the fluctuating propeller torque between model and full-scale ships.

Rudder effectiveness and speed correction in practice at tank test

The rudder effectiveness and speed correction (RSC) is a control method to ensure the similarity of manoeuvring motion of a free-running model ship to full-scale. RSC tells how to control a model propeller rate of revolution and auxiliary thrust depending on a model ship speed. The rudder effectiveness correction (REC) is a simplified method of RSC, controlling only the auxiliary thrust. This paper presents tank test data that show a clear difference between RSC and REC and confirm how well RSC works in practice. The tank test employed a duct fan type auxiliary thruster for RSC, REC, and the skin friction correction (SFC) for comparison. The ordinary free-running model ship not using the auxiliary thruster or with no correction (NC) are also in the test program. Comparisons are made in turning and zigzag manoeuvres in calm water, and course keeping manoeuvres in regular waves. Numerical simulations verify that RSC compensates for the scale effect with higher precision than REC, and also well explain the difference of tank test data characteristics among RSC, REC, SFC and NC.

Estimation of stopping ability of full-scale ship using free-running model

The authors discuss how to estimate full-scale stopping ability of ships using free-running model test equipped with an auxiliary thruster. Theoretical analysis based on a modular mathematical model clarified the similarity of three-degree-of-freedom stopping manoeuvre cannot be ensured by the use of the auxiliary thruster. The authors, however, propose J and speed correction, JSC, ensuring the equality of propeller advance ratio J and the similarity to full-scale of speed response of free-running model ship during stopping manoeuvre. JSC is a control method of free-running model ship equipped with an auxiliary thruster for estimating stopping ability of full-scale ship from the viewpoint of safety. Numerical simulation confirmed JSC gives safe side estimates of stopping ability in terms of track reach and stopping time with acceptable margin, which proved the advantage of JSC comparing with possible other control methods. Tank test data demonstrate how JSC works well.

Estimation of full-scale propeller torque and thrust using free-running model ship in waves

The authors propose a method to estimate full-scale propeller torque and thrust consisting of low-frequency and high-frequency components in waves by free-running model ship test. The duct fan auxiliary thruster (DFAT) (Tsukada et al., 2013, 2014) and the rudder-effectiveness and speed correction (RSC) (Ueno and Tsukada, 2015; Suzuki et al., 2014, 2015) ensure similar model ship motion to full-scale in wind and waves, where RSC controls the model ship propeller rate of revolution and the auxiliary thrust depending on instantaneous model ship speed. Analyzing wave component in the effective inflow velocity to propeller, the method estimates full-scale fluctuating propeller torque and thrust in waves. Trial application of the method exemplifies the property of full-scale fluctuating propeller torque and thrust comparing with those of a model ship.This method also makes it possible to incorporate into free-running model ship tests any engine model simulating interaction between propeller torque and engine torque.

Rudder effectiveness and speed correction for scale model ship testing

The authors once proposed a method, rudder effectiveness correction, to realize full-scale equivalent maneuvering motion using scale models with the auxiliary thruster developed by them. The method presumed a free-running model test with a constant propeller rate of revolution and approximated a constant value of rudder effective correction factor defined in a steady straight running condition. In this report the authors propose a detailed method ensuring more precisely the similarity of maneuvering motion than the former one. The detailed method takes into account the similarities both of the rudder effectiveness and speed response during maneuvering motion even in external forces. The time-varying control both of the propeller rate of revolution and the rudder effectiveness correction factor based on the new method enables scale model ships to realize the similar maneuvering motion to full-scale ships more accurately. Numerical simulations using the modular mathematical model of maneuvering motion clarifies how well the detailed method raises the precision of full-scale equivalent maneuvering motion in free-running model tests comparing with the former method.

実船の波浪中船速低下を直接計測する水槽試験法の開発

An experimental methodology of tank test, which enables the authors to directly obtain speed of actual ship under waves just by experimental result of model test under corresponding same wave condition, is newly developed. One of features of the methodology are controlling propeller rotational speed, managed by a self-propulsion motor set on a model ship, as power plant system of actual ship rotates its shaft speed against fluctuations of load torque. The authors call the intelligent motor system as “Marine Diesel Engine Simulator.” The other feature is, under using the MDES and the Auxiliary Thruster System, making total external forces acting on model ship, similar to those of actual ship under corresponding wave conditions. In this study, three fundamental components of the developed methodology are introduced, mainly focusing on similarity laws between model and actual ship. Thus, experimental results by the methodology are discussed by comparing with the conventional experimental methodology and numerical predictions. Finally, significances of the developed methodology are referred.

Rudder effectiveness correction for scale model ship testing

The authors propose an idea of rudder effectiveness correction for free-running manoeuvring tests using scale models. The idea aims to realize the full-scale-equivalent manoeuvring motion with scale models using the auxiliary thruster that the authors developed. The auxiliary thruster can generate time varying forward force needed for the rudder effectiveness correction. The auxiliary thrust is represented by the force required for the skin friction correction multiplied by the newly defined rudder effectiveness correction factor. The propulsive performance of the model and full-scale ships in steady straight running determines a value of the factor. Theoretical calculations using the modular mathematical model applied to a container ship and a tanker clarify characteristics of the factor. The tank tests and numerical simulations confirm the feasibility of the idea.

自由航走模型試験のための補助推力装置の開発

The free-running model ship test is one of effective measures to estimate ship performance and response in various situations. However, since Reynolds numbers are quite different between model and full-scale ships, phenomena of model ship especially those concerning propeller load are not necessarily similar to those of full-scale. The authors developed an auxiliary thruster to assist a free-running model ships’ propeller. The auxiliary thruster consists of a duct fan, a signal amplifier, a load cell, and a PC. The PC can control the longitudinal force of the duct fan arbitrarily using feed-back data of the force measured by the load cell and instantaneous model ship speed. A prototype confirms through verification test basic capabilities and adequacy of the authors' design of the auxiliary thruster.

Fuzzy side force control for missile against hypersonic target

An integrated fuzzy-logic-based missile side force control mechanism is proposed for the interception of ballistic targets in three-dimensional space. Stringent scenarios when the missile intercepts the ballistic target at higher attitudes are considered. Conventional guidance systems with the aerodynamically controlled mechanism alone are usually incapable of engaging a high-speed target at low-air-density layers. To overcome the difficulty because of insufficient manoeuvrability, a fuzzy side force control scheme configured with two additional auxiliary thrusters is proposed to generate extra transverse acceleration and thereby to reinforce the engagement performance. A simulation study proves the effectiveness of the proposed approach.

Advanced Fuzzy Side Force Control for Missile Against Hypersonic Target

An integrated fuzzy-logic-based missile side force control mechanism is proposed for interception of ballistic targets in the three-dimensional space. We consider the stringent scenarios when the missile intercepts the ballistic target at higher attitudes. The conventional guidance system with only aerodynamically control mechanism is usually not enough to encounter the high speed target at lower air density layers. To overcome the difficulty due to insufficient maneuverability of aerodynamic control, a fuzzy side force control mechanism configured with two additional auxiliary thrusters is proposed to offer extra transverse acceleration to increase the maneuverability.

DOUBLE HULL OIL TANKERS—HOW EFFECTIVE ARE THEY?

ABSTRACT The groundings of the Exxon Valdez on Bligh Reef in Prince William Sound, spilling more than 10 million gallons of Alaska North Slope crude, and the American Trader off Huntington Beach, spilling almost 400,000 gallons of Alaska North Slope crude, suggest that the construction of oil tankers be re-examined with respect to a design which could reduce both the number and magnitude of oil spills. This paper discusses state-of-the-art tanker technology with respect to spill prevention, effectiveness, and cost. The design features include double hulls, centralized bunker tankers, vacuum-retaining valves, cargo control systems, auxiliary thrusters, electronic charting, and the retransmission of the ship's position. Double hulls provide the highest probability of surviving damage, either from a collision or grounding, with no loss of cargo. Use of double hulls can reduce oil spill incidence by 90 percent in grounding situations and by 75 percent in collisions. The oil spill from the American Trader could have been completely avoided by double hull construction. The arrangement provides spaces below the cargo tanks and on the vessel's sides solely for the carriage of ballast water when the tanker is in ballast condition. These tanks are empty when the tanker is loaded and then also act as the first line of defense in the event of structural damage to the cargo tanks. Tanker design is integrated with port safety measures, including vessel monitoring systems, in this total spill prevention analysis. All aspects of the tanker transportation system are considered.