• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.6
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• pp.438-445
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• 2019

In this paper, we present a new approach to extract the g-sensitivity scale-factor error for a MEMS gyroscope. MEMS gyroscopes, based on the use of both angular momentum and the Coriolis effect, have a g-sensitivity error due to mass unbalance. Generally, the g-sensitivity error is not considered in general use of gyroscopes, but it deserves our attention if we are to develop for tactical class performance and reliability. The g-sensitivity error during vehicle flight increases navigation error; so it must be analyzed and compensated for the use of MEMS IMU for high dynamics vehicle systems. Therefore, we analyzed how to extract the g-sensitivity scale-factor error from the inertial sensor error model. Furthermore we propose a new method to extract the g-sensitivity error using flight motion simulator. We verified our proposed method with experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.10-18
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• 2007

A tested micro axial-type turbine consists of two stages and its mean radius of rotor flow passage is 8.4 mm. This turbine could be applied to a driver of micro power system, and its rotational speed in the unloaded state reaches to 100,000 RPM. The performance of this system is sensitive depending on the blade angles of the rotor and stator because it is operated in a low partial admission rate, so a performance test is conducted through measuring the specific output power and the net specific output torque with various blade angles on the nozzle, stator and rotor. The experimental results show that the net specific output torque is varied by 15% by changing the rotor blade angle, and the optimal incidence angle is about $10.3^{\circ}$.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.3
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• pp.26-37
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• 1998

In this study, the motion control techniques allied to the test ship NARAE are summarized and the results of sea trials are resented. NARAE adopted a hybrid hull form with lower hull and submerged foils. This type of ship has a substantial instability in heave, pitch and roll modes at the foil-borne stage due to little restoring force, so an active control is indispensable to keep the stability. 4-hydraulic actuators with servo valves were installed to drive foils, and several sensors were used to measure the motion of the ship. PID controller was adopted as a motion controller, and for the real-time control, Pentium-class industrial PC was used. Sea trials including take-off, landing, and banked turn maneuvering were carried out for a period of over 3 months and quite satisfactory results were obtained.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.151-151
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• 2023

An accurate prediction of the hydrodynamic maneuvering darivatives is essential to desing a robust control system of a UUV(unmanned underwater vehicle). Typically, these derivatives were estimated by either the towing tank experiment or semi-empirical methods. With the enhancement of high performance computing capacity, a numerical analysis using computational fluid dynamics has reach the level of experiment. Therefore, the aims of the present research are to numerically develop a computational model for the vertical planar motion mechanism of a UUV and to estimate the hydrodynamics loads in 6-DOF. The target structure of the present study was manta type UUV (12meter length). The numerical model was developed in 1/ 6 model scale. Numerical results were compared with the results of the towing tank experiment for validation. In the present study, a commercial RANS-based viscous solver STARCCM+ (ver 17.06) was used.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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• pp.350-360
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• 2018

Analysis of ship's manoeuverability in shallow water is an important task from the perspective of the vessels' navigational safety. Since the number of ships operated in restricted water has increased due to the enlargement of vessels and ships represent different characteristics of the manoeuverability when operated in shallow and deep water, it is significant to evaluate ship manoeuverability at initial design stage. At the initial stage of design, the estimation of manoeuverability is generally performed with hydrodynamic coefficients estimated based on empirical formula. However, the accuracy of estimating hydrodynamic coefficients by the empirical formula in shallow water is poor compared to that in deep water. Therefore, the error in the estimation of manoeuverability increases in shallow water. In this study, CFD is proposed to improve the accuracy of manoeuverability in shallow water at the initial design stage and hydrodynamic coefficients were obtained based on PMM test in shallow water. Furthermore, the ship manoeuverability was estimated both the proposed strategy and the empirical formula. At last, validity of the proposed strategy using CFD for the estimation of manoeuverability was confirmed by comparison with the manoeuverability estimation results from model test.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.200-207
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• 2017

The purpose in having a control surface on ships is to control the motion of the ship. The control surface may be composed entirely of a single movable surface or of a combination of fixed and movable portions. A control surface has one sole function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of this rotation and angle of attack then determine the manoeuvring characteristics of the ship. In this paper, two-dimensional flow characteristics of a flapped rudder and a water-blowing control rudder were accomplished respectively by PIV method in a circulating water channel. Model test has been carried out with different angles of attack of main foil (NACA 0012) and flap's deflection angles to predict the performance of the flapped rudder and the water-blowing control rudder. The 2-frame particle tracking method has been used to obtain the velocity distribution in the flow field. $Re{\fallingdotseq}3.0{\times}10^4$ has been used during the whole experiments and measured results have been compared with each other.

• The KSFM Journal of Fluid Machinery
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• v.9 no.6 s.39
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• pp.54-62
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• 2006

An experiment about performance characteristics is conducted on a double chamber vane-type rotor. Three different rotors, which have 6, 8 and 9 vanes, are applied to the driver and various lift holes at the rear plate are used to increase the effective vane height. The inner diameter of a double chamber cylinder is ${\phi}27mm$, and the length of the cylinder is 65 mm. The maximum offset length between the rotor outer surface and the cylinder inner surface is 4.5 mm. In this study, specific output torques and powers are measured, and also noise and vibration are measured at the real operating situation. The operating torque on the double chamber is increased to 17% compared to the operating torque obtained at the single chamber which has the same size. The experimental results of noise and vibration show that the operating sound and vibration are directly related to the operating power generated by the double chamber rotor.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.4
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• pp.275-284
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• 2001

The for this study, turning circle tests and maneuvering indices were conducted to study and evaluate the maneuverabilities of the fishery training ship M.S. A-RA(G/T : 990tons). The results obtained were summarized as follows : 1. The advances of the starboard and port of the turning circle were measured based on the dumb card test method were 198m, 192m, the size of tactical diameters of them were 194m, 188m, respectively. 2. The advances at the starboard and port of the turning circles were measured according to the DGPS positioning obtained 196m, 194m, the size of tactical diameters of them were 194m, 190m, respectively. 3. The results were compared which came from the sizes of turning circle measured up with the dumb card test method during the trial test and from the size of turning circle measured according to the DGPS positioning. The advance of the turning circle measured at the time of the starboard turning according to the DGPS positioning was 1m longer than that of the trial test. And it was 21m shorter at the time of the port turning. 4. The rudder was steered at $35^{\circ}$ of rudder angle each starboard and port while the ship M.S. A-RA was advancing at full speed of 13 k't. The velocity of the ship was reduced to 7.8 k't at $180^{\circ}$ of turning angle and 6.0 k't at $360^{\circ}$ of turning angle and mean values of turning angular velocity of the port and starboard were $2.4^{\circ}$/sec and $2.3^{\circ}$/sec, respectively. 5. The Z test at each $10^{\circ}$, $20^{\circ}$, and $30^{\circ}$ of rudder angle was carried out to have the maneuvering indices K and T measured. K for the each rudder angle were 1.24, 1.45, and 1.65 while T for the each rudder angle were 0.33, 0.20, and 0.14. That is, K at the Z test at $30^{\circ}$ was greater than at the Z test of $10^{\circ}$ and $20^{\circ}$ while T at the $30^{\circ}$ Z test was less than at the Z test of $10^{\circ}$ and 20.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.1-14
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• 1996

Especially in the case of a full form ship, the stability on course can be considered to become severest among 4 items of criteria in Interim Standards for Ship Maneuverability adopted by IMO in 1993. The purpose of this study is to find some ideas for the improvement of stability on course through changes in rudder area with reference to span distance. In this paper, we established the formula on the relation between the experimental constants relevant to rudder normal force and hydrodynamic derivatives of hull-propeller-rudder system. We carried out various kinds of captive model test relevant to rudder normal force etc., and evaluated hydrodynamic derivatives of hull-propeller-rudder system, and analyzed the stability on course with the parameter of changes in rudder area. Furthermore, we also discussed effects of changes in rudder area on maneuvering performance including stability on course, based on computer simulation. As a result, it is clarified that there is a possibility that stability on course may become bad through an increase of rudder area. The reason for the bad stability on course is that the void space between the upper edge of rudder and the lower part of stern overhang decreases. This space change exerts a great influence on straightening coefficient of incoming flow to rudder in maneuvering motion, which has close relation to stability on course.

• Journal of Navigation and Port Research
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• v.45 no.1
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• pp.16-25
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• 2021

Hydrodynamic coefficients should be accurately estimated to predict the maneuverability of underwater vehicles. Various captive model tests have been performed as part of estimation methods for these coefficients. Estimating hydrodynamic coefficients related to roll motion is important because underwater vehicles are sensitive to changes of roll moment. In this research, a pure roll motion equipment was newly designed to simply estimate hydrodynamic coefficients with respect to roll motion. Roll motion was implemented through a brief mechanical mechanism. The principle of operation, application process, and system identification of the equipment are described. An analysis method of the pure roll test is also suggested. Repeated tests of the newly equipment were carried out to check its reproducibility.