• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.454-461
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• 2019

In autonomous interventions using an underwater vehicle with a manipulator, grasping based on target detection and recognition is one of the core technologies. To complete an autonomous grasping task, the vehicle body approaches the target closely and then holds it through operating the end-effector of the manipulator, while the vehicle maintains its position and attitude without unstable motion. For vehicle motion control, it is very important to identify the hydrodynamic parameters of the underwater vehicle, including the propulsion force. This study examined the propulsion characteristics of the autonomous intervention ROV developed by KRISO, because there is a difference between the real exerted force and the expected force. First, the mapping between the input signal and thrusting force for each underwater thruster was obtained through a water tank experiment. Next, the real propulsion forces and moments of the ROV exerted by thrusting forces were directly measured using an F/T (force/torque) sensor attached to the ROV. Finally, the differences between the measured and expected values were confirmed.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.974-979
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• 1990

The system discussed in this paper is an integrated stand-alone system with the full functional capabilities required of a telerobot system. It is complete with a force-reflecting 6-DOF hand controller, driving a PUMA 560 or 762 robot, with an integrated force-torque sensing wrist sensor and servo-driven parallel jaw gripper. A mix of custom and standard electronics, distributed computers and microprocessors, with embedded and downloadable software, have been integrated into the system, giving rise to a powerful and flexible teleautonomous control system.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.106-109
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• 2013

It is desirable and advantageous to feed parallel propulsion with induction motors by a single voltage source inverter. However, effects of deviation of the wheel diameters on motor current, rotor speed and torque should be also considered for parallel operation. In order to understand the behavior and characteristics, a simple simulation model is developed by using a commercial Matlab Simulink. From the results, it is clear to manage the diameter deviation of the wheels which are connected to traction motors.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1166-1176
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• 2011

The prospect in opening the arctic trade transportation route on a year-round basis offers vast opportunity of exploring untapped resources and shortened navigational routes. In addition, the environment's remoteness and lack of technical experiences remains a big challenge for the maritime industry. With this, engine designers and makers are continually investigating, specifically optimizing propulsion shafting system design, to meet the environmental and technical challenges of the region. The International Association of Classification Society, specifically machinery requirements for polar class ships(IACS UR13), embodies the propulsion shafting design requirements for ice class vessels. However, the necessity to upgrade the various features of the unified rules in meeting current polar requirements is acknowledged by IACS and other classification societies. For the polar class propulsion shafting system, it is perceived that the main source of excitation will be the propeller - ice load interaction. The milling - and the impact load, in addition to the load cases interpreted by IACS, contribute greatly to the overall characteristic of the system and due considerations are given during the propulsion design stage. This paper will expound on the excitation load estimation factors affecting the dynamic response of the different propulsion shafting system design. It is anticipated that detailed understanding of these factors will have a significant role during propulsion shafting design in the future.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.121-126
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• 2013

Cycloconverter used as a power conversion device in the speed and torque control system of AC machines has the advantage of a simple control and a large torque at low speed. In addition, because a rectifier, a DC link, and an inverter are not installed, this system is simple and suitable for large power system. If a power conversion device, which is currently used as a propulsion motor of large vessel, is changed into cycloconverter, the system is simplified and then the installation costs can be significantly reduced. However, conventional cycloconverter has the increased harmonics because the power loss is large and the waveform of output voltage is distorted, due to the high-speed switching of power semiconductor devices. In order to improve these shortcomings, this paper describes a phase shifting filter which is composed of two inputs with different phases in the primary side and one output in the secondary one. As the voltage waveforms with two different phases are added and transformed into the secondary side, these outputs are close to sinusoidal waves. Thereby the voltage waveforms, which are applied to the propulsion motors, are improved and total harmonic distortions (THDs) are significantly reduced.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.1
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• pp.18-25
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• 2017

This study deals with numerically comparing performance according to rudder shape called 'Twisted rudder and Wavy twisted rudder'. In comparison with conventional rudder, rudder with wavy shape has showed a better performance at high angles of attack($30^{\circ}{\sim}40^{\circ}$) due to delaying stall. But most of study concerned with wavy shape had been performed in uniform flow condition. In order to identify the characteristics behind a rotating propeller, the present study numerically carries out an analysis of resistance and self-propulsion for KCS with twisted rudder and wavy twisted rudder. The turbulence closure model, Realizable $k-{\epsilon}$, is employed to simulate three-dimensional unsteady incompressible viscous turbulent and separation flow around the rudder. The simulation of self-propulsion analysis is performed in two step, because of finding optimization case of wavy shape. The first step presents there are little difference between twisted rudder and case of H_0.65 wavy twisted rudder in delivered power. So two kind of rudders are employed from first step to compare lift-to-drag ratio and torque at high angles of attack. Consequently, the wavy twisted rudder is presented as a possible way of delaying stall, allowing a rudder to have a better performance containing superior lift-to-drag ratio and torque than twisted rudder at high angles of attack. Also, as we indicate the flow visualization, check the quantity of separation flow around the rudder.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.123-126
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• 2003

The uncertainties generated by measurement parameters are propagated to the uncertainty of total-to-total efficiency on an experiment. The effect of uncertainties’ propagation are analyzed through a turbine performance test. A tested 3-D axial type turbine has a 0.373 degree of reaction at the mean radius and the performance test is conducted at the low pressure and cold temperature status. The uncertainty of turbine inlet and exit total pressure shows the strong propagation effect to the uncertainty of total-to-total efficiency. This means that a high precision pressure measuring system is required to reduce the uncertainty propagated by the pressure. In the uncertainty portion of each measurement parameters to the uncertainty of total-to-total efficiency, the uncertainty by torque is the highest and the uncertainty by RPM is the lowest. In case of the total pressure, the effect of the uncertainty by torque is increased with the increasing RPM. The uncertainty of total pressure at the turbine exit shows more influence to the results than that at the turbine.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.315-318
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• 2007

A dynamic simulation of a turbo-shaft engine was performed for analysis of transient-state and engine-starting characteristics using the MATLAB/SIMULINKTM. The turbo-shaft engine was modelled based on thermodynamic and rotor dynamic relations. The analysis of engine starting characteristics was performed by monitoring the rate of the pressure, temperature and mechanical torque changes along the engine stations by the torque input generated from the accessary power unit and transmitted to the power turbine. The simulation of the transient-state characteristics of the engine was performed under fuel flow rate increase from the steady-state condition. For the future study, engine control unit will be added to the basic turbo-shaft engine model to enhance capability of engine performance simulation.

• International Journal of Automotive Technology
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• v.4 no.2
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• pp.87-94
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• 2003

Recent advancements of permanent magnet (PM) materials and solid-state devices have contributed to a substantial performance improvement of permanent magnet machines. Owing to the rare-earth PMs, these motors have higher efficiency, power factor, output power per mass and volume, and better dynamic performance than induction motors without sacrificing reliability. Not surprisingly, they are continuously receiving serious considerations for a variety of automotive and propulsion applications. An electric vehicle (EV) requires a high-effficient propulsion system having a wide operating range and a capability of generating a high peak torque for short durations. The improvement of torque-speed performance for these systems is consequently very important, and researches in various aspects are therefore being actively pursued. A great emphasis has been placed on the efficiency and optimal utilization of PM machines. This requires attention to many aspects related to the machine design and overall performance. In this respect, the prediction of iron losses is particularly indispensable and challenging, especially for drives with a deep field-weakening range. The objective of this paper is to present iron loss estimations of a PM motor over a wide speed range. As aforementioned, in EV applications core losses can be significant during high-speed operation and it is imperative to evaluate these losses accurately and take them into consideration during the motor design stage. In this investigation, the losses are predicted by using an analytical model and a 2D time-stepped finite element method (FEM). The results from different analytical approaches are compared with the FEM computations. The validity of each model is then evaluated by these comparisons.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.241-248
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• 2013

In this study, bearings were developed for a high-power propulsion motor operating in inclined operation conditions through a simulation and similitude-experimental methods using commercial rotating machinery dynamics analysis software. The developed journal bearing is electrically insulated and has low thermal conductivity because each part is connected with 2-4 -mm-thick epoxy plates. To realize an appropriate oil thickness, an oil lift system is adopted, and a half separated structure is applied to ensure the feasibility of maintaining very heavy components. This study discusses some of the key design aspects of sleeve bearing design for high-torque and low-speed propulsion motor applications. Furthermore, the conditions of variable slope tests are examined to prevent oil leakage from the bearing lip seal on the test rig.