• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.1
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• pp.43-48
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• 2013

In this study, the performance of an impeller according to blade length and pitch angle was studied experimentally by building a variable pitch impeller while changing blade length to review the effect of blade length and pitch angle on a fan's performance. The pitch angle was changed in six steps from $20^{\circ}{\sim}45^{\circ}$ at intervals of $5^{\circ}$ while the blade lengths were changed to 90 mm, 100 mm, 110 mm and 120 mm with an identical airfoil shape while carrying out the experiment. The results are summarized as follows: The air flow per static pressure of axial fans increased linearly with increase of pitch angle, but the high static pressure showed a decrease at a pitch angle of $35^{\circ}$. The shaft power increased proportionally to the pitch angle at all blade lengths; the larger the pitch angle, the larger the measured increase of shaft power. This is because the drag at the fan's front increases with the pitch angle. In the axial fans considered in this research, the flow and increase of static pressure amount increased up to a pitch angle of $30^{\circ}$ but decreased rapidly above $35^{\circ}$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1065-1071
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• 2012

Wind energy is becoming one of the most preferable alternatives to conventional sources of electric power that rely on fossil fuels. For stable electric power generation, constant rotating speed control of a wind turbine is performed through pitch control and stall control of the turbine blades. Recently, variable pitch control has been implemented in modern wind turbines to harvest more energy at variable wind speeds that are even lower than the rated one. Although wind turbine pitch controllers are currently optimized using a step response via the Ziegler-Nichols auto-tuning process, this approach does not satisfy the requirements of variable pitch control. In this study, the variable pitch controller was optimized by a genetic algorithm using a neural network model that was constructed by the Latin Hypercube sampling method to improve the Ziegler-Nichols auto-tuning process. The optimized solution shows that the root mean square error, rise time, and settle time are respectively improved by more than 7.64%, 15.8%, and 15.3% compared with the corresponding initial solutions obtained by the Ziegler-Nichols auto-tuning process.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.366-369
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• 2007

This paper presents the general results of the conceptual design of a 3MW class offshore wind turbine named WinDS 3000 under development. In WinDS 3000, an integrated drive train design, three stage gearbox and permanent magnet generator (PMG) with fully rated converters have been introduced. A pitch regulated variable speed power control with individual pitch control has been adopted to regulate rotor torque while generator reaction torque can be adjusted almost instantaneously by the associated power electronics. Through the introduction of WinDS 3000, it is expected that helpful to understanding of the development status of 3MW offshore wind turbine.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1026-1030
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• 2011

This paper presented here contains development of variable stability system(VSS) control laws for the KIFS (Korean In-Flight Simulator) aircraft to simulate the dynamics of F-16 aircraft. Development of VSS Control law for pitch rate, roll rate, yaw rate simulation for three specified flight conditions using Model Following Technique with rate feedback autopilot for stability provision. The direct lift force controller was also added to the developed VSS control law to simulate the pitch rate and normal g-load simultaneously. The simulation results show high accuracy of F-16 aircraft's pitch, roll, yaw rate and g-load simulation.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.4
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• pp.412-418
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• 2014

This paper describes the development of variable stability system (VSS) control laws for the KFA-i to simulate the dynamics of KFA-m aircraft. The KFA-i is a single engine, Class IV aircraft and was selected as an in-flight simulator (IFS) aircraft, whereas the KFA-m is a simulated aircraft that is based on the F-16 aircraft. A 6-DoF math model of KFA-i aircraft was developed, linearized, and separated into longitudinal and lateral motion for VSS control law synthesis. The KFA-i aircraft has five primary control surfaces: two flaperons, two all movable horizontal tails, and one rudder. Flaperons are used for load control, the horizontal tails are used for pitch and roll rate control, and the rudder is used for yaw rate control. The developed VSS control law can simulate four parameters of the KFA-m aircraft simultaneously, such as pitch, roll, yaw rates, and load. The simulation results show that KFA-i follows the responses of KFA-m with high accuracy.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.8
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• pp.935-944
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• 2015

This study performs the dynamic modeling and the simulation of variable speed wind power system and implements the models of wind speed, wind turbine & PMSG, and MPPT & pitch control as well. The simulation of wind turbine was performed by using the power coefficient and other simulation parameters which were extracted with reference to the commercial 5MW class wind turbine data. As the result of this simulation, MPPT control is confirmed, maintaining the maximum power coefficient as far as the rated speed 12[m/s]. Over 12[m/s] wind speed, this wind power system makes it possible to keep the stable output by controlling the pitch angle.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2268-2277
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• 2017

As constantly increasing wind power penetrates power grid, wind power plants (WPPs) are exerting a direct influence on the traditional power system. Most of WPPs are using variable speed constant frequency (VSCF) wind turbines equipped with doubly fed induction generators (DFIGs) due to their high efficiency over other wind turbine generators (WTGs). Therefore, the analysis of DFIG has attracted considerable attention. Precisely measuring optimum reference speed is basis of utilized maximum wind power in electric power generation. If the measurement of wind speed can be easily taken, the reference of rotation speed can be easily calculated by known system's parameters. However, considering the varying wind speed at different locations of blade, the turbulence and tower shadow also increase the difficulty of its measurement. The aim of this study is to design fuzzy controllers to replace the wind speedometer to track the optimum generator speed based on the errors of generator output power and rotation speed in varying wind speed. Besides, this paper proposes the fuzzy adaptive PID control to replace traditional PID control under rated wind speed in variable-pitch wind turbine, which can detect and analyze important aspects, such as unforeseeable conditions, parameters delay and interference in the control process, and conducts online optimal adjustment of PID parameters to fulfill the requirement of variable pitch control system.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.560-567
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• 1998

The pitch of spot-weld is a important variable in a view of both production cost and strength of car-body. Various renditions for the selection of pitches have been researched and especially in this paper the buckling analysis is carried out for the 2-sheet pannel structures. The optimal pitch is obtained by optimization program and FEM, which can enhance the buckling strength.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.7 s.196
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• pp.75-82
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• 2007

This paper represents a study on the development of the conceptual design for the bicycle transmission by TRIZ. At first the problem of the transmission of commercial bicycles was analyzed. The problem was defined as "the variable sprocket pitch diameter with respect to the tension change of chain". The conceptual solutions were derived by Su-Field Model Analysis, IFR(Ideal Final Result), SLP(Smart Little People), and Contradiction Matrix. The here developed sprocket prototype shows the automatic change of sprocket pitch diameter with the tension change of chain.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.1
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• pp.42-48
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• 2009

A design methodology for control strategy and control structure gives a direct impact on wind turbine's performance and life cycle. A baseline control law which is a variable rotor speed and variable pitch control strategy is introduced, and a mathematic performance model of a wind turbine dynamics is derived. By using a numeric optimization algorithm, the steady state operating conditions of wind turbines are identified. Because aerodynamic interaction of winds with rotor blades is basically nonlinear, a linearization procedure is applied to analyze wind turbine dynamic variations for whole operating conditions. It turns out the wind turbine dynamics vary much depending on its operating condition.