• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.36.2-36.2
• /
• 2011

In variable-speed variable-pitch wind turbines, the conventional approach for controlling power-production operation relies on a generator-torque controller and a rotor-collective blade-pitch controller. Both controllers use the generator speed measurement as the sole feedback input. In order to mitigate unwanted excitation of the control system, many filters are adopted. In this study, the characteristics of some filters for signal processing are investigated based on frequency response function. They include low-pass filters, band-pass filters, and notch filters. Especially, this study focuses on design parameters of their filters.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.1
• /
• pp.135-147
• /
• 2000

Section design of vehicle structure has been developed by two methods. One is the section property method which uses section property as a design variable. This method shows the tendency of an optimum section approximately. The other method is the section shape method which utilizes geometric parameter of section as a design variable. Practical solutions are obtained by this method. However, it is very expensive for large-scale problems due to the large number of geometric parameters. These two methods are compared through several sample problems. The finite element method is used for the structural and sensitivity analyses. The results are analyzed based on the number of function evaluations, the quality of cost function, the complexity of programing, and etc. The applications of both methods are also discussed.

• International Journal of Aeronautical and Space Sciences
• /
• v.7 no.1
• /
• pp.65-72
• /
• 2006

A variable structure controller with an optimized sliding surface is proposed for slew maneuver of a rigid spacecraft. Rodrigues parameters are chosen to represent the spacecraft attitude. The quadratic type of performance index is used to design the sling surface. For optimization of the sliding surface, a Hamilton- Jacobi-Bellman equation is formulated and it is solved through the numerical algorithm using Galerkin approximation. The solution denotes a nonlinear sliding surface, on which the trajectory of the system satisfies the optimality condition approximately. Simulation result demonstrates that the proposed controller is effectively applied to the slew maneuver of a rigid spacecraft.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.3 no.3
• /
• pp.309-330
• /
• 2009

In this paper, we introduce the architecture of Genetic Algorithm(GA) based Feed-forward Polynomial Neural Networks(PNNs) and discuss a comprehensive design methodology. A conventional PNN consists of Polynomial Neurons, or nodes, located in several layers through a network growth process. In order to generate structurally optimized PNNs, a GA-based design procedure for each layer of the PNN leads to the selection of preferred nodes(PNs) with optimal parameters available within the PNN. To evaluate the performance of the GA-based PNN, experiments are done on a model by applying Medical Imaging System(MIS) data to a multi-variable software process. A comparative analysis shows that the proposed GA-based PNN is modeled with higher accuracy and more superb predictive capability than previously presented intelligent models.

• Proceedings of the KIEE Conference
• /
• 1987.11a
• /
• pp.552-554
• /
• 1987

A design principles of discontinuous control are studied and then are applied to position control of D. C. sevo drive fed by a four-quadrant chopper. Variable structure control with sliding mode gives fast dynamic response with no overshoot. And the resulting system bas good robust properties independent of the wide variations of electrical, mechanical parameters and external disturbances without any system identification. But the high frequency chatter component of control input in the sliding mode is undesirarable. A continuous control law that is a approximation to discontinuous control law is used for design.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.357-362
• /
• 2008

The present study has been conducted variable refrigerant flow system applied building. Multi air-conditioning system has some benefits : easier building management and maintenance and energy saving. Recently, the system heat pump has been employed in medium-sized and tall buildings. However, the performance data and design method for system heat pump are limited in literature due to complicated system parameters and operating conditions. In the present study, case study of a system heat pump applied various building. The aim of this paper is to application multi air-conditioners and to inform the benefits of multi air-conditioners.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2001.04a
• /
• pp.146-153
• /
• 2001

In this paper, the governing differential equations for the non-linear behavior of shear deformable variable-arc-length beams subjected to an end moment are derived. The beam model is based on the Bernoulli-Euler beam theory. The Runge-Kutta and Regula-Falsi methods, respectively, are used to integrate the governing differential equations and to compute the beam's rotation at the left end of the beams. Numerical results are compared with existing closed-form and numerical solutions by other methods for cases in which they are available. The characteristic values of deflection curves for various load parameters are calculated and discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.9
• /
• pp.810-817
• /
• 2001

Performance of a water-to-water multi-type heat pump system using R22 which has tow indoor units has been investigated experimentally. The refrigerant flow rate of each indoor unit was regulated by an electronic expansion valve and the total refrigerant flow rate of the system was controlled by a variable speed compressor. In the system, evaporator outlet pressure of refrigerant and outlet temperatures of secondary fluid from indoor units were selected as control variables. Experiments were executed for both cooling and heating modes using PID control method with fuzzy logic, and results of the test are compared with a classical PID method. In the case of PID control with fuzzy logic, the fuzzy control rules corrects PID parameters each time. Results show that PID control with fuzzy logic has the merits of quick response and reduced overshoot.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.2
• /
• pp.105-110
• /
• 2008

This paper presents a control method to maintain stable mold level for unsteady bulging in high speed casting. The stabilizing mold level is an important factor to get high quality products. But, for various reasons, there are several disturbance factors which make mold level unstable. Bulging is one of disturbance factors and considered for the current stage of study. We design a disturbance observer to attenuate the effect of bulging which is periodic mold level disturbance. Since the period of bulging varies with the casting speed, the parameters of disturbance observer are changed by the casting speed. Simulation is illustrated to demonstrate stable performance of the proposed method in comparison with a previous method in a variable operating frequency.

• Culinary science and hospitality research
• /
• v.12 no.4 s.31
• /
• pp.18-32
• /
• 2006

This research is to figure out how interpersonal relationships among the foodservice industry affected customer satisfaction and retention. Marketing strategy methods could be indicated to bear fruit in the food-industry based on this research. First, the properties of each factor related interpersonal relationship of foodservice industry, customer satisfaction and retention were obtained from previous studies. Second, interpersonal relationship was applied as an independent variable, retention between customers and the foodservice industry as a consequent variable and customer satisfaction as a parameters. The result reached through convergent validity came to satisfy all variables. Third, it was strongly maintained that the higher interpersonal relationship was, the more satisfied customers were and that the more satisfied customers were, the stronger retention was. It was shown that customers would repurchase and had strong loyalty to a certain enterprise if its services satisfied them and met their expectations.