• Tribology and Lubricants
• /
• v.27 no.4
• /
• pp.204-208
• /
• 2011

Yaw brakes are used in wind turbines to control the orientation of blades to be perpendicular to the wind. These devices are very important machine elements because they are closely related to the overall efficiency of wind turbines. One unit of yaw brakes is composed of a friction pad and a caliper. In this study, a tangential force between the friction pad and the disk is calculated when the brake is acting in 750 kW wind turbine. Then, stress distribution and the deformation of the caliper are calculated using a finite element analysis. An experimental equipment is also developed to verify the exactness of calculated results. The analytical and experimental results are presented and discussed.

• New & Renewable Energy
• /
• v.3 no.4
• /
• pp.114-122
• /
• 2007

This paper addresses the measurement of structural loads on the Unison U50 wind turbine. The load measurement are carried out to determine the actual loads acting on a wind turbine. This is needed not only the certification process but also improving the technical development for prototype wind turbine. The measurement system is consists of measuring load, operating quantities and meteorological signal. All data that occur during the operating of a WT are stored the data acquisition system automatically. With using the measured data, load spectrum and equivalent load are evaluated according to IEC61400-13 "Measurement of mechanical loads".

• Proceedings of the KIEE Conference
• /
• 2007.11b
• /
• pp.258-260
• /
• 2007

MAS based market simulator has attracted the attentions of people who are interested in using or developing electricity market simulator. MAS based approach makes it possible to model each market participant's strategic behaviors. Traditional market simulators have used optimization formulation to model market operation, which has been used since vertically integrated system. Optimization mainly uses cost minimization or welfare maximization of entire system. Therefore it is somehow difficult to model the independently strategic behaviors of market participants. MAS is one of AI technology based on distributed intelligence which makes it possible to model independently acting entities in competitive market. This paper proposes the method to model strategic participants in electricity market based on MAS.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2007.12a
• /
• pp.29-30
• /
• 2007

This paper deals with effect of wind forces and moment acting on the training ship SAE NUR/. The results of drift angle and counter rudder angle due to wind effect are calculated by using the static equilibrium method especially with nonlinear mathematical expression, and then the critical wind velocity is found out. The given results am be applied directly to T/S SAE NURI in handling under the wind condition and used for merchant ships as a referential tool.

• Journal of KSNVE
• /
• v.7 no.3
• /
• pp.439-447
• /
• 1997

In this study, the dynamic instabilities of a nonlinear elastic system subjected to follower forces are investigated. The two-degree-of-freedom double pendulum model with nonlinear geometry, cubic spring, and linear viscous damping is used for the study. The constant, the initial impact forces acting at the end of the model are considered. The chaotic nature of the system is identified using the standard methods, such as time histories, power density spectrum, and Poincare maps. The responses are chaotic and unpredictable due to the sensitivity to initial conditions. The sensitivities to parameters, such as geometric initial imperfections, magnitude of follower force, direction control constant, and viscous damping, etc., are analysed. Dynamic buckling loads are computed for various parameters, where the loads are changed drastically for the small change of parameters.

• International Journal of Automotive Technology
• /
• v.7 no.5
• /
• pp.547-554
• /
• 2006

This paper is concerned with an optimal control suspension system using the preview information of road input based on a quarter car model. The main purpose of the control is to combine good vibration isolation characteristics with improved attitude control. The optimal control law is derived with the use of calculus of variation, consisting of three parts. The first part is a full state feedback term that includes integral control acting on the suspension deflection to ensure zero steady-state deflection in response to static body forces and ramp road inputs. The second part is a feed-forward term which compensates for the body forces when they can be detected, and the third part depends on previewed road input. The performance of the suspension is evaluated in terms of frequency domain characteristics and time responses to ramp road input and cornering forces. The effects of each part of the suspension controller on the system behavior are examined.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.49 no.1
• /
• pp.6-12
• /
• 2000

This paper presents various processes of dynamic voltage collapse which is initiated by various power system disturbances, and the impacts of dynamic voltage controllers. According to the analysis results, the composition of induction motors with short time constants affects the voltage collapse strongly. Also, it is proved that the addition of fast acting reactive compensation devices, such as SVC, at high reactive loss sensitivity($$\delta$$Q$$_luss/\delta$$P$$_L$$) buses could be one of the best countermeasure to escape the voltage collapse.

• Proceedings of the KIEE Conference
• /
• 2006.10c
• /
• pp.539-541
• /
• 2006

Biped locomotion is a popular research area in robotics due to the high adaptability of a walking robot in an unstructured environment. When attempting to automate the motion planning process for a biped walking robot, one of the main issues is assurance of dynamic stability of motion. This can be categorized into three general groups: body stability, body path stability, and gait stability. A zero moment point (ZMP), a point where the total forces and moments acting on the robot are zero, is usually employed as a basic component for dynamically stable motion. In this rarer, learning based neuro-fuzzy systems have been developed and applied to model ZMP trajectory of a biped walking robot. As a result, we can provide more improved insight into physical walking mechanisms.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.25 no.1
• /
• pp.71-77
• /
• 2002

This study deals with noise occurring in the process of human information transmission. Human process many kinds of information by receiving them from the outside or using their own thought and express the processed information to the outside by acting. In this process, Channel Noise ($C_N$) is defined as the characteristics of noise generating the incomplete result for the external stimulus. To evaluate $C_N$, keyboard-typing experiment has been performed to the 87 subjects. In this experiment, the subject consists of college students who have abundant experience in computer usage. In the experiment, there were some cases that typing order was unconsciously reversed. In this study, we deal with only these cases since these cases can be used as important data to study humans information transmission system.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.229-232
• /
• 1997

In this paper, the case study of reducing rotational errors is done for a grinding spindle with an active magnetic bearing system. The rotational errors acting on the magnetic bearing spindle are due to mass unbalance of rotor, runout, grinding excitation and unmodeled nonlinear dynamics of electromagnets. For the most case, the electrical runout of sensor target is big even in well-finished surface; this runout can cause a rotation error amplified by feedback control system. The adaptive feedforward method based on LMS algorithm is discussed to compensate this kind of runout effects, and investigated its effectiveness by numerical simulation and experimental analysis. The rotor orbit size in both bearings is reduced about to 5 pin due to lX rejection by feedforward control up to 50,000 rpm.