• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2270-2273
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• 2003

Fuzzy logic control has been widely implemented in air conditioning and ventilation systems which has uncertainty or high robust system. Since the dynamic behaviors of the systems contain complexity and uncertainty in its parameters , several fuzzy logic controllers had been implemented to control room temperature in the field of air conditioning system. In this paper, the fuzzy logic control has been developed to control room temperature and humidity in the precision air conditioning systems. The nonlinear mathematical model was formulated using energy and continuity equations. MATLAB was used to simulate the fuzzy logic control of the multi-variable air conditioning systems. The simulation results show that fuzzy logic controller can reduce the steady-state errors of the room temperature and relative humidity in multivariable air conditioning systems. The offset are less than 0.5 degree Celsius and 3 percent in relative humidity respectively under random step disturbance in heating load and moisture load respectively

• Applied Microscopy
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• v.45 no.4
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• pp.218-224
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• 2015

A technical overview on the various sample preparation methods for electron backscattered diffraction (EBSD) analysis is carried out. The mechanical polishing with colloidal silica finish, electro-chemical polishing, dual layer coating and ion beam milling are introduced for the common sample preparation methods for EBSD observation and some issues that are frequently neglected by the common EBSD users but should be considered to get a reliable EBSD data are discussed. This overview would be especially helpful to the people who know what EBSD technique is but do not get a reliable EBSD data because of difficulties in sample preparation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.1062-1070
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• 1995

The study deals with controlling the velocity of hydraulic motor with PI controller through the control of displacement pump which has higher efficiency than valve-controlled system. This was done as follows. First, we modified original displacement pump and designed this electrohydraulic puma system. Second, after experimenting static and dynamic characteristics, we identified system parameter of approximated model. Lastly, to control the velocity of hydraulic motor we controlled the angle of the swash plate of displacement pump. Test carried out in the laboratory shows that transient and steady state response could be improved by PI controller reducing power loss.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.218-223
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• 2000

A both mixing process of electro-magnetic stirring and mechanical process technique were used to fabricate particulate metal matrix composites(PMMCs) for variation of particle size. The PMMCs were tested for their tensile test for with and without heat treatment with T6. PMMCs fabrication processing conditions for both electrical and mechanical process are also suggested. In order to thixoforming of PMMCs, fabricated billet are reheated by using the optimal coil designed as a function of length between PMMC billet and coil surface, coil diameter and billet length. The effect of reinforcement distribution on billet temperature variation are investigated with calculated solid fraction theory proposed as a function of matrix alloy and volume fraction of reinforcement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.347-354
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• 2000

This paper presents performance characteristics of a semi-active suspension featuring continuously variable ER (electro-rheological) dampers. These are evaluated through the field test of a passeng er car. Four ER dampers (two for front and two for rear part) are manufactured and their field-dependent damping properties are experimentally investigated. The damping force responses to step input fields are also identified by employing small size of high voltage amplifiers which are made adaptable to the field test. A skyhook controller considering the vertical, pitch and roll motions is formulated and incorporated with a car to be tested. The field test is then undertaken in order to evaluate both comfortability and steering stability showing bump, dive and squat responses.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.85-92
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• 2002

This paper presents the effects of design and operating parameters to meet the static and dynamic performances of the electro-mechanical valve(EMV) actuator which can provide more flexible controllability of valve events compared to conventional variable valve actuation devices. The model of the EMV system was also set up and applied to identify the dynamic behavior of the system. And the effects of external disturbances were also investigated such as cylinder pressure, armature neutral position and current supplying time effects and so on. Experiments were carried out to verify the model using the prototype actuator on test bench, it was found that there is a relatively good agreement between experimental data and modeling results. Also, the actuators meet the general engine speed range (over 6000rpm) and the variable valve event control for various VVT effects.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.3
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• pp.246-259
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• 2011

This study presents a structural health monitoring (SHM) method for bolted connections by using multi-channel wireless impedance sensor nodes and multiple PZT-interfaces. To achieve the objective, the following approaches are implemented. Firstly, a PZT-interface is designed to monitor bolt loosening in bolted connection based on variation of electro-mechanical(EM) impedance signatures. Secondly, a wireless impedance sensor node is designed for autonomous, cost-efficient and multi-channel monitoring. For the sensor platform, Imote2 is selected on the basis of its high operating speed, low power requirement and large storage memory. Finally, the performance of the wireless sensor node and the PZT-interfaces is experimentally evaluated for a bolt-connection model Damage monitoring method using root mean square deviation(RMSD) index of EM impedance signatures is utilized to estimate the strength of the bolted joint.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1988-1991
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• 2005

A micro fluid actuator driven by electromagnetic force at MEMS(Micro Electro Mechanical System) level has been designed. The operation of the actuator was simulated in three steps. First, fluid flow analysis has been performed to determine the actuator load. With the load, dynamic behavior of the actuator structure has been analysed. Finally, fluid-structure interaction analysis has been performed to predict the performance of the actuator. To avoid excessive amount of computation, axisymmetric and plane strain 2-D models were used.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.170-174
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• 2005

A numerical system to extract effective elastic properties of polycrystalline thin-films for MEMS devices is developed. In this system, the statistical model based on lattice system is used for modeling the microstructure evolution simulation and the key kinetics parameters of given micrograph, grain distributions and deposition process can be extracted by inverse method proposed in the system. In this work, effects of kinetics parameters on the extraction of effective elastic properties of polycrystalline thin-films are studied by using statistical method. Effects of the fraction of the potential site($f_p$) among the parameters for deposition process of microstructure on the extraction of effective elastic properties of polycrystalline thin-films are investigated. For this research, polysilicon is applied to this system as the polycrystalline thin-films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.2
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• pp.105-109
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• 2012

In this study, thickness vibration mode piezoelectric devices for AE sensor application were simulated using ATILA FEM program, and then fabricated. Trajectory resonant displacement and electro mechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electro mechanical coupling factor was obtained when the ratio of diameter/thickness($\Phi/T$) was 0.75. The piezoelectric device of $\Phi/T$=0.75 exhibited the optimum values of fr= 183 kHz, displacement= $4.44{\times}10^{-7}[m]$, $k_{33}$= 0.69, which were suitable for the application of AE sensor piezoelectric device.