• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1231-1236
• /
• 2007

This study presents the static and dynamic actuating performances of a bending piezoelectric actuator with a thin sandwiched PZT plate under a static load. The stored elastic energy within the actuators which occurs during a curing process is obtained through a flexural bending test. An actuating performance is evaluated in terms of an actuating displacement at the simply supported condition. The results reveal that an actuator that consists of a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at the alternating current voltage, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling their performances.

• 한국태양에너지학회 논문집
• /
• 제21권2호
• /
• pp.69-78
• /
• 2001

This paper introduces the physical phenomena involved in Direct Contact Heat Exchangers (DCHXs) and also investigates the possibility of applying of EIT(Electrical Impedance Tomography) technique for capturing the images of dispersed phases as they stream through a stagnant body of water. A number of cases are studied where two dimensional cross-sectional static images are given for fictitious and actual masses present in a column of water(saline solution). In most direct contact liquid-liquid heat exchangers, oil or hydrocarbon with a density different(lighter or heavier) from water is normally used as dispersed working fluid. The main difficulty that arises with this arrangement lies in the elucidation of complicated flow field where the dispersed phase fluid tends to change its shape and size constantly during its journey through the other phase(water). This paper presents a number of results with different types of dispersed phases that are immiscible with water. The EIT technique has been employed in this context to test its applicability in capturing the dynamic images of dispersed phases. It shows static images of dispersed phases where dynamic images could be obtained by simply extending the algorithms and strategies employed in the present analysis.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제48권1호
• /
• pp.23-28
• /
• 1999

Electrical breakdown characteristics of liquid nitrogen($LN_2$) used as both coolant and insulator for high $T_c$ superconductor system are very important. This paper presents dynamic breakdown characteristics fo $LN_2$ by quench phenomena of thermal bubble under high electric field. Experimental results revealed dynamic breakdown voltage fell down drastically compared with the static breakdown voltage without the quench. Because of increasing heat power, bubble size becomes big and breakdown voltage decreases. The breakdown voltage mechanism of $LN_2$ depends on thermal bubble effect. In the Electrode arrangement, electrical breakdown voltage of horizontal arrangement appears lower than that of vertical arrangement. Also, we observed the behavior of thermal bubbles in $LN_2$ which were generated after quench using camera.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2003년도 ICCAS
• /
• pp.1146-1151
• /
• 2003

Pneumatic servo valve is an electro-mechanical device which change electric signals to a proper pneumatic signals, that is, flowrate and pressure. In this study, a pneumatic servo valve was designed and each simulation was conducted on any variation in the flowrate depending upon the magnetic force of the linear force motor and the displacement of the spool. And permanent magnet was used as a material for the plunger of the servo valve. Thereby, a low electrical power consumption type coil was desinged. And a modeling for the coil design was conducted by using the magnetic circuit. also, the feasibility of the modeling was verified by using a commercial magnetic field analysis program. The designed and fabrication of the spool and sleeve, position sensor, servo controller and the dynamic characteristic verified by the experiment.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.448-452
• /
• 2001

This paper describes the nonlinear sensorless control of induction motor by using feedback linearization and current error; the feedback linearization technique and the current error are applied for independent between rotor flux and electric torque and for speed estimation. The dynamic characteristics of the proposed nonlinear control algorithm involving field weakening area are verified by simulation and experiment.

• Journal of Mechanical Science and Technology
• /
• 제18권9호
• /
• pp.1500-1511
• /
• 2004

In this paper, the anti-plane transient response of a central crack normal to the interface between a piezoelectric ceramics and two same elastic materials is considered. The assumed crack surfaces are permeable. By virtue of integral transform methods, the electro elastic mixed boundary problems are formulated as two set of dual integral equations, which, in turn, are reduced to a Fredholm integral equation of the second kind in the Laplace transform domain. Time domain solutions are obtained by inverting Laplace domain solutions using a numerical scheme. Numerical values on the quasi-static stress intensity factor and the dynamic energy release rate are presented to show the dependences upon the geometry, material combination, electromechanical coupling coefficient and electric field.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1993년도 추계학술대회 논문집
• /
• pp.402-405
• /
• 1993

This paper presents design.dynamic modeling and control issues of a novel type of an ER valve-cylinder system incorporating with an electro-rheological(ER) fluid. The yield stress of the ER fluid to be employed to the proposed system is evaluated as a function of applied electric fields. The design and manufacturing process of the ER valve which features fast system response and simple mechanism are undertaken on the basis of model parameters. The governing equation for the hydraulic and pneumatic model is constructed by incorporation with the field-dependent Bingham behavior of the ER fluid. An effective neuro controller is proposed to realize an accurate position control.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 제40회 하계학술대회
• /
• pp.609_610
• /
• 2009

This paper deals with experimental verifications and the electromagnetic characteristics analysis of multi-pole permanent magnet (PM) generator for small-scaled wind power system. Field distribution due to PMs and winding current, cogging torque considering skew effect are analyzed. In addition, using the equivalent circuit method and dynamic d-q method, generating performance analysis is performed. Analysis results are validated by comparison with nonlinear finite element analyses and experimental results.

• 전기학회논문지
• /
• 제56권4호
• /
• pp.683-692
• /
• 2007

An inverter driven induction motor has more superior dynamic characteristic than sine wave driven induction motor. But it has a problem with shaft voltage and bearing current in drive-motor system. This paper presents the analysis of bearing current in inverter-fed induction motor. The proposed method is based on using numerical method (FEM) to derive parasitic parameters in motor. Using the electric field analysis with FEM, the stored energy in dielectric materials of the motor can be calculated and the parasitic capacitances are obtained. Then we compared the proposed method with a conventional method in variable frequency and load conditions. From the comparision of simulation and experiment result, we confirmed that the proposed method is valid.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.669-671
• /
• 2001

This paper describes the operating characteristic analysis of PM-type magnetic circuit breaker for electromagnetic field, electric circuit and mechanical motion problems. Transient calculations are based upon the magnetic equivalent circuit analysis including non-linearity of materials and using iteration routines. The analysis results of this magnetic equivalent circuit are compared with those of FEM.