• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1185-1191
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• 2011

The kinematic characteristics of cutting device significantly affects cutting performance in 2-dimensional elliptical vibration cutting(EVC) where the cutting tool cuts workpiece, traversing a micro-scale elliptical trajectory in a trochoidal motion. In this study, kinematical characteristics of EVC device constructed with two parallel stacked piezoelectric actuators were analytically modeled and compared with the experimental results. The EVC device was subjected to step and low-frequency(0.1 Hz) sinusoidal inputs to reveal only its kinematical displacement characteristics. Hysteresis in the motion of the device was observed in the thrust direction and distinctive skew of the major axis of the elliptical trajectory of the cutting tool was also noticed. Discrepancy in the voltage-to-displacement characteristics of the piezoelectric actuators was found to largely contribute to the skew of the major axis of the elliptical trajectory of the cutting tool. Analytical kinematical model predicted the cutting direction displacement within 10 % error in magnitude with no phase error, but in estimating the thrust direction displacement, it showed a $27^{\circ}$ of phase-lag compared with the measured displacement with no magnitude error.

• Journal of Power Electronics
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• v.12 no.1
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• pp.75-82
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• 2012

Elimination of rotor position sensors mechanically coupled with the rotor shaft is attractive to variable speed drives primarily due to increased system reliability and cost reduction. In this regard, search for a simple and robust position sensorless control has been intensified in past few years specifically for low-cost, high-volume applications such as home appliances. This paper describes a new parameter insensitive position sensorless control for switched reluctance motor (SRM) drives satisfying such a need in this market segment. Two consecutive switch-on times of the controllable switch in hysteresis current control are compared to estimate the rotor position and speed. The proposed sensorless control algorithm is very simple to implement since it does not depend on extensive computation or any additional hardware. In addition, the proposed method is robust in that its dynamic performance is least affected by system parameter variations. The proposed approach is demonstrated on a single-controllable-switch-converter-driven SRM with two-phases that lends itself to a system with low cost and compact packaging which comes close to the intended applications. Analysis and simulation results followed by experimental verification are presented to demonstrate the feasibility of the proposed sensorless control method.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.2
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• pp.168-174
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• 2012

This paper describes a novel global on-chip interconnect scheme, in which a one UI-delayed symbol as well as the current symbol is sent for easing the sensing operation at receiver end. With this approach, the voltage swing on the channel for reliable sensing can be reduced, resulting in performance improvement in terms of power consumption, peak current, and delay spread due to PVT variations, as compared to the conventional repeater insertion schemes. Evaluation for on-chip interconnects having various lengths in a 130 nm CMOS process indicated that the proposed on-chip interconnect scheme achieved a power reduction of up to 71.3%. The peak current during data transmission and the delay spread due to PVT variations were also reduced by as much as 52.1% and 65.3%, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.8
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• pp.27-33
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• 2001

The performance of the ordinary Fiber Bragg Grating(FBG) sensor strain measurement system, which uses Fabry-Perot filter for scanning wavelength, has limitation for application because of hysteresis characteristics of PZT element in the filter, slow scan rate of the filter and the high cost of system. We proposed and experimented a multiple FBG sensor system using light emitting diode(LED) as a light source and adapting Code Division Multiplexing(CDM) method to separating out individual sensor signal. Output signals for a applied static and dynamic strain and crosstalk levels between sensor signals were measured. The price of the system is very loss and the response speed is very fast. Crosstalk levels between sensor signals below - 30 dB were demonstrated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.244-247
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• 2002

The performance of the precision micro-positioning 4-dof stage is presented. The compact design utilizes the monolithic mechanism to achieve the translation in the Z axis and rotation in the $\theta$ z, $\theta$ x and $\theta$ y axes with high stiffness and high damping. Hysteresis, nonlinearity, and drift of the piezoelectric effects are improved by incorporating the sensors in a feedback control. Experiments demonstrate that the micro-positioning stage is capable of 2nm resolution over the travel range of 25$\mu\textrm$ m in the Z axis, 0.0l7 $\mu\textrm$ rad resolution over the 170$\mu\textrm$ rad in the $\theta$ z and 0.011 $\mu\textrm$ rad resolution over the $\mu\textrm$ rad in the $\theta$ x and $\theta$ y axes. The cross-axis interferences among the axes are at a noise range. This stage is available for positioning error compensation of the XY stage with large stroke.

• Journal of Power Electronics
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• v.9 no.5
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• pp.781-790
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• 2009

This paper presents an implementation of a direct active and reactive power control for a doubly fed induction generator (DFIG), which is applied to a wind generation system as an alternative to the classical field-oriented control (FOC). The FOC has a complex control structure that consists of a current controller, a power controller and frame transformations. The performance of the FOC depends highly on parameter variations of the rotor and stator resistances and the inductances. The proposed direct power control (DPC) method produces a fast and robust power response without the need of complex structure and algorithms. One drawback, however, is its high power ripple during a steady state. In this paper, active and reactive power controllers and space-vector modulation (SVM) are combined to replace hysteresis controllers used in the original DPC drive, resulting in a fixed switching frequency of the power converter. Simulation results with the FOC and DPC for a 3kW DFIG are given and discussed, and the experimental results of a test involving identical machines are presented to illustrate the feasibility of the proposed control strategy.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.165-173
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• 2013

Core loss has a major effect on heat generation in synchronous motors with surface-mounted permanent magnets (SPMs). It is essential to perform heat transfer analysis considering core loss in SPM because core loss is seriously affected by torque and speed of motors. In the present study, mechanical loss, core loss and coil loss are evaluated by measuring input and output energies under various driving conditions. For a better understanding heat transfer paths in synchronous motors, we developed a lumped thermal system analysis model. Subsequently, heat transfer analysis has been performed based on acquired energy loss, temperature data and thermal resistance with three types of SPM. It is shown that the torque constants decrease by Max. 10% as speed increase. At the rated torque, the core loss is Max. 10.9 times greater than the coil loss and the hysteresis loss of magnets is dominant in total loss.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.40-47
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• 2006

Optical performance of the mirror for satellite camera is highly dependent on the adhesive properties of its support. Therefore, in this paper, the adhesive properties of three kinds of space adhesives are investigated. For this purpose, the lap shear test is performed with Zerodur-to-metal lap shear specimen as well as metal-to-metal one. And it is also investigated whether reliable adhesive strength can be secured after the specific thermal cycle. Finally, the properties of three adhesives are compared with each other.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.986-988
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• 2001

This paper presents a digitally speed sensorless control system for induction motor with direct torque control (DTC). Some drawbacks of the classical DTC are the relatively large torque ripple in a low speed range and notable current pulsation during steady state. They are reflected speed response and increased acoustical noise. In this paper, the DTC quick response are preserved at transient state, while better qualify steady state performance is produced by space vector modulation (SVM). The system are closed loop stator flux and torque observer for wide speed range that inputs are currents and voltages sensing of motor terminal, model reference adaptive control (MRAC) with rotor flux linkages for the speed fuming signal at low speed range, two hysteresis controllers and optimal switching look-up table. Simulation results of the suggest system for the 2.2 [kW] general purposed induction motor are presented and discussed.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.15-17
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• 2006

This paper proposes a compensation method for an air gapped current transformer (CT) in the steady state. An air gapped CT is used in order to reduce a remanent flux in the case of auto-reclosure. It causes larger ratio and angle errors than the closed core CT because the magnetizing inductance of an air-gapped CT is even smaller than the closed-core CT. The core flux is calculated and used to estimate the exciting current in accordance with the hysteresis curve of the air-gapped CT The correct current is obtained by adding the estimated exciting current to the measured secondary current. The performance of the method was investigated for the air gapped CTs with a gap of 0.083mm and 0.249mm for the 120%, 100% and 20% of the rated current. Various test results indicate that the proposed compensation algorithm can improves the accuracy significantly.