• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.563-565
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• 2009

We introduce the new modification approaches of photocrosslinkable poly (4-vinylphenol) (PVP) for low hysteresis organic thin film transistors (OTFTs). The dielectric layers were composed of different PVP resin, low molecular melamine, and halogen free photo-initiator. The low hysteresis OTFT from one of the organic gate dielectrics has been realized. The electrical performance of low hysteresis OTFT with photocrosslinkable PVP exhibited a field-effect mobility of 0.2 cm2/Vs, a threshold voltage of - 0.04V, hysteresis of 0.4V.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3A
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• pp.217-224
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• 2010

In this paper, we propose a hard handover algorithm for a base station's self-optimization, one of the automatic operational technologies for the 3GPP LTE systems. The proposed algorithm simultaneously considers a mixed target sell selection method for optimal selection and a multiple parameter based active hysteresis method with the received signal strength from adjacent cells and the cell load information of the candidate target cells from information exchanges between eNBs through X2 interface. The active hysteresis method chooses optimal handover hysteresis value considering the costs of the various environmental parameters effect to handover performance. The algorithm works on the optimal target cell and the hysteresis value selections for a base station's automatic operational optimization of the LTE system with the gathered informaton effects to the handover performance. The simulation results show distinguished handover performances in terms of the most important performance indexes of handover, handover failure rate and load balancing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.505-507
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• 2004

This paper attempts to compensate the nonlinearity between the input voltage and the output displacement of the piezoelectric stack in dynamic actuation by the following two ways. Firstly, the charge steering by circuit configuration reduces the hysteresis of piezoelectric actuator remarkably. However, it makes the ripple in positioning due to the phase lag and noise induced from the elements of the long closed loop. Secondly, the feedforward control by neural network compensates the hysteresis of the piezoelectric actuators effectively with the appropriate selection of the input variables for the training. The improvement of the dynamic performance of the piezoelectric actuators by the developed linearization technique is verified by experiments.

• Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.44-49
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• 2013

Passive attitude stabilization method has been widely used for attitude determination and control of cube satellite due to its advantage of system simplicity. In this paper, permanent magnet stabilization method for application of cube satellite attitude control has been introduced and its performance with and without hysteresis damper system has been investigated through a numerical simulation. The simulation results indicate that the permanent magnet stabilization combined with hysteresis damper shows much higher stabilization performance than the system without damper system.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.10
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• pp.50-57
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• 1997

A fast tool servo (FTS) for diamond turning improves machining accuracy by quickly compensating relative position errors between the cutter and the workpiece. Therefore, the FTS needs to have large band-width with good tracking performance. Serious hysteresis nonlinearity of PZT actuators used in the FTS, however, deteriorates fast tracking performance. Several types of feedforward hysteresis compensators and feedback controllers are tested to improve tracking performance. Through simulations and experiments, control structure which yields the smallest tracking error is selected. The maximum peak to peak error in tracking a sinusoidal waveform is reduced by one fifth compared to that of a regular PID controller.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.48-54
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• 2017

In this paper, hysteresis voltage control method is proposed to an unidirectional inverter control for piezoelectric load. Piezoelectric load has electrically RC characteristic, and is driven by the inverter to control the output voltage waveform. When controling the output waveform by PI control, appropriate gains need to be selected. However, hysteresis control may minimize the output distortion because it has maximum proportional gain. In addition, Hysteresis control algorithm has simple structure to realize and the response is fast. Although the switching frequency of the inverter by hysteresis control varies, the switching frequency for the piezoelectric load is lower than that by PI control for equivalent performance. In particular, on implementing the algorithm using FPGA, the algorithm can be implemented in fewer pabrics and the processing time can be reduced. The superiority of the proposed hysteresis voltage control was proved for piezoelectric load through simulation and experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.598-601
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• 2003

Most of all, DTC drive is very simple in its implementation because it needs only two hysteresis comparator and switching vector table for both flux and torque control. The switching strategy of a conventional direct torque control scheme which is based on hysteresis comparator results in a variable switching frequency which depends on the speed, flux, stator voltage and the hysteresis of the comparator. The amplitude of hysteresis band greatly influences on the drive performance such as flux and torque ripple and inverter switching frequency. In this paper the influence of the amplitudes of flux and torque hysteresis bands and sampling time of control program on the torque and flux ripples are investigated. Simulation results confirm the superiority of the DTC under the proposed method over the conventional DTC.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.267-270
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• 2002

The accuracy and the dynamic bandwidth are the two most important indices that an inductive position sensor is evaluated with. Eddy currents and magnetic hysteresis affect both of these performance indices. As the modulation frequency of the sensor increases to improve the dynamic bandwidth, the effects of eddy currents and hysteresis also increases, which results in the loss of accuracy. In this paper, a magnetic circuit model of the differential inductive sensor is developed. This model includes the effects of hysteresis and eddy currents. Experimental results confirm the validity of the model. The model predicts that the eddy current effects are not significant below the modulation frequency of 50kHz, as long as the lamination thickness is adequate.

• Journal of KSNVE
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• v.11 no.2
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• pp.265-275
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• 2001

This research has been performed to reveal the hysteresis phenomena of the hunting motion in a railway passenger cars. It is found that there are some factors and its operation region to make the nonlinear critical speed reacts to them more sensitively than the linear critical speed. The simulation results show that a self steering bogie system can be a substitute proposal to improve curving Performance together with the reduction of hysteresis of critical speed. Full scale roller rig test is carried out for the validation of the numerical results. Finally, it is certified that wear of wheel profile and stiffness discontinuities of wheelset suspension caused by deterioration have to be considered in the analysis to predict the hysteresis of critical speed precisely.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.219-224
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• 1996

Piezoelectric actuators exhibit limited accuracy in tracking control due to their hysteresis nonlinearity. In this study a digital tracking control approach for a piezoelectric actuator based on incorporating a feedback linearization loop with a PID feedback controller is presented. The hysteresis nonlinearity of the piezoelectric actuator is modeled in the feedback compensation loop using the Maxwell slip model. Experiments were performed on a piezoelectric 2-axis linear positioner for tracking linearly decaying sinusoidal waveforms and circles. The experimental results show that the tracking control performance is noticeably improved by augmenting the feedback loop with a model of hysteresis in the feedback compensation loop.