• Journal of Institute of Control, Robotics and Systems
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• v.6 no.11
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• pp.981-986
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• 2000

A pulse amplitude modulation(PAM) controller is designed for the 3 axis attitude control of a sounding rocket. a certain number of fixed level of thrust are used for the pulse amplitude modulation and the nonlinearity of the controller is considered to examine the existence of the limit cycles and the stability analysis is carried out with the aid of Nyquist plot.

• Korean Journal of Veterinary Research
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• v.37 no.3
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• pp.669-685
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• 1997

The present study was performed to evaluate the effects of xylazine and tiletamine + zolazepam on echocardiograms before and after experimental myocardial infarctions in clinically normal dogs taken preliminary examinations related to cardiac function. The results are as follows. With xylazine administration, left ventricle end-diastolic dimension, left ventricle end-systolic dimension, left atrium/aorta, ejection time and velocity of circumferential fiber shortening increased and mitral valve CD slope, % delta D decreased(p<0.01). In tiletamine+zolazepam administered group, interventricular septum amplitude(p<0.01), mitral valve DE slope(p<0.05) and ejection time(p<0.01) decreased and left atrium/aorta, ejection time also decreased compared with xylazine group(p<0.01). In 48 hours after experimental myocardial infarction group, anterior aortic wall amplitude decreased compared with control, xylazine, tiletamine + zolazepam group, respectively(p<0.01). Posterior aortic wall amplitude decreased compared with control(p<0.01). Left ventricle end systolic dimension increased compared with control and tiletamine + zolazepam group, respectively(p<0.01). Left ventricular posterior wall end systolic dimension decreased compared with control(p<0.01). Left ventricular posterior wall amplitude decreased compared with control and tiletamine+zolazepam group(p<0.01). Left atrium/aorta decreased compared with xylazine group(p<0.01). % thickening left ventricular posterior wall decreased compared with control(p<0.05). % delta D decreased compared with control and tiletamine+zolazepam group(p<0.01). Ejection time decreased compared with xylazine(p<0.01). Velocity of circumferential fiber shortening increased compared with control and tiletamine + zolazepam group(p<0.01). With xylazine administration 48 hours after experimental myocardial infarction, anterior aortic wall amplitude, posterior aortic wall amplitude decreased compared with control(p<0.01). Left ventricle end-diastolic dimension increased compared with control(p<0.01). Left ventricle end-systolic dimension increased compared with control and tiletamine + zolazepam group, respectively(p<0.01). Left ventricular posterior wall end-systolic dimension and left ventricular posterior wall end-diastolic dimension decreased compared with control(p<0.01). Left atrium/aorta decreased compared with xylazine group(p<0.01). % thickening left ventricular posterior. wall(p<0.05) and % delta D(p<0.01) decreased compared with control. Velocity of circumferential fiber shortening increased compared with tiletamine + zolazepam group(p<0.01). With tiletamine + zolazepam administration 48 hours after experimental myocardial infarction, anterior aortic wall amplitude decreased compared with control, xylazine and tiletamine+zolazepam group, respectively(p<0.01). Posterior aortic wall amplitude decreased compared with control(p<0.01). Left ventricle end-systolic dimension increased compared with control and tiletamine+zolazepam group(p<0.01). Left ventricular posterior wall end-systolic dimension, left ventricular posterior wall end-diastolic dimension and interventricular septum amplitude decreased compared with control(p<0.01). Left atrium/aorta decreased compared with xylazine group(p<0.01). % delta D decreased compared with control and tiletamine + zolazepam group(p<0.01). Ejection time decreased compared with xylazine group and velocity of circumferential fiber shortening increased compared withtiletamine+zolazepam group(p<0.01). Conclusively, echocardiography was proved to be a useful, diagnostic, non-invasive and simple method for establishing the diagnosis of myocardial infarction and evaluating the effects of drug on cardiac function before and after myocardial infarction.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.5
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• pp.563-569
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• 2014

This article focuses on a hemispherical resonator gyro driven by the Coriolis effect. A hemispherical shell, called a resonator, is maintained in the resonance state by amplitude control and phase locking control. Parametric excitation has been used to control the amplitude. For rate measurement mode or FTR mode, nodal points have been kept to an amplitude of zero. Angular rate measurement has been demonstrated by rotating a resonator. Frequency mismatch between two stiffness principal axes is a major cause of low performance: vibrating pattern drift and reduced control effectiveness. This mismatch has been reduced significantly by the addition of small mass. A negative spring effect, which lowers resonance frequencies, has been verified experimentally.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.3
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• pp.258-264
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• 2009

This paper presents two control algorithms for the frequency and amplitude of the resonator of a micro sensor. One algorithm excites the resonator at its a priori unknown resonant frequency, and the other algorithm alters the resonator dynamics to place the resonant frequency at a fixed frequency, chosen by the designer. Both algorithms maintain a specified amplitude of oscillations. The control system behavior is analyzed using an averaging method, and a quantitative criterion is provided for the selecting the control gain to achieve stability. Tracking and estimation accuracy of the natural frequency under the presence of measurement noise is also analyzed. The proposed control algorithms are applied to the MEMS dual-mass gyroscope without mechanical connecting beam between two proof-masses. Simulation results show the effectiveness of the proposed control algorithms which guarantee the proof-masses of the gyroscope to move in opposite directions with the same resonant frequency and oscillation amplitude.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.167-174
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• 1995

This paper experimentally demonstrates the feasibility of using shape memory alloy(SMA) actuators in controlling structural vibrations of a flexible cantilevered beam. The dynamic characteristics of the SMA actuator are identified and integrated with the beam dynamics. Three types of control schemes; constant amplitude controller(CAC), proportional amplitude controller (PAC) and sliding mode controller(SMC) are designed. The CAC and PAC are determined on the basis of physical phenomenon of the SMA actuator, while teh SMC is formulated in a mathematical manner. The proposed controllers are implemented and evaluated at various operating condirions by investigating the control level of suppression in transient vibration.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.843-850
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• 2017

The EMG amplitude estimator, which has been investigated as an indicator of muscle force, is utilized as the control input to artificial prosthetic limbs. This paper describes an application of the optimal EMG amplitude estimator to the surface EMG signals recorded during constant isometric %MVC (maximum voluntary contraction) for 30 seconds and reports on assessing performance of the amplitude estimator from the application. Surface EMG signals, a total of 198 signals, were recorded from biceps brachii muscle over the range of 20-80%MVC isometric contraction. To examine the estimator performance, a SNR(signal-to-noise ratio) was computed from each amplitude estimate. The results of the study indicate that ARV(average rectified value) and RMS(root mean square) amplitude estimation with forth order whitening filter and 250[ms] moving average window length are optimal and showed the mean SNR improvement of about 50%, 40% and 20% for each 20%MVC, 50%MVC and 80%MVC surface EMG signals, respectively.

• Journal of the Optical Society of Korea
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• v.16 no.4
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• pp.401-408
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• 2012

The amplitude error of phase modulator used in closed-loop fiber optic gyroscope has occurred by the temperature dependency of the electro-optic coefficient, and also can be due to the square-wave dither signal which is generally applied for eliminating the deadzone. This error can cause bias drift and scale factor error. This paper analyzes the temperature dependency of the modulation amplitude and the relationship with the scale factor of the gyroscope, and deals with an amplitude control method. The error calculation logic considering the dither signal is implemented on the signal processing module. The result of experiments from a prototype gyroscope shows the effect of the modulation amplitude control and a considerable improvement on performances.

• Journal of Drive and Control
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• v.14 no.2
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• pp.1-8
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• 2017

The spool displacement of a directional control valve can be considered as the standard signal for the measurement of its bandwidth frequency. When the spool displacement is not available, the metering-orifice system is suggested in this study as an alternative way to measure the - 3 dB amplitude-ratio bandwidth frequency of the hydraulic directional-control valve. The amplitude ratio of the metering-orifice pressure can be adjusted to equal that of the spool displacement through the controlling of the metering-orifice opening area. A series of experiments were conducted to verify the effectiveness of the metering-orifice system. The metering orifice was confirmed as adequate for the measurement of the - 3 dB amplitude-ratio bandwidth frequency.

• Journal of IKEEE
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• v.24 no.4
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• pp.975-981
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• 2020

A 10 GHz LC voltage-controlled oscillator (VCO), which controls an amplitude of output signal, is proposed to improve the phase noise. The proposed amplitude control circuit for the LC VCO consists of a peak detector, an amplifier, and a current source. The peak detector is performed detecting the lowest voltage of the output signal by using two diode-connected NMOSFET and a capacitor. The proposed 10 GHz LC VCO with an amplitude control circuit for output signal is designed using a 55 nm CMOS process with a supply voltage of 1.2 V. Its area is 0.0785 ㎟. The amplitude control circuit used in the proposed LC VCO reduces the amplitude variation 242 mV generated in the output signal of the conventional LC VCO to 47 mV. Furthermore, it improves the peak-to-peak time jitter from 8.71 ps to 931 fs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.297-300
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• 2005

This paper presents vibration control of an engine mount for a passenger vehicle utilizing ER fluid and piezoelectric actuator. The proposed engine mount can be isolated the vibration of wide frequency range with many types of amplitude. The main function of ER fluid is to attenuate vibration for low frequency with large amplitude, while the piezoelectric actuator is activated in hish frequency range with small amplitude. A mathematical model of the engine mount is derived using Hydraulic model and mechanical model. After formulating the governing equation of motion, then field-dependent dynamic stiffness of the engine mount is evaluated for various engine speed and excitation amplitude conditions. Then robust controller is designed to attenuate vibration of wide range frequency component. Computer simulation is undertaken in order to evaluate the vibration control performance such as transmissibility magnitude in frequency domains.