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Codeword-Dependent Distance Normalization and Smoothing of Output Probalities Based on the Instar-formed Fuzzy Contribution in the FVQ-DHMM (퍼지양자화 은닉 마르코프 모델에서 코드워드 종속거리 정규화와 Instar 형태의 퍼지 기여도에 기반한 출력확률의 평활화)

  • Choi, Hwan-Jin;Kim, Yeon-Jun;Oh, Yung-Hwan
    • The Journal of the Acoustical Society of Korea
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    • v.16 no.2
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    • pp.71-79
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    • 1997
  • In this paper, a codeword-dependent distance normalization(CDDN) and an instar-formed fuzzy smoothing of output distribution are proposed for robust estimation of output probabilities in the FVQ(fuzzy vector quantization)-DHMM(discrete hidden Markov model). The FVQ-DHMM is a variant of DHMM in which the state output probability is estimated by the sum oft he product of the output probability and its weighting factor for each codeword on an input vector. As the performance of the FVQ-DHMM is influenced by weighting factor and output distribution from a state, it is required to get a method to get robust estimation of weighting factors and output distribution for each state. From experimental results, the proposed CDDN method has reduced 24% of error rate over the conventional FVQ-DHMM, and also reduced 79% of error rate when the smoothing of output distribution is also applied to the computation of an output probability. These results indicate that the use of CDDN and the fuzzy smoothing of output distribution to the FVQ-DHMM lead to improved recognition, and therefore it may be used as an alternative to the robust estimation of output probabilities for HMMs.

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A low noise PLL with frequency voltage converter and loop filter voltage detector (주파수 전압 변환기와 루프 필터 전압 변환기를 이용한 저잡음 위상고정루프)

  • Choi, Hyek-Hwan
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.14 no.1
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    • pp.37-42
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    • 2021
  • This paper presents a jitter and phase noise characteristic improved phase-locked loop (PLL) with loop filter voltage detector(LFVD) and frequency voltage converter(FVC). Loop filter output voltage variation is determined through a circuit made of resistor and capacitor. The output signal of a small RC time constant circuit is almost the same as to loop filter output voltage. The output signal of a large RC time constant circuit is the average value of loop filter output voltage and becomes a reference voltage to the added LFVD. The LFVD output controls the current magnitude of sub-charge pump. When the loop filter output voltage increases, LFVD decreases the loop filter output voltage. When the loop filter output voltage decreases, LFVD increases the loop filter output voltage. In addition, FVC also improves the phase noise characteristic by reducing the loop filter output voltage variation. The proposed PLL with LFVD and FVC is designed in a 0.18um CMOS process with 1.8V power voltage. Simulation results show 0.854ps jitter and 30㎲ locking time.

Digital Control of an AC/DC Converter using the Power Balance Control Technique with Average Output Voltage Measurement

  • Wisutmetheekorn, Pisit;Chunkag, Viboon
    • Journal of Power Electronics
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    • v.12 no.1
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    • pp.88-97
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    • 2012
  • This paper presents a method for the digital control of a high power factor AC/DC converter employing the power balance control technique to achieve a fast response of the output voltage control. To avoid the effects of an output voltage ripple in the voltage control loop, the average output voltage is sampled and used as a feedback signal for the output voltage controller. The proposed control technique was verified by simulations using MATLAB/Simulink and its implementation was realized by a dsPIC30F4011 digital signal processor to control a CUK topology AC/DC converter with a 48V output voltage and a 250 W output power. The experimental results agree with the simulation results. The proposed control technique achieves a fast transient response with a lower line current distortion than is achieved when using a conventional proportional-integral controller and the power balance control technique with the conventional sampling method.

Analysis of the Output Ripple of the DC-DC Boost Charger for Li-Ion Batteries

  • Nguyen, Van-Sang;Tran, Van-Long;Choi, Woojin;Kim, Dae-Wook
    • Journal of Power Electronics
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    • v.14 no.1
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    • pp.135-142
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    • 2014
  • In the design of battery chargers, limiting the output ripple current according to the manufacturer's recommendation is important for reliable service and extended battery life. Ripple components can cause internal heating of the battery and thus reduce the service life of the battery. Care must be exerted in the design of the switching converter for the charge application through the accurate estimation of the output current ripple value. This study proposes a method to reduce the output current ripple of the converter and presents a detailed analysis of the output current ripple of the DC-DC boost converter to provide a guideline for the design of the battery charger.

On linear output feedback for uncertain nonlinear systems

  • Choi, Ho-Lim;Koo, Min-Sung;Lim, Jong-Tae
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.1604-1607
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    • 2004
  • In this paper, we consider a problem of asymptotic output regulation of a class of uncertain nonlinear systems by output feedback. The system under consideration is in the Parametric-Pure-Feedback Form, which does not satisfy the existing conditions such as the triangularity condition or the Lipschitz condition. We propose a linear output feedback controller with a scaling factor, which asymptotically regulates the output of the considered system.

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A Disturbance Observer-Based Output Feedback Controller for a DC/DC Boost Converter with Load Variation (부하변동을 고려한 DC/DC 승압형 컨버터의 외란 관측기 기반 출력 궤환 제어기)

  • Jeong, Goo-Jong;Kim, In-Hyuk;Son, Young-Ik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.7
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    • pp.1405-1410
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    • 2009
  • Output voltage of a DC/DC power converter system is likely to be distorted if variable loads exist in the output terminal. This paper presents a new disturbance observer(DOB) approach to maintain a robust regulation of the output voltage of a boost type DC/DC converter. Unlike the buck-type converter case, the regulation problem of the boost converter is very complicated by the fact that, with respect to the output voltage to be regulated, the system is non-minimum phase. Owing to the non-minimum phase property the classical DOB approach has not been applied to the boost converter. Motivated by a recent result on the application of DOB to non-mimimum phase system, an output feedback control law is proposed by using a parallel feedforward compensator. Simulation results using the Simulink SimPowerSystems prove the performance of the proposed controller against load variation.

Safety Requirements and Test Methods of a Radiofrequency Stimulator

  • Park, Sang-Geon
    • Journal of information and communication convergence engineering
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    • v.14 no.3
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    • pp.191-199
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    • 2016
  • In this study, we investigate the safety requirements and test methods of a radiofrequency stimulator. The main test items include controls of a minimum output, accommodation range, and output parameters that have been known as the safety requirements in conformity with international standards. As the test criteria for controlling the minimum output, an increase or decrease in a unit of 1 mA or 1 V or less was applied to the output amplitude regulator for both continuous and discontinuous control, and the output at the minimum setting was manipulated to not exceed 2% of the maximum setting. For controlling the output parameters, one of the representative test criteria states that the current limit of 250 mA should be equal to or less than 1,500 Hz. Consequently, when applying the radiofrequency stimulator on the human body, we need to ensure that the safety requirements conform to the international standards.

Linear Quadratic Regulation and Tracking using Output Feedback with Direct Feedthrough

  • Kang, Seungeun;Cha, Jihyoung;Ko, Sangho
    • International Journal of Aeronautical and Space Sciences
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    • v.17 no.4
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    • pp.593-603
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    • 2016
  • This paper presents the development of linear quadratic regulation and output tracking algorithms using output feedback when both the measurement and performance output equations contain direct feedthrough terms. Although all physical systems can be modeled without direct feedthrough, there are still many situations where system models with direct feedthrough are important. For this situation, we modify previous work on the same topic for systems without direct feedthrough. It is shown that for the regulation problem, the optimal output feedback gain for a direct feedthrough case can be directly obtained, via a transformation, from the approach used for systems without direct feedthrough. However, for the tracking problem, a new set of coupled matrix equations for determining the optimal output feedback gain is derived from the necessary conditions for minimizing the cost function. The effectiveness of the developed algorithms is demonstrated using numerical examples.

A Study on Design of Optimal Load Impedance for Broadband Characteristic Improvement of the Power Amplifier (전력증폭부의 광대역 특성 개선을 위한 최적의 부하 임피던스 설계 방안 연구)

  • Lee, Han-Young
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.6
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    • pp.1166-1173
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    • 2009
  • In this paper, we studied on the power amplifier which has the output of the optimal to 100MHz-2GHz band. Optimal output power match was fabricated using the two types; one is the linear tapering and the other is the impedance transformer. In the case of output power match using linear tapering, output power was 35.35dBm at 2GHz and 31.41dBm at 100MHz. The other case of output match using impedance transformer, output power was 34.8dBm at 2GHz and 33.25dBm at 100MHz. Comparison of the results in the two cases, impedance transformer type present the improved results by l.84dB of output power.

A Study of Power Output Characteristics for the Magnesium Metal Fuel Cell (마그네슘 금속연료전지의 출력특성에 관한 연구)

  • Kim, Yong-Hyuk
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.63 no.3
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    • pp.212-217
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    • 2014
  • The electric power output characteristics of magnesium fuel cell were investigated with regard to internal resistance. A equivalent circuit with the series-connected three internal resistance was introduced to analyze of the response to change of power. The power output analysis was employed in order to investigate the effect of internal resistances for the electrolyte concentration, air electrode area, Mg electrode area and distance between the electrodes. It was confirmed that internal resistance is generated by the electrolyte, air electrode and metal electrode, then those Internal resistances had a significant effect on the power output decrease. The power output was a maximum when the load resistance maches the internal resistance of the magnesium fuel cell. The fuel efficiency was only 50% at maximum power output. Higher fuel efficiency was achieved when the load resistance is greater than the internal resistance.