• Title, Summary, Keyword: Frequency Dependent Control

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A calculation method of root loci band and its applications to robust control system design

  • Okuyama, Yoshifumi;Chen, Hong;Takemori, Fumiaki
    • 제어로봇시스템학회:학술대회논문집
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    • pp.350-353
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    • 1994
  • This paper presents a method to calculate the characteristic root areas and loci band of control systems with uncertainties. First, equations of boundary curves of root areas in the case of additive and multiplicative perturbation are derived. Then, an algorithm for the calculation of the array of closed curves is presented. When the upper bound of the absolute values of frequency responses for the uncertain part, is also frequency-dependent, the frequency-dependent, terms are included in the characteristic equation of the nominal system. This lead to the boundary equations of the root, areas for control systems with frequency-dependent uncertainty. Numerical examples of the control systems with multiplicative perturbations including frequency-dependent terms are presented to verify this calculation method. Finally, its applications to the design of robust control systems, e.g., passive adaptive control systems are also discussed.

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A Frequency-dependent Single Cell Impedance Analysis Chip for Applications to Cancer Cell and Normal Cell Discrimination (주파수에 따른 단일세포의 임피던스 분석칩 및 암세포와 정상세포의 구별에의 적용)

  • Chang, YoonHee;Kim, Min-Ji;Cho, Young-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.12
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    • pp.1671-1674
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    • 2014
  • This paper presents a frequency-dependent cell impedance analysis chip for use in cancer and normal cell discrimination. The previous cell impedance analysis chips for flowing cells cannot allow enough time for cell-to-electrode contact to monitor frequency-dependent impedance response. Another type of the previous cell impedance analysis chips for the cells clamped by membranes need complex sample control for making stable cell-to-electrode contact. We present a new impedance analysis chip using the microchamber array, on which a PDMS cover is placed to make stable cell-to-electrode contact for the individual cell trapped in each microchamber; thus achieving frequency-dependent single-cell impedance analysis without complex sample control. Compared to the normal cells, the magnitude of NHBE cells is $60.07{\sim}97.41k{\Omega}$ higher than A549 cells in the frequency range of 95.6 kHz~2MHz and the phase of NHBE is $3.96^{\circ}{\sim}20.8^{\circ}$ higher than A549 cells in the frequency range of 4.37 kHz~2MHz, respectively. It is demonstrated experimentally that the impedance analysis chip performs frequency-dependent cell impedance analysis by making stable cell-to-electrode contact with simple sample control; thereby applicable to the normal cell and cancer cell discrimination.

Frequency Dependent Damping for a Nonlinear Vehicle Active Suspension System (비선형 차량능동현가시스템의 주파수 감응감쇠 특성연구)

  • Kim, J.Y.
    • Journal of the Korean Society of Mechanical Technology
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    • v.13 no.2
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    • pp.45-54
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    • 2011
  • A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. Among the various suspension systems, an active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. In the process of the linearization for the nonlinear active suspension system, the frequency dependent damping method is used for the exact modelling to the real model. The pressure control valve which is controlled by proportional solenoid is the most important component in the active suspension system. The pressure control valve has the dynamic characteristics with 1st order delay. Therefore, It's necessary to adopt the lead compensator to compensate the dynamics of the pressure control valve. The sampling time is also important factor for the control performances. The sampling time value is proposed to satisfy the system performances. After the modelling and simulation for the pressure control valve and vehicle dynamic, the performances of the vehicle ride quality and the stability are enhanced.

Swing Motion Control System Design Based on Frequency-shaped LQ Control (주파수 의존형 최적 레귤이터에 의한 크레인 흔들림 제어계 설계)

  • Kim, Y.B.;Jang, J.S.
    • Journal of Power System Engineering
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    • v.12 no.6
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    • pp.50-55
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    • 2008
  • In general, the swing motion of the crane is controlled and suppressed by activating the trolley motion. In many papers reported by us, we suggested a new type of anti-sway control system of the crane. In the proposed control system, a small auxiliary mass(moving-mass) is installed on the spreader and the swing motion is controlled by moving the auxiliary mass. The actuator reaction against the auxiliary mass applies inertial control forces to the container in order to reduce the swing motion in the desired manner. Futhermore the measuring systems based on image sensor have been proposed also. To obtain the robustness for our control system, $H_{\infty}$ based control techniques and other approach have been applied to suppress swing motion. As well known, the robust control technologies based on $H_{\infty}$ control need complicated and difficult process. In the result, the obtained closed-loop system becomes to high order system which may give us many difficulties to apply it to the real plants. Therefore, we introduce an easy approach which is based on LQ control theory. In this approach, we introduce the frequency dependent weighting matrices which give the system filters to shape frequency characteristics of the controlled system and guarantee the control performance.

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Mooring Winch Control System Design Based on Frequency Dependent LQR Control Approach (주파수 의존형 LQR 설계법에 의한 무어링 윈치 제어시스템 설계)

  • Goo, Ja-Sam;Kim, Young-Bok
    • Journal of Navigation and Port Research
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    • v.38 no.1
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    • pp.29-37
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    • 2014
  • In this paper, the author consider control system design problem of the surface vessel where any types of floating units are included. To keep their motion/position, the Dynamic Positioning System(DPS) is equipped in. Even though sometimes the thrust systems are installed on them, in general the mooring winch system with the rope/wire is used. Therefore, in this paper we consider a single type mooring winch control problem to keep the vessel's position. For this, we introduce an easy and useful control approach which is based on LQ control theory. In this approach, we introduce the frequency dependent weighting matrices which give the system filters to shape frequency characteristics of the controlled system and guarantee the control performance. Based on this, we will show that the proposed approach works well.

Determination of Secondary Reserve Requirement Through Interaction-dependent Clearance Between Ex-ante and Ex-post

  • Kim, Sun Kyo;Park, Joon-Hyung;Yoon, Yong Tae
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.71-79
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    • 2014
  • This paper discusses a method for the determination of frequency control reserve requirement with consideration of the interaction between ex-ante planning and real-time balancing. In proposed method, we consider the fact that the delivered energy for tertiary control reserve is determined based on required capacity for secondary control reserve and the expected amount of load errors. Uncertain load errors are derived by Brownian motion, an optimization method is suggested using a stochastic programming. In a short, we propose an interactive dependent method for determining secondary control reserve requirement based on the principle that it satisfies to minimize the total cost. As a result, this paper provides will analyze for an example model to demonstrate the capabilities of the method.

Power Smoothing of a Variable-Speed Wind Turbine Generator Based on the Rotor Speed-Dependent Gain (회전자 속도에 따라 변하는 게인에 기반한 가변속 풍력발전기 출력 평활화)

  • Kim, Yeonhee;Kang, Yong Cheol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.4
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    • pp.533-538
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    • 2016
  • In a power grid that has a high penetration of wind power, the highly-fluctuating output power of wind turbine generators (WTGs) adversely impacts the power quality in terms of the system frequency. This paper proposes a power smoothing scheme of a variable-speed WTG that can smooth its fluctuating output power caused by varying wind speeds, thereby improving system frequency regulation. To achieve this, an additional loop relying on the frequency deviation that operates in association with the maximum power point tracking control loop, is proposed; its control gain is modified with the rotor speed. For a low rotor speed, to ensure the stable operation of a WTG, the gain is set to be proportional to the square of the rotor speed. For a high rotor speed, to improve the power smoothing capability, the control gain is set to be proportional to the cube of the rotor speed. The performance of the proposed scheme is investigated under varying wind speeds for the IEEE 14-bus system using an EMTP-RV simulator. The simulation results indicate that the proposed scheme can mitigate the output power fluctuation of WTGs caused by varying wind speeds by adjusting the control gain depending on the rotor speed, thereby supporting system frequency regulation.

Robust Stability eEaluation of Multi-loop Control Systems Based on Experimental Data of Frequency Response

  • Chen, Hong;Okuyama, Yoshifumi;Takemori, Fumiaki
    • 제어로봇시스템학회:학술대회논문집
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    • pp.360-363
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    • 1995
  • In this paper, we describe the composition of frequency response bands based on experimental data of plants (controlled systems) with uncertainty and nonlinearity, and the robust stability evaluation of feedback control systems. Analysis and design of control systems using the upper and lower bounds of such experimental data would be effective as a practicable method which is not heavily dependent upon mathematical models such as the transfer function. First, we present a method to composite gain characteristic bands of frequency response of cascade connected plants with uncertainty and a recurrent inequality for the composition. Next, evaluation methods of the robust stability of multi-loop control systems obtained through feedback from the output terminals and multi-loop control systems obtained through feedback into the input terminals are described. In actual control systems, experimental data of frequency responses often depends on the amplitude of input. Therefore, we present the evaluation method of the nominal value and the width of the frequency response band in such a case, and finally give numerical examples based on virtual experimental data.

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Synthesis of lossy tapered transmission line (손실을 갖는 테이퍼 전송선로의 합성)

  • Park, Eui-Joon
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.8
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    • pp.56-63
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    • 1995
  • A new method is presented for the synthesis of lossy tapered transmission line having presecribed frequency characteristic in the passband. The theory of lossy case extends lossless cases suggested by Klopfenstein and others, and a special optimization process based on the Fourier transfrom pair and generalized Taylor's procedure is proposed for exact designs of frequency-dependent and distance-dependent lossy tapered line. The process is achieved by control of zero points of lobe-like input reflection coefficient. The validity of the suggested method is confirmed by synthesizing a lossy microstrip transformer and analyzing the simulation results.

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Frequency Dependent Properties of Tris(8-Hydroxyquinoline) Aluminum Thin Films

  • Lee, Yong-Soo;Park, Jae-Hoon;Choi, Jong-Sun
    • KIEE International Transactions on Electrophysics and Applications
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    • v.11C no.3
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    • pp.70-74
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    • 2001
  • Admittance or impedance spectroscopy is one of the powerful tools to study dielectric relaxation and loss processes in organic and inorganic materials. In this study, the frequency dependent properties of an indium tin oxide/tris(8-hydroxyquinoline) aluminum($Alq_3$)/aluminum structure have been studied. The conductance of the $Alq_3$ film increases with the DC applied voltage up to 4V and decreases above 4V in the low frequency region. This indicates that the resistance of the device decreases with the applied bias due to the carrier injection enhancement, thereafter the injected carriers form the space charge and the additional injection of carriers is prevented. The Cole-Cole plot of the admittance takes a one-semicircle shape, which means that the device can be modeled as a parallel resistor-capacitor network. The resistance and capacitance were estimated as 8.62k${\Omega}$ and 2.7nF, respectively, at 3V in the low frequency region. The dielectric constant ( ${\epsilon}'$ ) of the $Alq_3$ film is independent of the frequency in the low frequency region below 100kHz, while the frequency dependency was observed at above 100kHz. The dielectric loss factor ( ${\epsilon}"$ ) of the $Alq_3$ film shows the dielectric dispersion below 100kHz and dielectric absorption in higher frequency domain. The dispersion is thought to be related to the hopping process of the carriers. The ${\epsilon}"$ is proportional to the reciprocal of the frequency. The dielectric relaxation time was extracted to about 0.318${\mu}s$ from the dielectric absorption spectrum.

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