• Title, Summary, Keyword: Gain and phase margins

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Adjusting GPC Control Parameters Based on Gain and Phase Margins

  • Haeri, Mohammad
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1838-1842
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    • 2004
  • Gain and phase margins of a first order plus delayed time (FOPDT) process controlled by generalized predictive controller (GPC) are related to the control parameters ${\lambda}$ (control move suppression parameter) and ${\alpha}$ (smoothing filter coefficient) and the normalized delay of the process. Variation ranges of gain and phase margins are determined. It is shown that the margins cannot be assigned independently for a wide range of variation and the range is narrowing by increase of the normalized delay of the process. And finally curves are given to use for adjustment of the controller parameters in order to obtain a specific pair of gain and phase margins.

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Absolute Stability Margins in Missile Guidance Loop

  • Kim, Jong-Ju;Lyou, Joon
    • International Journal of Control, Automation, and Systems
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    • v.6 no.3
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    • pp.460-466
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    • 2008
  • This paper deals with the stability analysis of a missile guidance loop employing an integrated proportional navigation guidance law. The missile guidance loop is formulated as a closed-loop control system consisting of a linear time-invariant feed-forward block and a time-varying feedback gain. Based on the circle criterion, we have defined the concept of absolute stability margins and obtained the gain and phase margins for the system assuming 1 st order missile/autopilot dynamics. The correlation between the absolute stability margins and the margins derived from the frozen system analysis is also discussed.

Computation of robustness margins in multivariable LQG/LTR design when the plant is scalled (다변수 LQG/LTR 설계에서 스케일링 행렬에 의한 강인성 여유 계산)

  • 강진식
    • 제어로봇시스템학회:학술대회논문집
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    • pp.491-497
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    • 1993
  • In MIMO design, input and output units are different from each other. By this reason, the effect of larger units to smaller one is not trivial and there is no method of proper scaling, optimal scaling. In this paper, robust stability of MIMO LQG/LTR design are analised when the plnat inputs and outputs are scalled. The upper bound of model error to guarantee the robust stability is obtained, and gain margin and phase margins are computed with respect to scalling matrices.

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On the improvement of the guaranteed stability margins for the discrete time LQ regulator

  • Kwon, Wook-Hyun;Kim, Sang-Woo;Choi, Han-Hong
    • 제어로봇시스템학회:학술대회논문집
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    • pp.913-917
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    • 1989
  • In this paper, the selection method of weighting matrices in the discrete-time LQ problem are suggested in order to improve the guaranteed stability margins, i.e. the gain and phase margins. The asymptotic properties of the solution of the algebraic Riccati equations are investigated by using the closed form solution of the difference Riccati equations. It is shown that the solution of the algebraic Riccati equations monotonically increases as the state weighting matrix Q or the control weighting matrix R increase. The increasing rate of the solution is shown to be much less than that of R for large R. It is also proven that the guaranteed stability margins increases as the ratio between Q and R decreases.

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The Design of IMC-PID Controller Considering a Phase Scaling Factor (위상 조절 인자를 고려한 IMC-PID 제어기의 설계)

  • Kim, Chang-Hyun;Lim, Dong-Kyun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.9
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    • pp.1618-1623
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    • 2008
  • In this paper, a new design method for IMC-PID that adds a phase scaling factor of system identifications to the standard IMC-PID controller as a control parameter is proposed. Based on analytically derived frequency properties such as gain and phase margins, this tuning rule is an optimal control method determining the optimum values of controlling factors to minimize the cost function, integral error criterion of the step response in time domain, in the constraints of design parameters to guarantee qualified frequency design specifications. The proposed controller improves existing single-parameter design methods of IMC-PID in the inflexibility problem to be able to consider various design specifications. Its effectiveness is examined by a simulation example, where a comparison of the performances obtained with the proposed tuning rule and with other common tuning rules is shown.

Application of an Adaptive Autopilot Design and Stability Analysis to an Anti-Ship Missile

  • Han, Kwang-Ho;Sung, Jae-Min;Kim, Byoung-Soo
    • International Journal of Aeronautical and Space Sciences
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    • v.12 no.1
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    • pp.78-83
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    • 2011
  • Traditional autopilot design requires an accurate aerodynamic model and relies on a gain schedule to account for system nonlinearities. This paper presents the control architecture applied to a dynamic model inversion at a single flight condition with an on-line neural network (NN) in order to regulate errors caused by approximate inversion. This eliminates the need for an extensive design process and accurate aerodynamic data. The simulation results using a developed full nonlinear 6 degree of freedom model are presented. This paper also presents the stability evaluation for control systems to which NNs were applied. Although feedback can accommodate uncertainty to meet system performance specifications, uncertainty can also affect the stability of the control system. The importance of robustness has long been recognized and stability margins were developed to quantify it. However, the traditional stability margin techniques based on linear control theory can not be applied to control systems upon which a representative non-linear control method, such as NNs, has been applied. This paper presents an alternative stability margin technique for NNs applied to control systems based on the system responses to an inserted gain multiplier or time delay element.

PID Control Design with Exhaustive Dynamic Encoding Algorithm for Searches (eDEAS)

  • Kim, Jong-Wook;Kim, Sang-Woo
    • International Journal of Control, Automation, and Systems
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    • v.5 no.6
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    • pp.691-700
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    • 2007
  • This paper proposes a simple but effective design method of PID control using a numerical optimization method. In order to achieve both stability and performance, gain and phase margins and performance indices of step response directly compose of the cost function. Hence, the proposed approach is a multiobjective optimization problem. The main effectiveness of this approach results from the strong capability of the used optimization method. A one-dimensional example concerning gain margin illustrates the practical applicability of the optimization method. The present approach has many degrees of freedom in controller design by only adjusting related weight constants. The attained PID controller is compared with Wang#s and Ho#s methods, IAE, and ISE for a high-order process, and the simulation result for various design targets shows that the proposed approach achieves desired time-domain performance with a guarantee of frequency-domain stability.

A robust control system design by a parameter space approach based on sign difinite condition

  • Kimura, Tetsuya;Hara, Shinji
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1533-1538
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    • 1991
  • A parameter space approach for robust control system design is developed by reducing several design specifications to sign definite conditions. It is shown that the gain and phase margin constraints for the parametric perturbed plant hold if and only if the four Kharitonov systems satisfy the margins. On pole location, it is shown that D-stability of convex combinations (1-t)p(s)+tq(s) can be determined by the coefficients corresponding to p(s) and q(s) based on the sign definite condition. We show a method of PI-type robust control system design as a useful example.

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Time delay control with state feedback for azimuth motion of the frictionless positioning device

  • Jeong, Ho-Seop;Lee, Chong-Won
    • 제어로봇시스템학회:학술대회논문집
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    • pp.385-388
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    • 1996
  • A time delay controller with state feedback is proposed for azimuth motion control of the frictionless positioning device which is subject to the variations of inertia in the presence of measurement noise. The time delay controller, which is combined with a low-pass filter to attenuate the effect of measurement noise, ensures the asymptotic stability of the closed loop system. It is found that the low-pass filter tends to increase the robustness in the design of time delay controller as well as the gain and phase margins of the closed loop system. Numerical and experimental results support that the proposed controller guarantees a good tracking performance irrespective of the variation of inertia and the presence of measurement noise.

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An Optimal Approach to Rotational Vibration Suppression using Disturbance Observer in Disk Drive Systems

  • Park, Sung-Won;Kim, Nam-Guk;Chu, Sang-Hoon;Kang, Chang-Ik;Lee, Ho-Seong
    • Transactions of the Society of Information Storage Systems
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    • v.3 no.1
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    • pp.5-12
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    • 2007
  • This paper investigates the design of disturbance observer for rotational vibration suppression in disk drive systems. The design aims to provide an optimal controller which satisfies both vibration performance and robust stability. It consists of an inversion method, a special filter, and optimization scheme. Firstly a new inversion method is introduced, which provides more accurate inversion compared to conventional zero phase error method. The inversion is to deal with unstable zeros in the plant model. Secondly a special filter for disturbance selection is given, which features adjustable gain and band pass characteristics so that it enables flexible shaping of the loop considering the trade-off between performance and stability margins. And finally the parameters of disturbance observer are optimized in conjunction with external disturbance model. Simulation and experiment on commercial hard disk drives confirm that the design is very effective to such disturbance which is hard to be handled by conventional approach.

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