• Journal of the Korean Data and Information Science Society
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• v.22 no.5
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• pp.903-910
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• 2011

The von Bertalanffy growth function (VBGF) is the result of the antagonistic effects of anabolism and cataboliem. However VGBF has limitations for describing the growth of continuous spawning fishes. In the present work, a new equation is proposed where the growth parameter Kis substituted by a function related to the sea surface temperature of spawning period. Examples for natural population of Pacific Anchovy are presented.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.263-269
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• 1998

We use the slope bounded saturation nonlinear feedback element instead of relay to find ultimate gain and period of linear plant. Saturation nonlinear element reduces the high harmonics of plant output. The reduction of high harmonics improve the accuracy of describing function method used to find ultimate gain and period. We give a simple procedure to find ultimate gain and period with saturation nonlinear element. A PID controller design method with known time delay element is also given, which is very useful when oscillation is not occurred with nonlinear element.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.3
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• pp.237-242
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• 2015

This paper presents a method to enhance tracking performance of an input-constrained bilinear system using MPC (Model Predictive Control) when a feasible tracking control is known. Since the error dynamics induced by the known tracking control is asymptotically stable, there exists a Lyapunov function for the stable error dynamics. By defining a cost function including the Lyapunov function and describing tracking performance, an MPC law is derived. In simulation, the performance of the proposed MPC law is demonstrated by applying it to a converter model.

• Journal of the Chungcheong Mathematical Society
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• v.25 no.3
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• pp.475-489
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• 2012

A plateau in a Motzkin path is a sequence of three steps: an up step, a horizontal step, then a down step. We find three different forms for the bivariate generating function for plateaus in Motzkin paths, then generalize to longer plateaus. We conclude by describing a further generalization: a continued fraction form from which one can easily derive new multivariate generating functions for various kinds of path statistics. Several examples of generating functions are given using this technique.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.114-114
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• 2003

Fiber bundles output from a draft operation have linear density irregularity. This study is dealing with modeling the dynamics of fiber bundle during roll drafting based on continuity, momentum balance, and a constitutive assumption. The simulation results from this model are compared with experimental results and analyzed by applying the concept of the Describing Function(DF). It can be confirmed that the simulation results agree well with experiments in a steady state, if the model parameters are good adjusted.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1843-1850
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• 2015

Controlling nonlinear systems with linear feedback control methods can lead to chaotic behaviors. Order increase in system dynamics due to integral control and control parameter variations in PID controlled nonlinear systems are studied for possible chaos regions in the closed-loop system dynamics. The Lur’e form of the feedback systems are analyzed with Routh’s stability criterion and describing function analysis for chaos prediction. Several novel chaotic systems are generated from second-order nonlinear systems including the simplest continuous-time chaotic system. Analytical and numerical results are provided to verify the existence of the chaotic dynamics.

• Communications of the Korean Mathematical Society
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• v.10 no.1
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• pp.123-131
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• 1995

The notion of our non-associative algebra is obtained from the Lotka-Volterra system of differential equation describing competitiion between animals or vegetals species and also in the kinetic theory of gasses. For the structure of an algebra, the existence of idempotents is of particular interest. But also from the biological aspect the existence of such elements is of interest because the equilibria of a population which can be described by an algebra correspond to idempotents of this algebra. Thus we present some properties of the general natures for a Lotka-Volterra algebra associated to a weight function and idempotents elements.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.351-354
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• 1989

In a speed_controlled system with cascade control which shows an optimal performance in the linear case, limit cycles can occur due to backlash. The various effects observed can be explained with the aid of the describing function. With a first-order load torque observer these limit cycles can be avoided. Moreover the dynamic performance improves considerably and the range of application of cascade control is extended.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.299-304
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• 1991

A novel approach based on a nonlinear compensator is proposed to prevent 'windup', which is caused by the saturation of the actuator and the integration action of the controller. The anti-windup compensator is located between the conventional linear controller, designed neglecting the saturation, and the actuator. It was proven based on the describing function method that, if the closed loop control systems are stable assuming no saturation, then there exist a range of compensator gain which prevents any limit-cycle and hence, guarantees the system stability. The computer simulation results show that the compensator proposed in the manuscript can eliminate unstable limit cycle and improve the transient response.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.1091-1096
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• 1989

All mechanical systems have saturation nonlinearity in actuators or in final control elements. When controllers have integral action, reset windup can cause instability as well as make the system performance unsatisfactory. In this study, an intelligent limiter which needs no tuning of parameters is tested with the PDF controller used for control of a second order plant. This paper presents analysis of the stability of the system using the describing function method and the Nyquist stability theorem. The improvement of the system performance by the limiter is illustrated by computer simulations.