• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1198-1205
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• 2000

A two-degrees-of-freedom servosystem for step-type reference signals has been preposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. this paper considers robust stability of the servosystem incorporating an observer against both structured and unstructured uncertainties of the plant. A condition is obtained as a linear matrix inequality, under which the servosystem is robustly stable independently of the gain of the integral compensator. This result implies that we can tune the gain to achieve a desirable transient response of the servpsystem preserving robust stability. An example is presented to demonstrate that under the robust stability condition, the transient response can be improved by increasing the gain of the integral compensator.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.112-115
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• 1999

A new method to solve a Lyapunov equation for a discrete delay system is proposed. Using this method, a Lyapunov equation can be solved from a simple linear equation and N-th power of a constant matrix, where N is the state delay. Combining a Lyapunov equation and frequency domain stability, a new stability condition is proposed. The proposed stability condition ensures stability of a discrete state delay system whose state delay is not exactly known but only known to lie in a certain interval.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.1-8
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• 1997

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, if the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers robust stability of this 2DOF servosystem incorporating an observer to the structured and unstructured uncertainties of the controlled plant. A robust stability condition is obtained using Riccati inequality, which is written in a linear matrix inequality (LMI) and independent of the gain of the integral compensator. This result impies that if the plant uncertainty is in the allowable set defined by the LMI condition, a high-gain integral compensation can be carried preserving robust stability to accelerate the tracking response.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.3
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• pp.187-191
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• 2007

We analyze the stability property of a class of nonlinear time-delay systems. We show that the state variable is bounded both below and above, and the lower and upper bounds of the state are obtained in terms of a system parameter by using the comparison lemma. We establish a time-delay independent sufficient condition for the global asymptotic stability by employing a Lyapunov-Krasovskii functional obtained from a change of the state variable. The simulation results illustrate the validity of the sufficient condition for the global asymptotic stability.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.125-125
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• 1996

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers robust stability of this 2DOF servosystem to the unstructured uncertainty of the controlled plant. A robust stability condition is obtained using Riccati inequality, which is independent of the gain of the integral compensator. An example is presented, which demonstrates that the tracking response of the 2DOF servosystem with uncertainty becomes faster when the integral gain made larger under the robust stability condition.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.57-62
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• 1996

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers robust stability of this 2DOF servosystem to the unstructured uncertainty of the controlled plant. A robust stability condition is obtained using Riccati inequality, which is independent of the gain of the integral compensator. An example is presented, which demonstrates that the tracking response of the 2DOF servosystem with uncertainty becomes faster when the integral gain made larger under the robust stability condition.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.4
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• pp.1-6
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• 2010

In this paper, we present a new delay-dependent and parameter-dependent robust stability condition for uncertain singular systems with polytopic parameter uncertainties and time-varying delay. The robust stability criterions based on parameter-dependent Lyapunov function are expressed as LMI (linear matrix inequality). Moreover, the proposed robust stability condition is a general algorithm for both singular systems and non-singular systems. Finally, numerical examples are presented to illustrate the feasibility and less conservativeness of the proposed method.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.470-477
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• 2000

The states of control loops in existing actual systems are changed according to time varying conditions of controllest process and other system components. Adjusting control parameters properly at site which is performed generally by Ziegler & Nichols mthod is important for safe and efficient operation, but the method may require much time to adjust and not easy to inexperienced engineers. This study is aimed to propose more handy method to adjust control parameters by plotting operating conditions on the space of adjusting parameters. One loop of model control system without perturbation condition has been adopted and its stability limit was plotted on the coordinates of Gain and Integral time which was acquired after analyzing Nyquist diagrams and time domain responses. The result showed that the sets of adjusting parameters according to critical stability and proper stability could be acquired reasonably through both responses and the curves on parameter space revealed available patterns for the purpose of easy maintenance of control characteristics.

• Journal of the Korean Society of Combustion
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• v.10 no.4
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• pp.10-17
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• 2005

Sustaining of flame stability of the burner installed in Dielsel exhaust pipe is very difficult because of steep fluctuation of pressure and flow rate. A burner for DPF (Diesel Particulate Filter) which clogged by collected soot regeneration has been made of metal fiber for the purpose of realization of flame stability even in unfavorable condition of Diesel engine exhaust. Flame stability of the metal fiber burner has been investigated in various condition of engine operation. It has been identified that metal fiber burner with liner which has swirl guide vane presents excellent flame stability even in the higher engine revolutions than 3000rpm and sudden variation. The results offer the possibility of development of full flow burner system for DPF regeneration.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.1-9
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• 2018

All ships should ensure stability in accordance with IMO regulations. However, GM is only used to determine ship stability because it takes a lot of time to validate all regulations. This is a problem given that the safety of vessels cannot be guaranteed, potentially leading to accidents. There is a need for a more intuitive and comprehensive method of confirming the stability of ships. This study developed a stability index that expresses ship stability in one value. An index equation is defined based on the 6 stability criteria for ships prescribed by IMO and the result of calculating the ship stability of a model ship. A stability index has been derived for each loading condition by applying the index equation to the same ship. It can clearly be seen that this stability index appropriately explains the criteria. In other words, it is possible to assess ship stability with one value and confirm whether the ship stability satisfies IMO regulations. This index will help masters and officers more easily and accurately check ship stability.