• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.190-196
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• 2020

The step to obtain a process dynamic model through process experiments is very important because it needs times and expenditures. Step response method is one of the standard methods to have long been used for understanding process dynamics, obtaining dynamical models and designing control systems. For the step response, it is usually required to measure process output for a step input change in the open-loop manner. Its disadvantage criticized is the long open-loop operation. For this, a method based on the time-optimal control technique to minimize the test time for obtaining the step response has been recently presented. However, the method requires iterative computations for the minimization of test times. Here, a method where iterative computations are not required is proposed. Simulation results are presented to show that test times to obtain step responses are reduced considerably and an autotuning method based on the proposed method is compared with the relay feedback autotuning method accepted widely for the autotuning of controllers.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.832-835
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• 1997

In this paper, we first analyze the structural limitation of the conventional PID controller in controlling unstable processes through mathematical proof. To overcome this structural limitation, we add an internal feedback loop to the PID controller. Secondly, we obtain conditions when unstable processes can be stabilized by a controller through an analytical analysis. Finally, we propose a simple on-line process identification and autotuning method for unstable processes. Many simulation results show that, in spite of its simplicity, the proposed on-line process identification method provides good accuracy in modeling the unstable process and acceptable robustness to measurement noises and disturbances. Also, the proposed autotuner shows good control performances for both servo and regulatory problems.

• ICROS
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• v.2 no.1
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• pp.72-84
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• 1996

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.12
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• pp.542-548
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• 2002

We consider an unknown linear time invariant plan with static load disturbance. A saturation function nonlinear element is sued to find th one point information in the frequency domain. We analyze an asymmetric self-oscillation caused by static load disturbance with relay feedback and saturation function feedback. We propose a new method to tune a PID controller using a saturation nonlinear feedback element in the presence of asymmetric oscillation. The proposed method does not require the knowledge of plant d.c. gain with an asymmetric oscillation in the plat output.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.257-262
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• 1994

This paper describes an autotuning fuzzy PID controller for a position control of DC serve motor. Because ZNM(Ziegler-Nichols Method) with relay feedback has the difficulty in re-tuning the PID parameters and adaptive method has complex algorithm, a new method to overcome those problems is required. The proposed scheme determines the initial PID gains by using ZNM with relay feedback, and then re-tunes the optimal PID parameters by using fuzzy expert system whenever control conditions are changed. To show the validity of the proposed method, a position control of DC servo motor is illustrated by computer simulation and is experimented by a designed controller.

• 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 IKEEE
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• v.11 no.4
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• pp.193-197
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• 2007

We use a saturation function with memory instead of a pure saturation function to generate a limit cycle in order to find one point information of a plant in the frequency domain. The saturation function with memory is useful in the presence of noise and/or a short duration of short duration of external disturbances. We analyze the error caused by the approximation that the saturation function with memory treated as a pure saturation function. We propose a new tuning formula for PID controller which can be applied a saturation function having memory with an arbitrary memory size. We show that the proposed method is more accurate than that of the approximation method via an example.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.153-153
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• 2000

This paper is focused on the development of a Toolbox to support the design of the PID control]or and to check tile performance of tile controller designed. Although it is common to use the PID controller in the industrial field, any toolbox for the PID controller has not been provided yet, which is the main motivation to research in this paper. At first, the methods of PID autotuning are reviewed, and then contents, structures and how to use of the toolbox developed are explained. In addition, some application simulations of this toolbox are performed to exemplify the performance of the toolbox developed iii this paper.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.102-107
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• 2008

We propose an autotuning algorithm for PI controller with unknown plant. The proposed algorithm uses a saturation function and time delay element as a test signal. Since the integral element of PI controller reduces a phase margin in the closed loop system, the closed loop system could be resulted in unstable with PI controller. To avoid unstable in the closed loop system with PI controller, the proposed algorithm identifies one point information in the 3rd quadrant of Nyquist plot with a time delay element. The proposed method improves an accuracy of one point identified information with one saturation function. We demonstrate a performance of the proposed method via a simulation.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.431-432
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• 2008

플랜트의 정보를 알지 못 하는 경우 시험신호로 포화함수와 시간지연 요소를 이용하여 플랜트의 정보를 찾아내고 찾아낸 정보를 PI 제어기를 설계하는 방법을 제시하였다. 시간 지연요소를 이용함으로서 PI 제어기의 I 요소로부터 발생되는 위상 감소로 인해 발생되는 불안정성이 발생하지 않도록 플랜트의 Nyquist 그림에서 3/4 분면에 있는 한 점의 정보를 찾아내는 것이 가능하였다. 제안된 된 방법은 포화함수의 이용으로 정확성이 높고 한 개의 포화함수만을 이용하여 구조가 간단하다. 또한 모의시험을 통해 제안된 방법의 타당성을 보였다.