Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
권호 표지
DOI QR코드

DOI QR Code

Control Methods for Operation on the Saturation Edge

포화시작점에서의 운전을 위한 제어방법

  • Ahn, Gwang Noh (Department of Chemical Engineering, Kyungpook National University) ;
  • Lim, Sanghun (Department of Chemical Engineering, Kyungpook National University) ;
  • Sung, Su Whan (Department of Chemical Engineering, Kyungpook National University) ;
  • Lee, Jietae (Department of Chemical Engineering, Kyungpook National University)
  • 안광노 (경북대학교 화학공학과) ;
  • 임상훈 (경북대학교 화학공학과) ;
  • 성수환 (경북대학교 화학공학과) ;
  • 이지태 (경북대학교 화학공학과)
  • Received : 2020.03.05
  • Accepted : 2020.03.23
  • Published : 2020.08.01
Download PDF
⟨ Previous Next ⟩

Abstract

For some processes with saturations, economical operating points are on the saturation edges. Traditional feedback controllers cannot be used to regulate such processes on the saturation edges because there are abrupt dynamics changes and no feedback information at saturations. Optimization-based methods such as the model predictive control can treat this control problem without difficulty when the saturation levels and dynamics are known and not varying. Otherwise, an adaptation scheme to track the saturation levels and dynamics should be included. Here, for very simple methods to treat this control problem, two control methods based on the recent slope seeking method and the relay feedback method are proposed. Their performances are evaluated with simulations applying them to a second order liquid level system with saturation. Simulations show that these proposed control methods can find and maintain operating point of the saturation edge under 5% relative error.

몇몇 포화를 갖는 공정에서 경제적인 운전점이 포화시작점에 있게 된다. 고전적인 피드백 제어기는 포화시작점에서 동특성이 급박하게 바뀌고 포화가 된 상태에서는 피드백을 위한 정보가 없기 때문에 사용할 수가 없다. 포화점과 동특성이 알려져 있고 바뀌지 않을 때는 모델예측제어 같은 최적화를 기반으로 하는 방법들이 어려움 없이 이 제어 문제를 처리할 수 있다. 그렇지 않으면, 이 포화점과 등특성을 추적하는 적응 방법이 첨가되어야 한다. 여기서는, 이 제어 문제를 해결할 수 있는 매우 간단한 방법들로서, 최근의 slope seeking method와 relay feedback method에 기반한 두가지 제어 방법을 제안한다. 포화현상을 갖는 이차 액위제어 공정에 적용한 모사를 통하여 그 성능을 검사하였다. 모사결과는 제안하는 본 제어 방법들이 포화시작점을 5% 이내로 찾고 유지하는 것을 보여주고 있다.

Keywords

References

  1. Smith, R., Chemical Process Design and Integration, 2nd ed., Wiley, UK, 2016.
  2. Lee, J. and Kim, D. H., Control of Processes Whose Optimal Operating Conditions are on the Saturation Edge, 2015 AIChE Spring Meeting, April 26-30, Austin, Texas, U.S.A., 2015.
  3. Seborg, D. E., Mellichamp, D. A., Edgar, T. F. and Doyle III, F. J., Process Dynamics and Control, 4th ed. Wiley, New Jersey, 2016.
  4. Lee, J. and Edgar, T. F., "Globally Stable Control Systems for Processes with Input Multiplicities," Korean J. Chem. Eng., 33, 416-422(2016). https://doi.org/10.1007/s11814-015-0153-4
  5. Krstic, M. and Wang, H. H., "Stability of Extremum Seeking Feedback for General Nonlinear Dynamic Systems," Automatica 36, 595-601(2000). https://doi.org/10.1016/S0005-1098(99)00183-1
  6. Tan, Y., Moase, W. H., Manzie, C., Nesic, D. and Mareels, I. M., "Extremum seeking from 1922 to 2010," Proc. 29th Chinese Control Conference, July 29-31, Beijing, China, 2010.
  7. Dochain, D., Perrier, M. and Guay, M., "Extremum Seeking Control and Its Application to Process and Reaction Systems: A Survey," Mathematics and Computers in Simulation 82, 369-380(2011). https://doi.org/10.1016/j.matcom.2010.10.022
  8. Ariyur, K. A. and Krstic, M., "Slope Seeking: a Generalization of Extremum Seeking," Int. J. Adaptive Control and Signal Processing 18, 1-22(2004). https://doi.org/10.1002/acs.777
  9. Astrom, K. J. and Hagglund, T., "Automatic Tuning of Simple Regulators with Specifications on Phase and Amplitude Margins," Automatica 20, 645-651(1984). https://doi.org/10.1016/0005-1098(84)90014-1
  10. Brener, J., Hagglund, T. and Astrom, K. J., "Asymmetric Relay Autotuning - Practical Features for Industrial Use, " Control Engineering Practice 54, 231-245(2016). https://doi.org/10.1016/j.conengprac.2016.05.017
  11. Lee, J., Sung, S. W., Lee, F. Y., Baldea, M. and Edgar, T. F., "Full Closed-Loop Tests for the Relay Feedback Autotuning of Stable, Integrating, and Unstable Processes," ACS Omega 4, 18760-18770(2019). https://doi.org/10.1021/acsomega.9b02732
  12. Lee, H. C. and Kim, D. H., "Kinetics of CO and $H_2$ Oxidation over CuO-$CeO_2$ Catalyst in $H_2$ Mixtures with $CO_2$ and $H_2O$," Catal. Today 132, 109-116(2008). https://doi.org/10.1016/j.cattod.2007.12.028