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Extremum seeking control using a partial sum of input-output product
Jietae Lee,Kwang Soon Lee 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.11
Recent extremum seeking control that uses a continuous perturbation and the integral feedback of perturbation- output product is based on a static nonlinear process. The method can be applied to dynamic nonlinear processes for tracking and maintaining the optimal operating points. It has several tuning parameters, such as the integral controller gain and the magnitude and frequency of the continuous perturbation signal. The frequency of the continuous perturbation signal should be low enough to ensure the time-scale separation between the real-time optimization and the process dynamics for the closed-loop stability. However, for some processes, fast perturbations are preferred because they can be attenuated easily in subsequent processes such as buffers and storages. For this, we propose an extremum seeking control method where the partial sum of perturbation-output product is used for a faster squarewave perturbation. Simulations for two processes of parallel competing reactions have been given, and a simple liquid level system to test extremum seeking control methods is suggested.
Pulse Relay Method for Identification of Ultimate Data from Noisy Responses
Jietae Lee,Whan Sung 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
To avoid chattering of the original relay, a relay with hysteresis is used. However, its switching time fluctuates and average switching period is not the ultimate period. Here, by using the integral of the process output and a pulse relay producing a pulse output instead of the square output, a method to identify the ultimate data of process from noisy responses is proposed.
Simple High-order Approximations for Unsteady-state Diffusion, Adsorption and Reaction in Catalyst
Jietae Lee,Dong Hyun Kim 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
For unsteady-state diffusion, adsorption and a first-order reaction in a slab, cylinder and sphere catalyst, high-order approximations are developed. A continued fraction is developed as a function of the shape factor and the Thiele modulus in Laplace domain to unify the exact transfer functions of the three catalyst geometries. Inversion of the continued fraction to the time domain results in the approximation, the accuracy of which depends on the order of approximation and improves very quickly with each increment in the order. Construction of the proposed time-domain approximation is easy and systematic for any approximation order.
A Simple Method to Make the Quadruple Tank System Near Linear
( Jietae Lee ),( Inhyun Kyoung ),( Jea Pil Heo ),( Youngsu Park ),( Yugyeong Lim ),( Dong Hyun Kim ),( Yongjeh Lee ),( Dae Ryook Yang ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.6
Quadruple tank liquid level systems are popular in testing multivariable control systems for multivariable processes with positive or negative zeros. The liquid level system is nonlinear and it will help to illustrate the robustness of control systems. However, due to nonlinearity, it can be cumbersome to obtain process parameters for testing linear control systems. Perturbation sizes are limited for valid linearized process models, requiring level sensors with high pre-cision. A simple method where the outlet orifice is replaced to a long tube is proposed here. The effluent flow rate becomes proportional to the liquid level due to the friction loss of long tube and the liquid level system shows near lin-ear dynamics. It is applied to the quadruple tank system for easier experiments.
Global Approximation of Unsteady-State Diffusion and Reaction in Slab, Cylinder and Sphere Catalysts
Jietae Lee 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
For unsteady-state diffusion, adsorption and a first-order reaction in a slab, cylinder and sphere catalyst, high-order approximations in the form of coupled ordinary differential equations are developed to substitute the exact partial differential equations. An infinite continued fraction is developed, which unifies the exact transfer functions of the three geometries as a function of the shape factor and the Thiele modulus in the Laplace domain. The time-domain approximations are obtained from the truncated continued fractions. The coefficients in the time-domain approximations are very easy to determine, and increasing the order of approximation is simple and straightforward.