• Title, Summary, Keyword: chemical control

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Advances in Chemical Process Control and Operation -A view experienced in joint university-industry projects

  • Ohshima, Masahiro
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1.2-6
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    • 1994
  • A state or the arts in Japanese chemical process control is reviewed based on experience in applying advanced process control schemes to several industrial chemical processes. The applications validate model predictive control (MPC), the most popular advanced control scheme in the process control community, as, indeed, a powerful and practical control algorithm. However, at the same time, it is elucidated that MPC can solve only the control algorithm part of the problem and one needs chemical and systems engineering aspects to solve the entire problem. By illustrating several industrial process control problems, the need for chemical engineering aspects as well as the future direction for process control are addressed, especially in light or current attitudes toward product quality.

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Dynamic matrix control applied on propane-mixed refrigerant liquefaction process

  • Shin, Hyunjun;Lim, Yu Kyung;Oh, Se-Kyu;Lee, Seok Goo;Lee, Jong Min
    • The Korean Journal of Chemical Engineering
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    • v.34 no.2
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    • pp.287-297
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    • 2017
  • This study proposes a dynamic matrix control strategy that produces control input sequences which are more robust and reduce power consumption than conventional proportional-integral (PI) controllers when applied to the C3MR liquefaction process. First, a rigorous process dynamic model was constructed in Aspen HYSYS Dynamics 7.3 and MATLAB 2014a which calculates dynamic responses for two different scenarios of unmeasured step disturbances increasing the load of liquefaction energy. Then, a DMC module including the manipulation of the compressor speed was formulated. The simulations using the proposed DMC module demonstrate that the multivariable optimal control increases the energy efficiency and robustness of a complex liquefaction cycle process.

Property Control in a Continuous MMA Polymerization Reactor using EKF based Nonlinear Model Predictive Controller

  • Ahn, Sung-Mo;Park, Myung-June;Rhee, Hyun-Ku
    • 제어로봇시스템학회:학술대회논문집
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    • pp.468-473
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    • 1998
  • A mathematical model was developed for a continuous re-actor in which free radical polymerization of methyl methacrylate (MMA) occurred. Elementary reactions considered in this study were initiation, propagation, termination, and chain transfers to monomer and solvent. The reactor model took into account the density change of the reactor contents and the gel effect. A control system was designed for a continuous reactor using extended Kalman filter (EKF) based non-linear model predictive controller (NLMPC) to control the conversion and the weight average molecular weight of the polymer product. Control input variables were the jacket inlet temperature and the feed flow rate. For the purpose of validation of the control strategy, on-line digital control experiments were conducted with densitometer and viscometer for the measurement of the polymer properties. Despite the com-plex and nonlinear features of the polymerization reaction system, the EKF based NLMPC performed quite satisfactorily for the property control of the continuous polymerization reactor.

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Control of chaos in nonlinear chemical reactor

  • Lee, Joon-Suh;Yang, Dae-Ryook;Lee, In-Beum;Chang, Kun-Soo
    • 제어로봇시스템학회:학술대회논문집
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    • pp.48-53
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    • 1993
  • In this paper, it is shown that chaotic nonlinear chemical process can be controlled based on the Poincare map based control algorithm. An isothermal autocatalytic CSTR, which has chaotic dynamics, is successfully controlled and period 2 orbit is generated in a normal chaotic region with small perturbation of the control parameter.

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Analytical design of constraint handling optimal two parameter internal model control for dead-time processes

  • Tchamna, Rodrigue;Qyyum, Muhammad Abdul;Zahoor, Muhammad;Kamga, Camille;Kwok, Ezra;Lee, Moonyong
    • The Korean Journal of Chemical Engineering
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    • v.36 no.3
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    • pp.356-367
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    • 2019
  • This work presents an advanced and systematic approach to analytically design the optimal parameters of a two parameter second-order internal model control (IMC) filter that satisfies operational constraints on the output process, the manipulated variable as well as rate of change of the manipulated variable, for a first-order plus dead time (FOPDT) process. The IMC parameters are designed to minimize a control objective function composed of the weighted sum of the error between the process variable and the set point, and the rate of change of the manipulated variable, and to satisfy the desired constraints. The feasible region of the constrained IMC control parameters was graphically analyzed, as the process parameters and the constraints varied. The resulting constrained IMC control parameters were also used to find the corresponding industrial proportional-integral controller parameters of a Smith predictor structure.

Nonlinear Model Predictive Control Using a Wiener model in a Continuous Polymerization Reactor

  • Jeong, Boong-Goon;Yoo, Kee-Youn;Rhee, Hyun-Ku
    • 제어로봇시스템학회:학술대회논문집
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    • pp.49-52
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    • 1999
  • A subspace-based identification method of the Wiener model, consisting of a state-space linear block and a polynomial static nonlinearity at the output, is used to retrieve from discrete sample data the accurate information about the nonlinear dynamics. Wiener model may be incorporated into model predictive control (MPC) schemes in a unique way which effectively removes the nonlinearity from the control problem, preserving many of the favorable properties of linear MPC. The control performance is evaluated with simulation studies where the original first-principles model for a continuous MMA polymerization reactor is used as the true process while the identified Wiener model is used for the control purpose. On the basis of the simulation results, it is demonstrated that, despite the existence of unmeasured disturbance, the controller performed quite satisfactorily for the control of polymer qualities with constraints.

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Development of Multi-Chemical Supply System for Semiconductor Wafer Cleaning Station

  • Chung, Myung-Jin;Song, Young-Wook
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1309-1312
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    • 2005
  • A multi-chemical supply system is developed and applied to a wet station, which uses the multi-chemical process in one bath. To control the concentration of two chemicals, control logic of a supply pump is programmed using the programable logic controller (PLC). By using the multi-chemical supply system, wet station with single bath is applied to cleaning process using multi chemicals such as buffed oxide etchant (BOE) and standard clean 1 (SC-1). The concentration of each chemical is measured in the bath to verify the multi-chemical supply system. The control range in the each chemical concentration is measured to 1.33weight% in NH4OH and 0.23weight% in H2O2. The multi-chemical supply system can be movable and usable as an independent module of fixed wet station. By simply midifying the PLC, a multi-chemical supply system can be developed for a wet station.

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Optimal Learning Control Combined with Quality Inferential Control for Batch and Semi-batch Processes

  • Chin, In-Sik;Lee, Kwang-Soon;Park, Jinhoon;Lee, Jay H.
    • 제어로봇시스템학회:학술대회논문집
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    • pp.57-60
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    • 1999
  • An optimal control technique designed for simultaneous tracking and quality control for batch processes. The proposed technique is designed by transforming quadratic-criterion based iterative learning control(Q-ILC) into linear quadratic control problem. For real-time quality inferential control, the quality is modeled by linear combination of control input around target qualify and then the relationship between quality and control input can be transformed into time-varying linear state space model. With this state space model, the real-time quality inferential control can be incorporated to LQ control Problem. As a consequence, both the quality variable as well as other controlled variables can progressively reduce their control error as the batch number increases while rejecting real-time disturbances, and finally reach the best achievable states dictated by a quadratic criterion even in case that there is significant model error Also the computational burden is much reduced since the most computation is calculated in off-line. The Proposed control technique is applied to a semi-batch reactor model where series-parallelreactions take place.

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Application of sucessive quadratic programming to chemical process control

  • Cho, In-Ho;Yoon, En-Sup
    • 제어로봇시스템학회:학술대회논문집
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    • pp.879-884
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    • 1988
  • For more economical operation of chemical plants, optimal operating conditions are to be set and maintained as far as possible. For this purpose, optimizing control is applied to chemical plants. In this study, a process optimizer composed of a process simulator and an optimization routine using Successive Quadratic Programming as optimization technique is developed and the effect of optimizing control is tested on an example process, and a new process optimization strategy based on modified Jacobian matrix is developed.

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A fuzzy dynamic learning controller for chemical process control

  • Song, Jeong-Jun;Park, Sun-Won
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1950-1955
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    • 1991
  • A fuzzy dynamic learning controller is proposed and applied to control of time delayed, non-linear and unstable chemical processes. The proposed fuzzy dynamic learning controller can self-adjust its fuzzy control rules using the external dynamic information from the process during on-line control and it can create th,, new fuzzy control rules autonomously using its learning capability from past control trends. The proposed controller shows better performance than the conventional fuzzy logic controller and the fuzzy self organizing controller.

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