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  • 1
    Electronic Resource
    Electronic Resource
    New approach to constrained predictive control with simultaneous model identification (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2857-2868 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new framework to closed-loop process identification is proposed. It relies on simultaneous constrained model predictive control (MPC) and identification (MPCI). MPCI obtains sufficient model information on a process under constrained MPC, while minimally disturbing that process. To select a process input at each time step, MPCI solves a constrained optimization problem on-line with respect to process input values over a finite moving horizon. These process inputs should satisfy all conventional MPC constraints, as well as additional constraints that assure persistent excitation of the process by these inputs. The persistent excitation constraints can be enabled or disabled, according to process identification needs of the closed loop. An iterative scheme is proposed for the numerical solution of the on-line optimization problem. At each iteration, that iterative scheme finds a suboptimal feasible solution of the on-line optimization problem by solving a semidefinite programming problem whose global convergence is guaranteed. The effectiveness of the proposed new methodology is illustrated through simulations on a linear time-varying process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690421015
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  • 2
    Electronic Resource
    Electronic Resource
    Design of robust nonsquare constrained model-predictive control (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2582-2593 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model-predictive control (MPC) design methodology for processes with more manipulated inputs than outputs is developed. Essential features of the proposed approach are the following: the on-line optimization minimizes an objective function based on the l2 norm; an end-condition equation is utilized; model uncertainty is considered as upper and lower bounds on the pulse-response-model coefficients; hard constraints on the input and move-size variables and soft constraints on the output variables are posed. A major difference between square and nonsquare MPC is that in the former the end-condition can be used directly, while in the latter a nonlinear programming problem needs to be solved during the design phase to select values for the input move suppression coefficients. This technique is illustrated through a number of simulations and application to a real industrial process.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420919
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  • 3
    Electronic Resource
    Electronic Resource
    Performance bounds for robust quadratic dynamic matrix control with end condition (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2083-2097 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sufficient conditions for robust stability of multivariable quadratic dynamic matrix controllers with an end condition (EQDMC) are developed, and the effect of these conditions on closed-loop performance is examined. Hard and soft constraints on process inputs and outputs, and process modeling uncertainty are present Modeling uncertainty is quantified in the time domain as upper and lower bounds on the coefficients of a finite pulse response process model. The robust stability conditions that we develop involve the prediction and control horizon lengths, and a set of inequalities that the move-suppression coefficients in the on-line EQDMC objective function must satisfy. These conditions imply that for processes with modeling uncertainty, the move-suppression coefficients could be quite large and quite sensitive to the control horizon length and process modeling errors. This could make the EQDMC controller conservative, thus significantly deteriorating performance. To determine the optimal control horizon length corresponding to the best robust performance of the EQDMC controller for a class of disturbances, follow the proposed EQDMC controller design methodolo∼. To illustrate this methodology simulations on an SISO example and a 2 × 2 subsystem of the Shell Standard Control Problem are presented.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410908
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  • 4
    Electronic Resource
    Electronic Resource
    Design of robust constrained model-predictive controllers with volterra series (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2098-2107 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sufficient conditions are developed in this work for robust stability and pefformance of nonlinear model-predictive control systems that use an end-condition and second-order Volterra model with parametric uncertainty in the time domain. The robust stabilfly conditions involve the lengths of the prediction and control horizons, as well as the coefficients of the control move suppression terms in the on-line objective function. These conditions may be used for both analysis and synthesis purposes. A case study of a chemical reactor is presented to elucidate these issues.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410909
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  • 5
    Electronic Resource
    Electronic Resource
    Constrained MPCI: A weak persistent excitation approach (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2279-2288 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Model-predictive control and identification (MPCI) introduced by Genceli and Nikolaou in 1996 is a novel approach to the identification of processes under constrained model-predictive control. MPCI solves an on-line optimization problem that involves (a) a standard MPC objective; (b) standard MPC constraints; and (c) persistent excitation (PE) constraints. The on-line optimization problem is computationally demanding. To alleviate that problem, we take a frequency-domain approach to formulating the PE constraints. This approach relies on the following fact: a signal is persistently exciting of order n, if its two-sided power spectrum is nonzero at no fewer than n points. Therefore, persistently exciting input signals can be parametrized over a finite horizon as a sum of sinusoid terms with nonzero coefficients. Used in the MPCI framework, the last requirement generates a set of completely decoupled reverse-convex constraints that are combinatorially tractable from a computational point of view. The effectiveness of the proposed MPCI method is demonstrated through simulations. For the SISO systems studied, computation of the global optimum could be handled combinatorially in real-time using PC hardware.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430913
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  • 6
    Electronic Resource
    Electronic Resource
    New copolyamides based on adipic acid, aliphatic diamines and amino acids: Synthesis, characterization and biodegradability, 5Part 4: cf. ref. 59 (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 1129-1151 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel series of biodegradable copolyamides were synthesized via melt copolymerization. The statistical copolymides were produced by reaction of the salt of adipic acid (AA) and bis(para-aminocyclohexyl)methane (PACM) or isophoronediamine (IPD)/α-amino acids at 250°C. Elemental analyses, density, viscosity, differential thermal analysis (DTA) and gelpermeation chromatography (GPC) measurements and FT-IR spectroscopy were employed for the characterization of these copolyamides. The semicrystalline (AA/PACM/α-amino acids) or amorphous (AA/IPD/α-amino acids) nature of these copolyamides was shown with DTA and wide angle X-ray diffraction patterns. Several methods were used in order to investigate and assess their biodegradability such as alkaline hydrolysis (10% w/v NaOH, 80°C), burial in soil (microbial and bacterial attack) and enzymatic hydrolysis (α-trypsin and α-chymotrypsin). The degradation of the copolyamides was evaluated with the aid of GPC and DTA measurements and correlated to the α-amino acid content. These copolyamides could eventually find applications in the field of food packaging and agriculture (disposable plastics) and medicine (sutures).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1995.021960414
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