摘要:

AbstractRecursive Least Squares (RLS) is the most popular parametric identification method used for on‐line process model estimation and self‐tuning control. The basic least squares scheme is outlined in this paper and its lack of ability to track changing process parameters is illustrated and explained. Several variants of the basic algorithm which have appeared elsewhere in the literature are discussed. Some of these algorithms contain different modifications to the basic scheme which are intended to prevent this loss of alertness to changing process parameters. Other variations of the least squares algorithm are presented which attempt to deal with parameter estimation in the presence of disturbances and unmodelled process dynam

ISSN:0008-4034    

DOI:10.1002/cjce.5450690111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe adaptive Generalized Predictive Controller (Clarke et al., 1987a, b) is capable of controlling plants with variable dead‐time, unknown model orders and unstable poles and zeros. This paper shows how the GPC control law can be written in an equivalent general linear transfer function form which simplifies closed‐loop (eg. root locus) analysis. Three recommended strategies for selecting the design parameters during the commissioning stage allow the user to adjust the closed‐loop speed of response on‐line using only a single active tuning parameter. Experimental runs confirm the ability of adaptive GPC to provide a consistent closed‐loop response in spite of large proces

ISSN:0008-4034    

DOI:10.1002/cjce.5450690112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper investigates the development and industrial application of a multi‐input/single‐output adaptive‐predictive Kamyr digester chip level controller based on Generalized Predictive Control (GPC). The controller simultaneously manipulates the blow flow and the chip meter to control the chip level. The chip meter is manipulated in a way which tends to maintain the desired production rate, while still leaving some room for control. The idea was to use the chip meter as a second input variable to reduce blow flow manipulation and, thereby, reduce disruptions to the chip column movement. The two‐input strategy decreased blow flow manipulation by more than 50% (compared to an otherwise equivalent one‐input scheme) without sacrificing output performance. However, the anticipated improvements in permanganate‐number variability were not achieved. The multi‐input strategy was discontinued after six months

ISSN:0008-4034    

DOI:10.1002/cjce.5450690113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper examines the application of generalized predictive control (GPC), one in the class of long‐range predictive algorithms, to the control of conversion of methyl methacrylate (MMA) monomer in a simulated CSTR, and to the control of temperature in a pilot plant batch polymer reactor. The control objective is regulation in the presence of (i) stochastic disturbances due to impurities (in the case of the CSTR), and (ii) pulse disturbances from the addition of cold solvent and initiator (in the case of the batch reactor). The role of the observer polynomial as a detuning parameter for trading off performance against variability in the control action is emphasized. Also, the role of data prefiltering, prior to model parameter estimation, is examined. A frequency domain interpretation of the least squares estimation algorithm is used to clarify the role of the filte

ISSN:0008-4034    

DOI:10.1002/cjce.5450690114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe acceptance of CFB combustion in process and utility industries for generating steam has been increasing because of its ability to burn a wide variety of fuels efficiently and in an environmentally acceptable manner. Work on control of this emerging technology is beginning to appear. This paper evaluates the performance of two predictive control algorithms (the Dynamic Matrix Control and a simplified version) for control of temperature and pressure drop in a pilot scale CFB combustor. The robustness of the algorithms is studied on a model of the CFB combustor. The experimental and simulation results show the suitability of the two control algorithms for control of the CFB combustor.

ISSN:0008-4034    

DOI:10.1002/cjce.5450690115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA nonlinear predictive control (NLPC) strategy based on a nonlinear, lumped parameter model of the process is developed in this paper. A constrained optimization approach is used to estimate unmeasured state variables and load disturbances. Additional model/process mismatch is handled by using an additive output term which is equivalent to the Internal Model Control approach. Similar to linear predictive control methods, an optimal sequence of future control moves is determined in order to minimize an objective function based on a desired output trajectory, subject to manipulated variable constraints (absolute and velocity).Deadtime is explicitly included in the model formulation, giving NLPC the same deadtime compensation feature of linear model‐predictive techniques. The multi‐rate sampling nature of most chemical processes is also used to improve estimates of process disturbances. Infrequent composition measurements in conjunction with frequent temperature measurements are used to improve the “inferential” control of the composition in a continuous flow stirred tank reactor

ISSN:0008-4034    

DOI:10.1002/cjce.5450690116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe choice of the final time,tj, in the optimal control of nonlinear systems is shown to be very important. By choosingtfto be small, and repeatedly optimizing the system operation over the short time intervals gives a highly oscillatory type of control for a particular nonlinear chemical reactor. The cumulative profit as compared to that obtained by choosingtfto be large, is substantially lower. In the operation of a batch reactor it is shown that iftfis small, bang‐bang control with singular sub‐arcs results. Whentfis large, the optimal control policy tends to be relatively smooth and the profitability is substantially impro

ISSN:0008-4034    

DOI:10.1002/cjce.5450690117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper addresses the problem of finding optimal operational policies for an acetylene reactor for day to day operation. A lumped parameter model based on four main reactions is developed and used to examine the effects of the reactor manipulated variables on key reaction parameters. An optimal and a sub‐optimal operational policy which minimize the ethylene loss over time are formulated and the solution techniques are presented. The results indicate that the reactor model is in good agreement with industrial plant data. The performance of the optimal control policy is very similar to the performance of the sub‐optimal control policy. However, the sub‐optimal formulation, while retaining the dominant features of the optimal response, reduces the computational requirements. Finally, some issues concerning the real‐time implementation of an advanced acetylene reactor control scheme are presented. These include the estimation of the optimum regeneration cycle, a recursive model update algorithm, the process optimizer and their overall coordination. A preliminary analysis of the benefits associated with the advanced control scheme suggests a considerable reduction in the yearly ethyle

ISSN:0008-4034    

DOI:10.1002/cjce.5450690118

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractControl of crystal size distribution (CSD) in a 21.8 L continuous cooling KCl crystallizer was attempted. Feed saturated at 54°C with potash, nearly saturated with NaCl and containing 0.75 g MgSO4/100 g of H2O was cooled to the crystallizer temperature at 40°C. The control scheme consisted of a proportional‐integral controller with the rate of fines dissolution/removal as the input variable and the fines suspension density (crystals smaller than 150 μm) as the output variable. The measured/controlled variable was a temperature difference, ΔT, corresponding to the temperature of a slurry sample containing representative fines, before and after the fines were dissolved by heating. An increase in the product weight‐mean crystal size and a decrease in the coefficient of variation of product were observed in the controll

ISSN:0008-4034    

DOI:10.1002/cjce.5450690119

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA model for predicting head losses for coarse‐particle or settling slurries has been obtained. Experimental data for isothermal flows of sand, gravel and coarse coal slurries in pipes of industrial scale have been used to obtain the correlations in the model.The model differs from previous versions in the way it deals with the concentration of the lower layer and in the role ascribed to the finest (–74 μm) particles. The fraction of contact load, which contributes sliding friction at the pipe wall, is found to be primarily a function of the ratio of the mean flow velocity to the settling velocity of the mass median particle size in the (+74 μm) fraction. The correlations are restricted to mixtures containing less than 35% (+ 74 μm) particles by

ISSN:0008-4034    

DOI:10.1002/cjce.5450690120

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY