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  • Chemical Engineering  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 627-646 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Åström-Hägglund autotuner is extended to multivariable systems. The proposed multivariable automatic tuning performs the identification-design procedure in a sequential manner. Its advantages are discussed, as well as the process characteristics resulted from sequential design. One important feature is that the sequential design often leads to underdamped process characteristics. Given these characteristics, potential problems in the Ziegler-Nichols tuning are discussed and a modification is made. The sequential identification and the modified Ziegler-Nichols controller design method form the basic structure for the multivariable autotuner. The properties of convergence, the implications of tuning sequence, and the indications of undesirable pairing for the autotuner are explored. Consequently, a multivariable autotuning procedure is proposed. Two nonlinear distillation examples and a 3 × 3 linear system are used to illustrate the effectiveness of the autotuner. Simulation results show that good performance can be obtained with minimal engineering effort and the autotuner works well for very difficult processes in a very simple way.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1267-1271 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 617-628 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent advances in knowledge engineering have led to develop the qualitative (deep) model based diagnostic systems. As process knowledge accumulated, however, the diagnostic system remains strictly qualitative. This limits the usefulness of such systems. In this work, a framework is developed for integrating quantitative process knowledge into the qualitative model. Once quantitative process information, e.g., steady-state gains, is available, it can be incorporated into the simplest qualitative process model called the signed directed graph. The quantitative process knowledge is described in terms of membership functions of fuzzy set theory. According to the measurement pattern, the truth values of a hypothesis (e.g., a fault origin) can be calculated based on the fuzzy logic. Consequently, the diagnostic resolution can be improved significantly. Furthermore, the proposed method becomes a strictly qualitative diagnostic system, if no quantitative information is available. A chemical reactor example illustrates the design and performance of the qualitative/quantitative model-based diagnostic system. The proposed approach can also be extended to the multiple-fault situations in a straightforward manner.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 521-534 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Disturbance rejection capabilities of different controller structures, for example, diagonal, block diagonal or full multivariable controller, are discussed. A generalized version of Relative Disturbance Gain, Generalized Relative Disturbance Gain (GRDG), is defined to evaluate the disturbance rejection capabilities of all possible controller structures. Furthermore, the relative disturbance gain array (RDGA) is introduced. Basic properties of RDGA are derived. An important one is: GRDG of all possible controller structures can be calculated directly from the array. Therefore, with RDGA, the synthesis of the controller structure can be done in a straightforward manner. Physical implications and quantitative analyses of GRDG are given. These form the basis for the synthesis. Finally, frequency-dependent GRDG is developed which evaluates the performance further based on dynamic information. Several examples are used to illustrate the synthesis of the controller structure. The results show that better disturbance rejection can be achieved by selecting appropriate controller structure.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1174-1180 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1833-1838 
    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 approach is presented to overcome load disturbance problems. Based on the parallel cascade control structure, the primary controller is designed for the servo response, and the secondary controller is designed for the disturbance-rejection purpose. A perfect disturbance-rejection controller is derived for the secondary loop. Simulation studies show that improvement in load responses can be achieved for some cases. However, for some other cases, parallel cascade control simply worsens the load responses as a result of interaction between primary and secondary loops. A new interaction measure for load disturbance (γ) is proposed to determine whether improved load responses is achievable using cascade control structure. More importantly, the interaction measure also quantifies the margin of improvement that can be achieved over conventional single-loop control. A design procedure for improved load responses was proposed. The simulation results show that the new approach offers a simple and effective alternative for disturbance-rejection.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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