Regulation of periodic processes

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1973

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Abstract

Previous studies of cyclic process operation have been concerned with the discovery of examples which demonstrate the possible benefits of cyclic operation. In this work, we attack the important problem of regulation of periodic process: How to control a periodic chemical process so that it remains on a desirable dynamic path in the presence of upsets. The first part of this work concentrates on the development of regulating control laws for periodic system described by lumped models. For this purpose the optimal regulating control laws for the classical linear-quadratic problem are modified and extended. This results in two control principles which may be viewed as modern multivariable counterparts of proportional(P) control and proportional-integral(Pl) control. The Continuous Stirred Tank Reactor(CSTR) is used as an illustrative example to test the capabilities of these two control policies. Excellent regulation of the CSTR is achieved with these two control laws when the control adjusts the "programming variable", that is, the original periodic forcing function. However, the Pl-control eliminates some offsets and generates a more stable control than does P-control. The importance of weighting matrices in designing an optimal control system is also considered. The second part of this work concentrates on the development of regulating control laws for periodic distributed, systems. The parametric pumping system is used as an illustrative example to test the capabilities of the control laws developed. After deriving a regulating controller by the Minimum Principle for distributed systems, its implementation is simulated using the orthogonal collocation numerical technique. As in the lumped case, the regulators derived have performed well.

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