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Indexed by:期刊论文

Date of Publication:2013-10-01

Journal:PACIFIC JOURNAL OF OPTIMIZATION

Included Journals:SCIE

Volume:9

Issue:4,SI

Page Number:595-612

ISSN No.:1348-9151

Key Words:nonlinear time-delay system; constrained optimal control; control parametrization; improved differential evolution; fed-batch fermentation

Abstract:The main control goal in fed-batch fermentation is to maximize yield of target product and reduce operation costs. In this paper, we propose a controlled nonlinear time-delay system, in which the flow rate of glycerol is taken as the control function and the terminal time of the fermentation as the optimization variable, to model the 1,3-propanediol (1,3-PD) production in fed-batch process. Taking the mass of 1,3-PD per unit time as the performance index, we formulate a constrained optimal control model with free terminal time to optimize the production process. Using a time-scale transformation, the optimal control problem is equivalently transcribed into the one with fixed terminal time. A computational approach is then developed to seek the optimal control and the optimal terminal time. This method is based on the control parametrization in conjunction with an improved differential evolution algorithm. Numerical results show that the mass of 1,3-PD per unit time is increased considerably and the duration of the fermentation is shorted greatly compared with previous results.