Global stabilisation of continuous bioreactors: tools for analysis and design of feeding laws

TitleGlobal stabilisation of continuous bioreactors: tools for analysis and design of feeding laws
Publication TypeJournal Article
Year of Publication2017
AuthorsDe Battista H, Jamilis M, Garelli F, Picó J
JournalAutomatica
Abstract

Fast, robust and reliable control laws are essential to improve performance of bioprocesses at both industrial and lab scale. This work revisits the dynamic behaviour of stirred continuous bioreactors in which one substrate limits the growth. Conditions on the feeding strategy to avoid washing out the reactor and falling in batch operation are obtained. These conditions derive in a closed positively invariant region including the desired operating point. It is stated that no closed orbits may exist in this region and, furthermore, that no fixed point exists but on one of its borders. Therefore, global stability is achieved by finding a feeding law that fulfills the aforementioned invariant conditions and gives a single equilibrium for a first-order dynamics. These results are useful to determine the stability properties of different control laws and, more importantly, to design new ones. Differing from previous results, the main advantages of the proposed approach are that it does not rely on Lyapunov functions nor system linearisation, and that input saturation does not affect stability results. The potentiality of the developed tools is illustrated by means of classical and novel feeding laws.