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

HERNÁN DE BATTISTA; MARTÍN JAMILIS; FABRICIO GARELLI; JESÚS PICÓ

AUTOMATICA

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2018 vol. 89 p. 340 - 348

0005-1098

Fast, robust and reliable control laws are essential to improveperformance of bioprocesses at both industrial and lab scale. This workrevisits the dynamic behaviour of stirred continuous bioreactors inwhich one substrate limits the growth. Conditions on the feedingstrategy to avoid washing out the reactor and falling in batchoperation are obtained. These conditions derive in a closed positivelyinvariant region including the desired operating point. It is statedthat no closed orbits may exist in this region and, furthermore, thatno fixed point exists but on one of its borders. Therefore, globalstability is achieved by finding a feeding law that fulfills theaforementioned invariant conditions and gives a single equilibrium fora first-order dynamics. These results are useful to determine thestability properties of different control laws and, more importantly,to design new ones. Differing from previous results, the mainadvantages of the proposed approach are that it does not rely onLyapunov functions nor system linearisation, and that input saturationdoes not affect stability results. The potentiality of the developedtools is illustrated by means of classical and novel feeding laws.