This thesis concerns the controllability of fermentation processes. Fermentation
processes are often described by unstructured process models. A control system can
be used to reduce the effect of the uncertainties and disturbances.
A process is called controllable if a control system satisfying suitably defined control
objectives can be found. Controllability measures based on linear process models are
identified. The idealised control objective for perfect control allows fast evaluation
of the controllability measures. These measures are applied to compare different
designs of a continuous fermentation process by identifying the controllability properties
of the process design.
The operational mode of fed batch fermentations is inherently dynamic. General
control system design methods are not readily applicable to such systems. This work
presents an approach for the design of robust controllers suitable for these processes.
The control objective is to satisfy a set of robustness constraints for a given set of
model uncertainties and disturbances.
The optimal operation and design problems are combined into a single optimal control
problem. The controller design is integrated into the process design problem
formulation. In this way the control system and the process are designed simultaneously.
Different problem formulations are investigated. The proposed approach is
demonstrated on complex fermentation models. The resulting operating strategies
are controllable with respect to the aims of control
