A Gain-Scheduling Approach for Control of Dissolved Oxygen in Stirred Bioreactors

Abstract

This paper discusses control of dissolved oxygen in a bioreactor when the stirrer speed is used as control signal. During batch and fed-batch cultivations the operating conditions change significantly which causes tuning problems, especially when performance requirements are high. A linearized process model reveals that the variations in the oxygen dynamics are mainly due to changes in the volumetric oxygen transfer coefficient KLa. To account for the process variations, a control strategy based on PID control and gain scheduling from the stirrer speed is suggested. Controller parameters in different operating regions are obtained using auto-tuning experiments. The approach is easy to implement and does not require any exhaust-gas analysis. Experimental results from a laboratory reactor are presented.