ROBUST-CONTROL OF UNSTABLE BIOREACTORS

The design of a robust linear controller is proposed for the control o f an unstable bioreactor. The performance of the proposed controller i s compared with that of a Ziegler-Nichols type controller. The robustn ess of the controllers for perturbations in maximum specific growth ra te and yield factor (affecting the process gain and time constant) is evaluated by simulating the non-linear model equations. For uncertaint y in the process parameter values the PI controller gives a sustained oscillation in the servo response, whereas the proposed controller giv es a robust response.