Indian Journal of Science and Technology

Abstract

Objectives: To simulate the steady-state multiplicity behaviour exhibited by a continuous bioreactor following substrate inhibition kinetics and design an efficient control scheme corresponding to its unstable (optimum) operating condition. Methods/Statistical Analysis: A rigorous first principles based nonlinear model of continuous bioreactor following substrate inhibition kinetics is presented. IMC PID controller has been designed at the unstable steady-state (optimum) operating point to control the biomass concentration in the bioreactor, by manipulating the (inlet) Dilution rate. Findings: The bioreactor has been shown to exhibit steady-state multiplicity (three steady-states) corresponding to different operating conditions. One of the steady-states has been shown to be unstable as computed from the Eigen values of state space model matrix. Application/Improvements: IMC based PID controller parameters have been tuned based on various performance criteria such as IAE, ISE, ITAE, settling time, % overshoot and rise time so as to provide optimum performance of the bioreactor, based on an unstable transfer function. 

Keywords: Continuous Bioreactor, Controller Tuning, IMC PID Controller, Substrate Inhibition Kinetics, Unstable Transfer Function