Nonlinear PI controllers for continuous bioreactors using population balance models

Abstract

Continuous bioreactors are critical unit operations in many biological systems, but the unique modeling is very complicated due to the underlying biochemical reactions and the distributed properties of cell population. The scope of this paper considers a popular modeling method for microbial cell cultures by population balance equation models, and the control objective aims to attenuate undesired oscillations appeared in the nonlinear distributed parameter system. In view of pursuing the popular/practical control configuration and the lack of on-line sensors, an approximate technique by exploiting the "pseudo-steady-state" approach constructs a simple nonlinear control model. Through an off-line estimation mechanism for the system having self-oscillating behavior, two kinds of nonlinear PI configurations are developed. Closed-loop simulation results have confirmed that the regulatory and tracking performances of the control system proposed are good.

Output Regulation of Self-Oscillating Biosystems: Model-Based Proportional−Integral/Proportional−Integral−Derivative (PI/PID) Control Approaches

“…4 Nevertheless, the sustained oscillation or undesired perturbations could obviously deteriorate PI-or PID-controlled nonlinear processes. Recently, Kurtz et al 16 proposed nonlinear controller to attenuate undesired oscillations in microbial cultures described by corpuscular models, and our works 17 showed that the model-based PI control could be directly implemented to stabilize a self-oscillating bioreactor system using a nondistributed nonlinear observer and artificial oscillator. However, the model errors and disturbances could easily degrade the results from our previous works.…”