Nonlinear model-based controllers are developed to regulate the cell biomas
s exit concentration of continuous-flow bioreactor by manipulating the dilu
tion rate. "Plant-friendly" input sequences are used to identify a second-o
rder Volterra series model from a "virtual plant". A Volterra-Laguerre mode
l is produced by projection onto the orthonormal Laguerre basis functions.
A partitioned nonlinear inverse (PNLI) controller is synthesized and is sho
wn to be nominally stable over the manipulated variable range [0.941, 0.999
] h(-1) using the structured singular value. A referenced-based switching a
lgorithm is incorporated to improve the robustness and stability characteri
stics of the closed-loop system. Nonlinear model predictive control (NMPC)
alleviates the need for the switching controller, and an analytical NMPC so
lution incorporating recursive least squares avoids entrapment in local obj
ective function minima. This controller offers optimum tracking for unreach
able setpoints as well as tracking of the constrained local minimum for inp
ut-magnitude-constrained problems modeled by second-order Volterra-Laguerre
systems.