Nonlinear control of bioreactors with input multiplicities

Control of bioreactors exhibiting two input multiplicities, i.e., steady-state gains having opposite sign, is theoretically analyzed. The nonlinear system is represented by a unity gain linear system cascaded with a nonlinear gain. A conventional PI controller designed for the linear portion of the system followed by the solution of the nonlinear gain equation gives a nonlinear controller. The performance of the nonlinear controller is compared with that of the linear PI controller designed for the overall linear system. The nonlinear PI controller performance is superior to that of the linear PI controller. © 1994 Springer-Verlag.