NONLINEAR CONTROL OF BIOREACTORS WITH INPUT MULTIPLICITIES IN DILUTION RATE

Control problems of continuous bioreactors having two input multiplici ties in dilution rate on the productivity are analyzed. The nonlinear system is represented by a unity gain linear subsystem cascaded with a nonlinear gain subsystem. A conventional PI controller designed for t he linear subsystem followed by the solution of the nonlinear gain equ ation gives a nonlinear controller. The performance of the nonlinear c ontroller is compared with that of the conventional PI controller and also of the nonlinear controller [1] designed based on the output equa tion. The present nonlinear PI controller gives a superior performance . A single set of controller settings can be used for both the operati ng points. Whereas the linear PI controller and the nonlinear controll er proposed by Henson and Seborg [1] destabilize the system.