Nonlinear PID controller for a Bacterial Growth Bioprocess

This paper presents a nonlinear version of a PID controller and its applications in biotechnology. Design of the nonlinear controller consists of a series connection between a nonlinear function of the system error and a classic PID controller. This improvement enables the controller to adapt its response based on the different operation points of the closed-loop control system (a linear region around origin and a nonlinear behavior outside). The advantages of the nonlinear transformation applied to the error and the controller parameters selection are highlighted. The proposed control strategy is applied for substrate regulation of a bacterial growth bioprocess. The simulations are implemented in a MATLAB environment. Simulations of closed-loop system have confirmed that the regulatory and tracking performances of the presented control strategy are good.