Temperature control of fermentation bioreactor for ethanol production using IMC-PID controller.

Area of Science:

• Chemical Engineering
• Control Systems Engineering
• Process Control

Background:

• Accurate modeling is crucial for effective process control.
• Bioreactor temperature control presents challenges due to system dynamics.
• Existing control methods may not be optimal for unstable time-delay systems.

Purpose of the Study:

• To develop and validate an IMC-PID controller for an unstable second-order time-delay (USOPDT) system with a right-half plane zero.
• To apply the developed controller to a nonlinear bioreactor process model for temperature control.
• To evaluate the controller's performance against established metrics and compare it with other methods.

Main Methods:

• State-space model identification using MATLAB yielded a 99% data fit.
• Conversion of the state-space model to a simplified unstable second-order time-delay transfer function.
• Design of an IMC-PID controller specifically for the identified USOPDT model.
• Implementation and testing of the controller on a nonlinear bioreactor model.

Main Results:

• The IMC-PID controller successfully controlled bioreactor temperature during setpoint and disturbance changes.
• Performance metrics (IAE, ISE, ITAE) were recorded as 20.99, 49.02, and 292.50, respectively.
• The proposed controller demonstrated improved closed-loop performance, particularly in Integral Absolute Error (IAE) and settling time, compared to reported methods.

Conclusions:

• The proposed IMC-PID controller is effective for temperature control of nonlinear bioreactors with USOPDT characteristics.
• The controller offers enhanced performance over existing methods for this specific class of unstable systems.
• Accurate system modeling is a critical precursor to successful advanced controller design and implementation.