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

The state-space model is identified using the identification tool of MATLAB, and the best fit of 99% of measured and simulated data was obtained. Further, state-space model was converted to a transfer function model and finally simplified to an unstable second order time-delay transfer function model. Internal model control based proportional integral derivative (IMC-PID) controller design method was proposed for unstable second order time delay with RHP zero (USOPDT) and successfully tested to the nonlinear bioreactor process model. The temperature of the bioreactor was successfully controlled by proposed controller in both cases setpoint and disturbance change. The performance of the controller was evaluated in terms of IAE, ISE, ITAE and the corresponding values of 20.99, 49.02 and 292.50 were obtained respectively. Proposed method shows better closed-loop performance in terms of IAE and settling time than the other reported methods for temperature control of bioreactor.

IMC-PID design based on model matching approach and closed-loop shaping

Motivated by the limitations of the conventional internal model control (IMC), this communication addresses the design of IMC-based PID in terms of the robust performance of the control system. The IMC controller form is obtained by solving an H-infinity problem based on the model matching approach, and the parameters are determined by closed-loop shaping. The shaping of the closed-loop transfer function is considered both for the set-point tracking and for the load disturbance rejection. The design procedure is formulated as a multi-objective optimization problem which is solved by a specific optimization algorithm. A nice feature of this design method is that it permits a clear tradeoff between robustness and performance. Simulation examples show that the proposed method is effective and has a wide applicability.