Output Feedback Regulation via Sinusoidal Control with Application to Semi-Continuous Bio/Chemical Reactors

This work proposes a nonlinear control strategy, an output feedback control based on a sinusoidal control approach for output regulation purposes with application to semi-continuous (fed-batch) bio/chemical processes. A key feature of the proposed control scheme is its auto-stop property, which ensures that the required set points are reached while automatically ceasing control input. This is particularly advantageous in fed-batch reactors, where exceeding the maximum operative volume is a common concern; additionally, the proposed controller can be bounded by only selecting the amplitude of the sine function. The closed-loop stability of the designed auto-stop control law is analyzed via the Lyapunov–Krazovzkii framework, which allows us to claim that the closed-loop dynamic operation of the corresponding processes is stable. The proposed controller is applied to two typical examples of semi-continuous bio/chemical reactors for regulation purposes, which aim to increase the reactors’ productivity. In addition, a comparison with a well-tuned internal model control proportional–integral (IMC PI) controller is performed. To show the performance of the control schemes, numerical experiments were carried out to show the controllers’ performance under different and realistic operation conditions. Here, for the bioreactor example, the performance index does not reach a steady state, but the gap between the IMC PI controller and the proposed one is around 100, 200, and 250 units for the different set points, which is in favor of the proposed controller. Regarding the chemical reactor, the performance index of the corresponding gap between the steady-state values of the performance index is also in favor of the proposed control law.