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The present paper deals with the issue of measurement delays which constitute a very prominent problem faced by most control systems. The system considered is that of a bioreactor used for the biological treatment of wastewater. The recording of the output substrate concentration of such systems usually involves a delay which results from the dependency of the flow of the liquid on its consistency. A PI observer-based control is applied and its performance is analysed in terms of the maximum delay for which the system is stable and converges as well as in terms of the convergence times. Based on these parameters, the results are compared to those obtained by a feedback linearising observer-based system. This comparative analysis showed that the PI controller performed better than the feedback controller, hence confirming its efficiency in biomass regulation in the presence of delayed measurements.

This paper proposes the application of a Proportional-Integral (PI) controller for the observer-based regulation of biomass concentration for a continuous-discrete system. An observer is essential to estimate the values of biomass concentration since the controller depends on these measurements. The analysis focuses on the continuous-discrete nature of the system which is represented by a continuous bioreactor system with discrete output measurements. The maximum allowable sampling partition diameter is determined along with the corresponding convergence time. These results are then compared to another work that used a feedback linearising control to achieve biomass regulation. The results obtained with the PI controller proved to be far more superior both in terms of maximum possible sampling time and convergence time. These findings confirmed the satisfactory and improved performance of the proposed observer-based controller.

Wastewater treatment is a biological process which involves the streaming of solid waste products in tubes and makes use of sensors which provide outputs at distinct instants of time. These issues lead to problems in the control of the output, which is the substrate concentration. In this work, we present an observer and a controller which is used to control the biomass concentration of such bioreactors in the presence of delayed and discrete measurements. The aim of this paper is to make a realistic analysis of the proposed observer-based control system and conclude on the effects of delayed measurements on the maximum possible sampling partition diameter as well as to study the effect of the sampling rate on the maximum possible delay. The results obtained confirmed the satisfactory performance of the system.

This work provides the observation and control of biomass concentration in Waste Water Treatment Plants. To achieve this, a PI controller was designed together with an observer to form an observer-based control system. The optimal values of the proportional gain and integral gain were determined to obtain the convergence of the observer in the least amount of time without compromising on the time taken by the response to reach steady state. Encouraging results which shall provide a basis for further and more in-depth research on the system were obtained.

This paper proposes an observer-based control system to estimate and control biomass concentration in a simple microbial system under known output delays. More precisely, these delays are represented by time lags in the measurement of substrate concentration. We employ a feedback linearising controller that has previously been developed for a system without measurement delay. In the present work, the delay is applied to the controller and the maximum allowable delay that maintains stability is computed. Next, a nonlinear observer is proposed to predict the biomass concentration. The stability of the overall closed-loop feedback system incorporating the observer and the controller is analysed. Simulation study has revealed that the combination of the observer and controller provided a satisfactory response and was successful in regulating the biomass concentration. Finally some conclusions are drawn.

In this paper, an observer-based control system is presented for the regulation of biomass concentration in bioreactors. The importance of the observer is highlighted by the dependency of the feedback linearising controller on the measurements of biomass concentration. Further, the discrete nature of output substrate concentration is considered and the performance of the system proposed is analysed through a simulation study using Matlab/Simulink. This study is also used to determine the limit on the sampling partition diameter for which the observer and controller designed give satisfactory performance. The implemented observer-based control system showed satisfactory performance both in terms of stability and convergence for given values of sampling partition diameters.