Distributed Sliding Mode Control of pH in Tubular Photobioreactors

Abstract

This paper describes the development of a distributed sliding mode control controller to regulate the pH of a tubular photobioreactor using the total inorganic carbon as the controlled variable of the process. The main purpose of the control system is to maintain the pH around a desired reference value and, at the same time, attenuate the undesirable transients caused by the disturbances. To study this problem, it is considered that this system is written as a set of hyperbolic partial differential equations. The distributed parameter model of the photobioreactor is transformed into a finite dimensional system by the method of characteristics. Then, the control design is performed in the finite dimensional system instead of the original distributed parameter model. The proposal allows to characterize the sliding regimes and their fundamental properties by a geometric approach. Through simulation and experimental results, the method is shown to be effective in controlling a tubular photobioreactor.