Stability of digital discrete time controllers for water systems

All water systems with automatic controllers implemented by programs running on digital computers are sampled data systems. The water systems themselves are often non linear systems. This complicates the analysis of the stability of the combined system. In this paper we apply the second method of Lyapunov to a trunk sewer with a gate regulated by a discrete controller. This is intended as a feasibility study of a theoretical approach to the design and stability analysis of such controllers.