Control systems challenges in energy efficient portable UV based water sterilizer

This paper presents a real world challenge of constructing an energy efficient portable ultra-violet-based water sterilizer. We discuss a novel approach where UV radiation has a dual use, (i) to detect microbial activity through biofluorescence, and (ii) to sterilize the water. This dual use scenario enables us to propose a feedback control based operation scheme. The goal that we want to achieve is to make sure that the bacteria population does not exceed the allowed level, while keeping the energy usage as low as possible. We propose a mathematical model for both the detection and sterilization process, based on experimental data. We then formulate an optimal control problem that minimizes the energy consumption while meeting a probabilistic performance criterion. By using an idea from dynamic programming, we propose a solution where the optimization in the detection and sterilization processes can be decoupled.