Smith predictor based neural fuzzy controller applied in a water gas heater that presents a large time-delay and load disturbances

This paper presents a work in progress concerning the use of neuro-fuzzy based non-linear Smith predictor for control a real system with a large and variant time delay and load disturbances. The main objective is to control the output water temperature of one domestic water gas heater that presents a large time-delay and water flow, cold water temperature and wanted output temperature changes. It is presented a detailed description of the water gas heater in terms of non-linearity, time constants and time delay. The steps taken to arrive at the direct and inverse models using a neuro-fuzzy technique are described. The two control strategies, non-linear Smith predictor controller and an improved non-linear Smith predictor controller, were implemented in the 89C51RD PHILIPS micro-controller and the real time results are presented. The improved non-linear Smith predictor controller consists in a fuzzy compensation of the steady-state errors and a compensation for small variations of the time-delay.