An adaptive fuzzy algorithm for domestic hot water temperature control of a combi-boiler

This paper describes an innovative adaptive fuzzy control (AFC) algorithm f or regulating the domestic hot water temperature of a combi-boiler or insta ntaneous hot water heater when using a domestic hot water flow rate sensor. The AFC automatically learns the feedforward relationship between the dome stic hot water flow rate and the gas valve position and adapts to process c hanges such as variations in the inlet water temperature, controller set po int, gas composition, and flow sensor miscalibration without requiring addi tional sensors or a system identifier. Laboratory tests under typical operating conditions show that the AFC reduc es the set-point error between 18% and 70% and reduces control effort betwe en 23% and 41% when compared with a conventional proportional-integral-deri vative (PID) feedback controller with feedforward compensation. The AFC's m emory and processing requirements are comparable to those for a PID plus fe edforward algorithm, so it is a realistic replacement for a conventional PI D algorithm with feedforward compensation.