Estimation of Unmeasurable Input and States by Applying Fuzzy Control : 3rd Report, Fuzzy Control for Steam Temperature of a Boiler Heating Surface

In their first report, the authors proposed a fuzzy applied observer (FAO) as a solution to the nonlinear estimation problem with unmeasurable input. This paper deals with a steam-temperature control (STC) of a once-through boiler using FAO. The STC consists of a final superheater (FSH), spray attemperator at the FSH inlet, FAO and two compensators. One object of compensation is delay in the dynamic behavior of steam temperature and the other is the effect of unbalance between disturbances in heat absorption and steam flOW. The former is compensated by state-variable feedback and the latter is compensated using fuzzy control by way of temperature and the ratio of these two disturbances. Simulations are performed to confirm the control. The results show better control performances compared to the uncompensated case, with FAO being satisfactory.