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

Previous papers 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), a spray attemperator at the FSH inlet, the FAO and two compensators. One object of compensation is delay in the dynamic behavior of steam temperature and the other is the effect of imbalance between disturbances in heat absorption and steam flow. The former is compensated for by state variable feedback and the latter is compensated for using fuzzy control to deviations in the temperature and the ratio of these two disturbances. Simulations are performed to confirm the control. The results show better control performance due to the suitable fuzzy applied observer compared to the uncompensated case