An Observer with a Function of Estimating Unmeasurable Inputs : On an Observer of a Boiler Heating Surface

Abstract

It is assumed in an estimation problem with an observer that all inputs to a system can be measured and are available. However, there exists a system such as a boiler heating surface in which the observer causes estimated errors because the input called heat absorption is unmeasurable. This paper presents a solution to such a problem. The solution is based on the suggestion of the observer which acts as a feedback control that tracks its output to the system output and is found in the method of adding a feedback loop from the tracked error to the observer input corresponding to the unmeasurable input. The estimated input coincides with the unmeasurable input with infinite feedback gain which is realized by pI operation in an actual field. Favorable results are obtained in the application to boiler heating surface as shown by stability analysis and simulation.