THE OBSERVER DESIGN FOR NONLINEAR SYSTEM WITH BOTH INPUT AND OUTPUT UNKNOWN DISTURBANCES

The nonlinear observer design method for nonlinear system with unknown disturbances both in input and output is developed. It is an extension of only unknown input disturbance approach. The situation is happened in such as Automatic Generation Control (AGC)where both power generating inputs (such as in boiler and turbine unit) and frequency load output (as for the power demand user) disturbances are present. The approach used in this paper is to decouple the disturbances from the rest of the system through a series of transformations on the both state and output equations. Once total disturbance decoupling is achieved, an appropriate observer for the disturbance free part is proposed and designed. The observer gain matrix is determined by solving an algebraic Riccati equation. The designed observer is, subsequently, used for estimation of the unknown input and output disturbances, which then could be used as Fault Detection and Isolation (FDI).