Disturbance decoupled functional observers

If a state observer does not exist, it is possible to design a functional o bserver. principally, this is also true for systems with unknown inputs (te rmed as disturbances). Necessary and sufficient conditions for the existenc e of disturbance decoupled functional observers for linear time-invariant s ystems are provided. A method for designing such observers is given. Analys is and design are based on a matrix pencil approach. The design can also he used to obtain functional observers for descriptor systems with or without unknown inputs.