Construction of a reduce order observer for linear time invariant system with unknown inputs

In this paper a simple unknown input estimation method for linear time invariant systems is proposed. Here reduce order cumming observer is extended and used for this purpose. The approach is based on the knowledge of generalized matrix inverse. The proposed observer estimate states in presence of unknown input disturbance. Necessary conditions for existence such unknown i/p observer are derived regarding the proposed methodology. An illustrative numerical example two loop missile auto-pilot plant is shown in terms of MATLAB simulation.