Nonlinear observer design using invariant manifolds and applications

The problem of constructing (reduced-order) observers for general nonlinear systems is addressed. It is shown that an asymptotic estimate of the unknown states can be obtained by rendering attractive an appropriately selected (invariant) manifold in the extended state space. The proposed methodology is applicable to systems that are not necessarily linear in the unmeasured states. This is illustrated with two practical examples: a single-machine infinite-bus system and a perspective vision system.