Observing a subset of the states of linear systems

A selective state observer capable of asymptotically tracking any arbitrarily chosen subset of the state vector of linear time-invariant multivariable dynamic systems is introduced. The dynamics of the observer are derived from a model of the subset to be estimated. It is shown that the only condition for the asymptotic tracking of the subset is that the derived model be observable. A simple and systematic observer design method is presented and numerical examples are given to illustrate the properties of the new observer and its design method.