Observer Design for Non-Lexicographic-Fixed Time-Varying Continuous Systems

The state estimation problem is considered for linear time-varying systems with non-lexicographic-fixed observability basis. A two-stage design strategy is presented for constructing observers for this class of systems. At the first stage, by augmenting the given system with an auxiliary system, the original system is transformed into a new augmented model whose observability indices are lexicographic-fixed. A specific augmentation scheme is proposed in order to find this auxiliary system. At the second stage, a design procedure is given to construct minimum-order observers for the augmented system by utilizing the new input and output information. Canonical transformation technique is also employed to simplify the design procedure. Finally, with the help of a simple reverse transformation, solutions to the original problem are obtained. An example is given to illustrate the design procedure and techniques.