State estimation for linear switched systems with unstable invariant zeros and unknown inputs

In this paper the problem of continuous and discrete state estimation for a class of linear switched systems is studied. The class of systems under study can contain nonminimum phase zeros in some of their 'operating modes'. The conditions for exact reconstruction of the discrete state are given using structural properties of the switched system. The state-space is decomposed into the strongly observable part, the nonstrongly observable part and the unobservable part, to analyze the effect of the unknown inputs. A state observer based on high-order sliding-mode and Luenberger-like observers is proposed. For the case when the exact reconstruction of the state cannot be achieved, the ultimate bounds on the estimation errors are provided. The workability of the proposed method is illustrated by simulations.