Fault Identification via Sliding Mode Observers in Nonlinear Systems not Satisfying Matching and Minimum Phase Conditions

The paper is devoted to the problem of fault identification (reconstruction) in systems described by nonlinear models under the unmatched disturbances. A novel approach to construct sliding mode observer is suggested for systems which do not satisfy the general conditions required for fault identification, in particular, minimum phase and matching conditions. The suggested approach is based on the reduced order model of the original system insensitive to the disturbances. This allows to reduce the dimension of sliding mode observer and relax the limitations imposed on the original system.