Sliding Mode Tangent Space Observer for LTV Systems with Unknown Inputs

This paper presents a cascaded observer structure for linear time varying systems which yields finite-time exact state estimates despite an unknown input. The observer is based on a tangent space observer and a higher order sliding mode reconstruction scheme. Theoretical insights in the construction of the observer are given along with conditions for stability of the tangent space observer in the presence of unknown inputs. A numerical simulation example shows the applicability of the proposed approach.