A sliding observer for differential-algebraic (DAE) systems

A nonlinear observer for systems modeled as linear differential-algebraic equations (DAEs) is presented. The DAE system model is first realized by converting it into an equivalent control problem via the singularly perturbed sliding manifold approach. This process introduces errors, which are treated as disturbances to the "equivalent" state-space formulation obtained. A robust sliding observer is then designed, ensuring asymptotic stability in the presence of said disturbances. This observer architecture results in a coupled dual feedback loop structure, conditions for decoupling the two loops are given, and a design procedure is outlined. An illustrative numerical example is also included. The paper concludes with a brief description of future research issues in refining this approach.