Implicit-IMOR method for index-1 and index-2 linear constant DAEs

The index-aware model order reduction (IMOR) method for differential-algebraic equations (DAEs) is based on the decomposition of a DAE into differential and algebraic parts, depending on its tractability index. Then, the differential part is reduced by using existing MOR methods for ODE, and this reduction induces a reduction on the algebraic part, which can be further enhanced. However the IMOR method involves matrix inversions which may limit its practicability in some real-life examples. In this paper a modified IMOR method is presented, which does not involve matrix inversion.