Conference article

Differential-algebraic equations naturally arise in the modeling of dynamical processes; in particular using MODELICA as modeling language. In general; the model equations can be of higher index; i.e.; they can contain hidden constraints which lead to instabilities and order reductions in the numerical integration. Therefore; a regularization or remodeling of the model equations is required. One way to obtain the required information on the hidden constraints is a structural analysis based on the sparsity pattern of the system. For the determination of a regular index-reduced system formulation then; usually; a crucial step is the so-called state selection. In this paper; we will present a new approach for the remodeling of dynamical systems that uses the information obtained from the structural analysis to construct a regularized overdetermined system formulation. This overdetermined system can then be solved using specially adapted numerical integrators; in such a way that the state selection can be performed within the numerical integrator during runtime of the simulation.

DAEs; regularization; structural analysis; overdetermined system; state selection