Model order reduction for linear time delay systems: a delay-dependent approach based on energy functionals

This paper proposes a model order reduction technique for asymptotically stable linear time delay systems with point-wise delays. The presented delay-dependent approach, which can be regarded as an extension of existing balancing model order reduction techniques for linear delay-free systems, is based on energy functionals that characterize observability and controllability properties of the time delay system. The reduced model obtained by this approach is an asymptotically stable time delay system of the same type as the original model, meaning that the approach is both stability- and structure-preserving. It also provides an a priori bound on the reduction error, serving as a measure of the reduction accuracy. The effectiveness of the proposed method is illustrated by numerical simulations.