Left-coprimeness condition for the reachability in finite time of pseudo-rational systems of order zero with an application to difference delay systems
Sébastien Fueyo
TL;DR
The paper develops a finite-time reachability theory for pseudo-rational systems of order zero and applies it to difference-delay systems with distributed delays. It proves that quasi-reachability and reachability coincide in finite time above the universal bound $T>-l( ext{det}(Q))$, and provides a constructive left-coprimeness criterion for $L^1$ targets, with a deeper analysis for the scalar case and regularity-based sufficiency results for higher dimensions. For distributed-delay systems, a Hautus-type frequency-domain test and a matrix-rank condition yield a practical reachability criterion, together with a simple bound $T_{ ext{min}}\uparrow doldsymbol{ extLambda}_N$ for minimal time. The work is underpinned by Paley–Wiener–Schwartz and corona-type distribution results, extending previous scalar findings to the matrix setting and highlighting open questions on sufficiency of the frequency-domain criterion. Overall, the framework provides actionable criteria and input-construction methods for finite-time controllability of a broad class of delay systems with potential engineering and biological applications.
Abstract
The paper investigates the reachability in finite time of pseudo-rational systems of order zero. A bound on the minimal time of reachability is obtained and the reachability property for integrable functions is characterized in terms of a left-coprime condition. The results are applied to difference delay systems with distributed delays.
