Singular-Perturbations-Based Analysis of Dynamic Consensus in Directed Networks of Heterogeneous Nonlinear Systems

TL;DR

This paper presents a singular-perturbations framework to analyze emergent dynamics and synchronization behavior in heterogeneous nonlinear networks with directed couplings, revealing conditions for stability and periodic orbits.

Contribution

It introduces a novel analysis method based on slow-fast dynamics to understand synchronization and emergent behaviors in complex directed networks of nonlinear systems.

Findings

Conditions for stability of the network's slow dynamics.

Existence of a unique, almost-globally stable periodic orbit.

Emergent synchronization behavior as coupling strength increases.

Abstract

We analyze networked heterogeneous nonlinear systems, with diffusive coupling and interconnected over a generic static directed graph. Due to the network's hetereogeneity, complete synchronization is impossible, in general, but an emergent dynamics arises. This may be characterized by two dynamical systems evolving in two time-scales. The first, "slow", corresponds to the dynamics of the network on the synchronization manifold. The second, "fast", corresponds to that of the synchronization errors. We present a framework to analyse the emergent dynamics based on the behavior of the slow dynamics. Firstly, we give conditions under which if the slow dynamics admits a globally asymptotically stable equilibrium, so does the networked systems. Secondly, we give conditions under which, if the slow dynamics admits an asymptotically stable orbit and a single unstable equilibrium point, there exists a unique periodic orbit that is almost-globally asymptotically stable. The emergent behavior is thus clear, the systems asymptotically synchronize in frequency and, in the limit, as the coupling strength grows, the emergent dynamics approaches that of the slow system. Our analysis is established using singular-perturbations theory. In that regard, we contribute with original statements on stability of disconnected invariant sets and limit cycles.