Comment on “Synchronization in a ring of four mutually coupled van der Pol oscillators: Theory and experiment”

We have verified some results of Nana and Woafo [Phys. Rev. E 74, 046213 (2006)] in the area of the complete synchronization. We have found that the motion of the van der Pol network is quasiperiodic, not chaotic as the authors have written.

Figure 1

Quasiperiodic motion of the VDP oscillator: (a) Phase plane and (b) Poincaré section.

Figure 2

CS in the network of four coupled VDP oscillators; $k_1=k_2=k.$ (a) Synchronization error $z$, (b) MSF, (c) enlargements of the synchronization error $z$, and (d) MSF. White color: $z=0$ or ${\lambda }_1^T<0$; black color: $z>0$ or ${\lambda }_1^T>0$.