  This paper used multi-scale method and KBM method to get approximate solution
of coupled Van der Pol oscillators, based on which, researchers investigated
the impact several parameters have on the prerequisite of synchronization and
the time it takes to synchronize quantitatively. In addition, this paper has a
brief introduction of the usage of Kuramoto Model in plural metronomes'
synchronization and the derivation of Van der Pol oscillator from the discrete
model.
