High-Order Sub-Harmonic Synchronisation in a Rotor System with a Gear Coupling

Gear couplings transmit torque from driving to driven shafts whilst accommodating unavoidable misalignments and axial displacements. The friction forces at the sliding teeth transfer energy from the driving engine to the lateral oscillations of the shaft. Instability of the stationary motion, self-excitation, can result. The self-excited oscillations, in character related to the eigen-oscillations of the linear system, interact with the external excita-tion by unbalance forces. For a two degrees of freedom rotor-bearing system we show how to study systemati-cally cases of higher-order synchronisation (frequency locking) which can help to interpret observed motions; numerical calculations and perturbation techniques are combined