A flexible dynamic model for an electric propulsion shaft system with ball bearing supports

The underwater electric propulsion system suffers the unbalance magnetic pull and nonlinear bearing forces due to the elastic shaft deformations, then the system vibrations would be changed nonlinearly. In this paper, a dynamic model of a flexible electric propulsion shaft system with the nonlinear bearing forces is established. The model considers the coupling effects of the electric motor, ball bearings and propeller excitation. The effects of the shaft speed, bearing radial clearance and rotor eccentricity are studied. The results indicate that the bearing radial clearance and rotor eccentricity can increase the axis trajectory ranges and system vibrations, and the effects of the bearing radial clearance and rotor eccentricity would be enlarged by the shaft speed.