Platform-Motion Response Evolution and Predicted TDB-Clearance Risk of a Ship-Mounted Flexible Rotor–Active Magnetic Bearing System

Platform motion alters the flexible response and control demand of ship-mounted rotor–active magnetic bearing (AMB) systems and thereby the clearance margin at the touchdown bearings (TDBs). A closed-loop finite-element model of a flexible rotor–AMB system is subjected to prescribed heave, sway, pitch, and yaw motions at five rotational speeds and 4 × 4 amplitude–frequency levels (320 cases). Responses are evaluated at the TDBs, the disk, and 36 axial positions, together with the AMB control force and the ratio of peak TDB displacement to minimum clearance, assessed against the ISO 14839-2 zones. Stronger excitation increases the support and disk responses and moves the axial response peak; each platform motion has its own dominant direction and left–right support relation. Ten cases, all high-amplitude, high-frequency heave or sway, enter zone D; the maximum clearance ratio is 0.635, and its correlation with the maximum control force is 0.9995. A closed-form envelope derived from the closed-loop dynamic stiffness reproduces the simulated ratios and shows that the zone boundaries are set by the platform acceleration amplitude: zone D requires 4.9–7.1 g under heave or sway. The disk displacement peaks at 2500 rpm, whereas the control force and clearance ratio peak at 7000 rpm, so deformation, control demand, and clearance margin have to be assessed together.