Vibration of rotating-shaft HDD spindle motors with flexible stationary parts

The purpose of this paper is to develop a mathematical model that predicts forced vibration of HDD spindles with flexible stationary parts. The model assumes a rotating-shaft spindle design. The mathematical model consists of three parts: a rotating part, a stationary part, and bearings. The rotating part includes a flexible hub, a flexible shaft press-fit into the hub, and N elastic disks mounted on the hub. The stationary part can include motor bracket (stator), base casting, and top cover. The bearings under consideration can be ball bearings or fluid-dynamic bearings (FDB). The rotating disks are modeled through the classical plate theory. The rotating part (except the disks) and the stationary part are modeled through finite element analyses (FEA). With mode shapes and natural frequencies obtained from FEA, the kinetic and potential energies of the rotating and stationary parts are formulated and discretized. Finally, use of Lagrange equation results in the equations of motion.