Dynamic Modeling of a Hard Disk Drive Actuator Using Sub-component Finite Element Model and Modal Superposition

Abstract

The purpose ofthis study was to develop a methodology whereby complex structures, such as hard disk drive head stack assemblies, can be modeled accurately in a compact form. The head stack assembly was divided into three sub-components, the yoke/coil, the actuator arm, and the suspension. Finite element models of each subcomponent were created to provide the natural frequencies and corresponding mode shapes ofthe individual sub-components. Coupling terms were then derived that describe how the sub-components interact to form the overall system dynamics. The resulting sub-component fInite element analytical model was a 15 degree of freedom model that could quickly be solved using commercially available matrix manipulation software. The model proved to be accurate in predicting the off-track motion ofthe head stack assembly and helped provide understanding as to which resonances are the most detrimental to drive performance. Initial simulations showed that some of the boundary conditions and assumptions used in creating the sub-component finite element models were incorrect. However, by comparing the model results to measured data, the subcomponent fInite element analytical model provided direction to improve the accuracy of the sub-component fInite element models.