Vibration modelling of disc drive actuator

Abstract

The hard disk drive industry continues to strive for increased areal storage densities and reduced data access times. This necessitates performance improvements of the head positioning system in terms of fast transition from one track to another (track seeking), fast and accurate settling (settling), and precise track following of the target track. To meet these requirements, the servo bandwidth of the head positioning system must be increased to lower the sensitivity to disturbances such as disk flutter vibrations, spindle motor run-out, and external vibration. A dual-actuator system consisting of a voice coil motor (VCM) as a first-stage actuator and a push–pull-type piezo-electric transducer (PZT) as a second-stage actuator is considered. The VCM actuator has a large operating range and a low resonance frequency, and it is used for coarse positioning. The PZT actuator has a small operating range and a high resonance frequency, and it is used for fine positioning. In this project, modal analysis and Finite Element Modeling using commercial software ANSYS was conducted. Through modeling the SISO hard disk drive actuator and MIMO two-stage actuator, the optimal frequency mode was found. The modal analysis was also found to be a very useful tool to predict the mode shapes that were difficult to be obtained by modal testing.