Experimental dynamic characterizations and modelling of disk vibrations for HDDs

• Published in: ISA transactions 2008, Vol.47 (1), p.85-93
• Main Authors: Pang, Chee Khiang, Ong, Eng Hong, Guo, Guoxiao, Qian, Hua
• Format: Article
• Language: English
• Subjects: Algorithms; Applied sciences; Computer Simulation; Disk mode shapes; Electronics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Hard-disk drives; Linear Models; Magnetic and optical mass memories; Microcomputers; Models, Statistical; Physics; Rotation; SLDV; Solid mechanics; Storage and reproduction of information; Structural and continuum mechanics; Vibration; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...)
• ISSN: 0019-0578; 1879-2022
• DOI: 10.1016/j.isatra.2007.05.008

Currently, the rotational speed of spindle motors in HDDs (Hard-Disk Drives) are increasing to improve high data throughput and decrease rotational latency for ultra-high data transfer rates. However, the disk platters are excited to vibrate at their natural frequencies due to higher air-flow excitation as well as eccentricities and imbalances in the disk-spindle assembly. These factors contribute directly to TMR (Track Mis-Registration) which limits achievable high recording density essential for future mobile HDDs. In this paper, the natural mode shapes of an annular disk mounted on a spindle motor used in current HDDs are characterized using FEM (Finite Element Methods) analysis and verified with SLDV (Scanning Laser Doppler Vibrometer) measurements. The identified vibration frequencies and amplitudes of the disk ODS (Operating Deflection Shapes) at corresponding disk mode shapes are modelled as repeatable disturbance components for servo compensation in HDDs. Our experimental results show that the SLDV measurements are accurate in capturing static disk mode shapes without the need for intricate air-flow aero-elastic models, and the proposed disk ODS vibration model correlates well with experimental measurements from a LDV.