A Nontraditional Vibration Analysis of Rotating Disk/SpindleSystems and Its Applications to Computer Hard Disk Drives

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The primary focus of this research is to develop a new mathematical model to explain and predict the nontraditional vibration resonances observed in disk drive experiments. This new mathematical model is agumented to resolve five emerging vibration problems in the disk drive industry. They include damping, forced response, disk/spindle/head interaction, control of squealing noise, and nonlinear fluid- film bearings. In the past several years, advances in manufacturing and electronic technologies have substantially increased the capacity of computer disk drives by enhancing the data storage density(e.g., 4000 tracks per inch) and by stacking more disks (e.g., 10 disks) into modern disk drives. In the meantime, the computer industry continues to reduce the size and weight of disk drives by using smaller and thinner disks mounted on spindles with shorter bearing spans. As a result of these design trends, vibration resonances less than 500 Hz with significant amplitudes have been observed repeatedly in experiments. These vibration resonances are extremely detrimental to their performance, because their low frequencies and large amplitudes prevent the recording heads from reading or writing the data correctly and repeatedly. This new mathematical model is more realistic than the existing models, because it considers multiple flexible disks on a rigid spindle that has two flexible bearing supports. The theoretical predictions are verified experimentally through a full-scale disk drive test rig available in the Dynamics and Vibration Laboratory at the University of Washington.