Tracking Dynamics of Read/Write Head Suspensions in High-Performance Small Form Factor Rigid Disk Drives

Recording density of rigid disk drives is related to both linear and track density. High linear density requires submicron recording spacing which is made possible by using a gas-lubricated slider bearing to support the read/write transducer. This critical component has inspired much research effort in the past, both in industry and in academia. On the other hand, a major limitation in increasing the track density is the structural resonance of the suspension which connects the slider bearing to the actuator arm. In this paper, a nonintrusive measurement technique using a Laser Doppler Vibrometer is utilized to measure the submicron suspension vibration. Excitation of the suspension is provided by a miniature air-hammer, a piezoelectric transducer, and the voice-coil motor in commercial disk drives during normal operation. Natural frequencies and mode shapes are extracted from the measurements and compared with numerical data from finite element analysis. Correlation between suspension dynamics and off-track error is presented. Research shows that even for linear actuators, torsional vibration of the suspension causes substantial lateral head motions and contributes significantly to tracking error.