Inphase Design of the Two Lowest Natural Modes of Vibrations of Swing-Arm for a High Frequency Band Head Positioner

摘要

This paper describes an inphase design of the two lowest natural modes of vibrations of a swing-arm related to pivot bearing stiffness for a high frequency bandwidth head positioner for 3.5 in. magnetic disk storages. From a modal analysis of swing-arm mechanism whose pivot bearing has an anisotropic stiffiness, it was found that the inphase mode condition could be realized in a straight arm if the position of the arm's mass center was more than 5.6 mm in distance from the pivot. Based on conventional controller design with a lead filter and a notch filter, the control frequency bandwidth of the inphase mode swing-arm could be increased up to a higher value. This value was limited by the instability of the bending vibration mode of the swingarm.