Narrowband performance of active control on flow-induced vibrations inside hard disk drives

This paper presents an experimental study of narrowband active control on the flow-induced vibrations (FIV) on the head gimbals assembly (HGA) in a working hard disk drive (HDD). Firstly, experiments with an analog feedback close-loop were conducted as demonstration for narrowband active control on principal peaks in the spectrum of the off-plate FIV on the HGA whose signal was collected with a 1-D laser Doppler vibrometer (LDV). Secondly, the modal testing on the experimental HDD was carried out to find out where the spectrum principal peaks focused in current active control come from. Thirdly, a digital feedback control close-loop was implemented in experiments for narrowband suppression on the focused FIV spectrum peaks on the HGA. In those close-loops, the off-plate HGA vibrations detected by the LDV were used as feedback error signals, then the signals was passed through an analog or digital controller to generate feedback signals to drive a piezoelectric disk to actuate feedback acoustic pressure around the HGA. Active control experiments were conducted in narrow bands on five principal peaks in the HGA off-plate vibration spectrum, around 1,256, 1,428, 2,141, 2,519 and 3,469 Hz, respectively. It is shown that distinct narrowband suppression of at least 10 dB can be achieved on all these HGA vibration peaks.