Integration of Thin Film Strain Sensors Into Hard Drives for Active Feedback Vibration Suppression

The work described in this paper demonstrates a novel application of piezoelectric thin-film sensing technology by incorporating ZnO strain sensors into a hard disk drive (HDD) and deploying the sensors in a high-sample-rate feedback controller to suppress vibrations. First, thin-film ZnO sensors are fabricated directly onto a HDD suspension component, which was a unique and challenging process since the substrate is steel. The sensor geometry is designed to be selective to vibration modes that contribute to displacement in the off-track direction. The smart suspension structure is then packaged into an experimental HDD, along with a miniaturized conditioning circuit and lead zirconate titanate (PZT) actuation elements. The sensors demonstrate excellent sensitivity and selectivity to the desired modes. Finally, an active mode damping controller is implemented on the instrumented, PZT-actuated prototype. Feedback control using the thin film sensors effectively suppresses the high-frequency sway mode of the suspension.