Enhanced Vibration Suppression in Hard Disk Drives Using Instrumented Suspensions

Abstract

This paper summarizes work that has been completed to evaluate the use of high-resolution thin-film strain sensors for vibration suppression in hard disk drives (HDDs). In particular, we demonstrate the viability and necessity of symmetrical sensors for cancellation of common non-off-track modes in the measurement. Thin-film ZnO strain sensors have been successfully integrated into instrumented suspension prototypes, and strain signals were extracted from operating disk drives. High-resolution strain sensing allowed us to investigate the nature of airflow excitation of the suspension structure. Experimental measurements were used to construct both ideal and realistic models. Using the ideal model that ignored non-off-track modes, multirate nominal 2 control synthesis and simulation were employed to evaluate potential improvements in closed-loop vibration suppression in a multisensor framework. These simulations projected improved tracking performance using auxiliary high-resolution strain sensing with increased sample rate. However, when a robust 2 damping controller was designed using a more realistic model of the available hardware, performance in simulation and experiment was limited by numerous non-off-track modes in the sensor signal.Index Terms-2 control, hard disk drive servos, multisensor systems, piezoelectric thin films.

Control Methods in Data-Storage Systems

“…Other hardware modifications for the servo have been proposed such as instrumented suspensions for active damping of vibrations [90], [91], and accelerometers for feedforward compensation of shock and vibration [92]. So far it appears that performance improvements offered by instrumented suspensions have not justified their cost.…”

Innovation Strategy Selection Facilitates High-Performance Flexible Piezoelectric Sensors

“…Lately, owing to high flexibility, fast response, high sensitivity, broad frequency bandwidth, high dynamic range, low cost and ease of processing, piezoelectric sensors have found a large number of applications in wearable electronics [26][27][28][29], medical equipment [30,31], structural health monitoring [32][33][34][35][36], machining process monitoring [37][38][39][40][41], structural parameter measurement [42][43][44][45], surface acoustic wave detection devices [46], hard disk drive [47,48] and microphones [49]. The development history of piezoelectric sensor applications in recent years is shown in Figure 1 .…”

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

“…Furthermore, the additive and subtractive wafer-level processes involved with thin-film fabrication are similar to those used in existing stateof-the-art suspension fabrication. Felix et al [11] described the implementation of thin film sensors in feedback control with a VCM only. The results demonstrated that minimal performance improvements could be achieved with the VCM actuator alone.…”