Reduction of external vibration in hard disk drives using adaptive feed-forward control with single shock sensor

In recent years, an increasing number of portable electronic devices, such as portable computers and MP3 digital audio players, have been equipped with hard disk drives (HDDs) to store digital data. In these portable devices, HDDs are exposed to external vibrations and shocks. These external disturbances increase the position error, consequently reducing the performance of the HDDs. We propose adaptive feed forward (FF) control with a single shock sensor to improve the head positioning accuracy in magnetic hard disk drives. Since the transfer function relating the acceleration measured by a shock sensor and the position error signal (PES) depend on the characteristics of the applied force, such as the direction or the frequency, an on-line identification of the relating system is needed. Our proposed scheme applies an adaptive control technique to indirectly identify this relationship, i.e., the coefficients of the finite impulse response (FIR) controller are updated by a gradient algorithm so that the magnitude of the PES is minimized. Our numerical simulations and experiments illustrate the effectiveness of our proposed method