Shock-response-spectrum analysis of sampled-data polynomial for track-seeking control in hard disk drives

To decrease the seek time of hard disk drives, a feedforward control method was developed by using a sampled-data polynomial to compensate for discretization errors of the zero-order hold. The sampled-data polynomial satisfies the boundary conditions that include the characteristics of the zero-order hold, and compensates for the discretization error caused by the zero-order hold without the need for complicated calculations. The feedforward control with a polynomial enables real-time calculation without the need for look-up tables, which require a large amount of memory. Moreover, the waveform of the feedforward control input generated by using the polynomial is smooth and decreases the magnitude of the mechanical vibrations by using shock-response-spectrum (SRS) analysis. When the proposed method was applied on a hard disk drive it significantly reduced the amount of tracking error in the seek control and also reduced the seek time.