Performance enhancement of multi-rate controller for hard disk drives

Minimum variance functional filtering for multirate sampled systems

“…In applications such as hard disk drives [12], the output information cannot be acquired fast enough in comparison with update of input. In such circumstance, it is appropriate to incorporate multirate input control algorithms [15].…”

“…This situation is likely to occur when it is not possible to sample all the physical variables of a system at a single rate or it is implemented for purposefully. Multirate sampling is used in wide rage of applications [12]- [14]. Generally, the signals associated with control applications are input u (t ), output y(t), and controller r (t ).…”

“…x(k) = <I>�I x(k + 1) -<I>� 1 r ru(k) -<I>�I'P rw(k) (12) Substituting (12) in (11) and shifting one sampling interval backwards results into Y k = Co<l>�lx(k) +Dou(k -1) + Cww(k -1) + Cvv(k -1) (13) where Do, Cw given by …”

A new method of multirate state feedback control with application to an HDD servo system

“…With the fast development of micro-electronics and digital signal processing techniques, control system designers have long been resorting to multirate control techniques to deal with the problem of limited sampling frequency [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. It has been shown that multirate sampling technique may greatly improve the system performance such as improving the transient system behavior, improving the system stability margins by relocating the plant zeros and enhancing the disturbance rejection property.…”

“…[2]), the control outputs are calculated based on not only the state estimates at sampling instants, but also the inter-sample state estimates. Much computation is needed to get the inter-sample state estimates in the conventional design.…”