Optimal track-following design for the highest tracks per inch in hard disk drives

Abstract

This paper presents an optimal track-following control design procedure that can find the theoretical highest tracks per inch (TPI) achievable in hard disk drives. By formulation of the hard disk drive servo system into an H2 optimal control problem, achieving the highest achievable TPI is equivalent to minimizing the corresponding H2 norm from the disturbances and noise to the true PES. Thus, the standard output feedback H2 optimization procedure can be used. The design method is applied to a single-stage actuator system and a dual-stage actuator system, and the corresponding output feedback controllers have been found. Compared with other design approaches, a higher TPI rate can be achieved by the proposed method. The resultant TPI rate can be a criterion of evaluation of any other linear design work toward TPI budget improvement.