  Floating operation is very critical in power management in hard disk drive
(HDD), during which no control command is applied to the read/write head but a
fixed current to counteract actuator flex bias. External disturbance induced
drift of head may result in interference of head and bump on the disk during
drifting, leading to consequent scratches and head degradation, which is a
severe reliability concern in HDD. This paper proposes a unique systematic
methodology to minimize the chances of hitting bump on the disk during drive
floating. Essentially, it provides a heuristic solution to a class of max-min
optimization problem which achieves desirable trade-off between optimality and
computation complexity. Multivariable nonlinear optimization problem of this
sort is reduced from NP-hard to an arithmetic problem. Also, worst-case is
derived for arbitrary bump locations.
