Nonlinear dynamic model of a pivot ball bearing in hard disk drive including the hertzian contact force

An areal density in magnetic recording commercialization hard disk drives(HDD) is 1.2 TB/in². It will be 1.5 TB/in² in 2016. The head-positioning control should be more accuracy because of the high magnetic density in HDD. Previous studies of head-positioning control are considered pivot friction torque or dual actuator control system. These are not considered structural characteristic of pivot ball bearing.