Maintaining a constant small flying height of the read/write head is an important target in the design of the ultra high storage density hard disk drives. One effective way to achieve this goal is to use a feedback regulator to suppress the flying height variations. For low flying heights, the read/write head enters into intermittent contact with the disk surface, which results in a switched system regulation problem. In this paper a new control method is proposed to maintain the flying height at its desired value based on the switched system models, despite the unknown microwaviness in the disk surface profile and the unpredictability in the switching times. First, a switched system model is constructed. Then, a Q parameterized set of switched regulators is constructed and the stability of the resulting switched closed loop system is analyzed. Online adaptive regulator tuning is then performed by adjusting the Q parameter in the controller to achieve regulation. Simulation results are presented to illustrate the effectiveness of the proposed method.

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