| 摘要 |
PROBLEM TO BE SOLVED: To accurately determine stability of a storage device provided with a mechanism for controlling head positioning. SOLUTION: While a servo control unit 81 following-controls a head 12, an external disturbance application part 82 applies an external disturbance current to a VCM driving current output from a VCM driving part 90, and a measuring part 83 measures open-loop frequency characteristics of a gain and a phase from the external disturbance applied VCM driving current and a return VCM driving current. A distance (Nyquist distance) between a point of each frequency on Nyquist locus and a point (-1, 0) of a complex plane is measured when Nyquist locus is drawn based on the measuring results. A determination part 84 determines stability of the storage device based on Nyquist distance. COPYRIGHT: (C)2009,JPO&INPIT
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