| 摘要 |
In a magnetic disk drive, in the case of unloading a head, a carriage receives a driving force of a voice coil motor as a controlled object so as to drive the head, and then, a speed omega of the carriage is detected from a back electromotive voltage generated in a coil of the voice coil motor. A ramp collision discriminator makes a decision that the head collides with the ramp on the basis of at least one of the speed omega and a controlled manipulated variable fed back to the voice coil motor as being a controlled object from a speed controller. In the case where a ramp collision is discriminated, a gain changeover switch is controlled so that a speed feedback gain of the speed controller is changed into a high gain side. Therefore, when the head collides with the ramp, it is possible to prevent a great reduction of the carriage moving speed and a temporary stop of a carriage moving operation, and thus, to realize a stable head unload operation.
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