Magnetic disk device and controlling method of the same

1 . A magnetic disk device comprising:

a magnetic disk;

a magnetic head which writes data to and reads data from the magnetic disk;

a first actuator which causes the magnetic head to seek in a radial direction of the magnetic disk;

a second actuator which causes the magnetic head to be finely displaced in the radial direction of the magnetic disk;

a detection section which detects a flying amount of the magnetic head to the magnetic disk; and

a controller which controls drive of the first actuator and drive of the second actuator, wherein

the controller includes

a first control section which outputs and controls a drive voltage to the first actuator to cause the magnetic head to seek to a target position on the magnetic disk,

a second control section which outputs and controls a drive voltage to the second actuator to finely adjust the position of the magnetic head at the target position on the magnetic disk,

a voltage clipping section which changes the drive voltage to the second actuator, which is output from the second control section, in stages by a predetermined voltage clip value, and

an adjustment section which detects fluctuation in the flying amount detected by the detection section while superimposing a high frequency signal on the drive voltage to the second actuator, which is output from the second control section, and sets the predetermined voltage clip value of the voltage clipping section based on detection results.

2 . The device according to claim 1 , wherein

the adjustment section

sequentially sets a voltage clip value of the voltage clipping section to a plurality of test values when setting a test mode,

detects a maximum value of a flying amount detected by the detection section, while superimposing a first high frequency signal on a drive voltage output from the second control section to the second actuator and changing a frequency of the first high frequency signal, for each setting of the test values,

generates a first approximate curve of each of the detected maximum values, and

obtains the voltage clip value corresponding to the allowable value of the fluctuation of the flying amount from the generated first approximate curve, and sets the obtained voltage clip value as a voltage clip value of the voltage clipping section.

3 . The device according to claim 2 , further comprising:

a frequency filter which extracts a drive voltage of a predetermined frequency range among drive voltages output from the voltage clipping section to the second actuator, and

a protection section which stops write of the magnetic head and drive of the second actuator when the drive voltage extracted by the frequency filter exceeds a threshold value.

4 . The device according to claim 3 , wherein

the adjustment section

sets the frequency range of the first high frequency signal in which the maximum value of the flying amount is generated, as a frequency range which is to be a target of extraction of the frequency filter,

outputs a second high frequency signal from the adjustment section and sequentially sets a voltage amplitude value of the second high frequency signal to a plurality of test values,

detects a maximum value of a flying amount detected by the detection section, while superimposing the second high frequency signal on a drive voltage output from the voltage clipping section to the second actuator and changing a frequency of the second high frequency signal, for each setting of the test values,

generates an approximate curve of each of the detected maximum values, and

obtains a value of the drive voltage to the second actuator corresponding to the allowable value of the fluctuation of the flying amount from an approximate curve of each of the detection results, and set the obtained value as a threshold value of the protection section.

5 . The device according to claim 1 , wherein

the first actuator includes a voice coil motor, and causes the magnetic head to seek in a radial direction of the magnetic disk by drive of the voice coil motor, and

the second actuator includes a piezoelectric element, and causes the magnetic head to be finely displaced in a radial direction of the magnetic disk by drive of the piezoelectric element.

6 . A method of controlling a magnet disk device comprising a magnetic disk; a magnetic head which writes data to and reads data from the magnetic disk; a first actuator which causes the magnetic head to seek in a radial direction of the magnetic disk; a second actuator which causes the magnetic head to be finely displaced in the radial direction of the magnetic disk; and a detection section which detects a flying amount of the magnetic head to the magnetic disk:

the method comprising:

outputting and controlling a drive voltage to the first actuator to cause the magnetic head to seek to a target position on the magnetic disk;

outputting and controlling a drive voltage to the second actuator to finely adjust the position of the magnetic head at the target position on the magnetic disk;

changing the drive voltage to the second actuator, in stages by a predetermined voltage clip value, and

detecting fluctuation in the flying amount detected by the detection section while superimposing a high frequency signal on the drive voltage to the second actuator, and setting the predetermined voltage clip value of the voltage clipping section based on detection results.