Electrostatic fly-height control

A hard disk drive comprising:

• a housing;
• a disk pack mounted to said housing and having a disk that is rotatable relative to said housing, said disk pack defining an axis of rotation and a radial direction relative to said axis;
• an actuator mounted to said housing and being movable relative to said disk pack, said actuator having a slider containing heads for reading data from and writing data to said disk;
• and
• a mechanism for maintaining a constant fly-height of said slider above said disk, said mechanism comprising:
• a capacitive fly-height change sensor configured for coupling with a slider in a head gimbal assembly, said capacitive fly-height change sensor configured for measuring capacitance between said slider and a surface of a disk through the use of a fly-height change sensing signal, said capacitive fly-height change sensor further configured for outputting a sensor voltage which is substantially proportional to a sensed change in said capacitance;
• and
• an electrostatic fly-height controller coupled with said capacitive fly-height change sensor and configured to couple with said slider, said electrostatic fly-height controller configured to process said sensor voltage into a fly-height control signal for electrostatically maintaining a constant fly-height of said slider relative to said surface of said disk, said electrostatic fly-height controller including a voltage biaser configured for applying a small bias voltage to said slider such that a non-linear relationship between said fly-height control signal and a resultant electrostatic force between said slider and said surface of said disk becomes closer to a linear relationship.

A mechanism for maintaining a constant fly-height of a slider, said mechanism comprising:

• a means for measuring a capacitance between said slider and a surface of a disk through the use of a fly-height change sensing signal;
• a means for outputting a sensor voltage which is substantially proportional to a sensed change in said capacitance;
• and
• a means for processing said sensor voltage into a fly-height control signal for electrostatically maintaining a constant fly-height of said slider relative to said surface of said disk, said means for processing said sensor voltage into a fly-height control signal including a means for applying a small bias voltage to said slider such that a non-linear relationship between said fly-height control signal and a resultant electrostatic force between said slider and said surface of said disk becomes closer to a linear relationship.