Magnetic disk drive and method of setting a notch filter of the drive
AssigneesKabushiki Kaisha Toshiba, Toshiba Electronic Devices & Storage Corporation
InventorTakuji Matsuzawa
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Abstract
According to one embodiment, a magnetic disk drive includes a notch filter, a parameter storage unit and a computation unit, when the sampling period changes from a first sampling period to a second sampling period, the computation unit computes a damping ratio parameter related to the damping ratio in a second set of parameters at the second sampling period, based on a first absolute value at a first angular frequency of a first transfer function computed from a first set of parameters at the first sampling period and a second absolute value at the first angular frequency of a second transfer function computed from the first set of parameters at the second sampling period, and the notch filter is set with the second set of parameters at the second sampling period is computed.
Claims16
A magnetic disk drive in which a sampling period of positional information recorded on a magnetic disk changes according to a rotation speed of the magnetic disk, comprising:
- a notch filter provided in a controller which controls positioning of the magnetic head to suppress a specific angular frequency by setting a set of parameters related to at least a suppression angular frequency, a damping ratio and a depth in consideration of the sampling period;
- a parameter storage unit which stores a first set of parameters of the notch filter and a first sampling period assumed when the first set of parameters is designed;
- and
- a computation unit that computes a discrete-time system transfer function from the sampling period and the set of parameters using a continuous-time system transfer function and a bilinear transform,
- wherein:
- when the sampling period changes from the first sampling period to a second sampling period, the computation unit computes a damping ratio parameter related to the damping ratio in a second set of parameters at the second sampling period, based on a first absolute value at a first angular frequency of a first transfer function computed from the first set of parameters at the first sampling period and a second absolute value at the first angular frequency of a second transfer function computed from the first set of parameters at the second sampling period;
- and
- the notch filter is set with the second set of parameters at the second sampling period.
A method of setting a notch filter provided in a controller which controls positioning of a magnetic head of a magnetic disk drive in which a sampling period of positional information recorded on a magnetic disk changes, to suppress a specific angular frequency by setting a set of parameters related to at least a suppression angular frequency, a damping ratio and a depth in consideration of the sampling period, the method comprising:
- computing a discrete-time system transfer function from the sampling period and the set of parameters using a continuous-time system transfer function and a bilinear transform;
- when the sampling period changes from a first sampling period to a second sampling period, computing a damping ratio parameter related to the damping ratio in a second set of parameters at the second sampling period, based on a first absolute value at a first angular frequency of a first transfer function computed from a first set of parameters at the first sampling period and a second absolute value at the first angular frequency of a second transfer function computed from the first set of parameters at the second sampling period;
- and
- setting, in the notch filter, the second set of parameters at the second sampling period.
Dependencies are inferred from the claim text.