US 11,990,153 B2
Magnetic disk drive and method of setting a notch filter of the drive
Takuji Matsuzawa, Kashiwa Chiba (JP)
Assigned to KABUSHIKI KAISHA TOSHIBA, Tokyo (JP); and TOSHIBA ELECTRONIC DEVICES & STORAGE CORPORATION, Tokyo (JP)
Filed by KABUSHIKI KAISHA TOSHIBA, Tokyo (JP); and TOSHIBA ELECTRONIC DEVICES & STORAGE CORPORATION, Tokyo (JP)
Filed on Mar. 15, 2023, as Appl. No. 18/184,567.
Claims priority of application No. 2022-152352 (JP), filed on Sep. 26, 2022.
Prior Publication US 2024/0112699 A1, Apr. 4, 2024
Int. Cl. G11B 20/10 (2006.01); G11B 5/596 (2006.01); G11B 19/20 (2006.01)
CPC G11B 19/20 (2013.01) [G11B 5/59622 (2013.01)] 16 Claims
OG exemplary drawing
 
1. 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.