Patent ID: 8737010

Claim:
A disk drive comprising: a head for accessing a disk, an actuator for moving said head in a radial direction of said disk, and a controller for servo control of said actuator based on servo data read out from said disk by said head, wherein said controller is configured for maintaining a width of an adaptive chasing notch filter below a specified value in servo system control and estimating an oscillation frequency of said actuator, wherein said controller compares a magnitude of a value in a calculation of said estimate of said oscillation frequency to a threshold, and estimates said oscillation frequency and updates a center frequency of said adaptive chasing notch filter when said value is greater than said threshold, and wherein said controller compares a function value representing said oscillations of said actuator and a first threshold to judge whether said oscillations have stopped, and increases said width when said function value is between a second threshold which is less than said first threshold, and a value of said width of the adaptive chasing notch filter which stops said oscillations is less than a Wmin value, wherein said Wmin value is greater than said value of said width which stops oscillations to said width of said adaptive chasing notch filter.