Patent Number: 6,310,742

Title: Repeatable runout cancellation in sectored servo disk drive positioning system

Abstract: A method in a magnetic storage disk drive for independently learning and thereafter canceling repeatable runout that is written to the servo fields of each servo track during the servo writing process. The method does not require a servo writer because the disk drive may independently detect the runout without spinning out of control in response to such runout by operating its servo control loop in a low bandwidth mode so that it is less responsive to the higher frequency components of the runout, and by removing the effect of the DC component of the runout or selected harmonics on each revolution. The method takes several revolutions to "learn" the servo wedges of a current track by initializing a wedge runout value for each servo wedge and an average uncorrected runout value and then successively developing an interim wedge runout estimate for each servo wedge by adding a fractional portion .lambda. of a raw position error signal to a fractional portion (1-.lambda.) of the wedge runout value, computing a corrected position error signal by subtracting the interim wedge runout estimate from the raw position error signal, and computing a new wedge runout value by subtracting the average uncorrected runout value from the interim wedge runout estimate and, subsequent to each revolution, updating the average uncorrected runout value.

Inventors: Nazarian; Ara W. (Tustin, CA), Simmons; Charles W. (Phoenix, AZ), Trieu; Thao P. (Redwood City, CA), Wong; Richard K. (San Jose, CA)

Assignee: Western Digital Technologies, Inc.

International Classification: G11B 5/596 (20060101); G11B 005/596 ()

Expiration Date: 10/30/2018