Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Adaptive Repeatable Runout Cancellation Method and Algorithm for Disk Drives

IP.com Disclosure Number: IPCOM000010278D
Original Publication Date: 2002-Nov-14
Included in the Prior Art Database: 2002-Nov-14
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Abstract

A new method is disclosed to calibrate a hard disk drive to cancel repeatable runout (RRO) frequency components. The basic principle is to measure the position error signal (PES) in each servo sampling and the servo control system adaptively learns to cancel selected frequency components of the RRO in the PES.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 2

Adaptive Repeatable Runout Cancellation Method and Algorithm for Disk Drives

A new method is disclosed to calibrate a hard disk drive to cancel repeatable runout (RRO) frequency components. The basic principle is to measure the position error signal (PES) in each servo sampling. The servo control system adaptively learns to cancel selected frequency components of the RRO in the PES as a new part of the usual servo calibration process after the drive powers on or during the error recovery process. This adaptation process results in a feedforward table that is used after servo calibration to cancel the selected RRO components.

The PES that indicates the head position with respect to the write track center is obtained in each servo sampling, and along with the PES information in the previous samples, an adaptive control value is calculated for each servo sampling to minimize the PES. The adaptive control value is added to the normal positioning loop control before the combined control is fed to the DAC to drive the actuator to affect the PES. The adaptive control value at the current servo sector is recorded into a table that is indexed by the servo sector ID. The table entry for a particular servo sector ID may be updated when the same servo sector is encountered in the next disk revolution. As a result of this feedback adaptive control the PES is decaying to a low level, and the correct control is being recorded.

Figure 1 shows the adaptation process and the generation of the feedforward control table. The 1st curve shows the cylinder positions, the 2nd curve shows the PES is decaying during the learning process af...