Patent ID: 7672073
Filing Date: 2010-03-02
Classification: G11B

Abstract:
1. A method for operating a magnetic head tester or host hard disk drive using magnetic hard disks on which servo information has been pre-written, comprising: providing a magnetic head tester or host hard disk drive, either device including a motor driven rotating spindle on which a magnetic hard disk is to be mounted, a movable head actuator assembly, a slider encapsulated read/write head to be tested that is affixed to said head actuator assembly and is positioned at selected target locations on said disk by the movement of said actuator assembly and reads information stored within servo sectors thereat, and an electro-mechanical servo-control system, operable at various bandwidths, for responding to a stored position error signal (PES) that is storable within a data storage mechanism within said devices and of thereby controllably positioning said head at said target locations; mounting on said spindle a magnetic hard disk on which has already been pre-written, in an external apparatus, a plurality of concentric circular tracks, wherein each said track contain regularly spaced servo sectors, said servo sectors including embedded information defining radial and angular positions within each said track and wherein each said track is further characterized by written-in position errors and wherein said written-in position errors and repeatable runout produce repeatable position errors in each said track and generate corresponding first position error signals for each said track when said hard disk is operated in said head tester or said host hard disk drive; then nullifying said repeatable position errors by iteratively forming from each of said plurality of concentric circular tracks an IRON (Iterative Repeatable Run-Out Nulling) profile track wherein each said IRON profile track is characterized by a second position error signal that has a substantially zero magnitude whereby there is significantly reduced head acceleration during track-seeking, track-following and read/write operations along said IRON profile track and along which said IRON profile track the head effectively follows a circular track and wherein said IRON profile track is formed by a method comprising: (a) setting the servomechanism to a low bandwidth condition and locating a first concentric circular track; (b) measuring the initial time average PES profile in the time domain by averaging the PES at servo sectors located along the track location; (c) using a FFT (Fast Fourier Transform), finding the frequency domain profile of the PES measured in (b), then removing its fundamental rotation frequency; (d) measuring the dynamic rejection response of the complete servo system, including the head, the electro-mechanical components and the servo actuating system; (e) calculating the actual input PES freciuency domain profile by eliminating the dynamic rejection response measured in (d); (f) using an inverse FFT on the actual input PES frequency domain of (e), finding the actual time domain profile of the input PES time sequence; (g) using the profile obtained in (f) as the profile in (b), repeating steps (b) to (g) until an acceptable degree of rms (root mean square) accuracy for said PES time domain profile is obtained; then (h) using the resulting PES time domain profile of (g) as a reference profile to define said IRON profile track.