Patent ID: 7072134
Filing Date: 2006-07-04
Classification: G11B

Abstract:
1. A disk drive comprising: a rotatable magnetic recording disk having a plurality of concentric data tracks, the data tracks containing servo positioning information; a recording head movable across the disk, the head being capable of reading data and servo positioning information in the data tracks; a primary actuator for moving the head; a test location where movement of the primary actuator is substantially limited; a secondary actuator connected to the primary actuator, the head being connected to the secondary actuator; a relative-position sensor coupled to the secondary actuator for generating a secondary actuator relative-position signal (RPS) representing the position of the secondary actuator relative to its neutral position; and a servo control processor responsive to servo information read by the head and comprising a dual-stage controller for generating a primary actuator control signal and a secondary actuator control signal, the processor capable of (a) sending a location signal to the primary actuator for moving the primary actuator to the test location, (b) generating a test signal to the secondary actuator when the primary actuator is at the test location, the amount of movement of the secondary actuator as a function of test signal value being the stroke of the secondary actuator, and (c) calculating the stroke from the RPS in response to the test signal.