Non-destructive in-situ landing velocity determination of magnetic rigid

Abstract

A method is described for testing for slider/disk contact in a disk drive comprising a rotating disk and a head mounted by an actuator for selective positioning of the head over the disk, the head having a slider, and a spindle motor for rotating the disk. The method comprises the steps of providing power to the spindle motor to cause rotation of the disk at a preselected rotational velocity corresponding to a rotational velocity designed for the disk during normal read/write operation, and thereafter withdrawing the power from the spindle motor such that the disk spins down to zero rotational velocity. While the disk spins down to zero rotational velocity, an acoustic coupling is formed between an acoustic emission sensor having an electric output and the spindle motor to provide first electric signals representative of acoustic emissions from the spindle motor, including acoustic emissions caused by slider/disk contact. While the disk spins down to zero rotational velocity, an electric probe is coupled to the spindle motor to provide second electric signals representative of back EMF generated by the spindle motor as the disk spins down to zero velocity. The first electric signals are monitored for a first indication of slider/disk contact, and the second signals are utilized at the time of the first indication of slider/disk contact from the first electric signals, to calculate the rotational velocity of the disk at the time of the first indication of slider/disk contact. The calculated rotational velocity is compared to a threshold value relevant to a desired take-off or landing velocity for the head of the disk drive, and an indication is made when the calculated rotational velocity exceeds the threshold value.