Multivariate head-to-disk contact detection

Abstract

Magnetic disk drive systems and associated methods are described for precisely detecting contact of read/write elements of a recording head with a magnetic disk due to increasing a heating power applied to heating elements in the recording head. Contact is detected based on adjusted timing signals which are generated by measuring the current applied to a spindle motor, and generating an estimated timing signal from the measured motor current for increments of the heating power. An actual servo timing signal is simultaneously measured from servo fields on the magnetic disk, and the adjusted timing signals are calculated based on the difference between the estimated timing signal and the servo timing signal. Multivariate statistical analysis may also be performed on the adjusted timing signals and other contact indicative variables (such as off-track and slider vertical bouncing) to generate a likelihood of contact at the increments of the heating power.