Sensorless detection of a free-falling hard disk drive by electromechanical signal of a spindle motor

This paper numerically investigates the electromechanical signals of a spindle system of a hard disk drive when it is in freefall. Electromechanical simulation includes the time-stepping finite-element analysis of a speed-controlled brushless dc motor and the dynamic analysis of the stationary and rotating parts of the hard disk drive (HDD) under free-falling condition. It shows that the electromechanical characteristics of the spindle motor are affected by the relative motion between the stationary and rotating parts of a HDD and the gyroscopic moment of the rotating spindle during free-falling period. This research shows the possibility that the free-falling state can be detected by monitoring the electromechanical signals of a spindle motor without using any sensors.