Control of Termal Off-Tack Compensation System of a Magnetic Disk Drive with Fine Head Positioning Mechanism.

A thermal off-track compensation system for a dedicated-servo-type magnetic disk drive with a piezoelectric fine head positioning mechanism has been developed. It measures the amount of the off-track displacement of each head at the reference cylinder whose tracks on data surfaces have position information. If the off-track displacement exceeds the limit, it is compensated by displacement of the piezoelectric fine head positioning mechanism. The piezoelectric actuator is driven along a predetermined voltage trajectory with regard to its calibration curve in order to be free from the hysteresis effect. Heat-run tests show that the system effectively suppresses the thermal off-track displacement.