Method and apparatus for starting a hard disk drive having separate landing and data zones

Abstract

A contact start/stop architecture for disk drives overcomes problems introduced by low flying MR (magnets resistive) heads and textured landing zones. Takeoff velocity for heads vary from the textured landing zone to the data zone. Contact start/stop operations are controlled relative to a critical takeoff velocity between takeoff velocity in the data zone and takeoff velocity in the landing zone, which critical velocity is less than that required to achieve negligible contact between the head and disk surface while the head is within the landing zone, but greater than takeoff velocity within the data zone. An initial seek from the landing zone begins at critical takeoff velocity. The head drags along the disk surface in the landing zone, since it has not reached takeoff velocity within the landing zone, but will immediately be at fly height as soon as the head reaches the data zone, minimizing the total drag distance of the head in the landing zone. A similar control scheme is used during a contact stop operation with respect to the head's landing velocity, which is equal to takeoff velocity. During contact stop operations, the actuator arm retracts the head into the landing zone at critical takeoff velocity. The servo control for initial seek from the landing zone utilizes back EMF (elecromative force) from the actuator voice coil motor without relying on servo information read by the MR head while the head is within the landing zone, since the MR head cannot accurately transduce magnetic transitions on rough surfaces.