Hard Disk Drive Magnetic Heads Parking

Most hard disk drives have the special track which is designed for landing and launch of the magnetic heads. This track is named parking zone since in spite of the fact that the surface of a magnetic disk and a magnetic head are designed with a glance to possible casual contacts, it is still preferable to park heads on the part of a magnetic plate surface with no data recorded to. The hard disk drive is designed for certain quantity of parkings of magnetic heads, owing to deterioration of kinematics. In SMART technology two sensors are provided for tracing this parameter. The first one traces the quantity of connections to power supplies, and the second one traces the quantity of starts of the spindle motor without disconnecting from power supplies, e.g. at an exit of the disk drive from power-saving mode.

All the hard disk drives are provided with the mechanism of an automatic parking at power supply turn off. Usually the auto parking is carried out by kinetic energy of magnetic disks rotation. At deenergization spindle motor is used as the generator, and the energy extracted from its windings is used for moving the magnetic heads to parking position before lowering of speed of rotation below critical level at which magnetic heads start to touch the disk surface. After heads reach the parking zone, the blocking of system of positioning by a magnetic latch (a small constant magnet) is performed, and smooth landing of heads to the magnetic disk surface is carried out. In modern hard disk drives the alternative method is applied - instead of allowing magnetic heads to fall to a surface, heads are completely removed from magnetic disks on a special parking platform. At power-up the disks are being spun to the necessary speed, then heads "fly down" from the platform on a surface of plates which turns at speed high enough to avoid the contact of the heads with magnetic plates.