Magnetic recording-head positioning at very high track densities using a microactuator-based, two-stage servo system

The storage capacities and areal densities found in magnetic disk drives are increasing very rapidly. Data is recorded in ever-narrower tracks which must be followed with extreme precision. Also, the advent of portable applications exposes these smaller drives to higher levels of vibration and shock. A description is given of the many factors which contribute to recording track misregistration (TMR) in today´s drives. The mechanics of the drive and actuator and the architecture of the servo control system are also described. A projection is made for the TMR sensitivities and control system at an areal density of 10 Gb/in², having roughly 25000 tracks/in. A two-stage servo may be needed to achieve such track densities. This would comprise a high bandwidth microactuator for rapid position corrections of the recording head, coupled with a conventional actuator. The characteristics of such a microactuator are discussed, and operational examples of fabricated electroplated microactuators, driven electrostatically, are shown. The mechanical behavior of the devices and some of the factors which would affect their implementation are also described