International Business Machines Corporation

Alan J Betts

Peter J Elliott

A head positioning system with automatic gain control for use in disk information storage apparatus employs multiphase radial position error signals derived from position reference information on the disk to control the position of a transducing head by means of a head positioning actuator. A variable gain amplifier amplifies the signals from the transducing head prior to their application to a position error signal generating means. The gain of the amplifier is controlled in a gain control loop by a gain function. The gain function is derived by combining the differnet phase position error signals to provide, at any position of the head, a measurement of the rate of change of the position error signals per track of displacement. This system affords gain control which is substantially independent of head width and limits variations in offtrack gain between heads.

Head positioning system with automatic gain control

A magnetizable recording disk is divided into data and servo sectors. The servo sectors include position reference information comprising a circumferentially extending and radially repeated magnetization pattern. Each such pattern comprises at least three subsets of elements from each of which a different phase of radial position error signal, indicating displacement from a data track center line, can be derived. The subsets are radially offset from each other by less than the pitch of the data tracks and their individual elements each have a radial width greater than the pitch of a data track. By making the width of the individual element of the servo pattern greater than that of the data tracks and, necessarily, greater than the physical width of the electromagnetic transducing head for reading and writing information on the disk, the contribution of neighboring elements to the signal sensed by the head via its fringing field is reduced. This results in a more linear position error signal in all regions where the head straddles the boundary between elements. A disk file comprising such a disk comprises, in addition to the electromagnetic transducing head, a head positioning actuator, position error signal generating means for generating the multiple phase position error signals and combining them into a composite signal and feedback means for feeding back the composite position error signal to control the actuator to correct for displacement of the head from a selected data track center line.

Growing community of inventors

Romsey, United Kingdom

Alan J Betts