Servo system for data storage apparatus

A transducer positioning servo system for use in a random access disk memory which includes positioning means for moving the transducer from track to track in response to commands and corrective position error signals and a disk subdivided into sectors with data sector portions alternated circumferentially with servo sector portions and wherein the track portions within said servo sector portions are offset a half-track pitch from the tracks in said data sector portions;

• a sequence of radially adjacent servo tracks in each servo sector with each servo track having a timing mark signal followed by a sequence of four signal locations and a magnetic transition occurring in one of said four signal locations;
• said magnetic transitions occurring in said signal locations such that a sequence of four radially adjoining servo tracks has magnetic transitions at unique signal locations;
• and
• detection means connected to receive the magnetic transitions from said four signal locations and generate said position error signal substantially linearly representative of the deviation of the transducer from the data track center line identified by said sequence of four radially adjoining servo tracks.

In a data storage device of the type wherein a data track is aligned by locating a transducer with respect to the interface between adjoining servo tracks, a servo system for positioning the transducer relative to a given data track comprising:

• a first sequence of at least four radially adjacent servo track portions;
• a unique signal recorded in each of said four servo track portions of said first sequence;
• a quadrature servo portion following said first sequence of four radially adjacent servo track portions, said quadrature portion being divided into a second sequence of four radially adjacent servo track portions with each having a unique signal within said record sequence;
• analog sensing means including said transducer for sensing the signal magnitude received from said servo track portions;
• first circuit means for imparting a first signal strength to the value of the signals of a first pair of servo track portions of said first sequence that form the interface defining the centerline of the data track and a second, higher signal strength to the value of the signals of the servo track portions of said first sequence forming a second pair of servo track portions that immediately respectively adjoin the first pair of servo track portions of said first sequence,
• second circuit means for imparting a third signal strength to the values of the signals of the central pair of the second sequence of servo track portions and, a fourth, higher signal strength to the pair of said second sequence of servo track portions disposed at opposite radial sides of said central pair;
• and
• selectively gating said first and second circuit means to produce a substantially linear position error signal output over a three track range of transducer position.