4390912 Transducer Positioning System Nov80

This patent describes a transducer positioning system and a magnetic data disk for use in disk drive units within data processing systems.

The magnetic disk features:

• Interleaved sectors: Plural servo sectors are circumferentially spaced between data sectors.
• Servo blocks: Each servo sector contains at least two sets of spaced servo blocks.
• Servo signals: These blocks store first and second asymmetrical, time-displaced, complementary servo information signals, located in radially adjacent blocks.
• Track definition: Data track centerlines are precisely aligned with the phase boundaries of these servo signals.
• Sector indication: Includes a sector indicator to denote circumferential location.

The disk drive unit incorporates:

• A controller: This controller selects specific servo blocks.
• A null detector: Used to accurately position a movable transducer over a data track centerline by detecting null signals generated at the phase boundaries.
• A track difference counter: Responsive to the null detector, this counter counts zero crossings of phase boundaries during transducer movement. It indicates the displacement between the transducer and the desired data track and controls transducer movement for track seeking operations.

In essence, the invention provides a precise method for defining data tracks on a magnetic disk using specialized servo patterns and a control system that uses these patterns for both accurate track following and efficient track seeking.