Dynamic Tracking Servo System for High Density Digital Recording

Abstract

High-efficiency picture signal coding and high-density digital recording are important technical subjects for the next generation of digital VTR.
This paper proposes a new tracking control system for narrow-track digital recording.
We have developed a wideband dynamic tracking system using a voice-coil-type magnetic actuator to move the magnetic head and an observer based on modern control theory to suppress the mechanical resonance.
We have improved the stability of the tracking servo system so that it can fully track a recorded pattern with a 6, μm track pitch from the initial cross track condition.
We have also developed a method for generating the tracking error signal by using 12-15 modulation code with a built-in pilot signal.
When combined with a phase-sensing, this method accurately detects track linearity for digital recording.
We also confirmed the improvement of the tracking stability and accuracy when repetitive control is applied to the developed tracking system.