Positioning systems including reliable track crossing detection for high speed relative motions

摘要

A track-seeking apparatus of a disk recorder employs a track- crossing sensor to produce track-crossing signals. An oscillator is slaved to the sensor for supplying substitute track-crossing pulses in the absence of the sensor providing such pulses or when the radial velocity exceeds a threshold velocity. A velocity profile means alters the oscillator frequency so that the oscillator produces track-crossing pulses in accordance with the profile.