Transducer positioning servo mechanisms employing digital and analog circuits

摘要

A track-seeking system for an optical disk using a velocity control loop with partially-digitized velocity measurement. A quadrature signal is generated based on summing the halves of a position error signal to give directionality to track-crossing counts. A so-called piggy- back construction, wherein a fine positioner is carried by a coarse positioner, is employed. Feed-forward controls are provided from the fine to the coarse positioner. At track-capture time, the dynamic range of the fine positioner is momentarily increased.