The present invention reduces the time required for coefficient
convergence and thus improves time-to-ready. To that end, the present
invention provides an initial learn--preferably non-zero--coefficient.
The initial learn coefficient is based on a translation of timing
information to position information. One aspect of the present invention
uses address marks of a disc then translates them to phase position
information. The present invention measures the times between address
marks of adjacent servo sectors. Variations between those times is
related is related to disc runout, particularly disc eccentricity. Also,
the servo sectors are used to identify at which phase the maximum
amplitude (or magnitude) of the timing variations occur. This phase
information and maximum amplitude are used as variables in determining
the initial learn coefficient. The present invention also utilizes a
plant model to predetermine a variable. This variable is used in
conjunction with the phase and maximum amplitude variables to determine
the initial learn coefficient. Other aspects of the present invention use
approximations or statistical values to determine the initial learn
coefficient. For example, the maximum amplitude can be based on a
clearance between an inner diameter of a disc and a spindle. The phase
can be based on a value within a range of phases. The plant model can be
changed to include assumptions, approximations or other factors.