Initial learn of adaptive feedforward coefficients

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.