ROTATIONAL RECORDING APPARATUS AND CONTROL METHOD

A technique for adaptively and stably updating the feed forward value required to drive the head of a rotational recording apparatus. A trajectory of a target position is generated for each seek command by using a compound function comprising a ramp function and a sine-wave function. The sine-wave element of the target position is transmitted to an adaptive filter for updating coefficients of the compound formula. All elements other than the sine-wave element are removed to provide a smooth update of the compound function's coefficients.