HEAD POSITIONING SYSTEM FOR COMPENSATING FOR ERRONEOUS DETECTION OF RECORDED POSITION ERROR INFORMATION

A head positioning system includes a calculating circuit for outputting a signal u.sub.k corresponding to an equilibrium of a step motor for driving a head on the basis of a position error of the head detected at each sampling time. The calculating circuit includes a first calculator for calculating a temporary equilibrium u".sub.k on the basis of a position error, a memory for storing u.sub.k-1 to u.sub.k-N at respective sampling times, a predictor for calculating a predicted value u'.sub.k and an average value u'".sub.k in accordance with outputs from the first calculator and the memory, a comparator for comparing u'.sub.k with u".sub.k to check if they satisfy certain conditions, outputting u".sub.k as u.sub.k to a step motor driver when the conditions are satisfied, and outputting u'".sub.k as u.sub.k to the step motor driver when the conditions are not satisfied, and a second calculator, activated by the comparator when the conditions are not satisfied, for calculating back the position error using the output u.sub.k from the comparator so that the first calculator recalculates u".sub.k.