A position control apparatus which includes position error signal detection means
for detecting a position error signal of the mechanical part and position control
means for controlling the position of the mechanical part by supplying to it the
position error signal from the position error signal detection means, whereby the
apparatus has provided therein phase compensation means comprising a digital filter;
the position error signal is supplied to the phase compensation means to perform
phase compensation thereon and the phase-compensated position error signal is supplied
to the position control means; and, when starting a closed-loop control, filter
variables that were used at a time preceding by an amount of time equal to or greater
than that corresponding to the amount of one sampling time of the digital filter
have been reset.