A positioning control apparatus for a magnetic disk apparatus. Internal
models and a trajectory generation section are constructed in a control
program. Based on generated position trajectory and velocity trajectory
and an internal model position and velocity, a model control section
outputs a first operation signal Umf for a fixed sample time Tu and then
outputs a second operation signal Ums for Tu. The model control section
calculates Umf and Ums so as to cause a position Pm and a velocity Vm
output by an internal model 2Tu seconds later to coincide with the
generated position trajectory and velocity trajectory. When a detector has
detected a voice coil saturation current for head movement, a signal
obtained by subtracting a position feedback signal Uh from a detected
voice coil current is used as an internal model input to thereby cause the
model to track a control subject.
