A hard disk drive with a circuit that provides a control signal to a voice
coil motor to move a head across a disk of a drive. The circuit includes
a state estimator that provides a plurality of state estimates and a
disturbance estimator that provides a disturbance estimate that is
combined with the state estimates to define the control signal. The
disturbance estimator compensates for flex cable disturbances,
particularly during a settle mode of a seek routine.