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 the drive. The drive includes
a flex circuit that applies a bias force onto an actuator arm coupled to
the head. The circuit includes a state estimator that provides a
plurality of estimation errors and a bias estimator that creates a bias
estimate. The bias estimate includes an average of the estimation errors
and is a function of the flex circuit bias force. The bias estimate is
used to create the control signal provided to the voice coil motor. The
bias estimate reduces seek time during a seek routine.