Patent ID: 7420764

Claim:
A servo controller for a hard disk drive, comprising: means for obtaining a measured read-write head position Ycur; and means for calculating a control variable U based upon said measured read-write head position Ycur performing the steps: calculating an estimated state vector Xhat based upon a predicted state vector Xbar and based upon the difference between said measured read-write head position Ycur and a predicted read-write head position Ybar; calculating said control variable U based upon a regulator gain matrix K multiplied by said estimated state vector Xhat; replacing said predicted state vector Xbar based upon said estimated state vector Xhat and based upon said control variable U; and replacing said predicted read-write head position Ybar based upon said predicted state vector Xbar and based upon said control variable U; wherein each member of a state vector collection includes a read-write head position version, a read-write head velocity version and an unknown bias force version; wherein said state vector collection includes said estimated state vector Xhat and said predicted state vector Xbar; wherein said hard disk drive includes a disk surface accessed by a read-write head at said measured read-write head position Ycur; wherein said disk surface contains multiple physical tracks at a Track Per Inch (TPI); and wherein said TPI is at least 80,000 tracks per inch.