US 7,031,095 B2Granted

Servo controller method and apparatus for high tracks per inch hard disk drives using a delay accomodating state estimator

AssigneeSamsung Electronics Co., Ltd.

InventorsYoung-Hoon Kim, Sang Hoon Chu, Seong-Woo Kang, Dong-Ho Oh, Yun-Sik Han, Tae Yeon Hwang

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Abstract

The invention applies to servo controllers for at least the voice coil motor of a hard disk drive. Today, many control algorithms require 80 to 90 percent of the sampling period to complete their calculation of the next control, making computation time delay no longer negligible. The invention accommodates the transport delay, such as computation time delay, into the state estimator and into the whole control system. Experimental results using a commercial hard drive, as well as simulation results, show that the invention's method effectively improves the hard disk drive control system stability by increasing the phase margin and gain margin. The invention includes the method of operating the servo-controller, as well as the apparatus implementing that method. The invention also includes hard disk drives containing servo-controllers implementing the method, and program systems residing in accessibly coupled memory to a computer within the servo controller implementing the method.

Claims14

Dependent claims

A hard disk drive, comprising:

means for controlling a voice coil actuator contained in said hard disk drive by a control variable U based upon a measured read-write head position Ycur;
and said hard disk drive further comprising at least one member of the collection comprising:
means for seeking a first track located at a first head position by using said means for controlling said voice coil actuator to alter said measured read-write head position Ycur based upon said control variable U;
and
means for following said first track located at said first head position by using said means for controlling said voice coil actuator to maintain said measured read-write head position Ycur close to said first head position based upon said control variable U;
wherein the means for controlling said voice coil actuator is further comprised of:
means for obtaining said measured read-write head position Ycur;
and
means for calculating said control variable U based upon said measured read-write head position Ycur;
wherein the means for calculating said control variable U based upon said measured read-write head position Ycur performs the steps of:
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.

18 more elements

A method for controlling a voice coil actuator by a control variable U in a hard disk drive based upon a measured read-write head position Ycur, comprising the steps of:

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.

8 more elements

Dependencies are inferred from the claim text.