KR19980026197A - Hysteresis compensation method of hard disk drive - Google Patents

Abstract

end. TECHNICAL FIELD The present invention relates to a hard disk drive, and more particularly, to a bias calibration method for servo control of a hard disk drive.

I. The technical problem to be solved by the present invention: In the conventional track search operation, the bias value is different from the actual stored table value when the search operation is performed by changing the direction of the head which is actually moving forward. It occurs temporarily, which is similar to the hysteresis of magnets. In this case, if the offset between the forward bias value and the reverse bias value is different from each other by a large deviation, the hysteresis phenomenon acts as long as the track search time is long when the direction change is performed. Solve the problem.

All. SUMMARY OF THE INVENTION The present invention relates to a method of correcting a bias value to compensate for hysteresis caused by a large deviation when a search direction is changed during a track search operation of a hard disk drive.

la. Important use of the invention: hysteresis compensation method of hard disk drive.

Description

Hysteresis compensation method of hard disk drive

The present invention relates to a hard disk drive, and more particularly, to a bias calibration method for servo control of a hard disk drive.

In general, a hard disk drive is a device that magnetically writes / reads data on a rotating magnetic disk and is widely used as a secondary memory device of a computer system because it can access a large amount of data at high speed. do. Such hard disk drivers are stored in tracks arranged concentrically on a rotating magnetic disk. These tracks are accessed by a magnetic head for reading and writing data on the magnetic disk. The magnetic head is moved in the radial direction on the magnetic disk by head position servo control which can be selectively positioned on any one of the tracks. As such, the bias value for servo control to selectively position the head on a specific track must be effectively compensated. In this case, the bias value is a value that must be applied in advance in order to move the magnetic head at the position of each track during the track search operation by moving the magnetic head to each track on the disc.

Therefore, this bias value is measured by a bias calibration step when the power is initially applied, stored as a table value, and used as the target track at a faster time by using the stored value during track search or track tracking operation. The head can be positioned. However, as shown in FIG. 1, when the search operation is performed by changing the direction of the head which is actually moving forward in the track search operation in the backward direction (operation from point A to B to point C as a target track) When the head is moved), the bias value is different from the table value actually stored, which is similar to the hysteresis phenomenon of the magnet (between A point and B point). In this case, if the offset between the forward bias value and the reverse bias value is different from each other by a large deviation, the hysteresis phenomenon acts as long as the search time of the track is long when changing directions and the desired servo control cannot be performed. There was a problem.

An object of the present invention relates to a method of correcting a bias value to compensate for hysteresis caused by a large deviation when a search direction is changed during a track search operation of a hard disk drive.

The present invention for achieving the above object is a method for compensating for the hysteresis phenomenon of the bias occurring when the track search direction of the hard disk drive changes, from the innermost track to the outermost track on the disk when the power is initially applied Hysteresis gradient that occurs when the track search direction is changed during the track search operation by moving the magnetic head according to the stored bias table and moving the magnetic head according to the stored bias table. And calculating a bias value stored in a table by using a bias value corresponding to the hysteresis slope when performing track search by changing the track direction.

1 is a bias characteristic curve of a conventional hard disk drive.

Figure 2 is a block diagram of a general hard disk drive applied to the present invention.

3 is a general bias correction control flow chart applied to the present invention.

FIG. 4 is a detailed bias correction control flowchart considering hysteresis in FIG. 3.

5 is a control flow diagram for calculating the hysteresis slope in FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

2 is a block diagram of a general hard disk drive according to the present invention, in which the disks 210 are rotated by a spindle motor 234. The magnetic heads 212 are located on the corresponding one of the disks 210 and face the disks from the E-block assembly 214 coupled with the rotary voice coil actuator 230. Corresponding to the support arms extending toward 210, respectively. The preamplifier 216 preamplifies the signal picked up by one of the heads 212 at the time of read, and applies the analog read signal to the read / write channel circuit 218. Encoded write data applied from the read / write channel circuit 218 is written onto the disc through the corresponding one of the heads 212. The read / write channel circuit 218 detects and decodes a data pulse from a read signal applied from the preamplifier 216 and applies the read / write channel circuit 218 to the disk data controller 220. Decode and apply to preamplifier 216. The DDC 220 writes data received from the host onto the disc through the read / write channel circuit 218 and the preamplifier 216. The DDC 220 also interfaces the communication between the host computer and the microcontroller 224. The buffer RAM 222 temporarily stores data transferred between the host computer, the microcontroller 224 and the read / write channel circuit 218. The microcontroller 226 controls the DDC 220 in response to a read or write command received from the servo writer and controls track search and track following. The PROM 26 stores the execution program of the microcontroller 224 and various setting values. The servo driver 228 generates a driving current for driving the actuator 230 by a signal for controlling the position of the heads 212 generated from the microcontroller 224 and applies it to the voice coil of the actuator 230. . The actuator 230 moves the heads 212 on the disks 210 corresponding to the direction and level of the driving current applied from the servo driver 228. The spindle motor driver 232 rotates the disks 210 by driving the spindle motor 234 according to a control value for the rotation control of the disks 210 generated from the microcontroller 224. The disk signal controller 236 generates various timing signals necessary for read / write under the control of the microcontroller 224, decodes the servo information, and applies the decoded servo information to the microcontroller 224.

Hereinafter, the control flow diagrams of FIGS. 3, 4, and 5 will be described in detail with reference to the block diagram of FIG. 2 attached to the present invention.

First, FIG. 3 is a flow chart of bias correction control when general power is applied to the present invention. When power is initially applied in steps 310 to 320, the microcontroller 224 initializes all variables in the ROM 226. Then, in step 330, the microcontroller 224 generates a control signal to the servo driver 130, and the servo driver 130 drives the actuator 114 equipped with the magnetic head 212. The current is applied to the unlatching operation. Then, in step 340, the head is driven from the innermost track to the outermost track to measure the bias in each track and perform a bias correction step. Then, the process of entering the track search mode and performing the track search after performing the bias correction step will be described with reference to FIG. 4. When the track search mode is first performed, the microcontroller 224 may perform a track in step 410 to 420. When the search direction in the search is changed (that is, when the moving magnetic head passes the target track while searching for the track with the target track), the microcontroller 224 changes the track search direction and thus the search distance to the target track. When the difference minus the minimum hysteresis width (ie, γ distance shown in FIG. 1) from the SK-len distance shown in FIG. 1 is greater than the distance to continue searching (ie, the variable value α shown in FIG. 1), step 430. The track search is performed using a general bias insertion method, but the distance searched for by the difference from the search distance to the target track minus the minimum hysteresis width is continued. In step 440, the track search is performed by using a hysteresis bias insertion method when it is smaller than or equal to α) shown in FIG. 1. In this case, a method of obtaining the slope of the hysteresis bias used in the hysteresis bias insertion method will be described in detail with reference to FIG. 5. FIG. 5 is a control flowchart for calculating the hysteresis slope of FIG. 4. First, in step 502, the microcontroller 224 initializes the bias measurement variable i from the point where the track search direction is changed. Thereafter, in step 504, the microcontroller 224 detects whether the changed track search direction is in an outer data track (OD) direction from an ID (inner data track) direction. In this case, when the track search direction is changed from the ID direction to the OD direction, in step 506, the microcontroller 224 has a minimum hysteresis width (i.e., a distance of the point A shown in FIG. 1). , And the bias value of the point (point B in FIG. 1) minus the γ distance indicated in FIG. 1 is measured and inserted into the table. Then, in step 510 ~ 514 the microcontroller 224 calculates the slope of the hysteresis by the following equations (1, 2, 3).

[Equation 1]

[Equation 2]

[Equation 3]

However, when the track search direction detected in step 504 is changed from the OD direction to the ID direction, in step 508, the microcontroller 224 has a minimum distance to the start point cylinder distance (ie, the distance B point shown in FIG. 1). The bias value of the point (point A in FIG. 1) plus the hysteresis width (i.e., γ distance indicated in FIG. 1) is measured and inserted into the table. Then, in step 510 ~ 514 the microcontroller 224 calculates the slope of the history by the equations (1, 2, 3).

In conclusion, the method of calculating the hysteresis slope as described above is performed just before the track search direction is changed and the search operation is performed in the opposite direction, and the hysteresis calculated at the beginning of the search at a distance equal to the initial minimum hysteresis width during the actual search operation is performed. The hysteresis bias insertion method is used to compensate the bias value based on the slope, and when the distance passes by the minimum hysteresis width, the track search operation is performed to the target track using the bias insertion method according to a general method.

As described above, the present invention provides a method for correcting a bias value to compensate for hysteresis caused by a large deviation when a search direction is changed during a track search operation of a hard disk drive. There is an advantage to search and more effective servo control.

Claims (2)

In the method for compensating for the hysteresis of the bias occurring when the track search direction of the hard disk drive is changed, When the power is initially applied, the process of measuring and storing the bias value for positioning the magnetic head on the entire track from the innermost track to the outermost track on the disk to the table, Calculating a hysteresis slope that occurs when the track search direction is changed while the track search operation is performed by moving the magnetic head according to the stored bias table; And a bias value stored in a table using a bias value corresponding to the calculated hysteresis slope when the track search direction is changed and the track search direction is changed. The method of claim 1, The hysteresis bias compensation method is used within the distance of the minimum width of the hysteresis generated when the track search is changed by changing the track search direction, and the general bias insertion method is used after the distance of the minimum hysteresis width to the target track. A method for compensating for hysteresis of a hard disk drive, further comprising a process of searching for a track.