KR100403049B1 - Method for compensating for position error signal and timing deviation of hard disk drive - Google Patents

Abstract

PURPOSE: A method for compensating for the PES(Position Error Signal) and the timing deviation of an HDD(Hard Disk Drive) is provided to compensate for servo information written with different deviations according to each head owing to a distortion phenomenon of an actuator during a servo writing process, thereby shortening a settling time caused by offset components of each head. CONSTITUTION: When a data read/write command is received from a host computer, a micro controller decides whether head-switching is necessary in response to the data read/write command(40). If so, the micro controller performs a switching control process to select one head. The micro controller calculates a difference between a PES value read from a servo sector of a disk corresponding to the switched head and a PES value read from the disk corresponding to a previous head before the head switching, and temporarily stores the calculated difference in a register(42). The micro controller calculates a timing count value immediately after the head switching, and updates the calculated timing count value(44).

Description

How to compensate for position error signal and timing deviation of hard disk drive.

The present invention relates to servo control of a hard disk drive, and more particularly, to a method for compensating for a position error signal (hereinafter referred to as a PES) and a timing deviation generated during head switching.

Hard disk drives, which are widely used as auxiliary storage devices for computer systems, are generally divided into two parts. One part is a circuit subset in which most circuit components are mounted on a printed circuit board (PCB) and is commonly referred to as a printed circuit board assembly (PCBA). The other part is a set of instruments incorporating most of the mechanical components including some magnetic heads (or data transducers) and magnetic disks and some circuit components, commonly referred to as HDA (Head Disk Assembly).

The schematic mechanism structure of the above described HDA is shown as FIG. In FIG. 1 the disks 2 are installed in a stack form on one spindle 14 and are rotated by the spindle 14. The head 4 for reading, writing and erasing data on the disk 2 is lifted from the disk 2 as the disk 2 rotates. The head 4 is coupled via suspension to the support arm end of the rotary voice coil actuator 6 and the gap Gap of the head 4 coincides with the center of the pivot bearing shaft 8. . The actuator 6 moves the head 4 radially, ie in the inner circumferential direction or the outer circumferential direction, on the disk 2 about the pivot bearing shaft 8 through the current control of the VCM 10. The push rod pin 12 is used to control the head 4 to move at a constant track pitch interval on the disk 2 during servo writing. That is, a constant torque is applied to the actuator 6 by the current applied to the VCM 10, and the head 4 is moved and controlled by one track using a push rod pin.

In the hard disk drive having the mechanism structure as described above, servo information as positional information for positioning the head 4 on the target track (or target data sector) on the disk is usually written on the disk during the manufacturing process. At this time, depending on the contact point of the push rod pin that pushes the actuator 6 and the mechanical deformation of the actuator 6 according to the degree of tension of the mechanism, the servo information has different deviations depending on the head 4. do. This will be described in detail with reference to FIG. 2 as follows.

FIG. 2 shows a plan view of the actuator 6 in FIG. 1 with the head 4 gap coinciding with the center of the pivot bearing shaft 8. In this case, a line connecting the center of the head 4 gap and the pivot bearing shaft 8 will be defined as A in the following description. If a certain level of current is applied to the VCM 10 to move the head 4 one track in the C direction during servowriting, the DC bias force F and the push rod pin 12 of the VCM 10 are applied. The head 4 is moved one track in the C direction. At this time, according to the contact point and the tension of the push rod pin 12, a fine twist occurs in the actuator (6). That is, the line A connecting the gap of the head 4 and the center of the pivot bearing shaft 8 due to the torsion of the actuator 6 is represented by the deformed line B as shown in FIG. As a result, the actuator 6 writes the servo information in the offset state in the horizontal and vertical directions. After the servo light is terminated and the VCM DC bias force F is terminated, the actuator 6 is restored to its original state so that the horizontal and vertical offsets are represented by timing deviations of PES, t1 and t2 in the servo control mode. This is because the servo information written to the disk surface corresponding to each head 4 is written to physically different positions due to the torsional phenomenon of the actuator 6 during servowriting. That is, in the conventional hard disk drive, the servo information is written with different deviations according to each head 4 due to the torsion of the actuator 6 during servo writing. Accordingly, when the header switching is performed in the servo control mode, the servo information is written. There was a problem of delaying the settling time due to the offset for each head.

Accordingly, an object of the present invention is to provide a method for compensating for a position error signal written with different deviations for each head by mechanical deformation during servowriting in a hard disk drive.

In order to achieve the above object, the present invention provides a hard disk drive comprising: a position error signal read from a first servo sector on a disc corresponding to a switched head when a head switching occurs, and a position read from a servo sector before head switching. Calculating and storing an error signal deviation;

Counting the timing until the servo address mark is detected from the second servo sector after resetting the main counter when the servo address mark is detected from the first servo sector on the disk corresponding to the switched head;

Calculating a deviation between the counted timing value and a reference default value;

Characterized in that the final update of the calculated deviations.

Hereinafter, an operation according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description, many specific details are set forth to provide a more general understanding of the invention, such as a disc divided into three areas, specific tracks within each area and specific processing flows. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. And detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

3 is a block diagram of a general hard disk drive in which PCBA and HDA are combined. A multi-platter hard disk having two disks 2 and four heads 4 corresponding thereto is shown. An example of a drive is shown. In a hard disk drive using a multiple platter method, the disks 2 are typically installed in one spindle motor 30 in a stack form, and each disk surface corresponds to one head 4. The head 4 is located on the surface of the disk 2 and is mounted on a vertically extending arm of the arm assembly of the rotary voice motor (VCM) 24. The preamplifier 12 preamplifies the signal picked up by one of the heads 4 during data read and applies an analog read signal to the read / write channel circuit 14, and the data At the time of writing, encoded write data applied from the read / write channel circuit 14 is driven to drive the corresponding one of the heads 4 onto the disc 2. At this time, the preamplifier 12 selects one of the heads 4 under the control of the disk data controller (DDC) 32 controlled by the microcontroller 18. The read / write channel circuit 14 detects and decodes a data pulse from a read signal applied from the preamplifier 12 to generate read data RDATA, and decodes the write data WDATA applied from the DDC 32 to decode the preamplifier 12. ) Is applied. The read / write channel circuit 14 also demodulates the head position information which is a part of the servo information recorded on the disk to generate a position error signal (PES). The PES generated from the read / write channel circuit 14 is applied to an analog-to-digital converter 16, and the A / D converter 16 applies the PES to a digital step value corresponding to its level. To the microcontroller 18. The DDC 32 is controlled by the microcontroller 18 and writes data received from the host computer onto the disc 2 via the read / write channel circuit 14 and the preamplifier 12 or onto the disc 2. The data is read from and sent to the host computer. The DDC 32 also interfaces the communication between the host computer and the microcontroller 18. The microcontroller 18 controls the DDC 32 in response to read or write commands received from the host computer and controls track searching and track following. At this time, the microcontroller 32 controls the track following as described above using the PES value applied from the A / D converter 16. The digital-to-analog converter 20 converts the control values for position control of the heads 4 generated from the microcontroller 18 into analog signals. The VCM driver 22 generates a driving current I (t) for driving the actuator by a signal applied from the D / A converter 20 and applies it to the VCM 24. The VCM 24 moves the heads 4 horizontally on the disc 2 in correspondence with the direction and level of the drive current input from the VCM driver 22. The motor controller 26 controls the spindle motor driver 28 according to a control value for rotation control of the disks 2 generated from the microcontroller 18. The spindle motor driver 28 rotates the disks 2 by driving the spindle motor 30 under the control of the motor controller 26.

4 shows a general sector format of a track in which servo and data sectors are alternately arranged, and (A) shows any of a plurality of tracks arranged concentrically on the disc 2. Indicates the sector format for the track. The data sector generally includes an ID section in which ID information is recorded and a data section in which actual data is recorded, while the servo sector includes a preamble section for synchronizing with a system clock as shown in (B), and Servo Address Mark (SAM) section in which the reference pattern for generating servo timing is recorded, Index (IDX) section for providing disk rotation information, and Gray Code in which track information is recorded. Section and a servo burst (A, B, C, D) section for on-track control of the head. In this case, since the servo sectors are located on the same track at regular intervals, the position of the next servo sector can be predicted by reading the SAM information. Meanwhile, the recording patterns of the burst signals A, B, C, and D recorded in the servo burst section are as follows. First, burst signals A and B are used in track search in combination with track information recorded in the gray code section. That is, as shown in FIG. 4C, the burst signal A is recorded in the odd tracks (N-1, N + 1 tracks), and the burst signal B is recorded in the even tracks (N tracks). Provide information. On the other hand, the burst signals C and D are recorded as half values between adjacent tracks centering on a track center line (hereinafter referred to as TCL) to provide a PES in the track following mode.

5 illustrates a control flow diagram according to an embodiment of the present invention, and FIG. 6 illustrates a timing diagram according to an embodiment of the present invention, respectively. First, in FIG. 6, (A) shows a sector format for a predetermined track on the disk surface corresponding to the head Φ and head 1 as one embodiment of the present invention, and the head switching signal (HSS) is the microcontroller 24. As shown in FIG. It is shown that the head switching signal generated by the control of the switch to the head Φ ⇒ head 1 at the time point T1. Hereinafter, a PES and a timing deviation compensation process according to an embodiment of the present invention will be described with reference to FIGS. 5 and 6.

First, referring to FIG. 5, when the data read / write command is received from the host computer in step 40, the microcontroller 18 determines whether headswitching is required. If it is determined that head switching is necessary, the microcontroller 18 proceeds to step 42 after switching control to select one head 4. In the following description, it is assumed that the head Φ ⇒ head 1 is switched at the time T1 as shown in FIG. Thereafter, in step 42, the microcontroller 18 calculates a difference between the PES value read from the servo sector on the disk corresponding to the switched head 1 and the PES value read from the disk corresponding to the head Φ before head switching. Temporarily store in a register. Normally, the PES value is read after the servo interrupt shown in FIG. At this time, the difference between the PES values temporarily stored in the register becomes the PES offset value at the time of head switching, which is the offset value in the vertical direction due to the torsional phenomenon of the actuator 6 during servowriting. Meanwhile, the microcontroller 18 calculates and updates a timing count value immediately after the head switching in step 44. This will be described in detail as follows. Switching Immediately After Head Switching When a SAM pulse is detected in the servo sector on the disk corresponding to the selected Head 1, the main counter is reset and the system clock CLK is counted until the SAM pulse of the next servo sector is detected. At this time, the difference between the counted timing value and the reference default value becomes a horizontal offset value due to the torsion of the actuator 6. Therefore, the microcontroller 18 compensates for the output of the horizontal and vertical offset values calculated in the steps 42 and 44.

As described above, the present invention compensates the servo information written in the servo control mode with different deviations according to each head 4 due to the torsional phenomenon of the actuator 6 during servo writing. There is an advantage to shorten the settling time.

1 is a plan view of a typical hard disk drive.

2 is a plan view of the actuator 6 in FIG.

3 is a block diagram of a general hard disk drive.

4 is a general sector format diagram.

5 is a control flow diagram according to an embodiment of the present invention.

6 is a timing diagram according to an embodiment of the present invention.

Claims (2)

In the method for compensating position error signal and timing deviation of a hard disk drive, When head switching occurs, the deviation between the position error signal read out from the first servo sector on the disk corresponding to the switched head and the position error signal read out from the servo sector before head switching is calculated and the vertical offset value is calculated and stored. Process, Counting the timing until the servo address mark is detected from the second servo sector after resetting the main counter when the servo address mark is detected from the first servo sector on the disk corresponding to the switched head; Calculating a horizontal offset value by calculating a deviation between the counted timing value and a reference default value; And updating the position error signal and the timing deviation by using the calculated vertical offset value and the horizontal offset value. 2. The method of claim 1, wherein the first servo sector is a servo sector which is first accessed immediately after head switching.