KR100337841B1 - Method for compensating off-track caused by head switching - Google Patents

Abstract

PURPOSE: A method for compensating off-track caused by head switching is provided to follow a track in real time even when any deformation is generated in a head stack assembly by the external impact or vibration, thereby preventing the deterioration of the performance of a disc driving recording system. CONSTITUTION: A method for compensating off-track caused by head switching includes the steps of measuring off-track amounts of each head provided to a disc driving recording system whenever power is applied to the system, storing the off-track amounts in a head off-track table(44), compensating an off-track amount between a head immediately before head switching and a target head by a head switching compensator(42), and applying the compensated off-track amount to a servo driving part for the servo control of the head after scaling.

Description

Off-track compensation method by head switching

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc drive recording device and a servo control device, and more particularly, to an off track compensation method for compensating for an off track by head switching of a disc drive recording device using a multiple platter method.

Hard disk drives (HDDs) may be classified into seek mode and track following mode according to the head moving distances. The search mode is a mode in which the head moves between tracks to reach the target track, and the track tracking mode is a mode for reaching the final target track and positioning the head on the centerline of the track. Track search and track tracking in the hard disk drive are performed by using servo information previously recorded on the disc track by a servo writer. In this case, the same servo information is recorded in each track in a cylinder, so Head switching must be done to read or write data to the other disk surface. In general, an array of data sectors in a hard disk drive starts with the first sector from the index of the head of a particular track and the sector following the last sector of the head is the first sector of head1. In this case, it is common to use head skew in consideration of performance of data read and write. Therefore, head switching occurs frequently in hard disk drives. In general, the head stack assembly is connected to one actuator, so when a head in the cylinder tracks while the head is switched on and a new head is activated, the active head is also activated. Maintain on track status. However, due to assembly problems and vibration, the head stack alignment during servo write cannot be maintained, and thus an off track occurs during head switching. As a result, the performance of the hard disk drive is degraded due to the settling time delayed for the switched head to return to the on-track state.

Accordingly, an object of the present invention is to provide an off-track compensation method that can improve the performance of a disc drive recording apparatus by compensating for the off-track amount during head switching due to registration deformation of the head stack assembly generated by external shock or vibration.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Also in the following description the same components have been given the same reference numerals and many specific details, such as specific processing flows, are shown to provide a more general understanding of the invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

Fig. 1 shows a schematic block diagram of a disc drive recording apparatus according to the present invention. In FIG. 1 the magnetic disk 10 is rotated by a spindle motor 32. The head 12 is located on the surface of the magnetic disk 10 and is perpendicular to the arm assembly (not shown) of the Voice Coil Motor (VCM) 28 actuator. Installed in the kidney cancer. The preamplifier 14 preamplifies the signal picked up by the head 12 at the time of reading data. The preamplifier 14 drives the head 12 to read the encoded recording data applied from the read decoding and write encoding unit 16. Recording is made on the magnetic disk 10. The read decoding and write encoding part 16 is connected to the microprocessor 22, the preamplifier 14 and the disk data controller 34 and controlled by the disk microprocessor 22. do. Meanwhile, the read decoding and write encoding unit 16 receives the write data from the disk data controller 34, encodes the write data into an analog flux change signal, outputs the encoded data to the preamplifier 14, and outputs the preamplifier 14. The analog reading signal input from the digital conversion is decoded into an encoded read data signal (hereinafter referred to as an ERD signal) and output as read data. The gate array 18 is connected to the read decoding and write encoding unit 16 to receive the ERD signal, and detects each servo information such as a gray code in the servo region of the disk 10 from the ERD signal, and detects a timing clock. Output An analog / digital converter (hereinafter referred to as an analog / digital converter) 20 is connected to the read decoding and write encoding unit 32 to receive an analog servo reading signal and digitally convert the servo reading signal into a PES. The signal is converted and output to the microprocessor 22. The microprocessor (MICRO PROCESSOR) 22 is a programmable ROM (PROM) 36 and a static RAM that stores a disk data controller 34, a program executed in the microprocessor 22, and the like. Random Access Memory (hereinafter referred to as SRAM) 38 to control track search and track following. At this time, the microprocessor 22 performs track tracking using the PES value applied from the A / D converter 20. A digital-to-analog converter (hereinafter referred to as a D / A converter) 24 converts a control value for position control of the head 12 generated from the microprocessor 22 into an analog signal. The VCM driver 26 generates a driving current for driving the VCM 28 by the signal applied from the D / A converter 24 and applies it to the VCM 28. The VCM 28 moves the head 12 in the horizontal direction on the magnetic disk 10 in correspondence with the direction and level of the driving current applied from the VCM driver 26. The motor driver 30 rotates the spindle motor 32 in accordance with a control value for controlling the rotation of the magnetic disk 10 generated from the microprocessor 22. Spindle motor 32 rotates the disk 10 connected to the drive shaft. The disk data controller 34 records data received from the host computer on the magnetic disk 10 through the read decoding and write encoding unit 16 or data recorded on the magnetic disk 10. Read and send it to the host computer. The disk data controller 34 also interfaces the servo control of the microprocessor 22 in response to read / write commands received from the host computer.

2 shows a schematic configuration of a microprocessor 22 according to an embodiment of the present invention. The microprocessor 22 is connected to the A / D converter 20 to compensate for an offset amount. Following Compensator (40) for calculating the value, and the scaling factor (Scale) is applied to the D / A converter 24 by scaling (Scaling) the positioning value calculated in the following Compensator 40 through a multiplier Factor (46), a head off track table (44) which measures and stores the off track amount of each head at every power-up of the disc drive recording apparatus, and the head off track table (44) and the follow compensator (40). A head switching compensator 42 for compensating for the head off track amount immediately before head switching and the head off track amount immediately after head switching, and between the head switching compensator 42 and the multiplier, It consists of disabling (DISABLE) and the enable (INABLE) operation switch (SW) for the control of the controller 34.

3 shows a data format diagram on an arbitrary track for explaining an embodiment of the present invention, in which the servo sector and the data sector are located adjacent to each other and are not an accurate scale. In FIG. 3, the servo sector is a section in which servo information for position control of the head 12 is recorded, and the data sector is a section in which digital data information is recorded. Hereinafter, an operation example of the present invention will be described in detail with reference to FIGS. 1-3. First, the servo information read from a specific servo sector (eg, servo sector 2) during track following is input to the A / D converter 20 by analog PES through the preamplifier 14 and the read decoding and write encoding unit 16. do. At this time, the resolution of the PES is determined according to the number of bits of the A / D converter 20. If 8 bits including a sign bit are included, one track is the centerline of the track. It has a PES value of ± 128 on the basis of. The A / D converter 20 converts the input analog PES into a digital PES and applies it to the follow compensator 40. The tracking compensator 40 stores the digital PES in the CUR-PES (Current PES) register and stores the CUS-PES according to the previous servo information (for example, servo information of the servo sector 1) in the FRE-PES register. The follower compensator 40 then calculates a positioning value for compensating the head 12 by the CUR-PES by the amount of deviation from the center line of the track and applies it to the scale factor 46 through the multiplier. The scale factor 46 then scales the positioning value to follow the head to the track center line through the D / A converter 24. If head switching in accordance with the invention is required, the disk data controller 34 switches the head 12 via the preamplifier 14. At this time, the disk data controller 34 enables the switch SW to input the head track compensator 42 with the off-track amount from the head off-track table 44 to the head before switching with the head. At this time, the head switching compensator 42 calculates a switching compensation value for compensating the offtrack amount and applies it to the scale factor 46 through a multiplier. In the scale factor 46, the switching compensation value is scaled and applied to the VCM 28 through the D / A converter 24. The switching compensation value output from the head switching compensator 42 is output to the actuator through the D / A converter 24 before the first servo signal is read after the head switching, and the amount of off track for each head in the head off track table 44 is calculated. It is measured at every power-up of the disc drive recording apparatus. The method for measuring the amount of off-track for each head is calculated and stored as the difference between the FRE-PES by the sub information in the last sector before head switching and the CUR-PES after head switching. When the first servo signal is read after the switching compensation value is output, the PES at that time is input to the following compensator 40, and the following compensator 40 determines the difference between the PRE-PES by the last servo before switching and the CUR-PES after switching. To the head switching compensator 42. The head switching compensator 42 reads out a corresponding value in the head off track table 44, adds the off track value in the table and the off track value calculated in the follower 40, and stores it in the head off track table 44 again. It is used at the next head switching. In addition, the switching compensation value corresponding to the off-track amount of the follower 40 is output, and the switch SW is disabled. The switching compensation value is added to the positioning value output from the tracking compensator 40 to follow the head to the track center line.

As described above, the present invention has an advantage of preventing track deterioration due to real time even when deformation occurs in the head stack assembly due to external shock or vibration, thereby preventing the performance of the disc drive recording apparatus.

1 is a schematic block diagram of a general disc drive recording apparatus.

2 is a schematic block diagram of a microprocessor according to the present invention in FIG.

3 is a data format diagram located on an arbitrary track on a disc.

Claims (2)

In the off-track compensation method by the head switching of the disk drive recording apparatus, An off-track amount storing step of measuring an off-track amount of each head provided in the disc drive recording apparatus every time power is applied to the disc drive recording apparatus, and storing the off-track amount in a table; An off-track amount compensation step of compensating the off-track amount between the head immediately before switching and the target head for switching; And scaling the offtrack amount compensated in the offtrack amount compensating step and applying it to a servo driver for servo control of the head. The off-track compensation method according to claim 1, further comprising the step of storing the off-track amount compensated in the off-track amount compensation step in the table.