KR100640647B1 - Method for track following according to the characteristics which locations of disk and types of heads have and apparatus thereof - Google Patents

Abstract

A method and an apparatus for controlling track following are provided to compensate for non-repetitive run-out and secure the control margin for track following by setting track following controllers according to search locations of a hard disc drive. A loop gain and a servo band width proportional constant are measured and stored for each search location of a hard disc drive. When a command for track following is inputted for a specific location of the hard disc drive, a loop gain and a servo band width proportional constant corresponding to the specific location are searched. A first signal is generated by applying the searched loop gain to the control signal outputted from a track following controller(400). A second signal is generated by applying the searched proportional constant to the first signal, and transmitted to a head disc assembly(470).

Description

Method for track following according to characteristics of location and its device {Method for track following according to the characteristics which locations of disk and types of heads have and Apparatus

1 is a block diagram of a conventional track following controller.

2 shows a configuration of a hard disk drive to which the present invention is applied.

3 shows an electrical system capable of controlling a hard disk drive.

4 is a block diagram of a track tracking control device according to the present invention.

5 is a block diagram of a track following control apparatus according to an embodiment of the present invention.

6 is a flowchart of a track tracking control method according to the present invention.

FIG. 7 is a detailed flowchart illustrating a measurement process and a storage process of the loop gain and the proportional constant of FIG. 6.

FIG. 8 is a detailed flowchart illustrating an application process for a loop gain and a proportional constant and a process for setting a control constant of FIG. 6.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control system of a hard disk drive device, and more particularly, to a track tracking control method considering a positional characteristic in a hard disk drive and a device therefor.

Hard disk drives have the advantage of being able to reliably store large amounts of data and to access data at high speeds.

Hard disks usually consist of a plurality of disks and a plurality of heads and have different mechanical characteristics when the heads are different. In addition, even when the same head is used, mechanically different characteristics are shown depending on the position of an inner diameter zone (ID) or an outer diameter zone (OD) on the same disk. These different mechanical characteristics are mainly represented by non-repetitive run out (NRRO) characteristics of the position error signal (PES). In addition, such a non-repetitive runout characteristic acts as a big limitation condition when designing a track following controller, which causes a deterioration of the performance of the track following control of the drive. Such non-repetitive runouts include non-repetitive runout components caused by disc mode resonance occurring at the outer circumference of the disc, and non-repetitive runout caused by high frequency resonance of head gimbal assembly (HGA). Non-repetitive runouts caused by irregular winds generated by rotation.

Conventional track tracking control methods and apparatus use only the same controller, or add a separate non-repetitive runout compensator to compensate for a particular non-repetitive runout.

1 is a block diagram of a conventional track following controller.

The track following controller 100 receives information about the actual position of the head, the actual speed, and the actual acceleration from the estimator 130 and outputs a control signal for controlling the movement of the head. The loop gain unit (LOOP GAIN) 110 multiplies the loop gain by the control signal of the track follower controller 100 to change the bandwidth of the control signal to a predetermined reference servo bandwidth and transmits it to the head disk assembly (HDA) 120. The head disk assembly 120 receives a control signal having a reference servo bandwidth from the loop gain unit 100, and operates a voice coil motor according to the control signal to adjust the movement of the head.

As shown in FIG. 1, since the conventional track tracking controller uses only the same track tracking controller regardless of the search position, the track tracking controller cannot change the setting to have different characteristics according to the search position.

However, according to the conventional track tracking control method and apparatus there is a limit to completely compensate for the non-repetitive runout that appears in each position in the drive with a specific compensator, its implementation and application method is very complicated, regardless of the search position Since the track tracking controller has the same characteristics, there is a problem that it is difficult to secure a margin on the track tracking control that varies depending on various mechanical characteristics.

The technical problem to be achieved by the present invention is to set up a track tracking controller and estimator for each search position or head type of the drive to compensate for the non-repetitive runout according to the mechanical characteristics, to secure a margin in the track tracking control to a certain level or more To provide a track tracking control method that considers the characteristics of each location to improve the performance of the drive.

Another object of the present invention is to provide a track following control apparatus to which a track following control method is applied in consideration of the characteristics of each position.

In order to solve the above technical problem, the present invention is a track tracking control method of a hard disk drive, the step of measuring and storing the loop gain and servo bandwidth proportional constant for each search position of the hard disk drive, When a track tracking command for a specific position is input, searching for a loop gain and a servo bandwidth proportional constant corresponding to the specific position, and applying the searched loop gain to a control signal output from the track tracking controller, applies a first signal. Generating a second signal by applying the found proportional constant to the first signal and transmitting the second signal to the head disk assembly (HDA).

In order to solve the above technical problem, the present invention provides a track tracking controller for generating and transmitting the track tracking control signal in a hard disk drive, and when a track tracking command of a specific position is input to the track tracking controller, An initialization unit for setting the track tracking controller to a corresponding set value, and a loop gain multiplication for generating a first signal by converting a track tracking control signal servo bandwidth of the track tracking controller that is different for each position of the drive into a predetermined reference servo bandwidth A proportional constant multiplier for converting the servo bandwidth of the first signal generated by the loop gain multiplier to the servo bandwidth of the initialized track tracking controller to generate a second signal, and a second generated by the proportional constant multiplier A head disk assembly which receives a signal and moves the head according to the second signal do.

Hereinafter, the configuration of the present invention will be described with reference to the drawings.

2 shows a configuration of a hard disk drive 200 to which the present invention is applied.

The drive 200 includes at least one magnetic disk 220 that is rotated by the spindle motor 210. The drive 200 also includes a head 230 positioned adjacent to the disk 220 surface.

The head 230 can read or write information from the rotating disk 220 by sensing and magnetizing the magnetic field of each disk 220. Typically head 230 is coupled to the surface of each disk 220. Although illustrated and described as a single head 230, it should be understood that this consists of a recording head for magnetizing the disc 220 and a separate reading head for sensing the magnetic field of the disc 220. The read head is constructed from Magneto-Resistive (MR) elements.

Head 230 may be integrated into slider 231. The slider 231 is configured to create an air bearing between the head 230 and the surface of the disk 220. The slider 231 is coupled to the head gimbal assembly 232. Head gimbal assembly 232 is attached to an actuator arm 240 having a voice coil 241. The voice coil 241 is located adjacent to the magnetic assembly 250 that specifies a voice coil motor (VCM) 242. The current supplied to the voice coil 241 generates a torque to rotate the actuator arm 240 relative to the bearing assembly 260. Rotation of the actuator arm 240 will move the head 230 across the disk 220 surface.

The information is typically stored in an annular track of the disc 220. Each track 270 generally includes a plurality of sectors. Each sector includes a data field and an identification field. The identification field is composed of a gray code identifying a sector and a track (cylinder). Head 230 is moved across the surface of disc 220 to read or write information on other tracks.

 3 shows an electrical system 300 that can control the hard disk drive 200. System 300 includes a controller 310 coupled to head 230 by a read / write (R / W) channel circuit 320 and a pre-amp circuit 330. The controller 310 may be a digital signal processor (DSP), a microprocessor, a microcontroller, or the like. The controller 310 supplies a control signal to the read / write channel 320 to read from or write information to the disc 220. Information is typically sent from the R / W channel 320 to the host interface circuit 340. The host interface circuit 340 includes a buffer memory and control circuitry that allows a disk drive to interface to a system such as a personal computer. The controller 310 is also coupled to a VCM drive circuit 350 that supplies a drive current to the voice coil 241. The controller 310 supplies a control signal to the driving circuit 350 to control the excitation of the VCM and the movement of the head 230.

The controller 310 is coupled to a nonvolatile memory and a random access memory (RAM) device 370, such as a read only memory (ROM) or flash memory device 360. The memory elements 50 and 52 contain instructions and data used by the controller 310 to execute software routines. One software routine is a seek routine that moves head 230 from one track to another. The seek routine includes a servo control routine to ensure that the head 230 is moved to the correct track. In one embodiment, the memory device ROM 360 includes the acceleration, velocity, and position trajectory equations of the head, and these equations are stored in the memory device RAM 370 at the start of driving.

4 is a block diagram of a track tracking control device according to the present invention.

The track following controller 400 receives information about the actual position of the head, the actual speed, and the actual acceleration from the estimator 440 and outputs a control signal for controlling the movement of the head. K1 and K2 401 and 402 are set values of the track following controller. These setting values can have different values for each track position or for each head position by the track following controller itself or by other external control means. The adders 403 and 404 generate a control signal using information on the actual position, the actual speed, and the actual acceleration of the head received from the estimator 440. In the conventional track following controllers, these setting values were fixed values, but the present invention can set these setting values differently according to the search position, so that the effect of each having a track following controller suitable for the search position can be obtained.

In this case, the search position means a position corresponding to any one of a position of a zone constituted by a predetermined track unit or a plurality of head positions for reading / writing data on a plurality of discs. .

The loop gain multiplier 450 multiplies the loop gain by the control signal of the track following controller 400 to change the bandwidth of the control signal to a predetermined reference servo bandwidth, thereby proportionalizing the converted control signal, that is, the first signal. The signal is transmitted to the constant multiplication unit (Kbw, 460). In this case, the loop gain is obtained by obtaining a bandpass gain value that allows servo signals having different frequency characteristics to reach zero gain of a frequency-gain curve at the same frequency, and then obtains a ratio between the gain value and the original bandpass gain value of the servo signal. Can be. This loop gain can also be obtained by measuring the magnitude ratio of the system's response signal to the input signal at a particular frequency.

The proportional constant multiplier 460 receives the first signal of the loop gain multiplier 450 and converts the servo bandwidth of the first signal into a servo bandwidth corresponding to a track to be searched or a head of a location to be searched for, and then a second signal. Generate a signal and send it to the head disk assembly (HDA) 470. In this case, the servo bandwidth proportional constant may be determined by calculating a ratio between the servo bandwidth of the track following controller corresponding to each search position and the reference servo bandwidth determined by loop gain measurement.

The head disk assembly (HDA) 470 receives a second signal from the proportional constant multiplier 460 and operates the voice coil motor according to the second signal to adjust the movement of the head. The head disk assembly 470 includes an actuator, a voice coil motor, a head, and the like.

The estimator 440 is an estimator having a variable control constant, and uses a known state equation from a position error signal of a head disk assembly (HDA), using an equation of a state of a head, an actual velocity, and an actual acceleration. Can be determined. At this time, the position can be determined by reading the gray code of the track just under the head. L1, L2 and L3 are control constants 441, 442 and 443 of the estimator. The conventional estimator has a fixed value of these control constants, but the present invention can set such control constants differently according to the search position, so that an effect provided with an estimator suitable for the search position can be obtained.

5 is a block diagram of a track following control apparatus according to an embodiment of the present invention.

The track following controller 500 of FIG. 5 is a track following controller capable of varying the control constant. When the track following command is received for a specific position, the track following controller 500 activates the initialization unit 550 and generates a control signal for track following. The signal is transmitted to the loop gain multiplier 510.

The loop gain multiplier 510 multiplies the loop gain by the control signal to convert the servo bandwidth of the control signal into a reference servo bandwidth to generate a first signal, and transmits the first signal to the proportional constant multiplier 520.

The proportional constant multiplier 520 multiplies the servo bandwidth proportional constant by a control signal and converts the servo bandwidth into a servo bandwidth of a track tracking controller suitable for a specific search position to generate a second signal. 530).

The head disk assembly 530 receives a second signal from the proportional constant multiplier 520 and operates the voice coil motor according to the second signal to adjust the movement of the head. The head disk assembly 530 includes an actuator, a voice coil motor, a head, and the like.

The estimator 540 is an estimator capable of varying the control constant. The estimator 540 uses a known state equation from a position error signal of the head disk assembly 530 to calculate an actual position, an actual velocity, and an actual acceleration of the head. You can decide. The estimator 540 transmits such head actual position, actual velocity and actual acceleration information to the track following controller 500 to be fed back.

The initialization unit 550 sets the control constants of the track following controller 500 and the estimator 540 as the control constants suitable for the track following a specific position when a track following command for a specific position is input to the track following controller 500. do. At this time, the control constant refers to K1, K2, L1, L2, L3 of FIG. At this time, a control constant suitable for tracking the track of a specific position must be determined experimentally or statistically for each search position in the test process of the drive in advance. That is, the control constants of the track tracking controller 500 and the estimator 540 having the smallest search error in the inner diameter (ID: Inner Diameter) region of the disk are the control having the smallest search error in the outer diameter (OD: Outer Diameter) region of the disk. It can be different from the constant.

Therefore, when the head searches from the inner circumferential region to the outer circumferential region of the disk, the initialization unit 550 sets the control constants suitable for the inner circumferential region to the track following controller 500 and the estimator 540, and then fits the outer circumferential region. Control constants are set in the track following controller 500 and the estimator 540.

6 is a flowchart of a track tracking control method according to the present invention.

First, the loop gain and the servo bandwidth proportional constant of the servo signal are measured for each position in the drive (step 600). At this time, the position in the drive means a position corresponding to either the position of a zone constituted by a predetermined track unit or the position of a plurality of heads for reading / writing data on a plurality of discs. This process is a preparation process for standardizing the servo bandwidth that is different for each search position in the drive to the reference servo bandwidth and converting the servo bandwidth of the track tracking controller 500 that is different for each search position.

Next, the loop gain for each position and the servo bandwidth proportional constant are stored (step 610). This process is to store the loop gain and proportional constant measured at 600 in the system cylinder of the disk. Also, in this process, the set values of the track tracking controller and the estimator may be stored in the system cylinder. At this time, the set values of the track following controller and the estimator are determined experimentally or statistically so that the search error is minimized for each search position in the process step.

Next, the loop gain and the servo bandwidth proportionality constant according to the track tracking command of the specific position are searched and applied to the control signal (step 620). This process is a process of standardizing the servo bandwidth that is different for each search position in the drive to the reference servo bandwidth and converting the servo bandwidth of the track tracking controller 500 that is different for each search position. At this time, when the loop gain is applied to the control signal, the control signal is converted into the first signal, and when the servo bandwidth proportional constant is applied to the control signal, the first signal is converted into the second signal.

Finally, the track tracking controller 500 and the estimator 540 are set to track tracking at a specific position in step 630. This process is to set the control constants of the track following controller 500 and the estimator 540 as the control constants having the lowest search error at a specific position.

FIG. 7 is a detailed flowchart of the loop gain and proportional constant measurement process 600 and the storage process 610 of FIG. 6.

Referring to FIG. 7, first, a loop gain of a servo signal is measured for each position on a disk (step 700). This process is a preparation process for standardizing the servo bandwidth, which varies with each search position on the disc, to the reference servo bandwidth. In this case, the search position on the disc means a position corresponding to either a position of a zone configured by a predetermined track unit or a position of a plurality of heads for reading / writing data on a plurality of discs. This process may be performed by measuring the ratio of the magnitude of the response signal of the system to the input signal of a specific frequency.

Next, the loop gain of the servo signal is measured for each type of head (step 710). This process prepares for standardizing the servo bandwidth that is different for each head used in the drive as the reference servo bandwidth.

Next, a servo bandwidth proportional constant is calculated by dividing the servo bandwidth of the track tracking controller for each position by the reference servo bandwidth (step 720). The present invention is to minimize the search error by varying the track tracking controller for each search position or head type, and the track tracking controller may have an appropriate servo bandwidth for each search position. Therefore, this process is a preparation process for converting the reference servo bandwidth into an appropriate servo bandwidth for the search position.

Next, the measured loop gain and the servo bandwidth proportional constant are stored in the system cylinder of the disk (step 730). This process prepares the loop gain and servo bandwidth proportional constants from the system cylinder to be loaded into memory when the drive is driven.

Finally, the position-specific setting value of the track tracking controller and the position-specific setting value of the estimator are stored in the system cylinder of the disk (step 740). The set value at this time means a control constant with a position control gain value, a speed control gain value predetermined for each drive position in the track following controller, and a position gain value, speed gain value, and acceleration gain value predetermined for each drive position in the estimator. This process prepares the system cylinder to read the control constant for each position of the track tracking controller and the control constant for each position of the estimator and load it into the memory.

FIG. 8 is a detailed flowchart illustrating an application process 620 for a loop gain and a proportional constant and a setting process 630 for a control constant of FIG. 6.

Referring to FIG. 8, first, a loop gain value for each position, a servo bandwidth proportional constant for each position, a track tracking controller setting value for each position, and an estimator setting value for each position are loaded into a memory (operation 800). This process is to read the information stored in the system cylinder in the memory built in the drive in the process 730-740 of FIG.

Next, it is determined whether a track tracking command for a specific position is input (step 810). At this time, if the track following command is not input, the procedure is completed. At this time, if a track following command for a specific position is input, the process proceeds to the next step.

Next, a loop gain value for each position, a servo bandwidth proportional constant for each position, a track tracking controller setting value for each position, and an estimator setting value for each position are retrieved from the memory (step 820). This process may be performed by the initialization unit 550.

Next, the track tracking controller and the estimator are set to the searched track tracking controller setting value and the location estimator setting value (step 830). This process may be performed by the initialization unit 550 setting the track tracking controller and the estimator to the control constant value retrieved from the memory. At this time, the setting of the track following controller and the estimator by the initialization unit is a process of initializing the track following controller and the estimator to suit the search position.

Finally, the searched loop gain value for each position and the servo bandwidth proportional constant for each position are applied to the track following control signal (step 840). This process may be performed by the loop gain multipliers 450 and 510 and the proportional constant multipliers 460 and 520. At this time, the control signal output from the track following controller has a different servo bandwidth for each search position. The process of converting the bandwidth into the reference servo bandwidth multiplies the loop gain by the control signal. In addition, the control signal normalized to the reference servo bandwidth should be converted into a servo bandwidth suitable for the track tracking controller and the estimator which is set to minimize search errors in step 830. This process multiplies the servo bandwidth proportional constant by the control signal. . At this time, when the loop gain is applied to the control signal, the control signal is converted into the first signal, and when the servo bandwidth proportional constant is applied to the control signal, the first signal is converted into the second signal.

In step 840, the control signal is converted into a servo bandwidth suitable for the track tracking controller and the estimator which is set to minimize the search error at the search position, thereby enabling track tracking control in consideration of the characteristics of the drive.

Preferably, a track compensator in consideration of positional characteristics may include a bias compensator and a torque change compensator according to temperature.

Preferably, the track tracking controller may be provided with an initialization unit for optimizing the track tracking controller and the estimator.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary and will be understood by those of ordinary skill in the art that various modifications and variations can be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, according to the present invention, the track tracking controller and the estimator are set differently for each search position or head type of the hard disk drive, and the track tracking is performed by converting the servo bandwidth of the search position into the servo bandwidth of the track tracking controller. By controlling this, it is effective to compensate for non-repetitive runout according to the mechanical characteristics, to secure a track tracking control margin that varies depending on various mechanical characteristics to a certain level or more, and to improve the overall performance of the drive.

Claims (5)

In the track tracking control method of a hard disk drive, Measuring and storing a loop gain and a servo bandwidth proportional constant for each search position of the hard disk drive; Searching for a loop gain and a servo bandwidth proportional constant corresponding to the specific position when a track following command is input to the specific position of the hard disk drive; And Applying the retrieved loop gain to a control signal output from the track following controller to generate a first signal, and applying the searched proportional constant to the first signal to generate a second signal to generate the second signal. Track tracking control method considering the position-specific characteristics, characterized in that it comprises the step of transmitting to (HDA). The method of claim 1, wherein the measuring and storing of a loop gain and a servo bandwidth proportional constant for each search position of the hard disk drive comprises: Measuring the loop gain of the servo signal at each position in the drive; Obtaining a servo bandwidth proportional constant that is a ratio of the servo bandwidth of the track tracking controller and a predetermined reference servo bandwidth for each position in the drive; And And storing the measured loop gain and the servo bandwidth proportional constant in a system cylinder of the hard disk. The method of claim 1, wherein the search position of the drive is A track tracking control method in consideration of location-specific characteristics, characterized in that the location is divided into zones that are a predetermined track unit in the hard disk. The method of claim 1, wherein the search position of the drive is Track tracking control method considering the characteristics of each position, characterized in that the location is classified by the head (Head) type in the hard disk. In the hard disk drive, A track tracking controller for generating and transmitting the track tracking control signal; An initializing unit configured to set the track following controller to a setting value corresponding to a specific position when a track following command of a specific position is input to the track following controller; A loop gain multiplier for converting a track tracking control signal servo bandwidth of the track tracking controller that is different for each drive position into a predetermined reference servo bandwidth to generate a first signal; A proportional constant multiplier for generating a second signal by converting the servo bandwidth of the first signal generated by the loop gain multiplier into the servo bandwidth of the initialized track following controller; And And a head disk assembly configured to receive the second signal generated by the proportional constant multiplier and move the head according to the second signal.

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