KR20060065994A - Method for controlling restoration from alarm state to normal state and disk drive using the same - Google Patents

Abstract

The present invention relates to a method and apparatus for controlling a disk drive, and more particularly, to a servo control method and apparatus for quickly and stably restoring a normal state from an alarm state in which a servo drive cannot read servo information normally for a predetermined time during track tracking and searching. It is about.

An abnormal state restoration control method of a data storage system according to the present invention is a control method of a disk drive, the method comprising the steps of: (a) determining whether a servo alarm state that fails to read servo information for a predetermined time or more in a track search and tracking mode occurs; (b) turning off the normal servo control loop when the servo alarm condition occurs, and turning on the back EMF servo control loop to detect the back EMF of the voice coil; and (c) the step (b). Controlling the moving speed of the converter in correspondence with the counter electromotive force value detected in the above).

Description

Method for controlling restoration from alarm state to normal state and disk drive using the same}

1 is a block diagram of a head disk assembly of a hard disk drive to which the present invention is applied.

2 is a circuit diagram of an electrical system for controlling a disk drive to which the present invention is applied.

3 is a configuration diagram of a servo control apparatus for a disk drive according to the present invention.

4 is a flowchart illustrating a method of controlling an abnormal state restoration of a data storage system according to a first embodiment of the present invention.

5 is a flowchart illustrating a method of controlling an abnormal state restoration of a data storage system according to a second embodiment of the present invention.

The present invention relates to a method and apparatus for controlling a disk drive, and more particularly, to a servo control method and apparatus for quickly and stably restoring a normal state from an alarm state in which a servo drive cannot read servo information normally for a predetermined time during track tracking and searching. It is about.

Hard disk drives include a plurality of magnetic transducers capable of recording and reading information by sensing and magnetizing the magnetic field of each of a single or multiple rotating disks. This information is typically formatted in a plurality of sectors located in the annular track. There is a track number located across each surface of the disc. The number of vertically similar tracks is sometimes called a cylinder. Therefore, each track is also defined by a cylinder number.

Each transducer is typically integrated within a slider that is incorporated into a head gimbal assembly (HGA). Each head gimbal assembly is attached to an actuator arm. The actuator arm has a voice coil located adjacent to the magnetic assembly that specifies the voice coil motor together. Hard disk drives typically include controllers and drive circuits that supply current to excite the voice coil motor. The excited voice coil motor rotates the actuator arm to move the transducers across the surface of the disk (s).

When writing or reading information, the hard disk drive is likely to execute a seek routine to move the transducer from one cylinder to another. During the seek routine, the voice coil motor is excited by a current that moves the transducers to a new cylinder position on the disk surface. The controller also executes a servo routine that ensures that the transducer moves to the correct cylinder position and to the center of the track.

Hard disk drives have a structure that is very sensitive to disturbances caused by external shocks. As a result, when the disturbance exceeds the range allowed by the hard disk drive, malfunction may occur, and in severe cases, a collision between the converter and the disk surface may occur, which may cause fatal damage to the converter or the disk.

If the servo information cannot be read for a certain time during track following or track seek due to such disturbance, servo signal defect, servo pattern timing error, etc., the servo controller enters the servo alarm state and parks the head in the stable area for stable servo control. .

Hard disk drives have a higher altitude than the user data area because they process the parking area with laser texturing to reduce friction during initial disk rotation. However, as the hard disk drive becomes denser, the head flight height tends to decrease.

According to the related art, in the mode of moving the head to the parking area in the servo alarm state, a constant pattern of driving current is applied regardless of the current position of the head. As a result, the head's flight speed is variable according to the moving distance from the current position of the head to the parking area, which may cause physical damage to the head during the parking process, and is required to initialize the servo parameters and the servo channel block. There was a problem that takes a relatively long time.

The technical problem to be solved by the present invention is to detect the counter electromotive force of the voice coil in the event of a servo alarm condition in which the disc drive cannot read the servo information normally to solve the above problems, and based on the detected counter electromotive force, An abnormal state restoration control method of a data storage system which initializes servo parameters and servo channel blocks quickly and stably by controlling a moving speed, and a disk drive using the same.

In order to achieve the above technical problem, the control method for restoring an abnormal state of a data storage system according to the present invention is a control method of a disk drive, which includes (a) a servo alarm state in which the servo information cannot be read for a predetermined time or more in the track search and tracking mode. (B) turning off a general servo control loop when the servo alarm condition is generated, and turning on a counter electromotive force servo control loop to detect the counter electromotive force of the voice coil; and (c) controlling the moving speed of the converter in correspondence with the counter electromotive force value detected in step (b).

According to another aspect of the present invention, there is provided a disk drive in a data storage system, comprising: a state estimator for estimating a state information value of a head movement including a position, a speed, and control input information of a head from a position error signal A state feedback controller for generating state feedback control information by multiplying a state information value by a predetermined state feedback gain and back electromotive force control information for detecting back electromotive force from a voice coil motor driving signal and moving the actuator to a target speed using the detected back electromotive force. A reverse electromotive force servo controller for generating a switching unit, a switching unit for selecting and outputting one of the output of the state feedback controller or the output of the reverse electromotive force servo controller according to the state of the disk drive, and a voice coil motor driving current corresponding to the output of the switching unit. produce Key corresponding to the voice coil motor driving unit and the voice coil motor drive current to move the transducer, it characterized in that it comprises an actuator for generating a position error signal in accordance with the movement of the transducer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Hard disk drives consist of a combination of electrical circuits and a head disk assembly (HDA) consisting of mechanical components.

1 shows a configuration of a head disk assembly (HDA) 10 of a hard disk drive to which the present invention is applied.

The head disk assembly 10 includes at least one magnetic disk 12 that is rotated by the spindle motor 14. The disk drive also includes a transducer 16 located adjacent to the disk surface.

The transducer 16 can read or write information on the rotating disk 12 by sensing and magnetizing the magnetic field of each disk 12. Typically transducer 16 is coupled to each disk surface. Although illustrated and described as a single transducer 16, it should be understood that this consists of a write transducer for magnetizing the disc 12 and a separate read transducer for sensing the magnetic field of the disc 12. Read transducers are constructed from Magneto-Resistive (MR) devices. The transducer 16 is also commonly referred to as a head.

The transducer 16 can be integrated into the slider 20. The slider 20 is structured to create an air bearing between the transducer 16 and the disk surface. The slider 20 is integrated into the head gimbal assembly 22. The head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacent to the magnetic assembly 28 that specifies the voice coil motor 30 (VCM). The current supplied to the voice coil 26 generates a torque for rotating the actuator arm 24 relative to the bearing assembly 32. Rotation of the actuator arm 24 will move the transducer 16 across the disk surface.

The information is typically stored in an annular track of the disc 12. Each track 34 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). The transducer 16 is moved across the disc surface to read or write information on other tracks.

2 shows an electrical system 40 capable of controlling a hard disk drive. The electrical system 40 includes a controller 42 coupled to the converter 16 by a lead / write (R / W) channel circuit 44 and a pre-amp circuit 45.

The controller 42 may be a digital signal processor (DSP), a microprocessor, a microcontroller, or the like. The controller 42 controls the read / write channel circuit 44 to read from or write information to the disc 12. The controller 42 generates sector pulses specifying the positions to record and reproduce the data in the recording and reproducing modes, and also generates servo gate pulses for obtaining servo mark address signals.

The controller 42 is also coupled to a VCM drive circuit 48 that supplies a drive current to the voice coil 26. The controller 42 supplies a control signal to the VCM drive circuit 48 to control the excitation of the voice coil motor and the movement of the transducer 16.

The memory 50 stores firmware and various control data for controlling the disk drive.

First, the operation of a general disk drive will be described.

In the data read mode, the disc drive amplifies the electrical signal sensed by the transducer 16 from the disc 12 in the preamplifier 45 to facilitate signal processing. Then, the read / write channel circuit 44 encodes the signal read out from the disk 12 into a digital signal in accordance with the timing of the read sector pulse generated by the controller 42, converts it into stream data, and converts the host interface circuit into a host interface circuit. (54) to the host device.

Next, in the write mode, the disk drive receives data from the host device through the host interface circuit 54 and temporarily stores the data in an internal buffer (not shown) of the host interface circuit 54, and then stores the data in the buffer. The stored data are sequentially output and converted by the read / write channel circuit 44 into a binary data stream suitable for the recording channel of the disc 12, and then amplified by the preamplifier 45 at the time when a write sector pulse is generated. The recorded write current is recorded on the disc 12 via the converter 16.

Next, an abnormal state restoration control operation of the data storage system according to the present invention will be described.

3 is a configuration diagram of a servo control apparatus for a disk drive according to the present invention.

The servo control apparatus for a disk drive according to the present invention includes a state feedback controller 310, a state estimator 320, a counter electromotive force servo controller 330, a switching unit 340, a voice coil motor (VCM) driving unit 350, and an actuator ( 360).

The state estimator 320 executes a process of estimating the state variable value of the head movement including the position, the speed, and the control input information of the head using known state equations from the position error signal.

The state feedback controller 310 generates a state feedback control value obtained by multiplying a state feedback gain by a state variable value of the head motion estimated by the state estimator 320.

The counter electromotive force servo controller 330 detects the counter electromotive force from the output signal of the voice coil motor driver 350 and generates the counter electromotive force control information for moving the actuator 360 to the target speed using the detected back electromotive force.

That is, the counter electromotive force servo controller 330 calculates the counter electromotive force e (t) of the voice coil according to Equation 1 below.

From here,

v (t): Voltage detected at the voice coil terminal

L: Reactance constant of voice coil

R: Resistance seen from the voice coil motor drive toward the voice coil

i: Current applied to the voice coil.

Then, the counter electromotive force servo controller 330 may calculate the movement speed dLh / dt of the transducer, which is the transducer movement distance change amount ΔLh with respect to the change amount of time ?? t using Equation 2 below.

Where Ke is the counter electromotive force constant and Rh represents the distance from the pivot bearing to the transducer.

Then, the counter electromotive force servo controller 330 can calculate the moving speed of the transducer (also called head) from the detected back electromotive force value, and converts the voice coil motor driving current for converting the calculated moving speed of the transducer into a target speed. The generated counter electromotive force control information is calculated and output. For example, the target speed may be set to zero, and in some cases, it may be decided to move the transducer to the safe area of the disk drive at a constant speed. If the target speed is set to 0 (zero), control to fix the transducer so as not to move in the current position in the servo alarm state.

The switching unit 340 selects one of the output of the state feedback controller 310 or the output of the counter electromotive force servo controller 330 according to the switch control signal CTL according to the state of the disk drive to the voice coil motor driving unit 350. Output

The switching control signal selects and outputs the output of the counter electromotive force servo controller 330 in the servo alarm state in which the servo information is not normally detected for a predetermined time in the track search and tracking mode, and in the case of the normal state, the state feedback controller 310. Design to output to the voice coil motor drive unit 350 by selecting the output.

The voice coil motor driving unit 350 generates a voice coil motor driving current corresponding to the output of the switching unit 340 and outputs the generated current to the actuator 360.

The actuator 360 moves the transducer on the disk in accordance with the input voice coil motor driving current, and generates a position error signal according to the movement of the transducer.

Next, the abnormal state restoration control method of the data storage system according to the first embodiment of the present invention will be described with reference to the flowchart of FIG. 4.

First, the controller 42 determines whether the disk drive transitions to the servo alarm state (S401). The servo alarm state means a state in which the servo information cannot be read for a predetermined time due to a servo signal defect, a servo pattern timing error, or the like in the track search or tracking mode.

When the servo alarm state is detected as a result of the determination in step 401 (S401), the current cylinder position information is retrieved and stored in the memory 50 (S402).

Then, the general servo control loop is turned off, and the back electromotive force servo control loop is turned on (S403). This means that in the servo control block configuration of FIG. 3, the switching unit 340 selects the counter electromotive force servo controller 330 and controls the output to the voice coil motor driving unit 350.

Accordingly, the counter electromotive force is detected according to the counter electromotive force servo control loop by the counter electromotive force servo controller 330, and the actuator 360 is moved to the safe area of the disk drive at the target speed using the detected back electromotive force (S404A).

Next, the servo parameter and the servo channel block are initialized to the initial optimal design value (S405).

After executing step 405 (S405), the current cylinder position information stored in the memory 50 is read in step 402, and the head is moved to the corresponding cylinder position by the control process of the back EMF servo controller 330, and the servo address mark (SAM) is extracted and synchronized (S406).

If the servo address mark extracted in step 406 is synchronized, the back EMF servo control loop is turned off and the general servo control loop is turned on (S407), and the next instruction execution is awaited (S408).

5 is a flowchart illustrating a method of controlling an abnormal state restoration of a data storage system according to a second embodiment of the present invention. Compared to the abnormal state recovery control method of the data storage system according to the first embodiment of the present invention shown in FIG. 4, only step 404B (S404B) is different.

That is, in step 404B (S404B), the back EMF servo control loop is designed so that the moving speed of the head becomes zero. This is different from the first embodiment in which the head is moved to the safe area at a constant speed when the servo alarm condition occurs, and is controlled so that the head is fixed to be moved from the current position without moving to the safe area.

Accordingly, in the first embodiment of the present invention according to the flowchart of FIG. 4, when the disc drive enters the servo alarm state, the counter electromotive force of the voice coil is detected, and the moving speed of the head is calculated based on the detected counter electromotive force. By controlling the head to move to the safe area while performing speed control by counter electromotive force, it is possible to maintain a constant speed regardless of the moving distance of the head, thereby preventing damage to the head.

In addition, in the second embodiment of the present invention according to the flowchart of FIG. 5, when the disc drive enters the servo alarm state, the head damage is controlled by controlling the counter electromotive force of the voice coil so that the head does not move to the safe area and does not move from the current position. It is possible to quickly initialize the servo parameters and the servo channel block while restoring to a stable state.

The invention can be practiced as a method, apparatus, system, or the like. When executed in software, the constituent means of the present invention are code segments that inevitably perform necessary tasks. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROM (EROM), floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, Etc. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described.

As described above, according to the present invention, after the disc drive transitions to the servo alarm state, the back coil force control of the voice coil is executed to move the head to a safe area at a constant speed or after the back electromotive force control to be fixed at the current position. By initializing the servo parameters and the servo channel block, the effect of preventing damage to the head is generated, and the effect of shortening the recovery time from the servo alarm state to the normal state is generated.

Claims (9)

In the control method of a disk drive, (a) determining whether a servo alarm condition that fails to read servo information for a predetermined time or more occurs in the track search and tracking mode; (b) turning off a normal servo control loop when the servo alarm condition occurs, and turning on a back EMF servo control loop to detect back EMF of the voice coil; And and (c) controlling the moving speed of the converter in correspondence with the counter electromotive force value detected in the step (b). 4. The method of claim 1, wherein step (b) further comprises storing current cylinder position information in a memory before turning off the normal servo control loop. The abnormal state restoration control of the data storage system according to claim 1, wherein the step (c) generates the actuator drive current corresponding to the detected back EMF such that the moving speed of the converter becomes zero. Way. 2. The data storage according to claim 1, wherein said step (c) generates said actuator drive current corresponding to said detected back electromotive force such that the moving speed of said transducer moves to a safe area of a disk drive at a predetermined speed. How to control abnormal state restoration of the system. The method of claim 1, further comprising the step (d) of initializing a servo parameter and a servo channel block after moving the transducer to a safe area or controlling the movement speed of the transducer to zero by the step (c). An abnormal state restoration control method of a data storage system, characterized in that. The method according to claim 5, wherein after the step (d) is executed, the servo address mark is extracted, and when the synchronized servo address mark is synchronized with the extracted servo address mark, the back EMF servo control loop is turned off, and the general servo control loop is terminated. Waiting for the next command execution after the on further comprises the step of restoring an abnormal state of the data storage system. In a data storage system, A state estimator for estimating a state information value of a head movement including a head position, a speed, and control input information from the position error signal; A state feedback controller for generating state feedback control information obtained by multiplying the state information value by a predetermined state feedback gain; A counter electromotive force servo controller for detecting back electromotive force from the voice coil motor driving signal and generating back electromotive force control information for moving the actuator at a target speed using the detected back electromotive force; A switching unit which selects and outputs one of an output of the state feedback controller or an output of the back EMF servo controller according to a state of a disk drive; A voice coil motor driver for generating a voice coil motor driving current corresponding to the output of the switching unit; And And an actuator for moving the transducer corresponding to the voice coil motor driving current and generating a position error signal according to the movement of the transducer. The method of claim 7, wherein the switching unit selects and outputs an output of the back EMF servo controller when the servo information is not normally detected for a predetermined time in the track search and tracking mode. Otherwise, the switching unit selects and outputs the output of the state feedback controller. Disk drive. 8. The disk drive of claim 7, wherein the target speed of the counter electromotive force servo controller is set to zero.

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