JP3756640B2 - Disc recording / playback device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a disk recording / reproducing apparatus such as a hard disk drive.
[0002]
[Prior art]
Conventionally, in a hard disk drive (HDD), higher recording density of data recorded on a disk as a recording medium has been promoted. High recording density can be broadly classified into track density and track linear density. In order to increase the track density, the track pitch, which is an interval between tracks on the disk, is narrowed, and thus it is required to position the head on a target track that is a target position with high accuracy.
[0003]
By the way, in an HDD, a large number of tracks are concentrically formed on a disk. In each track, a plurality of servo areas (for example, 50) are arranged at predetermined intervals in the circumferential direction. Servo data used in a servo system (described later) for controlling the positioning of the head to the target position is recorded in advance in the servo area. In order to realize high-precision head positioning control as the recording density increases, the servo band is increased, specifically, the interval between servo areas arranged in each track is reduced, for example, 100 It is necessary to arrange servo areas. For this reason, the servo system is required to reproduce the servo data from the servo area and set the sampling frequency when performing positioning control based on the servo data to be higher than the current frequency (about 3.5 kHz to 4 kHz). .
[0004]
Here, as shown in FIG. 15, the HDD servo system is a feedback control system, and performs seek control and narrow positioning control based on the current position of the head 2 (detected by the position transducer 10). The seek control is control for moving the head 2 to the vicinity of the target position (target track) on the disk 1 by executing speed control (speed control calculation unit 22) for controlling the moving speed of the head 2. On the other hand, the positioning control in the narrow sense is the transient control (transient control calculation unit 23) for controlling the transition from the speed control to the position control and the position control (position) for positioning (setting) the head 2 within the allowable range of the target position. A control operation unit 24).
[0005]
In the seek control, the movement distance calculation unit 21 calculates an error (corresponding to the remaining distance) between the current position (track position) of the head 2 and the target position (target track). The speed control calculation unit 22 calculates a target speed (speed profile composed of acceleration and deceleration) of the head 2 according to the remaining distance. The control system 20 which is the main element of the system outputs a control value (digital value) corresponding to the target speed calculated by the speed control calculation unit 22. In the positioning control, the control system 20 outputs a control value corresponding to the calculation results of the calculation units 23 and 24. In addition, the control system 20 and each calculation part 21-24 are comprised by the microprocessor (CPU) which is a main control apparatus in HDD.
[0006]
The D / A conversion element (D / A converter) 15 converts the control value output from the control system 20 into an analog control voltage value and outputs the analog control voltage value to the power amplifier 12. The power amplifier 12 converts the control voltage value into a drive current and supplies it to the voice coil motor (VCM) 7. Specifically, the power amplifier 12 is included in the VCM driver. The VCM 7 is a drive source of an actuator for moving the head 2 and moves the head 2 by an amount according to the control voltage value (movement distance in seek control).
[0007]
On the other hand, the head 2 reads the servo data recorded in advance in the servo area of the disk 1. The head amplifier (read / write amplifier circuit) 8 outputs servo data read by the head 2 to the position transducer 10. A position signal detected by the position transducer (servo circuit) 10 is converted into a digital value by an A / D conversion element (A / D converter) 14 and input to each of the arithmetic units 21, 23 and 24. Here, in the seek control, a track address (data indicating a track position, also referred to as a cylinder code) included in the servo data is used as data indicating the current position of the head 2 (input of the moving distance calculation unit 21). . On the other hand, the servo data includes servo burst data for detecting a position within the range of each track. The position control calculation unit 24 calculates the position error of the head 2 with respect to the center of a certain track or the boundary with an adjacent track according to the position data (amplitude value obtained from the servo burst data) input from the A / D conversion element 14. .
[0008]
In such a servo system, as described above, in order to realize a high servo band accompanying an increase in recording density, it is required to increase the sampling frequency. The control system 20 synchronizes with the sampling frequency (specifically, the cycle of the sector pulse generated in response to detection of the servo area), and changes the digital control value from the D / A conversion element (D / A converter) 15. The corresponding analog control voltage value is output. That is, the drive current obtained by converting the control voltage value is supplied to the coil of the VCM 7 in synchronization with the sampling frequency.
[0010]
[Problems to be solved by the invention]
As described above, when the sampling frequency is increased in order to realize a high-band servo system, in particular, in order to increase the track density of the disk, the control voltage value and the drive current value are determined from the inductance characteristics of the VCM. There is a situation where is not equivalent. Therefore, a sufficient drive current cannot be supplied to the VCM at the time of seek control, and the seek speed performance when the head moves to the target position is lowered, resulting in deterioration of seek control performance.
[0011]
Here, in the seek control, the relationship between the sampling frequency and the drive current flowing through the coil of the VCM 7 is shown in FIGS. 6 shows the output voltage waveform (control voltage value) of the maximum amplitude value of the D / A converter 15 when the sampling frequency is 4 kHz, and FIG. The drive current waveform which flows into the coil of VCM7 according to an output voltage waveform is shown. Similarly, FIG. 7B shows the output voltage waveform of the D / A converter 15 when the sampling frequency is 6 kHz, and FIG. 7A shows the drive current waveform flowing in the coil of the VCM 7. FIG. 8B shows the output voltage waveform of the D / A converter 15 when the sampling frequency is 8 kHz, and FIG. 8A shows the drive current waveform flowing in the coil of the VCM 7. FIG. 9B shows the output voltage waveform of the D / A converter 15 when the sampling frequency is 10 kHz, and FIG. 9A shows the drive current waveform flowing in the coil of the VCM 7. FIG. 10B shows the output voltage waveform of the D / A converter 15 when the sampling frequency is 12 kHz, and FIG. 10A shows the drive current waveform flowing in the coil of the VCM 7. FIG. 11B shows the output voltage waveform of the D / A converter 15 when the sampling frequency is 14 kHz, and FIG. 11A shows the drive current waveform flowing in the coil of the VCM 7. FIG. 12B shows the output voltage waveform of the D / A converter 15 when the sampling frequency is 16 kHz, and FIG. 12A shows the drive current waveform flowing through the coil of the VCM 7.
[0012]
From these characteristic diagrams, it can be estimated that when the sampling frequency is 12 kHz or more (FIGS. 10 to 12), a sufficient drive current is not supplied to the coil of the VCM 7 according to the control voltage value. Here, in order to clarify the influence of the inductance of the VCM coil, a drive current waveform when a resistor having the same resistance value as that of the VCM coil is used instead of the VCM coil is shown in FIG. Show. FIG. 13A shows a drive current waveform corresponding to the control voltage value when the sampling frequency is 16 kHz, as shown in FIG. From this characteristic diagram, it can be seen that if the inductance is small enough to be ignored, a sufficient drive current flows even at a sampling frequency of 16 kHz.
[0013]
Further, in the positioning control (transient control and position control) shifted from the seek control, the control voltage value that is the output of the D / A converter 15 is very small compared to the seek control. For this reason, as shown in FIG. 14A, a sufficient drive current flows through the VCM coil even when the sampling frequency is 16 kHz. At this time, it can be seen that the drive current waveform corresponds to the output voltage waveform of the D / A converter 15 having the control voltage value shown in FIG. In short, when the sampling frequency is high, a sufficient drive current corresponding to the control voltage value cannot be supplied to the VCM coil during seek control with a large control voltage value.
[0014]
Therefore, an object of the present invention is to realize a high-band servo system that accompanies an increase in the track density of the disk by enabling a sufficient drive current corresponding to the control voltage value to be supplied to the VCM coil for seek control. However, an object of the present invention is to provide a disk recording / reproducing apparatus having a servo system capable of obtaining high control performance in a seek operation.
[0015]
[Means for Solving the Problems]
The present invention provides a servo system that performs seek control for controlling movement of a head to a target position and positioning control for positioning the head within an allowable range of the target position, according to the cases of seek control and positioning control. The disc recording / reproducing apparatus includes a servo system having a switching unit that switches a time interval when the control unit outputs a control value.
[0016]
Specifically, the CPU constituting the control means lengthens the time interval (cycle corresponding to the sampling frequency) when outputting the control voltage value from the D / A converter during seek control as compared with that during positioning control. . In other words, in the seek control, the sampling frequency is decreased as compared with the positioning control.
[0017]
With this method, when the control voltage value, which is the output of the D / A converter, is converted into a drive current and supplied to the VCM coil during seek control, sufficient drive current corresponding to the control voltage value is supplied to the VCM coil. Can be supplied. Therefore, even if the sampling frequency is increased in order to realize a high servo band as the track density increases, the sampling frequency is reduced as a result during seek control, and sufficient head speed performance is obtained. Can do. As a result, the positioning accuracy in the positioning control is improved by the high servo band, and high control performance can be realized by obtaining sufficient head speed performance in the seek control.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
FIG. 1 is a block diagram showing a main part of the HDD related to the embodiment, FIG. 2 is a block diagram for explaining a configuration of a servo system related to the embodiment, and FIG. 3 is a block diagram of the embodiment. FIG. 4 is a timing chart for explaining the operation of the servo system, and FIG. 4 is a flowchart for explaining the operation of the servo system of the embodiment.
[0020]
(Servo system configuration)
As shown in FIG. 2, the servo system according to the present embodiment includes switching means 30 that switches the sampling frequency in accordance with seek control and positioning control (transient control and position control). Specifically, the control system 20 switches the frequency of the sampling pulse supplied to each of the A / D conversion element (A / D converter) 14 and the D / A conversion element (D / A converter) 15, and The time interval of the output of the control voltage from the A converter 15 is switched. That is, at the time of positioning control, the control voltage is output from the D / A converter 15 to the power amplifier 12 at time intervals synchronized with the reference sampling frequency. On the other hand, at the time of seek control, a control voltage is output from the D / A converter 15 to the power amplifier 12 at a time interval (relatively long time interval) synchronized with the frequency obtained by reducing the reference sampling frequency.
[0021]
The other configuration of the servo system is the same as that of the conventional system shown in FIG. Hereinafter, a case where the servo system of this embodiment is applied to an HDD will be described.
[0022]
(HDD configuration)
As shown in FIG. 1, the HDD has a disk 1 and a head 2 which are recording media. A large number of tracks are concentrically formed on the disk 1. Each track has a plurality of servo areas arranged at predetermined intervals in the circumferential direction. Servo data for use in seek control and positioning control is recorded in advance in the servo area. Here, in the present embodiment, a sampling frequency of, for example, about 12.25 kHz is assumed in accordance with a high servo band accompanying an increase in recording density, and the servo area interval is set in accordance with this sampling frequency. The disk 1 is rotated at high speed by a spindle motor (SPM) 5. Note that the disc 1 is assumed to be one for convenience.
[0023]
The head 2 is a read / write separation type head having a structure in which a read head 3 which is an MR (magnetoresistive) head and a write head 4 which is an inductive head (induction type head) are separately mounted on the same slider. Assumed. The head 2 is provided to face each of both surfaces of the disk 1. The head 2 is held by the actuator 6 and moved in the radial direction of the disk 1 by the driving force of the VCM 7.
[0024]
The VCM 7 is driven by a drive current supplied from a motor driver (power amplifier in FIG. 2) 12. The motor driver is a double driver and includes a driver for SPM5. The motor driver 12 converts a control voltage (AP or AS described later) output from the D / A converter (D / A conversion element shown in FIG. 2) 15 into a drive current and supplies the drive current to the coil of the VCM 7.
[0025]
The HDD further includes a head amplifier circuit 8, a read / write circuit 9, a servo circuit 10, a microprocessor (CPU) 11, an A / D converter 14, and a disk controller (HDC) 13. A head amplifier circuit (read / write amplifier in FIG. 2) is a driver IC for the read head 3 and the write head 4, and a write current is supplied to the read amplifier and the write head 4 for amplifying a read signal read by the read head 3. Have a light amplifier to supply.
[0026]
The read / write circuit 9 is usually a dedicated integrated circuit (also referred to as a read channel or a read / write channel), and is a signal processing circuit for read / write signals. The read / write circuit 9 inputs the read signal read by the read head 3 via the head amplifier circuit 8, executes various signal processing, and decodes the original data (read data). The read / write circuit 9 outputs to the head amplifier circuit 8 a write signal obtained by modulating the write data transferred from the HDC 14 according to a predetermined modulation method (for example, RLL method). The head amplifier circuit 8 converts the write signal into a write current and outputs it to the write head 4.
[0027]
The HDC 14 constitutes an interface between the HDD and the host system (computer), and controls transfer of read / write data and an access command (read / write command) with the host computer.
[0028]
The servo system according to this embodiment includes a CPU 11, a servo circuit 10, an A / D converter 14, a D / A converter 15, and a motor driver 12. The servo circuit 10 corresponds to the position transducer of FIG. 2, extracts servo data (position information of the head 2), and generates a sector pulse (corresponding to an interrupt signal for the CPU 11) SP synchronized with the sampling frequency (FIG. 2). 3). As described above, the servo data mainly includes a track address (cylinder code) used for seek control and servo burst data for position detection within the track range. The servo circuit 10 outputs the track address CD extracted from the servo data to the CPU 11.
[0029]
The A / D converter 14 converts the servo burst data extracted from the servo circuit 10 into a digital value and outputs it to the CPU 11. The CPU 11 calculates the position of the head 2 within the range of a certain track (target track) (actually, a position error with respect to the center of the track or the boundary with the adjacent track) based on the servo burst data. Further, the CPU 11 recognizes the track position of the moving head 2 based on the track address.
[0030]
The CPU 11 implements the functions of the control system 20 and the arithmetic units 21 to 24 shown in FIG. 2 by executing a dedicated program prepared in advance. The CPU 11 receives an access command (read / write command) from the host system via the HDC 13 and executes seek control and positioning control related to the present embodiment. The CPU 11 outputs a control value (digital value) calculated by each control operation of seek control and positioning control to the D / A converter 15.
[0031]
(Seek control operation)
The seek control operation of this embodiment will be described below with reference to the timing chart of FIG. 3 and the flowchart of FIG. 4 together with FIG.
[0032]
First, when receiving an access command from the host system via the HDC 13, the CPU 11 determines a target position (target track) on the disk 1 to be accessed (steps S1 and S2). The CPU 11 starts seek control to seek the head 2 to the determined target position (step S3).
[0033]
In the seek control, as described above, the servo circuit 10 reproduces the servo data and generates a sector pulse SP to the CPU 11 at the servo area detection timing and outputs it as an interrupt signal. As shown in FIG. 3, the sector pulse SP is a pulse signal having a cycle Ts corresponding to the sampling frequency corresponding to the arrangement interval of the servo areas.
[0034]
The CPU 11 outputs a control value necessary for speed control of the head 2 to the D / A converter 15 at a time interval longer than the time interval Ts by the sector pulse SP at the time of seek control. A corresponding control voltage AS is output. That is, the CPU 11 decreases the reference sampling frequency (cycle Ts) and executes a seek operation based on the control voltage AS output from the D / A converter 15 (steps S4 and S5). Here, the delay time Td2 of the control voltage AS shown in FIG. 3 corresponds to a calculation time delay in seek control.
[0035]
When the head 2 approaches the target position by this seek operation, the CPU 11 switches from seek control to positioning control (YES in step S6, S7). That is, the CPU 11 performs transient control and position control to control the head 2 so as to position (set) the head 2 within the allowable range of the target track (see FIG. 2). At this time, as shown in FIG. 3, the CPU 11 outputs a control value necessary for positioning control of the head 2 to the D / A converter 15 in synchronization with the time interval Ts by the sector pulse SP, and the D / A converter The control voltage AS corresponding to the control value is output from 15. That is, the CPU 11 performs a positioning operation based on the control voltage AP output from the D / A converter 15 based on the reference sampling frequency (cycle Ts) (steps S8 and S9).
[0036]
As described above, according to the present embodiment, during the seek control, the set reference sampling frequency (cycle Ts) is reduced, and the seek operation is performed from the D / A converter 15 at a longer time interval than during the positioning control. The control voltage AS necessary for the output is output. Therefore, a sufficient amount of drive current obtained by converting the control voltage AS by the motor driver 12 can be supplied to the coil of the VCM 7. Therefore, the actuator 6 can seek the head 2 to the vicinity of the target position by a sufficient driving force of the VCM 7. In other words, by reducing the relatively high reference sampling frequency during seek control, a sufficient drive current is supplied to the VCM coil, and high seek control performance is obtained without degrading the speed performance of the seek operation. It becomes possible.
[0037]
FIG. 5 shows the relationship between the control voltage (control output of the D / A converter 15) and the drive current waveform of the VCM coil during seek control according to the present embodiment when the reference sampling frequency is set to about 12.25 kHz. It is the measurement result shown. In this case, the sampling frequency is reduced to 1/3 during seek control. Further, after about 8.4 ms from the start of seek, the transition from seek control to transient control included in positioning control is made. From this measurement result, it can be seen that a sufficient drive current is supplied to the VCM coil in accordance with the control voltage during seek control. In the experimental system based on this measurement, since the external gain is different by 8 times between seek control and transient control, the amount of drive current flowing through the VCM coil differs even in the case of the same D / A converter control output. .
[0038]
Although the present embodiment has been described particularly when applied to an HDD, the present invention can be applied to a disk recording / reproducing apparatus such as a magneto-optical disk apparatus as long as a similar servo system is used.
[0039]
【The invention's effect】
As described above in detail, according to the present invention, even when the reference sampling frequency of the system is high, the control voltage value is changed to the control voltage value by switching so as to decrease the sampling frequency during seek control in which the control voltage value is relatively large. A sufficient drive current can be supplied to the VCM coil. Therefore, even when a high-band servo system associated with an increase in disk track density is realized, high control performance can be realized as a result without reducing the speed performance in seek control.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main part of an HDD related to an embodiment of the present invention.
FIG. 2 is a block diagram for explaining a configuration of a servo system related to the embodiment;
FIG. 3 is a timing chart for explaining the operation of the servo system according to the embodiment;
FIG. 4 is a flowchart for explaining the operation of the servo system of the embodiment. FIG. 5 is a characteristic diagram for explaining the relationship between the control voltage and the drive current of the VCM coil during seek control of the embodiment.
FIG. 6 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (4 kHz) and a drive current of a VCM coil.
FIG. 7 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (6 kHz) and a drive current of a VCM coil.
FIG. 8 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (8 kHz) and a drive current of a VCM coil.
FIG. 9 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (10 kHz) and a drive current of a VCM coil.
FIG. 10 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (12 kHz) and a drive current of a VCM coil.
FIG. 11 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (14 kHz) and a drive current of a VCM coil.
FIG. 12 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (16 kHz) and a drive current of a VCM coil.
FIG. 13 is a characteristic diagram for explaining a relationship between a conventional sampling frequency (16 kHz) and a driving current of a resistor.
FIG. 14 is a characteristic diagram for explaining the relationship between the sampling frequency (16 kHz) and the drive current of the VCM coil during conventional positioning control.
FIG. 15 is a block diagram showing a configuration of a servo system applied to a conventional HDD.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Disk 2 ... Head 3 ... Read head (MR head)
4 ... write head 5 ... spindle motor 6 ... actuator 7 ... voice coil motor (VCM)
8 ... Head amplifier circuit 9 ... Read / write circuit 10 ... Servo circuit 11 ... Microprocessor (CPU)
12 ... Motor driver (power amplifier)
13: Disk controller (HDC)
DESCRIPTION OF SYMBOLS 14 ... A / D converter 15 ... D / A converter 20 ... Control system 21 ... Movement distance calculating part 22 ... Speed control calculating part 23 ... Transient control calculating part 24 ... Position control calculating part

Claims (3)

A disk recording / reproducing apparatus having a function for positioning and controlling a head to a target position on the disk based on servo data recorded in advance on the disk,
Head moving means for moving the head in the radial direction of the disk by the driving force of the motor means;
A seek control for controlling the movement of the head to a target position and a positioning control for positioning the head within an allowable range of the target position are executed, and a control value for driving and controlling the motor means at each control is obtained. Control means for outputting;
Drive means for converting the control value output from the control means into drive current and supplying it to the motor means;
Switching means for switching a time interval when the control means outputs the control value in accordance with the seek control and the positioning control ;
The switching means makes the time interval, which is an output cycle of the control value at the time of seek control, relatively longer than that at the time of positioning control, and the time which is an output cycle of the control value at the time of positioning control. A disc recording / reproducing apparatus characterized by switching so that the interval is relatively short . A plurality of tracks for recording data is configured, and a servo area in which servo data is recorded has a disk arranged at a predetermined interval in the circumferential direction of each track, based on the servo data, A disk recording / reproducing apparatus having a function for positioning and controlling a head to a target position on the disk,
Head moving means for moving the head in the radial direction of the disk by the driving force of the motor means;
Based on the servo data reproduced by the head according to a predetermined sampling frequency, a seek control for controlling the movement of the head to a target position and a positioning control for positioning the head within an allowable range of the target position are executed. And a control means for outputting a control value for driving and controlling the motor means during each control;
Drive means for converting the control value output from the control means into drive current and supplying it to the motor means;
Switching means for switching a time interval when the control means outputs the control value in accordance with the seek control and the positioning control;
The switching means relatively lengthens the time interval corresponding to the output period of the control value according to the predetermined sampling frequency during the seek control compared to the positioning control, and during the positioning control A disc recording / reproducing apparatus, wherein the time interval is switched to be set to an interval corresponding to the predetermined sampling frequency . A disk recording / reproducing apparatus having a function for positioning and controlling a head to a target position on the disk based on servo data recorded in advance on the disk,
Head moving means for moving the head in the radial direction of the disk by the driving force of the motor means;
A seek control for controlling the movement of the head to a target position and a positioning control for positioning the head within an allowable range of the target position are executed, and a control value for driving and controlling the motor means at each control is obtained. Control means for outputting;
Drive means for converting the control value output from the control means into drive current and supplying it to the motor means;
Generating means for generating a pulse signal for determining a sampling frequency when reproducing the servo data based on a read signal from the head;
Switching means for switching a time interval when the control means outputs the control value in accordance with the seek control and the positioning control;
Said switching means, it said seek during controlled relatively long compared to the time before Symbol positioning control said time interval by the period of said pulse signal, set to a time interval corresponding to the period of the pulse signal at the time of the positioning control A disc recording / reproducing apparatus characterized in that switching is performed.

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