JP2004118914A - Disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly control a disk to a desired revolution even if the disk is not an 8 cm or 12 cm disk. <P>SOLUTION: A controller 36 of an optical disk unit calculates the ratio of the moment of inertia to the standard disk (12 cm disk) and the kind of an optical disk 10 according to the revolution after a certain time from the start by using an FG signal 38 from a motor 12. When driving a disk other than a 12 cm disk, it adjusts the parameters of the disk motor servo circuit 14 depending on the ratio of the moment of inertia, and further readjusts the once adjusted parameters to increase the gain when the disk has a special shape and an eccentric mass. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a disk drive, and more particularly to a disk drive for driving a plurality of disks having different moments of inertia.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a disk device for reproducing or recording information by driving a recording medium such as an optical disk, a difference in moment of inertia between the disks has been detected in order to rotationally drive a plurality of types of disks. A technique for adjusting the circuit constant of the above is known. For example, in an optical disk device, since there are a 12 cm disk and an 8 cm disk, the circuit constants of the servo circuit are switched according to the difference in the moment of inertia between the 12 cm disk and the 8 cm disk in order to drive them at a desired rotation speed. Thus, for example, when the circuit constant of a 12 cm disk is used as a reference, the rotation can be controlled with the same servo characteristics as when a 12 cm disk is mounted by adjusting the circuit constant when an 8 cm disk is mounted.
[0003]
Hereinafter, the switching process of the circuit constant according to the type of the disk will be described by taking an optical disk device as an example of the disk device.
[0004]
FIG. 9 shows the loop characteristics (constant linear velocity mode) of the motor servo circuit in the optical disk device, and FIG. 10 shows the servo gain. In FIG. 9, the disturbance force (torque) is converted into a rotation speed (rpm) using a constant Kj, an inertia moment (inertia) J, and the like, and further converted into a frequency (Hz) by a rotation speed-frequency conversion constant Z. Note that S is a Laplace operator, and 1 / S represents an integrator. The angular velocity ω = Kj / (J · S). One half of the frequency is compared with a speed reference (reference frequency), and the difference is converted into a frequency detection counter value (Cnt) by a speed gain Kv. On the other hand, the other of the frequencies is converted into a phase (rad) by 2π / S (integrated and multiplied by 2π), compared with a phase reference, and the difference is converted into a phase comparison counter value (Cnt) by a phase gain Kφ. . The speed difference value and the phase difference value are added, converted into a digital voltage value (V) by a D / A conversion gain KD, and further, gain compensation and phase compensation are performed by a ripple filter (gain KF) to obtain a voltage-current conversion gain. It is converted into a torque value by Ki and the motor torque constant KT, and negatively fed back.
[0005]
The loop gain G (S) shown in FIG. 9 is represented by the following equation.
[0006]
(Equation 1)
G (S) = Ki · KT · Kj / JS · {Z · (1/2 · KV + 2π / S · Kφ) · KD} (1)
In FIG. 10, fF is the cut-on frequency of the ripple filter. When the cut-off frequency is sufficiently high and its influence can be ignored, fV and fφ are given as follows.
[0007]
(Equation 2)
fV = Ki · KT / (J · N) · C (2)
[Equation 3]
fφ = 2Kφ / KV (3)
Here, C is a constant.
[0008]
In such a servo circuit, servo characteristics can be adjusted by adjusting a circuit constant, for example, a gain KF of a ripple filter, and rotation control can be performed on a plurality of types of optical disks having different moments of inertia. For example, based on the case of driving a 12 cm disk, when an 8 cm disk is mounted, the ripple filter gain is adjusted downward based on the moment of inertia of the 8 cm disk, and the servo characteristics when the reference 12 cm disk is rotationally driven. To match.
[0009]
FIG. 11 shows how the gain of the ripple filter is adjusted based on the difference in the moment of inertia. In the figure, the horizontal axis is frequency and the vertical axis is gain. This is set as a target gain characteristic based on a 12 cm disk. When an 8 cm disk is driven with the servo characteristics of a 12 cm disk, the 8 cm disk has a smaller moment of inertia than the 12 cm disk, so that the gain intersection fV becomes as high as fV1 as shown in the figure, resulting in overgain. Therefore, by adjusting the ripple filter gain KF to lower the gain and adjusting the servo characteristic of the 12 cm disk even with the 8 cm disk, the gain intersection can be shifted from fV1 to fV to obtain the target characteristic.
[0010]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 02-263129 [Patent Document 2]
Japanese Patent Application Laid-Open No. 03-141076 [Patent Document 3]
JP 07-334919 A [Patent Document 4]
JP-A-10-341584
[Problems to be solved by the invention]
As described above, when driving two types of standard disks, that is, an 8 cm disk and a 12 cm disk, it is possible to obtain a desired servo characteristic simply by adjusting circuit constants such as a ripple filter gain. In addition to these discs, there are various discs, such as business card size discs and heart-shaped discs, as well as discs with character shapes.Especially shaped discs not only have different moments of inertia but also have eccentricity (In the present specification, the term “disc” is not limited to a simple disk shape, but includes a wide shape other than a disk shape, such as a heart shape or a character shape.) In the case of driving such a deformed disk or a nonstandard disk, the desired control cannot be obtained simply by switching or adjusting the circuit constants so as to obtain the servo characteristics of the reference disk as in the related art. It becomes remarkable.
[0012]
The present invention has been made in view of the problems of the related art, and an object of the present invention is to provide a disk device that can quickly adjust to a desired rotation servo characteristic even when a disk having a special shape other than a disk is mounted. To provide.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a drive unit for rotating a disk, a servo control unit for servo-controlling the drive unit, and an inertia moment detection for detecting a ratio of an inertia moment of the disk to a reference value. Means, and adjusting means for adjusting a servo parameter in the servo control means so as to match a predetermined servo characteristic of the disk having the reference value in accordance with the ratio, wherein the adjusting means further comprises: It is characterized in that the servo gain is increased with respect to the servo characteristics.
[0014]
It is preferable that the adjusting means increases the gain for the predetermined servo characteristic as a whole and also increases the low-frequency gain.
[0015]
The moment of inertia detecting means may detect a ratio of the moment of inertia based on a rotation speed of the disk after a lapse of a predetermined time after driving the disk by the driving means.
[0016]
In the present invention, the disk may be a disk other than a 12 cm optical disk or an 8 cm optical disk, or an eccentric disk.
[0017]
Further, the present invention provides a driving unit for rotationally driving a disk, a servo control unit for servo-controlling the driving unit, and a unit for detecting a rotation speed of the disk after a predetermined time from the start of driving by the driving unit. And adjusting means for adjusting servo parameters in the servo control means so as to match predetermined servo characteristics when the reference disk is driven based on the rotation speed, wherein the adjusting means further comprises: In the case of a nonstandard disc, the servo gain is increased for the predetermined servo characteristic.
[0018]
As described above, in the disk device of the present invention, not only the servo parameters are adjusted so as to match the reference servo characteristics when the reference disk is mounted, but also a non-standard disk, particularly a disk with an eccentric center is mounted. In this case, the servo characteristics after the adjustment are readjusted to increase the servo gain. Thus, even if a disk having an eccentricity or the like is mounted, disturbance can be quickly absorbed and the target rotational speed can be controlled.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking an optical disk device as an example.
[0020]
FIG. 1 shows a configuration block diagram of the present embodiment. The optical disk 10 is driven to rotate by a motor (spindle motor) 12. The motor 12 is controlled by a disk motor servo circuit 14, and the disk motor servo circuit 14 servo-controls the motor 12 to a desired rotation speed according to a control command from a system controller 36. For this reason, an FG signal 38 indicating a rotation speed generated by a Hall element or the like built in the motor 12 is supplied to the system controller 36. The rotation control of the motor 12 will be described in more detail.
[0021]
The pickup (PU) 16 includes a laser diode (LD) that is arranged to face the optical disc 10 and irradiates the surface of the optical disc 10 with laser light. The laser diode is driven by the light emission control circuit 22, and the laser light irradiation from the light emission control circuit 22 is controlled by the system controller 36. Further, the pickup 16 has a photodetector that converts the laser light reflected from the optical disk 10 into an electric signal, and outputs a reproduced signal to the amplification and operation circuit 24. The pickup 16 is driven in a radial direction or a track width direction of the optical disk 10 by a sled motor 18, and the sled motor 18 is controlled by a sled motor control circuit 20. When reproducing data recorded in a certain area of the optical disk 10, the sled motor control circuit 20 drives the sled motor 18 in accordance with a command from the system controller 36, and drives the pickup 16 in the radial direction to reproduce the data.
[0022]
The amplification and operation circuit 24 amplifies the reproduction signal, adds the signals to each other, and outputs the resultant signal to the reproduction signal processing circuit 30. The amplification and operation circuit 24 calculates a difference between the signals to generate a focus error signal and a tracking error signal, and respectively performs focus servo control. The signals are output to the circuit 26 and the tracking servo circuit 28. For example, in the case of a four-divided photodetector, a tracking error signal is generated from a difference between detectors divided in the radial direction, and a focus error signal is generated from a difference between diagonal sums of the four-divided photodetectors.
[0023]
The focus servo circuit 26 and the tracking servo circuit 28 perform servo control of the pickup 16 in the focus direction and the track width direction using the focus error signal and the tracking error signal, respectively, and maintain the on-focus state and the on-track state.
[0024]
The reproduction signal processing circuit 30 binarizes and demodulates the reproduction signal, and outputs it to a host device 34 such as a personal computer via the interface 32. When a wobble signal is formed on the optical disk 10 in advance, the wobble signal is supplied to the disk motor servo circuit 14 to perform servo control based on the wobble signal.
[0025]
In such a configuration, when the optical disk 10 is mounted, the system controller 36 outputs a drive command to the disk motor servo circuit 14, and the disk motor servo circuit 14 drives the motor 12 at a constant voltage. The rotation speed ω (T) after a time T from driving the motor 12 at a constant voltage is:
(Equation 4)
ω (T) = K · (1−exp [−T / τm])
τm = Ra · J / Kt / Ke (4)
It is. Here, K is a constant, Ra is the electric resistance of the motor 12, J is the moment of inertia, and Kt is the torque constant. Accordingly, as the inertia is smaller and the mechanical time constant τm is smaller, the rate of change of the rotation speed is larger, and the target rotation speed is reached sooner.
[0026]
FIG. 2 shows a temporal change of the rotation speed when the motor 12 is driven at a constant voltage, using various optical disks having different moments of inertia as parameters. In the figure, the horizontal axis is the elapsed time from the start of driving at a constant voltage, and the vertical axis is the rotation speed. There are four cases, ie, no disk, 8 cm disk, 12 cm disk, and non-standard disk having a special shape, all of which reach the maximum rotation speed ωmax after sufficient time has passed. When the rotational speeds are compared at a predetermined time T after the start of the rotational drive, the rotational speed changes according to the magnitude of the moment of inertia. Assuming that the magnitude of the moment of inertia is no disk <8 cm disk <special shape disk <12 cm disk, the rotational speed is no disk> 8 cm disk> special shape disk> 12 cm disk. Specifically, the threshold is ωth1 or less for a 12 cm disk, ωth2 (ωth1 <ωth2) or less for an 8 cm disk, and ωth2 or more when no disk is present. Is between the 8 cm disk and the 12 cm disk.
[0027]
Therefore, by monitoring the rotation speed after a predetermined time from the start of driving, it is possible to distinguish the presence / absence of a disk, and if the disk is present, whether it is an 8 cm disk, a 12 cm disk, or a nonstandard disk. is there. The system controller 36 determines a disk based on such a difference in rotation speed. Then, the system controller 36 calculates the ratio of the moment of inertia of the mounted disk based on the moment of inertia of the 12 cm disk, and based on this ratio, the servo characteristics are the same as those of the prior art based on the servo characteristics for the 12 cm disk. The circuit constants are adjusted so as to be the same, and the servo gain is readjusted as well as the circuit constants for a specially shaped disk (nonstandard disk).
[0028]
3 and 4 show flowcharts of the entire processing according to the present embodiment. First, in FIG. 3, a command voltage is output from the system controller 36 (S101), and a constant drive voltage is output from the disk motor servo circuit 14 to the motor 12 (S102). After outputting the drive voltage, the system controller 36 waits for a certain time T (S103). After the certain time T has elapsed, the system controller 36 inputs the FG signal 38 output from the motor 12, and measures the rotation speed ω of the motor 12 from the FG signal 38. (S104). The FG signal 38 outputs a fixed number of pulses (for example, 8 pulses) per one rotation of the motor 12, and the system controller 36 can calculate the frequency by counting the number of pulses of the FG signal 38 within a predetermined time. The rotation frequency of the motor 12, that is, the rotation speed ω can be measured by dividing the obtained frequency by the number of pulses per rotation (for example, 8 pulses).
[0029]
After measuring the rotation speed ω after a certain time T from the start of driving, the reference rotation speed ω0, that is, the speed ratio with the rotation speed obtained in the certain time T when the 12 cm disk as the reference disk is mounted is calculated. (S105). The reference rotation speed ω0 may be stored in advance in a memory of the system controller 36, for example. After calculating the rotation speed ratio, an inertia moment (inertia) ratio, that is, a ratio with respect to the inertia moment of a 12 cm disk, which is a reference of the mounted disk, is calculated from the speed ratio (S106). Since the rotational speed and the moment of inertia have a 1: 1 relationship as can be seen from the above equation, the calculation of the moment of inertia ratio based on the speed ratio is easy. By calculating the moment of inertia ratio, the size of the loaded disk can be determined (S107). For example, if the moment of inertia ratio (moment of inertia of mounted disc / moment of inertia of 12 cm disc) is extremely small, the disc is not yet mounted, and if 1 the disc is 12 cm, for example 0.5 cm and 8 cm. It is determined as a disk. The determination result is stored in the memory of the system controller 36.
[0030]
Next, as shown in FIG. 4, the system controller 36 determines whether a disk is mounted (S108). If it is determined in S107 that there is no disk mounted, the determination in this process is YES, and the system controller 36 stops the disk motor servo circuit 14 (S110). On the other hand, if a disk is mounted, it is determined whether or not the mounted disk is a reference 12 cm disk (S109). If it is determined in S107 that the disc is a 12 cm disc, YES is determined in this process, and the system controller 36 sets parameters in the disc motor servo circuit 14 (S111). The parameter at this time is a reference value, and when the disk motor servo circuit 14 is set to the reference value in a default state, there is no need to adjust the parameter.
[0031]
On the other hand, if the disc is not a 12 cm disc, the system controller 36 next determines whether the mounted disc is an 8 cm disc (S112). When the mounted disk is an 8 cm disk, the system controller 36 sets a servo parameter having a gain ratio according to the inertia moment ratio (inertia ratio) in the disk motor servo circuit 14 (S113). As can be seen from FIG. 11, when the moment of inertia is small, the crossover frequency fV shifts to fV1 with respect to the target gain characteristic, resulting in overgain. The gain intersection point fV is inversely proportional to the moment of inertia, and the shift amount from fV to fV1 is determined by the moment of inertia ratio. Therefore, the correction gain ratio is determined from the inertia moment ratio, and the reduction amount of the ripple filter gain KF can be determined from the correction gain ratio. By reducing (adjusting downward) the ripple filter gain KF, the same servo characteristics as in the case of a 12 cm disk can be obtained even with an 8 cm disk as shown in FIG.
[0032]
On the other hand, if the mounted disk is neither a 12 cm disk nor an 8 cm disk, the system controller 36 determines that the disk is a specially shaped disk (non-standard disk) (S 114) and gives the disk motor servo circuit 14 a response to the inertia moment ratio (inertia ratio). The servo parameter having the gain ratio is set (S115). This processing is the same as S113. Further, in the case of a special-shaped disk (non-standard disk), the system controller 36 re-adjusts the adjusted servo parameters so as to increase the overall servo gain (S116), and the gain intersection fv in FIG. To the high frequency side.
[0033]
FIG. 5 schematically shows the processing of S115 and S116. The gain characteristic indicated by A in the figure is a gain characteristic when the servo parameter (ripple filter gain KF) is adjusted according to the inertia moment ratio in S115, and is a basic servo characteristic for a 12 cm disk. The gain intersection is fv. On the other hand, the gain characteristic indicated by B in the drawing is a gain characteristic after the servo parameter (ripple filter gain KF) is readjusted in S116, and is a gain characteristic obtained by increasing the basic characteristic by a predetermined gain amount. The gain intersection increases from fV to fV (up). In the case of a heart-shaped or specially-shaped disk having a specific character shape, the position of the center of gravity is deviated, and disturbance cannot be suppressed particularly at high speed rotation with the basic gain characteristics. Therefore, by further increasing and adjusting the gain characteristic adjusted according to the inertia moment ratio, disturbance can be effectively suppressed even on a disk having a large eccentricity, and it is possible to quickly control the rotational speed to a desired value.
[0034]
It is also preferable that the amount of gain increase at the time of gain readjustment is made variable according to the degree of eccentricity instead of the predetermined amount.
[0035]
FIG. 6 shows another processing flowchart of the present embodiment. This is a process subsequent to S101 to S107 shown in FIG.
[0036]
The processing of S201 to S208 is the same as the processing of S108 to S115 in FIG. 4, and the ripple filter gain KF is reduced and adjusted in accordance with the inertia moment ratio with the 12 cm disk to match the basic servo characteristics of the 12 cm disk. On the other hand, in the case of a special-shaped disk (non-standard disk), after servo adjustment, the ripple filter is further adjusted to shift fV2 in FIG. 11 to the high frequency side, and increase only the low-frequency gain.
[0037]
FIG. 7 schematically shows the processing of S208 and S209. A in the figure is a basic characteristic obtained in S208, and is the same as the basic characteristic in FIG. In the figure, C is a gain characteristic obtained by readjusting in S209, where fV2 increases to fV2 (up), and only the low-frequency gain increases. In this way, instead of increasing the overall gain without changing the overall gain characteristics, increasing the gain only in the low frequency range and changing the gain characteristics itself also reduces the disturbance of the specially shaped disk with a large eccentricity. Can be suppressed.
[0038]
FIG. 8 shows a further processing flowchart in the present embodiment. This is a process subsequent to S101 to S107 shown in FIG.
[0039]
The processing of S301 to S308 is the same as the processing of S108 to S115 in FIG. 4 or the processing of S201 to S208 in FIG. On the other hand, after adjusting the servo parameter (ripple filter gain KF) according to the inertia moment ratio, it is determined whether or not wobble servo is being performed (S309). Here, the wobble servo controls the rotation speed based on a wobble signal formed in advance on the optical disc 10 as described above. The servo system includes a servo based on an FG signal, a servo based on an 11T signal in an RF signal, and a servo based on a wobble signal. In general, wobble servo requires higher-precision control than other systems. . Therefore, when the wobble servo is not used, readjustment is not performed, and when the wobble servo is used, the overall gain is increased (see S116 and FIG. 5), or only the low-frequency gain is increased (S209 and FIG. 7). Is readjusted (S310). This can also effectively cope with a specially shaped disk having a large eccentricity.
[0040]
As described above, the embodiments of the present invention have been described by taking the optical disk device as an example, but the present invention is not limited to this, and can be applied to any disk device.
[0041]
In the present embodiment, for example, as shown in S115 and S116 in FIG. 4, the gain adjustment processing (S115) and the gain increase processing (S116) according to the inertia moment ratio are sequentially executed. The controller 36 can perform the processing of S115 and the processing of S116 collectively, and can immediately adjust the gain characteristic shown in FIG. Also in this case, the gain characteristic B finally obtained is still in a relationship where the gain is increased with respect to the basic characteristic A. The same applies to S208 and S209 in FIG.
[0042]
Further, in the present embodiment, the inertia moment ratio is calculated from the rotation speed ratio in the fixed time T. However, it is also possible to immediately determine the type of the disk from the rotation speed ratio and adjust the servo parameters according to the rotation speed ratio. . This case is also technically equivalent to adjusting the servo parameters based on the inertia moment ratio. This is because the moment of inertia and the rotational speed correspond to 1: 1 (can be mutually converted).
[0043]
Also, the servo parameters may be adjusted based on the absolute value of the rotation speed during the fixed time T instead of the rotation speed ratio. That is, the rotation speed value of the 8 cm disk and the 12 cm disk after a certain time T and the servo parameter adjustment amount as a function of the rotation speed value are stored in the memory of the system controller 36 in advance, and the detected rotation speed value and the detected rotation speed value are stored in the memory. The type of the disc can be determined by comparing the obtained value with the obtained value, and the servo parameters can be adjusted based on the rotation speed value. Also in this case, the adjustment is performed using the difference from the rotation speed value of the 12 cm disk, and the adjustment is the same as the adjustment based on the inertia moment ratio.
[0044]
Further, in the present embodiment, a 12 cm optical disk is used as a reference disk. However, servo parameters can be adjusted by calculating an inertia moment ratio and a rotation speed ratio based on an 8 cm optical disk. Can be selected arbitrarily.
[0045]
【The invention's effect】
As described above, according to the present invention, the rotation can be quickly controlled even when an arbitrary disk is mounted.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment.
FIG. 2 is a graph showing a relationship between an elapsed time from the start of driving and a rotation speed.
FIG. 3 is an overall processing flowchart (part 1) of the embodiment;
FIG. 4 is an overall processing flowchart (part 2) of the embodiment;
FIG. 5 is a graph showing gain characteristics of the embodiment.
FIG. 6 is another processing flowchart of the embodiment.
FIG. 7 is a graph showing a gain characteristic corresponding to FIG. 6;
FIG. 8 is a flowchart illustrating still another process according to the embodiment.
FIG. 9 is a configuration diagram of a servo circuit.
FIG. 10 is an explanatory diagram showing gain characteristics in FIG. 9;
FIG. 11 is a graph showing adjustment of gain characteristics.
[Explanation of symbols]
10 optical disk, 12 motor (spindle motor), 14 disk motor servo circuit, 36 system controller.

Claims (6)

Driving means for rotating and driving the disk;
Servo control means for servo-controlling the driving means;
Moment of inertia detecting means for detecting the ratio of the moment of inertia to a reference value of the disk,
Adjustment means for adjusting servo parameters in the servo control means so as to match predetermined servo characteristics in the disk having the reference value according to the ratio,
The disk device according to claim 1, wherein the adjusting unit further increases a servo gain for the predetermined servo characteristic. The device of claim 1,
The disk device, wherein the adjusting means increases a low-frequency gain for the predetermined servo characteristic. The device of claim 1,
The disk device, wherein the moment of inertia detection means detects a ratio of the moment of inertia based on a rotation speed of the disk after a lapse of a predetermined time since the drive means drives the disk. The device according to any one of claims 1 to 3,
The disk device according to claim 1, wherein the disk is a disk other than a 12cm optical disk or an 8cm optical disk. The device according to any one of claims 1 to 3,
The disk device according to claim 1, wherein the disk is an eccentric disk. Driving means for rotating and driving the disk;
Servo control means for servo-controlling the driving means;
Means for detecting the rotation speed of the disk after a fixed time after starting driving by the driving means,
Based on the rotation speed, having an adjusting unit for adjusting servo parameters in the servo control unit to match predetermined servo characteristics when driving the reference disk,
The disk device, wherein the adjusting unit further increases a servo gain for the predetermined servo characteristic when the disk is a nonstandard disk.

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