JPH10106135A - Servo controller of spindle motor for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically adjust a feedback gain in the servo loop of a spindle motor without discriminating the size of an optical disk and the moment of intertia of the motor. SOLUTION: A PLL circuit 20 produces a reproducing clock based on an EFM signal from an optical disk 10 and a velocity fluctuation quantity detecting circuit 30 counts the reproducing clock and detects a velocity fluctuation quantity ΔW from the difference between the count number W and a target count number W1. A gain calculating part 46 calculates a gain based on the velocity fluctuation quantity and controls a feedback gain a little at the time of ΔW>0 and controls the feedback gain largely at the time of ΔW<0. The gain control part 46 performs the feedback control of the spindle motor based on the feedback gain calculated in the part in this manner. Moreover, a feedback gain may be calculated based on the size of a required period tt before the velocity fluctuation quantity ΔW becomes nearly zero by detecting the relation between the required period tt and a target required period TT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a servo control device for a spindle motor for an optical disk such as a CD (compact disk), and more particularly to a feedback gain control in a motor feedback control.

[0002]

2. Description of the Related Art To reproduce a signal recorded from an optical disk such as a CD or a CD-ROM, a linear velocity (CLV:
In the case of the constant liner velocity (Velocity) method, a spindle motor for rotating the optical disc is controlled so that a digital reproduction signal obtained by reading from the optical disc becomes a fixed amount within a fixed period.

FIG. 6 shows a schematic configuration of a conventional servo control device for a CLV type spindle motor. The optical disc 10 is driven to rotate by a spindle motor 13, and data stored on the optical disc 10 is extracted as an analog signal by a photodiode or the like of the pickup unit 12. This analog signal is RF (high frequency) amplified, further converted to a digital RF signal,
An FM (Eight to Fourteen Modulation) signal is obtained.

[0004] Phase comparator 22, filter 24, VCO2
The PLL circuit 20 including the frequency divider 6 and the frequency divider 28 generates a reproduced clock synchronized with the EFM signal from the obtained EFM signal.

[0005] The reproduced clock signal is supplied to a demodulation circuit 14 as a reproduced clock and also to a frequency comparator 15. The frequency comparator 15 compares the frequency fg of the recovered clock with the frequency fref of the reference frequency signal,
The frequency difference Δf (= fref−fg) is output.

The speed feedback gain control section 16 outputs a speed error Hv proportional to Δf based on the frequency difference Δf. Further, the phase feedback gain control unit 17 calculates the frequency difference Δ
and outputs a phase error Hp / s.
Add the two error signals of the speed error Hv and the phase error Hp / s, and the amplifier 19 amplifies the added signal with a fixed feedback gain g. Then, the output analog signal of the amplifier 19 is used as a drive signal by the motor drive circuit 62.
, The spindle motor 13 is driven to rotate the optical disk 10 accordingly.

[0007] By such feedback control of the servo loop, the frequency fg of the reproduced signal obtained from the PLL circuit 20 is controlled so as to match the frequency fref corresponding to the target rotation speed (target linear speed), and the spindle motor is operated. The speed is controlled so that the linear speed becomes constant.

The EFM signal is synchronously detected by the demodulation circuit 14 based on the reproduced clock and demodulated.
Further, the demodulated data is subjected to an error correction process or the like in a subsequent stage, and is reproduced as an audio signal, a video signal, or the like.

[0009]

In a conventional analog servo controller, a feedback gain is set in advance based on an inertia moment (α / (j · s)) corresponding to the size of an optical disk and a motor and an estimated disturbance torque. Have been. The spindle motor 13 is feedback-controlled by controlling the speed and phase based on the amount of deviation between the frequency of the reproduction signal and the target frequency.

However, the actual moment of inertia,
Further, disturbance torque (loss torque, torque ripple, friction torque of a bearing, wind receiver of an optical disk, etc.) generated by a motor or the like may be different from a value assumed by a driving environment or an individual motor.

Therefore, every time the motor changes, it is necessary to detect and adjust the feedback gain g corresponding to the motor. Further, since the disturbance torque and the like are not always constant when the motor is driven, the spindle motor cannot be driven with the feedback gain g suitable for the constantly driven state.

An object of the present invention is to provide a digital servo control device capable of easily, appropriately and automatically adjusting a feedback gain of a spindle motor according to an optical disk and a motor. With the goal.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a servo control device for performing feedback control of a spindle motor of an optical disk device, comprising a speed fluctuation amount detecting means for detecting a speed fluctuation amount of a rotation speed of an optical disk with respect to a target rotation speed. Gain calculation means for calculating a feedback gain for the spindle motor based on the magnitude of the speed fluctuation amount, wherein the feedback control is executed using the calculated feedback gain.

Further, the speed fluctuation detecting means includes, for example, a counter for counting a reproduction clock generated from an input signal obtained by reading from an optical disk at regular intervals, and a reproduction clock corresponding to the input signal in the counter. The difference ΔW between the count W of the above and the target count W1 of the reproduction clock corresponding to the target rotation speed of the optical disc in a certain period is detected as the speed variation.

If the speed fluctuation amount ΔW is within a certain period, ΔW ≒
If it does not become 0, that is, if the target count number and the actual reproduction clock count number do not match, it means that the feedback gain set at that time is not appropriate in the servo loop. Therefore, for example, by calculating a feedback gain corresponding to the speed fluctuation amount ΔW based on a predetermined arithmetic expression and using the feedback gain for feedback control, it is possible to drive the motor by adapting the gain to the driving situation with a simple configuration. Becomes possible.

Further, the gain calculating means calculates an equation [(1−a × ΔW) × g] where a is a constant with respect to the current feedback gain g based on the speed fluctuation amount ΔW. The obtained value is used as a new feedback gain g.

Further, the gain calculating means sets
A period tt until the predetermined target value is reached is detected, and a target period T until the speed fluctuation amount ΔW reaches the target value is detected.
Based on T and the detected period tt, an expression [tt] where b is a constant with respect to the current feedback gain g
/ TT × b × g], and the obtained value is used as a new feedback gain g.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 6 described above are denoted by the same reference numerals, and description thereof will be omitted.

[First Embodiment] FIG. 1 shows the configuration of a digital servo control device for a spindle motor for an optical disk according to the present embodiment.

[Overall Configuration] The PLL circuit 20 generates a reproduction clock from an EFM signal obtained by reading from the rotating optical disk 10. Then, based on the reproduced clock, the speed fluctuation detecting circuit 30 detects a speed deviation (speed fluctuation ΔW) from the target value. Arithmetic circuit 40
Calculates a speed error and a phase error based on the speed fluctuation amount ΔW, calculates a feedback gain based on ΔW, and outputs a feedback control signal obtained based on these calculation results. This feedback control signal is converted into an analog signal by the D / A 60 and supplied to the motor drive circuit 62 as an analog drive signal. The motor drive circuit 62 operates the spindle motor 13 based on the drive signal, The rotation speed is controlled to reach the target speed. In the servo control device of the present embodiment, by the servo loop as described above,
Feedback control of the spindle motor is performed.

When the spindle motor 13 is forcibly accelerated / decelerated instead of the feedback control by the servo loop, the spindle motor 13 is forcibly accelerated / decelerated for a predetermined period by a forced acceleration / deceleration control signal.

The speed variation detecting circuit 30 includes a counter 32
And a subtracter 34, and the counter 32 is a PLL circuit 2
The reproduction clock from 0 is counted every predetermined reference period T, and the subtracter 34 compares the count number W of the counter 32 with a preset target count number W1 (W-W
1) is obtained and output as the speed fluctuation amount ΔW. Here, the target count number W1 is the count number of the reproduction clock to be counted in the reference period T when the rotation of the optical disk 10 reaches the target speed, that is, in the present embodiment,
This is the count number corresponding to the target linear velocity.

The operation circuit 40 includes a gain operation section 46, a speed feedback gain operation section 42, a phase feedback gain operation section 44, an adder 50, a gain multiplication section 52, and further includes a forced acceleration / deceleration control section 48. I have. This forced acceleration / deceleration control unit 48
Outputs a forced acceleration / deceleration control signal when the spindle motor 13 is forcibly accelerated / decelerated.

The speed variation ΔW detected by the speed variation detection circuit 30 is supplied to a gain calculator 46, a speed feedback gain calculator 42, and a phase feedback gain calculator 44 of the calculation circuit 40. Therefore, the speed feedback gain calculator 42 calculates the speed feedback gain based on the speed variation ΔW.
A speed error Hv proportional to ΔW is obtained. Further, the phase feedback gain calculator 44 calculates the phase difference Hp / s by integrating the speed fluctuation amount ΔW to obtain a corresponding phase difference (integrated value of ΔW). The adder 50 calculates the speed error Hv and the phase error Hp
/ S, and outputs the added signal to gain multiplying section 52.

The gain calculating section 46 calculates a feedback gain based on the speed fluctuation amount ΔW at a predetermined measurement time, and outputs the obtained feedback gain to the gain multiplying section 52, as described later. Further, the gain multiplication unit 52
Multiplies the addition signal obtained from the adder 50 by the feedback gain obtained by the gain calculator 46.

On the output side of the arithmetic circuit 40, a switching circuit 54 is provided. The switching circuit 54 performs a switching operation in accordance with a switching signal separately supplied from a microcomputer or an arithmetic circuit 40 (not shown). When the switching signal indicates feedback control by the servo loop, the switching signal is connected to the gain multiplying unit 52 and supplies a feedback control signal corresponding to the feedback gain g calculated based on the speed variation ΔW to the D / A 60. When the switching signal indicates the forced acceleration / deceleration control by the open loop,
Connected to the forced acceleration / deceleration control unit 48 side of the arithmetic circuit 40,
A forced acceleration / deceleration control signal is supplied to the D / A 60. As described above, the switching operation of the switching circuit 54 drives the spindle motor 13 by one of the driving method of the forced acceleration / deceleration control driving and the driving by the CLV servo loop.

"Control of feedback gain"
Next, a control operation of the feedback gain based on the detected speed fluctuation amount ΔW will be described with reference to FIGS. 2 and 3.

For example, when the rotation of the motor 13 is started with the spindle motor 13 stopped, first, the switching circuit 54 is switched to the forced acceleration / deceleration side by the switching signal, and the spindle is switched by the forced acceleration control signal. The motor 13 is forcibly accelerated (S1). When the spindle motor 13 is stopped from the rotating state, the switching circuit 5
4 is switched to the forced acceleration / deceleration side, and the spindle motor 13 is decelerated by the forced deceleration control signal.

When the forced acceleration is performed, the rotation speed of the spindle motor 13 increases from the rotation stop state with an inclination corresponding to the set feedback gain gs, thereby obtaining from the optical disk 10 as shown in FIG. EF
The frequency of the reproduction clock of the M signal increases, the count W of the reproduction clock for each predetermined period T increases, and the count W gradually approaches the target count value W1.

After the start of the forced acceleration, for example, the generation of the forced acceleration control signal, when a predetermined period t theoretically assumed to be required to reach the target rotational speed elapses (S2), the gain calculator 46 detects this. The speed fluctuation amount ΔW output from the speed fluctuation amount detection circuit 30 is read (S3), and the magnitude thereof is determined (S4). The measurement of the elapse of the predetermined period t is easily performed by, for example, providing a timer in the arithmetic circuit 40 and supplying a time-up signal to the gain arithmetic unit 46 when the timer elapses from the forced acceleration signal. be able to.

As a result of the determination (S4), ΔW is other than 0 (ΔW
> 0, ΔW <0) (No), since the assumed inertia moment and feedback gain gs do not match the actual inertia moment and feedback gain g, the set feedback gain gs is changed to a more appropriate value. There is a need to.

For example, if the actual moment of inertia is smaller than expected and the set feedback gain gs is large, the rotational speed of the spindle motor 13 after the elapse of the predetermined period t becomes higher than the target value as shown in FIG. , ΔW> 0. Therefore, in the case of ΔW> 0, the feedback gain g is reduced by that amount to cope with the situation. On the other hand, when the actual moment of inertia is large and the set feedback gain gs is small, as shown in FIG.
Since the rotation speed of the spindle motor 13 after the elapse of the predetermined period t is lower than the target value, ΔW <0. Therefore, this case is dealt with by increasing the feedback gain g accordingly.

More specifically, when ΔW is other than 0 (ΔW> 0, ΔW <0), the gain calculator 46 calculates the following equation (1).
Is calculated to obtain a new feedback gain gp (S5).

[0034]

Gp = (1−ΔW × a) × gs gp: calculated feedback gain gs: set feedback gain a: constant (1) If ΔW> 0, the above equation (1) is calculated. By
A feedback gain gp smaller than the set feedback gain gs is calculated, and if ΔW <0, a feedback gain gp larger than the set feedback gain gs is calculated. Then, the gain calculator 46 calculates
The feedback gain gp obtained in this manner is set in the gain multiplying section 52, and thereafter, the obtained feedback gain gp is multiplied by the addition signal of the velocity error and the phase error, and a CLV servo loop is formed. Control is executed (S6).

The result of determining the read ΔW (S
4) If ΔW ≒ 0 (Yes), the gain multiplication unit 52
The feedback control by the CLV servo loop is performed using the set feedback gain gs without changing the feedback gain gs set in advance (S6). When ΔW ≒ 0, even if the above equation (1) is used to calculate ΔW, the obtained feedback gain gp is substantially equal to the set feedback gain gs. Therefore, even if ΔW ≒ 0, the gain calculation unit 4
6 may calculate the read ΔW by the equation (1) without determining the magnitude of the ΔW. However, as described above, if ΔW is determined and the feedback gain is not calculated when ΔW ≒ 0, this multiplication process can be omitted.

As described above, according to the first embodiment, the reproduction clock obtained by rotating the optical disk 10 by the spindle motor 13 without separately detecting the moment of inertia or disturbance torque that differs depending on the size of the optical disk, the motor, and the like. Is counted, and the difference between the count number and the target count number is obtained, whereby the speed fluctuation amount ΔW according to the actual moment of inertia, disturbance torque, or the like is obtained.

Further, a new feedback gain gp is calculated based on the speed variation ΔW digitally obtained as the difference between the clock counts, and the feedback control is performed by the feedback gain gp.
Servo control can be automatically performed with an appropriate feedback gain gp.

[Second Embodiment] In the first embodiment, the feedback gain gp is calculated based on the magnitude of ΔW after a certain period t has elapsed from the start of the forced acceleration / deceleration.
Then, the feedback gain gp is calculated based on a period required until the rotation speed of the optical disk 10 reaches near the target speed after the start of the forced acceleration / deceleration.

The processing method according to the second embodiment will be described below with reference to FIGS. The configuration itself of the servo control device is as shown in FIG. 1 as in the first embodiment.

When the rotation of the motor 13 is started while the spindle motor 13 is stopped, the switching circuit 54 is switched, and the spindle motor 13 is forcibly driven by a forced acceleration control signal from the forced acceleration / deceleration control unit 48. It accelerates (S11). When the spindle motor 13 is stopped from the rotating state, the switching circuit 54 is switched to the forced acceleration / deceleration side as in the first embodiment, and the spindle motor 13 is decelerated by the forced deceleration control signal.

When the forced acceleration is executed, similarly to FIG.
The rotation speed of the spindle motor 13 rises with a slope corresponding to the set feedback gain gs, and accordingly, as shown in FIG. 5, the count number W of the reproduction clock counted by the counter 32 every fixed period T increases. Then, it approaches the target count value W1.

The gain calculator 46 monitors the speed fluctuation amount ΔW output from the speed fluctuation amount detection circuit 30, and detects this when ΔW becomes a target value (specifically, ΔW） 0) (S12). .

Further, from the start of the forced acceleration, that is, the generation of the forced acceleration signal, the count number W of the reproduction clock increases, and Δ
The time tt required to reach W ≒ 0 is measured (S
13). The calculation of the period tt is performed by, for example, the arithmetic circuit 40.
The timer can be easily obtained by outputting a time counted by the timer as a period tt by providing a timer, starting the time measurement by the forced acceleration / deceleration signal, stopping the measurement by detecting ΔW ≒ 0.

Next, the gain calculator 46 compares the measured period tt with the ideal required period TT for the assumed moment of inertia (S14).

As a result of the comparison, if tt ≒ TT (Yes), the optical disk 10 is rotating as expected, so that the feedback gain gs preset in the gain multiplying unit 52 is not changed. The feedback control by the CLV servo loop is performed using the set feedback gain gs (S16).

In step S14, if tt does not match TT (tt <TT, tt> TT) (if the determination result is No), the assumed moment of inertia and feedback gain gs are set to the actual moment. And does not match the feedback gain g. Therefore, in this case, the feedback gain gs corresponding to the period tt is calculated and changed to a more appropriate value.

For example, when the actual moment of inertia is smaller than the assumed value and the set feedback gain gs is large, as shown in FIG. 5, the rotation speed of the spindle motor 13 becomes earlier than the ideal required time TT. Reaches the target value, and ΔW ≒ 0. Therefore, the actually required period tt is shorter than the ideal required period TT. Then, t
If t <TT, the feedback gain g is controlled to be smaller accordingly.

On the other hand, when the actual moment of inertia is larger than the assumed value and the set feedback gain gs is small, as shown in FIG. 5, the rotational speed of the spindle motor 13 lags behind the ideal required period TT. To reach the target value, and ΔW ≒ 0. Therefore, the actual required period t
t is longer than the ideal required period TT. Therefore, tt
If> TT, the feedback gain g is controlled to be larger.

More specifically, the gain calculating section 46
If tt does not match TT (tt <TT, tt> T
In T), the following equation (2) is calculated to obtain a new feedback gain gp (S15).

[0050]

Gp = (tt / TT) × b × gs b: constant (2) According to the above equation (2), when tt <TT, the feedback gain gp is smaller than the set feedback gain gs.
Is calculated, and when tt> TT, a feedback gain gp larger than the set feedback gain gs is calculated. Further, the gain calculator 46 sets the obtained feedback gain gp in the gain multiplier 52,
Thereafter, the obtained feedback gain gp is multiplied by the sum signal of the speed error and the phase error to obtain the CLV
And the feedback control is executed (S16).

As described above, according to the second embodiment, similarly to the first embodiment, the reproduction clock is counted without separately detecting the size of the optical disk, the inertia moment and the disturbance torque due to the motor and the like, and the counted number and the target number are set. By determining the difference from the count number, the speed variation ΔW according to the moment of inertia, disturbance torque, or the like is determined.

Further, if the feedback gain gp is calculated based on the period tt required until the speed fluctuation amount ΔW reaches ΔW ≒ 0, and the feedback control of the spindle motor is performed based on the feedback gain gp, it is automatically appropriate. Servo control can be performed with an appropriate feedback gain gp.

In the two embodiments described above, the case where an appropriate feedback gain is calculated at the time of transition from the forced acceleration / deceleration control to the feedback control has been described as an example. However, the present invention is not limited to the above transition, and the gain calculator 46 may continuously or periodically calculate the feedback gain based on the speed variation ΔW during the feedback control of the spindle motor by CLV (constant linear velocity). . In this case, the gain calculation unit 4
6 calculates a feedback gain suitable for driving conditions and the like by calculating the above equation (1) as needed based on ΔW supplied from the speed fluctuation amount detection circuit 30, and performs feedback control using the calculated feedback gain. Becomes possible.

[0054]

As described above, according to the present invention,
A feedback gain corresponding to a driving condition is calculated based on a speed fluctuation amount detected from a signal read from the optical disk without particularly detecting a size of the optical disk, an inertia moment due to a motor, a disturbance torque, and the like. Therefore, it is possible to drive the spindle motor with a simple configuration by automatically adjusting the feedback gain with high accuracy.

For example, a reproduction clock generated based on an input signal obtained by reading from an optical disk is counted, and the counted number and the target count number within a certain period of the reproduction clock corresponding to the target rotation speed of the optical disk are calculated. , The speed fluctuation amount can be detected. Thus, according to the present invention, it is possible to digitally and easily calculate the speed fluctuation amount. Further, since the speed fluctuation amount can be obtained as a digital amount, it is possible to simplify the calculation processing of the feedback gain according to the speed fluctuation amount and the configuration therefor.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a servo control device of a spindle motor for an optical disk according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a method for controlling a feedback gain gp based on the magnitude of a speed fluctuation amount ΔW according to the first embodiment.

FIG. 3 is a diagram for explaining a relationship between a magnitude of a speed fluctuation amount ΔW and an inertia moment and a feedback gain in a servo loop.

FIG. 4 shows ΔW ≒ 0 of the speed fluctuation amount ΔW according to the second embodiment.
6 is a flowchart illustrating a control method of a feedback gain gp based on a required time tt until arrival.

FIG. 5 is a diagram for explaining a relationship between a time tt required for the speed fluctuation amount ΔW to reach ΔW ≒ 0, and a moment of inertia and a feedback gain in a servo loop.

FIG. 6 is a diagram showing the configuration of a conventional servo control device for an optical disk spindle motor.

[Explanation of symbols]

Reference Signs List 10 optical disk, 12 pickup unit, 13 spindle motor, 14 demodulation circuit, 20 PLL circuit, 30
Speed fluctuation amount detection circuit, 32 counter, 34 subtractor, 40 operation circuit, 42 speed feedback gain operation section, 44
Phase feedback gain calculator, 46 gain calculator, 48 forced acceleration / deceleration controller, 50 adder, 52 gain multiplier,
54 switching circuit, 60 D / A, 62 motor drive circuit.

Claims (6)

[Claims] 1. A servo control device for performing feedback control of a spindle motor of an optical disk device, comprising: speed fluctuation amount detecting means for detecting a speed fluctuation amount of a rotation speed of an optical disk with respect to a target rotation speed; And a gain calculating means for calculating a feedback gain for the spindle motor based on the feedback control, wherein the feedback control is executed by the calculated feedback gain. 2. The servo control device for a spindle motor for an optical disk according to claim 1, wherein the speed fluctuation amount detection means counts a reproduction clock generated from an input signal obtained by reading from the optical disk at regular intervals. A counter number of a reproduction clock corresponding to an input signal in the counter, a target count number of a reproduction clock corresponding to a target rotation speed of the optical disc in a certain period,
A servo control device for a spindle motor for an optical disk, wherein the difference is detected as a speed variation. 3. The servo control apparatus for a spindle motor for an optical disk according to claim 2, wherein the gain calculating means includes a count number W and a target count number W of a reproduction clock of the input signal at a predetermined measurement time.
1, the speed fluctuation amount ΔW detected from the difference from Δ1 (ΔW = W−W
Based on 1), a formula [(1−a × ΔW) × g] where a is a constant is calculated for the current feedback gain g, and the obtained value is used as a new feedback gain g. Control device for spindle motor for optical disk. 4. The servo control device for a spindle motor for an optical disk according to claim 3, further comprising a forced acceleration control unit for forcibly accelerating the spindle motor, wherein the gain calculation unit is fixed from the start of the forced acceleration. A servo control device for a spindle motor for an optical disk, wherein a new feedback gain g is calculated according to the speed fluctuation amount ΔW after a lapse of a period. 5. The servo control device for a spindle motor for an optical disk according to claim 2, wherein the gain calculating means obtains a speed variation obtained from a difference between a count number W of a reproduction clock of the input signal and a target count number W1. The amount ΔW (ΔW = W−W1) is calculated from the reference time
A period tt until the predetermined target value is reached is detected. Based on the target period TT until the speed fluctuation amount ΔW reaches the target value and the detected period tt, the current feedback gain g is calculated. On the other hand, a servo control device for a spindle motor for an optical disk, wherein an expression [tt / TT × b × g] where b is a constant is calculated and the obtained value is used as a new feedback gain g. 6. The servo control apparatus for a spindle motor for an optical disk according to claim 5, further comprising a forced acceleration control unit for forcibly accelerating the spindle motor, wherein the gain calculation unit is configured to start the forced acceleration from the start of the forced acceleration. The period t until the speed fluctuation amount ΔW reaches the target value
A servo control device for a spindle motor for an optical disk, wherein a new feedback gain g is calculated according to t.