JPH0341678A - Positioning controller for disk device - Google Patents

Abstract

PURPOSE:To attain the processing even when a transient external disturbance is applied to the controller at a low frequency band by moving freely a data transducer in response to an object position command signal being the sum of a compensation signal outputted from a low frequency compensation means and a delay signal retarding only a period of position fluctuation. CONSTITUTION:The result of sum between a compensation signal outputted from a low frequency compensation means including a digital filter means having a low frequency high gain characteristic suppressing the low frequency component of a position error to improve the tracking performance of a data transducer and a delay signal outputted from a time delay means 9 is outputted to a driving means 4 as an object position command signal (u). Thus, even when a sudden external disturbance is applied to the data transducer 7, the position error due to the external disturbance is stored in the delay means 9. Thus, even when the detection sensitivity of the position error is fluctuated due to the dispersion of a disk medium or a head or temperature change or a secular change and the constant of the actuator being a controlled object is fluctuated due to the same cause, the stability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positioning control device for a magnetic/optical disk device capable of recording and reproducing data on a disk medium. More specifically, the present invention relates to a positioning control device for a disk device that is capable of embedding servo information in a predetermined area of a data surface and positioning a head on a selected information track of a disk medium with high precision in accordance with the servo information.

BACKGROUND OF THE INVENTION As the density and capacity of disk drives have increased, the spacing (pitch) between information tracks has become narrower, and the amount of track waviness due to disk eccentricity has become relatively large and cannot be ignored. Therefore, a floppy disk device (
Tracking control called a sector servo method is performed in magnetic disk devices such as FDDs and hard disk drives (HDDs). This sector servo method involves embedding a servo signal at the beginning or end of each sector of the information track and reading it with a magnetic head to detect and recognize the relative positional error between the magnetic head and the information track in a sampling manner. This is used to perform tracking control.

However, it is not possible to obtain sufficient tracking performance by simply feeding back the detected position error as is, so in recent years, better methods have come into use. This method utilizes the fact that the undulation of the information track due to disk eccentricity is repetitive (periodic) with respect to the rotation of the disk, and belongs to a method called iterative learning control.

FIG. 1O is a block diagram of a conventional positioning control device for a disk device, which has a discrete repeating control system. In Fig. 10, r is the position of the information track (target value with eccentricity and waviness), y is the current position of the data transducer (magnetic head), e is the position error signal obtained at each sampling period, and U is the drive 1 indicates a target position command signal to means 4; l is a position error recognition means which detects and recognizes a position error between the position r of the information track and the current position y of the data transducer from servo information recorded in advance on the information track; Outputs error signal e. 101 is an adder, and the output of the adder 101 is inputted as a target position command signal U to the driving means 4 and the time delay means 102. The time delay means 102 delays the manually input target position command signal U for a certain period of time.

The delayed signal is added to the position error signal e in an adder 101. That is, the adder 101 and the time delay means 102 constitute a repetition filter 103. The driving means 4 includes an actuator 6 that freely moves the data transducer 7 and a driving circuit 5 that supplies current to the actuator 6.
and a phase compensator 104 that stabilizes the control system.

FIG. 11 shows the configuration of a discrete repeating filter that can be used in the conventional positioning control device for a disk drive shown in FIG. In FIG. 11, 21 is a delay device such as a shift register, which shifts data by T time. P delay devices are connected in series and constitute time delay means 102. 111 is data human power point,
112 is a data output point. p is the number of sectors (the number of samples per disk rotation), and pXT is equal to the period of one disk rotation. When such a discrete repeating filter is included in the loop of the control system, each harmonic component whose fundamental frequency is the eccentricity of the information track can be suppressed.

FIG. 12 is a Bode diagram showing the frequency characteristics of the discrete repetition filter shown in FIG. 11. It can be seen that the gains of the fundamental frequency component and its harmonic components are high. In other words, if the eccentricity of the information track is periodic,
The delayed output of the time delay means 102 serves as a target position command signal for causing the data transducer 7 to almost accurately follow the information track.
The relative position error between the information tracks can be extremely small.

(For example, see Japanese Patent Publication No. 60-57085.) Problems to be Solved by the Invention In conventional positioning control devices for disk drives, position errors are detected due to variations in disk media and data transducers, temperature changes, and changes over time. As can be understood from FIG. 12, when the sensitivity fluctuates or the constants of the driving means, such as the actuator, change, there is a problem that the gain and phase change greatly in the high frequency region, making it easy to become unstable. Therefore, although the conventional positioning control device for a disk drive can be stabilized in principle, it is not practical.

Furthermore, conventional positioning control devices for disk drives are insufficiently responsive to suppressing positional errors between data transducers and information tracks. The M-defective iterative filter in the conventional example uses real-time iterative learning to obtain a target value (
The data transducer can be made to follow the information track (position of the information track) with little positional error,
For this purpose, it has a cyclic structure as shown in FIG. Therefore, when a transient position error occurs due to disturbance in a relatively low frequency range, it cannot be suppressed immediately. Also, sudden disturbances (vibration,
When a shock, etc.) is applied, the position error due to the disturbance is accumulated in the delay means 102, so that the influence of the disturbance remains for several cycles thereafter, and as a result, a certain learning period is required, resulting in a lack of quick response. There are challenges.

The present invention makes it possible to construct an extremely stable control system even when the detection sensitivity of position errors fluctuates due to variations in disk media and data transducers, temperature changes, and changes over time, and even when the actuator constants fluctuate. It is an object of the present invention to provide a positioning device for a disk device that has excellent responsiveness even when transient disturbances in the frequency domain are applied.

Means for Solving the Problems In order to achieve the above object, the positioning control device for a disk drive according to the present invention includes a data transducer that follows a target information track on a disk medium, and a data transducer that responds to a target position command signal. a driving means for freely moving the data transducer; a position detecting means for detecting the current position of the driving means or the data transducer and outputting a current position signal; and a positional error between the information track and the data transducer that is recorded in advance on the information track. position error recognition means that detects and recognizes the servo signal and outputs a position error signal; a time delay means that receives the current position signal and outputs a delayed signal delayed by the period of position fluctuation; and a position error signal that is input. low-frequency compensation means having a low-frequency high gain characteristic that suppresses the low-frequency components of the position error; and addition means that adds the compensation signal output from the low-frequency compensation means and the delayed signal to output a target position command signal. ′.

Effect By adopting the above-described configuration, the present invention limits the repeatability to a predetermined frequency, and lowers the repeatability to the frequencies higher than that in order to stabilize the frequency. As a result, rapid changes in the gain characteristics and phase characteristics in the high frequency region are reduced, making it easier to stabilize them. Therefore, for example, even if the position error detection sensitivity fluctuates due to variations in the disk medium or head, temperature changes, or changes over time, or if the constants of the drive means, such as the actuator, fluctuate, it is likely to become unstable as in the conventional example. Therefore, the stability of the control system can be easily ensured.

In general, the frequency components of eccentricity and waviness contained in the information track of a disk device have a property that the harmonic components are very small. The characteristics are most suitable for disk devices.

In addition, by adopting a configuration that combines time delay means and low frequency compensation means, even if a transient position error occurs due to disturbance in a relatively low frequency range, the data transducer can be quickly moved to the target information track. can be made to follow.

Therefore, a high-speed, highly accurate positioning control device for a disk device can be provided.

In addition, by inputting the result of addition of the current position signal indicating the position of the data transducer and the position error signal indicating the relative position between the data transducer and the information track to the time delay means, data can be Even if the transducer deviates from the target information track and the position error signal changes, the current position signal also changes with the opposite polarity at the same time, so the addition result does not change. Therefore, even if a sudden disturbance is applied to the data transducer, the position error due to the disturbance will not be accumulated in the delay means and the influence of the disturbance will not remain for several cycles thereafter.

Embodiment Hereinafter, a positioning control device for a disk drive according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a positioning control device for a disk device in an embodiment of the present invention. In FIG. 1, r indicates the position of the selected information track (target value of the information track position with eccentricity or undulation), and y indicates the current position of the data transducer 7 (so-called head position). e indicates both position error signals obtained at each sampling period T. U is a target position command signal, which is input to the driving means 4. The driving means 4 includes an actuator 6 for freely moving the data transducer 7 and a driving circuit 5 for supplying current to the actuator 6. Note that the drive circuit 5 is 1ii1
Contains a holder for serializing loss data. l
is a position error recognition means, which is mainly constituted by an electronic circuit to obtain the position error signal e at each sampling period T.
It includes an electronic circuit that generates a trigger signal to start each calculation. 8 is a position detecting means for detecting the current position of the data transducer 7 and outputting a current position signal. 9
is particularly closely related to the present invention, and is a time delay means for the purpose of improving the tracking performance of the data transducer against eccentricity and waviness of the information track of the disk, and receives the current position signal y output from the position detection means 8. . 2, like 9, is particularly related to the present invention, and is a low-frequency high gain that suppresses the low-frequency component of position error for the purpose of improving the tracking performance of the data transducer against eccentricity and waviness of the information track of the disk. A low frequency compensation means including a digital filter means having characteristics outputs a compensation signal. 3 is an addition means that adds the compensation signal output from the low frequency compensation means 2 and the delayed signal output from the time delay means 9. Then, the addition result is outputted to the driving means 4 as a target position command signal U. FIG. 2 is a block diagram showing the configuration of the time delay means 9. The time delay means 9 has m stages (m is an integer) of delay devices 21 such as data shift registers whose transfer function is described by 1 / z connected in series, and also has a transfer function described by 1 / z.
Digital filter means (hereinafter simply referred to as
It has a configuration in which a high-frequency attenuator Q(z-') 22 is connected in series. Here, 2 is the z-transform. Moreover, m+q≦p here. This p is the number of servo signal samples embedded in advance in the information track during one rotation of the disk, and in the case of the sector servo system, it is usually a positive integer equal to the number of sectors. Further, the delay time of the delay device 21 is equal to the sampling period T, and therefore pXT is normally equal to one rotation period of the disk.

FIG. 3 shows a high-frequency attenuator Q (z
-') 22 is a block diagram of a specific example. In FIG. 3, 31 is a delay device such as a data shift register, 32 is a data input point, 33 is a data output point, and 34.35 is a gain constant of 1a and a, respectively.

a is in the range O<a<1. The transfer function (numerator/denominator polynomial regarding 1/z) relating to human output in the block diagram shown in FIG. 3 is expressed by the following equation (1).

This is a first-order low-pass filter (LPF) and is one of the simplest implementations.

In the block diagram shown in FIG. 3, a delay device 1 /
Since one z is included, the input/output transfer function is 1 / z
Among the numerator and denominator polynomials for , the numerator polynomial is (1-
a) ・z −1 and linear (
It can be seen that q=1). FIG. 4 shows the frequency characteristics of the transfer function expressed by equation (1).

However, a=0.6. ro in the figure is the fundamental frequency component of the target value r of the information track position with eccentricity and waviness.

The operation of the positioning control device for a disk drive according to the present invention will be described in detail based on an embodiment configured as described above.

The time delay means 9 according to the present invention shown in FIG. 2 basically has a plurality of delay devices 21 such as shift registers connected in series, and is further connected to a high-frequency attenuator Q (see FIG. 3). Z
-') 22 are connected in series. If the number of stages of the delay device 21 is m and the number of stages of the delay device in the forward loop between the high-frequency attenuators 22 and the turnout is 9, normally, m
+q≦p.

Since q=l in the above embodiment, the number of stages of the delay device 21 satisfies m≦p−1. The general expression of the human output characteristic (transmission from the input of the adding means 3 to the current position y) when using the time delay means 9 according to the present invention configured as described above is expressed by equation (2).

However, for simplicity, it is assumed that the number of transmissions from the drive means 4 to the current position detection means 8 is 1.

FIG. 5 is a Bode diagram showing the frequency characteristics of the transfer function from the human power of the adding means 3 to the current position y in one embodiment of the present invention shown in FIG. In particular, in FIG.
), in (2), p-34, m=33, q=1.
The case where a=0.6 is shown. Therefore, m+q=p. [ in the figure. is the fundamental frequency component of the target value r of the information track position with eccentricity and waviness. This occurs, for example, due to eccentricity of the disk. The characteristics of the transfer function of this discrete repeating filter are different from the conventional example shown in Fig. 12, in that the peak gain of relatively low frequency components including the fundamental frequency component is high, but the higher the frequency, the lower the peak gain. It has become.

This is a high-frequency attenuator Q that aims to limit the repeatability of learning up to a predetermined frequency and lower the learningability of frequencies above that to ensure system stability.
Due to the action of (Z-'). As a result, the tracking performance of the control system for the high frequency components of r deteriorates, but as can be seen from the frequency characteristics in Figure 5, the change in the gain characteristics of the high frequency components decreases, making it easier to stabilize. .

In general, if you examine the frequency components of eccentricity and waviness included in r, you will find that the high frequency components are usually quite small. Therefore, this discrete repeating filter can be used as a deviation compensation means for the positioning control device of a disk drive. It can be said that it has optimal characteristics. Note that in Fig. 5, for simplicity, the transmission from the drive means 4 to the current position detection means 8 is assumed to be l, but the frequency characteristics of the drive means are generally delayed and can be considered as a type of low-pass filter (LPF). This driving means itself has the function of the above-mentioned high-frequency attenuator, which is very convenient for ensuring the stability of the system.

As a result of the above, it becomes possible to stabilize easily and with sufficient margin. However, as can be seen from the Bode diagram in Figure 5, the peak frequency is the fundamental frequency component of the eccentricity of the information disk. and a tuning deviation from the frequency of its harmonic components. This phenomenon tends to occur when the number of p is small, or when the number of a is large (close to l) and the cutoff frequency of the high-frequency attenuator Q (z-') is low. This is the high-frequency attenuator Q (
This is because the data delay time at Z-') is slightly longer than that of the q-stage delay device alone (9×T time) connected in series thereto. This is because a digital filter with high frequency attenuation characteristics is a phase lag filter. As a result, the delay time for one round of the discrete repeating filter in such a case becomes slightly longer than pXT=L. For that reason, the fifth
In the illustrated example, the peak frequency deviates slightly lower than the frequency of the fundamental frequency component and its harmonic components, such as the eccentricity of the information disc. Care must be taken because tracking performance will be impaired if the deviation becomes large. Therefore, it is necessary to select the number m of stages of delay devices 21 connected in series, taking into consideration the data delay time of the high-frequency attenuator Q (z-').

FIG. 6 is a boat diagram showing still another frequency characteristic of the transfer function from the human power of the adding means 3 to the current position y in one embodiment of the present invention shown in FIG. 1, similar to FIG. 5.

In Fig. 6, we particularly show the case of formula (11, (2)%).Therefore, m+q<p.Here too, the high-frequency attenuator Q(z-1) is the first-order attenuator shown in Fig. 3. A low-pass filter was used, p-34, m-32, q=1,
a=0', 6. In this example, m is one smaller and m+
This example differs from the example shown in FIG. 5 in that q<P. By doing so, it is possible to make the delay time of one round of the discrete repeating filter close to one rotation period of the disk. According to the Hoard diagram in FIG. 6, it is clear that the fundamental frequency component f.

and its harmonic peaks (tuning deviation)
It can be seen that there has been an improvement. In this way, when the cutoff frequency of the high-frequency attenuator is relatively low, it is practical to set m+q<P.

FIG. 7 is a block diagram of a specific embodiment of the digital filter means having low frequency high gain characteristics of the low frequency compensating means 2 of the positioning control device for a disk drive of the present invention shown in FIG. In FIG. 7, 71 is a delay device such as a data shift register, 72 is a data input point, 73 is a data output point, and 74 is a gain constant. This gain constant is o<b≦1, and both are first-order low-pass compensation filters or integral filters. For example, in FIG. 7, if b=1, the input/output transfer function becomes an integrator as shown in equation (3). This increases the number of models for the entire system.

FIG. 8 is a Bode diagram showing the frequency characteristics when b=1 is selected for the transfer function of equation (3). As can be understood from the figure, the gain in the low frequency range is high, and by using this gain, the position in the relatively low frequency range, where the defeative repetition filter alone of the deviation compensation means described above tends to be insufficient, can be achieved. This makes it possible to suppress errors or improve their responsiveness, and even when transient position errors occur due to disturbances in a relatively low frequency range, the data transducer can quickly follow the information and track. There is.

FIG. 9 is a block diagram showing the configuration of another embodiment of the positioning control device for a disk drive according to the present invention.

Components having the same functions as those in FIG. 1 are given the same numbers and redundant explanations will be omitted. In the embodiment shown in FIG. 1, only the output of the current position detecting means 8 is input to the time delay means 9 manually. On the other hand, in the embodiment shown in FIG. 9, the addition result of the addition means 10 is input to the time delay means 9. The adding means 10 receives the current position signal y output from the current position detecting means 8 and the position error L2. A position error signal e output from the recognition means 1 is input. There is a relationship expressed by equation (4) between the information track position r, the current position signal y of the transducer, and the position error signal e.

e=ry ・・・・・・・・・・・・・・・
(4) In other words, the adding means 10 calculates the current position signal y
Adding the position error signal e to the target information track position r (r=y+e) is equivalent to calculating the target information track position r (r=y+e).
will be done manually. Therefore, even if the data transducer 7 deviates from the target information track due to some reason (vibration, shock, etc.), the signal manually input to the time delay means 9 will not change (even if the position error signal e changes, the current position signal y also changes with opposite polarity, so there is no change in the target information track position r, which is the addition result). Therefore, even if a sudden disturbance is applied to the data transducer 7, the position error due to the disturbance will not be accumulated in the delay means 9 and the influence of the disturbance will not remain for several cycles thereafter.

Note that the arrangement of the m delay devices and high-frequency attenuators constituting the time delay means according to the present invention is not limited to the method shown in FIGS. 1 and 9. The order does not matter as long as they are arranged in series. For example, the high frequency attenuator may be at the beginning,
It can be somewhere in between.

In the above explanation, the block diagram of each transfer function has been explained in terms of hardware, but this is only for convenience, and it is most realistic to implement it by software. That is, for example, the time delay means 9 according to the present invention shown in FIG. 1 and each delay device 21 of the low frequency compensation means 2 can be allocated to a register or memory of a microprocessor, and also the time delay means 9 according to the present invention shown in FIG. It goes without saying that a series of operations can also be programmed and executed sequentially.

Effects of the Invention Since the present invention is configured as described above, it produces the effects described below.

In the positioning control device for a disk drive according to the present invention, the repeatability is limited to a predetermined frequency as a characteristic of the discrete repeating filter of the time delay means, and the repeatability is reduced for frequencies higher than that for stabilization. As a result, rapid changes in the gain characteristics and phase characteristics of high frequency components are reduced, making it easier to stabilize them. Therefore, even if the detection sensitivity of position errors fluctuates due to variations in disk media or heads, temperature changes, or changes over time, or if the constants of the controlled object, such as an actuator, fluctuate for the same reason, it will become unstable like in the conventional example. It has the excellent effect of being highly stable without having the disadvantage of being prone to. Furthermore, when examining the frequency components of eccentricity and waviness contained in the division track of a disk device, it is found that the harmonic components of high frequencies gradually decrease. It has excellent characteristics that make it ideal for disk devices.

Furthermore, the positioning control device for a disk device of the present invention includes:
By using a configuration that combines iterative learning and low-frequency compensation means, the transducer can quickly and responsively follow the data track even when transient position errors occur due to disturbances in a relatively low frequency range. It also has the excellent effect of being able to

In addition, by inputting the summation result of the current position signal indicating the position of the data transducer and the position error signal indicating the relative position of the data transducer and the information track to the time delay means, it is possible to input the result of addition of the current position signal indicating the position of the data transducer and the position error signal indicating the relative position of the data transducer and the information track. It also has the excellent effect that even if a disturbance is applied to the data transducer, the position error due to the disturbance will not be accumulated in the delay means and the influence of the disturbance will not remain for several cycles thereafter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the positioning control device for a disk drive according to the present invention, FIG. 2 is a block diagram showing the configuration of the time delay means shown in FIG. 1, and FIG. 3 is a block diagram showing the configuration of the time delay means shown in FIG. FIG. 4 is a block diagram showing a configuration example of a high-frequency attenuator constituting the time delay means in FIG. 4, a boat diagram showing frequency characteristics in the configuration example of the high-frequency attenuator shown in FIG. The figure is a Bode diagram showing the frequency characteristics of an embodiment of the positioning control device for a disk drive according to the present invention, FIG. 7 is a block diagram showing an example of the configuration of the low frequency compensating means according to the present invention, and FIG. 9 is a block diagram showing the configuration of another embodiment of the positioning control device for a disk drive of the present invention, and FIG. 1O is a conventional example. Block diagram showing the configuration of the positioning control device of the disk device, No. 11
The figure is a block diagram showing the configuration of a discrete repetition filter that can be used in a conventional positioning control device for a disk device, and FIG. 12 is a Bode diagram showing the frequency characteristics of the conventional positioning control device for a disk device. . l...Position error recognition means, 2...Low frequency compensation means, 3...Addition means, 4...Driving means, 7......・Data transducer, 8・
... Current position detection means, 9 ... Time delay means.

Claims (6)

[Claims] (1) A data transducer to follow a target information track on a disk medium, a drive means for freely moving the data transducer in response to a target position command signal, and a drive means for moving the data transducer freely according to a target position command signal, and a drive means for moving the data transducer at the current position of the drive means or the data transducer. a current position detection means for detecting and outputting a current position signal; and a position error for detecting and recognizing a position error between the information track and the data transducer from servo information recorded in advance on the information track and outputting a position error signal. recognition means; time delay means for receiving the current position signal and outputting a delayed signal delayed by a period of position fluctuation; low-frequency compensating means for receiving the position error signal and having low-frequency high gain characteristics; A positioning control device for a disk drive, comprising: an addition means for adding the compensation signal outputted by the low-frequency compensation means and the delay signal to output the target position command signal. (2) The position error recognition means is configured to discretely detect and recognize the position error between the information track and the data transducer using p pieces of servo information (p is an integer) per revolution recorded in advance on the information track. The positioning control device for a disk device according to claim 1, characterized in that: (3) The time delay means includes m (m is an integer) time delay means whose transfer function is described by 1/z (z is z of z transformation), and m (m is an integer) time delay means whose transfer function is described by 1/z with respect to 1/z (q 2. The positioning control device for a disk drive according to claim 1, further comprising a digital filter means having a high-frequency attenuation characteristic including a numerator polynomial (an integer satisfying m+q≦p). (4) A data transducer to follow a target information track on a disk medium, a drive means for freely moving the data transducer in response to a target position command signal, and a drive means for moving the data transducer freely in response to a target position command signal, and a drive means for moving the data transducer according to a target position command signal; position detection means for detecting and outputting a current position signal; and position error recognition for detecting and recognizing a position error between the information track and the data transducer from servo information recorded in advance on the information track and outputting a position error signal. means, time delay means for receiving the sum of the current position signal and the position error signal and outputting a delayed signal delayed by the period of position fluctuation; and for receiving the position error signal and having low-frequency high gain characteristics. a low-frequency compensation means; and an addition means for adding the compensation signal outputted by the low-frequency compensation means and the delayed signal to output the target position command signal. positioning control device. (5) The position error recognition means is configured to discretely detect and recognize the position error between the information track and the data transducer using p pieces of servo information (p is an integer) per revolution recorded in advance on the information track. A positioning control device for a disk device according to claim 4, characterized in that: (6) The time delay means includes m (m is an integer) time delay means whose transfer function is described by 1/z (z is z of z transformation), and m (m is an integer) time delay means whose transfer function is described by 1/z with respect to 1/z (q 5. The positioning control device for a disk drive according to claim 4, further comprising a digital filter means having a high-frequency attenuation characteristic including a numerator polynomial (an integer satisfying m+q≦p).