JPH0760577B2 - Positioning control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a positioning device for positioning a member at a target position. More specifically, information is recorded and / or reproduced by using magnetic, optical or physical means along a concentric circular or spiral information track provided on the disk-shaped medium surface. The present invention relates to a positioning control device such as a magnetic disk device or an optical disk device that enables the positioning.

2. Description of the Related Art In order to record / reproduce information along an information track on a disk surface, a data transducer for reading / writing data is always held on a target information track in accordance with rotation of the disk, that is, track following. Position control must be performed.

Next, the position detecting method on the disk surface of the data transducer for tracking the track will be described. Floppy disk drive (FDD) and hard disk drive (HD
In magnetic disk devices such as D), called the sector servo system, the disk is equally divided into areas called fan-shaped sectors, and identification data called sector servo signals are magnetically recorded on a part of the information track divided for each sector. In some cases, the signal is read for each sector by a data transducer according to the rotation of the disk, and the relative position error with respect to the information track is detected and recognized in a sampling manner to perform track following. Further, in the optical disk device, in the case of the sampling servo system, when the information tracks on the disk surface are provided with track-following pits at regular intervals and are optically detected and used as the identification data in the same manner as above. In the continuous servo system, there is a case in which a spiral or concentric guide groove is provided on the disk surface and the groove is optically detected to follow the track.

Furthermore, the position fluctuation of the information track that occurs during track following is described. In the optical disk device, the information track changes in position (eccentricity) as the disk rotates due to factors such as displacement of the center of rotation when the disk medium is replaced and deviation of the rotation width of the spindle motor that rotates the disk. The amplitude of this eccentricity may be from several tens of μm to one hundred and several tens of μm, and the width of the track to be followed (about 1.
6 μm), which is extremely large, hinders the realization of track following. In the FDD of the magnetic disk devices, in addition to the eccentricity similar to that of the optical disk device, another type of eccentricity occurs due to the base film of the disk medium expanding or contracting and being distorted by the influence of heat. The eccentricity of each eccentricity is smaller than that of the optical disk device, and is about several tens to several tens of μm at the most. However, this is an obstacle for increasing the recording capacity by increasing the track density.

In order to suppress the position fluctuation of the information track due to such eccentricity and realize the track following with sufficient accuracy, various contrivances have been made in the positioning control system. less than,
One of the conventional positioning control devices will be described with reference to the drawings.

FIG. 7 is a block diagram of a conventional positioning control device.
In the figure, reference numeral 108 denotes an actuator, which allows the data transducer 103 to freely move on the disk 101. The displacement of the selected information track 102 of the disk 101 immediately below the data transducer 103, that is, the amount of eccentricity of the information track, is r, and the displacement of the data transducer 103 is y.
Express with. Reference numeral 104 is a position error detector for detecting a relative position error e = ry between the information track 102 and the data transducer 103, and 106 is at least one of stabilization compensation and deviation compensation of a position control loop including an analog filter. A compensating circuit for performing the above, and a driving circuit 107 for applying a current to the actuator 108. The data transducer 103 is connected to the actuator 108 by a supporting member shown by a dotted line 109. The output signal of the compensation circuit 106 is branched and input to the simulation circuit 113 that simulates the transfer characteristic of the combined system of the drive circuit 107 and the actuator 108.

FIG. 8 is a signal transmission block diagram of a track following servo system of a conventional positioning control device, which mainly shows the flow of servo signals in FIG. This track-following servo system uses the data transducer 1 for the eccentricity r of the information track 102 which is generated as the disk 101 rotates.
Position error signal e to track 03 within a certain error range
= Ry must be operated to be as small as possible. However, the servo signal is the compensation circuit 106, the drive circuit 1
A delay occurs in the process of passing through 07, the actuator 108, the support member 109, and the position error detector 104. Therefore, a certain value of error remains between the center position of the data transducer 103 and the center position of the information track 102, and a positioning error remains.

Now, in FIGS. 7 and 8, the simulation circuit 113 is
The estimated amount ya of the displacement y of the data transducer 103 is output. On the other hand, the position error signal e and the output ya of the simulation circuit 113 are input to the adder 110, and ra = e + ya, that is, the information track 102.
The estimated amount of displacement (estimated amount of eccentricity) immediately below the data transducer 103 of is output. However, due to the above reason, the displacement y includes a certain delay with respect to the eccentricity amount r, and the estimated amount ya also includes the same delay. Therefore,
If the eccentricity estimation amount ra is obtained, then a virtual eccentricity amount rd obtained by advancing the phase by a certain time L is obtained, and if a servo system is configured to cause the data transducer 103 to follow this rd, the displacement y will be Will follow r well. In reality, it is impossible to advance the time, and therefore the periodicity of the eccentricity is used, and this is performed using the delay device 111 as follows. That is, if the estimated eccentricity ra is composed of harmonics having the fundamental frequency of the disk rotation frequency (1 / T) as with the eccentricity r, the output rd of the delay unit 111
Is rd = ra · e ^- multiplying the ^{(TL) S = ra · e} LS. That is, an eccentricity estimation amount with an advanced L time phase compared to ra can be obtained. By obtaining the difference between the estimated amount eccentricity rd and the estimated amount ya of displacement of the data transducer by the adder 112, the estimated amount ea = rd− of the position error signal without delay is obtained.
By obtaining ya and adding it to the drive circuit 107 via the compensation circuit 106 to drive the actuator 108, the tracking delay of the data transducer 103 can be eliminated. [For example, JP-A-53-106105] Problems to be Solved by the Invention However, the above-described configuration has problems as described below. First, due to the tolerances of the actuator 108, the data transducer 103, the support member 109, the drive circuit 107, changes over time, changes in temperature, and the like, the transfer characteristics of these combined systems vary. This is a simulated circuit if turned over
Unless the circuit constant of 113 is adjusted accordingly, an error is included in the transfer characteristic of the simulation circuit, and an error occurs in the estimated amount ya of displacement of the data transducer. The estimated amount ya further includes an error due to variation in the circuit constant of the simulation circuit 113 and temperature drift. Next, in the case of the track following servo system as shown in the conventional example, the estimated amount rd of the eccentricity and the estimated amount ya of the displacement of the data transducer 103 are not directly applied to the servo using the position error signal e.
Since the servo system is operated based on the estimated amount ea of the position error signal obtained from, there is no effect of suppressing the disturbance when the actuator 108 is disturbed.

In view of the above problems, the present invention provides not only high-accuracy track following performance, but also an error in the estimated amount of displacement of the data transducer can be made sufficiently small, and an effect of suppressing it when disturbance is applied to the actuator A positioning control device capable of having

Means for Solving the Problems In order to solve the above problems, a positioning control device of the present invention is a position error detector for detecting a relative position error between an information track to be followed by a target member, that is, a disk and a moving member, that is, a data transducer. A position detector for detecting the absolute position of the moving member, and a compensation means for performing at least one of stabilization compensation and deviation compensation of the position control loop based on the position error signal output from the position error detector. A first adder for adding the position error signal output by the position error detector and the position signal output by the position detector, and a delay for delaying the signal based on the output of the first adder Means, a second adder for adding a signal based on the output of the first adder and a signal based on the output of the delay means, and an output based on the output of the compensating means. And a signal based on the output of the second adder, and an actuator for freely moving the moving member by the signal based on the output of the third adder And a drive circuit for applying a current to the means.

Action The present invention, by adopting the above-described configuration, not only provides highly accurate track following performance, but also can sufficiently reduce the error in the estimated amount of displacement of the data transducer, and when disturbance is applied to the actuator. It is possible to provide a positioning control device capable of suppressing the effect.

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

FIG. 1 is a block diagram of a positioning control device according to an embodiment of the present invention. In the figure, reference numeral 8 denotes an actuator which allows the data transducer 3 to freely move on the disk 1. The displacement of the selected information track 2 of the disk 1 immediately below the data transducer 3, that is, the amount of eccentricity of the information track is represented by r, and the displacement of the data transducer 3 is represented by y. 4 is a relative position error e = r−y between the information track 2 and the data transducer 3.
Is a position detector that detects the absolute position of the data transducer 3, and is mechanically coupled to the movable portion of the actuator 8 by the transmission member 10. 6 is a compensation circuit for stabilizing and / or deviation compensating the position control loop consisting of an analog filter, and 11 is an adder for adding the output signal of the position error detector 4 and the output signal of the position detector 5. , 13 is a delay device that delays the output signal of the adder 11, 14 is an adder that adds the output signal of the adder 11 and the output signal of the delay device 13, 12 is the output signal of the compensation circuit 6 and the adder 14 An adder 7 for adding output signals is a drive circuit for receiving an output signal from the adder 12 and applying a current to the actuator 8. The data transducer 3 is connected to the actuator 8 by a supporting member shown by a dotted line 9.

FIG. 2 is a signal transmission block diagram of the track following servo system of the positioning control apparatus in one embodiment of the present invention, and mainly shows the flow of the servo signal in FIG.

The operation of the positioning control device of the present invention configured as described above will be described.

The track-following servo system shown in FIGS. 1 and 2 positions the data transducer 3 within a certain error range in order to follow the fluctuation of the absolute position of the information track 2 caused by the rotation of the disk 1, that is, the eccentricity r. Error signal e = r
-Y must be operated to be as small as possible. However, the servo signal is delayed in the process of passing through the drive circuit 7 and the actuator 8. That is, in the relatively low frequency region near the frequency of the eccentricity of the information track 2, the synthetic transfer characteristic from the drive circuit 7 to the actuator 8 is accompanied by some phase delay. Further, when the servo system is a discrete time system, a phase delay due to the sample holder is added to this. Therefore, a certain value of error is maintained between the center position of the data transducer 3 and the center position of the information track 2, and a positioning error remains.

In FIGS. 1 and 2, the position detector 5 outputs an estimated amount ya of the absolute position y of the data transducer 3.
The ya is called an estimator because the position detector 5 does not directly measure the displacement of the data transducer 3, but rather the transmission member.
By estimating the displacement of the data transducer 3 by measuring the displacement of the movable part of the actuator 8 via 10. Next, the position error signal e and the estimated amount ya are added by the adder.
It is input to 11, and ra = e + ya, that is, the estimated amount of displacement (estimated amount of eccentricity) of the information track 2 immediately below the data transducer 3 is output. However, due to the above-mentioned reason, the displacement includes a delay with respect to the variation (eccentricity amount) r of the position of the information track 2, and the estimated amount ya also includes a similar delay.
In addition, ya includes an electrical delay when the position detector 5 estimates. Therefore, the eccentricity estimation amount ra also includes the delay caused by these. In order to remove this delay, the phase of the eccentricity estimation amount ra is advanced for a certain period of time M, the signal amplitude is adjusted by an amplifier or attenuator (not shown), and then added to the original signal ra by the adder 14. Thus, an eccentricity estimation amount rc that has a phase approximately the same as the original eccentricity amount or rather a slightly advanced phase is obtained. This is added to the output signal of the compensation circuit 6 by the adder 12 and then input to the drive circuit 7,
By driving the actuator 8, the follow-up delay of the data transducer 3 can be eliminated.

Next, a method of advancing the phase of the above-described eccentricity estimation amount ra for a certain fixed time M will be described. In reality, it is impossible to advance the time, so this is performed as follows using the delay device 13 by utilizing the periodicity of the eccentricity amount. That is, the estimated eccentricity ra is the same as the eccentricity r, and the rotation frequency of the disk (1 /
Let T. ) As a fundamental wave, the output of the delay unit 13 is multiplied by ra · e ^{− (TM) S} = ra · e ^MS . That is, an eccentricity estimator having an advanced M time phase compared to ra can be obtained. By multiplying this by a coefficient and adding it to the original ra, the phase of ra can be advanced.

The operating principle of the positioning control device of the present invention will be described in more detail from another angle.

1 and 2, the eccentricity estimation amount rc is added to the adder 12
The remaining servo loop, which is obtained by removing the eccentricity estimation loop added to, is a normal track following servo system. In this normal servo system, in order to make the tracking error e = ry of the data transducer 3 to the information track 2 zero, the compensation circuit 6
It is necessary to make the gain of infinity. However, since it is impossible to make the gain infinite in reality, a slight error remains. In the present invention, the eccentricity of the information track 2 is estimated to obtain the estimated eccentricity ra, which is added to the operation amount of the normal loop and applied to the drive circuit 7 to further reduce the tracking error. However, information track 2
In the relatively low frequency region near the frequency of the eccentricity of
If the combined transfer characteristic from the drive circuit 7 to the actuator 8 is such that the phase delay is almost zero and the gain is almost 1, the phase advance by the delay device 13 as shown in FIGS. 1 and 2 is not performed. In both cases, it is possible to set y = ra by multiplying the eccentricity estimation amount ra by an appropriate gain and adding it to the adder 12. Further, at this time, the estimation accuracy of the eccentricity estimation amount ra is extremely high, and when ra = r, y = r, which is e =
No other than r−y = 0, that is, the tracking error can be zero. (By the way, although the output of the compensating circuit 6 at this time becomes zero, the compensating circuit 6 does not show the loop stability, the disturbance suppression and the central position of the data transducer 3 and the information track 2 in FIGS. 1 and 2. However, as described above, the servo signal causes a delay in the process of passing through the drive circuit 7 and the actuator 8. That is, in a relatively low frequency region near the frequency of the eccentricity of the information track 2, the combined transfer characteristic from the drive circuit 7 to the actuator 8 does not necessarily have a phase delay of zero and a gain of 1, and the servo system is discrete. When configured in time system,
A phase delay due to the sample holder adds to this. Therefore, a certain value of error is maintained between the center position of the data transducer 3 and the center position of the information track 2, and a positioning error remains. Therefore, as shown in FIG. 1 and FIG. 2, it is necessary to add a value obtained by advancing the eccentricity estimation amount ra by the delay device 13 to ra to advance the phase of ra.

Next, the signal waveform of each part in the track following servo system of the positioning control device of the present invention will be shown based on a specific example.

FIG. 3 is a block diagram of a concrete track following servo system. In this case, an FDD sector servo system is assumed, and the configuration is a discrete time servo system. Z means Z of Z transform, and Z ⁻¹ means delay of one sample time. Reference numeral 20 is a sampler, 21 is an integrator for compensating the deviation of the servo system, 22 is a multiplier for adjusting the loop gain, and 24 is a sample holder. Reference numeral 13 is a delay device for delaying n sample times, which has a configuration in which n delay devices Z ^-1 of 1 sample time are connected in series. Reference numeral 23 is a multiplier for adjusting the magnitude of the output of the delay device 13. The transfer functions of the drive circuit 7 and the actuator 8 shown in FIG. 2 are second-order delay systems as a whole, and the constants p and q are values such that the cutoff frequency is 300 Hz. Disk rotation speed is 600 rpm, sector number is 34, sampling frequency is 340H
z, the displacement r of the information track 2 has an amplitude of 20 μm and a frequency of 1
It shall be given as a 0 Hz sine wave. (However, ki ＝
1, kd = 0.2, n = 26. Note that the number n of delay devices and the coefficient kd of the multipliers are determined so that the track followability near 10 Hz, which corresponds to the frequency of eccentricity, is optimum.

FIG. 4 (a) shows the signal track displacement r, the data transducer displacement y, the position error detector output e, and the respective signal waveforms when the track following servo system shown in FIG. 3 is simulated on a computer program. ~ (C)
Shown in. In the figure, 0.1 [sec] corresponds to one rotation of the disk.

For comparison, FIG. 5 shows a configuration in which the eccentricity estimation amount rc is not added to the output of the multiplier 22. Further, the waveforms of the respective parts by the simulation in this case are shown in FIGS. 6 (a) to 6 (c). However, the position error signal e in FIGS. 4 and 6 is a signal after passing through the sampler 20.

When the position error signal e is compared between FIG. 4 and FIG.
In the figure, the amplitude is about 3.5 μm, while in FIG. 4, it is about 0.15 μm, and by adopting the servo system configuration in FIG. 3, the excellent effect that the position deviation becomes about 1/23 is there.

As described above, in the positioning control device of the present invention,
The position detector 5 estimates the displacement of the data transducer 3.
Is done indirectly using. Therefore, by sufficiently increasing the mechanical accuracy of the position detector 5, the support member 9, and the transmission member 10, the error in the estimated amount ya of the displacement of the data transducer 3 can be made sufficiently small. Further, as is apparent from the block diagram of the servo system in FIG. 2, even when a disturbance is applied to the actuator 8, the normal servo loop functions of the position error detector 4, the compensation circuit 6, the drive circuit 7, and the actuator 8 are performed. It has the effect of suppressing this.

Although the track following control system of the specific configuration example of the embodiment is configured by the discrete time system, it may be configured by the continuous time system.

EFFECTS OF THE INVENTION As described above, the positioning control device of the present invention includes a position error detector that detects a relative position error between a target member, that is, an information track to be followed by a disk and a moving member, that is, a data transducer, and a moving member. A position detector for detecting the absolute position of the position error compensation means, and a compensation means for performing at least one of stabilization compensation and deviation compensation of the position control loop based on the position error signal output from the position error detector, A first adder for adding the position error signal output by the error detector and the position signal output by the position detector; delay means for delaying the signal based on the output of the first adder; A second adder for adding a signal based on the output of the first adder and a signal based on the output of the delay means; a signal based on the output of the compensating means; A current is supplied to a third adder for adding a signal based on the output of the second adder and an actuator means for freely moving the moving member by the signal based on the output of the third adder. By including the drive circuit to be added, high-precision track following performance can be obtained, and the error in the estimated amount of displacement of the data transducer can be made sufficiently small, and it is possible to reduce the error when the actuator is disturbed. Has the effect of suppressing.

[Brief description of drawings]

FIG. 1 is a block diagram of a positioning control device according to an embodiment of the present invention, and FIG. 2 is a signal transmission block diagram of a track following servo system of the positioning control device according to the embodiment of the present invention shown in FIG. FIG. 2 is a block diagram of a concrete track following servo system of the positioning control device in one embodiment of the present invention shown in FIG. 2, and FIG. 4 is a signal waveform diagram of each part by simulation on a computer in the configuration of FIG. ,
FIG. 5 is a block diagram of a normal track following servo system, FIG. 6 is a signal waveform diagram of each part by simulation on a computer in the configuration of FIG. 5, FIG. 7 is a block diagram of a positioning control device in a conventional example, FIG. 8 is a signal transmission block diagram of the track following servo system of the positioning control device in the conventional example shown in FIG. 1 ... Disk, 2 ... Information track, 3 ... Data transducer, 4 ... Position error detector, 5 ... Position detector, 6 ... Compensation circuit, 7 ... Drive circuit, 8 ... Actuator, 9 ...... Support member, 10 ...... Transmission member, 11, 12,
14 ... Adder, 13 ... Delay device.

Claims (1)

[Claims] 1. A positioning control device for positioning a moving member with respect to a target member that repeats substantially equal position fluctuations at a fixed cycle, and a position error for detecting a relative position error between the target positioning position of the target member and the moving member. A detector, a position detector that detects the absolute position of the moving member, and at least one of stabilization compensation and deviation compensation of the position control loop based on the position error signal output from the position error detector. Compensating means, a first adder for adding the position error signal output by the position error detector and the position signal output by the position detector, and a signal based on the output of the first adder. A delay means for delaying by a difference between a cycle of the position variation of the target member and a target advance time, a signal based on the output of the first adder, and an output of the delay means A second adder for adding the signals and based on the signal and the second based on the output of said compensating means
A current is applied to a third adder for adding a signal based on the output of the adder and an actuator means for freely moving the moving member by the signal based on the output of the third adder. A drive circuit, and the target advance time is at least the delay time of the actuator means and the delay time of the actuator means more than the signal based on the output of the second adder. A positioning control device, wherein the position control loop is set so as to advance by a delay time of a position control loop including a delay time of a driving means.