JPH0769743B2 - Positioning control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning control device for positioning a member at a target position where position fluctuations are repeated at regular intervals. More specifically, information is recorded and / or reproduced by using magnetic, optical, or physical means along a concentric or spiral information track provided on the surface of a disk-shaped medium. 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 an optical disk device, due to factors such as displacement of the center of rotation when the disk medium is replaced and wobbling of the rotation axis of the spindle motor that rotates the disk, the information track moves in a fixed cycle with eccentricity, that is, eccentricity. To do. The amplitude of this eccentricity may be from several tens of μm to one hundred and several tens of μm, which is extremely large with respect to the width of the track to be followed (about 1.6 μm), which is an obstacle to realizing 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 10 to several tens of μm at the most,
This is an obstacle when trying to increase the recording capacity by increasing the track density.

In order to suppress the position variation of the information track due to such eccentricity and realize the track following with sufficient accuracy, the positioning control system has been variously devised conventionally. less than,
One of the conventional positioning control devices will be described with reference to the drawings.

FIG. 6 is a block diagram of a conventional positioning control device,
It is generally called a track following servo system. In the figure, 108 is an actuator, 103 is a data transducer of 101
It can be freely moved on the disc. Disc 10
1, the displacement of the selected information track 102 immediately below the data transducer 103, that is, the eccentricity of the information track is r,
The displacement of the data transducer 103 is represented by y. 104
Is a position error detector that detects a relative position error e = ry between the information track 102 and the data transducer 103, and 105 is a position detector that detects the absolute position of the data transducer 103. And the transmission member 110 are mechanically coupled to each other. 111 is an addition means for adding the output signal of the position error detector 104 and the output signal of the position detector 105, 112 is a delay means for delaying the output signal of the addition means 111 by a certain time L, and 113 is an output signal of the delay means 112. Adding means for subtracting the output signal of the position detector 105 from 1
Reference numeral 06 is a compensating means for performing at least one of stabilization compensation and deviation compensation of a position control loop composed of an analog filter, and 107 is a drive circuit which receives an output signal of the compensating means 106 and applies a current to the actuator 108. . The data transducer 103 is coupled to the actuator 108 by a support member 109 shown by a dotted line.

The operation principle of the conventional positioning control device configured as described above will be described.

The positioning control device shown in FIG. 6 minimizes the position error signal e = ry to make the data transducer 103 follow the eccentricity r of the information track 102 generated by the rotation of the disk 101 within a certain error range. Have to work like you do. However, the servo signal does not follow the center position of the information track 102 to a certain extent or more because the center position of the data transducer 103 exceeds a certain degree because a phase delay occurs in the process of passing through the compensating means 106, the drive circuit 107, and the actuator 108. The amplitude of e may not be less than a certain magnitude.

In FIG. 6, the position detector 105 outputs the estimated amount ya of the displacement y of the data transducer 103. The ya is called the estimator because the position detector 105 is the data transducer 1
By estimating the displacement of 03 by measuring the displacement of the movable part of the actuator 108 via the transmission member 110, rather than directly measuring it. On the other hand, the position error signal e and the output ya of the position detector 105 are input to the adding means 111, where ra =
e + ya, that is, the estimated amount of displacement (estimated amount of eccentricity) immediately below the data transducer 103 of the information track 102 is output. However, the displacement y is delayed in phase with respect to the eccentricity amount r for the reason described above, and the estimated amount ya is further delayed in phase.

In order to recover this phase delay, a virtual eccentricity amount obtained by advancing the phase with respect to the eccentricity estimation amount ra by a certain time L.
Displacement y is obtained by determining rd and configuring a servo system that causes the data transducer 103 to follow this rd.
Can be made to follow the eccentricity amount r very well.
In reality, it is impossible to advance the time, so the periodicity of the amount of eccentricity is used, and this is performed using the delay means 112 as follows. That is, if the estimated eccentricity ra is composed of harmonics having the fundamental frequency of the disk rotation frequency (f = 1 / T) as with the eccentricity r, exp (−T · S) = Since exp (−T · 2π · f) = 1, the output rd of the delay means 112 is multiplied by rd = ra · exp (− (T−L) · S) = ra · exp (L · S). (Here, S is S of Laplace transform) That is, the eccentricity estimation amount rd that is advanced in the L time phase compared to ra is obtained. By obtaining the difference between the estimated eccentricity rd and the estimated displacement ya of the data transducer by the addition means 113, an estimated quantity ea = rd−ya is obtained, which is added to the drive circuit 107 via the compensation means 106, By driving the actuator 108, the tracking delay of the data transducer 103 can be eliminated.

FIG. 7 is a vector diagram for more clearly explaining the gain-phase relationship of servo signals in the conventional positioning control device described above. The figure (a) shows that the position error signal e is given by the difference between the eccentricity r and the position y of the data transducer, and that the estimated amount ya of the displacement y is slightly behind the phase of y. ing. In the same figure (b), the eccentricity estimation amount ra is given by the sum of the estimation amount ya and the position error signal e, and the eccentricity estimation amount rd is ahead of ra by L · S [rad] in phase. It is shown that. In the figure (c), the estimated amount ea is the eccentricity estimated amount rd and the estimated amount ea.
It is given by the difference with ya, and the estimated quantity ea shows that the position of the data transducer becomes like y ′ which is in phase with respect to y because the phase is in advance with respect to the position error signal e. There is. Further, FIG. 6D shows that as a result, the position error signal e'is smaller than e.

Next, a specific example of a conventional positioning control device will be shown.

FIG. 8 is a block diagram of a specific track following servo system of a conventional positioning control device. In this case, an FDD sector servo system is assumed, and the configuration is a discrete time servo system. Z means Z of Z conversion, and Z ^{· 1} means a delay of one sample time. Reference numeral 112 denotes a delay means for delaying n sample times, which has a configuration in which n 1 sample time delay means Z- ¹ are connected in series (for example, n = 28 for the number of sectors m = 30). Or 29.) 114 and 115 are samplers, and 116 is a sample holder. In this case, the compensating means 106 is an integrator for compensating the deviation of the servo system. The combined transfer function of the drive circuit 107 and the actuator 108 is given by, for example, a second-order delay system.

[For example, Japanese Examined Patent Publication No. 57-51122] Problems to be Solved by the Invention However, the above-described configuration has the following problems.

Generally, in a disk device, when a track-following state is changed to a track-following state, a track jump operation or a track seek operation is performed to move the data transducer in the disk radial direction, and further to the information track. A stable and stable track following operation is performed after the follow-up pull-in operation. In the track pull-in operation, if the delay means 112 exists in the servo system as in the conventional example, the pull-in operation is delayed by the delay time.

Furthermore, when the above-mentioned conventional positioning control device is applied to a disk device using a sector servo system, since the delay means holds only the data of the discrete eccentricity estimation amount for each sector, the progress of the eccentricity estimation amount ra is Sometimes the phases can only be realized discontinuously and the desired advance cannot be achieved.

In view of the above problems, the present invention provides not only high-accuracy track-following performance, but also rapid operation in track pull-in operation, and a desired phase advance in a disk device using a sector servo system. A positioning control device that can be achieved is provided.

Means for Solving the Problems In order to solve the above problems, a positioning control device of the present invention is a positioning control device for positioning a moving member with respect to a target member that repeats position fluctuations at a constant cycle. Position error detector for detecting a relative position error between the position and the moving member, position detector for detecting an absolute position of the moving member, position error signal output by the position error detector and output of the position detector A position signal of the target member, a memory unit for holding a signal based on the position variation of the target member, a signal based on the output of the first addition unit, and a position variation of the target member. Second addition means for adding a signal based on the output of the memory means, which is output in synchronism with the above, and a signal based on the output of the second addition means and the position detection. Third addition means for subtracting a signal based on the output of the controller, and compensation means for performing at least one of stabilization compensation and deviation compensation of the position control loop based on the output of the third addition means. And a drive circuit for applying a current to the actuator means for freely moving the moving member by a signal based on the output of the compensating means.

The present invention, by adopting the above-mentioned configuration, not only provides highly accurate track following performance, but also enables quick operation even in the track pull-in operation and also in the disk device using the sector servo system. A positioning control device that can achieve a desired phase advance can be provided.

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. Reference numeral 11 is a first adding means for adding the output signal of the position error detector 4 and the output signal of the position detector 5, and 14 is a position change of the information track 2 which repeats fluctuations at a constant cycle as the disk 1 rotates. Memory means for holding, 12 is second adding means for adding the output signal of the first adding means 11 and the output signal of the memory means 14 output in synchronization with the rotation of the disk 1, and 13 is the second adding means. The position detector 5 from the output signal of the means 12
Of the output signal of the compensating means 6, and 6 is a compensating means for performing at least one of stabilization compensation and deviation compensation of the position control loop composed of an analog filter. Is a drive circuit for applying a current to the actuator 8. The data transducer 3 includes an actuator 8 and a supporting member 9 shown by a dotted line.
Are joined by. Further, the signal line 19 shown by a broken line is used when the position change of the information track 2 is held in the memory means 14.

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

The positioning control device of FIG. 1 uses the position error signal e = r in order to cause the data transducer 3 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 within a certain error range. -Y must be operated to be as small as possible. However, the servo signal causes a phase delay in the process of passing through the compensating means 6, the drive circuit 7, and the actuator 8. That is, information track 2
In a relatively low frequency range in which the eccentricity r of fluctuates,
The synthetic transfer characteristic from the compensating means 6 to the actuator 8 has 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, the center position of the data transducer 3 does not follow the center position of the information track 2 beyond a certain level, and the amplitude of the position error signal e may not fall below a certain magnitude.

In FIG. 1, the position detector 5 outputs an estimated amount ya of the absolute position y of the data transducer 3. Next, the position error signal e and the estimated amount ya are input to the first adding means 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 reason, the displacement y is delayed in phase with respect to the position fluctuation (eccentricity amount) r of the information track 2, and the estimated amount ya is an electrical quantity at the time of estimation by the position detector 5. Due to such a delay, the phase is further delayed. Therefore, the eccentricity estimation amount ra also includes the phase delay caused by these.

In order to recover this phase delay, the eccentricity estimation amount ra is held in the memory means 14 in advance by an amount corresponding to one rotation of the disk, and the eccentricity at that time is synchronized with the rotation of the disk 1 during the track following operation. The held signal is taken out at a timing which is ahead of the phase of the estimated amount ra, the signal amplification is adjusted by an amplifier or attenuator (not shown), and the second addition means 12 is added to the signal ra at that time. By adding in, the eccentricity estimation amount rc that is approximately the same phase as the original eccentricity amount r, or rather a slightly advanced phase, is obtained. An estimated amount ea is obtained by obtaining the difference between the estimated eccentricity amount rc and the estimated amount ya of the displacement of the data transducer by the third adding means 13. By adding this to the drive circuit 7 via the compensating means 6 and driving the actuator 8, it becomes possible to eliminate the tracking delay of the data transducer 3.

FIG. 2 is a signal waveform diagram of each part when the phase of the eccentricity estimation amount ra is advanced by the above method. In the figure, (a) is an eccentricity estimation amount ra, (b) is a signal obtained by multiplying the eccentricity estimation amount obtained by advancing the phase by 90 degrees from ra from the memory means 14, and (c) is a signal. It is a signal obtained by adding these two signals, and each can be described by the following equations.

(A): A ・ sin (ωt) (b): B ・ cos (ωt) (c): C ・ sin (ωt + φ) C ・ sin (ωt + φ) = A ・ sin (ωt) ＋ B ・ cos (ω
Since there is a relation of t), by rearranging this equation and comparing the coefficients, we obtain A = C · cos (φ) B = C · sin (φ), and from these, tan (φ) = B / A obtain.

Now, considering the case of B = 0.1 · A, we obtain φ = 5.7 °, C = 1.005 · A from the above equation. That is, the phase advances by 5.7 ° from the original signal ra, and a signal with almost the same amplitude is obtained. In FIG. 2, the signal (b) is shown as being advanced by 90 ° in phase with respect to the signal (a), but this is not always the case.

FIG. 3 is a vector diagram for more clearly explaining the relationship between the gain and phase of the servo signal in the positioning control device of the present invention described above. In the figure (a), the position error signal e indicates the eccentricity r and the position y of the data transducer.
And the estimated amount of displacement y, ya
Indicates that the phase is slightly behind y. In the same figure (b), the eccentricity estimation amount ra is the estimation amount ya and the position error signal e.
And the eccentricity estimator rc, which is obtained by multiplying the eccentricity estimator rc by 90 ° in advance of the eccentricity estimator rc from the memory means 14 by a coefficient of a certain magnitude and the eccentricity estimator ra. It is given as the sum of and. In the figure (c), the estimated amount ea is given by the difference between the eccentricity estimated amount rc and the estimated amount ya, and the estimated amount ea is the position error signal e.
It is shown that the position of the data transducer becomes y ', which is in phase with respect to y, because the phase is in advance with respect to y. Further, FIG. 6D shows that as a result, the position error signal e'is smaller than e.

Next, a specific example of the positioning control device of the present invention will be shown.

FIG. 4 is a block diagram of a specific track following servo system of the positioning control device in one embodiment of the present invention. 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 14 is a memory means for holding the eccentricity estimation amount ra in advance for the number of sectors m corresponding to one rotation of the disk, and 15 is synchronized with the rotation of the disk, and the phase is advanced from the phase of the eccentricity estimation amount ra at that time. At the timing (for example, the number of sectors m = 30
For 7 or 8 sectors), memory means 14
The magnitude of the signal extracted from is multiplied by k (for example, k = 0.
2) Multiplying means to be adjusted, 16 and 17 are samplers, and 18 is a sample holder. In this case, the compensating means 6 is an integrator for compensating the deviation of the servo system. The combined transfer function of the drive circuit 7 and the actuator 8 is given by, for example, a second-order delay system.

Next, the accuracy of adjusting the phase of the eccentricity estimation amount ra will be described.

FIG. 5 is a vector diagram for explaining the phase adjustment accuracy of the eccentricity estimation amount ra. 4A shows the case of a concrete track following servo system of the positioning control device in the embodiment of the present invention shown in FIG. 4, and FIG. 8B shows the conventional case shown in FIG. This is a case of a specific track following servo system of the positioning control device of FIG. In the figure (a), r
a ′ is obtained by advancing the eccentricity estimation amount ra held in the memory means 14 by h sectors in order to advance the eccentricity estimation amount ra at that time by the phase angle θ, and then multiplying it by k. The eccentricity estimator rc with advanced phase is
It is obtained by adding this ra 'to. In the same figure (b), rd
In order to advance the eccentricity estimation amount ra by the phase angle φ, the delay unit 112 advances and extracts ra by i (= m−n) sectors. (However, m is the number of sectors and n is the number of delay means Z ⁻¹ .) In FIG. 5 (b), the phase angle φ can take only discrete values corresponding to the number of i, while in FIG. In b), various values can be taken according to the value of h and the value of k. As a result, the positioning control device of the present invention has an excellent effect that the phase delay at the frequency where the amount of eccentricity of the transfer characteristic from the compensating means 6 to the actuator 8 varies can be flexibly and accurately adjusted.

Further, as described above, in general, in a disk device, when shifting from a state of following one track to a state of following another track, an operation of moving a data transducer in the disk radial direction called a track jump operation or a track seek operation. Then, a stable and stable track following operation is performed through the follow-up pull-in operation to the information track. In the track pull-in operation of these, in the conventional positioning control device shown in FIG. 8, if the delay means 112 is present in the servo system, the pull-in operation is delayed by the delay time. On the other hand, the fourth
The positioning control device of the present invention shown in the figure has an excellent effect that the pulling operation is not delayed because the delay means is not present in the servo system.

A method of holding the eccentricity amount r in the memory means 14 in advance will be described with reference to FIG.

The first example is a case where a time-series signal of the eccentricity estimation amount ra when the servo system is operated is input to the memory means 14 via the signal line 19 shown by the broken line to perform this. In this case, since the initial value is output to the output of the memory means 14, it is necessary to set the initial value to zero in advance.

The second example is a time series signal of the output ra of the first adder in a state where the servo system of FIG. 1 is not operated and the drive circuit is given a constant command value to fix the absolute position of the data transducer 3. Is input to the memory means 14 by the signal line 19 indicated by the broken line. In this case, the position error detector 4
Outputs a signal corresponding to the amount of eccentricity of the disk 1, and the output of the position detector 5 is zero. Therefore, the output of the first adding means 11
ra is the eccentricity estimator.

In the third example, the memory means 14 stores only the information on the amplitude and phase of each frequency component of the eccentricity of the information track 2. In this case, the time series signal of the eccentricity estimation amount ra when the servo system is operated, or the servo system is not operated,
Output of the first adder 11 in the state where the absolute position of the data transducer 3 is fixed by giving a constant command value to the drive circuit
The time series signal of ra is input to a frequency analysis means (not shown) via a signal line 19 shown by a broken line, the amplitude and phase of the result are stored in the memory means 14, and when output from the memory means 14, A sine wave signal is generated based on the amplitude value and the phase value of each frequency component, these are combined and then output.

Although the specific example of the positioning control device of the present invention is shown only in the case of the discrete time system, the same applies to the case of the continuous time system.

EFFECTS OF THE INVENTION As described above, the positioning control device of the present invention is a positioning control device that positions a moving member with respect to a target member that repeats position fluctuations at a fixed cycle. A position error detector for detecting a relative position error with a member, a position detector for detecting an absolute position of a moving member, a position error signal output by the position error detector, and a position signal output by the position detector. And a memory means for holding a signal based on the position variation of the target member, a signal based on the output of the first adding means, and a position variation of the target member in synchronization. Second addition means for adding the output signal of the memory means based on the output of the second addition means, and a signal based on the output of the second addition means and the output of the position detector. And a compensating means for performing at least one of stabilization compensation and deviation compensation of the position control loop based on the output of the third adding means, and this compensating means. And a drive circuit that applies a current to the actuator means that allows the moving member to move freely according to a signal based on the output of the track pull-in performance as well as the track pull-in performance. This has the effect that a quick operation is possible and a desired phase advance can be achieved even in a disk device using the sector servo system.

[Brief description of drawings]

FIG. 1 is a block diagram of a positioning control device in one embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining how to advance the phase of the eccentricity estimation amount ra, and FIG. 3 is in one embodiment of the present invention. Gain of servo signal in positioning controller
FIG. 4 is a vector diagram for explaining the phase relationship, FIG. 4 is a block diagram of a specific track following servo system of a positioning control device in one embodiment of the present invention, and FIG. 5 is a positioning control device in one embodiment of the present invention. Also, a vector diagram for explaining the adjustment accuracy of the phase of the eccentricity estimation amount ra of the conventional positioning control device, FIG. 6 is a block diagram of the conventional positioning control device, and FIG. 7 is a servo signal in the conventional positioning control device. FIG. 8 is a vector diagram for explaining the gain-phase relationship of FIG. 8 and FIG. 8 is a block diagram of a specific track following servo system of a conventional positioning control device. 1 ... Disk, 2 ... Information track, 3 ... Data transducer, 4 ... Position error detector, 5 ... Position detector, 6 ... Compensating means, 7 ... Drive circuit, 8 ... Actuator, 9 …… Support member, 10 …… Transmission member, 11,12,13
...... First, second and third adding means, 14 ...... Memory means.

Claims (2)

[Claims] 1. A position control device for positioning a moving member with respect to a target member that repeats position fluctuations at regular intervals, and a position error detector for detecting a relative position error between the target positioning position of the target member and the moving member. A position detector for detecting the absolute position of the moving member, first adding means for adding the position error signal output by the position error detector and the position signal output by the position detector, and the target member. Memory means for holding a signal based on the position variation of the first addition means, a signal based on the output of the first adding means, and a signal based on the output of the memory means output in synchronization with the position variation of the target member. Second adding means for adding
Third addition means for subtracting the signal based on the output of the second addition means and the signal based on the output of the position detector, and the stability of the position control loop based on the output of the third addition means. Compensation means for performing at least one of compensation compensation and deviation compensation, and a drive circuit for applying a current to actuator means for freely moving the movable member by a signal based on the output of the compensation means. A positioning control device comprising: 2. The positioning control device according to claim 1, wherein a signal based on the output of the first adding means is held in the memory means.