JPH0731551B2 - 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 the concentric circular or spiral information tracks 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 disc surface, a data transducer for reading / writing data is always held on a target information track according to the rotation of the disc, that is, the track is followed. Positioning must be controlled so that

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. Reference numeral 106 denotes a compensation means for performing at least one of stabilization compensation and deviation compensation of a position control loop formed of an analog filter, and 111 an output signal of the position error detector 104 and a position detector.
Addition means for adding the output signals of 105, 117 is addition means 111
Amplification means for amplifying the output signal of the compensation circuit 106, addition means 112 for adding the output signal of the compensation circuit 106 and the output signal of the amplification means 117, 1
07 receives the output signal of the addition means 112 and the actuator 108
It is a drive circuit that applies a current to the. The data transducer 103 includes an actuator 108 and a support member 10 shown by a dotted line.
Combined at 9.

The operation principle of the conventional positioning control device configured as described below 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.

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 the data transducer 103 by measuring the displacement of the movable part of the actuator 108 via the transmission member 110, rather than directly measuring the displacement of 03. On the other hand, the position error signal e and the output y of the position detector 105
The value a is input to the adding means 111 and outputs ra = e + ya, that is, the estimated amount of displacement (estimated amount of eccentricity) of the information track 102 immediately below the data transducer 103. This is amplification means 117
The addition means 1 for adding the signal amplified by and the output signal of the compensation circuit 106
After the addition in 12, the signal is input to the drive circuit 107 and the actuator 108 is driven, whereby the tracking operation of the data transducer 103 becomes possible. [For example, JP-A-63-1
DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the above-described configuration has the following problems.

In FIG. 6, the servo signal causes a phase delay while passing through the drive circuit 107 and the actuator 108. That is, in the comparatively low frequency range in which the eccentricity r of the information track 102 fluctuates, the combined transfer characteristic from the drive circuit 107 to the actuator 108 has some phase delay. Furthermore, when the servo system is composed of a discrete time system,
A phase delay due to the sample holder adds to this. For that reason, the center position of the data transducer 103 may not follow the center position of the information track 102 to some extent or more, and the amplitude of the position error signal e may not fall below a certain magnitude.

In view of the above problems, the present invention provides a positioning control device capable of obtaining a more accurate track following performance.

Means for Solving the Problems In order to solve the above problems, the positioning control device of the present invention has a relative position error between a track to be followed by a target member, that is, a disk, and a moving member, that is, a data transducer, which repeats position fluctuations at a constant cycle. A position error detector for detecting the position error, a position detector for detecting 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. And a first adding means for adding a position error signal output by the position error detector and a position signal output by the position detector, and a position variation of the target member. Memory means to
Second adding means for adding a signal based on the output of the first adding means and a signal based on the output of the memory means, which is output in synchronization with the movement of the target member, and the output of the compensating means. And the signal based on the output of the second adding means, and the signal based on the output of the third adding means to move the moving member freely. And a drive circuit for applying a current to the actuator means.

Effect The present invention can provide a positioning control device capable of obtaining a more accurate track following performance by adopting the above-mentioned configuration.

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 6 is a compensation means for performing at least one of stabilization compensation and deviation compensation of a position control loop composed of an analog filter, and 11 is a unit for adding an output signal of the position error detector 4 and an output signal of the position detector 5. 1 is an adding means, 14 is a memory means for holding the position change of the information track 2 which repeats a fluctuation at a constant cycle with the rotation of the disk 1, and 12 is an output signal of the first adding means 11 and the rotation of the disk 1. Second adding means for adding the output signal of the memory means 14 output in synchronization, 13 is a third adding means for adding the output signal of the compensating means 6 and the output signal of the second adding means 12,
A drive circuit 7 receives the output signal of the third adding means 13 and applies a current to the actuator 8. The data transducer 3 is connected to the actuator 8 by a support member 9 shown by a dotted line.

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 while passing through the drive circuit 7 and the actuator 8. That is, in the comparatively low frequency region where the eccentricity r of the information track 2 fluctuates, the combined transfer characteristic from the drive circuit 7 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 data transducer 3
When the center position of the position error signal e does not follow the center position of the information track 2 beyond a certain level, the amplitude of the position error signal e may not be less than 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) immediately below the data transducer 3 of the information track 2 is output.
However, due to the above reason, the displacement y is delayed in phase with respect to the fluctuation (eccentricity amount) r of the position of the information track 2, and ya which estimated this is an electrical delay at the time of estimation by the position detector 5. Causes the phase to be delayed further than that. 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 that is ahead of the phase of the estimated amount ra, the signal amplitude is adjusted by an amplifier or attenuator (not shown), and second addition means is added to the signal ra at that time.
By adding in 12, the estimated amount of eccentricity rc that is approximately the same phase as the original amount of eccentricity r, or rather a little advanced, is obtained. By adding this to the output signal of the compensating means 6 by the third adding means 13, it is input to the drive circuit 7 and the actuator 8 is driven, whereby the data transducer 3
It becomes possible to eliminate the following delay.

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) between these expressions ＋ 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, φ = 5.7 ° and C = 1.005 · A are obtained from the above formula, that is, the phase is advanced by 5.7 ° from the original signal ra and the signal with almost the same amplitude is obtained. Will be done. 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.

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

In FIG. 1, the remaining servo loop obtained by removing the eccentricity estimation loop for adding the eccentricity estimation amount rc to the third adding means 13 is a normal track following servo system. In this normal servo system, the information track 2 of the data transducer 3
In order to make the tracking error e = ry equal to zero, the gain of the compensating means 6 must be infinite. 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, in a relatively low frequency region where the eccentricity amount r of the information track 2 fluctuates, if the phase delay of the combined transfer characteristic from the drive circuit 7 to the actuator 8 is almost zero and the gain is almost 1, the eccentricity estimation amount is By adding ra to the third adding means 13, y =
Can be set to be ra. Further, at this time, the estimation accuracy of the eccentricity estimation amount ra is extremely high, and when ra = y, y
= R, which is none other than e = r−y = 0, that is, the tracking error can be zero. (By the way, the output of the compensation means 6 at this time becomes zero, but the compensation means 6
In the figure, it has functions of ensuring loop stability, suppressing disturbance, and eliminating direct current deviation between the central position of the data transducer 3 and the central position of the information track 2. ) However, as described above, the servo signal is transmitted to the drive circuit 7,
When a phase delay occurs in the process of passing through the actuator 8 and the servo system is constituted by a discrete time system, a phase delay due to the sample holder is added to this, so that the center position of the data transducer 3 exceeds a certain level of the information track 2. The center position may not be followed and the amplitude of the position error signal e may not exceed a certain level. Therefore, as shown in FIG. 1, the phase of ra is advanced by advancing the eccentricity amount previously stored in the memory means 14 more than the eccentricity estimation amount ra at that time and then adding to this ra. Will be required.

Next, the signal waveform of each part 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 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. 15 and 16 are samplers, and 17 is a sample holder. Compensation means 6
In this case, is an integrator for compensating the deviation of the servo system, and 18 is a multiplier for adjusting the magnitude of the output of the memory means 14. The combined transfer function of the drive circuit 7 and the actuator 8 is a second-order lag system, and the constants p and q are values such that the cutoff frequency is 400 Hz. Disc rotation speed is 600
It is assumed that rpm, the number of sectors is 30, the sampling frequency is 300 Hz, and the displacement r of the information track 2 is a sine wave having an amplitude of 20 μm and a frequency of 10 Hz. The data of the memory means 14 is extracted by advancing the phase with respect to the estimated eccentricity ra by 8 with respect to the data number 30 for one round of the disk, further multiplied by 0.2 by the multiplier 18, and then the second data is obtained. It shall be added to the addition means.

When the track following servo system shown in FIG. 3 is simulated on a computer, the displacement r of the information track, the displacement y of the data transducer, the output e of the position error detector,
The respective signal waveforms are shown in FIGS. 4 (a) to (c). In the figure, 0.1 [sec] corresponds to one rotation of the disk.

For comparison, waveforms of respective parts by simulation in the case of the conventional configuration in which the output of the memory means 14 is not applied to the multiplier 18 are shown in FIGS. 5 (a) to 5 (c). However, the position error signal e in FIGS. 4 and 5 is a signal after passing through the sampler 15.

Comparing the position error signal e between FIG. 4 and FIG.
In the figure, the amplitude is 0.9 μm, while in FIG.
It is 0.06 μm, and by adopting the servo system configuration of FIG. 3, there is an excellent effect that the position deviation becomes about 1/15 compared to the conventional one.

Although the specific track following servo system is a discrete time system in the embodiment, it may be a continuous time system.

Further, although the method of holding the eccentricity amount r in the memory means 14 in advance is not shown, for example, in FIG. 1, the servo system is operated in a state where the output of the memory means 14 is not added to the second adder 12. It is conceivable to input the estimated eccentricity ra at that time into the memory means 14 to perform this.

EFFECTS OF THE INVENTION As described above, the positioning control device of the present invention detects the relative position error between the information member to be tracked on the target member, that is, the disk, and the moving member, that is, the data transducer, which repeats the position fluctuation at a constant cycle. A position error 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, 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 memory means for holding the position fluctuation of the target member. ,
Second adding means for adding a signal based on the output of the first adding means and a signal based on the output of the memory means, which is output in synchronization with the movement of the target member, and the output of the compensating means. And the signal based on the output of the second adding means, and the signal based on the output of the third adding means to move the moving member freely. By including a drive circuit for applying a current to the actuator means for
This has the effect that a more accurate track following performance can be obtained.

[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. A block diagram of a specific track following servo system of the positioning control device, FIG. 4 is a signal waveform diagram of each part by simulation on a computer in the configuration of FIG. 3, and FIG.
FIG. 6 is a signal waveform diagram of each part by simulation on a computer in the case of the conventional configuration in which the output of the memory means is not added to the multiplier in the configuration of FIG. 3, and FIG. 6 is a block diagram of the positioning control device in the conventional example. Is. 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.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiromi Onodera 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-58-80167 (JP, A) JP-A-60-15872 (JP, A) JP-A-1-92813 (JP, A)

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, 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 addition means for adding the position error signal output by the position error detector and the position signal output by the position detector, a memory means for holding the position variation of the target member, and the first Second addition for adding the signal based on the output of the adding means and the signal based on the output of the memory means output in synchronization with the movement of the target member. A stage, a third adding means for adding a signal based on the output of the compensating means and a signal based on the output of the second adding means, and a signal based on the output of the third adding means. A positioning control device comprising: a drive circuit that applies a current to an actuator means that allows the moving member to move freely. 2. A signal based on the output of the first adding means,
The positioning control device according to claim 1, wherein the positioning control device is held in a memory means.