JPH0244411A - Positioning controller - Google Patents

Abstract

PURPOSE:To obtain track follow-up performance with accuracy higher than ever by moving a moving member by adding a quantity of eccentricity stored in a memory in advance on an estimated quantity of eccentricity after advancing a phase a head of the estimated quantity of eccentricity. CONSTITUTION:A position detector 5 outputs the estimated quantity ya of the absolute position (y) of a data transducer 3. Next, a position error signal (e) and the estimated quantity ya are inputted to a first addition means 11, and ra=e+ya i.e. the estimated quantity (estimated quantity of eccentricity) of displacement underneath the data transducer 3 on an information track 2 is outputted. The estimated quantity of eccentricity rc with almost the same phase as that of an original quantity of eccentricity (r) or with the phase advanced a little a head of that can be obtained by adding on the signal ra by a second addition means 12, and after it is added on the output signal of a compensation means 6 by a third addition means 13, it is inputted to a driving circuit 7, and an actuator 8 is driven, thereby, the delay of the follow-up of the data transducer 3 can be dissolved. In such a way, the track follow-up performance with high accuracy can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positioning control device for positioning a member at a target position by repeating positional changes at regular intervals. More specifically, information is recorded and/or reproduced using magnetic, optical, or physical means along concentric or spiral information tracks provided on the surface of a disk-shaped medium. The present invention relates to a positioning control device for a magnetic disk device, an optical disk device, etc. that enables the positioning of magnetic disk devices, optical disk devices, etc.

Conventional Technology In order to record and reproduce information along the information track on the disk surface, a data transducer for reading and writing data must be constantly held on the target information track as the disk rotates. positioning control must be performed to follow the

Next, a method for detecting the position of the data transducer on the disk surface for trunk tracking will be described. Floppy disk device (FDD) and hard disk device (
In magnetic disk drives such as HDDs, the sector servo method divides the disk into equal areas called fan-shaped sectors, and magnetically sends identification data called sector servo signals to part of the information track divided for each sector. There are some systems that perform track tracking by detecting and recognizing relative positional errors with the information track in a sampling manner by reading this signal sector by sector with a data transducer as the disk rotates. . Also, in optical disk devices, there is a sampling servo method.
There is a method called the continuous servo method, in which pits for track following are provided at regular intervals on the information track on the disk surface, and these are optically detected and used as identification data as described above. In some cases, a spiral or concentric guide groove is provided and the track is followed by optically detecting this groove.

Furthermore, we will discuss the positional fluctuations of the information track that occur during track following. In an optical disk device, the position of the information track changes at a constant cycle as the disk rotates due to factors such as a shift in the center of rotation when the disk medium is replaced and a wobbling of the rotation axis of the spindle motor that rotates the disk. Be eccentric. The amplitude of this eccentricity can range from several tens of μm to over 100 μm, which is extremely large compared to the width of the track to be followed (approximately 1.6 μm).
This becomes an obstacle when realizing trunk tracking. Among magnetic disk devices, FDDs experience eccentricity similar to that in optical disk devices, as well as a different kind of eccentricity caused by distortion of the disk medium's heath film due to expansion, expansion and contraction under the influence of heat. The amplitude of each eccentricity is small compared to the case of an optical disk device, each on the order of tens to tens of micrometers at most, but this becomes an obstacle in increasing the recording capacity by increasing the trunk density.

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

FIG. 6 is a block diagram of a conventional positioning control device,
Generally called a track following servo system.

In the figure, 108 is an actuator that allows the data transducer 103 to be freely moved on the disk 101. Selected information track of disc 101
The displacement directly below the data transducer 103 of 102, that is, the amount of eccentricity of the information track, is represented by r, and the displacement of the data transducer 103 is represented by y. A position error detector 104 detects a relative position error e=ry between the information trunk 102 and the data transducer 103, and a position detector 105 detects the absolute position of the data transducer 103. , are mechanically coupled to the movable portion of the actuator 108 by a transmission member 110. 106 is a compensation means for performing at least either stabilization compensation or deviation compensation for the position control loop consisting of an analog filter; 111 is an addition unit that adds the output signal of the position error detector 104 and the output signal of the position detector 105; means, 11
7 is an amplifying means for amplifying the output signal of the adding means 111;
12 is an adding means for adding the output signal of the compensation circuit 106 and the output signal of the amplifying means 117, and 107 is a driving circuit for receiving the output signal of the adding means 112 and applying a current to the actuator 108. The data transducer 103 is coupled to the actuator 108 by a support member 109 shown in dotted lines.

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

The positioning control device shown in FIG. 6 generates a position error signal e=ry in order to cause the data transducer 103 to follow the eccentricity r of the information track 102 that occurs as the disk 101 rotates within a certain error range. We must work to make it as small as possible.

In FIG. 6, the position detector 105 outputs an estimated amount ya of the displacement y of the data transducer 103. ya
is called an estimated amount because the position detector 105 does not directly measure the displacement of the data transducer 103, but measures the displacement of the movable part of the actuator 108 via the transmission member 110. 10
By estimating the displacement of 3. On the other hand, the position error signal e and the output ya of the position detector 105 are input to an adding means 111, which outputs ra=e+ya, that is, the estimated amount of displacement (eccentricity estimated amount) of the information track 102 directly below the data transducer 103. do. The signal amplified by the amplifying means 117 and the output signal of the compensation circuit 106 are added together by the adding means 112 and then inputted to the driving circuit 107 to drive the actuator 108, thereby enabling the data transducer 103 to follow the signal. become. [For example, Tokikai Sho 6
Publication No. 3-124346] Problems to be Solved by the Invention The above-described configuration had the following problems.

In FIG. 6, the servo signal undergoes a phase delay while passing through the drive circuit 107 and actuator 108. In other words, in a relatively low frequency region where the eccentricity r of the information track 102 varies, the combined transfer characteristic from the drive circuit 107 to the actuator 108 has some kind of phase lag. Furthermore, when the servo system is configured as a discrete time system, a phase delay due to the sample holder is added to this. For this purpose, the center position of the data transducer 103 may not follow the center position of the information trunk 102 beyond a certain level, and the amplitude of the position error signal e may not fall below a certain level.

In view of the above-mentioned problems, the present invention provides a positioning control device that can provide 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 provides a positioning control device that controls the relative position of the track to be followed by the target member, that is, the disk, whose position changes at regular intervals, and the moving member, that is, the data transducer. a position error detector that detects a position error; a position detector that detects the absolute position of the moving member;
a compensation means for performing at least either stabilization compensation or deviation compensation of the position control loop based on the position error signal output from the position error detector; and a position error signal output from the position error detector; a first addition means for adding the position signal output from the position detector; a memory means for retaining the positional fluctuation of the target member; and a signal based on the output of the first addition means and the position change of the target member a second addition means for adding a signal based on the output of the memory means outputted in synchronization with the movement; a signal based on the output of the compensation means and a signal based on the output of the second addition means; and a drive circuit that applies current to actuator means that allows the movable member to be freely moved by a signal based on the output of the third addition means. configured.

Function: By adopting the above-described configuration, the present invention can provide a positioning control device that can obtain more accurate track following performance.

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

FIG. 1 shows positioning it, II in one embodiment of the present invention.
In Figure 0, which is a block diagram of the control device, 8 is an actuator that allows the data transducer 3 to be freely moved on the disk 2.

Displacement of the selected information trunk 2 of the disk l directly below the data transducer 3, i.e. the eccentricity 1 of the information track
``, the displacement of the data transducer 3 is expressed by y,
11 is a position error detector that detects a relative 1αELQ difference er-y between the information trunk 2 and the data transducer 3; 5 is a position detector that detects the absolute position of the data transducer 3; The movable portion of the actuator 8 and the transmission member 10 are mechanically coupled. Reference numeral 6 denotes a compensation means for performing at least either stabilization compensation or deviation compensation for the position control loop consisting of an analog filter, and 11 a compensation means for adding the output signal of the position error detector 4 and the output signal of the position detector 5. 1 is an addition means; 14 is a memory means for retaining the positional changes of the information track 2 which repeats fluctuations at a constant period as the disk l rotates; 12 is a first addition means;
a second addition means for adding the output signal of the addition means 11 and the output j signal of the memory means 14 output in synchronization with the rotation of the disk l; 13 is the output signal of the compensation means 6 and the second addition; third summing means 7 for summing the output signals of the means 12;
is a drive circuit that receives the output signal of the third adding means 13 and applies a current to the actuator 8. The data transducer 3 is coupled to the actuator 8 by a support member 9 shown in dotted lines.

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

The positioning control device shown in FIG. 1 uses a position error in order to cause the data transducer 3 to follow within a certain error range the fluctuation in the absolute position of the information trunk 2, that is, the amount of eccentricity r, which occurs as the disk 1 rotates. It must operate to make the signal e=ry as small as possible. However, a phase delay occurs in the servo signal as it passes through the drive circuit 7 and actuator 8. In other words, the eccentricity i1r of information track 2
In a relatively low frequency region where the
The resultant transfer characteristic from the actuator 8 to the actuator 8 has some kind of phase lag. Furthermore, when the servo system is configured as 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 may 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 level.

In FIG. 1, the position detector 5 outputs an estimate ff1ya 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 addition means 11, which outputs ra=e+ya, that is, the estimated amount of displacement (eccentricity estimated amount) of the information trunk 2 directly below the data transducer 3. do. However, for the above-mentioned reason, the phase of the displacement y lags behind the fluctuation in the position of the information track 2 (eccentricity N), and the ya estimated from this is due to the electrical delay in estimation by the position detector 5. Therefore, the eccentricity estimation ira also includes the phase delay caused by these factors.

In order to recover this phase delay, the eccentricity estimation amount ``a'' is stored in the memory means 14 in advance by an amount corresponding to one rotation of the disk.
During the track following operation, this held signal is taken out in synchronization with the rotation of the disk 1 and at a timing that is ahead of the phase of the eccentricity estimation amount ra at that time, and is then sent to an amplifier (not shown). Alternatively, by adjusting the signal amplitude with an attenuator and then adding it to the signal ra at that time using the second addition means 12, the phase can be advanced to the same degree as the original eccentricity r, or rather slightly advanced. Obtain the eccentricity estimate rC. By adding this to the output signal of the compensation means 6 by the third addition means 13 and inputting it to the drive circuit 7 to drive the actuator 8, it becomes possible to eliminate the follow-up 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 the eccentricity estimate lra, ([)] is the signal obtained by multiplying the eccentricity estimate extracted from the memory means 14 by 90° phase ahead of ra, and (C) is the signal obtained by multiplying the eccentricity estimate by a coefficient of a certain size. This is a signal obtained by adding these two signals, and each can be described by the following formulas.

(a): A-s in (ωt) (b): B-cos (ωt) (c): C-5in (ωt+φ) Between these equations, C-3in (ω is 10φ) = A- s in (ωt)+B
-cos (ωL), so by rearranging this equation and comparing the coefficients, we get A=C-cos(φ) B=C-sin(φ), and from these, jan(φ)=B /A obtained.

Now, considering the case of B=0.1・A, from the above formula, φ=5
．． 7°, C=1.005·A is obtained, that is, a signal whose phase is 5.7° ahead of the original signal ra and whose amplitude is almost the same is obtained. In addition, in Figure 2 (b
Although the signal in ) shows a case where the phase is advanced by 90 degrees with respect to the signal in (a), this is not necessarily the case.

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

In FIG. 1, the estimated eccentricity rc is added to the third adding means 13.
The remaining servo loop after removing the eccentricity estimation loop added to the servo loop 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, it is necessary to make the gain of the compensation means 6 infinite. However, in reality, it is impossible to make the gain infinite, so a slight error remains. In the present invention, the eccentricity of the information track 2 is estimated to obtain the eccentricity estimate lra, and this is added to the operating gauge of the normal loop and applied to the drive circuit 7, thereby further reducing the tracking error. There is.

However, in a relatively low frequency range where the eccentricity ir of the information track 2 varies, if the phase delay of the composite transfer characteristic from the drive circuit 7 to the actuator 8 is approximately zero and the gain is approximately l, then the eccentricity estimate ra By adding y to the third addition means 13, it is possible to set y=ra. Furthermore, at this time, the estimation accuracy of the eccentricity estimation 11ra is extremely high, and when ra=y, y=r, which is nothing but e-r-y=0, that is, the tracking error can be made zero. (Incidentally, the output of the compensation means 6 at this time is zero, but the compensation means 6 is used to ensure loop stability, suppress disturbances, and adjust the center position of the data transducer 3 and the center of the information track 2 in FIG. However, as mentioned above, the servo signal causes a phase delay in the process of passing through the drive circuit 7 and actuator 8, and furthermore, the servo system is operated in a discrete time system. If configured, the phase delay due to the sample holder is added to this, so the data transducer 3
The center position of the information track 2 may 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 exceed a certain level. Therefore, as shown in FIG.
A configuration is required in which the phase of ra is advanced by adding it to a.

Next, signal waveforms 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 transformation, and Z-1 means a delay of one sample time. 15
．． 16 is a sampler, and 17 is a sample holder. In this case, the compensation means 6 is an integrator for compensating the deviation of the servo system, and the reference numeral 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 actuator 8 is a second-order lag system, and constants p and q have values such that the cutoff frequency is 400 Hz.

The rotation speed of the disk is 600rpr@, the number of sectors is 30,
It is assumed that the sampling frequency is 30011 z, and the displacement r of the information track 2 is given by a sine wave with an amplitude of 20 μm and a frequency of 10 Hz. Note that the data in the memory means 14 is extracted by advancing the phase for the eccentricity estimation ff1ra by 8 times relative to the number of data for one revolution of the disk, 30, and then multiplier 18 multiplies this by 0.2, and then outputs the second data. 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, and the output C2 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, FIGS. 5(a) to 5(C) show waveforms of various parts obtained by simulation in a conventional configuration in which the output of the memory means 14 is not applied to the multiplier 18. However, the position error signal e in FIGS. 4 and 5 shows the signal after passing through the sampler 15.

Comparing the position error signal e in FIG. 4 and FIG.
In the figure, the amplitude is 0.9 μm, while in Figure 4 it is approximately 0.06 μm, and by adopting the servo system configuration shown in Figure 3, the positional deviation is approximately 1/15th of that of the conventional one. It has an excellent effect.

In the embodiment, the specific track following servo system is configured as a discrete time system, but it may also be configured as a continuous time system.

Further, although the method for making the memory means 14 hold the amount of eccentricity in advance is not particularly shown, for example, the first
In the figure, it is conceivable to do this by inputting the estimated eccentricity ra when the servo system is operated into the memory means 14 without applying the output of the memory means 14 to the second adder 12.

As described in detail, the positioning control device of the present invention has the following features:
A position error detector detects the relative position error between the target member, ie, the information trunk to be followed by the disk, which repeats positional fluctuations at regular intervals, and the moving member, ie, the data transducer; and a position detector, which detects the absolute position of the moving member. a compensation means for performing at least either stabilization compensation or deviation compensation of the position control loop based on the position error signal output from the position error detector; and a position error output from the position error detector. a first addition means for adding a signal and a position signal output from the position detector; a memory means for storing positional fluctuations of the target member; and a signal based on the output of the first addition means and the target member. a second addition means for adding together a signal based on the output of the memory means output in synchronization with the movement of the member; and a signal based on the output of the compensation means and the output of the second addition means. and a drive circuit that applies current to actuator means that allows the movable section to freely move according to a signal based on the output of the third addition means. This configuration has the effect of providing more accurate track following performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a positioning control device in an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining how to advance the phase of the estimated eccentricity ra, and FIG. 3 is a block diagram of a positioning control device in an 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 based on computer simulation in the configuration of FIG. 3, and FIG. 5 is a diagram of the memory means in the configuration of FIG. 3. FIG. 6 is a block diagram of a positioning control device in a conventional example. 1... Disc, 2... Information track, 3... Data transducer, 4...
...Position error detector, 5...Position detector, 6.
... Compensation means, 7 ... Drive circuit, 8 ...
...Actuator, 9...Support member, 1
0...Transmission member, 11.12.13...
・First. Second. Third addition means, 14... Memory means. Figure 2 Figure Punara

Claims (2)

[Claims] (1) In a positioning control device that positions a movable member with respect to a target member whose position changes repeatedly at a constant cycle, a position error detector that detects a relative position error between the target positioning position of the target member and the movable member; a position detector that detects the absolute position of the moving member; and compensation means that performs 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 a position error signal output from the position error detector and a position signal output from the position detector; a memory means for retaining positional fluctuations of the target member; and the first addition means. a second addition means for adding a signal based on the output of the means and a signal based on the output of the memory means outputted in synchronization with movement of the target member; and a signal based on the output of the compensation means; A current is applied to a third adding means for adding a signal based on the output of the second adding means, and an actuator means for making the movable member freely movable by a signal based on the output of the third adding means. A positioning control device comprising: a drive circuit that provides a drive circuit; (2) The positioning control device according to claim (1), wherein the signal based on the output of the first addition means is held in the memory means.