JP2616601B2 - Disk servo controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is applied to a disk servo controller.

[0002]

2. Description of the Related Art FIG. 9 is an explanatory view of a conventional disk.
In FIG. 9, 301 and 302 are the centers of the disks,
Reference numeral 303 denotes an eccentricity, reference numerals 304 to 311 denote tracking errors, reference numeral 312 denotes an actual track position, and reference numeral 313 denotes an ideal track position.

As a conventional disk servo control device,
A circulating memory servo that samples a tracking error (304 to 311 in FIG. 9) over the entire track irrespective of the eccentric direction and corrects the current tracking error using the sampled tracking error so that the head follows the track. There is a control unit.

FIG. 6 is a block diagram of a general servo control system. 6, reference numeral 1 denotes a control unit (G _c (S));
Is a control target (G _p (S)), r is a reference signal, e0 is a tracking error, u is an operation signal, and y is an actual track position signal.

The tracking error e changes in synchronization with the rotation of the disk. Assuming that the angular velocity ω of the disk and the amplitude of the tracking error are a, the tracking error e can be expressed as e = a · sinωt. When the acceleration ea is obtained by differentiating this equation twice, ea = −a · ω ² · sin ωt. Therefore, the maximum acceleration K of the control target is K = a · ω ² . Since K is a constant value depending on the control target, the amplitude ap of the movement amount of the control target is ap = K / ω ^2. Therefore, when the angular velocity is doubled, ap becomes １ ／ times. In the case of a disk rotating at 3600 rpm, the frequency of the tracking error is 3600 rpm / 60 seconds = 60 Hz. In addition, the actual eccentricity of the disk is about 50 μm, and a compression ratio of 0.05 / 50 = 1/1000 = −60 dB is required to follow the track on the disk with an accuracy of ± 0.05 μm. It is. Compression rate at 60 Hz-60 dB
Considering the servo band, the servo characteristic 201 shown in FIG.
become. From the servo characteristics 201, a servo band of 4 kHz is required.

Next, consider a circular memory servo that samples a tracking error over the entire track. FIG. 7 is a block diagram of the orbiting memory servo control system. In FIG. 7, 1 is a control unit, 2 is a control object, 3 is a tracking error holding memory, e0 is a tracking error, e1 is a correction tracking error, and m is a holding tracking error. Since the tracking error in the entire circumference is held, the tracking error from the control target can be corrected to be the corrected tracking error e1. e1 = e0 + m Therefore, the compression ratio of the control unit can be made smaller than that of the normal servo system. The experimental value is about 10 times and the compression ratio is -40d
It is about B. The servo band at this time is as shown in the servo characteristic 202 shown in FIG. 8, and the servo band is 1 kHz. When the servo band is narrow, the maximum acceleration to be achieved by the controlled object is small, and the design of the controlled object is easy.

[0007]

In the conventional orbiting memory servo control device described above, it is necessary to increase the number of tracking error samples in order to increase the accuracy of servo control. Therefore, a memory capacity for storing the tracking error samples is required. However, there is a drawback that increases in proportion to the accuracy.

An object of the present invention is to provide a disk servo control device capable of reducing the memory capacity by eliminating the above-mentioned disadvantages.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a tracking control device comprising a disk and a tracking device for holding a sampled tracking error when a head is made to follow a track on the disk and outputting the tracking error as a holding tracking error. In a disk servo control device, comprising: an error holding memory; and a control unit that inputs a correction tracking error obtained by correcting a tracking error with the holding tracking error and outputs an operation signal for operating the object. A tracking error estimating means for estimating the tracking error of the remaining track half-circle that is not sampled from the tracking error of the track half-circle held by using the linear symmetry with respect to the eccentric direction of the disk, and outputting as the holding tracking error. It is characterized in.

Further, according to the present invention, the tracking error estimating means includes means for detecting the eccentric direction and the amount of eccentricity of the disk from a tracking error sampled at a constant period all around the track; Means for specifying a symmetry axis with respect to, a means for sampling a tracking error signal for a half track around the specified symmetry axis at a fixed period, and a method for not performing sampling using the sampled tracking error. Means for estimating a tracking error for a half circle on the side, and means for outputting the estimated tracking error as the holding tracking error.

[0011]

The tracking error estimating means utilizes the fact that the tracking error is linearly symmetric with respect to the eccentric direction, and calculates the tracking error for the opposite half circumference not sampled from the tracking error for the half track circumference sampled with respect to the axis of symmetry. Is estimated and output as a retention tracking error.

Therefore, the tracking error memory only needs to have half the capacity of the conventional one, and the memory capacity can be reduced.

For this reason, the tracking error estimating means first detects the eccentric direction and the amount of eccentricity of the disk from the tracking error sampled at a constant period over the entire circumference of the tracking, thereby specifying the axis of symmetry with respect to the eccentric direction, A tracking error for one half of the circumference with respect to the symmetric axis is sampled, a tracking error for the other half of the circumference which is not sampled is estimated, and the tracking error is output as a holding tracking error.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention.

In the first embodiment, the control object ( _GP (S)) 2 composed of a disk and a tracking error e0 sampled when the head is made to follow a track on the disk are held and held. A control unit ( _Gc (S) that inputs a tracking error holding memory 3 that outputs as an error m and a corrected tracking error e1 obtained by correcting the tracking error e0 by the tracking error m and outputs an operation signal u for operating the control target 2. )) 1
In the disk servo control device provided with the above, the tracking error e0 for a half track of the remaining track which is not sampled from the tracking error e0 for a half track of the track held in the tracking error holding memory 3, which is a feature of the present invention, A tracking error estimating circuit 4 and a switch 5 are provided as tracking error estimating means for estimating using the line symmetry with respect to the eccentric direction and outputting as a holding tracking error m.

The tracking error estimating circuit 4
As shown in FIG. 2, eccentric direction detecting means 41 for detecting the eccentric direction and the amount of eccentricity of the disk from a tracking error sampled at a constant period over the entire track, and an axis of symmetry with respect to the detected eccentric direction of the disk. And a half-tracking tracking error sampling means 4 for sampling a tracking error for a half track around the specified axis of symmetry at a constant period.
3 and a tracking error estimating means 44 for estimating the tracking error of the other half circumference on which sampling is not performed using the sampled tracking error.

FIG. 3 is an explanatory diagram of a disk according to the first embodiment. In FIG. 3, 101 is the center of the disk, 1
02 is the track center, 103 is the amount of eccentricity, 104 is the tracking error when the rotation angle θ = 0, 105 is the rotation angle θ
= Π / 4, 106 is a tracking error when the rotation angle θ is π / 2, 107 is a tracking error when the rotation angle θ is 3π / 4, and 108 is a tracking error when the rotation angle θ is π. Estimated tracking error,
109 is an estimated tracking error when the rotation angle θ = 5π / 4, 110 is an estimated tracking error when the rotation angle θ = 3π / 2, and 111 is a rotation angle θ = 7π.
The estimated tracking error at / 4, 112 is the actual track position, and 113 is the ideal track position.

Next, the operation of the first embodiment will be described with reference to FIG.
This will be described with reference to the flowchart shown in FIG.

The head moves to the actual track position 112 specified by the seek operation (step S1). Next, tracking errors 104, 10 and 10
Samples 6, 108 and 110 are performed (the number of samples N = 4) (step S2). The sampled data is held in the tracking error holding memory 3.

The sampled tracking error 104,
A combination of points 106, 108, and 110 that are half a circle apart, have opposite signs of displacement, and have the closest absolute value is searched for (step S3). In FIG. 3, since the combination of the tracking errors 104 and 108 meets this condition, the direction connecting these points is the eccentric direction. Also,
The absolute value of the tracking errors 104 and 108 at this time is the amount of eccentricity.

Next, assuming an axis of symmetry in the measured eccentric direction, the tracking errors 104, 105, 106 and 107 are sampled in a half track around the axis of symmetry (the number of samples N = 4) (step S4). The sampled data is held in the tracking error holding memory 3. The density of the sample points is doubled. Next, the tracking error estimating circuit 4 estimates the tracking error of the pointer not held in the tracking error holding memory 3. Since the tracking error is axisymmetric assuming the axis in the eccentric direction, the tracking error 10
9, 110 and 111 can be inferred from being equal to tracking errors 107, 106 and 105, respectively. Further, the tracking error 108 in the eccentric direction can be estimated from the fact that the sign is opposite to 104 and the absolute value is equal.

The tracking error 104 sampled,
The switching unit 105 switches between 105, 106 and 107 and the estimated tracking errors 108, 109, 110 and 111.
, The tracking error at each point is corrected, the control unit 1 creates an operation signal u, and performs servo control of the control target 2 (step S5).

FIG. 5 is a block diagram showing a second embodiment of the present invention.

The second embodiment differs from the first embodiment in FIG. 1 in that the tracking error estimating circuit 4 is realized by an arithmetic circuit in the control unit 1 to suppress an increase in circuit scale.
The same operation as in the first embodiment is performed.

[0026]

As described above, according to the present invention, the tracking error is sampled over the entire track, and the eccentric direction and the eccentricity of the eccentricity of the disk which is the main cause of the tracking error are determined using the sampled tracking error. To detect. Then, assuming a symmetry axis in the eccentric direction of the disk, the same number of tracking error samples are performed again at twice the track density in half a track around the symmetry axis, and the opposite half circle is used using the tracking error of the sampled half circle. By estimating the tracking error for one minute, and using the sampled tracking error and the estimated tracking error, the amount of movement of the head following the track is predicted over the entire circumference of the track, thereby halving the memory capacity for storing the sampled tracking error. There is an effect that can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing the tracking error estimation circuit.

FIG. 3 is an explanatory diagram of the disk.

FIG. 4 is a flowchart showing the operation.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a block diagram showing a conventional general servo control circuit.

FIG. 7 is a block diagram showing a conventional example.

FIG. 8 is a characteristic diagram showing servo control characteristics.

FIG. 9 is an explanatory view of a conventional disk.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Control part ( _Gc (S)) 2 Control object ( _Gp (S)) 3 Tracking error holding memory 4, 4a Tracking error estimating circuit 5 Switch 41 Eccentric direction detecting means 42 Symmetric axis specifying means 43 Half-round tracking error Sample means 44 Tracking error estimating means 101, 301 Disk center 102, 302 Track center 103, 303 Eccentricity 104-111, 304-311 Tracking error 112, 312 Actual track position 113, 313 Ideal track position 201, 202 Servo characteristics S1- S5 Step e0 Tracking error e1 Correction tracking error m Holding tracking error r Reference signal u Operation signal y Actual track position signal

Claims (2)

(57) [Claims] 1. A control object constituted by a disk, a tracking error holding memory for holding a sampled tracking error when a head is made to follow a track on the disk and outputting the tracking error as a holding tracking error; A control unit for inputting a correction tracking error corrected by the holding tracking error and outputting an operation signal for operating the object, wherein a half of the track held in the tracking error holding memory is provided. A disk comprising tracking error estimating means for estimating the tracking error of the remaining half track that is not sampled from the tracking error using the line symmetry with respect to the eccentric direction of the disk and outputting it as the holding tracking error. Servo control device. 2. The tracking error estimating means includes means for detecting an eccentric direction and an eccentric amount of a disk from a tracking error sampled at a constant period over the entire track, and determining a symmetric axis with respect to the detected eccentric direction of the disk. Means for specifying, a means for sampling a tracking error signal for a half track around the specified axis of symmetry at a fixed period, and a method for sampling on the opposite half circumference on which sampling is not performed using the sampled tracking error. 2. The disk servo control device according to claim 1, further comprising: means for estimating the tracking error of the above, and means for outputting the estimated tracking error as the holding tracking error.