JP3303363B2 - Head control method and head control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head control method and a head control apparatus, and more particularly, to a disk drive such as a magnetic disk drive or an optical disk drive, and a head moving speed estimated from a current head position and a head drive control amount. The present invention relates to a head control method and a head control device for performing speed following control using the same.

[0002]

2. Description of the Related Art In a disk drive such as a magnetic disk drive or a magneto-optical disk drive (hereinafter referred to as a disk drive), positioning of a head accompanying a track movement (seek operation) is usually performed in the vicinity of a target track as shown in FIG. Until (time t ₂ ), speed control for following a target moving speed curve (hereinafter, referred to as a speed profile) is performed, and thereafter (after time t ₂ ), switching to position control is performed to perform positioning on the target track.

In the above-described speed control, it is necessary to detect the moving speed of the head. In the case where the head control device is constituted by a digital circuit using a processor or the like, the head moving speed is recorded on a disk. This is performed based on the difference between each value at the current sample time and the previous sample time of the position signal obtained from the servo information. However, in such detection of the head moving speed, the detected speed has a time delay of about 1/2 sample, and the S / N of the detected speed is determined by the S / N of the position signal. There was a problem.

Therefore, in recent years, a head movement is performed based on a position signal obtained from servo information recorded on the disk and a control amount of the head, that is, a drive current of an actuator for moving the head in the radial direction of the disk. The speed is estimated (hereinafter, the estimated head moving speed is referred to as a speed estimation observer), and speed control is performed using the speed estimation observer.

That is, the speed estimation observer v (k) at time k is obtained by the calculation shown in the following equation 1, where y (k) is the value of the position signal at time k, and L is the design parameter of the observer. Can be

V (k) = w (k) + L × y (k) Equation 1

Note that w (k) in Equation 1 is an observer state variable, and is obtained by the following Equation 2 when there is no deviation between the position detection timing and the control amount output timing.
When there is a deviation, it is obtained by the following equation 3. Further, in Expressions 2 and 3, as described in Examples, u (k)
Is a control amount corresponding to the actuator drive current calculated from the speed estimation observer v (k), and A, K, B,
B1 and B2 are coefficients determined by the transfer function of the control object, the sampling period (B1 and B2 also include the control amount output delay time), and the observer design parameter L.

W (k) = A × w (k−1) + K × y (k−1) + B × u (k−1) Equation 2

W (k) = A × w (k−1) + K × y (k−1) + B1 × u (k−1) + B2 × u (k−2) Equation 3

The speed control is performed by using the speed estimation observer v (k) obtained as described above as the head moving speed, so that the head moving speed based on the difference between the position signals is used. Since the information of the control amount u (k) (actuator drive current) corresponding to the acceleration is also used, there is no time delay in the detection speed, and the coefficient A is 0 ≦ A <1 according to the observer design parameter L. Can be freely set in the range of the detection speed, which acts as an LPF on the position signal.
/ N can be improved.

The control amount u (k) is the actuator drive current itself. However, it is necessary to provide an analog circuit for current detection, and the device becomes complicated. Replaced with data.

Specifically, the speed estimation observer v (k)
As shown in FIG. 7, the speed control unit of the head control device using the current position (hereinafter referred to as the head current position)
Target moving speed v _ref (k) of the head based on y (k)
And the current head position y
(K) and a speed estimation observer 32 that generates a speed estimation observer v (k) based on the control amount u (k), a target moving speed v _ref (k) from the target speed generation circuit 31 and the speed estimation observer The adder 33 calculates a speed error v _err (k), which is the difference between the speed estimation observer v (k) from the target speed generator 32 and the acceleration of the target moving speed v _ref (k) from the target speed generating circuit 31. An acceleration feedforward circuit 34 for generating a control amount (hereinafter referred to as a feedforward control amount) and a proportional control for generating a control amount (hereinafter referred to as a proportional control amount) proportional to the speed error v _err (k) from the adder 33. The circuit 35 and the adder 33
Control circuit 36 that generates a control amount (hereinafter, referred to as an integral control amount) proportional to the integral value of the velocity error v _err (k) from
And the feedforward control amount from the acceleration feedforward circuit 34, the proportional control amount from the proportional control circuit 35, and the integral control amount from the integral control circuit 36, and output the added value as a control amount u (k). An adder 37 is provided.

The target speed generating circuit 31 outputs a target moving speed v _ref (k) based on the head current position y (k) and the positional deviation between the target track. For example, the target speed generating circuit 31 includes a memory in which a target moving speed v _ref (k) proportional to the square root of the position deviation is stored in advance, and when the current head position y (k) is input, the target moving speed v
_ref (k) is read out and the target moving speed v
_ref (k) is supplied to the adder 33.

The speed estimation observer 32 calculates the current head position y (k) and the control amount u supplied from the adder 37.
(K), and outputs a speed estimation observer v (k). Specifically, the speed estimation observer v (k) is calculated by the above equation 1, and the speed estimation observer v (k) is calculated.
(K) is supplied to the adder 33.

The adder 33 has a speed error v _err (k) which is a difference between the target moving speed v _ref (k) and the speed estimating observer v (k) supplied from the target speed generating circuit 31 and the speed estimating observer 32, respectively. And calculate the speed error v
_err (k) is supplied to the proportional control circuit 35 and the integral control circuit 36.

The acceleration feedforward circuit 34 is for preventing the occurrence of a steady-state deviation due to the target moving speed v _ref (k) changing with time. v
A feedforward control amount corresponding to the acceleration of _ref (k) is generated. For example, when the target moving speed v _ref (k) is given in proportion to the square root of the position deviation, the feedforward control amount becomes a constant value.

The proportional control circuit 35 and the integral control circuit 36
Is a feedback control circuit provided for compensating for an error due to an open loop caused by only the acceleration feedforward control, and a proportional control circuit 35 is supplied from the adder 33. A proportional control amount proportional to the speed error v _err (k) is generated.

On the other hand, the integral control circuit 36 is for eliminating a steady-state speed error generated by the influence of a parameter variation of a control object or an external force. As shown in FIG. 7, the integrator 36a and the multiplier 36b And an integral control amount proportional to the integral value of the velocity error v _err (k) supplied from the adder 33 is generated.

The adder 37 adds the feedforward control amount supplied from the acceleration feedforward circuit 34, the proportional control amount supplied from the proportional control circuit 35, and the integral control amount supplied from the integral control circuit 36, and obtains the sum. The added value is output as a control amount u (k), that is, an actuator drive current, and the control amount u (k) is supplied to the speed estimation observer 32.

Thus, the head moving speed is controlled to follow the target moving speed v _ref (k), that is, the speed profile.

[0021]

By the way, when the speed control is performed by using the above-described head control device, the following problems occur.

In the velocity estimating observer 32 (given by equation 1), the control amount u (k), which is the actuator drive current, is uniquely associated with the head acceleration a (k). It is assumed that the following relationship holds.

A (k) = Kf × u (k) Equation 4 where Kf is an acceleration constant (design value) of the control target.

However, since there is a variation due to the location of the force generated by the actuator, an individual difference, an acceleration generated by an external force (remaining portion if an external force correction circuit is provided separately), etc., the actual head acceleration a ' (k) is given by the following equation 5.

A ′ (k) = (Kf + ΔKf) × u (k) + d (5)

Therefore, the difference between the equations (4) and (5) is
Due to the modeling error in the observer 32, the speed
An error occurs in the estimated observer v (k), but it is proportional
Control circuit 35 and an integration control circuit 36.
The feedback control circuit calculates the target moving speed v_ref(K) and speed
Velocity error v of degree estimation observer v (k)_err(K) is zero
Acts as follows. As a result, the actual head moving speed
The degree is the target moving speed v _ref(K), ie the speed profile
Estimated error in speed estimation observer 32 for file
Will follow with speed deviation only,
There is a problem that performance is limited.

The present invention has been made in view of the above-described problems, and therefore, even when there is a variation in the generated force of the actuator, an individual difference, an external force (the remaining amount when an external force correction circuit is provided separately), etc. An object of the present invention is to provide a head control method and a head control device that can make a speed follow a speed profile with almost no error and have high speed following performance.

[0028]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a head control method according to the present invention is directed to a head control method for a disk drive for performing a seek operation by switching between speed control and position control. A target moving speed of the head is generated based on the position, an estimated value of the head moving speed is generated based on the current position of the head and the first control amount, and a second control amount corresponding to the acceleration of the target moving speed is generated. Generate
A difference between the target moving speed and the estimated value is detected, a third control amount proportional to the difference is generated, a fourth control amount proportional to the integral value of the difference is generated, and the second control amount and the third control amount are calculated. The control amount is added to generate a first control amount, the second, third, and fourth control amounts are added, and the head is calculated based on the added value of the second, third, and fourth control amounts. The disk is driven in the radial direction to control the speed of the head.

According to another aspect of the present invention, there is provided a head control device for a disk drive which performs a seek operation by switching between speed control and position control, based on a current position of a head. Target speed generating means for generating a target moving speed of the head, speed estimating means for generating an estimated value of the head moving speed based on the current position of the head and the first control amount, and target moving speed from the target speed generating means Acceleration feedforward means for generating a second control amount corresponding to the acceleration of the vehicle, speed difference detection means for detecting a difference between a target moving speed from the target speed generation means and an estimated value from the speed estimation means, and speed difference detection Proportional control means for generating a third control amount proportional to the difference from the means;
Integral control means for generating a fourth control amount proportional to the integral value of the difference from the speed difference detection means, and adding the second control amount from the acceleration feedforward means and the third control amount from the proportional control means And a second adding means for generating a first control amount, and a second adding means for generating a second control amount from the acceleration feedforward means.
And a second control means for adding the third control value from the proportional control means and the fourth control value from the integral control means. Drive in the radial direction to control the speed of the head.

[0030]

According to the present invention, the second control amount corresponding to the acceleration of the target moving speed, the third control amount proportional to the difference between the target moving speed and the estimated value of the head moving speed, and the second control amount proportional to the integral value of the difference. 4 is added, and the head is driven in the radial direction of the disk by the added value to control the speed of the head.
It is generated based on a first control amount obtained by adding the second control amount and the third control amount.

[0031]

Embodiments of a head control method and a head control apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of a main part of a head control device to which the present invention is applied, and FIG. 2 is a block diagram showing a circuit configuration of a magnetic disk device employing the head control device.

First, the entire magnetic disk drive will be described. As shown in FIG. 2, for example, this magnetic disk device records data on a magnetic disk 1 and drives the magnetic head 2 in a radial direction of the disk to reproduce the recorded data. A voice coil motor (hereinafter referred to as VCM) 3, a spindle motor 4 for rotatingly driving the magnetic disk 1, a reproduction amplifier circuit 5 for amplifying a reproduction signal or the like reproduced by the magnetic head 2, and a reproduction amplification circuit 5 A position signal generating circuit 6 for generating a position signal from the amplified reproduction signal, and an actuator for controlling the moving speed of the magnetic head 2 in the disk radial direction and its position based on the position signal from the position signal generating circuit 6 A head controller 10 for generating data (hereinafter simply referred to as an actuator drive current) corresponding to the drive current, and an address from the head controller 10 A digital / analog converter (hereinafter referred to D / A converter) 7 for converting Chueta drive current to an analog signal, the D / A converter 7
And a drive amplifier 8 for amplifying the actuator drive current converted into an analog signal to drive the VCM 3.

A servo pattern is recorded in advance on the magnetic disk 1 rotated and driven by the spindle motor 4, and the relative displacement of the magnetic head 2 with respect to the track is determined by the magnetic head 2 based on a signal obtained by reproducing the servo pattern. Is reproduced, and based on this position signal, V / A
By driving the CM 3, the magnetic head 2 is positioned at the target track.

Specifically, as shown in FIG. 1 described above, the reproduction amplifier circuit 5 includes a recording amplifier, a reproduction amplifier, and the like.
/ W amplifier 5a, an equalizer 5b for equalizing the reproduced signal amplified by the R / W amplifier 5a, an envelope detector 5c for detecting an envelope of the reproduced signal equalized by the equalizer 5b, The R / W amplifier 5a includes an integrator 5d for integrating the envelope of the reproduction signal detected by the envelope detector 5c.
, And the equalizer 5b equalizes the waveform of the amplified reproduction signal. Envelope detector 5c
Detects the envelope of the reproduced signal whose waveform has been equalized,
d integrates the envelope of this reproduced signal.

As shown in FIG. 1, the position signal generating circuit 6 is a track address decoder 6a for reproducing a track number from the reproduction signal waveform-equalized by the equalizer 5b.
An A / D converter 6b for converting the output of the integrator 5d into a digital signal, a track number from the track address decoder 6a and the A / D converter 6b
And a position generator 6c for generating a position signal based on the output of the magnetic disk 1. The position signal generation circuit 6 reproduces a track number from a reproduction signal obtained by reproducing a servo pattern recorded on the magnetic disk 1, Based on the integrated value obtained by integrating the track number and the envelope of the reproduction signal,
A position signal indicating the position of the magnetic head 2 is generated.

As shown in FIG. 1 described above, the head control device 10 includes a speed control unit 11 for performing speed control for causing the magnetic head 2 to follow a target moving speed curve (hereinafter referred to as a speed profile) to a position near a target track. A position control unit 12 for controlling the positioning of the magnetic head 2 on a target track, a changeover switch 13 for switching and selecting an output of the speed control unit 11 and an output of the position control unit 12, and outputting an actuator drive current. Is provided.

When the head control device 10 performs head positioning (seek operation) involving track movement, as described in the related art (see FIG. 6), the head control device 10 is located near the target track (time t _2). ) until performs speed control to follow the magnetic head 2 to the velocity profile, then (at time t ₂ later), performs control for positioning the magnetic head 2 to a target track by switching to the position control.

That is, the speed control unit 11 outputs an actuator drive current based on the estimated value of the head moving speed during the speed control period, as described later. The position control unit 12 includes a so-called PID compensation circuit, The magnetic head 2 outputs an actuator drive current during a position control period. The changeover switch 13 is controlled according to the distance to a target track of the magnetic head 2, and outputs the output of the speed control unit 11 and the output of the speed control unit 12. Select one.

Further, the head control device 10 is provided in the above-described FIG.
As shown in the figure, the external force compensator 14 generates data for compensating the external force (hereinafter simply referred to as an external force correction amount) based on the track number from the position signal generating circuit 6, and is selected by the changeover switch 13. And an adder 15 for adding the external force correction amount from the external force correction unit 14 to the actuator drive current. The external force correction unit 14 is for compensating external force received from a flexible cable or the like.
For example, the external force correction amount corresponding to the track number is stored in advance, and the external force correction amount is read based on the track number supplied from the position signal generation circuit 6. The adder 15 adds the external correction amount to the actuator drive current selected by the changeover switch 13 and supplies the D / A converter 7 with the actuator drive current to which the external correction amount has been added. The external force correction unit 14 and the adder 15
Are provided as needed and are not necessarily required. Further, the position generator 6c to the adder 1
5 may be composed of, for example, one processor.

The D / A converter 7 converts the actuator drive current (data) supplied from the adder 15 into an analog signal, and supplies the analog signal to the VCM 3 via the drive amplifier 8. Thus, the drive of the magnetic head 2 is controlled in the radial direction of the disk.

Next, the speed controller 11 will be described in detail with the value at time k of the position signal supplied from the position signal generation circuit 6 as y (k). Speed control unit 11
Is, for example, as shown in FIG.
A target speed generating circuit 21 for generating a target moving speed v _ref (k) of the magnetic head 2 based on the current position (hereinafter referred to as the head current position) y (k) of the magnetic head 2, and the position signal generating circuit 6 Head current position y (k) from
A speed estimation observer 22 for generating an estimated value (hereinafter referred to as a speed estimation observer) v (k) of the head moving speed based on a control amount u ′ (k) described later, and a target movement from the target speed generation circuit 21. An adder 23 for calculating a speed error v _err (k) which is a difference between the speed v _ref (k) and the speed estimation observer v (k) from the speed estimation observer 22.
And the target moving speed v from the target speed generating circuit 21
An acceleration feedforward circuit 24 that generates a control amount (hereinafter referred to as a feedforward control amount) corresponding to the acceleration of _ref (k), and a speed error v from the adder 23.
Control amount proportional to _err (k) (hereinafter referred to as proportional control amount)
, An integral control circuit 26 for generating a control amount (hereinafter, integral control amount) proportional to the integral value of the velocity error v _err (k) from the adder 23, and the acceleration feedforward circuit. The control amount u ′ (k) is generated by adding the feedforward control amount from the control signal 24 and the proportional control amount from the proportional control circuit 25, and the control amount u ′ (k) is supplied to the speed estimation observer 22 and the like. An adder 27; a control amount u '(k) from the adder 27;
And an adder 28 that adds the integral control amount from step 6 and outputs a control amount u (k) corresponding to the actuator drive current.

Then, the target speed generating circuit 21 outputs a target moving speed v _ref (k) based on the head current position y (k) and the positional deviation between the target track. For example, as described in the related art, the target speed generating circuit 21 is formed of a memory in which a target moving speed v _ref (k) proportional to the square root of the position deviation is stored in advance, and the current head position y (k) is input. And the target moving speed v _ref (k) is read, and the target moving speed v _ref (k) is supplied to the adder 23.

The speed estimation observer 22 calculates the current head position y (k) and the control amount u ′ supplied from the adder 27.
(k), and outputs a speed error v _err (k). Specifically, the speed estimation observer v (k) is calculated by Expression 1 as described in the related art, and the speed estimation observer v (k) is supplied to the adder 23. In addition,
When the controlled object moves at a relatively high speed as in the case of speed control and can be regarded as a pure inertial system, the coefficients A, K, B, B1, and B2 in Equations 2 and 3 described in the related art are expressed by the position. When there is no difference between the detection timing and the control amount output timing, they are obtained by the following equations 6 to 8, respectively. When there is a difference, they are obtained by the following equations 9 to 12, respectively.

A = 1−LT Equation 6

K = −L ² × T Equation 7

[0046] B = Kf × T-L × Kf × T 2/2 ··· formula 8

A = 1−LT Equation 9

K = −L ² × T Equation 10

[0049] B1 = Kf × T2-L × Kf × T2 2/2 ··· formula 11

[0050] B2 = Kf × T1-L × Kf × (T1 2/2 + T1 × T2) ··· formula 12

In the above equations 6 to 12, Kf
Is the acceleration constant (design value) of the control target, T is the sampling period, T1 is the control amount output delay time, and T2 is (T-T
1), and the observer design parameter L is 0 ≦ A <1 in consideration of the S / N of the position signal, that is, 0 <L ≦ 1 /
It is selected within the range of T.

The adder 23 has a speed error v _err (k) which is a difference between the target moving speed v _ref (k) and the speed estimating observer v (k) supplied from the target speed generating circuit 21 and the speed estimating observer 22, respectively. And calculate the speed error v
_err (k) is supplied to the proportional control circuit 25 and the integral control circuit 26.

The acceleration feedforward circuit 24 is for preventing the occurrence of a steady-state deviation due to the target moving speed v _ref (k) changing with time. v
A feedforward control amount corresponding to the acceleration of _ref (k) is generated. For example, when the target moving speed v _ref (k) is given in proportion to the square root of the position deviation, the feedforward control amount becomes a constant value.

Proportional control circuit 25 and integral control circuit 26
Is a feedback control circuit provided to compensate for the error due to an open loop due to the open loop only by the acceleration feedforward control. The proportional control circuit 25 is supplied from the adder 23. A proportional control amount proportional to the speed error v _err (k) is generated.

On the other hand, the integral control circuit 26 is for eliminating a steady-state speed error generated by the influence of a parameter variation of a control target or an external force. As shown in FIG. 1, the integrator 26a and the multiplier 26b And an integral control amount proportional to the integral value of the speed error v _err (k) supplied from the adder 23 is generated.

The adder 27 adds the feedforward control amount supplied from the acceleration feedforward circuit 24 and the proportional control amount supplied from the proportional control circuit 25, and obtains an added value as a control amount u '(k). It is supplied to the speed estimation observer 22 and the adder 28.

The adder 28 adds the control amount u '(k) supplied from the adder 27 and the integral control amount supplied from the integration control circuit 26, and obtains the added value as the control amount u (k), That is, it is output as an actuator drive current.

Thus, the head moving speed is controlled so as to follow the target moving speed v _ref (k), that is, the speed profile.

By the way, the speed controller of the conventional device (FIG. 7)
), The acceleration feedforward circuit 34
The control amount u (k) obtained by adding the feedforward control amount from the control unit, the proportional control amount from the proportional control circuit 35, and the integral control amount from the integration control circuit 36 is used as the output of the speed control unit, and this control is performed. The quantity u (k) is used in the calculation of the speed estimation observer v (k) in the speed estimation observer 32. On the other hand, in the present embodiment, the control amount u '(k) is first obtained by adding the feedforward control amount from the acceleration feedforward circuit 24 and the proportional control amount sum from the proportional control circuit 25. Control amount u '(k)
And the integral control amount from the integral control circuit 26 are added to obtain a control amount u (k). The control amount u (k) is used as an output of the speed control unit 11 and the control amount u ′ (k) is estimated for speed. It is used for calculating the speed estimation observer v (k) in the observer 22.

Here, a specific operation of the speed control unit 11 when performing a seek operation will be described. Speed control unit 1
6, the head operates until the head reaches the vicinity of the target track when performing a seek operation, as shown in FIG. 6 described in the background art. It is divided into an acceleration control period until the vehicle reaches the speed and a target speed follow-up control period thereafter.

In the acceleration control period, the proportional control circuit 25
And the integration control circuit 26 does not operate.
Operates as an open-loop steady-state current drive that performs control only by the feedforward control amount supplied from the acceleration feedforward circuit 24. The acceleration feedforward circuit 24 operates at time t as shown in FIG.
Up to ₁ , a maximum acceleration u _max is generated. Incidentally, the speed controller 11, when operating in a closed loop control using only the proportional control amount supplied from the proportional control circuit 25, the acceleration feedforward circuit 24, for example as shown in FIG. 4, to time t ₁ Generates zero acceleration.

On the other hand, during the target speed follow-up control period,
Acceleration feed forward circuit 24, proportional control circuit 2
5. All of the integration control circuit 26 operates and the speed control unit 11
Are the feedforward control amount supplied from the acceleration feedforward circuit 24 and the proportional control circuit 26 as the control amount used in the calculation by the speed estimation observer 22.
Is used as the control amount u ′ (k), which is the sum of the proportional control amounts supplied from. At this time, the acceleration feedforward circuit 2
4 is a time t ₁ as shown in FIG. 3 or FIG.
To generate the acceleration -u _prof in to time t _2.

Incidentally, the feedforward control amount from the acceleration feedforward circuit 24 is represented by u _ff (k), the proportional control amount from the proportional control circuit 25 is represented by u _P (k), and the integral control amount from the integral control circuit 26 is represented by u _p (k). the When u _I (k), the aforementioned control amount u '(k) the sum of the feedforward control amount and the proportional control amount _{(= u ff (k) +} u P (k)) , and the above control amount u ( k) is the sum of the feedforward control amount, the proportional control amount, and the integral control amount (= u _ff (k) + u
The _{P (k) + u I (} k)). In addition, the integral control amount u _I after a certain period of time has elapsed after switching to the target speed following control.
(K) is derived from the acceleration a _prof (k) of the velocity profile due to the influence of the deviation (ΔKf) of the acceleration constant of the actuator from the design value and the external force (remaining portion if an external force correction circuit is provided separately) d. Can be substantially regarded as a component for compensating the deviation of the actual generated acceleration a _ff (k) due to only the feedforward control amount u _ff (k).

Then, the acceleration a _prof (k) and the acceleration a _ff
(K) is represented by the following Expressions 13 and 14, respectively.

A _prof (k) = Kf × u _ff (k) Expression 13

A _ff (k) = (Kf + ΔKf) × u _ff (k) + d (14)

The integral control amount u _I (k) after a lapse of a predetermined time after switching to the target speed following control is obtained by the following equation (15).

[0068] _{u I (k) ≒ - (} ΔKf × u ff (k) + d) / (Kf + ΔKf) ··· formula 15

Therefore, the actual head acceleration a '(k) based on the control amount u (k) which is the actuator drive current is obtained by the following equation (16).

A ′ (k) = (Kf + ΔKf) × u (k) + d = (Kf + ΔKf) × (u ′ (k) + u _I (k)) + d (Kf + ΔKf) × u ′ (k) + d− (ΔKf × u _ff (k) + d) = Kf × u ′ (k) + ΔKf × u _P (k) Equation 16

By the way, when the head moving speed substantially follows the speed profile, the speed deviation ≒ 0
Therefore, the proportional control amount u _P (k) is sufficiently smaller than the feedforward control amount u _ff (k), and the following expression 17 holds. Therefore, the second term in the above expression 16 can be ignored. The actual head acceleration a '(k) is given by the following equation 1.
8

ΔKf × u _P (k) << Kf × u ′ (k) Expression 17

A ′ (k) ≒ Kf × u ′ (k) Expression 18

That is, the actual head acceleration a '(k)
Is the control value u ′ (k) of the design value Kf of the acceleration constant and the control amount u (k) obtained by removing the proportional control amount u _I (k) output from the integration control circuit 26 from the control amount u (k) that is the actuator drive current. It can be obtained by multiplication.

Thus, using the design value Kf as the acceleration constant of the control target in the speed estimation observer 22, the integral control amount u _I (k) which is the output of the integral control circuit 26 from the control amount u (k) which is the actuator drive current. Is used in the speed estimation calculation, the estimated speed (speed estimation observer v (k)) having almost no error can be obtained in the target speed following control period. , The accuracy of following the target moving speed v _ref (k), that is, the speed profile, can be improved. In other words, during the target speed follow-up control period, even when there is a variation in the generated force of the actuator, individual differences, and external force (the remaining amount if an external force correction circuit is provided separately), the estimated speed with little error Therefore, the following accuracy of the head moving speed with respect to the speed profile can be improved. Also,
The present invention can be realized with only simple modifications to the conventional device.

The present invention is not limited to the above-described embodiment. For example, as shown in FIG. 5, the feedforward control amount u _ff (k) from the acceleration feedforward circuit 24 and the proportional control circuit 25 Proportional control amount u
_P (k) and the integral control amount u from the integral control circuit 26
_The control amount u (k) obtained by adding _I (k) is used as the output of the speed control unit 11, and a new adder 29 is provided to integrate the control amount u (k) from the integration control circuit 26. controlled variable u _I (k) by subtracting the controlled quantity u '(k) to seek, in the calculation of the speed estimation observer 22 the control amount u'
(k) may be used. In the above embodiment, the present invention is applied to the magnetic disk drive.
The same effect can be obtained even when applied to an optical disk device or the like.

[0077]

As is apparent from the above description, in the head control method and the head control apparatus to which the present invention is applied, the second control amount corresponding to the acceleration of the target moving speed, the target moving speed and the head moving speed. A third control amount proportional to the difference between the estimated values and a fourth control amount proportional to the integral value of the difference are added, and the head is driven in the radial direction of the disk by the added value to control the speed of the head. At this time, by generating an estimated value of the head moving speed based on the current position of the head and the first control amount obtained by adding the second control amount and the third control amount, for example, the head is moved to the disk diameter. Even when there is a variation in the generated force of the actuator that is driven in the direction, individual differences, and external force (the remaining amount if an external force correction circuit is provided separately), an estimated value of the head moving speed with almost no error is obtained. That It can, therefore, can improve the tracking accuracy of the target moving velocity curve of the head moving speed (velocity profile).

[Brief description of the drawings]

FIG. 1 is a block diagram showing a specific circuit configuration of a main part of a head control device to which the present invention is applied.

FIG. 2 is a block diagram showing a circuit configuration of a main part of a magnetic disk drive using the head control device.

FIG. 3 is a diagram showing an output example of an acceleration feedforward circuit constituting the head control device.

FIG. 4 is a diagram showing another output example of the acceleration feedforward circuit.

FIG. 5 is a block diagram showing another specific circuit configuration of a main part of the head control device to which the present invention is applied.

FIG. 6 is a diagram showing a speed profile for explaining an operation of a seek operation.

FIG. 7 is a block diagram illustrating a circuit configuration of a speed control unit included in a conventional head control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic disk 2 ... Magnetic head 3 ... VCM 6 ... Position signal generation circuit 10 ... Head control device 11 ... Speed control part 12 ... Position control part 13 ... Changeover switch 21 ... Target speed generation circuit 22 ... Speed estimation observer 23 ... Adder 24 ... Acceleration feed forward circuit 25 ... Proportional control circuit 26 ... Integration control circuit 27, 28 ...・ Adder

Claims (2)

(57) [Claims] 1. A head control method for a disk drive for performing a seek operation by switching between speed control and position control, comprising: generating a target moving speed of a head based on a current position of the head; Generating an estimated value of the head moving speed based on the control amount; generating a second control amount corresponding to the acceleration of the target moving speed; detecting a difference between the target moving speed and the estimated value; Generating a third control amount that is proportional to the first control amount; generating a fourth control amount that is proportional to the integral value of the difference; adding the second control amount and the third control amount;
The second, third, and fourth control amounts are added, and the head is driven in the radial direction of the disk by the added value of the second, third, and fourth control amounts. And controlling the speed of the head. 2. A head control device for a disk drive, which performs a seek operation by switching between speed control and position control, comprising: target speed generating means for generating a target moving speed of the head based on a current position of the head; Speed estimating means for generating an estimated value of the head moving speed based on the position and the first control amount, and acceleration feedforward for generating a second control amount corresponding to the acceleration of the target moving speed from the target speed generating means Means, speed difference detecting means for detecting a difference between a target moving speed from the target speed generating means and an estimated value from the speed estimating means, and a third control amount proportional to the difference from the speed difference detecting means. Proportional control means for generating; an integral control means for generating a fourth control amount proportional to an integral value of a difference from the speed difference detecting means; First adding means for adding the second control amount from the forward means and the third control amount from the proportional control means to generate the first control amount; A second control means, a third control value from the proportional control means, and a second control means for adding the fourth control value from the integral control means. The output of the second addition means A head control device for controlling the speed of a head by driving the head in a radial direction of a disk.