JPH02246057A - Position control system - Google Patents

Abstract

PURPOSE:To shorten the access time of a head and to realize fast seek by attaching a deceleration signal with nature to help a position error signal on the position error signal generated by a position error generator, and increasing the apparent gain of the position error signal. CONSTITUTION:A servo circuit 10 and a servo object 30 are provided, and the servo object 30 is equipped with the head 31, a voice coil motor 32, and a disk 33. And the deceleration signal FFs with the nature to help the position error signal PE is attached on the position error signal generated by the position error generator 14, and the apparent gain the position error generator 14 is increased, thereby, the overload of the position error generator 14 can be blocked, and also, the settling of the head 31 can be stabilized. In such a way, the access time of the head 31 can be shortened, and the fast seek is realized.

Description

[Detailed Description of the Invention] [Summary] Regarding a position control method when head seek control is performed by a servo circuit in a magnetic disk drive, the present invention aims to eliminate overload of a position error generator during position control and achieve head settling. The aim is to stabilize the head, shorten the head access time, and enable high-speed seek.We have developed a seek control system that positions the head of a magnetic disk device at the target track on the disk by speed control and position control using a servo circuit. In the position control method when performing position control, a position error generator that generates a position error signal that indicates the error between the current position on the track and the target position, and a The present invention is configured to include a feedforward control generator that generates a deceleration signal having a characteristic of increasing the amplitude of the position error signal, and an adder circuit that adds the position error signal and the deceleration signal to generate an added position error signal for position control.

[Industrial application field]

The present invention relates to a position control method when seek control of a head is performed by a servo circuit in a magnetic disk device.

[Conventional technology]

When performing seek control to position the head on a target track using a servo circuit in a magnetic disk drive, first the head is brought to the target cylinder where the target track is located at high speed using speed control, and then position control is performed from speed control. Then, control is performed to accurately position the head at the center of the target track.

FIG. 6 shows a servo circuit for performing seek control in a conventional magnetic disk device, and FIG. 7 shows its operating waveform diagram.

In FIG. 6, 10 is a servo circuit, and 30 is a servo target.

In the servo circuit 10, 11 is a target speed generator, 12
is a current speed generator, 13 is a speed error generator, 14 is a position error generator, 15 is a position demodulator, 16 is a feedforward control generator, 17 is an external force correction generator, 18 is an addition circuit, and 19 is a core input. 20 is a power amplifier, and 21 is a controller. The controller 21 includes a processor (not shown) therein, and the servo circuit 10
In addition to controlling each operation of each circuit within the system, it also calculates the current cylinder (track) position and calculates the difference amount (i.e., remaining seek amount) DiF that indicates the difference between the set target cylinder (track) position and the current cylinder position. The calculation is performed, and furthermore, control is performed to switch the core input/fine switch 19.

In the servo target 30, 31 is a plurality of heads,
It is moved by a voice coil motor (hereinafter referred to as VCM) 32 and reads/writes onto a disk 33 . Note that there are a plurality of heads 31 and a plurality of disks 33, one of which is the servo head 31s and the servo disk 33.
It is used as 3. Servo data is recorded on the servo disk 333 and read by the servo head 313.

In this configuration, when the head 31 is positioned at the target track of the disk 33, speed control (coarse) control is first performed to perform a high-speed seek near the target track.
When the target track is reached, speed (coarse) control is switched to position control (fine control) to position the head 21 at the center of the target track. Therefore, initially, the core input/fine switch 19 is connected to the coarse side, that is, the speed error generator 13 side. Note that the head 31
When positioning on the target track of the disk 33,
Servo head 31. Servo disk 3 read by
3. The above read signal is used.

The position demodulation circuit 15 is connected to the servo head 31 . A position signal P3 indicative of the position is generated from the read signal of , and is supplied to the current speed generator 12 and the position error generator 14. Further, from the read signal of the servo head 31, the servo head 3
1. is the servo disk 33. Every time the upper track is passed, a track clocking pulse signal (hereinafter referred to as TXPL signal) is generated and supplied to the controller 21.

The controller 21 determines the current cylinder position, that is, the track position, from the input TXPL signal, calculates the difference amount from the set target cylinder position, that is, the remaining seek amount DiF, and outputs the target speed generator 11 and the feed control generator 16. supply to. In addition, the controller 21
supplies the target cylinder position to the external force correction generator 17.

The target speed generator 11 determines a target speed V corresponding to the input difference amount DiF according to a predetermined difference amount vs. target speed characteristic (not shown), and supplies it to the speed error generator 13. As a result, the target speed (3) having the characteristics shown in FIG. 7(A) is supplied to the speed error generator 13.

Based on the input position signal P3, the current speed generator 12
Servo head 21. The current speed ■γ of is generated and supplied to the speed error generator 13 and the controller 21. This current speed Vγ is a differential value of the position signal PS, and in the case of a digital system, it is the difference from the previous sample value.

The speed error generator 13 generates a speed error signal ΔV indicating the speed error between the target speed V input from the target speed generator 12 and the target speed Vr input from the current speed generator 12.
E is generated and supplied to the adder circuit 18. As a result, the speed error signal ΔVt having the characteristics shown in FIG. 7(B) is supplied to the adder 18 (the contents of the speed error signal will be further explained later). , in response to the difference amount DiF input from the controller 21, a deceleration signal FF having the characteristics shown in FIG. will be further explained later).

The adder circuit 1 adds the speed error signal ΔvE from the speed error generator 13 and the deceleration signal FF from the feedforward control generator 16 to generate an added speed error signal ΔVts, and switches the core input/fine switch 19. The power amplifier 20 is supplied through the power amplifier 20.

The power amplifier 20 receives the input added speed error signal ΔV.
A control current 1c proportional to t3 is generated and supplied to the VCM 32.

The VCM 32 uses this control current 1c to control the servo head 3.
1. The head 31 including the head 31 is driven in the direction of the target cylinder (track).

Thereafter, the speed control operation by the loop of each circuit described above starting with the position demodulation circuit 15 is repeated, and when the head 21 reaches the target cylinder (track), the current speed Vγ generated by the current speed generator becomes "0". .

At the beginning of the speed control, the speed of the heel 31 is smaller than the target speed V, so the current speed Vr generated by the current speed generator 12 is smaller than the target speed V.

Therefore, from the speed error generator 13, as shown in FIG.
A speed error signal ΔV0 of positive level is generated as shown in FIG.

As a result, acceleration control is performed, and the speed of the head 31 rapidly increases from "0" toward the target speed V, as shown in FIG. 7(A). Note that during this acceleration period, the deceleration signal FF generated by the feedforward control generator 16 is
As shown in Figure (c), the level is set to ``03''.

When the speed of the head 21 increases and the current speed Vγ generated by the current speed generator 12 reaches the target speed V, the speed error signal Δ■ generated by the speed error generator 13 becomes as shown in FIG. 7(B). As shown in , the level is reversed from positive to negative, and the acceleration control shifts to deceleration control.

On the other hand, when the feedforward control generator 16 enters deceleration control, it generates a deceleration signal FF having a negative characteristic as shown in FIG. 7(c), and supplies it to the addition circuit 18.

The adder circuit 18 outputs the negative level speed error signal ΔV from the speed error generator 13 and the feedforward control generator 1.
By adding the negative level deceleration signal FF from VCM3
Supply to 2.

As a result, deceleration control of the head 21 is performed, and the head 21 is decelerated.
1, that is, the current speed Vγ generated by the current speed generator 12, is decelerated in accordance with the target speed V, as shown in FIG. 7(A), and becomes "0" when the target cylinder (track) is reached.

Speed error ΔV generated by speed error generator 13.

By performing deceleration control using the added speed signal Δvis obtained by adding the deceleration signal FF generated by the feedforward control generator 16 to the deceleration signal FF, the deceleration control can be quickly completed and the seek control can be made stable and high-speed.

When the current speed Vγ inputted from the current speed generator 12 becomes "0", the controller 21 switches the coarse/fine switch 19 to the fine side, that is, to the position error generator 14 side.

A position signal P of the servo head 213 is inputted to the position error generator 14 from the position demodulator 15 .

On the other hand, the external force correction generator 17 generates an external force signal FS corresponding to the target cylinder based on the target cylinder information input from the controller 21, and inputs it to the position error generator 14. This external force signal F.

applies a constant force to the head 21 from the outside to the inside as shown on the position control side in FIG. 7(c). Thereby, seek control of the head 21 can be performed satisfactorily.

The position error generator 14 outputs the head 31 (servo head 31.
A position error signal ΔPt indicating the error between the current position on the track and the center position of the track is generated and supplied to the power amplifier 20 through the core input/fine switch 19.

The position error generator 14 generates a position error signal ΔP1 by adding the sum signal of the position signal P and the external force signal F3, and the differentiated and integrated signals thereof at a predetermined ratio. As a result, proportional+integral-sufficient differential control, ie, PID control, is performed. Proportional+integral (PI) control operation works to reduce the steady-state deviation to O, but tends to slow position control. Therefore, by adding differential (D) control operation to this, PID
By using a control operation, position control can be performed quickly.

The power amplifier 20, as in the case of speed control described above,
Head 31 (servo head 31.) by VCM32
to drive.

Below, position demodulation circuit 15 - position error generator 14 -> coarse/fine switch 19 -> power amplifier 20 - "V C
M32-'' The position control operation by the loop of the head 31 (head 313) is repeated, and the head 31 (head 31.) is positioned at the center of the target track as shown on the position control side of FIG. 7(A). will be held.

When switching from speed control to position control, due to mechanical vibrations remaining in the head 21, the speed error signal ΔP generated by the position error generator 14 changes as shown on the position control side in FIG. 7(c). A transient waveform changes between positive and negative, and the head 31 is positioned at the center of a predetermined track.

When the positioning operation to the center of the target track, that is, the seek operation, is completed, the data on the disk 33 is read by the head 31.

[Problem to be solved by the invention]

When seeking control of a head is performed by a servo circuit in a magnetic disk device, the head is positioned at a target track position at high speed by speed control and position control as described above. At this time, in order to improve speed control efficiency and quickly access the head to the target cylinder, a deceleration signal FF with predetermined characteristics is generated during deceleration control, and a speed error signal Δ
It was added to vE. Furthermore, in order to efficiently perform position control, an external force signal F having predetermined characteristics is generated and added to the position signal P.

This made it possible to sufficiently increase the speed control. However, when mechanical vibration occurs in the head, there is a problem in that sufficient settling cannot be achieved when switching from speed (coarse) control to position (fine) control.

That is, the position error generator 14 performs PID control operation, but if mechanical vibration occurs in the head and the target position changes during position control, the 0 integral (I
) value increases and the position error signal ΔP becomes saturated. As a result, the gain of the position error generator 14 cannot be made sufficiently high, and as a result, vibration of the head cannot be suppressed sufficiently, causing unstable centering and increasing access, ie, seeking, time.

The present invention speeds up speed control when performing head seek control using a servo circuit, eliminates overload of a position error generator during position control, stabilizes head settling, and increases head access time. It is an object of the present invention to provide an improved position control method that enables short and high-speed seek.

[Means to solve the problem]

The means adopted by the present invention to solve the above-mentioned problems are as follows:
This will be explained with reference to FIG. FIG. 1 is a block diagram showing the basic configuration of the present invention.

In FIG. 1, 10 is a servo circuit, and 3o is a servo target. The servo target 30 includes a head 31, a voice coil motor (VCM) 32, and a disk 33.

The servo circuit 10 performs seek control of the head 31 through speed control and position control, but only the position control portion related to the present invention is shown in the figure.

In the servo circuit 10, a position error generator 14 generates a position error signal ΔP indicating the error between the current position of the head 31 on the track and the target position.

occurs.

22 is a feedforward control generator, and a deceleration signal FF has a characteristic of increasing the amplitude in the polarity direction in accordance with the polarity of the position error signal ΔPa generated by the position error generator 14.
, occurs.

Reference numeral 23 denotes an adder circuit which adds the position error signal ΔP generated by the position error generator 14 and the deceleration signal FF generated by the feedforward generator 22 to generate an added position error signal Δpis for position control.

[For production]

The speed control of the servo circuit 10 of the present invention shown in FIG.
The position control method of the present invention will be described below with reference to FIG. 2, since it is performed in the same manner as the conventional servo circuit explained with reference to FIGS. FIG. 2 shows operational waveforms during position control according to the present invention.

When switching from speed control to position control, the position error generator 14 will generate a position error signal ΔP having positive and negative overshoots, as shown by the broken line in FIG. 2(A), like a conventional servo circuit. shall be.

The feedforward control generator 22 detects the polarity of the position error signal ΔP generated by the position error generator 14, and determines the polarity direction corresponding to each polarity as shown by the solid line in FIG. 2(B). A deceleration signal FF whose amplitude is increased is generated and supplied to the adder circuit 23.

The addition circuit 23 combines the position error signal ΔpEo input from the position error generator 14 and the feedforward control generator 2.
The deceleration signal FF3 input from 2 is added to generate an added position error signal ΔPES. This added position error signal Δp
A control current proportional to ts is applied to the VCM 32 to drive the head 31.

The moved position of the moved head 31 is detected as a new position signal P, and fed back to the position error generator 14. Thereafter, the head 31 is controlled by servo control similar to the conventional one.
Position control is performed to bring the vehicle to a target position on the track.

In that case, the added position error signal ΔPES output from the adder circuit 23 is the sum of the position error signal ΔPE from the position error generator 14 and the deceleration signal FF from the feedforward control generator 22. The amplitude of ΔPu3 increases more than Δpi, which is equivalent to an apparent increase in the gain of the position error generator 14. This eliminates overload on the position error generator 14, stabilizes settling, shortens the access time of the head 31, and enables high-speed seek.

That is, as the apparent gain of the position error generator 14 increases, the output level of the generated position error signal ΔP increases to ΔPl! shown by the solid line in FIG. 2(A). The amplitude decreases as follows. Therefore, the influence of the internal integral value is reduced, overload is eliminated, and good PID control can be performed.

As described above, by adding a deceleration signal that helps the position error signal generated by the position error signal and increasing the apparent gain of the position error generator, the position error generator is prevented from overloading. Coupled with this, the settling of the head can be stabilized. This reduces the head access time and enables high-speed seek.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 3 to 5. FIG. 3 is an explanatory diagram of the configuration of an embodiment of the present invention, FIG. 4 is an operational waveform diagram of the embodiment, and FIG. 5 is an explanatory diagram of the feedforward control generator of the embodiment.

(A) Configuration of Example In FIG. 3, 10 is a servo circuit, and 20 is a servo target. Components common to those of the conventional servo circuit shown in FIG. 6 described above are given the same reference numerals.

That is, in the servo circuit 10, 11 is a target speed generator, 12 is a current speed generator, 13 is a speed error generator,
14 is a position error generator, 15 is a position demodulation circuit, 17 is an external force correction generator, 18 is an addition circuit, 19 is a core input/fine switch, 20 is a power amplifier, and 21 is a controller.

Next, in the servo target 20, 21 is a head,
One of them is used as a servo head (indicated by 313). 32 is a VCM that drives the head 31.

33 is a disk, one of which is used as a servo disk (indicated by 333). Furthermore, regarding the feedforward control generator 22 and addition 23, the first
As explained in the figure.

The position demodulation circuit 15 in the servo circuit 10 is connected to the servo head 31 . A position signal P3 indicative of the position is generated from the read signal of , and is supplied to the current speed generator 12 and the position error generator 14. Further, from the read signal of the servo head 313, the servo head 31. is the servo disk 33.
Each time the upper track is passed, a track crossing pulse (TXPL) signal is generated and supplied to the controller 21.

The controller 21 has an internal processor (not shown) and controls the operation of each circuit in the servo circuit 10, and also calculates and sets the current cylinder (track) position from a track crossing pulse (TXPL) signal. Difference amount (i.e. remaining seek amount) D that indicates the difference between the target cylinder (track) position and the current cylinder position
Various processes such as calculation of iF and switching control of the core input/fine switch 19 are performed.

The target speed generator 11 generates a signal as shown in FIG.
The target speed v3 shown in A) is generated, and the speed error generator 13
supply to.

The current speed generator 12 generates the current speed vr of the servo head 31 from the position signal P3 input from the position demodulation circuit 15, and supplies it to the feedforward control generator 22 in this embodiment as well as the speed error generator 13. .

The speed error generator 13 generates a speed error signal ΔVt indicating the error between the target speed ■ inputted from the target speed generator 11 and the current speed Vγ inputted from the current speed generator 12.

The position error generator 14 generates a position error signal ΔP indicating the error between the current position on the track of the head 31 (servo head 31.) and the track center position from the input position signal P and external force signal F. Occur.

The position demodulation circuit 15 is connected to the servo head 31 . A position signal P is generated from the read signal and supplied to the current speed generator 12 and the position error generator 14. Furthermore, a track crossing pulse (TXPL) (No. 3) is generated and supplied to the controller 21.

The feedforward control generator 22 is also used as a feedforward control generator that generates a deceleration signal (indicated by FFv) during speed control, as will be explained later in FIG. D
A deceleration signal FFv is generated in response to iF.

The addition circuit 18 adds the speed error signal ΔV inputted from the speed error generator 13 during speed control and the deceleration signal FFv manually inputted from the feedforward control generator 22, and performs the speed control shown in FIG. 4(F). Added speed error signal Δ shown on the side
Generates VtS.

Based on the target cylinder information input from the controller 21, the external force correction generator 17 generates an external force signal F3 having the characteristics shown in FIG. do.

The position error generator 14 has a PID control circuit configuration, and uses the device signal ps configured from the position demodulation circuit 15 and the external force signal F input from the external force correction generator 17 to generate the head 31 (servo head 31.) A position error signal ΔP indicating the error between the current position on the track and the target position (center position) on the track is generated and supplied to the feedforward control generator 22 and the addition circuit 23.

The feedforward control generator 22 and the adder circuit 23 are as described in FIG. 1, and the adder circuit 23 generates the added position error signal ΔP0.

The coarse/fine switch 19 is connected to the adder circuit 18 during speed control and supplies the added speed error signal Δvis to the power amplifier 20 in response to a switching signal from the controller 21. During position control, the coarse/fine switch 19 is connected to the adder circuit 18. and supplies the added position error signal ΔPKS to the power amplifier 20.

The power amplifier 20 receives the input added speed error signal ΔV.
Control current 1 proportional to tS or added position error signal ΔP0
c is generated and supplied to the VCM32.

FIG. 5 shows an example of the feedforward control generator 22 used in this embodiment, in which the position error determination circuit 24 generates the position error determination signal S4 and the feedforward control generator 24 generates the deceleration signal FFV or FF3. It is constituted by a generating circuit 25.

In the position error determination circuit 24, 241 is a comparator, and the position error signal ΔP from the position error generator 14,
is input to the (+) terminal, and the (-) terminal is set to "0" volts. lly, ' and "V-" are power supplies.

242 is an analog switch, which is closed when the external force control signal pct from the controller 21 is on and open when it is off (the controller 21 turns on the external force control signal FC during speed control and turns it off during position control). do.

With this configuration, the position error determination signal S4 during speed control is always in an open state. In addition, during position control, if the position error signal ΔP is positive, the position error judgment signal S□ is “1”
'', and when Δpt is negative polarity, spt becomes 0''.

Next, in the feedforward generation circuit 25, 251
is a difference register, and each difference 1
The level of the deceleration signal corresponding to DiF is stored. That is, in response to the difference amount DiF input from the controller 21, as shown in FIG. 4(c) during speed control, the deceleration signal FF is at the "0" level during acceleration control;
is output, and during deceleration control, a deceleration signal FF with the characteristics shown in the figure is output.
During the position control period, a "0" level or a constant level is output.

252 is a D/A converter, which receives the digital deceleration signal FFv input from the difference register 251;
, is D/A converted.

Reference numeral 253 denotes an operational amplifier, which constitutes an adder circuit by an output terminal, a feedback resistor 254 connected to the (-) terminal, and an offset compensation resistor 255 connected to the (+) terminal.

256 to 258 are resistances for coupling and adjustment, and resistance 25
6 adjusts the deceleration signal FFv from the D/A converter 252 to a predetermined level and supplies it to the operational amplifier 253. The resistor 257 adjusts the current speed Vγ from the current speed generator 12 to a predetermined level and supplies it to the operational amplifier 253. resistance 2
58 adjusts the position error determination signal S from the position error determination circuit 24 to a predetermined level and supplies it to the operational amplifier 253.

With this configuration, during speed control, the D/A converter 25
The sum signal of the deceleration signal F F v from 2 and each signal proportional to the current speed Vr from the current speed generator 12 is the deceleration signal F
It is output as Fv. Note that the position error determination signal SPt
Since it is in an open state, it is not involved in the deceleration signal FFv during speed control.

In this way, by using the deceleration signal FFV to which a signal proportional to the current speed VT is added, speed control can be made more stable and faster than in the case of a deceleration signal to which the current speed Vγ is not added.

Furthermore, during position control, the current speed ■γ generated by the current speed generator 12 becomes "01", and the deceleration signal FFv generated by the D/A converter also becomes "0". As shown in FIG. 4(E), a signal proportional to the device error determination signal S□ constituted by the position error determination circuit 24 is output as the deceleration signal Ft's.

(B) Operation of the Embodiment The operation of the embodiment shown in FIG. 3 will be explained with reference to the operational waveform diagram of FIG. 4.

During speed control, the feedforward generation circuit 25
This corresponds to the feedforward control generator 16 in the conventional servo circuit shown in the figure, and generates the deceleration signal F F v. As explained earlier, this deceleration signal FFv adds the current speed Vγ component to the conventional deceleration signal FF, so it is possible to perform more stable and faster speed control than the conventional servo circuit. It is.

However, since the speed control operation itself, including acceleration control and deceleration control, is performed in the same manner as the speed control operation of the servo circuit explained in FIGS. 5 and 6, detailed explanation thereof will be omitted. The following will mainly explain the position control operation.

When the speed control ends, the current speed VT generated by the current speed generator 120 becomes "0".

The controller 21 detects the end of speed control since the current speed Vr input from the current speed generator 12 becomes "0", and switches the core input/fine switch 19 to the fine side, that is, to the addition circuit 23 side. . At the same time, an external force control signal FC3 is supplied to the position error determination circuit 24.
is turned on and its analog switch 242 is closed.

The position demodulation circuit 15 is connected to the servo head 31 . From the read signal of servo head 31. position signal P3 indicating the position of
is generated and supplied to the position error generator 14.

On the other hand, the external force correction generator 17 generates an external force signal F having the characteristics shown in FIG. 4(D) based on the target cylinder information input from the controller 21, and supplies it to the position error generator 14. The external force signal F, is generated only during the settling period as shown.

The position error generator 14 receives the position signal P from the position demodulation circuit 15 and the external force signal F from the external force correction generator 17, and uses the PID control circuit configuration to
Servo head 31. A position error signal ΔP indicating the error between the current position on the track and the target position (center position) of the track is generated and supplied to the feedforward position error determination circuit 24 and addition circuit 23 (see FIG. 4). (B)
(See Δpt on the position control side).

Due to the circuit configuration and operation described above with reference to FIG. 5, the position error determination circuit 24 becomes "1" when the polarity of the input position error signal Δpro is positive, and becomes "O" when the polarity is negative. Position error judgment signal SP! is generated and supplied to the feedforward generation circuit 25 (FIG. 4(E)).

On the other hand, if the difference amount DiF from the controller 21 input to the feedforward generation circuit 25 is “0”
The current speed Vr from the current speed generator 12 is also “0”.
It is.

As a result, the feedforward generation circuit 25 is configured as shown in FIG. 4 (E
) as shown in FIG.
It is generated as s and supplied to the adder circuit 23.

The addition circuit 23 adds the position error signal ΔP input from the position error generator 14 and the deceleration signal FF input from the feedforward generator 25, and performs the addition shown on the position control side in FIG. 4(F). generating a position error signal Δpts;
Power amplifier 2 via core input/fine switch 19
Supply to 0.

The power amplifier 20 generates a control current 1c proportional to this added position error signal Δpts and supplies it to the VCM 32.
The head 31 is driven.

The position of the moved head 31 is detected as a new position signal P by the position demodulation circuit 15 and fed back to the position error generator 14.

Below, the above-mentioned position demodulation circuit 15 - position error generator 14 -
Feedforward control generator 22. Adding circuit 23 - core input/fine switch 19 → power amplifier 20 → vC
The position control operation by the loop of M32→head 31 (servo head 31.) is repeated, and as shown on the position control side of FIG. 4(A), the head 31 (servo head 31.
) is positioned at the center of the target track.

Although one embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this embodiment. for example,
The feedforward generation circuit 25 may be provided separately for speed control and position control, and furthermore, the current speed Vγ supplied to the feedforward generation circuit 25 may be omitted. Further, the ON period of the external force control signal FC, which is generated by the controller 21 during position control, may be set to infinity (longer than the settling period).

〔Effect of the invention〕

As explained above, according to the present invention, the following effects can be obtained.

(1) A deceleration signal that helps the position error signal generated by the position error generator is added to increase the apparent gain of the position error generator, which prevents the position error generator from overloading. Coupled with this, the settling of the head can be stabilized.

(2) According to (1) above, the access time of the head can be shortened and high-speed seek can be realized.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the basic configuration of the present invention, FIG. 2 is an operational waveform diagram of the present invention, FIG. 3 is an explanatory diagram of the configuration of one embodiment of the present invention, and FIG. 4 is an illustration of the same embodiment. FIG. 5 is an explanatory diagram of the configuration of the feedforward control generator of the same example. FIG. 6 is an explanatory diagram of the configuration of the conventional servo circuit. FIG. 7 is an explanatory diagram of the configuration of the conventional servo circuit. FIG. In FIGS. 1 and 3, IO... Servo circuit, 11... Target speed generator, 1
2...Current speed generator, 13...Speed error generator,
14...Position error generator, 5...Position demodulation circuit,
17... External force correction generator, 18... Addition circuit, 19
...Core input/fine switching device, 20...Power amplifier, 21...Controller, 22...Feedforward control generator, 23...Addition circuit, 24...
Position error determination circuit, 25... Feedforward generation circuit, 3o... Servo target, 31... Head, 31
3... Servo head, 32... Voice coil motor (VCM), 33... Disk, 333... Servo disk. Figure 2

Claims (1)

[Claims] 1. The head (31) of the magnetic disk device is controlled by the speed control and position control using the servo circuit (10).
33) In a position control method when performing seek control to position the head (31) at the target track position above, (a) during position control, a position error signal indicating the error between the current position on the track of the head (31) and the target position is sent; (b) a feed forward that generates a deceleration signal having a characteristic of increasing the amplitude in the polar direction in response to the polarity of the position error signal generated by the position error generator (14); Control generator (2
(c) Addition of adding the position error signal generated by the position error generator (14) and the deceleration signal generated by the feedforward control generator (22) to generate an added position error signal for position control. A position control system comprising a circuit (23).