JPH0358357A - Magnetic head speed controller and magnetic disk device - Google Patents

Abstract

PURPOSE:To promote the following property of a speed control at the time of changing for an attenuation mode in the vicinity of a target track by providing a means for performing a gain compensation amt. of acceleration corresponding to a speed deviation when the attenuation mode is turned on. CONSTITUTION:This device is provided with a feed forward gain compensation adjuster 30. This compensation adjuster 30 is inputted with a position deviation and a speed deviation to decide a feed forward compensation amt. corresponding to an amt. of the speed deviation when the position deviation becomes smaller than a preset attenuation mode changeover position. This is outputted to an adder 27 for only a predetermined time corresponding to the position deviation (number of moving tracks) so as to correct the usual feed forward. By this method, the following property of the speed control at the changeover time for deceleration can be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head speed control device and a magnetic disk device that move a magnetic head to a target track on a magnetic disk using a sector servo method.

[Conventional technology]

In magnetic head speed control using the sector servo method, the magnetic head detects a sector servo signal area provided radially on the surface of the disk, determines the position and speed of the magnetic head based on the position information read from the signal area, and calculates the position and speed of the magnetic head based on the position information read from the signal area. Based on this, the magnetic head is moved from the starting point to the target track at a predetermined speed pattern.

By the way, in conventional magnetic head speed control that does not rely on the sector servo method, the acceleration that is obtained by differentiating or differentiating the target speed in the deceleration process of speed control in advance is added to the speed error signal as acceleration feedforward ( JP-A-58-182169, JP-A-Sho 5
9-117760, Japanese Patent Application Laid-open No. 61-39985)
. According to this, accurate speed control can be performed without widening the control band related to high-speed response. therefore,
When switching from speed control to position control near the target track, it is possible to prevent the overcoat phenomenon in which the magnetic head moves beyond the target track position and the undershoot phenomenon in which the magnetic head stops short of the target track.
Access time can be shortened. Furthermore, since the amount of speed feedback is reduced and abnormal vibrations of the positioning mechanism induced by this are reduced, head crashes can be prevented.

In addition, the amount of acceleration feedwaward is sequentially decreased according to the number of moving tracks and the difference in the number of tracks between the target track and the current number of tracks (
JP-A-58-211366, JP-A-59-19857
No. 2, Japanese Unexamined Patent Publication No. 1682/1982). according to this,
In particular, the head speed can be controlled smoothly and stably near the target track. Therefore, overshoot from the target track can be prevented from occurring.

Furthermore, conventionally, when the target speed is smaller than a predetermined value, the target acceleration is increased, and when the target speed exceeds a predetermined value, the target acceleration is decreased (Japanese Patent Application Laid-Open No. 1983-1989-1).
122709). According to this, when the target speed is large and the tracking accuracy becomes poor, the target acceleration becomes small, making it easier to follow the target speed.

Furthermore, as described in JP-A-61-122708, the target speed can be changed stepwise by adaptively changing the feedforward amount in a stepwise manner depending on the sign of the error between the target position and the actual position. This makes it possible to reduce the error that occurs immediately after a change to .

[Problem to be solved by the invention]

However, since the sector servo method can only obtain speed information at discrete time intervals, if the above-mentioned conventional technology is applied as is, the control band of speed feedback control will be narrowed, and speed control when switching to deceleration mode near the target track will be difficult. There is a problem in that the followability is poor and overshoots and undershoots occur.

In other words, the speed detection using the sector servo method uses a magnetic head to detect the position of sector servo signal units arranged radially at intervals on the magnetic disk surface. It is designed to calculate the speed of Therefore, speed information can only be obtained at regular sampling intervals.

Also, the '6N calculation processing time of speed feedback control,
During the sampling period, the manipulated variable is held at a constant value. When these time delay elements overlap, the control band of speed feedback control becomes narrow, and there is a problem that fine control with good followability cannot be performed.

In other words, since the time constant of speed control is large, it takes extra time to reduce the deviation between the target speed and the detected speed and make them follow the target speed. In particular, when the vehicle approaches the target track and the time to switch from constant speed mode to deceleration mode or directly from acceleration mode to deceleration mode falls in the middle of the sampling time, the necessary deceleration control will be delayed. As a result, the overshoot with respect to the target speed becomes large and it takes time to track the target speed, resulting in an overshoot phenomenon where the magnetic head moves beyond the target track position or an undershoot phenomenon where the magnetic head stops short of the target track. There is a problem with doing so.

An object of the present invention is to solve the above-mentioned conventional problems.In other words, it is an object of the present invention to provide a magnetic head speed control device for a sector servo type magnetic disk and a magnetic The purpose is to provide disk devices.

(Means for solving illM) In order to achieve the above object, the present invention detects a sector servo signal provided on a magnetic disk, determines the position and speed of a magnetic head based on the detected signal, and provides A target speed and a target acceleration are determined according to the positional deviation between the target position and the current position of the magnetic head, a speed command is determined according to the deviation between the target speed and the current speed, and the speed command is set according to the target acceleration. In a magnetic head speed control device that corrects the moving speed of the magnetic head based on the corrected speed command, detecting the switching of the deceleration mode based on the positional deviation reaching a predetermined value or less; The present invention is characterized in that a compensation adjusting means is provided for correcting the speed command by an amount of acceleration compensation corresponding to the speed deviation for a time period corresponding to the magnitude of the position deviation.

[Function] With this structure, according to the present invention, the above object is achieved by the following function.

That is, immediately after switching from acceleration or constant speed mode to deceleration mode, an acceleration compensation amount (feedforward) corresponding to the speed deviation is added, so speed overshoot is quickly reduced. Immediately after entering the deceleration mode, the deceleration mode is effectively continued for a predetermined time period during which the speed deviation is greatest (for example, the time determined by the number of moving tracks), so the above speed deviation is completely eliminated by the time the target track is reached. It can be suppressed to As a result, when switching from speed control to position control near the target track, it is possible to prevent the overshoot phenomenon in which the magnetic head moves beyond the target track position and the undershoot phenomenon in which the magnetic head stops short of the target track. I can do it.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 shows a schematic diagram of the main parts of a magnetic head speed control device according to an embodiment of the present invention. As shown in the figure, each surface of a disk-shaped magnetic disk 1 is equally divided into a plurality of fan-shaped sectors 2 for recording data. A sector servo signal section 3 is provided at the boundary between these sectors 2. Track numbers and position signals are recorded in this radially arranged sector servo signal section 3. The track position in the radial direction of the magnetic disk 1 is specified by this track number. Further, positional deviation from the center of the track width within the track can be recognized by the position signal. Further, the magnetic disk 1 is rotated at a constant rotation speed by a spindle motor (not shown).

A magnetic head 4 is provided on each surface of the magnetic disk 1 so as to float and face each other. The magnetic head 4 is attached to the carriage 5
The carriage 5 is supported by a voice coil motor 6. By driving this voice coil motor 6, the magnetic head 4 can be moved to any position in the radial direction of the magnetic disk l.

Next, the speed control system of the magnetic head will be explained. The sector servo signal read by the magnetic head 4 is input to the position detection means IO. The sector servo signal is input every several hundred μsec in accordance with the discretely provided signal section 3. The position detecting means 10 includes a track number demodulating circuit 11, a position signal demodulating circuit 12, an A/D converter l3, and an adder l4, and these detect the magnetic head 4.
Find the radial position of and output position information (current position). This position information is taken into the speed calculation circuit 15, and the speed of the magnetic head 4 (
@ Current speed) is detected and output.

On the other hand, the adder 16 calculates the difference between the given target track (position) and the current position. The positional deviation obtained thereby is input to the speed control system and the acceleration control system.

The speed control system includes a target speed table 17 and a speed deviation gain setter 18. Target speed setter 17
outputs a target speed command corresponding to the input positional deviation according to a preset relationship between the deviation and the target speed shown by the solid line in FIG. 2. Note that the target speed setter 17 can be realized as a table using a ROM or the like.

The target speed thus output is input to an adder 19, where the deviation from the current speed is determined. and,
A speed deviation gain setter 18 multiplies the speed deviation by a predetermined gain, and outputs the result to a D/A converter 21 via an adder 20 as a speed operation amount command. The D/A converter 21 holds the speed operation amount, converts it into a continuous analog amount (in this embodiment, the excitation current of the motor 6), and outputs it to the power amplifier 22. The power amplifier 22 drives the motor 6 according to the speed operation amount signal, and moves the magnetic head 4 according to the target speed.

On the other hand, the acceleration control system includes a target acceleration setter 25 and a feedforward gain setter 26. The target acceleration setter 25 operates according to the preset relationship between the positional deviation and the target acceleration shown by the single point 1fi line in FIG.
The target acceleration corresponding to the input positional deviation is output.

Note that during deceleration, negative acceleration is output. Further, like the target speed setter 17, it can be configured as a table. The target acceleration determined in this way is multiplied by a predetermined gain in the feedforward gain setting device 26,
It is outputted to the adder 2o via the adder 27. As a result, the speed operation amount is corrected in advance using the target acceleration in accordance with the increase/decrease in the target speed, thereby improving the followability of the speed control.

That is, in order to improve the accuracy of following the target speed through speed control and guide the vehicle to the target track with high precision, it is necessary to make the control band as wide as possible. but,
In many cases, it is not possible to obtain a wide range due to the phase margin of the speed control loop and the resonance frequency of the positioning mechanism system. Therefore, the acceleration obtained by differentiating or differentiating the target velocity is stored in advance as the target acceleration, and the target acceleration is determined by referring to the target acceleration from the target acceleration table or the like according to the positional deviation. This is multiplied by the feedforward gain to calculate the acceleration feedforward operation amount for reducing the speed deviation. This manipulated variable is added in parallel to the manipulated variable determined based on the speed deviation. By adding the acceleration feed in this manner, a drying amount, that is, a current corresponding to the currently required target speed, is immediately added. Therefore, it is possible to compensate for a time delay, that is, a phase delay, in a loop that controls the speed by feeding back the current speed, and it is possible to perform accurate speed control without widening the speed control band. An arbitrary amount of acceleration feedforward can be added by adjusting the forward gain. For example, if the acceleration feedforward is larger than the amount determined by the target force 11 speed, a larger deceleration than the target speed is possible, and the speed can be lower than the target speed. Note that the above-mentioned control is performed discretely in synchronization with the sampling interval at which the sector servo signal is input.

Here, the features of the present invention will be explained.

In this embodiment, the feed forward gain compensation adjuster 30
It is characterized by having the following. This compensation adjuster 30 inputs the position deviation and speed deviation, and when the position deviation becomes smaller than a preset deceleration mode switching position, it determines the amount of feedforward compensation corresponding to the speed deviation. is outputted to the adder 27 for a predetermined time according to the positional deviation (number of moving tracks) to correct the normal feedforward and improve followability of speed control during deceleration switching. It is.

The feedforward compensation operation of the above embodiment will be explained in detail with reference to FIG. FIG. 3(a) shows the time course of acceleration feedforward. FIG. 2(b) shows the time course of target speed and actual speed. These are examples of cases where the acceleration mode is immediately switched to the deceleration mode, and there is no constant speed mode. Further, acceleration feedforward and target speed actually exist only in discrete time determined by the number of sectors and the number of revolutions, but for the sake of clarity, they will be explained here as continuous time data.

In FIG. 3(a), the acceleration mode is in effect until time t1, and there is no acceleration feedforward. Time t,
Time t when switching from acceleration mode to deceleration mode at
The mode is a mode in which the vehicle is decelerated at a constant acceleration from to time t, and the acceleration feedforward is a constant value α determined based on the acceleration found by differentiating or subtracting the target speed. The period from time t2 to time t3 is a mode in which acceleration is decreased to reduce changes in progress in order to smoothly decrease speed near the target track.

In FIG. 3(b), in the case (i) in which compensation adjustment of acceleration feedforward is not performed, an overshoot with respect to the target speed occurs from time t1 when the acceleration mode is switched to the deceleration mode, and the speed deviation suddenly increases. Since the speed where the overshoot occurs is greater than the target speed,
Sufficient deceleration cannot be achieved with the predetermined acceleration feedforward α for the rotational speed. Therefore, speed feedback control needs to work for this, but since these control bands are narrow, it is not possible to reduce the speed deviation sufficiently quickly.

On the other hand, when the acceleration feedforward shown in FIG. 3(b) is used as a compensation adjustment (ii),
), from time t1 when the mode is switched to time t
While the value is 0, the acceleration feedforward is temporarily increased by the gain compensation addition to match the speed deviation. Therefore, the speed deviation is rapidly suppressed and the target speed can be followed in a short time. Once the target speed is approached, the relationship between the target speed and the target acceleration is established, so the gain compensation may be discontinued.

FIG. 4 shows a flowchart of the processing procedure in the feedforward gain compensation adjuster 30.

First, in step 101, it is determined whether the acceleration mode or constant speed mode has ended by looking at the speed deviation. If the vehicle is decelerating, it is determined whether the timer 110, which was started immediately after the mode switching, has timed out. The time t of this timer. is set as shown in FIG. 5. In FIG. 5, the horizontal axis is the number of moving tracks and the vertical axis is the time of this timer.

When the number of moving tracks is large, the timer time is the maximum value t. The time t of the timer increases as the number of required moving tracks decreases. shorten. This is based on the fact that when the number of moving tracks is large, the maximum speed is large, so there is a large overshoot when switching from acceleration mode or constant speed mode to deceleration mode, and it takes time to reduce the speed deviation. There is. Also, since the deceleration time is long,
There is no problem in choosing 1o for a long time. On the other hand, when the number of moving tracks decreases, the maximum speed also decreases and the overshoot decreases, so it takes less time to reduce the speed deviation. Also, the deceleration time is short, so t. must be kept short.

If the time is not up, a large acceleration gain compensation amount is selected with reference to the table 111 shown in FIG. 6 according to the magnitude of the speed deviation. In FIG. 6, the horizontal axis is the speed deviation, and the vertical axis is the acceleration gain compensation amount. Normally, when the speed deviation is small, this gain compensation amount is k. shall be. On the other hand, if the speed deviation increases, this corresponds to an increase in the target speed, so the acceleration gain compensation amount is increased. However, it is desirable that this gain compensation amount be saturated at a predetermined value.

Incidentally, although no explanation has been given regarding the switching from the constant speed mode to the deceleration mode, the same applies in this case as well.

Further, as shown in FIG. 1, the A/D converter 13 and the D
It is desirable that each part on the digital side with the /A converter 21 as a boundary is controlled by a digital controller using a microcomputer.

〔Effect of the invention〕

As explained above, when switching to deceleration mode, acceleration gain compensation is performed for the amount of acceleration according to the speed deviation for a time corresponding to the position deviation. Alternatively, there is an effect that speed deviation that increases rapidly immediately after switching from constant speed mode to deceleration mode can be quickly reduced. For this reason,
Since it will be possible to accurately follow the target speed,
It is possible to prevent an overshoot phenomenon in which the magnetic head moves beyond the target track position when switching from speed control to position control near the target track, and an undershoot phenomenon in which the magnetic head stops short of the target track. As a result, access time can be stabilized and shortened.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the main part of a magnetic head speed control device according to an embodiment of the present invention, FIG. Figure 1 is a time chart explaining the operation of the embodiment, Figure 4 is a flowchart showing the processing procedure of the feedforward gain compensation adjuster of the embodiment in Figure 1, and Figures 5 and 6 are respectively related to the flowchart in Figure 4. It is a line diagram of an operation explanatory diagram. DESCRIPTION OF SYMBOLS 1... Magnetic disk, 3... Sector servo signal part, 4... Magnetic head, 10... Position detection means,
15... Speed calculation circuit, 17... Target speed setter, 20... Speed deviation gain setter, 25... Target acceleration setter, 26... Feedforward gain setter, 30.・
・Feedforward gain compensation adjuster.

Claims (1)

[Claims] 1. Detect the sector servo signal provided on the magnetic disk, determine the position and speed of the magnetic head based on the detected signal, and calculate the positional deviation between the given target position and the current position of the magnetic head. A target speed and a target acceleration are determined accordingly, a speed command is determined according to the deviation between the target speed and the current speed, the speed command is corrected according to the target acceleration, and the magnetic head is adjusted according to the corrected speed command. in a magnetic head speed control device that controls a moving speed of a magnetic head, detecting switching of a deceleration mode based on the positional deviation reaching a predetermined value or less;
A magnetic head speed control device comprising a compensation adjustment means for correcting the speed command by an amount of acceleration compensation corresponding to the speed deviation for a time period corresponding to the magnitude of the position deviation. 2. A magnetic head that is placed close to the surface of a rotating magnetic disk and is capable of reading and writing data including sector servo signals recorded on the magnetic disk, and a drive device that moves the magnetic head in the radial direction of the magnetic disk. and position detection means for detecting the current position of the magnetic head based on the sector servo signal read by the magnetic head; speed calculation means for calculating the current speed of the magnetic head based on the interval of the position detection signal; positional deviation calculating means for calculating a positional deviation between a target position of the head and the current position; a target speed setting means for setting a predetermined target speed according to the positional deviation; and between the target speed and the current speed. A speed command setting means for outputting a speed command according to the deviation to the drive device; a target acceleration setting means for setting a predetermined target acceleration according to the positional deviation; and a speed command setting means for outputting the speed command according to the target acceleration. In a magnetic head speed control device including an acceleration correction means for correcting, the position deviation and the speed deviation are input, and when the position deviation reaches a predetermined value or less, it is determined that the deceleration mode is to be switched, and the position deviation is corrected. A magnetic head speed control device comprising an acceleration compensation adjusting means for further correcting the corrected speed command by an amount of acceleration compensation corresponding to the speed deviation for a corresponding time. 3. A magnetic disk device comprising the magnetic head speed control device according to claim 1 or 2.