JPH0273578A - Control method for head positioning speed - Google Patents

Abstract

PURPOSE:To attain high speed and stable head positioning by deciding an optimum target speed curve which stably makes a settling out of previously prepared plural target speed curves, adopting it and executing the head positioning when being in use. CONSTITUTION:A head positioning movable range is previously devided into plural intervals, one point in one of the intervals is selected, a target position is decided, a positioning quantity from a decided positioning position is decided and the head positioning is executed. In this case, the plural target speed curves which are previously prepared for the movement quantity of each head are set in order, and used it, an H level width and an L level width are counted with a count-lock signal on a positioning stability decision device 2 in a microcomputer 1, the target speed curve when the difference of the counted numbers is within an allowable value is adopted and decided by a target speed initializing device 3. This operation is repeatedly executed for every interval positions being devided into the plural intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a head positioning speed control method in a magnetic disk device, etc., and in particular, to a head positioning method that enables high-speed and stable head positioning to a target track. Regarding speed control method.

(Prior Art) Conventionally, as a smooth and stable head positioning speed control method for magnetic disk devices, Japanese Patent Laid-Open No. 60-1
As shown in Japanese Patent No. 682, the microcomputer in the device has 1. A target speed curve is set in advance such that the acceleration decreases within a certain distance from the target position (target track), and by moving the magnetic head along this target speed curve, the magnetic head is stably moved to the target position. There is a known method for positioning V
By taking into account conditions such as variations in the driving force of the CM (voice coil motor) and reductions in the driving force due to fluctuations in the drive voltage (power supply), access can be made smoothly and stably even in the event of such variations or reductions. In order for this to occur, a sufficiently slow (slowly sloped deceleration curve) target speed curve is set.

[Problem to be solved by the invention]

By the way, most head positioning systems in magnetic disk devices are servo systems, except for devices with low storage capacity layers. In recent years, as system performance has improved, the demand for shortening the magnetic head positioning time for magnetic disk devices has become a major issue, as has the demand for reducing the size of the device.

Since the mass of the head group to be moved is uniquely determined, reduction of head positioning time is ultimately achieved by increasing the driving force (driving torque) of the voice coil motor. In other words, in order to shorten the access time, a high-speed target speed curve is created in which the head is moved from the starting position to near the destination position at high speed, and then decelerated as rapidly and sharply as possible from near the destination position to the destination position. It is necessary to perform access servo, which requires the ability to generate a strong driving torque that enables control along the deceleration curve of the cylinder and inclination. Otherwise, control along the high-speed target speed curve will not be performed due to the drop in drive torque, and in particular, if the CM drive force (torque) decreases at or near the target position to be positioned, the target position An unstable positioning condition such as so-called overshoot occurs in which the positioning distance exceeds too much. Therefore, as mentioned above, for safety reasons, conventionally, in order to enable stable access servo that does not cause overshoot even if the drive torque slightly decreases, a target speed curve for low speeds with a gentle slope of the deceleration curve has been developed. is used. However, although this allows stable head positioning even when the driving force is small, a slow target speed is set, so there is a problem in that positioning takes a long time.

This reduction in driving torque is due to variations between devices,
In addition to being caused by a drop in power supply voltage during use, it is also caused by the position of the actuator's voice coil. In other words, the strength of the driving magnetic field at both ends of the voice coil's movable range (head moving range) that moves the head from the outermost track to the innermost track of the disk is greater than the strength of the driving magnetic field at the center of the movable range. Since the magnetic field is lower (which causes a so-called magnetic field droop), the driving torque (for a given current value) received by the voice coil is also lower at both ends than at the center.

In order to obtain sufficient driving torque even in the relatively low magnetic field parts at both ends, the strength of the overall magnetic field has been increased to increase the driving force (
Although it is conceivable to increase the torque (torque), this would require a larger VCM magnet, which would not be compatible with the above-mentioned demand for miniaturization of the device size.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to fully take into account the changes in the magnitude of the VCM driving force that are unique to the device and occur during each use and at each moving position of the head. The object of the present invention is to provide a head positioning speed control system using a small actuator, which enables high-speed and stable head positioning by adopting a target speed curve corresponding to the VCM driving force.

[Means for Solving the Problems] In order to achieve the above object, the head positioning speed control method of the present invention sequentially uses a plurality of target speed curves prepared in advance at the time of starting the head positioning device and before using the head positioning device. means for (repeatedly) attempting to position the head using a method; and means for selecting, based on the trial results, a target speed curve for which head positioning is performed with stability within an allowable value as the optimum target speed curve; and means for performing head positioning along the determined optimal target velocity curve.

Further, the range in which the head can move (the entire track range) is divided into a plurality of sections (for example, 14 sections), and the optimum target speed curve is selected for each section.

Within each divided section, a positioning target position is determined, each target position is associated with a plurality of head movement amounts (access distances), and the total movement amount and all target positions are determined.
The optimal target speed curve is selected for each.

As mentioned above, the stability of positioning and the positioning speed are affected by the slope near the end point of the target speed curve, so the 14 curves above were created by varying the degree of slope near the end point. It becomes.

[Effect]

The effect based on the above configuration will be explained.

As mentioned above, if the drive torque fluctuates (decreases) due to variations in drive force from device to device, a drop in power supply voltage, differences in drive force at each position even within the range of head movement, and even differences in environmental temperature, etc. If only one type of target speed curve is used, it will not match the driving force at that time and place, and as a result, positioning will become unstable and overshoots will occur. Upon each use,
If we can measure the driving force at that time and place,
You can select a target speed curve that matches the driving force.
It is possible to prevent such overshoot and perform stable positioning.

In the present invention, each time the power supply voltage is supplied when the apparatus is started, a head positioning operation is actually attempted using a plurality of target speed curves prepared in advance, for example, by a command from a test program built in a microcomputer. , the head positioning process at that time is monitored, and if unstable positioning such as overshoot occurs, the target speed curve used at that time is determined to be inappropriate, and the overshoot is stabilized when it is below the allowable value. When the vehicle is positioned at , it is determined that the target speed curve used at that time is the optimal one. This determination is made, for example, by digitally converting a head position analog signal successively output from the head and reading this with a microcomputer.

The target velocity curve selected as the optimum one is used when performing head positioning during subsequent use of the apparatus.

The head movement range (including from the outermost track to the innermost track of the disk) is divided into a plurality of sections, and for each section, an optimal target speed curve suitable for that section is selected. In addition, a target position (access end point) is determined within each section, and a plurality of head movement amounts (samples of various access amounts) are made to correspond to a target position within one section.
For each amount of movement, an optimal speed curve suitable for that amount of movement is selected. A group of optimal speed curves selected in this way is placed in a table (memory).

During use, when there is an access command for an arbitrary amount of movement to an arbitrary target position (track), the optimum target speed curve corresponding to the amount of movement closest to the amount of movement in the section including that target position is retrieved from the table. Since access control is performed based on this optimal target speed curve, stable positioning is performed.

The optimal target speed curve selected in this way is subject to variations in driving force from device to device, differences in driving force between the center and both ends of the head movement range, and fluctuations in the power supply voltage to the device. This method directly recognizes the actual operating conditions, such as positioning settling fluctuations based on environmental temperature, environmental temperature, etc., and then provides the best target speed under such conditions.

Therefore, there is no need to use a target speed curve with a gentle slope for the deceleration section in consideration of safety as in the conventional technology, and a target speed curve that is as high as possible is always used to achieve stability and the shortest access time. The target speed can be automatically set, control that exceeds the VCM drive capacity can be avoided, and stable and high-speed positioning settling can be performed with fewer malfunctions using a small device.

〔Example〕

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

First, the basic concept of the present invention will be explained with reference to FIG.

FIG. 4 is a diagram illustrating a flow of determining whether or not the head positioning is stable based on the VCM drive difference.

First, in step 41, the position to be determined by the VCM drive (that is, the stability during head positioning changes depending on the VCM drive force, so the VCM drive force that provides the optimum stability is searched for. position). This position is, for example, a certain point (midpoint) in one of the sections into which the head positioning movable range is divided into 14 in advance. next,
In step 42, head positioning is performed. In this case, in step 43, the positioning amount from the positioning position determined in step 41 is determined, for example, three different head movement amounts (positioning amounts) are determined, and this head positioning is executed. At this time, a plurality of (14) target speed curves prepared in advance are sequentially set and used for each head movement amount (step 44).
, Initially, the center curve among the 14 target speed curves is set. Then, in step 45, a stability determination is made for the positioning performed using each target velocity curve. Here, the head position analog signal is converted to a digital signal, this signal is counted by the microcomputer's count clock signal, the count amount at high level and the count amount at low level are compared, and the difference is determined as the tolerance value. When it is within the range, it is determined that stable positioning has been achieved. If it is determined in step 45 that the distortion is stable (above the allowable value), the process returns to step 44.
The next curve is set among the curves, and the determination is repeated until a stable curve appears. If the stability is determined to be good, in step 46, the target speed curve determined to be good in step 45 is determined (adopted) as the optimal target speed curve. This operation is repeated for all the 14 section positions (set at the beginning), and when it is determined that measurements have been performed at all positions in these sections (step 47), the access attempt ends. .

The above series of operations is executed every time the power is turned on.
In addition, since the process ends before the device becomes ready for use, it does not cause any trouble to the user of the device.

Next, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows a basic configuration block diagram of a head positioning speed control circuit. Reference numeral 1 denotes a microcomputer section, which is comprised of a positioning stability determiner 2, a target speed initial determiner 3, a target speed generator 4, and an access controller 5. 6 is a head position detector, 7 is an actual speed detector, 8 is a speed error generator, 9 is a position error generator, and 10 is a speed control? I/
Position control switch, 11 is VCM drive circuit, 12 is VCM
, 13 is a position information reading head, 14 is a recording disk (position information storage disk), and 15 is a digital position signal conversion circuit. The circuits added in the present invention are a positioning stability determiner 2 and a target speed initial setter 3.

The operation of the embodiment shown in FIG. 1 will be explained below while comparing it with the prior art.

As shown in FIG. 1, when a movement command is issued from the controller, the target speed generator 4 generates a target speed curve 21 as shown in FIG. 2 for each movement amount (seek distance). The current position and actual speed of the head 13 on the surface of the disk 14 are detected by a head position detector 6 and an actual head speed detector 7 connected to its output side. What is the target speed and actual speed according to the target speed curve?
The speed error signal is compared by the speed error generator 8 and applied to the VCM drive circuit 11 via the speed/position control switch 10, whereby the head 13 is set at a speed along the target speed curve according to the amount of movement. Accordingly, movement (access) is performed. At this time, if speed control is performed while sufficiently following the target speed as shown by curve 21 in FIG.
Head position analog signal (output of head position detector 6)
6a is shown as 6a-1 in FIG. 3 (details of section A in FIG. 2), and stable positioning settling can be obtained.

However, if the VCM driving force decreases due to the causes mentioned above (magnetic field sagging at the entrance and exit of the travel stroke, variations depending on the device, and a drop in the electric voltage), the VCM driving force may be lowered, and as a result, the target speed may not be fully tracked. If you reach the destination position,
As shown at 6a-2 in FIG. 3, an overshoot occurs in the head position analog signal, and positioning is performed with unstable settling.

The above is the operation in the conventional technology.

In contrast, in this embodiment, positioning is performed at high speed and always with stable settling as described below.

First, in this embodiment, when the power supply voltage is supplied to the device, the number of rotations of the disk reaches the required number of rotations, and preparations are complete, a test is conducted in advance before the device is used by the user, and the driving force is increased. Determine the optimal target speed curve according to the The test is performed as follows. First, when the above preparations are complete, the microcomputer controls the
The head movable range (from the outermost track to the innermost track of the recording disk 14, for example, about 900 tracks) is divided into regions of about 14 sections, for example. In addition, in the case of multiple heads having different amounts of movement, for example, if the amount of movement is 5.
．． 10. For each case of about 31 tracks, set multiple types of target speed curves as shown in 21 in Fig. ) in advance. The shape (degree of inclination) of the target speed curve 21, especially in the vicinity of the target position (target position, access end position), is an important factor for stable positioning, so the shape of this part (deceleration part) ( A variety of different slopes are prepared. Here, one of the plurality of sections (14 sections) (e.g., the first section) is first taken up, and by selecting one point (e.g., the middle point) within the section, the location to be positioned (target position) is determined. . This target position is accessed using the plurality of head movement amounts (three types with the number of tracks of 5° and 10.31), but first, the plurality of (14) target velocity curves 21 are Among these, an average curve (for example, the one with an intermediate slope of the deceleration section) is selected and access is attempted using this curve. At this time, the D/A converter 15 inputs a digital position signal shown at 15a-1 or 15a-2 in FIG. 3 to the microcomputer 1. This digital position signal is a digitized version of the head position analog signal, and as shown in Figure 3(a), when there is no overshoot (when settling is stable)
The period of H level and L level is almost the same, but
When there is an overshoot (settling is unstable) as shown in FIG. 3(b), the H level period is longer than the L level period. Therefore, the settling detector (positioning stability judger) in the microcomputer 1
2, the count clock signal 2a (FIG. 3)
The level width and L level width are counted, and if the overshoot is large and the difference in count exceeds the allowable value, it is determined that the target speed curve at that time is inappropriate, and a different target speed curve is determined. , and try positioning again using the same target position and the same amount of movement. The same access is repeated using various target speed curves, and the target speed curve when the difference in the above counts is within the tolerance value is
The target speed initial determiner 3 determines that this curve should be adopted as a curve passing through the divided sections and moving speed at that time (a curve in which stable settling is performed). Thereafter, in the same way, for all the 14 divided sections, the various movement amounts (3 sample values, 5
, 10, 31) racks), and select (determine) the optimal target speed curve for each divided section for each amount of movement.

Each optimal target speed curve adopted in this way is stored in a table (memory) in the target speed generator of the microcomputer. As can be understood from the above operations,
The adopted optimal target speed curve takes into consideration not only the amount of movement, but also changes in driving force based on changes in the magnetic field (magnetic field droop) at different locations within the head's movement range, reductions in driving force due to fluctuations in power supply voltage, Furthermore, after considering (calculating) the variation in driving force for each device, the optimal (
This provides a target velocity curve (with stable settling). The above operations are performed and completed from the time when power is supplied to the device until the device becomes ready for use by the user.

In the above operation, the speed control/position control switching circuit switches from the speed error generator 8 to the position error generator 9 at time t1 in FIG. 3.

Then, whenever access control is performed from the controller due to subsequent use by a user, etc., this initially determined target speed surface is always used! The operation is executed at the target speed according to fIA (the optimal target speed curve adopted above) (note that any movement amount is assigned to the sample movement amount closest to it), so the driving force state etc. is based on the actual use. It corresponds to the situation, and stable settling can be obtained at high speed.

〔Effect of the invention〕

As explained in detail above, according to the head positioning speed control method of the present invention, it is determined which of a plurality of target speed curves prepared in advance is the optimal target speed curve that stably settles under actual usage conditions. However, this optimal target curve that is as fast as possible is adopted (determined) for head positioning during use, so settling during head positioning, especially when stopping the head at the target position, can be done quickly and stably. This provides excellent effects such as improving the performance of the access system of a small disk device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the basic configuration of a head positioning speed control circuit according to an embodiment of the present invention, FIG. 2 is a waveform diagram of the position signal and target speed curve when the head is moving, and FIG. 3 is a diagram when the head is stopped (settling). FIG. 4 is a flowchart for explaining the basic concept of the present invention. 1--Microcomputer, 2-1111--Positioning stability determiner, 3-1111--Target speed initial determiner, 4° target speed generator, 5-----1- access controller, 6--head position detector, 7--head speed detector, 8--speed error generator, 9--position error generator, 10--. -Speed control/position control switch, 11-----VCM drive circuit, 12...-
・・・=・VCM, 13-------Position information reading head, 14--Magnetic disk, 15--
---A/D converter, 6a, 6a-1, 6a-
2 head position analog signals, 15a-1, 15a-2-
...--Digital position signal, 21---Target speed curve. Figure 1 Figure 2 Figure 3 Prisoner (G) (b)

Claims (1)

[Claims] 1. In a head positioning speed control method that automatically controls head positioning speed according to a target speed curve, when a head positioning device is started, head positioning is performed using a plurality of target speed curves prepared in advance in order. means for performing a trial, means for selecting a target speed curve for which head positioning is performed with stability within an allowable value as the optimum target speed curve; and performing head positioning in accordance with the optimum target speed curve during use. A head positioning speed control system characterized by comprising means. 2. The head positioning speed control method according to claim 1, wherein the range in which the head can move is divided into a plurality of sections, and the optimum target speed curve is selected for each divided section. . 3. A positioning target position was determined in each of the divided sections, a plurality of head movement amounts were associated with each target position, and an optimal target speed curve was selected for all head movement amounts and target positions. The head positioning speed control method according to claim 2, characterized in that: