JPH02179975A - Disk device access method - Google Patents

Abstract

PURPOSE:To shorten an access time and to make an access operation correct by controlling an access running instructing speed so that the access running instructing speed may be zero when the pickup arrives at a position before an access target position by a prescribed distance. CONSTITUTION:Based on the access running instructing speed, an optical pickup 2 is moved to an access target track on an optical disk 1. At such a time, the pickup 2 is moved for the prescribed distance at the comparatively fast access running instructing speed, at which the pickup 2 may move when the access running instructing speed is changed to zero later. Further, the access running instructing speed concerned is controlled so as to be zero when the pickup 2 arrives at the position before the access target position by the prescribed distance. Thus the access time is shortened, and the correct access is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an access method for a disk device for moving a pickup to a target track on a disk.

[Conventional technology]

In disk devices that use disk-shaped recording media (disks), reducing the time required to move the pickup to the target track on the disk will continue to be important, along with increasing disk capacity and improving data transfer speed. This can be said to be a serious issue. Conventionally, various methods have been proposed as methods for shortening access time. For example, modern control theory can be used to detect various conditions and perform feedback control based on the detected output, and unnecessary resonance in mechanical systems can be controlled as much as possible to expand the frequency band of access control. Some devices employ a special structure to move to higher frequencies outside the frequency band.

However, since such a method employs various detection means and special structures in order to shorten access time, the price of a disk device using this method becomes relatively high.

In a general optical disk device, as shown in FIG.
The optical pickup 2 is provided so as to be movable in the radial direction (tracking direction) of the optical disc 1 by, for example, a near motor 5 that drives it. The optical pickup 2 is equipped with a light source, an objective lens, etc. (not shown), and a light beam 3
is irradiated onto tracks 4 of the optical disc 1 to record and reproduce information.

As a means for knowing the current position and moving distance of the optical pickup 2, a position counter 7 that counts the output pulses of the linear scale 6 attached to the linear motor 5 or the track crossing signal detected by the optical pickup 2 is used. It is provided. A control section 8 consisting of a microcomputer is connected to the position counter 7. The control unit 8 not only controls the entire optical disk device, but also calculates the access travel instruction speed based on the position information from the position counter 7 and the speed information from the speed sensor 9 that detects the moving speed of the optical pickup 2. It has become. This access travel instruction speed and the aforementioned travel speed are input to a subtracter 10, where a difference signal between the two speeds is determined. This difference signal is output to an amplifier 11 and a driver 12, and this driver 12 drives the linear motor 5 based on the difference signal.

A speed control loop is formed by the speed sensor 9, subtracter 10, amplifier 11 driver 12, and linear motor 5, and thereby controls the speed of the linear motor 5 (i.e., the moving speed of the optical pickup) during the access operation. An operation is performed to follow the instructed speed.

In such an optical disk device, the access travel command speed generally exhibits a waveform that is constant in the first half and decelerated in the second half, as shown in FIG. 6, if the time axis is taken horizontally. The actual speed of the optical pickup 2 that follows the access travel command speed is shown in FIG.
) In contrast to the access travel instruction speed shown by the solid line in (b), a triangular or trapezoidal shape is shown as shown by the broken line. Of course, depending on the acceleration/deceleration method, the acceleration at that time, or the access distance, the above-mentioned isosceles triangle or isosceles trapezoid is not necessarily formed.

Here, the easiest method to shorten the access time (T, ・T,) is shown in FIGS. 8(a) and (b).
As shown in FIG. 3, it is conceivable to increase the access travel command speed from vr+ to V□' (increase the slope of the slope). In this case, the above access time T, ・T2 is tl
-t2.

[Problem to be solved by the invention]

However, as mentioned above, making the slope of the access travel instruction speed steeper means that the frequency components included in it will spread to a higher range, and the speed control loop mentioned earlier will also have a corresponding frequency band. (response) is required.

Even if an access travel command speed with a steep gradient is given to a speed control loop that does not have a sufficient frequency band, the optical pickup 2 will not be able to move accurately to follow it, and as shown in FIG. 9(a). As shown in b), an error occurs between the access travel command speed and the actual moving speed of the optical pickup 2, and the time the optical pickup 2 stops is also Δ1+.
It is delayed by Δt2. Additionally, along with this, a distance error occurs between the actual stop position es after the access run and the access target position e. If this error is large, it will take a lot of time to perform another access operation or to perform a track jump instead of this access operation, which will actually hinder the reduction of access time. become.

When providing a sufficient frequency band for the speed control loop, the frequencies of high-order resonance and characteristic distortion of components such as the linear motor 5 and the speed sensor 9 must be sufficiently higher than the frequency band. The speed sensor 9 and other components must be of high performance (that is, have a special structure or material), or a special compensation device must be provided. For the same reason, it becomes necessary to use lightweight linear motor 5 and optical pickup 2, which increases the price accordingly.

[Means to solve the problem]

In order to solve the above-mentioned problem, the access method for a disk device according to the present invention is based on the access travel instruction speed of the pickup, which is derived from the relationship between the access target position and the current position and/or current speed of the pickup. In an access method for a disk device in which a pickup is moved to a target access position on a disk, the above-mentioned pickup is moved to a target access position on a disk at a relatively high access travel instruction speed such that the pickup moves by inertia even if the access travel instruction speed later becomes zero. The present invention is characterized in that the pickup is moved a predetermined distance and the access travel instruction speed is controlled so that the access travel instruction speed becomes zero when the pickup reaches a predetermined distance before the access target position.

[For production]

According to the above configuration, it is possible to shorten the access time by setting the initial access travel instruction speed to a relatively high speed, and to reduce the inertia of the pickup due to the increase in the access travel instruction speed. Since the distance is absorbed at a predetermined distance before the target position, accurate access is possible.

In addition, since there is no need to provide a special compensation function or member in the disk device, it is possible to avoid an increase in the price of the disk device.

[Example 1] An example of the present invention will be described below based on FIGS. 1 and 5. Note that the optical disk device shown in FIG. 5 is assumed. Further, as in the past, the access travel instruction speed exhibits a waveform in which the first half is constant (uniform acceleration) and the second half is decelerated when viewed horizontally on the time axis.

The access method for a disk device according to the present invention is based on the access travel instruction speed derived from the relationship between the access target track on the optical disk 1 and the current position and/or current speed of the optical pickup 2. This is an access method of a disk device in which a constant speed Vr is moved to an access target track on an optical disk 1. First, a constant speed Vr is specified as an access running instruction speed by the control unit 8 and this is output to a subtracter IO (Sl). .

The speed Vr is set to a relatively high speed such that even if the speed Vr later becomes zero, the pickup will still move due to inertia. When optical pickup 2 starts moving,
The current position X of the optical pickup 2 is determined by the position counter 7 (S2).

When it is determined that the optical pickup 2 has reached half of the access distance (S3), the process moves to step 4.

At this point, the optical pickup 2 has reached its maximum speed, that is, Vr.

In step 4, a virtual end point e' that is a predetermined distance (hereinafter referred to as buffer distance) U from the access target track (position) e is determined (S4). Next, the current position X of the optical pickup 2 is determined (35), and the remaining access distance d is determined using the following first equation (S6).

d=e' -x ......First equation Next, it is determined whether this distance d is less than O or not (S7), and the distance d is 0.
If it is not less than or equal to, distance li! ! The access travel instruction speed Vref is determined from d using the second equation below (S8)
, after outputting this access travel command speed Vref to the subtractor 10 (S9), proceed to step 5 and repeat the access travel command speed V until the distance d becomes equal to or less than O.
Calculate ref and continue to output it.

Vref = k-d ""...2nd formula % formula %) In addition, the access travel command speed Vref can be calculated using a calculation formula other than the above-mentioned formula 2, as well as using the RO
Data may be stored in advance in the form of an M table, and the specific method is not critical.

If it is determined in step 7 that the distance d is less than 0 (that is, the optical pickup 2 has reached the virtual end point e'), the access travel instruction speed V ref is set to O (310).

At this point, the speed Vr as the access travel instruction speed
Because the optical pickup 2 was at a relatively high speed, the optical pickup 2 could not be stopped completely and the optical pickup 2 is still in a moving state. The optical pickup 2 is caused to travel by a buffer distance u (S11). As a result, the optical pickup 2 accesses the target track e.
will reach exactly.

In the above embodiment, the access travel instruction speed Vref is determined only based on the relationship between the current position X of the optical pickup 2 and the access virtual end point e', but as shown in steps 5' and 8', It is also possible to detect the current speed V of the optical pickup 2 and determine the access travel instruction speed Vref from the relationship between this and the virtual access end point e' or the current position X of the optical pickup 2.

With the above configuration, it is possible to shorten the access time by setting the initial access travel instruction speed Vr to a relatively high speed, and also to allow the optical pickup 2 to coast due to the increase in the access travel instruction speed Vr. Accurate access is possible because the distance between the bones is absorbed by the buffer distance U. In addition, since there is no need to provide special compensation functions or members in the optical disc device, it is possible to avoid an increase in the price of the optical disc device.

[Embodiment 2] Another embodiment of the present invention will be described below based on FIGS. 2 and 5. Note that FIG. 5 used in the above embodiment will be used again here.

In this embodiment, the buffer distance U is fixed according to the access distance, whereas the buffer distance U in the previous embodiment is fixed.
can be set appropriately, that is, the virtual end point e
′, the access distance y is calculated from the access start position S and the access target position e using the following third equation (521), and this distance M
A buffer distance U corresponding to y is determined (S22).

y=e-s ......For the third equation buffer distance, when assembling, manufacturing, and adjusting the optical disk device, test access operations are performed at various long and short access distances, and the value for the access distance y is calculated. Keep it as a function table. Of course, instead of using such a function table, it may be calculated from the access distance #y using a mathematical formula.

According to the above configuration, in addition to exhibiting the functions of the first embodiment, by making the buffer distance U variable according to the access distance y, even more accurate access operation is possible.

[Embodiment 3] Another embodiment of the present invention will be described below with reference to FIGS. 3 and 5. Note that FIG. 5 used in the above embodiment will be used again here.

In the embodiment described above, the buffer path i1u is variable, but its value is determined and fixed at the time of assembly, manufacturing, adjustment, etc. of each optical disk device. After the device is on the market, for example, when starting up an optical disk device, an actual access operation is performed based on a predetermined buffer distance U, and the above-mentioned access operation is performed based on the error between the access target position and the actual stop position of the optical pickup 2. The buffer distance U is corrected and the corrected value U′ is the buffer distance u
We plan to update it as follows.

Therefore, after the optical disk device is in the hands of consumers etc., due to changes over time and environmental changes after the optical disk device was manufactured,
Even if the reliability of the buffer distance U described above decreases,
When using the optical disk device, the buffer distance U can be investigated, updated, and optimized to maintain accurate access operations. Updating the buffer path jlu is also an update of the function that calculates the buffer distance U, or an update of the function table.

Although this embodiment differs in configuration from the second embodiment in the above points, the actual access operation itself is the same. That is, the method of the second embodiment has been added with a test access procedure for investigating and updating the buffer distance U. This difference will be explained based on FIG. 3. First, the distance and access direction of the trial access are determined (S31), and then the access end (target) position e is set from the trial access start position S, access distance y, and access direction (S32). After that, access travel instruction speed Vr
The optical pickup 2 is kept at a constant high level and travels at a constant acceleration (S33), and travels approximately half of the access distance (S34/535). Next, find the virtual end point e' (S36), check the current position X (or current speed V, or both) of the optical pickup 2 (S37), and check whether the current position X exceeds the virtual end position e'. Judgment 3
3B), if not exceeded, determine the access travel instruction speed Vrer from the above X or V and e'.
39), and outputs this Vref to the subtracter 10.

On the other hand, if the current position X exceeds the virtual end position e' (S3
B), set the access travel instruction speed Vref to 054L
), the optical pickup 2 waits for an overrun (inertial run) for a certain period of time (342), and then checks the stop position (actual access end position) P of the optical pickup 2 (S43). Next, based on this stopping position p, for example,
A correction value U' is obtained using the following fourth equation (S44).

u' = u-(e-p) ...4th formula And a function (formula) to calculate the buffer distance U so that a value corresponding to such a correction value U can be obtained from now on as well. , or update the function table. Note that if it is determined in step 45 following step 44 that further test access is necessary, the process moves to step 31 and the above procedure is repeated, while if it is determined that it is not necessary, the process ends.

In addition, in the above embodiment, the function for calculating the buffer distance U,
Alternatively, the update of the function table is based only on the difference between the access end position e and the actual end position p, but information such as the current speed V during the access may be taken into account, and the update operation may be based on the function or the actual end position p. Instead of updating by rewriting the table, a method may be adopted in which the buffer distance U is the average of the correction value U' and the value given by the original function or table.

The above test access and update operations are performed under the control described above, such as when the optical disk device starts up, when the ambient temperature changes, when the system is reset, and when access times become longer on average. It is executed when the unit 8 determines that it is necessary.

[Embodiment 4] Another embodiment of the present invention will be described below with reference to FIGS. 4 and 5. Note that FIG. 5 used in the above embodiment will be used again here.

In the embodiment described above, the access operation is actually performed based on the buffer distance U, and the buffer path M is adjusted based on the error between the access target position and the actual stop position of the optical pickup 2.
Although u is corrected and the corrected value U' is updated as the buffer distance U, the updating operation is performed by a test access operation that is separate from the actual access operation, whereas the access method of this embodiment This is a method of updating the buffer distance U as needed during actual access operations. That is, as shown in FIG. 4, in the actual access procedure, after the optical pickup 2 has traveled a certain distance, the access travel instruction speed is set to 0 (5IO), and the optical pickup 2 waits for a certain amount of time.
Wait for overrun (coast running) (311), and then move to the stop position of optical pickup 2 (actual access end position)
Check p (S23). Next, based on this stop position p, a corrected value U' is obtained using, for example, the above-mentioned equation 4 (S24).

Then, the function for calculating the buffer distance U or the function table is updated so that a value corresponding to such corrected value U' can be obtained from now on as well. Instead of updating by rewriting the function or table, a method may be adopted in which the buffer distance U is the average of the correction value U' and the original value of the function or table.

Therefore, even if the reliability of the buffer distance U described above decreases due to changes over time or environmental changes after the optical disk device is manufactured, the buffer distance U can be immediately investigated and updated during the actual access operation of the optical disk device. access operations can be performed and more accurate access operations can be maintained.

〔Effect of the invention〕

As described above, the access method for a disk device according to the present invention moves the pickup on the disk based on the access travel command speed derived from the relationship between the access target position and the current position and/or current speed of the pickup. In an access method for a disk device that moves to a target access position, the pickup is moved a predetermined distance at a relatively high access instruction speed such that the pickup will move by inertia even if the access travel instruction speed later becomes zero. At the same time, the access travel command speed is controlled so that the access travel command speed becomes zero when the pickup reaches a predetermined distance before the access target position.

As a result, access time can be shortened and access operations can be made more accurate, and there is no need to provide special compensation functions or components in the disk device.
This also has the effect of avoiding an increase in the price of the disk device.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, a flowchart showing the access procedure, and FIG. 2 shows another embodiment of the invention, a flowchart showing the access procedure. FIG. 3 shows another embodiment of the present invention, a flowchart showing the access procedure, and FIG. 4 shows another embodiment of the invention, a flowchart showing the access procedure. 5 is a schematic configuration diagram of the main parts of an optical disk device, FIG. 6 is a graph showing a general waveform of the access travel command speed, and FIGS. 7 to 9 show conventional examples. Figures (a) and (b) are graphs showing the relationship between the access travel command speed and the actual moving speed of the optical pickup, respectively.
) are graphs showing the relationship between the access travel command speed and the actual movement speed of the optical pickup when the access travel command speed is increased, respectively, and Figures 9(a) and (b) are graphs showing the relationship between the access travel command speed and the actual movement speed of the optical pickup when the access travel command speed is increased, respectively. 12 is a graph showing the relationship between the access travel command speed and the actual movement speed of the optical pickup when the access travel instruction speed cannot be followed. 2 is an optical disk, 2 is an optical pick-up tube, 4 is a track, 5 is a linear motor, 8 is a control unit, and 12 is a driver.

Claims (1)

[Claims] 1. A disk that moves the pickup to an access target position on the disk based on an access travel instruction constant speed derived from the relationship between the access target position and the current position and/or current speed of the pickup. In the access method of the device, the pickup is moved a predetermined distance at a relatively high access travel instruction speed such that the pickup will move by inertia even if the access travel instruction speed later becomes zero, and the pickup is moved a predetermined distance to the access target. An access method for a disk device, characterized in that the access travel command speed is controlled so that the access travel command speed becomes zero when the pickup reaches a predetermined distance before the position.