JPS58150171A - Controller for disk device - Google Patents

Abstract

PURPOSE:To reduce the time required for accessing a track, by installing a circuit which takes out a deviation in the following location based on a location signal from a track follow-up controlling circuit and obtains the feedback voltage related to the location after amplifying the deviation, and a circuit which adds a speed damping voltage obtaining when a location signal to which a nonlinearity is given is differentiated. CONSTITUTION:The gain of a nonlinear circuit 22 which gives nonlinearities is ''1'' in the area where the position voltage is small, but, when the position voltage exceeds a value, the gain becomes >=''1''. Therefore, when a head is under follow-up control near the center of a track, the deviation in location and the speed are very small and the head receives no influence of the nonlinearity and is controlled under a condition which almost reaches the critical damping. On the other hand, when the head is accessed toward a target track and advances toward the target track, the position voltage at the time when controlling mode is switched from the access speed control to the track follow-up control is large, and, therefore, a further large position voltage is obtained by a nonlinear circuit 22 which gives nonlinearities and the gain and volume of the speed damping voltage obtained by means of a circuit 23 which differentiates the position voltage are further increased. By increasing the final speed at the time of switching of the controlling mode from the track accessing speed control to the track follow-up control, the track accessing time can be reduced.

Description

[Detailed Description of the Invention] Recording in a non-inventive line disker device, especially a magnetic disker device,
This relates to the position control of the playback head, and relates to the improvement of the electronic control circuit that controls the F-tuta access.

Conventional) head positive s/! In a system in which an O-attuator is attached and controlled by a de-servo method, and a tracker positioning of a group of heads is performed, a read-only head (hereinafter referred to as a "S-BO head") is used to recognize one position, and a read-only head (hereinafter referred to as "S-BO head") is used to recognize one position. One side of the magnetic disk is provided with a permanent recording of a unique magnetic pattern (hereinafter referred to as Nabopern), so that the head position t can be recognized at all times. Close μ of positioning based on this gll
m deservo system is constructed.

As this known method, there is one as shown in the block diagram of FIG. In Figure 1, CI) is t-pohead,
(20 is a position signal generator i11 which demodulates the above-mentioned unique servo pattern signal read out by the servo head (1) and generates a voltage signal related to the position (hereinafter referred to as a position signal).
The circuit (3) is a track following control circuit that follows the track according to the above position signal and prevents on-track.This circuit usually includes a lead configuration for adding damping, an error amplification circuit, etc. Ru. (
4) is a speed value vuI adjustment circuit for speed control during track access, which normally differentiates the above Wjt inertia to obtain the speed signal voltage t''. Insertion) is a track counter, (s
+ Hari) Bratakaran! (6) is a speed reference generation circuit that gives the desired speed from time to time according to the contents; (7) is a speed error amplification circuit that compares the speed signal with the speed reference and amplifies it appropriately; (8) is a switch device for switching between speed control during track access and adhesion control during track follow-up control; 1g) a drive circuit for driving an actuator as a head positioner;
The sound is emitted by the actuator mentioned above.

FIG. 2 shows an example 1 of voltage waveforms at various parts when accessing from one track to another in the known method.
ω is the position signal E, (position signal OI-circuit (
2), the output of Figure 2 (■) is a triangular wave similar to the one-week period OII at the speed EvE s 2) rack.

The point where the voltage reaches zero potential corresponds to the center of each F footer. Velocity Signal] Ev Co., differentiates the position signal p on a straight line portion, and calculates the absolute value ratio (non-polarization) of the result. It is assumed that the curved portion does not capture the potential and holds the previous potential.

This figure 2 shows typical position and speed signals when the head accesses from the footer to another track located on the F track. At first there is an acceleration section, then a maximum speed section, and finally a deceleration section where the speed is sufficiently reduced, and then the vehicle moves slightly before the center of the target track (Ii).
The figure shows how the track following control starts at point P in Figure ω from time t''tp), on-track and maintains that position.From the acceleration section to the deceleration section (from time t-o to t= t) is called the access speed control section, and from ζ onward is called the rack following control section.The switching between ζO and ζ is performed by the set of changeover switch devices t.

In the series of controls described above, the point P at which access speed control switches to track following control is located slightly before the center of the target track (usually j!l is one-fifth to one-third of the tracker pitch). The speed of the head at this time is K (hereinafter referred to as the final '4 degree).
needs to be well managed. From the standpoint of track following control, time 1 = 1 - t! ! Control starts, and the initial condition at that time is the amount of displacement from the target track center at 1=1p.

is the final velocity. The track following control loop is normally designed to be close to critical braking by adding appropriate damping, but if the initial conditions are significantly different, it is difficult to expect perfect on-track.

For example, if the final speed is too large, it will pass through the center of the track and become thick (overshoot Y, and in the worst case, fail to pull in the F hook. In this sense, manage the final speed when moving to track following control. For this reason, as shown in Figure 2 ■, a low constant speed section (hereinafter referred to as pedestal ν) is provided one or two tracks before the target track, and the speed of the final part of speed control (final speed ) completely converges to the set target value.

) If you only want to ensure that the hook is settled without overburning the center of the hook, it is best to slow down the final speed as much as possible and move the position (point P) for transition to follow-up control closer to the center of the target track. Good, but if the final speed is slow, it will take longer to travel the pedestal V section, and the rack access time will be longer, which is disadvantageous. In addition, if the final speed is slow, there is a high risk of stalling (zero speed) when entering the pedestal lv. Therefore, it is better to move the position (point P) at which the follow-up control starts as far as possible from the center of the target track, approach it at a relatively high speed, and suppress variations in the final speed as much as possible. It can be said to be a method. However, the position of point P can be read from the voltage waveform of the position signal in Fig. ω.

w) There is a certain limit to the distance to the center of the rack, and the maximum distance is about one-third of the truck pitch. Therefore, it is actually impossible to increase the final uniformity of ζ, and the 3rd M is 1. The diagram shows the distance on the horizontal axis and the position signal E on the vertical axis. As mentioned above, point P is located slightly in front of the center of the target track (at most, the upper limit is about one-third of the pitch).
About switching from access speed control to track following control W
It shows M.

FIG. 4 is an example in which the state of the position signal from the Bedestar μ section until the head settles at the center of the target track was actually measured using the final velocity as a buff meta in the above-mentioned known conventional example. In this example, the position of point P is set approximately one third of the rack pitch (set by the track following control switching voltage) from the center of the target track, and the final speed is 3 m/sec.
, 1scraec.

In this example, among the three 2a*/@ec! 5csrs
c has the best stability. In the example of Fig. 4 of the octopus, if the final speed exceeds ``L5aIv@E, overshoot will occur, and it will take a long time to settle.If the overshoot reaches S degrees, it will jump out of the target track.
The present invention proposes a method for eliminating such drawbacks due to off-track failure, and the main focus of the present invention is to improve the rack following control circuit (as described above).Why? This is because the problem of settling to the center of the track will occur later, after the speed control during raster access is completed and the control is switched to track following control.

Conventional track following control circuits are basically position control circuits that prevent off-tracking from the track center according to position signals, and therefore serve as error amplification circuits that extract position deviations.

In order to increase the stability of V step 5 by giving damping (so-called Nyquist condition t), it is composed of ID9 and drag force y#.

Figure 4 shows the most basic circuit for realizing such a conventional OF track following control circuit 3), in which a lead dog fill and error amplification circuit is formed using an operational amplifier (ib), a resistor, and a conductor (f). ing.

FIG. 6 ω shows the pigeon wave number characteristic a of the circuit of FIG.

This frequency characteristic represents so-called phase lead compensation in position control, and the transfer function is expressed as follows.

Here, α is taken to be approximately Fi~1rjj-.

The frequency characteristics of Figure 6 ■ or Figure 6 ω are decomposed. Figure 6 ■ is the feedback gain related to position, only Vα, and Figure 6 ω is the feedback related to position differential (velocity, ie damping). It shows the gain.

This figure i, υ, (tit-if synthesized, hair911II6
The frequency characteristics shown in Figure 6-) are the same as the lead-lag filter characteristics.The reason why the high frequency region in Figure 6-) is made flat is because the components in this region become unnecessary and harmful to control. This is because there are many.

In this way, conventional track following control circuits can be thought of as basically consisting of a feedback component related to position and a feedback component related to the differential (velocity) of the position, which are then amplified by seven points. You can also do that.

By adding nonlinearity to the feedback component described above, the present invention satisfies the Nyquis condition when the head is near the center of one rack, and performs control in a state close to critical damping. When the head approaches from the outside of the track, a sudden large thrust is generated to prevent overshoot and to settle the head to the track center in a short time. This allows the head to enter the target track at a much faster final velocity than before.4. It becomes possible to stabilize extremely stably and in a short time. Also,
Also for the final velocity variation tkK.

Over V knee 1, although the settling time may be longer or shorter.
This allows for stable stabilization without causing any disturbance.

That is, one aspect of the present invention is a control device for a disk device that positions a head on a recording or reproduction track using a closed sheep servo system, which includes a head that recognizes the position, and a position signal obtained by demodulating the position information obtained from the head. with a position signal demodulation circuit.

The track following control circuit is provided with a track following control circuit for performing position control during track following based on this position signal, and this track following control circuit outputs and amplifies a following position deviation based on the position signal. a circuit that obtains a feedback voltage related to the position; a nonlinear circuit that provides nonlinearity to the voltage of the position signal; a circuit that obtains a speed damping voltage by differentiating the position signal given this nonlinearity; and a feedback voltage related to the position. and a circuit that adds a speed damping voltage given nonlinearity.This allows stable settling even if the final speed is set to a fairly large value, resulting in a reduction in access time. Furthermore, even with respect to variations in the final speed, it is possible to expect a more stable settling than in the past.

An embodiment of the present invention will be described below based on the drawings. 7th
The figure is a block diagram showing the basic configuration of the present invention (particularly a block diagram of the improved track following control circuit that is the main part of the present invention). In Figure 7, @l represents the feedback voltage related to position. This circuit provides the same characteristics as υ in Fig. 6. @ is a nonlinear circuit that gives nonlinearity to the position voltage % (2) is a circuit that obtains a nonlinear speed damping voltage by differentiating the position voltage that has been given nonlinearity by (2), as shown in Figure 6 (C ) has the same property as [it gives. (goods) is an addition circuit.

The nonlinear circuit that provides nonlinearity has a gain of 1 in the region where the position voltage is small, but when a certain voltage (a certain distance from the center of the dowel) is exceeded, the gain becomes 1 or more. Therefore, when the head is in follow-up control near the center of the F ripple.

Since both the positional deviation and the speed are quite small, there is no influence of non-linearity, and control is performed in a state close to critical braking (damping to critical force) as in the conventional track following control circuit. When the head is accessed toward a certain target track and the head enters the target track, the point at which access moderation control is switched to track following control (time 1 in Figure 1) Since the O position voltage is large at point P (=1.), a nonlinear circuit that gives nonlinearity generates an even larger voltage, and the speed damping obtained by the circuit that differentiates it. The voltage gain and mh increase even further. That is.

When approaching a target truck at a high final speed, it is possible to generate a very large braking force. Therefore, the head position V:ii approaches the track center while rapidly decreasing its speed.

When approaching the center of the track, the position voltage has a sufficiently small value, so the vehicle can stably on-track without control sag or overshoot in a state close to critical braking. This means that even if the final speed varies from the set value, the settling is always stable. That is, the higher the final speed, the greater the braking force will be.

In addition, in the circuit for producing speed damping in the present invention ((b) and - in Fig. 7), a nonlinear circuit (b) providing nonlinearity is provided in the circuit (2) for obtaining the speed damping voltage. There is. Therefore, for example, a configuration opposite to the configuration of the present invention (a configuration in which a circuit is first provided in M to obtain a speed damping voltage by differentiating the position voltage, and then a nonlinear circuit is provided to give nonlinearity to this speed damping voltage) In comparison, this circuit configuration, which is the opposite of the present invention, imparts nonlinearity to the noise that is amplified and generated along with the differential function, which increases the noise gain by 7 and extremely deteriorates the S layer ratio. As a result, when the head enters the target shiratsuta, it tends to enter the Km vibratingly and unstablely.

Furthermore, even when tracking control is being performed, the differentiated noise may extend into the nonlinear region, so this noise is further amplified by the nonlinear circuit, resulting in the head being susceptible to vibration and becoming unstable. . On this point, in the configuration of the present invention, since the nonlinearity t- is first given to the position signal and then differentiated, there is no function that increases the noise. By simply installing a low-pass filter at the rear of the track following control circuit, the head can be moved to the target track in a state close to critical braking without causing the head to vibrate or become unstable, and can be controlled in accordance with the tracking control circuit. It is possible to do so.

In addition, the configuration of the present invention does not have the above-mentioned noise increasing effect, so it is possible to make the gain in the nonlinear region of the nonlinear circuit that provides nonlinearity sufficiently large, and it is possible to cope with a considerably high final speed. It is what it is.

FIG. S is an actual measurement diagram of the head setting when the present invention is applied, and should be compared with the conventional example shown in FIG. In this example, when the position voltage exceeds 13 Vojt (75 μm from the center of the hook), the gain exceeds It-,
It is used in non-linear circuits where the number increases several times. As is clear from this example, a significant improvement can be seen.

FIG. 9 shows a specific embodiment of the basic configuration of the present invention shown in FIG. In Fig. 9, the button) is a circuit that obtains the feedback voltage related to the position. This is a well-known non-inverting amplifier constructed from an operational amplifier and a resistor. −
7 is a nonlinear circuit that imparts nonlinearity to the voltage of a position signal, and corresponds to the circuit shown in FIG. - is a circuit that obtains the speed dungeon pressure by differentiating the position voltage given nonlinearity by the nonlinear circuit, which corresponds to - in Figure 7 and is an omniscient circuit consisting of an operational amplifier, a resistor, and a capacitor for differentiation. It is an O differential circuit. (
7 is a circuit that synthesizes and adds z outputs of the circuit that provides feedback voltage regarding the position - the output of υ and the circuit that obtains the speed damping voltage 1 given nonlinearity.
This is a well-known summing amplifier consisting of an operational amplifier and a resistor.

According to the present invention as described in detail above.

<1)) Track access time can be shortened by increasing the final speed when switching from footer access speed ti control to track following control.

(2) By increasing the final speed, accidents due to stalling in the Bedesta V section can be prevented (〈shi.

It is possible to reduce the V-taehu rate and improve reliability.

@ Speed management becomes easier because the final speed can vary by Wfs to some extent.

14) When settling to the center of the target track, if the overshoot phenomenon is prevented and the settling time is shortened, at 11 o'clock,
It enables stable settling and prevents accidents such as ontook failure and seek-f.

(6) When follow-up control is performed near the center of the vehicle, optimal position control close to % critical damping can be achieved, and especially by applying the present invention, this position control will not be adversely affected. Never.

(Since it is possible to make the gain in the nonlinear region of the nonlinear circuit that provides -1 nonlinearity sufficiently large, it is possible to cope with extremely high final speeds.

(Since 1111 can be realized with a simple circuit, there is no disadvantage in terms of cost.

Magnetic disk drive mt- with many excellent features such as
This is something that can be achieved.

It should be noted that the present invention is not necessarily limited to those using a &1-ki disc, but generally has a recording capacity of 7, which is used for speed control, performs rung access of ^1, and then performs a rung access on the target shirasu. Needless to say, the present invention can be applied to all disk devices using a closed-disk drive system, such as one that performs follow-up control.

[Brief explanation of drawings]

Fig. 1 is a plotter diagram of a closed Y-deservo system for positioning the head of a conventional disk drive device, Fig. 3 shows the voltage waveforms of various parts during toft motor access in the case of Fig. 1, and the second drawing shows the position signal HP. , Fig. 3 ω is a waveform diagram of the speed signal Ema,
Fig. 3 is an enlarged view of the position signal IEp centered around the N-th shifter, and Fig. 4 shows the state of the position signal until the head settles at the center of the target shifter in relation to Figs. 1 and 3. of! l! Figure 5 is a basic circuit example diagram that realizes a conventional track following control circuit, Figure 6 is a frequency characteristic diagram of the circuit in Figure 5, and Figure 6 is a waveform diagram showing an example of a conventional track following control circuit. Figure 7 is a plotter diagram showing an example of the basic configuration of the present invention, and Figure 1 is a waveform diagram showing an actual measurement diagram of the head setting when the water rate invention is applied to Figure 1. , FIG. 9 is a circuit diagram showing a specific embodiment of the basic configuration of the present invention shown in FIG. 7. (1) Servo head, (position signal demodulation circuit % (stage) track following control circuit, (4) speed signal demodulation circuit +I+-track counter, (61.
...Speed reference generation circuit. (岨...Switch between access speed control section and Y-hook follow-up control section, @IM...Circuit for obtaining position-related feedback voltage, Foundation -...Nonlinear circuit for providing nonlinearity, (c) −・−・Circuit that obtains a speed damping voltage by differentiating the position, (foundation) −・・・The output of a circuit that obtains a feedback voltage related to position and the output of a circuit that obtains a speed damping voltage given nonlinearity. Circuit agent for synthetic addition
Ekenmoto Yoshihiroichi Ichiichimon (branch) 4g廿Ep> Figure 6-455- Figure 7

Claims (1)

[Claims] The head is configured to position the head on a recording or reproducing track using the LvA, v-p servo method, and the head opens the position #IIt, and the position information obtained by this head is demodulated. The track following control circuit is equipped with a position signal duplex circuit for overwriting the position signal with a position signal, and a track following control circuit for performing position control during track following based on this position signal. On the basis of the. A circuit that extracts the tracking position error and amplifies it to overwrite the feedback voltage related to the position, a nonlinear circuit that gives nonlinearity 1 to the voltage of the position signal, and a circuit that gives a nonlinearity 1 to the voltage of the position signal.
1. A control device for a disk drive comprising: a circuit that reads a lic signal to obtain a speed damping voltage; and a circuit that adds the position-related feedback voltage and nonlinearity to the speed damping voltage.