JPH052726A - Control method for recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent an influence due to the nonlinearity on the position detec tion of the position control system of a magnetic disk device and to attain a high speed access. CONSTITUTION:An input to a compensator 7 is switched from a position deviation signal 4 to a value calculated from the information of input currents to a VCM 1 or the like according to the size of the position deviation signal 4. A settling time at the time of a seek is shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control method for various information recording / reproducing devices such as magnetic disk devices.

[0002]

2. Description of the Related Art As a recording / reproducing apparatus which uses a rotating disk-shaped recording medium, there are a magnetic disk apparatus, an optical disk apparatus and the like. In either device, a converter for reading and writing signals is arranged in a recording area formed in a direction substantially perpendicular to the radius of the disk-shaped recording medium, that is, in the circumferential direction to record and reproduce information. This recording area is usually called a track.

Here, a magnetic disk device will be described as an example. A conventional example of a magnetic disk device is shown in FIG. In the case of a magnetic recording device, a magnetic head 21 is used as a converter. The magnetic head 21 is fixed to a drive device 22 for moving the position. In many cases, a voice coil motor (hereinafter referred to as VCM) is used as the drive device. For recording information on the recording medium 23, recording tracks 24 are formed at substantially constant intervals in the radial direction.

The most important specification of the magnetic disk drive is how large information can be recorded. In order to increase the capacity, it is necessary to increase the recording density in the track direction. In order to reliably perform recording and reproduction even at high track density, the magnetic head is tracked by feedback control based on a special signal on the normal track. It is being placed on top.

Such a position control system is constructed as follows. A track position shift signal is output due to the relative position shift between the magnetic head and the track, and the position shift of the magnetic head can be known from this and the information of the track number generated separately.

The positioning control system is constructed by feeding back the positional deviation information of the magnetic head thus obtained to the VCM through the compensator.

The performance required for the positioning control system is high speed and high position accuracy.

With respect to high speed, in order to improve the response of the position control system, speed information is often fed back together with position information in many cases. The speed information may be measured by a dedicated speed detector, but in the case of a discrete-time control system, a method of calculating it from position information or the like is widely used for price reduction.

By using the position information of the magnetic head, the speed is estimated from the amount of movement during a fixed time, and the position and speed are fed back to control the magnetic head to be placed on the target track.

When the target track and the track on which the magnetic head is actually located are far apart from each other, the position gain is made non-linear, but in any case, the position deviation information is accurate for position control. Need to know.

[0011]

In the magnetic disk drive, the positional deviation information is measured by the following means. Figure 5
In (a), a part of the magnetization pattern for measuring the positional deviation written in the track is shown. The arrow in the figure indicates the magnetization direction. Magnetization transitions A31 and B32 for position detection are written at positions shifted by a half pitch from the center of each track. The positional shift is obtained from the difference between the reproduction signals of the magnetization transition A and the magnetization transition B. The gap 33 of the magnetic head is N
When the position of the position shift x from the center of the track, the reproduction signal of the magnetic head has a larger amplitude of the output from the magnetization transition B32 than the output from the magnetization transition A31, and this difference (VB-
VA) is proportional to the displacement x.

However, the length Tw of the gap 33 of the magnetic head for reproduction is shorter than the track pitch P in order to prevent interference between adjacent tracks. With such a configuration, the position x of the magnetic head and the position shift signal (VB When the relationship of −VA) is measured, the result as shown in FIG. 6 is obtained. When the magnetic head is near the middle of the track, the position shift signal is saturated and the position shift amount cannot be accurately known.

FIG. 7 shows the relationship between the positional deviation signal and the positional deviation in which the track number is also taken into consideration. Discontinuity occurs near the middle of the track.

The effect of such a phenomenon on the positioning control system will be briefly described. For the sake of simplicity, FIG. 8 shows the position of the magnetic head when the magnetic head exponentially approaches the N + 1 track, the position deviation signal of the magnetic head measured intermittently, and the change of the magnetic head position. The measured speed of the magnetic head calculated from FIG. According to the characteristics shown in FIG. 7, when the magnetic head comes near the middle of the track, a jump occurs in the measured position deviation signal.
For this reason, the calculated value of the speed largely fluctuates as shown in FIG. 8C, and this signal is fed back to the VCM, so that vibration occurs in the entire drive system and the time required for positioning becomes long. As a countermeasure against this, conventionally, there has been a method of preparing two position detection patterns which are shifted by a half pitch and using each linear region. This is called a biphasic signal, whereas the above is called a monophasic signal.

However, this method has a problem in that the reproduction circuit for the positional deviation signal becomes complicated, and the area occupied by the positioning signal on the recording medium becomes large.

Therefore, an object to be solved by the present invention is to provide means for inexpensively constructing a positioning control system which does not cause inconvenience such as vibration even if a one-phase signal is used as a position detection signal. ..

[0017]

In order to solve the above problems, in the control method of the recording / reproducing apparatus of the present invention, concentric or spiral recording tracks are formed on a rotating recording medium to record information. In the control of the driving device that moves the transducer for recording / reproducing of the playback device to the target track and holds it on the track, in order to obtain the positional deviation information of the target track and the transducer, in the linear area of the position detector It is characterized by using the output of the detector and using the positional deviation information estimated by calculation in the nonlinear region.

[0018]

According to the magnitude of the displacement signal, if the displacement signal is within a predetermined range, the value of the displacement signal is used as the displacement amount. In order to perform feedback control using the track position and speed calculated from the track position and the input current of the drive device,
Even in the vicinity of the middle of the track where the non-linearity of the positional deviation detection is strong, the error of the speed estimation due to the non-linearity does not become large, so that the control loop does not vibrate due to the speed error and the high-speed position settling is possible.

[0019]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the block diagram of the present invention in FIG. The difference between the position of the VCM 1 which is the driving device and the off-track 2 of the recording medium is detected by the magnetic head 3 which is the converter, and the position deviation signal 4 is generated. If the position deviation 10 is small and linear, the position is selected by the selector 5. The shift signal 4 is input to the compensator 7 as the selected and estimated position shift 6. When the positional deviation is large and out of the linear range, the VCM drive current 8 at the previous sample time
And the value calculated from the position shift signal 9 at the previous sample time is used as the estimated position shift 6. The output of the compensator 7 goes to the current driver and drives the VCM 1. With that, the control system is closed. The selector 5 is configured as follows. The position shift signal 4 becomes zero if the magnetic head 3 is correctly placed on the track. The relationship between the positional deviation signal 4 and the positional deviation 10 is within the linear range when the magnetic head 3 is close to the center of the track, that is, when the absolute value of the positional deviation signal is smaller than a certain value. Therefore, as shown in FIG. 2, if the absolute value of the signal is smaller than V0, the position shift signal is used as the position signal, and if it is larger than V0, the value calculated from the information at the previous time is used.

The calculation is performed as follows.

When the current time is k and the previous time is k-1, one at k-1 hour is X (k-1) and the speed is V (k-).
1), the drive current is represented by I (k-1), and the time step is represented by Ts.

If the estimated position at time k is X (k),
X (k) is calculated by the following formula.

[0023]

[Equation 1]

The reason for this estimation is as follows. The VCM equation of motion is equal to the second derivative of the position being the input current times the torque multiplier A. The above formula is obtained by integrating this formula over the time interval Ts.

According to the modern control theory, such an estimation without feedback cannot guarantee that the estimation error is within an allowable value, but the fact that the magnetic head is at a half pitch position means that the magnetic head is at the target track. Since it means that the magnetic head is moving toward the head, the time during which the magnetic head stays in the non-linear region of the positional deviation signal is short, and therefore it can be expected that the probability that such an estimation is necessary continues. Therefore, the open-loop estimation as described above is sufficient. If it stays in the half pitch position for a long time, another exceptional treatment is required. In this case, since the estimated values are used continuously, a complicated estimation by an observer or the like is necessary instead of the simple open-loop estimation as described above. Observers require complex calculations. As a coping method that does not rely on an observer, a method of adopting a half-track pitch as an estimated position when the number of estimations exceeds a predetermined number can be considered.

FIG. 3 shows the case where such an estimation method is used.
The position shift signal, the estimated position shift and the measurement speed are shown.
The VCM position exponentially approaches the target track, ◯ indicates that the position detector signal is used as the estimated position deviation, and Δ indicates that the above calculated value is used. The measurement speed is smoother than that in FIG. 8. If feedback is performed based on this information, loop vibration does not occur and smooth settling can be performed.

The example of the magnetic disk device has been described above, but the present invention can be applied to the optical recording device because the positional deviation signal is non-linear. Further, even in the case of a driving device other than the VCM, the method of the present invention can be applied although the calculation formula is different from the above.

[0028]

As described above, according to the present invention, 1
It is possible to manufacture a disc-type recording / reproducing apparatus capable of high-speed access by improving the characteristics of the position control system by a simple and inexpensive method of using the phase signal and only changing the software of the control system.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a diagram showing a switching signal level of the present invention.

FIG. 3 is a time change diagram of a signal of the present invention.

FIG. 4 is a conceptual diagram of a conventional magnetic disk device.

FIG. 5 is a conventional magnetization pattern diagram for measuring a displacement signal.

FIG. 6 is a conventional positional shift signal diagram.

FIG. 7 is a positional deviation signal diagram expanded by a conventional track number.

FIG. 8 is a time change diagram of a conventional signal.

[Explanation of symbols]

 1 VCM 2 Off-track of recording medium 3 Magnetic head 4 Position shift signal 5 Selector 6 Estimated position shift 7 Compensator 8 VCM drive current at previous sample time 9 Position shift signal at previous sample time 10 Position shift

Claims (1)

Claim: What is claimed is: 1. A converter for recording / reproducing an apparatus for recording / reproducing information, which comprises forming a concentric or spiral recording track on a rotating recording medium and moving the transducer to the target track. In controlling the drive device to hold, the output of the position detector is used in the linear area of the position detector and the position deviation information estimated by calculation is used in the nonlinear area to obtain the position deviation information of the target track and the transducer. A method for controlling a recording / reproducing apparatus, comprising: