JPH01162279A - Control circuit for magnetic disk device - Google Patents

Abstract

PURPOSE:To always move a magnetic head while keeping prescribed height for a disk in floating with stable posture by driving an actuator by a signal in which a deviation signal is passed through a blind sector element. CONSTITUTION:The actuator 7 is driven by the signal in which the deviation signal is passed through the blind sector device, and in the neighborhood of a targeted track, the actuator 7 is driven by the signal in which the deviation signal is not passed through the blind sector element. In other word, targeted speed is taken by switching the positive and negative values of the deviation signal with a speed detecting signal frequently, however, the number of times of switching can be reduced by passing the signal through the blind sector element 4. In such a way, it can be reduced that the actuator 7 outputs the force in a positive direction and the one in a negative direction little by little. As a result, since the supporting mechanism of the magnetic head can be prevented from being oscillated frequently, it is possible to maintain the magnetic head being moved at high speed with the stable posture for the disk.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control circuit for a magnetic disk device, and particularly to a control circuit suitable for controlling the speed of a magnetic head.

[Conventional technology]

A conventional control circuit for controlling the speed to a target speed in order to move the magnetic head of a magnetic disk device to a target track is described in Japanese Patent Laid-Open No. 53-3308. The control circuit shown in these generates a target speed signal to the target track, amplifies the deviation signal between this signal and a speed detection signal that detects the actual moving speed of the magnetic head, and moves the magnetic head. The basic configuration is a feedback control circuit that drives the actuator. moreover,
In order to improve speed control performance, control circuits with feedforward control that directly drive the actuator using a target acceleration signal are also used. but,
No consideration was given to the fact that the magnetic head, which is controlled by an actuator to reach a target speed and moves at high speed, must always fly in a stable posture at a predetermined height relative to the disk.

Furthermore, in order to improve the control performance of the conventional speed control, the boundary between positive and negative switching of the control circuit is made so that they do not overlap at all, and the gap between positive and negative switching is made as much as possible. Therefore, when the control circuit signal approaches zero, it is inevitable that the frequency of switching will increase. but,
This result is seen as a result of improved speed control performance, and no consideration was given to making the magnetic head fly in a stable attitude.

[Problem that the invention seeks to solve]

In the above conventional technology, if the actuator is simply driven based on the deviation signal between the target speed and the speed detection signal,
The more the control performance of the control circuit is improved, the more frequently the deviation signal changes between positive and negative values around zero. Therefore, the actuator outputs a positive force and a negative force in small steps. This irregular force is transmitted to the magnetic head support mechanism attached to the tip of the actuator. This support mechanism is made of thin plates, rods, etc. to reduce weight, and has several natural frequencies ranging from several hundred to several kilometers H2. Therefore, when the support mechanism is vibrated at various frequencies, it vibrates significantly not only in the direction of the applied force but also in a direction perpendicular to it.

As a result, the magnetic head is no longer able to fly in a stable position at a predetermined height relative to the disk.
There was a problem that the magnetic head came into contact with the disk.

An object of the present invention is to provide a control circuit for controlling the speed at which a magnetic head is moved to a target track, which allows the magnetic head to move at a predetermined height relative to a disk while always flying in a stable posture. It is something to do.

[Means for solving problems]

The above object is to provide a control circuit for a magnetic disk that controls the speed of a magnetic head based on a deviation signal between a target speed signal and a speed detection signal, by driving an actuator using the deviation signal passed through a dead zone element.
achieved.

[Effect]

In the control circuit of the present invention, the deviation signal between the target speed and the speed detection signal is obtained by frequently switching between positive and negative values, but it is possible to reduce the number of times this switching occurs by passing this signal through a dead band element. can. As a result, the actuator is less likely to output positive and negative forces in small steps. As a result, the supporting mechanism for the magnetic head is not unnecessarily vibrated, so that the magnetic head, which moves at high speed, is maintained in a stable position floating relative to the disk. Therefore, even if the magnetic head is moved at high speed, contact between the magnetic head and the disk can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a control circuit of a magnetic disk device of the present invention. 1 is a target track indicator that specifies the destination of the magnetic head, 2 is a speed pattern generator that generates a target speed according to the number of tracks remaining to the target track, 3 is an acceleration pattern generator, and 4 is a target speed. A dead band element that passes the speed deviation signal between the speed detection signal and the speed detection signal.

5 is a low-pass filter that removes high frequency components from the signal obtained by adding the output signal of the dead band element 4 and the target acceleration; 6 is a power amplifier that amplifies the output of the low-pass filter; 7 is a voice coil motor driven by the output of the power amplifier, etc. 8 is a magnetic head moved by the actuator and its support mechanism; 9 is a position signal demodulation circuit that generates a position signal indicating the position of the magnetic head from a servo signal read when the magnetic head moves on the disk. , 10 is a speed detector that generates the speed of the magnetic head by differentiating the position signal, 11 is a track counter that calculates the number of tracks passed from the position signal, and 12 is whether or not the dead zone element 4 is used for speed feedback control. This is a switch that switches between

When the number of remaining tracks is larger than a predetermined value, the speed deviation signal is passed through the dead zone element, and when the number of remaining tracks is smaller than the predetermined value, that is, near the target track, the speed deviation signal is not passed through the dead band element. Make it. Therefore, the number of remaining tracks is input to the switch 12,
By comparing this with a predetermined number of tracks determined in advance, the time point of the switching operation is determined.

FIG. 2 is an example of the target velocity generated for each track from the velocity pattern generator 2 and the target acceleration generated for each track from the acceleration pattern generator 3. When the number of remaining tracks is large, the target speed is often limited to a constant value due to constraints for realizing the power amplifier and actuator, and when the number of remaining tracks is small.

To give a target speed that allows smooth positioning to a target track. On the other hand, since the target acceleration is an acceleration corresponding to movement at the target speed, as shown in FIG. 1, feedforward control is possible in which the actuator is directly driven according to the number of remaining tracks. With this control,
If disturbances and condition fluctuations are small, accurate speed control is possible.

FIG. 3 shows the function of the dead zone element 4.

When the speed deviation between the target speed and the speed detection signal detected by the speed detector 10 is input to the dead band element 4, if the absolute value of the deviation is smaller than a predetermined value, an output is output. Output is produced only if the value is greater than . When the control performance of the control circuit shown in FIG. 1 is improved, the deviation signal frequently switches between positive and negative values around zero in an attempt to achieve the target speed. When this deviation signal is passed through the dead band element 4, no output is produced for fluctuations smaller than a predetermined value, so the number of switching operations can be reduced. As a result, the actuator is less likely to output positive and negative forces in small steps. As a result, the support mechanism for the magnetic head is not unnecessarily vibrated, so that the magnetic head is maintained in a stable position floating relative to the disk.

FIG. 4 shows another example of the function of the dead zone element 4.

Functions similar to those shown in FIG. 3 can be realized using odd-order higher-order algebraic curves.

FIG. 5 is a time chart showing the functions of the switch 12. The horizontal axis represents time and shows the process of moving the magnetic head toward the target track. Since the velocity pattern is given as shown in FIG. 2, the velocity is trapezoidal. At this time, the speed deviation changes as shown in the figure, but this change can be alleviated by using the dead zone element 4.

Although it seems that the control performance of the velocity feedback loop is degraded by using the dead zone element 4, the performance of the control system as a whole hardly changes because the acceleration feedforward control is functioning. When there is a large number of tracks remaining to reach the target track, even if the control performance is degraded and the target speed cannot be accurately controlled, the time required for positioning to the target track will not be a hindrance to subsequent targets. No, in fact, since the moving speed is high, it is better not to induce extra vibrations in the support mechanism of the magnetic head in order to avoid contact between the magnetic head and the disk.

On the other hand, when the number of remaining tracks to the target track is small, the moving speed is small and the proportion of speed deviation becomes large. Therefore, if the control performance deteriorates and the target speed cannot be accurately controlled, accurate positioning with respect to the target track will not be possible. Therefore, it is better not to use the dead zone element 4.

〔Effect of the invention〕

According to the present invention, in the process of speed control for moving the magnetic head to a target track at high speed, unnecessary vibrations from the actuator are less likely to be applied to the support mechanism of the magnetic head. As a result, it is possible to maintain the magnetic head floating in a stable attitude relative to the disk. Therefore, contact between the magnetic head and the disk can be prevented, which has a significant effect on improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the functions of a velocity pattern generator and an acceleration pattern generator, and FIGS. 3 and 4 show the functions of the dead zone element 4. Explanatory diagrams FIGS. 5(a), 5(b), and 5(e) are explanatory diagrams showing the functions of the switching device 12. DESCRIPTION OF SYMBOLS 1... Target track indicator, 2... Speed pattern generator, 3... Acceleration pattern generator, 4... Dead zone element, 8... Magnetic head support mechanism, 10... Speed detector , ¥Jz Figure 3 Figure 4 Figure 5 Figure (^) (b) <C)

Claims (1)

[Claims] 1. In a control circuit of a magnetic disk device that controls the speed of a magnetic head based on a deviation signal between a target speed signal and a speed detection signal, the actuator is driven by the deviation signal passed through a dead band element, and the target track is tracked. A control circuit for a magnetic disk drive, characterized in that an actuator is driven by a signal that does not pass a deviation signal through a dead zone element near the .