JPS62212981A - Control circuit for magnetic disk device - Google Patents

Abstract

PURPOSE:To improve follow-up accuracy to a target track by providing a deviation correcting circuit giving a correcting command to cancel the deviation to a following control circuit in accordance with a deviation quantity from a target track center in a prescribed time and operating continuously or intermittently the circuit at the time of a following action. CONSTITUTION:In a feed-back control loop by the control circuit of a following action, the loop of a deviation correcting circuit 17 to generate a deviation correcting signal from a position signal is added. The deviation correcting signal is added to the control signal of the control circuit of an ordinary following action in an adding point 16. The switching from a seek action to a following action is executed in a time t0, even in a time t1, when there is the danger that a comparatively large return quantity remains like a curve (b), the reliability of reading and writing is reduced or the reading and writing themselves cannot be executed, the correcting command to cancel the deviation based upon the deviation quantity is calculated, added to a following control circuit by the deviation correcting circuit 17, and thus, the deviation quantity can be made smaller like a curve C and the reading and writing can be executed.

Description

[Detailed Description of the Invention] [Field of Application in Industry] The present invention relates to a control circuit for a magnetic disk device, and particularly improves the tracking accuracy when controlling a magnetic head to follow a target track. The present invention relates to a suitable following control circuit.

[Conventional technology]

The configuration of a conventional magnetic disk device is, for example,
It is described on pages 106 to 119 of Ikei Mechanical, published on the 3rd of May. In this magnetic disk device,
The operation of positioning the magnetic head from a track on a magnetic disk to a target track is called a seek operation.
The operation of reading and writing magnetic recording signals by tracking the center of the target track is called a following operation, and the access operation of the magnetic head consists of repeating these two operations. In a seek operation, in order to move the carriage assembly structure that supports the magnetic head at high speed,
Electric current is applied to the voice coil motor, which generates large acceleration and deceleration thrusts. Therefore, a large reaction force acts on the carriage assembly structure, the carriage block that supports it, and the base on which the carriage block and the spindle of the magnetic disk are loaded. This force deforms each part of the component described in -1-, and this influence remains even in the following operation following the seek operation, resulting in an offset position when tracking the center of the target track. When a deviation from the center of the target track occurs, feedback control functions to reduce the deviation to zero. The gain of this control is selected to be quite large, and it is possible to reduce the amount of deviation caused by normal disk vibration.

[Problems that the invention attempts to solve]

-1U: Conventional control circuits have a control function that corrects the amount of deviation from the target track during a following operation after a seek operation that generates a large force such as when moving a full stroke. There was a problem in that the amount of deviation from the center of the target track did not become small during following.

An object of the present invention is to provide a control circuit that improves the accuracy of tracking a target track during a following operation following a seek operation.

[Means for solving problems]

The above object of the present invention is to provide a control circuit for a magnetic disk device that controls a following operation to control the magnetic head to follow the center of the target track after the magnetic head reaches within a predetermined range from the center of the target track. A deviation correction circuit that applies a correction command to the following control circuit to cancel the deviation from the center of the target track within a predetermined time is provided, and this circuit is operated continuously or intermittently during the following operation. This is achieved by

[Effect]

The deviation correction circuit in the control circuit of the above magnetic head is
During the following operation, the amount of deviation from the center of the one-mark track is input, a deviation correction command corresponding to this is calculated, and this is applied to the following control circuit. As a result, a relatively large amount of deviation from the target track is forcibly corrected, thereby improving the accuracy of following the 11-mark track.

〔Example〕

Embodiments 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 according to the present invention. In this figure, the solid line loop is a feedback control loop by a normal following operation control circuit. This loop includes a position signal demodulation circuit 11, a low-pass filter 12 that removes noise from the position signal, and a filter 13 that performs notch correction on the resonance point of the mechanical system.

It consists of a hard love filter 14 that stabilizes this control system, a backup amplifier 15 that amplifies the control command, a voice coil motor that drives the mechanical system, and the first-mentioned structure 7. In the present invention, in addition to this normal loop, a loop of a deviation correction circuit is added which creates a deviation correction signal from a position signal shown by a dotted line. This deviation correction signal is added at the summing point 16 to the control signal of the control circuit for normal following operation.

FIG. 2 is a time chart showing the operation of the deviation correction circuit 17. The horizontal axis is time 1. , the vertical axis is a position signal indicating the amount of deviation from the center of the target track. The switching from the seek operation to the following operation is performed at times t and o), and from then on, the following control circuit shown in FIG. 1 operates and functions to make the magnetic head follow the center of the target track. do. Therefore, the position signal oscillates several times as it approaches the center of the target track, as shown in FIG. 2, and quickly becomes zero as shown by curve a. Therefore, at time t1, after a predetermined time (usually there is a slight waiting time until the system stabilizes by a following operation after a seek operation) from time t, l), reading and writing of the magnetic recording signal is performed. It becomes possible. However, in the above-mentioned case, a relatively large amount of parts such as one curve remains even at time t1, and there is a possibility that the reliability of reading and writing may decrease or that reading and writing may not be possible at all. In such a case, the above-mentioned deviation correction circuit 17 calculates a correction command to correct or erase the deviation based on the amount of deviation 1, and by adding the following control circuit number 7, the curve C As in, the amount of deviation is reduced and reading and writing is possible.

FIG. 3 is a block diagram showing the internal configuration of the deviation correction circuit 17. In this figure, 18 is a low-pass filter, and since the main deviation component is at a low frequency in the deviation amount as shown by the curve in FIG.
This frequency component is emphasized and extracted. Reference numeral 19 denotes a proportional circuit or a proportional-integral circuit, which creates a deviation correction signal for forcibly generating a deviation amount in the opposite direction to correct the extracted deviation position.

FIG. 4 is a block diagram 11 showing the internal configuration of another example of the deviation correction circuit 17. FIG. 5 is a tie 11 chart showing the functions of this block diagram 11. 2
0 is a timer setting circuit, which sets time t1, time t2, or input time interval T for inputting the amount of deviation.

Reference numeral 21 denotes an extraction circuit which extracts the amount of deviation to be corrected from the position signal at a set time or time interval. This is, for example, the maximum value at that time.

This may be a minimum value or a time average value. A proportional circuit 22 generates a deviation correction signal for generating a deviation in the opposite direction corresponding to the amount of deviation to be corrected.

〔Effect of the invention〕

According to the present invention, when a large force is generated such as when repeating a full-stroke seek operation, a relatively large amount of deviation that is generated during a following operation and which cannot be controlled by a conventional following control circuit can be detected. This can also be corrected for. Therefore, since the accuracy of following the target track is improved, reading and writing operations can be performed immediately after starting the following operation, which not only reduces waiting time but also significantly improves the reliability of reading and writing.

[Brief explanation of drawings]

FIG. 1 is a bronch diagram 11 showing the configuration of the control circuit of the present invention, FIG. 2 is an explanatory diagram showing the function of an example of the control circuit of the present invention, and FIG. 3 is the control circuit of the present invention shown in FIG. FIG. 4 is a diagram showing the configuration of an example of the deviation correction circuit used in the circuit, FIG. 4 is a diagram showing the configuration of another example of the deviation correction circuit, and FIG. 5 is an explanatory diagram showing its function. 11... Demodulation circuit, ]2... Low pass filter, 1
3... Notch filter, 14... Lead-lag filter, 15... Power amplifier, 16... Addition point, 17...
・・Deflection correction circuit, 18 ・・Low pass filter, 19
...Proportional integral circuit, 20...Timer setting circuit, 21
...Extraction circuit, 22...Proportional circuit.

Claims (1)

[Claims] 1. In a control circuit for a magnetic disk device that performs a following operation to cause the magnetic head to follow the center of the target track after the magnetic head reaches within a predetermined range from the center of the target track, A control circuit for a magnetic disk drive, comprising a deviation correction circuit that applies a correction command to a control circuit for a following operation to cancel the deviation amount from the center of a track. 2. A control circuit for a magnetic disk drive according to claim 1, wherein the deviation correction circuit comprises a low-pass filter and a proportional or proportional-integral circuit. 3. A control circuit for a magnetic disk device according to claim 1, wherein the deviation correction circuit comprises a deviation amount extraction circuit and a proportional circuit.