JPH04353676A - External force offset correction system for disc device - Google Patents

Abstract

PURPOSE:To correct an external force offset even when an external force blocking a head position is large abnormally in an initial state, for example, at the closing of a power source. CONSTITUTION:An external force offset measuring/correcting device 17 sets on a D/A converter 2 a reference offset data which serves to stop a head 10 at a specified position on a disc 18 when there is no external force. A drive circuit 8 operates an actuator 9 according to a value set to move the head 10. When an external force exists, the head 10 fails to stop at the specified position and the position at which the head stops actually is transmitted to a register 16 via a reading circuit 14 and an A/D converter 3. The external force offset measuring/correcting device 17 changes a value set on a D/A converter 2 until the head 10 stops at the specified position to drive the head 10. Thus, an external force offset value is measured from the value set on the D/A converter 2 as given when the head 10 stops at the specified position.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to head positioning control for magnetic disk drives, and more particularly to a method for correcting external force offsets that impede high precision head positioning control for positioning a head on a target track. External force offset is generated by external forces such as the reaction force of the FPC bonded to the magnetic disk drive mechanism, air resistance, friction of bearings on the rotating shaft, and offset of the electric circuit, but the magnitude of each is constant. Therefore, the amount of external force offset differs from magnetic disk device to magnetic disk device, which has been a major hindrance to increasing the accuracy of head positioning. Further, in some cases, the variation in external force may correspond to a force that moves the head from the outermost circumference to the innermost circumference, and it may be impossible to even position the head. (However, head positioning here means to make the head on-track to an arbitrary track.) Therefore, in the initial state such as when the power is turned on, external force is measured without positioning the head, and the magnetic disk drive It is essential to reduce the variation in external force offset at each time.

0002

[Prior Art] FIG. 4 shows, for example, Japanese Patent Laid-Open No. 63-15737
6 is a diagram showing an example of the configuration of a magnetic disk device that implements the conventional external force offset correction method for a magnetic disk device shown in FIG. In FIG. 4, 1 is a microprocessor unit, 2 is a D/A converter, 3 is an A/D converter, and 4 is a microprocessor unit.
5 is a target speed generation circuit, 5 is a speed error detection circuit, 6 is an offset measurement circuit, 7 is a multiplexer for switching between seek control mode and track following control mode, 8 is a drive circuit, 9 is an actuator, and 10 is a head for reproducing servo information. , 11 is a speed detection circuit, 12 is a position error detection circuit,
Reference numeral 13 indicates a position signal generation circuit, 14 indicates a readout circuit, and 15 indicates an offset correction circuit. Here, the seek control mode refers to the control mode from when the head starts moving in response to a seek command until it reaches the target track.
Target speed from target speed generation circuit 4 and speed detection circuit 11
A speed error detection circuit 5 detects the difference in actual speed from
By applying a value corresponding to the difference to the drive circuit 8 via the multiplexer 7, the actuator 9 is driven to move the head 10. On the other hand, the track following control mode is a control mode consisting of transient response control immediately after seek control and steady position control after on-track. By giving the drive circuit 8 a value that makes the error between the position signal that is proportional to the distance and the target position (usually the center of the track) preset in the position error detection circuit 12 to zero, the head 10 is on track.

The method for correcting the external force offset in such a magnetic disk device is as follows. The flow of processing is shown in FIG.

In an initial state such as when a magnetic disk device is powered on, the microprocessor unit 1 sets several sample cylinders at approximately equal intervals among all the cylinders on the disk medium, and causes the head to seek each sample cylinder. Positioning is performed by control and track following control. During track following control when positioning is completed in each sample cylinder, the offset measurement circuit 6 measures the offset, and the microprocessor unit 1 reads the measured offset via the A/D converter 3 (not shown). It is stored in the offset correction memory within the microprocessor unit 1.

The offset value measured in this way is
When executing a seek, the microprocessor unit 1 reads the offset value at the target cylinder position (selects the value closest to the target cylinder to be moved among the previously measured sample cylinders) from the memory, and sets this value to D.
It is output to the offset correction circuit 15 via the /A converter 2. Then, the offset correction value is applied to the speed detection circuit 11 and the position error detection circuit 12, respectively. In this way, the external force offset of the magnetic disk device is corrected.

[0006]

[Problems to be Solved by the Invention] Since the external force offset correction method of the conventional magnetic disk device is as described above, in the initial state such as when the power is turned on, the head is not directed to a specific track by seek control and track following control. must be positioned. However, as described above, when there are large variations in external force, head positioning itself may be impossible, and in such a case, it is not possible to correct the external force offset.

The present invention has been made to solve the above-mentioned problems, and it is possible to measure external forces that differ for each magnetic disk device in an initial state such as when the power is turned on, without positioning the head, and to calculate the external force offset. The purpose is to obtain a correction method.

[0008]

[Means for Solving the Problem] The external force offset correction method of the present invention measures the external force without positioning the head as a first step in an initial state such as when the power is turned on. and a control means for controlling the drive of the head based on the output of the discrimination means. External force is measured from the output of the control means. After taking measures to correct variations in the measured external force, as a second step, positioning is performed on sample tracks set at approximately equal intervals to measure the track-dependent external force offset, and when performing a seek, the above-mentioned first and second This method corrects the external force offset based on the external force offset value obtained in each step.

[0009]

[Operation] With the above configuration, it is possible to measure external forces that differ for each magnetic disk device and correct external force offsets without positioning the head to an arbitrary track in the initial state such as when the power is turned on. It becomes possible.

0010

【Example】

Example 1. First, the overall flow of the external force offset correction method of the present invention will be explained. In the initial state of a magnetic disk drive, such as when the power is turned on, if there is no external force, the head will be located approximately at the center of the data band on the disk, but if there is an external force, the head will move a distance corresponding to the magnitude of the external force. Located off center of the data band. Particularly when the external force is large, it may not be possible to position the head, so as a first step, the overall rough external force offset is measured without positioning the head. However, since the external force is not constant on all tracks, after performing the above external force offset correction, as a second step, sample tracks are set at approximately equal intervals among all tracks as in the conventional example, and each sample Position the head on the track and measure the track-dependent external force offset. When performing a seek, the track-dependent external force offset of the target track is calculated proportionally from the track-dependent external force offset value of the sample track, and
The external force offset correction value set in the first step is added to this to correct the external force offset.

FIG. 1 is a block diagram of a magnetic disk device according to an embodiment of the present invention. In FIG. 1, 18 is a disk, 10 is a head for reproducing data or servo information recorded on the disk 18, and information indicating whether it is a data band area or a guard band area is embedded in the servo information. . Further, 14 is a readout circuit, 3 is an A/D converter, 16 is a register, 19 is a position error signal detector, 20 is a speed signal detector, 21 is a target speed generator,
22 is a speed error signal detector, 23 is a compensator that calculates the control output value to be set in the D/A converter 2, 17 is an external force offset measurement/correction device, and 24 is added inside or outside the microprocessor unit 1. 25 is a switch for switching between a seek control mode, a track following control mode, and a mode for measuring an external force offset;
8 is a D/A converter that inputs the output from the external force offset measurement/corrector 17 or the compensator 23 and converts it into a D/A converter; 8 is a drive circuit that drives the actuator 9; Figure 2 shows
It is a processing flow chart of one example of this invention. FIG. 3 is a diagram showing the inner guard band area 26, data band area 27, and outer guard band area 28 on the disk 18.

The operation of the first step will be explained using FIGS. 1, 2 and 3. When the power is turned on, if there is no external force offset, the external force offset measurement/correction device 17 converts the value that causes the head to stop at the center of the data band area 27 via the C contact of the mode selector switch 25 and converts it into a D/A. I am giving it to vessel 2. However, if there is an external force offset,
When the power is turned on, the head remains at an arbitrary position on the disk. First, in step (1), the external force offset measurement/correction device 17 sets the D/A converter 2 to off-out. of-out is a value at which the head is stopped at the outer periphery 29 slightly from the boundary line between the data band area 27 and the guard band area 28 provided on the outer periphery side (standard offset) when there is no external force that generates an external force offset. data) and is stored in a register ax (not shown) in the microprocessor unit 1. Drive circuit 8
drives the actuator 9 according to the value set in the D/A converter 2, and the head 10 directly connected to the actuator 9 moves to an arbitrary position. At this time, if there is no external force that causes an external force offset, the head 10 should be located near the boundary between the data band area 27 and the outer guard band area 28, but the external force that causes the external force offset is In some cases, they are located elsewhere. Step (2) is a wait routine that sets a value in the D/A converter 2 and waits until the head starts moving until it is stopped.・I decided to include a routine. The servo information reproduced by the head 10 includes data.
Band area 27 or guard band area 26, 28
Since the information indicating whether the head 10 is currently located can be set in the register 16 via the readout circuit 14 and the A/D converter 3, it is possible to set a flag indicating in which area the head 10 is currently located. Therefore, in step (3),
The position where the head 10 is stopped is the data band area 2
7 or not is determined based on the flag of the register 16 shown in FIG. do.

In the case of branching to step (4), it is considered that there is an external force that offsets the head 10 inward, so that the value stored in the ax register in the microprocessor unit 1 is offset by β. The reduced value is stored in the bx register, and the external force offset measurement/corrector 17 converts the value stored in the bx register into D/
Set it on A converter 2 and move the head. head 1
If 0 is still in the data band area, store the value of the bx register in the ax register, store the value reduced by β further in the bx register, set that value in D/A converter 2, and continue. Move the head. This operation continues until the head 10 enters the outer guard band region. In this way, the value set in the D/A converter 2 is reduced by β, and the boundary between the data band area 27 and the outer guard band area 28 is found. At this time, the value immediately before the head 10 enters the outer guard band area 28 from the data band area 27 is stored in the ax register, and the value immediately after entering the guard band is stored in the bx register. In order to perform the next process, the value of the ax register and the value of the bx register are exchanged, and the process proceeds to step (6).

On the other hand, in step (5), it is determined whether or not the head 10 is restrained by the guard band area 26 on the inner circumference side, and the head 10 is stopped in the guard band area 26 on the inner circumference side.
If 0 is being restrained, the process proceeds to step (7), and if not, the process proceeds to step (8). Step (7)
From then on, by decreasing the value stored in the ax register by α until the head 10 enters the data band area 27, the value set in the D/A converter 2 is set to α.
The head 10 is moved gradually. After the head 10 enters the data band area 27, the state is the same as in step (4), so the process advances to step (4).

In step (8), the D/A converter 2 of
Set -in. of-in is slightly inner periphery 30 from the boundary between the data band area 27 and the guard band area 28 on the outer periphery side when there is no external force that generates an external force offset.
This value is stored in the ax register, and is a value that the head 10 controls at the time. Then, in step (9), it is determined whether the head 10 is stopped in the data band area 27 or not. Even without steps (8) and (9), it is possible to measure the external force offset in all cases, but the microprocessor
In order to reduce the processing time of unit 1, step (8
), (9) are being implemented. In the case of data band region 27, there is a boundary between of-out and of-in, and it is considered that there is almost no external force that causes an external force offset. Therefore, proceed to step (10), and perform external force offset correction. Set the value to 0 and end the process. If it is not the data band area 27, it is considered that there is an external force offset that moves the head 10 to the outer circumferential side, so the process proceeds to step (11), and the value stored in the ax register is increased by β to the bx Store in register. Then, the value of the bx register is transferred to the D/A converter 2.
The head is moved by setting it to . By repeating this operation, the boundary between the data band area 27 and the outer guard band area 28 is found. At this time,
The value immediately before passing through the boundary is stored in the ax register, and the value immediately after passing through the boundary is stored in the bx register. After that, proceed to step (6).

Step (6) and subsequent steps are routines for calculating the value of the external force offset with higher precision by the bisection method based on the values stored in the ax and bx registers. The value cx=(ax+bx)/2 is stored in the cx register, the value is set in the D/A converter, and the head 10 is moved. When the head 10 is stopped in the data band area 27, the value stored in the cx register is stored in the bx register, and the difference between the value in the bx register and the value in the ax register is checked. If the head 10 is not stopped in the data band area 27, the value stored in the cx register is stored in the ax register,
Look at the difference between the value of the bx register and the value of the ax register. bx
If the difference between bx and ax is γ or more, the process returns to the beginning of step (6) and repeats this operation until the difference between bx and ax becomes γ or less. When the difference between bx and ax becomes less than γ, process the difference between the value stored in the cx register and of-in, or the difference between the value stored in the cx register and of-out as an external force offset value. The measured external force offset value is stored in the microprocessor unit 1 or external memory 24.

Next, a method of measuring the track-dependent external force offset on the sample track in the second step will be described. The processing flow is the same as the conventional flow shown in FIG. First, the error between the target speed generated by the target speed generator 21 and the actual speed detected by the speed signal detector 20 is determined by the speed error signal detector 22. The head 10 is positioned on the sample track by seek control in which the compensator 23 compensates for the positional error detected by the positional error signal detector 19 and track following control in which the compensator 23 compensates for the positional error detected by the positional error signal detector 19. In the seek control mode, the mode changeover switch 25 is set to b.
In the track following control mode, it is connected to a. When performing this seek control and track following control, the compensator 23 reads out the external force offset value obtained in the first step stored in the memory 24 via the external force offset measurement/correction device, and adds that value. D/A converter 2
It is set to . Therefore, even if the external force offset is large, the head can be reliably positioned on the sample track, and the second step measurement can be performed. Then, in each sample track, during the track following control mode after positioning is completed, the external force offset measurement/correction device 17
calculates the external force offset by averaging the position error signals measured a plurality of times, and stores it in the memory 24. The above is the method for measuring the track-dependent external force offset on the sample track.

Example 2. In the above embodiment, the boundary between the data band area of the external force offset in the first step and the inner or outer guard band area is determined, but in addition to this, the boundary between the data band area of the external force offset and the guard band area on the inner or outer side is determined. It is also possible to measure the external force offset by determining the boundaries of concentrically divided areas, such as the boundaries between the two areas.

[0019]

As described above, in this external force offset correction method, the external force that generates the external force offset is measured without positioning the head in the initial state such as when the power is turned on, and the external force offset correction value to correct this is determined. Since the external force offset can be set, it is possible to correct the external force offset even when the external force offset is large.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a magnetic disk device in an embodiment of the present invention.

FIG. 2 is a processing flowchart of an embodiment of the present invention.

FIG. 3 is a diagram showing a guard band area and a data band area on a disk.

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

FIG. 5 is a conventional processing flowchart.

[Explanation of symbols]

1 Microprocessor unit 2 D/A converter 3 A/D converter 10 Head 14 Readout circuit 16 Register 17 External force offset measurement/corrector 18 Disk

Claims (1)

[Claims] 1. A disk device for reproducing servo information recorded on a disk and positioning a head on a predetermined track, a determining means for determining a predetermined position on the disk; The head is driven by changing the output of the control means in stages, and the head is driven by the output of the control means when the head stops at the predetermined position on the disk. An external force offset correction method for a disk device, characterized in that an external force that prevents the head from being held at a predetermined track position is measured, and an external force offset correction value is set based on the measured value.