JP2566616B2 - Track control self-diagnosis method for magnetic disk unit - Google Patents

Description

The present invention relates to a self-diagnosis method for diagnosing a track positioning control operation of a magnetic disk device.

(Prior Art) Conventionally, in a magnetic disk device, a step motor, a voice coil motor, a DC motor or the like is generally used as a drive source of a method of accessing a predetermined track position of a magnetic head. The step motor has a low access speed and is suitable for low-priced devices, and the voice coil motor has a high access speed and is suitable for high-end machines. DC motors are often used in mid-range devices.

In the case of a DC motor, an encoder is used at the same time to allow step-by-track movement and positioning to a defined track position. The encoder generally comprises a slit disk having a slit corresponding to the track pitch and rotating together with the motor shaft, and a photo sensor, and detects the rotation angle of the motor. Therefore, the magnetic head can access a predetermined track position by controlling the rotation of the DC motor by the encoder.

In the magnetic disk device, when the temperature changes, a track position shift occurs between the track position of the magnetic disk and the position of the magnetic head due to the difference in thermal expansion of each member. If this track position deviation is large, it will interfere with adjacent tracks and a read error will occur, so in order to prevent this,
A signal for detecting whether or not the magnetic head is located at the center of the track is written on the magnetic disk, and the signal is read by the magnetic head to calculate the amount of positional deviation, which is fed back to the DC motor. The position shift amount is corrected so that the position shift is eliminated.

FIG. 2 is a block diagram of a conventional track positioning circuit.

In the figure, 1 is a magnetic disk, 2 is a magnetic head,
3 is an arm to which the magnetic head 2 is attached, 4 is an arm 3
Is an access motor composed of a DC motor for driving the.
A capstan 5 is connected to the rotating shaft of the motor 4, and a flexible steel belt 6 having both ends fixed to the arm 3 is wound around the capstan 5. When the motor 4 rotates, the magnetic head 2 moves. To do. An encoder 7 outputs rotational position information of the motor 4, that is, operating position information P.

Reference numeral 8 denotes an AD converter which converts the deviation information of the magnetic head 2 with respect to the track read by the magnetic head 2 into a digital value. The deviation information may be, for example, on each side of each track centered on the center of the track.
Two kinds of burst signals are written as servo information on the magnetic disk 1 at positions shifted by 1/4 pitch, that is, at positions shifted by a half pitch from each other, and when each servo information is read by the magnetic head 2. Output voltages based on their mutual amplitudes are used. Reference numeral 9 denotes a microcomputer which digitally outputs two output voltages based on the value of the AD converter 8, that is, the track position deviation information based on the track position deviation amount when the magnetic head 2 is positioned at the track position and is in a stable state. The difference is calculated from the converted value and output as an 8-bit digital value. Then, the value is corrected every moment according to the change with time. Reference numeral 10 denotes a DA converter which converts the track position deviation information calculated by the microcomputer 9 into an analog amount of track position deviation information C. A subtracter 11 calculates an error signal E (track position error information) based on the difference (CP) between the track position shift information C and the operating position information P. 12 is an amplifier, 13 is a compensator,
14 is a drive circuit, the error signal E is amplified by the amplifier 12,
The frequency is compensated by the compensator 13, and the drive circuit 14 receives this, and when the magnetic head 2 is finely adjusted to the track position,
The motor 4 is driven so that the error signal E approaches 0.
When the error signal E becomes 0, the tracks are positioned in balance.

FIG. 3 is a diagram for explaining the positioning operation by the circuit of FIG. The vertical axis represents voltage (V), and the horizontal axis represents phase (motor rotation angle). The operating position information P is a sinusoidal signal whose voltage changes between + V _m and −V _m according to the rotation angle of the motor 4. Intersection P _n-1 in this operating position information P and 0 level, P _n, P _{n + 1} ... of the phase θ is, each track n-1 in the absence of track misregistration, n, n + 1 ... magnetic head above Corresponds to having 2. In this case, the motor 4 positions the track at this position. The temperature variation, the track misregistration occurs, for example, to track misregistration information C C ₁ when the track position deviation amount in terms of the rotation angle of the motor 4 d _1, and when d ₂ is the C ₂ The motor 4 is set to each phase that is set and the operating position information P is P ₁ and P ₂ , respectively.
The rotation angle is controlled and the track is positioned.

Here, on-track control (track positioning control)
Will be described in detail.

First, when the magnetic head 2 shown in FIG. 2 moves from the track M, which is currently located, to the track N, the operation position information during the head movement, that is, the rotational position information of the motor 4 from the encoder 7 is used to move from the track M. The rotation of the motor 4 is controlled so as to move to the track N. During this operation, the track position deviation information C of FIG. 2 is not used, and C = 0 (V) is actually output from the DA converter 10.

In the case of C = 0 (V), the error signal E output from the subtractor 11 becomes E = 0 (V) in the state of the operating position information P = 0 (V), for example, the position of Pn in FIG. Then, the motor 4 is stopped and becomes stable. The head 2 is on-track at this Pn position, and no track position deviation occurs.

When the temperature rises, a track position shift occurs due to the difference in thermal expansion of each member as described above, but when the motor 4 is stopped at the position Pn in FIG. 3, the head 2 moves from the track center. Cause a gap.

When the motor 4 stops at the position Pn and the positional deviation amount is converted into a rotation angle and is d1, the track positional deviation information C = C1 (V) as shown in FIG. 3, and the input of the subtractor 11 is P
= 0 (V), C = C1 (V), error signal E = C1 (V)
Does not become 0 (V).

Therefore, the motor 4 rotates so that P = 0 to P = P1 (= C1), the head 2 moves by a distance corresponding to the positional deviation amount d ₁ , is positioned at the center of the track, and is on-track.

In the on-track state, the stable state is achieved with P = C and E = 0. That is, the error signal E controls the rotation of the motor 4 so that P and C become equal.

Therefore, the on-track control when the track position deviation occurs acts as a servo mechanism that operates so that the error signal E becomes "0" (equilibrium state).

The value of the track position deviation information C is limited to the range of + Cm to -Cm. That is, the range larger than + C _{m and} smaller than -C _m is because the value P of the encoder 7 becomes unstable at the apex, and the range of the track position deviation amount that can compensate the track positioning control is as shown in the figure. It is from + d _m to −d _m .

In this case, the track position shift is automatically corrected and the on-track control is performed between the vertices in the waveform of the operating position information P in FIG. 3, that is, | ± Vm |> | ± C
The premise is that there is a relationship of m |.

(Problems to be Solved by the Invention) In a magnetic disk device, it is necessary that the track positioning control be stably performed when the track position deviation amount changes from each of the above limit values + dm to −dm due to temperature fluctuations or the like. However, for this reason, in the manufacturing inspection process, a test process is required in which the operation test is performed by changing the temperature environment until the track position deviation amount near each of the limit values occurs. There was a problem that it took time.

It is an object of the present invention to provide a track control self-diagnosis method for a magnetic disk device, which enables confirmation of track positioning control operation without changing the temperature environment.

(Means for Solving the Problems) In order to solve the above problems, the present invention calculates track position deviation information from deviation information for a track of a magnetic head read from a magnetic disk, and calculates the track position deviation information and the operating position. Track position error information based on the information and 0
In the track control self-diagnosis method of the magnetic disk device for controlling the track positioning by driving the access motor so as to approach the track position, the magnetic disk device presets the limit value of the track position deviation information necessary to compensate the track positioning control. The limit value is used in place of the calculated track position deviation information at the time of self-diagnosis, and positioning control is performed to check whether or not there is an abnormality in the positioning control.

(Operation) According to the present invention, the magnetic disk device presets and stores the limit value of the track position deviation information necessary for compensating the track positioning control. Track positioning control is performed so that the track position error information based on the information approaches 0, and self-diagnosis is performed by checking whether or not the positioning control is abnormal.

(Embodiment) FIG. 1 is a block diagram of a track positioning circuit showing an embodiment of the present invention.

In the figure, the same parts as those in FIG. 2 are shown with the same reference numerals, and the different parts will be mainly described below.

9A is a microcomputer, 15 is a track position deviation information calculation unit having the same function as that of the microcomputer 9 described in FIG. 2, and 16 is a third position which is permitted to ensure that the track positioning control is performed reliably. A limit value storage unit that presets and stores the limit values + C _m and −C _m of the track position deviation information in the figure, and 17 is a determination unit that determines whether or not there is an abnormality in the track positioning control. 18 is a changeover switch for switching between normal track positioning operation and track positioning operation during self-diagnosis, V _cc is a positive control power source, R is a pull-up resistor, and track change information is calculated when the changeover switch 18 is off. The operation of the unit 15 is designated, and when it is ON, the reading operation of the limit value storage unit 16 is designated. Reference numeral 19 denotes an E / O signal generation circuit, which receives the operating position information P of the encoder 7 and when the voltage + V _m is generated, sets the output to a low level,
When voltage -Vm is generated, it is set to high level and each track n
For example, if n is an even number, −1, n, n + 1 ... Outputs a high-level digital signal to the determination unit 17 when the number is even (E) and a low level when the number is odd (O). Judgment unit 17
Determines that the positioning is unstable when the E / O signal changes after the lapse of a predetermined settling time, or that the track positioning control is abnormal due to runaway.

Explaining this in more detail, when the track position deviation amount is normal, the error signal E = C-P = O, that is, P = ± Cm, even when the limit value ± dm (C = ± Cm) in FIG. Thus, the motor 4 rotates and stops, and becomes stable.

Therefore, the E / O signal of the E / O signal generation circuit 19 of FIG. 1 is stable at the high level when the number of tracks is even, and at the low level when the number of tracks is odd. .

In this case, the E /
The O signal does not change from high level to low level or low level to high level.

The track position deviation amount of the magnetic disk device is expected to be maximum + dm to −dm in FIG. 3, and although the position deviation correction amount at that time is designed to be + Cm to −Cm, an abnormality occurs and the track position If the deviation cannot be corrected from + Cm to -Cm, P for some reason is shown in FIG.
This is the case where the peak ± Vm of the waveform of becomes smaller than ± Cm.

That is, when the head 2 is located on an arbitrary track, C = + Cm or -Cm, and E = C-, under the above conditions and when the track position deviation is maximum (± dm).
The rotation of the motor 4 is controlled so that P = O, that is, P = + Cm or -Cm.

However, since the peak of the waveform of P is smaller than ± Cm as described above, P cannot reach ± Cm, the head 2 reaches the area of the next track, and as a result, the motor 4 cannot be controlled. Then, the head 2 further moves the tracks one after another, and the motor 2 runs out of control.

Therefore, the waveform of P reaches the peak ± Vm before it reaches ± Cm.
The E / O signal generated by the E / O signal generation circuit 19 changes repeatedly at high level and low level after the settling time of the motor or the like has elapsed.
The determination unit 17 in FIG. 1 detects this and determines that it is abnormal.

Therefore, if the device is capable of normal correction up to the limit value ± Cm, the correction value of C = ± Cm, the stable state at the position of P = ± Cm, and the limit value ± of the track position deviation information at this time Cm
As a result, the magnetic head is properly positioned at the center of the track, and on-track control is performed.

Next, the operation of the circuit shown in FIG. 1 will be described. FIG. 4 is a flow chart showing the operation.

As an initial condition, the limit value of track positioning information + Cm
Alternatively, the flag F designating the sign of -Cm is set to 0 (step S1).

When the changeover switch 18 is off (S ₂ ), the track position deviation information calculation unit 15 is in the operating state, and the normal access operation is performed. The track position deviation information calculation unit 15 determines the track position deviation information when there is a temporal change in the track position deviation from the reading result of the track position information when the magnetic head 2 is positioned and is in a stable state (S ₃ ). Calculated (S ₄ ), if there is no track position deviation information calculated previously, these are sent out, and the DA converter 10
This is converted into analog track position shift information C and sent to the subtractor 11 (S ₅ ). Although the access control is not shown in FIG. 1, the magnetic head 2 accesses the specified track under the control of the microcomputer 9A (S ₆ ), and the magnetic head 2 specifies the position by the track position deviation information C and the operation position information P. is controlled positioning of the track (S _7).
Then, the track position information in the stable state of the positioning is taken into the track position deviation information calculation unit 15 via the AD converter 8, and the operation after step S2 is repeatedly executed.

When the changeover switch 18 is turned on in step S2, the reading operation of the limit value storage unit 16 is performed. Flag F
= When the 0 (S _8), the limit value of the positive track misregistration information from the limit value storage unit 16 is read out, DA converter 10
Converts this into analog track position deviation information + C _m and sends it to the subtractor 11 (S ₉ ). Microcomputer 9 _A
The magnetic head 2 is accessed to the random track by the control of (S ₁₀ ), and the positioning is controlled to the random track by the limit value + Cm of the track position deviation information and the operation position information P (S ₁₁ ). Then, when the positioning control is normally performed (S ₁₂ ), F = 0 at this time (S ₁₃ ), and if the predetermined number of accesses are not completed (S ₁₄ ), each step S _{9 to} S ₁₄ operations are repeated. When the predetermined number of accesses are completed (S ₁₄ ), F = 1
To to (S _15), returns to the step S _8. At this time, F = 1
Therefore, the limit value of the negative track position deviation information is read from the limit value storage unit 16, the DA converter 10 converts this to the analog track position deviation information −Cm, and sends it to the subtractor 11 (S ₁₆ ). And each step S ₁₀ ~
If the operation of S ₁₃ is executed and the predetermined number of accesses are not completed (S ₁₇ ), each step S ₁₆ , S _{10 to} S ₁₃ , S ₁₇
Operation is repeated, and a predetermined number of accesses is ended (S _17), and terminates the self-diagnostic of the magnetic disk 1.

In step S _12, when the abnormality in the positioning control magnetic head 2 is unstable operation occurs, or runaway,
The determination unit 17 detects whether the signal of the E / O signal generation circuit 19 changes after the elapse of a predetermined settling time, determines that the signal is abnormal, and separately displays the error occurrence (S ₁₈ ). ,
The microcomputer 9 _A stops the drive of this magnetic disk device (S ₁₉ ).

As described above, according to the present invention, the magnetic disk device presets and stores the limit value of the track position deviation information necessary for compensating the track positioning control.
At the time of self-diagnosis, since it is confirmed that the magnetic head is positioned and controlled at the position corresponding to the limit value, no special equipment for changing the temperature environment is required and the test time is shortened.

[Brief description of drawings]

FIG. 1 is a block diagram of a track positioning circuit showing an embodiment of the present invention, FIG. 2 is a block diagram of a conventional track positioning circuit, FIG. 3 is an operation explanatory diagram of the circuit of FIG. 2, and FIG. 3 is a flowchart showing the operation of the circuit of FIG. 1 ... Magnetic disk, 2 ... Magnetic head, 4 ... Access motor, 7 ... Encoder, _9A ... Microcomputer, 11 ... Subtractor, 15 ... Track position deviation information calculation unit, 16 ... Limit Value storage section, 17 ... Judgment section, 18 ... Changeover switch, 19 ... E / O signal generation circuit.

Claims (1)

(57) [Claims] 1. A track position deviation information is calculated from deviation information for a track of a magnetic head read from a magnetic disk, and track position error information based on the track position deviation information and the operation position information of an access motor is brought close to zero. In a track control self-diagnosis method for a magnetic disk device in which track positioning control is performed by driving an access motor, the magnetic disk device presets and stores a limit value of track position deviation information necessary to compensate for track positioning control. During self-diagnosis, positioning control is performed using the limit value instead of the calculated track position deviation information, and a digital signal indicating whether the track created from the operation position information is even or odd changes after a predetermined settling time. To detect whether or not there is an abnormality in the positioning control A track control self-diagnosis method for a magnetic disk device, comprising: