JPH01154376A - Positioning method for magnetic head - Google Patents

Abstract

PURPOSE:To control a track positioning even when the quantity of the position dislocation of the track exceeds the half pitch of a track pitch by positioning to an access designated track based on a reception signal according to a servo pattern. CONSTITUTION:The servo patterns A-D have a constant frequency and the patterns A, B and C, D have respectively prescribed widths corresponding to even number tracks TR0, TR2,... and odd number tracks TR1, TR3,... by defining an index signal to be an origin and the respective patterns are mutually made different in a rotating phase and the patterns of the same code have a common phase to the respective tracks. Deviation signals P and Q corresponding to the tracks of the even numbers and the odd numbers are read by a head 7 and a positive code is applied to the respective patterns A, C and a negative code is applied to the patterns B, D, respectively by a microcomputer 10. Then, the signal P or Q is positioned to a point of zero.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for positioning a magnetic head of a magnetic disk drive.

(Prior Art) Hard disk drives are used as high-speed, large-capacity external storage devices for computers, word processors,
It has become widely used in engineering workstations. As the range of use has expanded in this way, the demand for increased capacity has also become stronger. An effective way to increase capacity is to increase the track density of the magnetic disk.

In order to accurately position a magnetic head on a high-density track in this way, generally a servo motor is combined with an encoder, which is its position detector, and track position deviation information is extracted from the magnetic disk. A servo system is used in which the position is corrected by

In magnetic disk drives, when there is a temperature change, a track position shift occurs between the track position of the magnetic disk and the position of the magnetic head due to differences in thermal expansion of each member.
If this track position deviation is large, it will interfere with adjacent tracks and cause reading errors, so to prevent this, track position information is written on the magnetic disk and read out with a magnetic head. and the rotation angle of the motor by the encoder, and feeds back to the servo motor to correct the positional deviation so that the positional deviation disappears.

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

In the figure, 1 is a servo motor as an access motor, 2 is a signal disk connected to the shaft of servo motor 1, and 3 is a servo motor as an access motor.
is a sensor that extracts rotational position information R of the servo motor 1,
4 is a pulley, 5 is a steel belt wrapped around the pulley 4, 6 is a carriage to which the steel belt 5 is attached,
7 is a magnetic head attached to the carriage 6, and 8 is a magnetic disk. The magnetic head 7 faces the magnetic disk 8 and reads and writes information.

9 is an AD converter which converts the deviation information of the magnetic head 7 with respect to the track read by the magnetic head 7 into a digital value. As the deviation information, for example, two types of burst signals shifted by half a pitch centering on each track are written as servo information on the magnetic disk 8, and when each servo information is read by the magnetic head 7. Values based on mutual amplitude ratios are used. A microcomputer 10 calculates track position deviation information based on the amount of track position deviation when the magnetic head 7 is positioned at a track position and in a stable state, based on the value of the AD converter 9, and outputs it as a digital value. Then, the value is successively corrected according to the change over time. Reference numeral 11 denotes a DA converter that converts the track position deviation information calculated by the microcomputer 10 into track position deviation information X in an analog quantity. A subtracter 12 calculates an error signal E (track position error information) based on the difference (x-R) between the track position deviation information X and the operating position information R. A drive circuit 13 drives the servo motor 1 to bring the error signal E close to 0 when the magnetic head 7 is finely adjusted to the track position. When the error signal E becomes 0, the track position is balanced.

FIG. 3 is an explanatory diagram of positioning operation by the circuit of FIG. 2. The operating position information R is a triangular wave signal whose voltage changes according to the rotation angle θ of the servo motor 1. The phase of the intersection of this operating position information R and the 0 level is the phase of each track (TRO, TRI,...) when there is no track position shift.
・) This corresponds to the fact that the magnetic head 7 is located on the top. In this case, the servo motor 1 performs track positioning at this position.

When a track position shift occurs due to temperature fluctuations, the rotation angle of the servo motor 1 is controlled at each phase of the intersection of the track position shift information X and the operating position information R to position the track.

(Problems to be Solved by the Invention) However, according to the above method, the value of the track position deviation information X is limited to a range extending from the straight line U shown in FIG. That is, the range larger than the straight line U and smaller than the straight line is because the value R of the sensor 3 becomes unstable at the vertex, and as a result, the range of the track position deviation amount is limited to approximately half the track pitch. Therefore, if a track position shift of more than half a pitch occurs due to temperature fluctuations, it cannot be corrected. Therefore, since it is necessary to set the track pitch so that the track position deviation does not exceed half a pitch, there is a problem that the track density cannot be increased and the storage capacity cannot be increased.

In view of the above-mentioned problems, the present invention moves the magnetic head by specifying which track side facing the magnetic head should be positioned based on a received signal from a servo pattern arranged on the magnetic disk. It is an object of the present invention to enable track positioning control even when the amount of track position deviation exceeds a half pitch of the track pitch by positioning the track to which the access is designated.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a magnetic head that controls the access motor by feeding back operation position information of the access motor to position the magnetic head on a track of a magnetic disk. In the positioning method, servo patterns of a predetermined width are arranged at equal distances from each other across the track center of the magnetic disk, and the corresponding rotational phase is common to even-numbered tracks and odd-numbered tracks, and the magnetic heads are opposed to each other. Calculate the deviation between the received level by the servo pattern on one side and the received level by the servo pattern on the other side with respect to the center of each track for two tracks in the vicinity of the track center, and based on the sign of the deviation for the two tracks. Then, the direction of movement of the magnetic head for positioning on that one track is specified, and the magnetic head is positioned at a position where the deviation for the specified track becomes zero.

(Function) According to the present invention, the mutual level deviation of each servo pattern arranged between two tracks facing each other is calculated, and the difference between the levels of the two tracks on which the magnetic head is formed is calculated. Since the sign of the deviation for the track differs depending on whether it is on one side or the other side, it is determined to which track side the magnetic head should be moved for subsequent positioning correction, and access is specified. The deviation with respect to the track becomes 0 as the device moves, and the device is positioned on the track.

(Embodiment) FIG. 1 is a diagram showing the principle of track positioning control as an embodiment of the present invention. The track positioning control according to the present invention is assumed to be performed by a circuit similar to that shown in FIG. 2, and will be described below with reference to FIG. 2 as well.

In Fig. 1, A, B, C, and D are burst signals (servo patterns) written in advance on the magnetic disk, and the servo patterns A, B, C, and D are patterns of a certain frequency ~ the index signal INDEX. Patterns A, B, C, and D are even numbers 0 and 2 as base points, respectively.
．． 4...tracks TRO, TR2, TR4... and odd-numbered tracks TRI, TR3, 1, 3.5...
. The patterns with the same code are arranged in a common phase in each track.

P and Q are deviation signals corresponding to each even track and each odd track, respectively, and each pattern A, C read by the magnetic disk 7 is given a positive sign;
Each of the patterns B and D is given a negative sign and calculated by the microcomputer 9 using the following equations.

P-(A-B)/(A+B) Q-(C-D)/(C+D) However, A, B, C, and D represent the read output level of each pattern.

Next, the operation of positioning control according to the present invention will be explained.

MO, , Ml . . . MIO . . . show examples of stop positions (referred to as motor stop positions) before temperature correction, that is, when there is no thermal off-track.

For example, track T with track number 10 (even number)
When positioning at R10, the servo motor 1 is driven to first position the magnetic head 7 at the motor stop position MIO.

At this time, the position MLO is almost the previous track TR9.
It's near.

Next, the servo motor 1 is driven approximately one track from the position MIO to the position of the track TRl0.
The driving direction is the direction in which the track number increases as the magnetic head 7 moves (hereinafter referred to as the FWD direction). Referring to FIG. 1, the conditions for driving in the FWD direction are that the deviation signal P or Q is P>0. This is due to the relationship of Q<0.

Next, when positioning on track TR, track number 9 (odd number), the condition for driving in the F W D direction is that the deviation signal P or Q is in the relationship of P<0, Q>0. It depends. In FIG. 1, the track position is the motor stop position MO.

In this case, the track number and the FWD and REV of each drive direction are
The relationship (in the direction in which the track number decreases) is summarized as shown in the table below.

Table This table shows in which direction the motor should be rotated when correcting positional deviation. Positioning is performed using the deviation signal P for coefficient tracks and the deviation signal Q for odd tracks. Position at the point where signal P or Q becomes 0. In addition, signal P.

In this case, since Q occurs only in a portion of one revolution of the magnetic disk 8, it is sampled and held and given to the DA converter 11 for servo control.

(Effects of the Invention) As explained above, according to the present invention, the code of information obtained from the servo pattern for a track is determined depending on whether the magnetic head is on one side of the track or on the other side. The movement direction of the magnetic head is specified based on the sign, and the positional deviation is corrected by moving toward the nearest track to which access is specified. The capacity can be reduced from about half a pitch in the past to about 1 pitch, thereby realizing a magnetic disk that can have a narrow track pitch and can be used even in a wide range of temperature fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of track positioning control as an embodiment of the present invention, FIG. 2 is a block diagram of a conventional track positioning circuit, and FIG. 3 is an explanatory diagram of positioning operation by the circuit of FIG. 2. 1... Servo motor (access motor) 3... Sensor 7... Magnetic head 8... Magnetic disk A, B, C, D... Servo pattern P... Deviation signal of even numbered track Q: Deviation signal for odd-numbered trucks Patent applicant: Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] A method for positioning a magnetic head in which operating position information of an access motor is fed back to control the access motor to position the magnetic head on a track on a magnetic disk, the method comprising: They are sandwiched and arranged at equal distances from each other, and the corresponding phase by rotation is common for even-numbered tracks and odd-numbered tracks. calculating the deviation between the received level by the servo pattern on the other side and the received level by the servo pattern on the other side, and based on the sign of the deviation for the two tracks, the moving direction of the magnetic head for positioning on that one track. , and positioning the magnetic head at a position where the deviation for the track designated for access is zero.