JPH04339371A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To compensate the hysteresis characteristic of a bias force resulted from the mechanism part of an actuator and to stabilize head positioning by correcting the bias force by means of plural tables in which a seek direction history is set. CONSTITUTION:The bias correction current characteristic is preliminarily set with respect to the number of moving tracks in the seek operations of the past several times. It is set in plural tables 301, 302,... of a table part 30, respectively. At the time of seek operation, the seek operations of the past several times are stored, and a seek operation direction storage part 31 is provided for selecting the characteristic in the table corresponding to the seek operation direction stored from the table part 30. Furthermore, a control part 32 is provided for outputting the bias correction current value based on the number of tracks commanded by a seek operation command and the characteristics from the seek operation direction storage part 31.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, and more particularly to a head positioning control system for a magnetic disk drive widely used as an external storage device for computers.

0002

2. Description of the Related Art FIG. 5 shows a configuration diagram of a conventional example. In the figure, a magnetic head 2 for recording and reproducing data on a magnetic disk 1 is moved at high speed (seek operation) by an actuator 3 and positioned on a target track having a width of about 10 μm (track following operation). This positioning to the target track is performed as follows. The position signal of the magnetic head 2 detected by the position signal demodulator 4 is converted into a control signal by the control circuit 5, amplified by the power amplifier 6, and then supplied to the voice coil motor (VCM) 7, which drives the actuator. 3 is driven and controlled, and the head 2 is positioned on the target track.

[0003] In an ideal track following operation in which the magnetic head 2 is correctly positioned, V
Although the current flowing through CM7 is zero, it actually does not become zero, and the bias correction current is applied to cancel the constant bias force (wind pressure, FPC (flexible printed circuit) spring force, etc.) applied to the actuator 3. It is necessary to flow.

FIG. 6 shows a block diagram of a conventional head positioning control system. In the figure, the difference between the target value r (target track) output from the host controller and the current position is given a constant gain through an integration circuit 8 and a gain (Ki (integral)) circuit 9, while a gain (Kp (proportional)) circuit 10, which is added to the signal which has been given a constant gain through the gain (Kd (differential)) circuit 11 in the adder 12, and is added to the signal which has been given a constant gain through the gain (Kd (differential)) circuit 11, and in the adder 13, a bias correction value. It is added to the bias current correction value set in the table 14, and is supplied to the controlled object, which is the actuator 3. The output (position signal) of the controlled object 3 is sent to the subtracter 15
The signal is fed back to the position signal demodulator 4 and subtracted from the control signal from the position signal demodulator 4 .Meanwhile, the speed estimator 16 amplifies the speed and feeds it back to the gain (Kd) circuit 11 . That is, this control method is a method in which a bias correction current is added to a PID (proportional-integral-derivative) control system that feeds back the position, position integral, and velocity of the head.

Conventionally, since the bias force applied to the actuator 3 depends on the position of the track where the head 2 is positioned, the bias correction value table 14 includes one type of bias correction value table (number of tracks versus bias correction current). only was used.

[0006]

However, due to the structure of the mechanism part (particularly the bearing part) of the actuator 3, in reality, as shown in FIG. There is a difference between the bias force generated when moving in the opposite direction (outer circumference → inner circumference), and the bias force generated when moving in the reverse direction (from outer circumference to inner circumference), that is, the bias force has hysteresis characteristics. For this reason, the conventional example that uses only one type of bias correction value table cannot appropriately correct the bias force corresponding to various random seek patterns, and the seek operation and track following operation become unstable due to the influence of the bias force. There was a problem with stability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic disk device that can perform stable head positioning control without being affected by the hysteresis characteristics of bias force.

[0008]

[Means for Solving the Problems] FIG. 1 shows a diagram illustrating the principle of the present invention. In the figure, reference numeral 30 denotes a table means, which determines in advance the number of moving tracks versus the bias correction current characteristic in multiple previous seek operations of the actuator 3 in combinations of forward and reverse directions, and displays this in a plurality of tables (301 , 302, ...). Reference numeral 31 denotes a seek direction storage section which stores a plurality of past seek operation directions during a seek operation, and selects a characteristic in a table corresponding to the stored seek operation direction from the table section 30. 32 is a control unit that outputs a bias correction current value based on the number of tracks according to the seek operation command and the characteristics from the seek direction storage unit 31.

[0009]

[Operation] Each table 301, 302 of the table section 30
, . . , the number of tracks vs. bias correction current characteristic in the previous two seek direction history patterns, such as forward→forward, forward→reverse, reverse→forward, and reverse→reverse, is set in . During a seek operation, the seek direction storage section 21 stores the past two seek direction histories, selects a characteristic corresponding to the stored seek direction history from a predetermined table in the table section 30, and selects the number of tracks and this selection. A bias correction current is output based on the determined characteristics. In this way, since the bias force is corrected using a table in which multiple seek direction histories are set, the hysteresis characteristic of the bias force caused by the mechanism of the actuator can be compensated for, and stable head positioning control can be performed. .

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a block diagram of an embodiment of the present invention, in which parts having the same functions as those in FIG. 5 are given the same numbers. In FIG. 2, reference numeral 20 denotes a higher-level controller, which issues a command to displace the actuator 3 to a target track by a seek operation and a track following operation. A control circuit 21 controls the entire system. The host controller 20 and the control circuit 21 are configured to perform control according to the operation flowchart shown in FIG. Reference numeral 22 denotes a seek direction history storage unit, which is composed of a memory and stores the output from the host controller 20 (the past two seek direction histories). Reference numeral 23 denotes a table section, which is composed of four tables 231 to 234, and has four types of tables of track number vs. bias force characteristics in the past two seek direction histories, as described later. Reference numeral 24 denotes a bias correction value determining section which determines a bias correction current value based on a certain characteristic output from the table section 23 and track number control from the control circuit 21. 25 is an adder.

Next, the operation of the present invention will be explained in conjunction with the flowchart shown in FIG.

First, considering the past two seek operations as a history of seek operations, ■ Forward (F) → Forward (F), ■ Forward (F) → Reverse (R),
Four types are possible: ■ Reverse (R) → Forward (F), ■ Reverse (R) → Reverse (R). Therefore, we created four types of bias correction tables according to these four types of seek operation patterns ■ to ■, and table 2
31 to 234, respectively. When creating a table, the control circuit 2
1 is operated, and the actuator 3 is operated to seek and follow the target track according to the patterns ① to ② above, but during the track following operation immediately after the seek operation, the VCM drive amount excluding the bias correction value becomes zero. Create a table by changing the bias value so that As a result, a table having four types of characteristics as shown in FIG. 4, for example, is created.

Next, actual recording and reproducing operations will be explained. When there is a seek command from the host controller 20 (step 50 in FIG. 3), the control circuit 21 performs seek control in accordance with the seek command (step 51), causing the actuator 3 to seek by a well-known operation. When the seek operation is completed (step 52), the control circuit 21 issues a seek direction storage command to the seek direction history storage section 22 (step 53), and performs track following control (
In step 54), a seek direction storage command is issued from the control circuit 21 every time such a seek operation is performed, and the seek direction history section 22 stores the seek direction.

Therefore, the seek direction history storage section 22 stores the past two seek direction histories (step 55).
), outputs a control signal corresponding to the past two seek direction histories of the currently executed seek command, and selects a predetermined table from the tables 231 to 234 of the table section 23. For example, if the history for the past two times is ■ Reverse (R) → Forward (F), table 233
is selected (step 56). Bias correction value determining unit 2
4 determines a bias correction current value based on the track number control from the control circuit 21 and the characteristics output from the table 233 (step 57), and outputs it.

The bias correction current value output from the bias correction value determining section 24 is sent to the control circuit 21 in the adder 25.
is added to the VCM drive current from power amplifier 6.
is supplied to VCM7 via. After the actuator 3 is subjected to seek control in a loop of steps 50 to 53, it is subjected to track following control using a bias-corrected drive current (step 54).

As described above, in the present invention, since the bias force is corrected using four types of tables (■ to ■) as shown in FIG. can be compensated for, and stable head positioning control can be performed.

[0017] In the above embodiment, the past two seek direction histories were considered, but this number is not limited to this, and may be set to a greater number within the limit of the memory capacity of the table means 23. Is possible.

[0018]

According to the present invention, it is possible to compensate for the hysteresis characteristic of the bias force caused by the mechanical characteristics of the actuator during random seek, and stable head positioning control can be performed.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a block diagram of one embodiment of the invention.

FIG. 3 is an operation flowchart of the present invention.

FIG. 4 is a bias force characteristic diagram of a correction table in the present invention.

FIG. 5 is a configuration diagram of a conventional example.

FIG. 6 is a block diagram of a conventional head positioning control system.

FIG. 7 is a diagram illustrating hysteresis characteristics of bias force.

[Explanation of symbols]

3 Actuator 7 VCM (voice coil motor) 20 Upper controller 21 Control circuit 22 Seek direction history storage unit 23, 30 Table part 24 Bias correction value determination unit 31 Seek direction storage unit 32 Control section

Claims (2)

[Claims] 1. When the actuator (3) performs a seek operation and then performs a track following operation to perform positioning on a target track, a function is provided to drive the actuator with a current to which a bias correction current value has been added to the target track. In the provided magnetic disk device,
The number of moving tracks versus the bias correction current characteristics in past multiple seek operations in combinations of forward and reverse directions is determined in advance and is stored in multiple tables (
301, 302,...), and a table section (30) that stores the plurality of past seek operation directions at the time of a seek operation, and retrieves the stored seek operation directions from the table section (30). Tables corresponding to (30
1 or 302...), and a control section (31) that outputs a bias correction current value based on the number of tracks according to the seek operation command and the characteristics from the seek direction storage section (31). 32) A magnetic disk device characterized by comprising: [Claim 2] A table (
301, 302,...), the table is created by moving the bias current so that the actuator drive amount excluding the bias correction current value becomes zero during the track following operation immediately after the seek operation. A magnetic disk device according to claim 1.