JPH0636289B2 - Offset torque correction circuit for magnetic disk unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a head positioning control circuit of a magnetic disk device,
Since the offset torque of the head positioning mechanism differs for each magnetic disk device, instead of supplying an offset torque correction current that is uniquely determined, an appropriate offset torque correction current is supplied to each device to the motor to position the head. Achieve higher control performance.

[Industrial application field]

The present invention relates to positioning control of a head of a magnetic disk device, and particularly when positioning the head at a target position, it is possible to correct the offset torque amount that differs for each magnetic disk device and improve the performance of head positioning control. The present invention relates to an offset torque correction circuit for a magnetic disk device.

A magnetic disk device is usually equipped with a magnetic disk composed of a plurality of magnetic disk disks according to the storage capacity, and both sides of each magnetic disk disk are data recording surfaces, and a head is provided for each data recording surface. . Then, the head is simultaneously positioned on each track of the target cylinder to write / read data.

In this case, one of the data recording surfaces is a servo surface for recording servo information, and by reading out the servo information,
Performs head positioning control.

That is, when a target cylinder for positioning the head is designated by the host device, the distance from the current position of the head to the target position, that is, the distance from the currently positioned cylinder to the target cylinder is calculated, and Moves the head at high speed, detects the position of the head based on the servo information read by the servo head, and after moving for a predetermined distance, performs coarse control to reduce the moving speed of the head as it approaches the target cylinder. , In the vicinity of the target cylinder, switch to fine control for precise positioning control.

By the way, the offset torque generated in the positioning mechanism part of the head is caused by mechanical imbalance of the mechanism part, stress caused by the spring and lead wire connected to the mechanism part, and air flow. However, the offset torque amount is not constant and varies greatly from one magnetic disk device to another, and it also changes depending on the installation condition of the magnetic disk device, which is a cause of hindering the high performance of head positioning control. Was there.

Therefore, when offset torque correction is performed, it is necessary to provide an appropriate offset torque correction amount for each magnetic disk device.

[Conventional technology]

FIG. 2 is a block diagram showing an example of a conventional offset torque correction circuit.

The target cylinder enters the movement distance calculation circuit 1 from the host device, calculates the distance to move the head, and sends it to the movement distance subtraction circuit 2. On the other hand, the servo information read by the servo head 22 is amplified by the amplifier circuit 23, and the automatic gain adjustment (A
It is amplified to a predetermined level by the GC) circuit 24. The peak hold circuit 25 sends a head position signal from the servo information amplified by the AGC circuit 24 to the moving distance subtracting circuit 2, the differentiating circuit 7 and the filter 10.

The moving distance subtraction circuit 2 sends the distance to the target cylinder to the D / A conversion circuit 4 and the control mode switching circuit 3 according to the head position signal sent from the peak hold circuit 25.
The distance converted into the analog value by the D / A conversion circuit 4 is sent to the subtraction circuit 6 as the target speed of the head by the nonlinear amplification circuit 5, and the control mode switching circuit 3 controls the coarse control based on the distance to the target cylinder. Signal to switch 16,
The fine control signal is sent to the switch 17.

The position signal of the head sent by the peak hold circuit 25 is differentiated by the differentiating circuit 7 and added by the integral value of the integrating circuit 8 that integrates the motor current signal, which will be described later, by the adding circuit 9 to obtain the moving speed of the head. It is sent to the subtraction circuit 6. In the subtraction circuit 6, the target speed and the moving speed are subtracted, and a speed deviation signal for coarse control is passed to the motor drive circuit 19 via the addition circuit 18 via the switch 16.
The motor drive circuit 19 drives, for example, a voice coil motor 20 that moves the head based on the speed deviation signal.

The motor current detection circuit 21 detects a current value for driving the voice coil motor 20 and sends it as a motor current signal to the integration circuits 8 and 14.

The position signal sent from the peak hold circuit 25 has its noise removed by the filter 10, amplified by the amplifier circuit 11, and enters the adder circuit 15. Further, the position signal output from the filter 10 is integrated by the integrating circuit 12 and becomes a position integrated signal and enters the adding circuit 15. Further, the position signal output from the filter 10 is differentiated by the differentiating circuit 13 and becomes a position differential signal and enters the adding circuit 15. On the other hand, the motor current detection circuit 21
The motor current signal sent from is integrated by the integrating circuit 14 and becomes a current integrated signal and enters the adding circuit 15.

The adder circuit 15 synthesizes a speed signal from the position differential signal sent from the differentiating circuit 13 and the current integration signal sent from the integrating circuit 14, and the speed signal, the position signal sent by the amplifying circuit 11 and the position sent by the integrating circuit 12 are combined. A position correction signal is created from the integrated signal and sent to the motor drive circuit 19 via the switch 17 and the adder circuit 18 to perform precise head positioning control. At this time, due to the offset torque,
Since an external force for moving the head is exerted from the target cylinder in which the head is positioned, the voice coil motor 20
It is necessary to pass a current to cancel this external force.

Therefore, the adder circuit 18 is supplied with a constant value of the offset torque correction current from the power source V through the resistor R, and during coarse control, the speed deviation signal corrected by the constant value of the offset torque correction current value is used as the motor drive circuit. 19
In the fine control, the position correction signal corrected by the constant offset torque correction current value is supplied. Therefore, the motor drive circuit 19 drives the voice coil motor 20 by the speed deviation signal and the position correction signal corrected by the constant offset torque correction current value.

[Problems to be solved by the invention]

As described above, conventionally, an offset torque correction amount that is uniquely determined by the constant of the resistance R is given to each magnetic disk device, but if there is a variation in the offset torque amount among the magnetic disk devices, it will be constant. The offset torque correction current cannot completely correct the offset torque amount, and after switching to the fine control, the uncorrected amount is gradually corrected by the action of the amplification circuit 11 and the integration circuit 12. There is a problem that it takes time to absorb the variation in the offset torque amount by the action of the amplifier circuit 11 and the integrating circuit 12.

In view of such a problem, the present invention detects the current based on the offset torque flowing in the voice coil motor 20,
Based on this, an appropriate offset torque correction current is supplied.

[Means for solving problems]

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention.

FIG. 1 shows an A / D conversion circuit 26, registers 27 and 29, a correction value detection circuit 28 and a D / A conversion circuit 30 added to FIG.

The correction value detection circuit 28 converts the motor current signal sent from the motor current detection circuit 21 into a digital value by the A / D conversion circuit 26, and converts the digital value stored in the register 27 into an offset torque flowing in the voice coil motor 20. Based on the detected current value, it is stored in the register 29, and D /
The A conversion circuit 30 is configured to create an offset torque correction current value corresponding to the value of the register 29.

[Action]

With the above configuration, it is possible to supply an appropriate offset torque correction current corresponding to the offset current different for each magnetic disk device.

〔Example〕

In FIG. 1, the A / D conversion circuit 26 converts the motor current signal sent from the motor current detection circuit 21 into a digital value and stores it in the register 27. The register 27 samples this motor current signal with a clock and sends it to the correction value detection circuit 28.

The correction value detection circuit 28 detects the motor current signal sent by the motor current detection circuit 21 when the voice coil motor 20 is stopped and the fine control is entered. That is, the motor current signal after the variation of the offset torque is absorbed by the actions of the fine control amplification circuit 11 and the integration circuit 12 is detected and stored in the register 29.

The D / A conversion circuit 30 converts the motor current signal stored in the register 29 into an analog value and sends it to the addition circuit 18. Therefore, the adder circuit 18 supplies the speed deviation signal and the position correction signal corrected by the signal indicating the correction current value based on the offset torque to the motor drive circuit 19. Therefore, the motor drive circuit 19 drives the voice coil motor 20 by the speed deviation signal and the position correction signal corrected by the current value for performing the appropriate offset torque correction for each magnetic disk device.

〔The invention's effect〕

As described above, the present invention can detect the current flowing through the voice coil motor based on the offset torque peculiar to each magnetic disk device and supply an appropriate offset torque correction current to each magnetic disk device. Even if there is a variation in the amount of offset torque, high performance of head positioning control can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional offset torque correction circuit. In the figure, 1 is a movement distance calculation circuit, 2 is a movement distance subtraction circuit, 3 is a control mode switching circuit, 4 and 30 are D / A conversion circuits, 5 is a non-linear amplification circuit, 6 is a subtraction circuit, and 7 and 13 are Differentiating circuit, 8, 12, 14 are integrating circuits, 9, 15, 18 are adding circuits, 10 are filters, 11 and 23 are amplifying circuits, 16 and 17 are switches, 19 is a motor drive circuit, 20 is a voice coil motor, Reference numeral 21 is a motor current detection circuit, 22 is a head, 24 is an AGC circuit, 25 is a peak hold circuit, 26 is an A / D conversion circuit, 27 and 29 are registers, and 28 is a correction value detection circuit.

Claims (1)

[Claims] 1. A magnetic disk drive comprising a positioning control circuit for supplying a driving current to a motor (20) for moving the head through a motor driving circuit (19) to position the head at a target position. The head is positioned at a predetermined position from the detection means (21, 26, 27) for detecting the current value flowing in (20) and the current value detected by the detection means (21, 26, 27). A sending means for detecting and storing a current value flowing through the motor (20) at the time, and sending the stored current value as a correction value for correcting the current for positioning control of the head supplied to the motor (20). (28, 29, 30) are provided, and the correction value sent by the sending means (28, 29, 30) is added to the input signal of the motor drive circuit (19), so that the motor (20 Offset torque correction circuit of a magnetic disk device drive current by correcting the supplied, characterized in that to perform positioning control of the head.