JPH0714325A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To provide a high precision servo system and to enable a high speed seek operation by making torque to be generated by a voice-coil motor always constant irrespective of the position of a magnetic head. CONSTITUTION:A microcomputer 6 for calculating a proper loop gain and selecting a torque constant including an observer for estimating a disturbance, a head speed and a head position, and a ROM 5 storing previously torque constant data corresponding to each individual cylinder position of a magnetic disk obtained by the spline interpolation method are provided in a position control circuit 4. Otherwise, the microcomputer 6 including the observer for estimating the disturbance, the head speed and position, and a ROM 5 storing previously loop gain data for modification and torque constant data in an observer model are provided in the position control circuit 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly to a magnetic disk drive having an actuator driven by a voice coil motor for moving the magnetic head to a designated cylinder position on the magnetic disk. The present invention relates to a magnetic disk device that performs a positioning operation.

[0002]

2. Description of the Related Art A conventional magnetic disk device having an actuator driven by a voice coil motor for moving a magnetic head to a designated cylinder position of a magnetic disk and performing a positioning operation of the magnetic head by a sampling servo system is known. At least one magnetic disk rotated by a spindle motor, a magnetic head for reading or writing information on the magnetic disk, and a voice coil motor for moving the magnetic head to a designated cylinder position on the magnetic disk. And a position control circuit that controls the operation of the actuator, and in the position control circuit,
It has a constant loop gain.

[0003]

In recent years, there have been increasing demands for miniaturization, large capacity, and high speed of magnetic disk devices. A surface for recording normal data (data surface) to prevent the storage capacity of the magnetic disk device from decreasing by providing a dedicated recording surface (servo surface) for recording only servo information on the recording surface of the disk Servo information (positional information) for positioning the magnetic head is provided in a distributed manner, and a position error signal is reproduced from these positional information to perform the positioning operation of the magnetic head by a so-called sampling servo method. Has been adopted.

Although such a small-sized magnetic disk device has the advantages that the moving distance of the magnetic head is short and the movable portion is lightweight, it is connected to the magnetic head to transmit signals.
Since the PC is easily affected by the external disturbance, an offset is a problem during the positioning operation of the magnetic head.

Since the torque generated by the voice coil motor of the conventional magnetic disk device changes depending on the position of the magnetic head, in the case of the sampling servo system as described above, it is possible to realize a highly accurate servo system or a high speed servo system. It has a drawback that it is difficult to realize the seek operation.

[0006]

A first magnetic disk device of the present invention comprises at least one magnetic disk rotated by a spindle motor, and a magnetic head for reading or writing information on the magnetic disk. ,
An actuator driven by a voice coil motor for moving the magnetic head to a designated cylinder position of the magnetic disk, and a position control circuit for controlling the operation of the actuator are provided, and the magnetic head is positioned by a sampling servo method. In a magnetic disk device that operates, a microcomputer that performs an appropriate loop gain calculation and a torque constant selection including an observer that estimates disturbance and head speed and head position, and each of the magnetic disks obtained by a spline interpolation method The position control circuit is provided with a ROM in which torque constant data corresponding to the cylinder position is stored in advance.
A torque constant corresponding to the position of the magnetic head is read from M, the torque constant in the observer is changed, the loop gain is calculated by the torque constant, and the loop gain is changed to the loop gain to make the torque generated in the voice coil motor constant. Includes holding in value.

According to a second magnetic disk device of the present invention, at least one magnetic disk rotated by a spindle motor, a magnetic head for reading information from or writing information to the magnetic disk, and the magnetic head are provided. A magnetic disk that includes an actuator driven by a voice coil motor to move the magnetic disk to a designated cylinder position and a position control circuit that controls the operation of the actuator, and performs a positioning operation of the magnetic head by a sampling servo method. In the apparatus, the position control circuit is provided with a microcomputer including an observer for estimating disturbance and head speed and position, and a ROM for preliminarily storing change loop gain data and torque constant data in the observer, in the position control circuit. When Reading the loop gain data corresponding to the position of the magnetic head and the torque constant data in the observer from the ROM and changing the data to the loop gain data to hold the torque generated in the voice coil motor at a constant value. There is.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the control system of the embodiment shown in FIG. 1, and FIG. 3 is a detailed view when the control target of FIG. 2 is a continuous system. 5 is a block diagram showing the details of the case where the control target of FIG. 2 is a discrete system, FIG. 6 is a block diagram showing the details of the Z-transform arithmetic element of FIG. 5, and FIG. 7 is the control target of FIG. FIG. 4 is a block diagram showing details of an observer built in the microcomputer with reference to the model of FIG. 4, FIG. 4 is a characteristic diagram showing a general relation of the torque generated by the voice coil motor with respect to the position of the magnetic head in the magnetic disk device, and FIG. FIG. 9 is a characteristic diagram showing the relationship between the magnetic head position and the torque constant of the voice coil motor obtained by converting the average value of the torque generated by the voice coil motors of a plurality of magnetic disk devices into a torque constant. FIG. To the law Is a characteristic diagram showing the relationship between the torque constant of the voice coil motor to the magnetic head position with smooth Kana curve I.

In FIG. 1, a magnetic disk 1 is rotated by a spindle motor to record information. The magnetic head 2 reads or writes information on the magnetic disk 1. The actuator 3 is driven by a built-in voice coil motor (not shown) to move the magnetic head 1 to a designated cylinder position on the magnetic disk 2. The position control circuit 4 incorporates a ROM 5 and a microcomputer 6 and controls the operation of the actuator 3.

The ROM 5 stores in advance torque constant data corresponding to each cylinder position of the magnetic disk 1 obtained by the spline interpolation method. The microcomputer (microcomputer) 6 includes an observer of the same dimension for estimating disturbance, head speed and head position,
Appropriate loop gain calculation and torque constant selection are performed.

In FIG. 2, the controller 7 is included in the position control circuit 4 and generates a target speed for the movement operation of the actuator 3. The loop gain 8 is included in the position control circuit 4 and amplifies the output signal of the controller 7.
A digital-analog converter (DAC) 9 is included in the position control circuit 4 and outputs a DAC output signal 21 obtained by converting the digital signal output from the loop gain 8 into an analog signal.
The DAC 9 has a sample-and-hold function, and a zero-order hold function that holds a constant value until the next sampling.

The power amplifier 10 is included in the position control circuit 4 and supplies a drive current 22 obtained by amplifying the DAC output signal 21 to the voice coil motor of the actuator 3. The power amplifier 10 and the actuator 3 are the control target 14.

Analog-to-digital converter (ADC) 12
Is included in the position control circuit 4, converts the head position information 23 output from the actuator 3 into a digital signal, and sends the digital signal to the observer 13. The observer 13 outputs the DAC output signal 2
1 and the output signal of the ADC 12 and the information from the ROM 5 are input, and an estimated position 24, an estimated velocity 25 and an estimated disturbance value 26 of the magnetic head are sent to the controller 7.

The controlled object 14 is a continuous system, but the controller 7 and the observer 13 operate in a discrete system.

In FIG. 3, a power amplifier (gain g
The drive current (S2) 22 output from m) 10 is input to the rotary type voice coil motor (torque constant Kt) 16 and the voice coil motor (torque constant Kt) 16 outputs torque (S7) 27. This torque (S7) 2
7 is output as head position information 23 via the reciprocal of the moment of inertia (1 / J) 17, the first integrator (1 / S) 18 and the second integrator (1 / S) 19.

At this time, the magnitude of the torque (S7) 27 generated by the voice coil motor is the drive current (S2) 22.
Proportional to. This relationship is expressed by the following equation.

S7 = S2 × Kt (Equation 1) Further, the magnitude of the torque required to be generated for the voice coil motor is the magnetic disk 2 of the magnetic head 1.
S7 = constant value (design value) (Equation 2) regardless of the position with respect to.

However, in an actual magnetic disk device, as shown by the curve 31 in FIG. 4, the magnetic head position (c
yl) changes the magnitude of the torque and does not reach a constant value.

FIG. 5 is a block diagram showing details of the case where the controlled object in FIG. 2 is a discrete system.

In FIG. 5, the Z-transform operation element 41 is an operator for Z-transform used in the control of the discrete system, and delays the time by the period T of the sampling period 20. That is, as shown in FIG.
Is the kth sampling data delayed by one sampling period when the Z conversion operator input (S8) 28, which is the (k + 1) th sampling data, is input.
The conversion operator output (S9) 29 is output.

FIG. 7 is a block diagram showing the details of the observer constructed in the microcomputer 6 with reference to the model of the controlled object of FIG.

In FIG. 7, the torque constant (Kt ₀ ) 11
Is a torque constant in the observer 13, and the feedback gains 45 and 46 are gains for feeding back the difference between the head position information 23 and the observer output 30 so that the error of the observer 13 converges to zero. Thereby, the observer 13 will give the same response as the response of the controlled object when the same input as the controlled object is given. This observer 13 is called the same-dimensional observer, and since the state at the (k + 1) th sampling point is estimated from the data at the kth sampling point, the influence of the calculation time can be ignored.

As shown by the curve 31 in FIG. 4, the torque generated in the voice coil motor changes depending on the position of the magnetic head. Further, in order to satisfy the expression 2, from FIG.
The following expression 3 needs to be established.

(Loop gain) × Kt = constant value (design value) (Equation 3) Then, for a suitable number of magnetic disk devices, the magnitude of torque in each cylinder is preset as shown in FIG. Of the magnetic head position (cyl) by converting the value into a torque constant as shown in FIG.
That is, the characteristic line 32 showing the torque constant with respect to the cylinder position is obtained.

Based on this data, the spline interpolation method is applied to create a smooth characteristic curve 33 as shown in FIG.
This is stored in the ROM 5 in advance.

The magnetic disk device configured as described above is
It works as follows.

First, the observer 13 in the microcomputer 6 calculates an estimated position 24 of the magnetic head at the next sampling time (k + 1) based on the head position information 23 at the sampling time k. At this time, according to the head position information 23 at the sampling time point k, the value of the torque constant (Kt ₀ ) 11 in the observer 13 is read from the data stored in the ROM 5 and changed to that value.
The estimated position 24 is calculated.

Further, when the calculation of the estimated position 24 of the magnetic head at the sampling time (k + 1) is completed, the value of the loop gain 8 corresponding to the estimated position is calculated by the equation 3, and the loop gain is calculated at the sampling time (k + 1). Switch the value of 8 to that value.

As described above, the value of the loop coil gain corresponding to the magnetic head position is obtained by the microcomputer provided in the position control circuit 4 and is changed to the value of the torque generated by the voice coil motor. It is possible to always set a constant value regardless of the value.

Furthermore, by changing the value of the torque constant (Kt ₀ ) 11 in the observer 13 according to the head position information 23, it is possible to reproduce the same torque fluctuation as the torque fluctuation of the controlled object in the observer 13. Become. Further, since the value of the loop gain is changed, the value of the torque calculated in the observer 13 is always a constant value regardless of the magnetic head position, and the estimation accuracy by the observer 13 can be improved.

These calculations and changes are made by the observer 1.
Since it can be performed within one sampling period by using the same dimension observer as 3, the influence of the calculation time can be ignored.

FIG. 10 is a plan view showing a second embodiment of the present invention.

The structure of this embodiment is the same as that of the embodiment of FIG. 1 in appearance, but the internal structures of the ROM 55 and the microcomputer 56 are different.

The ROM 5 measures the magnitude of the torque in each cylinder in advance for an appropriate number of magnetic disk devices as shown in FIG. 4, obtains an average value thereof, and converts it into a torque constant, as shown in FIG. Magnetic head position (c
yl), that is, the characteristic line 32 showing the torque constant with respect to the cylinder position is obtained, and based on this data, the loop gain data is calculated in advance so that the expression 3 is established and stored. The ROM 5 also stores torque constant data in the observer corresponding to the position of each magnetic head calculated from FIG. Microcomputer
Reference numeral 6 includes an observer for estimating disturbance, and selects an appropriate loop gain and torque constant from the data in the ROM 5.

The magnetic disk device configured as described above is
It works as follows.

First, the observer in the microcomputer 56 calculates the estimated position of the magnetic head at the next sampling time (k + 1) based on the head position information at the sampling time k. At this time, according to the head position information at the sampling time point k, the value of the torque constant in the observer is read from the data stored in the ROM 55 and changed to that value, and then the estimated position is calculated.

Further, when the calculation of the estimated position of the magnetic head at the sampling time (k + 1) is completed, the value of the loop gain corresponding to the estimated position is read from the data stored in the ROM 55, and the sampling time (k + 1).
At, the loop gain value is switched to that value.

Configurations and operations / effects other than the above are shown in FIG.
Is the same as the embodiment described above.

[0040]

As described above, the magnetic disk device of the present invention includes a microcomputer and a spline which include an observer for estimating disturbance, head speed and head position, and calculates an appropriate loop gain and selects a torque constant. ROM storing in advance the torque constant data corresponding to each cylinder position of the magnetic disk obtained by the interpolation method
Is provided in the position control circuit, or a microcomputer including an observer for estimating disturbance, head speed and position, and loop gain data for change and torque constant data in the observer model are stored in advance.
Providing M and M in the position control circuit has the effect that the magnitude of the torque generated by the voice coil motor can always be kept constant regardless of the position of the magnetic head. There is an effect that a servo system can be realized and a high-speed seek operation can be performed.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a control system of the embodiment shown in FIG.

FIG. 3 is a block diagram showing details when the control target in FIG. 2 is a continuous system.

FIG. 4 is a characteristic diagram showing a general relationship between torque generated by a voice coil motor and position of a magnetic head in a magnetic disk device.

FIG. 5 is a block diagram showing details of a case where the controlled object in FIG. 2 is a discrete system.

FIG. 6 is a block diagram showing details of a Z-conversion arithmetic element of FIG.

FIG. 7 is a block diagram showing details of an observer constructed in the microcomputer with reference to the model of the controlled object of FIG.

FIG. 8 is a characteristic diagram showing the relationship between the torque constant of the voice coil motor and the magnetic head position, which is obtained by converting the average value of the torque generated by the voice coil motors of the plurality of magnetic disk devices into a torque constant.

9 is a characteristic diagram showing the relationship of the torque constant of the voice coil motor with respect to the magnetic head position, in which the characteristic values of FIG.

FIG. 10 is a plan view showing a second embodiment of the present invention.

[Explanation of symbols]

 1 magnetic disk 2 magnetic head 3 actuator 4 position control circuit 5.55 ROM 6.56 microcomputer (microcomputer) 7 controller 8 loop gain 9 digital analog converter (DAC) 10 power amplifier 11 torque constant 12 analog digital converter (ADC) ) 13 observer 14 controlled object 15 power amplifier gain 16 voice coil motor (torque constant) 17 reciprocal of moment of inertia 18 first integrator (1 / S) 19 second integrator (1 / S) 20 sampling period 21 DAC output signal 22 Drive Current 23 Head Position Information 24 Estimated Position 25 Estimated Speed 26 Estimated Disturbance Value 27 Torque (S7) 28 Z Conversion Operation Element Input 29 Z Conversion Operation Element Output 30 Observer Output 31 Curve 32 Characteristic Line 41 Z Conversion Operation Element 45. 6 feedback gain

Claims (2)

[Claims] 1. At least one magnetic disk rotated by a spindle motor, a magnetic head for reading or writing information from or to the magnetic disk, and the magnetic head at a designated cylinder position of the magnetic disk. In a magnetic disk device which includes an actuator driven by a voice coil motor for moving and a position control circuit for controlling the operation of the actuator, and which performs a positioning operation of the magnetic head by a sampling servo system, disturbance, head speed and head A microcomputer that includes an observer that estimates the position and calculates an appropriate loop gain and selects a torque constant, and torque constant data corresponding to each cylinder position of the magnetic disk obtained by the spline interpolation method are stored in advance. ROM Are provided in the position control circuit,
In the positioning operation, the torque constant corresponding to the position of the magnetic head is read from the ROM within one sampling period, and the torque constant in the observer is changed,
A magnetic disk device comprising: maintaining a torque generated in the voice coil motor at a constant value by calculating a loop gain based on the torque constant and changing the loop gain. 2. A at least one magnetic disk rotated by a spindle motor, a magnetic head for reading or writing information from or to the magnetic disk, and the magnetic head at a designated cylinder position of the magnetic disk. In a magnetic disk device that includes an actuator driven by a voice coil motor for moving and a position control circuit that controls the operation of the actuator, and performs a positioning operation of the magnetic head by a sampling servo system, disturbance, head speed and position The position control circuit is provided with a microcomputer including an observer for estimating the above, and a ROM in which the loop gain data for change and the torque constant data in the observer are stored in advance, and the magnetic head is read from the ROM during the positioning operation. Place of The magnetic disk device is characterized in that the torque generated in the voice coil motor is held at a constant value by reading the loop gain data and the torque constant data in the observer corresponding to each position and changing them. .