JPH07111817B2 - Head positioning control device for disk drive and control method thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a head positioning control device for a disk drive, and more particularly to a circuit involved in detecting the head position and controlling the driving and positioning of the head in a direction across the tracks.

The disk drive on which the present invention is based is, for example, a magnetic disk drive, which reads servo data recorded on a disk medium and performs head position detection and drive control based on the read servo data.

In recent years, there has been an ever-increasing need for magnetic disk drives as external data storage devices, and while there is an increasing demand for larger capacity, there is also an increasing demand for smaller size, lower cost, and higher reliability.

[Background technology]

The prior art will be explained with reference to Fig. 1. Fig. 1 is a block diagram of a conventional head positioning control circuit.

In FIG. 1, number 10 is a magnetic disk, number 11 is a servo head, number 12 is a voice coil motor, number 13 is a control current detection circuit, number 14 is a target speed generation circuit, number 15 is a speed detection circuit, number 16 is a speed error detection circuit, number 17 is a position error detection circuit, number 18 is a power amplifier, number 19 is a
is a servo signal detection circuit, number 20 is a track crossing pulse generation circuit, number 21 is a main control unit, and number 22 is a switching circuit.

In addition to data, the magnetic disk 10 also stores servo data necessary for positioning the servo head 11. The servo head 11 is a head that reads the servo data from the magnetic disk 10. The voice coil motor 12 drives the servo head
11 and generates a force to move the data head in a direction across the tracks.

The servo signal detection circuit 19 reads the servo data recorded on the magnetic disk 10 with the servo head 11 and generates a position signal indicating the position of the servo head 11 .

The speed detection circuit 15 detects the moving speed of the servo head 11 from the position signal generated by the servo signal generation circuit 19 and the motor drive current detected by the control current detection circuit 13 .

During coarse control, the speed error detection circuit 16 detects the speed error between the target speed generated by the target speed generation circuit 14 and the moving speed of the servo head 11 detected by the speed detection circuit 15, and outputs a voltage corresponding to the speed error.

During fine control, the position error detection circuit 17 detects a position error from the position signal created by the servo signal detection circuit 19 and the motor drive current detected by the control current detection circuit 13, and outputs a voltage corresponding to the position error.

The switching circuit 22 outputs the input from the speed error detection circuit to the power amplifier 18 during coarse control (speed control) in response to a coarse/fine switching signal from the main control unit 21, and outputs the input from the position error detection circuit to the power amplifier 17 during fine control (position control).
The input from is output to the power amplifier 18.

The power amplifier 18 converts the signal voltage output from the speed error detection circuit 16 or the position error detection circuit 17 into a current and outputs it to the voice coil motor 12 .

A track crossing pulse generating circuit 20 generates a track crossing pulse indicating that the servo head 11 has crossed the boundary between tracks, based on the position signal generated by the servo signal detecting circuit 19 .

The main control unit 21 performs processes such as setting the number of tracks to move to the target track, starting speed control, switching from speed control to position control, and detecting the number of tracks remaining to the target track by counting track crossing pulses.

When a seek command is given to the main control unit 21 from the host device, the main control unit 21 instructs the target speed generating circuit 14 on the number of remaining tracks up to the target track.
14 generates the optimum target velocity for moving the servo head to the target track.

The main control unit 21 also counts the track crossing pulses from the track crossing pulse generating circuit 20, and when it detects that the servo head 11 has reached the target track, it sends a coarse/fine switching signal to the switching circuit 22 to switch from speed control to position control. When the servo head 11 stops at the target track, the seek operation is completed.

As mentioned above, the servo system of a conventional magnetic disk drive is composed entirely of individual circuits, which limits miniaturization, reduces reliability, and makes it difficult to reduce cost.

In particular, the track crossing pulse generating circuit required to detect the position of the servo head is composed of many analog elements, making it difficult to miniaturize the circuit.
It requires a relatively large mounting area compared to other circuits.
Therefore, this track crossing pulse generating circuit is a major obstacle to reducing the size of the entire magnetic disk drive.

Furthermore, the track crossing pulse generating circuit is made up of many analog elements, and in particular requires a very expensive comparator capable of high speed operation, making it difficult to reduce the cost of magnetic disk drives.

Furthermore, since the track crossing pulse generating circuit uses a comparator as described above, if large noise is present in the output of the servo signal detection circuit 19, an incorrect track crossing pulse may be generated, resulting in an incorrect count of the number of tracks traveled, which could result in the servo head being positioned on a track other than the target track.

Furthermore, as mentioned above, the track crossing pulse generating circuit is composed of many analog elements such as comparators, so not only is it time-consuming to adjust the circuit, but there is also the risk that the circuit performance will deteriorate over time due to changes in the analog elements, causing malfunctions.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a compact disk drive, a low-cost disk drive, or a disk drive with improved reliability.

It is another object of the present invention to provide a disk drive that uses fewer analog components in its head positioning control circuitry.

It is yet another object of the present invention to provide a method for digitally detecting the head position without using a track crossing pulse generating circuit.

It is yet another object of the present invention to provide a method for controlling the speed of a servo head to move from a current track position to a target track position.

Another object of the present invention is to provide a novel method for digitally calculating the position of a servo head using a high-speed digital arithmetic circuit, specifically, to provide a novel method for calculating the predicted position of the servo head when calculating the actual position of the servo head from the predicted position of the servo head and the value of the servo signal read by the servo head.

Furthermore, another object of the present invention is to provide a method for calculating the servo head movement speed required to calculate the initial predicted servo position when the actual position and predicted position of the servo head are completely undetermined, such as immediately after power is turned on.

Furthermore, another object of the present invention is to provide a method for correctly detecting the position of a servo head by digitally removing noise even if the servo signal read by the servo head contains noise when calculating the actual position of the servo head from the predicted position of the servo head and the value of the servo signal read by the servo head.

In order to achieve the above object, the present invention converts the servo signal read by the servo head into a digital signal at predetermined time intervals, and a digital calculation circuit performs calculations based on the digitally converted value to calculate the actual position of the servo head.

A feature of the present invention is that, as a method for calculating the predicted position of the servo head, which is necessary when calculating the actual position of the servo head, the moving speed of the servo head is calculated from the previous position of the servo head and the current position of the servo head, and the predicted position of the next servo head is calculated from this moving speed of the servo head and the time until the next position of the servo head is calculated.

Another feature of the present invention is that if the actual position of the servo head calculated from the predicted position of the servo head and the value of the digitally converted servo signal deviates significantly from the predicted position on which the calculation was based, it is assumed that there was noise in the servo signal, and instead of using the calculated value as the actual position of the servo head, the predicted position of the servo head is used as the actual position of the servo head.

Furthermore, another feature of the present invention is that after the disk drive is powered on, a predetermined drive current is supplied to the motor to create a state in which the servo head moves at a predetermined speed, and in this state, the period of the servo signal read from the servo head is measured, and the moving speed of the servo head is calculated from the measured servo signal period and a known distance corresponding to this servo signal period.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram of a head positioning control circuit of a conventional magnetic disk drive, Figure 2 is a block diagram of a head positioning control circuit of a magnetic disk drive of the present invention, Figure 3 is a diagram showing each calculated value of the head positioning control circuit of the present invention, Figure 4 is a diagram explaining the data structure of each calculated value, Figure 5 is a flowchart explaining the operation of the head positioning control circuit, Figures 6 and 7 are diagrams showing each calculated value when the head moves, Figure 8 is a diagram showing the servo head movement speed, motor drive current, and servo head position during seek, and Figure 9 is a flowchart explaining a method of calculating the initial value of the servo head movement speed.

BEST MODE FOR CARRYING OUT THE INVENTION

The head positioning control circuit according to the present invention reduces the number of analog elements, and in particular eliminates the need for a track crossing pulse generating circuit.

Therefore, a new circuit and method for detecting the position of the servo head must be provided to replace the conventional method of detecting the position of the servo head by counting the track crossing pulses generated by the track crossing pulse generating circuit.

Therefore, the present invention converts the servo signal read by the servo head into a digital signal at predetermined time intervals, and a digital arithmetic circuit processes the converted digital value to calculate the actual position of the servo head. Specifically, the digital arithmetic circuit corrects the predicted position of the servo head calculated by arithmetic based on the digital value of the servo signal read by the servo head to calculate the actual position of the servo head.

FIG. 2 shows an embodiment of the head positioning control circuit of the present invention.
2 is a block diagram of the head positioning control circuit of the present invention, FIG. 3 is a diagram showing each calculated value, FIG. 4 is a diagram explaining the data structure of each calculated value,
Figure 5 is a flowchart explaining the operation of the head positioning control circuit, Figures 6 and 7 are diagrams showing the calculated values when the head moves, Figure 8 is a diagram showing the servo head movement speed, motor drive current, and servo head position during seek, and Figure 9 is a flowchart explaining a method for setting the initial value of the servo head movement speed.

I. Explanation of the Configuration of the Head Positioning Control Circuit The configuration of the head positioning control circuit of this embodiment will be explained using FIG.

In the figure, reference numeral 30 denotes a magnetic disk, reference numeral 31 denotes a servo head,
Reference numeral 32 denotes a position signal generating circuit, reference numerals 33 and 34 denote analog-to-digital converters (ADCs), reference numeral 40 denotes a main control unit, and reference numeral 50 denotes a
denotes a digital signal processor (DSP), reference numeral 61 denotes a digital-to-analog converter (DAC), reference numeral 62 denotes a power amplifier, and reference numeral 63 denotes a voice coil motor.

The magnetic disk 30 comprises a plurality of magnetic disk media rotated by a single spindle motor, one side of one of which is used as a servo surface, and a known two-phase servo pattern, for example, is recorded on each track of the servo surface, while the other side is used as a data surface, on which data is recorded.

The servo head 31 is a head that reads out a two-phase servo pattern recorded on the servo surface, and inputs the read servo signal to a position signal generating circuit 32 .

The position signal generation circuit 32 generates a position signal indicating the position of the servo head 31 based on the servo signal read by the servo head 31. This position signal consists of two types of signals, PosN and PosQ, which are offset by 90° from each other, and both are analog sine wave signals.

The ADCs 33 and 34 convert the analog position signals PosN and PosQ generated by the position signal generation circuit 32 into digital signals, respectively, and output them to the DSP 50. The conversion into digital signals is instructed by the DSP 50, which will be described later.

The DSP 50 corrects the predicted position of the servo head calculated by arithmetic operation based on the digitally converted position signals PosN and PosQ, and calculates the actual position of the servo head.
The moving speed of the servo head is calculated from the previous position of the servo head and the current position of the servo head, and the next position of the servo head is predicted from the time until the next position of the servo head is calculated and the moving speed of the servo head.

In addition, the DSP 50 calculates the current value to be supplied to the motor to position the servo head at any track based on the difference between the calculated servo head movement speed and the target speed corresponding to the number of remaining tracks to the target track.

Furthermore, such a DSP 50 is required to perform high-speed calculations and input/output of data, and for example, a TMS320C25 from Texas Instruments is used.

The DSP 50 of this embodiment has an input port 51 and an output port 5
2. It has RAMs 53 to 55 for storing digital values and coefficients for various digital processes, an interrupt timer 56, etc.

The input port 51 of the DSP 50 is connected to registers Cy1Cmd and SvCm which store target tracks and servo commands instructed from the host.
The DSP 50 has a register DrvCur for storing the motor drive current value calculated by the DSP 50.

The RAM of the DSP 50 has a section 53 for storing various digital values such as digitally converted position signals, a section 54 for storing a table DCurve of target speeds corresponding to the number of remaining tracks, and a section 55 for storing coefficients for various digital processing.

DAC61 converts the motor drive current value stored in register DrvCur into an analog value. It operates asynchronously with DSP50, and every time the input value is updated, DAC61 starts analog conversion and outputs a voltage corresponding to the value of register DrvCur.

The power amplifier 62 converts the voltage output from the DAC 61 into a current and outputs it to the voice coil motor 63.
It supplies a current for driving the voice coil motor 63 .

The whirlwind motor 63 is a motor for moving the servo head and the data head in the radial direction of the magnetic disk 30, that is, in the direction across the tracks.

The main control unit 40 issues servo commands and target tracks to the DSP 50, and also performs other processes such as interface control between higher-level controllers and monitoring of the rotation control of the magnetic disk 30.

II. Explanation of Each Calculated Value in the Circuit Using Figure 3, we will explain each calculated value necessary to explain the operation of the circuit. Figure 3 is a diagram explaining each calculated value of the head positioning control circuit of this embodiment. Note that in Figure 3, each calculated value is shown as a continuous analog signal for convenience, but in reality it is a digital value converted to digital at predetermined time intervals or a digital value calculated by the DSP 50. However, PosN and PosQ are analog signals.

3, vertical lines indicate boundaries between servo tracks, and when either of the digitally converted position signals PosN and PosQ has a value of zero, this indicates that the servo head is located at the boundary between servo tracks. When the servo head is located at the boundary of a servo track, the data head that moves in conjunction with the servo head is configured to be on-track at the center of the data track.

The track numbers are assigned consecutively to each track. For example, if there are 2048 tracks, the track numbers are assigned from 0 to 2047.

The zone number is a number assigned consecutively in units of four tracks. For example, if the number of tracks is 2048,
Zone numbers are assigned from 0 to 511. The reason why zone numbers are assigned in units of four tracks is that the position signals PosN and PosQ are signals obtained with four tracks as one cycle. In other words, if the servo head is in the same relative position within each zone, the digitally converted position signal Po
The values of sN and PosQ will be the same.

PosN and PosQ are analog signals that indicate the position of the servo head, and signal waveforms such as those shown in Figure 3 are obtained according to the position of the servo head.
is generated by the position signal generating circuit 32 based on the servo data read by the servo head 31, and
It is converted to digital by DC34 and stored in the register Pos in DSP50.
It is incorporated into N and PosQ.

These position signals PosN and PosQ are 90 degrees out of phase with each other to determine the direction of movement of the servo head 31, and if the value of either the position signal PosN or PosQ is zero, it indicates that the servo head 31 is located at the boundary between servo tracks.

The position signals PosN and PosQ are periodically repeated every four tracks, i.e., every zone.
With sN and PosQ, it is possible to obtain relative position information within a zone, but it is not possible to detect in which zone the device is located.

The Phase indicates the track number in the zone where the servo head is located, and can take any of the values 0, 1, 2, and 3. This Phase is determined by the following conditions: PosN+PosQ>0, and PosN-PosQ>0.
It is determined based on the calculation and comparison of Q>0, and the method of determination will be described later.

PosFine indicates the precise position information of the servo head within the track. One track is divided into 256 parts,
This value is expressed in units of 1/256, and is a value between -0.5 and 0.5. This PosFine is calculated based on the value of Phase, PosN, PosQ,
It takes one of the values -PosN and -PosQ. The method for calculating PosFine will be described later.
e is obtained by extracting the linear portion of the position signal PosN or PosQ and calculating it so that it has a gradient in the same direction.

RRPos indicates the actual position information within the servo head zone, and values between -0.5 and 3.5 are divided by 256.
The RRPos is calculated by adding the in-zone track number Phase and the in-track position information PosFine. The in-zone measured position RRPos has discontinuous values as shown in Figure 3, and these discontinuous points correspond to the boundaries of the zones.

III. Explanation of Data Structure of Each Calculated Value Next, the data structure of each calculated value handled in the DSP 50 will be explained using FIG. 4. Each calculated value is stored in the RAM 53 in the DSP 50.
Each calculation value has a data length of 1 byte, 2 bytes, or 4 bytes.

4 shows the case where the data length handled within the DSP 50 is maximum, and the upper two bytes store data corresponding to the track number. For example, if the number of tracks is 2048, values from 0 to 2047 are stored. Here, the first lowest bit of the upper two bytes is the ones digit of the binary number, and the second lowest bit is the two digit of the binary number.

On the other hand, the lower two bytes store position information within the track, and a value less than 1 is stored.
The first most significant bit of the lower two bytes is the 1/2 place of the binary number, and the second most significant bit is the 1/4 place of the binary number.

In FIG. 4, each calculation value is 1 byte, 2 bytes,
The data length is either 4 bytes or 4 bytes.
The bit positions of the respective operation values are shown aligned vertically.

Next, each calculated value handled within the DSP 50 will be explained below.

Phase: Indicates the track number within the zone where the servo head is located. It consists of one byte and can have values of 0, 1, 2,
It takes a digital value indicating one of three things.

PosFine: Indicates the precise position information of the servo head within the track. It consists of 1 byte. One track is 25
Divide it into 6 and take a digital value in 1/256 units from -128/256 to +127/256. For example, when the servo head is positioned 0.25 tracks away from track number 5 towards track number 6, PosFine = 0.25. Also, when it is positioned midway between track numbers 5 and 6, PosFine =
It is −0.5.

RRPos: Indicates the actual position information within the servo head zone, including the track number phase within the zone,
It is created from the track position information PosFine. It consists of two bytes, with the upper byte containing the track number in the zone,
It is calculated by adding e to the lower byte and adding the intra-track position information PosFine to the lower byte. The value is between -0.5 and 3.5. For example, when the servo head is positioned 0.25 tracks away from track number 5 towards track number 6, RRPos = 5.25. When the servo head is positioned midway between track numbers 5 and 6, RRPos
=5.5.

ERPos: Indicates predicted position information within the servo head zone, and is the predicted absolute position EstLPo, which will be explained later.
This is the position information of s less than 4 tracks, and all digits of 4 tracks or more are set to zero. It consists of 2 bytes and takes the same value as the measured position in the zone RRPos.

Distance: Indicates the position error, which is the difference between the predicted position ERPos of the servo head in the zone and the measured position RRPos in the zone.
It consists of two bytes and its value is greater than -4.0 and is 4.0.
takes a value less than

LPos: Indicates the actual absolute position of the servo head. It consists of four bytes. The upper two bytes correspond to the track number, and the lower two bytes indicate precise position information within the track. However, the actual absolute position LPos is not an actual measured value, but rather a predicted absolute position EstLPos (described later) corrected based on the actual measured position within the zone RRPos, which is an actual measured value. Furthermore, if the number of tracks is 2048, for example, the actual absolute position LPos of the servo head will take a value between -0.5 and 2047.5.

LastLPos: Indicates the actual absolute position of the servo head at the time of the previous interrupt processing. It is composed of 4 bytes similar to the actual absolute position LPos of the servo head described above, and can take on values in the same range.

EstLPos: Indicates the predicted absolute position of the servo head. It is composed of 4 bytes similar to the actual absolute position LPos and takes the same value. This predicted absolute position EstLPos is the same as the previous actual absolute position Las
The servo head movement speed is calculated from tLPos and the current real absolute position LPos, and this movement speed is calculated based on the time until the next interrupt processing. The calculated predicted absolute position EstLPos is then used to calculate the next real absolute position of the servo head at the time of the next interrupt processing.

DiffLPos: The difference between the current actual absolute position of the servo head and the previous actual absolute position, and indicates the amount of movement of the servo head since the previous time.

The above are the calculated values shown in the figure, but the following are the values calculated by the DSP50 (not shown)
The calculation values handled within will also be explained.

Velocity: Indicates the moving speed of the servo head, calculated from the servo head movement amount DiffLPos.

VelObj: Indicates the target moving speed of the servo head.
Obj is a value according to the number of remaining tracks to the target track, and is stored in the speed table DCur stored in the RAM 54 in the DSP 50.
This can be obtained by referring to ve.

ClyDiff: Shows the number of remaining tracks to the target track.
The number of remaining tracks ClyDiff is calculated from the difference between the actual absolute position LPos and the target track number ClyCmd.

TaskNo: A value indicating the status of servo control. This is the DSP
Although it is not a calculated value of DSP 50, it is set by DSP 50 and used as a flag, so it will be explained here. The basic control states include speed control, position control, re-zero control, etc.

The above has described each of the calculated values stored in the RAM 53 of the DSP 50, but the registers in the input port 51 and the output port 52 will also be described.

ClyCmd: Indicates the track number of the target track specified by the upper controller. It consists of two bytes, and takes a value from 0 to 2047 if the number of tracks is 2048, for example.

SvCmd: Servo command issued by the main control unit 40 is stored. It consists of 2 bytes.

PosN: Position signal PosN generated by the position signal generation circuit 32
The digital converted value is stored.

PosQ: Position signal PosQ generated by the position signal generation circuit 32
The digital converted value is stored.

DrvCur: The drive current value of the voice coil motor 63 calculated by the DSP 50 is stored.

IV. Explanation of Operation of the Present Embodiment The operation of the head positioning control circuit of the present embodiment will be explained using FIGS. 5(a) to 5(c).
5(a) to 5(c) are flowcharts for explaining the processing of DSP50. When performing speed control or position control, DSP50
The processing is performed according to the flowchart shown in Fig. 1. Note that the processing for speed control and position control is partially common, and after the common part is completed, the DSP 50 determines whether it is speed control or position control, and branches to the processing for speed control or position control.

IV. Explanation of Operation of the Present Embodiment The operation of the head positioning control circuit of the present embodiment will be explained using FIGS. 5(a) to 5(c).
5(a) to 5(c) are flowcharts for explaining the processing of DSP50. When performing speed control or position control, DSP50
The processing is performed according to the flowchart shown in Fig. 1. Note that the processing for speed control and position control is partially common, and after the common part is completed, the DSP 50 determines whether it is speed control or position control, and branches to the processing for speed control or position control.

(Step S10) The DSP 50 performs the process described below at intervals of 38 μs set in the interrupt timer 56. Note that the DSP 50 continues to operate for a period from the end of this interrupt process until the start of the next interrupt process.
P50 performs processes such as determining whether the calculated head speed and head position satisfy the conditions for switching from speed control to position control, or determining whether a command has been received from the main control unit 40.

The set value of 38 μs for the interrupt timer 56 is set so that one interrupt processing time in this embodiment is completed in a time shorter than 38 μs, and processing other than the interrupt processing can be performed sufficiently. Also, although the detailed reason will be described later, when the predicted absolute position EstLPos of the servo head is corrected based on the measured position RRPos within the zone to calculate the actual absolute position LPos, this predicted absolute position
If the predicted error between EstLPos and the actual absolute position of the servo head (not the calculated real absolute position LPos) is not within ±2 tracks, the value of the calculated real absolute position LPos is not guaranteed, so the interrupt timer 56 is set so that the predicted error is always within ±2 tracks.

(Step S11) The DSP 50 instructs the ADCs 33 and 34 to start analog-to-digital conversion, and stores the digitally converted values of the position signals PosN and PosQ in the registers PosN and PosQ in the input port 51.

(Steps S12 to S18) In steps S12 to S18, the DSP 50 determines the magnitude relationship between PosN and PosQ in four ways, and performs the processing described below depending on the determination result to calculate the track number Phase within the zone where the servo head is located and the intra-track position information PosFine.

If the conditions PosN+PosQ<0 and PosN-PosQ<0 are satisfied, in step S15, the in-track position information Pos
Fine is set to -PosQ, and the track number Phase in the zone is set to 3.

If the conditions PosN+PosQ<0 and PosN-PosQ≧0 are satisfied, in step S16, the in-track position information Pos
Fine is set to PosN, and the track number Phase within the zone is set to 0.

If the conditions PosN+PosQ≧0 and PosN−PosQ≧0 are satisfied, in step S17, the in-track position information Pos
Fine is PosQ, and the track number Phase in the zone is 1.

If the conditions PosN+PosQ≧0 and PosN−PosQ<0 are satisfied, in step S18, the in-track position information Pos
Fine is set to -PosN, and the track number Phase within the zone is set to 2.

(Step S19) In steps S19 and S20, the DSP 50 calculates the actual position of the servo head within the zone from the in-zone track number Phase and in-zone position information PosFine, and sets the result to the variable RRPos. First, in step S19, the in-zone track number Phase is stored in the one or more track positions of the variable RRPos. At this point, the variable RRPos takes on a value of 0, 1, 2, or 3.

(Step S20) The DSP 50 adds the intra-track position information PosFine to the position information portion of the variable RRPos that is less than one track.
The in-zone location information RRPos takes a value between -0.5 and 3.5.

(Step S21) The DSP 50 extracts the part of the predicted absolute position EstLPos that corresponds to the in-zone position information, and sets the in-zone predicted position as the variable ERPos.
This predicted intra-zone position ERPos takes a value between −0.5 and 3.5, similar to the intra-zone actual measured position RRPos.

(Step S22) The DSP 50 calculates the actual measured position in the zone from the predicted position in the zone ERPos.
The RRPos is subtracted to calculate the position error, which is stored in the variable Distance. The position error Distance takes a value greater than -4.0 and less than 4.0.

(Steps S30 to S31) In steps S30 to S31, the DSP 50 calculates the predicted absolute position Est
The part of LPos corresponding to the zone number is extracted and stored in the working variable Work. First, in step S30, 0.5 is added to the predicted absolute position EstLPos and stored in the working variable Work. This is because the starting point for assigning zone numbers is shifted by 0.5 tracks from the starting point of the absolute position, and the quotient of 4 of the absolute position does not simply become the zone number; the quotient of 4 obtained by adding 0.5 to the absolute position becomes the accurate zone number. Next, in step S31, the digits less than 4 tracks of the working variable Work are cleared to zero. At this point, the variable Work
The part corresponding to the zone number of the predicted absolute position EstLPos is stored in the .

(Steps S32 to S36) In steps S32 to S36, the DSP 50 calculates the predicted absolute position Est
The actual absolute position LPos is calculated by correcting the actual position LPos using the actual position RRPos in the zone.
It is necessary to assume that the error between Pos and the actual position is within ±2.0 tracks. This is because the actual position RRPos in the measured zone is
is repeated periodically for each zone, and DSP5
The value 0 is set because the position within the zone can be determined from the measured position within the zone RRPos, but it is not possible to determine which zone the vehicle is located in.

Therefore, assuming that the error between the predicted absolute position EstLPos and the actual position is within ±2.0, the zone number of the actual position is
The zone number of the predicted overall position EstLPos can be either the same as the one in the predicted overall position EstLPos, or moved up or moved down. This determination is made by comparing the predicted in-zone position ERPos and the actual in-zone position RRP
The determination is made based on the magnitude of the position error Distance, which is the difference from os, and processing described below is performed depending on the determination result.

If the position error Distance is less than -2.0, in step S34, 1 is subtracted from the fourth track digit of the variable Work to obtain
The zone number is decremented by 1. Note that the 4th or higher digit of the variable Work corresponds to the zone number.

If the position error Distance is between -2 and 2, the variable Work
remains the same and the zone number remains the same.

If the position error Distance is greater than 2, step S35
In this example, 1 is added to the fourth track digit of the variable Work, and the zone number is incremented by 1.

(Step S36) At this point, the zone number of the actual position is stored in the work variable Work. The actual absolute position LPos of the servo head is calculated by adding the measured in-zone position RRPos to this work variable Work.

(Steps S37 to S40) In steps S37 to S40, the DSP 50 performs processing to remove noise from the analog signals before converting the position signals PosN and PosQ into digital signals, thereby improving the stability of servo control. First, in step S37, the real absolute position L
The position error, which is the difference between Pos and the predicted absolute position EstLPos, is stored in the work variable Work.

Next, if the value of the variable Work, which is the position error, is greater than 1.5 or less than -1.5, the DSP 50 determines that noise is present in the servo signal that is the basis of the in-zone actual measured position RRPos, which is the actual measured value. In this case, in step S40, the DSP 50 uses the predicted absolute position EstLPos itself as the actual absolute position LPos, and does not use it as the actual absolute position LPos calculated based on the in-zone actual measured position RRPos.

On the other hand, if the value of the variable Work, which is the position error, is other than the above, the actual measured value of the in-zone actual position RRPos is determined to be accurate, and the actual absolute position LPos calculated from the in-zone actual position RRPos is used as is. Note that if the position error is greater than 1.5 or less than -1.5, the DSP 50 determines that noise is present in the servo signal, but it does not have to be limited to 1.5.

(Step S41) The DSP 50 calculates the previous actual absolute position LastL from the actual absolute position LPos.
Pos is subtracted to calculate the servo head movement amount DiffPos.

(Step S42) In preparation for the next interrupt process, the DSP 50 calculates the next predicted absolute position EstLPos of the servo head. In this embodiment, this predicted absolute position EstLPos is calculated by adding the head movement amount DiffLPos to the current actual absolute position LPos. This is the simplest calculation method, and assuming that the servo head movement speed does not change, since the interrupt time is a constant interval, the next predicted absolute position EstLPos of the servo head can be calculated simply by adding the calculated servo head movement amount DiffLPos to the actual absolute position LPos of the servo head.
can be calculated.

Furthermore, the interrupt time does not need to be limited to a fixed interval, and the predicted position of the servo head in the next interrupt process may be calculated from the servo head movement speed and the time until the next interrupt process. Furthermore, the predicted position of the servo head in the next interrupt process may be calculated taking into account not only the servo head movement speed but also the servo head acceleration.

However, the predicted position can also be calculated taking into account the speed of the servo head.

(Step S43) The DSP 50 calculates the real absolute position L
Pos is set to the previous real absolute position LastLPos.

(Step S50) The DSP 50 determines whether to perform speed control or position control. Specifically, the current servo control state is set in the variable TaskNo, and by referencing the value of the variable TaskNo, it determines whether to perform speed control or position control.
The setting of this variable TaskNo is performed by the DSP 50 during background processing other than interrupt processing, or in step S67, which will be described later.

(Step S51) When it is determined in step S50 that speed control should be performed, the DSP 50 performs calculations related to speed control in steps S51 to S54. First, in step S51, the position error DiffL
Pos is subjected to low-pass filtering, and head velocity Velocity
y is calculated. Low-pass filtering is performed by digital calculations to remove high-frequency components. In other words, while it is possible to use the position error DiffLPos as is as the head speed, there is a risk that the high-frequency components will make servo control unstable. Therefore, by applying low-pass filtering to the position error DiffLPos, the high-frequency components are removed and servo control is stabilized.

(Step S52) The DSP 50 calculates the real absolute position LPos from the target track number CylCmd.
Subtract CylDiff from the remaining number of tracks to the target track.
Calculate.

(Step S53) The DSP 50 refers to the target speed table DCurve using the number of remaining tracks CylDiff up to the target track as an index.
Get the target velocity VelObj.

(Step S54) The current value for driving the voice coil motor 63 is calculated from the actual head velocity Velocity calculated in step S51 and the target velocity VelObj determined in step S53, and stored in register DurCur within the output port of the DSP 50. The formula for calculating the motor drive current DrvCur is DrvCur = -Kp * (Gobj * VelObj - Gvel * Velciey), where Kp, Gvel, and Gobj are coefficients.

The motor drive current value stored in the register is then input to DAC6.
The DAC 61 converts the input value into a digital signal and outputs a voltage corresponding to the input value to the power amplifier 62. The power amplifier 62 outputs a current corresponding to the voltage to the voice coil motor 63, thereby driving the voice coil motor 63.

V. Explanation of Position Control Next, the position control will be explained.
If it is determined that position control should be performed, the process branches to step S60, and position control processing of steps S60 to S67 is performed.

(Step S60) The DSP 50 calculates the real absolute position LPos from the target track position CylCmd.
is subtracted to calculate the servo head position error PosErr.

(Step S61) The DSP 50 performs integration processing on the position error PosErr to obtain IntgrErr
This integration process is a method for compensating for the low-frequency loop gain, and is a process for absorbing the steady-state deviation of the control error.

(Step S62) The DSP 50 adds IntgrErr and Kpp*PosErr and stores the result in the work variable Work1, where Kpp is a preset coefficient.

(Step S63) The DSP 50 performs low-pass filtering on Work1 and
This low-pass filtering process is a process for removing high frequency components and for stabilizing servo control.

(Step S64) The DSP 50 performs phase compensation filtering on Work2 and outputs Work3.
This phase compensation filter processing is processing for compensating for phase delay or phase advance due to differences in frequency bands.

(Step S65) The DSP 50 performs notch filtering on Work 3 to calculate the motor drive current value DrvCur. This notch filtering is performed to prevent the motor drive current from oscillating and causing the servo head to vibrate.

(Step S66) The DSP 50 refers to the register SvCmd of the input port 51 to determine whether a servo command has been received.
If no servo command has been received, the series of interrupt processes ends in step S70, and the DSP 50 returns to background processing.

(Step S67) If the DSP 50 has received a servo command, it sets a variable TaskNo indicating the status of servo control based on the servo command. Then, in step S70, the DSP 50 returns to background processing.

The above steps S66 and S67 may be performed as background processing by the DSP 50. However, since background processing is always interrupted by interrupt processing, there is no guarantee that reception of a servo command can be confirmed between each interrupt processing.
At the end of position control, the reception of the servo command is confirmed.

In conventional position control, the processes corresponding to steps S60 to S65 are performed by analog circuits, but in the present invention, these processes are all performed by a digital signal processor.

Since the present invention allows speed control to be performed by a digital signal processor, position control is also performed by a digital signal processor.

VII. Explanation of Calculated Values When Servo Head Moves The detailed processing of the DSP 50 in speed control will be explained using FIGS.

In these figures, the horizontal axis represents the absolute position of the servo head, and the vertical axis represents the measured position RRPos within the zone and the position error Distance. The upper figure shows the measured position RRPos within the zone relative to the absolute position of the servo head, and the lower figure shows the predicted position within the zone relative to the absolute position of the servo head.
The position error Di is the difference between ERPos and the measured position RRPos within the zone.
This indicates the stance.

6 shows an example in which the actual absolute position in the previous interrupt process was 62.1, and the current predicted absolute position is 72.4. The predicted in-zone position ERPos of this predicted absolute position is 0.4, its zone number is 18, and its in-zone track number is 0.

The bottom graph in FIG. 6 shows the position error Distan with respect to the absolute position of the servo head when the predicted position within the zone ERPos is set to 0.4.
This position error Distance is the actual measured position within the zone.
Since RRPos is discontinuous at the zone boundary, it is also discontinuous at the zone boundary. If the zone is the same as the predicted absolute position, the position error Distance is within ±2.0. If the zone number is rounded down, the position error Dist
ance is less than -2.0.

Therefore, when the position error Distance is within ±2.0, the zone number of the predicted absolute position and the zone number of the actual position are the same, and the actual absolute position can be calculated by extracting the position information corresponding to the zone number of the predicted absolute position and adding the actual measured value, that is, the in-zone actual position RRPos, to it.

On the other hand, if the position error Distance is smaller than −2.0, the zone number of the actual position is 1 less than the zone number of the predicted absolute position, and the actual absolute position can be calculated by extracting the position information corresponding to the zone number of the predicted absolute position, subtracting 1 from the zone number, and then adding the actual measured value, that is, the in-zone actual position RRPos.

The shaded area A in FIG. 6 indicates the difference between the predicted overall position and the actual position.
This indicates the area where the actual absolute position LPos calculated by the DSP50 is 1.5 or more.
os is not used as the actual absolute position, but as the predicted absolute position EstLPos
is used as the real absolute position LPos.

Next, Figure 7 shows an example of the case where the zone number of the predicted absolute position is incremented. In this example, the actual absolute position in the previous interrupt process is 31.0, and the predicted absolute position this time is 31.0.
The predicted absolute position in the zone ERPos is 2.5, the zone number is 9, and the track number in the zone is 3.

The bottom graph in FIG. 7 shows the position error Dist relative to the absolute position of the servo head when the predicted position in the zone ERPos is set to 2.5.
If the zone number of the predicted absolute position is the same as the zone number of the actual position, the position error Distance is within ±2.0, and if the zone number of the predicted absolute position is carried forward, the position error Distance becomes a value greater than 2.0.

The shaded area A in FIG. 7 indicates the area where the difference between the predicted overall position and the actual position is 1.5 or more, as in FIG. 6.
There is a possibility that the actual absolute position LPos calculated by SP50 is not accurate, so this LPos is not used as the actual absolute position, and the predicted absolute position ERPos is used as the actual absolute position.

VIII. Initialization of the Head Positioning Control Circuit Next, the initialization of the head positioning control circuit of the present invention will be described. That is, when the power is turned on to the disk drive, the actual absolute position LPos of the servo head,
The predicted absolute position EstLPos, the position error DiffLPos between the actual absolute position and the predicted absolute position, and the movement velocity Velocity are all undetermined, and the head positioning control circuit cannot operate according to the flowchart of FIG.

Therefore, the head positioning control circuit must initialize the above-mentioned values rather than immediately performing the operation shown in FIG. 5 after the disk drive is powered on.

In reality, after power is turned on, the head positioning control circuit performs re-zero control to position the servo head on the track with track number 0.
The speed control is the same as that shown in the flowchart in Fig. 1. However, in the re-zero control, the speed is not controlled according to the number of tracks up to the track with track number 0, but is simply controlled at a constant speed. In this re-zero control, the absolute position of the servo head is unknown to the DSP 50, and only a provisional position is known, assuming one of the tracks to be zero. When the re-zero control is completed, the servo head is positioned on the track with track number 0, and the absolute position of the servo head can be determined by setting the absolute position of the servo head to zero at that point.

Therefore, the DSP50 of the head positioning control circuit must determine the moving speed Velocity of the servo head before entering this re-zero control. Once the moving speed Velocity of the servo head is determined, the DSP50 can perform speed control in the re-zero control by processing similar to that shown in the flowchart in Figure 5. During this re-zero control, the servo head is simply controlled at a constant speed, and after the servo head crosses track number 0, it detects a guard band in which a predetermined servo pattern is recorded, decelerates the head, and drives it at a low speed in the reverse direction, positioning the servo head on track number 0. Thereafter,
The actual absolute position LPos, predicted absolute position EstLPos, and previous absolute position LastLPos of the head calculated at that time are cleared to zero for initialization.

Next, using FIG. 9, the moving velocity of the servo head, Velocity
Explain how to calculate ty.

(Step S80) After the disk drive is powered on, the DSP 50 starts the process described below.

(Step S81) The DSP 50 resets the time counter to zero. This time counter is, for example, a software-based counter. This time counter is used to measure the period of the position signal.

(Step S82) The DSP 50 sets the motor drive current value DrvCur to -100 in the register in the output port 52. Assume that the servo head is stopped, for example, in the innermost landing zone of the magnetic disk when power is turned on. The motor drive current value of -100 is a current value for driving the servo head toward the inner side, and is sufficiently smaller than the value when driving the servo head at maximum acceleration.

(Step S83) The DSP 50 waits for 100 ms. This time is measured by a timer separate from the time counter mentioned above. 100 ms is sufficient time to move the servo head to the inner side of the magnetic disk and press the actuator that moves the servo head against a mechanical stopper, preventing any further movement. Of course, if the disk drive is operating normally, the servo head will be stopped in the landing zone of the magnetic disk when the power is turned off. However, there is a possibility that the servo head will not stop in the landing zone due to some external force or abnormality, and will be positioned, for example, on the outermost side.
Therefore, 100 ms is a sufficient time for the servo head to reach the innermost side from any position.

(Step S84) The DSP 50 sets the motor drive current value DrvCur to 100 in the register in the output port 52. This motor drive current value of 100 is the current value for moving the servo head toward the outer side. In other words, after the servo head reaches the innermost side, the servo head is then moved toward the outer side.

(Step S85) The DSP 50 waits for 20 ms. As in step S83, this time is measured by a timer separate from the time counter described above. This 20 ms value is used to give the servo head a predetermined speed, after which the DSP 50 calculates the servo head movement speed by sampling the position signal. This time is set so that the servo head is positioned sufficiently in front of the outermost position.

(Step S86) The DSP 50 sets the motor drive current value DrvCur to 0 in the register in the output port 52. As a result, the motor drive current becomes zero and the motor moves by inertia. Then, in a step described later, the DSP 50 samples the position signal and calculates the movement speed of the servo head.

(Step S87) The DSP 50 instructs the digital conversion of the position signal PosN. Alternatively, the signal to be digitally converted may be PosQ, and either one is sufficient.

(Step S88) The DSP 50 determines whether the digitally converted value is zero.
If it is not zero, the process returns to step S87, and step S87 is repeated until the digitally converted value becomes zero.

(Step S89) When the position signal PosN becomes zero, the DSP 50 starts the time counter.

(Step S90) The DSP 50 then instructs digital conversion of the position signal PosN.

(Step S91) The DSP 50 determines that the digitally converted value is zero.
If it is not zero, the process returns to step S89, and step S89 is repeated until the digitally converted value becomes zero.

(Step S92) The DSP 50 increments the time counter. This time counter counts the time it takes for the position signal PosN to change from zero to zero. On the other hand, as is clear from FIG. 3, the position signal PosN changing from zero to zero indicates that the servo head has moved across two tracks.

(Step S93) The DSP 50 calculates the moving speed of the servo head. The moving distance of the servo head is two tracks, and the distance between these two tracks is a predetermined value. In addition, the time required to move these two tracks has been measured.
The moving speed of the servo head can be calculated.

This is how the velocity of the servo head is calculated.

Next, the DSP 50 calculates the actual position RRPos within the zone and sets this RRPos as the provisional position LPos of the servo head. In other words, since the absolute position of the servo head is unknown until the servo head is positioned on track number 0 by re-zero control, the actual position RRPos within the zone of the servo head at the time the velocity is calculated is assumed to be the absolute position LPos of the servo head.

Next, the DSP 50 calculates the assumed absolute position L of the servo head.
Pos is set to LastLPos, the previous actual absolute position of the servo head.

Next, the DSP 50 multiplies the servo head movement speed (Velocity) calculated in step S93 by the time until the next interrupt process to calculate the servo head movement distance, and adds the servo head movement distance to the value of the tentative actual absolute position (LPos) to calculate the predicted absolute position (EstLPos) of the servo head in the next interrupt process. Note that this predicted absolute position (EstLPos) is also a tentative position.

By the above process, all the information required for speed control is set.
At the time when city is calculated, the servo head is moving toward the outer side due to inertia, and the DSP 50 immediately transitions to re-zero control.

In the re-zero process, the DSP 50 performs the same speed control as in the flowchart shown in Fig. 5. However, the target speed is not changed according to the number of remaining tracks, and the target speed is a constant value.

Subsequently, when the re-zero control is completed and the servo head is positioned at track number 0, the DSP 50 converts the values of the actual absolute position LPos, predicted absolute position EstLPos, and LastLPos into absolute positions by resetting these values to zero.

Next, the DSP 50 performs position control on the track with track number 0 and waits for a servo command to be received. This position control is performed in accordance with the flowchart shown in FIG.

IX. Explanation of Head Speed and Motor Drive Current in Speed Control Specific signals and calculated values when the head positioning control circuit of this embodiment performs speed control will be explained using Figure 8. In the figure, the horizontal axis is the time axis.

Velocity indicates the moving speed of the servo head during velocity control. In the figure, the dotted line indicates the target velocity VelObj.

PADrv indicates the output voltage signal of the DAC 61 during speed control, and the motor drive current value DrvCu calculated by the DSP 50
r is converted into an analog voltage signal by the DAC61.

PosFine indicates an in-track position signal calculated by the DSP 50 during a seek, and is a calculated value calculated based on the servo signal read by the servo head.

LPos indicates the absolute position of the servo head during a seek, and is a calculated value calculated by the DSP 50. It can be seen that the servo head moves from the current track position to the target track position.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications are possible within the scope of the present invention.

[Effects of the present invention]

According to the present invention, analog elements, particularly track crossing pulse generating circuits which require a large mounting area, can be eliminated from the head positioning control circuit of a disk drive, making it possible to provide a compact disk drive.

Furthermore, since no expensive analog elements are used, a low-cost disk drive can be provided.
Since the head positioning control circuit is constructed using a digital circuit, the circuitry is not subject to deterioration over time, making it possible to provide a disk drive with improved reliability.

Furthermore, in the present invention, if noise is present in the servo signal read from the servo head, the noise is digitally removed when the position of the servo head is digitally calculated, so that the absolute position of the servo head can be calculated accurately, and a disk drive can be provided that prevents seek errors that result in seeking the wrong track.

Claims (13)

[Claims] [Claim 1] A disk drive having the following configuration: a disk (30) having a plurality of tracks on which servo data is recorded; a servo head (31) for reading the servo data; and a motor (63) for moving the servo head in a direction across the tracks of the disk. The head positioning control device has the following configuration. a position signal generating means (32) for generating an analog position signal indicating the position of the servo head in a zone, each zone consisting of a predetermined number of consecutive tracks, based on servo data read from the disk; a digital conversion means (33, 34) for digitally converting the analog position signal generated by the position signal generating means; a digital calculation means (50) that operates at predetermined time intervals and has the following functions: a function for instructing the analog-to-digital conversion means to perform digital conversion; a function for calculating the position of the servo head in the zone based on the digitally converted value; a function for calculating the actual position of the servo head based on the previously calculated predicted position of the servo head and the calculated position of the servo head in the zone; a function for calculating the moving distance of the servo head based on the calculated actual position of the servo head and the previously calculated actual position of the servo head; a function for calculating the next predicted position of the servo head based on the calculated actual position of the servo head and the calculated moving distance of the servo head; and a function for calculating the moving speed of the servo head based on the calculated actual position of the servo head and the previously calculated actual position of the servo head; A function for calculating the number of remaining tracks to the target track based on the calculated actual position of the servo head; a function for determining the target speed of the servo head based on the calculated number of remaining tracks; a function for calculating a current value for driving the motor based on the calculated moving speed of the servo head and the target speed of the servo head; a function for outputting the calculated motor drive current value; and means (61, 62) for converting the current value for driving the motor output from the digital calculation means into analog and generating an analog motor drive current signal. [Claim 2] The function of calculating the next predicted position of the servo head of the digital calculation means of claim 1 is characterized in that the predicted position of the next servo head is calculated by adding the calculated actual position of the servo head and the calculated movement distance of the servo head. [Claim 3] A disk drive having the following configuration: a disk (30) having a plurality of tracks on which servo data is recorded; a servo head (31) for reading the servo data; and a motor (63) for moving the servo head in a direction across the tracks of the disk; the head positioning control device has the following configuration. a position signal generating means (32) for generating an analog position signal indicating the position of the servo head in a zone, each zone consisting of a predetermined number of consecutive tracks, based on servo data read from the disk; a digital conversion means (33, 34) for digitally converting the analog position signal generated by the position signal generating means; a digital calculation means (50) which operates at predetermined time intervals and has the following functions: a function for instructing the analog-to-digital conversion means to perform digital conversion; a function for calculating the position of the servo head in the zone based on the digitally converted value; a function for calculating the actual position of the servo head based on the previously calculated predicted position of the servo head and the calculated position of the servo head in the zone; a function for calculating the moving speed of the servo head based on the calculated actual position of the servo head and the previously calculated actual position of the servo head; a function for calculating the next predicted position of the servo head based on the calculated actual position of the servo head and the calculated moving speed of the servo head; a function for calculating the number of remaining tracks to the target track based on the calculated actual position of the servo head; and a function for determining the target speed of the servo head based on the calculated number of remaining tracks. A function for calculating a current value for driving the motor based on the calculated servo head movement speed and the target speed of the servo head; a function for outputting the calculated motor drive current value; and means (61, 62) for converting the current value for driving the motor output from the digital calculation means into analog to generate an analog motor drive current signal. [Claim 4] The function of calculating the next predicted position of the servo head of the digital calculation means of claim 1 has the following functions: a function to calculate the head movement distance in the predetermined time by multiplying the calculated servo head movement speed by the predetermined time; and a function to calculate the next predicted position of the servo head by adding the calculated actual position of the servo head and the calculated servo head movement distance in the predetermined time. [Claim 5] A disk drive having the following configuration: a disk (30) having a plurality of tracks on which servo data is recorded; a servo head (31) for reading the servo data; a motor (63) for moving the servo head in a direction across the tracks of the disk; a head positioning control device having the following configuration: position signal generating means (32) for generating an analog position signal indicating the position of the servo head in a zone made up of a predetermined number of consecutive tracks based on the servo data read from the disk; and analog-to-digital conversion means (33, 34) for converting the analog position signal generated by the position signal generating means into a digital signal.
4); and digital calculation means (50) which operates at predetermined time intervals and has the following functions: a function to instruct the analog-to-digital conversion means to perform digital conversion; a function to calculate the position of the servo head in the zone based on the digitally converted value; a function to calculate the actual position of the servo head based on the previously calculated predicted position of the servo head and the calculated position of the servo head in the zone; a function to correct and calculate the calculated actual position of the servo head based on the calculated actual position of the servo head and the previously calculated predicted position of the servo head; a function to calculate the next predicted position of the servo head based on the calculated actual position of the servo head and the previously calculated actual position of the servo head; a function to calculate the moving speed of the servo head based on the calculated actual position of the servo head and the previously calculated actual position of the servo head; a function to calculate the number of remaining tracks to the target track based on the calculated actual position of the servo head; and a function to obtain a target speed of the servo head based on the calculated number of remaining tracks; A function for calculating a current value for driving the motor based on the calculated servo head movement speed and the target speed of the servo head; a function for outputting the calculated motor drive current value; and means (61, 62) for converting the current value for driving the motor output from the digital calculation means into analog to generate an analog motor drive current signal. [Claim 6] The function of the digital calculation means of claim 6 to correct and calculate the actual position of the servo head has the following functions: a function to calculate a prediction error by subtracting the calculated actual position of the servo head from the predicted position of the servo head calculated previously; a function to set the predicted position of the servo head calculated previously as the actual position of the servo head if the calculated prediction error exceeds a predetermined value; and a function to set the calculated actual position of the servo head as the actual position of the servo head if the calculated prediction error is smaller than the predetermined value. [Claim 7] The function of calculating the servo head movement speed of the digital calculation means of claim 1, 3 or 5 has the following functions: a function of calculating the movement distance of the servo head from the difference between the calculated actual position of the servo head and the previously calculated actual position of the servo head; and a function of calculating the movement speed of the servo head by digitally performing low-pass filter processing on the calculated movement distance of the servo head. [Claim 8] The means for generating a motor drive current according to claim 1, 3 or 5 comprises: analog conversion means (61) for converting the current value for driving the motor output from the digital calculation means into an analog voltage signal, and amplifier means (62) for converting the voltage signal into a current signal and supplying the current to the motor. 9. A disk (30) having a plurality of tracks on which servo data is recorded, a servo head (31) for reading the servo data, and based on the servo signal read by the servo head,
A head positioning control method for a disk drive having a position signal generating circuit (32) that generates an analog position signal indicating the position of a servo head in a zone, each zone consisting of a predetermined number of consecutive tracks, and a motor (63) that moves the servo head across the tracks of the disk, comprises the following steps: converting the position signal into a digital signal at predetermined time intervals (S10-S11); calculating the position of the servo head within the zone based on the digitally converted value (S12-S20); calculating the actual position of the servo head based on the previously calculated predicted position of the servo head and the previously calculated position of the servo head within the zone (S21-S36); calculating the movement distance of the servo head from the difference between the calculated actual position of the servo head and the previously calculated actual position of the servo head (S41); and calculating the next predicted position of the servo head based on the calculated movement distance of the servo head (S42).
a step (S51) of calculating a moving speed of the servo head based on the calculated moving distance; and a step (S52) of calculating the number of remaining tracks to the target track based on the calculated actual position of the servo head.
2); a step (S53) of calculating a target speed of the servo head based on the calculated number of remaining tracks; and a step (S54) of calculating a current value for driving the motor based on the calculated moving speed of the servo head and the target speed of the servo head. [Claim 10] The step of calculating the predicted position of the next servo head of claim 9 is characterized in that the predicted position of the next servo head is calculated by adding the calculated actual position of the servo head and the calculated movement distance of the servo head. 11. A disk (30) having a plurality of tracks on which servo data is recorded, a servo head (31) for reading the servo data, and based on the servo signal read by the servo head,
A head positioning control method for a disk drive having a position signal generating circuit (32) that generates an analog position signal indicating the position of a servo head in a zone that is a unit of a predetermined number of consecutive tracks, and a motor (63) that moves the servo head in a direction across the tracks of the disk, comprises the following steps: The method includes the steps of: converting the position signal into a digital signal at predetermined time intervals (S10-S11); calculating the position of the servo head within the zone based on the digitally converted value (S12-S20); calculating the actual position of the servo head based on the previously calculated predicted position of the servo head and the calculated position of the servo head within the zone (S21-S36); calculating the movement distance of the servo head from the difference between the calculated actual position of the servo head and the previously calculated actual position of the servo head (S41); calculating the movement speed of the servo head based on the calculated movement distance of the servo head; multiplying the calculated movement speed of the servo head by the predetermined time to calculate the movement distance of the head during the predetermined time; calculating the predicted position of the servo head next time by adding the calculated actual position of the servo head and the calculated movement distance of the servo head during the predetermined time. Calculating the number of remaining tracks to the target track based on the calculated actual position of the servo head (S5).
2); a step (S53) of calculating a target speed of the servo head based on the calculated number of remaining tracks; and a step (S54) of calculating a current value for driving the motor based on the calculated moving speed of the servo head and the target speed of the servo head. 12. A disk (30) having a plurality of tracks on which servo data is recorded, a servo head (31) for reading the servo data, and based on the servo signal read by the servo head,
A head positioning control method for a disk drive having a position signal generating circuit (32) that generates an analog position signal indicating the position of a servo head in a zone that is a unit of a predetermined number of consecutive tracks, and a motor (63) that moves the servo head in a direction across the tracks of the disk, comprises the following steps: Steps (S10-S11) of converting the position signal into digital form at predetermined time intervals; Steps (S12-S20) of calculating the position of the servo head within the zone based on the digitally converted value; Steps (S21-S36) of calculating the actual position of the servo head based on the previously calculated predicted position of the servo head and the calculated position of the servo head within the zone; Steps (S37-S40) of setting the previously calculated predicted position of the servo head as the actual position of the servo head if the error between the calculated actual position of the servo head and the previously calculated predicted position of the servo head is equal to or greater than a predetermined value; Steps (S42-S42) of calculating the next predicted position of the servo head based on the calculated actual position of the servo head and the previously calculated actual position of the servo head; Step (S51) of calculating the moving speed of the servo head based on the calculated actual position of the servo head and the previously calculated actual position of the servo head and the calculated moving distance; A step (S5) of calculating the number of remaining tracks to the target track based on the calculated actual position of the servo head.
2); a step (S53) of calculating a target speed of the servo head based on the calculated number of remaining tracks; and a step (S54) of calculating a current value for driving the motor based on the calculated moving speed of the servo head and the target speed of the servo head. 13. A head positioning control method for a disk drive, comprising the steps of: supplying a predetermined driving current to the motor (S8);
2 to S86); a step (S87) of converting the position signal into a digital signal; and when the digitally converted value reaches a first predetermined value,
Steps (S88-S89) of starting a timer; and when the digitally converted value reaches a second predetermined value,
Steps of stopping the timer (S91 to S92); and Step of calculating the initial moving speed of the servo head in speed control based on the measured value of the timer (S93).