JPH0362371A - Track tracing controller for disk device - Google Patents

Abstract

PURPOSE:To avoid a time consuming calculation by estimating a track deflection based on a signal being the sum of a tracking error signal and a current position signal obtained from a position encoder so as deflection estimate. CONSTITUTION:A tracking error detection section 7 detects a relative tracking error signal e1 between an information track 13 and a data transducer 2 and the relation of e2=r-ys is obtained, where ys is the absolute position of the data transducer 2 and (r) is the position of the information track (track deflection). A position encoder 3 detects the position of the actuator 1 and outputs a current position signal ya. The tracking error signal e1 and the current position signal ya are added by a track deflection (r) is considered to be a feedforward signal and the feedforward control is implemented based thereupon.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a track-following control device for a data transducer to an information recording track of a disk storage device, and more particularly, the present invention relates to a track following control device for a data transducer to an information recording track of a disk storage device. The present invention relates to a track following control device for a disk device, which has the function of moving to a track at high speed and controlling its position relative to an information recording track.

BACKGROUND OF THE INVENTION In recent years, the performance of information recording and reproducing devices has improved dramatically, and as a result, smaller and smaller positioning drive devices are being used to track recording or reproducing data transducers such as magnetic disk devices and optical disk devices to target information tracks. A highly accurate track following control device is also required. The demand for miniaturization comes from the desire to obtain a larger recording capacity with the same size, and the demand for higher precision comes from the desire to increase the recording capacity by increasing the track density.

First, the magnitude of track deviation of the information track that occurs during tracking will be explained. In optical disk drives, the amplitude of track runout due to factors such as a shift in the center of rotation when replacing a disk medium and runout of the rotating shaft of the spindle motor that rotates the disk can range from several tens of micrometers to more than 100 micrometers. Yes, the width of the track to follow (
(approximately 1.6 μm). Among magnetic disk devices, floppy disk drives (FDDs) suffer from a different kind of track runout, which is caused by the expansion or contraction of the base film of the disk medium due to the influence of heat and distortion, in addition to the same track runout as in optical disk drives. occurs. The amplitude of these track runouts is small compared to the case of optical disk devices, each on the order of tens to tens of micrometers at most, but when achieving high track density, that is, when reducing the track width, the relative It becomes so large that it cannot be ignored.

In order to minimize the tracking error due to such track wobbling, the following method has been used in conventional track following control devices for disk devices.

In the first example, the following method is used.

That is, the track runout is estimated by further differentiating the signal obtained by adding the tracking error signal and the signal obtained by integrating twice the input signal of the drive unit that freely moves the data transducer. An estimated signal corresponding to one rotation of the disk is stored in memory. This is read out during tracking mode and added to the input signal of the drive section.

This aims to improve the tracking performance of the data transducer against track runout, for example:
It is described in US Pat. No. 4,594,622. However, in estimating track runout, this method
The challenge is to suppress the deviation that occurs during integral calculations and the noise that occurs during differential calculations, and it is not easy to put it into practical use.

In the second example, the following method is used.

That is, the repetitive signal component included in the trunking error signal representing the deviation between the data transducer and the target information track is extracted using the Fourier analysis method, the Fourier coefficient for the repetitive frequency is determined, and the repetitive error is calculated based on this. Calculate the correction signal. This repetitive error correction signal is then added to the drive input signal of the data transducer.

This is intended to improve the tracking performance of the data transducer for the disc rotational frequency component included in track runout.
6.276. However, this method requires a lot of time and effort to perform Fourier analysis, and
There were drawbacks such as insufficient suppression of rotational asynchronous components.

Problems to be Solved by the Invention As mentioned above, the track following control device for disk drives using the conventional method has the problem of suppressing deviation and noise when estimating track runout, and it has been repeatedly reported that it is not easy to put it into practical use. The problem has been that it takes time and effort to calculate the error correction signal.

The purpose of the present invention is to provide a data transducer and an information transducer.
It is an object of the present invention to provide a track following control device which achieves higher tracking performance by reducing the tracking error between two tracks, and which can further suppress the track deviation of an information track that is noticeable in interchangeable media. The object of the present invention is to provide a follow-up control device.

Another object of the present invention is to provide a track following control device for a disk device that is excellent in terms of practical application, such that suppression of deviation and noise is not a problem when estimating track runout, and calculations do not require much time and effort. There is a particular thing.

Means for Solving the Problems In order to solve the above problems, a track following control device for a disk device according to the present invention records/reproduces information on an information track of an information recording disk having a plurality of information tracks on its surface. a data transducer capable of moving the data transducer; a driving means capable of freely moving the data transducer according to a target position command signal; and a drive means capable of freely moving the data transducer in accordance with a target position command signal, and detecting the amount of operational displacement of the data transducer to indicate its current position. position encoder means for outputting a current position signal;
tracking error detection means for detecting a positional error between the position of the data transducer and the information track and outputting a tracking error signal; and tracking error detection means for detecting a positional error between the position of the data transducer and the information track, and estimating track runout due to eccentricity or waviness of the information track, and based on this estimation. track runout estimating means for generating a feedforward signal based on the tracking error signal; and a discrete time control loop for controlling the drive unit based on the tracking error signal, and the M number time control loop is configured to generate a feedforward signal based on the tracking error signal. a compensation position calculation means for calculating a compensation position command signal based on the feedforward signal and the compensation position command signal; and an interpolation calculation means for performing an interpolation calculation based on the feedforward signal and the compensation position command signal to generate an interpolation signal to be applied to the drive means. The precepts include:

Further, the track runout estimating means includes a first addition means for adding a tracking error signal and a current position signal obtained from the position encoder means, and a track runout based on the output of the first addition means according to the rotation of the disk. A memory means constituted by a finite number of unit memory means for holding an estimated signal in advance, and a finite number of compensation means which receives as input a signal based on the output of each unit memory means and a signal based on the output of the first addition means. and a second addition means for adding signals based on the outputs of the respective compensation means, and is configured to output a signal based on the output of the second addition means as a feedforward signal.

Effects The present invention has the following effects due to the above-described configuration.

First, the eccentricity and waviness of the information track are estimated by the track runout estimating means, and feedforward control is performed based on the estimated track runout information, thereby making it possible to obtain stable and even higher tracking performance.

In addition, since track runout estimation is performed based on a signal that is the sum of the tracking error signal and the current position signal obtained from the position encoder, there is no problem with suppressing deviation or noise during estimation, and calculations are not time-consuming. .

Further, by configuring the track shake estimating means as described above, even higher tracking performance can be obtained since a feedforward signal with an improved signal phase is applied to the drive section.

Furthermore, the position encoder means allows the current position of the drive means to be recognized with high precision and high resolution, making it possible to make delicate positioning adjustments and at the same time increasing stiffness and suppressing vibration impact forces, making it possible to increase the density of information tracks. .

Furthermore, the interpolation calculation means performs interpolation calculation based on the feedforward signal and the compensation position calculation means to produce an interpolation signal, and by adding this to the target position command, even higher tracking performance can be obtained. can.

Embodiment Hereinafter, a track following control device for a disk drive according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a track following control device for a disk drive in one embodiment of the present invention.

In FIG. 1, reference numeral 12 denotes a drive unit, which has a function of making the data transducer 2 freely movable on the disk surface, and is configured as follows. 3 is an actuator that actually moves the data transducer 2, and 3 is a position encoder that constantly detects the position of the actuator 1 and outputs a current position signal ya, which is mechanically coupled to the movable part of the actuator 1. . 4 is a power supply circuit for driving the actuator 1 based on the output of the compensator 5, 15 is a sample holder that converts the discrete time signal ya output from the position encoder into a continuous quantity, and 6 is a target position command signal rs. and the output of the sample holder 15 e
This is a comparator that calculates 2.

The above-mentioned compensator 5 determines the amount of restriction '4TJ for the actuator based on this deviation e2. A servo loop from the output of the position encoder 3 to the actuator 1 via the comparator 6, the compensator 5, and the power supply circuit 4 constitutes a positioning control loop. The position encoder 3 is capable of constantly detecting the movement of the movable part, and its output current position signal linearly represents the amount of displacement with respect to a predetermined reference point within the movable range of the data transducer 2 over the entire movable range. It is configured as follows. Further, the compensator 5 is configured to be able to quickly follow the target position command signal rs with as few errors as possible.

Since this servo loop is basically an absolute positioning system, it alone cannot follow the information track that swings as the disk rotates.

Next, the magnitude of eccentricity or waviness of the selected information track 13 of the disk 14 directly below the data transducer 2, that is, the track runout amount, is r, and the data transducer 2
The absolute position of is expressed as ys.

7 is a tracking error detection unit that detects a relative position error e1 between the information track 13 and the data transducer 2; 8 is a tracking error detection unit that performs a predetermined control calculation based on the tracking error e1 and outputs a compensation position command signal rd; This is a compensation position calculation section. Further, reference numeral 9 denotes a track runout estimating unit that receives the tracking error signal e1 and the current position signal ya, estimates the magnitude of the track runout amount, and outputs a feedforward signal rc. The compensation position command signal rd and the feedforward signal rc are input to an interpolation calculation section 10, where predetermined interpolation calculation processing is performed.

Its output is the target position command signal rs.

The operating principle of the track following control device for a disk drive according to the present invention configured as described above will be explained.

The embodiment shown in FIG. 1 is based on a tracking servo system called a sector servo system or a sampling servo system. In this method, servo information necessary for tracking is embedded in the boundaries of sectors divided into fan shapes on the disk surface, and based on this information, a relative position signal (tracking error) of the data transducer with respect to the target information track is embedded. This is a method for positioning in a closed loop by detecting signals (signals) in a discrete time manner and feeding them back. As shown in FIG. 1, the tracking error signal e1 is minimized and the data transducer 2
It is mainly composed of a discrete time control loop for performing follow-up control to the information track 13 of . This discrete time control loop is a servo loop that runs from the data transducer 2 to the drive section 12 via the trunking error detection section 7, the compensation position calculation section 8, and the interpolation calculation section 10.

Data transducer 2 and selected information track 1
3 changes continuously over time, but in the sector servo method, the position of the information track can only be obtained intermittently, so the tracking error signal e1 is output from the tracking error detection section 7 as a discrete time signal. This trunking error signal e1 is subjected to a predetermined control calculation by the compensation position calculation section 8 to generate a compensation position command signal rd. The compensation position calculation unit 8 is composed of a discrete time processing system including a deviation compensation element and, in some cases, a stabilization compensation element.
Its main role is to suppress the amount of offset.

Next, the operation of the track runout estimating section 9 in the embodiment of the present invention shown in FIG. 1 will be explained.

The tracking error detection unit 7 can detect a relative tracking error signal e1 between the information track 13 and the data transducer 2, and the absolute position of the data transducer 2 is ys, and the position of the information track (track If r is the runout), then equation (1) holds true.

e2=r-ys ・・・・・・(
1) Next, the position encoder 3 detects the position of the actuator 1 and outputs the current position signal ya. Since the current position signal ya indirectly represents the absolute value fys of the data transducer 2, equation (2) holds true.

ystaya ......(2
) Therefore, formula (1) and formula (2) are combined to yield formula (3).

r 鵡e, +ya ・・・・・・(3
) This equation (3) shows that the information recording track deflection can be approximately estimated from the tracking error signal e1 and the current position signal ya. The track shake estimation section 9 includes an adder that adds the tracking error signal e and the current position signal ya, and estimates the track shake based on equation (3). The estimated value rc of the track runout r of the information track obtained in this way is considered to be a feedforward signal. Feedforward control is a control method that applies a signal from outside the servo loop into the servo loop. This is a method that can improve control performance without impairing the stability of the servo loop itself even if a signal is applied from outside the servo loop. In the track following control device for a disk drive according to the present invention, the estimated value rc of the track runout r can be considered as a signal outside the servo loop, that is, the discrete time control loop. Inputting this to the interpolation calculation unit 10 indicates that it is being applied to the servo loop. However, for the reasons mentioned above, the stability of the loop is not compromised in this case.

The tracking performance is improved by applying the feedforward signal rc to the servo loop for the following reason. Since the positioning control loop constituting the movable part 12 is a closed loop servo system that follows the target position command signal rs, equation (4) approximately holds true.

rs絽ya -・・・・・・(4
) On the other hand, from equation (2), equation (4) is transformed as shown below.

ysnursφ・・
(5) Equation (5) means that the position ffys of the data transducer 2 approximately follows the target position command signal rs. Therefore, if a signal based on the track runout r is added to the target position command signal rs, the data transducer 2 should follow it. Especially in this case, r
szr, equation (6) holds true.

ysrirs7r・・・・・・(6)
Equation (6) shows that data transducer 2 is information track 1.
This means that the track runout r of No. 3 is followed almost exactly. At this time, the tracking error signal e1 has an extremely small value.

However, in reality, even if the target position command signal rs is input, the drive unit 12 does not respond immediately, but there is a certain time delay. In other words, the transmission characteristic of the drive unit 12 has a certain phase lag in the same wave number region of the fundamental wave and harmonics of the disk rotation frequency that are mainly included in the track runout r of the information track. Furthermore, a phase delay associated with the sample-and-hold processing of the discrete-time control loop is added to this.

Therefore, the data transducer 2 may not follow the information track beyond a certain level. Therefore, in the track following control device for a disk drive according to the present invention, the track runout estimating section 9 is configured as shown below.

FIG. 2 is a block diagram of a track runout estimator in one embodiment of the present invention. In FIG. 2, the track runout estimating section includes a memory section 21, a digital compensator, and 2.
．． ..., Kn-), Kn, and an adder 22. However, Z・1 is a unit memory that holds the estimated track runout signal ra only for a time T that is the same as the sampling period of the discrete-time control loop, and this unit memory is used for the number of sectors of the disk (n is The memory unit 21 is connected in series (a positive integer) to hold the track runout estimation signal ra corresponding to one rotation of the disk.
It consists of The output of the highest stage of the memory section 21 is connected to the input side, and the internally held track runout estimation signal ra is cyclically moved in each unit memory in synchronization with the rotation of the disk. More specifically, the memory unit 21 includes:
It may also be configured with a shift register or the like.

Digital compensator J + K2, -, Kyl-1,
K n is each composed of an adder, a multiplier, etc., and amplifies or digitally filters the output signal of each unit memory of the memory section 21 . 22 is an adder that sums up the outputs of each digital compensator and outputs a feedforward signal rc.

Next, the operating principle of the track runout estimation section shown in FIG. 2 will be explained. In Fig. 2, the track runout estimation signal ra is stored in advance in n unit memories for an amount corresponding to one rotation of the disk, and these held signals are transferred to each unit in synchronization with the rotation of the disk during tracking operation. By extracting the signals from each memory, inputting them to each digital compensator, and summing them in the adder 22, a track runout estimation signal rc having a phase similar to that of the original track runout r or slightly ahead of it is obtained. obtain. This is input to the interpolation calculation unit 10 together with the output signal rd of the compensation position calculation unit 8 shown in FIG. It becomes possible to eliminate follow-up delay. Note that the track runout estimating section may be configured using hardware as described above, or may be configured using a microprocessor or the like so that equivalent processing is executed by software.

FIG. 3 shows the track runout estimation signal ra in the track runout estimator shown in FIG. 2, and the digital compensator Ki(i
1-n) and the output signal of the adder 22. FIG. Here, in this embodiment, the digital compensator Ki is constituted by a multiplier that multiplies the signal by 0.1. Further, i means the i-th unit memory counted from the beginning of the unit memory shown in FIG. 2, and i=n·3/4. Also,
For digital compensators other than Ki salt, K, 2.・
...Kn-1 is removed, and Kn is made into an amplifier with a gain of 1.

Now, it is assumed that the memory unit 21 shown in FIG. 2 stores in advance a track runout estimation signal for one rotation of the disk. The signal is a periodic signal containing a frequency component proportional to the rotational frequency of the disk. Therefore, the output signal of the i-th unit memory is 360' · (
The phase is advanced by 1-3/4) = 90°. In Fig. 3, (a) is a track runout estimation signal ra, (b) is a signal obtained by multiplying the output signal of the i-th unit memory by a coefficient of 0.1 in a multiplier, and (C) is a signal obtained by multiplying these signals by an adder. This is the output signal rc added in step 22. Here, let us consider the case where the rotational angular frequency of the disk is ω, and the track runout includes only the fundamental wave component. The signal waveforms shown in FIG. 3 can be approximately described by the following equations.

(a): A-s in (ωt) (b): B-cos(ωt) (c): C-s in (ωt+φ) There is a relationship between these equations as shown in equation (7).

C・5in(ωt+φ)=A-sin(ωt)+B-cos(ω1)・・・・・・
(7) If we rearrange this equation and compare the coefficients, we get equations (8), 9, and (9).
get.

A=C-cos(φ)...(8)B=C-si
n(φ) (9) Furthermore, formula (10) is obtained from these.

tan (φ) = B /A ・−・−
・・O■ Now, B=0.1・A, so from equation (10), φ=5.7°C=1. (105·A. That is, the output signal rc of the adder 22 has almost the same amplitude as the signal ra, and is 5.7° ahead of the signal ra in phase.

In Fig. 3, the signal in (b) is 9 compared to the signal in (a).
Although the case where the phase is advanced by 0° is shown, this is not necessarily the case. Furthermore, in Figure 3, each waveform is drawn as if it were continuous, assuming the case where the value of n is very large, but in reality, when the value of n is small, it becomes a step-like waveform. become.

FIG. 4 is a block diagram showing a track runout estimation method in a track runout estimator according to an embodiment of the present invention. Fourth
In the figure, an adder 41 outputs a track runout estimation signal ra based on equation (11).

r a = e, + y a
...1ll) 42 is a multiplier n that multiplies this track runout estimation signal ra by α (α≦1, α is a real number), 43
44 is a multiplier that multiplies the output signal rb of the last stage of the memory section 21 by (1-.alpha.), and 44 is an adder that adds the output of the multiplier 42 and the output of the multiplication 'A43.

Next, the operating principle of the track runout estimation method shown in FIG. 4 will be explained. In FIG. 4, the value of α is set to 1 during the first rotation of the disk, and the initial value of the track runout estimation signal is set in the memory section 21 in synchronization with the rotation of the disk. After the second rotation of the disk, the value of α is set to, for example, 0.5. At this time, the track runout estimation signal ra is transmitted to the multiplier 42.
The track runout estimation signal rb output from the memory section 21 is multiplied by 0.5 by the multiplier 43. After adding the respective outputs in the adder 44, the memory unit 2
Hold at 1. Thereafter, by repeating this operation as the disk rotates, track runout estimation signals can be accumulated one by one. However, since the coefficient of the multiplier 43 is set to (1-α) with respect to the coefficient α of the multiplier 42, the amplitude of the signal stored in the memory section 21 is always standardized to a constant value.

The feature of this track runout estimation method is that the track runout estimation signal ra stored in the memory unit 21 at a certain point in time is multiplied by 0.25 times in the second rotation, 0.125 times in the third rotation, etc. As a result, its proportion to the whole decreases. Therefore, the closer the αΦ value is to zero, the more the memory unit 21
The probability that past estimated signals remain remains increases. The purpose of this method is to smooth out amplitude fluctuations in the track runout estimation signal and random noise components contained in the signal by repeating the above operations. Note that the track runout estimating section may be configured using hardware as described above, or may be configured using a microprocessor or the like so that equivalent processing is executed by software.

The method of estimating track runout will be explained in more detail using some examples.

The first method is to follow a certain track with a data transducer. That is, with the discrete time control loop 11 operating in FIG. 1, track runout is estimated based on the method shown in FIG. 4.

The second case is the case in which the 1li11 failure time control loop 11 in FIG. 1 is not operated and the absolute position of the data transducer 2 is fixed by giving a constant command value to the drive section 12. In this case, the trunking error detection section 7 outputs a signal corresponding to track shake, and the output of the position encoder 3 is a certain DC value.

Next, preferred locations on the disk surface for estimating track runout will be explained.

The first is 5. In accordance with the above example, the data transducer follows an unspecified track or is fixed near the track.

The second case is a case where track runout is estimated between track seeks.

That is, the data transducer follows an unspecified track or performs a time estimation process with the data transducer fixed near the track, and then moves to another track and performs the same process repeatedly.

Before or after the above processing, other types of processing such as writing data to the disk or reading data from the disk may occur.

Next, the timing for estimating track runout will be explained.

For example, in the case of a floppy disk drive, the spindle motor is stopped when there is no access from the host computer for a certain period of time, so track runout estimation must be performed between track accesses. However, track runout estimation requires at least disk-rotation time, and in order to perform good estimation with less influence of noise, the same track needs to be rotated two to three more times for smoothing. It takes time.

So I put the disk into the floppy disk drive and
It is desirable to estimate track runout immediately after the spindle motor starts rotating or before stopping the spindle motor. Also, if the spindle stops for a long time and the track runout changes during that time,
Track runout may be estimated by measuring the time from when the spindle motor stops rotating until it starts rotating again, and when this time exceeds a certain period of time.

Next, an explanation will be given of the operation of the track shake estimating section during track seek in one embodiment of the present invention.

FIG. 5 is a block diagram of the track following control device of the disk device in one embodiment of the present invention during track seeking.

In FIG. 5, during track seeking, the drive section 12 is the main component, and the adder 51 receives the track seek command rk and the output rC of the track runout estimating section 9.
Furthermore, the output of the adder 51 is input to the drive section 12. Among the structural requirements of the track runout estimation section 9, the memory section 21 (
(not shown) is configured cyclically as in FIG. 2, and outputs the output of its last stage directly without going through a digital compensator.

The driving section 12 is driven according to the output signal of the adder 51. Considering the case where the output of the track runout estimator is not added to the adder 51, when the track seek command rk is input as a position command, the data transducer moves from one track to another according to the command. Can be moved freely. However, since track runout occurs as the disk rotates even during track seek, the track to which the data transducer moves immediately after the seek is shifted to a position corresponding to the track runout. In FIG. 5, the output rc of the track shake estimating section 9 is input to the adder 51 together with the track seek command rk in order to correct the deviation of the target track immediately after this seek.

Next, the configuration and operation of the interpolation calculation unit IO in the embodiment of the present invention shown in FIG. 1 will be explained.

In one embodiment of the present invention shown in FIG. 1, a sector servo system is used. This sector servo method has the following design trade-off regarding the number of sectors.

When the number of sectors is increased, the sampling frequency of the discrete time control system becomes higher, and the band of the control system can be wider. On the other hand, the servo area occupies a larger area in the total recording area of the disk. Therefore, the storage capacity becomes smaller when the disk is formatted. For these reasons, it is necessary to reduce the number of sectors in order to improve the utilization efficiency of the disk recording area. If the number of sectors is made small, the sampling frequency of the control system becomes low, making it impossible to widen the control band. Therefore, it becomes difficult to obtain high track following performance. Normally, the control band is set to several times to ten times the frequency of the fundamental wave of track runout, so the suppression gain of the separation time compensator for suppressing track runout can be made sufficiently large. Is it restricted for this reason?
If the i4tF region cannot be widened, it is difficult to increase the suppression gain. Furthermore, when the number of sectors is small, the sampling interval becomes long, and only a constant total finger signal is input to the actuator that drives the data transducer during that time. During this time, the track is continuously fluctuating due to track runout, so if the track runout is large, off-tracking may occur even if the suppression gain is set high. As a method of obtaining high track following performance when the number of sectors is small, there is a method of interpolating the target position command signal input to the drive unit 12 in a discrete time manner from temporally preceding and succeeding signals. This method provides the same effect as increasing the number of sectors by interpolating the target position command signal.

FIG. 6 is a block diagram of an interpolation calculation section in one embodiment of the present invention. In FIG. 6, 61 is an adder that adds the compensation position command signal rd and the feedforward signal rc, 62 is an interpolator that receives the output W of the adder 61 and performs an interpolation operation, and 63 is the output of the interpolator 62. It is a sample holder that converts a discrete time signal V into a continuous quantity. however,
In the interpolator, the sampling period T of the discrete-time control loop
is interpolated more finely, so the hold time Th of the sample holder 63 has a relationship as shown in equation (+21).

Th<T...
(13) Note that the interpolation calculation unit is not limited to the configuration shown in FIG. 6, but may be configured, for example, to add the feedforward signal rc to a signal obtained by interpolating the compensation position command signal rd, Alternatively, the opposite configuration may be considered.

In general, interpolation is m points X1°X2 of a function f (x)
．． ..., when the value of f(X) at Xm is known, the value of r(x) at points X other than these points is expressed as the known f
It is determined based on the value of x. Strictly speaking, when the value of X falls between the minimum and maximum values of the above m values, it is called interpolation, and when it falls outside of that range, it is called extrapolation. As the interpolation method, there are known methods such as Lagrange's interpolation method. In the following, the specific functions and operations of the interpolator 62 will be explained by taking as an example the simplest case where the number m of points X is 2, that is, interpolation or extrapolation is performed using two pieces of data. . Further, in the following, for the sake of simplicity, the difference between the above-mentioned extrapolation and interpolation will not be clearly distinguished, and the term "interpolation" will be used instead.

FIG. 7 shows the track runout r, the output W of the adder 61, and the target position command signal rs when no interpolation calculation is performed in the track following control device for the disk drive of the present invention shown in FIGS. 1 and 6. , the absolute position ys of the data transducer, and the actual tracking error es. Here, the actual tracking error es means the actual trunking error between the data transducer and the target information track, and is given by the following equation.

es=rys --03) Figure (b) shows a discrete time signal, where the sampling interval is T and the horizontal axis is kT (k is a positive integer).

In FIG. 7, the waveform of the target position command signal rs obtained by sampling and holding the output W of the adder 61 has a large step-like shape. The response of the drive unit 12 to the signal rs, ie, the waveform of the data transducer position ys, similarly has a large step-like shape. As a result, the actual tracking error es becomes an oscillatory waveform with a large amplitude.

FIG. 8 is a block diagram showing a specific configuration of an interpolator for realizing the first interpolation method described below. In FIG.
/m sampler for more detailed sampling,
82 is a disk filter Hz, both of which have a period T
/ m interpolation pulses. The digital filter 82 is composed of an integral filter that smoothes the input signal.

83 is a multiplier that multiplies the signal by a (a is a positive real number, a<1), and 84 is a multiplier that multiplies the signal by (1-a). Also,
Zl is a register that holds data during the sample period T/m. The interpolator may be configured using hardware as described above, or may be configured using a microprocessor or the like so that equivalent processing is executed by software.

FIG. 9 is a signal waveform diagram of each part when interpolation calculation is performed using the first interpolation method (m=2)
. In FIG. 90)), the sample signal indicated by a black circle is the input w (KT) before interpolation.

The sample amount indicated by the white circle is the interpolated signal.

This signal w(K-T/m) is input to a digital filter 82 that operates based on an interpolation pulse with a period of T/m. The signal V smoothed by the digital filter is held by the sample holder 63 in FIG. 6 to obtain the signal rs. Compared with the signal rs in FIG. 7(C), the height of the stairs is smaller.

As a result, the amplitude of the actual tracking error es is small and the waveform is smooth. Furthermore, by increasing the number of interpolation points m, the response of es can be made smoother and the amplitude smaller. As described above, track followability is improved by sampling the output W of the discrete time compensator more finely and then further performing digital integral filtering. This method is called -S oversampling. When this method is compared with simply interpolating the input signal, this method is superior in that servo system noise can be removed using a digital filter.

FIG. 10 is a block diagram showing a specific configuration of an interpolator for implementing the second interpolation method described below. In the figure, 1 (11 is a register for holding the input signal W for a period T, and operates in synchronization with the sector detection pulse. 102 is a register that holds the input signal W for a period T. 102 is a register that holds the input signal W for a period T.
(K-1)T); 103 is a multiplier that multiplies the output of adder 102 by 1/m (m=2);
4) is an adder that adds the output of the multiplier 103 and the current input w (KT), and operates based on interpolation pulses.

The interpolator may be configured using hardware as described above, or may be configured using a microprocessor or the like so that equivalent processing is executed by software.

FIG. 11 is a signal waveform diagram of each part when interpolation calculation is performed using the second interpolation method. In the same figure (b),
The sample signal indicated by the black circle is the input before interpolation w (KT)
It is. The interpolation process in this case is based on the current sample signal w
(KT) and the previous sample signal w((K−
1) Take the signal value (indicated by white circles) obtained by dividing the extension line of the line (indicated by a broken line) connecting the apex of T) into m equal parts in the next sample period.

Next, the interpolated output V as shown in FIG. 9(C) is
It is held in a sample holder 63 in FIG. 6 to obtain a signal rs. Here, the difference from the case without interpolation processing is shown by diagonal lines. That is, the waveform of the signal rs has smaller steps than that shown in FIG. 7(C).

Therefore, the response ys of the drive section 6 is also smoother than in FIG. 7(d). As a result, the amplitude of the actual tracking error es is small and the waveform becomes smooth. Furthermore, by increasing the number of interpolation points m, the response of es can be made smoother and the amplitude smaller. As described above, by interpolating the signal W, track followability is improved.

Next, another method of configuring the interpolator will be described.

That is, in the first and second interpolation methods described above, interpolation calculations are performed based on the current or several sample time previous discrete time output W, but in the following, the discrete time signal W is preliminarily or repeatedly periodically calculated. A method of holding the data and performing interpolation calculations based on this will be explained.

FIG. 12 is a block diagram showing a specific configuration of an interpolator for implementing the third interpolation method described below. In the figure, reference numeral 121 denotes a memory section that holds in advance the signal W for one revolution of the disk, and operates cyclically in synchronization with the sector detection pulse. Reference numeral 122 denotes an adder that calculates the difference between x(KT) and the output x ((k+1)T) immediately after it in time. 123 multiplies the output of the adder 122 by 1/m (m=2
), the multiplier 124 is an adder that adds the output of the multiplier 123 and the current input w(KT), and operates based on the interpolation pulse. The interpolator may be configured using hardware as described above, or may be configured using a microprocessor or the like so that equivalent processing is executed by software.

FIG. 13 is a signal waveform diagram of each part of the interpolator when interpolation calculation is performed using the interpolation method shown in FIG. Figure 13 (
Figure a) shows a # several-hour signal that has been stored in advance in the memory unit 121 in a learning or repeated periodic manner. In Figure (b), the sample signal indicated by a black circle is input to the interpolator in real time. A discrete time signal w (KT) is shown. This sample signal is interpolated as follows based on the sample signal held in the memory section 121. That is, the slope (indicated by a broken line) between the current sample time and the next sample time is determined from the sample signal held in the memory unit 121, and the next sample period is interpolated (indicated by a white circle) based on this slope. )do. By performing this procedure for each sample input, interpolation for one rotation of the disk can be performed. The signal V that has been interpolated using the above method is transferred to the sample holder 63 in FIG.
By holding the signal rs and inputting it to the drive unit 12, the first signal rs is held. Similarly to the second interpolation method, track followability can be improved.

The interpolation method shown in Figure 13 is the extrapolation method described above.
corresponds to Comparing this method with interpolation, −
Extrapolation is better when used in a servo system in that the phase of the signal advances when interpolated to i. In addition, the first
2), the memory section 121 is the same as the memory section 2 in FIG.
Different from 1. However, if the interpolation calculation section is not configured as shown in FIG. 6, but is configured to perform interpolation processing on the feedforward signal rc and then add it to the compensation position command signal rd, then the memory section shown in FIG. 2nd as 121
The memory section 21 shown in the figure can be used.

Next, the specific configuration of the compensation position calculation section will be described.

FIG. 14 is a block diagram of the compensation position calculation section in one embodiment of the present invention. (shown in the same figure), Zl is a unit memory that holds the signal for several hours apart from the sampling time T, and Ha
(z) is a low-frequency compensation digital filter, Hb (Z) is a recursive digital filter, and LPF is a digital low-pass filter inserted into the recursive digital filter for stabilization. Also, Ll, L2. L8. L,
is a multiplier that multiplies the input signal by a certain coefficient.

FIG. 15 is an example of the frequency characteristic of the transfer function from the tracking error e1 to the compensation position command signal rd when using the compensation position calculation section as shown in FIG. FIG. 5(b) is a phase characteristic diagram. 1st
In FIG. 5, fO is the rotation frequency of the disk. It can be seen that a predetermined high gain is obtained even for harmonic components that are integral multiples of the harmonic components. Note that the configuration of the compensation position calculation section is not limited to the above configuration, and may include a low-frequency compensator that increases the gain of low-frequency components included in the trunking error signal at -C. It is also possible.

As described in detail, the track following control device for a disk drive of the present invention records/records information on the information track of an information recording disk having a plurality of information tracks on its surface.
a data transducer capable of reproducing; a driving means capable of freely moving the data transducer according to a target position command signal; position encoder means for outputting a current position signal indicating the position;
trunking error detection means for detecting a positional error between the position of the data transducer and the information track and outputting a tracking error signal; and a discrete time control loop that controls the drive section based on the tracking error signal, the discrete time control loop is configured to detect the track knocking error. Compensation position calculation means for calculating a compensation position command signal based on the signal; and interpolation for performing an interpolation calculation based on the feedforward signal and the compensation position command signal to obtain an interpolation signal applied to the drive means. The tracking error estimating means includes a first adding means for adding the tracking error signal and the current position signal obtained from the position encoder means, and the first adding means for adding the tracking error signal and the current position signal obtained from the position encoder means; a memory means constituted by a finite number of unit memory means for pre-holding a track runout estimation signal based on the output of the adding means; a signal based on the output of each unit memory means and a signal based on the output of the first adding means; and a second addition means that adds signals based on the output of each compensation means, and a signal based on the output of the second addition means as a feedforward signal. Since it is configured to output, it has the following excellent effects.

First, the eccentricity and waviness of the information track are estimated by the track runout estimating means, and feedforward control is performed based on the estimated track runout information, thereby making it possible to obtain stable and even higher tracking performance.

Furthermore, since the track runout estimation is performed based on a signal obtained by adding the tracking error signal and the current position signal obtained from the position encoder, suppression of deviation and noise is not a problem during estimation, and calculations do not require much effort.

Further, by configuring the track shake estimating means as described above, a feedforward signal with an improved signal phase is applied to the drive section, so that even higher tracking performance can be obtained.

In addition, the position encoder means can recognize the current position of the drive means with high precision (and high resolution), making it possible to make delicate positional adjustments.At the same time, it is possible to increase stiffness and suppress vibration and impact forces, making it possible to increase the density of information tracks. .

Furthermore, the interpolation calculation means performs interpolation calculation based on the feedforward signal and the compensation position calculation means to produce an interpolation signal, and by adding this to the target position command, even higher tracking performance can be obtained. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a track following control device of a disk drive in an embodiment of the present invention, FIG. 2 is a block diagram of a track runout estimating section in an embodiment of the present invention, and FIG. 3 is a block diagram of a track deflection estimation section in an embodiment of the present invention. 4 is a block diagram showing a track runout estimation method in the track runout estimating section in an embodiment of the present invention. FIG. 5 is a diagram of the track following control device of a disk device in an embodiment of the present invention. FIG. 6 is a block diagram of an interpolation calculation unit in an embodiment of the present invention, and FIG. 7 is a block diagram of the track seeking control device for a disk drive of the present invention, when the interpolation calculation is not performed. The waveform diagram of Fig. 8 is the first waveform diagram.
FIG. 9 is a block diagram showing the specific configuration of an interpolator to implement the first interpolation method, FIG. 9 is a signal waveform diagram of each part when interpolation calculation is performed using the first interpolation method, and FIG. Figure 11 is a block diagram showing the specific configuration of an interpolator for implementing the second interpolation method. Figure 11 is a signal waveform diagram of each part when performing interpolation calculations using the second interpolation method. A block diagram showing a specific configuration of an interpolator for realizing the third interpolation method, FIG. 13 is a signal waveform diagram of each part of the interpolator when interpolation calculation is performed using the third interpolation method, FIG. 14 is a block diagram of the compensation position calculation unit in an embodiment of the present invention, and FIG. 15 is a frequency characteristic diagram of an example of the transfer function from the tracking error el to the compensation position command signal "d." 1... ...Actuator, 2...Data transducer, 3...Position encoder, 4
...Power supply circuit, 5...Compensator, 6
... Comparator, 7 ... Tiger 1. King error detection means, 8... Compensation position calculation section, 9...
. . . Track shake estimating section, 10 . . . Interpolation calculation unit, 11 .・Information track, 14...Disc, 15...
・Sample holder, 21... Memory section, 22.
...Adder.

Claims (16)

[Claims] (1) A track following control device for a disk device including a data transducer capable of recording/reproducing information on an information track of an information recording disk having a plurality of information tracks on its surface, the data transducer drive means capable of freely moving the data transducer in accordance with a target position command signal; a position encoder means for detecting the amount of operational displacement of the data transducer and outputting a current position signal indicating the current position; tracking error detection means for detecting a positional error with the information track and outputting a tracking error signal; and a track for estimating track runout due to eccentricity or waviness of the information track and generating a feedforward signal based on this estimation. and a discrete time control loop for controlling the drive means based on the tracking error signal, the discrete time control loop for calculating a compensated position command signal based on the tracking error signal. position calculation means;
Track following control for a disk device, comprising: interpolation calculation means for performing interpolation calculation based on the feedforward signal and the compensation position command signal to generate an interpolation signal to be applied to the drive means. Device. (2) The track shake estimating means includes a first adding means for adding a tracking error signal and a current position signal obtained from the position encoder means, and a tracking based on the output of the first adding means according to the rotation of the disk. A memory means constituted by a finite number of unit memory means for pre-holding a shake estimation signal, and a finite number of compensation units receiving as input a signal based on the output of each unit memory means and a signal based on the output of the first addition means. and a second addition means for adding signals based on the outputs of the respective compensation means,
2. The track following control device for a disk device according to claim 1, wherein the device is configured to output a signal based on the output of the adding means as a feedforward signal. (3) The track runout estimating means smoothes and generates the track runout estimation signal over multiple past revolutions of the disk based on the signal based on the output of the first addition means and the signal already stored in the memory means. Claims characterized (
2) Track following control device for a disk device as described above. (4) The track runout estimation means includes a multiplication means for multiplying a signal based on the output of the memory means by a constant, and an addition means for adding a signal based on the output of the first addition means and a signal based on the output of the multiplication means. Claim (3) characterized in that it is configured to include an adding means for adding a signal based on the output of the adding means and a signal based on the output of the adding means, and inputs a signal based on the output of the adding means to the memory means. A track following control device for the disk device described above. (5) Track runout estimating means for a disk device according to claim (3), wherein the track runout estimation means smoothes and generates a track runout estimation signal for an unspecified track on the disk over a plurality of past rotations of the disk. Follow-up control device. (6) Track following of a disk device according to claim (3), wherein the track runout estimation means smoothes and generates track runout estimation signals for a plurality of tracks on the disk over a plurality of past rotations of the disk. Control device. (7) The track runout estimating means cyclically moves the track runout estimation signal stored in advance in a finite number of unit memory means among the unit memory means according to the rotation of the disk during track seek, and the memory means 3. The track following control device for a disk drive according to claim 2, wherein the output signal of the output signal is inputted to the drive means. (8) The track following control device for a disk drive according to claim (1), wherein the track runout estimating means performs the track runout estimation at least either immediately after the rotation of the disk starts or immediately before the rotation of the disk is stopped. (9) According to claim (1), the track runout estimating means performs track runout estimation when the time from when the disk stops rotating until when it starts rotating again exceeds a certain period of time. track following control device for disk drives. (10) The interpolation calculation means includes sampling means for interpolating at least either the compensation position command signal or the feedforward signal in a discrete time series finer than the discrete time series. 1)
A track following control device for the disk device described above. (11) The interpolation calculation means includes a first memory means for storing past compensated position command signals, a second memory means for storing past feedforward signals, and the first memory means or the second memory means for storing past feedforward signals. 2. The track following control device for a disk drive according to claim 1, further comprising arithmetic means having at least an addition function for performing a predictive calculation based on at least one output signal of the memory means. (12) The interpolation calculation means includes a memory means that stores at least one of the compensation position command signal or the feedforward signal learningly or repeatedly, and performs an interpolation calculation in the calculation means based on the output signal of the memory means. 2. The track following control device for a disk device according to claim 1, further comprising arithmetic means having at least an addition function. (13) The disk device according to claim (1), wherein the compensation position calculation means includes low-frequency compensation means for increasing the gain of low-frequency components included in the tracking error signal. track following control device. (14) The compensation position calculation means is configured to include a cyclic digital filter for obtaining a predetermined high gain for the fundamental frequency component and harmonic component of the rotational frequency of the disk included in the tracking error signal. A track following control device for a disk device according to claim 1, characterized in that: (15) The position encoder means is configured to output a current position signal that linearly represents the amount of displacement of the data transducer relative to a predetermined reference point within the movable range over the entire movable range. (1
) track following control device for a disk device. (16) The drive means includes an actuator means that can freely move the data transducer, and a comparison means that outputs a deviation amount according to the deviation between the target position command signal and the current position signal output by the position encoder means; 2. The track following control device for a disk drive according to claim 1, further comprising power supply means for supplying current to said actuator means based on the output signal of said comparison means.