CN1005298B - Method and apparatus for detecting error signal of disk drive using magnetic test disk - Google Patents

Abstract

A method and procedure for detecting error signals of a disc drive using a test disc having a plurality of test tracks distributed over a recording area and having a number of special test signals for direction, adjustment and azimuth signals To make a difference, if a stepping motor is used in the positioning device, according to the normal position of the recording track of the disk, the interval of the test track depends on the type of the stepping motor. Through special control, except for the track error, eccentricity error and azimuth error In addition, the hysteresis error can also be measured. The advantage of using is that the method and steps are applicable to various types of disk drive devices, especially FlexyDisk drive devices.

Description

Method and apparatus for detecting error signal of disk drive using magnetic test disk

The present invention relates to a method and steps for detecting an error signal of a disk drive equipped with a head positioning system, and a magnetic test disk for implementing the method. The method uses a magnetic test disc, test signals on the disc are recorded on a plurality of test tracks distributed in a recording area thereof, the test signals in the test tracks are read out, and deviation of the read-out signals from a predetermined position and amplitude is determined, thereby obtaining an average value.

The positioning of the head over the disk for each movement will determine the quality of the read-write function of the disk drive apparatus. In particular in the case of an activity recording device such as Flexy Disks (registered trade name registered by the company of the soda stock of the bardenamine, hildebrand) and its associated reader/writer, it is important to enable the device, in particular the head and/or the head regulator, to be moved relative to the recording device. This operation is called track conditioning. To achieve this, a conditioning disk, or CE disk, with a control signal is used. For example, according to german published application No. DOS2,554,083, the control signals are formed by variations in magnetic flux that alternately extend on each side of the center line of the recording track and are recorded on a single test track in the center region of the disk. These control signals are adjustment signals that appear around the test track and are divided into groups by directional signals of different amplitudes.

The signals can be well distinguished and displayed on an oscilloscope in a simple manner using different adjustment signals and direction signals so that a complete image of the test track can be formed, thereby making it easy to correct the head position and adjust the head. German published application DOS3,117,911 discloses the use of test elements having pairs of tracks that are partially or completely adjacent to each other with a positive and negative track offset relative to the normal test track position. The scanning head is aligned to read out the test track with the offset, and as soon as a read error of a predetermined value occurs, an average of the read signals of the pair of test tracks is obtained and used to calibrate the scanning head. The above publication also discloses that in case of an equivalent error generated by two non-adjacent test tracks, it is possible to average the read signal of the first positive test track with the read signal of the second negative test track and to use this average value to generate a signal for adjusting the head. The above publication further describes that for a maximum value, the deviations of the test signal readout can still be processed and the absolute value of the specific positive track deviation can be recorded with the absolute value of the specific negative track deviation, with which the mean value of the constituent quality parameters can be determined.

In summary, the two error signals are averaged, and the quality of head positioning is measured as this average. With the pair of test tracks described above, twice its read-out time is required compared to a single track scan period. Moreover, the maximum number of allowable test tracks is only half the theoretical number of test tracks. Using the same number of indistinguishable test signals on one track, information about the angular position, i.e. about the eccentricity, can only be derived using a complex procedure. If the track is kept free for the control test program, the off-signal disappears in this track area just after.

It is an object of the invention to provide a method for improved, more comprehensive detection and evaluation of error signals.

We have found that this object is achieved according to the invention if the following conditions are met.

The test signal is composed of a regulating signal and a direction signal. The adjustment signals are alternately recorded on both sides of the center line of the recording track and have the same amplitude, and the direction signals divide the adjustment signals into a plurality of groups, and the direction signals have different amplitudes from the adjustment signals.

-The actual position and the actual amplitude of the adjustment signal are determined among each set of adjustment signals, thereby deriving an average value of a set.

The group average value for each individual test track is used to calculate the average value for one track and store the latter.

The track averages of the plurality of test tracks are used to calculate the total average and stored.

The error signal of all possible test tracks can be detected to the maximum extent according to the required accuracy as a function of a particular parameter or in relation to a particular error effect in the normal case, if necessary evaluated, for example quality check, if appropriate for head adjustment during the manufacture of the device, for calibration of the head during the read operation, if necessary for theoretical correction of the read signal during the read operation of the device.

The average and the total average of the stored tracks may be used at least effectively to make corrections to the head positioning system.

In further testing using a drive equipped with a stepper motor positioning system, the position and number of test tracks on the test disc are selected and scanned so that they do not correspond to the number of motor phases of the stepper motor. It is particularly easy to detect the error signals of the steps of the stepping motor in this way and suppression of these signals can be avoided.

Thus, in a disk drive having a three-phase stepping motor positioning system, the test signals of every third recording track can be easily read out and evaluated, whereas in a four-phase stepping motor positioning system, the signals of every second recording track can be read out and evaluated.

By this method, the combination of test signals of the second, fifth, seventh, etc. recording tracks on the magnetic test disc can also be scanned and evaluated appropriately.

In fact, it is also convenient to continuously read out and process the test signal if starting from the reference test track. For example, from the first direction, i.e. the direction in which the number of tracks is increased or decreased, the continuous process is performed. After reversing the read direction, the tracks are continuously read and processed in a second direction. The averages in both directions are accumulated to obtain a total average.

Thus, the hysteresis effect of head positioning can be tested by scanning both directions of a predetermined track. Thus, hysteresis effects are included in the overall average.

The next step in the method is to subtract the stored total average value from the track average value for the reference test track, the remaining average value being used to correct the head position for the reference test track.

Thus, if the reference tracks are properly arranged, the best error compensation is obtained within the available recording area.

As described above, the magnetic test disk used in the present method has a test signal consisting of an adjustment signal and a direction signal. The adjustment signals are alternately recorded on both sides of the center line of the recording track and have the same amplitude. The direction signals divide the adjustment signals into groups, the amplitude of the direction signals being different from the adjustment signals. According to the present invention, a plurality of test tracks are provided on a test disc, and are recorded in a recording area on the test disc in an evenly distributed manner every second or third track.

The CE disk thus provided is simple to manufacture and has a wide range of uses. For example, if there are as many test tracks as possible on the test disk equipped with test signals, any desired series of recording tracks can of course be manipulated, for example, the error signal can be detected every third or every fourth recording track, depending on the stepper motor used. Therefore, the test disc is very widely used in detecting various types of devices.

The test disc of the present invention may alternately record the test tracks at least in a part of the recording area, every second recording track, and every second recording track. This provides a combined test tray with three or four phase stepper motors.

In practicing the method described above with the new test disc having multiple tracks, recording is performed every second or every third recording track, or every second and then every second recording track. In an apparatus in the recording area of a disk having uniformly distributed tracks, a circuit is provided which includes a control stage (controlling a head positioning system in a three-track, four-track or two-track scanning cycle), an evaluation stage (connected to a scanning head), an average calculation stage, an error signal storage stage, a total average display and writing stage.

Such a circuit can be economically assembled with commercial electronic components.

In another embodiment the control stage controls the positioning system such that the scanning head system reads the test track in a first direction increasing or decreasing the number of tracks starting from a predetermined initial test track, in particular from a reference test track, and after turning the read direction to a second, opposite direction, the tracks of the second direction are readable. Such a circuit is suitable for testing the positioning hysteresis effect and the circuit itself is not substantially complex.

Another embodiment of the circuit arrangement is that after storing the total average value, the control stage controls the guidance of the scanning head system over the reference test track by means of the positioning system, the track average value of the reference track being either redefined or derived from the above-mentioned storage stage. The total average is then subtracted from the track average for the reference track, and the remaining average is displayed and/or used in an automatic head adjustment device.

This allows the scanning head system to be adjusted simply by manual means or by automatic head adjustment means.

The test disc used in this method and procedure is shown in the following figure, which is a specific apparatus.

FIG. 1 is a schematic diagram of a test disc incorporating a disk drive of the present invention;

FIG. 2 is a geometric diagram of a series of test signals serially connected to test tracks on a test disk;

FIG. 3 is a set of test signals between dashed lines 20 and 21 in FIG. 2;

FIG. 4 is a graph of measured skew for a plurality of test tracks on a test disk;

fig. 5 is a novel circuit diagram for implementing the method.

The primary devices that make up the conditioning and control system 19 are a drive shaft 16 (as shown), a magnetic test disk 15, a head positioning system 11 with a long axis 12, and a head 13 of a magnetic scanning head system. The magnetic head 13 is movable in the direction indicated by a double-headed arrow d on a long axis 12, and 14 on a magnetic disk 15 represents a central circular recording track (hereinafter referred to as "track"). Arrow a indicates the direction of rotation of the drive shaft 16, with the portion 17 of the drive shaft protruding from the disk 15 and being slightly tapered to facilitate centering of the disk 15.

Fig. 2 shows the series geometry of the test signal TS, which extends outwardly along the centerline 18 of the track, i.e. the central circular recording track 14 described above, b representing the width of the track. The test signal TS is composed of a plurality of variable magnetic fluxes. Six sets of signals (I to VI) can be seen in fig. 2, each set being of length C. Each group consists of three direction signals 1 to 3 and six adjustment signals 4, 5 and 8, 9. The direction signals are symmetrically arranged on either side of the track centerline 18. The adjustment signal alternates on both sides of the center line 18. The amplitudes of the direction signals and the adjustment signals are chosen to be suitable such that they can be distinguished (which can be done in a simple way), e.g. the direction signals 1 to 3 can be composed of alternating signals 2f,1f,2f of different frequencies. Here, the frequency f is a recording frequency of the data system. In the case of a removable disk system, the frequency f is 250 kilohertz at a rotational speed of 360 revolutions per minute. In this case, the adjustment signal is preferably 1f.

Fig. 3 is a waveform diagram of signals between the broken lines 20 and 21. It contains group III direction signals 1 to 3 and adjustment signals 4,5 and 8, 9, and group IV direction signals 1 to 3, the azimuth signals 6 and 7 not being shown in the figure. As shown, the read voltage U scanned by the head 13 is a function of time t on the x-axis in the y-axis direction.

Direction signals 1 through 3 are distinguished by sense voltages U _2fc,U_1fc and U _2fc, voltage U _1fc having a magnitude ratio U _2fc. In the figure, the magnitude of the sense voltage U _1fi is the same as U _1fo. Since the magnitude of the read voltage is generated based on the position of the head 13 relative to the test track 14, the fact that the read voltages U _1fi and U _1fo have the same magnitude is indicative.

1) The head and disk adjustments are correct;

2) The test disk is exactly in the center of the drive shaft;

3) The magnetic disk or the movable magnetic disk is in a precise circular shape;

4) The drive shaft is precisely centered;

5) The magnetic head functions normally.

If the magnitudes of U _1fi and U _1fo are not the same, a positive difference indicates that the test disk 15 is moving toward the axis, while a negative difference indicates that it is moving in the opposite direction, i.e., away from the axis.

The equation for the displacement DeltaS of a track from an ideal position is

In the expression, the track displacement Δs and the track width S of the playback head are expressed in μm (micrometers). The correction can be made relatively accurately by adjusting the head on the long axis 12, or at least such head/track adjustment errors can be compensated for. This compensation is achieved by adjusting the difference between the read voltage of signal group n (n being one of groups I through VI) and the read voltage of group n +3 to be equal, which is achieved by adjusting the heads. This at least minimizes the radial eccentricity. In this eccentricity compensation example, the total number of signal groups is assumed to be 6. In case the total number N of signal groups is not the same, the track offset of signal group N should be introduced into signal group N + N/2 by the same displacement in order to reduce the radial error.

Frequencies 1f and 2f may be used, but in general all frequencies suitable for the scanning speed or signal length described above may also be used. To adjust the azimuth angle of the head, the frequency 2f of the read voltage U _2fc may be used. However, the azimuth angle can be well adjusted using the measurement method described below.

In fig. 2, for example, there may be two azimuth signals 6 and 7 between the adjustment signals 5 and 8 for controlling the azimuth angle of the head H, the azimuth signals 6 and 7 being available in any one of the groups I to VI. But preferably in only one track, for example on track 1 of the test disc.

The test signal, the direction signal, the adjustment signal and the azimuth signal are hereinafter collectively referred to as test signal TS.

The test disc (15) may have a plurality (or a number) of test tracks of this type. Conventional Flexy Disks discs have 37 or 74 tracks, every second or every third track, or alternatively every second and then every second track, with test signals. In principle, the number of test tracks may be determined based on the maximum amplitude of the test signal, e.g. the width of two active tracks plus a guard pitch extending to the appropriate width of the adjacent test tracks. In order to be widely applicable and to increase the accuracy of the adjustment and control, it is desirable to use and record as many test tracks as possible.

The test tracks of the entire recording area of a combined test disc may also be alternately distributed, i.e. every other two tracks apart. In such an apparatus, for example, the test track may be recorded on the tracks of the second, fifth, seventh, etc. Of course, in this case, only every other or every second track is scanned when testing an instrument, depending on whether a 3-phase or 4-phase stepper motor is incorporated into the positioning system (11).

The error signal is detected by adjusting a scanning head H consisting of a single head or a double head to any predetermined track, and the test signal (direction signal and adjustment signal) is read. In view of the recording capability of the region between the outer and inner edges of the test disc, particularly suitable for use as the reference track S _R is 16 tracks or 32 tracks (48 tracks or 96 tracks for the Flexy Disks disc) because this track is approximately in the center of the disc. The direction signal and the adjustment signal are propagated in a sine wave by the scanning head H and converted into a DC signal in the sense amplifier by means of a peak response rectifier AM. The direction signal is separated by a filter F with a response frequency 2F and then directly sent to the microprocessor MP for synchronization to eliminate the unstable phenomenon of the rotation speed. The conditioning signal is also supplied to the microprocessor through an analog-to-digital converter. The microprocessor MP determines the amplitude of the signal, obtains an average value, and supplies the single signal or the averaged signal to an electrically programmable read only memory or a random access memory as a storage stage, and is connected to the drive interface SS via a conductor L for controlling the control functions required for detecting the error signal. The microprocessor MP is also connected to a display or writing device and/or to an automatic scanning head adjusting device D and an input device, for example a keyboard T. The arrangement of the entire line is within the box of the dashed line 25 in fig. 5.

After determining the amplitude and synchronization of the adjustment signals with the direction signals, the microprocessor MP first averages the individual adjustment signals (individual average), then averages the adjustment signals of each of the I to VI groups (group average), and finally averages the entire test track (track average).

Before the average value can be calculated, the track error TE as one party and the eccentricity error ES as the other party are always determined by adjusting the instantaneous amplitude of the signal, respectively, and stored in a random access memory.

After the error signal detection on the reference track S _R is completed, the next test track, track 19, is processed, and the process is repeated until the last test track, 35 or 74 tracks, is scanned, the measured value is stored, or the average value (total average value) of all the test tracks is calculated.

[ Note that for the present invention, average means the average value of the algorithm ]

For 37 tracks, there may be six track averages (16, 20..times., 36) for a 4 track model, and there may be eight track averages (16, 19,) for the 3 track model, from which the overall average IM can be easily derived. These numbers are applicable to unidirectional testing.

The above is also possible for tracks 2,5,7,10,12,15,17,20,22,25,27,30,32,35 and 37, i.e. every second further every second track there is an up test signal TS, so that in the case of 37 tracks 8 or 7 test values can be obtained.

In order to obtain a complete distribution of the error signal TE (see the left S-curve in fig. 4), the test track S can also be scanned in the range of tracks 0 to 16. Arrow a indicates the direction of arrival of the track. In this case, the arrival is through the reference track S _R from the outer track S _X to the inner track S ₁.

Thus detecting the TE signal may form a solid curve S. The dashed line adjacent to the S-curve represents the distribution of eccentricity values (ES).

According to the above method, after reaching the innermost test track S ₁, the track arrival direction is changed from a (first direction) to B (second direction) (shown by the arrow in fig. 4), and the above error signal detection routine is repeated until the outermost test track is detected. Preferably, the total average is taken from the two (first and second) track-going-direction error signals TE and TE' to facilitate the measurement and evaluation of the positioning lag. The right parallel S-curve is obtained at a distance HY, which contains the TE' signal consisting of the solid curve S and the ES-profile dashed curve. This method of detection in both directions gives twice the number of measured displacements, while also giving an average value in both directions.

The zero displacement between the individual heads on track S _R can also be determined with a dual head drive and used to determine the maximum error signal TE _max.

The total average taken by the direction of arrival a or B or by both directions of advance a and B can be described by a straight line IM (actual total average). The distance DeltaTE between the straight line and the track average of the reference track S _R coincides with the difference between the total average TM and the track average. In order to minimize the error signal across the recording area, i.e. to optimize the recording and playback of the instrument, the scanning head H on the reference track S _R must be moved a distance Δte. In fig. 4, this corresponds to a parallel straight line Φm. In connection with this, a positive maximum value PMX (bottom right) is obtained, here taking into account the zero displacement in the case of a dual head and the maximum eccentricity value E, a negative maximum value NMX occurring at the top left, yielding a maximum TE value TE _max. Thus, the positive and negative TE _max values differ greatly in magnitude.

For display purposes, these maximum values TE _max (positive and negative), the Δte values, and the associated hysteresis values HY may be fed to a stage D (e.g., a visual display) for display and constitute quality criteria for testing a particular instrument. The delta TE value can also be used to adjust the manual scan head or be transmitted by an automated means to a motor driven scan head adjustment device that can be used as a device on stage D. However, each TE value may be determined based on the average value OM of each track without adjusting the scanning head, and the writing or reading signal may be appropriately corrected by calculation and electronic means in order to directly compensate for or minimize errors in writing and reading.

In fig. 5, according to the invention, the control instructions for performing the method of the invention are contained in an electrically programmable read only memory that can be eliminated, and thus are easy to modify. The input means T may be a keypad for initiating a measuring or adjusting procedure.

The use of the new method and procedure for this purpose actually increases the compatibility of the equipment by about 20%, reduces the reject rate during manufacture by about 15% and minimizes maintenance.

Claims (11)

1. A method of detecting an error signal comprising a disc drive (19) of a head positioning system, the method employing a magnetic test disc (15) having a plurality of test tracks (S) on which Test Signals (TS) are recorded, the test tracks being located on the recording tracks and being distributed over the recording area of the test disc, at least one of the test tracks being predetermined as a reference test track (S _R), the Test Signals (TS) in said test track (S) being readable and the offset of the read signal from the desired position and amplitude being determinable so as to obtain an average value, the test signal (TE) being composed of adjustment signals (4, 5 and 8, 9) and direction signals (1 to 3) which are alternately recorded on both sides of a center line (18) of the recording track and have the same amplitude, the direction signals dividing said adjustment signals (4, 5 and 8, 9) into groups (I to VI) whose amplitudes are different from the adjustment signals,

Within each set (I to VI) of adjustment signals (4, 5 and 8, 9) their actual position and actual amplitude are determined, from which the average value of a set of signals can be derived,

The group average value of each individual test track (S) is used to calculate the average value of the tracks, which will be stored,

-The track average of the test track (S) is used to calculate a total average (IM) which is also stored.

2. A method as claimed in claim 1, characterized in that, when the drive means is a stepper motor positioning system (11), the position of the test track (S) on the test disc (15) is exactly inconsistent with the number of phases of the particular stepper motor.

3. A method as claimed in claim 2, characterized in that the Test Signal (TS) is read out and calculated every second recording track when the drive means is a 4-phase stepper motor positioning system (11).

4. A method as claimed in claim 2, characterized in that when the drive means is a 3-phase stepper motor positioning system (11), the Test Signal (TS) is read out and calculated every third recording track.

5. A method as claimed in claim 2, characterized in that when the drive means is a 3-phase or 4-phase stepper motor positioning system (11), the Test Signal (TS) on the same test disc (15) is read and calculated every other recording track or every second recording track.

6. A method according to claim 1 or 2 or 3 or 4 or 5, characterized in that starting from a given first test track, in particular the aforementioned reference test track (S _R), the number of tracks is gradually increased or decreased in a first direction, the Test Signal (TS) is read out and processed continuously, and the direction of reading is then turned in the opposite direction, the Test Signal (TS) of the test track is read out and processed continuously in a second direction, and the total average (IM) is obtained from the sum of the averages in both directions.

7. A method according to claim 1 or 6, characterized in that the stored total average value is subtracted from the track average value of the reference test track (S), the remaining average value being displayed and/or used as a head position correction on the reference test track (S _R).

8. The method of claim 1 wherein the stored track average and total average (IM) are used at least to modify the head positioning system.

9. A magnetic test disc according to the method of claim 1 or 2 or 3 or 4, characterized in that the magnetic test disc is composed of a plurality of test tracks (S) recorded every second or every third recording track and distributed evenly over the recording area of the test disc (15).

10. A magnetic test disc according to the method of claim 1 or 2 or 3 or 4, characterized in that the test tracks (S) are recorded alternately at every other recording track and every second recording track at least in part of the recording area.

11. Apparatus for detecting error signals in a disk drive comprising a head positioning system, characterized in that it comprises a circuit part in which there are a control part (for controlling the 3-track, 4-track or 2-track scanning period), a calculator (connected to the scanning head), an average calculator and memory for average signals, and a display and/or write memory for the total average (IM).

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