JP2008052900A - Universal head medium evaluation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that time and effort are needed for always obtaining satisfactory evaluation and enhancing reliability of measurement. <P>SOLUTION: In a universal head medium evaluation device (universal disk tester) (UDT) provided with a nonvolatile memory 18 for storing frequency characteristics for every UDT element which constitutes a signal transmission system of the UDT for every UDT element, a system control part 12 has a function for reading frequency characteristics from the nonvolatile memory 18 for every UDT element, calculating frequency characteristics of the whole system, setting a measurement limit according to given algorithm based on the frequency characteristics of the whole system, displaying the measurement limit on a screen and presenting the same to an operator and the like. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a general-purpose head medium evaluation apparatus that evaluates characteristics of various heads and media (disks) used for writing / reading information in a magnetic disk apparatus or the like in a design and manufacturing process. In recent years, a general-purpose head medium evaluation apparatus (hereinafter also referred to as “UDT”) has been used, and the following has been required for this apparatus.

  1. In UDT, it is desired that an operator can grasp a measurement limit according to variation in frequency characteristics of the entire system between UDT models or between units of the same model. In this case, the UDT element usually has variations as circuit elements. At present, aiming to limit the circuit, it is difficult to adjust the variation between the circuits and match the characteristics between the UDTs.

  Further, a part of the system (for example, a head IC) may be frequently replaced depending on the measurement purpose, and performing the readjustment each time causes a waste of time. Therefore, there has been a demand for UDT in which the measurement limit according to the UDT elements constituting the system is clearly shown to the operator when the configuration is changed.

  2. It is desired not to cause a difference in measurement results between UDTs according to variations in frequency characteristics between UDTs. In this case, even if there is a difference in the frequency characteristics of the UDT elements between the UDT system configuration and the units, it is desired that the entire system has a measurement result with the same frequency characteristics.

  3. In UDT, it is necessary to replace the medium mounting hub according to the dimensions of the measurement medium. However, the mass balance of the spindle stand may be lost during the replacement. Measurement and adjustment of mass balance is time consuming, so it was desirable to be able to easily determine whether the mass balance is within an acceptable level without using a measuring instrument. I do).

  4). : UDT is a precision motor that moves the entire moving stage that supports the head / arm at a fine pitch. For precision motors, systems such as ultrasonic motors and air levitation motors are often used to eliminate vibrations due to driving force by turning off the driving force after movement. Even if the positioning accuracy deteriorates, these motors can maintain the measurement accuracy if they reach the target position by retry.

  However, since the moving frequency of the moving stage in the evaluation is high, the load on the motor becomes large and the performance is likely to deteriorate. Therefore, it is necessary to change the control method according to the change with time. In addition, for measurement by precise positioning, there has been a demand for retry control that efficiently processes a position error that happens to occur.

  5. : In the MR head, there is a phenomenon (hereinafter referred to as “pinned layer reversal”) in which the magnetization direction of the layer whose magnetization state must be aligned in a specific direction is reversed. If pin layer inversion occurred during measurement, accurate measurement could not be performed, and a function of recognizing pin layer inversion was desired.

(Conventional technology)
A conventional example will be described below.

§1: Description of conventional example (1)
FIG. 5 is an explanatory diagram of a conventional example. Conventionally, a magnetic disk device has a magnetic disk (hereinafter referred to as “medium”) for recording information, and a write / read head (write / read) for writing / reading information to / from the medium (write / read). / Readhead) and the like. Such heads and media need to be evaluated for performance and the like in the design and manufacturing process of the magnetic disk device. For this reason, a general-purpose head medium evaluation device (hereinafter referred to as “UDT”) has been used.

  In the evaluation by UDT (UDT: Universal Disk Tester), if the head and the medium are evaluated separately, the evaluation result is different from the case where the head is mounted on the actual magnetic disk device. Hereinafter, a combination of a head and a medium is referred to as a “head medium”).

  As shown in FIG. 5, the UDT has a spindle mechanism 1, a medium 2 attached to the spindle mechanism 1, a head 3, a slider 4 to which the head 3 is attached, and a slider 4 attached and moved. A movable stage 5 and a control device 6 are provided.

  The spindle mechanism 1 is driven by the control of the control device 6 and rotationally drives the medium 2. The moving stage 5 is configured to be movable under the control of the control device 6, and the head 3 is moved by the movement of the moving stage 5. The head 3 is positioned on a designated track on the medium 2 by the movement of the moving stage 5, and writes / reads information (write / read) on the medium 2.

  The control device 6 controls the movement of the moving stage 5, controls the writing / reading of information with respect to the medium 2 via the head 3, and evaluates the head medium based on the data obtained by the writing / reading. Is to do. In this case, the UDT is designed and manufactured so that various evaluation objects are required to have an evaluation capability equal to or higher than that of the device mounted state due to the versatility and the evaluation equipment.

  When the head medium is evaluated, the head 3 and the medium 2 are exchanged (removable), and tests are sequentially performed by UDT to evaluate the characteristics of the head medium. In this case, the moving stage 5 is moved by the control of the control device 6 to perform the positioning control of the head 3, but the positioning control of the control device 6 is the open control and the close control is not performed.

  Then, information is written / read to / from the medium 2 through the head 3 under the control of the control device 6 to obtain data at the time of evaluation. Then, the control device 6 evaluates the head medium based on the obtained data.

§2: Description of conventional example (2)
Hereinafter, specific examples of evaluation in the UDT will be described.

  (a): The measurement conditions are determined in advance by evaluating the frequency characteristics of the entire system between UDT units. In this case, in order to eliminate the effort to re-evaluate the frequency characteristics of the entire system, measurement conditions with margins are determined in anticipation of circuit variations based on the initial evaluation results of the entire system. When the UDT element is replaced, the frequency characteristic is not evaluated again.

  In this case, the frequency characteristics are not re-evaluated, but the system gain is adjusted to maintain the measurement accuracy. However, if it is necessary to perform the measurement using the upper limit of the UDT measurement capability, the measurement conditions are determined by evaluating the frequency characteristics of the entire system in accordance with the UDT element to be exchanged even if it takes time.

  (b): The measurement result is not corrected according to the frequency characteristics of the UDT. The measurement is performed according to the frequency characteristics of the UDT, and only the measurement within the limited range is performed.

  (c): The vibration evaluation of the spindle mechanism 1 uses a mass balance measuring instrument. When a condition that is thought to be caused by spindle vibration, such as deterioration of positioning accuracy, is developed, a mass balance measuring instrument is installed for evaluation and readjustment.

  (d): A uniform setting is applied to the retry condition of the moving stage 5. When the position error exceeds a predetermined allowable error, a retry is performed.

  (e): The pin layer inversion in the MR head is determined by a person observing the dibit waveform of the measurement result.

  The conventional apparatus as described above has the following problems.

  (1): With regard to (a) above, it is currently necessary to perform measurement using the measurement limit. For this reason, when replacing or changing a UDT element such as a head IC, it is necessary to evaluate the entire system again. However, these series of operations take time and effort. On the other hand, circuit variations cannot be completely eliminated. That is, by providing a plurality of adjusting means, it is possible to reduce variations, but it is not practical because it takes too much time and labor for the adjustment.

  (2): Regarding (b), as in (a) above, a means for dynamically grasping the frequency characteristic of the UDT element and a means for grasping the frequency characteristic of the entire system from the information are provided, and the frequency A means for correcting the measured value based on the characteristics is required. Therefore, it is not practical because it takes too much time and time.

  (3): Regarding (c), it takes time and effort to measure and adjust mass balance. In other words, measurement and adjustment of mass balance is necessary when mass balance is lost, and a means for determining whether mass balance has been lost by a simple method is desired (mass balance is lost). Only when it is determined that the mass balance is remeasured and readjusted).

  In addition, it is necessary to grasp the vibration state of the spindle without extending the current function (modifying the control software) without using a mass balance measuring instrument, but this is difficult to achieve.

  (4): With regard to (d) above, there is a need for a means by which the system can select the optimum retry condition, and even if there is a malfunction in the system, the retry condition is dynamically changed to some extent cause system degradation. There is a need for a means to allow and maintain the UDT in a usable state, but no such means are provided.

  (5): Regarding (e) above, a means capable of automatically detecting pinned layer inversion and measuring only accurate data is required, but such a means is not provided.

  SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem, to always perform good evaluation without manpower and time, and to improve measurement reliability.

  In order to achieve the above object, the present invention is configured as follows. FIG. 1 is a diagram illustrating the principle of the present invention. Hereinafter, a description will be given with reference to FIG.

  (1): Spindle mechanism 1 for rotating medium 2, moving stage 5 for moving a head for writing and reading information on medium 2, and information writing / reading control for various head media In a general-purpose head medium evaluation apparatus having a control device 6 for evaluating the characteristics of the head medium based on the data obtained at that time, the relationship between the rotational speed of the spindle mechanism 1 and the positioning accuracy of the moving stage 5 is evaluated. When the mass balance of the spindle mechanism 1 is adjusted so that the positioning accuracy is less than or equal to the target value at all rotational speeds, and the vibration of the spindle mechanism 1 is reduced at the total rotational speed, and the positioning accuracy exceeds the target value. Is provided with spindle vibration evaluation means (a part of the control device 6) that uses as an index for readjustment of the mass balance of the spindle mechanism 1.

  (2): A spindle mechanism for rotating the medium 2, a moving stage 5 for moving a head for writing and reading information on the medium, and information writing / reading control for various head media, In a general-purpose head medium evaluation apparatus having a control apparatus that evaluates the characteristics of the head medium based on the data obtained at that time, the retry condition according to the positioning accuracy of the moving stage 5 is dynamically changed according to the retry rotational speed. It is provided with positioning accuracy control means (a part of the control device 6) for maintaining the positioning accuracy by changing.

(Function)
The operation of the present invention based on the above configuration will be described.

  (a): In the above (1), the spindle vibration evaluating means evaluates the relationship between the rotational speed of the spindle mechanism 1 and the positioning accuracy of the moving stage 5 so that the positioning accuracy is less than the target value at all rotational speeds. The mass balance of the spindle mechanism 1 is adjusted, and the vibration of the spindle mechanism 1 is reduced at the full rotation speed. In this case, the case where the positioning accuracy exceeds the target value is used as an index for mass balance readjustment of the spindle mechanism 1. In this way, the vibration of the spindle can be easily evaluated with the current UDT, so that the measurement can be performed with confidence and the reliability of the measurement can be improved.

  (b): In the above (2), the positioning control means maintains the positioning accuracy by dynamically changing the retry condition according to the positioning accuracy of the moving stage 5 according to the retry rotational speed. In this way, even if the mechanical system of the system is somewhat degraded, the positioning accuracy can be maintained in a good state by dynamically changing the retry conditions, so that the measurement reliability can be improved.

  As described above, the present invention has the following effects.

  (1): In claim 1, the spindle vibration evaluating means evaluates the relationship between the rotational speed of the spindle mechanism and the positioning accuracy of the moving stage, so that the positioning accuracy is less than the target value at all rotational speeds. The mass balance is adjusted to reduce the spindle mechanism vibration at full rotation speed. In this case, the case where the positioning accuracy exceeds the target value is used as an index for mass balance readjustment of the spindle mechanism 1.

  In this way, the vibration of the spindle can be easily evaluated with the current UDT, so that the measurement can be performed with confidence and the reliability of the measurement can be improved.

  (2) In claim 2, the positioning control means maintains the positioning accuracy by dynamically changing the retry condition according to the positioning accuracy of the moving stage according to the retry rotation speed. In this way, even if the mechanical system of the system is somewhat degraded, the positioning accuracy can be maintained in a good state by dynamically changing the retry conditions, so that the measurement reliability can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

§1: Description of UDT
(1): Description of entire system FIG. 2 is an external view of a UDT. Hereinafter, the configuration of the UDT will be described with reference to FIG. As shown in FIG. 2, the UDT (universal head medium evaluation apparatus) has a spindle mechanism 1 for attaching and rotating a medium (magnetic disk) 2 and a slider 4 having a head (write / read head) 3. A movable stage 5 configured to be movable and a control device 6 are provided. In this case, the head 3 and the medium 2 are detachable, and various head media can be evaluated while exchanging the head 3 and the medium 2.

  The control device 6 includes a control circuit 10, an evaluation circuit 11, a system control unit 12, and a nonvolatile memory 18, and is configured to evaluate the head medium. The control circuit 10 includes a signal writing control unit 13 that performs signal writing control on the medium 2, a signal reading control unit 14 that performs signal reading control on the medium 2, and a stage movement control unit that performs movement control on the moving stage 5. 15 and a spindle rotation control unit 16 that performs rotation control on the spindle mechanism 1 is provided.

  The evaluation circuit 11 includes, for example, a DSP (digital signal processor), and by this DSP, a signal is written to the medium 2 via the head 3 under the control of the control circuit 10, or the head medium is read from the read data. Is to evaluate.

  The system control unit 12 is configured by a personal computer, a computer such as a workstation, or the like, and controls the entire system. In this case, the system control unit 12 performs various controls on the control circuit 10, the evaluation circuit 11, and the nonvolatile memory 18.

  The spindle mechanism 1 rotates the medium 2 as instructed based on a control signal from the control circuit 10. The moving stage 5 is configured to be movable by a control signal from the control device 6, and the head 3 is positioned by the movement of the moving stage 5. The head 3 is positioned at a designated track on the medium 2 by the movement of the moving stage 5, and performs signal writing / reading (writing / reading) on the medium 2.

  The UDT configured as described above is designed and manufactured to satisfy the evaluation capability required for the various evaluation objects, which is equal to or higher than the device mounting state, due to the versatility and the characteristics of the evaluation equipment. In order to evaluate the head medium using the UDT, the moving stage 5 is moved under the control of the control circuit 10 to control the positioning of the head 3. At this time, the control of the control circuit 10 is open control, and close control is not performed.

  Then, information is written / read (write / read) to / from the medium 2 via the head 3 under the control of the control circuit 10 to obtain data at the time of evaluation. Then, the evaluation circuit 11 evaluates the characteristics of the head medium based on the obtained data. A part of the evaluation information is digitized and processed by the system control unit 12. The read head signal and the like are digitized and transferred to the system control unit 12 and evaluated on the system control unit 12.

(2): Explanation on signal reading side FIG. 3 is a block diagram of a UDT read system. On the signal reading side of the UDT, a head IC 21 connected to the head 3, a preamplifier 22 that amplifies the output of the head IC 21, a main amplifier 23 that amplifies the output of the preamplifier 22, and an output of the main amplifier 23 An ADC (analog / digital converter) 24 or the like for converting the signal into a digital signal is provided, and the system controller 12 is configured to take in a signal digitized by the ADC 24. The head IC 21, the preamplifier 22, the main amplifier 23, and the ADC 24 are UDT elements.

§2: Outline of UDT evaluation Outline of the UDT evaluation is as follows.

  (1): The UDT includes a non-volatile storage means (non-volatile storage such as a flash memory or a RAM backed up by a battery) that stores the frequency characteristics of each UDT element constituting the UDT signal transmission system for each UDT element. A memory 18 and a hard disk device, etc., and a means for obtaining a frequency characteristic of the entire system by reading out a frequency characteristic for each UDT element from the storage means, and a given algorithm based on the frequency characteristic of the entire system The measurement limit is set in accordance with the above and provided to the operator or the like.

  For example, the system control unit (for example, personal computer) 12 reads out the frequency characteristic for each UDT element from the storage means, and calculates and obtains the frequency characteristic of the entire UDT system from the information of the individual frequency characteristics. Then, based on the frequency characteristics of the entire UDT system, a measurement limit is set according to an algorithm given by the operator so that it can be clearly shown to the operator.

  In this case, the frequency characteristic information for each UDT element may be a calculation formula (approximation formula), spectrum information (gain and phase, or complex Fourier coefficient), or band limit information such as a flatness band or a normal band. (Eg, -3 dB down). The flatness band obtained from the frequency characteristics of the entire system is set as the upper limit of the signal writing frequency to be measured. Furthermore, the band obtained from the frequency characteristics of the entire system is set as the upper limit of the noise measurement band.

  In this way, even if system conditions (frequency characteristics) change, such as by exchanging UDT elements, measurement limits can be presented accordingly, so measurement in an unsuitable measurement range can be avoided, and measurement reliability Can be improved.

  (2): The UDT includes non-volatile storage means for storing the frequency characteristics of each element constituting the signal transmission system of the UDT for each element, and the frequency characteristics for each element are stored from the storage means. Readout is performed to obtain a frequency characteristic of the entire system, correction data is obtained from the frequency characteristic of the entire system, and the correction data is used to correct the frequency characteristic of the entire system to be flat.

  In this case, the frequency characteristic correction process is performed by the system control unit 12. In this process, the measured value (time-domain digital signal) obtained by converting the signal waveform into a digital signal by the A / D converter and taking it in the system control unit 12 is used. Value) is subjected to discrete Fourier transform to be converted to the frequency domain. Next, after performing frequency characteristic correction calculation in the frequency domain, a discrete inverse Fourier transform is performed on the result, and a measurement item is calculated from the signal waveform reproduced in the time domain. Further, the range of the frequency region in which the frequency characteristic is corrected is limited to the write signal upper limit or the noise measurement upper limit.

  In this way, even if the system conditions (frequency characteristics) of the UDT change, measurement can be performed under measurement conditions that do not depend on it. Therefore, the measurement can always be performed under the same conditions, and the measurement reliability can be improved.

  (3): Evaluate the relationship between the rotational speed of the spindle mechanism 1 and the positioning accuracy of the moving stage 5 with UDT, and adjust the mass balance of the spindle mechanism 1 so that the positioning accuracy is less than the target value at all rotational speeds. And a means for reducing the vibration of the spindle mechanism 1 at the total rotational speed and using as an index of mass balance readjustment of the spindle mechanism 1 when the positioning accuracy exceeds a target value.

  That is, when the mass balance is lost, the spindle mechanism 1 vibrates. When the spindle mechanism 1 vibrates, the head / arm moving stage 5 causes mechanical resonance, which deteriorates the positioning accuracy. For this reason, means for indirectly evaluating the vibration of the spindle mechanism 1 from the evaluation of the positioning accuracy of the moving stage 5 is provided.

  Further, at the frequency at which the mechanical resonance is maximum (the rotational speed of the spindle mechanism 1), the amplitude of the positioning error becomes large and the vibration of the spindle mechanism 1 can be easily detected. Therefore, the spindle rotational speed at which the mechanical resonance is maximized. A means for adjusting the mass balance is provided. In this way, the vibration of the spindle mechanism 1 can be easily evaluated with the current UDT system, so that the measurement can be performed with confidence and the reliability of the measurement can be improved.

  In this case, the mass balance is adjusted with high sensitivity by adjusting the mass balance of the spindle mechanism 5 so that the positioning accuracy is equal to or less than the target value at the spindle rotation speed that causes the mechanism of the moving stage 5 to resonate. It can be performed. The mass balance is adjusted so that the change in displacement obtained by measuring the vibration of the spindle mechanism 5 through the housing and double integrating the acceleration of the vibration becomes zero.

  In the above-described case, the mass balance adjustment is performed at the spindle rotation speed at which the deterioration of the positioning accuracy due to the resonance is maximized among the spindle rotation speeds that cause the mechanism of the moving stage 5 to resonate.

  (4): The UDT is provided with means for maintaining the positioning accuracy by dynamically changing the retry condition according to the positioning accuracy of the moving stage 5 according to the retry rotation speed. In other words, means for dynamically changing the retry condition of the moving stage 5 and responding to the deterioration of the state of the entire system is provided. In this case, means for changing the allowable error according to the number of retries is provided. In this way, even if the mechanical system of the system is somewhat degraded, the positioning accuracy can be maintained in a good state by dynamically changing the retry conditions, so that the measurement reliability can be improved.

  The retry condition is a condition such as an allowable value of a position error for determining whether to end the positioning operation or to perform positioning again. For example, in the case of a feedback control method using a position sensor that generates a position as a digital value, a positioning tolerance is set at an integer multiple of the resolution (step) of the position sensor, and the tolerance is exceeded. Generate a retry. Then, the allowable error is set to zero until the specified number of times (zero set number), and after that number, the allowable error is set to a value other than zero.

  Further, a movement error is generated when the number of retries exceeds a predetermined number (error set number). The number of zero setting is selected from 1 or 2, or a proportional number of times of error setting (1/2 times, 1 time, etc.) based on the positioning accuracy of the moving stage 5. Also, depending on the current positioning accuracy capability of the system, select the number of zero settings, select 1 from the state where the positioning accuracy is good, then select 2, and even if the moving stage 5 is defective, UDT Set a proportional number if it must be activated.

  Further, the zero setting number is changed from 1 → 2 → proportional number in accordance with the deterioration of the positioning accuracy of the moving stage 5 due to the secular change (lifetime). Degradation is determined by monitoring the number of retries and determining its frequency.

  (5): When writing a dibit waveform to UDT, create a window function that sets “1” to the time position of the positive peak of the write waveform, “−1” to the time position of the negative peak, and zeros to the other. When reading the above, the maximum value obtained by multiplying the waveform by scanning the window function in the time direction and the window function obtained by multiplying the window function by "-1" are similarly obtained by multiplying the waveform. A means for comparing the values and determining that the pinned layer is reversed when the latter is large is provided.

  That is, there is provided means for detecting the polarity inversion of the dibit waveform caused by the pin layer inversion when the MR head is used by pattern matching. By providing a means for detecting pinned layer inversion in this way, erroneous measurement can be avoided and measurement reliability can be improved.

§3: Description of specific evaluation processing Hereinafter, specific evaluation processing for each example will be described.

(Example 1)
Example 1 is an example in which a measurement limit is set and limited from the frequency characteristics of the entire system. As shown in FIG. 3, a circuit block related to frequency characteristics is divided into UDT element units (head IC 21, preamplifier 22, main amplifier 23, ADC 24), and frequency characteristics are measured in advance for each UDT element, Information is stored in the nonvolatile memory 18 separately for each UDT element.

  In this case, the frequency characteristic for each UDT element is measured by using another measuring device instead of the UDT, and the measurement data is stored in the nonvolatile memory 18 separately for each element. When there is no room for the non-volatile memory 18, an information file (for example, a file on a storage medium of a hard disk device provided in the system control unit 12) is used instead of the non-volatile memory 18. .

  The system control unit 12 reads the frequency characteristics of each UDT element from the nonvolatile memory 18 (or the hard disk device provided in the system control unit 12), calculates (multiplies), and calculates the frequency characteristics of the entire system. To do. The measurement limit is set based on this frequency characteristic. For example, the frequency characteristics of the UDT element in FIG.

  If so, the frequency characteristic of the whole system is

  As required.

  Usually, when measuring by writing an evaluation signal, the signal is written in a range where the flatness of the frequency characteristic of the entire system is established. That is, the upper limit of the flatness is set as the upper limit of the measurement signal. Further, the noise measurement is performed with the measurement upper limit up to the system bandwidth (-3 dB down). Note that these settings are merely examples, and may be arbitrarily determined according to the evaluation criteria of the operator.

(Example 2)
Example 2 is an example in which flatness is corrected from the frequency characteristics of the entire system. In the same manner as described above, the frequency characteristic of the entire system is calculated, and the correction frequency characteristic is calculated therefrom. The frequency characteristic for correction is obtained as an inverse characteristic of the frequency characteristic of the entire system, or as an inverse characteristic of the frequency characteristic of the entire system in a region where the range is limited to flatness or a band. That is,

  When performing bandwidth limitation,

  At the time of measurement, the measurement result and the frequency characteristic for correction are subjected to discrete Fourier transform and converted to the frequency domain, and the frequency characteristic is corrected by multiplying the measurement result in the frequency domain, and further, the discrete inverse Fourier transform is performed to obtain the original time. Return to the signal waveform of the area. At this time, high frequency components unnecessary for the measurement are removed in the frequency domain calculation. In this case, the calculation is performed with spectral components (Fourier transform values) up to the necessary frequency band, but the Fourier coefficient corresponding to the frequency component to be removed may be zero.

The same evaluation as before is performed using the corrected signal waveform. Bandwidth limiting filter

Assuming that the Fourier coefficient is X (i) (where i = 0 to N), when the band is Fc and the sampling is Fs, the upper limit Nc of the band limitation is expressed as Nc = N × Fc / Fs. , X (i) = 1 (where i = 0 to Nc), X (i) = 0 (i = N _{c + 1} to N). When the result to be obtained is a spectrum, it is not necessary to use the result obtained in the frequency domain as it is and return to the time domain. The calculation formula used for the Fourier transform is as follows.

(Example 3)
Example 3 is an example in which the vibration state of the spindle mechanism 1 is evaluated with the positioning accuracy of the moving stage 5. When an imbalance or the like occurs in the spindle mechanism 1, the spindle mechanism 1 vibrates. The moving stage 5 receives the vibration of the spindle mechanism 1 and the positioning accuracy deteriorates. In particular, when the spindle mechanism 1 and the moving stage 5 cause mechanical resonance, the positioning accuracy is greatly deteriorated. Therefore, the vibration of the spindle mechanism 1 can be indirectly evaluated by evaluating the positioning accuracy.

  Further, by evaluating the frequency at which the mechanical resonance is remarkable by changing the rotation speed of the spindle mechanism 1, the evaluation value is expanded and the evaluation becomes easier than in the case where there is no mechanical resonance. That is, the measurement gain appears to have increased. By evaluating the positioning accuracy, the vibration of the spindle mechanism 1 can be indirectly grasped. However, it is not easy to grasp the absolute value of the magnitude of vibration of the spindle mechanism 1 from the positioning accuracy.

  Accordingly, if the positioning accuracy is within a predetermined level, the head medium is determined to be normal, and if it is above the predetermined level, it is determined to be abnormal, and the mass balance of the spindle mechanism 1 is readjusted. . If the positioning accuracy does not improve even after readjustment, it can be determined that the cause is other than the vibration of the spindle mechanism 1 (the motor of the moving stage 5 is broken). The predetermined level only needs to satisfy the positioning accuracy that does not hinder the measurement of the head medium or the positioning accuracy guaranteed by the moving stage 5.

  As a measuring method, first, a program for measuring positioning accuracy is created while changing the rotation speed of the spindle mechanism 1, and measurement is performed using this program. In general, the system control unit 12 of the UDT is configured to set the rotation speed of the spindle mechanism 1 and to grasp position error information, so that it can be dealt with only by modifying the current software. Normally, no hardware modification is required, and the present invention can be easily applied.

  Next, while changing the rotation speed of the spindle mechanism 1, the positioning accuracy is evaluated, the rotation speed at which the positioning accuracy is deteriorated to the maximum is obtained, the unbalance adjustment of the spindle mechanism 1 is performed at the rotation speed, and the vibration is reduced. . Since vibration is emphasized by mechanical resonance, it is easy to evaluate.

  On the other hand, if the positioning accuracy is good without depending on the rotation speed, the UDT may be used for evaluation with confidence. If the system usage conditions are limited (when only a specific rotation speed is used), the positioning accuracy can be evaluated at a specific rotation speed because the system can be used if the positioning accuracy is good under those conditions. . However, unbalance adjustment is performed at a rotational speed that causes mechanical resonance, which leads to improved measurement accuracy.

(Example 4)
Example 4 is an example in which the positioning accuracy is maintained by changing the retry condition according to the state of the moving stage 5. In a control system that performs a readjustment (retry) operation with a positioning error at the end of the movement to the target position, the moving stage 5 is controlled by dynamically switching the retry conditions.

  An allowable value (allowable error) for the position error is set. If (Position error)> (Allowable error), retry is performed. Normally, the tolerance is fixed for a single movement to the target position (the same value is applied for each retry), but in the present invention, it is dynamically changed (the value is changed according to the number of retries) and moved. Combines efficiency and improved positioning control.

  It is assumed that the moving stage 5 used in the evaluation system such as UDT is an ultrasonic motor that operates a driving mechanism (driving circuit) during movement and cuts the driving force of the driving unit after movement. When these motors finish moving to the target position, the position (positioning accuracy) is maintained, so it is only necessary to reach the target position by retrying or the like.

  In a system with good positioning accuracy, the tolerance is set to 0 (zero) only for the first time. From the second time on, it is assumed that the tolerance ≠ 0. In a good system, the target position is usually reached at the first time. However, when a disturbance or the like occurs and the target deviates, the allowable error is set to 0 (zero) only for the first time in order to guarantee the positioning accuracy. In the second and subsequent times, the allowable error ≠ 0 is to prevent the retry control from coming out in the event of a system failure such as deterioration of the stage moving motor, and to limit positioning in the event of slight deterioration. This is to keep the measurement a little sweeter.

  If the frequency of retries increases by evaluating the degree of system failure with positioning accuracy, the number of times that the allowable error ≠ 0 is further increased. For example, if the number of retries exceeds 4, or if it is set as an error end, the moving stage 5 that has been normal and has been retried only once will deteriorate, and the number of retries will always exceed 4 times. In such a case, the error termination is eliminated by setting the number of retries to about 6 times.

  In this case, of course, the set time of the moving stage 5 increases due to the retry, but it is effective when the evaluation of the head medium has to be prioritized over the repair and replacement of the moving stage 5 such as use in a production line. As a result, the number of retries increases, but the probability of reaching the target position by the retry operation increases. In other words, a trade-off between the movement time and the positioning accuracy is performed for the malfunction of the system.

  As another method, the allowable error is increased as the number of retries increases. For example, if the maximum allowable positioning accuracy is P, the number of retries is 0 to n1, the allowable error is 0, the number of retries is n1 + 1 to n2, the allowable error is P / 2, and the number of retries is n2 to 1 to n3. = P.

  If the motor is normal, the movement is completed by the first time, but if the motor deteriorates, it will not stop with a small tolerance but will stop with a large tolerance. It is ideal to stop at the minimum allowable error, but there is an advantage that if the head medium needs to be evaluated according to the actual situation, the evaluation can be continued with the positioning accuracy lowered.

  Deterioration due to secular change is considered as a malfunction of the system. Depending on the degree, the number of times of allowable error = 0 is dynamically changed once, twice or more. If the system is normal, the target position is reached in the first or second time. If more is needed, it is considered that the system needs to be improved. However, because of the provisional treatment (waiting for repair) prioritizing measurement, the number of retries is increased to reach the target position in order to maintain positioning accuracy.

  Therefore, the set number of times of allowable error = 0 is dynamically increased. When increasing the number of times of setting, fine step division is not necessary. A guideline for the number of times beyond that may be set as a proportional value such as 1/2 or 1 times the limit on the number of retries set by the system (an error will occur if more retries are made). For example, when the retry upper limit is 8, the number of retries with allowable error = 0 is increased to 1, 2, 4, 8, and the like.

  Note that the aging of the system may be shifted to the next stage when the current setting retry count is monitored and increased. Alternatively, the frequency of movement error is evaluated and the set number of times is changed.

(Example 5)
Example 5 is an example in which pin layer inversion of the MR head is detected. Write window function of dibit waveform Create a window function with “1” at the time position of the positive peak, “−1” at the time position of the negative peak, and 0 for others. The maximum value obtained by multiplying the function while operating in the time direction and the window function obtained by multiplying the window function by “−1” (the window function obtained by inverting the sign of the window function) are similarly multiplied by the waveform. The obtained maximum values are compared, and if the latter is larger, it is determined that pinned layer inversion has occurred.

  FIG. 4 is an explanatory diagram of processing, (1A) is a normal output waveform, (1B) is an abnormal output waveform (inverted pin layer), (2A) is a window function pattern that matches the normal output waveform, and (2B) is an inverted output. A window function pattern (reverse polarity of 2B) that matches the waveform is shown.

  As shown in FIG. 4, the evaluation is performed by multiplying the waveforms of (1A) and (1B) by the window functions of (2A) and (2B). Assuming that the peak of the output waveform is Vop (for the sake of simplicity, explanation will be made with the same level of positive and negative), a data string obtained by multiplying the time axis (horizontal direction in the figure) of (2A) and (2B) while shifting The maximum value is obtained from the following.

  That is, in the case of a normal output waveform, (1A) × (2A) = 4 Vop (Vop: peak value), (1A) × (2B) = 2 Vop. In the case of an abnormal output waveform, (1B) × (2A) = 2 Vop, and in the case of pinned layer inversion, (1B) × (2B) = 4 Vop.

  For a normal output waveform, the result is greater when multiplied by a pattern that matches the normal output waveform, whereas for an abnormal output waveform, the result is greater when multiplied by a pattern that matches the abnormal output waveform. From this, the presence or absence of pinned layer inversion can be confirmed.

§4: Description of recording medium and program In the evaluation process performed by the UDT, a program necessary for the evaluation process is stored in advance in the hard disk device of the system control unit (for example, personal computer) 12, and the system control The CPU of the unit 12 executes the program of the hard disk device. However, the present invention is not limited to such an example, and can be realized by storing a program in the hard disk device as follows.

  (a): The program stored in the removable disk (program created by another device) is read by the removable disk drive of the system control unit 12 and stored in the recording medium (hard disk) of the hard disk device. The removable disk includes an optical disk such as a CD-ROM, a magneto-optical disk, and a floppy disk.

  (b): A program transmitted from another device via a communication line such as a LAN is received via the communication control unit of the system control unit 12, and the data is stored in the recording medium (hard disk) of the hard disk device. To do.

It is a principle explanatory view of the present invention. It is an external view of UDT in an embodiment of the invention. It is a lead system block diagram of UDT in an embodiment of the invention. It is processing explanatory drawing in embodiment of this invention. It is explanatory drawing of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spindle mechanism 2 Medium 3 Head 4 Slider 5 Moving stage 6 Control apparatus 10 Control circuit 11 Evaluation circuit 12 System control part 13 Signal writing control part 14 Signal reading control part 15 Stage movement control part 16 Spindle rotation control part 21 Head IC
22 Preamplifier 23 Main Amplifier 24 ADC (Analog / Digital Converter)

Claims (2)

A spindle mechanism for rotating the medium, a moving stage for moving the head for writing and reading information on the medium, and data writing / reading control for various head media and data obtained at that time In a general-purpose head medium evaluation apparatus provided with a control device for evaluating the characteristics of the head medium based on
Evaluate the relationship between the rotation speed of the spindle mechanism and the positioning accuracy of the moving stage, adjust the mass balance of the spindle mechanism so that the positioning accuracy is below the target value at all rotation speeds, and adjust the spindle mechanism vibration to the full rotation speed. A general-purpose head medium evaluation device comprising: spindle vibration evaluation means that reduces the positioning accuracy when the positioning accuracy exceeds a target value, and uses as an index for readjustment of mass balance of the spindle mechanism. A spindle mechanism for rotating the medium, a moving stage for moving the head for writing and reading information on the medium, and data writing / reading control for various head media and data obtained at that time In a general-purpose head medium evaluation apparatus provided with a control device for evaluating the characteristics of the head medium based on
General-purpose head medium evaluation apparatus comprising positioning accuracy control means for maintaining positioning accuracy by dynamically changing a retry condition according to the positioning accuracy of the moving stage according to the retry rotational speed .

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