KR100675003B1 - Method for adjusting characteristic of notch filter and disk drive using the same - Google Patents

Abstract

A characteristic adjusting method of notch filters and a disk drive using the method are provided to automatically adjust filter coefficients of the notch filters so as to minimize generation of a boost phenomenon in cutoff neighboring frequency bands of the notch filters, thereby stably controlling a system as effectively removing resonant frequencies. It is decided whether cutoff frequency intervals between notch filters are smaller than the first threshold value(S301). If so, it is decided whether gain changes, which occur by the results showing whether the notch filters are used in frequency bands between cutoff frequencies of the notch filters, exceed the second threshold value(S302-S305). If so, notch filter coefficients are adjusted to lower cutoff gains of the notch filters(S306).

Description

Method for adjusting characteristic of notch filter and disk drive using the same}

1 is a plan view of a configuration of a disk drive to which the present invention is applied.

2 is a configuration diagram of an apparatus for adjusting characteristics of a notch filter according to the present invention.

3 is a flowchart of a characteristic adjusting method of a notch filter according to the present invention.

The present invention relates to a filter design method and apparatus, and more particularly to a method and apparatus for adaptively adjusting the characteristics of a notch filter that eliminates the mechanical resonant frequency present in a system.

In general, a hard disk drive (HDD), which is a data storage system, is a combination of a head disk assembly (HDA) composed of mechanical components and an electric circuit. In a head stack assembly (HSA) constituting the HDA, The harmful resonance generated appears directly in the position error signal PES, which causes a problem of worsening the stability of the servo tracking control of the hard disk drive.

By solving this problem, the resonance frequency adversely affecting the hard disk drive is analyzed from the frequency of the head position error signal (PES), and the notch filter with the sharp cutoff slope characteristic to remove the analyzed resonance frequency is very sharp. (notch filter) was used.

In general, since a plurality of resonance frequencies are detected in a hard disk drive, a plurality of notch filters are used to prevent resonance of the hard disk drive.

However, as the cutoff gain (i.e., depth) of the notch filter increases, overshoot of the surrounding frequency increases, thereby causing an adverse effect of increasing the gain of the unwanted frequency region.

In particular, the closer the cutoff frequencies between notch filters that cut off different frequencies, the more severely the frequency components between the cutoff frequencies are boosted.

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a method of adjusting the characteristics of a notch filter and adaptively adjusting the characteristics of the notch filter in consideration of the interval of adjacent cutoff frequencies between the notch filters. To provide.

In order to achieve the above technical problem, the method for adjusting the characteristics of a notch filter according to the present invention includes: (a) determining whether cutoff frequency intervals between the notch filters are smaller than a first threshold value; (b) when the cutoff frequency interval between the notch filters is smaller than a first threshold as a result of the determination of step (a), gain according to whether the notch filter is used or not in the frequency band between the cutoff frequencies between the notch filters; Determining whether the change of the value exceeds the second threshold value; And (c) adjusting notch filter coefficients to lower the cutoff gain of the notch filter when a change in gain according to whether or not the notch filter is used exceeds the second threshold as a result of the determination of step (b). Characterized by including.

Disc drive according to the present invention to achieve the above another technical problem is to move the transducer in response to the servo control signal, the voice coil motor actuator for generating a control signal; Generating a servo control signal for controlling the voice coil motor by using the control signal, generating control signals corresponding to a notch filter adjustment mode, and the notch when the cutoff frequency interval between the notch filters is within a predetermined range. A controller that adjusts the notch filter coefficients so as to vary the cutoff gain of the notch filter so that a change in gain according to whether the notch filter is used or not is not generated in a frequency band between cutoff frequencies between filters; An excitation signal generator for generating an excitation signal for exciting a disc drive in accordance with the control signal; A synthesizer for synthesizing the excitation signal with the control signal; A plurality of notch filters for filtering and outputting the servo control signal by applying the notch filter coefficients adjusted by the controller; And a servo control signal output from the controller to a first input terminal and a filtered servo control signal output to the plurality of notch filters to a second input terminal, respectively, and input to the first input terminal according to the control signal. And a multiplexer for outputting a signal to the voice coil motor actuator or for switching a signal input to a second input terminal to the voice coil motor actuator.

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

The hard disk drive, which is a data storage device to which the characteristic adjustment method of the notch filter according to the present invention is applied, is composed of a combination of an electrical circuit and a head disk assembly (HDA) composed of mechanical components.

1 shows a configuration of a head disk assembly (HDA) 10 of a hard disk drive to which the present invention is applied.

The head disk assembly 10 includes at least one magnetic disk 12 that is rotated by the spindle motor 14. The disk drive also includes a transducer 16 located adjacent to the surface of the disk 12.

The transducer 16 can read or write information on the rotating disk 12 by sensing and magnetizing the magnetic field of each disk 12. Typically transducer 16 faces the surface of each disk 12. Although illustrated and described as a single transducer 16, it should be understood that this consists of a write transducer for magnetizing the disc 12 and a separate read transducer for sensing the magnetic field of the disc 12. Read transducers are constructed from Magneto-Resistive (MR) devices. The transducer 16 is also commonly referred to as a head.

The transducer 16 can be integrated into the slider 20. The slider 20 is structured to create an air bearing between the transducer 16 and the surface of the disk 12. The slider 20 is coupled to the head gimbal assembly 22. The head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacent to the magnetic assembly 28 that specifies the voice coil motor 30 (VCM). The current supplied to the voice coil 26 generates a torque for rotating the actuator arm 24 relative to the bearing assembly 32. Rotation of the actuator arm 24 will move the transducer 16 across the disk 12 surface.

The information is typically stored in an annular track of the disc 12. Each track 34 generally includes a plurality of sectors. Each sector includes a data field and an identification field. The identification field is composed of a gray code identifying a sector and a track (cylinder). The transducer 16 is moved across the surface of the disc 12 to read or write information on other tracks.

The disk 12 is largely divided into a user area and a non-user area. The user area is an area where the user can substantially write or read data, and the non-user area is an area for storing information related to the disk drive.

2 shows a circuit configuration of the characteristic adjusting device of the notch filter according to the present invention.

The characteristic adjusting device of the notch filter according to the present invention includes a controller 210, an excitation signal generator 220, a synthesis unit 230, a plurality of notch filters 240; 240-1, 240-2, ..., 240 N), multiplexer 250, voice coil motor (VCM) actuator 260, and memory 270.

First, a method of detecting the resonant frequency of the disc drive will be described.

In order to detect the resonance frequency, the controller 210 generates an excitation signal by turning on the excitation signal generator 220. The excitation signal is a synthesized signal of all predicted resonant frequency components.

The excitation signal generated by the excitation signal generator 220 is synthesized by the servo control signal generated by the VCM actuator 260 and the synthesis unit 230 and applied to the controller 210. Here, the servo control signal is a position error signal PES.

The controller 210 generates a servo control signal for controlling the voice coil motor so that the transducer is located at the center of the target track using the servo control signal synthesized with the excitation signal.

The multiplexer 250 directly applies the servo control signal generated by the controller 210 to the VCM actuator 260 or after passing the notch filter 240 through the servo control signal generated by the controller 210. Whether to apply to 260 is selected according to the control signal of the controller 210.

In the resonance frequency detection mode, the controller 210 generates a control signal to directly apply the servo control signal to the VCM actuator 260 without passing through the plurality of notch filters 240.

Accordingly, the VCM actuator 260 is vibrated by the excitation signal generated by the excitation signal generator 220 driven according to the current applied to the voice coil motor.

The excitation signal is reflected on the position error signal PES generated by the VCM actuator 260 and output.

The controller 210 performs a function of estimating the resonance frequency from the position error signal, and a detailed principle of estimating the resonance frequency is disclosed in Korean Patent Application Publication No. 10-2004-70478 filed by the present applicant. Mechanical resonance compensation apparatus and method using a type notch filter ".

Then, filter coefficients of each of the plurality of notch filters 240 are determined to remove resonance frequency components affecting the system based on the determined resonance frequency, and the filter coefficients are stored in the memory 270.

At this time, the cutoff gain of the notch filters for removing the resonance frequency is constantly determined to be a default value sufficient to remove the resonance frequency.

Next, a method of adaptively adjusting the initial filter coefficients of the notch filters thus determined will be described in detail.

In the notch filter adjustment mode, the controller 210 does not generate a boost greater than a certain amount due to the use of the notch filter in the frequency band between the cutoff frequencies between the notch filters within a predetermined range. Adjust the notch filter coefficients to vary the cutoff gain of the notch filter.

That is, the controller 210 determines the adjacent cutoff frequencies between the notch filters when adjacent cutoff frequency intervals f _ci ˜ f _cj between the notch filters constituting the plurality of notch filters are smaller than the first threshold value f _th . A process for determining whether a boost phenomenon occurs due to the use of a notch filter in the frequency band between (f _ci , f _cj ) and a boost phenomenon due to the use of a notch filter in the frequency band between cutoff frequencies between the notch filters. Is designed to execute a process of adjusting the notch filter coefficients to lower the cutoff gain of the notch filter within a range where the frequency response characteristic of the notch filter satisfies the design specification.

Next, a method of adjusting the characteristics of the notch filter according to the present invention, which is executed under the control of the controller 210, will be described in detail with reference to the flowchart of FIG. 3.

First, the controller 210 determines whether adjacent cutoff frequency intervals f _ci ˜ f _cj of the notch filters for removing the resonance frequency are smaller than the first threshold value f _th (S301). Here, the first threshold value f _th corresponds to a width of a critical frequency interval in which a boost phenomenon may be generated by the notch filter, and may be determined through an experiment.

As a result of the determination in step 301 (S301), when the adjacent cutoff frequency intervals of the notch filters are smaller than the first threshold value f _th , the controller 210 controls the excitation signal generator 220 to control the frequency between the cutoff frequencies. The band f _ci to f _cj is _excited (S302).

After having the band f _ci to f _cj between the corresponding cutoff frequencies according to step 302 (S302), the gain value GAIN_ON in the band f _ci to f _cj between the cutoff frequencies is obtained in the notch filter ON mode. In the notch filter OFF mode, the gain value GAIN_OFF in the band f _ci to f _cj between cutoff frequencies is obtained (S303). The notch filter OFF mode refers to a mode in which the servo control signal output from the controller 210 is directly applied to the VCM actuator 260 without passing through a plurality of notch filters by controlling the multiplexer 250. The notch filter ON mode refers to a mode in which the multiplexer 250 is controlled to apply the servo control signal output from the controller 210 to the VCM actuator 260 after passing through a plurality of notch filters.

Then, from the gain value GAIN_ON obtained from the bands f _ci to f _cj between the cutoff frequencies in the notch filter ON mode, the gain value obtained from the band f _ci to f _cj between the cutoff frequencies in the notch filter OFF mode is then obtained ( The difference G_diff of GAIN_OFF) is calculated (S304).

Next, the size of the G_diff calculated in step 304 (S304) and the second threshold value G _th is compared (S305).

When the comparison result of step 305 (S305), G_diff is greater than the second threshold (G _th ), it corresponds to the case where a boost phenomenon occurs, in this case notch filter NF (i) having a cutoff frequency f _ci and f _cj And filter coefficients are adjusted to lower each cutoff gain currently set in NF (j) by [Delta] G (S306). Here, ΔG means the amount of gain change in units of one step. Here, the filter coefficients may be adjusted using a lookup table that sets the filter coefficient value according to the cutoff gain value as an example. In this case, of course, the lookup table is stored in the memory 270.

After adjusting the filter coefficients according to step 306 (S306), the notch filter frequency characteristic, which is a performance of removing resonance frequencies in notch filters NF (i) and NF (j), is examined (S307). In other words, after the system is provided that the resonant frequency component can be sufficiently removed even after adjusting the filter coefficients, the gain value at the cutoff frequency is obtained and the notch filter frequency characteristic is examined.

Then, it is determined whether the notch filter frequency characteristic test result standard is satisfied (S308). That is, if the gain value at the cutoff frequency exceeds a predetermined value after excitation of the notch filter frequency characteristic test result, it is outside the specification, otherwise it corresponds to the case where the specification is satisfied.

If the result of the determination in step 308 (S308) is satisfied, it is fed back to step 302 (S302) to check whether or not a boost has occurred.

If the determination result of step 308 (S308) does not satisfy the specification, each cutoff gain currently set in the notch filters NF (i) and NF (j) is increased by ?? G again and the step ends (S309). . This is to adjust the cutoff gain to attenuate the boost characteristic within a range that satisfies the frequency characteristic for resonant frequency rejection of the notch filter.

When G_diff is not greater than the second threshold value G _{th as a} result of the comparison in step 305 (S305), since the boost phenomenon does not occur, the step is terminated without changing the currently set filter coefficients.

By such a method, the notch filter coefficients can be adaptively adjusted to prevent the occurrence of a boost phenomenon due to the use of the notch filter within a range satisfying the resonance frequency component removal characteristic of the notch filter.

 The invention can be practiced as a method, apparatus, system, or the like. When implemented in software, the constituent means of the present invention are code segments that necessarily perform the necessary work. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROM (EROM), floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, Etc. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described.

As described above, according to the present invention, by automatically adjusting the filter coefficients of the notch filter to minimize the occurrence of a boost phenomenon in the cutoff adjacent frequency band of the notch filters, it is possible to stably control the system while effectively removing the resonance frequency. That effect is produced.

Claims (5)

(a) determining whether cutoff frequency intervals between the notch filters are less than the first threshold value; (b) when the cutoff frequency interval between the notch filters is smaller than a first threshold as a result of the determination of step (a), gain according to whether the notch filter is used or not in the frequency band between the cutoff frequencies between the notch filters; Determining whether the change of the value exceeds the second threshold value; And (c) adjusting the notch filter coefficients to lower the cutoff gain of the notch filter when a change in gain according to whether or not the notch filter is used exceeds the second threshold as a result of the determination of step (b). And a method for adjusting the characteristics of a notch filter. The method of claim 1, wherein the adjustment of the notch filter coefficient is performed within a range that satisfies the design specification of the cutoff frequency response characteristic of the notch filter. A voice coil motor actuator for moving the transducer in response to the servo control signal and generating a control signal; Generating a servo control signal for controlling the voice coil motor using the control signal, generating control signals corresponding to a notch filter adjustment mode, and when the cutoff frequency interval between the notch filters is within a predetermined range. A controller for adjusting the notch filter coefficients so as to vary the cutoff gain of the notch filter so that a change in gain according to whether or not the notch filter is used in a frequency band between cutoff frequencies between the notch filters is not generated by a predetermined amount or more; An excitation signal generator for generating an excitation signal for exciting a disc drive in accordance with the control signal; A synthesizer for synthesizing the excitation signal with the control signal; A plurality of notch filters for filtering and outputting the servo control signal by applying the notch filter coefficients adjusted by the controller; And The servo control signal output from the controller is connected to the first input terminal and the filtered servo control signal output to the plurality of notch filters to the second input terminal, respectively, and the signal input to the first input terminal according to the control signal. And a multiplexer for outputting the signal to the voice coil motor actuator or outputting a signal input to a second input terminal to the voice coil motor actuator. 4. The disk drive according to claim 3, wherein the adjustment of the notch filter coefficient is performed within a range that satisfies the design specification of the cutoff frequency response characteristic of the notch filter. The disk drive of claim 3, wherein the notch filter coefficients are adjusted using a lookup table that sets notch filter coefficient values according to a cutoff gain value.

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