EP0361786A2
Expired / Lapsed
EP
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Disk file digita servo control
Assignee: International Business Machines Corp
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Filing: 1989-09-21
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Granted: —
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Expires: 2009-09-21
Abstract
Abstract A disk file digital servo control system utilizes a state estimator wherein the voice coil motor (VCM) (40) current is modeled, rather than measured, thereby eliminating the need for analog-to-digital conversion of the actual VCM current. The VCM current is fed back directly to the input to the power amplifier (42) where it is summed with the control signal output. This effectively changes the integrating power amplifier into a low pass filtering power amplifier, with linear input-output characteristics. Thus, during track following or short seeks, the VCM current is estimated based on this linear model. During long seeks, when the power amplifier is saturated, the VCM current is modeled based upon the known VCM characteristics during saturation, which include the effects of the back electromotive force and the coil current rise time. The microprocessor (50) in the digital servo control system determines which VCM current model to use by a determination of when the power amplifier is in saturation. In the preferred embodiment, the microprocessor determines power amplifier saturation based upon a value of the head velocity error, which is the difference between the commanded velocity and the estimated velocity.
Inventors
- 👤 James Chien-Chiung Chen
- 👤 Shih Ming Shih
- 👤 Mantle Man-Hon Yu
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 23:09
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/48; G11B5/54; G11B5/55; G11B5/5521; G11B5/5552; G11B5/5556; G11B5/556; G11B21/00; G11B21/02; G11B21/10; G11B21/106
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
207 words
A data recording disk file having at least one rotatable disk (10, 12) with generally concentric data tracks thereon, the data disk or a separate servo disk having servo information recorded thereon, at least one head (32) for reading the servo information during rotation of the disk, a voice coil motor (VCM) (40) attached to the head for positioning the head relative to the data tracks, means for deriving from the servo information a digital head position error signal (PES), a processor (50) for estimating the state variables of the VCM and for generating, from the estimated state variables and the digital PES, a digital control signal, means (62) for converting the digital control signal to an analog control signal, and a power amplifier (64) for amplifying the analog control signal and generating an input current for use by the VCM; the disk file being characterised by including means for providing direct feedback of the VCM current to the input of the power amplifier; and means for determining if the power amplifier is saturated; and by said processor (50) including means for making a first estimate of VCM current and for making a second estimate of VCM current in response to a determination of power amplifier saturation.
Claim 2
Dependent Claim
207 words
A data recording disk file having at least one rotatable disk (10, 12) with generally concentric data tracks thereon, the data disk or a separate servo disk having servo information recorded thereon, at least one head (32) for reading the servo information during rotation of the disk, a voice coil motor (VCM) (40) attached to the head for positioning the head relative to the data tracks, means for deriving from the servo information a digital head position error signal (PES), a processor (50) for estimating the state variables of the VCM and for generating, from the estimated state variables and the digital PES, a digital control signal, means (62) for converting the digital control signal to an analog control signal, and a power amplifier (64) for amplifying the analog control signal and generating an input current for use by the VCM; the disk file being characterised by including means for providing direct feedback of the VCM current to the input of the power amplifier; and means for determining if the power amplifier is saturated; and by said processor (50) including means for making a first estimate of VCM current and for making a second estimate of VCM current in response to a determination of power amplifier saturation.
Claim 3
Dependent Claim
50 words
A disk file as claimed in claim 1, wherein said saturation determining means further comprises means coupled to the power amplifier and the processor for comparing the power amplifier voltage with a predetermined threshold and for generating a signal to the processor when said voltage is above said predetermined threshold.
Claim 4
Dependent Claim
74 words
A disk file as claimed in claim 1 or claim 2, wherein the disk file includes means for generating a commanded velocity of the head and wherein the estimated head velocity is one of the state variables of the VCM estimated by the processor, and wherein said power amplifier saturation determining means further comprises means in said processor for comparing the difference between the commanded velocity and the estimated velocity with a predetermined value.
Claim 5
Dependent Claim
255 words
A data recording disk file having at least one rotatable disk with generally concentric data tracks thereon, the data disk or a separate servo disk having servo information recorded thereon, at least one head for reading the servo information during rotation of the disk, a voice coil motor (VCM) attached to the head and responsive to an input current for positioning the head relative to the data tracks, and means for deriving from the servo information a digital head position error signal (PES); a microprocessor coupled to the digital PES deriving means and responsive to the digital PES for generating a digital control signal, the microprocessor including means for estimating the VCM state variables, including VCM current, from predetermined estimator constants; means coupled to the microprocessor for converting the digital control signal to an analog control signal; a power amplifier coupled between the digital-to-analog conversion means and the VCM and responsive to the analog control signal for generating a VCM input current; means for providing direct feedback of the VCM input current to the input of the power amplifier, whereby the VCM input current is summed with the analog control signal; means for determining if the power amplifier is saturated; and wherein said estimating means in the microprocessor includes means for computing a first estimate of VCM current from a predetermined value of power amplifier bandwidth, and means responsive to a determination of power amplifier saturation for computing a second estimate of VCM current from predetermined values of VCM coil current resistance and rise time.
Claim 6
Dependent Claim
255 words
A data recording disk file having at least one rotatable disk with generally concentric data tracks thereon, the data disk or a separate servo disk having servo information recorded thereon, at least one head for reading the servo information during rotation of the disk, a voice coil motor (VCM) attached to the head and responsive to an input current for positioning the head relative to the data tracks, and means for deriving from the servo information a digital head position error signal (PES); a microprocessor coupled to the digital PES deriving means and responsive to the digital PES for generating a digital control signal, the microprocessor including means for estimating the VCM state variables, including VCM current, from predetermined estimator constants; means coupled to the microprocessor for converting the digital control signal to an analog control signal; a power amplifier coupled between the digital-to-analog conversion means and the VCM and responsive to the analog control signal for generating a VCM input current; means for providing direct feedback of the VCM input current to the input of the power amplifier, whereby the VCM input current is summed with the analog control signal; means for determining if the power amplifier is saturated; and wherein said estimating means in the microprocessor includes means for computing a first estimate of VCM current from a predetermined value of power amplifier bandwidth, and means responsive to a determination of power amplifier saturation for computing a second estimate of VCM current from predetermined values of VCM coil current resistance and rise time.
References Cited (Backward Citations)
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