Digital servo system with loop gain calibration
DC CAFC
First Claim
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1. A method of calibrating a loop gain of a loop gain amplifier in a digital servo system, comprising:
- receiving optical signals from an optical pick-up unit in an optical disk drive;
closing the digital servo system with a first loop gain, the digital servo system calculating a control signal based on the optical signals;
applying a sinusoidal disturbance at a cross-over frequency to the control signal generated by the digital servo system to form a second control signal;
controlling a position of the optical pick-up unit with the second control signal;
calculating a discrete Fourier transform of the sinusoidal disturbance at the cross-over frequency to form a disturbance DFT;
calculating a discrete Fourier transform of the control signal to form a signal DFT;
calculating a measured loop gain from a ratio of the disturbance DFT and the signal DFT; and
calculating the loop gain from a ratio between the first loop gain and the measured loop gain.
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Abstract
A calibration of a loop gain in a digital servo system is presented. The loop gain can be calibrated measuring the response in a control signal generated by the digital servo system when the control signal is replaced by a sum of the control signal and a sinusoidal disturbance. The loop gain can be set to provide a desired gain, for example unity, between the control signal and the sinusoidal disturbance at a cross-over frequency.
66 Citations
16 Claims
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1. A method of calibrating a loop gain of a loop gain amplifier in a digital servo system, comprising:
- receiving optical signals from an optical pick-up unit in an optical disk drive;
closing the digital servo system with a first loop gain, the digital servo system calculating a control signal based on the optical signals;
applying a sinusoidal disturbance at a cross-over frequency to the control signal generated by the digital servo system to form a second control signal;
controlling a position of the optical pick-up unit with the second control signal;
calculating a discrete Fourier transform of the sinusoidal disturbance at the cross-over frequency to form a disturbance DFT;
calculating a discrete Fourier transform of the control signal to form a signal DFT;
calculating a measured loop gain from a ratio of the disturbance DFT and the signal DFT; and
calculating the loop gain from a ratio between the first loop gain and the measured loop gain. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- receiving optical signals from an optical pick-up unit in an optical disk drive;
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9. An optical disk drive, comprising:
- an optical pick-up unit;
an analog processor coupled to receive signals from detectors in the optical pick-up unit and provide digital signals;
at least one processor coupled to receive the digital signals, the at least one processor calculating at least one control signal; and
a driver coupled to control a position of the optical pick-up unit in response to the at least one control signal, wherein the at least one processor executes an algorithm that closes a digital servo system with a loop gain amplifier with a first loop gain, the digital servo system calculating a control signal based on the digital signals, applies a sinusoidal disturbance at a cross-over frequency to the control signal generated by the digital servo system to form a second control signal, substitutes the second control signal for the control signal, calculates a discrete Fourier transform of the sinusoidal disturbance at the cross-over frequency to form a disturbance DFT, calculates a discrete Fourier transform of the control signal to form a signal DFT, calculates a measured loop gain from a ratio of the disturbance DFT and the signal DFT, and calculates a loop gain from a ratio between the first loop gain and the measured loop gain. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
- an optical pick-up unit;
Specification
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Litigation Data
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Current AssigneeRPX Corporation
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Original AssigneeDPHI Acquisitions, Inc.
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InventorsWatt, Charles R., Wach, Hans B., Kadlec, Ron J.
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Primary Examiner(s)EDUN, MOHAMMAD N
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Application NumberUS09/950,519Publication NumberTime in Patent Office1,366 DaysField of Search369/44.27, 369/44.28, 369/44.29, 369/44.31, 369/44.32, 369/44.35, 369/44.36, 369/47.1, 369/53.1, 369/53.28, 369/59.1, 369/124.01, 369/124.11, 369/124.12, 369/124.13US Class Current369/44.29CPC Class CodesG11B 7/0945 Methods for initialising se...G11B 7/0946 specially adapted for opera...G11B 7/0948 specially adapted for detec...
