Digital servo system with loop gain calibration
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.
62 Citations
17 Claims
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1. A method of calibrating a loop gain of a loop gain amplifier in a digital servo system, comprising:
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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)
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9. An optical disk drive, comprising:
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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)
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17. An optical disk drive, comprising:
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means for controlling a position of an optical pick-up unit based on optical signals; and
means for calibrating a loop gain of the means for controlling.
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Specification
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Current AssigneeRPX Corporation
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Original AssigneeDataPlay, Inc. (DPHI Incorporated)
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InventorsKadlec, Ron J., Wach, Hans B., Watt, Charles R.
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Granted Patent
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Time in Patent OfficeDays
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Field of Search
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US Class Current369/44.29
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CPC Class CodesG11B 7/0945 Methods for initialising se...G11B 7/0946 specially adapted for opera...G11B 7/0948 specially adapted for detec...
