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Detection of mechanical defects in a disc drive using injected test signals

  • US 5,654,841 A
  • Filed: 07/07/1995
  • Issued: 08/05/1997
  • Est. Priority Date: 07/07/1995
  • Status: Expired due to Fees
First Claim
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1. In a disc drive having a disc and an actuator adjacent the disc, the actuator having a transducer positionably adjacent any selected one of a plurality of tracks on the disc surface, the disc drive having a servo control circuit operable as a servo loop for generating a correction signal in response to an incoming servo position error signal received from the transducer, the servo position error signal indicative of the relative position of the transducer to the selected track, the correction signal controlling the output of current from an actuator driver to an actuator coil to position the transducer with respect to the selected track in response to the servo position error signal, wherein the servo position error signal is obtained from the transducer in each of a succession of time intervals, a method for detecting mechanical defects in the disc drive comprising the steps of:

  • injecting a test signal having a selected frequency and magnitude into the incoming servo position error signal to generate a modified servo position error signal;

    using the modified servo position error signal to generate a correction signal to control the current supplied to the actuator coil by the actuator driver;

    sampling and accumulating data from the incoming servo position error signal to characterize the magnitude of a resonant signal in the incoming servo position error signal, the resonant signal having a frequency substantially equal to the test signal frequency;

    determining a ratio of the magnitude of the resonant signal in the incoming servo position error signal to the magnitude of the test signal in the modified servo position error signal; and

    providing an indication when the ratio exceeds a preselected limit.

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