Method for harmonic frequency identification in a disc drive

A disc drive device, comprising:

• a base;
• a disc rotatably attached to the base;
• an actuator arm for carrying a transducer head in a transducing relation with respect to the disc;
• a disc drive controller, coupled to the actuator arm, the disc drive controller further including a servo controller, coupled to the actuator arm, the servo controller monitoring a position error signal in order to follow a track on the disc drive;
• and
• a microprocessor for determining a dominant frequency in the disc drive, the microprocessor
• sampling the position error signal,
• determining a rate of change of the position error signal with respect to time,
• calculating a quotient of the rate of change of the position error signal with respect to time and the position error signal, and
• comparing the quotient to a selected quotient value.

A disc drive, comprising:

• a base;
• an actuator arm rotatably attached to the base;
• at least one disc rotatably attached to the base, where the actuator arm carries a transducer head in a transducing relation with respect to the disc;
• means for determining a dominant frequency for the disc drive based on an observed rate of change of a position error signal associated with the transducing relation.