Abstract: A method and apparatus for efficiently calculating notch filter coefficients for a disc drive actuator arm control system is disclosed. In a preferred embodiment, filter coefficients for a z-domain notch-filter transfer function are calculated in fixed-point arithmetic from polynomial interpolations of the non-linear functions that define the coefficients in terms of the notch frequency. These non-linear functions may be derived and interpolated a priori by applying the bilinear transform to an s-domain notch transfer function. Since, in a preferred embodiment, the z-domain transfer function can be expressed as a fraction, the numerator and denominator of the transfer function can be scaled so as to allow the coefficients to be expressed as integers, thus making it possible to calculate the filter coefficients from the aforementioned polynomial interpolations using fixed-point math.

Abstract: A shared state controller is provided that optimizes for settle, rotational vibration, and track following. The shared state controller uses the same state update equation with different output equations for settle and track follow. Two or more different track follow output equations may also be used. Switching logic determines which output equation to use in the controller. The shared state controller switches between a settle controller and a track follow controller based on the state of the actuator. In addition, the shared state controller may also switch between two or more track follow controllers based upon other parameters.

Abstract: A disc drive assembly includes a magnetic disc mounted on a hub of a spindle motor. The spindle motor includes a base portion supporting the hub for rotation about a spindle axis. A bottom surface of the base portion extends outside of an internal disc drive environment, and a damper affixed to the bottom surface of the base portion attenuates vibrations within the base portion of the spindle motor. A constrain layer of the damper is secured to the bottom surface of the base portion by an adhesive, and the constrain layer is sufficiently stiff to dampen resonant vibrations such as rocking mode vibrations.

Abstract: A disc drive assembly includes a magnetic disc mounted on a hub of a spindle motor. The spindle motor includes a base portion supporting the hub for rotation about a spindle axis. A bottom surface of the base portion extends outside of an internal disc drive environment, and a damper affixed to the bottom surface of the base portion attenuates vibrations within the base portion of the spindle motor. A constrain layer of the damper is secured to the bottom surface of the base portion by an adhesive, and the constrain layer is sufficiently stiff to dampen resonant vibrations such as rocking mode vibrations.