Abstract: A magnetic recording disk drive has a disturbance sensor and a disturbance frequency identifier that are used to adjust the frequency of a peak filter as the disturbance frequency changes. The sensor and the frequency identifier are separate from the servo control loop and thus do not rely on the head position error signal (PES) to predict the disturbance frequency. The adjustable peak filter is coupled in parallel with the servo feedback controller. The peak filter modifies the open loop transfer function and the error rejection function of the servo control loop to provide a higher rejection at the identified frequency. The peak filter may be switched out of or uncoupled from the servo feedback controller during track-seeking or as desired, depending on the amplitude of the sensor signal or the amplitude of the PES.

Abstract: A method and tool for measurement of the roll static attitude and y-misalignment of magnetic recording sliders within the head stack assembly having reference elements placed on the deposited end of the magnetic recording slider, which are optically analyzed by a video camera connected to a computer. For fast measurement the head stack assembly is clamped in a fixture mounted on motorized stages, which move each slider into the measurement position. In a two step imaging and analyzing process, the orientation and location of one or more edges of the reference element are computed and compared with known control parameters.