Abstract: In a hard disk drive (HDD), biases are measured across all zones of a disk, and nonlinear bias components are extracted. Upon a change in operational condition of the HDD, biases are measured at two reference positions on the disk so as to estimate a corresponding change in a linear bias component across all zones of the disk. The bias at a given position of the disk is then calculated based on the estimated linear bias component and the extracted nonlinear bias component.

Abstract: A servo control method of controlling a plant to track a reference trajectory with enhanced accuracy using a reference signal and its derivative signals, an apparatus and a recording medium suitable for same. The servo control method includes: determining a polynomial indicating a reference trajectory desired by a plant and derivatives of the polynomial; sampling a plant output with respect to a plant input; generating a reference signal and its derivative signals with reference to a time between samples (a relative time); and determining a plant input at a sampling time using the generated reference signal and its derivative signals, a delayed plant input and a delayed plant output. Accordingly, a plant is controlled to track a reference trajectory with enhanced accuracy using a reference signal and its derivative signals.

Abstract: In a hard disk drive (HDD), biases are measured across all zones of a disk, and nonlinear bias components are extracted. Upon a change in operational condition of the HDD, biases are measured at two reference positions on the disk so as to estimate a corresponding change in a linear bias component across all zones of the disk. The bias at a given position of the disk is then calculated based on the estimated linear bias component and the extracted nonlinear bias component.

Abstract: A method, an apparatus and a computer readable recording medium storing a program for correctly detecting a free fall by referring to an acceleration and an integration of the acceleration. The method includes sensing an acceleration of the mobile device; integrating the sensed acceleration with respect to time; and determining the free fall by comparing the result of the integrating with a predetermined area threshold.

Abstract: A servo control method of controlling a plant to track a reference trajectory with enhanced accuracy using a reference signal and its derivative signals, an apparatus and a recording medium suitable for same. The servo control method includes: determining a polynomial indicating a reference trajectory desired by a plant and derivatives of the polynomial; sampling a plant output with respect to a plant input; generating a reference signal and its derivative signals with reference to a time between samples (a relative time); and determining a plant input at a sampling time using the generated reference signal and its derivative signals, a delayed plant input and a delayed plant output. Accordingly, a plant is controlled to track a reference trajectory with enhanced accuracy using a reference signal and its derivative signals.