Optimization method and apparatus for a generalized fourier seek trajectory for a hard disk drive servomechanism

Abstract

A method and apparatus for moving a transducer across a disk surface in accordance with generalized Fourier seek trajectories for position, velocity, and acceleration control. The generalized Fourier acceleration trajectory includes one or more sine functions with the coefficients determined using a least-mean-square-error technique, which optimizes the selection of the trajectory. The corresponding velocity and position trajectories are derived based on the selected acceleration trajectory. The generalized Fourier seek method and apparatus provides improved performance and robustness of hard disk drive servomechanism, including shorter seek time. Additionally, the hard disk drive is more immune to external disturbances, and the acoustic noise caused by seeking is reduced. Using the generalized Fourier seek method, the duration of acceleration and deceleration modes may be equal or different. An acceleration seek trajectory, in general, is typically composed of an acceleration phase for acceleration mode, a zero acceleration phase for coast mode, and a negative acceleration phase for deceleration mode. The deceleration is a negative mirror image of the acceleration when the durations of acceleration and deceleration modes are the same. The acceleration (or deceleration as its mirror image) mode can be divided into a ramp-up acceleration stage, a constant acceleration stage, and a ramp-down acceleration stage. The introduction of the constant acceleration (or deceleration) stage eliminates the updates of sine states and cosine states, which are necessary when following design seek trajectories. Consequently, computational time taken by a digital signal processor is saved, further enhancing the efficiency of the generalized Fourier seek method.

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