Transient Response Improvement of the Robust Servomechanism Problem for Sinusoidal Signals

In this paper, the multi-input multi-output robust servomechanism problem for sinusoidal reference and/or disturbance signals having possibly unknown magnitude and/or phase components is examined. For the situation where such sinusoidal harmonic components are calibrated, for instance, via a priori tuning methods, simple initialization results are presented to reduce undesirable transient responses, and can be applied advantageously in a continuous-or discrete-time setting. Using this framework, additional optimization techniques then are developed and presented to minimize potentially undesirable tuning transients. Simulations are given using these new control design results when applied to a conventional hard disk drive system, where multiple harmonic disturbances may arise due to, for example, disk eccentricity or clamping effects. A comparison with another commonly-used harmonic cancellation method demonstrates and emphasizes the practical advantages and benefits that can be attained when using the proposed solution approach.