A variable structure multirate State estimator for seeking control of HDDs

This paper is concerned with a new multirate state estimator for the seeking control of hard disk drives (HDDs), which has a proportional, integral, and discontinuous error feedback structure to improve robustness. Conventional linear state estimators do not have sufficient accuracy under the existence of external disturbances and model uncertainty. With our proposed estimator, output-tracking performance can achieve improved robustness. Integral and discontinuous actions are introduced to alleviate the estimation error caused by disturbances and model uncertainty, while the multirate technique is used to obtain a smoother control input and higher bandwidth. Integral action and the multirate technique also alleviate the chattering caused by the discontinuous control action. Simulations and experiments have been carried out to validate our proposed multirate state estimator. Finally, an experimental implementation of proposed seeking control for single-stage and dual-stage actuated hard disk drives is demonstrated.