A Variable Structure Multi-rate State Estimator and Its Application to Seeking Control of HDDs

Abstract

In this paper, we propose a new multi-rate state estimator, which has a proportional, integral, and discontinuous error feedback structure to improve robustness. Conventional linear state estimators do not have enough accuracy under the existence of external disturbance and model uncertainty. With our proposed estimator, output tracking performance can have better robustness. We mainly focus its application on a system that has a hardware difficulty of obtaining high enough measurement sampling frequency, e.g., Hard Disk Drives. Integral and discontinuous actions are introduced to alleviate the estimation error caused by the disturbance and model uncertainty, while multi-rate technique is to obtain a smoother control input and higher bandwidth. Integral action and multi-rate technique also work as reducing the chattering motion caused by the discontinuous action. Simulations and experiments have been carried out to validate our proposed multi-rate state estimator. Finally, an experimental example of seeking control for a single stage actuated hard disk drive is demonstrated.