Abstract
The hard disk drive (HDD) industry continues to meet the ever growing demand for storage capacity by increasing both the number of tracks on the disk surface and the number of bits recorded per track. Basically, the contact dynamics of slider involves strong nonlinearity and uncertainty. How to control slider to reduce touchdown instability and eventually eliminate bouncing has been a pressing and challenging research topic. To improve the active slider system performance, it is necessary to reduce or eliminate vibration induced by the uncertain dynamics. There are many control methods dedicated to address this challenging issue. Fewer results are available in the case when not all states are directly measured. The velocity is usually measured by a velocity tachometer, which is expensive and often contaminated by noise. One possible solution is to implement a velocity estimation, so it is very meaning to study state estimate- based dynamics control of active slider in touchdown. This paper aims to develop a state estimate- based adaptive fuzzy control techniques for controlling active slider in touchdown. A fuzzy state estimator is proposed to estimate the state variables for velocity variable. Under some conditions, it is shown that such a state estimator guarantees the uniformly ultimate bounded (UUB) of the estimate error. Based on system input-output data and our proposed state estimator, a robust adaptive fuzzy output-feedback control scheme is presented to control uncertain active slider in touchdown. The adaptive fuzzy output-feedback controller can guarantee the uniformly ultimate bounded of the tracking error of the closed-loop system. The results demonstrate that our proposed techniques have good potential in controlling active slider with uncertainty and unknown state.
