Abstract
In hard disk drives (HDD), an important issue related to increased storage density is the tribological problem of the head/disk interface. The conventional head gimbal assembly (HGA) of the HDD is used in a contact start/stop mode which results in wear particles and debris. This may cause a serious problem for the read/write function. In this paper, we propose a new type of suspension featuring a shape memory alloy (SMA) actuator in order to prevent friction between the head (slider) and disk. As a first step, a finite element analysis is undertaken to investigate modal characteristics of the proposed HGA. Using the principal modal parameters, such as natural frequency, a control system model is established and a sliding mode control algorithm to achieve a non-contact start/stop (non-CSS) mode is formulated. The key control principle for accomplishing the non-CSS mode is that the control input is to be employed in the SMA actuator before the disk rotates, and is disconnected when the angular velocity of the disk is fully developed to achieve a certain flying height. In order to demonstrate the effectiveness of the proposed control system, a conventional HGA is modified to integrate the SMA actuator. The control algorithm is experimentally realized and controlled motions for the non-CSS mode are presented in the time domain.
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