Control Methods in Data-Storage Systems

Abstract

Abstract-The recording performance of data-storage devices, in which write/read elements move relative to a storage medium to reliably store and retrieve information, depends on the capability of servo mechanisms to provide the necessary positioning accuracy. The desired characteristics of servo mechanisms for datastorage systems include robustness against variations of environmental parameters, high resolution, accuracy, stability, and fast response. This paper presents a comprehensive overview of advanced servo-control methods for data storage. The applications are to well-established recording technologies, including magnetic tape and magnetic disk systems as well as CD/DVD/Blue-Ray optical data-storage systems. Moreover, newer holographic and nearfield optical systems and the emerging probe-storage technology are also addressed. Emphasis is given to the potential exhibited by the technologies considered for achieving ultra-high storage capacity, as required by the exploding demand in data-storage capacity for archival systems and massive multimedia data storage.Index Terms-Control systems, hard-disk drive, holographic data storage, optical-disk drive, scanning-probe data storage, servomechanism, tape drive.

Sinusoidal Servocompensator Implementations With Real-Time Requirements and Applications

“…Theorem 3, together with (4) and (5) in Lemma 1, unifies the different feedforward forms given by (6), (16) [with (a, b) = (1, 2)], and (3), and can facilitate direct conversions or initializations between these autonomous configurations when e(k) = 0. For instance, with (ι, j, ϕ) = (0, 1, 0), it follows using (6) that…”

“…When inherent rotational or repetitive processes need to be controlled, for instance, in data storage devices, such as hard disk drives (HDDs), CD-ROM, and DVD/Blu-Ray disk players, regulation and rejection of multiple sinusoidal harmonic signals play an important role in attaining acceptable overall system performance [5]. Given the vast proliferation and continual usage of these electromechanical devices and their constantly increasing areal density storage and reliability requirements, it, therefore, is necessary to have computationally accurate, robust, and efficient methods to asymptotically regulate or reject such sinusoidal harmonic signals.…”

Analysis of beam spot deviation considering vibration of components in optical pickup

“…A vibration model for an optical pickup is commonly substituted with the mechanical dynamics of an objective lens actuator using a frequency response function, which is represented as the ratio of the displacement of the objective lens to the current applied to the coils (Kim et al, 2011 andCherubini et. al., 2012), referred to as HA ( f ).…”

Dynamic Head-Disk Interface Modeling and Adaptive Control of a Hybrid Actuator for Optical Data Storage Systems

“…Therefore, NFR will not be achieved until the issue of flying height control is successfully addressed. [3,4] Considering the proven technique of flying slider application in hard disk drives (HDD), which can effectively eliminate the collision phenomenon, in this article a hybrid actuator system combining the traditional voice coil actuator with the flying slider technology is studied. [5,6] As the optical disk rotates, the flying slider relies on an air bearing surface (ABS) with positive and negative pressure pockets to build up the air pressure on which the slider floats.…”

“…In DVD systems, the PID controller or lead-lag controller are normally used in the focus servo loop to deal with the lens-disk gap variation which is mainly caused by the disk surface vibration. [3,4] The controller should be properly designed in order to obtain a satisfactory open loop sensitivity curve, where a high gain of the controller is expected in the disturbance frequency range. Since the disturbances are closely related to the disk rotational frequency, the lens-disk gap variation can be handled by increasing the low frequency gain of the controller.…”