Control of Dual-Stage HDDs With Enhanced Repetitive Disturbance Rejection

2017 ◽  
Author(s):  
Shiying Zhou ◽  
Minghui Zheng ◽  
Xu Chen ◽  
Masayoshi Tomizuka
Keyword(s):  
Data Storage ◽  
Disturbance Rejection ◽  
Hard Disk Drives ◽  
Cost Effective ◽  
Error Tolerance ◽  
Disk Drives ◽  
Control Performance ◽  
Solid State Drives ◽  
Control Task ◽  
Dual Stage

Nowadays, despite the emerging adoption of the solid state drives, hard disk drives (HDDs) are still used extensively as cost-effective and reliable solutions for data storage. In addition to its usual application in desktops and laptops, HDDs become the primary storage medium for the data centers. The track following control task in HDD requires that the read/write head be positioned over the data track center at nano-scale accuracy, which requires an error tolerance about 7nm. Therefore, the dual-stage HDD is introduced to enhance the HDD control performance for extended bandwidth and improved disturbance rejection.

Application of Mixed H2/H∞ Data Driven Control Design to Dual Stage Hard Disk Drives

2018 ◽  
Author(s):  
Omid Bagherieh ◽  
Prateek Shah ◽  
Roberto Horowitz
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Hard Disk Drives ◽  
Control Design ◽  
Hard Disk ◽  
Data Driven ◽  
Disk Drives ◽  
Design Strategies ◽  
Data Driven Approach ◽  
Dual Stage

A data driven control design approach in the frequency domain is used to design track following feedback controllers for dual-stage hard disk drives using multiple data measurements. The advantage of the data driven approach over model based approach is that, in the former approach the controllers are directly designed from frequency responses of the plant, hence avoiding any model mismatch. The feedback controller is considered to have a Sensitivity Decoupling Structure. The data driven approach utilizes H∞ and H2 norms as the control objectives. The H∞ norm is used to shape the closed loop transfer functions and ensure closed loop stability. The H2 norm is used to constrain and/or minimize the variance of the relevant signals in time domain. The control objectives are posed as a locally convex optimization problem. Two design strategies for the dual-stage hard disk drive are presented.

scholarly journals Design and Implementation of Dual-Stage Track-Following Control for Hard Disk Drives

2009 ◽  
Author(s):  
Jianbin Nie ◽  
Roberto Horowitz
Keyword(s):  
Hard Disk Drives ◽  
Servo System ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Drives ◽  
Outer Loop ◽  
Servo Systems ◽  
Design And Implementation ◽  
Integral Action ◽  
Dual Stage

This paper discusses the design and implementation of two track-following controllers for dual-stage hard disk drive servo systems. The first controller is designed by combining an outer loop sensitivity-decoupling (SD) controller with an inner loop disturbance observer (DOB). The second is designed by combining mixed H2/H∞ synthesis techniques with an add-on integral action. The designed controllers were implemented and evaluated on a disk drive with a PZT-actuated suspension-based dual-stage servo system. Position error signal (PES) for the servo system was obtained by measuring the slider displacement with an LDV and injecting a simulated track runout.

High-bandwidth controller design for dual-stage actuator system in hard disk drives

2022 ◽  
pp. 107754632110623
Author(s):  
Shota Yabui ◽  
Takenori Atsumi
Keyword(s):  
Controller Design ◽  
Hard Disk Drives ◽  
Voice Coil Motor ◽  
Hard Disk ◽  
Disk Drives ◽  
Positioning Accuracy ◽  
Micro Actuator ◽  
Dual Stage ◽  
Actuator System ◽  
Dual Stage Actuator

Large-capacity hard disk drives are important for the development of an information society. The capacities of hard disk drives depend on the positioning accuracy of magnetic heads, which read and write digital data, in disk-positioning control systems. Therefore, it is necessary to improve positioning accuracy to develop hard disk drives with large capacities. Hard disk drives employ dual-stage actuator systems to accurately control the magnetic heads. A dual-stage actuator system consists of a voice coil motor and micro-actuator. In micro-actuators, there is a trade-off between head-positioning accuracy and stroke limitation. In particular, in a conventional controller design, the micro-actuator is required to actuate such that it compensates for low-frequency vibration. To overcome this trade-off, this study proposes a high-bandwidth controller design for the micro-actuator in a dual-stage actuator system. The proposed method can reduce the required stroke of the micro-actuator by increasing the gain of the feedback controller of the voice coil motor at low frequencies. Although the voice coil motor control loop becomes unstable, the micro-actuator stabilizes the entire feedback loop at high frequencies. As a result, the control system improves the positioning accuracy compared to that achieved by conventional control methods, and the required micro-actuator stroke is reduced.

Multi-frequency disturbance rejection via blending control technique for hard disk drives

Automatica ◽  
2009 ◽  
Vol 45 (10) ◽  
pp. 2244-2249 ◽  
Author(s):  
Chunling Du ◽  
Lihua Xie ◽  
F.L. Lewis ◽  
Youyi Wang
Keyword(s):  
Disturbance Rejection ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Control Technique ◽  
Disk Drives

NANOSCIENCE AND NANOTECHNOLOGY FOR MEMORY AND DATA STORAGE

COSMOS ◽  
2011 ◽  
Vol 07 (01) ◽  
pp. 25-30
Author(s):  
T. TAHMASEBI ◽  
S. N. PIRAMANAYAGAM
Keyword(s):  
Data Storage ◽  
Hard Disk Drives ◽  
Random Access ◽  
Hard Disk ◽  
Recording Media ◽  
Disk Drives ◽  
Magnetic Recording Media ◽  
Access Memory ◽  
Magnetic Random Access Memory ◽  
The Core

Data storage is one area of technology where nanotechnology has been used even before the term nanotechnology became very popular. The magnetic recording media — the disk that stores information in hard disk drives — used nanotechnology in the late 1990s, in the form of grains which are 15 nm or less in diameter (the grains in current technology are about 8 nm in diameter). The reading sensors of hard disk also make use of thin nanostructures in several dimensions to read information from the recording media. This paper introduces the technology behind the magnetic random access memory and related topics, which form the core of the symposium L of ICMAT 2011, which is titled "Memory, Nanomagnetics, Materials and Devices".

Rupture and Reformation of Ultra-Thin Surface Films

2010 ◽  
Author(s):  
William W. F. Chong ◽  
Mircea Teodorescu ◽  
Homer Rahnejat
Keyword(s):  
Thin Film ◽  
Data Storage ◽  
Surface Film ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Surface Films ◽  
Disk Drives ◽  
Film Rupture ◽  
Near Surface ◽  
Ultra Thin Film

In lubricated contact conjunctions film ruptures close to the exit boundary. This significantly affects the load carrying capacity and can lead to direct surface interactions. Nano-scale films (several molecular diameters of the lubricant) are no exception, a fact that has been observed using ellipsometry studies for ultra-thin film conjunctions representative for high storage capacity hard disk drives. Immediately beyond the film rupture an area of cavitation occurs and the continuity of flow condition is breached. It has been shown that for molecularly smooth surfaces solvation effect becomes dominant. This means that the contact exit is subject to discrete drainage of lubricant and may be devoid of a sufficient lubricant for film reformation to occur. This can be a stumbling block in an increasing quest to increase the data storage density of hard disk drives. Wear can become a problem as well as non-uniformity of free surface film at the inlet meniscus. It has been noted that peaks of lubricant can gather in some places, a phenomenon referred to as lubricant mogul. These localized piles of lubricant can exceed the nominally aimed for lubricant film thickness necessary for a given data storage level. This paper carries out an in-depth prediction of ultra thin film lubricant behavior through the contact. Hydrodynamic as well as near surface effects and intermolecular interactions responsible for the supply, formation, cavitation and reformation of thin films in the slider-disk conjunction have been considered.

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