Robust Control Synthesis Techniques for Multirate and Multisensing Track-Following Servo Systems in Hard Disk Drives

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Ryozo Nagamune ◽  
Xinghui Huang ◽  
Roberto Horowitz
Keyword(s):  
Controller Design ◽  
Linear Time ◽  
Hard Disk Drives ◽  
General System ◽  
Hard Disk ◽  
Disk Drive ◽  
Synthesis Problem ◽  
Control Synthesis ◽  
Linear Matrix ◽  
Advantages And Disadvantages

This paper proposes controller design methods, specially for track-following control of the magnetic read/write head in a hard disk drive (HDD). The servo system to be considered is a general dual-stage multisensing system, which encompasses most of the track-following configurations encountered in the HDD industry, including the traditional single-stage system. For the general system, a robust track-following problem is formulated as a time-varying version of the robust H2 synthesis problem. Both dynamic and real parametric uncertainties, which are typical model uncertainties in track-following control, are taken into account in the formulation. Three optimal robust controller design techniques with different robustness guarantees are applied to solve the synthesis problem. These are mixed H2/H∞, mixed H2/μ, and robust H2 syntheses. Advantages and disadvantages of each method are presented. Multirate control, which is inherent to control problems in HDDs, is obtained by reducing multirate problems into linear time-invariant ones, for which there are many useful theories and algorithms available. Most of the techniques proposed in this paper heavily rely on efficient numerical tools for solving linear matrix inequalities.

Event-triggered optimal reset control of hard disk drive head-positioning servo systems

2018 ◽  
Vol 233 (5) ◽  
pp. 582-590 ◽  
Author(s):  
Haoping Wang ◽  
Feinan Zhu ◽  
Yang Tian
Keyword(s):  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Linear Matrix ◽  
Disk Drives ◽  
Servo Systems ◽  
Positioning Systems ◽  
Head Positioning ◽  
Reset Control ◽  
Event Triggered

This article proposes a state-feedback-based optimal law with reset control for two typical kinds of head-positioning systems with nonlinearities of hard disk drives which combine the improved event-triggering reset condition and an optimal reset law design problem. First, a reset control law is proposed to reset the state of the system at the instants or some reset surfaces which have been proved can overcome the linear limitations. The reset surface is considered as a function of event or it can be defined as an event-triggered system, in which some states of the controller are subjected to impulsive actions. Second, a model predictive optimal law is proposed to the design of the after-reset value which was finally calculated through series linear matrix inequalities. Finally, in comparison with recent linear or nonlinear control methods applied to hard disk drives, our proposed approach shows the simplicity in design process and the robustness to nonlinear uncertainties in plant.

Superlubricity Relevant in Hard Disk Drive Applications

2016 ◽  
Author(s):  
Shou-Mo Zhang ◽  
Cuong-C. Vu ◽  
Qun-Yang Li ◽  
Norio Tagawa ◽  
Quan-Shui Zheng
Keyword(s):  
Temperature Dependence ◽  
Hard Disk Drive ◽  
Large Scale ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Force Sensor ◽  
Lubricant Layer ◽  
Single Crystalline ◽  
Crystalline Graphite

Reduction of head-media spacing (HMS) keeps crucial during the increase of areal density of hard disk drives (HDD). The design of hard disk drive with a superlubric interface is reported with two schemes for HDI design to realize superlubricity. For the first scheme, the DLC layer is kept on the disk while removing the lubricant layer. The DLC layer on the transducer is replaced by graphene-like layer. The direct contact between head and disk could reduce the HMS to about 2.3 nm. For the second scheme, the DLC layer on disk is further replaced by graphene and the HMS could be reduced to below 1 nm. For the first scheme, the basic proof of concept experiments are conducted using micro-scale graphite island samples. Ultralow COF, with the average of 0.0344 on the interface of single crystalline graphite surface and DLC substrate is demonstrated by AFM. What’s more, the temperature dependence of friction between single crystalline graphite and DLC is measured by micro-force sensor mounted on micro-manipulator. The results show that heating helps to significantly decrease the friction. Desorption of contaminants along the interface is speculated to be the key mechanism for temperature dependence of friction. This work provides the concept of large-scale superlubricity relevant in HDD applications, which could be a promising technology to ultimately reduce HMS for future HDI development.

scholarly journals Strain Sensing With Piezoelectric Zinc Oxide Thin Films for Vibration Suppression in Hard Disk Drives

2008 ◽  
Author(s):  
Sarah Felix ◽  
Stanley Kon ◽  
Jianbin Nie ◽  
Roberto Horowitz
Keyword(s):  
Vibration Suppression ◽  
Transfer Functions ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Strain Sensing ◽  
Linear Quadratic ◽  
H2 Control ◽  
Hard Drives ◽  
Optimization Methodology

This paper describes the integration of thin film ZnO strain sensors onto hard disk drive suspensions for improved vibration suppression for tracking control. Sensor location was designed using an efficient optimization methodology based on linear quadratic gaussian (LQG) control. Sensors were fabricated directly onto steel wafers that were subsequently made into instrumented suspensions. Prototype instrumented suspensions were installed into commercial hard drives and tested. For the first time, a sensing signal was successfully obtained while the suspension was flying on a disk as in normal drive operation. Preliminary models were identified from experimental transfer functions. Nominal H2 control simulations demonstrated improved vibration suppression as a result of both the better resolution and higher sensing rate provided by the sensors.

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.

Robust time optimal controller design for hard disk drives

1999 ◽  
Vol 35 (5) ◽  
pp. 3598-3600 ◽  
Author(s):  
Bong Keun Kim ◽  
Wan Kyun Chung ◽  
Ho Seong Lee ◽  
Hyun-Taek Choi ◽  
Il Hong Suh ◽  
...  
Keyword(s):  
Controller Design ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Optimal Controller ◽  
Disk Drives ◽  
Time Optimal

Optimization of Air Bearing Contours for Shock Performance of a Hard Disk Drive

2003 ◽  
Author(s):  
Eric M. Jayson ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Element Model ◽  
Time Dependent ◽  
Air Bearing ◽  
Disk Interface ◽  
Shock Response ◽  
Shock Event

Hard disk drives must be designed to withstand shock during operation. Large movements of the slider during shock impulse can cause reading and writing errors, track misregistration, or in extreme cases, damage to the magnetic material and loss of data. The design of the air bearing contour determines the steady state flying conditions of the slider as well as dynamic flying conditions, including shock response. In this paper a finite element model of the hard disk drive mechanical components was developed to determine the time dependent forces and moments applied to the slider during a shock event. The time dependent forces and moments are applied as external loads in a solution of the dynamic Reynolds equation to determine the slider response to a shock event. The genetic algorithm was then used to optimize the air bearing contour for optimum shock response while keeping the steady flying conditions constant. The results show substantial differences in the spacing modulation of the head/disk interface after a shock as a function of the design of the air bearing contour.

Flying Clearance Distribution With Thermo-Mechanical Actuation of Hard Disk Drive

2008 ◽  
Author(s):  
Sung-Chang Lee ◽  
George W. Tyndall ◽  
Mike Suk
Keyword(s):  
Environmental Change ◽  
Temperature Change ◽  
Temperature Sensitivity ◽  
Temperature Compensation ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Disk Drives ◽  
Compensation Scheme ◽  
Mechanical Actuation

Flying clearance distribution with thermo-mechanical actuation is characterized. Especially, what factors contributing to variation of flying clearance are identified based on thermo-mechanical actuation profiles taken from burn-in process of hard disk drives and Gage R&R test of touch down repeatability. In addition, the effect of static temperature compensation scheme on flying clearance distribution is investigated and disadvantages of static adaptation to temperature change are identified. In order to avoid catastrophic early HDI failures due to poor static temperature compensation, we need to dynamically adjust flying clearance whenever environmental change is detected. Otherwise we need to utilize individual temperature sensitivity values of each flying head to adjust thermo-mechanical actuation amount accordingly with temperature change.

Narrowband Performance of Active Control on Flow-Induced Vibrations Inside Hard Disk Drives

2013 ◽  
Author(s):  
Hequn Min ◽  
Xiaoyang Huang ◽  
Qide Zhang ◽  
Xin Xia
Keyword(s):  
Active Control ◽  
Hard Disk Drives ◽  
Laser Doppler Vibrometer ◽  
Hard Disk ◽  
Disk Drive ◽  
Modal Testing ◽  
Disk Drives ◽  
Feedback Error ◽  
Flow Induced Vibrations ◽  
Narrow Bands

This paper presents an experimental study of digital narrowband active control on the flow-induced vibrations (FIV) on the head gimbals assembly (HGA) in a working hard disk drive (HDD). Firstly, the modal testing on the HDD was carried out, in which the disk modes were analyzed with a 1-D laser Doppler vibrometer (LDV) and the HGA vibration modes with a 3-D LDV. Secondly, a digital feedback control close-loop was implemented in experiments to suppress the FIV spectrum peaks on the HGA. In this close-loop, the HGA vibrations detected by the LDV were used as feedback error signals, then the signals was passed through a digital controller to generate feedback signals to drive a piezoelectric disk to actuate feedback acoustic pressure around the HGA. Active control experiments were conducted in narrow bands on five principal peaks in the HGA off-plate vibration spectrum, around 1256Hz, 1428Hz, 2141Hz, 2519Hz and 3469Hz, respectively. It is shown that distinct suppression of at least 10 dB can be achieved on all these HGA vibration peaks.

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