Online Identification of System Uncertainties Using Coprime Factorizations With Application to Hard Disk Drives

2015 ◽  
Author(s):  
Omid Bagherieh ◽  
Behrooz Shahsavari ◽  
Roberto Horowitz
Keyword(s):  
Hard Disk Drive ◽  
Closed Loop ◽  
Transfer Functions ◽  
Feedforward Control ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Estimation Algorithm ◽  
Disk Drive ◽  
Dual Stage ◽  
Coprime Factorizations

In hard disk drive (HDD) magnetic recording bit patterned media (BPM), data are written in predetermined paths. The deviation of these paths from the perfect circle is categorized as repeatable run-out (RRO) which needs to be tracked. An adaptive RRO following algorithm was developed in [1,2] in order to track the RRO. This algorithm uses models of the closed-loop sensitivity transfer functions, from the feedforward injection points to position error signal (PES), to estimate the feedforward control actions that are needed to track the RRO. The phase difference between these models and the actual transfer functions must be less than 90 degrees, in order to guarantee the convergence of the adaptive RRO following algorithm. The dual-stage actuators’ gains and resonance modes are affected by temperature variations, which in turn affect all closed loop sensitivity transfer functions. As a consequence, the 90-degree criteria may be violated unless these transfer functions are periodically updated. In this paper, the coprime factorizations method has been used to factorize and identify the uncertain part of the model instead of identifying the entire transfer function of the model. Experimental results conducted on a hard disk drive equipped with dual-stage actuation, confirm the effectiveness of the proposed estimation algorithm.

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.

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.

Comparison of Robust Track-Following Control Systems for a Dual Stage Hard Disk Drive

1999 ◽  
pp. 101-118 ◽  
Author(s):  
Toshiya Suzuki ◽  
Takamasa Usui ◽  
Minoru Sasaki ◽  
Fumio Fujisawa ◽  
Takashi Yoshida ◽  
...  
Keyword(s):  
Control Systems ◽  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Dual Stage

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.

scholarly journals Reduction of flow-induced suspension vibrations in a hard disk drive by dual-stage suspension control

2003 ◽  
Vol 39 (5) ◽  
pp. 2237-2239 ◽  
Author(s):  
A.P. Teerhuis ◽  
S.J.M. Cools ◽  
R.A. De Callafon
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Suspension Control ◽  
Dual Stage

Application of Piezoelectric Materials for Use as Actuators and Sensors in Hard Disk Drive Suspension Assemblies

1999 ◽  
Vol 604 ◽  
Author(s):  
J. R. Heffelfinger ◽  
D. A. Boismier
Keyword(s):  
Hard Disk Drive ◽  
Piezoelectric Materials ◽  
Hard Disk ◽  
Disk Drive ◽  
Critical Material ◽  
Piezoelectric Motors ◽  
Dual Stage ◽  
Voltage Generation ◽  
Aging Rates ◽  
Fft Analysis

AbstractSuspension assemblies, the mechanical arm that supports the read/write head in a Hard Disk Drive (HDD), are incorporating piezoelectric motors for dual-stage actuation. With high displacements and high Curie Temperatures, lead zirconium titanate (PZT) is the preferred piezoelectric material for this application. In this study, commercially available PZT is studied for critical material properties that include strength, aging and particulate generation. An average PZT strength of 111.7 MPa and a Weibull parameter (m) of 12.18 was measured for the material. Aging rates of the dielectric constant vary between 1.9 to 3.2 % per time decade depending on the test condition. The attachment of PZT motors to the suspension assembly provides a method of sensing suspension resonance, shock and temperature fluctuations. Fast Fourier Transform (FFT) analysis of voltage generation of the PZT during drive operation identified a frequency of 6509 Hz that is within 0.2% of the measured resonance frequency of the suspension. The PZT generated several volts for shock events between 500 to 2000 G's of the suspension. Implications of the material parameters and potential sensing capabilities of the PZT are discussed.

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