344 research outputs found
INVESTIGATION INTO SUBMICRON TRACK POSITIONING AND FOLLOWING TECHNOLOGY FOR COMPUTER MAGNETIC DISKS
In the recent past some magnetic heads with submicron trackwidth have been
developed in order to increase track density of computer magnetic disks, however a
servo control system for a submicron trackwidth head has not been investigated. The
main objectives of this work are to investigate and develop a new servo pattern
recording model, a new position sensor, actuator, servo controller used for submicron
track positioning and following on a computer hard disk with ultrahigh track density, to
increase its capacity.
In this position sensor study, new modes of reading and writing servo
information for longitudinal and perpendicular magnetic recording have been
developed. The read/write processes in the model have been studied including the
recording trackwidth, the bit length, the length and shape of the transition, the
relationship between the length of the MR head and the recording wavelength, and
the SIN of readout. lt has also been investigated that the servo patterns are
magnetized along the radial direction by a transverse writing head that is aligned at
right angles with the normal data head and the servo signals are reproduced by a
transverse MR head with its stripe and pole gap tangential to the circumferential
direction. lt has been studied how the servo signal amplitude and linearity are affected
by the length of the MR sensor and the distance between the shields of the head.
Such things as the spacing and length of the servo-pattern elements have been
optimised so as to achieve minimum jitter and maximum utilisation of the surface of
the disk. The factors (i.e. the skew angle of the head) affecting the SIN of the position
sensor have been analysed and demonstrated. As a further development, a buried
servo method has been studied which uses a servo layer underneath the data layer,
so that a continuous servo signal is obtained.
A new piezo-electric bimorph actuator has been demonstrated. This can be
used as a fine actuator in hard disk recording. The linearity and delay of its response
are improved by designing a circuit and selecting a dimension of the bimorph element.
A dual-stage actuator has been developed. A novel integrated fine actuator using a
piezo-electric bimorph has also been designed. A new type of construction for a
magnetic head and actuator has been studied.
A servo controller for a dual-stage actuator has been developed. The wholly
digital controller for positioning and following has been designed and its performances
have been simulated by the MAL TAB computer program.
A submicron servo track writer and a laser system measuring dynamic micro-movement
of a magnetic head have been specially developed for this project.
Finally, track positioning and following on 0.7 µm tracks with a 7% trackwidth
rms runout has been demonstrated using the new servo method when the disk-was
rotating at low speed. This is one of the best results in this field in the world
Multi-level fine pointing test-bed for space applications
For space applications that need high accuracy pointing of the payload, fine pointing system is an indispensable tool. To reach high level of high accuracy pointing and tracking, proper synchronization between the attitude of the satellite and each stage of the pointing module should be considered. This study focuses on developing and demonstrating staging control for fine pointing system. Currently, an experimental model for multi-stage control has been built in the laboratory to be used as a testbed and a teaching tool to validate the control strategies. This paper gives a brief introduction of the study, experimental model design criteria and staging control strategy. An example of a controller synthesis for multi-stage actuators based on Hinfinity is also presented
THE DEVELOPMENT OF A NOVEL SUSPENSION ARM WITH 2-DIMENSIONAL ACTUATION, FOR USE IN ADVANCED HARD DISK DRIVES
As magnetic computer disks are developed to ever-greater data storage densities, the accuracy
required for head positioning is moving beyond the accuracy provided by present technology using
single-stage voice-coil motors in hard disk drives. This thesis details work to develop a novel active
suspension arm with 2-dimensional actuation for use in advanced hard disk drives. The arm
developed is capable of high-bandwidth data tracking as well as precision head flying height control
motion. High-bandwidth data tracking is facilitated by the use of piezoelectric stack actuator,
positioned closer to the head.
The suspension arm is also capable of motion in the orthogonal axis. This motion represents active
flying height control to maintain the correct altitude during drive operation. To characterise the
suspension arm's structural dynamics, a high-resolution measurement system based on the optical
beam deflection technique has been developed. This has enabled the accurate measurement of
minute end-deflections of the suspension arm in 2-dimensions, to sub-nanometre resolution above
noise. The design process of the suspension arm has led into the development of novel
piezoelectric-actuated arms. In the work involving lead zirconate titanate (PZT) thick films as
actuators, work in this thesis shows that reinforcing the films with fibre improves the overall
actuation characteristics of the thick films. This discovery benefits applications such as structural
health monitoring.
The final suspension arm design has been adopted because it is simple in design, easier to integrate
within current hard disk drive environment and easier to fabricate in mass. Closed-loop control
algorithms based on proportional, integral and derivative (PID) controller techniques have been
developed and implemented to demonstrate high bandwidths that have been achieved. The
suspension arm developed presents an important solution in head-positioning technology in that it
offers much higher bandwidths for data tracking and flying height control; both very essential in
achieving even higher data storage densities on magnetic disks at much reduced head flying heights,
compared to those in existing hard disk drives
Modeling and control of hard disk drive in mobile applications
Master'sMASTER OF ENGINEERIN
Robust periodic disturbance compensation via multirate control
Master'sMASTER OF ENGINEERIN
Vibration analysis and control in hard-disk drive servo systems
Master'sMASTER OF ENGINEERIN
Advance Servo Control for Hard Disk Drive in Mobile Application
Ph.DDOCTOR OF PHILOSOPH
CHALLENGES OF CONTROL DESIGN FOR PRECISION SERVO SYSTEM WITH APPLICATION ON HARD DISK DRIVE
Ph.DDOCTOR OF PHILOSOPH
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