11,534 research outputs found
Disturbance Observer-based Robust Control and Its Applications: 35th Anniversary Overview
Disturbance Observer has been one of the most widely used robust control
tools since it was proposed in 1983. This paper introduces the origins of
Disturbance Observer and presents a survey of the major results on Disturbance
Observer-based robust control in the last thirty-five years. Furthermore, it
explains the analysis and synthesis techniques of Disturbance Observer-based
robust control for linear and nonlinear systems by using a unified framework.
In the last section, this paper presents concluding remarks on Disturbance
Observer-based robust control and its engineering applications.Comment: 12 pages, 4 figure
Beyond the Waterbed Effect: Development of Fractional Order CRONE Control with Non-Linear Reset
In this paper a novel reset control synthesis method is proposed: CRONE reset
control, combining a robust fractional CRONE controller with non-linear reset
control to overcome waterbed effect. In CRONE control, robustness is achieved
by creation of constant phase behaviour around bandwidth with the use of
fractional operators, also allowing more freedom in shaping the open-loop
frequency response. However, being a linear controller it suffers from the
inevitable trade-off between robustness and performance as a result of the
waterbed effect. Here reset control is introduced in the CRONE design to
overcome the fundamental limitations. In the new controller design, reset phase
advantage is approximated using describing function analysis and used to
achieve better open-loop shape. Sufficient quadratic stability conditions are
shown for the designed CRONE reset controllers and the control design is
validated on a Lorentz-actuated nanometre precision stage. It is shown that for
similar phase margin, better performance in terms of reference-tracking and
noise attenuation can be achieved.Comment: American Control Conference 201
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
NSSDC Conference on Mass Storage Systems and Technologies for Space and Earth Science Applications, volume 1
Papers and viewgraphs from the conference are presented. This conference served as a broad forum for the discussion of a number of important issues in the field of mass storage systems. Topics include magnetic disk and tape technologies, optical disks and tape, software storage and file management systems, and experiences with the use of a large, distributed storage system. The technical presentations describe, among other things, integrated mass storage systems that are expected to be available commercially. Also included is a series of presentations from Federal Government organizations and research institutions covering their mass storage requirements for the 1990's
DSN advanced receiver: Breadboard description and test results
A breadboard Advanced Receiver for use in the Deep Space Network was designed, built, and tested in the laboratory. Field testing was also performed during Voyager Uranus encounter at DSS-13. The development of the breadboard is intended to lead towards implementation of the new receiver throughout the network. The receiver is described on a functional level and then in terms of more specific hardware and software architecture. The results of performance tests in the laboratory and in the field are given. Finally, there is a discussion of suggested improvements for the next phase of development
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
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