2,685 research outputs found
A Two-Degree-Of-Freedom Time-Optimal Solution for Hard Disk Drive Servo Problems
This paper deals with the hard disk drive (HDD) servo problems. A novel discrete time-optimal control solution is proposed in a two-degree-of-freedom (2DOF) structure, employing both the feedback and feedforward controllers. The time-optimal feedback controller, derived from a simple, double integral plant model, shows remarkable robustness and disturbance rejection in the presence of resonant modes, measurement noises and position and torque disturbances. It eliminates the needs for two separate controllers for track-seeking and track-following operations. The proposed feedforward controller in this 2DOF structure proves to be quite beneficial in reducing the seek time. It also allows the feedback controller to be tuned more aggressively, which helps to improve the quality of track following. The proposed control scheme offers a novel basic control structure for HDD servo, upon which numerous further improvements can be made. It is successfully tested in simulation on an industrial 13.0-kTPI HDD
A Two-Degree-Of-Freedom Time-Optimal Solution for Hard Disk Drive Servo Problems
This paper deals with the hard disk drive (HDD) servo problems. A novel discrete time-optimal control solution is proposed in a two-degree-of-freedom (2DOF) structure, employing both the feedback and feedforward controllers. The time-optimal feedback controller, derived from a simple, double integral plant model, shows remarkable robustness and disturbance rejection in the presence of resonant modes, measurement noises and position and torque disturbances. It eliminates the needs for two separate controllers for track-seeking and track-following operations. The proposed feedforward controller in this 2DOF structure proves to be quite beneficial in reducing the seek time. It also allows the feedback controller to be tuned more aggressively, which helps to improve the quality of track following. The proposed control scheme offers a novel basic control structure for HDD servo, upon which numerous further improvements can be made. It is successfully tested in simulation on an industrial 13.0-kTPI HDD
Sequential Randomized Algorithms for Convex Optimization in the Presence of Uncertainty
In this paper, we propose new sequential randomized algorithms for convex
optimization problems in the presence of uncertainty. A rigorous analysis of
the theoretical properties of the solutions obtained by these algorithms, for
full constraint satisfaction and partial constraint satisfaction, respectively,
is given. The proposed methods allow to enlarge the applicability of the
existing randomized methods to real-world applications involving a large number
of design variables. Since the proposed approach does not provide a priori
bounds on the sample complexity, extensive numerical simulations, dealing with
an application to hard-disk drive servo design, are provided. These simulations
testify the goodness of the proposed solution.Comment: 18 pages, Submitted for publication to IEEE Transactions on Automatic
Contro
Youla-Kucera parameterized adaptive tracking control for optical data storage systems
In the next generation optical data storage systems, the tolerance of the tracking error will become even smaller under various unknown working situations. However, the unknown external disturbances caused by vibrations make it difficult to maintain the desired tracking precision during normal disk operation. It is proposed in this paper to use an adaptive regulation approach to maintain the tracking error below its desired value despite these unknown disturbances. The design of the regulator is formulated by augmenting a base controller into a Youla-Kucera (Q) parameterized set of stabilizing controllers so that both the deterministic and the random disturbances can be deal with properly. The adaptive algorithm is developed to search the desired Q parameter which satisfies the Internal Model Principle and thus the exact regulation against the unknown deterministic disturbance can be achieved. The performance of the proposed control approach is evaluated with experimental results that illustrate the capability of the proposed adaptive regulator to attenuate the unknown disturbances and achieve the desired tracking precision
Optimal control issues related to the hard disk drive servo systems
Ph.DDOCTOR OF PHILOSOPH
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
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