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Control of Chaotic Waves in Hard Disk Drives

Rajabi, Majid | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39362 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Jalali, Mir Abbas
  7. Abstract:
  8. Hard disk drives are the main component of computers for permanent data storage. The security of the stored data is related closely to the air gap between the read-write head and the surface of disk. This gap which is created by the aerodynamic force between head and the disk is altered continually by lateral oscillations of disk. In the extreme condition of zero gap and contact between the protective coating layer and subsequently the magnetic material of the disk with the head, the disk will be scratched and damaged. Therefore, the active or passive control of these vibrations has a particular importance in the technology of manufacturing of hard disks. The first step in active control of this component is the accurate prediction of dynamical behavior of system. According to this, control of chaos in this component attained a great significance. َAlthough the study of regular oscillations of spinning disks (with especial emphasis on hard disk drives) has a long history, it was only two years ago that the existence of unpredictable circumferential chaotic waves, in both the single mode oscillations and multi-mode interaction of spinning disk was unveiled. The purpose of the present thesis is design and analysis of a control algorithm in order to suppress the chaotic single mode oscillations of spinning disks under the lateral point force (the proper model for hard disk drives). Our purpose of control is escape from chaotic responses toward the stable periodic orbits of system. The controlling process is based on the radial maneuvering of the read-write head on the surface of disk which is itself the main cause of chaos appearance in system. Regard to the constraints of system and the necessity of a small energy controlling signal, we nominate the optimal control technique as the first candidate to do this. Ultimately, we discussed the capability of execution of the designed controlling process on the hard disk drives and the reliability of the results
  9. Keywords:
  10. Chaos Control ; Optimal Control ; Unstable Periodic Orbit ; Nonlinear Eigenvalue Problem ; Direct Collocation Method ; Hard Disk Drives ; Stable Periodic Orbit

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