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Semi-Active Intelligent Control for an Offshore Steel Jacket Platform with Magnetorheological Damper Wave-Induced Forces

Sarrafan, Atabak | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 41976 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Khayyat, Amir Ali Akbar
  7. Abstract:
  8. Due to the inherent non-linear nature of the MR damper, an intelligent non-linear neuro-fuzzy control strategy is designed for control of wave-induced vibration of an offshore steel jacket platform equipped with MR dampers. In the proposed control system, a dynamic-feedback neural network is employed to model non-linear dynamic system and the fuzzy logic controller is used to determine the control forces of MR dampers. Required voltages and actual forces of MR dampers are obtained by use of two feedforward neural networks, in which the first neural network and second one act as the inverse and forward dynamics model of the MR dampers, respectively. The most important characteristic of the proposed intelligent control strategy is its inherent robustness and its ability to handle the non-linear behavior of the system. Besides, no mathematical model is needed for calculating forces produced by MR dampers. Wave-induced forces are determined according to linearized Morison equation. The performance of the proposed neuro-fuzzy control system is compared with that of a traditional semi-active control strategy, i.e., clipped optimal control system with LQG-target controller, through computer simulations, while the uncontrolled system response is used as the baseline. It is demonstrated that the proposed control system design framework is more effective than that of the clipped optimal control scheme with LQG-target controller in reducing the vibration of offshore structures
  9. Keywords:
  10. Structural Vibration ; Optimal Controller ; Neuro-Fuzzy Systems ; Magnetorheological Damper ;

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