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Design of Fractional Order Controllers for Preservation of Phase Margin in the Presence of Parametric Uncertainties

Basiri, Mohammad Hossein | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47668 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Tavazoei, Mohammad Saleh
  7. Abstract:
  8. In the present thesis, first of all we consider a particular class of fractional order plants which have uncertainty in their time constant.In order to make the closed loop system robust against variations of the aforementioned parameter, a robust fractional order controller will be designed and the corresponding tuning rule will be expressed. By using the proposed controller, phase margin of the system will be preserved on a desired value for any value of the uncertain parameter and also gain crossover frequency of the system, in the nominal case, will be adjustable.Also another class of fractional order system will be considered. For these systems, the problem is the same as the former one. Corresponding robust fractional order controller will be designed and its tuning rule will be stated. In addition, sufficient conditions for exisiting of the proposed controller will be derived. Furthermore, achievable region of this controller will be obtained. After that, we will consider first order pluse time delay systems which have uncertainty in their gain. Through a numerical method, a robust fractional order controller will be designed in order to achieve some design specifications. First of them is, preserving phase margin of the system on a desired value in nominal case. Second one is, achieving a flat phase Bode diagram of the loop transfer function in the gain crossover frequency and also having maximum gain margin.Finally, a particular class of fractional order systems containing time delay which have uncertainty in their order will be considered.For these systems, we will design a robust fractional order controller, which preserves phase margin of the system in the desired value and make gain crossover frequency equal to desired one in the nominal case
  9. Keywords:
  10. Fractional Order Controller ; Uncertainty ; Phase Margin ; Robust Controller ; Tuning Rule

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