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Design Non-Fragile Controllers Based on Stability Region Centroids

Sheikholeslami, Zia | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46027 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Tavazoei, Mohammad Saleh
  7. Abstract:
  8. The present thesis introduces a new method to design non-fragile controllers. The idea of design is to set the centroid of the stability region as the tuning point of two-parameter controllers. This ideahas been motivated by the fact that the centroid of a convex region belongs to a set of pointsthat have farthest distance from its boundary. In case that stability region is not convex, a correction may be needed because the centroid of non-convex region may be very near to or out of its boundary. One modified version of design method when stability region is not convex, is to find maximum convex sub-area inside stability region and set its centroid as the tuning point of controller parameters. The algorithm of obtaining maximum convex area is proposed in this thesis.
    However the Ziegler-Nichols method introduces simple tuning rules for PI case, it yields to a more fragile controller in comparison with the designed controller based on stability region centroids. The fragility problem becomes bold when the practical issues of digital implementation, such as signal quantization and the effect of the fixed word length on the parameters of the controller are not considered in typical procedure of the controller design. In the present thesis a new optimization based approach, considering the practical issues is proposed to tune the parameters of two-parameter controller. The models of real world plantswhich have small stability region are used to apply the proposed tuning method. The effectiveness of the proposed method is shown by numerical simulations
  9. Keywords:
  10. Controller Design ; Stability Region ; Non-fragility Controller ; Practical Issues ; Centroid

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