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Adaptive Controller Design for Ducted Fans in Vertical Plane Phases

Fadaeian, Ehsan | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43403 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Banazadeh, Afshin
  7. Abstract:
  8. Ducted fan vertical take-off and landing (VTOL) aerial vehicles have drawn many attentions in the world because of their capability to offer high power to weight ratio for a certain vehicle diameter relative to open rotors or helicopters. However, due to inherent uncertainties in dynamics and inefficient and poor quality responses, significant control challenges are still unsolved and exciting fields for research. In the current study, a nonlinear dynamic model is proposed for the controller design purpose. This model is validated against simulation by performing several standard scenarios. An adaptive control method, named model reference (MRAC), is utilized to design a perfect controller in hover. Noticeable capability of an adaptive control is the existence of an online update mechanism, known as adaptive law, for tuning the controller gains. So, despite the erratic model and aleatory uncertainties in dynamics, it is able to well-adapt the gains to any given circumstances. The structure of the controller is an adaptive state feedback for output tracking. The system is single input multi output and must track the reference model. After checking the controllability and observability of the system dynamic, high frequency gain matrix (K_p) and modified left interactor matrix (ζ_m) are calculated according to Tao, 2003. Then, the reference model matrix is obtained. The results show that the altitude and pitch controller are able to regulate the state variables and follow the prompt commands in the presence of a wide range of uncertainties when the vehicle moves in vertical plane and near hovering condition. After putting in the command, a sudden change in the input variable occurs and it jumps off to a new position. Following this sudden change, which results in a new working condition, the controller still proceeds to adapt the system gains to attain the required position. To end with, in this research for the first time the model reference adaptive control (MRAC) is applied to a nonlinear model of a ducted fan aerial vehicle. The capability of the adaptive law to update the controller gains are evaluated for different initial and input conditions. Other considerations for transition flight from one phase to another, is the purpose of the future study.
  9. Keywords:
  10. Hover Flight ; Model Reference Adaptive Control ; Vertical Take-Off and Landing (VtOL) ; Aerial Vehicles ; Nonlinear Dynamic Model

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