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Dynamics, Stability, and Aero-servo-elasticity of Airships with Flexible Body and Fins

Mirhashemi, Sajad | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54042 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Haddadpour, Hassan
  7. Abstract:
  8. In this research, the dynamics, aero-elasticity, and control of an airship with a flexible body hull and fins are investigated. The flexible airship is modeled as a combination of several beams with specific boundary conditions. So that the dynamics and vibration of its body hull and fins can be taken into account regarding the aerodynamic, gravity, aerostatic, and control input forces. The governing equations of motion of the system are derived by using the velocity of an arbitrary point on each component and integration over the component and substituting them into the Euler-Lagrange equations in a body frame. Afterward, the added mass acting on the hull is calculated. Then, a perturbation approach is employed to divide the problem into two problems: a) nonlinear algebraic rigid dynamics for steady lever flight and b) linear extended aero-elasticity problem. This approach is supposed to dedicate large and small orders of magnitude to the coordinates. Applying this method gives the constant control inputs for the zero-order problem. The first-order problem which is linear can be controlled actively using an LQR approach. Finally, the time response of the system to gust input is calculated and it is shown that the closed-loop system is stable and tolerates low amplitude perturbations. Also, a linear stability analysis is performed to obtain the effect of two different structure materials, conventional and ultra-thin materials, on the instability forward velocity of the airship. The analysis indicates that consuming the ultra-thin material significantly reduces the instability forward velocity of the airship
  9. Keywords:
  10. Aeroelasticity ; Perturbation Method ; Linear Quadratic Requlator (LQR) ; Aeroservoelasticity ; Non-Rigid Airship ; Airship Dynamics ; Potential Flow Aerodynamics

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