Advanced Modelling of Helicopter Nonlinear Dynamics and Aerodynamics

Castillo-Rivera, Salvador (2014). Advanced Modelling of Helicopter Nonlinear Dynamics and Aerodynamics. (Unpublished Doctoral thesis, City University London)

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The work presented here provides a comprehensive dynamic and aerodynamic helicopter model. The possible applications of this work are wide including, control systems applications, reference and trajectory tracking methods implementation amongst others. The model configuration corresponds to a Sikorsky helicopter; a main rotor in perpendicular combination with a tail rotor. Also, a particular model of unmanned aerial vehicle has been modelled as part of collaboration with the La Laguna University (Spain). The modelling tool is VehicleSim, a program that builds rigid body systems, solves the nonlinear equations of motion and generates the time histories of the corresponding state variables of the vehicle under study. VehicleSim is able to provide the linearised equations of motion in a Matlab file and the symbolic state-space model. This is useful when control systems are to be designed. The main rotor model accounts for flap, lag and feather motions for each blade as well as for their nonlinear dynamic coupling. The tail rotor is modelled including the flap-feather coupling via delta three angle. The main and tail rotors' angular velocities are implemented by PID controllers. Main rotor linear and nonlinear equations are derived and validated by comparison with the theory. Main rotor flap and lag degrees of freedom are validated using frequency domain approaches in the absence of external forces. Also, fuselage-main rotor interaction is studied and validated by using modal analysis and root locus methodology. Vibrations originated at the main rotor are simulated and their effects on the fuselage are examined by a Short Time Fourier transformation. The aerodynamic model uses blade element theory on the main-tail rotors. Hover, climb, descent and forward flight conditions are simulated and they allow the helicopter to follow certain trajectories. Finally, the ensuing vibrations when an external perturbation is applied to the main rotor are investigated.

Item Type: Thesis (Doctoral)
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Divisions: School of Engineering & Mathematical Sciences

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