Helicopter dynamics and robust control
Nielsen, Agnar Kenneth Nygaard
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The overall objective of the thesis "Helicopter Dynamics and Robust Control" is modeling of the Futura SE model helicopter and the construction of robust controllers to handle parameter uncertainties and disturbances. In this thesis system identification or parameter estimation are not included. The developed model has been verified using two different models. The used model parameters has been made available by a graduate project, which simultaneously with this thesis have been working on modeling, system identification and control of the Futura SE model helicopter. The used parameters have not been verified and the values in the state space model can therefore only be used with some measure of reserve. The focus in this thesis is on modeling, model verification, and the principles in construction of a robust controller for the Futura SE model helicopter. For the robust controller the gross weight (mass) is chosen as the uncertainty, disregarding the shift in the centre of gravity and inertia. Wind gusts and turbulence are chosen as disturbances, which are simulated as a sine function superimposed with a stochastic process. During the development of the controllers the main priority has been on attenuation of the disturbance on the yaw rate. The yaw rate is the most fatale state to lose controllability of in helicopter flight dynamics. Both an H ∞ and a μ controller are developed and their performance is compared on a linear state space model using SimuLink. The performance of the controllers are compared and both came out as resistant against disturbance in wind and uncertainties in mass. The conducted tests shows, that both controllers can be used in control of a helicopter in hover in mid air. The μ controller gives the best results and is therefore recommended for further investigation.