Aeroelastic Response And Stability Analysis Of Cyclicless Pitch Rotor Of Side-by-Side Helicopter

To overcome the disadvantages of conventional helicopter, it is necessary to research new concept helicopters. The dynamic problem of helicopter rotor is significant for developing new concept helicopter.This thesis focuses on the new side-by-side helicopter, which has rigid rotor blades fixed on the hub. The hub is connected to main axle through a universal joint. Without flap and lag joint, the hub is controlled by two joysticks attached on the bottom of universal joint. So there is no need to apply cyclic pitch control.It’s assumed that the rotor blade is an elastic beam. Based on finite element method, dynamic model of elastic blade of side-by-side helicopter was established by Hamilton principle. Two gimbal degrees of freedom were introduced to capture the unique structural feature. Quasi-steady aerodynamic model and Glauert inflow model were included in aerodynamic modeling. The fundamental frequency and vibration mode of sample helicopters were calculated, and the comparisons between the results and experimental data verified the developed model.The aeroelastic responses of side-by-side helicopter rotor system in different initial conditions were analyzed using modal analysis method and numerical method. The study showed that the aeroelastic responses tend to be constant in hover and periodic oscillating in forward flight.At last, the modal frequency and damping characteristics were researched using eigenvalue analysis method in continuous state space format. The influence for system stability of some important parameters, such as gimbal stiffness, collective pitch, precone angle, forward velocity and structural stiffness, were studied.The research of side-by-side helicopter in aeroelastic response and stability analysis are limited, so the research of structural modeling, aerodynamic modeling and stability analysis in this thesis can provide some reference.