Flight Dynamics Of A Tail-Sitter Coaxial Rotor Aircraft

The tail-sitter coaxial rotor aircraft is a new configuration aircraft with the ability of vertical take-off and landing and high speed forward flight.It is a new direction for the research and development of shipborne UAV.In this paper,the flight dynamics of the tail-sitter coaxial rotor aircraft is studied by establishing the flight dynamics model of the aircraft.Firstly,the nonlinear flight dynamics model is established.The rotor aerodynamics model is established using the blade element theory.The rotor induced velocity is obtained by the dynamic inflow theory.The lift,drag and torque of the whole aircraft at a wide range of attack angle are obtained by the CFD method,and the nonlinear quasi-steady aerodynamics model of the whole aircraft is established.Dynamic models of the engine and the landing gears are established.Based on the mathematical modeling theory,a 6-DoF nonlinear flight dynamics model of the aircraft is established.Secondly,the aircraft is trimmed under steady flight condition,and the trim characteristics of the forward and lateral flight are obtained.The control strategy is analyzed by evaluating the control effectiveness under the whole flight envelope including the helicopter mode,the transition mode and the plane mode.Thirdly,according to the small perturbation theory,the nonlinear flight dynamics model is linearized to obtain the linear state equation of the aircraft motion.The stability of the longitudinal and lateral mode of the aircraft is analyzed.The nonlinear response of the aircraft is calculated,the coupling characteristics are analyzed.Finally,the safe operation envelope are calculated through the theoretical method.Combined with the results of lateral flight trim,a set of feasible strategy for aircraft landing is summarized.The visualized flight simulation of the aircraft is carried out using the MATLAB/FlightGear simulation technique,the effectiveness of the flight dynamics model is verified through the flight simulation.