Flight Mechanics And Control Of Unmanned Coaxial Tilt-rotor Flying Wing Aircraft

New configuration aircraft is current cutting edge research area. Nonlinear flight dynamics modeling and flight control law design are critical technologies.In this paper, the unmanned coaxial tilt-rotor flying wing aircraft is presented and developed. The nonlinear flight dynamics model has been developed based on the basic principle modeling theory, which considers interference between rotors and fuselage. Through the trim analysis of nonlinear model in the helicopter flight mode, conversion flight mode and airplane flight mode, the changing process of flight states and the control variables are obtained. Based on those results, the reasonable conversion path is concluded, and the control allocation strategy of aircraft in different flight modes are determined. According to the control response analysis in different flight modes, the characteristics of stability change and the coupling characteristics of control are used to control law desigh.In flight control law design, the control law of time-varying nonlinear system is designed by combining PID control method and Dynamic Inversion control method. The smooth conversion of full flight modes of coaxial tiltrotor is achieved through reasonable controller switching strategy. At the last, some flight control law reconfiguration verifications in fault cases of aircraft are carried out by means of Pseudo-Inverse Method, then the specific reconfiguration simulations are researched in longitudinal and heave channel by means of nonlinear model. The simulation result shows that the flight control law reconfiguration control is feasible under fault condition and has extensive engineering perspective.