Flight Control Of Unmanned Tiltrotor Aircraft

Tiltrotor aircraft has the flight characteristics of helicopter and propeller airplane. Its flightcontrol, especially in the conversion flight is very difficult. In this thesis, taking a small unmannedtiltrotor aircraft as a research example, the theoretical and experimental investigations on the flightcontrol of unmanned tiltrotor aircraft have been carried out, mainly in the modeling of nonlinear flightdynamics, design of flight control law, design of micro-strapdown inertial navigation system (SINS)and flight tests of a small unmanned tiltrotor aircraft. The main innovations include:(1) The nonlinear flight dynamic model of unmanned tiltrotor aircraft has been established toobtain the flight operation laws of the full flight modes including the helicopter flight mode,conversion flight mode and airplane flight mode and the conversion corridor. The operational analysisof the nonlinear flight dynamic model was carried out to obtain the coupling characteristics of thedifferent flight modes of unmanned tiltrotor aircraft. In order to simplify the calculation of thenonlinear model, several linear flight dynamic models were synthesized and to simulate the nonlinearflight dynamic model, obtaining the consistent operational responses.(2) The control laws of full flight modes have been established. In the helicopter hover andlow-speed flight modes, the flight control laws were designed by using the explicit model followingcontrol system. In the tilting and airplane flight modes, the flight control laws were designed by usingtheH loop shaping design procedure (LSDP), so that the control system has good robust stability.To be suitable for the operational characteristics of the different flight modes of tiltrotor aircraft, themulti-model adaptive control was use to conduct the switching design of flight control laws for fullflight modes. The simulation results verified the feasibility of the switching strategy of the full modeflight control laws.(3) The flight control and embedded strapdown inertial navigation system used for smallunmanned tiltrotor aircraft has been developed, including the hardware system design ofmicro-inertial sensors and flight control computer, development of flight control software and groundcontrol systems, and communication protocols. In the hover and low speed flight conditions, theangular velocity integration was used to establish the process equations, the Kalman filter of attitudeestimation was constructed, and the filtering algorithm of the speed, position, height was derived. Inthe accelerating flight conditions, the speed differential with high-precision GPS was used to correctthe measurement error of fuselage accelerometers, and the error quaternion based attitude estimation algorithm was designed. The simulation and experiment indicated that the strapdown inertialnavigation system had good estimation accuracy.(4) The flight test system of unmanned tiltrotor aircraft has been built. The groundcommunication test, ground engine test and full mode flight test of unmanned tiltrotor aircraft verifiedthe effectiveness of the flight control of unmanned tiltrotor aircraft established in this thesis.