Research On Flight Dynamics Modeling And Control Technology For Coaxial Rotor /Fan Unmanned Helicopter

Coaxial rotor fan unmanned helicopter is a novel unmanned aerial vehicle which has the capabilities of vertical takeoff and landing.Compared with the conventional structured unmanned helicopters,it has shown excellent efficiency for hovering low speed flight statues,which is especially suitable for signal relay,tactical reconnaissance and target indication tasks.This thesis carried out a systematic research on the flight dynamics modeling and flight control technology of the unmanned helicopter.The main research contents and results are as follows:Firstly,the aerodynamic structure and control characteristics of coaxial rotor fan unmanned helicopter are introduced.Based on flight mechanics principle and wind tunnel test,the full-scale nonlinear dynamic model and the aerodynamic coupling model of ground effect in takeoff and landing stages of the unmanned helicopter are established.The motion model of the typical flight mode of the unmanned helicopter is analyzed based on the small perturbation linearization theory.State characteristics,manipulation coupling and stability characteristics.Secondly,aiming at the problem of actuator saturation caused by the change of flight mode of a sample unmanned helicopter,a nonlinear attitude controller for unmanned helicopter with anti-saturation performance is designed by introducing the amplitude of command signal as a constraint condition into the solving process of the nonlinear control algorithm,and the stability of the proposed control algorithm is analyzed theoretically.The simulation results show that the proposed attitude control algorithm can effectively suppress the actuator saturation phenomenon,and track the attitude command more quickly to meet the control requirements of the attitude loop.Finally,in order to deal with flight dynamics variations caused by ground effect during taking off and landing,a nonlinear control law was designed based on the framework of switching system,which allows for the controller adapting itself based on the height information.The stability of the proposed method is proved and analyzed using multiple Lyapunov functions theory.Comparative simulations have shown that the proposed switching control algorithm is able to effectively accomplish the takeoff and landing task,meeting the demands of attitude and speed constraints in the process of the takeoff and landing.