Research Of Autonomous Control Technology For The Flapping-wing Aircraft

At present,the application of unmanned aircrafts is widespread,and its value in the fields of civil and military applications is constantly increasing.From the viewpoint of flight platform,UAVs(Unmanned Aerial Vehicles)can be classified as fixed wing UAVs,unmanned helicopters,multi-rotor drones,and flapping-wing aircrafts.Currently,fixed-wing UAVs and multirotor drones predominate the UAV market,but they have the limitations of high noise and short battery life.However,the bionic flapping-wing aircraft has the characteristics of bionics,quietness,lightness,and high flight efficiency.It has unique advantages in scenarios such as infiltration reconnaissance,airport bird repellence,and cherish bird protection.Based on the research of the principles of insect and bird flight,this thesis designs two types of flapping-wing aircraft: single-section and double-section flapping-wing aircraft.The former uses a spatial four-link structure and the latter uses a double crank-and-rocker structure.Both of them use the conventional full linkage tail structure.They have been successfully tested by flight and show excellent flight performance.Due to the complex aerodynamic characteristics and lift mechanism of flapping-wing aircraft,autonomous flight control of it has always been a problem.This thesis designs and implements an autonomous control system for the flapping-wing aircraft: the Pixhawk,GPS module,Wi Fi module,etc.are used to build the on-board electronic system;based on the PX4 flight control software,the flapping-wing aircraft control system is designed,and realized the design of the mixer,autonomous take-off and autonomous landing;According to the actual flight effect,the flight parameters were iteratively optimized;the QGC(QGround Control)ground station was used to realize the state monitoring and visual control of the aircraft.This thesis also introduces the design method of QGC ground station software,and discusses the multi-aircraft networking method.The flapping-wing aircraft has the characteristics of unsteady,low Reynolds number,strong coupling,and non-linearity.During the flapping process,the wing deformation is uncertain,so its dynamic modeling is complicated.In this thesis,a system identification method is used to establish a multi-input multiple-output dynamic model of the flapping-wing aircraft.The error between thepredicted state value and the true value is optimized by the least square method,and the real flight data is processed by low-pass filtering for model training.The experimental results show that the trained model can relatively accurately calculate the current state of acceleration,velocity,angular velocity,and angle of the aircraft based on system inputs.The core of autonomous control of flapping-wing aircraft is attitude control and position control.This thesis uses the cascade PID algorithm to control the attitude of the aircraft,and introduces the control principle and code implementation method of the cascade PID in detail.In terms of position control,this thesis uses the L1 guidance algorithm.It is based on the idea of a pseudo target,it first calculates the L1 distance from the target point,and then calculates the centripetal force required by the aircraft based on the geometric relationship;the thesis introduces in detail the aircraft’s method of tracking straight lines,curves,arcs and the implementation of the L1 guidance algorithm.In addition,this thesis introduces the tuning method of the controller parameters through the established dynamic model.A large number of experiments show that the single-section and double-section flapping-wing aircraft designed in this thesis have achieved good flight performance.The flight control system realizes functions such as autonomous take-off,autonomous landing,and flight according to the planned waypoint,thereby verifying the effectiveness and stability of the cascade PID algorithm and L1 guidance algorithm in attitude and position control.On the basis of stable and autonomous control,through coordinated route planning,networked flight of 3 aircrafts and visual control of ground stations were realized.