Design Of Small UAV Flight Control System

Recently,with the application of unmanned aerial vehicle(UAV)expanded from military field to civilian field,especially in the fields of meteorological monitoring,aerial photography,mapping,forest fire prevention,disaster area search and rescue,agriculture and so on,there is a great demands for UAVs.In these fields,they need UAVs with smaller size and longer flight time.Therefore,the UAV's flight control system also needs to be improved to meet the requirements of flight missions.So,it's meaningful for us to design a small UAV flight control system.Firstly,the structure of the quadrotor is introduced.The flight status of quadrotors: lifting,pitching,rolling and yawing are described.The transformation relation of coordinate systems is established.The mathematical model of a quadrotor is developed using Newton-Euler formula.The model is decoupled and simplified and the control law of the flight control system is designed.When UAV state parameters are changed,the least aquare method is used to identify the parameters and the PID controller is adjusted to eliminate the errors.Through that,the control system works well.Secondly,an extended Kalman filter(EKF)is introduced.The attitude estimation system based on the extended Kalman filter is established using the quaternion method.The attitude estimation system is also built by the vision information get from the pinhole camera modeling.Thirdly,the design of software and hardware for the UAV flight control system is completed.In terms of the hardware,the inertial attitude measurement unit and the motherboard of the flight controller are designed respectively.The attitude measurement unit is modularized,which facilitates the flight control system for redundancy backup and subsequent upgrades.Meanwhile,in order to make full use of the flight control board's interface resources,8 kinds of interfaces are designed.In the software part,the structure of the program is divided into three parts.Including a main function and two interrupt functionsFinally,the performance of the flight control system is tested.The temperature characteristic test of the attitude measurement unit is conducted.Also,the static accuracy and dynamic accuracy of the attitude measurement unit is tested.The attitude controller shows high performance.