Research On Flight Control Algorithm Based On Qball-X4 Quad-rotor UAV

Quad-rotor UAV (Unmanned Aerial Vehicle) is a kind of flexible aircraft with symmetrical structure. It can achieve a variety of flight attitude by respectively controlling four rotors’speed, including vertical take-off and landing and hovering in the air and other special flight attitude. The UAV has great application prospects in the military and civilian market. But its nonlinear, multivariable, coupling and under-actuated characteristics greatly increased the difficulty in study. In the thesis, the main contents is to design the flight controller based on the Qball-X4 UAV developed by Quanser company.Firstly, this thesis analyzed the structural characteristics and mechanism of four-rotor UAV flight. Then combined with the parameters of Qball-X4, the nonlinear dynamics model is established. According to the characteristics of the small-angle indoor flight the model is simplified. And some properties are obtained by analyzing the Quad-rotor UAV dynamics model.Secondly, this thesis designed a controller using the linear quadratic regulator (LQR) adjusting the PID control parameters. The form of state space linear model is regarded as controlled object. The LQR-PID controller constructs the double closed loop control system of position and attitude. In order to introduce an integrator in the controller, reducing the steady-state error, the paper creatively added a state variable in the model. Then, the thesis does hovering flight and spiral flight experiments in the simulation to test the flight performance of the controller.Thirdly, in order to consider the complexity of actual flight environment, improving the robustness of the control system, a loop shaping method based on control theory has been presented to realize the designing of system controller. This method makes a quantitative mathematical description for norm, system normalized coprime factors uncertainty and robustness. This is a kind of design method, which applies the shaping system open-loop frequency curve to ensure the robust performance and control quality of the closed loop control system. This method can achieve a well robust performance and robust stability. Finally, the the simulation experiments for the reduced order controller has been done. And the performance indicators have reached the preset goal.Finally, the Qball-X4 four rotor UAV system is introduced, including steps of the OptiTrack camera calibrating 3D space and Simulink/QUARC system. Then the feasibility of the controller in real environment is verified through the semi physical simulation experiment. And the tracking performance of position and attitude angle are analyzed.