| With sufficient actuators and an appropriate mechanical structure design,multirotor unmanned aerial vehicle(UAV)can fulfill the capability of fully-actuation,which means it can control the linear motion and angular motion of itself separately.With the ability,UAVs can strengthen its agility by a large margin while requiring a more suitable motion controller to achieve large angle attitude trajectory.The research object of this master thesis is about the motion control of a fully-actuation hexarotor UAV.The research contents and innovations are illustrated below:1)A flying platform is designed and manufactured with motors which can generate bidirectional thrust.The thrusters are tilted to fulfill the feature of fully-actuation.Some experiments are made to acquire key coefficients of mechanical structure and thruster,which is essential for modeling and controller design.2)A mathematical model is created to describe the features of kinematics,dynamics and wrench.The model of wrench can be used for any kinds of multirotor,including the fully-actuated hexarotor with rotor failures.3)In order to strengthen the flexibility and robustness,geometric controller with sliding mode structure is applied to the fully-actuated UAVs.Combined with a nonlinear disturbance observer,the controller can conquer high-amplitude disturbance better.The stability of the controller with an observer is proved by creating a Lyapunov function.The fully-actuation,robustness and anti-disturbance ability is validated by both simulations and experiments.4)Fully-actuated UAVs can hover statically even with rotor failures.A hierarchical fault-tolerant control approach is designed to guarantee complete position control and it’s validated in a simulation. |
