Control System Design Of Quadrotor UAV Based On Fixed-time Convergence Theory

Quad-rotor unmanned aerial vehicles(UAVs)are widely used in military,commercial and civilian fields due to their simple structure,easy maintenance and high flexibility.However,the quad-rotor UAV is a complex system with nonlinear,multi-variable,strong coupling and underactuated characteristics,and it is very vulnerable to model uncertainty,external gust disturbance and other factors in flight.All these lead to difficulties in the design of its position and attitude control system.In addition,due to the limited anti-interference ability,field of view and load capacity of a single UAV when performing tasks,the formation control of multiple UAVs has been extensively studied.In order to improve the robustness and rapidity of the control system,combined with the fixed-time convergence theory and event-triggered control strategy,the observer-based control system design of quad-rotor UAV is studied in this thesis.First,the position and attitude control of a single quadrotor UAV is studied.A double-power switched extended state observer with fixed-time convergence is proposed to observe external disturbances and system states in real time.Based on the above observer,a non-singular terminal sliding mode controller with fixed-time convergence is designed to make the system output track the given target value within a fixed-time upper bound without singularity.In order to further improve the transient performance,a tracking error performance function is designed to convert the tracking error to achieve the prescribed performance.Second,an adaptive-gain fast super-twisting disturbance observer is designed to estimate the unknown external disturbances smoothly by using the equivalent control method to solve the problem of observation spikes of the fixed-gain disturbance observer.Based on the above observer,the attitude control of a single quadrotor UAV is studied.A tracking differentiator is designed to arrange the transition process for the reference input.Using barrier Lyapunov function and back-stepping method,a double-power add-form controller with fixed-time convergence is designed to make the attitude output track the given target value within a fixed-time upper bound.Moreover,the tracking trajectory satisfies the prescribed asymmetric output tracking error constraint.Third,the position consensus control of multiple quadrotor UAVs is studied.Aiming at the problem of communication network congestion,a double-power addform extended state observer with fixed-time convergence based on event-triggered strategy is designed to observe external disturbances rapidly.Based on the above observer,a multi-UAV position consensus controller with fixed-time convergence based on event-triggered strategy is designed by using the power-integral method.The controller is used to make the quadrotor UAV cluster form a given position formation within a fixed-time upper bound.The above control methods are verified by stability analysis,Zeno phenomenon analysis and simulation.