Sliding Mode Controller Design And Stability Analysis Of Multi-rotor UAV

In many types of aircraft,both four and three rotor quadrotors are belong to unmanned aerial vehicle(UAV)which holds great prospects in military and civilian fields.But the current research on flight control of multi-rotor UAV still faces many difficulties,such as a multi-input and multi-output of the under-actuated system,strong coupling characteristics,nonlinear dynamic characteristics,the model uncertainty and air flow disturbance of the UAV,which makes the control of multi-rotor UAV become more complicated.The paper studies the attitude adjustment and position tracking problem of multi-rotor UAV by the use of sliding mode control.The main contents of this paper include:1.For a type of four rotor UAV,the paper studies the attitude tracking problem.According to the nonlinear model of the attitude of four rotor UAV,a new nonsingular terminal sliding mode controller based on super-twisting algorithm is proposed,which ensures that the attitude tracking errors of four rotor UAV converge to zero in finite time,and improves the convergence rate and capacity of resisting disturbance of the system.Finally,the stability of the closed loop system is proved by Lyapunov theory2.According to the strong coupling characteristics of the six degree of freedom full state nonlinear model of UAV,the system is decomposed into a full-actuated subsystem and under-actuated subsystem.For the full-actuated subsystem,a nonsingular terminal sliding mode controller based on super-twisting algorithm is proposed to make the tracking errors of the attitude and position converge to zero in finite time.For the under-actuated subsystem,we rebuilds the system model by coordinate transformation.Then,based on the transformed dynamic equation,we propose a sliding mode controller,which makes the attitude and position tracking errors converge to zero asymptotically.Finally the stability of closed loop system is obtained by Lyapunov theory.3.For a class of three rotor UAV,we establish a full state nonlinear dynamic model based on its structure and flight dynamic characteristic.The system mode is decomposed into a full-actuated subsystem and under-actuated subsystem.A compound sliding mode control method is designed to solve the attitude andposition tracking control problem.Finally,the stability of the closed loop system is proved by Lyapunov theory.