Adaptive Sliding Mode Control For Trajectory Tracking Of Quadrotor UAV

Multi-rotor UAV is an aerial robot capable of autonomous hovering and vertical take-off and landing.In recent years,the quadrotor UAV has developed rapidly and been widely used in many fields and its control problem has also become a popular and difficult topic in the field of robot control.Based on nonlinear quadrotor UAV system with underactuated and high coupled features,this thesis solves the control problem about trajectory tracking of quadrotor UAV by adopting sliding mode control,adaptive technique,fuzzy control,super-twisting algorithm,nonlinear disturbance observer and Lyapunov stability theory.The main contents are concluded as follows:(1)An adaptive fast nonsingular terminal sliding mode controller is proposed for trajectory tracking of quadrotor in the presence of external disturbances,parametric perturbation and actuator saturation.Firstly,the dynamics model of quadrotor UAV is established based on Newton-Euler method.Besides,the proposed reaching law makes the sliding mode surface reachable quickly.A global fast nonsingular terminal sliding mode surface is used to ensure finite time convergence of errors.Meanwhile,this thesis employs not only the observer to compensate for disturbances,but also the adaptive method to compensate for the unknown upper bound of the observer error.The robustness is further enhanced and the chattering caused by switching control gains is further attenuated.Considering the actuator saturation,an anti-saturation compensator compensates for the unknown saturation error and ensures that the control gain is bounded.Finally,simulation results prove the effectiveness of the proposed control scheme.(2)Considering the unmodeled dynamics,external disturbances and timevarying parameters,a robust adaptive fuzzy nonsingular fast terminal sliding mode controller that converges according to the error performance index function is proposed to realize the trajectory tracking of the quadrotor UAV.Firstly,an arctangent nonsingular terminal sliding mode surface is designed to ensure finite time convergence of errors.Moreover,an error index function is used to limit tracking errors and ensures that the system achieves a certain convergence precision.To eliminate the effects of uncertainties such as time-varying parameters,the switching gains and the ideal control laws are approximated by the adaptive fuzzy system,thus obtaining continuous control laws and suppressing chattering effectively.Finally,simulation results prove the effectiveness of the proposed control scheme.(3)For the trajectory tracking of single quadrotor and the multi-rotors formation control,an improved adaptive super-twisting sliding mode fault-tolerant controller based on input saturation and an improved adaptive super-twisting sliding mode formation controller are designed respectively.Firstly,an arctangent nonsingular terminal sliding mode surface is designed to ensure finite time convergence of errors.Considering the partial failure and actuator saturation,the anti-saturation compensator and adaptive technology are used to solve the actuator fault effectively.Secondly,a single-quadrotor fault-tolerant controller is designed with an adaptive improved super-twisting algorithm,thus strengthening the system robustness.Then,the integrated sliding mode surface is designed for the formation control problem based on the single-quadrotor controller,so that the initial state of the system is on the sliding mode surface and the convergence time is shortened.Based on Lyapunov stability theory,it is proved that an adaptive improved super-twisting sliding mode formation controller made the sliding mode surface built in a finite time,and after this the tracking error would finally asymptotically converge to zero on the sliding mode surface.Finally,simulation results prove the effectiveness of the proposed control scheme.