Research On Robust Adaptive Control And Path Planning For A Quadrotor Uav

In recent years,quadrotor unmanned aerial vehicles(UAVs)have received extensive attention from researchers due to their simple mechanical structure,portable operation,and some unique advantages,such as hovering,vertical take-off and landing.In this dissertation,the controller design of quadrotor UAV is studied in the presence of parametric uncertainty,input saturation and external disturbance.Meanwhile,the path planning of quadrotor UAV is investigated under a complex environment with multiple obstacles of different shapes.In summary,the main contributions of the dissertation lie in the following three aspects:First,the adaptive sliding mode control for a quadrotor UAV subject to parametric uncertainty and external disturbance is studied.The dynamic model of quadrotor system has many physical parameters,some of which are difficult to measure accurately,and the parameters are coupled with each other.To address the problem,a group-parameter adaptive law is proposed to estimate all the physical parameters of quadrotor UAV.The signum function term in sliding mode controller is used to suppress external disturbance.Then,an adaptive sliding mode controller is constructed for a quadrotor UAV under the consideration of parametric uncertainty and external disturbance with a known upper bound.Furthermore,in order to deal with external disturbance without any prior knowledge,an adaptive law is designed to estimate the upper bound of external disturbance.By combining with the group-parameter adaptive algorithm,an adaptive sliding mode controller is developed for a quadrotor UAV under parametetric uncertainty and fully unknown disturbance.Lyapunov stability theory and La Salle’s invariant principle are employed to rigorously prove the asymptotic convergence of tracking error of closed-loop system.Second,the finite-time control based on fast terminal sliding mode approach for a quadrotor UAV in the presence of input saturation and external disturbance is studied.To address the problem of the control input saturation of quadrotor UAV,a second-order auxiliary system is designed to compensate for input saturation.Thereby,the amplitude of control input is limited,which avoids the full output of quadrotor UAV motor in one cycle.Meanwhile,considering the influence of external disturbance on the stability of quadrotor UAV,a finite-time nonlinear disturbance observer is designed to estimate external disturbance.Therefore,the compensation for external disturbance is achieved.Furthermore,based on the designed second-order saturation auxiliary system and the finite-time nonlinear disturbance observer,a finite-time fast terminal sliding mode controller is constructed for a quadrotor UAV.Lyapunov stability theory is used to prove the finite-time convergence of disturbance observation error and tracking error of closed-loop system,respectively.Third,the path planning of quadrotor UAV using improved artificial potential field algorithm based on parallel search under a complex environment with multiple obstacles of different shapes is studied.A method of moving around the nearest obstacle is proposed to address the problem of local minimum in the traditional artificial potential field algorithm.Then,an approach of moving around the nearest obstacle and detecting the obstacles between current position and target position simultaneously is presented to addess the problem of unreachable target in the traditional artificial potential field algorithm.To achieve the tracking of the planned path,the three desired attitude angles of quadrotor UAV are calculated according to the planned path points.Meanwhile,considering the influence of external disturbance on the stability of quadrotor UAV,a nonlinear disturbance observer is designed to compensate for external disturbance.Furthermore,a backstepping controller based on the designed nonlinear disturbance observer is proposed for a quadrotor UAV.Lyapunov stability theory is used to rigorously prove the exponential convergence of disturbance observation error and tracking error of closed-loop system,respectively.